JPH04372447A - Automotive braking device - Google Patents

Abstract

PURPOSE:To improve the turning responsiveness in the four-wheel steering, etc., by allowing a brake power to be supplied as a brake power for assisting steering to one between the left and right brake mechanisms and setting the supply timing and supply direction of the brake power according to the traveling state. CONSTITUTION:A brake power generating means C which generated a brake power separately from the operation of a brake pedal 22 and consists of a hydraulic pump 32 and an accumulator 33 for storing a hydraulic pressure is provided, and the generated brake power is adjusted so as to secure a necessary distribution ratio by a brake power supply adjusting means A consisting of a hydraulic control valve and applied as brake power for assisting steering to the brake mechanisms LB and RB for left and right wheels. The brake power supply adjusting means A control the supply timing and supply direction of the brake power, in order to assist steering according to the sreened state of a vehicle, by a supply state setting means 15A in an ECU 15. Accordingly, a moment in the yaw direction is generated on a car body, and the high steering responsiveness is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking system for a motor vehicle, and more particularly to a braking system for a motor vehicle that can generate a moment that can assist turning motion by means of braking force.

0002

2. Description of the Related Art Conventionally, a 4WS (four-wheel steering) system has been developed for steering the rear wheels in addition to the front wheels in automobiles as a means of improving steering performance such as steering response.

For example, by steering the rear wheels in the same phase as the front wheels, it is possible to improve the steering response at high speeds.

0004

However, since such conventional steering means only control force in the vehicle width direction (lateral direction), steering responsiveness such as turning performance is not necessarily sufficient. In other words, when starting a turn or changing the steering direction due to a change in diagonal line, there is a limit to the yaw moment that can be obtained by steering only the four wheels, making it difficult to follow faster steering, and in case of emergency avoidance. The responsiveness during sudden steering and sports driving is not sufficient.

The present invention was devised in view of the above-mentioned problems, and an object of the present invention is to provide a braking device for an automobile that can provide sufficient steering response.

[0006]

[Means for Solving the Problems] Therefore, the braking device for an automobile of the present invention includes a braking force generating means for generating braking force, and a left wheel braking mechanism for braking the left wheel of the automobile, in the braking system of the automobile. , a right wheel braking mechanism for braking the right wheels of the automobile, and a braking force from the braking force generating means is applied to either the left wheel braking mechanism or the right wheel braking mechanism for steering assistance when the automobile turns. A braking force supply adjusting means capable of supplying braking force for use as a braking force, and a timing and direction of supply of a braking force for steering assistance by the braking force supply adjusting means capable of assisting steering according to a steering state of the automobile. The present invention is characterized in that it is provided with a supply state setting means for setting the supply state as follows.

Preferably, the automobile is provided with a steering wheel angle sensor for detecting a steering wheel angle, and the supply state setting means is configured to control when changing the steering wheel angle direction based on the steering wheel angle information from the steering wheel angle sensor. It is configured to set the supply timing of the auxiliary braking force and to set the inner wheel side of the turn at this time in the supply direction.

[0008]

[Operation] In the above-mentioned braking device for an automobile of the present invention, the supply state setting means sets the timing and direction of supply of the steering assisting braking force by the braking force supply adjusting means in accordance with the steering state of the automobile. Set to assist steering. The braking force supply adjusting means supplies the braking force from the braking force generating operation means to the left wheel braking mechanism or the right wheel braking mechanism as a steering assist braking force in accordance with the set conditions. As a result, a moment is generated in the vehicle body in the yaw direction due to the braking force applied to one of the left and right wheels, and this moment can be used to assist in steering the vehicle.

In particular, the supply state setting means is provided with a steering wheel angle sensor for detecting the steering wheel angle, and the supply state setting means sets the steering assist braking force to be supplied when the steering wheel angle direction is changed based on the steering wheel angle from the steering wheel angle sensor. By setting the turning inner wheel side at this time in the supply direction, the timing and direction of the yaw direction moment generated in the vehicle body can be appropriately controlled, and steering assistance can be reliably performed using this moment.

0010

[Embodiment] Hereinafter, embodiments of the present invention will be explained with reference to the drawings. Figs. 1 to 3 show a braking device for an automobile as an embodiment of the present invention, and Fig. 1 is a schematic diagram showing the configuration. 2 is a flowchart showing the operation of the main part, FIG. 3 is a graph showing the operating characteristics of the main part, and FIG. 4 is a graph for explaining the operating state of the main part.

As shown in FIG. 1, the automobile braking system B of this embodiment includes a brake pedal 22 that performs an artificial braking operation, and a braking force generator that generates braking force separately from the operation of the brake pedal 22. Means C, and a left wheel braking mechanism L that brakes the left wheels of the automobile (that is, the left front wheel 1L and the left rear wheel 13L).
B and the right wheels of the car (that is, the right front wheel 1R and the right rear wheel 13)
A right wheel braking mechanism RB and a left wheel braking mechanism LB that brake R)
and a braking force supply adjusting means A that adjusts the supply of braking force to the right wheel braking mechanism RB, and a supply state setting means 15A that sets the braking force supply state by the braking force supply adjusting means A.

The brake pedal 22 is connected to a master cylinder 22A, and braking hydraulic pressure is delivered from the master cylinder 22A in accordance with the amount by which the brake pedal 22 is depressed.

The braking force generating means C consists of a hydraulic pump 32 and an accumulator 33 that stores the pressure oil pressurized by the hydraulic pump 32, and is designed to always store a predetermined hydraulic pressure regardless of the brake pedal 22. .

The left wheel braking system LB includes a front left wheel 1L and a rear left wheel 1.
3L with a required distribution ratio, and is comprised of hydraulic braking mechanisms 311 and 313 such as hydraulic piping, cylinders, and brake shoes driven by the cylinders. The right wheel braking system RB, like the left wheel braking system LB, is composed of hydraulic braking mechanisms 312 and 314, and applies braking force to the front right wheel 1R and the rear right wheel 13R at a required distribution ratio. There is.

[0015] Then, the left wheel braking system LB and the right wheel braking system RB
are designed to operate independently of each other, and the braking force acting on the right wheel braking system RB and the braking force acting on the left wheel braking system LB are distributed as required through the braking force supply adjustment means A. It is now adjusted to follow the ratio.

The braking force supply adjustment means A is constituted by a hydraulic control valve, and the hydraulic control valve A connects the hydraulic pressure of the master cylinder, which is delivered in response to depression of the brake pedal 22, to the hydraulic control valve A. The braking force is distributed to each hydraulic system of the right-wheel braking system RB and the left-wheel braking system LB at a predetermined distribution ratio, and the braking force is supplied by the supply state setting means 15A even if the brake pedal 22 is not depressed. Then, an appropriate amount of braking force from the braking force generating means C is supplied to either the left wheel braking mechanism LB or the right wheel braking mechanism RB as a steering assist braking force.

The supply state setting means 15A is provided in an electronic control unit (ECU) 15 mounted on the automobile, and adjusts the timing of supply of the braking force for steering assistance by the braking force supply adjusting means A and this timing according to the driving condition of the automobile. This is to set the time supply direction.

The ECU 15 includes a vehicle speed sensor 29 that detects the speed of the vehicle, a yaw rate sensor 23 that detects the turning state of the vehicle, a lateral G sensor 27 that detects the lateral acceleration of the vehicle, and an operating angle of the steering wheel 4 (steering wheel angle). ) is connected to a steering wheel angle sensor 16 that detects the angle.

To further explain the supply state setting means 15A, the supply state setting means 15A calculates the handle angular velocity θ' (=
dθ/dt) and steering wheel angular acceleration θ″ (=d2 θ/
dt2) and calculate these steering wheel angular velocities θ'
Based on the steering wheel angular acceleration θ'' and the vehicle speed V detected by the vehicle speed sensor 29, the timing of supplying the braking force for steering assistance, the supply direction and the supply amount at this time are set.

In other words, as shown in the θ' characteristic diagram in FIG. This is the timing for supplying braking force for steering assistance. In addition, since we are aiming for instantaneous steering assistance to change the turning direction, the braking force supply time is set to a fairly short time (Δt), and after braking for this short period of time Δt, the braking is immediately stopped. It is set to be stopped.

As shown in the characteristic diagram of left wheel braking force and right wheel braking force in FIG. Set the supply amount as follows.

That is, a characteristic map as shown in FIG. 3 is stored in the ROM of the ECU 15, and the supply amount (supplied braking force) is determined based on the control standard corresponding to the vehicle speed V and the steering wheel angular acceleration θ''. It can be set as pressure P. For example, when vehicle speed V is Vi and steering wheel angular acceleration θ'' is θ''
If i, the steering wheel angular acceleration θ at the vehicle speed Vi is determined from the map.
The control reference pressure Pi corresponding to "i" or the supply braking force BPi (BPi∝Pi) corresponding to this can be set.

[0023] However, this braking force BPi is the maximum value BP
When a braking force greater than MAX is required, the time Δt for applying the braking force BPi is increased to prevent excessive braking. In addition,
The maximum value BPMAX is PMAX = load x road surface μ x 0
．． It is set to about 3, so that the front and rear slip of the wheels is within about 4%.

Such braking force supply control is performed in an open loop regardless of whether or not the brake pedal 22 is depressed. For example, when the brake pedal 22 is not depressed, the right wheel braking system RB and the left wheel braking system are System L
The braking force BPi is applied only to one of the braking mechanisms B (the braking mechanism on the inside of the turn). Furthermore, if the brake pedal 22 is depressed, until the braking hydraulic pressure (corresponding to the total braking force applied to the front wheels) reaches the braking force BPi from the master cylinder 22A, which is output according to the amount of depression,
If braking force is applied to only one of the above-mentioned braking mechanisms and the braking hydraulic pressure from the master cylinder 22A that is output according to the amount of depression exceeds the braking force BPi, the excess amount will be adjusted to a predetermined ratio (for example, 1:1). Then, it is distributed to the right wheel braking system RB and the left wheel braking system LB.

[0025] As a result, regardless of whether or not the brake pedal 22 is depressed, a moment M is generated by the braking force BPi in a direction that assists turning, thereby increasing the turning response.
When the brake pedal 22 is depressed, the braking force is increased according to the amount of depression.

With the above-described configuration, the braking system B for an automobile of this embodiment controls braking in the following manner.

Right wheel braking system R by braking force supply adjustment means A
The supply state of the braking force to the braking system LB and the left wheel braking system LB is set by the supply state setting means 15A, and the control by the supply state setting means 15A and the braking force supply adjusting means A is performed as shown in the flowchart of FIG. 2, for example. It is done according to the procedure.

First, the steering wheel angular acceleration θ'' obtained from the steering wheel angle θ from the steering wheel angle sensor 16 and the vehicle speed V from the vehicle speed sensor 9 are read (step S1).

Next, a control reference pressure Pi is set using the map shown in FIG. 3 (step S2). That is, from the vehicle speed value Vi and the steering wheel angular acceleration value θ''i, a corresponding control reference pressure Pi is set.

Then, in step S3, the steering wheel angular velocity θ' determined from the steering wheel angle θ is read.

Furthermore, in step S4, it is determined whether or not there is a sign change in the steering wheel angular velocity θ', and when this sign change occurs, it is determined that the steering direction is being changed and that it is the timing for supplying the braking force for steering assistance. , performs steering assist control.

If there is a sign change, the steering wheel angular velocity θ'
The sign of changes from positive to negative (here, from right to left)
It is determined whether the value is from negative to positive (here, from left to right) (step S5).

According to this judgment, if it is from positive to negative (here, from right to left), it is a left turn, and step S6
Proceed to , activate the left wheel braking mechanism LB, which is the inner wheel of the turn,
If it is from negative to positive (here, from left to right), it is a right turn, and the process proceeds to step S7, where the right wheel braking mechanism RB, which is the inner wheel of the turn, is operated for a short time (Δt).

The braking force at this time is obtained by generating brake fluid pressure corresponding to the control reference pressure calculated in step S2.

Such an operation will be explained with reference to FIG. 4. When the steering wheel angle θ changes from increasing to rightward to decreasing, the steering wheel angular velocity θ' crosses the time axis from positive to negative. At this time, the steering is changed from rightward steering to leftward steering, and the left wheel side, which is the inner wheel of the left turn, is braked for a short time Δt at the reference pressure Pi (step S6
).

On the other hand, when the steering wheel angle θ changes from increasing to leftward to decreasing, the steering wheel angular velocity θ' crosses the time axis from negative to positive. At this time, the steering is changed from leftward steering to rightward steering, and the right wheel side, which is the inner wheel of the rightward turn, is braked for a short time Δt at the braking reference pressure Pi (step S7).

[0037] As a result, the yaw moment due to the braking force acts in the turning direction by an appropriate amount, and steering assistance is provided when changing the steering direction, resulting in smooth steering during sudden steering or sports driving. This is done with good responsiveness.

[0038] In step S4, the handle angular velocity θ'
If there is no sign change or after the braking operation is performed in steps S6 and S7, the above control is repeated again.

As a result, the yaw behavior of the vehicle body is quickly and reliably controlled to a stable state, making it possible to achieve a high level of suppression of spin and drift during turns, and particularly to improve the control effect near the limits of vehicle behavior. You will get more. It also has the effect of improving straight-line stability, which tends to be impaired depending on poor road conditions, accelerator on/off, and braking operations.

[0040] Furthermore, it is highly conceivable that this automobile braking device be installed in an automobile equipped with a 4WS system to stabilize the yaw behavior in cooperation with the 4WS system. Performance can be further improved.

[0041]

As described in detail above, according to the automobile braking device of the present invention, the braking system of the automobile includes a braking force generating means that generates a braking force, and a left wheel braking device that brakes the left wheel of the automobile. and a right-wheel braking mechanism for braking a right-side wheel of the automobile, and the braking force from the braking force generating means is applied to either the left-wheel braking mechanism or the right-wheel braking mechanism when the automobile turns. A braking force supply adjustment means that can be supplied as a braking force for steering assistance, and a timing and direction of supply of the braking force for steering assistance by the braking force supply adjustment means to assist steering according to the steering state of the vehicle. By providing a supply state setting means that allows the driver to control the vehicle, it is possible to greatly improve turning response, which was considered insufficient with conventional four-wheel steering, and to make lane changes more agile. This has the advantage that it is possible to ensure the responsiveness required during sudden steering for emergency avoidance and the responsiveness required during sports driving.

The above-mentioned automobile is equipped with a steering wheel angle sensor for detecting a steering wheel angle, and the supply state setting means is configured to adjust the braking force for steering assistance when changing the steering wheel angle direction based on the steering wheel angle information from the steering wheel angle sensor. By setting the supply timing and setting the turning inner wheel side at this time in the supply direction, the above-mentioned effects can be reliably obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a schematic configuration of a braking device for an automobile as an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of essential parts of a braking system for an automobile as an embodiment of the present invention.

FIG. 3 is a graph showing operating characteristics of essential parts of a braking device for an automobile as an embodiment of the present invention.

FIG. 4 is a graph for explaining the operating state of essential parts of a braking device for an automobile as an embodiment of the present invention.

[Explanation of symbols]

1L Front left wheel 1R Front right wheel 4 Handle 13L Rear left wheel 13R Rear right wheel 15 ECU 15A Supply state setting means 16 Handle angle sensor 22 Brake pedal 22A as braking operation means
Master cylinder 23 Yaw rate sensor 27 Lateral G sensor 29 Vehicle speed sensor 32 Hydraulic pump 33 Accumulators 311 to 314 Hydraulic braking mechanism A Braking force supply adjustment means (hydraulic control valve)
B Automotive braking system LB Left wheel braking system RB Right wheel braking system

Claims (2)

[Claims] Claim 1: A braking system for an automobile, comprising a braking force generating means for generating a braking force, a left wheel braking mechanism for braking a left wheel of the automobile, and a right wheel braking mechanism for braking a right wheel of the automobile. Also, a braking force supply adjusting means capable of supplying the braking force from the braking force generating means to either the left wheel braking mechanism or the right wheel braking mechanism as a braking force for assisting steering during a turning operation of the automobile; Supply state setting means is provided for setting the timing and direction of supply of the braking force for steering assistance by the power supply adjustment means so as to assist the steering according to the steering state of the vehicle. Features: Braking device for automobiles. 2. The automobile is equipped with a steering wheel angle sensor for detecting a steering wheel angle, and the supply state setting means comprises:
Based on the steering wheel angle information from the steering wheel angle sensor, the steering assist braking force is set to be supplied when the steering wheel angle direction is changed, and the inner wheel side of the turning at this time is set as the supply direction. characterized by
The braking device for an automobile according to claim 1.