CN107339160B

CN107339160B - Apparatus and method for predicting exhaust gas recirculation rate

Info

Publication number: CN107339160B
Application number: CN201710264319.9A
Authority: CN
Inventors: T·A·布鲁贝克; C·W·维格德; D·勒特格; M·J·V·尼乌斯塔特
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2016-04-29
Filing date: 2017-04-21
Publication date: 2021-10-08
Anticipated expiration: 2037-04-21
Also published as: DE102016207358A1; CN107339160A; DE102016207358B4

Abstract

The present application relates to an apparatus and method for predicting exhaust gas recirculation rate. An apparatus for predicting an exhaust gas recirculation rate of an internal combustion engine is described, the apparatus comprising an inlet system and at least one exhaust gas recirculation valve. The arrangement comprises a sensor arranged in the inlet system for determining the composition of the gas, a sensor for determining the position of the exhaust gas recirculation valve and an evaluation device. The evaluation device is configured to determine and output a prediction of the exhaust gas recirculation rate based on a corrected estimate of the exhaust gas recirculation rate, wherein the estimate is based on the position of the exhaust gas recirculation valve and is corrected based on the composition of the gas as determined using the sensor.

Description

Apparatus and method for predicting exhaust gas recirculation rate

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from german patent application No.102016207358.3 filed on 29/4/2016. The entire contents of the above referenced applications are incorporated herein by reference in their entirety for all purposes.

Technical Field

The present disclosure relates to systems and methods for predicting an exhaust gas recirculation rate of an internal combustion engine and for determining or estimating a fresh air flow to the internal combustion engine.

Background

Current control of Exhaust Gas Recirculation (EGR) during operation of an internal combustion engine, such as a diesel engine, of a vehicle relies on a Mass Air Flow (MAF) sensor in order to determine and adjust the amount of recirculated exhaust gas. In this context, the flow of fresh air to the engine is adjusted by setting the position of the EGR valve.

Documents DE 19628852 a1 and US 5,520,161 describe systems for exhaust gas recirculation in a compression ignition engine and methods for controlling exhaust gas recirculation in a compression ignition engine. In this context, a first pressure sensor is used for sensing the absolute gas pressure in the intake air collecting line of the engine, a second pressure sensor is used for sensing the absolute gas pressure in the exhaust gas collecting line of the engine, and an engine rotational speed sensor, a fuel rate sensor, a temperature sensor in the intake air collecting line and further components are used for controlling the position of the exhaust gas recirculation valve.

Document US 6,944,530B 2 discloses a system for exhaust gas recirculation in which exhaust gas from an exhaust manifold is led through a control valve and through a measuring nozzle before it reaches an inlet manifold. The pressure upstream of the nozzle and the corrected pressure downstream of the nozzle are used to measure and control exhaust flow.

Document US 6,035,639 describes a method for estimating the inlet air flow into an internal combustion engine. Here, the amount of exhaust gas recirculation flow is determined based on the inlet manifold pressure, the outlet manifold pressure, the position of the exhaust gas recirculation valve, and the temperature of the exhaust gas flowing through the exhaust gas recirculation system. The value of the inlet air flow is also used to control the position of the exhaust gas recirculation valve.

Document US 6,098,602 describes an exhaust gas recirculation system for an internal combustion engine comprising an exhaust gas recirculation valve operated by a stepper motor. In particular, controlling an engine to achieve a desired exhaust gas recirculation mass flow rate is described.

However, the inventors herein have recognized potential issues with such systems. For example, the above-mentioned systems and methods do not address effects such as MAF sensor drift, tolerances of components, and aging of components, which may affect the determination of EGR flow rate, for example. Thus, as the vehicle ages, the reduction in NO can be significantly reduced_xEfficiency of EGR control of emissions.

Disclosure of Invention

An advantage of the present disclosure is to obtain a method and apparatus for predicting an exhaust gas recirculation rate of an internal combustion engine, in particular, wherein aging processes and/or sensor differences are taken into account. In one example, the above-described problem may be solved by a system comprising an inlet system (inlet system) coupled to an internal combustion engine; an Exhaust Gas Recirculation (EGR) valve coupled between an exhaust of the engine and the inlet system; and means for predicting an EGR rate based on the composition of gas in the inlet system and the position of the EGR valve. In this way, the exhaust gas recirculation rate may be accurately predicted without the MAF sensor.

As one example, the position of the EGR valve may be adjusted in response to the predicted EGR rate differing from the desired EGR rate in order to achieve the desired EGR rate. Thus, the means for predicting the EGR rate may be used to generate feedback for accurate EGR control. As another example, the predicted EGR rate may be used to determine EGR mass flow. Still further, the determined EGR mass flow may be used to determine a fresh air mass flow. Thus, the fresh air mass flow may be determined based on the output of the means for predicting the EGR flow rate rather than using a dedicated air flow sensor, and degraded EGR control due to, for example, aging of the air flow sensor may be avoided.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. The above summary is not intended to identify key features or essential features of the claimed subject matter, the scope of which is defined uniquely by the appended claims. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

Drawings

FIG. 1 is a schematic illustration of a motor vehicle including an internal combustion engine with an Exhaust Gas Recirculation (EGR) system and means for predicting an EGR rate.

FIG. 2 is a flow chart of an example method for predicting an EGR rate using an apparatus according to the present disclosure and for further determining an EGR mass flow and a fresh air mass flow into an internal combustion engine.

Fig. 3 is a schematic illustration of an embodiment variant of a signal processing method for determining a fresh air mass flow into an internal combustion engine.

Fig. 4 is a schematic illustration of a further embodiment variant of the signal processing method for determining the fresh air mass flow into the internal combustion engine.

FIG. 5 is a flow chart of an example method for adjusting the position of an EGR valve based on a predicted EGR rate.

Detailed Description

An apparatus according to the present disclosure is provided for predicting an Exhaust Gas Recirculation (EGR) rate of an internal combustion engine. An internal combustion engine may include an inlet system (e.g., intake pipe) and at least one EGR valve, such as the example engine system shown in FIG. 1. The device comprises a sensor arranged in the intake pipe for determining (e.g. measuring) the composition of the gases flowing through the intake pipe and entering the internal combustion engine. For example, the gas may include a mixture of fresh air and recirculated exhaust gas. The arrangement additionally comprises an EGR position sensor for determining the position (e.g. valve setting) of the EGR valve and an evaluation device, for example in the form of a dynamic observation device. The EGR valve position sensor can be configured to measure a position of the exhaust gas recirculation valve. In this way, the actual valve position may be used for further prediction or evaluation. For example, using the method of FIG. 2, the actual valve position may be used in conjunction with the composition of the gas flowing through the intake pipe to predict the EGR rate. The EGR rate may further be used to determine an EGR mass flow and a fresh air mass flow, as illustrated in the signal processing diagrams of fig. 3 and 4. The evaluation device is thus configured for receiving a signal with information about the composition of the gas in the inlet system from a sensor of the arrangement, receiving a signal with information about the position or setting of the EGR valve from an EGR valve position sensor, evaluating the received signal and determining and outputting a value for the EGR rate. Further, for example, according to the method of fig. 5, the evaluation device can be configured to output a feedback signal for adjusting the position of the EGR valve.

Since the EGR rate estimated based on the position of the EGR valve is corrected based on the composition of the gas as determined using the sensor, the EGR rate can be accurately predicted. The sensor for determining the composition of the gas can be an oxygen sensor, for example, configured as an FMan sensor arranged in the intake pipe, where FMan refers to the mass fraction burned of the gas burned in the intake gas.

The evaluation device can additionally be designed to predict the EGR mass flow and/or to predict the fresh air mass flow through an air filter arranged upstream of the EGR valve. For example, the predicted EGR rate can be multiplied by the charge air mass flow entering the internal combustion engine through the inlet valve. Thus, if the EGR rate is multiplied by the charge air mass flow, then to predict the EGR mass flow, it is possible to use a dynamically corrected prediction of the EGR rate.

The previously described arrangement according to the present disclosure has the advantage that the flow of fresh air to the internal combustion engine can be determined and estimated or predicted based on the corrected (e.g. predicted) EGR rate without having to use a corresponding air flow sensor such as a hot film probe, a hot film sensor or a hot wire probe. The present disclosure thus achieves a method of regulating a portion of exhaust gas recirculated into an inlet without the use of an air flow sensor or an air mass sensor.

The previously described device according to the present disclosure may be comprised in a motor vehicle. In particular, the motor vehicle predicts with higher accuracy of EGR rate than methods based on air flow sensors and thereby more accurate EGR rate adjustment and reduced NO_xThe discharge is well known.

A method for predicting an EGR rate of an internal combustion engine according to the present disclosure includes determining a composition of gas in an inlet system of the internal combustion engine, the internal combustion engine including the inlet system or intake pipe and at least one EGR valve, determining a position of the EGR valve, estimating the EGR rate based on the determined position of the EGR valve, and predicting the EGR rate by correcting the estimation of the EGR rate based on the determined composition of gas in the inlet system of the internal combustion engine. In particular, the method can be implemented using the previously described device according to the present disclosure. In another example, the method can be implemented by a vehicle controller communicatively coupled to the previously described apparatus. In addition, this method has the same advantages as the previously described device according to the present disclosure.

The determination of the composition of the gas in the inlet system can advantageously be carried out using an oxygen sensor. In particular, the composition of the gas can be determined by measurement. Further, the internal combustion engine can include an intake manifold, wherein the oxygen sensor is disposed in the intake manifold. The oxygen sensor can thus be configured as an FMan sensor. The oxygen concentration or oxygen content in the intake manifold can be determined (e.g., measured).

In a further variation, the EGR mass flow can be predicted based on the EGR rate. In particular, this can be done using an evaluation device, wherein the predicted EGR rate is advantageously multiplied by the charge air mass flow through the inlet valve to the internal combustion engine. In this context, the charge air mass flow can be determined, for example, by measurement (e.g., using a mass air flow sensor).

In a further variant, the fresh air mass force is predicted for an air filter arranged upstream of the exhaust gas recirculation valve. To this end, the predicted EGR rate can likewise be multiplied by the charge air mass flow entering the internal combustion engine through the inlet valve.

Turning now to the drawings, FIG. 1 schematically illustrates aspects of an example engine system 100 in a motor vehicle 1 that includes an internal combustion engine 10. In the depicted embodiment, engine 10 is a boosted engine coupled to turbocharger 13, turbocharger 13 including a compressor 114 mechanically coupled to a turbine 116 via a shaft 19, wherein turbine 116 is driven by expanding exhaust gases. In some examples, the turbine 116 may be configured as a Variable Geometry Turbine (VGT). Fresh air having an ambient air pressure Pamb is introduced through the inlet (or intake) system 60 along the intake passage 42 and through the air filter 112 before flowing to the compressor 114. The direction of flow is indicated by arrow 11. The compressor 114 may be any suitable intake air compressor, such as a motor-driven or drive-shaft driven supercharger compressor. In the engine system 100, the compressor is a turbocharger compressor driven by a turbine 116. Wastegate actuator 92 may be actuated open to relieve (relieve) at least some exhaust gas pressure from upstream of turbine 116 to a location downstream of the turbine via wastegate 90. By reducing the exhaust pressure upstream of the turbine, the turbine speed may be reduced, which in turn reduces the compressor speed and the resulting boost pressure.

The compressed air charge flows from the compressor 114 through a Charge Air Cooler (CAC)17 and a throttle 20 to an intake manifold 22 of the engine 10. In some examples, intake manifold 22 may include an intake manifold pressure sensor 124 for estimating a manifold pressure (MAP) and/or an intake air flow sensor 122 for estimating a Mass Air Flow (MAF) in intake manifold 22. In other examples, the MAF sensor 122 may be omitted, as described herein. For example, a speed-density model may be used to determine the charge air mass flow, as further described with respect to fig. 2, and a fresh air mass flow may be determined based on the determined EGR mass flow and the determined charge air mass flow, as also schematically illustrated with respect to fig. 3 and 4.

The intake manifold 22 is coupled to a series of combustion chambers (e.g., cylinders) 30 via a series of intake valves (not shown). Combustion chamber 30 is further coupled to an exhaust manifold 36 via a series of exhaust valves (not shown). For example, each combustion chamber 30 may include one or more intake valves for receiving an air charge from intake manifold 22 and one or more exhaust valves for exhausting combustion reaction products (e.g., exhaust gases) to exhaust manifold 36. In the depicted embodiment, a single exhaust manifold 36 is shown. However, in other embodiments, the exhaust manifold may include a plurality of exhaust manifold segments. Configurations having multiple exhaust manifold segments may enable effluent to be directed from different combustion chambers to different locations in an engine system.

In one embodiment, each of the exhaust and intake valves may be electrically actuated or controlled. In another embodiment, each of the exhaust and intake valves may be cam actuated or cam controlled. Whether electrically actuated or cam actuated, the timing of the exhaust and intake valve openings and closings may be adjusted as needed for desired combustion and emission-control performance.

Combustion chambers 30 may be supplied with one or more fuels, such as gasoline, an ethanol fuel blend, diesel, biodiesel, compressed natural gas, etc., via fuel injectors 66 (although only one fuel injector is shown in FIG. 1, each combustion chamber includes a fuel injector coupled thereto). Fuel may be delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail. Fuel may be supplied to the combustion chamber via direct injection, port injection, throttle body injection, or any combination thereof. In the example of FIG. 1, fuel injector 66 is shown injecting fuel directly into combustion chamber 30. In the combustion chamber, combustion may be initiated via spark ignition and/or compression ignition.

As shown in FIG. 1, exhaust gas is directed from exhaust manifold 36 to turbine 116 to drive the turbine. The combined flow from the turbine 116 and the wastegate 90 then flows through an emission control device 170 positioned within the exhaust system (or exhaust pipe) 61. Generally, the one or more emission control devices 170 may include one or more exhaust aftertreatment catalysts configured to catalytically treat the exhaust gas and thereby reduce the amount of one or more substances in the exhaust gas. For example, an exhaust aftertreatment catalyst may be configured to trap NO from the exhaust gas when the exhaust gas is lean_xAnd reducing the trapped NO when the exhaust is rich_x. In other examples, the exhaust aftertreatment catalyst may be configured for disproportionating NO_xOr selective reduction of NO with the aid of a reducing agent_x. In still other examples, the exhaust aftertreatment catalyst may be configured to oxidize residual hydrocarbons and/or carbon monoxide in the exhaust stream. Different exhaust aftertreatment catalysts having any such functionality may be arranged separately or together in a washcoat (wash coat) or elsewhere in the exhaust aftertreatment stage. In some embodiments, the exhaust aftertreatment stage may include a regenerable soot filter configured to trap and oxidize soot particulates in the exhaust gas. All or a portion of the treated exhaust from emission control device 170 may flow in the direction of arrow 21 and be released to the atmosphere via exhaust passage 102 after passing through muffler 172. In the exhaust passage 102, the exhaust gas has a pressure PMufFun at a position upstream of the muffler 172 and downstream of the emission control device 170.

A portion of the exhaust gas from the exhaust passage 102 may be recirculated to the inlet system 60 via an external Exhaust Gas Recirculation (EGR) system. In the example of FIG. 1, the EGR system 140 is a low pressure exhaust gas recirculation (LP-EGR) delivery system. In other examples, EGR system 140 may be a high pressure exhaust gas recirculation (HP-EGR) delivery system. In still other examples, both the LP-EGR delivery system and the HP-EGR delivery system may be included in EGR system 140.

As shown in FIG. 1, EGR passage 180 may be fluidly coupled to exhaust passage 102 at a location downstream of emission control device 170. A portion of the exhaust gas from exhaust passage 102 is delivered from downstream of turbine 116 to inlet system 60 upstream of compressor 114 via EGR passage 180 and EGR valve 52. The direction of flow of exhaust gas in EGR passage 180 is shown by arrow 26. The air or gas mixture flowing into the compressor 114 upstream of the compressor 114 and downstream of the EGR valve 52 in the intake passage 42 is at a pressure PCompFun. The opening of the EGR valve 52 may be adjusted to control the flow of exhaust gas from the exhaust passage 102 to the inlet system 60, thereby changing the proportion of exhaust gas in the gas mixture. For example, the degree of opening of the valve flap 23 may be adjusted to allow a controlled amount of exhaust gas to flow through the valve opening of the EGR valve 52 and to the compressor 114 for desired combustion and emission control performance. The position of the valve flap 23, and thus the position of the EGR valve 52, may be determined (e.g., measured) by an EGR valve position sensor 4, which EGR valve position sensor 4 may be included in the means 2 for predicting the EGR rate, as described further below. Further, an EGR cooler 184 may be coupled to EGR passage 180 to cool the exhaust gas before it is delivered to inlet system 60.

A gas composition sensor 3 may also be included in the device 2. In one example, the gas composition sensor 3 is an oxygen sensor. For example, the gas composition sensor 3 may be an oxygen sensor configured as an FMan sensor in order to determine the mass fraction burned of the gas in the inlet system 60. The gas composition sensor 3 may be arranged upstream of the compressor 114 and downstream of the GER valve 52, as shown in fig. 1, but alternatively, the gas composition sensor 3 may be arranged between the compressor 114 and the combustion chamber 30 of the engine 10.

The arrangement 2 may further comprise an evaluation device 5, the evaluation device 5 being configured for receiving a signal with information about the gas composition in the inlet system 60 from the gas composition sensor 3, receiving a signal with information about the position or setting of the EGR valve from the EGR valve position sensor 4, evaluating the received signal and determining and outputting a value for the EGR rate. Further, the evaluation device may be configured to output a feedback signal for adjusting the position of the EGR valve, as further described below with respect to FIG. 2.

Additional sensors, such as temperature sensors, pressure sensors, and/or humidity sensors may be coupled to the EGR passage 180 for providing further details regarding the composition and conditions of the EGR. Alternatively, EGR conditions may be inferred by one or more of a temperature sensor 55, a pressure sensor 56, and a humidity sensor 57 coupled to the intake passage 42 upstream of the compressor 114. For example, a temperature sensor 55, a pressure sensor 56, and a humidity sensor 57 may also be used to provide details regarding the composition and condition of the fresh intake air entering the intake manifold 22. The amount of EGR directed through EGR system 140 may be requested to achieve a desired engine dilution to improve fuel efficiency and emission quality, as further described with respect to fig. 2. The amount of EGR requested may be based on engine operating conditions, including engine load, engine speed, engine temperature, and the like.

The engine system 100 may further include a control system 14. The control system 14 may include a controller 12. For example, the controller 12 may be a microcomputer including a microprocessor unit, input/output terminals, an electronic storage medium (such as a read-only memory chip) for executable programs and correction values, a random access memory, a keep alive memory and a data bus. The controller 12 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 18 (various examples of which are described herein). As one example, the sensors 16 may include a MAP sensor 124, a MAF sensor 122, an exhaust gas temperature sensor 128, an exhaust gas pressure sensor 129, an exhaust gas oxygen sensor 126, a gas composition sensor 3, an EGR valve position sensor 4, an inlet temperature sensor 55, an inlet pressure sensor 56, an inlet humidity sensor 57, a crankshaft sensor, a pedal position sensor, and an engine coolant temperature sensor. Other sensors such as additional pressure sensors, temperature sensors, air/fuel ratio sensors, and constituent sensors may be coupled to various locations in the engine system 100. Actuator 18 may include, for example, throttle 20, EGR valve 52, wastegate valve 92, and fuel injector 66. The controller 12 may receive input data from various sensors, process the input data, and trigger various actuators in response to the processed input data based on instructions or code corresponding to one or more programs programmed therein. The controller 12 can also send signals to the evaluation device 5 of the arrangement 2 and receive these signals from the evaluation device 5 of the arrangement 2 regarding the EGR flow rate, the EGR mass flow, the charge air mass flow, the fresh air mass flow, etc. In one example, the evaluation device 5 is a dedicated microcomputer included in the control system 14 for determining the EGR flow rate and the relevant parameters (EGR mass flow, etc.). For example, the controller 12 may use information generated by the evaluation device 5 to adjust the position of the EGR valve 52, determine the EGR mass flow, and/or determine the mass flow of fresh air flowing through the air filter 112, as described further below. In another example, the evaluation device 5 may determine an EGR mass flow and/or a fresh air mass flow.

FIG. 2 shows a flow diagram of an example method 200 for predicting an EGR rate. For example, an EGR rate may be predicted using a device (e.g., device 2 of fig. 1) that includes an EGR valve position sensor (e.g., EGR valve position sensor 4 of fig. 1), a gas composition sensor (e.g., gas composition sensor 3 of fig. 1), and an evaluation apparatus (e.g., evaluation apparatus 5 of fig. 1). The means for predicting the EGR rate may be located in an inlet system of the internal combustion engine downstream of a junction where the recirculated exhaust gas is introduced into the inlet system. The instructions for implementing the method 200 and the remaining methods included herein may be executed by a controller, such as the controller 12 of fig. 1, based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference to fig. 1. The controller may utilize engine actuators of the engine system to adjust engine operation according to the methods described below. Further, aspects of the method 200 may be performed by an evaluation device based on instructions stored on a memory of the evaluation device and/or a controller to which the evaluation device is communicatively coupled.

Method 200 begins at 202 and includes estimating and/or measuring engine operating conditions. The estimated conditions may include, for example, engine temperature, engine load, driver torque demand, boost demand, manifold air flow, manifold air pressure, engine speed, throttle position, exhaust pressure, exhaust air/fuel ratio, ambient conditions (e.g., ambient temperature, pressure, and humidity), and so forth.

At 204, it is determined whether EGR is requested. For example, EGR may be desired after the exhaust catalyst has reached its light-off temperature. Further, EGR may be requested to achieve a desired engine dilution, thereby improving fuel efficiency and emission quality.

If EGR is not requested, method 200 proceeds to 206 and includes maintaining current engine operating conditions without EGR supply. Therefore, the flow rate of EGR need not be determined because EGR is not requested. However, the controller may confirm that the EGR valve (e.g., EGR valve 52 of FIG. 1) is in a closed position, thereby using the EGR valve position sensor to block EGR flow. After 206, the method 200 ends.

If EGR is requested, the method 200 proceeds to 208 and includes determining an amount of EGR requested. The amount of EGR requested may be based on engine operating conditions, including engine load, engine speed, engine temperature, and the like. For example, the controller may access a (refer) look-up table having as inputs engine speed and engine load and as output a signal corresponding to an opening degree applied to the EGR valve, the opening degree providing an amount of dilution corresponding to the input engine speed-load. In still other examples, the controller may rely on a model that correlates engine load changes to engine dilution demand changes and further correlates engine dilution demand changes to EGR demand changes. For example, as the engine load increases from a low load to an intermediate load, the EGR demand may increase and a larger EGR valve opening may be requested. Then, as the engine load increases from a medium load to a high load, the EGR demand may decrease and a smaller EGR valve opening may be requested. The controller may further determine the amount of EGR requested by an optimal fuel economy map that takes into account the desired dilution rate.

At 210, method 200 includes opening an EGR valve to supply the requested amount of EGR. For example, the EGR valve may be adjusted to a position corresponding to a desired amount of dilution, where the degree of EGR valve opening increases as the amount of requested EGR increases, as described above. In another example, the position of the EGR valve may be adjusted in response to a change in the dilution requirement, also as described above.

At 212, the method 200 includes determining a composition of the gas in the inlet system. The output of the gas composition sensor may be used to determine the composition of the gas, such as the proportion of gas burned (e.g., FMan). For example, the gas composition sensor may be an oxygen sensor.

At 214, the method 200 includes determining a position of the EGR valve (e.g., an actual position of the EGR valve). The position of the EGR valve may be measured by an EGR valve position sensor, and the position of the EGR valve may be determined by an evaluation device based on an output of the EGR valve position sensor. For example, if the EGR valve includes a valve flap (e.g., valve flap 23 of fig. 1), a position of the valve flap may be determined, where the position of the valve flap corresponds to a degree or setting of an opening of the EGR valve.

At 216, method 200 includes estimating an EGR rate based on a position of the EGR valve. For example, the evaluation device may access a lookup table having as input the determined position of the EGR valve (e.g., as determined at 214) and as output the estimated EGR rate. In another example, the controller may access a model that correlates the position of the EGR valve with an estimated EGR rate.

At 218, the method includes correcting the estimated EGR rate based on the determined composition of gas in the inlet system and outputting a predicted EGR rate. In one example, particularly if the engine is operating in a lean fuel supply condition, the recirculated exhaust gas may contain a significant portion of oxygen, such that the estimated EGR rate based on the position of the EGR valve (as determined at 214) is inaccurate with respect to the actual engine dilution achieved by EGR. Accordingly, a more accurate EGR rate may be predicted by considering the composition of the gases (e.g., as determined at 212), including recirculated exhaust gas and fresh air. The evaluation device may access a look-up table with the determined composition of the gas and the position of the EGR valve as inputs and the corrected predicted EGR rate as an output. For example, the evaluation device may output the predicted EGR rate to the controller.

At 220, method 200 optionally includes adjusting a position of the EGR valve based on the predicted EGR rate. For example, if the predicted EGR rate is not equal to (e.g., differs from the requested EGR rate by a threshold amount) the requested EGR rate (e.g., as determined at 208), the controller may increase (if the predicted EGR rate is lower than the requested EGR rate) or decrease (if the EGR rate is greater than the requested EGR rate) the opening degree of the EGR valve, as further described with respect to fig. 5.

At 222, method 200 includes determining a charge air mass flow. In one example, charge air mass flow may be measured by a mass air flow sensor (e.g., MAF sensor 122 of FIG. 1) positioned in an intake manifold of the engine. In another example, a speed-density model may be used to determine charge air mass flow based on the output of a manifold pressure sensor (e.g., MAP sensor 124 of FIG. 1) in combination with other engine operating parameters such as engine speed, intake air temperature, and throttle position.

At 224, method 200 includes determining an EGR mass flow based on the predicted EGR flow rate and the determined charge air mass flow. For example, the controller may access a lookup table with the predicted EGR rate and the determined charge air mass flow as inputs, and output the EGR mass flow.

At 226, method 200 includes determining a fresh air mass flow based on the determined EGR mass flow and the determined charge air mass flow. Because the charge air includes recirculated exhaust gas and fresh air flowing through an air filter of the inlet system (e.g., air filter 112 of fig. 1), the fresh air mass flow may be determined by subtracting the EGR mass flow from the charge air mass flow, as further described below with respect to fig. 3 and 4. After 226, the method 200 ends.

Thus, method 200 provides a method for accurately predicting an EGR rate without using a mass air flow sensor. Further, the predicted EGR flow rate may be used in conjunction with the charge air mass flow to determine both the EGR mass flow and the fresh air mass flow. Still further, the predicted EGR flow rate may optionally be used as feedback for adjusting the position of the EGR valve to achieve a desired EGR flow rate, as further described with respect to FIG. 5.

Fig. 3 and 4 show an embodiment variant of the signal processing diagram, in which the input is processed for outputting a predicted fresh air mass flow (abbreviated WAir _ p) flowing through an air filter of an inlet system of the internal combustion engine. For example, the functions illustrated in fig. 3 and 4 may be performed as part of the method 200 of fig. 2. In one example, this function may be performed by a controller, such as controller 12 of FIG. 1. In another example, the function may be performed by an evaluation device (e.g., evaluation device 5 of apparatus 2 of fig. 1) included in the means for determining the EGR flow rate that is communicatively coupled to the controller. For example, both the controller and the evaluation device may be included in a control system of the engine. Like elements in fig. 3 and 4 are labeled with like reference numerals and are not re-introduced (e.g., 330 of fig. 3 corresponds to 430 of fig. 4).

At arrow 330, a predicted mass fraction burned level for EGR ("FLpEGR _ p") is obtained (e.g., based on an output of an exhaust gas oxygen sensor, such as exhaust gas oxygen sensor 126 of fig. 1). At arrow 331, a predicted exhaust gas recirculation rate ("RLpEGR _ p") is obtained (such as according to method 200 of FIG. 2). The predicted exhaust gas recirculation rate is generated, for example, based on an EGR valve position determined via an EGR valve position sensor (e.g., EGR valve position sensor 4 of FIG. 1).

The signal 331 is normalized by means of a summing junction or adder element 333 and converted into a signal 334. Signal 334 corresponds to a normalized estimated exhaust gas recirculation rate. Signal 334, the normalized estimated exhaust gas recirculation rate ("RLpEGR _ e"), and signal 330, the predicted EGR mass fraction burn level, are converted by means of multiplier 332 into signal 335, which signal 335 is fed to adder element 336.

Within the scope of summer element 336, a signal 337 corresponding to a predicted mass fraction burned ("FMan _ p") in the intake manifold of the engine is subtracted from signal 335. The resulting signal 338 is filtered by a delay element or filter 1/tau _ s 339 and fed to an adder element 340. The adder element 340 adds the filtered signal 338 to the tuning parameter Ks generated by the tuning device 341 as further described below.

Subsequently, the generated signal 243 is scaled up by an amplifier 343, where appropriate the amplifier 343 comprising a sampler and converting said generated signal 342 into a signal 337, the signal 337 being fed to the adder element 336 as mentioned above. The signal 337 is also input to a further summer element 334, the summer element 334 adding the signal 337 to the measured mass fraction burned in the intake manifold ("FMan _ m"). For example, signal 345 may be generated based on the output of a gas composition sensor (e.g., gas composition sensor 3 of fig. 1) positioned at the engine inlet. The resulting signal 346 generated by the adder element 344 is fed to a tuning means 341 which generates a tuning parameter Ks and, after being set or tuned with a tuning parameter Ki at a tuning means 347, is also fed to an amplifier 348 which can comprise a sampler.

Signal 349 generated by amplifier 348 is available to adder element 333 for addition to signal 331. The signal 334 generated by the adder element 333 as described above is fed to the multiplier 332 as well as to the multiplier 350. Within the range of multiplier 350, the signal 334 is multiplied by a predicted mass flow ("WAp _ p") 351 into the internal combustion engine. The predicted mass flow may be generated using a velocity-density model as described with respect to fig. 2. This signal 351 is also fed to an adder element 352. In addition, the signal 353 generated by the multiplier 350 is fed to an adder element 352, wherein the signal 353 is subtracted from the signal 351. The resulting signal 354 is the predicted fresh air mass flow, i.e., the mass flow through the air filter ("WAir _ p"). Thus, the fresh air mass flow may be determined without using a dedicated air flow sensor based on the predicted EGR rate.

In contrast to the embodiment variant in fig. 3, in the embodiment variant shown in fig. 4 a step 455 is inserted between the multiplier 432 and the summing point or adder element 436. At step 455, the signal 435 generated by the multiplier 432 is modeled to account for mixing dynamics and/or transport delays before being fed to the adder element 436.

Turning now to FIG. 5, a method of using a device for predicting an EGR rate (e.g., device 2 of FIG. 1) to help control a position of an EGR valve (e.g., EGR valve 52 of FIG. 1) is shown. For example, method 500 may be performed as part of method 200 of fig. 2 (e.g., at 220) in order to accurately control the amount of EGR entering an inlet system of an internal combustion engine.

Method 500 begins at 502 and includes determining whether a predicted EGR rate (e.g., 218 from FIG. 2) is greater than a requested EGR rate (e.g., 208 from FIG. 2). For example, if the predicted EGR rate is greater than the requested EGR rate by at least a threshold amount, the predicted EGR rate may be determined to be greater than the requested EGR rate.

If the predicted EGR rate is greater than the requested EGR rate, method 500 proceeds to 504 and includes decreasing the opening of the EGR valve. For example, the controller may access a lookup table having as input the difference between the requested EGR rate and the predicted EGR rate and having as output a signal corresponding to the new reduced opening degree applied to the EGR valve. In still other examples, the controller may rely on a model that correlates a difference between a requested EGR rate and a predicted EGR rate to a change in EGR valve position and further correlates the change in EGR valve position to a signal applied to the EGR valve. Method 500 then proceeds to 512, as will be described below.

At 502, if the predicted EGR rate is not greater than the requested EGR rate, method 500 proceeds to 506 and includes determining whether the predicted EGR rate is less than the requested EGR rate. For example, if the predicted EGR rate is less than the requested EGR rate by at least a threshold amount, the predicted EGR rate may be determined to be less than the requested EGR rate.

If the predicted EGR rate is not less than the requested EGR rate, the method proceeds to 508 and includes maintaining the EGR valve position. Because the predicted EGR rate is effectively equal to the requested EGR rate, no EGR valve position adjustment is required to provide the desired engine dilution. After 508, the method 500 ends.

At 506, if the predicted EGR rate is less than the requested EGR rate, method 500 proceeds to 504 and includes increasing an opening of an EGR valve. For example, the controller may access a lookup table having as input the difference between the requested EGR rate and the predicted EGR rate and having as output a signal corresponding to the new increased opening degree applied to the EGR valve. In still other examples, the controller may rely on a model that correlates a difference between a requested EGR rate and a predicted EGR rate to a change in EGR valve position and further correlates the change in EGR valve position to a signal applied to the EGR valve to further open the EGR valve.

At 512, method 500 includes determining a new EGR valve position. For example, an EGR valve position sensor (e.g., EGR valve position sensor 5 of FIG. 1) included in the apparatus for predicting an EGR rate may be used to determine EGR valve position, as further described with respect to FIG. 2 (e.g., at 214)

At 514, method 500 includes updating the predicted EGR rate based on the new EGR valve position. The updated predicted EGR rate may be determined by an evaluation apparatus (e.g., evaluation apparatus 5 of fig. 1) included in the means for predicting an EGR rate. For example, the evaluation device may update the estimated EGR rate based on the new EGR valve position and correct the estimated EGR rate based on the composition of the gas in the inlet system (e.g., as measured by a gas composition sensor included in the means for predicting the EGR rate), as further described with respect to fig. 2. After 514, the method 500 ends.

In this way, the fresh air mass flow of the internal combustion engine may be determined based on a predicted EGR rate determined using the means for predicting an EGR rate without using a dedicated air flow sensor. The predicted EGR rate may be an estimate of a corrected EGR rate, where the EGR rate is estimated based on a position of an EGR valve that limits EGR flow into an inlet of the engine, and the correction is made based on a measured composition of gas in the inlet. In particular, the EGR rate may be predicted with greater accuracy as compared to methods based on air flow sensors. For example, the predicted EGR rate will not be affected by factors such as air flow sensor drift and aging. Further, the position of the EGR valve may be adjusted based on the predicted EGR rate to accurately provide the requested engine dilution.

The technical effect of using an apparatus for predicting EGR rate that includes an EGR valve position sensor, a gas composition sensor, and an evaluation device is that the EGR rate may be more accurately adjusted, resulting in reduced NO_xAnd (5) discharging.

As one example, a system is provided that includes an inlet system coupled to an internal combustion engine; an Exhaust Gas Recirculation (EGR) valve coupled between an exhaust of the engine and the inlet system; and means for predicting an EGR rate based on the composition of gas in the inlet system and the position of the EGR valve. In the foregoing example, additionally or optionally, the prediction of the EGR rate is based on a correction to an estimate of the EGR rate, wherein the estimate is based on a position of the EGR valve and the correction is based on a composition of the gas in the inlet system as determined using a sensor disposed in the inlet system. In any or all of the foregoing examples, additionally or optionally, the EGR valve is configured as a low pressure EGR valve. In any or all of the preceding examples, additionally or optionally, the sensor comprises an oxygen sensor. In any or all of the foregoing examples, additionally or alternatively, the means for predicting an EGR rate is further configured to predict an EGR mass flow and predict a fresh air mass flow of an air filter disposed upstream of the EGR valve in the inlet system.

As another example, a method is provided that includes determining a composition of a gas in an inlet system of an internal combustion engine; determining a position of an exhaust gas recirculation valve coupled between an exhaust of an engine and an inlet system; estimating an exhaust gas recirculation rate based on the determined position of the exhaust gas recirculation valve; and predicting an exhaust gas recirculation rate by correcting the estimate of the exhaust gas recirculation rate based on the determined composition of the gas in the inlet system of the internal combustion engine. In the foregoing example, additionally or optionally, the composition of the gas in the inlet system is estimated using an oxygen sensor. In any or all of the foregoing examples, additionally or optionally, the exhaust gas recirculation valve is a low pressure exhaust gas recirculation valve. In any or all of the foregoing examples, additionally or optionally, the position of the exhaust gas recirculation valve is determined by measuring a position of the exhaust gas recirculation valve with an exhaust gas recirculation valve sensor. In any or all of the foregoing examples, the method additionally or optionally further comprises adjusting a position of an exhaust gas recirculation valve if the predicted exhaust gas recirculation rate differs from the requested exhaust gas recirculation rate by at least a threshold amount. In any or all of the foregoing examples, the method additionally or optionally further comprises predicting an exhaust gas recirculation mass flow based on the predicted exhaust gas recirculation rate. In any or all of the foregoing examples, additionally or alternatively, the predicted exhaust gas recirculation mass flow is determined by multiplying the predicted exhaust gas recirculation rate by a charge air mass flow entering the internal combustion engine through an inlet valve coupled to each cylinder of the internal combustion engine. In any or all of the foregoing examples, additionally or optionally, the charge air mass flow is determined based on signals from engine sensors including at least one of engine speed, manifold absolute pressure, intake air temperature, and intake mass air flow. In any or all of the foregoing examples, the method additionally or optionally further comprises predicting a fresh air mass flow through an air filter disposed upstream of the exhaust gas recirculation valve based on the predicted exhaust gas recirculation mass flow and the charge air mass flow.

As another example, a system for a vehicle is provided that includes an internal combustion engine coupled to an inlet system and an exhaust system, the internal combustion engine including a plurality of cylinders; an air filter coupled to the inlet system; a turbocharger comprising a turbine arranged in the exhaust system and a compressor arranged in the inlet system; a low pressure Exhaust Gas Recirculation (EGR) system for recirculating exhaust gas from downstream of the turbine in the exhaust system to upstream of the compressor and downstream of an air filter in the exhaust system via an EGR passage; an EGR valve coupled to the EGR passage configured to restrict or initiate EGR flow; an apparatus for predicting an EGR flow rate comprising a gas composition sensor, an EGR valve position sensor, and an evaluation device; an intake air temperature sensor and an absolute pressure sensor coupled to the inlet system; an engine speed sensor; and a control system holding one or more computer readable instructions stored on one or more persistent memories that, when executed, cause the control system to: determining a requested EGR rate based on the engine speed and the engine load; opening the EGR valve to a position corresponding to the requested EGR rate; determining an actual position of the EGR valve; determining an estimated EGR rate based on an actual position of an EGR valve; determining a composition of gas in the inlet system downstream of the EGR valve; and determining the predicted EGR rate as a correction to the estimated EGR rate based on the composition of gas in the inlet system downstream of the EGR valve. In the foregoing example, additionally or optionally, the gas composition sensor is an oxygen sensor. In any or all of the preceding examples, additionally or optionally, the control system holds further instructions that, when executed, cause the control system to: further opening the EGR valve in response to the predicted EGR rate being less than a threshold amount below the requested EGR rate; the EGR valve is further closed in response to the predicted EGR rate being greater than a threshold amount above the requested EGR rate. In any or all of the preceding examples, additionally or optionally, the control system holds further instructions that, when executed, cause the control system to: determining a mass flow of charge air into the internal combustion engine, wherein the charge air is comprised of fresh air introduced through an air filter and recirculated exhaust gas introduced through an EGR passage; determining EGR mass flow; and determining a fresh air mass flow. In any or all of the foregoing examples, additionally or alternatively, the EGR mass flow is determined by multiplying the predicted EGR rate by the mass flow of charge air. In any or all of the foregoing examples, additionally or optionally, the fresh air mass flow is determined by subtracting the EGR mass flow from the mass flow of charge air.

It should be noted that the example controllers and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and programs disclosed herein may be stored as executable instructions in persistent memory and may be implemented by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and/or functions may be repeatedly performed depending on the particular processing strategy being used. Further, the acts, operations, and/or functions may graphically represent code to be programmed into the persistent store of the computer readable storage medium in the engine control system, wherein the acts are implemented by executing instructions in a system comprising the various engine hardware components in combination with an electronic controller.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above techniques can be applied to V-6, I-4, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.

Claims

1. A system for a vehicle, the system comprising:

an inlet system coupled to an internal combustion engine;

an exhaust gas recirculation valve (EGR valve) coupled between an exhaust of the engine and the inlet system;

an apparatus comprising a microcomputer, wherein the apparatus predicts an EGR rate based on a composition of gas in the inlet system and a position of the EGR valve, the composition of gas and the position of the EGR valve based on sensor output received at the apparatus, wherein the EGR rate is predicted by determining an estimated EGR rate and correcting the estimated EGR rate, the estimated EGR rate is determined based on the position of the EGR valve, and the estimated EGR rate is corrected based on the composition of the gas; and

a controller communicatively coupled to the device, the controller comprising computer-readable instructions stored on a persistent memory that, when executed, cause the controller to:

receiving the predicted EGR rate from the device; and

adjusting the position of the EGR valve in response to the predicted EGR rate differing from a desired EGR rate.

2. The system of claim 1, wherein the sensor output is determined at least in part by a sensor disposed in the inlet system.

3. The system of claim 1, wherein the EGR valve is configured as a low pressure EGR valve.

4. The system of claim 2, wherein the sensor comprises an oxygen sensor.

5. The system of claim 1, wherein the means for predicting the EGR rate is further structured to predict EGR mass flow based on the sensor output and predict fresh air mass flow for an air filter disposed in the inlet system upstream of the EGR valve.

6. A method for a vehicle, the method comprising:

determining a composition of a gas in an inlet system of an internal combustion engine;

determining a position of an exhaust gas recirculation valve coupled between an exhaust of the engine and the inlet system;

estimating an exhaust gas recirculation rate based on the determined position of the exhaust gas recirculation valve;

predicting an exhaust gas recirculation rate by correcting the estimate of the exhaust gas recirculation rate based on the determined composition of the gas in the inlet system of the internal combustion engine; and

adjusting the position of the exhaust gas recirculation valve in response to the predicted exhaust gas recirculation rate differing from a requested exhaust gas recirculation rate.

7. The method of claim 6, wherein the composition of the gas in the inlet system is determined using an oxygen sensor.

8. The method of claim 6, wherein the exhaust gas recirculation valve is a low pressure exhaust gas recirculation valve.

9. The method of claim 6, wherein the position of the exhaust gas recirculation valve is determined by measuring the position of the exhaust gas recirculation valve with an exhaust gas recirculation valve sensor.

10. The method of claim 6, the method further comprising:

an exhaust gas recirculation mass flow is predicted based on the predicted exhaust gas recirculation rate.

11. The method of claim 10, wherein the predicted exhaust gas recirculation mass flow is determined by multiplying the predicted exhaust gas recirculation rate by a charge air mass flow entering the internal combustion engine through an inlet valve coupled to each cylinder of the internal combustion engine.

12. The method of claim 11, wherein the charge air mass flow is determined based on signals from engine sensors, the signals including at least one of engine speed, manifold absolute pressure, intake air temperature, and intake mass air flow.

13. The method of claim 11, the method further comprising:

predicting a fresh air mass flow through an air filter disposed upstream of the exhaust gas recirculation valve based on the predicted exhaust gas recirculation mass flow and the charge air mass flow.

14. A system for a vehicle, the system comprising:

an internal combustion engine coupled to the inlet system and the exhaust system, the internal combustion engine including a plurality of cylinders;

an air cleaner coupled to the inlet system;

a turbocharger including a turbine disposed in the exhaust system and a compressor disposed in the inlet system;

a low-pressure exhaust gas recirculation system, i.e., a low-pressure EGR system, for recirculating exhaust gas in the exhaust system downstream from the turbine to upstream of the compressor and downstream of the air filter in the inlet system via an EGR passage;

an EGR valve coupled to the EGR passage configured to restrict or initiate EGR flow;

an apparatus for predicting an EGR flow rate comprising a gas composition sensor, an EGR valve position sensor, and an evaluation device, wherein the evaluation device is a microcomputer;

an intake air temperature sensor and an absolute pressure sensor coupled to the inlet system;

an engine speed sensor; and

a control system holding one or more computer readable instructions stored on one or more persistent memories, the computer readable instructions when executed cause the control system to:

determining a requested EGR rate based on the engine speed and the engine load;

opening the EGR valve to a position corresponding to the requested EGR rate;

determining an actual position of the EGR valve;

determining an estimated EGR rate based on the actual position of the EGR valve;

determining a composition of gas in the inlet system downstream of the EGR valve;

determining a predicted EGR rate as a correction to the estimated EGR rate based on the composition of gas in the inlet system downstream of the EGR valve; and

adjusting the position of the EGR valve in response to a difference between the predicted EGR rate and the requested EGR rate.

15. The system of claim 14, wherein the gas composition sensor is an oxygen sensor.

16. The system of claim 14, wherein adjusting the position of the EGR valve in response to the difference between the predicted EGR rate and the requested EGR rate comprises:

opening the EGR valve in response to the predicted EGR rate being less than the requested EGR rate by a threshold amount;

closing the EGR valve in response to the predicted EGR rate being greater than the requested EGR rate by the threshold amount.

17. The system of claim 14, wherein the control system holds further instructions that, when executed, cause the control system to:

determining a mass flow of charge air into the internal combustion engine, wherein the charge air consists of fresh air introduced through the air filter and recirculated exhaust gas introduced through the EGR passage;

determining EGR mass flow; and

a fresh air mass flow is determined.

18. The system of claim 17, wherein the EGR mass flow is determined by multiplying the predicted EGR rate by the mass flow of the charge air.

19. The system of claim 17, wherein the fresh air mass flow is determined by subtracting the EGR mass flow from the mass flow of the charge air.