JP2009196494A - Vehicle running control apparatus - Google Patents

Abstract

[PROBLEMS] To improve acceleration and behavioral stability of a vehicle during straddle road surface acceleration traveling control. SOLUTION: A driving wheel on a road surface having a low friction coefficient side while the vehicle is straddling road surface acceleration traveling (for example, left rear wheel _WRL). ) Is in the slip state, the target braking force setting means (electronic control unit 1) for setting the target braking force for suppressing the slip of the driving wheel to be controlled based on the wheel slip state value, and the lateral force of the wheel Lateral force sensors 42 _FL , 42 _FR , 42 _RL , 42 _RR to be detected and the braking force increase gradient or the braking force decrease until the braking force of the driving wheel to be controlled for braking reaches the target braking force during straddling road acceleration traveling Braking force increase / decrease gradient setting means (electronic control unit 1) for setting the gradient to be gentler as the lateral force is larger, a target braking force during straddling road surface acceleration traveling, and a braking force increasing gradient or braking force during straddling road surface acceleration traveling Decreasing slope Braking control means (electronic control unit 1) for controlling the braking force of the driving wheel to be braked in the slip state based on the distribution.
[Selection] Figure 1

Description

  The present invention relates to a vehicle travel control device that improves the acceleration performance and behavior stability of a vehicle during execution of straddle road surface acceleration travel control.

  Conventionally, when a driving wheel slips as the driver depresses the accelerator pedal (that is, acceleration operation), the braking force and engine output of the driving wheel in the slip state are adjusted, and the optimum driving force is applied to the driving wheel. A so-called traction control system is known that allows it to work against. For example, in Patent Document 1 below, when traveling on a so-called straddle road surface having different friction coefficients on the left and right, the vehicle is slipping on a road surface on the low friction coefficient side (hereinafter referred to as “low μ road”). By applying braking force to the drive wheels, the wheel speed difference with the other drive wheels on the same axle is reduced, thereby creating a so-called differential limiting effect and for crossing road surface travel control that transmits sufficient drive force to the wheels. There is a description of such technology.

JP-A-10-59157

  By the way, even when the travel on the straddle road surface is acceleration travel, the acceleration performance of the vehicle can be improved by performing the conventional straddle road surface travel control. Hereinafter, the control in this case is referred to as straddling road surface acceleration traveling control.

  Here, when straddling road surface acceleration traveling control is performed, the braking force of the driving wheel on the low μ road, which works in the opposite direction, and the road surface on the high friction coefficient side (hereinafter referred to as “high μ road”). Combined with the driving force of the driving wheels, a yaw moment is generated in the vehicle body. During this straddling road surface acceleration traveling control, the wheel slip state value (wheel slip ratio or wheel slip amount) of the drive wheel on the low μ road, for example, when the target drive force on the drive wheel increases or decreases rapidly. In order to improve acceleration, it is necessary to quickly increase or decrease the braking force applied to the drive wheels on the low μ road in accordance with the change in the wheel slip state value. Therefore, the yaw rate fluctuates in the vehicle body at that time. In particular, when the increase / decrease change of the braking force per unit time is large, the fluctuation of the yaw rate also increases. Therefore, the crossing road surface acceleration traveling control is not preferable from the viewpoint of vehicle behavior stability because the behavior of the vehicle in the yaw direction tends to be disturbed as the fluctuation of the yaw rate increases.

  Accordingly, the present invention provides a vehicle travel control device that improves the disadvantages of the conventional example and can improve the vehicle behavior stability while improving the acceleration performance of the vehicle during cross-road acceleration control. And its purpose.

  In order to achieve the above object, according to the first aspect of the present invention, the braking control means for controlling the braking force generating device capable of individually adjusting the braking force of each wheel to apply the target braking force to the driving wheel to be controlled. When the vehicle is accelerating on a straddled road surface with different friction coefficients on the left and right, and the driving wheels on the road surface on the low friction coefficient side are in a slipping state, the braking control target driving wheels in the slipping state A target braking force setting means for setting a target braking force during straddling road surface acceleration traveling that suppresses slip based on a wheel slip state value; and a lateral force detecting means for detecting a lateral force of a wheel in a vehicle travel control device comprising: The braking force increasing gradient or braking force decreasing gradient until the braking force of the driving wheel subject to braking control in the slip state reaches the target braking force while straddling on the road surface is set to a gentler gradient as the lateral force of the wheel increases. And a braking force decreasing gradient setting unit that, the provided. Then, the braking control means controls the braking force of the driving wheel to be braked in the slip state based on the target braking force during straddle road acceleration traveling and the braking force increase gradient or braking force decrease gradient during straddle road acceleration traveling. Is configured to do.

  In order to achieve the above object, according to a second aspect of the present invention, in the vehicle travel control apparatus according to the first aspect, the lateral force of each wheel during straddling road surface acceleration traveling is determined according to the respective lateral force. The braking force increase / decrease gradient setting means is configured to obtain the braking force increase gradient or the braking force decrease gradient during the acceleration on the straddled road surface, and further, the braking control in which the smallest value among the respective braking force increase gradients is in the slip state. Set as the braking force increase gradient for the target drive wheel, or set the smallest value among the braking force decrease gradients as the braking force decrease gradient for the braking control target drive wheel in the slip state It is configured to do.

  In order to achieve the above object, according to a third aspect of the present invention, in the vehicle travel control device according to the first or second aspect, the accelerator off for the drive wheel that is the subject of braking control during straddling road surface acceleration travel is provided. The target braking force setting means is configured to set the target braking force after detection to a value smaller than the target braking force immediately before detection of accelerator-off. The braking force increase / decrease gradient setting means is configured to set the braking force decrease gradient until reaching the target braking force after detecting the accelerator off to a gentler gradient as the lateral force of the wheel increases, and when the accelerator off is detected, the accelerator Based on the target braking force after detection of off and the braking force decrease gradient after detection of accelerator-off, the braking control is performed so as to control the braking force of the drive wheel that was subject to braking control during straddling road acceleration traveling. Constitute a.

  In order to achieve the above object, according to a fourth aspect of the present invention, in the vehicle travel control device according to the third aspect, the lateral force of each wheel is detected based on the lateral force of each wheel after detection of accelerator-off. Obtain the braking force decrease gradient after detecting accelerator-off, and set the smallest value among the braking force decrease gradients as the braking force decrease gradient for the drive wheels that were subject to braking control during road surface acceleration running. Thus, the braking force increase / decrease gradient setting means is configured.

  The vehicle travel control device according to the present invention increases or decreases the target braking force with respect to the drive wheel in accordance with the increase or decrease in the wheel slip state value of the drive wheel subject to braking control in the slip state, during crossing road surface acceleration travel control. In this case, the fluctuation of the yaw rate can be suppressed. Therefore, this vehicle travel control device can improve the vehicle behavior stability while improving the acceleration performance of the vehicle by straddling road surface acceleration travel control. Further, this vehicle travel control device gradually reduces the braking force applied to the drive wheel without abruptly decreasing when straddling road surface acceleration travel control is terminated. For this reason, since this vehicle travel control device can also suppress fluctuations in yaw rate at that time, it is possible to finish straddling road surface acceleration travel control while keeping the behavior of the vehicle stable.

  Embodiments of a vehicle travel control device according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

[Example]
An embodiment of a vehicle travel control device according to the present invention will be described with reference to FIGS.

  In the following, the vehicle travel control device of the present embodiment will be described while showing an example of a vehicle to be applied.

  The vehicle travel control device of the present embodiment mainly controls the vehicle travel state (acceleration state, deceleration state, behavior, etc.) by controlling the output of the driving force of the driving wheels and the braking force of each wheel. An electronic control unit (ECU) 1 as means, a driving force generation device that generates a driving force on driving wheels, and a braking force generation device that generates a braking force on each wheel are mounted on the vehicle. .

  The electronic control unit 1 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores a predetermined vehicle travel control program in advance, and a RAM (Random Access) that temporarily stores the calculation result of the CPU. Memory) and a backup RAM for storing information prepared in advance. The electronic control device 1 is provided with various means to be described later for performing calculations, settings, and the like necessary for executing vehicle travel control.

Here, in this embodiment, a so-called FR (front engine rear drive) vehicle that uses a prime mover mounted on the front side of the vehicle as a driving source and transmits the driving force to the rear wheels is taken as an example. Therefore, as shown in FIG. 1, the vehicle includes an internal combustion engine 10 as a prime mover, a transmission 11 that changes the rotation speed (output torque) of the internal combustion engine 10 at a predetermined or desired speed ratio, and outputs this. A propeller shaft 12 to which the output torque of the transmission 11 is transmitted, and a differential device (what is called an open differential) 14 that transmits the torque input from the propeller shaft 12 to the axles 13 _RL and 13 _RR on the rear side of the vehicle, and Are mounted as a driving force generator. Therefore, a driving force is applied to the rear wheels W _RL and W _RR of the vehicle by the driving torques of the left and right axles 13 _RL and 13 _RR distributed by the differential device 14. At that time, the drive control means of the electronic control unit 1 controls the driving force of the rear wheels W _RL and W _RR by performing output control of the internal combustion engine 10 and shift control of the transmission 11. The output control, the shift control, and the driving force control of the rear wheels W _RL and W _RR are executed by a well-known method in the technical field.

In addition, the vehicle includes a brake pedal 21 operated by a driver, a braking booster (brake booster) 22 that doubles the pedal depression force input to the brake pedal 21, and a braking booster 22 that doubles the vehicle. Master cylinder 23 for converting the pedal depression force into the hydraulic pressure (hydraulic pressure) of the brake fluid, and the hydraulic pressure adjusting means capable of adjusting the converted hydraulic pressure for each wheel W _FL , W _FR , W _RL , W _RR (Hereinafter referred to as “brake actuator”) 24 and hydraulic pipes 25 _FL , 25 _FR , 25 _RL , 25 _{RR of the} wheels W _FL , W _FR , W _RL , W _{RR to which} the hydraulic pressure passed through the brake actuator 24 is transmitted And hydraulic braking means 26 _{FL for} supplying the hydraulic pressures of the hydraulic pipes 25 _FL , 25 _FR , 25 _RL , 25 _RR and generating a braking force to the respective wheels W _FL , W _FR , W _RL , W _RR , 26 _FR And 26 _RL, 26 _RR, are mounted as a braking force generator. In other words, this braking force generator is configured to generate a braking force of an individual magnitude for each wheel W _FL , W _FR , W _RL , W _RR .

The brake actuator 24 includes various valve devices such as an oil reservoir, an oil pump (not shown), and an increase / decrease control valve for increasing / decreasing the oil pressure of each of the hydraulic pipes 25 _FL , 25 _FR , 25 _RL , 25 _RR. The valve device is driven and controlled by the braking control means of the electronic control device 1.

In this brake actuator 24, in normal times, the pressure increasing / decreasing control valve is controlled by the master cylinder 23 to adjust the hydraulic pressures of the hydraulic pipes 25 _FL , 25 _FR , 25 _RL , 25 _RR , respectively, and each wheel W _FL , W _FR , W _RL , W _RR are _subjected to normal braking force control.

On the other hand, when the so-called ABS control, brake assist control, traction control, etc., the braking control means of the electronic control device 1 controls the duty ratio of the pressure increase / decrease control valve according to the control mode, and each hydraulic pipe 25 The hydraulic pressures of _FL , 25 _FR , 25 _RL , and 25 _RR are individually adjusted to appropriate sizes corresponding to the control mode. At this time, the brake actuator 24 can generate a braking force only for one wheel to be subjected to braking control. Therefore, the braking control means and the braking force generator of the present embodiment can execute the conventional straddle road surface acceleration traveling control described above. In addition, the conventional straddle road surface acceleration travel control is a control of the running state executed from the start of acceleration travel on the straddle road surface having different friction coefficients on the left and right until the completion of the acceleration travel. A braking force is applied to the drive wheel on the low μ road that has slipped (hereinafter referred to as “drive-side slip wheel”), thereby reducing the wheel speed difference with the other drive wheel on the same axle. This produces a differential limiting effect. Therefore, when straddle road surface acceleration traveling control is performed, a sufficient driving force can be transmitted to the drive wheels on the high μ road, and the acceleration performance of the vehicle can also be improved on the straddle road surface.

  By the way, in the conventional straddle road surface acceleration traveling control, as described above, for example, the wheel slip state value (wheel slip ratio or wheel slip amount) of the driving wheel on the low μ road due to a sudden increase / decrease change in the target driving force of the driving wheel. ) Changes suddenly, the faster the change, the faster the change in braking force applied to the drive wheels on the low μ road. For this reason, in this conventional straddle road surface acceleration traveling control, the braking force is quickly increased or decreased as the target driving force increases or decreases suddenly, so that the fluctuation of the yaw rate increases. Therefore, in order to suppress the fluctuation of the yaw rate and stabilize the behavior of the vehicle, the gradient of the braking force toward the target braking force (the amount of increase or decrease of the braking force per unit time) may be moderated.

  Here, when a yaw moment is applied to the vehicle body, a lateral force is generated on the wheels even when the vehicle is traveling straight. At that time, as the yaw moment of the vehicle body increases, the slip angle increases and the lateral force also increases. Therefore, there is a high possibility that the resultant force of the braking force and the lateral force will exceed the friction circle and lose the grip. If the steered wheel is steered at that time, the steered wheel has a larger slip angle and the resultant force tends to exceed the friction circle. Further, since the friction circle becomes smaller as the friction coefficient of the road surface becomes lower, the resultant force of the wheel may exceed the friction circle even with a small lateral force. Further, the resultant force of the wheel tends to exceed the friction circle as the braking force increases, and the lateral force that can be generated decreases as the braking force increases. For this reason, if a yaw moment is applied to the vehicle body while a large braking force is applied to the wheel, the wheel tends to lose its grip because the resultant force exceeds the friction circle even with a small yaw moment. From this, the behavior of the vehicle when the yaw moment is acting on the vehicle body changes not only due to the braking force applied to the wheel, but also due to the lateral force of the wheel. Therefore, unless an appropriate increase or decrease gradient of braking force is set in consideration of the lateral force of the wheel, for example, if the braking force increase gradient or braking force decrease gradient is too large, the resultant force of the wheel is There is a possibility that the friction circle will be exceeded. On the other hand, if the braking force increase gradient or braking force decrease gradient is too small, the braking force of the driving side slip wheel may be insufficient and the acceleration performance may be impaired.

  Therefore, in this embodiment, the straddle road acceleration traveling control is executed as follows. Specifically, as the lateral force of the wheel increases, the time until the driving wheel (driving side slip wheel) on the low μ road to be controlled for braking reaches the target braking force is moderated. That is, in the straddle road surface acceleration traveling control of the present embodiment, the braking force increasing gradient or the braking force decreasing gradient is reduced as the lateral force of the wheel increases, and both the vehicle behavior stability and acceleration performance according to the lateral force are achieved. The braking force of the driving side slip wheel is controlled using a braking force increasing gradient or a braking force decreasing gradient.

  Below, the operation | movement at the time of the straddle road surface acceleration traveling control of the vehicle traveling control apparatus of a present Example is demonstrated using the flowchart of FIG.

First, various detection values are input to the electronic control unit 1 (step ST1). The detection values input here include at least the wheel speeds and lateral forces Fy _FL , Fy _FR , Fy _RL , Fy _RR of the wheels W _FL , W _FR , W _RL , W _RR , and the accelerator pedal 31 by the driver. The on / off state value.

As the wheels _{W FL, W FR, W RL} , W for the wheel speeds of the _RR, each of the wheels _{W FL, W FR, W RL} , W wheel speed sensor 41 shown in FIG. 1 provided in the _{RR FL,} 41 _FR, 41 _RL and 41 _RR are detected. Further, for each lateral force Fy _FL , Fy _FR , Fy _RL , Fy _RR , a lateral force sensor (lateral force detecting means) 42 shown in FIG. 1 provided on each wheel W _FL , W _FR , W _RL , W _RR . _FL , 42 _FR , 42 _RL , 42 _RR are detected. The accelerator pedal opening degree of the accelerator pedal 31 is used as the on / off state value of the accelerator pedal 31. The accelerator opening is detected by using an accelerator opening sensor 32 shown in FIG.

  The electronic control unit 1 determines whether or not traction control is being performed (step ST2). During the traction control is a state in which a so-called traction control system is in operation, and the engine output of the internal combustion engine 10 is suppressed in order to suppress slipping of wheels (slip wheels) that are in an accelerating running and in a slip state. Or when adjusting the braking force of the slip wheel. Therefore, when it is determined that the traction control is being performed, this indicates that the vehicle is accelerating.

  If it is determined in step ST2 that the traction control is not being performed, the electronic control unit 1 once ends this operation and returns to step ST1.

On the other hand, if it is determined in step ST2 that the traction control is being performed, the target braking force setting means of the electronic control unit 1 determines the wheel slip state value (wheel slip) of each wheel W _FL , W _FR , W _RL , W _RR. Rate and wheel slip amount), and for a slip wheel, a target braking force corresponding to the wheel slip state value is obtained (step ST3).

The wheel slip state values of the wheels W _FL , W _FR , W _RL , and W _RR are based on, for example, changes in the respective wheel speeds detected by the wheel speed sensors 41 _FL , 41 _FR , 41 _RL , and 41 _RR. Find it. The target braking force of the slip wheel is a braking force necessary for suppressing wheel slip. In step ST3, the target braking force may increase or decrease with respect to the current braking force.

Next, the traveling path determination means of the electronic control unit 1 determines whether or not the vehicle is traveling on a straddling road surface based on the wheel slip state values of the wheels W _FL , W _FR , W _RL , W _RR. (Step ST4). That is, in this step ST4, the wheel slip state value of either the left or right front wheel and the rear wheel is compared with the wheel slip state value of the other front wheel or rear wheel, and the wheel slip state value is greatly different on the left and right. If the value is indicated, it is determined that the vehicle is traveling across the road. Here, since it is already determined that the traction control is being performed, it is strictly determined that the vehicle is running across the road.

  If it is determined in step ST4 that the vehicle is not straddling on the road surface, the electronic control unit 1 proceeds to step ST10, which will be described later, and executes normal traction control. Note that the normal in this case is that the control is not performed while straddling the road surface.

  On the other hand, if it is determined in step ST4 that the vehicle is straddling the road surface, the braking force increase / decrease gradient setting means of the electronic control unit 1 determines the target braking force obtained in step ST3 and the current braking force of the slip wheel. To determine whether the target braking force is increasing or decreasing with respect to the current braking force (step ST5).

As the current braking force, for example, information on the target braking force for the slip wheel set by the target braking force setting means at the time of the previous calculation may be used. Here, since the vehicle is running across the road, the driving wheel on the low μ road is a slip wheel. For example, in the case of the vehicle shown in FIG. 1, if the left side is a low μ road, the left rear wheel W _RL becomes a drive side slip wheel. Accordingly, in step ST5, the target braking force of the drive side slip wheel is compared with the current braking force.

If it is determined in step ST5 that the target braking force has increased with respect to the current braking force, the braking force increase / decrease gradient setting means determines the lateral force Fy of each wheel W _FL , W _FR , W _RL , W _{RR. FL,} Fy _FR, Fy _RL, braking force incremental gradient S1, corresponding to Fy _RR, S2, S3, S4 respectively determined (step ST6).

The braking force increase gradients S1, S2, S3, and S4 are derived from, for example, map data shown in FIG. The map data of FIG. 3, the lateral force _{Fy FL, Fy FR, Fy RL} , braking force increases with each higher Fy _RR increases slope S1, S2, S3, S4 is one that was set to be gentle. The correspondence relationship between the lateral force and the braking force increasing gradient is set as a value capable of improving both the behavioral stability and acceleration of the vehicle by conducting experiments and simulations in advance. 3 is the maximum value of the braking force that the braking force generator can increase per unit time, and the lower limit value is the minimum braking force that the braking force generator can increase per unit time. Value.

Here, in this embodiment, the correspondence relationship between the lateral force and the braking force increasing gradient is made common to the wheels W _FL , W _FR , W _RL , W _RR , but map data indicating the correspondence relationship is, for example, the front wheel W _FL , W _FR and rear wheels W _RL , W _RR may be provided separately, or different for each wheel W _FL , W _FR , W _RL , W _RR may be prepared. . In particular, the lateral forces Fy _FL , Fy _FR , Fy _RL , Fy _RR generally increase as the slip angles of the wheels W _FL , W _FR , W _RL , W _RR increase. For this reason, when the steered wheels (here, the front wheels W _FL , W _FR ) are steered in the rank phase or in the opposite phase with respect to the turning direction due to the yaw moment of the vehicle body, the slip angle becomes the rear wheels W _RL , W _RR. The lateral forces Fy _FL and Fy _{FR of} the steered wheels may be larger than the lateral forces Fy _RL and Fy _{RR of the} rear wheels W _RL and W _RR . Therefore, in consideration of the difference between the steered wheels (front wheels W _FL , W _FR ) and the rear wheels W _RL , W _RR , the map data indicating this correspondence is the front wheels W _FL , W _FR and the rear wheels W _RL , W _RR . It is preferable that the _RR is different and that the braking force increase gradient is selected precisely.

  Thereafter, the braking force increase / decrease gradient setting means sets the smallest one of the braking force increase gradients S1, S2, S3, S4 as the braking force increase gradient of the drive side slip wheel on the low μ road (step ST7). ).

On the other hand, if it is determined in step ST5 that the target braking force has decreased with respect to the current braking force, the braking force increase / decrease gradient setting means is provided next to each wheel _WFL , _WFR , _WRL , _WRR . The braking force decreasing gradients Sa, Sb, Sc, and Sd corresponding to the forces Fy _FL , Fy _FR , Fy _RL , and Fy _RR are obtained (step ST8).

The braking force decrease gradients Sa, Sb, Sc, Sd are derived from, for example, map data shown in FIG. The map data in FIG. 4 is set such that the braking force decreasing gradients Sa, Sb, Sc, and Sd become gentler as the lateral forces Fy _FL , Fy _FR , Fy _RL , and Fy _RR increase. The correspondence relationship between the lateral force and the braking force decrease gradient is set as a value capable of improving both the behavior stability and the acceleration performance of the vehicle through experiments and simulations in advance. 4 is the maximum value of the braking force that can be reduced by the braking force generator per unit time, and the lower limit value is the minimum value of the braking force that can be reduced by the braking force generator per unit time. Value.

Here, in the present embodiment, the correspondence relationship between the lateral force and the braking force decrease gradient is also common to the wheels W _FL , W _FR , W _RL , W _RR , but map data indicating the correspondence relationship is, for example, Different front wheels W _FL , W _FR and rear wheels W _RL , W _RR may be prepared, or different ones may be prepared for each wheel W _FL , W _FR , W _RL , W _RR. Good. Also for the map data indicating this correspondence relationship, different from each other in consideration of the difference between the steered wheels (front wheels W _FL , W _FR ) and the rear wheels W _RL , W _RR as in the case of the braking force increase gradient described above. It is preferable to select the braking force decreasing gradient precisely.

  Thereafter, the braking force increase / decrease gradient setting means sets the smallest one of the braking force decrease gradients Sa, Sb, Sc, Sd as the braking force decrease gradient of the drive side slip wheel on the low μ road (step ST9). ).

The braking control means of the electronic control unit 1 executes the braking force control of the driving side slip wheel on the low μ road (step ST10). At this time, the braking control means performs the target setting based on the target braking force and the braking force increase gradient S1 (S2, S3, S4) set in steps ST3 and ST7, or the steps set in steps ST3 and ST9, respectively. The brake actuator 24 is controlled based on the braking force and the braking force decrease gradient Sa (Sb, Sc, Sd). Thereby, when the braking force of the driving side slip wheel tends to increase, the braking force of the driving side slip wheel becomes the target braking force with the increase amount per unit time of the braking force increasing gradient S1 (S2, S3, S4). It gradually increases until. At this time, the braking force of the drive side slip wheel increases more gradually as the lateral force Fy _FL (Fy _FR , Fy _RL , Fy _RR ) increases. On the other hand, when the braking force of the driving side slip wheel tends to decrease, the braking force of the driving side slip wheel becomes the target by the amount of decrease per unit time of the braking force decreasing gradient Sa (Sb, Sc, Sd). It gradually decreases to the braking force. At this time, the braking force of the drive side slip wheel decreases more gradually as the lateral force Fy _FL (Fy _FR , Fy _RL , Fy _RR ) increases. Therefore, since the fluctuation of the yaw rate accompanying the straddle road surface acceleration traveling control can be suppressed, the vehicle accelerates with its behavior stabilized. That is, by executing the straddle road surface acceleration traveling control of the present embodiment, both the behavior stability and acceleration of the vehicle can be improved.

  Here, when the straddle road surface acceleration traveling is finished, that is, when the driver removes the foot from the accelerator pedal 31, the straddle road surface acceleration traveling control is set to be terminated. That is, the vehicle travel control device of the present embodiment stops the braking force control of the drive-side slip wheel on the low μ road, which is the target of braking control during straddling road surface acceleration travel, when the accelerator is off. At that time, if the target braking force of the driving side slip wheel is lowered to “0” at a time, a yaw moment with a large yaw rate is applied to the vehicle body by the driving force of the driving wheel on the opposite side at the moment of the reduction. For this reason, in this embodiment, if accelerator-off is detected during straddle surface acceleration traveling control, the target braking force of the drive side slip wheel is eventually set to be “0”, which is higher than the current braking force. Try to make it gradually smaller.

  Therefore, as shown in the flowchart of FIG. 5, the electronic control unit 1 of the present embodiment, when detecting the accelerator off based on the accelerator opening of the accelerator opening sensor 32 (step ST11), straddles road surface acceleration traveling so far. It is determined whether or not the control has been executed (step ST12).

  Then, the target braking force setting means of the electronic control unit 1 obtains the target braking force after the accelerator-off detection for the driving-side slip wheel during the straddle road surface acceleration traveling if the straddle road surface acceleration traveling control is executed ( Step ST13). The target braking force is smaller than the target braking force immediately before the accelerator-off detection, and is set to “0” here.

Thereafter, the braking force increase / decrease gradient setting means of the electronic control unit 1 reduces the braking force according to the lateral forces Fy _FL , Fy _FR , Fy _RL , and Fy _RR of each wheel W _FL , W _FR , W _RL , W _RR. The gradients Sa, Sb, Sc, and Sd are obtained (step ST14).

  Here, the braking force decrease gradients Sa, Sb, Sc, and Sd derived from the map data shown in FIG. 4 are used. However, the braking force decrease gradient after the accelerator off detection is dedicated to after the accelerator off detection. May be prepared separately. Even in this case, the correspondence relationship between the lateral force and the braking force decrease gradient is set as a value capable of improving both the behavioral stability and acceleration of the vehicle by conducting experiments and simulations in advance. Further, the set correspondence relationship is such that the braking force decrease gradient decreases as the lateral force increases.

  The braking force increase / decrease gradient setting means sets the braking force decrease gradient of the driving slip wheel during the road surface acceleration travel across the smallest one of the braking force decrease gradients Sa, Sb, Sc, Sd (step ST15). .

Then, the braking control means of the electronic control device 1 executes the braking force control of the drive side slip wheel (step ST16). At this time, the braking control means controls the brake actuator 24 based on the target braking force and the braking force decrease gradient Sa (Sb, Sc, Sd) set in steps ST13 and ST15, respectively. As a result, the braking force of the drive-side slip wheel gradually decreases the target braking force to “0” with a reduction amount per unit time of the braking force decrease gradient Sa (Sb, Sc, Sd). At this time, the braking force of the drive side slip wheel decreases more gradually as the lateral force Fy _FL (Fy _FR , Fy _RL , Fy _RR ) increases. Therefore, since the fluctuation of the yaw rate when the straddle road surface acceleration traveling control is terminated can be suppressed by turning off the accelerator, the vehicle decelerates with its behavior stabilized. The control of the brake actuator 24 is terminated when the braking force of the drive side slip wheel becomes “0”.

  On the other hand, when it is determined in step ST12 that straddle road acceleration traveling control is not being executed, the electronic control unit 1 sets the target braking force of the slip wheel during traction control to “0” for the target braking force setting means. (Step ST17), the braking force of the slip wheel is set to “0”, and the control of the brake actuator 24 is terminated by the braking control means so that the braking force control is terminated (step ST18).

  The vehicle travel control device according to the present embodiment provides a target for the drive side slip wheel according to increase / decrease of the wheel slip state value (wheel slip ratio or wheel slip amount) of the drive side slip wheel, if crossing road surface acceleration travel control is being performed. When the braking force increases or decreases, fluctuations in the yaw rate can be suppressed. Therefore, this vehicle travel control device can improve the vehicle behavior stability while improving the acceleration performance of the vehicle by straddling road surface acceleration travel control. Further, this vehicle travel control device gradually reduces the braking force applied to the drive side slip wheel without abruptly decreasing when straddling road surface acceleration travel control is terminated. For this reason, since this vehicle travel control device can also suppress fluctuations in yaw rate at that time, it is possible to finish straddling road surface acceleration travel control while keeping the behavior of the vehicle stable.

By the way, when the vehicle body is about to turn due to the yaw moment, the driver himself or the vehicle automatically turns the steering wheels (front wheels W _FL , W _FR ) in the direction opposite to the turning direction. , May stabilize the behavior of the vehicle. In this case, most of the slip angle of the steered wheel is the steered angle of the steered wheel. In general, when the slip angle of a wheel increases, the lateral force of the wheel also increases. Therefore, for the steered wheels, the braking force increase gradient and the braking force decrease gradient may be set using information on the steered wheel turning angle. For example, the turning angle of the steered wheel can be detected by using a turning angle sensor prepared in a steering device (not shown). Further, the braking force increase gradient and the braking force decrease gradient may be set using information on a steering angle of a steering wheel (not shown) that is uniquely related to the turning angle of the steered wheel. For example, the steering angle of the steering wheel can be detected using a steering angle sensor disposed on a steering shaft (not shown). Further, the braking force increase gradient and the braking force decrease gradient may be set using information on the torsion torque of the steering shaft that is uniquely related to the steering angle of the steering wheel and the steering angle of the steering wheel. For example, the twisting torque of the steering shaft can be detected by using a torque sensor on the steering shaft when controlling the turning angle of the steered wheels in a so-called electronically controlled power steering system.

  As described above, the vehicle travel control device according to the present invention is useful for improving the acceleration performance and behavior stability of a vehicle during straddle road surface acceleration travel control.

It is a figure shown about the structure of the vehicle travel control apparatus which concerns on this invention. It is a flowchart explaining the operation | movement in the straddle road surface acceleration travel control of the vehicle travel control apparatus which concerns on this invention. It is a figure which shows an example of the map data which calculates | requires braking force increase gradient. It is a figure which shows an example of the map data which calculates | requires braking force decreasing gradient. It is a flowchart explaining the operation | movement at the time of the straddle road surface acceleration travel control end of the vehicle travel control apparatus which concerns on this invention.

Explanation of symbols

1 Electronic control unit (ECU)
_DESCRIPTION OF _SYMBOLS 10 Internal combustion engine 13 _RL , 13 _RR axle 14 Differential device 21 Brake pedal 22 Braking boost means 23 Master cylinder 24 Brake actuator 25 _FL , 25 _FR , 25 _RL , 25 _RR hydraulic piping 26 _FL , 26 _FR , 26 _RL , 26 _RR hydraulic braking means 31 Accelerator pedal 32 Accelerator opening sensor 41 _FL , 41 _FR , 41 _RL , 41 _RR wheel speed sensor 42 _FL , 42 _FR , 42 _RL , 42 _RR lateral force sensor (lateral force detecting means)
W _FL , W _FR , W _RL , W _RR wheels

Claims (4)

Braking control means that controls the braking force generator that can individually adjust the braking force of each wheel to apply the target braking force to the driving wheel to be controlled, and the vehicle accelerates on a crossing road surface with different friction coefficients on the left and right When the driving wheel on the road surface on the low friction coefficient side is in a slipping state, the target braking force during the acceleration of the straddling road surface that suppresses the slipping of the driving wheel subject to braking control in the slipping state is wheel slip. In a vehicle travel control device comprising target braking force setting means for setting based on a state value,
Lateral force detection means for detecting the lateral force of the wheel;
The braking force increasing gradient or braking force decreasing gradient until the braking force of the driving wheel subject to braking control in the slip state reaches the target braking force during straddle road acceleration traveling is made gentler as the lateral force of the wheel increases. Braking force increase / decrease gradient setting means to be set;
Provided,
The braking control means is configured to control the driving wheel to be braked in the slip state based on the target braking force during the straddle road acceleration traveling and the braking force increase gradient or the braking force decrease gradient during the straddle road acceleration traveling. A vehicle travel control device configured to perform power control.   The braking force increase / decrease gradient setting means obtains a braking force increase gradient or a braking force decrease gradient during the straddle road surface acceleration traveling according to the respective lateral force based on the lateral force of each wheel during the straddle road surface acceleration travel, The smallest value among the respective braking force increasing gradients is set as the braking force increasing gradient for the driving wheel to be braked in the slip state, or the smallest value among the respective braking force decreasing gradients. 2. The vehicle travel control device according to claim 1, wherein the vehicle travel control device is configured to set a braking force decrease gradient with respect to a driving wheel to be controlled in the slip state.   The target braking force setting means sets the target braking force after detection of accelerator off for a drive wheel that is subject to braking control during the crossing road acceleration traveling to a value smaller than the target braking force immediately before detection of accelerator off, The braking force increase / decrease gradient setting means determines the braking force decrease gradient until the braking force of the driving wheel, which is the subject of braking control during the crossing road surface acceleration travel, reaches the target braking force after detecting the accelerator-off. The braking control means sets the straddle on the basis of the target braking force after detecting the accelerator off and the braking force decreasing gradient after detecting the accelerator off when the accelerator off is detected. The vehicle travel control device according to claim 1, wherein the vehicle travel control device is configured to perform a braking force control of a driving wheel that is a subject of braking control during road surface acceleration traveling.   The braking force increase / decrease gradient setting means obtains the braking force decrease gradient after the accelerator off detection according to the respective lateral force based on the lateral force of each wheel after the accelerator off detection, and determines each braking force decrease gradient. 4. The vehicle travel control device according to claim 3, wherein the smallest value is set as a braking force decreasing gradient for a drive wheel that is subject to braking control during the straddling road surface acceleration traveling. .

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