WO2014034695A1 - Control device for diesel engine - Google Patents

Control device for diesel engine Download PDF

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Publication number
WO2014034695A1
WO2014034695A1 PCT/JP2013/072935 JP2013072935W WO2014034695A1 WO 2014034695 A1 WO2014034695 A1 WO 2014034695A1 JP 2013072935 W JP2013072935 W JP 2013072935W WO 2014034695 A1 WO2014034695 A1 WO 2014034695A1
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WO
WIPO (PCT)
Prior art keywords
pilot injection
injection
injection amount
pilot
diesel engine
Prior art date
Application number
PCT/JP2013/072935
Other languages
French (fr)
Japanese (ja)
Inventor
西澤　透
佳宏 今岡
秀一 飯尾
清史 大賀
Original Assignee
日産自動車株式会社
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 日産自動車株式会社 filed Critical 日産自動車株式会社
Priority to JP2014533034A priority Critical patent/JP5900626B2/en
Publication of WO2014034695A1 publication Critical patent/WO2014034695A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
    • F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
    • F02D41/064—Introducing corrections for particular operating conditions for engine starting or warming up for starting at cold start
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F02D41/403—Multiple injections with pilot injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P19/00—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition
    • F02P19/02—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition electric, e.g. layout of circuits of apparatus having glowing plugs
    • 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
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to a control device for a diesel engine.
  • JP2003-97329A discloses a diesel engine that includes a variable compression ratio mechanism, relatively increases the compression ratio at start-up and when the load is low, and relatively decreases the compression ratio when the load is high.
  • pilot injection at another stage for example, five times is performed at a high load at which the compression ratio is low.
  • multi-stage pilot injection is executed even at the start of a high compression ratio or at a low load.
  • the pilot injection is executed a plurality of times in this manner, the ignition of the fuel injected by the pilot is accelerated, the combustion in the combustion chamber becomes diffusion combustion, and a large amount of hydrocarbon (HC) is generated. Therefore, at the time of start-up or at a low load, the first half pilot injection is stopped, and the amount of the pilot injection that has been stopped is added to the second half pilot injection amount.
  • JP2003-97329A does not discuss improvement in combustibility in a low compression ratio state. Therefore, improvement of combustibility at the time of cold start under energization of the glow plug and a low outside air temperature condition cannot be expected only by making the pilot injection multistage in the low compression ratio state.
  • An object of the present invention is to provide a control device for a diesel engine capable of improving combustibility when a glow plug is energized and at a cold start under a low outside air temperature condition.
  • a glow plug that heats a combustion chamber of a diesel engine during cold start, a common rail fuel injection device that can execute pilot injection prior to main injection in multiple stages, and a common rail fuel injection device And a control unit for controlling the diesel engine.
  • the control unit controls the common rail fuel injection device so that the pilot injection is executed in multiple stages of two or more times when the glow plug is energized and at the cold start when the outside air temperature is 0 ° C. or less.
  • the control unit sets the injection amount of the first pilot injection in a range from 35% to 80% with respect to the total pilot injection amount that does not exceed the injection amount of the main injection and is the sum of the injection amount of each pilot injection. Set in.
  • the control unit sets the injection amount for one remaining pilot injection executed after the first time to be smaller than the injection amount for the first pilot injection.
  • FIG. 1 is a schematic configuration diagram of a control device for a diesel engine according to an embodiment of the present invention.
  • FIG. 2 is a schematic view of one cylinder of the diesel engine as viewed from above.
  • FIG. 3 is a diagram illustrating four different cases of pilot injection patterns studied by the present inventors.
  • FIG. 4 is a characteristic diagram showing the relationship between the value obtained by differentiating the amount of heat generated by the entire multistage pilot injection with the crank angle and the indicated mean effective pressure.
  • FIG. 5 is a diagram showing the indicated mean effective pressure and the indicated mean effective pressure fluctuation rate of four different pilot injection patterns.
  • FIG. 6A is a diagram showing an average glow plug vicinity temperature of four different pilot injection patterns.
  • FIG. 6B is a diagram showing an average glow plug vicinity equivalent ratio of four different pilot injection patterns.
  • FIG. 7 is a characteristic diagram showing a heat generation rate during one combustion in the combustion chamber of the diesel engine.
  • FIG. 8 is a characteristic diagram showing the relationship between the cooling water temperature and the initial pilot injection amount ratio.
  • FIG. 9 is a flowchart showing a fuel injection control process routine executed by the controller.
  • FIG. 1 is a schematic configuration diagram of a control system for a diesel engine 1 according to an embodiment of the present invention.
  • the diesel engine 1 is a vehicle engine and includes an intake passage 2.
  • the intake air supplied to the diesel engine 1 is supercharged by an intake air compressor 10 ⁇ / b> A of a supercharger 10 provided in the intake passage 2.
  • the supercharged intake air is cooled by the intercooler 3, passes through the intake throttle valve 4, and then flows into the combustion chamber of each cylinder through the collector 5.
  • the diesel engine 1 further includes a common rail fuel injection device 6.
  • the common rail fuel injection device 6 includes a high pressure fuel pump 7, a common rail 8, and a fuel injection valve 9.
  • the fuel stored in the fuel tank is supplied to the diesel engine 1 by the common rail fuel injection device 6. That is, the fuel is sent from the fuel tank to the common rail 8 by the high-pressure fuel pump 7, and the high-pressure fuel in the common rail 8 is injected and supplied from each fuel injection valve 9 to each combustion chamber.
  • the intake air flowing into the combustion chamber and the fuel injected from the fuel injection valve 9 are combusted by compression ignition in the combustion chamber, and the exhaust after combustion is discharged to the exhaust passage 11.
  • a part of the exhaust discharged to the exhaust passage 11 is recirculated to the intake side through the EGR passage 12 as EGR gas.
  • the EGR passage 12 is provided with an EGR valve 13 for controlling the flow rate of EGR gas flowing through the EGR passage 12.
  • the remaining exhaust gas that is not recirculated is guided to the downstream side of the exhaust passage 11 and drives the exhaust turbine 10B when passing through the exhaust turbine 10B of the supercharger 10.
  • a variable nozzle 10D is provided at the scroll inlet of the exhaust turbine 10B.
  • the turbocharger 10 is provided with a hydraulically driven or electrically driven actuator 10E.
  • variable nozzle 10D is throttled to reduce the variable nozzle opening, the exhaust flow rate increases and the rotational speed of the exhaust turbine 10B increases. As a result, the rotational speed of the intake compressor 10A connected coaxially with the exhaust turbine 10B increases, and the intake air is supercharged by the intake compressor 10A.
  • variable nozzle 10D when the variable nozzle 10D is opened and the variable nozzle opening is increased, the flow rate of the exhaust gas decreases, and the rotational speed of the exhaust turbine 10B decreases. As a result, the rotational speed of the intake compressor 10A also decreases, and the supercharging of intake air by the intake compressor 10A is stopped.
  • the diesel engine 1 is controlled by a controller 21 as a control unit.
  • the controller 21 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).
  • the controller 21 receives an accelerator pedal depression amount (accelerator opening signal) detected by the accelerator sensor 22 and an engine speed signal detected by the crank angle sensor 23.
  • the controller 21 calculates the fuel injection timing and the fuel injection amount of the main injection based on the engine load (accelerator opening) and the engine rotation speed, and outputs a valve opening command signal corresponding thereto to the fuel injection valve 9. Further, the controller 21 performs EGR control and supercharging pressure control in a coordinated manner so that the target EGR rate and the target intake air amount can be obtained.
  • a filter 14 for collecting particulates contained in the exhaust is disposed in the exhaust passage 11 downstream of the exhaust turbine 10B.
  • the controller 21 performs the regeneration process of the filter 14 by performing the post injection in the expansion stroke or the exhaust stroke immediately after the main injection.
  • the controller 21 stores a post-injection amount and a post-injection timing at which a target regeneration temperature is obtained corresponding to the engine load and the engine speed. Then, the controller 21 performs post-injection at the optimal post-injection amount and post-injection timing according to the engine load and engine speed. Thereby, the particulates accumulated on the filter 14 are removed by combustion, and the filter 14 is regenerated.
  • the temperature (particulate combustion temperature) in the filter 14 is set within a range not exceeding the allowable temperature of the filter 14 during the regeneration process. It is necessary to raise. Therefore, an oxidation catalyst 15 is disposed in the exhaust passage 11 upstream of the filter 14.
  • HC and CO contained in the exhaust gas flowing in by the post-injection during the regeneration process are burned by the catalyst 15 to increase the temperature in the filter 14 and promote the burning of the particulates in the filter 14.
  • the catalyst 15 is not limited to the oxidation catalyst, and may be a catalyst having an oxidation function (for example, a three-way catalyst).
  • the carrier constituting the filter 14 may be coated with an oxidation catalyst.
  • the oxidation reaction when the particulates burn is promoted, the temperature in the filter 14 is likely to rise, and the particulate combustion can be promoted efficiently.
  • the diesel engine 1 since the startability of the diesel engine 1 is lowered when it is cold, the diesel engine 1 is provided with a glow plug 31 for cold start for each combustion chamber.
  • the glow plug 31 is provided so as to face the combustion chamber, and assists ignition by increasing the temperature of the air-fuel mixture in the combustion chamber at the time of cold start or the like.
  • FIG. 2 is a schematic view of one cylinder 41 of the diesel engine 1 as viewed from above.
  • a combustion chamber 43 is formed above the cylinder bore 42 of the cylinder 41, and the fuel injection valve 9 is provided facing the combustion chamber 43 and is disposed at an upper central position of the combustion chamber 43.
  • Two intake valves 44 and 45 and two exhaust valves 46 and 47 are arranged around the fuel injection valve 9.
  • eight injection holes are formed at the tip of the fuel injection valve 9, and fuel is injected from each injection hole toward the wall surface of the cylinder bore 42.
  • the fuel injected from the fuel injection valve 9 is injected in eight directions at equal intervals in the circumferential direction.
  • a swirl flow in the direction of the arrow in the figure is generated in the combustion chamber 43, and the sprayed fuel F is bent in the clockwise direction in FIG. 2 by this swirl flow.
  • the glow plug 31 is provided, for example, so as to face the combustion chamber 43 from a position between the two intake valves 44 and 45.
  • current is supplied to the glow plug 31.
  • the atomized fuel F from the fuel injection valve 9 is supplied to the periphery of the glow plug 31 heated by energization, the air-fuel mixture in the vicinity of the glow plug 31 is ignited to become a seed flame, and burns and spreads throughout the air-fuel mixture.
  • the position where the glow plug 31 is provided is not limited to between the two intake valves 44, 45, but between the intake valves 44, 45 and the exhaust valves 46, 47 or between the two exhaust valves 46, 47. It may be. Further, the number of intake valves, the number of exhaust valves, and the number of injection holes of the fuel injection valve are arbitrarily set as necessary.
  • the engine compression ratio tends to be set to a low compression ratio of around 15, more specifically 15.5 or less.
  • the merit of lowering the compression ratio in this way is that the output of the diesel engine 1 can be improved, NOx in the exhaust can be reduced, and the pumping loss can be reduced. That is, it is possible to inject more fuel into the combustion chamber 43 from the fuel injection valve 9 as much as the maximum value of the cylinder internal pressure decreases due to the low compression ratio, thereby improving the output of the engine.
  • the compression ratio By reducing the compression ratio, the combustion temperature in the combustion chamber 43 can be lowered, thereby suppressing the generation of NOx. Further, since the compression ratio is lowered, the pumping loss is also reduced.
  • the combustibility of the air-fuel mixture in the combustion chamber 43 deteriorates, for example, misfiring occurs during cold start under a low outside air temperature condition of, for example, ⁇ 25 ° C.
  • the present inventors have focused on the fact that it is important to effectively utilize the function of the glow plug 31 as a fuel ignition source in order to suppress misfire during cold start under low outside air temperature conditions. .
  • the fuel by pilot injection that is performed prior to the main injection is led to the vicinity of the glow plug 31 to form a fire type that becomes the core of combustion, thereby improving the combustion stability at the cold start. Plan.
  • the fuel amount of the pilot injection per one time is obtained by making the pilot injection multistage more than twice. Need to be reduced. If the pilot injection amount per one time is reduced, the amount of heat taken from the glow plug 31 per predetermined time is reduced, and the temperature drop of the glow plug 31 can be suppressed.
  • JP2003-97329A described above discloses a diesel engine that includes a variable compression ratio mechanism, that makes the compression ratio relatively high at start-up or low load, and relatively low at high load. Yes.
  • a plurality of pilot injections are executed at a high load at which the compression ratio is low, and a plurality of pilot injections are executed at a start and at a low load at which the compression ratio is high.
  • JP2003-97329A1 has not studied improvement of combustibility in the low compression ratio state, and when pilot injection is made multistage in the low compression ratio state, the glow plug is energized and under the low outside air temperature condition. The improvement of combustibility at the time of cold start cannot be expected.
  • the glow plug 31 when the glow plug 31 is energized and cold start is performed under a low outside air temperature condition, a value obtained by differentiating the heat generation amount of a plurality of pilot injections by the crank angle is determined in advance.
  • the number of pilot injections and each pilot injection amount are determined so as to be equal to or greater than the predetermined value.
  • the temperature drop of the glow plug 31 at the time of ignition can be suppressed, and the equivalent ratio in the vicinity of the glow plug 31 can be kept high.
  • the combustibility of the air-fuel mixture in the combustion chamber 43 can be improved when the glow plug 31 is energized and during cold start under a low outside air temperature condition.
  • FIG. 3 is a diagram showing four different pilot injection patterns examined by the present inventors.
  • Case 4 is an injection pattern of this embodiment, and Cases 1 to 3 are injection patterns as Reference Examples 1 to 3.
  • a plurality of pilot injections are executed, and the main injection is executed after the final pilot injection.
  • IT1 to IT4 indicate the injection timing of pilot injection
  • IT5 indicates the injection timing of main injection.
  • IT5 is set immediately before the compression top dead center TDC.
  • the fuel amount of the pilot injection and the main injection is represented by the height of the triangle mark, and the higher the height, the greater the fuel amount.
  • the fuel amount of the main injection fuel amount (hereinafter referred to as “main injection amount”) and the sum of all pilot injection amounts (total pilot injection amount) is set to be the same in cases 1 to 4 . Further, in all cases 1 to 4, the total pilot injection amount is larger than the main injection amount.
  • Case 1 as Reference Example 1, the first pilot injection amount Q3 is injected by IT1, and the second pilot injection amount Q4 is injected by IT3.
  • Case 1 is an injection pattern in which pilot injection is performed twice before main injection, and the second pilot injection amount Q4 is set to be larger than the initial pilot injection amount Q3.
  • the first pilot injection in case 1 is divided into two, the injection timing is IT1, IT2, and the injection timing of the third pilot injection is IT4.
  • Each divided pilot injection amount Q5 is set to half of Q3, and the third pilot injection amount is set to Q4.
  • the first pilot injection is performed by IT1, and the second pilot injection is performed by IT3. Further, the main injection amount is decreased from Q1 to Q2, and the reduced amount of fuel (Q1-Q2) is added to the initial pilot injection amount. Accordingly, the initial pilot injection amount is set to Q6 obtained by adding (Q1-Q2) to Q3. The second pilot injection amount is set to Q4.
  • the first pilot injection is performed by IT1
  • the second pilot injection is performed by IT2
  • the third pilot injection is performed by IT4.
  • the ratio of the initial pilot injection amount Q4 to the total pilot injection amount Qpital is set to be larger than the ratio of the sum of the second pilot injection amount Q5 and the third pilot injection amount Q5 to the total pilot injection amount Qpital. Is done.
  • the ratio of the initial pilot injection amount to the total pilot injection amount is referred to as the initial pilot injection amount ratio
  • the ratio of the sum of the second and third pilot injection amounts to the total pilot injection amount is the remaining pilot injection amount ratio. That's it.
  • the injection quantity Q4 of the first pilot injection is set smaller than the injection quantity Q1 of the main injection
  • the injection quantity Q5 of the second and third pilot injections is the injection quantity Q4 of the first pilot injection. Is set smaller than.
  • FIGS. 4 and 5 The experiments shown in FIGS. 4 and 5 were performed when the glow plug 31 was energized and during a cold start under a low outside air temperature condition by conducting experiments with the above four cases. Further, by performing simulations for the four cases, the characteristics shown in FIGS. 6A and 6B were obtained when the glow plug 31 was energized and during cold start under a low outside air temperature condition.
  • FIG. 4 shows the characteristics found by the present inventors for the first time.
  • the horizontal axis of FIG. 4 shows a value dQpilot / d ⁇ [J / deg] obtained by differentiating the amount of heat generated by the entire multistage pilot injection with respect to the crank angle.
  • the vertical axis in FIG. 4 represents the indicated mean effective pressure Pi [MPa] obtained by one-cycle combustion by multistage pilot injection and main injection.
  • one cycle means a period of four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke in one cylinder.
  • FIG. 7 represents the crank angle [deg]
  • the vertical axis in FIG. 7 represents the heat generation rate [J / deg] in the combustion chamber during one cycle.
  • the heat generation rate becomes a waveform having a low peak P1 (first peak) due to heat generation in a plurality of pilot injections, and the heat generated by the main injection thereafter.
  • the generation rate of heat becomes a waveform having a high peak P2 (second peak).
  • the heat generation rate waveform becomes a waveform having two peaks, and the heat generation amount Qpilot [J] by the entire pilot injection is obtained by calculating the area of the first mountain (the area of the hatched portion in FIG. 7). It is done.
  • the low peak P1 of heat generation occurs at the compression top dead center TDC because the diesel engine used in the actual machine experiment happens to have a peak of heat generation at the compression top dead center TDC. is there. Therefore, the present invention can be applied not only to such an engine but also to a diesel engine in which a low peak P1 occurs before or after the compression top dead center TDC.
  • the indicated mean effective pressure Pi increases from A to B as dQpilot / d ⁇ increases.
  • the indicated mean effective pressure Pi has a substantially constant value.
  • dQpilot / d ⁇ in cases 1 to 3 shown in FIG. 3 is included in a region less than D
  • dQpilot / d ⁇ in case 4 is included in a region greater than D.
  • dQpilot / d ⁇ when dQpilot / d ⁇ is in the region of the predetermined value D or more, the fire types formed in the vicinity of the glow plug 31 are growing smoothly, and the combustion of the air-fuel mixture in the combustion chamber is stable.
  • the degree of heat generation is small even if the multi-stage pilot injection is executed, and fire is not formed in the vicinity of the glow plug 31. Or, even if a fire type is formed, it does not grow smoothly and misfire may occur.
  • the number of pilot injections and each pilot are set so that dQpilot / d ⁇ is equal to or greater than a predetermined value D. It is only necessary to determine the injection amount.
  • the trend of the indicated mean effective pressure shown in FIG. 4 does not change depending on the engine specification, but the indicated mean effective pressure Pi value and the predetermined value D in the period B to C change depending on the engine specification. Therefore, a characteristic as shown in FIG. 4 is obtained for each engine specification, and the predetermined value D is determined based on the characteristic.
  • FIG. 5 is a diagram showing the indicated mean effective pressure Pi and the indicated mean effective pressure fluctuation rate (Pi fluctuation rate) in cases 1 to 4.
  • the indicated mean effective pressure Pi is represented by a bar graph, and the Pi variation rate is represented by a broken line.
  • the indicated mean effective pressure in case 2 is higher than the indicated mean effective pressure in cases 1 and 3, but the indicated mean effective pressure in cases 1 to 3 is the indicated mean effective pressure in case 4. It is lower than the pressure.
  • the Pi fluctuation rate increases in the order of Case 1, Case 2, and Case 3, and Case 4 has the smallest.
  • the Pi fluctuation rate is small.
  • FIG. 6A is a diagram showing an average glow plug vicinity temperature in cases 1 to 4.
  • FIG. 6B is a diagram showing an average glow plug vicinity equivalent ratio in cases 1 to 4.
  • the temperature near the glow plug is a value calculated by simulation of the temperature near the glow plug 31 in the combustion chamber.
  • the equivalent ratio is a value obtained by dividing the reciprocal of the air-fuel ratio by the reciprocal of the stoichiometric air-fuel ratio, and the equivalence ratio of 1.0 corresponds to the stoichiometric air-fuel ratio.
  • the glow plug vicinity equivalent ratio is a local equivalent ratio in the vicinity of the glow plug 31, and is not an average equivalent ratio of the entire combustion chamber.
  • the glow plug vicinity equivalent ratio is a value calculated by simulation of the equivalent ratio in the vicinity of the glow plug 31.
  • the case 2 has a higher average glow plug temperature and a higher average glow plug equivalent ratio in the case 2 than in the case 1.
  • the average glow plug vicinity equivalent ratio is increased, but the average glow plug vicinity temperature is lowered. This phenomenon is caused by increasing the initial pilot injection amount in case 3 instead of decreasing the main injection amount. Therefore, in case 3, the amount of fuel that reaches the vicinity of the glow plug 31 at a time by the first pilot injection is large, and the glow plug 31 is cooled, and misfire is likely to occur.
  • the average glow plug vicinity temperature is higher and the average glow plug vicinity equivalent ratio is higher than in any of cases 1 to 3.
  • the air-fuel mixture in the combustion chamber is in a state of stably burning.
  • FIG. 8 is a characteristic diagram showing the relationship between the cooling water temperature and the initial pilot injection amount ratio.
  • the initial pilot injection amount ratio is a value used to determine the injection amount of the initial pilot injection.
  • the initial pilot injection amount ratio is set to increase as the cooling water temperature Tw [° C.] decreases in the region below zero.
  • the initial pilot injection amount ratio is set to about 35%
  • the initial pilot injection amount ratio is set to about 80%.
  • the reason why the initial pilot injection amount ratio is increased as the cooling water temperature Tw becomes lower is to improve the probability that the injected fuel contacts the glow plug 31 even in an extremely low temperature range of ⁇ 30 ° C. .
  • the characteristics shown in FIG. 8 hardly change depending on the engine specifications, and the initial pilot injection amount ratio is set to a value between 35% and 80% regardless of the engine specifications.
  • the horizontal axis in FIG. 8 may be the outside air temperature or the temperature of oil used for lubricating the diesel engine 1 instead of the cooling water temperature Tw. Since the present embodiment is intended for the cold start at the time of energizing the glow plug 31 and the low outside air temperature condition, the cooling water temperature, the oil temperature, and the outside air temperature can be equated in such a state.
  • FIG. 9 is a flowchart showing a routine of the fuel injection control process executed by the controller 21.
  • the fuel injection control process is a process for calculating and outputting the main injection amount and each of the three pilot injection amounts.
  • the fuel injection control process is executed once at a timing before a predetermined crank angle from the initial pilot injection timing at the time of the current fuel injection.
  • step 1 the controller 21 determines that the main injection amount Qmain [mm3 / st. ] Is calculated.
  • the controller 21 reads a predetermined main injection amount Qmain.
  • the main injection amount Qmain is a constant value, and when the target idle rotation speed cannot be obtained with the main injection amount Qmain, the main injection amount Qmain is adjusted by feedback control to obtain the target idle rotation speed. .
  • the controller 21 determines whether or not all of the following conditions [1] to [4] are satisfied, and executes the process of S6 when all are satisfied. On the other hand, if any of the conditions [1] to [4] is not satisfied, the controller 21 executes the process of S13 and outputs the main injection amount Qmain to the register. In S13, the main injection amount Qmain may be stored in the memory. As described above, when any one of the conditions [1] to [4] is not satisfied, the pilot injection is not executed and only the main injection is executed.
  • the outside temperature Ta is 0 ° C or lower.
  • the cooling water temperature Tw is less than a predetermined value.
  • the period during which the glow plug 31 is energized is a short period of, for example, several tens of seconds after the engine cold start.
  • the above condition [1] is used in order to effectively utilize the function of the glow plug 31 as a fuel ignition source at an extremely low temperature in the low-compressed diesel engine 1.
  • the condition is that the combustion becomes unstable under the low outside air temperature condition where the outside air temperature Ta is 0 ° C. or less.
  • the outside air temperature Ta is detected by the outside air temperature sensor 32 (see FIG. 1).
  • the condition is that combustion is most unstable in the idle operation state.
  • the controller 21 determines that the engine is in an idle operation state.
  • the condition is that the combustion becomes unstable when the engine is cold when the coolant temperature Tw is less than a predetermined value.
  • the cooling water temperature Tw is detected by a water temperature sensor 33 (see FIG. 1).
  • the conditions [3] and [4] may be omitted as necessary.
  • the controller 21 determines that the total pilot injection amount Qpital [mm3 / st. ] Is calculated.
  • the total pilot injection amount Qpitotal is calculated by searching a total pilot injection amount map from the engine load and the engine speed. When the glow plug 31 is energized and during cold start under a low outside air temperature condition, the total pilot injection amount Qpital may be larger than the main injection amount Qmain.
  • the controller 21 calculates the initial pilot injection amount ratio by searching the table shown in FIG. 8 from the coolant temperature Tw. As shown in FIG. 8, the initial pilot injection amount ratio is set to be larger as the cooling water temperature Tw is lower. This is because the fuel spray is less likely to vaporize as the temperature becomes extremely low, and it is necessary to increase the probability that the fuel spray contacts the glow plug 31 by injecting more fuel.
  • the outside air temperature Ta is used in S3, and the cooling water temperature Tw is used in S5 and S7.
  • the present invention is not limited to this.
  • the oil temperature may be used instead of the cooling water temperature Tw.
  • the oil temperature may be used instead of the cooling water temperature Tw.
  • the outside air temperature Ta may be used instead of the cooling water temperature Tw, and in this case, the process of S3 can be omitted.
  • the controller 21 determines whether or not the angular speed of the engine rotation has decreased to the extent that misfire occurs.
  • the controller 21 calculates the angular speed of engine rotation at intervals of 180 degrees. Since the engine rotational speed Ne detected by the crank angle sensor 23 (angular speed detector) is in units of rpm, dividing this by 60 gives a rotational speed V [times / s] with the denominator as seconds.
  • the controller 21 determines that the angular speed ⁇ of the engine rotation is decreasing, and executes the process of S9.
  • the controller 21 determines that the angular speed ⁇ of the engine rotation has decreased when the angular speed ⁇ of the engine rotation calculated based on the engine rotational speed detected by the crank angle sensor 23 has decreased below the misfire determination threshold value. May be.
  • the controller 21 multiplies the initial pilot injection amount ratio calculated in S7 by a constant decrease rate, and calculates the initial pilot injection amount ratio again.
  • the decreasing rate is a value that is adapted in advance.
  • the controller 21 uses the initial pilot injection amount ratio calculated in S7 or the initial pilot injection amount ratio reduced in S9 to calculate the initial pilot injection amount Qpi1 [mm 3 / st. ] Is calculated.
  • the initial pilot injection amount Qpi1 is set so as not to exceed the main injection amount Qmain calculated in S1.
  • the controller 21 uses the Qpital calculated in S6 and the Qpi1 calculated in S10 to calculate the second pilot injection amount Qpi2 [mm3 / st. ]
  • the second and third pilot injection amounts Qpi2, Qpi3 are set smaller than the initial pilot injection amount Qpi1.
  • the initial pilot injection amount Qpi1, the second pilot injection amount Qpi2, and the third pilot injection amount Qpi3 calculated as described above are large when the glow plug 31 is energized and during cold start under a low outside air temperature condition.
  • the value obtained by differentiating the amount of heat generated by the entire pilot injection at the stage with respect to the crank angle is a value adapted to be equal to or greater than the predetermined value D in FIG.
  • the controller 21 outputs the main injection amount Qmain, the initial pilot injection amount Qpi1, the second pilot injection amount Qpi2, and the third pilot injection amount Qpi3 to the register.
  • each injection amount may be stored in the memory.
  • Each injection timing of the first pilot injection, the second pilot injection, the third pilot injection, and the main injection is set to a predetermined timing as shown in case 4 of FIG. That is, the injection timing of the first pilot injection is set to the timing IT1, the injection timing of the second pilot injection is set to the timing IT2, and the injection timing of the third pilot injection is set to the timing IT4. Further, the injection timing of the main injection is set to the timing IT5.
  • the controller 21 controls to open the fuel injection valve 9 at the injection timings of the first pilot injection, the second pilot injection, the third pilot injection, and the main injection. Thereby, the fuel injection valve 9 supplies fuel of each injection amount of Qpi1, Qpi2, Qpi3, and Qmain to the combustion chamber.
  • the control device for the diesel engine 1 includes a glow plug 31 that heats the combustion chamber during cold start, a common rail fuel injection device 6 that can execute pilot injection prior to main injection in multiple stages, and a common rail fuel. And a controller 21 for controlling the injection device 6.
  • the controller 21 predetermines a value (dQpilot / d ⁇ ) obtained by differentiating the amount of heat generated by the entire multistage pilot injection with the crank angle when the glow plug 31 is energized and during cold start under a low outside air temperature condition.
  • the number of pilot injections and the injection amount of each pilot injection are determined so as to be equal to or greater than the predetermined value D.
  • the controller 21 performs a common rail fuel injection device so as to execute pilot injection in two or more stages at the time of cold start when the glow plug 31 is energized and the outside air temperature is 0 ° C. or less. 6 is controlled. Then, the controller 21 sets the injection amount of the first pilot injection in a range from 35% to 80% with respect to the total pilot injection amount that does not exceed the injection amount of the main injection and is the sum of the injection amount of each pilot injection. Set in. At this time, the controller 21 sets the injection amount of one remaining pilot injection executed after the first time to be smaller than the injection amount of the first pilot injection.
  • the number of pilot injections is preferably about 3 as in case 4 in FIG.
  • the pilot injection is performed in multiple stages of two or more configured by the initial pilot injection and the remaining pilot injection following this, and the initial pilot injection amount ratio is set larger than the remaining pilot injection amount ratio.
  • the vaporization of the fuel can be promoted by multistage pilot injection twice or more, and the equivalent ratio in the vicinity of the glow plug 31 can be increased.
  • the absorption of heat from the glow plug 31 immediately before the main injection can be reduced, and the temperature drop of the glow plug 31 can be suppressed.
  • the equivalence ratio in the vicinity of the glow plug 31 and the temperature of the glow plug 31 can be kept high, and combustion of the air-fuel mixture in the combustion chamber can be stabilized.
  • the initial pilot injection amount ratio is set to be larger as the cooling water temperature Tw is lowered as shown in FIG.
  • optimal fuel injection control according to the cooling water temperature Tw at the time of the cold start in the energization to the glow plug 31 and the low outside air temperature condition can be executed.
  • the equivalence ratio in the vicinity of the glow plug 31 and the temperature of the glow plug 31 can be kept high regardless of the outside air temperature or the like, and combustion in the combustion chamber can be further stabilized.
  • the initial pilot injection amount ratio is corrected to be small. As a result, a good combustion state can be obtained even when the angular speed of engine rotation is reduced due to misfire during energization of the glow plug 31 and during cold start under a low outside air temperature condition.
  • the number of pilot injections is three as shown in case 4 of FIG. 3, but the number of pilot injections may be two or more. Further, in the present embodiment, the second pilot injection amount and the third pilot injection amount are set to the same amount, but it is sufficient that the second and third pilot injection amounts are smaller than the initial pilot injection amount. It is not necessary to set the amount to the same amount.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

A control device for a diesel engine equipped with: a glow plug that heats the combustion chamber of the diesel engine during a cold start; a common rail fuel injection device capable of executing a multi-stage pilot injection before a main injection; and a control unit that controls the common rail fuel injection device. When power is supplied to the glow plug and when a cold start is performed with an outside temperature of 0°C or lower, the control unit controls the common rail fuel injection device so as to execute a multi-stage injection of two or more pilot injections. In addition, the control unit sets the injection amount for the initial pilot injection so as not to exceed the injection amount of the main injection and to be within a range of 35-80% of the total pilot injection amount, which is the sum of the injection amounts for all of the pilot injections. Furthermore, the control unit sets the injection amount for each pilot injection executed after the initial pilot injection so as to be less than the injection amount for the initial pilot injection.

Description

ディーゼルエンジンの制御装置Diesel engine control device
　本発明は、ディーゼルエンジンの制御装置に関する。 The present invention relates to a control device for a diesel engine.
　ＪＰ２００３－９７３２９Ａには、可変圧縮比機構を備え、始動時や低負荷時に圧縮比を相対的に高くし、かつ高負荷時に圧縮比を相対的に低くするディーゼルエンジンが開示されている。このディーゼルエンジンでは、低圧縮比となる高負荷時に、他段階（例えば５回）のパイロット噴射が実行される。 JP2003-97329A discloses a diesel engine that includes a variable compression ratio mechanism, relatively increases the compression ratio at start-up and when the load is low, and relatively decreases the compression ratio when the load is high. In this diesel engine, pilot injection at another stage (for example, five times) is performed at a high load at which the compression ratio is low.
　ＪＰ２００３－９７３２９Ａに記載のディーゼルエンジンでは、高圧縮比となる始動時や低負荷時にも、多段階のパイロット噴射が実行される。このように複数回のパイロット噴射が実行されると、パイロット噴射された燃料の着火が早まり、燃焼室内での燃焼が拡散燃焼となって、炭化水素（ＨＣ）が多く発生する。そのため、始動時や低負荷時には、前半のパイロット噴射を中止し、中止した分のパイロット噴射量を後半のパイロット噴射量に加算するようにしている。 In the diesel engine described in JP2003-97329A, multi-stage pilot injection is executed even at the start of a high compression ratio or at a low load. When the pilot injection is executed a plurality of times in this manner, the ignition of the fuel injected by the pilot is accelerated, the combustion in the combustion chamber becomes diffusion combustion, and a large amount of hydrocarbon (HC) is generated. Therefore, at the time of start-up or at a low load, the first half pilot injection is stopped, and the amount of the pilot injection that has been stopped is added to the second half pilot injection amount.
　しかしながら、ＪＰ２００３－９７３２９Ａでは、低圧縮比状態での燃焼性の改善は検討されていない。そのため、低圧縮比状態においてパイロット噴射を多段化するだけでは、グロープラグへの通電時かつ低外気温条件での冷間始動時における燃焼性の改善は望めない。 However, JP2003-97329A does not discuss improvement in combustibility in a low compression ratio state. Therefore, improvement of combustibility at the time of cold start under energization of the glow plug and a low outside air temperature condition cannot be expected only by making the pilot injection multistage in the low compression ratio state.
　本発明の目的は、グロープラグへの通電時かつ低外気温条件での冷間始動時において、燃焼性を改善可能なディーゼルエンジンの制御装置を提供することである。 An object of the present invention is to provide a control device for a diesel engine capable of improving combustibility when a glow plug is energized and at a cold start under a low outside air temperature condition.
　本発明のある態様によれば、冷間始動時にディーゼルエンジンの燃焼室を加熱するグロープラグと、メイン噴射に先立つパイロット噴射を多段階で実行可能なコモンレール式燃料噴射装置と、コモンレール式燃料噴射装置を制御する制御部と、を備えるディーゼルエンジンの制御装置が提供される。制御部は、グロープラグへの通電時かつ外気温が０℃以下での冷間始動時に、パイロット噴射を２回以上の多段階で実行するようにコモンレール式燃料噴射装置を制御する。また、制御部は、初回のパイロット噴射の噴射量を、メイン噴射の噴射量を超えず、かつ各パイロット噴射の噴射量の和である総パイロット噴射量に対して３５％から８０％までの範囲内で設定する。さらに、制御部は、初回以降に実行される残りのパイロット噴射の１回分の噴射量を、初回のパイロット噴射の噴射量よりも小さく設定する。 According to an aspect of the present invention, a glow plug that heats a combustion chamber of a diesel engine during cold start, a common rail fuel injection device that can execute pilot injection prior to main injection in multiple stages, and a common rail fuel injection device And a control unit for controlling the diesel engine. The control unit controls the common rail fuel injection device so that the pilot injection is executed in multiple stages of two or more times when the glow plug is energized and at the cold start when the outside air temperature is 0 ° C. or less. Further, the control unit sets the injection amount of the first pilot injection in a range from 35% to 80% with respect to the total pilot injection amount that does not exceed the injection amount of the main injection and is the sum of the injection amount of each pilot injection. Set in. Furthermore, the control unit sets the injection amount for one remaining pilot injection executed after the first time to be smaller than the injection amount for the first pilot injection.
図１は、本発明の実施形態によるディーゼルエンジンの制御装置の概略構成図である。FIG. 1 is a schematic configuration diagram of a control device for a diesel engine according to an embodiment of the present invention. 図２は、ディーゼルエンジンの１つの気筒を上から見た模式図である。FIG. 2 is a schematic view of one cylinder of the diesel engine as viewed from above. 図３は、本発明者らが検討した異なる４つのケースのパイロット噴射パターンを例示した図である。FIG. 3 is a diagram illustrating four different cases of pilot injection patterns studied by the present inventors. 図４は、多段階のパイロット噴射全体による熱発生量をクランク角で微分した値と、図示平均有効圧との関係を示した特性図である。FIG. 4 is a characteristic diagram showing the relationship between the value obtained by differentiating the amount of heat generated by the entire multistage pilot injection with the crank angle and the indicated mean effective pressure. 図５は、異なる４つのパイロット噴射パターンの図示平均有効圧及び図示平均有効圧変動率を示す図である。FIG. 5 is a diagram showing the indicated mean effective pressure and the indicated mean effective pressure fluctuation rate of four different pilot injection patterns. 図６Ａは、異なる４つのパイロット噴射パターンの平均グロープラグ近傍温度を示す図である。FIG. 6A is a diagram showing an average glow plug vicinity temperature of four different pilot injection patterns. 図６Ｂは、異なる４つのパイロット噴射パターンの平均グロープラグ近傍当量比を示す図である。FIG. 6B is a diagram showing an average glow plug vicinity equivalent ratio of four different pilot injection patterns. 図７は、ディーゼルエンジンの燃焼室内における１回の燃焼時の熱発生率を示す特性図である。FIG. 7 is a characteristic diagram showing a heat generation rate during one combustion in the combustion chamber of the diesel engine. 図８は、冷却水温と初回パイロット噴射量比率との関係を示す特性図である。FIG. 8 is a characteristic diagram showing the relationship between the cooling water temperature and the initial pilot injection amount ratio. 図９は、コントローラが実行する燃料噴射制御処理のルーチンを示すフローチャートである。FIG. 9 is a flowchart showing a fuel injection control process routine executed by the controller.
　以下、図面等を参照して、本発明の実施形態を説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
　図１は、本発明の実施形態によるディーゼルエンジン１の制御システムの概略構成図である。 FIG. 1 is a schematic configuration diagram of a control system for a diesel engine 1 according to an embodiment of the present invention.
　図１に示すように、ディーゼルエンジン１は、車両用のエンジンであって、吸気通路２を備えている。ディーゼルエンジン１に供給される吸気は、吸気通路２に備えられる過給器１０の吸気コンプレッサ１０Ａによって過給される。過給された吸気は、インタークーラ３で冷却され、吸気絞り弁４を通過した後、コレクタ５を経て各気筒の燃焼室内へ流入する。 As shown in FIG. 1, the diesel engine 1 is a vehicle engine and includes an intake passage 2. The intake air supplied to the diesel engine 1 is supercharged by an intake air compressor 10 </ b> A of a supercharger 10 provided in the intake passage 2. The supercharged intake air is cooled by the intercooler 3, passes through the intake throttle valve 4, and then flows into the combustion chamber of each cylinder through the collector 5.
　ディーゼルエンジン１は、コモンレール式燃料噴射装置６をさらに備えている。コモンレール式燃料噴射装置６は、高圧燃料ポンプ７と、コモンレール８と、燃料噴射弁９と、を備えている。燃料タンクに貯蔵されている燃料は、コモンレール式燃料噴射装置６によってディーゼルエンジン１に供給される。つまり、燃料は高圧燃料ポンプ７により燃料タンクからコモンレール８に送られ、コモンレール８内の高圧状態の燃料は各燃料噴射弁９からそれぞれの燃焼室に噴射供給される。燃焼室内に流入した吸気と燃料噴射弁９から噴射された燃料は燃焼室内で圧縮着火により燃焼し、燃焼後の排気は排気通路１１へ排出される。 The diesel engine 1 further includes a common rail fuel injection device 6. The common rail fuel injection device 6 includes a high pressure fuel pump 7, a common rail 8, and a fuel injection valve 9. The fuel stored in the fuel tank is supplied to the diesel engine 1 by the common rail fuel injection device 6. That is, the fuel is sent from the fuel tank to the common rail 8 by the high-pressure fuel pump 7, and the high-pressure fuel in the common rail 8 is injected and supplied from each fuel injection valve 9 to each combustion chamber. The intake air flowing into the combustion chamber and the fuel injected from the fuel injection valve 9 are combusted by compression ignition in the combustion chamber, and the exhaust after combustion is discharged to the exhaust passage 11.
　排気通路１１に排出された排気の一部は、ＥＧＲガスとして、ＥＧＲ通路１２を通じて吸気側に還流される。ＥＧＲ通路１２には、当該ＥＧＲ通路１２を流れるＥＧＲガスの流量を制御するためのＥＧＲ弁１３が設けられている。 A part of the exhaust discharged to the exhaust passage 11 is recirculated to the intake side through the EGR passage 12 as EGR gas. The EGR passage 12 is provided with an EGR valve 13 for controlling the flow rate of EGR gas flowing through the EGR passage 12.
　還流されない残りの排気は、排気通路１１の下流側へと導かれ、過給器１０の排気タービン１０Ｂを通過する時に当該排気タービン１０Ｂを駆動する。排気タービン１０Ｂのスクロール入口には、可変ノズル１０Ｄが設けられている。なお、可変ノズル１０Ｄを駆動するため、過給器１０には油圧駆動式又は電気駆動式のアクチュエータ１０Ｅが設けられている。 The remaining exhaust gas that is not recirculated is guided to the downstream side of the exhaust passage 11 and drives the exhaust turbine 10B when passing through the exhaust turbine 10B of the supercharger 10. A variable nozzle 10D is provided at the scroll inlet of the exhaust turbine 10B. In order to drive the variable nozzle 10D, the turbocharger 10 is provided with a hydraulically driven or electrically driven actuator 10E.
　可変ノズル１０Ｄを絞って可変ノズル開度を小さくすると、排気の流速が増加し、排気タービン１０Ｂの回転速度が上昇する。これにより、排気タービン１０Ｂと同軸に連結された吸気コンプレッサ１０Ａの回転速度が上昇し、吸気コンプレッサ１０Ａによって吸気が過給される。 If the variable nozzle 10D is throttled to reduce the variable nozzle opening, the exhaust flow rate increases and the rotational speed of the exhaust turbine 10B increases. As a result, the rotational speed of the intake compressor 10A connected coaxially with the exhaust turbine 10B increases, and the intake air is supercharged by the intake compressor 10A.
　一方、可変ノズル１０Ｄを開いて可変ノズル開度を大きくすると、排気の流速が低下し、排気タービン１０Ｂの回転速度が低下する。これにより、吸気コンプレッサ１０Ａの回転速度も低下し、吸気コンプレッサ１０Ａによる吸気の過給が停止される。 On the other hand, when the variable nozzle 10D is opened and the variable nozzle opening is increased, the flow rate of the exhaust gas decreases, and the rotational speed of the exhaust turbine 10B decreases. As a result, the rotational speed of the intake compressor 10A also decreases, and the supercharging of intake air by the intake compressor 10A is stopped.
　ディーゼルエンジン１は、制御部としてのコントローラ２１によって制御される。コントローラ２１は、中央演算装置（ＣＰＵ）、読み出し専用メモリ（ＲＯＭ）、ランダムアクセスメモリ（ＲＡＭ）及び入出力インタフェース（Ｉ／Ｏインタフェース）を備えたマイクロコンピュータで構成されている。 The diesel engine 1 is controlled by a controller 21 as a control unit. The controller 21 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).
　コントローラ２１には、アクセルセンサ２２によって検出されるアクセルペダル踏込量（アクセル開度信号）と、クランク角センサ２３によって検出されるエンジン回転速度信号とが入力される。 The controller 21 receives an accelerator pedal depression amount (accelerator opening signal) detected by the accelerator sensor 22 and an engine speed signal detected by the crank angle sensor 23.
　コントローラ２１は、エンジン負荷（アクセル開度）及びエンジン回転速度に基づいて、メイン噴射の燃料噴射時期及び燃料噴射量を算出し、これらに対応する開弁指令信号を燃料噴射弁９に出力する。また、コントローラ２１は、目標ＥＧＲ率と目標吸入空気量とが得られるようにＥＧＲ制御と過給圧制御を協調して行う。 The controller 21 calculates the fuel injection timing and the fuel injection amount of the main injection based on the engine load (accelerator opening) and the engine rotation speed, and outputs a valve opening command signal corresponding thereto to the fuel injection valve 9. Further, the controller 21 performs EGR control and supercharging pressure control in a coordinated manner so that the target EGR rate and the target intake air amount can be obtained.
　排気タービン１０Ｂよりも下流の排気通路１１には、排気に含まれるパティキュレートを捕集するフィルタ１４が配置されている。フィルタ１４のパティキュレート堆積量が所定の閾値に達すると、コントローラ２１は、メイン噴射直後の膨張行程又は排気行程でポスト噴射を行うことにより、フィルタ１４の再生処理を実行する。 In the exhaust passage 11 downstream of the exhaust turbine 10B, a filter 14 for collecting particulates contained in the exhaust is disposed. When the particulate accumulation amount of the filter 14 reaches a predetermined threshold, the controller 21 performs the regeneration process of the filter 14 by performing the post injection in the expansion stroke or the exhaust stroke immediately after the main injection.
　コントローラ２１には、目標となる再生温度が得られるポスト噴射量及びポスト噴射時期がエンジン負荷とエンジン回転速度とに対応して記憶されている。そして、コントローラ２１は、エンジン負荷とエンジン回転速度とに応じた最適なポスト噴射量とポスト噴射時期で、ポスト噴射を行う。これにより、フィルタ１４に堆積しているパティキュレートを燃焼除去し、フィルタ１４を再生する。 The controller 21 stores a post-injection amount and a post-injection timing at which a target regeneration temperature is obtained corresponding to the engine load and the engine speed. Then, the controller 21 performs post-injection at the optimal post-injection amount and post-injection timing according to the engine load and engine speed. Thereby, the particulates accumulated on the filter 14 are removed by combustion, and the filter 14 is regenerated.
　フィルタ１４に堆積しているパティキュレートの全てを燃焼除去する完全再生を実行するためには、再生処理時にフィルタ１４の許容温度を超えない範囲で、フィルタ１４内の温度（パティキュレート燃焼温度）を高めることが必要となる。そのため、フィルタ１４よりも上流の排気通路１１には、酸化触媒１５が配置されている。 In order to perform complete regeneration in which all of the particulates accumulated on the filter 14 are burned and removed, the temperature (particulate combustion temperature) in the filter 14 is set within a range not exceeding the allowable temperature of the filter 14 during the regeneration process. It is necessary to raise. Therefore, an oxidation catalyst 15 is disposed in the exhaust passage 11 upstream of the filter 14.
　再生処理時におけるポスト噴射によって流入する排気に含まれるＨＣ及びＣＯを触媒１５により燃焼させることで、フィルタ１４内の温度を高めて、フィルタ１４でのパティキュレートの燃焼を促進させる。 HC and CO contained in the exhaust gas flowing in by the post-injection during the regeneration process are burned by the catalyst 15 to increase the temperature in the filter 14 and promote the burning of the particulates in the filter 14.
　なお、触媒１５は、酸化触媒に限られず、酸化機能を備える触媒（例えば三元触媒）であってもよい。 The catalyst 15 is not limited to the oxidation catalyst, and may be a catalyst having an oxidation function (for example, a three-way catalyst).
　また、触媒１５をフィルタ１４の上流側に別体で設けるのではなく、フィルタ１４を構成する担体に酸化触媒をコーティングしてもよい。この場合には、パティキュレートが燃焼する際の酸化反応が促進されるので、フィルタ１４内の温度が上昇しやすく、パティキュレートの燃焼を効率的に促進させることが可能となる。 Further, instead of providing the catalyst 15 separately on the upstream side of the filter 14, the carrier constituting the filter 14 may be coated with an oxidation catalyst. In this case, since the oxidation reaction when the particulates burn is promoted, the temperature in the filter 14 is likely to rise, and the particulate combustion can be promoted efficiently.
　ところで、ディーゼルエンジン１では冷間時に始動性が低下するため、ディーゼルエンジン１は、燃焼室ごとに冷間始動用のグロープラグ３１を備えている。グロープラグ３１は、燃焼室内に臨むように設けられており、冷間始動時等に燃焼室内の混合気の温度を上昇させて着火を補助する。 Incidentally, since the startability of the diesel engine 1 is lowered when it is cold, the diesel engine 1 is provided with a glow plug 31 for cold start for each combustion chamber. The glow plug 31 is provided so as to face the combustion chamber, and assists ignition by increasing the temperature of the air-fuel mixture in the combustion chamber at the time of cold start or the like.
　図２は、ディーゼルエンジン１の１つの気筒４１を上から見た模式図である。 FIG. 2 is a schematic view of one cylinder 41 of the diesel engine 1 as viewed from above.
　図２に示すように、気筒４１のシリンダボア４２の上部に燃焼室４３が形成され、燃料噴射弁９は燃焼室４３内に臨んで設けられるとともに燃焼室４３の上部中央位置に配置される。燃料噴射弁９の周囲には、２つの吸気弁４４、４５と２つの排気弁４６、４７が配置されている。燃料噴射弁９の先端には例えば８つの噴孔が形成されており、燃料は各噴孔からシリンダボア４２の壁面に向けて噴射される。燃料噴射弁９から噴射された燃料は、周方向に等しい間隔をあけて８方向に噴射される。燃焼室４３内には図中矢印方向のスワール流が生じるようになっており、このスワール流によって噴霧燃料Ｆは図２において時計回転方向に曲げられる。 As shown in FIG. 2, a combustion chamber 43 is formed above the cylinder bore 42 of the cylinder 41, and the fuel injection valve 9 is provided facing the combustion chamber 43 and is disposed at an upper central position of the combustion chamber 43. Two intake valves 44 and 45 and two exhaust valves 46 and 47 are arranged around the fuel injection valve 9. For example, eight injection holes are formed at the tip of the fuel injection valve 9, and fuel is injected from each injection hole toward the wall surface of the cylinder bore 42. The fuel injected from the fuel injection valve 9 is injected in eight directions at equal intervals in the circumferential direction. A swirl flow in the direction of the arrow in the figure is generated in the combustion chamber 43, and the sprayed fuel F is bent in the clockwise direction in FIG. 2 by this swirl flow.
　グロープラグ３１は、例えば２つの吸気弁４４、４５の間の位置から燃焼室４３内に臨むように設けられている。エンジン冷間時には、グロープラグ３１に電流が通電される。燃料噴射弁９からの噴霧燃料Ｆが、通電によって加熱されたグロープラグ３１の周辺に供給されると、グロープラグ３１近傍の混合気が着火して種火となり、混合気全体に燃え広がる。 The glow plug 31 is provided, for example, so as to face the combustion chamber 43 from a position between the two intake valves 44 and 45. When the engine is cold, current is supplied to the glow plug 31. When the atomized fuel F from the fuel injection valve 9 is supplied to the periphery of the glow plug 31 heated by energization, the air-fuel mixture in the vicinity of the glow plug 31 is ignited to become a seed flame, and burns and spreads throughout the air-fuel mixture.
　なお、グロープラグ３１が設けられる位置は、２つの吸気弁４４、４５の間に限られるものでなく、吸気弁４４、４５と排気弁４６、４７の間や２つの排気弁４６、４７の間であってもよい。また、吸気弁の数や排気弁の数、燃料噴射弁の噴孔の数は、必要に応じて任意に設定される。 The position where the glow plug 31 is provided is not limited to between the two intake valves 44, 45, but between the intake valves 44, 45 and the exhaust valves 46, 47 or between the two exhaust valves 46, 47. It may be. Further, the number of intake valves, the number of exhaust valves, and the number of injection holes of the fuel injection valve are arbitrarily set as necessary.
　最近のディーゼルエンジン１においては、エンジン圧縮比は、１５前後、より具体的には１５．５以下の低圧縮比に設定される傾向にある。このように低圧縮比化することのメリットは、ディーゼルエンジン１の出力を向上させ、排気中のＮＯｘを低減し、ポンピングロスを低減できる点にある。つまり、低圧縮比化により気筒内圧の最大値が低下する分、燃料噴射弁９から燃料をより多く燃焼室４３内に噴射することが可能となり、これによってエンジンの出力が向上する。低圧縮比化により燃焼室４３内における燃焼温度を低下させることができ、これによりＮＯｘの発生を抑制することが可能となる。また、圧縮比が低下するため、ポンピングロスも低減される。 In recent diesel engines 1, the engine compression ratio tends to be set to a low compression ratio of around 15, more specifically 15.5 or less. The merit of lowering the compression ratio in this way is that the output of the diesel engine 1 can be improved, NOx in the exhaust can be reduced, and the pumping loss can be reduced. That is, it is possible to inject more fuel into the combustion chamber 43 from the fuel injection valve 9 as much as the maximum value of the cylinder internal pressure decreases due to the low compression ratio, thereby improving the output of the engine. By reducing the compression ratio, the combustion temperature in the combustion chamber 43 can be lowered, thereby suppressing the generation of NOx. Further, since the compression ratio is lowered, the pumping loss is also reduced.
　その一方で、低圧縮比化により、例えば－２５℃といった低外気温条件での冷間始動時に、失火が発生する等、燃焼室４３内における混合気の燃焼性が悪化する。 On the other hand, due to the low compression ratio, the combustibility of the air-fuel mixture in the combustion chamber 43 deteriorates, for example, misfiring occurs during cold start under a low outside air temperature condition of, for example, −25 ° C.
　本発明者らは、低外気温条件での冷間始動時における失火を抑制するためには、グロープラグ３１の有する燃料着火源としての機能を有効活用することが重要であることに着目した。つまり、ディーゼルエンジン１では、メイン噴射に先立って行われるパイロット噴射による燃料をグロープラグ３１の近傍に導いて燃焼の核となる火種を形成することで、冷間始動時における燃焼安定性の改善を図る。 The present inventors have focused on the fact that it is important to effectively utilize the function of the glow plug 31 as a fuel ignition source in order to suppress misfire during cold start under low outside air temperature conditions. . In other words, in the diesel engine 1, the fuel by pilot injection that is performed prior to the main injection is led to the vicinity of the glow plug 31 to form a fire type that becomes the core of combustion, thereby improving the combustion stability at the cold start. Plan.
　しかしながら、グロープラグ３１近傍に導く燃料が多すぎると、燃料気化時にグロープラグ３１から奪われる熱量が増えてしまう。そうすると、グロープラグ３１が冷却されすぎて、グロープラグ３１によって火種を形成させることができなくなる。 However, if too much fuel is guided to the vicinity of the glow plug 31, the amount of heat taken away from the glow plug 31 when the fuel is vaporized increases. If it does so, the glow plug 31 will be cooled too much and it will become impossible to form a fire type with the glow plug 31.
　１回のパイロット噴射による燃料過多に起因するグロープラグ３１の冷却を回避するためには、パイロット噴射を２回以上に多段化することによって、１回当たりのパイロット噴射の燃料量（パイロット噴射量）を低減する必要がある。１回当たりのパイロット噴射量を低減すれば、所定時間当たりにグロープラグ３１から奪われる熱量が少なくなり、グロープラグ３１の温度低下を抑制することが可能となる。 In order to avoid the cooling of the glow plug 31 due to excessive fuel by one pilot injection, the fuel amount of the pilot injection per one time (pilot injection amount) is obtained by making the pilot injection multistage more than twice. Need to be reduced. If the pilot injection amount per one time is reduced, the amount of heat taken from the glow plug 31 per predetermined time is reduced, and the temperature drop of the glow plug 31 can be suppressed.
　ところで、上述したＪＰ２００３－９７３２９Ａには、可変圧縮比機構を備え、始動時や低負荷時に圧縮比を相対的に高くし、かつ高負荷時に圧縮比を相対的に低くするディーゼルエンジンが開示されている。このディーゼルエンジンでは、低圧縮比となる高負荷時に複数回のパイロット噴射を実行し、高圧縮比となる始動時や低負荷時にも複数回のパイロット噴射を実行する。しかしながら、ＪＰ２００３－９７３２９Ａ１では低圧縮比状態での燃焼性の改善は検討されておらず、低圧縮比状態においてパイロット噴射を多段化する場合には、グロープラグへの通電時かつ低外気温条件での冷間始動時における燃焼性の改善は望めない。 By the way, JP2003-97329A described above discloses a diesel engine that includes a variable compression ratio mechanism, that makes the compression ratio relatively high at start-up or low load, and relatively low at high load. Yes. In this diesel engine, a plurality of pilot injections are executed at a high load at which the compression ratio is low, and a plurality of pilot injections are executed at a start and at a low load at which the compression ratio is high. However, JP2003-97329A1 has not studied improvement of combustibility in the low compression ratio state, and when pilot injection is made multistage in the low compression ratio state, the glow plug is energized and under the low outside air temperature condition. The improvement of combustibility at the time of cold start cannot be expected.
　これに対して、本実施形態では、グロープラグ３１への通電時かつ低外気温条件での冷間始動時に、複数回分のパイロット噴射全体の熱発生量をクランク角で微分した値が予め定められた所定値以上となるように、パイロット噴射の回数及び各パイロット噴射量を決定する。これによって、着火時のグロープラグ３１の温度低下を抑制でき、かつグロープラグ３１の近傍の当量比を高く維持することが可能となる。その結果、グロープラグ３１への通電時かつ低外気温条件での冷間始動時に、燃焼室４３内での混合気の燃焼性を改善することができる。 On the other hand, in the present embodiment, when the glow plug 31 is energized and cold start is performed under a low outside air temperature condition, a value obtained by differentiating the heat generation amount of a plurality of pilot injections by the crank angle is determined in advance. The number of pilot injections and each pilot injection amount are determined so as to be equal to or greater than the predetermined value. As a result, the temperature drop of the glow plug 31 at the time of ignition can be suppressed, and the equivalent ratio in the vicinity of the glow plug 31 can be kept high. As a result, the combustibility of the air-fuel mixture in the combustion chamber 43 can be improved when the glow plug 31 is energized and during cold start under a low outside air temperature condition.
　図３は、本発明者らが検討した異なる４つのパイロット噴射パターンを示す図である。 FIG. 3 is a diagram showing four different pilot injection patterns examined by the present inventors.
　図３に示すように、ケース４は本実施形態の噴射パターンであり、ケース１～３は参考例１～３としての噴射パターンである。各パイロット噴射パターンでは、複数回のパイロット噴射が実行され、最終回のパイロット噴射後にメイン噴射が実行される。ＩＴ１～ＩＴ４はパイロット噴射の噴射時期を示し、ＩＴ５はメイン噴射の噴射時期を示す。ＩＴ５は、圧縮上死点ＴＤＣの直前に設定されている。パイロット噴射及びメイン噴射の燃料量は三角印の高さで表されており、その高さが高いほど燃料量が多いことを意味している。 As shown in FIG. 3, Case 4 is an injection pattern of this embodiment, and Cases 1 to 3 are injection patterns as Reference Examples 1 to 3. In each pilot injection pattern, a plurality of pilot injections are executed, and the main injection is executed after the final pilot injection. IT1 to IT4 indicate the injection timing of pilot injection, and IT5 indicates the injection timing of main injection. IT5 is set immediately before the compression top dead center TDC. The fuel amount of the pilot injection and the main injection is represented by the height of the triangle mark, and the higher the height, the greater the fuel amount.
　メイン噴射の燃料量（以下「メイン噴射量」という。）と、全てのパイロット噴射量の合計（総パイロット噴射量）とを合わせた燃料量は、ケース１～４においてそれぞれ同じに設定されている。さらに、ケース１～４とも、メイン噴射量よりも総パイロット噴射量のほうが多くなっている。 The fuel amount of the main injection fuel amount (hereinafter referred to as “main injection amount”) and the sum of all pilot injection amounts (total pilot injection amount) is set to be the same in cases 1 to 4 . Further, in all cases 1 to 4, the total pilot injection amount is larger than the main injection amount.
　参考例１としてのケース１では、初回のパイロット噴射量Ｑ３をＩＴ１で、２回目のパイロット噴射量Ｑ４をＩＴ３で噴射する。ケース１はメイン噴射の前にパイロット噴射が２回行われる噴射パターンであり、２回目のパイロット噴射量Ｑ４の方が初回のパイロット噴射量Ｑ３よりも多く設定されている。 In Case 1 as Reference Example 1, the first pilot injection amount Q3 is injected by IT1, and the second pilot injection amount Q4 is injected by IT3. Case 1 is an injection pattern in which pilot injection is performed twice before main injection, and the second pilot injection amount Q4 is set to be larger than the initial pilot injection amount Q3.
　参考例２としてのケース２では、ケース１の初回のパイロット噴射を２回に分割して噴射時期をＩＴ１、ＩＴ２とし、３回目のパイロット噴射の噴射時期をＩＴ４としたものである。分割された各パイロット噴射量Ｑ５はＱ３の半分に設定され、３回目のパイロット噴射量はＱ４に設定される。 In case 2 as reference example 2, the first pilot injection in case 1 is divided into two, the injection timing is IT1, IT2, and the injection timing of the third pilot injection is IT4. Each divided pilot injection amount Q5 is set to half of Q3, and the third pilot injection amount is set to Q4.
　参考例３としてのケース３では、初回のパイロット噴射をＩＴ１で行い、２回目のパイロット噴射をＩＴ３で行う。また、メイン噴射量をＱ１からＱ２へと減少させ、その減少分の燃料（Ｑ１－Ｑ２）を初回のパイロット噴射量に加算している。したがって、初回のパイロット噴射量は、Ｑ３に（Ｑ１－Ｑ２）を加算したＱ６に設定される。２回目のパイロット噴射量はＱ４に設定される。 In Case 3 as Reference Example 3, the first pilot injection is performed by IT1, and the second pilot injection is performed by IT3. Further, the main injection amount is decreased from Q1 to Q2, and the reduced amount of fuel (Q1-Q2) is added to the initial pilot injection amount. Accordingly, the initial pilot injection amount is set to Q6 obtained by adding (Q1-Q2) to Q3. The second pilot injection amount is set to Q4.
　本実施形態としてのケース４では、初回のパイロット噴射をＩＴ１で行い、２回目のパイロット噴射をＩＴ２で行い、三回目のパイロット噴射をＩＴ４で行う。初回のパイロット噴射量はＱ４であり、２回目及び３回目のパイロット噴射量はＱ５（＝Ｑ３の半分）である。これにより、初回のパイロット噴射量Ｑ４が総パイロット噴射量Ｑｐｉｔｏｔａｌに占める比率は、２回目のパイロット噴射量Ｑ５及び３回目のパイロット噴射量Ｑ５の和が総パイロット噴射量Ｑｐｉｔｏｔａｌに占める比率よりも大きく設定される。以下、初回のパイロット噴射量が総パイロット噴射量に占める比率を初回パイロット噴射量比率といい、２回目及び３回目の各パイロット噴射量の和が総パイロット噴射量に占める比率を残りパイロット噴射量比率という。 In Case 4 as the present embodiment, the first pilot injection is performed by IT1, the second pilot injection is performed by IT2, and the third pilot injection is performed by IT4. The initial pilot injection amount is Q4, and the second and third pilot injection amounts are Q5 (= half Q3). As a result, the ratio of the initial pilot injection amount Q4 to the total pilot injection amount Qpital is set to be larger than the ratio of the sum of the second pilot injection amount Q5 and the third pilot injection amount Q5 to the total pilot injection amount Qpital. Is done. Hereinafter, the ratio of the initial pilot injection amount to the total pilot injection amount is referred to as the initial pilot injection amount ratio, and the ratio of the sum of the second and third pilot injection amounts to the total pilot injection amount is the remaining pilot injection amount ratio. That's it.
　なお、ケース４では、初回のパイロット噴射の噴射量Ｑ４はメイン噴射の噴射量Ｑ１よりも小さく設定されており、２回目及び３回目のパイロット噴射の噴射量Ｑ５は初回のパイロット噴射の噴射量Ｑ４よりも小さく設定されている。 In case 4, the injection quantity Q4 of the first pilot injection is set smaller than the injection quantity Q1 of the main injection, and the injection quantity Q5 of the second and third pilot injections is the injection quantity Q4 of the first pilot injection. Is set smaller than.
　上記４つのケースについて実機での実験を行うことにより、グロープラグ３１への通電時かつ低外気温条件での冷間始動時における図４及び図５に示す特性を得た。また、４つのケースについてシミュレーションを行うことにより、グロープラグ３１への通電時かつ低外気温条件での冷間始動時における図６Ａ及び図６Ｂの特性を得た。 The experiments shown in FIGS. 4 and 5 were performed when the glow plug 31 was energized and during a cold start under a low outside air temperature condition by conducting experiments with the above four cases. Further, by performing simulations for the four cases, the characteristics shown in FIGS. 6A and 6B were obtained when the glow plug 31 was energized and during cold start under a low outside air temperature condition.
　図４は、本発明者らが初めて見い出した特性である。図４の横軸は、多段階のパイロット噴射全体による熱発生量をクランク角で微分した値ｄＱｐｉｌｏｔ／ｄθ［Ｊ／ｄｅｇ］を示す。図４の縦軸は、多段階のパイロット噴射及びメイン噴射による１サイクルの燃焼により得られる図示平均有効圧Ｐｉ［ＭＰａ］を示す。ここで、１サイクルとは、１つの気筒における吸気行程、圧縮行程、爆発行程、排気行程の４行程分の期間を意味する。 FIG. 4 shows the characteristics found by the present inventors for the first time. The horizontal axis of FIG. 4 shows a value dQpilot / dθ [J / deg] obtained by differentiating the amount of heat generated by the entire multistage pilot injection with respect to the crank angle. The vertical axis in FIG. 4 represents the indicated mean effective pressure Pi [MPa] obtained by one-cycle combustion by multistage pilot injection and main injection. Here, one cycle means a period of four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke in one cylinder.
　パイロット噴射全体による熱発生量Ｑｐｉｌｏｔの計算の仕方について、図７を参照して説明する。図７の横軸はクランク角［ｄｅｇ］を示し、図７の縦軸は１サイクル中における燃焼室での熱発生率［Ｊ／ｄｅｇ］を示す。 A method of calculating the heat generation amount Qpilot by the entire pilot injection will be described with reference to FIG. The horizontal axis in FIG. 7 represents the crank angle [deg], and the vertical axis in FIG. 7 represents the heat generation rate [J / deg] in the combustion chamber during one cycle.
　図７に示すように、パイロット噴射を実行する場合には、複数回のパイロット噴射全体にる熱発生で熱発生率は低ピークＰ１（１山目）を有する波形となり、その後のメイン噴射による熱発生で熱発生率は高ピークＰ２（２山目）を有する波形となる。このように熱発生率の波形は２つのピークを有する波形となり、１山目の面積（図７のハッチング部の面積）を計算することで、パイロット噴射全体による熱発生量Ｑｐｉｌｏｔ［Ｊ］が得られる。 As shown in FIG. 7, when pilot injection is performed, the heat generation rate becomes a waveform having a low peak P1 (first peak) due to heat generation in a plurality of pilot injections, and the heat generated by the main injection thereafter. The generation rate of heat becomes a waveform having a high peak P2 (second peak). Thus, the heat generation rate waveform becomes a waveform having two peaks, and the heat generation amount Qpilot [J] by the entire pilot injection is obtained by calculating the area of the first mountain (the area of the hatched portion in FIG. 7). It is done.
　このように得られたパイロット噴射全体による熱発生量Ｑｐｉｌｏｔ［Ｊ］を複数回のパイロット噴射によって熱発生が生じたクランク角区間［ｄｅｇ］で除算することで、ｄＱｐｉｌｏｔ／ｄθ［Ｊ／ｄｅｇ］を算出することができる。 By dividing the heat generation amount Qpilot [J] obtained in this way by the pilot injection as a whole by the crank angle section [deg] in which heat generation is caused by a plurality of pilot injections, dQpilot / dθ [J / deg] is obtained. Can be calculated.
　図７では、圧縮上死点ＴＤＣで熱発生の低ピークＰ１が生じているが、これは実機実験に使用したディーゼルエンジンがたまたま圧縮上死点ＴＤＣで熱発生のピークが生じるエンジンであったからである。したがって、本発明は、このようなエンジンにのみ適用されるのではなく、圧縮上死点ＴＤＣよりも前や後ろで低ピークＰ１が生じるディーゼルエンジンにも適用可能である。 In FIG. 7, the low peak P1 of heat generation occurs at the compression top dead center TDC because the diesel engine used in the actual machine experiment happens to have a peak of heat generation at the compression top dead center TDC. is there. Therefore, the present invention can be applied not only to such an engine but also to a diesel engine in which a low peak P1 occurs before or after the compression top dead center TDC.
　図４に戻り、実機実験により得られた図示平均有効圧特性について説明する。 Returning to FIG. 4, the illustrated mean effective pressure characteristics obtained by actual machine experiments will be described.
　図４に示すように、ｄＱｐｉｌｏｔ／ｄθが大きくなるほど、図示平均有効圧ＰｉはＡからＢへと増加する。ｄＱｐｉｌｏｔ／ｄθが所定値Ｄ以上の領域（Ｂ～Ｃの範囲）では、図示平均有効圧Ｐｉはほぼ一定値となる。ここで、図３に示したケース１～３におけるｄＱｐｉｌｏｔ／ｄθはＤ未満の領域に含まれ、ケース４におけるｄＱｐｉｌｏｔ／ｄθはＤ以上の領域に含まれることが判明した。 As shown in FIG. 4, the indicated mean effective pressure Pi increases from A to B as dQpilot / dθ increases. In a region where dQpilot / dθ is equal to or greater than a predetermined value D (range from B to C), the indicated mean effective pressure Pi has a substantially constant value. Here, it is found that dQpilot / dθ in cases 1 to 3 shown in FIG. 3 is included in a region less than D, and dQpilot / dθ in case 4 is included in a region greater than D.
　図４において、ｄＱｐｉｌｏｔ／ｄθが所定値Ｄ未満の領域は、ｄＱｐｉｌｏｔ／ｄθの値が大きいほど、多段階のパイロット噴射全体による発熱量が大きくなり、この影響を受けて図示平均有効圧Ｐｉが上昇することを示している。一方、ｄＱｐｉｌｏｔ／ｄθが所定値Ｄ以上の領域は、図示平均有効圧Ｐｉが所定値Ｄでの値より大きくならず平衡値となることを示している。 In FIG. 4, in the region where dQpilot / dθ is less than the predetermined value D, the larger the value of dQpilot / dθ, the greater the amount of heat generated by the multistage pilot injection, and the average effective pressure Pi shown in the figure increases as a result. It shows that On the other hand, the region where dQpilot / dθ is equal to or greater than the predetermined value D indicates that the indicated mean effective pressure Pi does not become larger than the value at the predetermined value D and becomes an equilibrium value.
　つまり、ｄＱｐｉｌｏｔ／ｄθが所定値Ｄ以上の領域にある場合には、グロープラグ３１の近傍に形成される火種が順調に成長しており、燃焼室内での混合気の燃焼が安定している。この逆に、ｄＱｐｉｌｏｔ／ｄθが所定値Ｄ未満の領域にある場合には、多段階のパイロット噴射を実行しても発熱の程度が小さく、グロープラグ３１の近傍に火種が形成されていないか、又は火種が形成されていても順調に成長しておらず、失火が生じる可能性がある。したがって、グロープラグ３１への通電時かつ低外気温条件での冷間始動時における燃焼性を改善するためには、ｄＱｐｉｌｏｔ／ｄθが所定値Ｄ以上となるように、パイロット噴射の回数及び各パイロット噴射量を決定すればよいこととなる。 That is, when dQpilot / dθ is in the region of the predetermined value D or more, the fire types formed in the vicinity of the glow plug 31 are growing smoothly, and the combustion of the air-fuel mixture in the combustion chamber is stable. On the other hand, if dQpilot / dθ is in the region less than the predetermined value D, the degree of heat generation is small even if the multi-stage pilot injection is executed, and fire is not formed in the vicinity of the glow plug 31. Or, even if a fire type is formed, it does not grow smoothly and misfire may occur. Therefore, in order to improve the combustibility when the glow plug 31 is energized and during cold start under a low outside air temperature condition, the number of pilot injections and each pilot are set so that dQpilot / dθ is equal to or greater than a predetermined value D. It is only necessary to determine the injection amount.
　なお、図４に示した図示平均有効圧の傾向はエンジン仕様によって変化しないが、Ｂ～Ｃの期間における図示平均有効圧Ｐｉの値及び所定値Ｄの値はエンジン仕様によって変化する。したがって、エンジン仕様毎に図４に示すような特性を得て、その特性に基づいて所定値Ｄは定められる。 The trend of the indicated mean effective pressure shown in FIG. 4 does not change depending on the engine specification, but the indicated mean effective pressure Pi value and the predetermined value D in the period B to C change depending on the engine specification. Therefore, a characteristic as shown in FIG. 4 is obtained for each engine specification, and the predetermined value D is determined based on the characteristic.
　次に、図５は、ケース１～４における図示平均有効圧Ｐｉ及び図示平均有効圧の変動率（Ｐｉ変動率）を示す図である。図示平均有効圧Ｐｉは棒グラフで表わされており、Ｐｉ変動率は折れ線で表わされている。 Next, FIG. 5 is a diagram showing the indicated mean effective pressure Pi and the indicated mean effective pressure fluctuation rate (Pi fluctuation rate) in cases 1 to 4. The indicated mean effective pressure Pi is represented by a bar graph, and the Pi variation rate is represented by a broken line.
　図５に示すように、ケース２における図示平均有効圧はケース１及びケース３の図示平均有効圧よりも高くなっているものの、これらケース１～３の図示平均有効圧はケース４の図示平均有効圧よりも低くなっている。これは、図４を参照して説明した通りである。これに対して、Ｐｉ変動率は、ケース１、ケース２、ケース３の順に大きくなり、ケース４が最も小さくなっている。燃焼室内の燃焼が安定している場合には、Ｐｉ変動率は小さくなる。 As shown in FIG. 5, the indicated mean effective pressure in case 2 is higher than the indicated mean effective pressure in cases 1 and 3, but the indicated mean effective pressure in cases 1 to 3 is the indicated mean effective pressure in case 4. It is lower than the pressure. This is as described with reference to FIG. On the other hand, the Pi fluctuation rate increases in the order of Case 1, Case 2, and Case 3, and Case 4 has the smallest. When the combustion in the combustion chamber is stable, the Pi fluctuation rate is small.
　次に、図６Ａ及び図６Ｂを参照して、ケース１～４における平均グロープラグ近傍温度及び平均グロープラグ近傍当量比を説明する。図６Ａは、ケース１～４における平均グロープラグ近傍温度を示す図である。図６Ｂは、ケース１～４における平均グロープラグ近傍当量比を示す図である。 Next, the average glow plug vicinity temperature and the average glow plug vicinity equivalent ratio in cases 1 to 4 will be described with reference to FIGS. 6A and 6B. FIG. 6A is a diagram showing an average glow plug vicinity temperature in cases 1 to 4. FIG. FIG. 6B is a diagram showing an average glow plug vicinity equivalent ratio in cases 1 to 4.
　ここで、グロープラグ近傍温度とは、燃焼室内においてグロープラグ３１の近傍の温度をシミュレーションによって算出した値である。また、当量比は空燃比の逆数を理論空燃比の逆数で除した値であり、当量比１．０が理論空燃比に相当する。グロープラグ近傍当量比は、グロープラグ３１の近傍の局所的な当量比であり、燃焼室全体の平均的な当量比ではない。グロープラグ近傍当量比は、グロープラグ３１の近傍の当量比をシミュレーションによって算出した値である。グロープラグ近傍当量比が１．０より大きい場合にはグロープラグ３１の近傍の混合気はリッチとなり、グロープラグ近傍当量比が１．０より小さい場合にはグロープラグ３１の近傍の混合気はリーンとなる。 Here, the temperature near the glow plug is a value calculated by simulation of the temperature near the glow plug 31 in the combustion chamber. The equivalent ratio is a value obtained by dividing the reciprocal of the air-fuel ratio by the reciprocal of the stoichiometric air-fuel ratio, and the equivalence ratio of 1.0 corresponds to the stoichiometric air-fuel ratio. The glow plug vicinity equivalent ratio is a local equivalent ratio in the vicinity of the glow plug 31, and is not an average equivalent ratio of the entire combustion chamber. The glow plug vicinity equivalent ratio is a value calculated by simulation of the equivalent ratio in the vicinity of the glow plug 31. When the glow plug vicinity equivalence ratio is larger than 1.0, the air-fuel mixture near the glow plug 31 becomes rich, and when the glow plug vicinity equivalence ratio is smaller than 1.0, the air-fuel mixture near the glow plug 31 becomes lean. It becomes.
　図６Ａ及び図６Ｂに示すように、ケース１の場合よりケース２の場合の方が、平均グロープラグ近傍温度が高く、かつ平均グロープラグ近傍当量比も大きくなっている。ところが、ケース３の場合は、ケース２の場合と比較して、平均グロープラグ近傍当量比は大きくなるものの、平均グロープラグ近傍温度は低下している。この現象は、ケース３ではメイン噴射量を低下させる代わりに初回のパイロット噴射量を増加させていることに起因している。したがって、ケース３では、初回のパイロット噴射によってグロープラグ３１の近傍に一度に到達する燃料が多く、グロープラグ３１が冷却され、失火が生じやすい状態になっている。 As shown in FIGS. 6A and 6B, the case 2 has a higher average glow plug temperature and a higher average glow plug equivalent ratio in the case 2 than in the case 1. However, in the case 3, compared with the case 2, the average glow plug vicinity equivalent ratio is increased, but the average glow plug vicinity temperature is lowered. This phenomenon is caused by increasing the initial pilot injection amount in case 3 instead of decreasing the main injection amount. Therefore, in case 3, the amount of fuel that reaches the vicinity of the glow plug 31 at a time by the first pilot injection is large, and the glow plug 31 is cooled, and misfire is likely to occur.
　一方、ケース４の場合には、ケース１～３のいずれの場合よりも、平均グロープラグ近傍温度が高く、かつ平均グロープラグ近傍当量比が大きくなっている。このようにケース４の場合は、燃焼室内の混合気が安定的に燃焼する状態となっている。 On the other hand, in case 4, the average glow plug vicinity temperature is higher and the average glow plug vicinity equivalent ratio is higher than in any of cases 1 to 3. As described above, in the case 4, the air-fuel mixture in the combustion chamber is in a state of stably burning.
　次に、図８を参照して、初回パイロット噴射量比率の特性について説明する。図８は、冷却水温と初回パイロット噴射量比率との関係を示す特性図である。初回パイロット噴射量比率は、初回のパイロット噴射の噴射量を決定するために用いられる値である。 Next, the characteristics of the initial pilot injection amount ratio will be described with reference to FIG. FIG. 8 is a characteristic diagram showing the relationship between the cooling water temperature and the initial pilot injection amount ratio. The initial pilot injection amount ratio is a value used to determine the injection amount of the initial pilot injection.
　図８に示すように、初回パイロット噴射量比率は、零下の領域において冷却水温Ｔｗ［℃］が低くなるほど大きく設定される。冷却水温が０℃では初回パイロット噴射量比率は約３５％に設定され、冷却水温が－３０℃では初回パイロット噴射量比率は約８０％に設定される。このように冷却水温Ｔｗが低くなるほど初回パイロット噴射量比率を大きくするのは、－３０℃といった極低温の温度域においても、噴射された燃料がグロープラグ３１に接触する確率を向上させるためである。図８の特性はエンジン仕様によってほとんど変化することがなく、初回パイロット噴射量比率はエンジン仕様によらず３５％から８０％の間の値に設定される。 As shown in FIG. 8, the initial pilot injection amount ratio is set to increase as the cooling water temperature Tw [° C.] decreases in the region below zero. When the cooling water temperature is 0 ° C., the initial pilot injection amount ratio is set to about 35%, and when the cooling water temperature is −30 ° C., the initial pilot injection amount ratio is set to about 80%. The reason why the initial pilot injection amount ratio is increased as the cooling water temperature Tw becomes lower is to improve the probability that the injected fuel contacts the glow plug 31 even in an extremely low temperature range of −30 ° C. . The characteristics shown in FIG. 8 hardly change depending on the engine specifications, and the initial pilot injection amount ratio is set to a value between 35% and 80% regardless of the engine specifications.
　図８の横軸は、冷却水温Ｔｗの代わりに、外気温や、ディーゼルエンジン１の潤滑に使用される油の温度であってもよい。本実施形態はグロープラグ３１への通電時かつ低外気温条件での冷間始動時を対象とするので、このような状態では冷却水温、油温、及び外気温を同一視することができる。 The horizontal axis in FIG. 8 may be the outside air temperature or the temperature of oil used for lubricating the diesel engine 1 instead of the cooling water temperature Tw. Since the present embodiment is intended for the cold start at the time of energizing the glow plug 31 and the low outside air temperature condition, the cooling water temperature, the oil temperature, and the outside air temperature can be equated in such a state.
　次に、図９を参照して、コントローラ２１が実行する燃料噴射制御処理について説明する。 Next, the fuel injection control process executed by the controller 21 will be described with reference to FIG.
　図９は、コントローラ２１が実行する燃料噴射制御処理のルーチンを示すフローチャートである。燃料噴射制御処理は、メイン噴射量及び３回の各パイロット噴射量を算出して出力するための処理である。燃料噴射制御処理は、今回の燃料噴射時における初回のパイロット噴射時期よりも所定クランク角前のタイミングで一回実行される。 FIG. 9 is a flowchart showing a routine of the fuel injection control process executed by the controller 21. The fuel injection control process is a process for calculating and outputting the main injection amount and each of the three pilot injection amounts. The fuel injection control process is executed once at a timing before a predetermined crank angle from the initial pilot injection timing at the time of the current fuel injection.
　Ｓ１（ステップ１）では、コントローラ２１は、メイン噴射量Ｑｍａｉｎ［ｍｍ3／ｓｔ．］を算出する。 In S1 (step 1), the controller 21 determines that the main injection amount Qmain [mm3 / st. ] Is calculated.
　例えばアイドル運転状態であれば目標アイドル回転速度が予め定めており、この目標アイドル回転速度が得られるようにメイン噴射量Ｑｍａｉｎが予め定められている。したがって、コントローラ２１は、予め定められているメイン噴射量Ｑｍａｉｎを読み出す。メイン噴射量Ｑｍａｉｎは一定値であり、メイン噴射量Ｑｍａｉｎで目標アイドル回転速度が得られない場合には、フィードバック制御することで、目標アイドル回転速度が得られるようにメイン噴射量Ｑｍａｉｎが調整される。 For example, in the idling operation state, the target idle rotation speed is determined in advance, and the main injection amount Qmain is determined in advance so as to obtain this target idle rotation speed. Therefore, the controller 21 reads a predetermined main injection amount Qmain. The main injection amount Qmain is a constant value, and when the target idle rotation speed cannot be obtained with the main injection amount Qmain, the main injection amount Qmain is adjusted by feedback control to obtain the target idle rotation speed. .
　Ｓ２～５では、コントローラ２１は、以下の条件〔１〕～〔４〕が全て成立するか否かを判定し、全て成立する場合にＳ６の処理を実行する。一方、条件〔１〕～〔４〕のいずれかかが成立しない場合には、コントローラ２１は、Ｓ１３の処理を実行してメイン噴射量Ｑｍａｉｎをレジスタに出力する。なお、Ｓ１３において、メイン噴射量Ｑｍａｉｎをメモリに保存してもよい。このように条件〔１〕～〔４〕のいずれかかが成立しない場合には、パイロット噴射は実行されず、メイン噴射だけが実行されることとなる。 In S2 to 5, the controller 21 determines whether or not all of the following conditions [1] to [4] are satisfied, and executes the process of S6 when all are satisfied. On the other hand, if any of the conditions [1] to [4] is not satisfied, the controller 21 executes the process of S13 and outputs the main injection amount Qmain to the register. In S13, the main injection amount Qmain may be stored in the memory. As described above, when any one of the conditions [1] to [4] is not satisfied, the pilot injection is not executed and only the main injection is executed.
　〔１〕グロープラグ３１への通電中であること。 [1] The glow plug 31 is being energized.
　〔２〕外気温Ｔａが０℃以下であること。 [2] The outside temperature Ta is 0 ° C or lower.
　〔３〕アイドル運転状態であること。 [3] Must be in idle operation.
　〔４〕冷却水温Ｔｗが所定値未満であること。 [4] The cooling water temperature Tw is less than a predetermined value.
　グロープラグ３１に通電する期間は、エンジン冷間始動時から例えば数十秒といった短い期間である。上記〔１〕を条件とするのは、低圧縮化したディーゼルエンジン１での極低温時にグロープラグ３１の燃料着火源としての機能を有効活用するためである。 The period during which the glow plug 31 is energized is a short period of, for example, several tens of seconds after the engine cold start. The above condition [1] is used in order to effectively utilize the function of the glow plug 31 as a fuel ignition source at an extremely low temperature in the low-compressed diesel engine 1.
　上記〔２〕を条件とするのは、外気温Ｔａが０℃以下である低外気温条件で、燃焼が不安定となるからである。外気温Ｔａは、外気温センサ３２（図１参照）によって検出される。 [2] The condition is that the combustion becomes unstable under the low outside air temperature condition where the outside air temperature Ta is 0 ° C. or less. The outside air temperature Ta is detected by the outside air temperature sensor 32 (see FIG. 1).
　上記〔３〕を条件とするのは、アイドル運転状態で最も燃焼が不安定となるためである。コントローラ２１は、例えばアクセル開度がゼロの場合に、アイドル運転状態であると判定する。 [3] The condition is that combustion is most unstable in the idle operation state. For example, when the accelerator opening is zero, the controller 21 determines that the engine is in an idle operation state.
　上記〔４〕を条件とするのは、冷却水温Ｔｗが所定値未満であるエンジン冷間時に燃焼が不安定となるためである。冷却水温Ｔｗは、水温センサ３３（図１参照）によって検出される。なお、条件〔３〕及び条件〔４〕については必要に応じて省略してもよい。 [4] The condition is that the combustion becomes unstable when the engine is cold when the coolant temperature Tw is less than a predetermined value. The cooling water temperature Tw is detected by a water temperature sensor 33 (see FIG. 1). The conditions [3] and [4] may be omitted as necessary.
　Ｓ６では、コントローラ２１は、総パイロット噴射量Ｑｐｉｔｏｔａｌ［ｍｍ3／ｓｔ．］を算出する。総パイロット噴射量Ｑｐｉｔｏｔａｌは、エンジン負荷とエンジン回転速度から総パイロット噴射量マップを検索することにより算出される。グロープラグ３１への通電時かつ低外気温条件での冷間始動時には、総パイロット噴射量Ｑｐｉｔｏｔａｌはメイン噴射量Ｑｍａｉｎより多くなることがある。 In S6, the controller 21 determines that the total pilot injection amount Qpital [mm3 / st. ] Is calculated. The total pilot injection amount Qpitotal is calculated by searching a total pilot injection amount map from the engine load and the engine speed. When the glow plug 31 is energized and during cold start under a low outside air temperature condition, the total pilot injection amount Qpital may be larger than the main injection amount Qmain.
　Ｓ７では、コントローラ２１は、冷却水温Ｔｗから図８に示したテーブルを検索することにより、初回パイロット噴射量比率を算出する。図８に示したように、初回パイロット噴射量比率は冷却水温Ｔｗが低くなるほど大きく設定される。これは、極低温になるほど燃料噴霧が気化しにくくなり、その分多く燃料を噴射することで燃料噴霧がグロープラグ３１に接触する確率を高める必要があるためである。 In S7, the controller 21 calculates the initial pilot injection amount ratio by searching the table shown in FIG. 8 from the coolant temperature Tw. As shown in FIG. 8, the initial pilot injection amount ratio is set to be larger as the cooling water temperature Tw is lower. This is because the fuel spray is less likely to vaporize as the temperature becomes extremely low, and it is necessary to increase the probability that the fuel spray contacts the glow plug 31 by injecting more fuel.
　本実施形態では、Ｓ３で外気温Ｔａを用い、Ｓ５及びＳ７で冷却水温Ｔｗを用いているが、これに限られるものでない。例えば、Ｓ５及びＳ７では、冷却水温Ｔｗに代えて、油温を用いてもよい。また、Ｓ７のみで、冷却水温Ｔｗに代えて、油温を用いてもよい。さらに、Ｓ７では冷却水温Ｔｗに代えて外気温Ｔａを用いてもよく、この場合にはＳ３の処理を省略することができる。 In this embodiment, the outside air temperature Ta is used in S3, and the cooling water temperature Tw is used in S5 and S7. However, the present invention is not limited to this. For example, in S5 and S7, the oil temperature may be used instead of the cooling water temperature Tw. Further, only in S7, the oil temperature may be used instead of the cooling water temperature Tw. Further, in S7, the outside air temperature Ta may be used instead of the cooling water temperature Tw, and in this case, the process of S3 can be omitted.
　Ｓ８では、コントローラ２１は、失火が発生する程度までエンジン回転の角速度が低下しているか否かを判定する。 In S8, the controller 21 determines whether or not the angular speed of the engine rotation has decreased to the extent that misfire occurs.
　例えば４気筒直列エンジンではクランク角で１８０度毎に燃料噴射時期が訪れるので、コントローラ２１は１８０度間隔でエンジン回転の角速度を算出する。クランク角センサ２３（角速度検出部）により検出されるエンジン回転速度Ｎｅは単位がｒｐｍであるので、これを６０で除算すると、分母を秒とする回転速度Ｖ［回／ｓ］が得られる。前々サイクルに得た回転速度Ｖから前サイクルに得た回転速度Ｖを差し引いた回転速度差ΔＶに（３６０／所定時間）［ｄｅｇ／（回・ｓ）］を乗ずれば、エンジン回転の角速度ωを時間で微分した角加速度α［ｄｅｇ／ｓ2］が得られる。 For example, in a four-cylinder in-line engine, the fuel injection timing comes every 180 degrees in crank angle, so the controller 21 calculates the angular speed of engine rotation at intervals of 180 degrees. Since the engine rotational speed Ne detected by the crank angle sensor 23 (angular speed detector) is in units of rpm, dividing this by 60 gives a rotational speed V [times / s] with the denominator as seconds. If the rotational speed difference ΔV obtained by subtracting the rotational speed V obtained in the previous cycle from the rotational speed V obtained in the cycle before the previous cycle is multiplied by (360 / predetermined time) [deg / (times · s)], the angular speed of the engine rotation An angular acceleration α [deg / s 2] obtained by differentiating ω with respect to time is obtained.
　燃焼が良好であるか、あるいは失火が生じているかは、エンジン回転の角速度ωに現れる。失火が生じているときには、エンジン回転の角速度ωが低下する。エンジン回転の角速度ωが低下するときには、エンジン回転の角加速度αはマイナスとなるので、絶対値で扱えばよい。コントローラ２１は、角加速度αの絶対値が閾値以上となっている場合に、エンジン回転の角速度ωが低下していると判断し、Ｓ９の処理を実行する。 Whether combustion is good or misfiring occurs in the angular speed ω of the engine rotation. When misfire occurs, the angular speed ω of the engine rotation decreases. When the angular velocity ω of the engine rotation decreases, the angular acceleration α of the engine rotation becomes negative, so it can be handled with an absolute value. When the absolute value of the angular acceleration α is equal to or greater than the threshold, the controller 21 determines that the angular speed ω of the engine rotation is decreasing, and executes the process of S9.
　なお、コントローラ２１は、クランク角センサ２３により検出されるエンジン回転速度に基づいて算出されるエンジン回転の角速度ωが失火判定用閾値よりも低下した場合に、エンジン回転の角速度ωが低下したと判定してもよい。 The controller 21 determines that the angular speed ω of the engine rotation has decreased when the angular speed ω of the engine rotation calculated based on the engine rotational speed detected by the crank angle sensor 23 has decreased below the misfire determination threshold value. May be.
　Ｓ９では、コントローラ２１は、Ｓ７で算出された初回パイロット噴射量比率に一定値である減少割合を乗算し、改めて初回パイロット噴射量比率を算出する。減少割合は、予め適合された値である。 In S9, the controller 21 multiplies the initial pilot injection amount ratio calculated in S7 by a constant decrease rate, and calculates the initial pilot injection amount ratio again. The decreasing rate is a value that is adapted in advance.
　エンジン回転の角速度ωが低下し、失火が生じている場合には、ディーゼルエンジン１のシリンダ内に燃焼していない燃料が残留する。シリンダ内に残留する燃料は加熱されているので、着火性が高くなっている。したがって、今サイクルの燃料噴射時における初回のパイロット噴射時には、前サイクルの燃料噴射時における初回のパイロット噴射量より少ない燃料を供給すればよい。そのため、Ｓ９において、今回の初回パイロット噴射量比率を減少させる。上記したＳ８及びＳ９の処理を実行することで、エンジン回転の角速度ωが低下している場合であっても良好な燃焼状態を得ることが可能となる。 When the angular speed ω of the engine rotation is reduced and misfire occurs, unburned fuel remains in the cylinder of the diesel engine 1. Since the fuel remaining in the cylinder is heated, the ignitability is high. Therefore, at the time of the first pilot injection at the time of fuel injection in the current cycle, it is only necessary to supply less fuel than the amount of the first pilot injection at the time of fuel injection in the previous cycle. Therefore, in S9, the current initial pilot injection amount ratio is decreased. By executing the processes of S8 and S9 described above, it is possible to obtain a good combustion state even when the angular speed ω of engine rotation is reduced.
　一方、Ｓ８においてエンジン回転の角速度ωが低下していないと判定された場合には、コントローラ２１は、失火が生じていないと判断してＳ１０の処理を実行する。 On the other hand, if it is determined in S8 that the angular speed ω of the engine rotation has not decreased, the controller 21 determines that no misfire has occurred and executes the process of S10.
　Ｓ１０では、コントローラ２１は、Ｓ７で算出された初回パイロット噴射量比率又はＳ９で減量された初回パイロット噴射量比率を用いて、次式により初回パイロット噴射量Ｑｐｉ１［ｍｍ3／ｓｔ．］を算出する。初回パイロット噴射量Ｑｐｉ１は、Ｓ１で算出されたメイン噴射量Ｑｍａｉｎを超えないように設定される。 In S10, the controller 21 uses the initial pilot injection amount ratio calculated in S7 or the initial pilot injection amount ratio reduced in S9 to calculate the initial pilot injection amount Qpi1 [mm 3 / st. ] Is calculated. The initial pilot injection amount Qpi1 is set so as not to exceed the main injection amount Qmain calculated in S1.
Figure JPOXMLDOC01-appb-M000001
 　　
Figure JPOXMLDOC01-appb-M000001
 　　
　Ｓ１１では、コントローラ２１は、Ｓ６で算出されたＱｐｉｔｏｔａｌ及びＳ１０で算出されたＱｐｉ１を用いて、次式により２回目のパイロット噴射量Ｑｐｉ２［ｍｍ3／ｓｔ．］、３回目のパイロット噴射量Ｑｐｉ３［ｍｍ3／ｓｔ．］を算出する。２回目及び３回目のパイロット噴射量Ｑｐｉ２、Ｑｐｉ３は、初回パイロット噴射量Ｑｐｉ１よりも小さく設定される。 In S11, the controller 21 uses the Qpital calculated in S6 and the Qpi1 calculated in S10 to calculate the second pilot injection amount Qpi2 [mm3 / st. ] The third pilot injection amount Qpi3 [mm3 / st. ] Is calculated. The second and third pilot injection amounts Qpi2, Qpi3 are set smaller than the initial pilot injection amount Qpi1.
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
　上記のように算出される初回パイロット噴射量Ｑｐｉ１、２回目パイロット噴射量Ｑｐｉ２、及び３回目パイロット噴射量Ｑｐｉ３は、グロープラグ３１への通電時かつ低外気温条件での冷間始動時において、多段階のパイロット噴射全体による熱発生量をクランク角で微分した値が図４の所定値Ｄ以上となるように適合された値となっている。 The initial pilot injection amount Qpi1, the second pilot injection amount Qpi2, and the third pilot injection amount Qpi3 calculated as described above are large when the glow plug 31 is energized and during cold start under a low outside air temperature condition. The value obtained by differentiating the amount of heat generated by the entire pilot injection at the stage with respect to the crank angle is a value adapted to be equal to or greater than the predetermined value D in FIG.
　Ｓ１２では、コントローラ２１は、メイン噴射量Ｑｍａｉｎ、初回パイロット噴射量Ｑｐｉ１、２回目パイロット噴射量Ｑｐｉ２、及び３回目パイロット噴射量Ｑｐｉ３をレジスタに出力する。なお、Ｓ１２において、各噴射量をメモリに保存してもよい。 In S12, the controller 21 outputs the main injection amount Qmain, the initial pilot injection amount Qpi1, the second pilot injection amount Qpi2, and the third pilot injection amount Qpi3 to the register. In S12, each injection amount may be stored in the memory.
　初回のパイロット噴射、２回目のパイロット噴射、３回目のパイロット噴射、及びメイン噴射の各噴射時期は、図３のケース４に示すように予め定められた時期に設定されている。つまり、初回パイロット噴射の噴射時期は時期ＩＴ１に設定され、２回目パイロット噴射の噴射時期は時期ＩＴ２に設定され、３回目パイロット噴射の噴射時期は時期ＩＴ４に設定される。また、メイン噴射の噴射時期は時期ＩＴ５に設定される。 Each injection timing of the first pilot injection, the second pilot injection, the third pilot injection, and the main injection is set to a predetermined timing as shown in case 4 of FIG. That is, the injection timing of the first pilot injection is set to the timing IT1, the injection timing of the second pilot injection is set to the timing IT2, and the injection timing of the third pilot injection is set to the timing IT4. Further, the injection timing of the main injection is set to the timing IT5.
　コントローラ２１は、初回のパイロット噴射、２回目のパイロット噴射、３回目のパイロット噴射、及びメイン噴射の各噴射時期となった時に、燃料噴射弁９を開弁制御する。これにより、燃料噴射弁９は、Ｑｐｉ１、Ｑｐｉ２、Ｑｐｉ３、及びＱｍａｉｎの各噴射量の燃料を燃焼室に供給する。 The controller 21 controls to open the fuel injection valve 9 at the injection timings of the first pilot injection, the second pilot injection, the third pilot injection, and the main injection. Thereby, the fuel injection valve 9 supplies fuel of each injection amount of Qpi1, Qpi2, Qpi3, and Qmain to the combustion chamber.
　ここで、本実施形態によるディーゼルエンジン１の制御装置の作用効果について説明する。 Here, the effect of the control device for the diesel engine 1 according to the present embodiment will be described.
　本実施形態によるディーゼルエンジン１の制御装置は、冷間始動時に燃焼室を加熱するグロープラグ３１と、メイン噴射に先立つパイロット噴射を多段階で実行可能なコモンレール式燃料噴射装置６と、コモンレール式燃料噴射装置６を制御するコントローラ２１と、を備える。コントローラ２１は、グロープラグ３１への通電時かつ低外気温条件での冷間始動時において、多段階のパイロット噴射全体による熱発生量をクランク角で微分した値（ｄＱｐｉｌｏｔ／ｄθ）が予め定められた所定値Ｄ以上となるように、パイロット噴射の回数及び各パイロット噴射の噴射量を決定する。 The control device for the diesel engine 1 according to the present embodiment includes a glow plug 31 that heats the combustion chamber during cold start, a common rail fuel injection device 6 that can execute pilot injection prior to main injection in multiple stages, and a common rail fuel. And a controller 21 for controlling the injection device 6. The controller 21 predetermines a value (dQpilot / dθ) obtained by differentiating the amount of heat generated by the entire multistage pilot injection with the crank angle when the glow plug 31 is energized and during cold start under a low outside air temperature condition. The number of pilot injections and the injection amount of each pilot injection are determined so as to be equal to or greater than the predetermined value D.
　より具体的には、コントローラ２１は、グロープラグ３１への通電時かつ外気温が０℃以下での冷間始動時に、パイロット噴射を２回以上の多段階で実行するようにコモンレール式燃料噴射装置６を制御する。そして、コントローラ２１は、初回のパイロット噴射の噴射量を、メイン噴射の噴射量を超えず、かつ各パイロット噴射の噴射量の和である総パイロット噴射量に対して３５％から８０％までの範囲内で設定する。この時、コントローラ２１は、初回以降に実行される残りのパイロット噴射の１回分の噴射量を、初回のパイロット噴射の噴射量よりも小さく設定する。なお、パイロット噴射の回数は、図３におけるケース４のように３回程度が好ましい。 More specifically, the controller 21 performs a common rail fuel injection device so as to execute pilot injection in two or more stages at the time of cold start when the glow plug 31 is energized and the outside air temperature is 0 ° C. or less. 6 is controlled. Then, the controller 21 sets the injection amount of the first pilot injection in a range from 35% to 80% with respect to the total pilot injection amount that does not exceed the injection amount of the main injection and is the sum of the injection amount of each pilot injection. Set in. At this time, the controller 21 sets the injection amount of one remaining pilot injection executed after the first time to be smaller than the injection amount of the first pilot injection. The number of pilot injections is preferably about 3 as in case 4 in FIG.
　上記のように設定された多段階のパイロット噴射を実行することで、着火時のグロープラグ３１の温度低下を防止しつつ、グロープラグ３１近傍の当量比を高く維持することが可能となる。その結果、低外気温条件での冷間始動時に、燃焼室での混合気の燃焼を安定させることができる。 By executing the multistage pilot injection set as described above, it is possible to maintain a high equivalent ratio in the vicinity of the glow plug 31 while preventing a temperature drop of the glow plug 31 at the time of ignition. As a result, combustion of the air-fuel mixture in the combustion chamber can be stabilized at the cold start under the low outside air temperature condition.
　本実施形態では、パイロット噴射を初回のパイロット噴射とこれに続く残りのパイロット噴射とで構成される２回以上の多段とし、初回パイロット噴射量比率を残りパイロット噴射量比率より大きく設定する。パイロット噴射の２回以上の多段化により燃料の気化を促進して、グロープラグ３１近傍の当量比を高めることができる。また、初回パイロット噴射量比率の増大及び残りパイロット噴射量比率の減少により、メイン噴射直前でのグロープラグ３１からの熱の吸収を低減し、グロープラグ３１の温度低下を抑制できる。これにより、グロープラグ３１近傍の当量比、グロープラグ３１の温度を高く保つことが可能となり、燃焼室での混合気の燃焼を安定させることができる。 In the present embodiment, the pilot injection is performed in multiple stages of two or more configured by the initial pilot injection and the remaining pilot injection following this, and the initial pilot injection amount ratio is set larger than the remaining pilot injection amount ratio. The vaporization of the fuel can be promoted by multistage pilot injection twice or more, and the equivalent ratio in the vicinity of the glow plug 31 can be increased. Further, by increasing the initial pilot injection amount ratio and decreasing the remaining pilot injection amount ratio, the absorption of heat from the glow plug 31 immediately before the main injection can be reduced, and the temperature drop of the glow plug 31 can be suppressed. As a result, the equivalence ratio in the vicinity of the glow plug 31 and the temperature of the glow plug 31 can be kept high, and combustion of the air-fuel mixture in the combustion chamber can be stabilized.
　本実施形態では、初回パイロット噴射量比率は、図８に示すように冷却水温Ｔｗが低下するほど大きく設定される。これにより、グロープラグ３１への通電時かつ低外気温条件での冷間始動時における冷却水温Ｔｗに応じた最適な燃料噴射制御を実行することができる。その結果、外気温等によらず、グロープラグ３１近傍の当量比及びグロープラグ３１の温度を高く保つことが可能となり、燃焼室内における燃焼をより安定させることができる。 In this embodiment, the initial pilot injection amount ratio is set to be larger as the cooling water temperature Tw is lowered as shown in FIG. Thereby, optimal fuel injection control according to the cooling water temperature Tw at the time of the cold start in the energization to the glow plug 31 and the low outside air temperature condition can be executed. As a result, the equivalence ratio in the vicinity of the glow plug 31 and the temperature of the glow plug 31 can be kept high regardless of the outside air temperature or the like, and combustion in the combustion chamber can be further stabilized.
　本実施形態では、クランク角センサ２３により検出されるエンジンの角速度ωが失火判定用閾値よりも低下している場合に、初回パイロット噴射量比率が小さくなるように補正する。これにより、グロープラグ３１への通電時かつ低外気温条件での冷間始動時に、失火によりエンジン回転の角速度が低下した場合であっても、良好な燃焼状態を得ることができる。 In this embodiment, when the engine angular velocity ω detected by the crank angle sensor 23 is lower than the misfire determination threshold, the initial pilot injection amount ratio is corrected to be small. As a result, a good combustion state can be obtained even when the angular speed of engine rotation is reduced due to misfire during energization of the glow plug 31 and during cold start under a low outside air temperature condition.
　以上、本発明の実施形態について説明したが、上記実施形態は本発明の適用例の一部を示したに過ぎず、本発明の技術的範囲を上記実施形態の具体的構成に限定する趣旨ではない。　 The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent. *
　本実施形態では、図３のケース４に示すようにパイロット噴射の回数は３回であるが、パイロット噴射の回数は２回以上であればよい。また、本実施形態では、２回目のパイロット噴射量と３回目のパイロット噴射量を同量としているが、初回パイロット噴射量よりも２回目及び３回目のパイロット噴射量が少なければよく、これらパイロット噴射量を同量に設定する必要はない。 In the present embodiment, the number of pilot injections is three as shown in case 4 of FIG. 3, but the number of pilot injections may be two or more. Further, in the present embodiment, the second pilot injection amount and the third pilot injection amount are set to the same amount, but it is sufficient that the second and third pilot injection amounts are smaller than the initial pilot injection amount. It is not necessary to set the amount to the same amount.
　本願は２０１２年９月３日に日本国特許庁に出願されたＪＰ２０１２－１９２９４１、及び２０１２年９月７日に日本国特許庁に出願されたＪＰ２０１２－１９７７７０に基づく優先権を主張し、これら出願の全ての内容は参照により本明細書に組み込まれる。 This application claims priority based on JP2012-192941 filed with the Japan Patent Office on September 3, 2012 and JP2012-197770 filed with the Japan Patent Office on September 7, 2012. Is hereby incorporated by reference in its entirety.

Claims (4)

  1. 　ディーゼルエンジンの制御装置であって、
    　冷間始動時に前記ディーゼルエンジンの燃焼室を加熱するグロープラグと、
    　メイン噴射に先立つパイロット噴射を多段階で実行可能なコモンレール式燃料噴射装置と、
    　前記コモンレール式燃料噴射装置を制御する制御部と、を備え、
    　前記制御部は、
    　前記グロープラグへの通電時かつ外気温が０℃以下での冷間始動時に、前記パイロット噴射を２回以上の多段階で実行するように前記コモンレール式燃料噴射装置を制御し、
    　初回のパイロット噴射の噴射量を、前記メイン噴射の噴射量を超えず、かつ各パイロット噴射の噴射量の和である総パイロット噴射量に対して３５％から８０％までの範囲内で設定し、
    　初回以降に実行される残りのパイロット噴射の１回分の噴射量を、前記初回のパイロット噴射の噴射量よりも小さく設定する、
    　ディーゼルエンジンの制御装置。     A control device for a diesel engine,
    A glow plug for heating the combustion chamber of the diesel engine during cold start;
    A common rail fuel injection device capable of performing pilot injection in multiple stages prior to main injection;
    A control unit for controlling the common rail fuel injection device,
    The controller is
    Controlling the common rail fuel injection device so that the pilot injection is performed in multiple stages of two or more times when the glow plug is energized and during cold start when the outside air temperature is 0 ° C. or less;
    The initial pilot injection amount is set within a range of 35% to 80% with respect to the total pilot injection amount that does not exceed the main injection amount and is the sum of the injection amounts of the pilot injections,
    Setting the injection amount of one remaining pilot injection to be executed after the first time smaller than the injection amount of the first pilot injection,
    Diesel engine control device.
  2. 　請求項１に記載のディーゼルエンジンの制御装置であって、
    　前記制御部は、前記グロープラグへの通電時かつ外気温が０℃以下での冷間始動時に、前記パイロット噴射を３回以上の多段階で実行するように前記コモンレール式燃料噴射装置を制御する、
    　ディーゼルエンジンの制御装置。     A control device for a diesel engine according to claim 1,
    The control unit controls the common rail fuel injection device so that the pilot injection is performed in multiple stages of three or more times when the glow plug is energized and at a cold start when the outside air temperature is 0 ° C. or less. ,
    Diesel engine control device.
  3. 　請求項１又は２に記載のディーゼルエンジンの制御装置であって、
    　前記制御部は、冷却水温、油温、外気温の少なくとも一つの温度が低下するほど、前記初回のパイロット噴射量の前記総パイロット噴射量に占める比率が大きくなるように、前記初回のパイロット噴射量を設定する、
    　ディーゼルエンジンの制御装置。     A control device for a diesel engine according to claim 1 or 2,
    The control unit sets the initial pilot injection amount such that the ratio of the initial pilot injection amount to the total pilot injection amount increases as at least one of the cooling water temperature, the oil temperature, and the outside air temperature decreases. Set
    Diesel engine control device.
  4. 　請求項１から３のいずれかに記載のディーゼルエンジンの制御装置であって、
    　エンジンの角速度を検出する角速度検出部をさらに備え、
    　前記制御部は、前記角速度検出部により検出されたエンジンの角速度が閾値より低下した場合に、前記初回のパイロット噴射量の前記総パイロット噴射量に占める比率が小さくなるように、前記初回のパイロット噴射量を設定する、
    　ディーゼルエンジンの制御装置。     A control device for a diesel engine according to any one of claims 1 to 3,
    An angular velocity detector for detecting the angular velocity of the engine;
    The control unit performs the initial pilot injection so that a ratio of the initial pilot injection amount to the total pilot injection amount becomes small when the angular velocity of the engine detected by the angular velocity detection unit falls below a threshold value. Set the amount,
    Diesel engine control device.
PCT/JP2013/072935 2012-09-03 2013-08-28 Control device for diesel engine WO2014034695A1 (en)

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JP2007262897A (en) * 2006-03-27 2007-10-11 Nippon Soken Inc Starting control device
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JP7010139B2 (en) 2018-05-21 2022-01-26 株式会社豊田自動織機 Glow plug controller

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