JP7154476B2 - Vehicle control system and method - Google Patents

Description

VEHICLE CONTROL SYSTEM AND METHOD BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a vehicle control system and, more particularly, to a vehicle control system and method for controlling a vehicle having rear wheels driven by a prime mover.

Japanese Patent No. 5143103 (Patent Document 1) describes a motion control device for a vehicle. In the vehicle motion control device described in Patent Document 1, the vehicle is automatically decelerated as the vehicle is steered, thereby preventing the vehicle from skidding in the limit driving range and improving the steering stability of the vehicle. are improving.

Japanese Patent No. 6202478 (Patent Document 2) describes a vehicle behavior control device. In the vehicle behavior control device described in Patent Document 2, the driving force of the vehicle is reduced so as to add the target additional deceleration to the vehicle based on the steering speed of the vehicle. As described above, in the vehicle behavior control device described in Patent Document 2, the vertical load on the front wheels of the vehicle is increased by reducing the driving force of the vehicle in accordance with the steering speed. We have succeeded in improving responsiveness and linearity.

Japanese Patent No. 5143103 Japanese Patent No. 6202478

However, when the inventor of the present invention attempted to apply the control that decelerates the vehicle as the vehicle is steered, as described in Patent Document 1 and Patent Document 2, to a rear-wheel drive vehicle, the patent The effects of improved steering stability, responsiveness of vehicle behavior, and improved linear feel obtained in the inventions described in Documents 1 and 2 could not be obtained.

That is, the inventor of the present application applied control for decelerating the vehicle in accordance with the steering operation of the vehicle, as described in Patent Documents 1 and 2, etc., as the vehicle attitude control. However, when such conventionally known vehicle attitude control is applied to a rear-wheel drive vehicle, it is impossible to obtain the effects of improving vehicle responsiveness and linearity that have been obtained in front-wheel drive vehicles. I couldn't. As a result of intensive research by the inventors of the present invention to solve this newly discovered problem, it has surprisingly been found that, in a rear-wheel drive vehicle, it is possible to increase the driving torque of the vehicle in accordance with the steering by the driver. It became clear that the vehicle responsiveness and linear feeling are improved.

In general, when deceleration is applied to a vehicle, the inertial force acting on the center of gravity of the vehicle causes pitching motion in which the front side of the vehicle sinks. thought to improve. However, in a rear-wheel-drive vehicle, when the driving torque of the rear wheels is reduced and deceleration is applied to the vehicle, in addition to the above-mentioned inertial force, the vehicle body is tilted backward from the rear wheels via the suspension (rear side sinking) force is generated instantaneously. Since this instantaneous force acts to reduce the load on the front wheels, in a rear-wheel drive vehicle, even if deceleration is applied to the vehicle in accordance with the steering by the driver, vehicle responsiveness and linear feel are maintained as expected. could not be improved.

On the contrary, in a rear-wheel-drive vehicle, by increasing the drive torque of the rear wheels, a force that causes the vehicle body to lean forward (sink the front side) momentarily acts from the rear wheels via the suspension. As a result, the load on the front wheels increases, which is thought to improve vehicle responsiveness and linear feel. That is, in a rear-wheel drive vehicle, when acceleration is applied by increasing the driving torque of the rear wheels, an inertial force that tilts the vehicle body backward and an instantaneous force that tilts the vehicle body forward are generated. It is considered that the momentary forward tilting force of the vehicle body dominantly contributes to the responsiveness and linear feeling.

The inventors of the present invention set the increased torque so as to increase the basic torque based on the increase in the steering angle of the steering system mounted on the vehicle. It was found that the responsiveness of the vehicle to the steering operation and the linear feeling can be improved. However, when the driver increases the steering angle of the steering system to turn the vehicle, the basic torque is increased and the vehicle is accelerated. did. The present invention was made to solve this new technical problem.
Therefore, even when controlling a vehicle in which the rear wheels are driven by a prime mover, the present invention can improve the responsiveness or linear feeling of the vehicle to the steering operation while suppressing the sense of discomfort given to the driver. It is an object to provide a control system and method.

In order to solve the above-described problems, the present invention provides a method for controlling a vehicle in which the rear wheels are driven by a prime mover, in which a basic torque to be generated by the prime mover is set by a controller based on the driving conditions of the vehicle. a basic torque setting step for setting an increased torque that is a value for increasing the basic torque by the controller based on an increase in the steering angle of the steering device mounted on the vehicle; and a torque generating step of controlling the prime mover by the controller to generate a torque summed with the increased torque, wherein when the base torque is low, the increase in the increased torque setting step is greater than when the base torque is high. The torque value is limited, and in the increased torque setting process, when the basic torque is low, the upper limit of the increase rate of the increased torque per unit time is set lower than when the basic torque is high . .
According to the present invention, in order to solve the above-described new technical problem, when the basic torque is low, the increase in the basic torque in the increasing torque setting process is restricted more than when the basic torque is high. As a result, the ratio of the increased torque to the basic torque that is set based on the driving state of the vehicle can be reduced, so that the driver's discomfort caused by the intervention of the control can be reduced. As described above, according to the present invention, in the control of a vehicle in which the rear wheels are driven by the prime mover, it is possible to improve the responsiveness or linearity of the vehicle with respect to the steering operation while suppressing the sense of discomfort given to the driver.

According to the present invention configured in this way, when the basic torque is low, the upper limit of the increase rate of the torque increase per unit time is set lower than when the basic torque is high. As a result, when the basic torque is low, it is possible to prevent the torque generated by the prime mover from increasing rapidly with respect to the basic torque, thereby further suppressing the sense of discomfort given to the driver.

In the present invention, preferably, in the increased torque setting step, when the basic torque is low, the upper limit of the increased torque is set lower than when the basic torque is high.

According to the present invention configured in this way, when the basic torque is low, the upper limit value of the increased torque is set lower than when the basic torque is high. As a result, when the basic torque is low, it is possible to prevent the basic torque from being excessively increased, thereby further suppressing the sense of discomfort given to the driver.

Preferably, the present invention further includes a reduced torque setting step for reducing the torque added as the increased torque by the controller based on a decrease in the steering speed of the steering system mounted on the vehicle, and the reduced torque setting step 2, when the basic torque is low, the upper limit value of the torque reduction rate per unit time is set lower than when the basic torque is high.

In the present invention configured as described above, the torque added to the basic torque is reduced by the reduction torque setting step. In this reduction torque setting step, when the basic torque is low, the upper limit of the torque reduction rate per unit time is set lower than when the basic torque is high. As a result, when the basic torque is low, it is possible to prevent the torque that was increased in the torque increase setting process from suddenly decreasing, and to suppress the driver's sense of discomfort due to a sudden change in torque.

In the present invention, preferably, the increased torque is set in the increased torque setting step when the steering angle of the steering device becomes equal to or greater than a predetermined threshold value, and when the basic torque is low, the increase torque is set more than when the basic torque is high. Also, the threshold is set high.

In the present invention configured as described above, when the steering angle is less than the predetermined threshold value, the increased torque is not set and the base torque is generated by the prime mover. When the basic torque is low, the predetermined threshold value is set higher than when the basic torque is high. Therefore, when the basic torque is low, it is difficult to set the increased torque, and the intervention of the control suppresses the sense of incompatibility given to the driver. can do.

Further, the present invention is a vehicle control system for controlling a vehicle in which rear wheels are driven by a prime mover, and includes a driving state sensor for detecting the driving state of the vehicle and a steering angle of a steering device mounted on the vehicle. a steering angle sensor; and a controller for controlling a prime mover based on a detection signal from the driving state sensor and a detection signal from the steering angle sensor. When the steering angle sensor detects an increase in the steering angle , an increased torque, which is a value for increasing the basic torque, is set, and a torque obtained by adding the increased torque to the basic torque is generated. is configured to control the prime mover, wherein the controller is configured to limit the value of the increased torque when the base torque is low than when the base torque is high , and the controller further comprises: When the basic torque is low, the upper limit of the increase rate of the torque increase per unit time is set lower than when the basic torque is high .

According to the vehicle control system and method of the present invention, even when controlling a vehicle in which the rear wheels are driven by a prime mover, the responsiveness or linearity of the vehicle to the steering operation can be improved while suppressing the sense of discomfort given to the driver. can be improved.

1 is a block diagram showing the overall configuration of a vehicle equipped with a vehicle control system according to an embodiment of the invention; FIG. 1 is a block diagram showing an electrical configuration of a vehicle control system according to an embodiment of the invention; FIG. 4 is a flowchart of engine control processing in which the PCM provided in the vehicle control system according to the embodiment of the present invention controls the engine; FIG. 4 is a flowchart of torque addition amount setting processing in which the PCM determines an increased torque in the embodiment of the present invention; FIG. 4 is a map showing the relationship between the target additional acceleration determined by the PCM and the steering speed in the embodiment of the present invention; 4 is an increased torque upper limit map that defines the upper limit of increased torque determined by the PCM in the embodiment of the present invention. 4 is an increase torque increase rate upper limit value map that defines the upper limit value of the increase rate per unit time of increase torque determined by the PCM in the embodiment of the present invention. FIG. 4 is an increase torque decrease rate upper limit value map that defines a decrease rate per unit time of increase torque determined by the PCM in the embodiment of the present invention. FIG. 4 is a time chart showing an example of the operation of the vehicle control system according to the embodiment of the invention;

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.
First, a vehicle equipped with a vehicle control system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of a vehicle equipped with a vehicle control system according to an embodiment of the invention.

In FIG. 1, reference numeral 1 denotes a vehicle equipped with a vehicle control system according to this embodiment.
Left and right front wheels 2a, which are steered wheels, are provided at the front portion of the vehicle body of the vehicle 1, and left and right rear wheels 2b, which are driving wheels, are provided at the rear portion of the vehicle body. A front wheel 2a and a rear wheel 2b of the vehicle 1 are respectively supported by suspensions 3 with respect to the vehicle body. An engine 4, which is a prime mover for driving the rear wheels 2b, is mounted on the front portion of the vehicle body of the vehicle 1. As shown in FIG. In this embodiment, the engine 4 is a gasoline engine, but an internal combustion engine such as a diesel engine or an electric motor can also be used as the prime mover. In this embodiment, the vehicle 1 is a so-called FR vehicle in which the engine 4 mounted in the front of the vehicle body drives the rear wheels 2b through the transmission 4a, the propeller shaft 4b, and the differential gear 4c. The present invention can be applied to any vehicle in which the rear wheels are driven by a prime mover, such as a so-called RR vehicle in which the rear wheels 2b are driven by the engine 4 mounted at the rear.

The vehicle 1 is also equipped with a steering device 7 that steers the front wheels 2a based on the rotation operation of the steering wheel 6 . Further, the vehicle 1 detects a steering angle sensor 8 that detects the rotation angle of the steering wheel 6, an accelerator opening sensor 10 that is a driving state sensor that detects the depression amount (accelerator opening) of the accelerator pedal, and a vehicle speed. It has a vehicle speed sensor 12 . Each of these sensors outputs respective detection values to a PCM (Power-train Control Module) 14, which is a controller. The vehicle control system according to the embodiment of the present invention comprises these steering angle sensor 8, accelerator opening sensor 10, vehicle speed sensor 12, and PCM 14. FIG.

Next, with reference to FIG. 2, the electrical configuration of the vehicle control system according to the embodiment of the invention will be described. FIG. 2 is a block diagram showing the electrical configuration of the vehicle control system according to the embodiment of the invention.

In addition to the detection signals of the sensors 8 to 12 described above, the PCM 14 detects each part of the engine 4 (for example, the throttle valve 5a, the injector 5b, the spark plug 5c, variable valve mechanism 5d, etc.) to output a control signal.

The PCM 14 has a basic torque setting section 16 , an increased torque setting section 18 , a reduced torque setting section 20 and an engine control section 22 . The basic torque setting unit 16 is configured to set a basic torque to be generated by the engine 4 based on a detection signal from the accelerator opening sensor 10 or the like, which is a driving state sensor. The increase torque setting unit 18 is configured to set an increase torque so as to increase the basic torque when the steering angle sensor 8 detects an increase in the steering angle. The decrease torque setting section 20 is configured to decrease the increase torque added to the basic torque. The engine control unit 22 is configured to control the engine 4 so as to generate a torque obtained by adding the increased torque to the basic torque.

These components of the PCM 14 include a CPU, various programs interpreted and executed on the CPU (including basic control programs such as an OS, and application programs activated on the OS to achieve specific functions), programs and It is composed of a computer equipped with internal memory such as ROM and RAM for storing various data.

Although not shown in FIG. 2, in addition to the accelerator opening sensor 10 and the vehicle speed sensor 12, a brake sensor, an engine speed sensor, and the like may be provided as driving state sensors. In addition, the engine control unit 22 controls the fuel injection valve, spark plug, intake throttle valve, intake variable valve mechanism (not shown), etc. provided in the engine 4 to control the torque generated by the engine 4. is configured to

Next, a vehicle control method according to an embodiment of the present invention executed by the vehicle control system will be described with reference to FIGS. 3 to 8. FIG.
FIG. 3 is a flow chart of engine control processing for controlling the engine 4 by the PCM 14 provided in the vehicle control system according to the embodiment of the present invention.

The engine control process of FIG. 3 is started and repeatedly executed when the ignition of the vehicle 1 is turned on and the vehicle control system is powered on.
When the engine control process is started, as shown in FIG. 3, the PCM 14 reads and acquires various sensor signals regarding the driving state of the vehicle 1 in step S1. Specifically, the PCM 14 stores the steering angle detected by the steering angle sensor 8, the accelerator opening detected by the accelerator opening sensor 10, the vehicle speed detected by the vehicle speed sensor 12, and the gear currently set in the transmission of the vehicle 1. The detection signals output by the various sensors described above, including the stages, are acquired as information about the operating state.

Next, in step S2, the basic torque setting unit 16 of the PCM 14 sets the target acceleration based on the operating conditions of the vehicle 1 including the operation of the accelerator pedal and the vehicle speed obtained in step S1. Specifically, the basic torque setting unit 16 selects the current vehicle speed and gear position from acceleration characteristic maps (created in advance and stored in a memory or the like) defined for various vehicle speeds and gear positions. is selected, and the target acceleration corresponding to the current accelerator opening is determined with reference to the selected acceleration characteristic map.

Next, in step S3, the basic torque setting section 16 determines the basic torque of the engine 4 for realizing the target acceleration determined in step S2. That is, the basic torque setting unit 16 sets the basic torque to be generated by the engine 4 as the prime mover based on the driving state of the vehicle 1 as the basic torque setting step. In this case, the basic torque setting unit 16 determines the basic torque within the range of torque that the engine 4 can output based on the current vehicle speed, gear stage, road surface gradient, road surface μ, and the like.

On the other hand, in parallel with the processing of steps S2 and S3, in step S4, the increased torque setting unit 18 and the decreased torque setting unit 20 determine the increased torque for adding acceleration to the vehicle 1 based on the steering operation. Execute volume setting processing. That is, in step S4, based on an increase in the steering angle of the steering device 7, an increase torque setting step for setting an increase torque so as to increase the basic torque, or a decrease torque for decreasing the torque added as the increase torque. A setting process is performed. This torque addition amount setting process will be described later with reference to FIG.

After performing the processes of steps S2 and S3 and the torque addition amount setting process of step S4, in step S5, the increased torque determined in the torque addition amount setting process of step S4 is added to the basic torque determined in step S3. determines the final target torque. Here, while the basic torque is torque set according to the driver's driving operation such as operation of the accelerator pedal, the increased torque is automatically set by the PCM 14 so that the vehicle 1 behaves more like the driver's intention. is the torque applied

Next, at step S6, the PCM 14 sets the actuator control amount for realizing the final target torque set at step S5. Specifically, the PCM 14 determines various state quantities necessary to achieve the final target torque based on the final target torque set in step S5, and based on these state quantities, each component of the engine 4 Set the control amount for each actuator that drives the . In this case, the PCM 14 sets a limit value and a limit range according to the state quantity, and sets a control amount for each actuator such that the state value complies with the limit set by the limit value and the limit range.

Subsequently, at step S7, the PCM 14 outputs a control command to each actuator based on the control amount set at step S6.
For example, when the engine 4 is a gasoline engine, the PCM 14 adjusts the ignition timing of the spark plug 5c to generate the basic torque when the final target torque is set by adding the increased torque to the basic torque in step S5. advance the ignition timing of the Also, instead of advancing the ignition timing, or in conjunction therewith, the PCM 14 increases the throttle opening or advances the closing timing of the intake valve set after the bottom dead center, thereby increasing the intake air. Increase quantity. In this case, the PCM 14 increases the amount of fuel injected by the injector 5b in accordance with the increase in intake air amount so as to maintain a predetermined air-fuel ratio.

Further, when the engine 4 is a diesel engine, when the final target torque is set by adding the increased torque to the basic torque in step S5, the PCM 14 adjusts the fuel injection amount by the injector 5b to generate the basic torque. increase the fuel injection amount.
After step S7, the PCM 14 ends one engine control process according to the flowchart shown in FIG.

Next, the torque addition amount setting process executed in step S4 of FIG. 3 will be described with reference to FIGS. 4 to 8. FIG.
FIG. 4 is a flowchart of torque addition amount setting processing in which the PCM 14 determines the increased torque in the embodiment of the present invention, and FIG. This is a map showing FIG. 6 is an increase torque upper limit map that defines the upper limit of the increase torque, FIG. 7 is an increase torque increase rate upper limit map that defines the upper limit of the increase rate per unit time of the increase torque, and FIG. is an increase torque decrease rate upper limit value map that defines the increase torque decrease rate per unit time.

When the torque addition amount setting process shown in FIG. 4 is started, at step S21, the PCM 14 determines whether or not the steering angle of the steering device 7 acquired at step S1 of the flowchart shown in FIG. 3 is increasing. That is, the steering angle (absolute value) is zero when the vehicle 1 is traveling straight ahead, and increases when the steering wheel 6 is rotated clockwise or counterclockwise. In the present embodiment, the steering angle is detected by the steering angle sensor 8 provided on the steering shaft that constitutes the steering device 7, but any sensor such as a sensor that detects the angle of the front wheels 2a (steered wheels) may be used. A steering angle can be detected by a sensor.

If it is determined in step S21 that the steering angle has not increased (the steering wheel 6 has not rotated clockwise or counterclockwise), the processing of the flow chart shown in FIG. 4 is performed once. Terminates and the process returns to the main routine shown in FIG. That is, when the steering operation is not performed by the driver, no increase torque is set (increase torque=0), and the basic torque set in step S3 of FIG. 3 is determined as the final target torque. .

If it is determined in step S21 that the steering angle has increased, the process proceeds to step S22, in which it is determined whether or not the steering speed is equal to or greater than a predetermined value. That is, the PCM 14 calculates the steering speed based on the steering angle obtained in step S1 of FIG. 3, and determines whether or not the calculated value is equal to or greater than a predetermined threshold value T _S1 . If the steering speed is not equal to or greater than the predetermined threshold value T _S1 , one processing of the flow chart shown in FIG. 4 ends and the processing returns to the main routine shown in FIG. That is, when the steering speed is extremely low, it is considered that the driver does not have the intention to steer the vehicle. As a result, it is possible to prevent an unnecessary torque addition amount setting process from intervening when the driver has no intention of steering.

If it is determined in step S22 that the steering speed is equal to or higher than the predetermined value, the process proceeds to step S23, where it is determined whether or not the steering speed is decreasing. When the driver starts turning the steering wheel 6 (Turn-in), the steering speed first increases and the steering angle also increases. Next, the steering speed begins to decrease immediately before the steering wheel 6 is turned by the driver to hold the steering. When the steering is held, the steering angle becomes constant and the steering speed becomes zero.

If it is determined in step S23 that the steering speed has not decreased, the process proceeds to step S24. In the process from step S24 onwards, as an increase torque setting step, the increase torque setting unit 18 sets the increase amount (increase torque) of the output torque of the engine 4 required to apply the acceleration to the vehicle 1 .
First, in step S24, the increased torque setting unit 18 acquires the target additional acceleration based on the steering speed. This target additional acceleration is the acceleration that should be applied to the vehicle 1 according to the steering operation in order to accurately realize the vehicle behavior intended by the driver.

Specifically, the increased torque setting unit 18 acquires the target additional acceleration corresponding to the steering speed calculated in step S23 based on the relationship between the target additional acceleration and the steering speed shown in the map of FIG.
The horizontal axis in FIG. 5 indicates the steering speed, and the vertical axis indicates the target additional acceleration. As shown in FIG. 5, when the steering speed is less than or equal to the threshold T _S1 , the corresponding target additional acceleration is zero. That is, when the steering speed is equal to or less than the threshold value T _S1 , the PCM 14 does not execute control for adding acceleration to the vehicle 1 based on the steering operation (returns to the main routine without setting the increased torque).

On the other hand, when the steering speed exceeds the threshold value _TS1 , the target additional acceleration corresponding to the steering speed gradually approaches the predetermined upper limit _Dmax as the steering speed increases. That is, as the steering speed increases, the target additional acceleration increases, and the rate of increase in the amount of increase decreases. This upper limit value D _max is set to an acceleration that does not make the driver feel that there has been control intervention even if acceleration is applied to the vehicle 1 in response to the steering operation (for example, 0.5 m/s ² ≈0.05 G). ). Furthermore, when the steering speed is equal to or greater than the threshold T _S2 which is larger than the threshold T _S1 , the target additional acceleration is maintained at the upper limit value D _max .

In this embodiment, the steering speed threshold T _S1 is set to a constant value _. can also be configured to In this case, when the basic torque is low, the threshold _TS1 should be set higher than when the basic torque is high. As another modification, the setting of the increased torque (target additional acceleration) is performed when the steering angle of the steering device 7 becomes equal to or greater than a predetermined steering angle threshold value, and when the basic torque is low, the basic torque The present invention can also be configured such that the steering angle threshold is set higher than when .

Next, in step S25, the increased torque setting unit 18 sets the increased torque, which is the increased amount of torque required to achieve the target additional acceleration acquired in step S24.

Next, in step S26, the increased torque set in step S24 is corrected according to the basic torque set in step S3 of FIG. That is, when the basic torque is low, the increase in the basic torque due to the increased torque is restricted more than when the basic torque is high. Specifically, the increased torque value [Nm] set in step S25 is limited based on the increased torque upper limit map shown in FIG. Therefore, when the increased torque value [Nm] set in step S25 exceeds the increased torque upper limit value [Nm], the increased torque value is set to the upper limit value set in the increased torque upper limit map. Fixed.

As shown in FIG. 6, the torque increase upper limit map is a map that defines the allowable upper limit value [Nm] of torque increase for each basic torque value [Nm]. In this embodiment, the increase torque upper limit map is set so that the allowable upper limit torque increase monotonously increases as the basic torque increases. Also, the amount of increase in the upper limit value of the increased torque with respect to the amount of increase in the basic torque (slope of the map shown in FIG. 6) is set to decrease as the basic torque increases. As shown in the increased torque upper limit map of FIG. 6, when the basic torque is low, the increased torque upper limit is set lower than when the basic torque is high.

Further, in step S27, the increase rate of the increased torque per unit time set in step S25 is limited according to the basic torque set in step S3 of FIG. That is, in step S27, when the basic torque is low, the upper limit value of the increase rate of the increased torque per unit time is set lower than when the basic torque is high.

Specifically, based on the torque increase value [Nm] set in step S25 and the torque increase value when the flowchart shown in FIG. ] is calculated and the upper limit of this value is restricted. That is, in the flowchart of FIG. 4, the difference between the value of the increased torque set this time and the value of the increased torque set last time, and the elapsed time from the time when the increased torque was set last time to the time when it was set this time (the flow chart of FIG. 4 (execution time interval of ), the rate of increase in torque per unit time is calculated. Next, this increase rate is limited based on the increase rate upper limit value map of the increased torque shown in FIG. If the calculated increase rate of increased torque per unit time [Nm/sec] exceeds the upper limit of increase rate of increased torque [Nm/sec], the increase rate of increased torque does not exceed the upper limit. As such, the value of the incremental torque is modified.

As shown in FIG. 7, the torque increase rate upper limit value map is a map that defines an allowable torque increase rate upper limit value [Nm/sec] for each basic torque value [Nm]. . In the present embodiment, the torque increase rate upper limit value map is set so that the allowable torque increase rate upper limit value increases monotonically as the basic torque increases. Also, the increment of the upper limit value of the increase rate of the increasing torque with respect to the increment of the basic torque (slope of the map shown in FIG. 7) is set to decrease as the basic torque increases.

When the process in step S27 is performed, one process in the flow chart of FIG. 4 ends, and the process returns to step S5 of the flow chart shown in FIG. 3, which is the main routine. In step S5 of FIG. 3, as described above, the increased torque determined in the torque addition amount setting process (FIG. 4) is added to the basic torque to determine the final target torque, and the engine is operated to generate this torque. controlled (steps S6, S7).

On the other hand, when it is determined in step S23 of the flowchart shown in FIG. 4 that the steering speed is decreasing, the processing from step S28 onward is executed as a decreasing torque setting step. As described above, when the driver starts turning the steering wheel 6 (Turn-in), the steering speed first increases and the steering angle also increases. Next, after the steering angle increases at a substantially constant steering speed, the steering speed begins to decrease just before the steering wheel 6 turns to hold the steering (steering speed = 0), and when the steering shifts to holding, the steering angle remains constant. As a result, the steering speed becomes zero. Typically, the processing from step S28 onwards is executed in a state in which the steering speed is decreasing immediately before shifting to steering holding.

First, in step S28, the reduction torque setting unit 20 acquires the target additional acceleration based on the steering speed. In the process in step S28, the target additional acceleration corresponding to the steering speed calculated in step S22 is obtained based on FIG. 5, similarly to the process in step S24.

Next, in step S29, the reduced torque setting unit 20 sets the torque required to achieve the target additional acceleration acquired in step S28. Here, the torque set in step S29 is the torque added to the basic torque in step S5 of FIG. 3, but the target additional acceleration is set so as to increase as the steering speed increases (FIG. 5). , the added torque value tends to be smaller than during an increase in steering speed. Therefore, while the steering speed is decreasing, the value of the increased torque tends to decrease, and the final target torque determined in step S5 of FIG. 3 also tends to decrease.

Furthermore, in step S30, the rate of decrease per unit time of the torque (increased torque) set in step S29 is limited according to the basic torque set in step S3 of FIG. That is, in step S30, when the basic torque is low, the upper limit value of the torque decrease rate per unit time is set lower than when the basic torque is high.

Specifically, based on the torque increase value [Nm] set in step S29 and the torque increase value when the flowchart shown in FIG. ] is calculated and the upper limit of this value is bounded. That is, in the flowchart of FIG. 4, the difference between the value of the increased torque set this time and the value of the increased torque set last time, and the elapsed time from the time when the increased torque was set last time to the time when it was set this time (the flow chart of FIG. 4 execution time interval), the rate of decrease per unit time of the increased torque is calculated. Next, the absolute value of this rate of decrease is limited based on the map of the rate of increase upper limit of torque increase shown in FIG. If the calculated reduction rate (absolute value) of the increased torque per unit time [Nm/sec] exceeds the upper limit of the increased torque reduction rate [Nm/sec], the increased torque reduction rate is The torque increase value is modified so that the upper limit is not exceeded.

As shown in FIG. 8, the increasing torque decreasing rate upper limit value map is a map that defines the allowable increasing torque decreasing rate upper limit value [Nm/sec] for each basic torque value [Nm]. . In the present embodiment, the increase torque decrease rate upper limit value map is set so that the allowable increase torque decrease rate upper limit value increases monotonically as the basic torque increases. Also, the increment of the upper limit value of the reduction rate of the increasing torque with respect to the increment of the basic torque (slope of the map shown in FIG. 8) is set to decrease as the basic torque increases.

After the processing in step S30 is performed, one processing in the flow chart of FIG. 4 ends, and the processing returns to step S5 of the flow chart shown in FIG. 3, which is the main routine.

Next, operation of the vehicle control system according to the embodiment of the present invention will be described with reference to FIG.
FIG. 9 is a time chart showing an example of the operation of the vehicle control system according to the present embodiment. , additional acceleration [m/sec ² ], increased torque [N·m], and ignition timing.

First, from time t ₀ to t ₁ in FIG. 9, the driver of the vehicle 1 is not steering, the steering angle is 0 [deg] (neutral position), and the steering speed is also 0 [deg/sec]. there is Further, from time t ₀ to t ₁ , the operating state of the vehicle 1 (for example, the depression amount of the accelerator pedal) is also constant, so the basic torque [N·m] is also constant. In this state, in the flow chart shown in FIG. 4, since the process of step S21→return is repeated, additional acceleration and increased torque are not set (additional acceleration=0, increased torque=0). Therefore, from time t ₀ to t ₁ , the basic torque (constant value) is determined as the final target torque (step S5 in FIG. 3). Also, the ignition timing of the ignition plug 5c is set to the ignition timing for generating the basic torque.

Next, at time t1 in FIG. ₉ , when the driver starts steering, the steering angle and steering speed (absolute values thereof) increase. When the steering speed becomes equal to or higher than T _s1 , steps S21→S22→S23→S24→S25→S26→S27 are repeated in the flow chart shown in FIG. 4, so that additional acceleration and increased torque are set. That is, in step S24 of FIG. 4, the additional acceleration is set using the map shown in FIG. 5, and in step S25, the additional torque required to realize the set additional acceleration is calculated. In the example shown in FIG. 9, since no driving operation such as depressing the accelerator pedal is performed between times t ₁ and t ₂ , the value of the basic torque is constant (from the value between times t ₀ and t ₁ ). not changed).

As a result, from time t ₁ to t ₂ , as the additional acceleration increases, the value of the set increased torque also increases, and the final target torque obtained by adding the increased torque to the basic torque (constant value) increases. The actuator control amount set in step S6 of FIG. 3 is used to generate the final target torque in which the increased torque is added to the basic torque. Specifically, in the present embodiment, the ignition timing of the ignition plug 5c is advanced from the ignition timing for generating the basic torque, as shown in the lowermost part of FIG.

The torque increase due to the addition of the increased torque begins to rise within about 50 msec after the steering speed reaches T _s1 (after step S24 and subsequent steps are executed in the flow chart of FIG. 4). The maximum value is reached in about 200 to about 250 msec. Due to the rise of the drive torque of the rear wheels 2b based on this increased torque, a force that causes the vehicle 1 to lean forward (the front side of the vehicle sinks) acts instantaneously via the suspension 3, and the front wheels 2a that are steered wheels. load increases. This momentary increase in the load on the front wheels 2a improves the vehicle responsiveness to the steering operation and the linear feeling.

On the other hand, the increase in the driving torque of the rear wheels 2b based on the increased torque accelerates the vehicle 1, and this acceleration also generates a force that tilts the vehicle 1 backward (sinks the rear side of the vehicle). However, after the driving torque starts to increase, the vehicle 1 is accelerated, and there is a certain amount of time lag until this acceleration causes the vehicle 1 to substantially tilt backward. Therefore, the decrease in the load on the front wheels 2a due to the acceleration of the vehicle 1 has little effect on the vehicle responsiveness to the steering operation and the linear feeling.

In the time chart of the increased torque in FIG. 9, the solid line indicates the case where the correction in steps S26 and S27 in FIG. 4 is not executed. That is, if the increased torque and its rate of increase per unit time set in step S25 do not exceed the upper limit values shown in FIGS. is added to the basic torque as it is. The action when the corrections in steps S26 and S27 are executed will be described later.

Next, at time t2 in _FIG . 9, when the (absolute value of) the steering speed becomes a constant value, the steering angle increases linearly. During this period, the processing of steps S21->S22->S23->S24->S25->S26->S27 is repeated in the flowchart of FIG. In the example shown in FIG. 9, since no driving operation such as depressing the accelerator pedal is performed between times t ₂ and t ₃ , the value of the basic torque is constant (from the value between times t ₀ and t ₁ ). not changed). In addition, since the steering speed (absolute value) is also constant during time t ₂ to t ₃ , the value of the increased torque is also set to be constant. Along with this, the advance angle of the ignition timing for increasing the basic torque by the increased torque is also set to a constant value.

Further, when the steering speed starts to decrease at time t3 in FIG. ₉ , the processing of steps S21→S22→S23→S28→S29→S30 is repeated in the flowchart of FIG. In this state, the value of the additional acceleration set in step S28 also decreases as the steering speed (the absolute value thereof) decreases. Therefore, from time t ₃ to t ₄ , the torque increase value set in step S29 also tends to decrease. In the example shown in FIG. 9, since no driving operation such as depressing the accelerator pedal is performed from time t ₃ to t ₄ , the value of the basic torque is constant, and the basic torque (constant value) plus the increased torque The value of the final target torque to which is added tends to decrease. Along with this, the advance angle of the ignition timing for increasing the basic torque by the increased torque also tends to decrease.

Next, when the driver starts holding the steering at time t4 in FIG. ₉ , the steering angle becomes a constant value and the steering speed (the absolute value thereof) becomes zero. Therefore, in the flowchart of FIG. 4, the process from step S21 to return is repeated. Since the steering speed becomes 0, the values of the additional acceleration and the increased torque also become 0, and the value of the basic torque is determined as the final target torque during the steering holding.

On the other hand, when the basic torque is low, the increase in the basic torque is restricted in steps S26 and/or S27 of FIG. 4, or the decrease rate of the increased torque is restricted in step S30. That is, when the basic torque is low, the upper limit of the increase torque (Fig. 6), the upper limit of the increase rate of the increase torque per unit time (Fig. 7), and the upper limit of the decrease rate of the increase torque per unit time ( 8) is set to a low value, making it susceptible to limitations by each upper limit.

In the time chart of the increased torque in FIG. 9, the two-dot chain line indicates the case where the increased torque is limited in step S26 of FIG. In the case shown by the two-dot chain line in FIG. 9, the value of the increased torque reaches the upper limit value ( _FIG . ₆ ) before time t2 when the increase in steering speed ends, and before time t2 is a constant value.

Furthermore, in the time chart of the increased torque in FIG. 9, the dashed-dotted line indicates the case where the increase rate of the increased torque is restricted in step S27 of FIG. 4 and the decrease rate of the increased torque is restricted in step S30. In the case shown by the dashed-dotted line in FIG. ₉ , the steering speed begins to increase at time t1, and the value of the increased torque also begins to increase. However, since it exceeds the upper limit value (FIG. ₇ ), the rise of the increased torque from time t1 is moderate. Furthermore, at time t3 _, the steering speed begins to decrease, and the value of the increased torque also begins to decrease. The decrease in torque increase from ₃ is gradual.

In the example shown in FIG. 9, the value of the basic torque is a constant value. However, if the basic torque changes due to the driver's operation of the accelerator pedal or the like, the increased torque increases according to the value of the basic torque. Limited. That is, when the basic torque changes, the maps of FIGS. 6 to 8 are applied according to the value of the basic torque, and the upper limit of the increased torque, the upper limit of the increase rate of the increased torque, and the decrease of the increased torque are determined. Increased torque is limited by setting the upper limit of the ratio. However, since the time from turning the steering wheel 6 by the driver to holding the steering and turning back is generally relatively short (usually less than 1 to 2 seconds), the basic torque during this period is considered constant. can also In this case, each upper limit value may be set by applying the value of the basic torque when the driver starts turning the steering wheel 6 to the maps shown in FIGS.

According to the vehicle control method of the embodiment of the present invention, the increased torque is set so as to increase the basic torque ( FIG. 5 ) based on an increase in the steering angle of the steering device 7 mounted on the vehicle 1 and Since the load increases, it is possible to improve vehicle responsiveness and linear feeling to steering operation. Further, according to the vehicle control method of the embodiment of the present invention, when the basic torque is low, the increase in the basic torque in the increased torque setting process (steps S24 to S27 in FIG. 4) is more than when the basic torque is high. limited (Figs. 6 and 7). As a result, the ratio of the increased torque to the basic torque that is set based on the driving state of the vehicle 1 can be reduced, so that the driver's discomfort caused by the intervention of the control can be reduced.

Further, according to the vehicle control method of the present embodiment, when the basic torque is low, the upper limit of the increase rate of the increased torque per unit time is set lower than when the basic torque is high (FIG. 7). As a result, when the basic torque is low, it is possible to prevent the torque generated by the engine 4 from suddenly increasing with respect to the basic torque, thereby further suppressing the sense of discomfort given to the driver.

Further, according to the vehicle control method of the present embodiment, when the basic torque is low, the upper limit value of the increased torque is set lower than when the basic torque is high (FIG. 6). As a result, when the basic torque is low, it is possible to prevent the basic torque from being excessively increased, thereby further suppressing the sense of discomfort given to the driver.

Furthermore, according to the vehicle control method of this embodiment, the torque added to the basic torque is reduced by the reduction torque setting process (steps S28 to S30 in FIG. 4). In this reduction torque setting step, when the basic torque is low, the upper limit of the torque reduction rate per unit time is set lower than when the basic torque is high (FIG. 8). As a result, when the basic torque is low, it is possible to prevent the torque that was increased in the torque increase setting process from suddenly decreasing, and to suppress the driver's sense of discomfort due to a sudden change in torque.

Although preferred embodiments of the present invention have been described above, various modifications can be made to the above-described embodiments. In particular, in the above-described embodiment, the present invention was applied to a vehicle equipped with a gasoline engine, but the present invention can be applied to vehicles equipped with various prime movers such as diesel engines and electric motors.

1 vehicle 2a front wheel (steering wheel)
2b rear wheel (drive wheel)
3 Suspension 4 Engine (prime mover)
5a throttle valve 5b injector 5c spark plug 5d variable valve mechanism 6 steering wheel 7 steering device 8 steering angle sensor 10 accelerator opening sensor (driving condition sensor)
12 vehicle speed sensor 14 PCM (controller)
16 basic torque setting unit 18 increasing torque setting unit 20 decreasing torque setting unit 22 engine control unit

Claims (5)

A method of controlling a vehicle having rear wheels driven by a prime mover comprising:
a basic torque setting step of setting a basic torque to be generated by the prime mover by means of a controller based on the operating state of the vehicle;
an increase torque setting step of setting an increase torque, which is a value for increasing the basic torque, by a controller based on an increase in the steering angle of the steering device mounted on the vehicle;
a torque generating step of controlling the prime mover by a controller so as to generate a torque obtained by adding the increased torque to the basic torque;
has
When the basic torque is low, the value of the increased torque in the increased torque setting step is restricted more than when the basic torque is high ,
The vehicle control method, wherein in the step of setting the increased torque, when the basic torque is low, the upper limit of the increase rate of the increased torque per unit time is set lower than when the basic torque is high. . 2. The vehicle control method according to claim 1 , wherein, in the increased torque setting step, when the basic torque is low, the upper limit of the increased torque is set lower than when the basic torque is high. Further, a reduction torque setting step for reducing the torque added as the increase torque by the controller based on a decrease in the steering speed of the steering device mounted on the vehicle, wherein the reduction torque setting step includes the basic 3. The vehicle control method according to claim 1, wherein when the torque is low, the upper limit of the rate of torque decrease per unit time is set lower than when the basic torque is high. The setting of the increased torque in the increased torque setting process is executed when the steering angle of the steering device becomes equal to or greater than a predetermined threshold value. 4. The vehicle control method according to any one of claims 1 to 3 , wherein the threshold is set high. A vehicle control system for controlling a vehicle having rear wheels driven by a prime mover,
a driving state sensor that detects the driving state of the vehicle;
a steering angle sensor for detecting a steering angle of a steering device mounted on the vehicle;
a controller for controlling the prime mover based on a detection signal from the driving state sensor and a detection signal from the steering angle sensor;
The controller is
setting a basic torque to be generated by the prime mover based on the detection signal of the operating state sensor;
when an increase in the steering angle is detected by the steering angle sensor, setting an increase torque, which is a value for increasing the basic torque,
configured to control the prime mover so as to generate a torque obtained by adding the increased torque to the basic torque;
the controller is configured to limit the value of the increased torque when the base torque is low than when the base torque is high ;
Further, the vehicle control system is characterized in that, when the basic torque is low, the controller sets the upper limit of the increase rate of the increased torque per unit time lower than when the basic torque is high .

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