JPH0811527B2 - Braking hydraulic pressure control method for hydraulic braking system for automobile - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking hydraulic pressure control method for an automotive hydraulic braking device.

2. Description of the Related Art In a braking device for an automobile, when sudden braking is applied during running of a vehicle, wheels are stuck (locked) on a road surface having a low friction coefficient between a tire and a road surface to cause slipping or irregular rolling ( Ass). In order to prevent this, an anti-skid device that detects a slip or irregular rolling state (wheel lock) in advance and controls the brake fluid pressure of the brake device based on the detected signal has already been developed (for example, Japanese Patent Application Laid-Open No. No. 60-61354).

In addition, a mechanism that positively generates friction torque is added to the inside of the differential gear so that the driving force of the other driving wheels does not decrease significantly even if the driving force of one driving wheel slips and the driving force decreases. A differential limiting device (differential lock) designed to recover is also widely used.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a hydraulic braking device of an automobile equipped with the above-described differential limiting device, a variation in wheel speed of each wheel is detected to detect front wheels for left and right wheels and rear wheels for left and right wheels at the same time. In the case where the anti-skid device for controlling the braking hydraulic pressure is provided, the friction torque generated inside the differential gear causes the braking force due to the braking hydraulic pressure to be transmitted between the left and right rear shafts, and the rear wheels are connected. There is a problem in that the road surface transmission braking force at the point causes an unbalance between the left and right to generate a yaw moment in the vehicle.

The present invention aims to address such problems.

Means for Solving the Problems The present invention relates to a rear wheel differential that incorporates an anti-skid device and a differential limiting device for a hydraulic braking system for an automobile that detects a variation in wheel speed of each wheel and controls a braking hydraulic pressure. In a vehicle equipped with a dynamic device, when the differential limiting device is activated, the control of the braking hydraulic pressure for the rear wheels is performed based on the lower wheel speed of the front wheel speeds. is there.

Action The present invention adopts the above-mentioned configuration, thereby advancing the timing of reducing the braking fluid pressure to the rear wheels to reduce the rotational speed difference between the left and right rear wheels, and the rear wheel braking force based on the rotational speed difference. It is possible to prevent an imbalance between the left and right sides of.

Embodiments The present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 is a brake pedal, 2 is a master cylinder, and when the brake pedal 1 is depressed, the master cylinder 2 is actuated to operate the brake devices 3a, 4a of the front wheels 3, 4 respectively.
Also, braking fluid pressure is supplied to the wheel cylinders of the brake devices 5a, 6a of the rear wheels 5, 6 to apply the brakes.

Brake device 3 from the master cylinder 2 to the front wheels 3 and 4
An actuator 10 for controlling the brake hydraulic pressure is installed in the rear hydraulic pipes 9 communicating with both the front hydraulic pipes 7 and 8 communicating with a and 4a and the brake devices 5a and 6a of the rear wheels 5 and 6. Is
The actuator 10 is a brake pedal switch that detects that the brake pedal 1 is depressed and outputs a signal.
11 said signals and wheel speed sensors 3b, 4 of each wheel 3, 4, 5, 6
It is controlled by the pressurizing and depressurizing signals of the control circuit 12 which issues the pressurizing and depressurizing signals of the brake hydraulic pressure for each hydraulic piping system based on the wheel speed signals V _W output from b, 5b and 6b. ing.

That is, as shown in FIG. 2, the control circuit 12 controls the wheel speed sensors 3b, 4b, 5 during braking when the brake pedal 1 is depressed and the brake pedal switch 11 outputs a signal.
b, regarded as a vehicle speed signal V _V the maximum value of the wheel speed signals V _W output from 6b, the pseudo signal V to follow at a predetermined speed difference △ V which is lower than the vehicle body speed signal V _V Let _{T be} a wheel speed signal V _W from a wheel speed sensor 3b of a wheel, for example wheel 3.
When the value falls below the threshold value, a signal for activating the actuator 10 is output to reduce the braking fluid pressure of the brake device 3a of the wheel 3, and then the wheel speed signal V _W due to friction between the tire and the road surface.
From the decrease via the low peak value V _LP to the first predetermined value V ₀
(E.g. wheel speed signal V _W is recovered by 15% of the difference between the wheel speed signals V _W when the low peak value V _LP and the pseudo signal V _T the wheel speed signal V _W is below than the low peak value V _LP Point), a signal for operating the actuator 10 is output to stop the reduction of the brake fluid pressure to keep the brake fluid pressure constant, and a second predetermined value V higher than the first predetermined value V ₀ is obtained. ₁ (e.g., 80% content by recovery of the difference between the wheel speed signals V _W when the wheel speed signal V _W is low peak value V _LP from the low peak value V _LP and the pseudo signal V _T the wheel speed signal V _W falls below When the point (1) is reached, a signal for operating the actuator 10 is output to repressurize the braking fluid pressure to perform the braking fluid pressure.

Reference numeral 13 is a rear-wheel differential gear in which a differential limiting device (differential lock) is incorporated. The rear-wheel differential gear 13 is a differential lock switch 14
The differential limiting operation is performed by the operation of.

In the conventional anti-skid device configured as described above, when the differential lock switch 14 is operated to perform the differential limiting operation, the braking force by the braking hydraulic pressure is transmitted between the left and right rear shafts. , The road transfer braking force at the ground contact point may cause an unbalance between left and right to generate a yaw moment in the vehicle.

That is, the rear wheels that are differentially locked as shown in FIG.
Assuming that the right rear wheel 5 is located on a low μ road where the friction coefficient between the tire and the road surface is relatively small and the left rear wheel 6 is located on a high μ road out of 5, 6 Each brake device 5a, 5a
The rear hydraulic pressure is applied to the rear wheels via the rear hydraulic piping 9.
Even if the braking forces T _BR and T _{BL applied} to 5 and 6 are the same, the right rear wheel 5 located on a low μ road is on a high μ road due to the difference in the friction coefficient between the tire and the road surface. Since the wheel speed drops more than the left rear wheel 6 located, the shaft of the friction torque T _{BL '} generated in the differential limiting device is applied to the right rear wheel 5 which is the lower speed side than the left rear wheel 6 which is the higher speed side. Transmission is performed between the road surface transmission braking force B _{L of the} left rear wheel 6 represented by T _BL −T _{BL ′} and the road surface transmission braking force B _R of the right rear wheel 5 represented by T _BR + T _{BL ′.} An imbalance is caused, which gives a yaw moment to the vehicle and impairs the stability of the vehicle.

In the vehicle provided with the anti-skid device and the differential limiting device configured as described above, the present invention causes the wheel speed sensor for the front wheels to control the braking hydraulic pressure for the brake device for the rear wheels when the differential limiting device is activated. It is characterized in that it is configured so as to be performed based on the lower wheel speed signal of the wheel speed signals.

Generally, the braking force distribution of the front and rear wheels is selected by selecting the actual braking force line shown by the chain line so that the front wheel is locked first, as opposed to the ideal braking line shown by the solid line in FIG. Since the irregular rotation (swing) caused by the front lock is prevented, the control of the braking fluid pressure to the brake device of the rear wheel when the differential limiting device is operated as in the present invention is performed by controlling the wheel speed of the front wheel. By performing it based on the wheel speed signal of the lower one of the wheel speed signals generated by the sensor, the timing of reducing the braking fluid pressure of the rear wheels is advanced and the difference in the road surface friction coefficient between the left and right rear wheels 5, 6 is reduced. Since it is possible to reduce the occurrence of the rotational difference based on the rotational speed difference, the inter-shaft transmission of the friction torque T _{BL ′} generated by the rotational speed difference is minimized, and the road surface transmission braking forces B _R , B of the left and right rear wheels 5, 6 are reduced. The occurrence of _L imbalance can be reduced.

In the above embodiment, the common rear hydraulic pipe 9 is used for the brake devices 5a and 6a of the rear wheels 5 and 6, but it is of course possible to use independent hydraulic pipes like the front wheels. is there.

EFFECTS OF THE INVENTION As described above, according to the present invention, a rear wheel incorporating an anti-skid device and a differential limiting device for a hydraulic braking system for an automobile, which detects a variation in wheel speed of each wheel and controls a braking hydraulic pressure. In an automobile equipped with a differential device, when the differential limiting device is operated, the control of the braking fluid pressure for the rear wheels is performed based on the wheel speed of the lower one of the front wheel speeds, so that the rear wheel Since the timing of depressurizing the braking hydraulic pressure can be advanced to reduce the difference in the number of revolutions based on the difference in the road friction coefficient between the left and right rear wheels, the occurrence of an imbalance in the road surface transmission braking force based on the difference in the number of revolutions can be reduced. However, the stability of the vehicle in the yaw direction can be improved, and a great effect can be brought about in practical use.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a braking hydraulic pressure system and control system diagram, FIG. 2 is a time chart showing changes in vehicle body speed signal, wheel speed signal, and pseudo signal, and FIG.
FIG. 4 is an explanatory diagram of the inter-shaft transmission of friction torque generated in the differential limiting device, and FIG. 4 is a front / rear wheel braking force diagram. 1 ... Brake pedal, 2 ... Master cylinder, 3,4 ...
… Front wheels, 5,6 …… Rear wheels, 7,8 …… Front hydraulic piping, 9…
Rear hydraulic piping, 10 Actuator, 11 Brake pedal switch, 12 Control circuit, 13 Rear wheel differential, 14 Diff lock switch.

Claims (1)

[Claims] 1. An automobile provided with a rear wheel differential device incorporating an anti-skid device and a differential limiting device of a hydraulic brake system for an automobile for detecting a variation in wheel speed of each wheel to control a braking hydraulic pressure. When the differential limiting device is operated, the control of the brake fluid pressure for the rear wheels is performed based on the wheel speed of the lower one of the front wheel speeds. Pressure control method.