JPH1035460A - Brake controller for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure stability of steering by providing a braking means which detects a behavior change of a vehicle during running on a low μ road so as to generate yawing moment suppressing the behavior change. SOLUTION: At least a pair of auxiliary brake actuators 58, 60 are arranged at a certain interval in the width direction of a vehicle, and when a brake control unit 2 determines a vehicle behavior change above the predetermined value on the basis of parameters representing varied traveling condition quantities and road surface condition quantities v1-v2, θ, 7, P1-P4, G detected by means of wheel speed sensors 12, 14, 16, 18, a steering angle sensor 22, a yaw rate sensor 24, brake fluid pressure detecting sensors 40, 42, 54, 56, and an acceleration sensor 26, braking rods arranged in the auxiliary brake actuators 58, 60 individually are pressed onto the road surface. At the same time, the pressing forces of the respective rods are regulated, so that yawing moment canceling the rotation of the vehicle is generated so as to suppress the behavior change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake control device for a vehicle for suppressing the behavior of the vehicle and ensuring the operability.

[0002]

2. Description of the Related Art Conventionally, this type of apparatus has been disclosed in
One disclosed in Japanese Patent Publication No. 215193 is known.
This device suppresses the behavior of the vehicle by determining the behavior state of the vehicle and applying a brake oil pressure to the front, rear, left and right wheels based on the determination result to control the braking force on each wheel.

[0003]

The above-mentioned conventional apparatus applies a braking force most suitable for a friction coefficient between a running wheel and a road surface to each wheel, and maximizes the braking capacity of each wheel. It exerts an excellent effect of securing maneuverability while suppressing changes in the behavior of the vehicle. However, on a road with a low friction coefficient such as snow compacted or frozen (hereinafter referred to as a low μ road), even if brake oil pressure is applied to the brake of each wheel, the braking force generated on the wheels becomes extremely small because the friction coefficient of the road surface is low. Therefore, there is a problem that it is difficult to effectively suppress a change in the behavior of the vehicle.

[0004] The present invention has been made in view of such problems, and an object of the present invention is to provide a vehicular braking control device that effectively suppresses changes in vehicle behavior even on a low μ road. .

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a vehicular braking control device for controlling a braking force based on a state quantity of a vehicle. At least a pair of auxiliary braking means arranged, detecting means for detecting a traveling state quantity and a road surface state quantity of the vehicle, and grounding the auxiliary braking means on a road surface based on the traveling state quantity and the road surface state quantity; Control means for increasing the braking force between the auxiliary braking means and the road surface is provided.

Further, in a vehicle braking control device for controlling a braking force based on a state quantity of a vehicle, a friction material for increasing a frictional force between the road surface and a wheel with respect to a contact portion between the road surface and at least a pair of right and left wheels. Auxiliary braking means for spraying, a detecting means for detecting the traveling state quantity and the road surface state quantity of the vehicle,
And control means for spraying the friction material to the auxiliary braking means based on the traveling state quantity and the road surface state quantity.

[0007] In the vehicle brake control device,
Further, a driving force detecting means for detecting a driving force of an actuator for braking the wheel, a lock state detecting means for detecting a locked state of the wheel, and a threshold for determining the driving force at the time of detecting the locked state. And determining means for permitting operation of the auxiliary braking means by the control means when the value is lower than the value.

[0008]

According to the first aspect of the present invention, the braking force is increased by bringing the auxiliary braking means into contact with the road surface based on the traveling state amount of the vehicle and the road surface state amount. Thus, changes in the behavior of the vehicle are suppressed.

According to the second aspect of the present invention, the braking force is increased by spraying a friction material on a ground contact portion between the wheel and the road surface based on the traveling state amount and the road surface state amount of the vehicle. Thus, a change in the behavior of the vehicle is suppressed.

In the vehicle braking control device according to the third aspect, the auxiliary braking means is actuated according to the braking force when the locked state of the wheel is detected, thereby suppressing a change in the behavior of the vehicle.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vehicle braking control device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the vehicle braking control device. In FIG. 1, a brake control unit 2 that includes a microcomputer system and controls a vehicle by executing a program based on a brake control algorithm is provided. A wheel speed sensor 12 for detecting the rotational speeds v1, v2, v3, v4 of the front, rear, left and right wheels 4, 6, 8, 10;
14, 16, 18; a steering angle sensor 22 for detecting the steering angle θ of the steering wheel 20; a yaw rate sensor 24 installed near the center of gravity of the vehicle body for detecting the actual yaw rate γ of the vehicle body; An acceleration sensor 26 for detecting the acceleration G of the vehicle is provided, and a detection signal representing these running state quantities v1, v2, v3, v4, θ, γ, and G is supplied to the brake control unit 2.

A master cylinder 30 is provided for sending brake oil pressure from the first and second ports in response to a depression operation of the brake pedal 28. The first port of the master cylinder 30 and the brakes 32 of the left and right front wheels 4, 6
34, an actuator (brake pressure modulator) 36, which receives a control command from the brake control unit 2 and increases or decreases the brake oil pressure of each of the brakes 32, 34,
38 are provided. Each of the actuators 36 and 38 has a hydraulic sensor 40 for detecting a brake oil pressure P1, P2 which is a driving force for driving each of the brakes 32, 34.
A detection signal indicating the brake oil pressures P1 and P2 is supplied to the brake control unit 2.

On the other hand, a proportional valve 44 is connected to the second port of the master cylinder 30, and the proportional valve 44 and the brakes 4 of the left and right rear wheels 8, 10 are provided.
6 and 48, an actuator (brake pressure modulator) 5 that receives a control command from the brake control unit 2 and increases or decreases the brake oil pressure of each of the brakes 46 and 48.
0, 52 are provided. Each actuator 50, 5
2 includes a hydraulic pressure sensor 5 for detecting brake hydraulic pressures P3 and P4, which are driving forces for driving the brakes 46 and 48.
4, 56 are provided, and these brake oil pressures P3, P4
Is supplied to the braking control unit 2.

FIG. 2 shows the vehicle body near the left and right rear wheels 8, 10.
As shown in (a), a pair of auxiliary brakes spaced apart from the virtual center line X at equal distances La and Lb in the width direction orthogonal to the virtual center line X extending through the center of gravity Q of the vehicle body and extending in the vehicle front-rear direction. Auxiliary braking means including actuators 58 and 60 and a hydraulic tank 62 for hydraulically driving these actuators is provided.

Each of the auxiliary braking actuators 58, 60
For example, a double-acting hydraulic cylinder 64 shown in FIG. 2 (b) is provided, and pressure oil from the hydraulic tank 62 is introduced into both sides of a piston 68 provided in a cylinder tube 66 fixed to the vehicle body, and a braking control unit is provided. By controlling the pressure difference between the two sides of the piston 68 according to the control command from 2, the piston rod 70, one end of which is connected to the piston 68, moves forward and backward with respect to the road surface, and at the same time, is provided at the other end of the piston rod 70. The brake rod 72 is configured to move forward and backward with respect to the road surface. A tip 74 of the brake rod 72 is formed at the tip of the brake rod 72 toward the road surface.

In an operating state in which it is not necessary to operate the auxiliary braking means, the brake rod 72 is retracted into the hydraulic cylinder 64, and when a behavior change requiring the auxiliary braking occurs, FIG. As described above, the auxiliary braking actuator 5
The brake rods 72a, 72b of the respective 8, 60 are extended to press the cusps 74a, 74b against the road surface.

The brake control unit 2 independently controls the auxiliary brake actuators 58 and 60 to control the respective pistons 6.
8, the spire portion 74 is made different.
The pressing forces Fa and Fb of the a and 74b against the road surface can be adjusted independently.

Next, the operation of the brake control device having such a configuration will be described with reference to the flowcharts of FIGS. 3 to 5 and the principle explanatory diagram of FIG. In this embodiment,
The vehicle behavior control for securing the steering performance by applying the braking force to the wheels 4, 6, 8, and 10 for the vehicle behavior during traveling, and the locking of the wheels 4, 6, 8, and 10 during braking. Anti-lock brake (ABS) control to shorten the braking distance and ensure stability by preventing
By applying a braking force to the brake device provided on these wheels,
In the brake control for obtaining the deceleration force by the frictional force between the wheels and the road surface, the auxiliary braking means is operated when it is difficult to obtain the deceleration force.

Referring to FIG. 3, the vehicle behavior control will be described. The braking control unit 2 starts executing the program when the vehicle is started, and repeatedly executes a subroutine-type program consisting of steps S100 to S210 at a predetermined cycle.

In steps S100 to S130, each of the running state quantities γ, θ, G, v1, v, v, detected by the yaw rate sensor 24, the steering angle sensor 22, the acceleration sensor 26, and the wheel speed sensors 12, 14, 16, 18 are detected. The detection signals representing v3 and v4 are input. In step S140, the operation of the following equation (1) is performed to calculate a stability factor Kh representing a characteristic parameter of the vehicle behavior, and the behavior state of the vehicle is differentiated by the acceleration G to calculate the behavior state of the vehicle. An evaluation value dKh / dG for determination is obtained.

[0021]

(Equation 1)

In the equation (1), variables N and L are a predetermined steering gear ratio and a wheel base, respectively, and a variable V is a vehicle speed obtained from an average value of rotation speeds v1 to v4 of the respective wheels. It is.

Here, the relationship between the stability factor Kh, the acceleration G, and the evaluation value dKh / dG will be described based on the principle explanatory diagram shown in FIG. The characteristic curves in the figure are measured in advance experimentally and stored in the braking control unit 2 as map data. Stability factor Kh
Becomes larger than the predetermined reference value, the vehicle tends to be in the understeer state. Further, as the stability factor Kh becomes smaller than the predetermined reference value, the vehicle tends to be oversteered.

In step S150, the stability factor Kh and the evaluation value dKh / dG are evaluated based on the map data shown in FIG. 6 to determine whether the vehicle is in an understeer state equal to or more than a predetermined value. I do. U
When max ≦ Kh and G1 ≦ dKh / dG, it is determined in step S160 that the vehicle is in an understeer state equal to or greater than a predetermined value, and in step S170, braking control for suppressing the understeer state is executed. That is, in step S170, the time differential value dγ / dt of the actual yaw rate γ detected by the yaw rate sensor 24 is obtained, and the turning direction of the vehicle is determined based on the polarity of the differential value dγ / dt. By actuating the actuator 36 or 38 to apply a braking force to the front wheels on the inside of the turn (the left front wheel 4 in the case of a left turn and the right front wheel 6 in the case of a right turn), an inward yawing moment is generated. Then, the actuator 50 or 52 is actuated to apply a stronger braking force to the rear inner wheel (left rear wheel 8 in the case of left turning, right rear wheel 10 in the case of right turning). Further, while checking the fluctuations of the brake oil pressures P1, P2, P3, P4 detected by the oil pressure sensors 40, 42, 54, 56, the front, rear, left and right wheels 4, 6, and 6 do not cause a further behavior state.
The vehicle is decelerated while adjusting the braking forces of 8 and 10 in a well-balanced manner, thereby suppressing the vehicle behavior in the understeer state.

On the other hand, if an understeer state equal to or more than the predetermined value is not confirmed in step S150, step S18 is executed.
The process proceeds to 0, and the stability factor Kh and the evaluation value dKh / dG are evaluated based on the map data to determine whether or not the vehicle is in an oversteer state equal to or more than a predetermined value. Kh ≦ Lmax and dKh / dG ≦
In the case of G2, it is determined in step S190 that the vehicle is in an oversteer state that is equal to or greater than a predetermined value.
At 00, the braking control for suppressing the oversteer state is executed.

That is, in step S200, a time differential value dγ / dt of the actual yaw rate γ detected by the yaw rate sensor 24 is obtained, and the vehicle turns left or right based on the polarity of the differential value dγ / dt. To determine if In the oversteer state, since the grip force of the rear wheels 8, 10 is insufficient, no braking force is applied to the rear wheels 8, 10, and the front wheels located outside the turning direction (in the case of a left turn, the right front wheels 6). In the case of a right turn, the actuator 36 or 38 is actuated to apply a braking force to the left front wheel 4) to generate a yawing moment to turn toward the outside of the turn, thereby reducing the vehicle behavior in the oversteer state. Suppress.

When the understeer state or the oversteer state is eliminated by the braking control in step S170 or S200, these braking controls are released in step S210, and the wheels 4, 6, 8,. 10 will be braked.

Next, the operation of the auxiliary braking control will be described with reference to FIGS. The braking control unit 2 starts the execution of the program by starting the vehicle, performs the processes of FIGS. 4 and 5 independently and in parallel with respect to the vehicle behavior control shown in FIG. Repeat the process with.

The process shown in FIG. 4 is for detecting the road surface state quantity and determining whether or not the state in which the auxiliary braking means should be operated. In step S300, it is determined whether the brake control unit 2 is performing the ABS control and the vehicle behavior control in step S170 or S200 in FIG. When it is determined that these controls are being executed,
In step S310, the oil pressure sensors 40, 42, 54, 5
The state of the brake oil pressures P1, P2, P3, and P4 detected in step 6 is checked, and if at least one of the brake oil pressures Pb is lower than a predetermined threshold value Pb ^* (Pb <Pb ^* ), the step In S320, it is determined that the vehicle is traveling on the low μ road.

That is, a brake operation is performed while traveling on a medium friction coefficient road (hereinafter, medium friction road) or a high friction coefficient road (hereinafter, high friction road), and one of the wheels 4, 6, 8, and 10 is locked. 32, 3 when ABS control is being performed
4, 46, 48, and the brake operation is performed while traveling on a low μ road, and the wheels 4, 6, 8, 10
Are compared with the brake hydraulic pressure supplied to the brakes 32, 34, 46, and 48 when the ABS control is performed by locking any of the brakes 32, 34, 46, and 48.
It has been experimentally confirmed that the brake oil pressure supplied to the motors 34, 46, and 48 is lower than the brake oil pressure during traveling on a medium μ road or a high μ road. Therefore, the boundary value of the brake oil pressure when the wheels are locked during traveling on the low μ road and traveling on the middle and high μ roads is stored in advance in the brake control unit 2 as the threshold value Pb ^{*, and this} is determined in step S310. The low μ road is determined by comparing the threshold value Pb ^* with the actual brake oil pressure Pb.

On the other hand, if the determination in step S300 or S310 is negative (No), the result of the determination that the vehicle is not running on a low μ road or that has been once determined to be a low μ road is canceled in step S340, and the flow proceeds from step S100. Is repeated.

FIG. 5 shows the actual processing of the auxiliary braking control.
In step S400 in FIG.
At 320, it is confirmed whether or not it is determined that the vehicle is traveling on a low μ road.
If the vehicle is traveling on a low μ road, in step S410, the stability factor Kh is set to a predetermined lower limit Lover.
If Kh ≦ Lover, it is determined that the vehicle is in an understeer state that exceeds the normal vehicle behavior control range. If it is not determined in step S410 that the vehicle is in the understeer state, it is further determined in step S420 whether or not the stability factor Kh is larger than a predetermined upper limit Uover. It is determined that the state is oversteer beyond the area.

In step S430, step S410
Alternatively, the auxiliary braking means is operated based on the determination result of the understeer state or the oversteer state determined in S420. Here, the principle of the auxiliary braking control will be described with reference to FIG. 2. The distance from the virtual center line X of the vehicle to one auxiliary braking actuator 58 is La, and the distance between the virtual center line X and the other auxiliary braking actuator 60 is La. Lb, and the pressing force exerted on the road surface by the pointed head 74a by extending the braking rod 72a of the auxiliary braking actuator 58 is represented by Fb.
a, when the pressing force exerted on the road surface by the cusp 74b by extending the brake rod 72b of the auxiliary braking actuator 60 is Fb, and the friction coefficient between the road surface and these cusps 74a, 74b is μ, the vehicle weight center Q Is obtained from the following equation (2).

[0034]

(Equation 2)

Then, a target yaw rate γ ^* is obtained based on the steering angle θ detected by the steering angle sensor 22 and the vehicle speed V, and the actual yaw rate γ detected by the yaw rate sensor 24 is obtained.
Is controlled to the target yaw rate γ ^* by controlling the hydraulic pressure supplied to each of the auxiliary braking units 58 and 60,
By controlling the pressing forces Fa and Fb of the vehicle 74b against the road surface, a yawing moment M for canceling the yawing in the understeer state or the oversteer state is generated, thereby suppressing the change in the behavior of the vehicle.

On the other hand, steps S400, S410 and S
If the answer is 420 (No), step S44
At 0, the auxiliary braking unit is not operated, or if the auxiliary braking unit is operating, the operation is released, and the processing from step S400 is repeated again.

As described above, according to this embodiment, an understeer state or an oversteer state during traveling on a low μ road where it is difficult to suppress a change in the behavior of the vehicle even by the vehicle behavior control and the ABS control is detected. By operating the auxiliary braking means, a yawing moment for suppressing the vehicle behavior is generated, so that the steering stability can be further improved. For example, the present invention exerts a great effect in suppressing a change in the behavior of the vehicle when the vehicle enters an understeer state or an oversteer state while traveling on a low μ road such as a snowy or frozen road.

It should be noted that this embodiment is merely an example, and modifications of the form without departing from the gist of the present invention are included in the present invention. For example, in the auxiliary braking control processing shown in FIG. 5, it is determined whether or not to perform the braking control based on the stability factor Kh required during the vehicle behavior stabilization control shown in FIG. It is not limited to the one based on the factor Kh.

For example, the flowchart of FIG. 7 shows a modified example of the auxiliary braking control shown in FIG. FIG.
In step S500, the yaw rate sensor 24
The actual yaw rate γ is detected at step S510, and at step S510, the vehicle speed V and the vehicle speed V obtained from the average value of the wheel rotation speeds v1, v2, v3, v4 detected by the wheel speed sensors 12, 14, 16, 18 are obtained. The target yaw rate γ ^* is calculated based on the steering angle θ obtained by the angle sensor 22. In step S520, it is determined whether or not the vehicle is traveling on a low μ road based on the determination result in the low μ road determination processing of FIG.

If the vehicle is traveling on a low μ road, in step S530, the lower limit value γ ^* −α based on the target yaw rate γ ^*
It is checked whether or not the actual yaw rate γ is within the range between the upper limit value γ ^* + β and the actual yaw rate γ. If the actual yaw rate γ is within the range, the auxiliary braking means is not operated in step S550, or Release the operation of the braking means. still,
The constants α and β are determined in advance by experiments or the like, and are stored in the braking control unit 2. On the other hand, when the actual yaw rate γ is not in the range between the lower limit γ ^* −α and the upper limit γ ^* + β, that is, when γ <γ ^* −α or γ ^* −β <γ, the vehicle behavior control is performed. It is determined that the vehicle is in a vehicle behavior state that exceeds the range of the vehicle. In step S540, the auxiliary braking means is operated, and the same auxiliary braking control as in step S170 or S200 in FIG. A moment M is generated to ensure stability.

The auxiliary braking means in this embodiment drives the auxiliary braking actuators 58 and 60 by hydraulic pressure to control the pointed head 74 of each of the braking rods 72a and 72b.
The yaw moment M is generated by pressing the a and 74b against the road surface. However, the auxiliary braking means of the present invention is not limited to using an actuator driven by a hydraulic drive, for example, by applying a mechanical or electric actuator or the like. Is also good.

Further, the auxiliary braking means of the present invention is limited to a configuration in which the above-mentioned various actuators are applied to generate a yawing moment M for suppressing a vehicle behavior by applying a pressing force to a road surface. is not.

That is, the gist of the auxiliary braking means of the present invention is to generate a yawing moment M which can suppress the behavior of the vehicle. For example, wheels 4, 6, 8, 1
0, by spreading a friction material such as sand on a road contact portion of at least a pair of left and right wheels, and increasing a friction force between the wheel and the road surface, a wheel to which a braking force is applied by vehicle behavior control, The occurrence of deceleration can be increased. Further, by automatically adjusting the amount of the friction material sprayed to each wheel contact portion, a yawing moment M in a direction that suppresses the vehicle behavior may be generated to ensure the steering stability.

In this embodiment, the left and right rear wheels 8,
10, a pair of auxiliary braking actuators 58, 60
Is described, but the present invention is not limited to such a configuration. Near the left and right front wheels 4, 6 and all the wheels 4,
A pair may be provided at least in the width direction of the vehicle body in the vehicle body portion not limited to the vicinity of 6, 8, 10 or the vicinity of the wheels.

[0045]

As described above, according to the vehicle brake control device of the first invention, at least a pair of auxiliary brake means spaced apart in the width direction of the vehicle are brought into contact with the road surface, and each of the auxiliary brake means is By increasing the braking force between the vehicle and the road surface, it is possible to generate a yawing moment that counteracts the turning of the vehicle due to the behavior of the vehicle. it can.

According to the vehicle braking control device of the second aspect of the present invention, the friction material is sprayed on at least the ground contact portion between the pair of left and right wheels and the road surface by the auxiliary braking means, so that the friction between the road surface and each wheel is increased. By increasing the frictional force, it is possible to generate a yawing moment for canceling the turning of the vehicle due to the change in the behavior of the vehicle. Therefore, it is possible to suppress the change in the behavior of the vehicle and to ensure the steering stability.

According to the vehicle brake control device of the third invention, the operation of the auxiliary braking means is permitted in accordance with the braking oil pressure when the wheel lock state is detected. It is possible to prevent the auxiliary braking means from being damaged due to the operation of the braking means.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a vehicle braking control device according to an embodiment.

FIG. 2 is an explanatory diagram for explaining an installation position, a main part structure, and an operation of an auxiliary braking unit.

FIG. 3 is a flowchart for explaining processing by vehicle behavior stabilization control.

FIG. 4 is a flowchart illustrating a low μ road determination process.

FIG. 5 is a flowchart illustrating a process of auxiliary braking control.

FIG. 6 is a principle explanatory diagram for explaining a principle of determining a drift-out state and a spin state.

FIG. 7 is a flowchart illustrating a modified example of the auxiliary braking control.

[Explanation of symbols]

2 ... Brake control unit, 4,6,8,10 ... Wheels, 1
2, 14, 16, 18 ... wheel speed sensor, 20 ... steering wheel, 22 ... steering angle sensor, 24 ... yaw rate sensor, 26 ... acceleration sensor, 28 ... brake pedal,
30: master cylinder, 32, 34, 46, 48: brake, 36, 38, 50, 52: actuator, 4
0, 42, 54, 56: hydraulic pressure sensor, 58, 60: auxiliary braking actuator, 62: hydraulic tank.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B62D 111: 00 113: 00

Claims (3)

[Claims] 1. A vehicle brake control device for controlling a braking force based on a state quantity of a vehicle, comprising: at least one pair of auxiliary braking means arranged at least apart in a width direction of the vehicle; Detecting means for detecting a road surface state quantity; and control means for increasing a braking force between the auxiliary braking means and the road surface by contacting the auxiliary braking means with a road surface based on the traveling state quantity and the road surface state quantity. And a braking control device for a vehicle. 2. A vehicular braking control device for controlling a braking force based on a state quantity of a vehicle, comprising: a ground contact portion between a road surface and at least a pair of left and right wheels;
Auxiliary braking means for spraying a friction material for increasing the frictional force between the road surface and the wheel; detecting means for detecting a traveling state amount and a road surface state amount of the vehicle; and the auxiliary braking based on the traveling state amount and the road surface state amount. Control means for spraying the friction material on the means. 3. A driving force detecting means for detecting a driving force of an actuator for braking the wheel, a lock state detecting means for detecting a locked state of the wheel, and the driving force at the time of detecting the locked state is determined in advance. 3. The vehicle braking control device according to claim 1, further comprising: a determination unit that permits the control unit to operate the auxiliary braking unit when the threshold value is lower than the threshold value.