JPS60193750A - Antiskid braking device - Google Patents

Abstract

PURPOSE:To simplify a control means attached to a 4-wheel driven car, by a method wherein an antiskid brake force is exerted on the 4-wheel driven car through control of a brake hydraulic regulating means with the aid of the control means by means of a signal from a 4-wheel drove detecting sensor. CONSTITUTION:During running on a slippy road surface, with a clutch 9 engaged through control of a transfer surface, with a clutch 9 engaged through control of a transfer control lever 32, a 4-wheel drive detecting signal is outputted from a 4-wheel drive detecting sensor 33. When front wheels 1 and 2 produces a lock tendency resulting from braking, a control unit 22 actuates a valve means 23 to reduce the brake liquid pressure of a wheel cylinder 16 of rear wheels 3 and 4. The fornt wheels 1 and 2 and the rear wheels 3 and 4 are in an 1:1 coupling condition, and thereby the restoring rotation forces of the rear wheels 3 and 4 forcibly rotate the front wheels so as to prevent locking of the front wheels 1 and 2. This causes unlocking of the front wheels and ensures maneuverability of a handle.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing wheel locking during sudden braking, and particularly to an anti-skid braking device that focuses on preventing wheel locking of a four-wheel drive vehicle on special road surfaces with a low coefficient of friction.

In order to improve directional stability and shorten the braking distance when a vehicle suddenly brakes, anti-skid technology controls the brake fluid pressure to keep the wheel slip rate within a predetermined range and prevents the wheels from locking while still applying the brakes. Brake devices are known.

If such an anti-skid brake device is installed on the front or rear drive wheels of a Heart Time 4-wheel drive vehicle, the movements of the front and rear wheels may interfere with each other, especially when the brakes are applied during 4-wheel drive. , if the brake fluid pressure exhibits complex behavior, the control logic for the brake fluid pressure becomes complicated. Therefore, the brake fluid pressure control logic for two-wheel drive cannot be used as is for four-wheel drive, and a different control logic is required. In this way, installing an anti-skin brake device on the front or rear wheels of a part-time four-wheel drive vehicle requires complicated control means and is relatively expensive.

By the way, the wheels of a running vehicle are locked due to the braking force depending on the coefficient of friction μ of the road surface. In this case, it is desirable for the front and rear wheels to lock at the same time, but normally one of the front and rear wheels tends to lock earlier. control becomes impossible. Normally, as shown in Figure 1, it is ideal to have a distribution of forces as shown by a quadratic curve A according to the friction coefficient μ of the road surface. ing. As is clear from a comparison with the actual braking force distribution line B, this means that on roads with a high friction coefficient, rear lock is prevented and the front braking force is relatively strengthened to prevent tail swing, and conversely, on roads with a low friction coefficient, the front brake force is relatively strengthened. It is effective in preventing front lock and relatively strengthening rear braking force to ensure steering operability. Note that this tendency is usually more pronounced when the vehicle is loaded (indicated by the dashed line in FIG. 1) than when the vehicle is empty (indicated by the broken line in FIG. 1).

Thus, on road surfaces with a low coefficient of friction, for example, slippery roads such as snowy roads, it is important to apply brake fluid pressure while preventing the front wheels from locking. Furthermore, in the case of a four-wheel drive vehicle, it is common knowledge that four-wheel drive driving is often used on road surfaces with a lower coefficient of friction than the conditions of use. For this reason, in a four-wheel drive vehicle, performing the anti-skid operation only when the vehicle is in four-wheel drive does not cause any major inconvenience, and this allows the device to be simplified.

SUMMARY OF THE INVENTION An object of the present invention is to provide an anti-skid brake device that can be installed on a part-time four-wheel drive vehicle and that can simplify control means.

In the anti-skid brake device according to the present invention, the control means outputs a brake fluid pressure increase/decrease signal based on a rotational speed signal of the front wheel or front groper wheel of a four-wheel drive vehicle that can selectively perform four-wheel drive or two-wheel drive. , the four-wheel drive detection sensor issues an output signal when the four-wheel drive vehicle is in four-wheel drive, and the fluid pressure adjustment means adjusts the brake fluid to the wheel cylinder of the rear wheel of the four-wheel drive vehicle in accordance with the brake fluid pressure increase/decrease signal. When the four-wheel drive vehicle is in four-wheel drive, the control means controls the hydraulic pressure adjustment means to apply an anti-skin braking force to the four-wheel drive vehicle.

The present invention will be explained below with reference to the drawings.

FIG. 2 shows a power transmission system of a vehicle equipped with an anti-skin braking device as an embodiment of the present invention. The vehicle is a part-time 4-wheel drive vehicle, and can be driven in either 2WD or 4WD. - The set of front wheels 1, 2 and the set of rear wheels 3.4 are connected and disconnected at a transfer 7 via a front propeller shaft 5 and a rear propeller shaft 6. Third
As shown in the figure, the transfer 7 has a transmission ratio of 1 to
This is received at the front end (left end in FIG. 3) of the engine, and is transmitted from the rear end to the rear propeller/yaft 6 side, and is also transmitted to the front propeller/yaft 5 via the medium-heat clutch 9, painter's belt 32, and front output shaft 10. You can also tell the other side. That is, the clutch 9 connects and disconnects the rear output shaft 8, the ratchet hub 11 that is integrated with the rear output shaft 8, and the ratchet wheel 13 on the drive sprocket 12 side through the sleeve 14. The direction of the sleeve 14 can be changed by operating the transfer control lever 32 via a fork (not shown). When switching to (contact), this lever 32
That is, a 4WD detection sensor 33 that is turned on during 4WD is provided oppositely. In addition, three vehicle speed sensors τj, which are necessary in a well-known pulse generator, are installed at the end of the front output shaft 10, and generate a rotational speed signal as an output corresponding to the rotational speed of the front propeller shaft 5 side. . In the brake system of the vehicle, when the mask cylinder 15 is operated by a pedal, the brake sensor 34 is turned on, and two hydraulic circuits, front and rear, are activated simultaneously, and each wheel cylinder 16 is activated to apply brakes to each wheel. Among these, the front brake system transmits brake fluid pressure according to the amount of pedal depression to each wheel cylinder 16 in front of it, and the rear brake system has a fluid pressure adjustment means that increases or decreases the brake fluid pressure in a predetermined pattern. A modulator 17 is provided. The modulator 17 uses well-known engine negative pressure to increase or decrease the brake fluid pressure, and as shown in FIG. 4, the hydraulic plunger 1
Hydraulic nolinder 19 into which 8 is inserted, and hydraulic plunger 18
a cylindrical body 21 housing a diaphragm 20 directly connected to the diaphragm 20;
It is formed with a valve means 23 consisting of a solenoid valve connected to a control unit 22 which will be described later. The hydraulic cylinder 19 is provided with a cut valve 26 on its tip end side, the opening of this valve is connected to the mask cylinder 15 via a hydraulic pipe 24, and the side wall side of the center portion is connected to the wheel cylinder 16 via a hydraulic pipe 25, respectively. The inside of the cylinder body 21 is divided into an upper chamber 27 and a lower chamber 28 by the Guiaphram 20, and the upper chamber 27 is selectively connected to an intake manifold 29 of the engine (not shown) or an atmosphere opening port 30 via a valve means 23, and the lower chamber 27 is The chamber 28 is connected to an intake manifold 29. The control unit 22 is composed of a microcomputer fff, and a speed sensor 31 emits a signal with a frequency proportional to the rotational speed of the front wheels 1 and 20.
and 4WD detection sensor 33 that outputs an on signal when on the 4th side
are connected to each other. Then, when on the 4th side, the slip ratios of the front wheels 1 and 2 are detected based on the rotational speed signal and acceleration and deceleration signals obtained by differential processing of the rotation speed signal, and the locking tendency of the front wheels 1 and 2 is detected from the sudden change. In order to prevent this wheel lock, a pulse signal with a predetermined duty ratio is output to the valve means 23, and the diaphragm 20, that is, the hydraulic plunger 18 is actuated to reduce the brake fluid pressure at a predetermined turn. When the tendency to lock is eliminated, a pulse signal with a predetermined duty ratio is output to the valve means 23 again, and control is performed to increase the brake fluid pressure at a predetermined turn.

When a four-wheel drive vehicle equipped with such an anti-skid brake device is running, the driver immediately operates the transfer control lever 32 and releases the clutch 9 ( While the control unit 22 does not receive the 4-side detection signal and stops outputting to the valve means 23, the modulator 17 connects the mask cylinder 15 and the rear set via the hydraulic cylinder 19. It communicates with the wheel cylinder 16. For this reason, each of the front and rear wheel cylinders 16 receives brake fluid pressure according to the pressing force of the pre- and rear pedals, and the distribution of the brake force at that time is approximated to that shown by line B in Fig. 1. Show characteristics. On the other hand, when the driver enters a slippery road such as a snowy road, the transfer control lever 32 is operated by the driver and the clutch 9 is disengaged. 7 (contact)
and the 4th side detection signal is output. Then, the reversing control unit 22 responds to the ON signal of the brake sensor 34.
enters anti-skid brake operation control 1111.

When a locking tendency of the front wheels is detected based on the rotational speed signals of the front wheels 1 and 2, the valve means 23 is actuated to reduce the brake fluid pressure in the wheel cylinder 16 of the rear wheels to loosen the locking tendency of the front wheels. When the brake fluid pressure is exhausted, the brake fluid pressure is output to the valve means 23 to increase the brake fluid pressure again, and control is repeated to reduce the braking force reinforcement for the rear wheels. That is, during this time, the front wheel/cylinder 16 works to uniformly apply braking force to the front wheels 1 and 2 due to the normal uniform increase in brake fluid pressure. 3 and 4 are connected one-to-one in the transfer, and when the front wheels tend to lock, the brake fluid pressure on the rear wheels is relaxed, and the rotational force of the rear wheels is forcibly applied to prevent the front wheels from locking. During this operation, the steering wheel can be operated easily.

As described above, the anti-skid brake device according to the present invention performs an anti-skid brake operation in which the rear wheels 3 and 4 rotate the front wheels 1 and 2 so as not to cause the front wheels 1 and 2 to lock when the brakes are applied during four-wheel drive. Do this.

This means that when braking is performed on a low-friction road surface,
As is clear from the curve in FIG. 1, this also corresponds to the purpose of the brake force distribution, which is to make the rear brake force relatively stronger than the front brake force in order to prevent the front brake from locking. In other words, most part-time 4-wheel drive vehicles use 4-wheel drive on low-friction roads, and there is also a strong need to prevent the front wheels from locking due to brake activation and ensure steering operability. It is effective to activate the anti-skin brake to prevent locking. Moreover, since the anti-skid brake is activated on the rear wheel side based on the rotational speed signal of the front wheel, the device is simplified and costs can be reduced.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the front and rear brake force distribution of the vehicle, Fig. 2 is a schematic diagram of an anti-skid brake device as an embodiment of the present invention, and Fig. 3 is an explanatory diagram of the operation of a transfer to which the same device is attached. , and FIG. 4 each show a cross-sectional view of a modulator used in the above device. ■, 2. Front wheel, 3. 4. Rear wheel, 5, 6. Front and rear propeller/Yant, 16. Wheel cylinder, 17.
・Modulator, 22...Control unit, 33
・4WD detection sensor. )/Different front player power■/mouth

Claims (1)

[Claims] A control means for outputting a brake fluid pressure increase/decrease signal based on a rotational speed signal of a front wheel or a front propeller shaft of a four-wheel drive vehicle capable of selectively performing four-wheel drive or two-wheel drive; It has a four-wheel drive detection sensor that issues an output signal when the vehicle is in four-wheel drive, and a fluid pressure adjustment means that applies brake fluid pressure to the wheel cylinder of the rear wheel of the four-wheel drive vehicle in accordance with the brake fluid pressure increase/decrease signal. and above 4
An anti-skid brake device configured such that, when the four-wheel drive vehicle is in four-wheel drive, the control means controls the hydraulic pressure adjustment means to apply an anti-skid braking force to the four-wheel drive vehicle.