JPH1148926A - Vehicle attitude control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform attitude control without giving an ill feeling to a driver and improve the performance of attitude control. SOLUTION: A vehicle attitude control device has two-system brake pipings formed with the first piping (a) connecting a wheel cylinder FR to a wheel cylinder RL and the second piping (b) connecting a wheel cylinder FL to a wheel cylinder RR, a supply selector valve (e) to switch two-system supply sources formed with a driver supply source (c) and a control supply source (d), a pressure control valve (f) and a control means (h). In this case, during under-steering and acceleration, front inner wheel control is performed with the supply source for the piping in the system of a pre-turn inner wheel and a post-turn outer wheel formed as a control supply source (d) and the supply source for the other piping formed as a drive supply source (c) and, during under-steering and non-acceleration, rear inner wheel control is performed with the supply source for the piping in the system of a pre-turn outer wheel and a post-turn inner wheel formed as the control supply source (d) and the supply source for the other pipe formed as the driver supply source (c).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle attitude control device, and more particularly, to a vehicle for driving front wheels, which controls a vehicle attitude by changing brake fluid pressure of each wheel according to the attitude of the vehicle. Related to the device.

[0002]

2. Description of the Related Art Conventionally, as a device for controlling the attitude of a vehicle, a device that reduces the output torque of an engine to generate a braking force to stabilize the vehicle attitude, or a desired device according to the attitude of the vehicle. A device for controlling a posture by generating a braking force on a wheel is known. For example, a device disclosed in Japanese Patent Application Laid-Open No. 6-247269 is known as the latter conventional technology. The vehicle attitude control device described in the conventional publication determines the attitude angle of the vehicle based on the yaw speed of the vehicle, the steering angle, and the like. When the attitude angle exceeds a predetermined limit value, it is determined that control is to be started, and the hydraulic device is used. Change the wheel cylinder pressure of the brake device, thereby increasing the attitude angle,
Alternatively, it is possible to prevent the posture angle from being unable to be generated at the time of turning.

[0003]

However, in the above-described conventional vehicle attitude control device, during attitude control, a braking force is generated by generating pressure on a wheel cylinder or reducing engine torque. To reduce the side force,
Even if the driver intends to accelerate,
When the posture is likely to be disturbed as in the understeer state, a braking force is generated to control the turning moment, and a behavior opposite to the driver's intention or operation occurs in the vehicle, giving the driver a sense of incongruity, There is a problem that it leads to a decrease in the ability. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and has as its object to execute attitude control without giving a driver an uncomfortable feeling and to improve attitude control performance.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and the invention according to claim 1 is, as shown in FIG. There are two systems, a first pipe a that connects the wheel cylinder FR of the right front wheel and the wheel cylinder RL of the left rear wheel, and a second pipe b that connects the wheel cylinder FL of the left front wheel and the wheel cylinder RR of the right rear wheel. And a driver supply source c for supplying a brake pressure generated by a driver's braking operation to each brake pipe a and b, and a pressure source formed independently and independently of the driver's braking operation. Two supply sources, a control supply source d for supplying the brake pressure, are connected, and whether the supply source of the brake pressure for each brake pipe a, b is the driver supply source c or the control supply source d is determined. Supply switching valve e for switching is provided A pressure control valve f for controlling each wheel cylinder pressure is provided. When it is determined that the vehicle is in the understeer state by an input from the vehicle behavior detecting means g for detecting the behavior of the vehicle, the understeer state is avoided. Therefore, in a vehicle attitude control device provided with control means h for controlling the operation of the supply switching valve e and the pressure control valve f, the control means h determines that the vehicle is in the understeer state when executing the understeer avoidance control. In addition to the above, when it is determined that the vehicle is accelerating at the same time, the supply source of the brake pipe connecting the inner wheel before turning and the outer wheel after turning is set as the control supply source d, and the system connecting the outer wheel before turning and the inner wheel after turning is used. The supply source of the brake pipe is the driver supply source c.
In addition to executing the inner wheel control before switching the supply switching valve e, and when determining that the vehicle is not accelerating in addition to determining that the vehicle is in the understeer state, the brake piping of the system connecting the outer wheel before turning and the inner wheel after turning is performed. A rear inner wheel control is performed in which a supply source is a control supply source d and a brake pipe connecting the inner wheel before turning and the outer wheel after turning is a driver supply source c.

According to a second aspect of the present invention, in the vehicle attitude control device according to the first aspect, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the front inner wheel control, the vehicle is controlled after the turn. The wheel cylinder pressure of the outer ring is set to zero.

According to a third aspect of the present invention, in the vehicle attitude control apparatus according to the first aspect, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the front inner wheel control, the turning outer wheel is turned. Is set to 0%.

[0007] The invention according to claim 4 is the invention according to claims 1 to 3.
In the vehicle attitude control device described above, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the rear inner wheel control, the slip ratio target value of the inner wheel after turning is set in a range of 0 to -5%. It is characterized by restriction.

[0008] The invention according to claim 5 is the invention according to claims 1 to 3.
In the vehicle attitude control device described above, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the rear inner wheel control, the slip rate target value SLIPM of the inner wheel after turning is set to -SLIPlim [1- (BETA). / BETAlim) ² ]
^1/2 <SLIPM <0% (where, SLIPlim is a slip ratio at which a predetermined tire braking force is linear, BETAlim is a slip angle at which a predetermined tire side force is linear, BETA
Is a vehicle body slip angle or a rear wheel tire slip angle. ).

The invention according to claim 6 is the invention according to claims 1 to 5
In the vehicle attitude control device described above, a wheel cylinder pressure of a rear wheel of a brake pipe of a system using the driver supply source as a supply source is set to 0 during the understeer avoidance control.

[0010] The invention according to claim 7 is the first to fifth aspects.
In the vehicle attitude control device described above, a target slip ratio of a rear wheel of a brake pipe of a system using the driver supply source as a supply source is set to 0% during the understeer avoidance control.

[0011] The invention according to claim 8 is the invention according to claim 1 or 4.
8. The vehicle attitude control device according to any one of Items 7 to 7, wherein the slip ratio target value of the inner wheel before turning is set to 0% during the front inner wheel control.

[0012] The ninth aspect of the present invention is the first to seventh aspects.
In the vehicle attitude control apparatus described above, the slip ratio target value SLIPM of the front inner wheel during turning is set to -SLIPlim [1- (BETAf / BETAlim) ² ] ^1/2 <SLIPM <SLIPlim [1- (BETAf / BETAlim) during the front inner wheel control. ) ² ] ^1/2 (BETaf is the front tire slip angle.)
Is limited to the range.

According to a tenth aspect of the present invention, in the vehicle attitude control apparatus according to the first or fourth to seventh aspects, when the vehicle body slip angle or the rear wheel tire slip angle is inward during the front inner wheel control, the turning outer wheel is turned. Slip rate target value S
LIPM is SLIPM <-SLIPlim [1- (BETA / BET
Alim) ² ] The wheel cylinder pressure control is executed only when it becomes ^1/2, and the wheel cylinder pressure or the slip ratio target value SLIPM is set to 0 when the above conditions are not satisfied.

According to an eleventh aspect of the present invention, in the vehicle attitude control device according to any one of the first to tenth aspects, there is provided a means for detecting a throttle valve opening as the vehicle behavior detecting means. An engine torque control actuator for arbitrarily controlling engine torque, wherein the throttle valve opening is controlled to be larger than a pedal stroke converted throttle opening operated by a driver during the front inner wheel control based on the understeer and acceleration determination. It is characterized by.

[0015]

In a front-wheel drive vehicle, the understeer characteristic tends to be strong during acceleration turning, but in the present invention, when the understeer state becomes a predetermined level or more during turning, the understeer state is controlled as follows. To avoid. That is, when the control unit determines that the vehicle is in the understeer state and is accelerating based on the input from the vehicle behavior detecting unit during turning of the vehicle, the control unit performs two systems of the first piping and the second piping. Of the brake pipes, the supply source of the brake pipe connecting the inner wheel before turning and the outer wheel after turning is used as the control supply source, and the supply source of the brake pipe connecting the outer wheel before turning and the inner wheel after turning is the driver source. Then, the supply switching valve is operated. Therefore, while the braking force is generated on the inner wheel before turning and the outer wheel after turning, the driving force of the engine works in the steering direction on the outer wheel before turning, and the yaw moment is generated on the vehicle body inside the turning by the braking force and the driving force. As a result, the understeer state is alleviated. The driving force of the engine by the driver's acceleration operation is transmitted to the outer wheel side before turning, so that the driver can feel a sense of acceleration. hard.
When the driver performs a braking operation in this state, a brake pressure is generated at the driver supply source, and the brake pressure is supplied to a brake pipe of a system connecting the outer wheel before turning and the inner wheel after turning. Therefore, a braking force corresponding to the driver's operation is generated, and the driver does not feel uncomfortable. On the other hand, when turning, if the vehicle is not accelerating even if it is understeered,
The control means, contrary to the above, performs the two-way operation of the first pipe and the second pipe.
Of the brake pipes of the system, the supply source of the brake pipe of the system connecting the outer wheel before turning and the inner wheel after turning is a control supply source,
The supply switching valve is operated so that the supply source of the brake pipe connecting the inner wheel before turning and the outer wheel after turning is used as the driver supply source. In this case, the understeer is controlled by controlling the wheel cylinder pressure of the inner wheel after turning high. Can be generated. If the driver performs a braking operation during the non-acceleration, the brake fluid pressure generated at the driver supply source is transmitted to a brake pipe connecting the inner wheel before turning and the outer wheel after turning, and this braking force is applied. The understeer can also be eliminated by the yaw moment generated by.

According to the present invention, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during front inner wheel control,
By setting the wheel cylinder pressure of the outer wheel after turning to 0 (claim 2) or setting the slip ratio target value of the outer wheel after turning to 0% (claim 3), the braking force on the outer wheel after turning is minimized. That is, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction,
In the outer wheel after turning, a side force is generated in a direction opposite to the turning direction so as to increase the yaw moment. Therefore,
When a braking force is generated in this state, the side force decreases and the yaw moment decreases. Therefore, in the present invention, the braking force is not generated at the rear wheels outside the turning, the side force is kept high, the reduction of the yaw moment is prevented, and the vehicle posture can be stabilized.

According to the fourth or fifth aspect of the invention, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the rear inner wheel control, the slip ratio target value of the inner wheel after turning is set to 0 to 0. It is limited to the range of -5% (claim 4), or the slip ratio target value SLIPM of the inner wheel after turning is -SLIPlim [1- (BETA / BETAlim) ² ].
^It is limited to the range of ^1/2 <SLIPM <0% (claim 5). That is, during non-acceleration, a side force in the direction opposite to the turning direction is generated on the inner wheel after turning so as to generate a yaw moment. Therefore, by executing the above control, a yaw moment is generated by the braking force in a range where the side force of the inner wheel after turning does not decrease, and the vehicle posture can be stabilized.

In the invention according to claim 6 or 7, the wheel cylinder pressure of the rear wheel of the brake pipe of the system using the driver supply source as the supply source during the understeer avoidance control is set to 0 (claim 6). Alternatively, the slip ratio target value of the rear wheel of the brake pipe of the system using the driver supply source is set to 0% (claim 7). Thus, even if the driver performs the braking operation, the vehicle posture can be stabilized without reducing the side force of the rear wheels.

In the ninth aspect of the present invention, at the time of front inner wheel control, the slip ratio target value SLIPM of the front inner wheel is set to -SLIPlim [1- (BETAf / BETAlim) ² ] ^1/2 <SLIPM <SLIPlim [1- (BETAf) / BETAlim) ² ] Restrict within ^1/2 . That is, in the inner wheel before turning,
When an extra slip occurs, the side force decreases and understeer is promoted. Therefore, by setting the slip ratio target value SLIPM to a limit value as described above, the maximum braking force is provided within a range where the side force does not decrease. Obtainable. Since the above calculation is complicated, the calculation can be simplified in consideration of the worst value of the tire side slip angle of the front wheels. This is the eighth aspect of the present invention, in which the target slip ratio of the inner wheel before turning is set to 0% during front inner wheel control. Therefore, the engine torque can be applied in the steering direction without reducing the side force due to the braking force on the front inner wheel and promoting understeer.

According to the tenth aspect of the present invention, when the vehicle body slip angle or the rear wheel tire slip angle is inward during front inner wheel control, the slip ratio target value SLIPM of the outer wheel after turning is provided.
Is SLIPM <−SLIPlim [1- (BETA / BET)
Alim) ² ] The wheel cylinder pressure control is executed only when it becomes ^1/2, and the wheel cylinder pressure or the slip ratio target value SLIPM is set to 0 when the above conditions are not satisfied. That is, when the vehicle body slip angle or the rear wheel tire slip angle is inward,
The rear wheels generate side forces in the same direction as the turning direction so as to cancel the yaw moment. Therefore, it is preferable that the braking be performed when the slip ratio target value is outside the range of the friction circle of the tire, and the braking not be performed within the range of the friction circle.
Therefore, by controlling the slip ratio target value SLIPM as described above, the required maximum side force can be obtained.

According to the eleventh aspect of the invention, the throttle valve opening is controlled to be larger than the pedal stroke converted throttle opening operated by the driver during front inner wheel control based on understeer and acceleration judgment. Therefore, the engine torque is increased, the surplus engine torque is transmitted to the outer wheel before turning by the differential effect of the differential, the turning moment of the vehicle is increased, and the understeer state can be avoided.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is an overall view showing one embodiment of the present invention. Reference numerals 1 to 4 denote wheel speed sensors (vehicle behavior detecting means) for detecting the rotation speed of the wheels, each of which outputs a frequency signal corresponding to the rotation speed of the wheel using, for example, a pickup coil.

Reference numeral 5 denotes a steering angle sensor (vehicle behavior detecting means) for detecting the steering angle of the steering wheel. For example, a frequency signal corresponding to the steering angular velocity is output by a phototransistor or the like, and this is integrated to process the steering angle. Is detected.

6 is a yaw speed sensor (vehicle behavior detecting means)
Then, for example, a yaw speed is detected by receiving a Coriolis force from a tuning fork type strain gauge or the like.

Reference numeral 7 denotes a lateral acceleration (hereinafter referred to as lateral G) sensor (vehicle behavior detecting means) which detects lateral acceleration by receiving a lateral force with a cantilever type strain gauge or the like.

Reference numeral 8 denotes a vehicle behavior control device (control means) which determines the vehicle behavior state based on signals from the sensors 1 to 7 and controls the operation of the valves 13a to 13h of the brake hydraulic control actuator 13. By doing so, switching of a hydraulic supply source described later to the wheel cylinder 20 of each wheel,
In addition, the brake fluid pressure supplied to each wheel cylinder 20 is controlled to control the braking force of each wheel. Also,
Similarly, a required throttle opening is calculated based on each signal from each of the sensors 1 to 7, and the required throttle opening is transmitted to the engine control device 9.

The brake hydraulic control actuator 13
Is for supplying brake fluid pressure to the wheel cylinders 20 of the respective wheels and for controlling the brake fluid pressure, and is provided in the middle of the brake pipes 21, 22, 23.

That is, the brake pipes 21 to 23
Is a brake pipe (first pipe) 21 connecting the right front wheel and left rear wheel wheel cylinders 20, 20, and a brake pipe (second pipe) 22 connecting the left front wheel and right rear wheel wheel cylinders 20, 20. A master cylinder (driver supply source) 14 for generating a brake operation hydraulic pressure in response to the driver's pedal operation, and a control hydraulic source (control supply Source) Brake pipe 2 connecting 13i and pipes 21 and 22
And 3.

The brake hydraulic control actuator 13 is provided in the middle of the brake pipes 21 and 22 and controls hydraulic pressures (pressure control valves) 13 a to 13 b to control the brake hydraulic pressure supplied to each wheel cylinder 20. 1
3d, an in-side gate valve provided in the middle of the brake pipe 23 and serving as a supply switching valve for switching between a master cylinder 14 and a control hydraulic source 13i as a hydraulic pressure supply source for each brake pipe 21. 13e and an out-side gate valve 13g, and an in-side gate valve 13f and an out-side gate valve 13h as supply switching valves for performing similar switching to the brake pipe 22. Accordingly, the control for switching the pressure supply source to the wheel cylinder 20 and the control of the brake fluid pressure of each wheel cylinder 20 are performed independently for each system. In addition, each gate valve 13e, 13f, 13
In normal times, the out-side gate valves 13g and 13h are opened and the in-side gate valves 13g and 13h are opened in the OFF state where power is not supplied so that the brake fluid pressure generated in the master cylinder 14 is transmitted to the brake pipes 21 and 22. Gate valve 13e,
13f is closed.

Reference numeral 15 denotes an engine speed sensor (vehicle behavior detecting means) for detecting the engine speed. For example, like the wheel speed sensors 1 to 4, a frequency signal is detected by a pickup coil or the like. Reference numeral 16 denotes a throttle opening sensor (vehicle behavior detecting means), which converts the throttle opening into a voltage value by using, for example, a potentiometer, and performs detection as an analog signal.

The signals from these sensors 15 and 16 and the required engine torque transmitted from the vehicle behavior control device 8 are input to an engine control device (control means) 9 to convert the required engine torque into a required throttle opening degree, It is transmitted to the control device (control means) 10. The throttle control device 10 is configured to control the engine torque by supplying a motor drive current corresponding to the required throttle opening to a throttle actuator (engine torque control actuator) 11 attached to the engine 12.

Next, the control operation of the vehicle behavior control device 8 will be described with reference to the flowcharts of FIGS. FIG.
Is a flowchart of a portion for performing understeer determination based on a signal indicating vehicle behavior detected by various sensors. First, in step 201, each of the wheel speed sensors 1 to 4
Then, in step 202, the vehicle speed Vi is calculated by using a select high signal of each wheel.

Next, in steps 203 to 205, the yaw rate speed YAW, the lateral acceleration YG, and the steering angle ANG detected by the yaw speed sensor 6, the lateral G sensor 7, and the steering angle sensor 5.
L is taken in.

Next, at step 206, the vehicle body side slip angle BETA, the front wheel side slip angle BETAf, and the rear wheel side slip side BETAr are calculated. The value BETA is calculated by, for example, the following method.

BETA = ∫ [(Y _G / Vi) −YAW] dt BETAf = BETA + (Lf / Vi) · YAW-AN
GL BETAr = BETA- (Lr / Vi) where Lf is the distance between the front wheel axis and the yaw center, and Lr is the distance between the rear wheel axis and the yaw center.

Next, at step 207, the yaw rate target value YAWS is calculated. In this case, the yaw rate target value YAWS is obtained by referring to a predetermined map from the vehicle speed Vi and the steering angle ANGL.

Next, at step 208, the vehicle speed V
i is compared with the wheel speed Vw, and when the vehicle speed Vi is higher than the wheel speed Vw, it is determined that a deceleration slip is being performed, and the routine proceeds to step 209, where SLIP =
The slip ratio S is calculated based on the formula of (Vw−Vi) / Vi.
LIP is calculated, and when the wheel speed Vw is higher than the vehicle body speed Vi, SLIP = (Vw−
The slip ratio SLIP is calculated based on the equation of Vi) / Vw.

Steps 211 to 216 are means for determining whether or not the vehicle is in an understeer state. First, in step 211, the yaw rate target value YAWS calculated from the steering angle and the vehicle speed and the sensor detected yaw rate YAW
When the difference YAWE is larger than a predetermined control start threshold value YAEEER in step 212, the actual yaw rate of the right turning yaw rate is set to be positive. It is determined that the yaw rate is small, and in step 214, the right turn understeer control flag FUSRR = 1. Conversely, when -YAWER is smaller than YAWE in step 213, the left turning understeer control flag FUSRL = 1 is set in step 215 as left turning understeer. Other than the above, that is, −YAWER ≦ YAWE ≦ YA
If WER, it is determined that the vehicle is not in the understeer state, and in step 216, both control flags FUSR
R and FUSRL are both reset to 0.

Next, steps 217 to 220 in FIG. 4 are one means for detecting the driver's intention to accelerate. First, in step 217, the throttle opening ACCEL, which is the output of the throttle opening sensor 16, is read.
At 18, a predetermined acceleration determination threshold value ACTV
Compare with O. When the throttle opening ACCEL is larger than the acceleration determination threshold value ACCTVO, it is determined that the driver intends to accelerate, and the acceleration determination flag FACEL is set to 1 in step 219. On the other hand, when the throttle opening ACCEL is smaller than the acceleration determination threshold value ACCTVO, it is determined that the driver does not intend to accelerate, and the acceleration determination flag FACEL = 0 is reset in step 220.

Steps 221 to 227 are controls for switching the booster system which is a part of the present invention. First, in Steps 221 and 222, it is determined whether the vehicle is turning right or under understeer based on the set / reset state of each understeer control flag FUSRR, FUSRL. In Steps 223 and 224, the acceleration judgment flag FACEL is set / reset. Judgment of acceleration / non-acceleration is performed based on the state.

When it is determined that the vehicle is turning right understeer and acceleration, or when it is determined that the vehicle is turning left understeer and not accelerating, in step 225, the right front wheel and the left rear wheel of one of the two brake pipes 21 and 22 are determined. The in-side gate valve 13e is opened so that the hydraulic pressure of the control hydraulic pressure source 13i can be supplied to the brake pipe 21 of the system, and the out-side gate valve 1 is connected to shut off the master cylinder 14.
3 g are closed. On the other hand, the brake pipe 22, which is the other system, is not controlled, that is, the in-side gate valve 13f is closed, and the out-side gate valve 13h is maintained in order to keep the hydraulic pressure of the master cylinder 14 available.
Is kept open.

Next, contrary to the above, when it is determined that the vehicle is turning left understeer and accelerated, or when it is determined that the vehicle is turning right understeer and not accelerated, in step 226, the brake pipe 22 which is a system of the left front wheel and the right rear wheel is determined. Gate valve 13f so that the hydraulic pressure of the control hydraulic pressure source 13i can be supplied to the
Is opened, and the out-side gate valve 13h is closed to shut off from the master cylinder 14 side. On the other hand, with respect to the brake pipe 21 which is the other system, in order to maintain a state in which the hydraulic pressure of the master cylinder 14 can be supplied,
The non-control state, that is, the state in which the in-side gate valve 13e is closed and the out-side gate valve 13g is opened is maintained.

When it is not in the understeer state, it is determined that the pump pressure is not increased, and in step 227, the in-side gate valves 13e and 13f are kept closed (OFF), and the out-side gate valves 13g and 13h.
Is kept in an open state (OFF), and a normal brake state is set.

Next, at step 228 shown in FIG. 5, the yaw rate target value YAWS and the actual yaw rate YA
W is multiplied by a predetermined gain K1 to calculate a drive wheel left / right wheel speed difference SLIPYD. In step 229, a throttle opening ACCEL and an acceleration determination threshold value ACCTVO are calculated.
Is multiplied by a predetermined gain K2 to calculate an average driving wheel left / right speed SLIPACC.

Steps 230 to 243 are for determining the slip ratio target value. First, in step 230, it is determined whether or not the vehicle is turning right under understeer based on the set / reset of the right turning understeer control flag FUSRR. If FUSRR = 1, the process proceeds to step 231.
If FUSRR = 0, the process proceeds to the flowcharts shown in FIGS. Note that the flow charts of FIGS. 8 and 9 are obtained by reversing the control at the time of the right turn understeer in FIGS. 5 and 6, which will be described later, and thus the detailed description thereof will be omitted.

Next, in step 231, it is determined whether or not the vehicle is accelerating based on the acceleration determination flag FACEL.
If the vehicle is accelerating, the process proceeds to step 232. If the vehicle is not accelerating, the process proceeds to the flowchart shown in FIG.

Steps 232 to 239 are for the slip ratio target value during the right turn understeer and the acceleration judgment. First, in step 232, step 2
Drive wheel left / right average SLIPAC calculated in steps 28 and 229
A right front wheel slip rate target value SLIPMFR and a left rear wheel slip rate target value SLIPMRL are calculated based on C and the drive wheel left / right wheel speed difference SLIPYD.

Next, in steps 233 to 236,
A limiter process is performed on the right front wheel slip rate target value SLIPMFR. This creates an extra slip on the front wheels,
Since the tire side force is reduced and understeer is promoted, it is considered that control should be performed within a range where the side force does not decrease.

Here, the range in which the side force does not decrease is the case where the resultant force of the braking or driving force and the side force is within the tire friction circle limit, and assuming that the tire friction circle is a perfect circle. When the following conditions are satisfied, it is approximated to be within the tire friction circle limit, and the relational expression shown in the following equation is established. [(Β / βlim) ² + (SLIP / SLIPlim)
² ] ^1/2 <1 where β is the tire slip angle and SL
IP is a tire slip ratio, βlim is a predetermined side force peak slip angle, and SLIPlim is a predetermined braking / driving force peak slip ratio.

In order to control the front wheel slip rate target value so as to satisfy the relational expression shown in the above equation, the right front wheel slip rate target value SLIPMFR is limited to the range of the following equation. -SLIPlim [1- (BETAf / BETAlim) ² ] ^1/2 <SLIPMFR <SLIPlim [1- (BETAf / BETAlim) ² ] ^1/2 Also, since the above calculation is complicated, the worst of the front tire slip angle BETAf is complicated. Considering the value, it is conceivable to control SLIPMFR as 0%.

Next, in steps 237 to 239,
A limiter is applied to the left rear wheel slip ratio SLIPMRL.
First, in step 237, the rear wheel tire side slip angle B
The rear wheel side force generation direction is determined based on ETAr. Step 2 when the right turn understeer and the rear tire skidding are inward with respect to the turning direction.
Proceed to 38.

At this time, since the rear wheel generates side force in the same direction as the turning direction so as to cancel the yaw moment, the rear wheel is braked to the outside of the tire friction circle where the side force is reduced for the opposite reason to steps 233 to 236. Need to be applied.

Therefore, in step 238, when the left rear wheel slip rate request is out of the friction circle range, braking is performed, and in step 239, the left rear wheel slip rate target value SLIPMRL = 0 is set so as not to brake in the friction circle range. . See FIG. 10A.

If it is determined in step 237 that the rear wheel side force is outward in the turning direction, the left rear wheel generates a side force in the direction opposite to the turning direction so as to increase the yaw moment. In step 239, SLIPMRL = 0 is set in order to avoid the reduction of the side force and the reduction of the yaw moment due to the increase of the braking force. See FIG. 10B.

In step 237, the determination of the direction in which the rear wheel side force is generated is determined by determining the rear tire side slip angle BETA.
However, since the rear wheels are not steered in the case of a general vehicle, the rear wheels can be approximated to BETAr ≒ BETA, and the calculation can be simplified by performing the determination based on the vehicle body slip angle BETA and performing the limiter calculation thereafter. It is possible.

When it is determined in step 231 that the vehicle is not accelerating, the process proceeds to step 240 in FIG. 6 to calculate a left front wheel slip rate target value SLIPMFL and a right rear wheel slip rate target value SLIPMRR.

Next, in step 241, the generation direction of the rear wheel side force is determined based on the rear wheel tire slip angle BETAr, similarly to step 237, and if it is outward with respect to the turning direction, the process proceeds to step 243.

At this time, since the right rear wheel generates a side force in the direction opposite to the turning direction so as to generate a yaw moment, the yaw moment is generated by the braking force within a range in which the side force is not reduced by the braking. I want to.
Therefore, as described above, in order to control the slip ratio in the tire friction circle limit range in which the side force does not decrease, in steps 242 to 243, the right rear wheel slip ratio target value SLIPMRR is represented by the following formula. I try to limit to. FIG. 11 (d)
See also. SLIPMRR> -SLIPlim [1- (BETAr
/ BETALim) ² ] ^{1/2 Further} , since the above calculation is complicated, the following equation is obtained from the representative value of the rear tire side slip angle BETAr practically generated during understeer.
LIPMRR> −5%.

In step 241, when the rear wheel side force is inward with respect to the turning direction, the right rear wheel generates a side force in the direction opposite to the turning direction so as to cancel the yaw moment. The reduction of the side force and the increase of the yaw moment due to the braking force can be performed at the same time. Therefore, the yaw moment increases both inside and outside the tire friction circle range. In particular, no limiter is provided, and the next control is performed. See FIG. 11 (c).

Steps 244 to 252 shown in FIG. 7 are a part for controlling the engine torque, and calculate the target throttle valve opening DKV. First, step 244
, The engine speed Ne detected by the engine speed sensor 15 is read. Next, steps 245 to
At 246, an acceleration judgment and an understeer judgment are performed.
When it is determined that the vehicle is accelerating and in the understeer state, the routine proceeds to step 247, where the torque increase amount TACC is calculated from a value obtained by multiplying a difference between the yaw rate target value YAWS and the actual yaw rate YAW by a predetermined gain K3.

Next, the routine proceeds to step 248, where the torque increase TACC is multiplied by the gear position correction coefficient KGEAR to calculate the engine torque increase TACCR. In the non-acceleration or non-understeer state, TACCR = 0 is set in step 249 as there is no acceleration request and no yaw moment generation request.

Then, the program proceeds to a step 250, wherein the required engine torque Teg is calculated by referring to a map based on the engine speed and the accelerator opening, and at step 251 the engine torque increase calculated at the step 248 is added. The final output engine torque Tout is calculated.

Next, the routine proceeds to step 252, where Ne, To
The target throttle valve opening DKV is calculated with reference to the map based on ut.

By the above procedure, the hydraulic control valves 13a to 13d and the throttle actuator 11 are controlled so as to converge to the slip ratio target value SLIPM and the target throttle opening DKV shown in FIG.

At this time, when the hydraulic pressure of the rear wheel of the master cylinder booster is released, the vehicle deceleration is generated by the front wheel of the master cylinder booster and the rear wheel can be reduced by the wheel speed divided by the vehicle speed. A highly accurate slip ratio can be calculated without affecting the speed.

In this embodiment, in the understeer state, the hydraulic control system is switched during acceleration / non-acceleration to generate a yaw moment due to the differential effect of the front wheel drive wheels, improve the driving force, and improve the steering kickback and the like. Faster switching to oversteer correction control by tuck-in is possible, and appropriate yaw moment control is possible by applying a limiter to the slip ratio according to the direction of tire side force so that it falls within the tire friction circle range. Become.

Further, since one system is a pressure-increasing system using a master cylinder, it is possible to avoid deceleration failure due to a defect or the like and to improve the pedal feeling at the same time.

[0068]

As described above, in the vehicle attitude control device of the present invention, when the vehicle enters the understeer state, it is further determined whether the vehicle is accelerating or not accelerating.
During acceleration, the brake pressure supply source for the brake pipe connecting the inner wheel before turning and the outer wheel after turning is used as the control supply source, and the brake pressure supply source for the brake pipe connecting the outer wheel before turning and the inner wheel after turning is supplied to the driver. During the non-acceleration, the brake pressure supply source of the brake pipe connecting the outer wheel before turning and the inner wheel after turning is used as a control source, and the inner wheel before turning and the outer wheel after turning are performed during non-acceleration. During the acceleration, the yaw moment due to the braking force on the turning inner wheel and the differential between the driving wheels on the outside of the turn are made during acceleration because the front outer wheel control using the brake pressure supply source of the brake pipe connecting the The understeer state is avoided by utilizing the generation of the yaw moment due to the effect, and the effect that the understeer avoidance control can be executed without the driver feeling uncomfortable is obtained. Effect that ring kickback and tuck faster switching to oversteer correction control according becomes possible. Furthermore, since one system is a booster system using a driver supply source, it is possible to avoid a deceleration failure due to a defect or the like and to improve the pedal feeling at the same time.

Further, according to the present invention, the yaw moment due to the braking force is effectively generated by controlling the side force so as not to decrease in accordance with the direction in which the rear wheel generates the side force. In particular, according to the fifth aspect of the present invention, a proper yaw moment control can be performed by providing a limiter such that the slip ratio target value falls within the tire friction circle range.

According to the sixth and seventh aspects of the present invention,
During understeer avoidance control, the wheel cylinder pressure of the rear wheel of the brake pipe of the system using the driver supply source is set to 0 or the slip ratio of the rear wheel of the brake pipe of the system using the driver supply source Since the target value is set to 0%, even if the driver performs the braking operation, the side force of the rear wheels does not decrease and the vehicle posture can be stabilized.

According to the eighth aspect of the present invention, since the slip ratio target value of the front inner wheel is set to 0% at the time of front inner wheel control, the side force is reduced at the front inner wheel while performing simple arithmetic processing. Thus, the engine torque can be applied in the steering direction.

According to the ninth aspect of the present invention, since a limiter is provided for the slip ratio target value SLIPM of the inner wheel before turning at the time of front inner wheel control, the maximum braking force can be obtained as long as the side force does not decrease. .

In the tenth aspect of the present invention, when the vehicle body slip angle or the rear wheel tire slip angle is inward during front inner wheel control, the slip ratio target value SLIPM of the outer wheel after turning is provided.
However, the wheel cylinder pressure control is executed only when the wheel cylinder pressure is smaller than the limit value, and the wheel cylinder pressure or the slip ratio target value SLIPM is set to 0 when the above conditions are not satisfied. When it is outside, braking is performed, and braking is not performed within the friction circle range, so that the necessary maximum side force can be obtained.

In the eleventh aspect of the present invention, the throttle valve opening is controlled to be larger than the pedal stroke converted throttle opening operated by the driver during front inner wheel control based on understeer and acceleration judgment. By transmitting the surplus engine torque to the outer wheel before turning by the effect, the turning moment of the vehicle can be increased and the understeer state can be avoided.

[Brief description of the drawings]

FIG. 1 is a view corresponding to a claim showing a vehicle attitude control device of the present invention.

FIG. 2 is an overall view of a vehicle attitude control device according to an embodiment.

FIG. 3 is a flowchart illustrating a control flow according to the embodiment.

FIG. 4 is a flowchart illustrating a control flow according to the embodiment.

FIG. 5 is a flowchart illustrating a control flow according to the embodiment.

FIG. 6 is a flowchart illustrating a control flow according to the embodiment.

FIG. 7 is a flowchart illustrating a control flow according to the embodiment.

FIG. 8 is a flowchart illustrating a control flow according to the embodiment.

FIG. 9 is a flowchart illustrating a control flow according to the embodiment.

FIG. 10 is an operation explanatory view of the embodiment.

FIG. 11 is an explanatory diagram of a control state according to the embodiment.

[Explanation of symbols]

FR, FL, RL, RR Wheel cylinder a First pipe b Second pipe c Driver supply source d Control supply source e Supply switching valve f Pressure control valve g Vehicle behavior detection means h Control means 1, 2, 3, 4 wheels Speed sensor (vehicle behavior detection means) 5 Steering angle sensor (vehicle behavior detection means) 6 Yaw speed sensor (vehicle behavior detection means) 7 Lateral acceleration sensor (vehicle behavior detection means) 8 Vehicle behavior control device (control means) 9 engine control Device (control means) 10 Throttle control device (control means) 11 Throttle actuator (engine torque control actuator) 12 Engine 13 Brake hydraulic control actuator 13a, 13b, 13c, 13d Hydraulic control valve (pressure control valve) 13e, 13f In-side gate Valve (supply switching valve) 13g, 13h Out side gate valve (supply switching valve) 13 Control hydraulic pressure source (control supply source) 14 Master cylinder (driver supply source) 15 Engine speed sensor (vehicle behavior detection means) 16 Throttle opening sensor (vehicle behavior detection means) 20 Wheel cylinder 21 Brake pipe (first pipe) ) 22 Brake piping (second piping) 23 Brake piping

Claims (11)

[Claims] 1. A brake pipe of a front wheel drive vehicle has a first pipe connecting a wheel cylinder of a right front wheel and a wheel cylinder of a left rear wheel, and a second pipe connecting a wheel cylinder of a left front wheel and a wheel cylinder of a right rear wheel. And two systems of pipes are provided. Each brake pipe is provided with a driver supply source for supplying a brake pressure generated by a driver's braking operation, and a pressure source formed independently and independently of the driver's braking operation. Two supply sources, a control supply source for supplying the brake pressure, are connected, and a supply switching valve is provided for switching between the supply source of the brake pressure for each brake pipe as the driver supply source and the control supply source. A pressure control valve for controlling each wheel cylinder pressure is provided, and when it is determined that the vehicle is in the understeer state by an input from the vehicle behavior detecting means for detecting the behavior of the vehicle. In a vehicle attitude control device provided with control means for controlling the operation of the supply switching valve and the pressure control valve in order to avoid an understeer state, the control means determines that an understeer state is detected when executing the understeer avoidance control. In addition, when it is determined that the vehicle is accelerating at the same time, the supply source of the brake pipe that connects the inner wheel before turning and the outer wheel after turning is used as the control supply source, and the system that connects the outer wheel before turning and the inner wheel after turning is used. When the inner-wheel control before switching the supply switching valve is performed to make the supply source of the brake pipe the driver supply source, and when it is determined that the vehicle is not accelerating in addition to determining the understeer state, The supply source of the brake pipe connecting the inner wheel after turning is the control supply source, and the supply source of the brake pipe connecting the inner wheel before turning and the outer wheel after turning is the driver supply source. Vehicle attitude control apparatus characterized by being configured to perform post inner control. 2. The wheel cylinder pressure of the outer wheel after turning is set to 0 when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the front inner wheel control. The vehicle attitude control device according to any one of the preceding claims. 3. The slip ratio target value of the outer wheel after turning is set to 0% when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the front inner wheel control. 2. The vehicle attitude control device according to claim 1. 4. When the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction during the rear inner wheel control, the slip ratio target value of the inner wheel after turning is limited to a range of 0 to -5%. 4. The vehicle attitude control device according to claim 1, wherein: 5. In the rear inner wheel control, when the vehicle body slip angle or the rear wheel tire slip angle is outward with respect to the turning direction, the slip ratio target value SLIPM of the inner wheel after turning is set to -SLIPlim [1- (BETA / BETAlim)]. ² ]
^1/2 <SLIPM <0% (where SLIPlim is a slip ratio at which a predetermined tire braking force is linear, BETAlim is a slip angle at which a predetermined tire side force is linear, BETAlim
Is a vehicle body slip angle or a rear wheel tire slip angle. 4. The vehicle attitude control device according to claim 1, wherein the vehicle attitude control device is limited to the range of (1). 6. The wheel cylinder pressure of a rear wheel of a brake pipe of a system using the driver supply source as the supply source during the understeer avoidance control.
6. The vehicle attitude control device according to any one of claims 5 to 5. 7. The slip ratio target value of a rear wheel of a brake pipe of a system using the driver supply source as a supply source during the understeer avoidance control is set to 0%. Vehicle attitude control device. 8. The vehicle posture control device according to claim 1, wherein a target slip ratio of the inner wheel before turning is set to 0% during the front inner wheel control. 9. The slip ratio target value SLIPM of the inner wheel before turning is set to -SLIPlim [1- (BETAf / BETAlim) ² ] ^1/2 <SLIPM <SLIPlim [1- (BETAf / BETAlim) ² ] during the front inner wheel control. ^1/2 (BETaf is the front wheel tire slip angle)
8. The method according to claim 1, wherein the range is limited to
The vehicle attitude control device according to any one of the preceding claims. 10. The slip ratio target value SLIPM of the outer wheel after turning is SLIPM <-SLIPlim [1- (BETA / BET) when the vehicle body slip angle or the rear wheel tire slip angle is inward during the front inner wheel control.
Alim) ² ] The wheel cylinder pressure control is executed only when the ratio becomes ^1/2, and the wheel cylinder pressure or the slip ratio target value SLIPM is set to 0 when the above conditions are not satisfied.
Or the vehicle attitude control device according to 4 to 7. 11. The vehicle behavior detecting means includes means for detecting a throttle valve opening, and the control means includes an engine torque control actuator for arbitrarily controlling engine torque, wherein the understeer and acceleration are performed. 11. The vehicle attitude control device according to claim 1, wherein the throttle valve opening is controlled to be larger than a pedal stroke converted throttle opening operated by a driver during the front inner wheel control.