WO2015166658A1 - Air bypass valve control device - Google Patents

Air bypass valve control device Download PDF

Info

Publication number
WO2015166658A1
WO2015166658A1 PCT/JP2015/002262 JP2015002262W WO2015166658A1 WO 2015166658 A1 WO2015166658 A1 WO 2015166658A1 JP 2015002262 W JP2015002262 W JP 2015002262W WO 2015166658 A1 WO2015166658 A1 WO 2015166658A1
Authority
WO
WIPO (PCT)
Prior art keywords
flow rate
compressor
air bypass
surge
bypass valve
Prior art date
Application number
PCT/JP2015/002262
Other languages
French (fr)
Inventor
Yasuhiro Kuze
Original Assignee
Toyota Jidosha Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Jidosha Kabushiki Kaisha filed Critical Toyota Jidosha Kabushiki Kaisha
Publication of WO2015166658A1 publication Critical patent/WO2015166658A1/en

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • F02B37/007—Engines characterised by provision of pumps driven at least for part of the time by exhaust with exhaust-driven pumps arranged in parallel, e.g. at least one pump supplying alternatively
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • F02B37/12—Control of the pumps
    • F02B37/16—Control of the pumps by bypassing charging air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • F02B37/12—Control of the pumps
    • F02B2037/125—Control for avoiding pump stall or surge
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to an air bypass valve control device for a supercharged engine.
  • Patent Literature 1 A specific technique for controlling an air bypass valve is disclosed in Japanese Patent No. 5195142 (Patent Literature 1).
  • the flow rate of air passing through a throttle valve is estimated based on the degree of opening of a throttle valve.
  • a nozzle equation that takes a supercharging pressure and a pressure downstream of the throttle valve as parameters is used to estimate the flow rate.
  • the estimated flow rate and a reference value that is determined based on the current supercharging pressure are then compared.
  • the reference value corresponds to the upper limit of a flow rate at which a surge occurs under the current supercharging pressure. If the estimated flow rate becomes less than or equal to the reference value, a surge will definitely occur immediately thereafter.
  • the air bypass valve is opened at a time that the estimated flow rate becomes less than or equal to the reference value. It is thereby possible to lower the supercharging pressure while returning air from downstream of the compressor to upstream thereof before a surge state is entered, and thus prevent the occurrence of a surge.
  • each intake system is equipped with a compressor.
  • V-type supercharged engines are equipped with a compressor in an intake passage for a right bank and an intake passage for a left bank, respectively.
  • inline-type supercharged engines a plurality of (for example, six) cylinders are divided into two cylinder groups, and a compressor is provided in respective intake passages for the two cylinder groups.
  • the control technique disclosed in Patent Literature 1 can also be applied to control of an air bypass valve in such kind of supercharged engines.
  • Patent Literature 2 Japanese Patent Laid-Open No. 2013-096372
  • Patent Literature 2 Japanese Patent Laid-Open No. 2013-096372
  • the present invention has been conceived in view of the above described problem, and an object of the present invention is to provide an air bypass valve control device that, in a supercharged engine in which a compressor is disposed in each of two upstream intake passages and a throttle valve is disposed in a downstream intake passage that is formed by merging of the two upstream intake passages, can suppress the release of air into the atmosphere from inside the system that is caused by operations of an air bypass valve for avoiding the occurrence of a surge.
  • a supercharged engine to which an air bypass valve control device includes a first upstream intake passage and a second upstream intake passage that draw in air, and a downstream intake passage formed by merging of the first upstream intake passage and the second upstream intake passage.
  • a first compressor is installed in the first upstream intake passage, and a first air bypass valve is disposed in a flow path that bypasses the first compressor.
  • a second compressor is installed in the second upstream intake passage, and a second air bypass valve is disposed in a flow path that bypasses the second compressor.
  • a throttle valve is disposed in the downstream intake passage.
  • the air bypass valve control device is configured to execute synchronous opening control that always opens both of the first air bypass valve and the second air bypass valve simultaneously. This means that, for example, in a case where a reason for opening the valve arises with respect to the first air bypass valve, not only does the first air bypass valve opened, but the second air bypass valve also opens at the same time.
  • the air bypass valve control device according to the present invention may also be configured to, in combination with the synchronous opening control, execute synchronous closing control that always closes both of the first air bypass valve and the second air bypass valve simultaneously.
  • the air bypass valve control device is configured to execute a surge prediction process and an air bypass valve opening process.
  • the surge prediction process prediction of an occurrence of a surge is performed based on respective operating conditions of the first compressor and the second compressor.
  • the air bypass valve opening process in a case where an occurrence of a surge in at least one of the first compressor and the second compressor is predicted by the surge prediction process, both of the first air bypass valve and the second air bypass valve are opened.
  • prediction of the occurrence of a surge may always be performed with respect to both of the first compressor and the second compressor or may be performed only with respect to a compressor for which there is a high possibility that a surge will occur.
  • calculation of a ratio of a flow rate of the first compressor and a ratio of a flow rate of the second compressor is performed based on an output of a first air flow meter that is installed in the first upstream intake passage and an output of a second air flow meter that is installed in the second upstream intake passage.
  • calculation of a surge flow rate that is an upper limit of a flow rate at which a surge occurs in the first and second compressors is performed based on a supercharging pressure.
  • calculation of a predicted flow rate of air that passes through the throttle valve is performed based on a degree of opening of the throttle valve.
  • the order of performing the first, second, and third processes is not limited.
  • calculation of a predicted flow rate of a compressor in which a flow rate is smaller among the first compressor and the second compressor is performed based on a smaller ratio among the two ratios that are calculated in the first process and the predicted flow rate that is calculated in the third process.
  • it is determined whether or not the predicted flow rate that is calculated in the fourth process is less than or equal to the surge flow rate that is calculated in the second process.
  • Fig. 1 is a view for describing the overall configuration of a system according to Embodiment 1 of the present invention.
  • Fig. 2 is a graph for describing a surge prediction method according to Embodiment 1 of the present invention.
  • Fig. 3 is a flowchart illustrating a routine for surge avoidance control according to Embodiment 1 of the present invention.
  • Fig. 4 is a view for describing operations of an air bypass valve according to Embodiment 1 of the present invention.
  • Fig. 5 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention.
  • Fig. 6 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention.
  • Fig. 1 is a view for describing the overall configuration of a system according to Embodiment 1 of the present invention.
  • Fig. 2 is a graph for describing a surge prediction method according to Embodiment 1 of the present invention.
  • FIG. 7 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention.
  • Fig. 8 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention.
  • Fig. 9 is a time chart with respect to a degree of opening of a throttle valve, a supercharging pressure, a predicted flow rate, and a degree of opening of an air bypass valve according to surge avoidance control of Embodiment 1 of the present invention.
  • Fig. 10 is a time chart with respect to a degree of opening of a throttle valve, a supercharging pressure, a predicted flow rate, and a degree of opening of an air bypass valve according to Comparative Example 1.
  • Fig. 10 is a time chart with respect to a degree of opening of a throttle valve, a supercharging pressure, a predicted flow rate, and a degree of opening of an air bypass valve according to Comparative Example 1.
  • Fig. 11 is a time chart with respect to a degree of opening of a throttle valve, a supercharging pressure, a predicted flow rate, and a degree of opening of an air bypass valve according to Comparative Example 2.
  • Fig. 12 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 2 of the present invention.
  • Fig. 13 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 3 of the present invention.
  • Fig. 14 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 4 of the present invention.
  • Fig. 15 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 5 of the present invention.
  • Embodiment 1 Fig. 1 is a view for describing the overall configuration of a system according to Embodiment 1 of the present invention.
  • the system of Embodiment 1 includes a supercharged engine 1 and an ECU (electronic control unit) 100.
  • the supercharged engine 1 is a V-type engine that has a left bank 2L and a right bank 2R.
  • one cylinder 4L is illustrated in the bank 2L and one cylinder 4R is illustrated in the bank 2R.
  • the respective banks 2L and 2R have a plurality of cylinders.
  • the supercharged engine 1 in Embodiment 1 is a spark-ignition type in-cylinder direct injection engine, in which a spark plug and an in-cylinder injection valve are installed in each cylinder. Note that, in the following description of the embodiments, identical members that are disposed in each of the left bank 2L and the right bank 2R are denoted by reference characters obtained by adding the character "L” or "R" after the same number for the respective members.
  • An intake system of the supercharged engine 1 will be described.
  • An intake manifold 18L is connected through an intake valve 6L to the cylinder 4L of the left bank 2L.
  • An intake manifold 18R is connected through an intake valve 6R to the cylinder 4R of the right bank 2R.
  • the left and right intake manifolds 18L and 18R are connected to a common surge tank 22.
  • the surge tank 22 is integrated with a water-cooled intercooler 24, and a pressure sensor 98 that outputs a signal in accordance with an internal pressure of the surge tank 22 is installed therein.
  • a single intake passage 16 is connected to the surge tank 22.
  • a throttle valve 20 is disposed in the intake passage 16.
  • a degree-of-throttle-opening sensor 90 that outputs a signal in accordance with the degree of opening of the throttle valve 20 is installed in the throttle valve 20.
  • the intake passage 16 is formed as a result of the two intake passages 10L and 10R that are provided for the respective banks 2L and 2R merging.
  • a position at which the throttle valve 20 is provided is, with respect to the flow of air, downstream of the position at which the intake passages 10L and 10R merge.
  • the intake passages 10L and 10R that are located on the upstream are each referred to as “upstream intake passage”, and the intake passage 16 that is located on the downstream side is referred to as "downstream intake passage”.
  • a pressure sensor 94 that outputs a signal in accordance with the pressure in the relevant space and a temperature sensor 96 that outputs a signal in accordance with the temperature in the relevant space.
  • Air cleaners 12L and 12R as well as air flow meters 92L and 92R that output a signal in accordance with the flow rate of drawn-in air are disposed in an air intake port of the upstream intake passages 10L and 10R, respectively.
  • the supercharged engine 1 includes turbochargers 60L and 60R in the left and right banks 2L and 2R, respectively.
  • a compressor (first compressor) 62L of a turbocharger 60L is installed in the upstream intake passage 10L.
  • a compressor (second compressor) 62R of a turbocharger 60R is installed in the upstream intake passage 10R.
  • a bypass flow path 30L that bypasses the compressor 62L is provided in the upstream intake passage 10L of the left bank 2L.
  • An air bypass valve (first air bypass valve) 32L that controls blocking/communication of the bypass flow path 30L is disposed in the bypass flow path 30L.
  • a bypass flow path 30R that bypasses the compressor 62R is provided in the upstream intake passage 10R, and an air bypass valve (second air bypass valve) 32R is disposed in the bypass flow path 30R.
  • the air bypass valves 32L and 32R are electromagnetically-driven valves that are driven by means of a solenoid.
  • the term “air bypass valve” may be abbreviated as "ABV”.
  • An exhaust manifold 40L is connected through an exhaust valve 8L to the cylinder 4L of the left bank 2L.
  • An exhaust manifold 40R is connected through an exhaust valve 8R to the cylinder 4R of the right bank 2R.
  • a turbine 64L of the turbocharger 60L is installed in the exhaust manifold 40L.
  • a bypass flow path 48L that bypasses the turbine 64L is provided, and a waste gate valve 50L is disposed in the bypass flow path 48L.
  • a turbine 64R of the turbocharger 60R is installed in the exhaust manifold 40R, a bypass flow path 48R that bypasses the turbine 64R is provided, and a waste gate valve 50R is disposed in the bypass flow path 48R.
  • a first front-stage catalyst 52L is installed in an outlet of the turbine 64L, and an exhaust passage 42L is connected to the first front-stage catalyst 52L.
  • an exhaust passage 42R is connected via a first front-stage catalyst 52R to an outlet of the turbine 64R.
  • Second front-stage catalysts 54L and 54R are disposed in the respective exhaust passages 42L and 42R.
  • the two exhaust passages 42L and 42R merge to form a single exhaust passage 44, and diverge again into two exhaust passages 46L and 46R under the floor of the vehicle.
  • Under-floor catalysts 56L and 56R are disposed in the exhaust passages 46L and 46R, respectively.
  • Mufflers 58L and 58R are also installed in the respective exhaust passages 46L and 46R. Note that, the first front-stage catalysts 52L and 52R, the second front-stage catalysts 54L and 54R, and the under-floor catalysts 56L and 56R are all three-way catalysts.
  • the supercharged engine 1 is equipped with an EGR mechanism 70 that recirculates one part of exhaust gas from the exhaust system to the intake system.
  • the EGR mechanism 70 is configured to take out exhaust gas from between the first front-stage catalyst 52L and the second front-stage catalyst 54L in the exhaust passage 42L of the left bank 2L by means of an upstream EGR flow path 72L, and to also take out exhaust gas from between the first front-stage catalyst 52R and the second front-stage catalyst 54R in the exhaust passage 42R of the right bank 2R by means of an upstream EGR flow path 72R.
  • the two upstream EGR flow paths 72L and 72R merge to form a single midstream EGR flow path 74.
  • EGR coolers 78L and 78R are disposed in the upstream EGR flow paths 72L and 72R, respectively, and an EGR valve 80 is disposed in a midstream EGR flow path 74.
  • the midstream EGR flow path 74 diverges into two downstream EGR flow paths 76L and 76R at a distal end thereof.
  • the downstream EGR flow path 76L is connected at a position between an air cleaner 12L and the compressor 62L in the upstream intake passage 10L.
  • the downstream EGR flow path 76R is connected at a position between an air cleaner 12R and the compressor 62R in the upstream intake passage 10R.
  • the supercharged engine 1 configured as described above is controlled by the ECU 100.
  • the ECU 100 has an input/output interface, a memory and a CPU.
  • the input/output interface is provided in order to take in sensor signals from various sensors installed in the supercharged engine 1 and the vehicle, and also to output actuating signals to actuators included in the supercharged engine 1.
  • the sensors form which the ECU 100 takes in signals also include an unshown air-fuel ratio sensor, an accelerator pedal sensor, an engine speed sensor, and an atmospheric pressure sensor.
  • the actuators to which the ECU 100 outputs an actuating signal also include an unshown ignition device, fuel injection device and variable valve timing device.
  • Various control programs for controlling the supercharged engine 1 are stored in a memory. The CPU reads a control program from the memory and executes the control program, and generates actuating signals based on sensor signals that were taken in.
  • the control programs that the ECU 100 executes include a control program for controlling the air bypass valves 32L and 32R.
  • the ECU 100 When executing the control program, the ECU 100 functions as an air bypass valve control device.
  • control of the air bypass valves 32L and 32R is referred to as "ABV control". More specifically, the ABV control includes synchronous opening control and synchronous closing control.
  • the synchronous opening control is control that simultaneously opens both of the air bypass valve 32L and the air bypass valve 32R, while the synchronous closing control is control that simultaneously closes these two air bypass valves 32L and 32R.
  • Surge avoidance control for avoiding a surge in the compressors 62L and 62R is included in the synchronous opening control of the ABV control. According to the surge avoidance control, first prediction of a surge in the compressors 62L and 62R is performed. Hereunder, this process is described using Fig. 2.
  • Fig. 2 is a graph for describing a surge prediction method.
  • the horizontal axis of this graph represents a pressure ratio of a pressure downstream of a compressor to a pressure upstream thereof, and the vertical axis represents a flow rate of the compressor.
  • An upper limit of a flow rate at which a surge occurs is a surge flow rate, and the surge flow rate depends on the pressure ratio.
  • a curve is drawn that shows the relation between the pressure ratio and the surge flow rate.
  • both of the compressors 62L and 62R have the surge characteristics shown in Fig. 2.
  • a pressure downstream of the compressor is a supercharging pressure that is measured by the pressure sensor 94
  • a pressure upstream of the compressor is an atmospheric pressure.
  • surge characteristics may be defined by taking the atmospheric pressure as a fixed value, and using a supercharging pressure instead of the pressure ratio.
  • Patent Literature 1 estimates the flow rate of air through the throttle valve 20 based on the degree of opening of the throttle valve 20, and predicts that a surge will occur if the flow rate through the throttle valve is less than or equal to the surge flow rate.
  • the size of a flow rate through the throttle valve is represented by "mt”
  • the size of a surge flow rate is represented by "ms”.
  • the above described conventional technology can be easily applied in the supercharged engine 1 of Embodiment 1 also by regarding half of the flow rate through the throttle valve mt as the predicted value of the flow rate for each of the compressors 62L and 62R.
  • the actual flow rate of the compressor having the smaller flow rate among the left and right compressors 62L and 62R is less than or equal to the surge flow rate ms.
  • a surge occurs in the compressor at which the flow rate has become less than or equal to the surge flow rate ms.
  • the air flow meters 92L and 92R are disposed in the inlets of the respective upstream intake passages 10L and 10R.
  • the flow rate of air that flows into the compressor 62L of the left bank 2L can be obtained based on the output of the air flow meter 92L.
  • the flow rate of air that flows into the compressor 62R of the right bank 2R can be obtained based on the output of the air flow meter 92R.
  • the size of a flow rate measured by the air flow meter 92L is represented by "GaL”
  • the size of a flow rate measured by the air flow meter 92R is represented by "GaR”.
  • surge prediction is performed by the following method in the surge avoidance control employed in Embodiment 1.
  • a ratio that the flow rate of the compressor 62L occupies with respect to the overall flow rate of the engine during steady operation can be expressed by GaL/(GaL + GaR), and a ratio that the flow rate of the compressor 62R occupies can be expressed by GaR/(GaL + GaR).
  • the respective ratios of the flow rates of the two compressors 62L and 62R do not differ significantly between a time of steady operation and a time of transient operation. Further, the total flow rate of the two compressors 62L and 62R during transient operation can be regarded as being equal to the flow rate through the throttle valve mt.
  • the predicted flow rate of each of the compressors 62L and 62R during transient operation can be calculated by the respective equations shown hereunder.
  • Predicted flow rate of left bank compressor 62L mt ⁇ GaL/(GaL + GaR)
  • Predicted flow rate of right bank compressor 62R mt ⁇ GaR/(GaL + GaR)
  • the smaller predicted flow rate is the flow rate that first reaches the surge flow rate.
  • the flow rate ratio kGa is calculated using the above described equations. Further, a compressor flow rate that is the object of the surge prediction is calculated by the following equation using the flow rate ratio kGa and the flow rate through the throttle valve mt.
  • a compressor flow rate mt ⁇ kGa that is calculated by the following equation has become less than or equal to the surge flow rate ms, it is predicted that a surge will occur in the compressor having the smaller flow rate.
  • Compressor flow rate that is object of surge prediction mt ⁇ kGa
  • the surge prediction method described above is used for surge avoidance control.
  • the surge avoidance control of Embodiment 1 is executed in accordance with a flowchart illustrated in Fig. 3.
  • the routine for surge avoidance control illustrated in the flowchart is repeatedly executed for each predetermined control period corresponding to the clock speed of the ECU 100.
  • step S101 the flow rate ratio kGa is calculated based on the flow rates GaL and GaR measured by the left and right air flow meters 92L and 92R.
  • smoothing processing is performed to prevent abrupt variations in the value of the flow rate ratio kGa.
  • step S102 it is determined whether or not the supercharged engine 1 is in a deceleration state. Whether or not the supercharged engine 1 is in a deceleration state can be determined based on the output of the degree-of-throttle-opening sensor 90 and the rate of change thereof. If the result determined in step S102 is negative, the current processing of the present routine ends. In this case, the air bypass valves 32L and 32R are maintained in a closed state that is the fundamental state thereof.
  • step S103 If the result determined in step S102 is affirmative, calculation of the surge flow rate ms is performed in step S103.
  • a previously prepared surge characteristics map is referred to calculate the surge flow rate ms.
  • the surge characteristics map is a map in which the relation between a surge flow rate and a pressure ratio between a supercharging pressure and the atmospheric pressure is defined.
  • the surge flow rate ms at the current supercharging pressure is calculated by calculating the pressure ratio based on the current supercharging pressure measured by the pressure sensor 94, and performing a search in the surge characteristics map using the calculated pressure ratio as an argument.
  • step S104 calculation of the flow rate through the throttle valve mt is performed.
  • a nozzle equation that is also used in the conventional technology described in Patent Literature 1 is used to calculate the flow rate through the throttle valve mt.
  • the nozzle equation is a known equation that is used to model a throttle valve.
  • a degree of throttle opening TA that is measured by the degree-of-throttle-opening sensor 90, a pressure Pm downstream of the throttle valve 20 that is measured by the pressure sensor 98, a pressure Pa upstream of the throttle valve 20 that is measured by the pressure sensor 94, and a temperature Ta upstream of the throttle valve 20 that is measured by the temperature sensor 96 are input to the nozzle equation, and the flow rate through the throttle valve mt is calculated based on those parameters.
  • the calculation in step S104 may be performed before the calculation in step S103.
  • step S105 the compressor flow rate that is the object of the surge prediction, i.e. mt ⁇ kGa, is calculated using the flow rate ratio kGa calculated in step S101 and the flow rate through the throttle valve mt calculated in step S104. Further, it is determined whether or not the compressor flow rate mt ⁇ kGa is less than or equal to the surge flow rate ms. If the result of this determination is negative, the situation is not one in which a surge will occur immediately thereafter. Hence, in this case, in step S107, the air bypass valves 32L and 32R are maintained in a closed state that is the fundamental state thereof.
  • step S105 If the result determined in step S105 is affirmative, it is predicted that a surge will occur immediately thereafter. Hence, in this case, in order to lower the supercharging pressure and avoid a surge, opening of the air bypass valves 32L and 32R is performed. As described in the foregoing, because the surge avoidance control is included in the synchronous opening control, the air bypass valves 32L and 32R of the two compressors 62L and 62R are simultaneously opened, and not just the air bypass valve of the compressor at which the occurrence of a surge is predicted. The advantages of performing the air bypass valve opening process in this way will now be described using Fig. 4 to Fig. 8.
  • Fig. 4 illustrates the flow of air during normal operation in the intake system.
  • the left and right air bypass valves 32L and 32R are closed, and air is pressure-charged in the left and right compressors 62L and 62R.
  • the air that was pressure-charged in the compressors 62L and 62R is supplied to the surge tank 22 through the throttle valve 20.
  • the degree of opening of the throttle valve 20 is decreased in order to cause the engine to decelerate, the flow of air in the intake system changes as shown in Fig. 5. That is, when decelerating, the flow rate of air to the surge tank 22 decreases as a result of closing the throttle valve 20, and consequently the supercharging pressure rises.
  • Fig. 6 is a view illustrating the flow of air in a case where only the air bypass valve 32L of the left bank was opened. Since the compressor for which the occurrence of a surge was predicted is the compressor 62L of the left bank, if the purpose is only to avoid a surge, it is sufficient to open only the air bypass valve 32L of the left bank. However, since the air bypass valve 32R of the right bank is closed, supercharging is continued in the compressor 62R of the right bank. Therefore, air that was pressure-charged in the compressor 62R of the right bank flows to the upstream intake passage 10L of the left bank through the upstream intake passage 10R of the right bank, and is released into the atmosphere through the air bypass valve 32L that is open.
  • FIG. 7 illustrates the flow of air at a moment at which both of the air bypass valves 32L and 32R of the left and right banks are simultaneously opened.
  • Fig. 8 illustrates the flow of air in a case where the air bypass valves 32L and 32R of the left and right banks are both open.
  • the two air bypass valves 32L and 32R are open, although air from the downstream side of the respective compressors 62L and 62R is returned to the upstream side via the air bypass valves 32L and 32R, the returned air is drawn in again by the compressors 62L and 62R. That is, in the left and right banks, a loop is formed with respect to the air that circulates through the compressors 62L and 62R and the air bypass valves 32L and 32R. Consequently, a case does not arise in which air from inside the system is continuously released into the atmosphere as in the case illustrated in Fig. 6.
  • Embodiment 1 it is possible to suppress the occurrence of a situation in which air inside the system is released into the atmosphere as the result of operations of the air bypass valves 32L and 32R that are performed to avoid the occurrence of a surge. Further, as long as the flow path capacity of the upstream intake passages 10L and 10R from the air cleaners 12L and 12R to the compressors 62L and 62R is sufficient, it is possible to prevent air inside the system that was returned via the air bypass valves 32L and 32R from being released into the atmosphere.
  • Fig. 9 is a time chart with respect to the degree of opening of the throttle valve, the supercharging pressure, the predicted flow rate and the degree of opening of the air bypass valves according to the surge avoidance control of Embodiment 1.
  • Fig. 9 is a time chart with respect to the degree of opening of the throttle valve, the supercharging pressure, the predicted flow rate and the degree of opening of the air bypass valves according to the surge avoidance control of Embodiment 1.
  • FIG. 10 is a time chart illustrating an example (Comparative Example 1) in a case where a surge determination is made by means of a comparison between the average flow rate (mt ⁇ 1/2) of the left and right compressors 62L and 62R and the surge flow rate ms.
  • Fig. 11 is a time chart illustrating an example (Comparative Example 2) in a case where a surge determination is made by means of a comparison between flow rates GaL and GaR measured by the air flow meters 92L and 92R and the surge flow rate ms. Note that, this time chart do not represent actual experimental data, but represent an image of control results.
  • the opened air bypass valves 32L and 32R are closed once more at a time that the supercharged engine 1 is caused to accelerate again.
  • the ECU 100 simultaneously closes the left and right air bypass valves 32L and 32R by synchronous closing control so that supercharging starts simultaneously in the left and right compressors 62L and 62R. This is done in order to prevent air inside the system being released into the atmosphere.
  • Embodiment 2 The configuration of the system of Embodiment 2 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 2 and Embodiment 1.
  • Fig. 12 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 2. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
  • step S201 it is determined whether or not the left and right air bypass valves 32L and 32R were closed the previous time that the routine was executed.
  • the air bypass valves 32L and 32 are open, the flow rate of fresh air that is drawn into the upstream intake passages 10L and 10R decreases by an amount corresponding to the flow rate of air that is returned to upstream through the air bypass valves 32L and 32R.
  • the proportion of the decrease in the flow rate of the fresh air as the result of the air bypass valves 32L and 32 being open differs between the left and right upstream intake passages 10L and 10R.
  • step S202 the value of the flow rate ratio kGa is updated.
  • the method of updating the value of the flow rate ratio kGa is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3.
  • step S203 the previous value of the flow rate ratio kGa is retained. That is, when the left and right air bypass valves 32L and 32R are open, updating of the value of the flow rate ratio kGa is not performed.
  • measured flow rates GaL and GaR obtained when the air bypass valves 32L and 32R are closed are always used to calculate the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt ⁇ kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
  • Embodiment 3 The configuration of the system of Embodiment 3 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 3 and Embodiment 1.
  • Fig. 13 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 3. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
  • step S301 it is determined whether or not a supercharging pressure measured by the pressure sensor 94 is greater than the atmospheric pressure, that is, whether or not a pressure ratio is greater than 1.
  • a difference between the measured flow rates GaL and GaR for the left and right arises due to a difference between the resistances of the left and right upstream intake passages 10L and 10R and a difference between the efficiencies of the left and right compressors 62L and 62R.
  • a difference between the efficiencies of the left and right compressors 62L and 62R does not affect the flow rates. Therefore, a difference arises in the ratio for measured flow rates GaL and GaR for the left and right between a state in which the pressure ratio is greater than 1 and a state in which the pressure ratio is less than or equal to 1.
  • step S302 the value of the flow rate ratio kGa is updated.
  • the method of updating the value of the flow rate ratio kGa is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3.
  • step S303 the previous value of the flow rate ratio kGa is retained. That is, in a state in which the pressure ratio is less than or equal to 1, updating of the value of the flow rate ratio kGa is not performed.
  • a time that a surge occurs is a time when the engine is operating in a supercharging region in which the pressure ratio is greater than 1, and information that is necessary for surge prediction cannot be obtained from the measured flow rates GaL and GaR that are obtained in a non-supercharging region in which the pressure ratio is less than or equal to 1. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
  • measured flow rates GaL and GaR obtained at a time that supercharging is being performed by the compressors 62L and 62R are always used to calculate the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt ⁇ kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
  • Embodiment 3 can be combined with the surge avoidance control of Embodiment 2. That is, a configuration may be adopted so as to perform updating of the flow rate ratio kGa only in a case in which the left and right air bypass valves 32L and 32R were closed the previous time the routine was executed and in which the supercharging pressure that is measured the current time is greater than the atmospheric pressure.
  • Embodiment 4 The configuration of the system of Embodiment 4 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 4 and Embodiment 1.
  • Fig. 14 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 4. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
  • step S401 it is determined whether or not the EGR valve 80 is closed.
  • the EGR valve 80 When the EGR valve 80 is closed, only fresh air flows through the left and right upstream intake passages 10L and 10R.
  • the EGR valve 80 when the EGR valve 80 is open, a gas in which fresh air and EGR gas are combined flows through the left and right upstream intake passages 10L and 10R.
  • a ratio of the flow rate of EGR gas to the flow rate of fresh air depends on the resistance and back pressure in the EGR flow path and the state of the EGR valve 80. Consequently, a difference arises in the ratio of the measured flow rates GaL and GaR for the left and right between a time when the EGR valve 80 is closed and a time when the EGR valve 80 is open.
  • step S402 the value of a flow rate ratio kGaEC is updated.
  • the flow rate ratio kGaEC is calculated based on the measured flow rates GaL and GaR for the left and right when the EGR valve 80 is closed.
  • the method of calculating the flow rate ratio kGaEC is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3.
  • step S403 the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaEC that was updated in step S402. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
  • step S404 the value of a flow rate ratio kGaEO is updated.
  • the flow rate ratio kGaEO is calculated based on the measured flow rates GaL and GaR for the left and right when the EGR valve 80 is open.
  • the method of calculating the flow rate ratio kGaEO is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3.
  • step S405 the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaEO that was updated in step S404. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
  • the flow rate ratio kGaEC at a time that the EGR valve 80 is closed and the flow rate ratio kGaEO at a time that the EGR valve 80 is open are respectively prepared as the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt ⁇ kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
  • Embodiment 4 can be combined with the surge avoidance control of Embodiment 2 or the surge avoidance control of Embodiment 3. That is, a condition that the left and right air bypass valves 32L and 32R were closed the previous time the routine was executed or a condition that the supercharging pressure that is measured the current time is greater than the atmospheric pressure may be adopted as a condition for performing updating of the flow rate ratios kGaEC and kGaEO.
  • Embodiment 5 The configuration of the system of Embodiment 5 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 5 and Embodiment 1.
  • Fig. 15 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 4. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
  • step S501 it is determined whether or not the left and right waste gate valves 50L and 50R are closed.
  • the efficiency of the compressors 62L and 62R varies depending on whether the waste gate valves 50L and 50R are in an open or closed state. Consequently, a difference arises in the ratios of the measured flow rates GaL and GaR for left and right between a time when the waste gate valves 50L and 50R are closed and a time when the waste gate valves 50L and 50R are open. Note that the left and right waste gate valves 50L and 50R are controlled to open/close synchronously by the ECU 100.
  • step S502 the value of a flow rate ratio kGaWC is updated.
  • the flow rate ratio kGaWC is calculated based on the measured flow rates GaL and GaR for the left and right when the waste gate valves 50L and 50R are closed.
  • the method of calculating the flow rate ratio kGaWC is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3.
  • step S503 the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaWC that was updated in step S502. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
  • step S504 the value of a flow rate ratio kGaWO is updated.
  • the flow rate ratio kGaWO is calculated based on the measured flow rates GaL and GaR for the left and right when the waste gate valves 50L and 50R are open.
  • the method of calculating the flow rate ratio kGaWO is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3.
  • step S505 the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaWO that was updated in step S504. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
  • the flow rate ratio kGaWC at a time that the waste gate valves 50L and 50R are closed and the flow rate ratio kGaWO at a time that the waste gate valves 50L and 50R are open are respectively prepared as the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt ⁇ kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
  • the surge avoidance control of Embodiment 5 can be combined with the surge avoidance control of Embodiment 2 or the surge avoidance control of Embodiment 3. That is, a condition that the left and right air bypass valves 32L and 32R were closed the previous time the routine was executed or a condition that the supercharging pressure that is measured the current time is greater than the atmospheric pressure may be adopted as a condition for performing updating of the flow rate ratios kGaWC and kGaWO. Further, the surge avoidance control of Embodiment 5 can be combined with the surge avoidance control of Embodiment 4. That is, a number of flow rate ratios that corresponds to the number of combinations between an open/closed state of the EGR valve 80 and an open/closed state of the waste gate valves 50L and 50R may be respectively prepared.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Supercharger (AREA)

Abstract

An air bypass valve control device according to this invention is applied to a supercharged engine in which a compressor is disposed in each of two upstream intake passages, and a throttle valve is disposed in a downstream intake passage that is formed by merging of the two upstream intake passages. The air bypass valve control device executes synchronous opening control that simultaneously opens both of a first air bypass valve that is provided for a first compressor and a second air bypass valve that is provided for a second compressor. By this means, the occurrence of a situation in which air inside the system is released into the atmosphere due to operations of an air bypass valve that are performed to avoid a surge is suppressed.

Description

AIR BYPASS VALVE CONTROL DEVICE
The present invention relates to an air bypass valve control device for a supercharged engine.
In a supercharged engine, as a result of the degree of opening of a throttle valve being decreased at a time of deceleration, in some cases air that has passed through a compressor has no place to go and flows back into the compressor and consequently a surge occurs in the compressor. Therefore, conventional supercharged engines are provided with a flow path that bypasses the compressor, and an air bypass valve that opens/blocks off the flow path. By opening the air bypass valve, a supercharging pressure that had risen can be decreased, and air that passed through the compressor can be returned via the bypass flow path to the upstream side of the compressor from the downstream side thereof.
A specific technique for controlling an air bypass valve is disclosed in Japanese Patent No. 5195142 (Patent Literature 1). According to the technique disclosed in Patent Literature 1, the flow rate of air passing through a throttle valve is estimated based on the degree of opening of a throttle valve. A nozzle equation that takes a supercharging pressure and a pressure downstream of the throttle valve as parameters is used to estimate the flow rate. The estimated flow rate and a reference value that is determined based on the current supercharging pressure are then compared. The reference value corresponds to the upper limit of a flow rate at which a surge occurs under the current supercharging pressure. If the estimated flow rate becomes less than or equal to the reference value, a surge will definitely occur immediately thereafter. Therefore, according to the control technique disclosed in Patent Literature 1, the air bypass valve is opened at a time that the estimated flow rate becomes less than or equal to the reference value. It is thereby possible to lower the supercharging pressure while returning air from downstream of the compressor to upstream thereof before a surge state is entered, and thus prevent the occurrence of a surge.
In some supercharged engines, two intake systems are provided, and each intake system is equipped with a compressor. For example, some V-type supercharged engines are equipped with a compressor in an intake passage for a right bank and an intake passage for a left bank, respectively. Furthermore, in some inline-type supercharged engines, a plurality of (for example, six) cylinders are divided into two cylinder groups, and a compressor is provided in respective intake passages for the two cylinder groups. The control technique disclosed in Patent Literature 1 can also be applied to control of an air bypass valve in such kind of supercharged engines.
Note that, Japanese Patent Laid-Open No. 2013-096372 (Patent Literature 2) can be mentioned as prior art literature that describes the state of the art of the technical field of the present invention.
In this connection, among the current supercharged engines that have been proposed, there are some engines in which a surge tank is shared by two intake systems. In such a configuration, two intake passages (upstream intake passages) in which compressors are arranged merge upstream of the surge tank to form a single intake passage (downstream intake passage). A throttle valve can be provided in each of the two upstream intake passages, or a single throttle valve can be provided in the downstream intake passage.
However, in a configuration in which a single throttle valve is disposed in the downstream intake passage, the following problem arises due to the relation with respect to operations of an air bypass valve for avoiding the occurrence of a surge.
According to the above described configuration, although air is drawn into each of the two upstream intake passages, the flow rates of the air that is drawn in are not always the same in the two upstream intake passages. Therefore, conditions under which a surge occurs when decelerating will differ between the two compressors, and operating conditions at one of the compressors may become conditions under which a surge occurs before the operating conditions at the other compressor become conditions under which a surge occurs. Hence, it is preferable to predict the occurrence of a surge at each compressor based on the operating conditions of the respective compressors. If the occurrence of a surge is predicted first at either one of the two compressors, the surge occurrence can be avoided by opening the air bypass valve of the relevant compressor. In addition, since a supercharging pressure is common according to the above described configuration, by opening the air bypass valve of one of the compressors, a surge in the other compressor can be simultaneously avoided because the supercharging pressure decreases.
However, in this case, since supercharging continues in the compressor for which the air bypass valve remains closed, and the degree of opening of the throttle valve is decreased for deceleration, a steady flow of air is formed from the upstream intake passage in which the air bypass valve is closed to the upstream intake passage in which the air bypass valve is open. This means that there is a risk that air which has been drawn into the intake passage will be released to outside the system through the air bypass valve that is open. In most modern-day engines, EGR gas or blow-by gas is introduced into the intake system thereof. Consequently, if a steady flow of air is formed to outside the system, there is a risk that emissions contained in EGR gas or blow-by gas will also be released into the atmosphere.
The present invention has been conceived in view of the above described problem, and an object of the present invention is to provide an air bypass valve control device that, in a supercharged engine in which a compressor is disposed in each of two upstream intake passages and a throttle valve is disposed in a downstream intake passage that is formed by merging of the two upstream intake passages, can suppress the release of air into the atmosphere from inside the system that is caused by operations of an air bypass valve for avoiding the occurrence of a surge.
A supercharged engine to which an air bypass valve control device according to the present invention is applied includes a first upstream intake passage and a second upstream intake passage that draw in air, and a downstream intake passage formed by merging of the first upstream intake passage and the second upstream intake passage. A first compressor is installed in the first upstream intake passage, and a first air bypass valve is disposed in a flow path that bypasses the first compressor. Further, a second compressor is installed in the second upstream intake passage, and a second air bypass valve is disposed in a flow path that bypasses the second compressor. A throttle valve is disposed in the downstream intake passage.
According to a first aspect of the present invention, the air bypass valve control device is configured to execute synchronous opening control that always opens both of the first air bypass valve and the second air bypass valve simultaneously. This means that, for example, in a case where a reason for opening the valve arises with respect to the first air bypass valve, not only does the first air bypass valve opened, but the second air bypass valve also opens at the same time. The air bypass valve control device according to the present invention may also be configured to, in combination with the synchronous opening control, execute synchronous closing control that always closes both of the first air bypass valve and the second air bypass valve simultaneously.
According to a second aspect of the present invention, the air bypass valve control device is configured to execute a surge prediction process and an air bypass valve opening process. In the surge prediction process, prediction of an occurrence of a surge is performed based on respective operating conditions of the first compressor and the second compressor. In the air bypass valve opening process, in a case where an occurrence of a surge in at least one of the first compressor and the second compressor is predicted by the surge prediction process, both of the first air bypass valve and the second air bypass valve are opened.
In the above described surge prediction process, prediction of the occurrence of a surge may always be performed with respect to both of the first compressor and the second compressor or may be performed only with respect to a compressor for which there is a high possibility that a surge will occur. In the case of executing the latter process as the surge prediction process, it is preferable to execute the following first to fifth processes. In the first process, calculation of a ratio of a flow rate of the first compressor and a ratio of a flow rate of the second compressor is performed based on an output of a first air flow meter that is installed in the first upstream intake passage and an output of a second air flow meter that is installed in the second upstream intake passage. In the second process, calculation of a surge flow rate that is an upper limit of a flow rate at which a surge occurs in the first and second compressors is performed based on a supercharging pressure. In the third process, calculation of a predicted flow rate of air that passes through the throttle valve is performed based on a degree of opening of the throttle valve. The order of performing the first, second, and third processes is not limited. In the fourth process, calculation of a predicted flow rate of a compressor in which a flow rate is smaller among the first compressor and the second compressor is performed based on a smaller ratio among the two ratios that are calculated in the first process and the predicted flow rate that is calculated in the third process. In the fifth process, it is determined whether or not the predicted flow rate that is calculated in the fourth process is less than or equal to the surge flow rate that is calculated in the second process.
Fig. 1 is a view for describing the overall configuration of a system according to Embodiment 1 of the present invention. Fig. 2 is a graph for describing a surge prediction method according to Embodiment 1 of the present invention. Fig. 3 is a flowchart illustrating a routine for surge avoidance control according to Embodiment 1 of the present invention. Fig. 4 is a view for describing operations of an air bypass valve according to Embodiment 1 of the present invention. Fig. 5 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention. Fig. 6 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention. Fig. 7 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention. Fig. 8 is a view for describing operations of the air bypass valve according to Embodiment 1 of the present invention. Fig. 9 is a time chart with respect to a degree of opening of a throttle valve, a supercharging pressure, a predicted flow rate, and a degree of opening of an air bypass valve according to surge avoidance control of Embodiment 1 of the present invention. Fig. 10 is a time chart with respect to a degree of opening of a throttle valve, a supercharging pressure, a predicted flow rate, and a degree of opening of an air bypass valve according to Comparative Example 1. Fig. 11 is a time chart with respect to a degree of opening of a throttle valve, a supercharging pressure, a predicted flow rate, and a degree of opening of an air bypass valve according to Comparative Example 2. Fig. 12 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 2 of the present invention. Fig. 13 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 3 of the present invention. Fig. 14 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 4 of the present invention. Fig. 15 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 5 of the present invention.
Embodiments of the present invention are described hereunder with reference to the accompanying drawings. However, it is to be understood that even when the number, quantity, amount, range or other numerical attribute of an element is mentioned in the following description of the embodiments, the present invention is not limited to the mentioned numerical attribute unless it is expressly stated or theoretically defined. Further, structures or steps or the like described in conjunction with the following embodiments are not necessarily essential to the present invention unless expressly stated or theoretically defined.
Embodiment 1
Fig. 1 is a view for describing the overall configuration of a system according to Embodiment 1 of the present invention. As shown in Fig. 1, the system of Embodiment 1 includes a supercharged engine 1 and an ECU (electronic control unit) 100. The supercharged engine 1 is a V-type engine that has a left bank 2L and a right bank 2R. In Fig. 1, one cylinder 4L is illustrated in the bank 2L and one cylinder 4R is illustrated in the bank 2R. However, in practice the respective banks 2L and 2R have a plurality of cylinders. The supercharged engine 1 in Embodiment 1 is a spark-ignition type in-cylinder direct injection engine, in which a spark plug and an in-cylinder injection valve are installed in each cylinder. Note that, in the following description of the embodiments, identical members that are disposed in each of the left bank 2L and the right bank 2R are denoted by reference characters obtained by adding the character "L" or "R" after the same number for the respective members.
First, an intake system of the supercharged engine 1 will be described. An intake manifold 18L is connected through an intake valve 6L to the cylinder 4L of the left bank 2L. An intake manifold 18R is connected through an intake valve 6R to the cylinder 4R of the right bank 2R. The left and right intake manifolds 18L and 18R are connected to a common surge tank 22. The surge tank 22 is integrated with a water-cooled intercooler 24, and a pressure sensor 98 that outputs a signal in accordance with an internal pressure of the surge tank 22 is installed therein. A single intake passage 16 is connected to the surge tank 22. A throttle valve 20 is disposed in the intake passage 16. A degree-of-throttle-opening sensor 90 that outputs a signal in accordance with the degree of opening of the throttle valve 20 is installed in the throttle valve 20.
The intake passage 16 is formed as a result of the two intake passages 10L and 10R that are provided for the respective banks 2L and 2R merging. A position at which the throttle valve 20 is provided is, with respect to the flow of air, downstream of the position at which the intake passages 10L and 10R merge. Hereunder, the intake passages 10L and 10R that are located on the upstream are each referred to as "upstream intake passage", and the intake passage 16 that is located on the downstream side is referred to as "downstream intake passage". Upstream of the throttle valve 20, that is, in the vicinity of the location at which the two upstream intake passages 10L and 10R merge, are provided a pressure sensor 94 that outputs a signal in accordance with the pressure in the relevant space and a temperature sensor 96 that outputs a signal in accordance with the temperature in the relevant space. Air cleaners 12L and 12R as well as air flow meters 92L and 92R that output a signal in accordance with the flow rate of drawn-in air are disposed in an air intake port of the upstream intake passages 10L and 10R, respectively.
The supercharged engine 1 includes turbochargers 60L and 60R in the left and right banks 2L and 2R, respectively. In the left bank 2L, a compressor (first compressor) 62L of a turbocharger 60L is installed in the upstream intake passage 10L. In the right bank 2R, a compressor (second compressor) 62R of a turbocharger 60R is installed in the upstream intake passage 10R.
A bypass flow path 30L that bypasses the compressor 62L is provided in the upstream intake passage 10L of the left bank 2L. An air bypass valve (first air bypass valve) 32L that controls blocking/communication of the bypass flow path 30L is disposed in the bypass flow path 30L. Likewise, in the right bank 2R also, a bypass flow path 30R that bypasses the compressor 62R is provided in the upstream intake passage 10R, and an air bypass valve (second air bypass valve) 32R is disposed in the bypass flow path 30R. The air bypass valves 32L and 32R are electromagnetically-driven valves that are driven by means of a solenoid. Hereunder, the term "air bypass valve" may be abbreviated as "ABV".
Next, the exhaust system of the supercharged engine 1 will be described. An exhaust manifold 40L is connected through an exhaust valve 8L to the cylinder 4L of the left bank 2L. An exhaust manifold 40R is connected through an exhaust valve 8R to the cylinder 4R of the right bank 2R. In the left bank 2L, a turbine 64L of the turbocharger 60L is installed in the exhaust manifold 40L. Further, a bypass flow path 48L that bypasses the turbine 64L is provided, and a waste gate valve 50L is disposed in the bypass flow path 48L. In the right bank 2R also, a turbine 64R of the turbocharger 60R is installed in the exhaust manifold 40R, a bypass flow path 48R that bypasses the turbine 64R is provided, and a waste gate valve 50R is disposed in the bypass flow path 48R.
In the left bank 2L, a first front-stage catalyst 52L is installed in an outlet of the turbine 64L, and an exhaust passage 42L is connected to the first front-stage catalyst 52L. Likewise, in the right bank 2R also, an exhaust passage 42R is connected via a first front-stage catalyst 52R to an outlet of the turbine 64R. Second front- stage catalysts 54L and 54R are disposed in the respective exhaust passages 42L and 42R. The two exhaust passages 42L and 42R merge to form a single exhaust passage 44, and diverge again into two exhaust passages 46L and 46R under the floor of the vehicle. Under- floor catalysts 56L and 56R are disposed in the exhaust passages 46L and 46R, respectively. Mufflers 58L and 58R are also installed in the respective exhaust passages 46L and 46R. Note that, the first front- stage catalysts 52L and 52R, the second front- stage catalysts 54L and 54R, and the under- floor catalysts 56L and 56R are all three-way catalysts.
The supercharged engine 1 is equipped with an EGR mechanism 70 that recirculates one part of exhaust gas from the exhaust system to the intake system. The EGR mechanism 70 is configured to take out exhaust gas from between the first front-stage catalyst 52L and the second front-stage catalyst 54L in the exhaust passage 42L of the left bank 2L by means of an upstream EGR flow path 72L, and to also take out exhaust gas from between the first front-stage catalyst 52R and the second front-stage catalyst 54R in the exhaust passage 42R of the right bank 2R by means of an upstream EGR flow path 72R. The two upstream EGR flow paths 72L and 72R merge to form a single midstream EGR flow path 74. EGR coolers 78L and 78R are disposed in the upstream EGR flow paths 72L and 72R, respectively, and an EGR valve 80 is disposed in a midstream EGR flow path 74. The midstream EGR flow path 74 diverges into two downstream EGR flow paths 76L and 76R at a distal end thereof. In the left bank 2L, the downstream EGR flow path 76L is connected at a position between an air cleaner 12L and the compressor 62L in the upstream intake passage 10L. Further, in the right bank 2R, the downstream EGR flow path 76R is connected at a position between an air cleaner 12R and the compressor 62R in the upstream intake passage 10R.
The supercharged engine 1 configured as described above is controlled by the ECU 100. The ECU 100 has an input/output interface, a memory and a CPU. The input/output interface is provided in order to take in sensor signals from various sensors installed in the supercharged engine 1 and the vehicle, and also to output actuating signals to actuators included in the supercharged engine 1. In addition to the above described sensors 90, 92L, 92R, 94, 96, and 98, the sensors form which the ECU 100 takes in signals also include an unshown air-fuel ratio sensor, an accelerator pedal sensor, an engine speed sensor, and an atmospheric pressure sensor. In addition to the throttle valve 20, the air bypass valves 32L and 32R and the waste gate valves 50L and 50R, the actuators to which the ECU 100 outputs an actuating signal also include an unshown ignition device, fuel injection device and variable valve timing device. Various control programs for controlling the supercharged engine 1 are stored in a memory. The CPU reads a control program from the memory and executes the control program, and generates actuating signals based on sensor signals that were taken in.
The control programs that the ECU 100 executes include a control program for controlling the air bypass valves 32L and 32R. When executing the control program, the ECU 100 functions as an air bypass valve control device. Hereunder, control of the air bypass valves 32L and 32R is referred to as "ABV control". More specifically, the ABV control includes synchronous opening control and synchronous closing control. The synchronous opening control is control that simultaneously opens both of the air bypass valve 32L and the air bypass valve 32R, while the synchronous closing control is control that simultaneously closes these two air bypass valves 32L and 32R.
Surge avoidance control for avoiding a surge in the compressors 62L and 62R is included in the synchronous opening control of the ABV control. According to the surge avoidance control, first prediction of a surge in the compressors 62L and 62R is performed. Hereunder, this process is described using Fig. 2.
Fig. 2 is a graph for describing a surge prediction method. The horizontal axis of this graph represents a pressure ratio of a pressure downstream of a compressor to a pressure upstream thereof, and the vertical axis represents a flow rate of the compressor. An upper limit of a flow rate at which a surge occurs is a surge flow rate, and the surge flow rate depends on the pressure ratio. In the graph, a curve is drawn that shows the relation between the pressure ratio and the surge flow rate. Although the relation between the pressure ratio and the surge flow rate, that is, the surge characteristics, differ depending on the specifications of the compressor, in Embodiment 1 the specifications of the left and right compressors 62L and 62R are the same. Hence, both of the compressors 62L and 62R have the surge characteristics shown in Fig. 2. Note that, in the system illustrated in Fig. 1, a pressure downstream of the compressor is a supercharging pressure that is measured by the pressure sensor 94, and a pressure upstream of the compressor is an atmospheric pressure. If the system does not have an atmospheric pressure sensor, surge characteristics may be defined by taking the atmospheric pressure as a fixed value, and using a supercharging pressure instead of the pressure ratio.
It is necessary to predict the flow rates of the left and right compressors 62L and 62R in order to predict the occurrence of a surge. The conventional technology described in Patent Literature 1 estimates the flow rate of air through the throttle valve 20 based on the degree of opening of the throttle valve 20, and predicts that a surge will occur if the flow rate through the throttle valve is less than or equal to the surge flow rate. Hereunder, the size of a flow rate through the throttle valve is represented by "mt", and the size of a surge flow rate is represented by "ms". The above described conventional technology can be easily applied in the supercharged engine 1 of Embodiment 1 also by regarding half of the flow rate through the throttle valve mt as the predicted value of the flow rate for each of the compressors 62L and 62R.
However, in practice, there is a difference between the operating conditions of the compressor 62L and the compressor 62R, and the flow rates of the left and right compressors 62L and 62R are not necessarily equal. Conceivable examples of a case where there is a difference between the aforementioned operating conditions include a case where there is a difference in the intake resistance between the left and right banks 2L and 2R due to a difference between the piping in the intake passages thereof, and a case where a difference in the intake resistance arises as the result of foreign matter being stuck in the air cleaner. Hence, a value of half of the flow rate through the throttle valve mt is merely the average flow rate of the left and right compressors 62L and 62R. As shown in Fig. 2, in some cases, even when the average flow rate (mt×1/2) is not equal to or less than the surge flow rate ms, the actual flow rate of the compressor having the smaller flow rate among the left and right compressors 62L and 62R (compressor of the right bank in the example in Fig. 2) is less than or equal to the surge flow rate ms. A surge occurs in the compressor at which the flow rate has become less than or equal to the surge flow rate ms.
In order to reliably avoid the occurrence of a surge, it is necessary to accurately determine the flow rate of air that actually passes through the compressors 62L and 62R. In this respect, in the configuration of the supercharged engine 1 shown in Fig. 1, the air flow meters 92L and 92R are disposed in the inlets of the respective upstream intake passages 10L and 10R. The flow rate of air that flows into the compressor 62L of the left bank 2L can be obtained based on the output of the air flow meter 92L. The flow rate of air that flows into the compressor 62R of the right bank 2R can be obtained based on the output of the air flow meter 92R. Hereunder, the size of a flow rate measured by the air flow meter 92L is represented by "GaL", and the size of a flow rate measured by the air flow meter 92R is represented by "GaR".
However, there is a response delay in the output of the respective air flow meters 92L and 92R. Consequently, during transient operation in which the flow rate of air is changing, a deviation arises between the flow rates GaL and GaR measured by the air flow meters 92L and 92R and the actual flow rates. In terms of a deceleration time when a surge occurs, the flow rates GaL and GaR measured by the air flow meters 92L and 92R decrease in a delayed manner relative to a decrease in the actual flow rates. Therefore, the occurrence of a surge cannot be predicted before the surge actually occurs based on the GaL and GaR measured by the air flow meters 92L and 92R.
Based on the results of the above-described considerations, surge prediction is performed by the following method in the surge avoidance control employed in Embodiment 1.
First, a ratio that the flow rate of the compressor 62L occupies with respect to the overall flow rate of the engine during steady operation can be expressed by GaL/(GaL + GaR), and a ratio that the flow rate of the compressor 62R occupies can be expressed by GaR/(GaL + GaR). The respective ratios of the flow rates of the two compressors 62L and 62R do not differ significantly between a time of steady operation and a time of transient operation. Further, the total flow rate of the two compressors 62L and 62R during transient operation can be regarded as being equal to the flow rate through the throttle valve mt. Hence, the predicted flow rate of each of the compressors 62L and 62R during transient operation can be calculated by the respective equations shown hereunder.
Predicted flow rate of left bank compressor 62L = mt×GaL/(GaL + GaR)
Predicted flow rate of right bank compressor 62R = mt×GaR/(GaL + GaR)
Among the two predicted flow rates, the smaller predicted flow rate is the flow rate that first reaches the surge flow rate. As will be understood from the above equations, when GaL is less than GaR the predicted flow rate of the left bank compressor 62L is smaller, and when GaR is less than GaL the predicted flow rate of the right bank compressor 62R is smaller. Therefore, the flow rate ratio of the compressor having the smaller flow rate is expressed as "kGa", and kGa is defined as follows:
When GaR > GaL, kGa = GaL/(GaL + GaR)
When GaR ≦ GaL, kGa = GaR/(GaL + GaR)
According to the method for predicting a surge of Embodiment 1, the flow rate ratio kGa is calculated using the above described equations. Further, a compressor flow rate that is the object of the surge prediction is calculated by the following equation using the flow rate ratio kGa and the flow rate through the throttle valve mt. When a compressor flow rate mt×kGa that is calculated by the following equation has become less than or equal to the surge flow rate ms, it is predicted that a surge will occur in the compressor having the smaller flow rate.
Compressor flow rate that is object of surge prediction = mt×kGa
The surge prediction method described above is used for surge avoidance control. The surge avoidance control of Embodiment 1 is executed in accordance with a flowchart illustrated in Fig. 3. The routine for surge avoidance control illustrated in the flowchart is repeatedly executed for each predetermined control period corresponding to the clock speed of the ECU 100.
In step S101, the flow rate ratio kGa is calculated based on the flow rates GaL and GaR measured by the left and right air flow meters 92L and 92R. Preferably, smoothing processing (moderation processing) is performed to prevent abrupt variations in the value of the flow rate ratio kGa. When a value of the flow rate ratio kGa that is calculated by the above described equations is referred to as "updated value", the value of the flow rate ratio kGa that is currently being used is referred to as "current value", the value of the flow rate ratio kGa used the previous time is referred to as "previous value", and a weighting factor is referred to as "α", the current value of the flow rate ratio kGa that is obtained by the smoothing processing can be expressed by the following equation.
Current value = α×updated value + (1 - α)×previous value
In step S102, it is determined whether or not the supercharged engine 1 is in a deceleration state. Whether or not the supercharged engine 1 is in a deceleration state can be determined based on the output of the degree-of-throttle-opening sensor 90 and the rate of change thereof. If the result determined in step S102 is negative, the current processing of the present routine ends. In this case, the air bypass valves 32L and 32R are maintained in a closed state that is the fundamental state thereof.
If the result determined in step S102 is affirmative, calculation of the surge flow rate ms is performed in step S103. A previously prepared surge characteristics map is referred to calculate the surge flow rate ms. The surge characteristics map is a map in which the relation between a surge flow rate and a pressure ratio between a supercharging pressure and the atmospheric pressure is defined. The surge flow rate ms at the current supercharging pressure is calculated by calculating the pressure ratio based on the current supercharging pressure measured by the pressure sensor 94, and performing a search in the surge characteristics map using the calculated pressure ratio as an argument.
Further, in step S104, calculation of the flow rate through the throttle valve mt is performed. A nozzle equation that is also used in the conventional technology described in Patent Literature 1 is used to calculate the flow rate through the throttle valve mt. The nozzle equation is a known equation that is used to model a throttle valve. A degree of throttle opening TA that is measured by the degree-of-throttle-opening sensor 90, a pressure Pm downstream of the throttle valve 20 that is measured by the pressure sensor 98, a pressure Pa upstream of the throttle valve 20 that is measured by the pressure sensor 94, and a temperature Ta upstream of the throttle valve 20 that is measured by the temperature sensor 96 are input to the nozzle equation, and the flow rate through the throttle valve mt is calculated based on those parameters. Note that, the calculation in step S104 may be performed before the calculation in step S103.
Next, in step S105, the compressor flow rate that is the object of the surge prediction, i.e. mt×kGa, is calculated using the flow rate ratio kGa calculated in step S101 and the flow rate through the throttle valve mt calculated in step S104. Further, it is determined whether or not the compressor flow rate mt×kGa is less than or equal to the surge flow rate ms. If the result of this determination is negative, the situation is not one in which a surge will occur immediately thereafter. Hence, in this case, in step S107, the air bypass valves 32L and 32R are maintained in a closed state that is the fundamental state thereof.
If the result determined in step S105 is affirmative, it is predicted that a surge will occur immediately thereafter. Hence, in this case, in order to lower the supercharging pressure and avoid a surge, opening of the air bypass valves 32L and 32R is performed. As described in the foregoing, because the surge avoidance control is included in the synchronous opening control, the air bypass valves 32L and 32R of the two compressors 62L and 62R are simultaneously opened, and not just the air bypass valve of the compressor at which the occurrence of a surge is predicted. The advantages of performing the air bypass valve opening process in this way will now be described using Fig. 4 to Fig. 8.
Fig. 4 illustrates the flow of air during normal operation in the intake system. During normal operation the left and right air bypass valves 32L and 32R are closed, and air is pressure-charged in the left and right compressors 62L and 62R. The air that was pressure-charged in the compressors 62L and 62R is supplied to the surge tank 22 through the throttle valve 20. If the degree of opening of the throttle valve 20 is decreased in order to cause the engine to decelerate, the flow of air in the intake system changes as shown in Fig. 5. That is, when decelerating, the flow rate of air to the surge tank 22 decreases as a result of closing the throttle valve 20, and consequently the supercharging pressure rises. In this case, it is assumed that, because of a variation between the flow rate characteristics of the left and right banks, it is predicted that a surge will occur first in the compressor 62L of the left bank.
Fig. 6 is a view illustrating the flow of air in a case where only the air bypass valve 32L of the left bank was opened. Since the compressor for which the occurrence of a surge was predicted is the compressor 62L of the left bank, if the purpose is only to avoid a surge, it is sufficient to open only the air bypass valve 32L of the left bank. However, since the air bypass valve 32R of the right bank is closed, supercharging is continued in the compressor 62R of the right bank. Therefore, air that was pressure-charged in the compressor 62R of the right bank flows to the upstream intake passage 10L of the left bank through the upstream intake passage 10R of the right bank, and is released into the atmosphere through the air bypass valve 32L that is open. That is, a steady flow of air from the upstream intake passage 10R of the right bank to the upstream intake passage 10L of the left bank is formed. Since EGR gas from the exhaust system is supplied at a position that is upstream of the compressor 62R, when air which has been drawn into the intake system is released to outside the system through the air bypass valve 32L, emissions contained in the EGR gas are also released to outside the system.
In contrast, Fig. 7 illustrates the flow of air at a moment at which both of the air bypass valves 32L and 32R of the left and right banks are simultaneously opened. As the result of simultaneously opening the two air bypass valves 32L and 32R, air inside the upstream intake passages 10L and 10R is returned to upstream of the compressors 62L and 62R through the two air bypass valves 32L and 32R. As a result, the supercharging pressure inside the upstream intake passages 10L and 10R rapidly decreases and the occurrence of a surge is avoided. However, there is a response delay with respect to the decrease in the supercharging pressure after opening the air bypass valves 32L and 32R. Hence, even if there a lag of a certain extent between the opening timings of the left and right air bypass valves 32L and 32R, a risk that air that was pressure-charged in a compressor on the side of the air bypass valve that is not yet open will be released to outside the system from the air bypass valve that was opened first is not high. Thus, although preferably the opening timings of the left and right air bypass valves 32L and 32R are the same, a lag of a certain extent between the two timings is permissible.
Fig. 8 illustrates the flow of air in a case where the air bypass valves 32L and 32R of the left and right banks are both open. When the two air bypass valves 32L and 32R are open, although air from the downstream side of the respective compressors 62L and 62R is returned to the upstream side via the air bypass valves 32L and 32R, the returned air is drawn in again by the compressors 62L and 62R. That is, in the left and right banks, a loop is formed with respect to the air that circulates through the compressors 62L and 62R and the air bypass valves 32L and 32R. Consequently, a case does not arise in which air from inside the system is continuously released into the atmosphere as in the case illustrated in Fig. 6.
As described above, according to the surge avoidance control of Embodiment 1, it is possible to suppress the occurrence of a situation in which air inside the system is released into the atmosphere as the result of operations of the air bypass valves 32L and 32R that are performed to avoid the occurrence of a surge. Further, as long as the flow path capacity of the upstream intake passages 10L and 10R from the air cleaners 12L and 12R to the compressors 62L and 62R is sufficient, it is possible to prevent air inside the system that was returned via the air bypass valves 32L and 32R from being released into the atmosphere.
Further, according to the surge avoidance control of Embodiment 1, the occurrence of a surge can be more accurately predicted in comparison to the case of merely applying the conventional technology disclosed in Patent Literature 1 or the case of simply using the respective outputs of the air flow meters 92L and 92R. Fig. 9 is a time chart with respect to the degree of opening of the throttle valve, the supercharging pressure, the predicted flow rate and the degree of opening of the air bypass valves according to the surge avoidance control of Embodiment 1. On the other hand, Fig. 10 is a time chart illustrating an example (Comparative Example 1) in a case where a surge determination is made by means of a comparison between the average flow rate (mt×1/2) of the left and right compressors 62L and 62R and the surge flow rate ms. Further, Fig. 11 is a time chart illustrating an example (Comparative Example 2) in a case where a surge determination is made by means of a comparison between flow rates GaL and GaR measured by the air flow meters 92L and 92R and the surge flow rate ms. Note that, this time chart do not represent actual experimental data, but represent an image of control results.
According to Comparative Example 1 illustrated in Fig. 10, a surge occurs before the average flow rate (mt×1/2) becomes equal to or less than the surge flow rate ms. This is because the flow rate of one of the compressors is invariably less than the average flow rate, and the flow rate of the relevant compressor becomes equal to or less than the surge flow rate ms before the average flow rate (mt×1/2) does. Therefore, in Comparative Example 1, the air bypass valves cannot be opened so as to avoid the occurrence of a surge.
Similarly, in Comparative Example 2 illustrated in Fig. 11, a surge occurs before either one of the measured flow rates GaL and GaR becomes equal to or less than the surge flow rate ms. This is because, due to a response delay in the output of the air flow meters, the measured flow rates GaL and GaR change in a delayed manner relative to the actual compressor flow rates. Consequently, in Comparative Example 2 also, the air bypass valves cannot be opened so as to avoid the occurrence of a surge.
In contrast to the foregoing comparative examples, according to the surge avoidance control of Embodiment 1, as shown in Fig. 9, the air bypass valves are opened before the supercharging pressure rises and a surge occurs. By this means, according to the surge avoidance control of Embodiment 1, the occurrence of a surge is reliably avoided.
Note that, after the supercharging pressure decreases and the risk of a surge occurring has disappeared, the opened air bypass valves 32L and 32R are closed once more at a time that the supercharged engine 1 is caused to accelerate again. At such time, the ECU 100 simultaneously closes the left and right air bypass valves 32L and 32R by synchronous closing control so that supercharging starts simultaneously in the left and right compressors 62L and 62R. This is done in order to prevent air inside the system being released into the atmosphere. However, there is a response delay with respect to an increase in the supercharging pressure after the air bypass valves 32L and 32R are closed. Hence, even if there is a lag of a certain extent between the closing timings of the left and right air bypass valves 32L and 32R, a risk that air that was pressure-charged in a compressor on the side of the air bypass valve that closed first will be released to outside the system from the air bypass valve that is open is not high. Thus, a lag of a certain extent between the closing timings of the left and right air bypass valves 32L and 32R is permissible.
Embodiment 2
The configuration of the system of Embodiment 2 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 2 and Embodiment 1. Fig. 12 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 2. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
According to the surge avoidance control of Embodiment 2, in step S201 it is determined whether or not the left and right air bypass valves 32L and 32R were closed the previous time that the routine was executed. When the air bypass valves 32L and 32 are open, the flow rate of fresh air that is drawn into the upstream intake passages 10L and 10R decreases by an amount corresponding to the flow rate of air that is returned to upstream through the air bypass valves 32L and 32R. The proportion of the decrease in the flow rate of the fresh air as the result of the air bypass valves 32L and 32 being open differs between the left and right upstream intake passages 10L and 10R. This is because a disparity exists between the respective flow path resistances of the air bypass valves 32L and 32R, and due to the influence thereof a difference arises between the respective flow rates of the air that is returned to the upstream side through the air bypass valves 32L and 32R. Consequently, a difference arises in a ratio between the measured flow rates GaL and GaR for the left and right with respect to a time that the air bypass valves 32L and 32R are closed and a time that the air bypass valves 32L and 32R are open.
If the result determined in step S201 is affirmative, in step S202 the value of the flow rate ratio kGa is updated. The method of updating the value of the flow rate ratio kGa is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3. In contrast, if the result determined in step S201 is negative, in step S203, the previous value of the flow rate ratio kGa is retained. That is, when the left and right air bypass valves 32L and 32R are open, updating of the value of the flow rate ratio kGa is not performed. This is because a time that a surge occurs is a time when the air bypass valves 32L and 32R are closed and supercharging is being performed, and information that is necessary for surge prediction cannot be obtained from the measured flow rates GaL and GaR that are obtained when the air bypass valves 32L and 32R are open. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
According to the surge avoidance control of Embodiment 2, measured flow rates GaL and GaR obtained when the air bypass valves 32L and 32R are closed are always used to calculate the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt×kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
Embodiment 3
The configuration of the system of Embodiment 3 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 3 and Embodiment 1. Fig. 13 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 3. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
According to the surge avoidance control of Embodiment 3, in step S301, it is determined whether or not a supercharging pressure measured by the pressure sensor 94 is greater than the atmospheric pressure, that is, whether or not a pressure ratio is greater than 1. A difference between the measured flow rates GaL and GaR for the left and right arises due to a difference between the resistances of the left and right upstream intake passages 10L and 10R and a difference between the efficiencies of the left and right compressors 62L and 62R. However, in a state in which the compressors 62L and 62R do not function and the pressure ratio is less than or equal to 1, a difference between the efficiencies of the left and right compressors 62L and 62R does not affect the flow rates. Therefore, a difference arises in the ratio for measured flow rates GaL and GaR for the left and right between a state in which the pressure ratio is greater than 1 and a state in which the pressure ratio is less than or equal to 1.
If the result determined in step S301 is affirmative, in step S302 the value of the flow rate ratio kGa is updated. The method of updating the value of the flow rate ratio kGa is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3. In contrast, if the result determined in step S301 is negative, in step S303, the previous value of the flow rate ratio kGa is retained. That is, in a state in which the pressure ratio is less than or equal to 1, updating of the value of the flow rate ratio kGa is not performed. This is because a time that a surge occurs is a time when the engine is operating in a supercharging region in which the pressure ratio is greater than 1, and information that is necessary for surge prediction cannot be obtained from the measured flow rates GaL and GaR that are obtained in a non-supercharging region in which the pressure ratio is less than or equal to 1. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
According to the surge avoidance control of Embodiment 3, measured flow rates GaL and GaR obtained at a time that supercharging is being performed by the compressors 62L and 62R are always used to calculate the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt×kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
Note that the surge avoidance control of Embodiment 3 can be combined with the surge avoidance control of Embodiment 2. That is, a configuration may be adopted so as to perform updating of the flow rate ratio kGa only in a case in which the left and right air bypass valves 32L and 32R were closed the previous time the routine was executed and in which the supercharging pressure that is measured the current time is greater than the atmospheric pressure.
Embodiment 4
The configuration of the system of Embodiment 4 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 4 and Embodiment 1. Fig. 14 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 4. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
According to the surge avoidance control of Embodiment 4, in step S401 it is determined whether or not the EGR valve 80 is closed. When the EGR valve 80 is closed, only fresh air flows through the left and right upstream intake passages 10L and 10R. On the other hand, when the EGR valve 80 is open, a gas in which fresh air and EGR gas are combined flows through the left and right upstream intake passages 10L and 10R. A ratio of the flow rate of EGR gas to the flow rate of fresh air depends on the resistance and back pressure in the EGR flow path and the state of the EGR valve 80. Consequently, a difference arises in the ratio of the measured flow rates GaL and GaR for the left and right between a time when the EGR valve 80 is closed and a time when the EGR valve 80 is open.
If the result determined in step S401 is affirmative, in step S402 the value of a flow rate ratio kGaEC is updated. The flow rate ratio kGaEC is calculated based on the measured flow rates GaL and GaR for the left and right when the EGR valve 80 is closed. The method of calculating the flow rate ratio kGaEC is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3. Next, in step S403, the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaEC that was updated in step S402. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
In contrast, if the result determined in step S401 is negative, in step S404, the value of a flow rate ratio kGaEO is updated. The flow rate ratio kGaEO is calculated based on the measured flow rates GaL and GaR for the left and right when the EGR valve 80 is open. The method of calculating the flow rate ratio kGaEO is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3. Next, in step S405, the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaEO that was updated in step S404. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
According to the surge avoidance control of Embodiment 4, the flow rate ratio kGaEC at a time that the EGR valve 80 is closed and the flow rate ratio kGaEO at a time that the EGR valve 80 is open are respectively prepared as the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt×kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
Note that the surge avoidance control of Embodiment 4 can be combined with the surge avoidance control of Embodiment 2 or the surge avoidance control of Embodiment 3. That is, a condition that the left and right air bypass valves 32L and 32R were closed the previous time the routine was executed or a condition that the supercharging pressure that is measured the current time is greater than the atmospheric pressure may be adopted as a condition for performing updating of the flow rate ratios kGaEC and kGaEO.
Embodiment 5
The configuration of the system of Embodiment 5 is the same as that of Embodiment 1, but the contents of the surge avoidance control differ between Embodiment 5 and Embodiment 1. Fig. 15 is a flowchart illustrating a routine of surge avoidance control according to Embodiment 4. In this flowchart, steps in which processing is executed that is the same as processing executed in the surge avoidance control of Embodiment 1 are denoted by the same step numbers as in Embodiment 1.
According to the surge avoidance control of Embodiment 5, in step S501 it is determined whether or not the left and right waste gate valves 50L and 50R are closed. The efficiency of the compressors 62L and 62R varies depending on whether the waste gate valves 50L and 50R are in an open or closed state. Consequently, a difference arises in the ratios of the measured flow rates GaL and GaR for left and right between a time when the waste gate valves 50L and 50R are closed and a time when the waste gate valves 50L and 50R are open. Note that the left and right waste gate valves 50L and 50R are controlled to open/close synchronously by the ECU 100.
If the result determined in step S501 is affirmative, in step S502 the value of a flow rate ratio kGaWC is updated. The flow rate ratio kGaWC is calculated based on the measured flow rates GaL and GaR for the left and right when the waste gate valves 50L and 50R are closed. The method of calculating the flow rate ratio kGaWC is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3. Next, in step S503, the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaWC that was updated in step S502. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
In contrast, if the result determined in step S501 is negative, in step S504, the value of a flow rate ratio kGaWO is updated. The flow rate ratio kGaWO is calculated based on the measured flow rates GaL and GaR for the left and right when the waste gate valves 50L and 50R are open. The method of calculating the flow rate ratio kGaWO is the same as the method of calculating the flow rate ratio kGa in step S101 in the flowchart illustrated in Fig. 3. Next, in step S505, the value of the flow rate ratio kGa used in step S105 is replaced with the value of the flow rate ratio kGaWO that was updated in step S504. From step S102 onwards, the same processing is performed as the processing executed in the surge avoidance control of Embodiment 1.
According to the surge avoidance control of Embodiment 5, the flow rate ratio kGaWC at a time that the waste gate valves 50L and 50R are closed and the flow rate ratio kGaWO at a time that the waste gate valves 50L and 50R are open are respectively prepared as the flow rate ratio kGa that is used for surge prediction. Consequently, it is possible to determine the compressor flow rate mt×kGa that is the object of surge prediction with greater accuracy, and thus the accuracy of the surge prediction can be further enhanced.
Note that the surge avoidance control of Embodiment 5 can be combined with the surge avoidance control of Embodiment 2 or the surge avoidance control of Embodiment 3. That is, a condition that the left and right air bypass valves 32L and 32R were closed the previous time the routine was executed or a condition that the supercharging pressure that is measured the current time is greater than the atmospheric pressure may be adopted as a condition for performing updating of the flow rate ratios kGaWC and kGaWO. Further, the surge avoidance control of Embodiment 5 can be combined with the surge avoidance control of Embodiment 4. That is, a number of flow rate ratios that corresponds to the number of combinations between an open/closed state of the EGR valve 80 and an open/closed state of the waste gate valves 50L and 50R may be respectively prepared.
Other Embodiments
Although in the above described embodiments the two air bypass valves are simultaneously opened in the surge avoidance control, synchronous control may also be performed so as to always open the two air bypass valves simultaneously in a situation in which an air bypass valve is to be opened, regardless of surge avoidance. By doing so, in a case where the occurrence of a surge is predicted in either one of the two compressors, the air bypass valve of the compressor with respect to which the occurrence of a surge is not predicted will also always be simultaneously opened. By this means, it is possible to reliably prevent air that has been pressure-charged in a compressor whose air bypass valve is closed from being released into the atmosphere from inside the system through the air bypass valve.
1 Supercharged engine
2L Left bank
2R Right bank
10L, 10R Upstream intake passage
16 Downstream intake passage
20 Throttle valve
22 Surge tank
32L, 32R Air bypass valve
34L, 34R Bypass flow path
50L, 50R Waste gate valve
62L, 62R Compressor
92L, 92R Air flow meter
100 ECU

Claims (4)

  1. An air bypass valve control device for a supercharged engine that comprises: a first upstream intake passage that draws in air; a first compressor installed in the first upstream intake passage; a first air bypass valve disposed in a flow path that bypasses the first compressor; a second upstream intake passage that draws in air; a second compressor installed in the second upstream intake passage; a second air bypass valve disposed in a flow path that bypasses the second compressor; a downstream intake passage formed by merging of the first upstream intake passage and the second upstream intake passage; and a throttle valve disposed in the downstream intake passage;
    wherein the air bypass valve control device is configured to execute synchronous opening control that always opens both of the first air bypass valve and the second air bypass valve simultaneously.
  2. An air bypass valve control device for a supercharged engine that comprises: a first upstream intake passage that draws in air; a first compressor installed in the first upstream intake passage; a first air bypass valve disposed in a flow path that bypasses the first compressor; a second upstream intake passage that draws in air; a second compressor installed in the second upstream intake passage; a second air bypass valve disposed in a flow path that bypasses the second compressor; a downstream intake passage formed by merging of the first upstream intake passage and the second upstream intake passage; and a throttle valve disposed in the downstream intake passage;
    wherein the air bypass valve control device is configured to execute:
    a surge prediction process that predicts an occurrence of a surge based on respective operating conditions of the first compressor and the second compressor; and
    an air bypass valve opening process that, in a case where an occurrence of a surge in at least one of the first compressor and the second compressor is predicted, opens both of the first air bypass valve and the second air bypass valve.
  3. The air bypass valve control device according to claim 2, wherein the surge prediction process includes:
    a first process that calculates a ratio of a flow rate of the first compressor and a ratio of a flow rate of the second compressor based on an output of a first air flow meter that is installed in the first upstream intake passage and an output of a second air flow meter that is installed in the second upstream intake passage;
    a second process that, based on a supercharging pressure, calculates a surge flow rate that is an upper limit of a flow rate at which a surge occurs in the first and second compressors;
    a third process that calculates a predicted flow rate of air that passes through the throttle valve based on a degree of opening of the throttle valve;
    a fourth process that, based on a smaller ratio among the two ratios that are calculated in the first process and the predicted flow rate that is calculated in the third process, calculates a predicted flow rate of a compressor in which a flow rate is smaller among the first compressor and the second compressor; and
    a fifth process that determines whether or not the predicted flow rate that is calculated in the fourth process is less than or equal to a surge flow rate that is calculated in the second process.
  4. The air bypass valve control device according to claim 1, the air bypass valve control device being configured to further execute synchronous closing control that always closes both of the first air bypass valve and the second air bypass valve simultaneously.
PCT/JP2015/002262 2014-04-28 2015-04-27 Air bypass valve control device WO2015166658A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2014-092569 2014-04-28
JP2014092569 2014-04-28
JP2015089452A JP2015222075A (en) 2014-04-28 2015-04-24 Air bypass valve control device
JP2015-089452 2015-04-24

Publications (1)

Publication Number Publication Date
WO2015166658A1 true WO2015166658A1 (en) 2015-11-05

Family

ID=53191804

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2015/002262 WO2015166658A1 (en) 2014-04-28 2015-04-27 Air bypass valve control device

Country Status (2)

Country Link
JP (1) JP2015222075A (en)
WO (1) WO2015166658A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108463624A (en) * 2016-01-14 2018-08-28 标致雪铁龙汽车股份有限公司 The method for controlling motor vehicles turbo-compressor Thermal Motor
CN110159418A (en) * 2019-05-22 2019-08-23 安徽江淮汽车集团股份有限公司 Turbocharging method, pressurization control equipment, storage medium and device

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7230792B2 (en) * 2019-12-20 2023-03-01 トヨタ自動車株式会社 Control device for internal combustion engine
CN111425305B (en) * 2020-04-01 2022-06-07 广西玉柴机器股份有限公司 Air-break valve with high safety

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5195142B2 (en) 2008-08-06 2013-05-08 トヨタ自動車株式会社 Air bypass valve control device
US20130118166A1 (en) * 2011-11-10 2013-05-16 Ford Global Technologies, Llc Compressor flow control
JP2013096372A (en) 2011-11-04 2013-05-20 Toyota Motor Corp Control device of internal combustion engine with supercharger

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5195142B2 (en) 2008-08-06 2013-05-08 トヨタ自動車株式会社 Air bypass valve control device
JP2013096372A (en) 2011-11-04 2013-05-20 Toyota Motor Corp Control device of internal combustion engine with supercharger
US20130118166A1 (en) * 2011-11-10 2013-05-16 Ford Global Technologies, Llc Compressor flow control

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108463624A (en) * 2016-01-14 2018-08-28 标致雪铁龙汽车股份有限公司 The method for controlling motor vehicles turbo-compressor Thermal Motor
CN108463624B (en) * 2016-01-14 2021-04-09 标致雪铁龙汽车股份有限公司 Method for controlling a turbo-compression heat engine of a motor vehicle
CN110159418A (en) * 2019-05-22 2019-08-23 安徽江淮汽车集团股份有限公司 Turbocharging method, pressurization control equipment, storage medium and device

Also Published As

Publication number Publication date
JP2015222075A (en) 2015-12-10

Similar Documents

Publication Publication Date Title
JP5527435B2 (en) PCV system for internal combustion engine
EP2963263B1 (en) Control device for internal combustion engine
EP3059427B1 (en) Control device for a supercharged internal combustion engine provided with a plurality of cylinder groups and with a plurality of turbochargers
US10494988B2 (en) Control device for internal combustion engine that controls fuel supply to cylinders and prevents misfiring
WO2015166658A1 (en) Air bypass valve control device
JP6011576B2 (en) Control device for internal combustion engine
JP2015143473A (en) Supercharged engine controller and supercharged engine control method
US8788180B2 (en) EGR control system for internal combustion engine
CN102265020B (en) Controller for internal combustion engine
EP3587776A1 (en) Forced induction system
JP6269583B2 (en) EGR control method for internal combustion engine
JP6252006B2 (en) Engine control device
JP2018071486A (en) Control device for internal combustion engine
JP5930288B2 (en) Internal combustion engine
JP4517951B2 (en) Control device for internal combustion engine
JP2016089804A (en) Control device of internal combustion engine
JP2013241834A (en) Exhaust gas recirculation device for internal combustion engine
JP5107214B2 (en) Exhaust gas recirculation device for internal combustion engine
JP2015113800A (en) Control device for internal combustion engine
JP2021124111A (en) Control device of internal combustion engine
JP6394629B2 (en) Turbocharged engine
JP2016151242A (en) Control device of internal combustion engine
JP2016130476A (en) Air quantity estimation device of internal combustion engine
JP2020084871A (en) Supercharging system
JP2012229622A (en) Egr control apparatus for internal combustion engine

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15723771

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15723771

Country of ref document: EP

Kind code of ref document: A1