JPH0455905B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an anti-skid control method for a four-wheel vehicle.

[Background of the invention]

As is well known, in order to prevent the risk of wheel locking that occurs when braking a vehicle, brake hydraulic pressure must be reduced or
Various methods and devices for anti-skid control including holding, repressurization, etc. have been proposed.

Here, these methods and devices that have been proposed in the past detect excessive braking force applied to the wheels using the upper limit of wheel deceleration that should occur during braking as a guide, and detect excessive braking force when the braking force is excessive. Generally, the brake force is varied (specifically, the brake oil pressure is varied) so as to eliminate the wheel lock that occurs.

In other words, anti-skid control is considered as a control system that matches the braking force (input) to be applied to the wheels and the resulting change in the wheel rotational speed (output).

However, the brake control system, which includes the wheels of a running vehicle, is typically influenced by the coefficient of friction of the road surface (hereinafter referred to as road surface μ), and is therefore not unrelated to environmental conditions. However, the ease of locking the wheels is significantly different. Therefore, if antiskid control is performed in the same mode, the control effect will only be obtained under specific conditions, so many proposals have been made to incorporate such environmental parameters into control. ing.

However, the incorporation of these environmental parameters into the control system cannot be carried out continuously and immediately, but instead requires a so-called on/off control method.

By the way, the reason why the anti-skid control system for a vehicle is not configured by incorporating the environmental parameters described above is that the vehicle that has this control system is a running vehicle, and the ground speed of the vehicle during braking (absolute This can be said to be due to the fact that it is difficult to measure the vehicle speed (vehicle speed).If the absolute vehicle speed could be measured, it would be possible to calculate the road surface This means that adaptive control using the parameter as a parameter can be preferably realized.

From this point of view, the present inventor has conducted repeated studies to provide a suitable anti-skid control method for the current vehicle brake system by using a reference vehicle speed signal based on the above-mentioned absolute vehicle speed, and as a result has accomplished the present invention. It has been reached.

[Purpose of the invention]

An object of the present invention is to realize braking control that can automatically adapt to various road surfaces by applying a reference vehicle speed signal that can be regarded as an absolute vehicle speed to anti-skid control.

Another object of the present invention is to prevent wheel lock while maintaining a favorable slip ratio between the road surface and the wheels, thereby achieving effective use of braking force and preventing unnecessary extension of braking distance. It is in.

Another object of the present invention is to effectively maintain the side force of the vehicle by maintaining a favorable slip ratio between the road surface and the wheels, thereby preventing the vehicle from turning.

[Summary of the invention]

The gist of the present invention, which has been made to achieve the above-mentioned various objects, is that in a four-wheeled vehicle, during anti-skid control associated with detection of a sudden drop in wheel speed during braking, either of the two rear wheels The brake force on one of the wheels is released, and the wheel speed of this wheel is detected and used as a reference vehicle speed signal, and the brake force on the other three wheels is determined based on the reference vehicle speed signal and the wheel speed signal of each wheel. An anti-skid control method is characterized in that the anti-skid control method is controlled to maintain a predetermined slip rate by comparing the above.

In the above, the wheel speed signal obtained from the wheel whose brake force has been released can be regarded as approximately indicating the vehicle speed signal, and therefore can be used as the reference vehicle speed signal V (hereinafter referred to as vehicle speed V). .

In addition, these wheel speeds are detected along with the other three wheel speed signals υ ₁ , υ ₂ , υ ₃ (hereinafter referred to as wheel speeds υ ₁ , υ ₂ , υ ₃ ) using analog speed sensors using appropriate speed sensors. It may be detected as a signal (voltage signal) or a digital signal.

The slip rate (V-υ/V), which is the target value when controlling the braking force of the other three wheels in comparison with the vehicle speed V, is generally set in the range of 10 to 30%, preferably 20%. That's good.

The brake hydraulic pressure control device used in concretely realizing the method of the present invention can be a known anti-skid device proposed as it is or with appropriate modifications. It is equipped with a hydraulic pressure reducing means for reducing the pressure, a hydraulic pressure holding means, and a repressurizing means for transmitting the hydraulic pressure from the accumulator, etc. to the brake device again. Normally, these hydraulic pressure switches are controlled by a solenoid valve or the like to ensure high-speed response. It is configured as a format that is carried out using .

[Embodiments of the invention]

An embodiment of the method of the present invention will be described below with reference to the drawings.

In the figure, 1 and 2 are the left and right front wheels of a four-wheeled vehicle.
3 and 4 indicate the left and right rear wheels. 5, 6, 7,
8 is a brake device attached to each wheel; 9;
Reference numerals 10, 11, and 12 are hydraulic control devices interposed between these brake devices and the master cylinder 13, which normally communicate between the master cylinder 13 and each brake device, and during anti-skid control, reduce the brake hydraulic pressure, It operates to reduce, hold, and repressurize the hydraulic pressure in the brake device in response to each signal input for holding and repressurizing. Specifically, it is composed of a combination of a jet valve that closes a flow path, a modulator, a pressure oil pump, an accumulator, an electromagnetic switching valve, and the like.

14 is a brake pedal, and 15 is a hydraulic pressure transmission pipe. Reference numerals 16, 17, 18, and 19 are speed sensors attached to each wheel, which detect the rotational speed of the wheels and input this detection signal to the anti-skid control circuit 20.

Note that 21 is a handle for turning the two front wheels 1 and 2 in any direction.

In the above configuration, the anti-skid control circuit 20 starts anti-skid control by detecting a sudden drop in wheel speed during braking. This can be done in accordance with a known method by comparing a pseudo wheel speed signal generated by the vehicle with the actual wheel speed.

In the control according to the embodiment, the hydraulic control device 12 is operated to release the brake hydraulic pressure of the brake device 8 for the left rear wheel 4 at the same time as the anti-skid control is started.

The reason why the brake hydraulic pressure of the left rear wheel is released here is because the vehicle is turning left as shown in the figure and the left rear wheel is the inside wheel, and the braking force of this inside wheel is applied to the outside wheel of the turn. This is because the degree of contribution to braking is low compared to that of . Note that this selection may be made based on the detection signal of a rotational direction detection means of the handle 21 provided. Furthermore, when the vehicle is not turning, either of the two rear wheels may be selected.

When the brake hydraulic pressure of the left rear wheel is released, the left rear wheel becomes a so-called rolling wheel and rotates at a speed corresponding to the traveling speed of the vehicle, and the vehicle speed V at this time is detected by the speed sensor 19 as the wheel speed. Detected.

Then, the wheel speeds υ ₁ , υ ₂ , υ ₃ of the other three wheels are compared with this vehicle speed V, and for the wheel that has a tendency to lock, for example, V-(υ ₁ , υ ₂ , υ ₃ )/V=20(%), the hydraulic control devices 9 and 1 of each wheel system are
0 and 11 are actuated and a predetermined brake oil pressure is transmitted to the brake devices 5, 6, and 7. In other words, the control circuit 20 constitutes a feedback system that outputs a brake oil pressure release signal when V-υ/V>20 (%), and outputs a brake oil pressure increase signal when V-υ/V<20 (%).

According to the above, the braking force of the front two wheels and the rear one wheel is controlled to control the vehicle while maintaining a suitable slip ratio with the road surface, and a preferable braking operation that is not affected by the condition of the road surface μ is realized. Ru.

It should be noted that the above-mentioned embodiments have been presented in a way that makes it easy to understand the method of the present invention, so the actual equipment to which the method is applied is not limited to this example. It may be a type of control, or it may be a two-system control with cross piping.

〔Effect of the invention〕

According to the method of the present invention described above, the braking force of each wheel can be controlled while maintaining a suitable slip ratio without being affected by the state of the road surface μ, based on a signal that can be substantially regarded as the vehicle speed. In addition to being effective, it is extremely useful in that it prevents braking distance from being extended and prevents unintended vehicle turns by ensuring side force.

[Brief explanation of the drawing]

The drawing is a schematic diagram illustrating the configuration of a brake hydraulic control system when the method of the present invention is applied. 1, 2, 3, 4...wheels, 5, 6, 7, 8...
Brake device, 9, 10, 11, 12... Hydraulic control device, 13... Master cylinder, 14... Brake pedal, 15... Hydraulic pressure transmission pipe, 16, 1
7, 18, 19... Speed sensor, 20... Control circuit, 21... Handle.

Claims (1)

[Claims] 1. In a four-wheeled vehicle, during anti-skid control associated with detection of a sudden drop in wheel speed during braking, the rear two
The brake force on one of the wheels is released, and the wheel speed of this wheel is detected and used as a reference vehicle speed signal, and the brake force on the other three wheels is calculated based on the reference vehicle speed signal and each wheel. An anti-skid control method characterized by controlling to maintain a predetermined slip rate by comparison with a wheel speed signal. 2. The anti-skid control method as set forth in claim 1, wherein the rear wheel to which the brake force is released is the inner wheel when the vehicle is turning.