Control method for vehicle and control device for vehicle

Abstract

To prevent deterioration of driving performance when reducing an intake air amount while maintaining an air-fuel ratio.SOLUTION: During an operation of an internal combustion engine 2 at a power generation air-fuel ratio as a lean air-fuel ratio, a request for treating NOx adhered to an NOx trap catalyst 8 is made, a vehicle 1 reduces an intake air amount with the power generation air-fuel ratio maintained before execution of a rich spike, reduces a valve overlap amount of an intake valve and an exhaust valve from a power generation valve overlap amount in accordance with a decrease of the intake air amount, and sets a decrease amount rate of a fuel injection amount to be directly injected into a cylinder at a last stage in one combustion cycle so that the decrease amount rate becomes moderate relative to a decrease amount rate of the intake air amount. When the intake air amount is decreased to a predetermined treatment air amount for NOx treatment, the vehicle 1 starts the rich spike.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vehicle control method and a vehicle control device.

Background Art

[0002] For example, Patent Document 1 discloses a technique in which when switching the air-fuel ratio from a lean air-fuel ratio larger than the stoichiometric air-fuel ratio to the stoichiometric air-fuel ratio, the intake air amount is decreased while maintaining the air-fuel ratio at the lean air-fuel ratio. When the intake air amount reaches a predetermined air amount threshold value, the air-fuel ratio is changed to the stoichiometric air-fuel ratio, and a rich spike is implemented in which the fuel injection amount is temporarily increased during operation at the stoichiometric air-fuel ratio in a state where the intake air amount is less than the lean air-fuel ratio.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, since the intake air amount is decreased while maintaining the lean air-fuel ratio, negative pressure on the intake passage side develops, and a part of the residual gas in the cylinder flows into the intake passage side, increasing the amount of residual gas in the cylinder and possibly deteriorating drivability or causing misfires.

[0005] That is, when decreasing the intake air amount while maintaining the air-fuel ratio at the lean air-fuel ratio during operation, there is room for further improvement in order to prevent deterioration of drivability and misfires.

Means for Solving the Problems

[0006] When the vehicle of the present invention is operating an internal combustion engine at a predetermined lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, and a processing requirement for NOx adsorbed on a NOx trap catalyst provided in the exhaust passage occurs, the air-fuel ratio is maintained at the lean air-fuel ratio while reducing the intake air amount, and the valve overlap amount of the intake valve and the exhaust valve is reduced compared to the valve overlap amount before the occurrence of the processing requirement. When the intake air amount decreases to a predetermined processing air amount for NOx processing, the fuel injection amount is temporarily increased.

Advantages of the Invention

[0007] When a processing requirement for NOx adsorbed on a NOx trap catalyst occurs in the vehicle of the present invention, before temporarily increasing the fuel injection amount, the intake air amount is reduced while maintaining the lean air-fuel ratio, and by reducing the valve overlap amount, an increase in the residual gas amount is suppressed, and deterioration of drivability and misfire can be prevented.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0010] FIG. 1 is an explanatory diagram schematically showing the outline of the drive system of a vehicle 1 to which the present invention is applied.

[0011] The vehicle 1 is equipped with an internal combustion engine 2 for power generation to drive a generator 3.

[0012] The internal combustion engine 2 is a direct injection spark ignition internal combustion engine using a so-called piston crank mechanism, and is capable of varying the air-fuel ratio. More specifically, the internal combustion engine 2 can vary the air-fuel ratio between a predetermined lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio and a predetermined rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio. A generator 3 is connected to the output shaft (crankshaft) of the internal combustion engine 2.

[0013] Further, the internal combustion engine 2 is capable of performing stratified combustion. Stratified combustion forms, for example, a relatively homogeneous air-fuel mixture in the cylinder by a first injection (main injection) injected during the intake stroke and a second injection (stratification injection) injected during the compression stroke immediately before the ignition timing to locally form an air-fuel mixture with an appropriate equivalence ratio near the spark plug. That is, the internal combustion engine 2 can directly inject fuel into the cylinder in multiple divisions during one combustion cycle.

[0014] Note that the internal combustion engine 2 can also form a relatively homogeneous air-fuel mixture in the cylinder and perform homogeneous combustion by not performing the above-described stratification injection.

[0015] The internal combustion engine 2 has a first variable valve mechanism (first VTC) 4 capable of varying the valve timing of the intake valve, which is an engine valve, and a second variable valve mechanism (second VTC) 5 capable of varying the valve timing of the exhaust valve, which is an engine valve. Here, the valve timing is the opening timing and closing timing of the engine valve.

[0016] The first variable valve mechanism 4 is, for example, a phase variable mechanism that continuously advances or retards the phase of the center angle of the lift of the intake valve (phase with respect to the crankshaft). The second variable valve mechanism 5 is, for example, a phase variable mechanism that continuously advances or retards the phase of the center angle of the lift of the exhaust valve (phase with respect to the crankshaft). The phase variable mechanism is already known, for example, from Japanese Patent Application Laid-Open No. 2002-89303 and the like.

[0017] In the exhaust passage 6 of the internal combustion engine 2, a three-way catalyst 7 and a NOx trap catalyst 8 capable of adsorbing NOx are provided as catalysts for purifying exhaust gas.

[0018] The three-way catalyst 7 can simultaneously purify NOx, HC, and CO in the exhaust gas with the maximum conversion efficiency when the air-fuel ratio is within a so-called window centered on the stoichiometric air-fuel ratio. The three-way catalyst 7 is located on the exhaust upstream side of the NOx trap catalyst 8.

[0019] The NOx trap catalyst 8 traps NOx (nitrogen oxides) in the exhaust gas when the exhaust air-fuel ratio is lean, and reduces and purifies the trapped NOx using HC (hydrocarbons) and CO in the exhaust gas as reducing agents when the exhaust air-fuel ratio is stoichiometric or rich.

[0020] The generator 3 generates electric power to supply the driving motor 10, which serves as an electric motor for driving the left and right drive wheels 9, 9 of the vehicle 1. The electric power generated by the generator 3 is charged to the battery 11. Note that the electric power generated by the generator 3 can also be supplied to the driving motor 10.

[0021] The driving motor 10 is a direct driving source of the vehicle 1 and is driven by, for example, alternating current power from the battery 11. The driving motor 10 functions as a generator when the vehicle 1 decelerates. That is, the driving motor 10 is a motor-generator capable of charging the battery 11 with the regenerative energy during vehicle deceleration as electric power.

[0022] The rotation of the driving motor 10 is transmitted to the left and right drive wheels 9, 9 via the reduction gear 12 and the differential gear 13.

[0023] The reduction gear 12 reduces the rotation of the driving motor 10 and increases the motor torque to ensure the driving torque for running.

[0024] The differential gear 13 transmits the same driving torque to the left and right drive wheels 9, 9 while allowing a difference in the rotational speeds of the left and right drive wheels 9, 9.

[0025] That is, the vehicle 1 is a so-called series hybrid vehicle that runs by driving the drive motor 10 with the electric power from the generator 3 driven by the internal combustion engine 2 and the electric power from the battery 11.

[0026] The air-fuel ratio of the internal combustion engine 2 and the valve timing of the intake valve and the exhaust valve are controlled by an ECM (Engine Control Module) 14 as a control unit. That is, the ECM 14 controls the first variable valve mechanism 4 and the second variable valve mechanism 5 to enable control of the valve overlap amount, which is a period of valve overlap during which the intake valve opening period and the exhaust valve opening period overlap. Also, the generator 3 and the drive motor 10 are controlled by a VCM (Vehicle Control Module) 15 as a control unit.

[0027] The ECM 14 and the VCM 15 are well-known digital computers equipped with a CPU, a ROM, a RAM, and an input / output interface. The ECM 14 can communicate with the VCM 15, for example, by CAN communication.

[0028] The ECM 14 controls the internal combustion engine 2 to operate at a predetermined power generation operating point. Specifically, when generating electricity with the generator 3, the ECM 14 operates the internal combustion engine 2 at a power generation operating point where the engine speed is a predetermined power generation rotation speed and the engine load (engine torque) is a predetermined power generation load. Also, when operating the internal combustion engine 2 at the power generation operating point, the ECM 14 controls so that the intake air amount is a predetermined power generation air amount, the air-fuel ratio of the air-fuel mixture in the cylinder is a predetermined power generation air-fuel ratio, and the valve overlap amount between the intake valve and the exhaust valve is a predetermined power generation valve overlap amount. The engine load is proportional to the amount of electricity generated by the generator 3. The above-mentioned power generation air-fuel ratio is, for example, a significantly lean air-fuel ratio compared to the stoichiometric air-fuel ratio when charging the battery 11. The power generation valve overlap amount is, for example, a predetermined amount greater than "0".

[0029] Based on the output signals from various sensors, the ECM 14 can estimate the amount of NOx adsorbed by the NOx trap catalyst 8. The amount of NOx adsorbed by the NOx trap catalyst 8 can be estimated (calculated), for example, by integrating the amount of NOx estimated from the operating conditions such as the engine speed and fuel injection amount of the internal combustion engine 2 according to the operation history.

[0030] Also, when the adsorption amount of NOx adsorbed by the NOx trap catalyst 8 becomes equal to or greater than a preset predetermined amount and a treatment request for the NOx adsorbed by the NOx trap catalyst 8 (NOx treatment request) occurs, the ECM 14 performs a rich spike to temporarily increase the fuel injection amount so that the air-fuel ratio becomes the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio, thereby reducing the air-fuel ratio to remove the NOx adsorbed by the NOx trap catalyst 8. This rich spike temporarily enriches the air-fuel ratio so that the exhaust becomes a reducing atmosphere for NOx. The trap catalyst NOx treatment request is maintained, for example, until the adsorption amount of NOx adsorbed by the NOx trap catalyst 8 becomes "0".

[0031] The VCM 15 can detect the SOC (State Of Charge), which is the ratio of the remaining charge to the charging capacity of the battery 11. When the SOC of the battery 11 becomes equal to or less than a preset predetermined value during the running of the vehicle 1 based on the information from the VCM 15, for example, the ECM 14 drives the internal combustion engine 2 to charge the battery 11.

[0032] When a NOx treatment request adsorbed by the NOx trap catalyst 8 occurs during the operation of the internal combustion engine 2 at the air-fuel ratio for power generation as the lean air-fuel ratio, before the execution of the rich spike, the intake air amount is decreased from the air-fuel ratio for power generation while maintaining the air-fuel ratio at the air-fuel ratio for power generation, the fuel injection amount injected during one combustion cycle is decreased, the torque (power generation torque) generated by the internal combustion engine 2 is decreased in response to the decrease in the intake air amount, the valve overlap amount of the intake valve and the exhaust valve is decreased from the valve overlap amount for power generation (the valve overlap amount during operation at the lean air-fuel ratio before the occurrence of the NOx treatment request) in response to the decrease in the intake air amount, and the reduction ratio (decrease ratio) of the fuel injection amount directly injected into the cylinder at the end of one combustion cycle is set to be gentler than the reduction ratio (decrease ratio) of the intake air amount. The fuel injection directly injected into the cylinder at the end of one combustion cycle is, for example, injected during the compression stroke immediately before the ignition timing. Then, when the intake air amount decreases to a predetermined treatment air amount for NOx treatment, the vehicle 1 starts the rich spike in which the fuel injection amount is temporarily increased. The treatment air amount is set, for example, so that the torque when the rich spike is executed becomes the torque during operation at the air-fuel ratio for power generation.

[0033] Further, the rich spike is carried out (continued) until the adsorption amount of NOx adsorbed by the NOx trap catalyst 8 becomes equal to or less than a predetermined amount (for example, "0").

[0034] Then, when the rich spike ends, the vehicle 1 switches the air-fuel ratio to the power generation air-fuel ratio with the intake air amount in the state of the processing air amount, and increases the intake air amount from the processing air amount to the intake air amount during operation at the power generation air-fuel ratio before the NOx processing requirement occurs in the state where the air-fuel ratio is the power generation air-fuel ratio, and increases the valve overlap amount of the intake valve and the exhaust valve. The valve overlap amount of the intake valve and the exhaust valve is increased, for example, to the power generation valve overlap amount at the timing when the intake air amount becomes the power generation air amount. That is, when the rich spike ends, the vehicle 1 controls the intake air amount, the valve overlap amount, and the fuel injection amount so as to perform an operation opposite to the operation when the rich spike is performed.

[0035] Figure 2 is a timing chart showing changes in various state quantities in the vehicle 1 when the rich spike is performed. In Figure 2, the internal combustion engine 2 is operated at the above-described power generation operating point before time t1 and after time t5, and the intake air amount becomes the power generation air amount and is constant.

[0036] Time t1 is the timing when the amount of NOx adsorbed on the NOx trap catalyst 8 becomes equal to or more than a preset predetermined amount and a NOx processing requirement occurs. At the timing of time t1, the throttle valve opening degree is controlled to decrease, the intake air amount decreases, and the engine torque decreases. The valve overlap amount of the intake valve and the exhaust valve is controlled to decrease at a constant rate toward "0" from the timing of time t1 so as to finally become "0".

[0037] The air-fuel ratio is not changed at time t1, and the power generation air-fuel ratio is maintained.

[0038] The fuel injection amount is controlled to decrease from the timing of time t1 so that the air-fuel ratio maintains the air-fuel ratio for power generation. Here, the fuel injection amount indicated by the characteristic line P1 (broken line) in FIG. 2 is the fuel injection amount by the main injection (injection during the intake stroke), and is controlled (set) to decrease according to the reduction ratio of the intake air amount from the timing of time t1. The fuel injection amount indicated by the characteristic line P2 (dotted line) in FIG. 2 is the fuel injection amount by the stratified injection (injection during the compression stroke immediately before the ignition timing), and shows the case where the reduction ratio is controlled (set) to be gentle with respect to the reduction ratio of the intake air amount.

[0039] The fuel injection amount by the main injection and the fuel injection amount by the stratified injection are controlled so that the total air-fuel ratio in one combustion cycle maintains the air-fuel ratio for power generation between time t1 and time t2.

[0040] Note that the stratified injection may be controlled (set) to decrease at the same reduction ratio as the reduction ratio of the intake air amount, as shown by the characteristic line P3 (solid line) in FIG. 2.

[0041] When the reduction ratio of the fuel injection amount by the stratified injection is made gentle with respect to the reduction ratio of the intake air amount, the air-fuel ratio around the ignition plug, which is the air-fuel ratio near the ignition plug of the internal combustion engine 2, becomes richer from the timing of time t1 than before time t1, as shown by the characteristic line Q1 (solid line) in FIG. 2.

[0042] Note that the air-fuel ratio around the ignition plug indicated by the characteristic line Q2 (dotted line) in FIG. 2 shows the case where the stratified injection during time t1 to t2 is controlled (set) to decrease at the same reduction ratio as the reduction ratio of the intake air amount.

[0043] Also, the air-fuel ratio around the ignition plug indicated by the characteristic line Q3 (broken line) in FIG. 2 shows the air-fuel ratio around the ignition plug in the case of homogeneous combustion where only the main injection is performed without performing the stratified injection.

[0044] Time t2 is the timing when the intake air amount decreases to the processing air amount. The rich-lean flag changes from lean to stoichiometric at the timing of time t2, and the rich spike described above is started.

[0045] The engine torque increases to the power generation load at the timing of time t2.

[0046] The air-fuel ratio is switched to the rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio at the timing of time t2.

[0047] The fuel injection amount by the main injection increases at the timing of time t2 so that the air-fuel ratio becomes the rich air-fuel ratio. On the other hand, the fuel injection amount by the stratification injection becomes "0" from the timing of time t2.

[0048] Time t3 is the timing when a predetermined time set in advance has elapsed from time t2, and is the timing when the air-fuel ratio is switched from the rich air-fuel ratio to the stoichiometric air-fuel ratio. The fuel injection amount by the main injection decreases at the timing of time t3 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio. Also, the fuel injection amount by the stratification injection resumes from the timing of time t3.

[0049] The predetermined time is set to be shorter than the time (period) during which the rich spike is implemented, that is, the time until the amount of NOx adsorbed on the NOx trap catalyst 8 becomes "0" by the rich spike.

[0050] The vehicle 1 can more surely reduce the possibility of NOx flowing out to the downstream side of the NOx trap catalyst 8 by setting the air-fuel ratio to the rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio for a certain period immediately after the start of the rich spike.

[0051] Time t4 is the timing when the amount of NOx adsorbed on the NOx trap catalyst 8 becomes "0" and the NOx treatment requirement disappears. Note that the air-fuel ratio may be kept constant as the rich air-fuel ratio or the stoichiometric air-fuel ratio from time t2 to time t4.

[0052] At the timing of time t4, the throttle valve opening degree is controlled to increase, the intake air amount increases, and the engine torque increases.

[0053] The valve overlap amount of the intake valve and the exhaust valve is maintained in the state of "0" at the timing of time t4. The valve overlap amount of the intake valve and the exhaust valve is controlled to increase at a constant rate at the timing after time t4 so as to be the valve overlap amount for power generation at the timing of time t5 described later.

[0054] The air-fuel ratio is switched to the air-fuel ratio for power generation at the timing of time t4.

[0055] The fuel injection amount is controlled to increase from the timing of time t4 so that the air-fuel ratio becomes the air-fuel ratio for power generation. The fuel injection amount by the main injection (injection during the intake stroke) is controlled (set) to increase according to the increment ratio (increase ratio) of the intake air amount from the timing of time t4 as shown by the characteristic line P1. The stratified injection (injection during the compression stroke immediately before the ignition timing) is controlled (set) so that the increment ratio (increase ratio) becomes gentle with respect to the increment ratio (increase ratio) of the intake air amount from the timing of time t4 as shown by the characteristic line P2 (dotted line).

[0056] The fuel injection amount by the main injection and the fuel injection amount by the stratified injection are controlled so that the total air-fuel ratio in one combustion cycle maintains the air-fuel ratio for power generation after time t4.

[0057] Note that the stratified injection may be controlled (set) to increase at the same increment ratio (increase ratio) as the increment ratio (increase ratio) of the intake air amount as shown by the characteristic line P3 (solid line).

[0058] The air-fuel ratio around the spark plug becomes leaner than the stoichiometric air-fuel ratio from the timing of time t4.

[0059] Time t5 is the timing when the intake air amount has increased to the above-described air amount for power generation.

[0060] In the vehicle 1 of the above-described embodiment, before executing the rich spike of the internal combustion engine 2, the intake air amount is decreased while maintaining the lean air-fuel ratio, and the valve overlap amount is decreased. That is, the vehicle 1 decreases the valve overlap amount when decreasing the intake air amount while maintaining the air-fuel ratio of the internal combustion engine 2 at the lean air-fuel ratio. Therefore, even when the vehicle 1 decreases the intake air amount while maintaining the air-fuel ratio of the internal combustion engine 2 at the lean air-fuel ratio, it is possible to suppress the in-cylinder residual gas from flowing into the intake passage side, suppress an increase in the in-cylinder residual gas amount of the internal combustion engine 2, and prevent deterioration of drivability and misfire.

[0061] Further, the vehicle 1 also suppresses an increase in the in-cylinder residual gas amount of the internal combustion engine 2 and can prevent deterioration of drivability and misfire by setting the reduction ratio of the fuel injection amount by the above-described stratified injection to be gentle with respect to the reduction ratio (decrease ratio) of the intake air amount without changing the valve overlap amount while decreasing the intake air amount while maintaining the lean air-fuel ratio before executing the rich spike of the internal combustion engine 2.

[0062] When the rich spike of the internal combustion engine 2 ends, the vehicle 1 switches the air-fuel ratio to the above-described air-fuel ratio for power generation with the intake air amount in the state of the air amount for treatment, and increases the intake air amount from the air amount for treatment to the intake air amount during operation at the above-described air-fuel ratio for power generation before the NOx treatment request occurs while the air-fuel ratio is the above-described air-fuel ratio for power generation, and increases the valve overlap amount. That is, when the rich spike ends, the vehicle 1 controls the intake air amount, the valve overlap amount, and the fuel injection amount so as to perform an operation opposite to the operation when performing the rich spike.

[0063] As a result, when the vehicle 1 finishes the rich spike of the internal combustion engine 2, the intake air amount is increased with the air-fuel ratio being set to a lean air-fuel ratio, and the valve overlap amount is increased, thereby suppressing an increase in the amount of residual gas in the cylinder of the internal combustion engine 2 and preventing deterioration of drivability and misfire.

[0064] As described above, specific embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit thereof.

[0065] For example, the internal combustion engine 2 mounted on the vehicle 1 may be a port injection type spark ignition internal combustion engine. In this case, the vehicle 1 is configured such that the internal combustion engine 2 performs only fuel injection by the main injection. When a NOx treatment requirement occurs, before executing the rich spike, the intake air amount is decreased from the power generation intake air amount while maintaining the air-fuel ratio at the power generation air-fuel ratio, and the torque (power generation torque) generated by the internal combustion engine 2 is decreased in accordance with the decrease in the intake air amount. The valve overlap amount between the intake valve and the exhaust valve is decreased from the power generation valve overlap amount (the valve overlap amount during operation at the lean air-fuel ratio before the occurrence of the NOx treatment requirement) in accordance with the decrease in the intake air amount. Even when the vehicle 1 is equipped with a port injection type spark ignition internal combustion engine, it can achieve substantially the same operational effects as those of the above-described embodiments.

[0066] For example, the internal combustion engine 2 mounted on the vehicle 1 may be configured such that either the valve operating mechanism of the intake valve or the exhaust valve is a variable valve operating mechanism, enabling the valve overlap amount between the intake valve and the exhaust valve to be variable. That is, the internal combustion engine 2 mounted on the vehicle 1 may have either the first variable valve operating mechanism 4 of the intake valve or the second variable valve operating mechanism 5 of the exhaust valve as a valve operating mechanism with a fixed valve timing.

[0067] Further, the present invention may be implemented by appropriately combining the above-described description within a range not departing from the spirit thereof.

[0068] The above-described embodiments relate to a vehicle control method and a vehicle control device.

Explanation of Reference Numerals

[0069] 1…Vehicle 2…Internal combustion engine 3…Generator 4…First variable valve mechanism 5…Second variable valve mechanism 6…Exhaust passage 7…Three-way catalyst 8…NOx trap catalyst 9…Drive wheel 10…Drive motor 11…Battery 12…Reducer 13…Differential gear 14…ECM 15…VCM

Claims

1. When a processing request for NOx adsorbed on a NOx trap catalyst provided in an exhaust passage occurs during operation of an internal combustion engine at a predetermined lean air-fuel ratio that is leaner than the theoretical air-fuel ratio, the intake air amount is decreased while maintaining the air-fuel ratio at the lean air-fuel ratio, and the valve overlap amount between the intake valve and the exhaust valve is decreased from the valve overlap amount before the occurrence of the processing request. When the intake air amount decreases to a predetermined processing air amount for NOx processing, the fuel injection amount is temporarily increased. A vehicle control method characterized by this.

2. A vehicle control method for a vehicle equipped with a spark ignition internal combustion engine capable of injecting fuel in a plurality of divided injections during one combustion cycle, When a processing request for NOx adsorbed on a NOx trap catalyst provided in an exhaust passage occurs during operation of the internal combustion engine at a predetermined lean air-fuel ratio that is leaner than the theoretical air-fuel ratio, the intake air amount is decreased while maintaining the air-fuel ratio at the lean air-fuel ratio, and the reduction ratio of the fuel injection amount directly injected into the cylinder at the end of one combustion cycle is set to be gentler than the reduction ratio of the intake air amount. When the intake air amount decreases to a predetermined processing air amount for NOx processing, the fuel injection amount is temporarily increased. A vehicle control method characterized by this.

3. When the intake air amount is decreased while maintaining the air-fuel ratio at the lean air-fuel ratio when a processing request for NOx occurs, the valve overlap amount between the intake valve and the exhaust valve is decreased from the valve overlap amount before the occurrence of the processing request for NOx. The vehicle control method according to claim 2, characterized by this.

4. When the temporary increase in the fuel injection amount is completed, the air-fuel ratio is switched to the lean air-fuel ratio with the intake air amount in the state of the processing air amount, and the intake air amount is increased from the processing air amount while the air-fuel ratio is set to the lean air-fuel ratio. At the same time, the valve overlap amount between the intake valve and the exhaust valve is increased to the valve overlap amount before the occurrence of the processing request. The vehicle control method according to claim 1, characterized by this.

5. When ending the temporary increase in the fuel injection amount, the intake air amount switches the air-fuel ratio to the lean air-fuel ratio in the state of the air amount for the above processing, and in the state where the air-fuel ratio is the lean air-fuel ratio, while increasing the intake air amount from the air amount for the above processing, the increase rate of the fuel injection amount directly injected into the cylinder at the end of one combustion cycle is set to be gentler than the increase rate of the intake air amount, and the vehicle control method according to claim 2, characterized in that the fuel injection amount directly injected into the cylinder at the end of one combustion cycle is increased. Yes.

6. The temporary increase in the fuel injection amount is carried out until the amount of NOx adsorbed on the NOx trap catalyst becomes equal to or less than a predetermined amount, and the vehicle control method according to any one of claims 1 to 5.

7. The air amount for the above processing is set such that the torque generated when temporarily increasing the fuel injection amount becomes the torque during operation at the lean air-fuel ratio before the above processing requirement occurs, and the vehicle control method according to any one of claims 1 to 5.

8. The internal combustion engine is mounted on the vehicle for power generation, and the intake air amount during operation before the above processing requirement occurs is constant, and the vehicle control method according to any one of claims 1 to 5.

9. An internal combustion engine, An NOx trap catalyst provided in the exhaust passage for adsorbing NOx in the exhaust gas, A variable valve mechanism capable of varying the valve overlap amount of the intake valve and the exhaust valve, When a processing requirement for NOx adsorbed on the NOx trap catalyst occurs during operation of the internal combustion engine at a predetermined lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, while maintaining the air-fuel ratio at the lean air-fuel ratio, the intake air amount is decreased, and the valve overlap amount of the intake valve and the exhaust valve is decreased from the valve overlap amount before the occurrence of the NOx processing requirement. When the intake air amount decreases to a predetermined air amount for NOx processing, a control unit that temporarily increases the fuel injection amount, and a vehicle control device characterized by having the above.

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