JPH069957B2 - Anti-skidding brake device - Google Patents

Description

The present invention relates to a device for preventing wheel lock during sudden braking, and more particularly to prevent wheel lock of a four-wheel drive vehicle on a special road surface having a low friction coefficient. Anti-skid brake device.

(Prior art) To prevent wheel lock by controlling the brake fluid pressure to keep the slip ratio of the wheel within a predetermined range in order to measure directional stability and shorten the braking distance during sudden braking of the vehicle. An anti-skid brake device for performing the above is known. When such an anti-skid brake device is attached to the front and rear drive wheels of a part-time four-wheel drive vehicle, in particular, when the brake is activated during four-wheel drive, the front and rear wheels are connected by the drive system. Due to this, the movements of the front and rear wheels interfere with each other and exhibit complicated behavior, which complicates the control logic of the brake fluid pressure. Therefore, the control logic of the brake fluid pressure when driving two wheels cannot be used as it is when driving four wheels, and another control logic is required. As described above, mounting the anti-skid brake device on the front and rear wheels of a part-time four-wheel drive vehicle requires complicated control means and is relatively expensive.

(Problems to be Solved by the Invention) By the way, a traveling vehicle locks its wheels by a braking force according to a friction coefficient μ of a road surface. In this case, it is desirable to lock the front and rear wheels at the same time, but usually one of the front and rear wheels tends to lock faster. You lose control. Usually, as shown in FIG. 1, it is ideal that the front and rear braking forces are distributed as shown by a quadratic curve A according to the friction coefficient μ of the road surface. As is clear from the actual braking force distribution line B, on a road surface with a high friction coefficient, rear locking is prevented to prevent tail swings and the front braking force is relatively strengthened, and conversely, on a road surface with a low friction coefficient. Then, it is effective to prevent the front lock and to strengthen the rear brake force relatively in order to secure the steering operability. It should be noted that this tendency is usually from when the vehicle is empty (shown by the broken line in FIG. 1) to when it is loaded (1 in FIG. 1).
(Indicated by a dashed line) is more prominent.

In this way, on a road surface having a low coefficient of friction, for example, on a slippery road surface such as a snowy road, it is important to apply brake fluid pressure while preventing the front wheels from locking. Further, in the case of a four-wheel drive vehicle, it is common knowledge that four-wheel drive traveling is often used on a road surface having a low friction coefficient due to its use condition. For this reason, four-wheel drive vehicles have four
Even if the anti-skid operation is performed only when the wheels are driven, there is no great inconvenience, and thus the apparatus can be simplified.

It is an object of the present invention to provide an anti-skid brake device which is attached to a part-time type four-wheel drive vehicle and can simplify the control means.

(Means for Solving the Problem) An anti-skid brake device according to the present invention includes a four-wheel drive detection sensor that outputs an output signal during four-wheel drive of a four-wheel drive vehicle that can selectively perform four-wheel drive or two-wheel drive. A single rotation speed sensor for detecting the rotation speed of the drive system of the four-wheel drive vehicle, and a hydraulic pressure provided on either one of all wheels or rear wheels of the four-wheel drive vehicle to adjust the brake fluid pressure. Adjusting means, and control means for outputting a brake fluid pressure increase / decrease signal based on the output signal of the rotation speed sensor to the hydraulic pressure adjusting means when the four-wheel drive detection sensor detects that the vehicle is in the four-wheel drive state. It is characterized by having.

(Operation) The present invention focuses on the fact that the front and rear wheels simultaneously exhibit a tendency to lock due to the fact that the front and rear wheels are connected by the drive system during four-wheel drive. A single rotational speed sensor for detecting the above is used, and a hydraulic pressure adjusting means provided on either one of the front wheel and the rear wheel for adjusting the brake hydraulic pressure is used.

That is, since a single rotation speed sensor is used, there is only one control system that outputs the brake fluid pressure increase / decrease signal, and the control interference caused by the fact that the front and rear wheels are connected by the drive system Does not occur.

Further, since the front and rear wheels are connected by the drive system during four-wheel drive, if either the front wheel or the rear wheel is controlled, the other is also controlled via the drive system. The front wheel and the rear wheel can be controlled by the hydraulic pressure adjusting means provided on either one of the rear wheels, and the control for the front wheel and the rear wheel can be realized with a simple structure.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

FIG. 2 shows a power transmission system of a vehicle equipped with an anti-skid brake device as an embodiment of the present invention. Note that the vehicle is a part-time four-wheel drive vehicle, and
You can select a drive and drive. A pair of front wheels 1 and 2 and a pair of rear wheels 3 and 4 are connected and disconnected at a transfer 7 via a front propeller shaft 5 and a rear propeller shaft 6. As shown in FIG. 3, the transfer 7 has a transmission ratio of 1: 1 and receives rotation from the transmission side (not shown) at the front end (the left end in FIG. 3) of the rear output shaft 8 and the rear end thereof. It can be transmitted to the rear propeller shaft 6 side as well as to the front propeller shaft 5 side via the central clutch 9, the toothed belt 32 and the front output shaft 10. That is, the clutch 9 connects and disconnects the clutch hub 11 integrated with the rear output shaft 8 and the ratchet wheel 13 on the side of the drive sprocket 12 through the sleeve 14, and is shown in FIG. In this direction, the sleeve 14 can be switched by operating the transfer control lever 32 via a fork (not shown). This lever 32 is provided with a 4WD detection sensor 33 that is turned on when switching to (contact), that is, 4WD. In addition,
A vehicle speed sensor 31, which is a well-known pulse generator, is attached to an end of the front output shaft 10 and outputs a rotation speed signal as an output according to the rotation speed on the front propeller shaft 5 side. In the brake system of the vehicle, the brake sensor 34 is turned on by pedaling the master cylinder 15, and the front and rear 2
The hydraulic circuit of the system operates at the same time, and each wheel cylinder 16 operates to cause each wheel to operate the brake. Among these, the front brake system transmits the brake fluid pressure according to the amount of depression of the pedal to each front wheel cylinder 16 as it is, and the rear brake system serves as a fluid pressure adjusting means for increasing or decreasing the brake fluid pressure in a predetermined pattern. The modulator 17 of is deployed. The modulator 17 uses the well-known engine negative pressure to increase or decrease the brake fluid pressure, and as shown in FIG.
A cylinder for accommodating a hydraulic cylinder 19 into which the hydraulic plunger 18 is inserted and a diaphragm 20 directly connected to the hydraulic plunger 18.
21 and a valve means 23, which is an electromagnetic valve connected to a control unit 22 for posterior surgery. The hydraulic cylinder 19 is provided with a cut valve 26 at its tip end side, and the opening of this valve is used as a hydraulic pipe.
It is connected to the master cylinder 15 via 24, and the central side wall side is connected to the wheel cylinder 16 via a hydraulic pipe 25, respectively.
The inside of the cylindrical body 21 is divided into an upper chamber 27 and a lower chamber 28 by the diaphragm 20, and the upper chamber 27 is selectively connected to an intake manifold 29 or an atmosphere opening port 30 of an engine (not shown) through a valve means 23, and the lower chamber 28 Is connected to the intake manifold 29. The control unit 22 is formed by a microcomputer,
A speed sensor 31 that outputs a signal having a frequency proportional to the rotation speed of the front wheels 1 and 2 and a 4WD detection sensor 33 that outputs an ON signal during 4WD are connected to each other. Then, in 4WD, the slip ratios of the front wheels 1 and 2 are detected based on the rotation speed signal and the acceleration / deceleration signals obtained by differentiating the rotation speed signal, and the lock tendency of the front wheels 1 and 2 is determined from the sudden change. In order to prevent this wheel lock, a pulse signal having a predetermined duty ratio is output to the valve means 23, the diaphragm 20 or the hydraulic plunger 18 is operated, the brake fluid pressure is reduced in a predetermined pattern, and conversely, the wheel lock tendency is generated. When the above condition disappears, a pulse signal having a predetermined duty ratio is output again to the valve means 23, and control is performed to increase the brake fluid pressure in a predetermined pattern.

When a four-wheel drive vehicle equipped with such an anti-skid brake device travels, first, in order to drive the two wheels by the rear two wheels 3 and 4, the driver operates the transfer control lever 32 to disengage the clutch 9. ), While traveling, the control unit 22 does not receive the 4WD detection signal,
The output to the valve means 23 is stopped, and the modulator 17 connects the master cylinder 15 and the subsequent pair of wheel cylinders 16 via the hydraulic cylinder 19. Therefore, each of the front and rear wheel cylinders 16 receives the brake fluid pressure corresponding to the pedaling force of the brake pedal as it is, and the front and rear distribution of the braking force at that time shows a characteristic similar to that shown by the line B in FIG. . On the other hand, when the vehicle enters a slippery road surface such as a snowy road, the driver operates the transfer control lever 32 to switch the clutch 9 from (disengaged) to (contact), and the 4WD detection signal is output. Then, the ON signal of the brake sensor 34 causes the control unit 22 to start the control of the anti-skid brake operation. When the lock tendency of the front wheels is detected on the basis of the rotation speed signals of the front wheels 1 and 2, the valve means 23 is activated to reduce and loosen the brake fluid pressure of the wheel cylinder 16 of the rear wheels to prevent the lock tendency of the front wheels. When it disappears, the brake fluid pressure is output again to the valve means 23, and the control of increasing the braking force of the rear wheels is repeated. That is, during this period, the wheel cylinder 16 on the front wheel side acts so as to uniformly apply the braking force to the front wheels 1 and 2 by the uniform increase of the normal brake fluid pressure. ，
No. 4 is in a one-to-one connection with the transfer, and when the front wheel lock tendency occurs, the brake fluid pressure on the rear wheel side is released, and the rotational force of the rear wheel is forced to rotate to prevent locking of the front wheel. The operation of letting go is started, and the handle operability can be secured during this time.

(Effects of the Invention) According to the present invention, it is possible to provide an anti-skid brake, which can control the front and rear wheels without trouble during four-wheel drive of a part-time four-wheel drive vehicle, with an extremely simple and inexpensive structure. Therefore, there is an advantage that it is possible to effectively improve the safety at the time of four-wheel drive, which often runs on a slippery road surface.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing front-rear braking force distribution of a vehicle, FIG. 2 is a schematic diagram of an antiskid brake device as one embodiment of the present invention, and FIG. 3 is an operation explanatory diagram of a transfer to which the same device is attached. , FIG. 4 shows sectional views of modulators used in the same apparatus. 1, 2 ... Front wheels, 3, 4 ... Rear wheels, 5, 6 ... Front and rear propeller shafts, 16 ... Wheel cylinders, 17 ... Modulator, 22 ... Control unit, 33 ... 4 drive detection sensors.

Claims (1)

[Claims] 1. A four-wheel drive detection sensor that outputs an output signal during four-wheel drive of a four-wheel drive vehicle capable of selectively performing four-wheel drive or two-wheel drive, and a rotational speed of a drive system of the four-wheel drive vehicle. A single rotational speed sensor for detecting the four-wheel drive vehicle, a hydraulic pressure adjusting means for adjusting the brake hydraulic pressure provided on either one of all wheels or rear wheels of the four-wheel drive vehicle, and four wheels by the four-wheel drive detection sensor. An anti-skid brake device comprising: a control unit that outputs a brake fluid pressure increase / decrease signal based on an output signal of the rotation speed sensor to the hydraulic pressure adjusting unit when it is detected that the vehicle is in a driving state.