JPS63207762A - Control method for anti-skid brake device - Google Patents

Abstract

PURPOSE:To optimumly control braking operation by detecting precise slip rate and friction coefficient of a road surface at drive wheels during running of a vehicle so that the brake operation is controlled at a slip rate which is fixed such that a maximum friction coefficient is obtained being adapted to the friction coefficient of the road surface during braking operation. CONSTITUTION:There are provided a sensor 4 for detecting the speed of a wheel 3 and a sensor 9 for detecting the absolute speed of a vehicle from which signals are delivered to a control unit 1 whose control signal is delivered to a hydraulic unit 2. Further, when a brake pedal 8 is depressed so that a master cylinder 7 exerts braking pressure to a brake 5, the hydraulic unit 2 controls a hydraulic control valve 6 to adjust the braking pressure to an optimum value in order to prevent the wheel being locked. In this arrangement, precise slip rate and friction coefficient of the road surface are detected during running of the vehicle so as to control the braking operation in such a way that the slip rate is fixed to obtain a maximum friction coefficient adapted to the friction coefficient of the road surface during braking operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brake system for a vehicle, and particularly to an anti-skid brake system suitable for improving the braking characteristics and stability of a passenger car.

[Conventional technology]

Conventional devices are widely used in general literature (e.g. Automatic East Branch Technique VOQ).
, 39. As shown in N (11, 1985 PP48-57), vehicle speed is required to control slippage between tires and road surface during braking, but since there is no sensor that directly measures vehicle speed, changes in wheel speed cannot be measured. We use a method to estimate vehicle speed while observing the vehicle, and this is a publicly known technology.

In the case of a 2-wheel drive vehicle, this method can somehow simulate the vehicle speed although it contains an error from the non-drive wheel side, but in the case of a 4@drive vehicle, the 4@ is combined in some way. In such cases, it is not possible to simulate the vehicle speed well, and even in two-wheel drive vehicles, the calculated slip ratio contains errors from the beginning, making it difficult to accurately control slipping vehicles. there were. Furthermore, even if the vehicle speed can be estimated, the road surface condition, such as whether it is a low-friction road (low-μ road) or a high-friction road (high-μ road), is estimated by looking at changes in wheel speed over time after skid control is started. It took time to estimate at which slip rate S the coefficient of friction μ between the tires and the road surface would be the highest, and ideal optimal control could not be achieved.

[Problem that the invention seeks to solve]

With the above conventional technology, the vehicle speed could not be detected accurately, so there was an error in estimating the slip ratio, and since the friction coefficient of the road surface was not known in advance, there was ambiguity in control, and the braking characteristics were not optimal. There was a problem that it could not be adapted to four-wheel drive vehicles. It is an object of the invention to overcome one or more problems.

[Means for solving problems]

To achieve the above objective, the vehicle speed required for accurate detection of slip ratio is determined from an absolute vehicle speed sensor, and the friction coefficient of the road surface before braking is measured from the difference between the absolute vehicle speed and wheel speed during driving. We used an unconventional method that calculates the slip ratio and friction coefficient in that order.

[Effect]

Since the absolute vehicle speed can be obtained regardless of the movement of the wheels, accurate slippage of the vehicle can be determined regardless of the road surface condition and whether the vehicle is in four-wheel drive or two-wheel drive. Furthermore, since the road surface condition can be predicted before braking, the slip ratio can be brought to the optimum value, and the best braking characteristics can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 2, the configuration of this embodiment includes a sensor 4 for detecting wheel speed V, a sensor 9 for detecting absolute vehicle speed V, and control for processing signals from the sensors and sending control signals to hydraulic unit 2. It consists of a unit 1, and its operation will be briefly explained. When a driver steps on a brake pedal 8, brake pressure is transmitted to the brake 5 as braking pressure via a mask cylinder 7. Braking force is applied from the tires 3 to the road surface, but if the braking pressure is too strong, the tires will lock, so the hydraulic control valve 6 must be plowed to adjust the braking pressure at a certain point. Here, when the wheel speed V is plotted on the horizontal axis, the coefficient of friction μ between the road surface and the tires takes a maximum value at a certain slip rate S as shown in FIG. The slip ratio S, which shows this maximum value, differs depending on whether the road surface is concrete, soil, or wet, but this means that the better the grip, the larger the maximum value tends to be when the slip ratio S is small. have. Here, the grip force F can be expressed as the product of the road surface friction coefficient μ and the load Fv applied to the tire.

F,=μFv Therefore, assuming that the load is constant, the relationship between the grip force Fr and the slip ratio S will also have the same form as in FIG. 3. FIG. 3 holds true not only for braking force but also for driving force.

From the above, if we know the relationship between the grip force Fr and the slip rate S in advance, we can know at which slip rate S the road surface friction will be maximum from the relationship shown in Figure 3, so we can accurately control the slip rate S using the absolute vehicle speed. There are benefits to doing so. Based on this, the control flow of the embodiment will be explained with reference to FIG.

First, the absolute vehicle speed V and wheel speed V are taken in by the sensor. 16
, and calculate the slip rate S17゜Here, the slip rate S is found for all axles with wheel speed sensors, but
Here, we will pay particular attention to the drive wheels. It is determined whether this slip rate S is positive or negative.

18, when it is positive, the brake is applied, so 23
The control flow is from 19. When S is negative, the driving force is applied, so the driving torque T is estimated. This estimation method requires consideration of all forces applied to the vehicle body, but here the estimation is performed simply by replacing it with engine torque. Engine 1-lux can be estimated from a map table of engine speed N and load. The load may be either the intake air amount Q or the intake pressure V s t. Note that in the injection system, it is also possible to estimate the engine torque from the pulse width P of the injector.

Next, the road surface friction coefficient μ is estimated from the above-mentioned slip rate S and drive torque T using a characteristic map corresponding to FIG. 3.
゜This map data needs to be matched in advance. Then, determine the appropriate slip rate Sa21
゜This is calculated from the daple for μ estimated in 20, but there is no problem even if it is directly entered into the ST map of 20.

Next, this determined appropriate slip ratio Sa is determined in an appropriate time cycle, and is determined as an average value within a certain time period.

22° Then, always rewrite this value into memory.

Then, this time, in the second determination 18, it is determined that S>O5, that is, braking is in progress, but in this embodiment, it is determined whether the slip ratio S exceeds the appropriate slip ratio Sa determined during driving (23). , if the brake pressure exceeds 24°, the brake pressure is adjusted so that S ” S a is reached.24° There are many ways to adjust the brake pressure, but even if you simply repeat pressure reduction and increase as in the past, it will take a lot of calculation processing. It is fast and provides sufficient control.

The reason for the fast processing is that there is no need to perform complex processing to determine the vehicle speed from the wheel speeds as in the past.

This concludes the explanation, but if the road surface condition changes during this control, it will not be possible to say that the one-stroke motion is optimal for the road surface, but if S = 0.1 to 0.3, then Enough cornering force can also be secured.

There is no problem with braking characteristics.

〔Effect of the invention〕

According to the present invention, since the road surface condition is predicted before braking, it is possible to control the slipping vehicle to an optimal position with respect to the road surface at the time of fifth braking, which is effective in shortening the braking distance.

[Brief explanation of the drawing]

FIG. 1 is a control flowchart of an embodiment of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between the slip rate and friction coefficient between the road surface and the tire. ■...Electronic control unit, 4...Wheel speed sensor, 9
...Representative Patent attorney Katsuo Ogawa -' Tomiguchi 8 Kuzu 20

Claims (1)

[Claims] 1. In a braking device that detects the speed of a wheel with a wheel speed sensor, detects the vehicle speed with an absolute vehicle speed sensor, and controls a vehicle slipping between the wheels and the road surface during braking based on the results. , an anti-skid brake characterized by detecting an accurate slip rate and road surface friction coefficient from the driving wheels while driving, and controlling the slip rate to be fixed at a maximum friction coefficient that is adapted to the road surface friction coefficient during braking. How to control the device. 2. A control method for an anti-skid brake device according to claim 1, characterized in that detection is performed from drive torque estimated from slip ratio and engine torque.