JPH0439151A - Anti-lock brake device - Google Patents

Abstract

PURPOSE:To improve braking characteristics by providing the rotating speed detecting device of a wheel, and controlling a brake control means with the detected signal of the road surface friction force and the brake fluid pressure. CONSTITUTION:The depression force D from a brake pedal sensor 2, the friction force mu from a road surface friction force detecting device 1 and the wheel speed omega from a wheel speed detecting device 3 are inputted to the control device 4 of an anti-lock brake device. When the depression force D becomes a preset value or above, an anti-lock brake action is started, and the brake fluid pressure is mitigated when the rising speed of the road surface friction force mu is made smaller than a fixed value and when the wheel speed omega is reduced beyond the preset deceleration. The lock-up caused by the delay of the transition to the process decompressing the brake fluid pressure based on the judgment by mu can be surely prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an anti-lock braking system (ABS) that prevents wheels from locking (sticking) when a vehicle is suddenly braked.

[Conventional technology]

Anti-lock braking systems (ABS), which are currently in practical use in vehicles, such as automobiles, automatically control braking so that the slip ratio falls within a certain range based on the vehicle speed and wheel speed. The method of
1354). The relationship between the road surface friction coefficient and the slip ratio can change depending on the road surface conditions.
Therefore, with the above method, depending on the road surface condition, the braking force may not be maximized, and in that case, the minimum braking distance cannot be obtained. In addition, since the vehicle speed is an estimated value from the wheel speed, in controlling the slip ratio,
There is a problem with accuracy. In order to accurately determine the vehicle speed, it is necessary to use a ground speed sensor (for example, JP-A-63-6486
Publication No. 1), vehicle deceleration sensor (for example, Japanese Patent Application Laid-Open No. 63
In the device described in JP-A-63-25169, which is characterized by a complicated device, such as JP-A-170157 a),
Torque of road friction force acting on the wheels (tire torque)
is calculated from the wheel angular acceleration and the brake fluid pressure, and the beginning of the decrease in tire torque while the brake fluid pressure is rising is used as one of the criteria for determining whether the wheels are about to lock. However, with this device, tire torque is calculated indirectly from wheel angular acceleration and brake fluid pressure, and due to the existence of uncertain constants such as wheel inertia rate and brake braking efficiency, the calculated value cannot be calculated. There is a problem with accuracy.

To solve this problem, a patent application filed by the same applicant on February 1, 1990 titled ``Wheel shaft torque detection device, vertical load detection device, road surface friction coefficient detection device, load detection device, vehicle The anti-lock brake system for a vehicle described in ``Anti-lock brake system and traction control system'' has a means for directly comparing the road surface friction force or the road surface friction coefficient, and based on the output signal of this means. This is a device that controls brake operation so that the road surface friction force or road surface friction coefficient is optimized.

This device controls brake operation based on road surface friction force or road surface friction coefficient, and provides an anti-lock brake device with even higher precision.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an anti-lock brake device that eliminates the problems that conventional devices have and has even better braking characteristics.

[Means for Solving the Problems] The present invention is an anti-lock brake device having the features described in any one of claims 1 to 6.

[Effect]

The anti-lock brake device based on the road friction force and the anti-lock brake device based on the road surface friction coefficient according to the present invention are equipped with a means for directly measuring the road surface friction force or the road surface friction coefficient, and are equipped with a means for directly measuring the road surface friction force or the road surface friction coefficient. Accurate brake operation is performed in order to perform brake control not only while accurately searching, but also while measuring wheel rotational speed and detecting wheel movement, or even while monitoring brake oil pressure. control, and can achieve braking characteristics that exceed those of conventional anti-lock brakes.

〔Example〕

An example will be described taking an example of application to a vehicle, particularly an automobile. It is also applicable to vehicles other than automobiles. Note that what is shown here is an example of a preferred embodiment, and the scope of the claims is not limited to the example shown here.

FIG. 1 is a block diagram showing the configuration of an embodiment of an anti-lock brake device according to any one of claims 1 to 6. In the embodiment of the structure of the anti-lock brake device described in claim 1 or 2, the brake fluid pressure detection device 7 is not provided. Further, in the embodiment of the configuration of the anti-lock brake device described in claim 3 or 4, the wheel speed detection device 3 is not provided.

In these embodiments, the control device 4 controls the brake pedal force and the detected value ω of the wheel rotation speed or the brake fluid pressure P in addition to the detected value μ of the road surface friction coefficient or the detected value μ of the road surface friction force. The brake fluid pressure is controlled with reference to either or both. The brake pedal depression force sensor 2, the wheel rotation speed detection device 3, the brake fluid pressure generation device 5, the brake device 6, and the brake fluid pressure detection device 7 utilize known techniques.

The control device 4 is composed of an electronic circuit including a microprocessor, memory, and input/output interface, and operates according to a program written in the memory in advance.

The second embodiment of the program that defines the operation of the control device 4 is described below.
This is shown in the flowchart of FIG.

When the brake pedal force exceeds a set value, the anti-lock brake device according to the embodiment of the present invention starts operating and shifts from normal braking operation to anti-lock braking operation. That is, the main routine shown in FIG. 2 starts. In the main routine, the steps are repeated at fixed time intervals (for example, 5m5e) until the pedal force reading falls below a predetermined value Do.
Execute the interrupt routine performed in c). The control variable N is set to O before the first interrupt is performed.

When the read value of the pedal effort falls below a predetermined value Dc, the main routine is terminated and a transition is made to normal braking operation.

The flowcharts shown in FIGS. 3 to 6 show an interrupt routine in an embodiment of the anti-lock brake device according to claim 1 or 2. In this example, not only when the speed of increase in road surface friction force or road surface friction coefficient μ due to an increase in brake fluid pressure during sudden braking becomes smaller than a certain value, but also when wheel speed ω becomes smaller than a predetermined deceleration ( A feature of this system is that the brake fluid pressure is released or relaxed even when the absolute value increases in the negative direction. This makes it possible to reliably prevent lock-up due to a delay in the transition to the process of reducing the brake fluid pressure based on the determination by μ depending on the road surface.

The meanings of the symbols in the flowchart are as follows. The variable N is a variable that controls the flow at the beginning of the year, the variable is the brake pedal depression force, Dc is a predetermined reference value for the brake pedal depression force, μ is the road surface friction force or the road surface friction coefficient, ω
is the rotational speed of the wheel, μt, μt-1, μP, ωt, ωt
−1 is a variable that stores μ and ω, μC1μc2 is a predetermined reference value for the difference in μ, and α is a constant between O and 1. It is desirable to set μC to a small value of positive tJ\. Further, μC2 is set to a larger positive value than μC.

In order to more reliably prevent lock-up, it is desirable not to pressurize the brake fluid excessively during the process of pressurizing the brake fluid. This can be accomplished by monitoring brake fluid pressure. As one embodiment of the anti-lock brake device according to any one of claims 3 to 6, an anti-lock brake device having such a function can be constructed.

Wheel rotation speed ω, road friction force F or road friction coefficient μ,
Mechanically, the relationship between brake fluid pressure P is Iω:rF
-kP (1) or ■・(d
It is expressed as ω/dω)=rNμmkP(2). Here, ■, r, k, and N are the moment of inertia around the axis of the wheel, the radius of the wheel, the proportionality coefficient between the brake torque and the brake fluid pressure, and the normal force acting on the wheel from the road surface, respectively.

The road surface friction coefficient μ is a function μ(S) of the wheel slip ratio S.
It is expressed as Slope of μ vs. S curve near S=0 m=d
By adjusting the rate of increase in brake fluid pressure depending on the magnitude of μ/dS (S~0), it is possible to prevent excessive brake fluid pressure from being generated.

Considering that dS/dt knee (dω/dt)/ω0 (3), dμ/dt = (dμ/dS) (dS/dt) =
−m(dω/dt)/c, +o (4). Here, ωO is the wheel rotation speed before the brake is applied.

From (2) and (4), (■・007m)dμ/dt+rNμ=kP (5) or F=Nμ (6)
Considering (1), (4), and (6), (I・ω0
/m/N)dF/dt + rF 2kP (7
) Therefore, as one embodiment of the anti-lock brake device according to claim 5 or 6, the control device 4 can be constructed according to the following procedure.

In the flowchart of FIG. 3, at the stage of reading μ, the brake fluid pressure P is read at the same time.

The main routine starts, the first interrupt,
That is, in the interrupt processing when N=0, the read ω is set to ω0. In the first to several interrupt processes, based on the values of μ or F (in the flowchart, the symbol μ means both road friction force F and road friction coefficient μ) and P that are read. , the value of m is calculated based on equation (6) or equation (7).

Based on the magnitude of the calculated value of m,
Adjust the speed of increasing the pressure of the brake fluid at each step in the figure when instructing the increase of the brake fluid pressure.

Further, even when N once has a value of 3 and becomes 1 again, the read ω is set to ω0 in the first interrupt processing after N has a value of 1. In the interrupt processing from the first time to several times, the μ or F(
In the flowchart, the symbol μ means both the road friction force F and the road friction coefficient μ) and the value of P, (6)
The value of m is calculated based on the formula or formula (7). Claims characterized by the rate of pressure increase of the brake fluid at each stage of instructing the pressure increase of the brake fluid in FIGS. 4 and 5 again based on the magnitude of the calculated value of m. As the configuration of the embodiment of the anti-lock brake device described in item 3 or 4, the control device 4
However, I can present something that works according to the following steps. In the flowchart shown in Fig. 3, there is no stage for reading the wheel speed ω, a stage for determining the values of the variables ωt and ωt-1, and a stage for comparing ωt-ωt-1 with the constant ωC, and there is no stage for reading μ. and read the brake fluid pressure P at the same time.

When the main routine starts, the read μ (or F) and P are
Based on the value of m, the value of m is calculated based on equation (6) or (7). At this time, the value of ωO is taken in with reference to the indicated value of the speedometer of the vehicle. Based on the magnitude of the calculated value of m, the instructions for increasing the pressure of the brake fluid at the step of instructing the increase in pressure of the brake fluid in FIGS. 4 and 5 are adjusted. Also, when N once has a value of 3 and then becomes 1 again, the μ( Alternatively, based on the values of F) and P, the value of m is calculated based on equation (6) or equation (7). At this time as well, the value of ω0 is taken in with reference to the indicated value of the speed needle of the vehicle. Based on the magnitude of the calculated value of m, the rate of pressure increase of the brake fluid at each stage of instructing the pressure increase of the brake fluid in FIGS. 4 and 5 is adjusted again.

〔effect〕

The anti-lock brake device according to the present invention not only further improves braking characteristics compared to conventional anti-lock brake devices, but also achieves highly reliable performance in completely preventing wheel lock-up. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an anti-lock brake device according to an embodiment of the present invention, and FIG. 2 defines the operation of a control device 4 constituting the anti-lock brake device according to an embodiment of the present invention. FIG. 3 is a flowchart showing the main routine of the procedure; FIG. 3 is a flowchart showing the interrupt routine of the procedure defining the operation of the control device 4 constituting the anti-lock brake device according to the embodiment of the present invention; FIG. FIG. 5 is a flowchart showing details of the initial pressurization routine in the interrupt routine of the procedure for regulating the operation of the control device 4 constituting the anti-lock brake device according to the embodiment of the present invention. FIG. 6 is a flowchart showing the details of the pressurization routine in the interrupt routine of the procedure that defines the operation of the control device 4 forming the brake device. FIG. 2 is a flowchart showing details of a pressure reduction routine in an interrupt routine of a procedure that defines the operation of FIG. Patent applicant: Japan Electronics Industries Co., Ltd.

Claims (1)

[Claims] 1. An anti-lock brake device that includes means for directly measuring road friction force and controls brake operation to prevent wheels from locking based on an output signal from the means, A brake control means comprising a wheel rotation speed detection device and constituting an anti-lock brake device controls brake fluid pressure by referring to an output signal from the rotation speed detection device together with a road surface friction force detection signal. Features an anti-lock brake device. 2. In an anti-lock braking device that is equipped with a means for directly measuring the road surface friction coefficient and controls the operation of the brake to prevent the wheels from locking based on the output signal of the means, a wheel rotation speed detection device An anti-lock brake, characterized in that the brake control means constituting the anti-lock brake device controls the brake fluid pressure by referring to the output signal from the rotational speed detection device as well as the detection signal of the road surface friction coefficient. Device. 3. In an anti-lock brake device that is equipped with a means for directly measuring road friction force and controls brake operation to prevent wheel locking based on an output signal from the means, a brake fluid pressure detection device is used. An anti-lock brake, wherein the brake control means constituting the anti-lock brake device controls the brake fluid pressure by referring to the output signal from the brake fluid pressure detection device together with the road friction force detection signal. Device. 4. In an anti-lock braking device that is equipped with a means for directly measuring the road surface friction coefficient and controls the operation of the brake to prevent wheel locking based on the output signal of the means, a brake fluid pressure detection device is used. An anti-lock brake, wherein the brake control means constituting the anti-lock brake device controls the brake fluid pressure by referring to the output signal from the brake fluid pressure detection device together with the road surface friction coefficient detection signal. Device. 5. In an anti-lock braking device that is equipped with a means for directly measuring road surface friction force and controls brake operation to prevent wheel locking based on an output signal of the means, a wheel rotation speed detection device. The brake control means constituting the anti-lock brake device also includes a brake fluid pressure detection device, and a brake control means that constitutes the anti-lock brake device detects the brake fluid by referring to the output signal from the rotational speed detection device and the brake fluid pressure detection device together with the detection signal of the road friction force. An anti-lock brake device characterized by pressure control. 6. In an anti-lock braking device that is equipped with a means for directly measuring the road surface friction coefficient and controls the operation of the brake to prevent the wheels from locking based on the output signal of the means, a wheel rotation speed detection device The brake control means constituting the anti-lock brake device also includes a brake fluid pressure detection device, and a brake control means that constitutes the anti-lock brake device detects the brake fluid by referring to the output signal from the rotational speed detection device and the brake fluid pressure detection device together with the detection signal of the road friction force. An anti-lock brake device characterized by pressure control.