Internal combustion engine controller and method for estimating pumping loss

An internal combustion engine to which a controller is applied includes a cylinder, a turbocharger, an intake passage, a throttle valve, and an exhaust passage. The turbocharger includes a turbine wheel, a compressor wheel, and a wastegate valve. The controller executes a loss estimating process that calculates an estimated value of a pumping loss of the internal combustion engine from an intake air pressure, which is air pressure at a downstream side of the throttle valve in the intake passage, an engine speed of the internal combustion engine, and a charging pressure.

RELATED APPLICATIONS

The present application claims priority of Japanese Application Number 2022-078849 filed on May 12, 2022, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

The following description relates to an internal combustion engine controller and a method for estimating pumping loss.

2. Description of Related Art

Japanese Laid-Open Patent Publication No. 2015-140724 discloses a controller applied to an internal combustion engine that includes an exhaust-driven turbocharger. The controller executes a calculation process that calculates the pumping loss of the internal combustion engine.

When the turbocharger includes a wastegate valve, the controller controls the charging pressure by adjusting the opening degree of the wastegate valve. A change in the opening degree of the wastegate valve changes a turbine upstream pressure, which is the exhaust pressure at the upstream side of where a turbine wheel of the turbocharger is arranged in an exhaust passage of the internal combustion engine. A change in the turbine upstream pressure will change the pumping loss of the internal combustion engine.

SUMMARY

In one general aspect, an internal combustion engine controller for an internal combustion engine is provided. The internal combustion engine includes a cylinder, a turbocharger, an intake passage through which air flows into the cylinder, a throttle valve arranged in the intake passage, and an exhaust passage through which exhaust gas discharged from the cylinder flows. The turbocharger includes a turbine wheel arranged in the exhaust passage, the turbine wheel being rotated by the flow of exhaust gas through the exhaust passage, a compressor wheel arranged at an upstream side of the throttle valve in the intake passage, the compressor wheel being rotated in synchronization with the turbine wheel, and a wastegate valve that adjusts a flow rate of the exhaust gas bypassing the turbine wheel in the exhaust passage. The internal combustion engine controller includes processing circuitry configured to execute a loss estimating process that calculates an estimated value of a pumping loss of the internal combustion engine from an intake air pressure, which is air pressure at a downstream side of the throttle valve in the intake passage, an engine speed of the internal combustion engine, and a charging pressure.

In another general aspect, a method for estimating a pumping loss in an internal combustion engine is provided. The internal combustion engine includes a cylinder, a turbocharger, an intake passage through which air flows into the cylinder, a throttle valve arranged in the intake passage, and an exhaust passage through which exhaust gas discharged from the cylinder flows. The turbocharger includes a turbine wheel arranged in the exhaust passage, the turbine wheel being rotated by the flow of exhaust gas through the exhaust passage, a compressor wheel arranged at an upstream side of the throttle valve in the intake passage, the compressor wheel being rotated in synchronization with the turbine wheel, and a wastegate valve that adjusts a flow rate of the exhaust gas bypassing the turbine wheel in the exhaust passage. The method includes executing a loss estimating process that calculates an estimated value of a pumping loss of the internal combustion engine from an intake air pressure, which is air pressure at a downstream side of the throttle valve in the intake passage, an engine speed of the internal combustion engine, and a charging pressure.

DETAILED DESCRIPTION

An internal combustion engine controller according to one embodiment will now be described with reference toFIGS.1to4.

FIG.1shows an internal combustion engine10and a controller70controlling the operation of the internal combustion engine10. The controller70corresponds to an internal combustion engine controller.

Internal Combustion Engine

The internal combustion engine10includes cylinders11and a crankshaft12.FIG.1shows one of the cylinders11. The cylinder11accommodates a piston13. The piston13is coupled to the crankshaft12by a connecting rod14. The piston13reciprocates in the cylinder11to rotate the crankshaft12.

The internal combustion engine10includes an intake passage16and a throttle valve17arranged in the intake passage16. Air flows through the intake passage16into the cylinders11. The throttle valve17is an electronically controlled valve that adjusts the amount of the air flowing through the intake passage16. The flow rate of the air flowing through the intake passage16increases as the opening degree of the throttle valve17increases.

The internal combustion engine10includes fuel injection valves18, ignitors19, and an exhaust passage20. The cylinders11each include a fuel injection valve18and an ignitor19. The fuel injection valve18injects fuel into the cylinder11. The ignitor19ignites and burns the mixture of air and fuel in the cylinder11. Exhaust gas generated by the combustion of the air-fuel mixture is discharged from the cylinder11into the exhaust passage20. Thus, the exhaust gas discharged from the cylinders11flows through the exhaust passage20.

The internal combustion engine10includes an exhaust-driven turbocharger30. The turbocharger30includes a turbine wheel31, a compressor wheel32, and a wastegate valve34. The turbine wheel31is arranged in the exhaust passage20. The compressor wheel32is arranged at the upstream side of the throttle valve17in the intake passage16. The compressor wheel32is coupled to the turbine wheel31by a coupling shaft33. Thus, when the flow of exhaust gas in the exhaust passage20rotates the turbine wheel31, the compressor wheel32rotates in synchronization with the turbine wheel31. This pressurizes the air flowing through the intake passage16.

The wastegate valve34adjusts the flow rate of the exhaust gas that bypasses the turbine wheel31. The flow rate of the exhaust gas bypassing the turbine wheel31increases as the opening degree of the wastegate valve34increases. This lowers the charging pressure produced when the turbocharger is driven.

Controller

The controller70receives detection signals from sensors. The sensors include, for example, a throttle sensor51, a crank angle sensor52, an air flowmeter53, a charging pressure sensor54, an intake air pressure sensor55, and an atmospheric pressure sensor56. The throttle sensor51detects the depression amount of an accelerator pedal101. The depression amount corresponding to the detection value of the throttle sensor51is referred to as the throttle opening degree AC. The crank angle sensor52detects the rotation angle of the crankshaft12. The speed of the crankshaft12corresponding to the detection value of the crank angle sensor52is referred to as the engine speed NE. The air flowmeter53detects the flow rate of air flowing through the intake passage16. The flow rate of the air corresponding to the detection value of the air flowmeter53is referred to as the intake air amount GA. The charging pressure sensor54detects the air pressure at a portion between the downstream side of the compressor wheel32and the upstream side of the throttle valve17. The air pressure corresponding to the detection value of the charging pressure sensor54is referred to as the charging pressure PB. The intake air pressure sensor55detects the air pressure at the downstream side of the throttle valve17in the intake passage16. The air pressure corresponding to the detection value of the intake air pressure sensor55is referred to as the intake air pressure PM. The atmospheric pressure sensor56detects the atmospheric pressure. The atmospheric pressure corresponding to the detection value of the atmospheric pressure sensor56is referred to as the atmospheric pressure KPA.

The controller70controls the opening degree of the throttle valve17, the fuel injection amount of the fuel injection valves18, the ignition timing of the ignitors19, and the opening degree of the wastegate valve34based on the detection signals of the sensors described above.

The controller70includes a central processing unit (CPU)71and a memory72. The memory72stores various control programs executed by the CPU71.

As shown inFIG.2, the CPU71executes the control programs to perform a required value setting process M1, a required value leveling process M3, an opening degree adjusting process M5, an intake air pressure obtaining process M7, a normalization process M9, and a loss estimating process M11.

In the required value setting process M1, the CPU71sets a required charging pressure PBRq, which is the required value of the charging pressure PB. Specifically, the CPU71, in the required value setting process M1, sets the required charging pressure PBRq to a greater value as the required torque output of the internal combustion engine10increases. When a driver of a vehicle depresses the accelerator pedal101, a larger throttle opening degree AC increases the required torque output of the internal combustion engine10. Thus, the CPU71sets, for example, the required charging pressure PBRq to a greater value as the throttle opening degree AC increases.

In the required value leveling process M3, the CPU71calculates a smoothed required charging pressure value PBRqLv, which is a value obtained by leveling the required charging pressures PBRq. For example, the CPU71, in the required value leveling process M3, sets the smoothed required charging pressure value PBRqLv to the moving average of a time series of consecutive required charging pressures PBRq.

In the opening degree adjusting process M5, the CPU71adjusts the opening degree of the wastegate valve34based on the required charging pressure PBRq. For example, the CPU71operates the wastegate valve34and adjusts the opening degree so that the opening degree decreases as the required charging pressure PBRq increases.

In the intake air pressure obtaining process M7, the CPU71obtains the intake air pressure PM.

In the normalization process M9, the CPU71normalizes the intake air pressure PM and the smoothed required charging pressure value PBRqLv under the atmospheric pressure KPA. Specifically, the CPU71normalizes the intake air pressure PM by dividing the intake air pressure PM by the atmospheric pressure KPA. The intake air pressure normalized under the atmospheric pressure KPA is referred to as the normalized intake air pressure PMa. The CPU71also normalizes the smoothed required charging pressure value PBRqLv by dividing the smoothed required charging pressure value PBRqLv by the atmospheric pressure KPA. The smoothed required charging pressure value normalized under the atmospheric pressure KPA is referred to as the normalized smoothed required charging pressure value PBRqLva.

In the loss estimating process M11, the CPU71calculates a pumping loss estimated value TqPLE of the internal combustion engine10based on the intake air pressure PM, the engine speed NE, and the charging pressure PB. In the present embodiment, the CPU71calculates the pumping loss estimated value TqPLE based on the normalized intake air pressure PMa, the engine speed NE, and the normalized smoothed required charging pressure value PBRqLva. The CPU71, in the loss estimating process M11, uses a map MP to obtain the pumping loss estimated value TqPLE.

The map MP is used to obtain a value corresponding to the intake air pressure, the engine speed, and the charging pressure as the pumping loss estimated value TqPLE. In the map MP, the pumping loss estimated value TqPLE increases as the intake air pressure decreases, the pumping loss estimated value TqPLE increases as the engine speed increases, and the pumping loss estimated value TqPLE increases as the charging pressure increases.

In the present embodiment, the CPU71uses the map MP to obtain a value corresponding to the normalized intake air pressure PMa, the engine speed NE, and the normalized smoothed required charging pressure value PBRqLva. The calculated value is the pumping loss estimated value TqPLE.

The relationship between a turbine upstream pressure PEX and the charging pressure will now be described with reference toFIG.3. The turbine upstream pressure PEX is the exhaust pressure at the upstream side of the turbine wheel31in the exhaust passage20. InFIG.3, section (A) shows the turbine upstream pressure PEX, and section (B) shows the charging pressure. In section (B) ofFIG.3, the fine solid line indicates the required charging pressure PBRq, the bold solid line indicates the smoothed required charging pressure value PBRqLv, and the broken line indicates the charging pressure PB, which is a detection value of the charging pressure sensor54. As shown inFIG.3, the turbine upstream pressure PEX decreases as the smoothed required charging pressure value PBRqLv decreases. In this manner,FIG.3shows the correlation between the charging pressure and the turbine upstream pressure PEX.

FIG.4is a graph showing the pumping loss TqPL when changing the required charging pressure PBRq on the condition that the intake air pressure PM is fixed. As shown inFIG.4, the pumping loss TqPL increases as the required charging pressure PBRq increases.

Operation and Advantages of Present Embodiment

(1) It is understood based on experiments and simulations that there is a correlation between the charging pressure and the turbine upstream pressure PEX, which is the exhaust pressure at the upstream side of the turbine wheel31in the exhaust passage20. That is, when the charging pressure changes as the opening degree of the wastegate valve34changes, the turbine upstream pressure PEX will also change.

When the turbine upstream pressure PEX changes as the required charging pressure PBRq changes, the pumping loss TqPL will also change. As shown inFIG.4, the pumping loss TqPL increases as the required charging pressure PBRq increases.

In the present embodiment, the controller70calculates the pumping loss estimated value TqPLE based on the required charging pressure PBRq in addition to the intake air pressure and the engine speed. Since a change in the turbine upstream pressure PEX will indicate that the required charging pressure PBRq has changed, the pumping loss estimated value TqPLE will also change. Thus, the controller70improves the estimation accuracy of the pumping loss.

(2) When the throttle opening degree AC suddenly changes, the required charging pressure PBRq will be changed greatly. Section (B) ofFIG.3shows the required charging pressure PBRq when the throttle opening degree AC suddenly decreases. In such a case, the required charging pressure PBRq may deviate from the actual charging pressure. Under a situation in which the required charging pressure PBRq is deviated from the actual charging pressure, if the pumping loss estimated value TqPLE is calculated from the required charging pressure PBRq, the estimation of the pumping loss will not be accurate.

As shown in section (B) ofFIG.3, the smoothed required charging pressure value PBRqLv changes gradually even when the throttle opening degree AC suddenly changes. That is, even when the throttle opening degree AC suddenly changes, deviation of the smoothed required charging pressure value PBRqLv from the actual charging pressure will be limited.

Further, when the required charging pressure PBRq suddenly changes, the charging pressure PB, which is the detection value of the charging pressure sensor54, may fluctuate as shown by the broken line in section (B) ofFIG.3.

In this case, the controller70calculates the pumping loss estimated value TqPLE based on the smoothed required charging pressure value PBRqLv obtained by leveling the required charging pressure PBRq. Thus, the controller70maintains accuracy in the estimation of the pumping loss when the required charging pressure PBRq suddenly changes.

(3) The controller70uses the normalized intake air pressure PMa, which is the intake air pressure normalized under the atmospheric pressure KPA, to calculate the pumping loss estimated value TqPLE. The controller70also uses the normalized smoothed required charging pressure value PBRqLva, which is the smoothed required charging pressure value PBRqLv normalized under the atmospheric pressure KPA, to calculate the pumping loss estimated value TqPLE. Thus, the controller70maintains accuracy in the estimation of the pumping loss resulting from a change in the atmospheric pressure KPA.

(4) The controller70calculates a value that reflects a change in the turbine upstream pressure PEX as the pumping loss estimated value TqPLE without using a sensor that detects the turbine upstream pressure PEX.

Modification

The above-described embodiment may be modified as follows. The above-described embodiment and the following modifications can be combined if the combined modifications remain technically consistent with each other.

The calculation of the pumping loss estimated value TqPLE does not have to use the intake air pressure normalized under the atmospheric pressure KPA. That is, the controller70may use the intake air pressure PM instead of the normalized intake air pressure PMa to calculate the pumping loss estimated value TqPLE.

The calculation of the pumping loss estimated value TqPLE does not have to use the smoothed required charging pressure value PBRqLv normalized under the atmospheric pressure KPA. That is, the controller70may use the smoothed required charging pressure value PBRqLv instead of the normalized smoothed required charging pressure value PBRqLva to calculate the pumping loss estimated value TqPLE.

The controller70may calculate the pumping loss estimated value TqPLE using the charging pressure PB based on a detection value of the charging pressure sensor54instead of the required charging pressure PBRq. In this case, a smoothed value of the charging pressure PB may be used.

The map MP does not need to be used if the pumping loss estimated value TqPLE is calculated from the charging pressure, the engine speed, and the charging pressure. For example, the controller70calculates a base value of the pumping loss based on the charging pressure and the engine speed. Further, the controller70calculates a corrected value of the pumping loss based on the charging pressure. In this case, the controller70calculates the corrected value that is greater as the charging pressure PB becomes higher. Then, the controller70calculates the sum of the base value and the corrected value as the pumping loss estimated value TqPLE. The pumping loss estimated value TqPLE may be calculated in this manner in accordance with a change in the turbine upstream pressure PEX.

In the intake air pressure obtaining process M7, the CPU71obtains the intake air pressure PM based on a detection value of the intake air pressure sensor55. Instead, in the intake air pressure obtaining process M7, the CPU71may obtain the intake air pressure PM based on an estimated value that is derived from a physical model of the intake system of the internal combustion engine10.

The controller70is not limited to a device that includes a CPU and ROM and executes software processing. That is, the controller70may be modified to have any one of the following configurations (a) to (c).(a) The controller70includes a processor that executes various types of processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions configured to cause the CPU to execute processes. The memory, or computer readable media, include any type of media that are accessible by general-purpose computers and dedicated computers.(b) The controller70includes one or more dedicated hardware circuits that executes various types of processes. Examples of the dedicated hardware circuits include an application-specific integrated circuit such as ASIC or FPGA. ASIC is an acronym for an application-specific integrated circuit, and FPGA is an acronym for a field programmable gate array.(c) The controller70includes a processor that executes part of various types of processes according to a computer program and a dedicated hardware circuit that executes the remaining part of the various types of processes.

In other words, the above processes may be executed by processing circuitry that includes at least one of a processor and a dedicated hardware circuit. A plurality of processors and/or a plurality of dedicated hardware circuits may be included in the processing circuitry.