JP2001018777A - Vehicle brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle brake control device which can surely stop a vehicle while reducing rocking-back behavior just before the vehicle stops. SOLUTION: A wheel speed sensor 24 is provided and vehicle speed is computed on the basis of detection outputs of the sensor 24. When the vehicle speed is not greater than a certain speed and detection is made that the vehicle is about to stop, loads applied to front and rear wheels are computed on the basis of detection outputs of an acceleration sensor 23 and the wheel cylinder pressure of the rear wheels is increased according to the computation result so as to increase the proportion of braking forces allocated to the rear wheels. As a result, braking forces on the front wheels are weakened and pitching behavior is reduced so as to reduce rocking-back behavior. The total of the braking forces applied to the front and rear wheels after the ratio of the braking forces allocated to the front wheels versus the rear wheels is varied is about the same as it is before the ratio is varied, so that the vehicle can be surely stopped.

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 applying a braking force to a front wheel and a rear wheel of a vehicle to control a brake device for stopping the vehicle, thereby alleviating a swing-back behavior of the vehicle. It is.

[0002]

2. Description of the Related Art When a brake device provided in a vehicle is actuated to stop the vehicle, a load shift of the vehicle body occurs in a forward direction of the vehicle, and the forward side of the vehicle body sinks with the load shift. On the other hand, a phenomenon in which the rear side is lifted, that is, a pitching behavior occurs. Therefore, a forward acting force is applied to the upper body of the occupant riding the vehicle, and the upper body of the occupant tends to move forward.

[0003] In addition, although the load has moved to the front side of the vehicle body in this way, immediately after the vehicle stops, the load moves to the rearward side of the vehicle body in reverse to the pitching behavior so as to return to the normal state. Movement occurs. Then, with this load movement, the suspension expands and contracts in the direction opposite to that immediately before the vehicle stops, and the vehicle body swings back and forth. When the body swings back in this way,
The upper body of the occupant is acted on in a direction opposite to the acting force acting in the forward direction at the time of braking, that is, in the backward direction of the vehicle body.

In order to alleviate such swingback behavior, the vehicle speed is detected by a wheel speed sensor, and the acceleration applied to the vehicle body in the longitudinal direction of the vehicle is detected by an acceleration sensor. There has been proposed a technique for detecting occurrence of swingback of a vehicle and performing the following brake control. That is, when the vehicle swings back, the brake fluid pressure (hereinafter, referred to as “wheel cylinder pressure”) applied to the wheel cylinders on the front wheel side and the rear wheel side is automatically reduced, and the braking force is weakened. Swing back can be reduced.

[0005]

However, in the above proposed example, the braking force itself is reduced in order to alleviate the swing-back behavior. The power must be set low, and the amount of reduction in wheel cylinder pressure must be set delicately. For example, if the amount of pressure reduction is too large, the swing-back behavior is eased, but there is a problem that a sufficient braking force cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to reduce the swing-back behavior immediately before stopping the vehicle,
It is an object of the present invention to provide a vehicle brake control device that can surely stop a vehicle.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a brake control device for controlling a brake device for stopping a vehicle by applying a braking force to a front wheel and a rear wheel of the vehicle to alleviate a swing-back behavior of the vehicle. In order to achieve the above object, the brake device is controlled so as to increase the ratio of the braking force generated from the brake device to the rear wheels immediately before the vehicle stops.

Normally, the braking force distribution of the front and rear wheels in the vehicle is set so that the front wheels are locked before the rear wheels, but in the present invention, the braking force is applied immediately before the vehicle stops. The distribution ratio of the braking force applied to the rear wheels from the device is increased, the road surface reaction force received by the rear wheels is increased immediately before the vehicle stops, and the pitching behavior is suppressed. As a result, the swing-back behavior of the vehicle is reduced. In addition, although the braking force distribution of the front and rear wheels is changed immediately before the vehicle stops, the total braking force applied to the front and rear wheels does not change.
The vehicle will definitely stop.

The distribution ratio of the braking force to the rear wheels is determined by detecting the acceleration applied to the vehicle body by an acceleration sensor, and determining the distribution of the braking force immediately before the vehicle stops immediately after the vehicle stops according to the detection result of the acceleration sensor immediately before the vehicle stops. The distribution ratio to the wheels can be determined. By controlling the brake device so as to achieve the distribution ratio determined in this way, the swing-back behavior of the vehicle can be appropriately and reliably alleviated.

If the ratio of the braking force to the rear wheels is increased, the rear wheels may be locked and the stability of the vehicle may be reduced. Therefore, according to the present invention, after increasing the distribution ratio of the braking force to the rear wheels, the possibility of locking the rear wheel is detected, and if such possibility exists, the distribution ratio of the braking force to the rear wheels is determined. To avoid locking the rear wheels.

When an emergency such as a sudden decrease in the inter-vehicle distance with a vehicle in front occurs, an emergency brake is applied. In this case, decelerating and stopping the vehicle is more effective than relaxing the swing back behavior. Should be prioritized. Therefore,
According to the present invention, immediately after the braking by the braking device is started, the urgency of the braking is detected, and when the urgency is equal to or more than a predetermined value, the distribution ratio of the braking force applied to the front wheels and the rear wheels is changed. You are forbidden to do so. Here, the urgency of the braking may be detected based on the master cylinder pressure of the brake device and the acceleration of the vehicle body in the front-rear direction of the vehicle.

Further, if the brake device is controlled so that the braking force is continuously applied to the rear wheels by the brake device even after the vehicle stops, the vehicle shifts to the rear wheel brake immediately before the vehicle stops, and after the stop, the automatic side brake (hill holder). Function as

[0013]

FIG. 1 is a diagram showing an embodiment of a vehicle brake control device according to the present invention. This brake control device controls a brake device that applies a braking force to wheels to alleviate the swingback behavior of the vehicle. In the following, a brake device for a vehicle will be described first, and then a brake control device for controlling the brake device will be described.

In the vehicle brake device, as shown in FIG.
The hydraulic pressure is applied to the hydraulic unit 14 from the master cylinder 11 via the brake hydraulic system 13 in response to the occupant depressing the brake pedal 12.
Is output. In addition, also in the case of automatic braking accompanying the automation of vehicle running, the brake fluid pressure is output from the master cylinder 11 to the hydraulic unit 14 in accordance with the automatic braking operation in the same manner as described above.

The hydraulic unit 14 includes: a wheel cylinder 18FR of a right front wheel brake 17FR mounted on a right front wheel 16FR via a brake hydraulic system 15FR.
Wheel cylinder 18FL of left front wheel brake 17FL mounted on left front wheel 16FL via brake hydraulic system 15FL
A wheel cylinder 18RR of a right rear wheel brake 17RR mounted on a right rear wheel 16RR via a brake hydraulic system 15RR.
Wheel cylinder 18RL of left rear wheel brake 17RL mounted on left rear wheel 16RL via brake hydraulic system 15RL
It is connected to the. The brake fluid pressure generated in the master cylinder 11 is distributed at an appropriate distribution ratio according to a command from a brake control device described later and transmitted to the wheel cylinders 18FR, 18FL, 18RR, 18RL, and the brakes 17FR, 17FL. , 17RR, and 17RL exert a braking force corresponding to each wheel cylinder pressure.

Next, the configuration of the brake control device for controlling the brake device of the vehicle configured as described above will be described with reference to FIG.
This will be described with reference to FIG.

As shown in FIG. 1, the brake control device according to this embodiment includes a pressure sensor 21 connected to a brake fluid pressure system 13 of the brake device and detecting a brake fluid pressure generated in the master cylinder 11. ing. The pressure sensor 21 is electrically connected to a controller 22 having a CPU, and supplies the controller 22 with an electric signal corresponding to the brake fluid pressure.

In addition to the pressure sensor 21, the controller 22 controls an acceleration sensor 23 for detecting a vehicle acceleration in the longitudinal direction of the vehicle, a wheel speed sensor 24 for detecting a rotation speed of the wheel, and a brake device. Are electrically connected to a memory 25 for storing programs and various data necessary for the program. And the controller 22
Controls the braking force distribution ratio of the brake device based on the information provided from these components 21, 23, and 24, thereby mitigating the swing-back behavior of the vehicle. Thus, in this embodiment, the controller 22 functions as the control means of the present invention.

Next, the swing-back easing operation by the brake control device configured as described above will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation of the brake control device of FIG. FIG.
5 is a flowchart showing the content of the swing-back relaxation process. FIG. 4 is a graph showing the details of the swing-back relaxation process.

When the occupant of the vehicle depresses the brake pedal 12 or starts braking by automatic braking at a certain timing t1 (FIG. 4), the controller 22 of the brake control device detects the start of braking (step S1). Then, a control command is given to the hydraulic unit 14 via the interface 27 so that braking is performed on the front and rear wheels at the braking force distribution ratio stored in the memory 25 in advance (step S2). In response to this control command, the wheel cylinder pressure applied from the hydraulic unit 14 to each of the wheel cylinders 18FR, 18FL, 18RR, 18RL gradually increases. Normally, the front wheel-side wheel cylinder pressure (dotted line in the lower graph of FIG. 4) is changed to the rear wheel-side wheel cylinder pressure (FIG. 4) so that the front wheel side locks ahead of the rear wheel side wheel. (Dashed line in lower graph)
It is set higher than. Note that the solid line in the lower graph in the figure indicates the brake fluid pressure generated in the master cylinder 11, that is, the master cylinder pressure, and the time t
Up to 3, the solid line and the dashed line overlap.

Then, each wheel cylinder 18FR, 18F
When the wheel cylinder pressure is applied to L, 18RR, and 18RL and the braking force starts to act, acceleration acts in the forward direction, and the running speed of the vehicle, as shown in the upper graph of FIG. From time t2.

The controller 22 determines whether this braking is an emergency braking (step S).
3) When it is determined that the brake is not an emergency brake, the process proceeds to step S4 to perform a swing-back mitigation process. While maintaining the ratio (Step S5), the braking is continued until the braking is completed (Step S6). As described above, in the present embodiment, when the braking is started, the swing-back mitigation process is not executed uniformly, but is selectively used according to the urgency of the brake.
This is because, as described above, the emergency brake is applied in the event of an emergency such as a sudden decrease in the inter-vehicle distance to the vehicle in front. This is because the deceleration stop should be given priority. Therefore, in this embodiment, the rise of the master cylinder pressure detected by the pressure sensor 21 (the slope Δ in FIG. 4).
If both 1) and the change in the vehicle body acceleration detected by the acceleration sensor 23 (inclination Δ2 in FIG. 4) are steep, the controller 22 determines that the emergency brake has been applied, and proceeds to step S5 to proceed to the wheel cylinder. The pressure distribution ratio is maintained as it is, giving priority to decelerating and stopping the vehicle.

If it is determined in step S3 that the brake is not an emergency brake, that is, it is a normal brake, a swing-back relaxation process is executed. In the swing-back mitigation process, as shown in FIG. 3, the vehicle speed is calculated based on the detection output of the wheel speed sensor 24 (step S41), and as shown in the upper graph of FIG. 4, the vehicle speed becomes a constant speed V0, for example, several km / km. h or less, it is detected that the vehicle is just before stopping (step S4).
2) and the load applied to the front and rear wheels is calculated based on the detection output of the acceleration sensor 23 (step S43).

Then, a front-rear distribution ratio of the wheel cylinder pressure is obtained based on the calculation result. Normally, the vehicle is accelerated forward by braking, and a large load is applied to the front wheel side. At this time, as shown in the lower part of FIG. 4, the wheel cylinder pressure on the front wheel side immediately after the vehicle stops (time t3) or later (time t3). When the wheel cylinder pressure on the rear wheel side (broken line in the figure) is increased while the distribution ratio of the braking force to the rear wheels is increased, the braking force on the front wheel side is reduced. Pitching behavior can be suppressed, and as a result, swing-back behavior can be reduced. Moreover, in this embodiment, before and after the braking force distribution ratio is changed, the sum of the braking forces applied to the front wheels and the rear wheels is substantially the same, and the braking force distribution ratio to the rear wheels is increased to ease the swingback behavior. Even if it does, the vehicle can be reliably stopped.

In this embodiment, the relationship between the load applied to the front and rear wheels and the optimum front-rear distribution ratio corresponding to the load is determined in advance by experiments, simulations, and the like, and the relation table and the relational expression are stored in the memory 25. Aside
When the load on the front and rear wheels is obtained in step S43, the optimum front-rear distribution ratio corresponding to the load is read from the memory 25.

As is well known in the art, it is desirable to set the rear wheels so that they do not tend to lock as much as possible. Therefore, in this embodiment, when the braking force distribution ratio to the rear wheels is increased, the tendency of locking of the rear wheels (not shown) is monitored (Electric Brake Distributio).
n), it is determined whether there is a possibility that the rear wheels are locked (step S46). Then, only when there is a possibility that the rear wheel is locked, the distribution ratio of the braking force to the rear wheel is reduced (step S47) to prevent the rear wheel from locking although the effect of alleviating the swingback behavior is slightly reduced. Has been prevented.

As shown in FIG. 2, the above-described swing-back relaxation process is executed until the completion of the braking is confirmed in step S6. After the completion of the braking (time t4), the wheel cylinder pressure on the rear wheel is reduced to the hill. It is set and maintained at the holder level and functions as an automatic side brake (step S
7). In this manner, in this embodiment, as shown by the broken line in the lower graph of FIG. 4, the wheel cylinder pressure on the rear wheel side is continuously changed before and after the braking is completed (time t4), and the side brake state is smoothly changed. Can be transferred to.

The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the vehicle speed is calculated based on the detection output of the wheel speed sensor 24 to detect the state immediately before the vehicle stops. However, the state immediately before the vehicle stop is detected based on the output of the wheel speed sensor 24 itself. You may.

[0029]

As described above, according to the present invention, the distribution ratio of the braking force applied to the rear wheels from the brake device is increased immediately before the vehicle stops. It increases immediately before and suppresses the pitching behavior, thereby reducing the swingback behavior of the vehicle. Further, although the distribution of the braking force of the front and rear wheels is changed immediately before the vehicle stops, the total braking force applied to the front and rear wheels does not change, so that the vehicle can be reliably stopped.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a vehicle brake control device according to the present invention.

FIG. 2 is a flowchart illustrating an operation of the brake control device of FIG. 1;

FIG. 3 is a flowchart illustrating the content of a swing-back relaxation process.

FIG. 4 is a graph showing the details of a swing-back relaxation process.

[Explanation of symbols]

 14… Hydraulic unit 16FL… Left front wheel 16FR… Right front wheel 16RL… Left rear wheel 16RR… Right rear wheel 17FL… Left front wheel brake 17FR… Right front wheel brake 17RL… Left rear wheel brake 17RR… Right rear wheel brake 18FR, 18FL, 18RR , 18RL: Wheel cylinder 21: Pressure sensor 22: Controller (control means) 23: Acceleration sensor 24: Wheel speed sensor (Speed detecting means)

Claims (7)

[Claims] 1. A brake control device for applying a braking force to a front wheel and a rear wheel of a vehicle to control the brake device for stopping the vehicle to reduce the swing-back behavior of the vehicle. A brake control device for a vehicle, wherein the brake device is controlled so as to increase a distribution ratio of a braking force generated from the vehicle to rear wheels. 2. An acceleration sensor for detecting an acceleration of the vehicle body in the front-rear direction of the vehicle, and a distribution ratio of braking force to rear wheels immediately before and after the vehicle is stopped is determined according to a detection result of the acceleration sensor immediately before the vehicle is stopped. 2. The vehicle brake control device according to claim 1, further comprising control means for controlling the brake device so as to achieve the distribution ratio. 3. After increasing the distribution ratio of the braking force to the rear wheels,
3. The vehicle according to claim 1, wherein a possibility that the rear wheel is locked is detected, and if the possibility exists, the brake device is controlled so as to reduce a distribution ratio of the braking force to the rear wheel. 4. Brake control device. 4. Immediately after the braking by the braking device is started, the urgency of the braking is detected, and if the urgency is equal to or greater than a predetermined value, a distribution ratio of the braking force applied to the front wheels and the rear wheels. The brake control device for a vehicle according to any one of claims 1 to 3, wherein changing of the brake force is prohibited. 5. Based on a master cylinder pressure of the brake device and an acceleration of a vehicle body in a longitudinal direction of the vehicle,
The vehicle brake control device according to claim 4, wherein the urgency of braking is detected. 6. The vehicle brake control device according to claim 1, wherein the brake device is controlled such that the braking device continues to apply a braking force to a rear wheel even after the vehicle stops. 7. A vehicle according to claim 1, further comprising a speed detecting means for detecting a speed of the vehicle, wherein when the vehicle speed detected by the speed detecting means is reduced to a certain speed or less, it is detected that the vehicle is about to stop. 7. The vehicle brake control device according to any one of claims 6 to 6.