JP2014240206A - Vehicle control device and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid misfire at deceleration from an exhaust reflux region, and at the same time, to compensate deficiency in deceleration degree in a case where closing operation of a throttle valve is delayed.SOLUTION: An internal combustion engine includes a low pressure exhaust reflux device for refluxing a low pressure exhaust from a downstream side of an exhaust turbine of a turbocharger to an upstream of a compressor. Although an exhaust reflux control valve is totally closed when an accelerator open degree is decreased by a driver, a closing operation of a throttle valve is applied with a delay time ΔT, for preventing misfire. During the delay time ΔT, since there is no engine brake action, a brake device is operated to compensate deficiency of deceleration degree.

Description

  The present invention relates to a control device and a control method for a vehicle provided with an internal combustion engine having an exhaust gas recirculation device as a vehicle drive source.

  In Patent Document 1, as an example of an exhaust gas recirculation device that recirculates part of exhaust gas from an exhaust system to an intake system, in an internal combustion engine equipped with a turbocharger, relatively low-pressure exhaust gas downstream of an exhaust turbine is supplied upstream of a compressor. A low-pressure exhaust gas recirculation device that recirculates to the side is disclosed.

  In an internal combustion engine equipped with such an exhaust gas recirculation device, as explained in Patent Document 1, when the engine is decelerating when the throttle valve opening is reduced, the actual exhaust gas recirculation amount decreases due to a delay in response. Thus, misfire is likely to occur.

  In Patent Document 1, in order to avoid such misfire due to a delay in the reduction of the exhaust gas recirculation amount during engine deceleration, a decrease in the throttle valve opening is delayed in response to a deceleration request (a decrease in the accelerator opening). Is disclosed. That is, the opening degree of the exhaust gas recirculation control valve immediately decreases (for example, fully closed) in response to a deceleration request, but the introduction of fresh air is continued for an appropriate period, which causes the exhaust gas recirculation rate to be temporarily excessive. Is avoided.

JP 2012-82737 A

  However, in the method of continuing the introduction of fresh air as described above, since the reduction of the shaft torque of the internal combustion engine is delayed, the vehicle deceleration, so-called engine brake, accompanying the driver's accelerator opening reduction operation is used as the vehicle internal combustion engine. Run short.

  Therefore, in order to satisfy the vehicle deceleration generally required for an internal combustion engine for a vehicle, the exhaust gas recirculation rate in a steady state is set so that the introduction of fresh air necessary for avoiding misfire is small (or the delay period is short). As a result, there is a problem that a fuel consumption improvement effect due to exhaust gas recirculation cannot be obtained sufficiently.

The present invention provides a vehicle control device comprising an internal combustion engine having an exhaust gas recirculation device that recirculates a part of exhaust gas from an exhaust system to an intake system, and a brake unit that applies a braking force to the vehicle based on a control signal.
The internal combustion engine has a throttle valve whose opening degree is controlled based on a control signal in response to a driver's accelerator operation,
When there is a request for deceleration of the internal combustion engine due to the accelerator operation in an operating region where exhaust gas recirculation is performed by the exhaust gas recirculation device, a delay of a predetermined period is given to the closing operation of the throttle valve, and the vehicle in this delay period The brake means is actuated so as to compensate for the shortage of deceleration.

  The brake means is, for example, a general hydraulic brake device capable of braking based on a control signal regardless of a brake pedal operation by a driver, or a vehicle drive system so that a vehicle braking force can be applied as a regenerative brake. Motor / generator connected to The braking means operates during the delay period without depending on the driver's braking operation, and applies braking force to the vehicle.

  Therefore, the vehicle deceleration required as a so-called engine brake can be satisfied, and the misfire avoidance under the setting of a high exhaust gas recirculation rate and the vehicle deceleration intended by the driver can be made compatible.

  According to the present invention, since the vehicle deceleration required when the driver decreases the accelerator opening is compensated by the operation of the brake means, the introduction of fresh air is continued even when the exhaust gas recirculation rate is set high. By doing so, misfire can be avoided reliably. Therefore, it is possible to increase the setting of the exhaust gas recirculation rate in a steady state, which contributes to improvement in fuel consumption.

BRIEF DESCRIPTION OF THE DRAWINGS Configuration explanatory drawing which shows the system configuration | structure of the vehicle which is one Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which shows the structure of the exhaust gas recirculation apparatus etc. of the internal combustion engine used for this Example. The flowchart which shows the flow of control at the time of engine deceleration of this Example. The time chart which shows changes, such as deceleration at the time of engine deceleration of this Example.

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

  FIG. 1 is an explanatory diagram showing a system configuration of the entire vehicle according to the present invention. The vehicle 1 includes an internal combustion engine 2 as a drive source, and the internal combustion engine 2 is driven via a transmission 3. For example, the rear wheel 4 which is a wheel is driven. The rear wheel 4 and the front wheel 5 are each provided with a hydraulic brake device 6 (the brake device 6 for the front wheel 5 is omitted in the figure). The brake device 6 performs braking by supplying hydraulic pressure from a master cylinder (not shown) serving as a hydraulic pressure source via a hydraulic control unit 8. The hydraulic pressure supplied to each brake device 6 is controlled by a brake controller 9. Controlled by.

  The brake controller 9 performs braking control corresponding to the driver's braking request via a brake pedal, and also by so-called ABS control and braking operation by the driver such as braking for each wheel necessary for behavior control of the vehicle 1. There is also no braking control. The brake controller 9 always communicates with an engine controller 10 that controls the internal combustion engine 2 via a network in the vehicle. In the illustrated example, the brake controller 9 and the engine controller 10 are separate units. However, they can be configured as a single controller.

  The brake controller 9 includes a vehicle speed V based on a detection signal of a wheel speed sensor 11 (not shown in the figure, the wheel speed sensor 11 of the front wheel 5 is omitted) provided on each wheel and the rotation speed of the output shaft of the transmission 3. The detection signal of the vehicle speed sensor 12 for detecting the above is input.

  Further, the engine controller 10 includes a detection signal from the air flow meter 14 that detects the intake air amount Qa of the internal combustion engine 2, a detection signal from the rotational speed sensor 15 that detects the rotational speed Ne of the internal combustion engine 2, and a driver's operation. A detection signal of an accelerator opening sensor 16 for detecting an accelerator pedal depression amount (accelerator opening) APO is input.

  Next, the configuration of the exhaust gas recirculation device and the like of the internal combustion engine 2 will be described based on the explanatory diagram of FIG.

  An exhaust turbine 24 of a turbocharger 23 is disposed in the exhaust passage 22 of the internal combustion engine 2 that is a gasoline engine, and a catalytic converter 26 using, for example, a three-way catalyst is disposed downstream thereof. An exhaust silencer (not shown) is provided further downstream of the exhaust passage 22, and the exhaust passage 22 is opened to the outside through the exhaust silencer. The exhaust turbine 24 includes a known wastegate valve 27 for supercharging pressure control. The internal combustion engine 2 has, for example, a direct injection type structure, and includes a fuel injection valve (not shown) for injecting fuel into the cylinder for each cylinder.

  In the intake passage 30 of the internal combustion engine 2, an air cleaner 31, the above-described air flow meter 14, and a throttle valve 33 are disposed in order from the upstream side. The compressor 25 of the turbocharger 23 is connected to the air flow meter 14. It is arranged between the throttle valve 33. In this embodiment, a water-cooled or air-cooled intercooler 34 is interposed downstream of the throttle valve 33, for example. The throttle valve 33 is controlled in opening degree by a control signal output from the engine controller 10 based on the detection signal of the accelerator opening degree sensor 16 described above.

  Further, an EGR passage 41 constituting the exhaust gas recirculation device branches off from the downstream side of the catalytic converter 26 in the exhaust passage 22, and the tip thereof is connected to the upstream side of the compressor 25 in the intake passage 30. The EGR passage 41 is provided with a water-cooled or oil-cooled EGR gas cooler 43 for cooling the EGR gas, and an exhaust gas for controlling the exhaust gas recirculation amount downstream of the EGR passage 41 so as to follow the target exhaust gas recirculation rate. A reflux control valve 44 is interposed. The opening degree of the exhaust gas recirculation control valve 44 is controlled by the engine controller 10 based on engine operating conditions using the load and rotation speed of the internal combustion engine 2 as parameters.

  The exhaust gas recirculation device of the illustrated example is a so-called low pressure exhaust gas recirculation device that recirculates low-pressure exhaust gas from the downstream side of the exhaust turbine 24 of the turbocharger 23 to the upstream side of the compressor 25. In this low pressure exhaust gas recirculation device, the volume from the exhaust gas recirculation control valve 44 to each cylinder is relatively large, and therefore there is a response delay from the change in the opening degree of the exhaust gas recirculation control valve 44 to the actual change in the exhaust gas recirculation amount in the combustion chamber. It will be big.

  Next, FIG. 3 is a flowchart showing a control flow at the time of engine deceleration executed by the engine controller 10. This process is repeatedly executed during the operation of the internal combustion engine 2. In step 1, it is determined whether or not the current operating condition is the exhaust gas recirculation region in which exhaust gas recirculation is performed. For example, in step 2, it is repeatedly determined whether or not there is a request for deceleration to a low load range where the target exhaust gas recirculation rate becomes zero. Specifically, the presence or absence of a deceleration request is determined based on the accelerator opening APO operated by the driver.

  If it is determined in step 2 that there is a deceleration request, the process proceeds to step 3 and subsequent steps. In step 3, the exhaust gas recirculation control valve 44 is fully closed. At the same time, in step 4, in order to compensate for the lack of deceleration as a so-called engine brake, a braking command is output to the brake controller 9 and the brake device 6 of each wheel is operated. Specifically, the target engine deceleration torque is obtained from the engine rotational speed Ne and the accelerator opening APO change amount at that time, and the engine shaft torque is obtained based on the amount of fresh air introduced through the throttle valve 33. As a difference, a necessary braking torque is obtained. The brake controller 9 receives a necessary braking torque command from the engine controller 10 and drives each brake device 6 via the hydraulic control unit 8.

  In step 5, a timer for measuring the delay time until the throttle valve 33 is closed is started, and in step 6, it is determined whether a predetermined delay time ΔT has elapsed. This delay time ΔT corresponds to the time until the exhaust gas remaining after the exhaust gas recirculation control valve 44 is fully closed disappears due to the continuation of fresh air introduction, and may be a fixed value, or It may be variably set in consideration of the previous exhaust gas recirculation rate, the engine rotational speed Ne, and the like.

  When the delay time ΔT has elapsed, in step 7, the closing operation of the throttle valve 33 is permitted. Thereby, the opening degree of the throttle valve 33 becomes a fully closed position or a small opening degree corresponding to the request of the accelerator opening degree APO by the driver. In step 8, the brake controller 9 is commanded to end the operation of the brake device 6.

  FIG. 4 shows a time chart at the time of engine deceleration by the control as described above. This shows an example of so-called coasting driving in which the driver releases the accelerator pedal while driving at a constant vehicle speed (that is, accelerator opening APO = 0). , The amount of fresh air in the internal combustion engine 2, the opening degree of the throttle valve 33, the actual exhaust gas recirculation rate in the combustion chamber, the opening degree of the exhaust gas recirculation control valve 44, the engine shaft torque, the braking torque by the brake device 6, and the accelerator opening degree The change is shown in contrast.

  Time t1 is the timing when the driver sets the accelerator opening APO to 0, and at the same time, the opening of the exhaust gas recirculation control valve 44 becomes 0. However, since the recirculated exhaust gas remains in the intake system, the actual exhaust gas recirculation rate in the combustion chamber does not decrease. Therefore, if the opening degree of the throttle valve 33 is set to 0 at time t1, the actual exhaust gas recirculation rate temporarily increases temporarily due to a decrease in fresh air, which may lead to misfire.

  In order to avoid such misfire, in this embodiment, a delay time ΔT is given, and the opening of the throttle valve 33 is maintained until time t2. Accordingly, the amount of fresh air does not decrease, and the exhaust gas recirculation rate does not excessively increase. As shown in the figure, the actual exhaust gas recirculation rate gradually decreases and becomes 0 at time t2.

  On the other hand, since the opening degree of the throttle valve 33 is maintained even after the time t1, the engine shaft torque does not basically decrease until the time t2. That is, during the time t1 to t2, an amount of fuel corresponding to the amount of fresh air measured by the air flow meter 14 is injected, and the operation with the equivalent shaft torque is continued. Therefore, a so-called engine braking action cannot be obtained, but since braking torque is applied by the brake device 6 at time t1, an appropriate vehicle deceleration can be obtained from the time t1, and the vehicle speed decreases rapidly. To go.

  The phantom lines in the column of vehicle speed and vehicle deceleration in FIG. 4 are characteristics when braking by the brake device 6 is not applied. In this case, the deceleration is not obtained until time t2, and the decrease in vehicle speed is delayed. Become.

  In this way, in the above embodiment, misfire due to recirculation exhaust is avoided by continuing the introduction of fresh air at the time of deceleration request, and the lack of deceleration is compensated by applying braking torque by the brake device 6 during that time. . Accordingly, it is possible to set a relatively high target exhaust gas recirculation rate during steady operation, and it is possible to further reduce fuel consumption by exhaust gas recirculation.

  The present invention has been described above with respect to engine deceleration in a mode in which the opening of the exhaust gas recirculation control valve 44 decreases from a certain opening degree to 0. However, the present invention is not necessarily limited to this, and the target exhaust gas is not limited thereto. The present invention can be applied in the same manner when the engine is decelerating in such a manner that the recirculation rate is greatly reduced to some extent.

  Further, the present invention is not limited to an internal combustion engine equipped with a low pressure exhaust gas recirculation device, but may be an internal combustion engine equipped with a so-called high pressure exhaust gas recirculation device that introduces high pressure exhaust gas from an upstream side of an exhaust turbine to a compressor downstream of an intake system. The same applies. Moreover, the internal combustion engine which does not comprise a turbocharger may be sufficient.

  Further, in the above embodiment, the brake device 6 that performs mechanical braking is used as the brake means. However, when the vehicle drive system includes a motor / generator capable of regenerative braking, the motor / generator is braked. It can also be used as a means.

2 ... Internal combustion engine 6 ... Brake device 9 ... Brake controller 10 ... Engine controller 23 ... Turbocharger 33 ... Throttle valve 41 ... EGR passage 44 ... Exhaust gas recirculation control valve

Claims (4)

In a vehicle control device comprising: an internal combustion engine having an exhaust gas recirculation device that recirculates part of exhaust gas from an exhaust system to an intake system; and a brake unit that applies a braking force to the vehicle based on a control signal;
The internal combustion engine has a throttle valve whose opening degree is controlled based on a control signal in response to a driver's accelerator operation,
When there is a request for deceleration of the internal combustion engine due to the accelerator operation in an operating region where exhaust gas recirculation is performed by the exhaust gas recirculation device, a delay of a predetermined period is given to the closing operation of the throttle valve, and the vehicle in this delay period A control apparatus for a vehicle, wherein the brake means is operated so as to compensate for a shortage of deceleration.   An engine shaft torque is obtained based on a fresh air amount introduced through the throttle valve during the delay period, and a braking torque required for the brake means is determined as a deficiency with respect to a target engine deceleration torque. The vehicle control device according to claim 1.   3. The internal combustion engine includes a turbocharger, and the exhaust gas recirculation device is a low pressure exhaust gas recirculation device that recirculates low pressure exhaust gas on the downstream side of the exhaust turbine to the upstream side of the compressor. The vehicle control device described. An internal combustion engine having an exhaust gas recirculation device that recirculates a part of exhaust gas from an exhaust system to an intake system; and a brake means that applies a braking force to the vehicle based on a control signal in response to a driver's brake operation. The engine has a throttle valve whose opening degree is controlled based on a control signal in response to the driver's accelerator operation.
When there is a request for deceleration of the internal combustion engine due to the accelerator operation in an operating region where exhaust gas recirculation is performed by the exhaust gas recirculation device, a delay of a predetermined period is given to the closing operation of the throttle valve, and the vehicle in this delay period A vehicle control method, wherein the brake means is operated so as to compensate for a shortage of deceleration.

Images