JPS602223B2 - Anti-skid braking system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid braking system for a vehicle, and more particularly to an anti-skid braking system for rear wheels.

In order to make the vehicle stop in the shortest distance and safely during braking, it is preferable to apply a braking force equal to the maximum frictional force between the tires and the road surface.If the braking force exceeds this maximum frictional force, This is dangerous because the wheels lock and the tires skid, impairing maneuverability and lengthening the braking distance.

Therefore, when the wheels lock during braking, the braking force is weakened to release the lock, and then when the wheels lock again, the braking force is weakened again so that the braking force is as close as possible to the maximum frictional force. An anti-skid braking device that performs a braking action is the third most popular anti-skid braking device, as described in Mochiseki No. 51-39367. This anti-skid braking device is equipped with a brake pressure control valve equipped with a piston consisting of a large diameter part and a small diameter part, and connects the cylinder chamber of the small piston part to the master cylinder, and connects the cylinder chamber of the large piston part to the wheel cylinder. It is connected. When the wheels are locked, the brake hydraulic line that directly communicates between the master cylinder and the wheel cylinder is closed, and at the same time, the brake hydraulic line that connects the cylinder chamber in the large part of the piston and the wheel cylinder is closed, thereby increasing the pressure ratio at both ends of the piston. The braking oil in the wheel cylinder is sucked into the cylinder chamber of the large diameter portion of the piston until it reaches a constant level, thereby weakening the braking force and preventing the wheels from locking. However, if the braking oil in the wheel cylinder is sucked into the cylinder chamber of the piston's largest part until the pressure ratio at both ends of the piston becomes constant, it is impossible to avoid wheel locking when the wheel rotation speed is low. There is. That is, when the rotational speed of the wheels is high, the inertial force against the rotation of the wheels is large, so if the wheels lock and the braking is weakened, the rotational speed of the wheels immediately increases, so there is no skid. However, when the rotational speed of the wheels is low, even a small braking force causes the wheels to lock, so even if the brake oil pressure in the wheel cylinder is lowered until the pressure ratio at both ends of the piston becomes constant when the wheels are locked, the brake oil pressure is low to begin with and the brakes are not activated. Oil pressure doesn't drop that much. When the rotational speed of the wheels is low, the inertial force against the rotation of the wheels is small, so the wheels continue to be locked even if the braking oil pressure decreases to some extent, making it difficult to avoid skids. SUMMARY OF THE INVENTION An object of the present invention is to provide an anti-skid braking device that can avoid skids regardless of the driving condition of the vehicle.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, 1 is a front wheel, 2 is a front wheel brake system, 3 is a rear wheel, 4 is a wheel cylinder for rear wheel braking, and 5 is a master cylinder connected to a foot brake pedal 6 provided in the driver's cabin. 7 is a brake hydraulic line connecting the master cylinder 5 and the brake device 2; 8 is a brake hydraulic line connecting the master cylinder 5 and the rear wheel cylinder 4; 9 is provided in the brake hydraulic line 8; The anti-skid valve device is a deceleration detector that detects the deceleration of the rear wheels and generates a detection signal when this deceleration exceeds a predetermined deceleration, that is, when the wheels are locked. Anti-skid valve device 9
A cylinder bore 11 is formed in the housing, and a spool valve 12 having four lands A, B, C, and 0 is reciprocatably inserted into the cylinder bore 11. One end of the spool valve 12 is connected to the movable plunger 4 of the electromagnetic device 13, while the solenoid 15 is connected to the deceleration detector 1. In addition, the spool valve 12 is normally compressed by the compression spring 1.
The spring force of 6 causes it to rest in the position shown in FIG. Hydraulic chambers E are provided between adjacent lands A, B, C, and D, respectively.
. Each of them is connected via a conduit 20 to a vacuum chamber 21, which will be explained in detail later. An annular groove 22 is formed on the inner wall of the cylinder bore 11, and the annular groove 22 has a diameter approximately equal to the spacing between the lands B and C. When the spool valve 12 is in the position shown in FIG. F is in communication, and when the solenoid 15 is energized and the spool valve 12 is moved to the left, the communication between the hydraulic chambers E and F is cut off, and the hydraulic chambers F and G are arranged so that they can be connected to each other. . The spool valve 12 therefore forms a switching valve that selectively connects the wheel cylinder 4 to the master cylinder 5 or to the vacuum chamber 21 . A cylinder bore 2 is further provided in the housing of the anti-skid valve device 9.
3 is formed, and a spool valve 24 having a pair of lands 1, 1 is slidably inserted into the cylinder pore 23.

These cylinder bores 23 and spool valves 24 form a pressure reducing spool valve arrangement. The cylinder bore 23 is closed by a thread 25 screwed onto one end thereof, which thread 25 integrally forms on its inner end a stop 26 extending towards the spool valve 24. This spool valve 24 is constantly pressed toward the right by the spring force of the compression spring 27.
Normally, it rests in the position shown in Figure 1. Cylinder bore bottom wall 2
A reduced pressure chamber 21 is formed between 3a and the land 1, and this reduced pressure chamber 21 is connected to the hydraulic chamber G via the oil passage 28, the conduit 20, and the oil passage 19, as described above. When hydraulic pressure is applied in the decompression chamber 21, the spool valve 24 moves by a certain stroke until it comes into contact with the stopper 26. In the housing of the anti-skid valve device 9, a cylinder bore 29 and a threaded hole 30 having a larger diameter than the cylinder bore 29 are further screwed, and a cylinder bore having a smaller diameter than the cylinder bore 29 is screwed into the screw 31 screwed into the threaded hole 30. 32 is formed. Inside these cylinder bores 29, 32 is a large diameter portion 33 as shown in FIG.
A piston 35 consisting of a small diameter portion 34 is slidably inserted, and the piston 35 normally rests at the position shown in FIG. 1 by the spring force of a compression spring 36. A threaded hole 37 is screwed into the threaded hole 301, thereby forming a hydraulic chamber 38 within the threaded hole 30. This hydraulic chamber 38 is the oil passage 3
9, is constantly connected to the master cylinder 5 via the hydraulic chamber E and the oil passage 17. Further, a hydraulic chamber 40 formed in the large diameter cylinder bore 29 is connected to the cylinder bore 29 through an oil passage 41.
The opening of this oil passage 41 to the cylinder bore 23 is arranged so as to face the inside of the decompression chamber 21 when the spool valve 24 comes into contact with the stopper 26 that has moved to the left. Furthermore, the hydraulic chamber 4 is connected to the conduit 20 via an oil passage 42 and a check valve 43 on one side, and an oil passage 44 and a check valve 4 on the other side.
5 and is connected to the hydraulic chamber E via an oil passage 46. These check valves 43 and 45 are configured to allow flow only to the left in FIG. 1. FIG. 2 is a graph showing oil pressure changes during braking, where the vertical axis x represents the braking oil pressure in the wheel cylinder 4, and the machine axis Y represents the master cylinder 5.
Shows the braking oil pressure in each case.

The anti-skid valve device 9 is normally in the state shown in FIG. Concatenated. Therefore, when the brake pedal 6 is depressed, the brake oil pressure Y in the master Z cylinder 5 increases as shown by the straight line ○a in FIG. 2, and as a result, the brake oil pressure x in the wheel cylinder 4 increases. . Then, if the rear wheel 3 is locked, this is the deceleration detector 10
The detection signal causes the solenoid 15 to
is energized. As a result, the movable plunger 14 is attracted by the solenoid 15, and the spool valve 12 is pulled by the compression spring 16.
move to the left against the spring force. Consequently, the hydraulic chamber E,
The lotus communication between F is blocked, while the hydraulic chambers F and G communicate with each other. As a result, the wheel cylinder 4 is connected to the decompression chamber 21 via the conduit 8, the two oil pressure chambers F, G, and the conduit 20, and the spool valve 24 resists the spring force of the compression spring 27 to close the stopper 26. Move to the left until it touches the. In this way, part of the braking oil in the wheel cylinder 4 is transferred to the decompression chamber 2.
1, the braking oil pressure x in the wheel cylinder 4 is temporarily reduced as shown by the straight line ab in FIG. 22, and as a result, the rear wheel is unlocked. On the other hand, when the spool valve 24 moves to the left, the oil passage 41 closes into the decompression chamber 21, and as a result, the oil passage 41, 3
1, connected to the wheel cylinder 4 via a conduit 20, hydraulic chambers G, F, and a conduit 8; Therefore, after the wheels are unlocked, when the brake pedal is further depressed and the braking oil pressure in the hydraulic chamber 38 exceeds a predetermined pressure, the braking oil pressure in the master cylinder 5 is increased between the large diameter part 33 and the small diameter part 34 of the 3-ton piston 35. The pressure is reduced by the ratio determined by the area ratio of wheel sea J
The data is transmitted to the reader 4. Thus, the braking oil pressure increase rate in the wheel cylinder 4 at this time is smaller than the increase rate ○a before the wheel lock is released, as shown by the straight line cd in FIG. As the brake pedal is depressed, the piston 35 moves to the right against the spring force of the compression spring 36 until it abuts against a shoulder 47 on the inner wall of the cylinder bore 29. After the piston 35 contacts the shoulder 47, the braking oil pressure within the wheel cylinder 4 does not change even if the brake pedal is further depressed. Next, when the brake pedal is released, the braking oil pressure in the master cylinder 5 decreases, and accordingly, the oil pressure in the hydraulic chamber 38 also decreases.

On the other hand, part of the braking oil in the wheel cylinder 4 and the decompression chamber 21 flows into the hydraulic chamber 40 via the check valve 43 and returns the piston 35 to its initial position, while most of it flows through the check valve 43. It is returned into the master cylinder 5 via 45.
When the vehicle stops, the solenoid 15 is energized so that the spool valve 12 returns to the position shown in FIG. 1, and the piston 35 and spool valve 24 also return to the position shown in FIG.
As described above, according to the present invention, when the wheels are locked, the spool valve 24 moves by a certain stroke, so a certain amount of braking oil flows from the wheel cylinder 4 into the decompression chamber 21, and as a result, the braking inside the wheel cylinder 4 is reduced. Oil pressure decreases.

When the wheels are rotating at high speeds, this reduction in brake hydraulic pressure immediately increases the rotational speed of the wheels, thus avoiding skids. On the other hand, when the wheels are rotating at a low speed, the wheels are locked with low braking oil pressure, so the amount of braking oil supplied into the wheel cylinders 4 at this time is small. However, even if the amount of brake oil supplied to the wheel cylinder 4 is small, the amount of brake oil that flows into the decompression chamber 21 when the wheels are locked is constant, so the wheel cylinder 4
The rate of decrease in braking oil pressure within the vehicle is considerably greater than when the wheels are rotating at high speed. Therefore, even when the wheels are rotating at low speeds, where the inertial force against the rotation of the wheels is small, the braking force is greatly weakened, so that the rotational speed of the wheels immediately increases, thus making it possible to avoid skids. Thus, according to the present invention, skids can be avoided regardless of the operating condition of the vehicle.

[Brief explanation of the drawing]

FIG. 1 is an overall view of the anti-skid braking device according to the present invention, showing the anti-skid valve device in cross section, and FIG. 2 is a graph showing the relationship between the braking oil pressure in the mask cylinder and the braking oil pressure in the wheel cylinder. 3...Rear wheel, 4...Wheel cylinder, 5
...Master cylinder, 6...Brake pedal,
7, 8...Braking hydraulic line, 9...Anti-skid valve device, 10...Deceleration detector, 12,
24... Spool valve, 13... Solenoid valve device, 21... Decompression chamber, 35... Piston, 43, 45... Reverse Stop valve. Figure 1 Figure 2

Claims (1)

[Claims] 1. A switching valve operated by a wheel lock detection signal is arranged on the brake hydraulic pipe connecting the master cylinder and the wheel cylinder, and the switching valve communicates with the brake hydraulic pipe when the wheels are locked, and connects the brake hydraulic pipe when the wheels are locked. The pressure reducing spool valve device includes a spool valve whose stroke is regulated to a constant stroke, and the wheel cylinder is connected to the pressure reducing chamber of the pressure reducing spool valve device. is defined, and is further provided with a piston consisting of a large diameter part and a small diameter part, which constantly connects the hydraulic chamber formed in the cylinder bore of the small diameter part to the master cylinder, and also connects the hydraulic chamber formed in the cylinder bore of the large diameter part to the master cylinder. An anti-skid braking device for a vehicle connected to a pressure reducing spool valve device so as to communicate with the pressure reducing chamber when the spool valve moves a certain stroke when the wheels are locked.