JP4600126B2 - Vehicle attitude control device - Google Patents

Description

  The present invention relates to a distribution of driving force from a front wheel to a rear wheel or a distribution of driving force from a rear wheel to a front wheel when side stability control (hereinafter referred to as ESC) is performed in a four-wheel drive vehicle. The present invention relates to a vehicle attitude control device that can optimize the above.

Conventionally, for example, a power distribution control device in a four-wheel drive vehicle as disclosed in Patent Document 1 is known. In this power distribution control device, when an ESC device that controls vehicle behavior by applying braking force to wheels is provided, when applying braking force, the driving force transmitted to the front wheels or rear wheels is higher than usual. The driving force distribution control is performed so as to be a small value. As a result, in the traveling situation when ESC is performed, the influence of the control interference and the sudden change in the driving force distribution is suppressed, and the stability of the vehicle behavior is ensured.
JP 2003-231428 A

  However, the driving force distribution control for stabilizing the vehicle behavior differs depending on which of the four wheels to be controlled by the ESC, and in the method shown in Patent Document 1 above, The vehicle behavior cannot be sufficiently stable.

  In view of the above points, an object of the present invention is to provide a vehicle attitude control device that can perform appropriate driving force distribution control according to a wheel to be controlled by ESC.

  In order to achieve the above object, according to the first aspect of the present invention, the skid prevention control means (11) or the driving force distribution setting means (10) corresponds to a wheel to be controlled by the skid prevention control performed by the skid prevention control means. And a drive transmission force limit amount setting means (120 to 145) for setting a limit amount of the drive transmission force to the driven wheels in the distribution of the drive force, and when the side slip prevention control is executed by the side slip prevention control means. Is characterized in that the driving force distribution set by the driving force distribution setting means is limited to a limit amount or less set by the drive transmission force limit amount setting means.

  Thus, when the braking force by the side slip prevention control is applied, the limit amount of the driving transmission force in the driving force distribution control is controlled according to the wheel to which the braking force is applied. That is, even in the same oversteer state and understeer state, the limit amount of the drive transmission force is different depending on the control target wheel to which the braking force is applied by the skid prevention control. This makes it possible to further stabilize the vehicle in accordance with the way of applying the braking force by the side slip prevention control.

Specifically, the lateral slip prevention control means, when skidding of the vehicle was oversteering state, sets the front or rear wheel of the turning outer as the control target wheels, skid prevention control means or the driving force distribution setting unit The limit amount of the drive transmission force to the driven wheel in the drive force distribution is changed depending on whether the wheel to be controlled by the skid prevention control means is the front wheel or the rear wheel of the outer turning wheel.

As shown in claim 4, when the vehicle is a front drive base to auxiliary driving wheels to the rear wheels a front wheel as the main drive wheels, side slip prevention control means when a was the oversteer a front wheel of the turning outer When set as the wheel to be controlled, the skid prevention control means or the driving force distribution setting means sets the limit amount of the driving transmission force to the rear wheel in the driving force distribution as the first value, thereby reducing the driving force of the front wheels. The driving force transmitted to the rear wheels is made smaller than when the driving force distribution with the driving force of the rear wheels is 50:50. When the side-slip prevention control unit sets the rear wheel of the turning outer wheel as the control target wheel in the oversteer state, the side-slip prevention control unit or the driving force distribution setting unit transmits the drive transmission to the rear wheel in the driving force distribution. the limit amount of force by setting a smaller second value than the first value, and a small fence, the driving force distribution between the front wheel drive force and the rear wheel driving force compared with the case of the 50:50 The driving force transmitted to the rear wheel is controlled so as to be smaller than when the control target wheel is the front wheel.

In the oversteer state, when the wheel to be controlled by the anti-skid control is the front wheel, it is better to perform the control to increase the driving force on the front wheel side even if the moment due to the braking force generated on the front wheel is taken into account. preferable. Therefore, in this case, it reduces the limit amount as the driving transmission force is limited by the large value, the amount of transmission power limit may be such that the first value.

Further, when the limit amount is set as the first value, as shown in claim 5 , the driving force distribution setting means changes the driving force of the rear wheels from the 50:50 driving force distribution to the first value. It is preferable that the amount of change be changed at a slower reduction rate than when the limit amount is set as the second value until the value is reached. That is, if the driving force distribution to the rear wheel side is suddenly reduced to the set limit amount, the vehicle behavior may become unstable. For this reason, it is preferable to set a longer time until the amount is reduced to the limit amount, that is, to reduce the reduction rate to the transmission force limit amount.

On the other hand, in the oversteer state, when the wheel to be controlled by the skid prevention control is a rear wheel, the smaller the rear driving force, the greater the effect of the braking force generated on the rear wheel. Therefore, in this case, it reduces the limit amount as the driving transmission force is limited to a small value, the amount of transmission power limit may be such that a small second value than the first value.

Furthermore, as shown in claim 2, sideslip prevention control unit, when skidding of the vehicle was under-steering state, to set the front wheels or rear wheels of the turning inner wheel as a control target wheels, skid prevention control means or drive The force distribution setting means determines the limit amount of the drive transmission force to the driven wheel in the driving force distribution depending on whether the wheel to be controlled by the skid prevention control means is the front wheel or the rear wheel of the turning inner wheel. It can also be changed.

For example, as shown in claim 6, when the vehicle is a front drive base having a front wheel as a main drive wheel and a rear wheel as a sub drive wheel, the side slip prevention control means can When the rear wheel is set as the control target wheel, the skid prevention control means or the driving force distribution setting means sets the limit amount of the driving transmission force to the rear wheel in the driving force distribution as the third value, thereby The driving force transmitted to the rear wheels is made smaller than when the driving force distribution between the driving force and the driving force of the rear wheels is 50:50. When the skid prevention control means sets the front wheel of the turning inner wheel as the control target wheel in the case of the understeer state, the skid prevention control means or the drive force distribution setting means determines the drive transmission force to the rear wheels in the drive force distribution. Is set as a fourth value that is larger than the third value, so that the driving force transmitted to the rear wheels is increased as compared with the case where the wheel to be controlled is the rear wheel.

In the understeer state, when the wheel to be controlled by the side slip prevention control is the rear wheel, considering the moment due to the braking force generated on the rear wheel, the driving force on the rear wheel side is made smaller rather than larger. The vehicle is more stable. Therefore, in this case, when such a third value Den Itaruryoku limit amount is a small value may.

  Further, when the limit amount is set as the third value, as shown in claim 7, the driving force distribution setting means changes the driving force of the rear wheel from 50:50 to the third driving force distribution. It is preferable that the limit amount is changed at a faster reduction rate as compared with the case where the limit amount is set as the fourth value until the value is reached. That is, in order to quickly obtain the effect of the moment due to the braking force applied to the rear wheel, it is preferable to increase the reduction rate to the transmission force limit amount by setting a short time until the limit amount is reduced. .

On the other hand, in the understeer state, when the wheel to be controlled by the skid prevention control is the front wheel, control is performed to increase the driving force on the rear wheel side even if the moment due to the braking force generated on the front wheel is taken into account. Is preferable. Therefore, in this case, a large value transfer Itaruryoku limit amount, that is, when it made to be larger fourth value than the third value may.

  Further, as shown in claim 8, when the vehicle is a rear drive base having a front wheel as a main drive wheel and a rear wheel as a secondary drive wheel, the side slip prevention control means is provided for the turning outer wheel when the vehicle is in an oversteer state. When the front wheel is set as the wheel to be controlled, the skid prevention control means or the driving force distribution setting means sets the limit value of the driving transmission force to the front wheel in the driving force distribution as the fifth value and is in an oversteer state. When the side slip prevention control means sets the rear wheel of the turning outer wheel as the control target wheel, the side slip prevention control means or the drive force distribution setting means sets the limit amount of the drive transmission force to the front wheels in the drive force distribution to the fifth value. Is set as a sixth value that is equal to or smaller than.

  Further, as shown in claim 10, when the vehicle is a rear drive base having a front wheel as a main drive wheel and a rear wheel as a secondary drive wheel, when the vehicle is in an understeer state, the skid prevention control means When the front wheel is set as the wheel to be controlled, the skid prevention control means or the driving force distribution setting means sets the limit value of the driving transmission force to the front wheel in the driving force distribution as the seventh value, thereby driving the driving force of the front wheel. Compared with the case where the driving force distribution between the rear wheel and the driving force of the rear wheel is 50:50, the driving force transmitted to the front wheel is reduced. When set as the wheel to be controlled, the skid prevention control means or the driving force distribution setting means sets the limit value of the drive transmission force to the front wheels in the driving force distribution to an eighth value smaller than the seventh value. By setting and, compared to the case where the controlled wheel is a front wheel, so that driving force transmitted to the front wheels is increased.

  Thus, also in the case of a rear drive base vehicle, the same effect as in the case of the front drive base can be obtained by changing the setting of the limit amount according to the control target wheel of the skid prevention control.

  When the limit amount is set as the fifth value, as shown in claim 9, the driving force distribution setting means sets the driving force distribution of the front wheels from the 50:50 to the fifth value. It is preferable to change at a relatively large reduction rate until

  Further, when the limit amount is set as the seventh value, as shown in claim 11, the driving force distribution setting means converts the driving force of the front wheels from 50:50 to the seventh driving force distribution. It is preferable to change at a relatively small reduction rate until the value is reached.

  Note that, as described in claim 12, the limit amount described above can be made variable according to the road surface friction coefficient (μ). Specifically, as shown in claim 13, the limit amount is set to be larger as the road surface friction coefficient is higher and smaller as the road surface friction coefficient is lower.

  Further, the reduction rate can be made variable according to the road surface friction coefficient (μ), as shown in claim 14. Specifically, as shown in claim 15, the higher the road surface friction coefficient, the faster the road surface friction coefficient, and the lower the road surface friction coefficient.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing an overall system configuration of the vehicle attitude control device according to the first embodiment of the present invention. Here, a case where the vehicle attitude control device according to an embodiment of the present invention is applied to a front-drive-based four-wheel vehicle in which the front wheel side is a main drive wheel and the rear wheel side is a slave drive wheel will be described. However, the present invention can also be applied to a rear drive base four-wheel vehicle having a drive configuration in which the rear wheel side is a main drive wheel and the front wheel side is a slave drive wheel.

  As shown in FIG. 1, the engine output (engine torque) generated by the engine 1 is transmitted to the transmission 2 and converted by a gear ratio corresponding to the gear position set by the transmission 2, and then driving force distribution control is performed. This is transmitted to the driving force distribution control actuator 3 corresponding to the means. The driving force is transmitted to the front propeller shaft 4 and the rear propeller shaft 5 in accordance with the driving force distribution determined by the driving force distribution control actuator 3.

  For example, in the case of a front drive base four-wheel drive vehicle as in this embodiment, the ratio of the drive force applied to the front wheels FR and FL to the drive force applied to the rear wheels RR and RL (drive force distribution). ) Can be varied between 100: 0 and 50:50, and the driving force distribution control actuator 3 controls, for example, the engagement hydraulic pressure to the hydraulic clutch so as to obtain this ratio, thereby distributing the driving force. To control.

  Then, the front propeller shaft 4 is connected to the front wheels FR and FL through the front drive shaft 7 connected via the front differential 6, and a driving force according to the driving force distribution on the front wheel side is applied to the rear propeller shaft 5. Through the rear drive shaft 9 connected through the rear wheel RR, a driving force according to the driving force distribution on the rear wheel side is applied to the rear wheels RR and RL.

  The driving force distribution by the driving force distribution control actuator 3 is set by the driving force distribution controller 10. The driving force distribution controller 10 corresponds to a driving force distribution setting unit and executes a driving force distribution control that is generally performed. In the present embodiment, in addition to this, the ESC- The transmission force limit amount command signal is received from the ECU 11, and the drive force distribution control is executed so that the drive force transmitted to the rear wheels RR and RL is suppressed by the limit amount indicated by the transmission force limit amount command signal.

  For example, when the driving force distribution between the front wheels FR and FL and the rear wheels RR and RL is set at 50:50, the transmission force limit amount of the driving force to the rear wheels RR and RL is set to 30%. In this case, the transmission force to the rear wheels RR and RL is limited so that the driving force distribution is 70:30 or less.

  In this way, the driving force distribution controller 10 limits the transmission force to the rear wheels RR and RL based on the transmission force limit amount command signal from the ESC-ECU 11, and accordingly the front wheels FR and FL and the rear wheels. Driving force distribution with RR and RL is set. When the driving force distribution is set, a driving force distribution command signal indicating the driving force distribution is output from the driving force distribution controller 10, and the driving force indicated by the driving force distribution command signal is output. Based on the distribution, the driving force transmitted to the transmission 2 is distributed so that the driving force distribution control actuator 3 achieves the set driving force distribution.

  The ESC-ECU 11 corresponds to a skid prevention control means, and includes detection signals from the steering angle sensor 12 and the yaw rate sensor 13, and wheel speed sensors 14FR, 14FL, 14RR provided in the wheels FR, FL, RR, RL. , 14RL are received and various physical quantities are obtained. Specifically, the ESC-ECU 11 obtains the steering angle based on a detection signal corresponding to the operation amount of the steering wheel 15 output by the driver output from the steering angle sensor 12 or is generated in the vehicle output from the yaw rate sensor 13. An actual yaw rate (yaw angular velocity) is obtained based on a detection signal corresponding to the actual yaw rate. Further, based on detection signals from the wheel speed sensors 14FR, 14FL, 14RR, 14RL, the wheel speeds and vehicle speeds (estimated vehicle body speeds) of the wheels FR, FL, RR, RL are obtained by the ESC-ECU 11. .

  Further, the ESC-ECU 11 outputs an ESC command signal to the brake fluid pressure control actuator 16 in order to perform ESC. The ESC executed by the ESC-ECU 11 is a situation where the vehicle can skid based on the actual yaw rate, the rudder angle, or the rudder angular velocity obtained by time differentiation of the rudder angle. In the situation where skidding is possible, the wheel to be controlled is determined according to the form of skidding, and the skidding is applied to prevent skidding.

  For example, whether or not the vehicle is capable of skidding is determined based on the ideal yaw rate required from the steering angle and vehicle speed, that is, the yaw rate required to follow the trajectory when no skidding (hereinafter referred to as the target yaw rate) and the actual yaw rate. It is determined by whether or not the absolute value of the difference exceeds a predetermined threshold level. Then, the target yaw rate is compared with the actual yaw rate, and it is determined whether the vehicle is in an oversteer (OS) state or an understeer (US) state depending on which is greater, and a control target wheel is set according to the vehicle state, and control is performed. A skid is avoided by applying a braking force to the target wheel.

  Specifically, in the oversteer state, a braking force is applied with the turning outer wheel as the control target wheel, and in the understeer state, the turning inner wheel is set as the control target wheel. At this time, whether the front wheel or the rear wheel of the turning outer wheel or the turning inner wheel is to be controlled is determined by the actual yaw rate, rudder angle, or rudder angular speed. ing.

  The brake fluid pressure control actuator 16 is configured as a brake system that can automatically pressurize wheel cylinders (hereinafter referred to as W / C) 17FR, 17FL, 17RR, and 17RL. As the brake fluid pressure control actuator 16, both a hydraulic brake system that generates W / C pressure by hydraulic pressure and an electric brake system such as a brake-by-wire that generates W / C pressure electrically can be used. The brake fluid pressure control actuator 16 pressurizes one of the W / C 17FR, 17FL, 17RR, and 17RL that corresponds to the wheel to be controlled, thereby causing the disc rotors 19FR, 19FL by the calipers 18FR, 18FL, 18RR, 18RL. , 19RR and 19RL are sandwiched so that a braking force is generated. The brake hydraulic pressure control actuator 16, W / C 17FR to 17RL, calipers 18FR to 18RL, and disc rotors 19FR to 19RL shown here correspond to the braking force generating means in the present invention.

  Next, the operation of the vehicle attitude control device configured as described above will be described.

  First, a mechanism for improving the stability of vehicle travel by the vehicle attitude control device will be described.

  2 to 5 are diagrams showing the relationship between how the braking force is generated by the ESC in accordance with the behavior of the vehicle and the distribution of the driving force between the front wheels FR and FL and the rear wheels RR and RL. In each of these drawings, (a) is a diagram showing the relationship between the driving force and braking force generated in each wheel FR, FL, RR, RL, and (b) is the case where the ideal trajectory and ESC are not performed. The figure which showed the relationship with the assumed actual vehicle locus | trajectory, (c) is the figure which showed the relationship of the driving force distribution of front-wheel FR, FL and rear-wheel RR, RL. In FIG. 2A to FIG. 5A, the white arrow indicates the magnitude of the driving force, and the black arrow indicates the magnitude of the braking force.

  In an oversteer state in which the actual vehicle track cuts inward from the ideal track, the turning outer wheel is set as the control target wheel. At this time, if the oversteer state occurs in the right turn as shown in FIGS. 2 (b) and 3 (b), the left front wheel FL as shown in FIG. 2 (a) or as shown in FIG. 3 (a). Thus, the braking force is generated with the left rear wheel RL as the control target wheel.

  On the other hand, in the case of an understeer state in which the actual vehicle track is pushed outward from the ideal track, the turning inner wheel is set as the control target wheel. At this time, if the understeer state occurs in the right turn as shown in FIGS. 4B and 5B, the right front wheel FR as shown in FIG. 4A or the state shown in FIG. Thus, the braking force is generated with the right rear wheel RR as the control target wheel.

  Basically, if the control is performed to increase the driving force on the front wheels FR and FL in the oversteer state and increase the driving force on the rear wheels RR and RL in the understeer state, Can be achieved. However, when a braking force is generated by ESC, a moment is generated by this braking force. Therefore, even if the above control is performed, the vehicle is not necessarily stabilized from the relationship with the moment by this braking force. It may not be possible to plan.

  Therefore, even in the same oversteer state and understeer state, it is better to adopt different control modes depending on whether the wheel to be controlled to which the braking force by the ESC is applied is the front wheels FR, FL or the rear wheels RR, RL. It is desired to further stabilize the vehicle.

  For this reason, when each case shown by FIGS. 2-5 was examined, the result that the stabilization of a vehicle could be achieved if it did as follows was obtained.

First, as shown in FIG. 2B, in the oversteer state, when the wheel to be controlled by the ESC is the left front wheel FL, the front wheel is considered even if the moment due to the braking force generated on the left front wheel FL is taken into consideration. It is preferable to perform control to increase the driving force on the FR and FL sides. Therefore, in this case, it reduces the limit amount as the driving transmission force is limited by the large value, the amount of transmission power limit may be such that the first value.

  However, in this case, if the driving force distribution to the rear wheels RR and RL is suddenly reduced to the set transmission force limit, the vehicle behavior may become unstable. For this reason, it is preferable to reduce the rate of reduction to the transmission force limit amount by setting a long time until the transmission force limit amount is reduced.

  Such a change in the transmission force limit amount is expressed as shown in FIG. 2C. Compared with the case where the driving force distribution is 50:50, a large driving force is applied to the front wheels FR and FL, The driving force on the rear wheels RR, RL side is small or zero. The rate of reduction to the transmission force limit amount, that is, the decreasing gradient of the driving force distribution on the rear wheels RR and RL side is a relatively small gradient. Therefore, when the ESC control target wheel is the left front wheel FL in the oversteer state, for example, the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL is gradually reduced from 50:50 to 90:10. Specifically, as described later, it is preferable that the transmission force limit amount be changed at a slower reduction rate than when the transmission force limit amount is set as the second value.

Next, as shown in FIG. 3B, in the oversteer state, when the wheel to be controlled by the ESC is the left rear wheel RL, the moment due to the braking force generated on the left rear wheel RL is The smaller the driving force, the greater the effect. Therefore, in this case, it reduces the limit amount as the driving transmission force is limited by the small value, the amount of transmission power limit may be such that a small second value than the first value.

Such a change in the transmission force limit amount is expressed as shown in FIG. 3C, and the driving force applied to the front wheels FR and FL is relatively large as compared with the case where the driving force distribution is 50:50. 100, and the driving force on the rear wheels RR and RL side is small and equal to zero . Therefore, when the ESC control target wheel is the left rear wheel RL in the oversteer state, for example, the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL is changed from 50:50 to 100: 0. It is preferable to make it possible.

In addition, as shown in FIG. 4B, when the ESC control target wheel is the right front wheel FR in the understeer state, the rear side even if the moment due to the braking force generated on the right front wheel FR is taken into consideration. It is preferable to perform control to increase the driving force on the wheels RR and RL side. Therefore, in this case, the limit amount is decreased so that the change in the drive transmission force is reduced, and the transmission force limit amount becomes a large value (a fourth value larger than a third value described later). Good.

In this case, since the necessity for limiting the drive transmission force is small, the time until the transmission force limit is reduced is set longer .

  Such a change in the transmission force limit amount is expressed as shown in FIG. 4C, and the driving force applied to the front wheels FR and FL is increased as compared with the case where the driving force distribution is 50:50. However, the relationship is not much different from the driving force applied to the rear wheels RR and RL. The rate of reduction to the transmission force limit amount, that is, the decreasing gradient of the driving force distribution on the rear wheels RR, RL side, is a relatively large gradient. Therefore, when the ESC control target wheel is the right front wheel FR in the understeer state, for example, the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL is changed from 50:50 to 60:40. It is preferable to do so.

Furthermore, as shown in FIG. 5 (b), when the ESC control target wheel is the right rear wheel RR in the understeer state, considering the moment due to the braking force generated on the right rear wheel RR, Rather than increasing the driving force on the rear wheels RR, RL side, the vehicle is stabilized rather than decreasing it. Therefore, in this case, it is preferable to reduce the limit amount so that the change in the drive transmission force is increased and to set the transmission force limit amount to a small value (third value).

  In this case, in order to quickly obtain the effect of the moment caused by the braking force applied to the right rear wheel RR, the time until the transmission force limit amount is reduced is set short, thereby reducing the transmission force limit amount. It is preferable to increase the reduction rate.

  Such a change in the transmission force limit amount is expressed as shown in FIG. 5C. Compared to the case where the driving force distribution is 50:50, a large driving force is applied to the front wheels FR and FL, The driving force on the rear wheels RR, RL side is small or zero. And the reduction rate to the transmission force limit amount becomes steep. Therefore, when the ESC control target wheel is the right rear wheel RR in the oversteer state, for example, the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL is changed from 50:50 to 100: 0. It is preferable to make it possible.

  Based on the above examination, in the present embodiment, the ESC-ECU 11 performs the following transmission force limit amount setting control. FIG. 6 shows a flowchart of the transmission force limit amount setting control, which will be described with reference to this figure. The steps shown in the figure correspond to means for executing various processes.

  The transmission force limit amount setting control shown in FIG. 6 is executed every predetermined calculation cycle when an ignition switch (not shown) provided in the vehicle is turned on or during traveling of the vehicle.

  First, in step 100, reading of various sensor signals is executed. Specifically, detection signals from the steering angle sensor 12 and the yaw rate sensor 13 and detection signals from the wheel speed sensors 14FR, 14FL, 14RR, and 14RL are input. Based on the detection signals, the steering angle, the steering angular speed, the actual yaw rate, the wheel speed of each wheel FR, FL, RR, RL and the vehicle speed (estimated vehicle speed) are obtained.

  In step 105, a target yaw rate calculation process is executed. This process is to obtain a target yaw rate that is assumed when the vehicle follows an ideal trajectory, and is obtained by a known method from the rudder angle, vehicle speed, and the like obtained in step 100.

  Then, the process proceeds to step 110, and it is determined whether or not the absolute value of the difference between the target yaw rate obtained in step 105 and the actual yaw rate obtained in step 100 exceeds the threshold level. The threshold level here is set as a threshold value indicating whether or not to perform control intervention by ESC.

  If a negative determination is made in this step, the braking force by the ESC is not generated, so that it is not necessary to perform the driving force distribution control assuming the braking force by the ESC, and the processing is completed as it is. If an affirmative determination is made in this step, it is assumed that a braking force by ESC is generated, and the routine proceeds to step 115.

  In step 115, it is determined whether or not control for suppressing the oversteer state by ESC is executed (that is, control for suppressing the understeer state is executed). Here, the above-described target yaw rate is compared with the actual yaw rate, and if the target yaw rate is smaller than the actual yaw rate, it is determined as an oversteer state, and vice versa.

  If the determination in step 115 is affirmative, that is, if it is determined that the vehicle is in an oversteer state, the process proceeds to step 120, and whether or not the wheel to be controlled by ESC is the front wheels FR and FL in the oversteer state (that is, the rear wheel RR). , RL). This determination is made based on the actual yaw rate, rudder angle, or rudder angular velocity. For example, if the actual yaw rate is larger than a predetermined value, the front wheel FR, FL side is determined. It has come to be.

  If an affirmative determination is made in step 120, the process proceeds to step 125, and in the oversteer state, the transmission force when the ESC-controlled wheels are the front wheels FR and FL is calculated. Specifically, since this case corresponds to the case shown in FIG. 2 described above, for example, the driving force distribution between the front wheels FR and FL and the rear wheels RR and RL is 50:50 to 90:10. It is set so that it can be changed gradually.

  On the other hand, if a negative determination is made in step 120, the process proceeds to step 130, and in the oversteer state, the transmission force is calculated when the wheels to be controlled by ESC are the rear wheels RR and RL. Specifically, since this case corresponds to the case shown in FIG. 3 described above, for example, the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL is 50:50 to 100: 0. It is set so that it can be changed.

  If the determination in step 115 described above is negative, that is, if it is determined that the vehicle is in an understeer state, the process proceeds to step 135, and in the understeer state, whether or not the wheel to be controlled by the ESC is the front wheels FR and FL (that is, the rear wheel). Wheel RR, RL) is determined. This determination is also made based on the actual yaw rate, the rudder angle, or the rudder angular speed. For example, if the actual yaw rate is larger than a predetermined value, the front wheels FR and FL are determined. It has come to be.

  If the determination in step 135 is affirmative, the process proceeds to step 140, and the transmission force when the ESC controlled wheels are the front wheels FR and FL in the understeer state is calculated. Specifically, since this case corresponds to the case shown in FIG. 4 described above, for example, the driving force distribution between the front wheels FR and FL and the rear wheels RR and RL is 50:50 to 60:40. It is set so that it can be changed.

  On the other hand, if a negative determination is made in step 135, the process proceeds to step 145, and in the understeer state, the transmission force is calculated when the wheels to be controlled by ESC are the rear wheels RR and RL. Specifically, since this case corresponds to the case shown in FIG. 5 described above, for example, the driving force distribution between the front wheels FR and FL and the rear wheels RR and RL is 50:50 to 100: 0. It is set so that it can be changed quickly. As described above, the transmission force calculation process is performed in steps 120 to 145, and the portion of the ESC-ECU 11 that executes this transmission force calculation process corresponds to the drive transmission force limit amount setting means.

  When the transmission force calculation process is performed in this way, the process proceeds to step 150, and the result of the transmission force calculation process, that is, the transmission force limit amount is output as a command signal (transfer force limit amount command signal). When this transmission force limit amount command signal is transmitted to the driving force distribution controller 10, the driving force distribution control is executed such that the driving force transmitted to the rear wheels RR and RL is suppressed by the limit amount indicated by the transmission force limit amount command signal. Is done. Thus, the driving force distribution by the driving force distribution control actuator 3 is such that the driving force transmitted to the rear wheels RR and RL can be suppressed by the limit amount indicated by the transmission force limit amount command signal.

  Thereafter, the process proceeds to step 155, where actuator drive processing is executed. The actuator driving process here is for generating a braking force for the wheel to be controlled by ESC, and for outputting an ESC command signal to the brake fluid pressure control actuator 16. Thereby, the brake fluid pressure control actuator 16 automatically pressurizes the W / C 17FR, 17FL, 17RR, 17RL corresponding to the wheel to be controlled, and thereby the disc rotors 19FR, 19FL, 19RR, 19RL is sandwiched and a braking force is generated.

  As described above, according to the vehicle attitude control device of the present embodiment, when the braking force by the ESC is applied, the wheel to which the braking force is applied is any of the front wheels FR, FL and the rear wheels RR, RL. Depending on whether or not, the limit amount of the drive transmission force in the drive force distribution control is controlled. That is, even in the same oversteer state and understeer state, the limit amount of the drive transmission force differs depending on whether the control target wheel to which the braking force is applied by the ESC is the front wheels FR, FL or the rear wheels RR, RL. It is supposed to be. This makes it possible to further stabilize the vehicle in accordance with how the braking force is applied by the ESC.

(Second Embodiment)
A second embodiment of the present invention will be described. In the above embodiment, the case where the vehicle attitude control device is applied to a front drive-based vehicle has been described. Here, a case where the vehicle posture control device is applied to a rear drive-based vehicle will be described.

  Since the configuration of the vehicle attitude control device of the present embodiment is a rear drive base, it differs in that it is a drive configuration in which the rear wheel side is a main drive wheel and the front wheel side is a slave drive wheel. For this reason, the ratio (driving force distribution) between the driving force applied to the front wheels FR and FL and the driving force applied to the rear wheels RR and RL can be varied between 0: 100 and 50:50. The driving force distribution control actuator 3 controls the engagement hydraulic pressure to the hydraulic clutch, for example, to control the driving force distribution so that this ratio is obtained.

  In the case of such a drive mode, the mechanism for improving the stability of the vehicle traveling by the vehicle attitude control device is the same as that of the above-described front drive base, but the limit amount of the drive transmission force in the drive force distribution control Will be different. Hereinafter, a method of limiting the drive transmission force when the rear drive base is used as in the present embodiment will be described.

  First, in the oversteer state, if the wheel to be controlled by the ESC is the left front wheel FL, the driving force on the front wheels FR, FL side is increased even when the moment due to the braking force generated on the left front wheel FL is taken into consideration. It is preferable to perform such control. Therefore, in this case, the limit of the drive transmission force may be reduced, that is, the transmission force limit amount may be a large value (fifth value).

  For this reason, in this case, for example, the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL is kept at 50:50 so that the driving force on the front wheels FR, FL side can be increased. preferable. At this time, it is preferable to change at a relatively large reduction rate until the transmission force limit amount is reached.

  Next, in the oversteer state, if the wheel to be controlled by the ESC is the left rear wheel RL, it occurs in the left rear wheel RL even if control is performed to increase the driving force on the front wheels FR and FL sides. From the relationship with the moment caused by the braking force to be applied, the effect as much as the case where the above-described left front wheel FL is the wheel to be controlled cannot be obtained. Therefore, in this case, if the drive transmission force is slightly limited, that is, the transmission force limit amount is a relatively small value (that is, a sixth value that is equal to or smaller than the fifth value). good.

  Therefore, in this case, for example, it is preferable that the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL be changed from 50:50 to 40:60.

  Further, when the ESC control target wheel is the right front wheel FR in the understeer state, the driving force on the rear wheels RR and RL side is increased even when the moment due to the braking force generated on the right front wheel FR is taken into consideration. It is preferable to perform such control. Therefore, in this case, it is preferable that the limit of the drive transmission force is reduced, that is, the transmission force limit amount is a small value (that is, an eighth value smaller than a seventh value described later).

  Therefore, in this case, for example, it is preferable that the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL be changed from 50:50 to 0: 100.

  Furthermore, when the ESC control target wheel is the right rear wheel RR in the understeer state, the driving force on the rear wheels RR, RL side is increased in consideration of the moment due to the braking force generated on the right rear wheel RR. Rather than too much, the vehicle is stabilized when the driving force is applied to the front wheels FR and FL. Therefore, in this case, it is preferable that the drive transmission force is slightly restricted, that is, the transmission force restriction amount is a relatively large value (seventh value).

  Therefore, in this case, for example, it is preferable that the driving force distribution between the front wheels FR, FL and the rear wheels RR, RL be changed from 50:50 to 30:70. At this time, it is preferable to change at a relatively small reduction rate until the transmission force limit amount is reached.

  Based on the above consideration, in the present embodiment, when the ESC-ECU 11 executes the transmission force limit amount setting control shown in FIG. 6 described above, the limit amount of the drive transmission force in the drive force distribution control is set. I have to. The other processes in the transmission force limit amount setting control are the same as those in the first embodiment.

  As described above, when the braking force by the ESC is applied to the rear drive base four-wheel drive vehicle as well, the wheels to which the braking force is applied are the front wheels FR, FL. And the rear wheels RR and RL, the limit amount of the drive transmission force in the drive force distribution control can be controlled. This makes it possible to further stabilize the vehicle in accordance with how the braking force is applied by the ESC.

(Other embodiments)
In the above-described embodiment, the case where the limit amount of the driving force transmission force is shown as a ratio represented by the driving force distribution has been described, but the ratio is not necessarily a ratio. For example, the limit amount can be shown as the magnitude of the drive transmission force itself. In this case, for example, even if the driving force distribution is 50:50, the upper limit value of the driving transmission force is determined by the set limit amount, so that the driving force equivalent to the driving force distribution is applied to the driven wheels. It will be restricted so as not to be.

  In the above embodiment, detection signals from the steering angle sensor 12, the yaw rate sensor 13, and the wheel speed sensors 14FR, 14FL, 14RR, 14RL are input to the ESC-ECU 13, and the ESC-ECU 13 controls the steering angle, yaw rate, wheel speed, and After obtaining the vehicle speed and the like, the transmission force is calculated by the ESC-ECU 13, and a transmission force limit command signal indicating the result is transmitted to the driving force distribution controller 10. However, this is merely an example, and detection signals from the steering angle sensor 12, the yaw rate sensor 13, or the wheel speed sensors 14FR, 14FL, 14RR, and 14RL are directly input to the driving force distribution controller 10, and the driving force distribution controller In FIG. 10, various physical quantities may be obtained.

  In particular, as in recent years, in a situation where ECUs mounted on vehicles are being integrated, various processes may be executed by one ECU. For this reason, it is possible that these are not two different ECUs such as the ESC-ECU 13 and the driving force distribution controller 10, but they are integrated. In such a case, each of the above processes is executed by one ECU, and the driving force distribution by the driving force distribution control actuator 3 is controlled based on the transmission force calculation result performed there. .

  Furthermore, in the above-described embodiment, examples relating to the limit amount and the reduction rate are shown, but these are merely examples, and the above-described example is not necessarily required. In addition, since the optimum values of the limit amount and the reduction rate change according to the road surface friction coefficient μ, the road surface friction coefficient μ is detected by a well-known method and is made variable according to the detected road surface friction coefficient μ. It is also possible. In this case, the limit amount is set to be larger as the road surface friction coefficient μ is higher and smaller as the road surface friction coefficient μ is lower. The reduction rate is set faster as the road surface friction coefficient μ is higher and slower as the road surface friction coefficient μ is lower.

1 is a diagram illustrating an overall system configuration of a vehicle attitude control device according to a first embodiment of the present invention. It is the figure which showed how to generate the braking force by ESC according to the behavior of the vehicle and the relationship between the driving force distribution of the front wheels FR and FL and the rear wheels RR and RL. It is the figure which showed how to generate the braking force by ESC according to the behavior of the vehicle and the relationship between the driving force distribution of the front wheels FR and FL and the rear wheels RR and RL. It is the figure which showed how to generate the braking force by ESC according to the behavior of the vehicle, and the relationship between the driving force distribution of the front wheels FR and FL and the rear wheels RR and RL. It is the figure which showed how to generate the braking force by ESC according to the behavior of the vehicle, and the relationship between the driving force distribution of the front wheels FR and FL and the rear wheels RR and RL. It is a flowchart of the transmission force restriction amount setting control executed by the ESC-ECU.

Explanation of symbols

1 ... engine, 2 ... transmission, 3 ... driving force distribution control actuator,
4 ... Front propeller shaft, 5 ... Rear propeller shaft,
6 ... Front differential, 7 ... Front drive shaft,
8 ... Rear differential, 9 ... Rear drive shaft,
DESCRIPTION OF SYMBOLS 10 ... Driving force distribution controller, 11 ... ESC-ECU, 12 ... Rudder angle sensor,
13 ... Yaw rate sensor, 14FR-14RL ... wheel speed sensor,
15 ... steering, 16 ... brake hydraulic pressure control actuator,
17FR-17RL ... W / C.

Claims (15)

Braking force generation means (16, 17FR to 17RL, 18FR to 18RL, 19FR to 19RL) for generating a braking force for each wheel (FR, FL, RR, RL) provided in the vehicle;
Side slip prevention control means for detecting a side slip of the vehicle and outputting a signal to the braking force generation means in order to execute a side slip prevention control for generating a braking force on the wheel to be controlled in order to prevent the side slip. 11) and
Driving force distribution setting for setting the driving force distribution between the driving force applied to the main driving wheels (FR, FL) and the driving force applied to the slave driving wheels (RR, RL) among the wheels. Means (10);
Driving force distribution control means for distributing the driving force applied to the main driving wheel and the driving force applied to the slave driving wheel according to the driving force distribution set by the driving force distribution setting means ( 3)
The side-slip prevention control means or the driving force distribution setting means is configured to control the drive transmission force to the driven wheel in the driving force distribution according to the control target wheel of the side-slip prevention control performed by the side-slip prevention control means. Drive transmission force limit amount setting means (120 to 145) for setting the limit amount;
When the skid prevention control is executed by the skid prevention control means, the driving force distribution set by the driving force distribution setting means is less than or equal to a limit amount set by the drive transmission force limit amount setting means. Limited ,
The skid prevention control means sets the front wheel or the rear wheel of the turning outer wheel as the control target wheel when the vehicle skid is in an oversteer state,
The side-slip prevention control means or the driving force distribution setting means determines whether the side-slip prevention control means sets the control target wheel as a front wheel or a rear wheel of the outer turning wheel. A vehicle attitude control device that changes a limit amount of a drive transmission force to the driven wheels . Braking force generation means (16, 17FR to 17RL, 18FR to 18RL, 19FR to 19RL) for generating a braking force for each wheel (FR, FL, RR, RL) provided in the vehicle;
Side slip prevention control means for detecting a side slip of the vehicle and outputting a signal to the braking force generation means in order to execute a side slip prevention control for generating a braking force on the wheel to be controlled in order to prevent the side slip. 11) and
Driving force distribution setting for setting the driving force distribution between the driving force applied to the main driving wheels (FR, FL) and the driving force applied to the slave driving wheels (RR, RL) among the wheels. Means (10);
Driving force distribution control means for distributing the driving force applied to the main driving wheel and the driving force applied to the slave driving wheel according to the driving force distribution set by the driving force distribution setting means ( 3)
The side-slip prevention control means or the driving force distribution setting means is configured to control the drive transmission force to the driven wheel in the driving force distribution according to the control target wheel of the side-slip prevention control performed by the side-slip prevention control means. Drive transmission force limit amount setting means (120 to 145) for setting the limit amount;
When the skid prevention control is executed by the skid prevention control means, the driving force distribution set by the driving force distribution setting means is less than or equal to a limit amount set by the drive transmission force limit amount setting means. Limited ,
The skid prevention control means sets the front wheel or the rear wheel of the turning inner wheel as the wheel to be controlled when the skid of the vehicle is in an understeer state.
The side-slip prevention control means or the driving force distribution setting means determines whether the side-slip prevention control means sets the control target wheel as a front wheel or a rear wheel of the turning inner wheel. A vehicle attitude control device that changes a limit amount of a drive transmission force to the driven wheels . The skid prevention control means sets the front wheel or the rear wheel of the turning outer wheel as the control target wheel when the vehicle skid is in an oversteer state,
The side-slip prevention control means or the driving force distribution setting means determines whether the side-slip prevention control means sets the control target wheel as a front wheel or a rear wheel of the outer turning wheel. The vehicle attitude control device according to claim 2 , wherein a limit amount of a drive transmission force to the driven wheels is changed. When the vehicle is a front drive base having a front wheel as the main drive wheel and a rear wheel as the slave drive wheel,
When the skid prevention control means sets the front wheel of the turning outer wheel as the control target wheel in the oversteer state,
The skid prevention control means or the driving force distribution setting means sets a limit amount of the drive transmission force to the rear wheel in the driving force distribution as a first value, so that the driving force of the front wheel and the rear wheel are set. Compared with the case where the driving force distribution with the driving force is 50:50, the driving force transmitted to the rear wheel is reduced,
When the skid prevention control means sets the rear wheel of the turning outer wheel as the control target wheel in the oversteer state,
The skid prevention control means or the driving force distribution setting means sets the limit amount of the drive transmission force to the rear wheel in the driving force distribution as a second value smaller than the first value, front wheel drive force and a small fence and the driving force distribution compared with the case of the 50:50 and the driving force of the rear wheel and, as the controlled wheel is reduced as compared with when it is to the front wheels, the The vehicle attitude control device according to claim 1 , wherein a driving force transmitted to the rear wheel is controlled. When the limit amount is set as the first value, the driving force distribution setting unit determines the driving force of the rear wheel until the driving force distribution reaches the first value from 50:50. 5. The vehicle attitude control device according to claim 4 , wherein the limit amount is changed at a slower reduction rate than when the limit amount is set as the second value. In the case where the vehicle is a front drive base having a front wheel as the main drive wheel and a rear wheel as the slave drive wheel,
When the skid prevention control means sets the rear wheel of the turning inner wheel as the control target wheel in the understeer state,
The skid prevention control means or the driving force distribution setting means sets a limit amount of the driving transmission force to the rear wheel in the driving force distribution as a third value, so that the driving force of the front wheel and the rear wheel are set. Compared with the case where the driving force distribution with the driving force is 50:50, the driving force transmitted to the rear wheel is reduced,
When the skid prevention control means sets the front wheel of the turning inner wheel as the control target wheel in the understeer state,
The skid prevention control means or the driving force distribution setting means sets the limit amount of the driving transmission force to the rear wheel in the driving force distribution as a fourth value larger than the third value, 4. The vehicle attitude control device according to claim 2 , wherein a driving force transmitted to the rear wheel is increased as compared with a case where the wheel to be controlled is the rear wheel. 5.   When the limit amount is set as the third value, the driving force distribution setting unit determines the driving force of the rear wheel until the driving force distribution reaches the third value from 50:50. The vehicle attitude control device according to claim 6, wherein the limit amount is changed at a faster reduction rate compared to a case where the limit amount is set as the fourth value. In the case where the vehicle is a rear drive base having a front wheel as the slave drive wheel and a rear wheel as the main drive wheel,
When the skid prevention control means sets the front wheel of the turning outer wheel as the control target wheel in the oversteer state,
The skid prevention control means or the driving force distribution setting means sets, as a fifth value, a limit amount of driving transmission force to the front wheels in the driving force distribution,
When the skid prevention control means sets the rear wheel of the turning outer wheel as the control target wheel in the oversteer state,
The skid prevention control means or the driving force distribution setting means sets a limit amount of the drive transmission force to the front wheels in the driving force distribution as a sixth value that is equal to or smaller than the fifth value. The vehicle attitude control device according to claim 1 , wherein   When the limit amount is set as the fifth value, the driving force distribution setting unit relatively reduces the driving force of the front wheels until the driving force distribution reaches the fifth value from 50:50. The vehicle attitude control device according to claim 8, wherein the vehicle attitude control device is changed at a large reduction rate. In the case where the vehicle is a rear drive base having a front wheel as the slave drive wheel and a rear wheel as the main drive wheel,
When the skid prevention control means sets the front wheel of the turning inner wheel as the control target wheel in the understeer state,
The skid prevention control means or the driving force distribution setting means sets a limit value of the driving transmission force to the front wheels in the driving force distribution as a seventh value, so that the driving force of the front wheels and the rear wheel Compared to the case where the driving force distribution with the driving force is 50:50, the driving force transmitted to the front wheels is reduced,
When the skid prevention control means sets the rear wheel of the turning inner wheel as the control target wheel in the understeer state,
The skid prevention control means or the driving force distribution setting means sets the limit amount of the driving transmission force to the front wheel in the driving force distribution as an eighth value smaller than the seventh value, thereby controlling the control. 4. The vehicle attitude control device according to claim 2 , wherein a driving force transmitted to the front wheel is increased as compared with a case where the target wheel is the front wheel. 5.   When the limit amount is set as the seventh value, the driving force distribution setting unit relatively reduces the driving force of the front wheels until the driving force distribution reaches the seventh value from 50:50. The vehicle attitude control device according to claim 10, wherein the vehicle attitude control device is changed at a small reduction rate.   The vehicle attitude control device according to any one of claims 1 to 11, wherein the limit amount is variable according to a road surface friction coefficient (µ).   The vehicle attitude control device according to claim 12, wherein the limit amount is set to be larger as the road surface friction coefficient is higher and smaller as the road surface friction coefficient is lower. The vehicle attitude control device according to any one of claims 5 , 7, 9, and 11, wherein the reduction rate is variable according to a road surface friction coefficient (µ).   15. The vehicle attitude control device according to claim 14, wherein the reduction rate is set faster as the road surface friction coefficient is higher and slower as the road surface friction coefficient is lower.

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