JP2024086322A - Control device for internal combustion engine - Google Patents

Abstract

An object of the present invention is to provide a control device for an internal combustion engine that can operate the internal combustion engine well when returning from a fuel cut.
[Solution] The engine comprises a plurality of cylinders 5, an intake variable valve mechanism 3A capable of changing the opening characteristics of the intake valve 14 of the cylinders 5, an exhaust variable valve mechanism 3B capable of changing the opening characteristics of the exhaust valve 24 of the cylinders 5, and a control unit 51 that controls to execute exhaust introduction control in which the intake variable valve mechanism 3A closes the intake valve 14 and the exhaust variable valve mechanism 3B opens the exhaust valve 24 while the supply of fuel to all cylinders 5 is stopped, and when there is an all-cylinder fuel cut request to stop the supply of fuel to all cylinders 5, the control unit 51 controls to execute exhaust introduction control after introducing fresh air into all cylinders 5.
[Selected Figure] Figure 1

Description

The present invention relates to a control device for an internal combustion engine.

Patent Document 1 describes an engine control device equipped with a variable cylinder system that sets each cylinder of the engine as an operating cylinder or a deactivated cylinder under specified operating conditions, and a variable valve timing mechanism that variably controls the timing of opening and closing the intake and exhaust valves. The ECU closes the intake valve of the deactivated cylinder and opens the exhaust bypass valve in the exhaust bypass passage, introducing a portion of the exhaust gas from the exhaust pipe of the operating cylinder into the deactivated cylinder.

JP 2006-336579 A

However, when fuel supply is resumed to a cylinder to which fuel supply has been stopped, there is a shortage of air necessary for combustion in the cylinder, so fresh air must first be introduced into the cylinder, making it difficult to quickly restart the engine.

The present invention aims to provide a control device for an internal combustion engine that can operate the engine well when returning from a fuel cut.

To solve the above problems, the present invention provides a control device for an internal combustion engine having multiple cylinders, an intake variable valve mechanism capable of changing the opening characteristics of the intake valves of the cylinders, and an exhaust variable valve mechanism capable of changing the opening characteristics of the exhaust valves of the cylinders, and includes a control unit that controls the intake variable valve mechanism to close the intake valves and the exhaust variable valve mechanism to open the exhaust valves while fuel supply to all of the cylinders is stopped, and when there is an all-cylinder fuel cut request that stops fuel supply to all of the cylinders, the control unit controls the exhaust introduction control to be executed after introducing fresh air into all of the cylinders.

In this way, the present invention allows the internal combustion engine to operate smoothly when returning from a fuel cut.

FIG. 1 is a schematic diagram of an internal combustion engine and a control device thereof according to an embodiment of the present invention. FIG. 2 is a flow chart showing a procedure for judging a requirement for exhaust gas introduction during fuel cut in the control device for an internal combustion engine according to one embodiment of the present invention. FIG. 3 is a flow chart showing a procedure of exhaust gas introduction control processing during fuel cut in the control device for an internal combustion engine according to one embodiment of the present invention.

The control device for an internal combustion engine according to one embodiment of the present invention is a control device for an internal combustion engine having a plurality of cylinders, an intake variable valve mechanism capable of changing the opening characteristics of the intake valves of the cylinders, and an exhaust variable valve mechanism capable of changing the opening characteristics of the exhaust valves of the cylinders, and is provided with a control unit that controls the intake variable valve mechanism to close the intake valves and the exhaust variable valve mechanism to open the exhaust valves while the supply of fuel to all cylinders is stopped, and is configured to control the exhaust introduction control to be executed after introducing fresh air into all cylinders when there is an all-cylinder fuel cut request that stops the supply of fuel to all cylinders.

As a result, the control device for an internal combustion engine according to one embodiment of the present invention can operate the internal combustion engine smoothly when returning from a fuel cut.

The following describes in detail an internal combustion engine control device according to an embodiment of the present invention with reference to the drawings.

As shown in FIG. 1, an internal combustion engine 1 according to one embodiment of the present invention is, for example, an in-line four-cylinder gasoline engine. Note that the number of cylinders in the internal combustion engine 1 is not limited to four. Also, the internal combustion engine 1 is not limited to a gasoline engine, and may be a diesel engine.

The internal combustion engine 1 is composed of a cylinder block 2 and a cylinder head 3 fastened to the upper part of the cylinder block 2. The cylinder block 2 is formed with a cylinder 5. The cylinder 5 contains a piston 6 that can reciprocate up and down within the cylinder 5. A combustion chamber 7 is provided at the upper part of the cylinder 5.

The internal combustion engine 1 is a so-called four-stroke gasoline engine that performs a series of four strokes consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston 6 reciprocates inside the cylinder 5.

The piston 6 is connected to the crankshaft 9 via a connecting rod 8. The connecting rod 8 converts the reciprocating motion of the piston 6 into the rotational motion of the crankshaft 9.

The cylinder head 3 is provided with an ignition plug 10, an intake port 11, and an exhaust port 12. The ignition plug 10 is provided in the cylinder head 3 with an electrode protruding into the combustion chamber 7, and its ignition timing is adjusted by an igniter (not shown).

The intake port 11 communicates with the combustion chamber 7 and an intake passage 16a, which will be described later. The intake port 11 is provided with an intake valve 14, which serves as an intake valve. The exhaust port 12 communicates with the combustion chamber 7 and an exhaust passage 26a, which will be described later. The exhaust port 12 is provided with an exhaust valve 24, which serves as an exhaust valve.

The intake valve 14 and exhaust valve 24 are opened and closed by a timing chain or timing belt (not shown) wrapped around the crankshaft 9.

An intake pipe 16 is connected to the intake port 11 side of the cylinder head 3. An intake passage 16a that communicates with the intake port 11 is formed inside the intake pipe 16. An electronically controlled throttle valve 18 is provided in the intake passage 16a.

The throttle valve 18 is electrically connected to the ECU 50, which will be described later. Therefore, the throttle valve 18 adjusts the amount of intake air for the internal combustion engine 1 by controlling the throttle opening in response to a command signal from the ECU 50.

The internal combustion engine 1 also includes an injector 13. The injector 13 is a port-injection type fuel injection valve that injects fuel pumped from a fuel tank (not shown) by a fuel pump into the combustion chamber 7 through the intake port 11.

In the internal combustion engine 1 configured in this manner, the air passing through the intake passage 16a is introduced into the intake port 11 after the flow rate is adjusted by the throttle valve 18. The air introduced into the intake port 11 is then mixed with fuel injected from the injector 13 and introduced into the combustion chamber 7.

On the other hand, an exhaust pipe 26 is connected to the exhaust port 12 side of the cylinder head 3. Inside the exhaust pipe 26, an exhaust passage 26a that communicates with the exhaust port 12 is formed. A catalyst 27 is provided on the exhaust passage 26a. The catalyst 27 purifies the exhaust gas discharged from the combustion chamber 7. The catalyst 27 is a three-way catalyst that simultaneously purifies the harmful substances contained in the exhaust gas, such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), and exhibits maximum exhaust gas purification performance at the theoretical air-fuel ratio.

The internal combustion engine 1 is equipped with a water temperature sensor 28, an O2 sensor 29, a crank angle sensor 32, an intake air temperature sensor 41, an air flow sensor 42, and an accelerator opening sensor 43.

The water temperature sensor 28 detects the temperature of the cooling water flowing through the water jacket 2a formed in the cylinder block 2 (the cooling water temperature), i.e., the engine water temperature.

The O2 sensor 29 is provided upstream of the catalyst 27 in the exhaust direction. The O2 sensor 29 is an oxygen sensor that has an output characteristic in which the output changes suddenly between the rich side and the lean side with respect to the air-fuel ratio based on the theoretical air-fuel ratio. Note that instead of the O2 sensor 29, an A/F sensor that has a linear output characteristic with respect to the air-fuel ratio may be used as the oxygen sensor.

The crank angle sensor 32 detects the rotation angle of the crankshaft 9 and outputs a detection signal to the ECU 50. Therefore, the crank angle sensor 32 detects the engine rotation speed.

The intake air temperature sensor 41 detects the temperature of the air passing through the intake passage 16a upstream of the throttle valve 18 (intake air temperature) and outputs a detection signal to the ECU 50.

The airflow sensor 42 detects the amount of air (intake air volume) passing through the intake passage 16a downstream of the throttle valve 18 and outputs a detection signal to the ECU 50.

The accelerator opening sensor 43 detects the amount of depression of the accelerator pedal (not shown) (accelerator opening) and outputs a detection signal to the ECU 50.

The internal combustion engine 1 is equipped with an intake variable valve mechanism 3A and an exhaust variable valve mechanism 3B. The intake variable valve mechanism 3A is provided on a camshaft (not shown) for the intake valve 14, and controls the valve timing (opening and closing timing) of the intake valve 14. In more detail, the intake variable valve mechanism 3A controls the valve timing so that the closing timing of the intake valve 14 can be varied to the retard side or advance side.

The exhaust variable valve mechanism 3B is provided on a camshaft (not shown) for the exhaust valve 24, and controls the valve timing (opening and closing timing) of the exhaust valve 24. In detail, the exhaust variable valve mechanism 3B controls the valve timing so that the closing timing of the exhaust valve 24 can be varied to the retard side or advance side.

The internal combustion engine 1 configured as described above has its operating state controlled by an ECU (Engine Control Unit) 50, which serves as a control device for the internal combustion engine. The ECU 50 includes a microcomputer equipped with, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an input/output interface, etc., and the CPU uses the temporary storage function of the RAM and performs signal processing according to a program pre-stored in the ROM. Various control constants, various maps, etc. are pre-stored in the ROM.

Various sensors, such as a water temperature sensor 28, an O2 sensor 29, a crank angle sensor 32, an intake air temperature sensor 41, an air flow sensor 42, and an accelerator opening sensor 43, are connected to the input side of the ECU 50 via a communication line conforming to a standard such as CAN.

On the other hand, the output side of the ECU 50 is connected to various devices such as the spark plug 10, injector 13, throttle valve 18, intake variable valve mechanism 3A, and exhaust variable valve mechanism 3B via a communication line conforming to a standard such as CAN.

The ECU 50 controls the spark plug 10, the injector 13, the throttle valve 18, the intake variable valve mechanism 3A, and the exhaust variable valve mechanism 3B based on the driver's operation and the operating state of the internal combustion engine 1. The ECU 50 also has a communication function that communicates with various sensors, actuators, and other control units via communication lines. The ECU 50 controls the timing and amount of fuel injection into the internal combustion engine 1 by controlling the supply of electricity to the injector 13.

When certain conditions are met, including the accelerator pedal not being depressed, the ECU 50 executes a fuel cut to stop fuel injection into the internal combustion engine 1.

The ECU 50 cuts fuel to some or all of the cylinders 5 depending on the operating state of the internal combustion engine 1.

For example, the ECU 50 determines that the exhaust gas introduction request during fuel cut is satisfied when the current engine water temperature is equal to or lower than a predetermined water temperature set value, or when the intake air temperature is equal to or lower than a predetermined intake air temperature set value.

The ECU 50 is equipped with a control unit 51 that, when a fuel cut request is made while an exhaust introduction request during fuel cut is established, executes exhaust introduction control to close the intake valve 14 using the intake variable valve mechanism 3A and open the exhaust valve 24 using the exhaust variable valve mechanism 3B while the fuel cut is being performed.

In exhaust intake control, the intake valve 14 is closed to minimize the intake of fresh air, and the exhaust valve 24 is opened during both the intake and exhaust strokes to introduce warm air from the exhaust manifold into the cylinder 5, thereby suppressing a drop in temperature inside the cylinder 5.

When there is an all-cylinder fuel cut request to stop the supply of fuel to all cylinders 5, the control unit 51 controls the system to introduce fresh air into all cylinders 5 and then executes exhaust introduction control.

When there is an all-cylinder fuel cut request to stop the supply of fuel to all cylinders 5, the control unit 51 may control the engine to fill all cylinders 5 with fresh air and then execute exhaust gas introduction control.

For example, when there is a request for fuel cut for all cylinders, the control unit 51 performs first set value cycle ventilation for all cylinders 5, and then executes exhaust introduction control for all cylinders 5. Note that the first set value is set to, for example, the number of cycles required to fill all cylinders 5 with fresh air during fuel cut, which is calculated based on the internal EGR rate of the internal combustion engine 1.

Fresh air is introduced when fuel is cut off for all cylinders in order to prevent the temperature inside the cylinders 5 from dropping by moving the fresh air back and forth between the exhaust pipe 26 and the cylinders 5, and also to allow fuel to be injected immediately the next time the accelerator pedal is depressed to obtain power.

The control unit 51 cuts fuel to some of the cylinders 5, performs exhaust gas introduction control for those cylinders 5, introduces fresh air into those cylinders 5, and then restarts those cylinders 5.

The control unit 51 may cut fuel to some of the cylinders 5, execute exhaust gas introduction control for those cylinders 5, fill those cylinders 5 with fresh air, and then restart those cylinders 5.

The control unit 51, for example, executes fuel cut to some of the cylinders 5, executes exhaust introduction control for those cylinders 5, and then, when the fuel cut for those cylinders 5 ends, performs second set value cycle ventilation for those cylinders 5 and then restarts those cylinders 5. Note that the second set value is set to, for example, the number of cycles required to fill those cylinders 5 with fresh air after the fuel cut, which is calculated based on the internal EGR rate for each cylinder 5.

When fuel is cut off for some cylinders 5, exhaust from other cylinders 5 is present in the exhaust pipe 26. Even if control similar to that for all cylinders is executed, the fresh air mixes with the exhaust and cannot be burned immediately. However, this is not a problem because the delay in output can be covered by the ignition timing of other cylinders 5 that are not undergoing fuel cut. For this reason, the priority is given to preventing a drop in temperature inside the cylinders 5, and fresh air is introduced after exhaust introduction control.

The process of judging whether or not exhaust gas introduction is required during fuel cut by the control device for an internal combustion engine according to this embodiment, which is configured as described above, will be described with reference to FIG. 2. Note that the process of judging whether or not exhaust gas introduction is required during fuel cut, which will be described below, starts when the ECU 50 starts operating.

In step S1, the ECU 50 acquires data on the current engine water temperature and intake air temperature. After executing the process of step S1, the ECU 50 executes the process of step S2.

In step S2, the ECU 50 determines whether the engine water temperature is equal to or lower than the water temperature setpoint.

If the ECU 50 determines that the engine water temperature is equal to or lower than the water temperature setpoint, the ECU 50 executes the process of step S4. If the ECU 50 determines that the engine water temperature is not equal to or lower than the water temperature setpoint, the ECU 50 executes the process of step S3.

In step S3, the ECU 50 determines whether the intake temperature is equal to or lower than the intake temperature setting.

If it is determined that the intake air temperature is equal to or lower than the intake air temperature set value, the ECU 50 executes the process of step S4. If it is determined that the intake air temperature is not equal to or lower than the intake air temperature set value, the ECU 50 executes the process of step S5.

In step S4, the ECU 50 determines that the exhaust gas introduction request during fuel cut is satisfied. After executing the process of step S4, the ECU 50 executes the process of step S1.

In step S5, the ECU 50 determines that the exhaust gas introduction request during fuel cut is not satisfied. After executing the process of step S5, the ECU 50 executes the process of step S1.

The exhaust gas introduction control process during fuel cut performed by the control device for an internal combustion engine according to this embodiment will be described with reference to FIG. 3. Note that the exhaust gas introduction control process during fuel cut described below is started when the ECU 50 starts operating, and is executed at preset time intervals.

In step S11, the ECU 50 determines whether or not a request for exhaust gas introduction during fuel cut is being satisfied.

If it is determined that the exhaust gas introduction request during fuel cut is satisfied, the ECU 50 executes the process of step S12. If it is determined that the exhaust gas introduction request during fuel cut is not satisfied, the ECU 50 executes the process of step S18.

In step S12, the ECU 50 determines whether or not there is a fuel cut request.

If it is determined that there is a fuel cut request, the ECU 50 executes the process of step S13. If it is determined that there is no fuel cut request, the ECU 50 executes the process of step S18.

In step S13, the ECU 50 determines whether the fuel cut request is for all cylinders.

If it is determined that there is a request to cut fuel for all cylinders, the ECU 50 executes the process of step S14. If it is determined that there is not a request to cut fuel for all cylinders, the ECU 50 executes the process of step S17.

In step S14, the ECU 50 determines whether first set value cycle ventilation has been completed for all cylinders 5.

If it is determined that the first set value cycle ventilation has been completed for all cylinders 5, the ECU 50 executes the process of step S16. If it is determined that the first set value cycle ventilation has not been completed for all cylinders 5, the ECU 50 executes the process of step S15.

In step S15, the ECU 50 performs the normal fuel cut and introduces fresh air. After executing the process of step S15, the ECU 50 executes the process of step S14.

In step S16, the ECU 50 closes the intake valves 14 of all cylinders 5 and executes exhaust introduction control for all cylinders 5. After executing the process of step S16, the ECU 50 executes the process of step S11.

In step S17, the ECU 50 performs fuel cut for the cylinder 5 in which fuel cut is to be performed, closes the intake valve 14 for the cylinder 5 in which fuel cut is to be performed, and performs exhaust introduction control for the cylinder 5 in which fuel cut is to be performed. After performing the process of step S17, the ECU 50 performs the process of step S11.

In step S18, the ECU 50 determines whether or not fuel cut has been experienced in any cylinder other than all cylinders.

If it is determined that fuel cut has been performed on all cylinders other than the cylinders, the ECU 50 executes the process of step S19. If it is determined that fuel cut has not been performed on all cylinders other than the cylinders, the ECU 50 executes the process of step S21.

In step S19, the ECU 50 determines whether the cylinder 5 that experienced the fuel cut has completed second set value cycle ventilation.

If it is determined that the second set value cycle ventilation has been completed, the ECU 50 executes the process of step S21. If it is determined that the second set value cycle ventilation has not been completed, the ECU 50 executes the process of step S20.

In step S20, the ECU 50 introduces fresh air into the cylinder 5 that experienced the fuel cut. After executing the process of step S20, the ECU 50 executes the process of step S19.

In step S21, the ECU 50 determines whether or not a request for exhaust gas introduction during fuel cut is in effect.

If it is determined that the exhaust gas introduction request during fuel cut is satisfied, the ECU 50 executes the process of step S11. If it is determined that the exhaust gas introduction request during fuel cut is not satisfied, the ECU 50 ends the exhaust gas introduction control process during fuel cut.

In this way, in this embodiment, when there is an all-cylinder fuel cut request to stop the supply of fuel to all cylinders 5, the control unit 51 controls the system to introduce fresh air into all cylinders 5 and then executes exhaust introduction control.

As a result, when there is a request for fuel cut for all cylinders, fresh air is introduced into all cylinders 5 and then exhaust gas introduction control is executed, which suppresses the decrease in temperature inside cylinder 5 during fuel cut and allows the internal combustion engine 1 to operate smoothly when fuel cut is resumed.

In addition, when there is an all-cylinder fuel cut request to stop the supply of fuel to all cylinders 5, the control unit 51 performs control to fill all cylinders 5 with fresh air and then executes exhaust introduction control.

As a result, when there is a request for all cylinders to be fuel-cut, all cylinders are filled with fresh air and then exhaust gas introduction control is executed, which suppresses the drop in temperature inside the cylinders during fuel cut and allows the internal combustion engine 1 to operate smoothly when fuel cut is resumed.

The control unit 51 also cuts fuel to some of the cylinders 5, performs exhaust gas introduction control for those cylinders 5, introduces fresh air into those cylinders 5, and then restarts those cylinders 5.

As a result, after exhaust gas introduction control is performed for some of the cylinders 5 during fuel cut, fresh air is introduced into some of the cylinders 5, and then some of the cylinders 5 are restarted, which suppresses the decrease in temperature inside the cylinders 5 during fuel cut and allows the internal combustion engine 1 to operate smoothly when fuel cut is resumed.

The control unit 51 cuts fuel to some of the cylinders 5, and then performs exhaust gas introduction control for those cylinders 5, fills those cylinders 5 with fresh air, and then restarts those cylinders 5.

As a result, after exhaust gas introduction control is performed for some of the cylinders 5 during fuel cut, some of the cylinders 5 are filled with fresh air, and then some of the cylinders 5 are restarted, which suppresses the drop in temperature inside the cylinders 5 during fuel cut and allows the internal combustion engine 1 to operate smoothly when fuel cut is resumed.

In this embodiment, the case of port injection in which fuel is injected into the intake port 11 is shown, but it can also be applied to the case of in-cylinder fuel injection in which fuel is injected directly into the cylinder 5.

In this embodiment, an example has been described in which the ECU 50 performs various determinations and calculations based on various sensor information, but the present invention is not limited to this. The vehicle may have a communication unit capable of communicating with an external device such as an external server, and the external device may perform various determinations and calculations based on the detection information of the various sensors transmitted from the communication unit. The communication unit may receive the determination results and calculation results, and the received determination results and calculation results may be used to perform various controls.

Although an embodiment of the present invention has been disclosed, it is apparent that modifications may be made by one of ordinary skill in the art without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 Internal combustion engine 3A Intake variable valve mechanism 3B Exhaust variable valve mechanism 5 Cylinder 13 Injector 14 Intake valve
24 Exhaust valve
43 Accelerator opening sensor 50 ECU
51 Control unit

Claims (4)

A plurality of cylinders;
an intake variable valve mechanism capable of changing an opening characteristic of an intake valve of the cylinder;
a variable exhaust valve mechanism capable of changing an opening characteristic of an exhaust valve of the cylinder;
A control device for an internal combustion engine comprising:
a control unit that performs control to execute exhaust introduction control in which the intake valve is closed by the intake variable valve mechanism and the exhaust valve is opened by the exhaust variable valve mechanism while the supply of fuel to all of the cylinders is stopped,
The control unit is a control device for an internal combustion engine that, when there is a request for all-cylinder fuel cut to stop the supply of fuel to all of the cylinders, controls the exhaust introduction control to be executed after introducing fresh air into all of the cylinders. The control device for an internal combustion engine according to claim 1, wherein the control unit, when there is an all-cylinder fuel cut request to stop the supply of fuel to all of the cylinders, controls to execute the exhaust gas introduction control after filling all of the cylinders with fresh air. The control device for an internal combustion engine according to claim 1 or 2, wherein the control unit performs fuel cut for some of the cylinders and the exhaust gas introduction control, then introduces fresh air into the cylinders, and then restarts the cylinders. The control device for an internal combustion engine according to claim 3, wherein the control unit executes fuel cut for some of the cylinders and executes the exhaust introduction control, then fills the cylinders with fresh air, and then restarts the cylinders.

Images