JP2011185189A - Vehicle control system - Google Patents

Abstract

To provide a vehicle control system capable of suppressing oxygen in a cylinder from becoming excessive when returning from fuel cut control.
An engine as a power source of a vehicle, a communication passage that connects an exhaust passage and an intake passage of the engine, and an open / close valve that opens and closes the communication passage, and supplies fuel to the engine while the vehicle is running. The fuel cut control can be executed to stop the gas, and the gas in the exhaust passage is opened by opening the open / close valve and opening the communication passage during the fuel cut control (S1-Y). A release control (S6) that allows the intake passage to flow through the communication passage can be executed, and a physical quantity corresponding to the amount of oxygen supplied into the cylinder of the engine during the intake stroke during the execution of the release control is obtained. When the predetermined amount or more is reached (S7-Y), the on-off valve is closed (S8).
[Selection] Figure 1

Description

  The present invention relates to a vehicle control system.

  Conventionally, a vehicle including an EGR passage (a communication passage that connects an intake passage and an exhaust passage of an engine) and an EGR valve (an opening / closing valve that opens and closes the communication passage) is known. For example, Patent Document 1 discloses a technique of a control device for an internal combustion engine that executes a valve opening process for opening an EGR valve during a fuel cut (fuel cut).

JP 2009-191791 A

  Here, if the state where the on-off valve is opened for a long time during the execution of the fuel cut control continues, the mixing ratio of fresh air increases. When the on-off valve is opened, the air discharged from the engine combustion chamber (inside the cylinder) to the exhaust passage flows into the communication passage, and the air flowing through the communication passage flows into the intake passage. As a result, a larger amount of air is accumulated in the intake passage than when the on-off valve is closed. The influence of the air accumulated in the intake passage continues thereafter, and a lot of air is supplied into the cylinder when the fuel cut is completed and the fuel supply is resumed. As a result, oxygen in the cylinder becomes excessive, and a large torque may be generated when returning from the fuel cut, causing a shock.

  An object of the present invention is to provide a vehicle control system capable of suppressing an excess of oxygen in a cylinder when returning from fuel cut control when the on-off valve is opened and the communication path is opened during execution of fuel cut control. Is to provide.

  A vehicle control system according to the present invention includes an engine as a power source of a vehicle, a communication passage that communicates an exhaust passage and an intake passage of the engine, and an on-off valve that opens and closes the communication passage. The fuel cut control for stopping the fuel supply to the engine can be executed, and the open / close valve is opened during the fuel cut control to open the communication passage. Thus, it is possible to execute an opening control that allows the gas in the exhaust passage to flow into the intake passage through the communication passage, and the air is supplied into the cylinder of the engine during an intake stroke during the execution of the opening control. The on-off valve is closed when a physical quantity corresponding to the amount of oxygen is equal to or greater than a predetermined quantity.

  In the vehicle control system, it is preferable that the opening control is executed when the fuel cut control is being executed and the accelerator opening is larger than the opening corresponding to accelerator off.

  In the vehicle control system, it is preferable that the opening degree of the on-off valve is determined so that the required torque for the engine based on the accelerator opening degree can be realized in the opening control.

  In the vehicle control system, in the opening control, when the physical quantity is large, it is preferable that the opening degree of the on-off valve is reduced more than when the physical quantity is small.

  In the vehicle control system, it is preferable that when the physical quantity becomes equal to or greater than the predetermined quantity, the timing for starting the supply of the fuel to the engine is after the opening / closing valve is closed.

  In the vehicle control system, the physical quantity is preferably an oxygen concentration of a gas flowing through the exhaust passage or an oxygen concentration of a gas flowing from the exhaust passage to the intake passage via the communication passage.

  In the vehicle control system according to the present invention, the gas in the exhaust passage flows into the intake passage through the communication passage by opening the on-off valve in the closed state and opening the communication passage during the fuel cut control. Permissible open control can be performed. Also, when the physical quantity corresponding to the amount of oxygen supplied into the cylinder of the engine in the intake stroke becomes greater than a predetermined amount during the opening control, the on-off valve is closed. Therefore, according to the vehicle control system of the present invention, it is possible to suppress the oxygen in the cylinder from being excessive when returning from the fuel cut control.

FIG. 1 is a flowchart illustrating the operation of the vehicle control system according to the embodiment. FIG. 2 is a diagram illustrating a main part of the vehicle to which the vehicle control system according to the embodiment is applied. Drawing 3 is a figure showing an example of a time chart in case control by a vehicle control system of an embodiment is performed. Drawing 4 is another figure showing an example of a time chart in case control by a vehicle control system of an embodiment is performed.

  Hereinafter, an embodiment of a vehicle control system according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

(Embodiment)
The embodiment will be described with reference to FIGS. 1 to 4. The present embodiment relates to a vehicle control system including a communication path that connects an exhaust path and an intake path of an engine, and an on-off valve that opens and closes the communication path. FIG. 1 is a flowchart showing the operation of the vehicle control system according to the embodiment of the present invention, and FIG. 2 is a diagram showing the main part of the vehicle to which the vehicle control system according to the embodiment is applied.

  When engine negative torque is required, the vehicle control system 1-1 according to the present embodiment introduces EGR remaining in the exhaust passage during fuel cut to reduce pumping loss and reduce power train friction. To do. However, if this state continues for a long time, the mixing ratio of fresh air increases, and a shock occurs when returning from the fuel cut control, or an emission problem occurs. Therefore, when the EGR is introduced during the fuel cut, the vehicle control system 1-1 causes a shock when returning from the fuel cut control by closing the EGR valve if the O2 concentration in the exhaust passage exceeds a certain value. Suppress.

  The vehicle control system 1-1 of the present embodiment is premised on including a fuel supply device, an EGR valve, an O2 sensor, and an engine friction reduction request calculation unit. As will be described in detail below, the vehicle control system 1-1 realizes the engine torque (negative torque) as requested without restarting fuel injection when there is a request for engine friction reduction during the fuel cut. If possible, open the EGR valve to reduce intake negative pressure. When the oxygen concentration in the exhaust passage exceeds the threshold value, the EGR valve is closed even when the engine friction reduction request is continued, and the introduction of EGR is stopped and the engine torque (negative torque) as required is realized. The fuel injection will be restarted. This makes it possible to suppress a shock at the time of return from the fuel cut control while responding to the driver's request for engine friction reduction.

  In FIG. 2, the code | symbol 1 shows the engine as a motive power source of the vehicle which is not shown in figure. An intake passage 3 and an exhaust passage 4 are connected to the combustion chamber 2 of the engine 1. An intake valve 5 is provided at a connection portion between the combustion chamber 2 and the intake passage 3. Further, an exhaust valve 6 is provided at a connection portion between the combustion chamber 2 and the exhaust passage 4. A throttle valve 7 that adjusts the flow rate of air flowing through the intake passage 3 and an air flow meter 8 that detects the flow rate of the air are arranged in the intake passage 3. The air flow meter 8 also serves as an intake air temperature sensor that detects the temperature of the air flowing through the intake passage 3. The opening degree of the throttle valve 7 is controlled by a throttle motor 16. Further, the vehicle is provided with a throttle position sensor 17 for detecting the opening degree of the throttle valve 7.

  In the exhaust passage 4, an A / F sensor 9, a three-way catalyst 10 (10A, 10B), and an O2 sensor 11 are provided. The three-way catalyst 10A is disposed upstream of the three-way catalyst 10B in the exhaust passage 4. In the exhaust passage 4, the A / F sensor 9 is disposed upstream of the three-way catalyst 10A, and the O2 sensor 11 is disposed downstream of the three-way catalyst 10A. Both the A / F sensor 9 and the O2 sensor 11 can detect the oxygen concentration.

  The vehicle is provided with an engine control computer (ECU) 30 that controls the engine 1. The engine 1 includes an injector 12, an oil control valve 13, a cam position sensor 14, and an ignition coil 15. The injector 12 injects fuel supplied from the fuel tank 27 into the intake passage 3. The oil control valve 13 makes the valve timing of the intake valve 5 variable. The cam position sensor 14 detects the rotation angle of the camshaft that drives the intake valve 5. The ignition coil 15 supplies current to a spark plug that ignites the air-fuel mixture in the combustion chamber 2. The engine 1 also includes a crank position sensor 18, a water temperature sensor 19, and a knock sensor 20. The crank position sensor 18 detects the rotation angle of the crankshaft 28. The ECU 30 can detect the engine speed Ne based on the detection result of the rotation angle of the crankshaft 28. The water temperature sensor 19 detects the cooling water temperature of the engine 1. Knock sensor 20 detects the occurrence of knocking in engine 1.

  The ECU 30 is connected with an A / F sensor 9, an O2 sensor 11, a cam position sensor 14, a throttle position sensor 17, a crank position sensor 18, a water temperature sensor 19, and a knock sensor 20, and signals indicating the detection results of the sensors. Is input to the ECU 30. The ECU 30 is connected to an injector 12, an oil control valve 13, an ignition coil 15, and a throttle motor 16, and the ECU 30 controls each device. For example, the ECU 30 controls the fuel injection timing and the injection amount by the injector 12. Further, the ECU 30 controls the ignition timing for the air-fuel mixture in the combustion chamber 2 by adjusting the current supply timing by the ignition coil 15. Further, the ECU 30 controls the amount of air supplied to the combustion chamber 2 by adjusting the opening of the throttle motor 16.

  The engine 1 of this embodiment includes an EGR passage 21, an EGR valve 22, an EGR cooler 23, and an EGR gas temperature sensor 24. The EGR passage 21 is a communication passage that connects the exhaust passage 4 and the intake passage 3. The EGR passage 21 communicates the downstream side of the intake passage 3 with respect to the throttle valve 7 and the upstream side of the exhaust passage 4 with respect to the A / F sensor 9. The EGR valve 22 is an open / close valve that opens and closes the EGR passage 21. The EGR valve 22 can be adjusted to an arbitrary opening degree. The EGR valve 22 can close the EGR passage 21 and can adjust the flow rate of the gas flowing through the EGR passage 21 by being opened to an arbitrary opening degree. When the EGR valve 22 is opened, the gas in the exhaust passage 4 is allowed to flow into the intake passage 3 via the EGR passage 21.

  The EGR cooler 23 cools the gas flowing through the EGR passage 21. The EGR gas temperature sensor 24 detects the temperature of the gas flowing through the EGR passage 21. The EGR gas temperature sensor 24 is connected to the ECU 30, and a signal indicating the detection result of the EGR gas temperature sensor 24 is input to the ECU 30. The EGR valve 22 is connected to the ECU 30, and the EGR valve 22 is controlled by the ECU 30. The ECU 30 can adjust the opening degree of the EGR valve 22 to an arbitrary opening degree from the fully closed state where the EGR passage 21 is closed to the fully opened state by a control command.

  The ECU 30 is connected to an accelerator position sensor 25 that detects an opening (operation amount) of an accelerator pedal (not shown), and a signal indicating the detected accelerator opening is input to the ECU 30. A vehicle speed sensor 26 that detects the vehicle speed is connected to the ECU 30, and a signal indicating the detected vehicle speed is input to the ECU 30. In addition to the above, an air conditioner switch and an ignition switch are connected to the ECU 30, and signals from each switch and sensor are input to the ECU 30. Moreover, ECU30 is connected with the connector (DLC3) for a diagnostic tool. The vehicle control system 1-1 of the present embodiment includes an engine 1, an EGR passage 21, an EGR valve 22, and an ECU 30.

  The ECU 30 executes fuel cut control for stopping the fuel supply to the engine 1 when a predetermined fuel cut execution condition is satisfied during traveling. The fuel cut execution condition is determined with respect to the accelerator opening and the engine speed Ne, for example. The fuel cut execution conditions include, for example, a condition that the accelerator opening is equal to or less than a predetermined opening, and a condition that the engine speed Ne is equal to or higher than a predetermined rotation, and all of these conditions are satisfied. Then, fuel cut control is permitted. At the start of fuel cut control, the opening of the EGR valve 22 is, for example, in a fully closed state (valve closed state).

  When there is a request to reduce engine friction during execution of fuel cut control, the ECU 30 opens the EGR valve 22 in the closed state. For example, the driver may perform an accelerator operation in order to slightly weaken the deceleration with respect to a deceleration state that occurs when the accelerator is released (accelerator off). In response to this engine friction reduction request, as one of the techniques for reducing the friction of the engine 1 while maintaining the fuel cut state, there is a technique of reducing the intake negative pressure by opening the throttle valve 7 to reduce the friction. . In this method, the amount of air flowing into the combustion chamber 2 is increased as compared with the case where the throttle valve 7 is closed, so that a large torque is generated at the time of return from the fuel cut control and a shock occurs, or the air-fuel ratio is lean. This may cause exhaust emission problems (increased emissions of harmful substances).

  In the present embodiment, the ECU 30 opens the EGR valve 22 during the fuel cut and introduces the gas in the exhaust passage 4 into the intake passage 3 as a means for reducing the intake negative pressure and not increasing the air amount. When the EGR valve 22 in the closed state is opened and the EGR passage 21 is opened, the gas in the exhaust passage 4 is allowed to flow into the intake passage 3 through the EGR passage 21. In the following description, the EGR valve 22 in the closed state is opened during the fuel cut and the EGR passage 21 is opened to allow gas to flow from the exhaust passage 4 to the intake passage 3 through the EGR passage 21. This control is referred to as “open control”. In the opening control, for example, the EGR valve 22 is opened with the throttle valve 7 fully closed. By this opening control, the intake negative pressure can be reduced, the pumping loss can be reduced, and the engine friction can be reduced. However, if the EGR valve 22 is opened for a long time, a large amount of air is accumulated in the intake passage 3. As a result, as will be described below, there is a possibility that oxygen in the combustion chamber 2 becomes excessive at the time of return from the fuel cut control, resulting in a shock or emission problem.

  The ECU 30 increases or decreases the fuel injection amount at the time of return from the fuel cut control based on the O2 concentration in the exhaust passage 4 detected by the O2 sensor 11. When the O2 concentration in the exhaust passage 4 is large, the O2 concentration of the gas introduced into the intake passage 3 via the EGR passage 21 becomes large. Therefore, if the O2 concentration in the exhaust passage 4 is large, the amount of oxygen supplied into the cylinder during the intake stroke during execution of the opening control (hereinafter simply referred to as “in-cylinder oxygen amount”) is large. Become. Thereby, when the O2 concentration in the exhaust passage 4 is large, the ECU 30 determines the fuel injection amount at the time of return from the fuel cut control to a larger value than when the O2 concentration is small. Therefore, if the O2 concentration in the exhaust passage 4 becomes large, the torque fluctuation becomes large when the fuel cut control is restored, and a shock may occur. Further, when returning from fuel cut control, the in-cylinder oxygen amount may become excessively lean with respect to the fuel injection amount.

  In contrast, in this embodiment, when the O2 concentration (oxygen concentration) in the exhaust passage 4 exceeds the threshold value, the EGR valve 22 is closed even when the engine friction reduction request is continued. . When the EGR valve 22 is closed, fuel injection is resumed in order to achieve the engine torque (negative torque) as required instead of introducing EGR. Thereby, while responding to the driver's request for reducing engine friction, it is possible to suppress the oxygen in the combustion chamber 2 from being excessive, and to suppress the occurrence of shock and emission problems.

  The operation of this embodiment will be described with reference to FIG. The control flow shown in FIG. 1 is executed during traveling, and is repeatedly executed at a predetermined cycle, for example. 3 and 4 are diagrams showing examples of time charts when the control by the vehicle control system of the present embodiment is executed. 3 and 4, (a) is the vehicle speed, (b) is the accelerator opening, (c) is the fuel injection request, (d) is the EGR opening rate (the opening of the EGR valve 22), and (e) is O2 Each of the O2 concentrations detected by the sensor 11 is shown. FIG. 3 shows a time chart when the O2 concentration in the exhaust passage 4 exceeds the threshold value α during the opening control and the fuel cut control is resumed. FIG. 4 shows a time chart in the case where the accelerator opening increases during the opening control and a request for engine torque that cannot be realized in the fuel cut state occurs.

  Referring to FIG. 1, first, in step S1, ECU 30 determines whether or not there is a fuel cut request. The ECU 30 determines whether or not a fuel cut execution condition is satisfied and a fuel cut request is made. As a result of the determination, if it is determined that there is a fuel cut request (step S1-Y), the process proceeds to step S2, and if not (step S1-N), the process proceeds to step S9.

  In step S2, the ECU 30 executes a fuel cut. The ECU 30 stops fuel injection by the injector 12 when fuel has been supplied to the engine 1 and starts fuel cut control. If fuel cut is already being executed, the fuel injection is performed. Continue to stop.

  Next, in step S3, the ECU 30 determines whether or not there is an engine friction reduction request. The ECU 30 performs the determination in step S3 based on, for example, the accelerator opening detected by the accelerator position sensor 25. For example, the ECU 30 makes an affirmative determination in step S3 when the accelerator opening is larger than the opening corresponding to accelerator-off. As a result of the determination, if it is determined that there is an engine friction reduction request (step S3-Y), the process proceeds to step S4, and if not (step S3-N), the process proceeds to step S2 to continue the fuel cut. .

  In step S4, the ECU 30 determines whether the fuel cut can be continued. The ECU 30 performs the determination in step S4 based on whether or not the required engine torque (negative torque) can be achieved without restarting the fuel injection. The ECU 30 determines the output torque required for the engine 1 based on the accelerator opening detected by the accelerator position sensor 25. The ECU 30 stores in advance, for example, a map of the correspondence between the accelerator opening, the vehicle speed, and the requested acceleration (or the requested driving force), and the engine 1 is based on this correspondence (because the correspondence can be realized). A required torque that is a required output torque is determined. If the determined required torque exceeds the output torque (maximum value) of the engine 1 that can be realized without restarting the fuel injection, a negative determination is made in step S4.

  Here, the output torque of the engine 1 that can be realized without resuming the fuel injection is an output torque that can be realized by the opening control that opens the EGR valve 22 and opens the EGR passage 21. The maximum value of the output torque of 1 is, for example, an output torque that can be realized when the opening degree of the EGR valve 22 is maximized (fully opened). As a result of the determination in step S4, if it is determined that the fuel cut can be continued (step S4-Y), the process proceeds to step S5. If not (step S4-N), the process proceeds to step S9.

  In the example shown in FIG. 4, it is not determined that the accelerator opening increases at time t3 and the fuel cut can be continued, the EGR valve 22 is closed, and fuel injection is resumed.

  In step S5, the ECU 30 determines whether or not the EGR valve 22 is being opened. For example, the ECU 30 performs the determination in step S5 based on the command value of the current opening degree for the EGR valve 22. As a result of the determination, if it is determined that the EGR valve 22 is open (step S5-Y), the process proceeds to step S7, and if not (step S5-N), the process proceeds to step S6.

  In step S6, the EGR valve 22 is opened by the ECU 30. The opening of the EGR valve 22 at this time is, for example, the opening of the EGR valve 22 capable of realizing the required torque for the engine 1 determined in step S4. That is, the opening command value for the EGR valve 22 is an opening that can reduce the friction (pumping loss) and make the output torque of the engine 1 the required torque. In addition, the command value of the opening degree with respect to the EGR valve 22 is not limited to this, and may be a constant opening degree such as a full opening or a predetermined opening between the full opening and the full closing. That is, the opening command value for the EGR valve 22 may be an opening that can increase the engine output torque (decrease the negative torque) in response to the engine friction reduction request. The ECU 30 outputs a command value of the opening degree to the EGR valve 22 and opens the EGR valve 22. As a result, engine friction is reduced, and the engine friction reduction request by the driver is realized. When step S6 is executed, the process proceeds to step S7.

  In step S7, the ECU 30 determines whether or not the O2 concentration is equal to or higher than a predetermined concentration α that is a predetermined threshold value. The ECU 30 performs the determination in step S7 based on the comparison result between the O2 concentration detected by the O2 sensor 11 and the predetermined concentration α. The predetermined concentration α is, for example, a value that can suppress the amount of oxygen (in-cylinder oxygen amount) contained in the intake air supplied to the cylinder (combustion chamber 2) of the engine 1 from being equal to or greater than a predetermined oxygen amount. It has been established. During execution of the opening control in which the EGR valve 22 is opened, the gas flowing through the exhaust passage 4 is guided to the intake passage 3 through the EGR passage 21. Accordingly, the in-cylinder oxygen amount varies depending on the O 2 concentration in the exhaust passage 4. When the O2 concentration in the exhaust passage 4 is high, the in-cylinder oxygen amount increases as compared with the case where it is low. That is, the O2 concentration in the exhaust passage 4 is a physical quantity corresponding to the amount of oxygen supplied into the cylinder of the engine 1 during the intake stroke during the execution of the opening control.

  The predetermined concentration α is set based on, for example, the amount of torque fluctuation when returning from fuel cut control and restarting the supply of fuel to the engine 1. For example, when the upper limit of the allowable torque fluctuation amount is determined, the O2 concentration of the exhaust passage 4 at which the generated torque fluctuation amount becomes the upper limit of the determined torque fluctuation amount can be set to the predetermined concentration α. The predetermined concentration α may be set based on, for example, the result of the adaptation experiment. If the relationship between the O2 concentration in the exhaust passage 4 and the amount of torque fluctuation that occurs at the time of return from fuel cut control changes depending on the operating condition such as the engine speed Ne, the predetermined concentration α can be varied according to the operating condition. You may make it. As described above, when the O2 concentration in the exhaust passage 4, which is a physical quantity corresponding to the oxygen amount (in-cylinder oxygen amount) supplied into the cylinder in the intake stroke during execution of the opening control, becomes equal to or higher than the predetermined concentration α (predetermined amount). By closing the EGR valve 22, the amount of oxygen in the cylinder is suppressed from becoming excessive.

  As a result of the determination in step S7, if it is determined that the O2 concentration in the exhaust passage 4 is equal to or higher than the predetermined concentration α (step S7-Y), the process proceeds to step S8, and if not (step S7-N), The control flow returns. In the time chart shown in FIG. 3, the O2 concentration reaches the predetermined concentration α at time t2, and an affirmative determination is made in step S7.

  In step S8, the EGR valve 22 is closed by the ECU 30. The ECU 30 outputs a command signal for fully closing the opening degree to the EGR valve 22 to close the EGR valve 22. When step S8 is executed, the process proceeds to step S9.

  In step S9, the fuel injection is performed by the ECU 30. The ECU 30 outputs a command signal for performing fuel injection to the injector 12. The command value of the fuel injection amount at this time is set to an injection amount corresponding to the amount of oxygen supplied into the cylinder, for example. That is, according to the vehicle control system 1-1 of the present embodiment, when the O2 concentration reaches the predetermined concentration α (step S7-Y), the fuel cut control is restored with torque fluctuation that does not cause a shock. Can do. When step S9 is executed, the control flow returns.

  As described above, according to the vehicle control system 1-1 of the present embodiment, when there is an engine friction reduction request during execution of the fuel cut control, the engine friction is reduced by the opening control, so that the engine It is possible to meet the driver's torque request without restarting 1. Since it is possible to execute the negative torque control while continuing the fuel cut control, it is possible to improve the fuel consumption. Further, when the O2 concentration in the exhaust passage 4 becomes equal to or higher than the predetermined concentration α during the opening control, the fuel cut control is resumed, and the fuel injection is resumed so that the combustion is performed at the time of return from the fuel cut control. Excessive oxygen in the chamber 2 is suppressed. Therefore, it is possible to suppress the occurrence of a shock when returning from the fuel cut control or the problem of exhaust emission due to the lean air-fuel ratio.

  In addition, when the O2 concentration in the exhaust passage 4 becomes equal to or higher than the predetermined concentration α, the timing at which the fuel supply to the engine 1 is resumed is after the EGR valve 22 is closed. As a result, the amount of intake air flowing into the cylinder of the engine 1 is reduced as compared with the case where the fuel supply is resumed before or simultaneously with the closing of the EGR valve 22. Therefore, since an increase in the amount of oxygen supplied into the cylinder of the engine 1 during the intake stroke is suppressed, torque fluctuation at the time of return from the fuel cut control can be reduced.

  In the present embodiment, the release control is performed when the driver requests engine friction reduction, but the present invention is not limited to this. For example, even when the opening control is executed for a reason different from the engine friction reduction request, if the EGR valve 22 is closed when the O2 concentration in the exhaust passage 4 increases, when returning from the fuel cut control, The occurrence of shock can be suppressed.

  In the present embodiment, the EGR valve 22 is determined to be closed based on the O2 concentration detected by the O2 sensor 11, but instead, based on the O2 concentration detected by the A / F sensor 9. Thus, the closing timing of the EGR valve 22 may be determined. The valve closing timing of the EGR valve 22 is not limited to the O2 concentration in the exhaust passage 4 but based on the O2 concentration of the gas flowing from the exhaust passage 4 to the intake passage 3 via the EGR passage 21 such as the O2 concentration in the EGR passage 21. May be determined.

(First Modification of Embodiment)
In the above embodiment, the closing timing of the EGR valve 22 is determined based on the O2 concentration in the exhaust passage 4, but the present invention is not limited to this. Even if the physical quantity is different from the O2 concentration in the exhaust passage 4, if the physical quantity corresponds to the in-cylinder oxygen quantity, the closing timing of the EGR valve 22 can be determined based on the physical quantity. For example, the execution time of opening control (elapsed time from the start of opening control, etc.) may be used as the physical quantity corresponding to the in-cylinder oxygen amount. Further, instead of the physical quantity corresponding to the in-cylinder oxygen amount, EGR is based on the physical quantity corresponding to the oxygen concentration (in-cylinder oxygen concentration) of the intake air supplied into the cylinder of the engine 1 during the intake stroke during execution of the opening control. The valve closing timing of the valve 22 may be determined. The O2 concentration in the exhaust passage 4 is a physical quantity corresponding to the in-cylinder oxygen concentration.

(Second Modification of Embodiment)
In addition to the opening control of the EGR valve 22 in the opening control of the above embodiment, the command value for the opening of the EGR valve 22 may be determined according to the oxygen concentration in the exhaust passage 4 during the execution of the opening control.

  For example, even when the accelerator opening (the required torque for the engine 1) is the same, the opening of the EGR valve 22 may be decreased in accordance with an increase in the O2 concentration in the exhaust passage 4. That is, when the O2 concentration in the exhaust passage 4 which is a physical quantity corresponding to the in-cylinder oxygen amount is large, the opening degree of the EGR valve 22 may be reduced as compared with the case where the O2 concentration in the exhaust passage 4 is small. Similarly to the above embodiment, when the O2 concentration in the exhaust passage 4 is equal to or higher than the predetermined concentration α, the EGR valve 22 is closed. In this way, it is possible to suppress the increase in the O2 concentration in the exhaust passage 4 while realizing the engine friction reduction request by the driver, and to extend the duration of the opening control and improve the fuel efficiency.

  As described above, the vehicle control system according to the present invention is useful in a vehicle including a communication path that connects the intake path and the exhaust path and an on-off valve that opens and closes the communication path, and in particular, during execution of fuel cut control. When the on-off valve is opened to open the communication path, it is suitable for suppressing the oxygen in the cylinder from becoming excessive when returning from the fuel cut control.

1-1 Vehicle control system 1 Engine 2 Combustion chamber (in-cylinder)
3 Intake passage 4 Exhaust passage 11 O2 sensor 12 Injector 21 EGR passage 22 EGR valve 25 Accelerator position sensor 30 ECU

Claims (6)

An engine as a power source for the vehicle,
A communication passage communicating the exhaust passage and the intake passage of the engine;
An on-off valve that opens and closes the communication path,
Fuel cut control for stopping the supply of fuel to the engine while the vehicle is running can be executed,
Opening that allows the gas in the exhaust passage to flow to the intake passage through the communication passage by opening the on-off valve in the closed state during the fuel cut control to open the communication passage. When the control is executable and the physical quantity corresponding to the amount of oxygen supplied into the cylinder of the engine in the intake stroke during execution of the opening control is greater than or equal to a predetermined amount, the on-off valve is closed. A vehicle control system characterized by valve. The vehicle control system according to claim 1, wherein the release control is executed when the fuel cut control is being executed and the accelerator opening is larger than an opening corresponding to accelerator off. The vehicle control system according to claim 2, wherein in the opening control, the opening degree of the on-off valve is determined so that a required torque for the engine based on the accelerator opening degree can be realized. The vehicle control system according to any one of claims 1 to 3, wherein, in the opening control, when the physical quantity is large, the opening degree of the on-off valve is reduced as compared with a case where the physical quantity is small. The timing for starting the supply of the fuel to the engine when the physical quantity is equal to or greater than the predetermined amount is after the on-off valve is closed. Vehicle control system. The physical quantity is an oxygen concentration of a gas flowing through the exhaust passage or an oxygen concentration of a gas flowing from the exhaust passage to the intake passage via the communication passage. Vehicle control system.

Images