JPS602224B2 - Anti-skid device for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a brake system in which one of the front wheels of the left and right wheels and a rear wheel of one of the left and right wheels is engaged, and the other brake system is engaged with the brake devices of the remaining wheels. This invention relates to an anti-skid device for wheels equipped with a brake device separated into two systems.

Accordingly, such an anti-skid device detects the rotational speed of the front wheels and rear wheels belonging to one system of brake piping, selects the lower of the wheel speeds, and detects when the wheel starts to shift to skid. A device has been proposed that prevents the wheels belonging to the system from skidding by lowering the brake fluid pressure within the system when such a system occurs, thereby ensuring the steering performance and directional stability of the vehicle.

However, anti-skid control using this method has the disadvantage that the braking distance increases. This problem will be discussed below.

When the brake is operated, the braking force that the wheel receives from the road surface is given by the product of the friction coefficient between the wheel's tire and the road surface and the load acting on the wheel.

The load acting on the wheels is influenced by the deceleration that occurs in the vehicle body when braking, and moves forward in proportion to the magnitude of the deceleration.
Furthermore, the deceleration that occurs in the vehicle body during braking increases in proportion to the coefficient of friction between the tires and the road surface (hereinafter referred to as the coefficient of friction of the road surface). Therefore, as the friction coefficient between the tires and the road surface increases, the braking force that the front wheels and rear wheels receive from the road surface becomes larger for the front wheels, but the increase in braking force for the rear wheels becomes smaller. In other words, the ratio between the front wheel braking force and the rear wheel braking force received from the road surface (hereinafter referred to as the brake force ratio) changes depending on the friction coefficient of the road surface, and the larger the friction coefficient of the road surface, the more
Further, there is a relationship in which the shorter the distance between the axles and the higher the vehicle's weight D position, the greater the change in the braking force ratio. This relationship and the ratio of braking force applied by the braking device will be described below with reference to FIG. In the figure, the machine axis indicates the friction coefficient of the road surface, and the vertical axis indicates the ratio of the front wheel braking force to the rear wheel braking force. In the figure, the solid line a shows the relationship between the friction coefficient of the road surface and the ratio of the maximum braking force that can act between road tires;
As mentioned above, the change in the braking force ratio is about 4 in the range where the friction coefficient of the road surface is small, but increases as the friction coefficient of the road surface increases. On the other hand, the broken line b is the ratio of the braking force applied to the front and rear wheels by the braking device,
constant. That is, since the same brake fluid pressure is applied to the front and rear wheel brake devices by one brake master cylinder, the ratio of the braking forces generated by the brake devices is constant. And this constant value is
In terms of vehicle steering performance and braking efficiency during brake operation, the brake force is set to match the ratio of braking force between road tires on a road surface with a large friction coefficient (French = Mountain A) such as a dry concrete road surface. ing. In other words, the front and rear wheels are set to lock at the same time on a dry concrete road surface, etc. Therefore, when the coefficient of friction of the road surface is smaller than rA, the front wheels tend to lock earlier than the rear wheels because the broken line b is larger than the solid line a, and when the coefficient of friction of the road surface is larger than 〆A, The rear wheels tend to lock up earlier than the front wheels.

Therefore, if the wheel speeds of the front and rear wheels are detected, a skid is detected by the lower one of them, and the signal is used to control the front and rear wheels with the same hydraulic pressure using one brake fluid pressure control device. , the coefficient of friction between the tires and the road surface is French A.
On road surfaces like this, both the front and rear wheels skid, so the fluid pressure controlled by the brake fluid pressure control device is optimal for both the front and rear wheels. However, if the coefficient of friction of the road surface is 4 points lower than A, the front wheels will skid faster than the rear wheels, so both front and rear brake fluid pressures are controlled by the front wheel skid signal. Therefore, for the front and rear wheels, the brakes can be applied by maximizing the frictional force generated between the tires and the road surface, but for the rear wheels, when the front wheels start to skid, the maximum braking force that can be generated by that frictional force is applied. On the other hand, the braking force applied by the brake device only reaches a value of 4 mm, and is maintained at that value by the brake fluid pressure control device. When the coefficient of friction of the road surface is greater than A, the rear wheel brake fluid pressure is optimally controlled, but the front wheel fluid pressure is kept lower than necessary. That is, on a specific road surface with a friction coefficient of A, both the front and rear wheels are optimally controlled, but on other contact surfaces, this results in a loss of braking force and increases the braking distance, which is extremely dangerous. Particularly in the case of commercial vehicles with a short distance between the axles and a high center of gravity, the load applied to the vehicle changes significantly due to the deceleration of the vehicle body during braking, and the braking distance due to the operation of the anti-skid device changes significantly. The growth is more than ten percent.
In the case of commercial vehicles, similar results can occur depending on the presence or absence of cargo and its weight. The present invention was made in view of the above problems, and aims to provide an anti-skid device for a vehicle that can effectively apply the brakes and shorten the braking distance. The vehicle is equipped with a brake system that is separated into two systems: one brake system that engages the brake system for one of the front wheels and the rear wheel of one of the left and right wheels, and the other brake system that engages the brake system for the remaining wheels. , only one front wheel and one rear wheel associated with the one brake system are provided with a wheel speed detector that detects their rotational speed and transmits an electronic signal proportional to this; The smaller of the output signals is selected by the low wheel far selection circuit, and based on the selected signal, a control signal is sent to control the brake fluid pressure according to the skid state of the wheels. In the vehicle anti-skid device configured to operate a control device to control only the brake fluid pressure of the one brake system, the brake fluid pressure control device and a rear wheel brake device belonging to the one brake system are connected to each other. In between, an auxiliary brake fluid pressure control valve is interposed to reduce the brake fluid pressure supplied to the other brake system in a predetermined relationship, and the brake fluid pressure of the other brake system is directly applied to the brake system of the remaining wheels. It was designed to be supplied to

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 2, 1 is a right front wheel, 2 is a left front wheel, 3 is a right rear wheel, and 4 is a left rear wheel.

The brake master cylinder 5 is separated into two systems,
One system is connected to the brake system 7 of the right front wheel 1 and the brake system 8 of the left rear wheel 4 by means of a brake line 6.
In this single system, the hydraulic pressure from the master cylinder 5 is supplied to each brake device 7, 8 without being restricted.

The other system passes through the piping 9 and the brake fluid pressure control Z device 10, one goes through the piping 11 to the brake device 12 of the left front wheel 2, and the other goes through the piping 13, the auxiliary brake fluid pressure control valve 14, and the piping 15 to the right side. It is conveyed to the brake device 16 of the rear wheel 3. That is, the brake piping is diagonally separated into two systems. Wheel speed detectors 17 and 18 are provided on the front left wheel 2 and the rear right wheel 3, and these wheel speed detectors 17 and 18 send electrical signals (hereinafter referred to as wheel speed signal) is generated.
Reference numeral 19 denotes an electronic control device to which the output signals of the wheel speed detectors 17 and 18 are applied, and issues an operation command to the brake hydraulic pressure control device 10 in accordance with the speed signals from the wheel speed detectors 17 and 18.

The brake fluid pressure control device 10 is the brake device 1 in the left front section 2.
2 via a pipe 11, and a brake device 16 for the right rear wheel 3 via a pipe 11, an auxiliary brake fluid pressure control valve 14, and a pipe 15. 12 and 16, the brake fluid pressure is raised, lowered, and maintained. This will be explained in more detail using FIG.

Each wheel speed signal detected by the wheel speed detectors 17, 18 is converted by converters 20, 21 in the electronic control unit 19 into a DC voltage indicative of the wheel distance.

The lower wheel speed of these two wheel speed signals is selected by the low wheel far selection circuit 22, and is sent to the differentiator 23, where the deceleration of the wheel speed is detected. The output side of the differentiator 23 is connected to a deceleration signal generator 24 and an acceleration signal generator 25. The deceleration signal generator 24 generates a deceleration signal (a signal of "1") when the deceleration of the wheels is reduced to a certain value (for example, 1.4 m) or more.Acceleration signal generator 2
5 generates an acceleration signal (a signal of ``1'') when an acceleration of a certain value (for example, 0.59) or more occurs when the wheels are recovering from a skid state.The input side of the OR circuit 26 is turned off. The output side of the deceleration signal generator 24 via the delay time limit circuit 27 and the output side of the acceleration signal generator 25 are connected.
At the same time a deceleration signal is generated, that signal is sent to OR circuit 2.
However, after the deceleration signal disappears, the deceleration signal is held for a certain period of time (for example, 0.09 seconds). The actuating portion of the two-way solenoid valve 29 of the brake fluid pressure control device 10 is connected to the OR circuit 26, and the actuating portion of the three-way solenoid valve 28 is connected to the deceleration signal generator 24. Both solenoid valves 28 and 29 are reduced,
When the acceleration signal generators 24 and 25 are inactive, they are in the position shown in FIG.
Connect 2 and 16. When the brake is applied, both electromagnetic valves 28 and 29 are operated by a signal from the deceleration signal generator 24. When the two-way solenoid valve 29 operates, the brake master cylinder 5 and the brake devices 12 and 16 are immediately disconnected, and the
When the solenoid valve 28 is actuated, both brake devices 12, 16 are connected to the reservoir 44.

That is, when both electromagnetic valves 28 and 29 operate, the brake fluid pressure in both brake devices decreases. When the wheel speed is restored, the two-way solenoid valve 29 is activated by the output of the acceleration signal generator 25. Therefore, the brake pressure fluid when the two-way solenoid valve 29 operates is neither discharged nor supplied, and the fluid pressure at that time is maintained within the brake device. 45 is a hydraulic pump whose suction side is connected to the reservoir 44 and its output side is connected to the piping 9 via a check valve 46. The pump 45 is activated when the three-way solenoid valve 28 is activated and the brake pressure fluid in the brake devices 12 and 16 flows into the reservoir 44, and pumps the brake fluid to the brake master cylinder 5. An auxiliary brake fluid pressure control valve 14 is inserted between pipes 13 and 15 connected to the right rear wheel 3, and this auxiliary brake fluid pressure control valve 14 controls the brake fluid pressure from the brake fluid pressure control device 10. The relationship shown in FIG. 4 is changed to act on the brake device 16 of the right rear wheel 3. The main body 30 of the auxiliary brake fluid pressure control valve 14 has an inlet 30 1 communicating with the pipe 13 and a pipe 1
5, and a stepped piston 33 having a large flange L and a small flange S inside the main body 30.
A stepped cylinder portion is formed on which the cylinder slides. The piston 33 divides the inside of the main body 30 into chambers 34, 35, and 36. The chamber 36 and the chamber 36 are also separated in a liquid-tight manner by a sealing material 38 attached to the small diameter outer circumference of the piston 33. Room 3
5 communicates with the outside of the main body 30 through a hole 39 and is maintained at atmospheric pressure. A spring seat 40 is engaged with the left end of the piston 33, and a compression spring 41 mounted in the chamber 36 is engaged with the left end of the piston 33.
The valve 4 is pushed to the right in the drawing by the compressive load of
Houses 34 and 36 are usually auspicious, since they are kept apart from 3. Valve 43 is slidable within locking member 42a and is biased to the right by spring 43a. Further, the locking member 42a has a side hole 42b. Now, when brake pressure fluid is supplied to inlet 31, the pressure fluid is transmitted to chambers 36 and 34.

Therefore, a compression spring 41 is attached to the piston 33 from the left side of the drawing.
The added force of the imitation force and the hydraulic pressure acting on the cross-sectional area of the small diameter portion S of the piston 33 acts. On the other hand, from the right side in the drawing, hydraulic pressure is applied to the area of the large diameter portion L of the piston 33 facing the chamber 34. Therefore, while the hydraulic pressure acting on the large pot portion of the piston 33 is smaller than the sum of the force acting on the 4 diameter portion of the piston 33 and the spring force of the compression spring 41 (brake hydraulic pressure is relatively low), the piston 33 It is pushed by the compression spring 41 and is in the position shown in the figure, and since the left end of the hole 42 is open, the chambers 36 and 34 are kept at the same pressure, and the hydraulic pressure generated in the brake master cylinder 5 is directly transmitted to the brake device 16. It will be done. Then, the brake fluid pressure increases and the force applied to the end surface of the piston 33 on the chamber 34 side (fluid pressure in the chamber 34 x piston 33
) is the force applied to the end surface of the small diameter portion S of the piston 33 on the chamber 36 side (hydraulic pressure in the chamber 36 x piston 33
When the piston 33 becomes larger than the sum of the spring force of the compression spring 41 and the spring force of the compression spring 41, the piston 33 moves to the left and closes the hole 4.
2 is closed by valve 43, so that chamber 34 and chamber 36 are disconnected from each other. If the brake hydraulic pressure at the time when the hydraulic pressure from the brake master cylinder 5 starts to act and the communication is broken for the first time is Po, the force applied to the end face on the chamber 36 side acting in the chamber 36 is It is larger than the force applied to the end face. Therefore, when the piston 33 moves rightward and the valve seat of the hole 42 and the valve 43 are slightly separated, the hydraulic pressure in the chamber 34 increases and the hole 42 is closed by the valve 43 again. In this way, the brake fluid pressure in the chamber 34 is determined by the brake fluid pressure acting on both end surfaces of the piston 33 and the force relationship of the spring 41. Room 34
The amount of increase in the brake fluid pressure Po or more is given by the product of the amount of increase in the brake fluid pressure Po or more in the chamber 36 and the ratio of the pressure receiving area of the small diameter portion S to the pressure receiving area of the large portion L of the piston 33. That is, an increase in the brake fluid pressure applied to the brake device 16 is limited by the pressure receiving area ratio of the piston 33. This relationship is shown in FIG.

In FIG. 4, the horizontal axis represents the brake fluid pressure in the chamber 36 of the auxiliary brake fluid pressure control valve 14 (same as the fluid pressure in the front wheel brake device 12), and the vertical axis represents the brake fluid pressure in the chamber 34 (rear wheel brake fluid pressure). (same as the hydraulic pressure inside the brake device 16).

As is clear from the figure, until the brake fluid pressure reaches Po, the fluid pressure at the inlet 31 and the fluid pressure at the outlet 32 increase at a ratio of 1:1 (that is, the same pressure); The amount of increase in pressure is reduced to the ratio of the pressure receiving area of the small diameter part to the pressure receiving area of the large diameter part of the piston, and becomes gradual. When the brake fluid pressure is relaxed, the piston 33 and the valve 43 slide together to the left and the volume of the chamber 34 increases, so that the outlet 32 (brake device 16) The pressure of the piston 33 gradually decreases according to the pressure receiving area ratio at both ends of the piston 33, and when the brake fluid pressure becomes less than Po, the valve 43 opens, and after that, the chamber 34 and the chamber 36 communicate through the hole 42, so that the pressure is the same as that of the inlet 31. descend to The brake fluid pressure Po shown in FIG. 4 is set at a point B corresponding to the friction coefficient peak B of the road surface shown in FIG. In other words, on a road surface where the brake force ratio between the front and rear wheels applied from the road surface is close to a constant value, the increase in brake fluid pressure in the above discussion is defined as: 1, and above that (
When the friction coefficient of the road surface reaches B), the increase in brake fluid pressure of the rear wheels is limited. Therefore, the braking force ratio applied by the brake device can be approximated to the braking force ratio applied from the road surface, as shown by the dashed line in FIG. Now, when excessive braking is applied to the vehicle and the wheels begin to decelerate, the wheel speeds of wheels 2 and 3 are detected by the wheel speed detectors 17 and 18, so the one with the lower deceleration is selected as the lower wheel speed. It is detected by the circuit 22, and when the deceleration of the far wheel exceeds a certain reference value, a deceleration signal is generated in the deceleration signal generator 24.

This deceleration signal operates the three-way solenoid valve 28, and at the same time operates the two-way solenoid valve 29 through the off-delay time circuit 27 and the OR circuit 26. It is shut off by the solenoid valve 29, and the brake devices 12 and 16 are connected to the reservoir 44 by the three-way solenoid valve 28, so that the brake fluid pressure acting on the brake devices 12 and 16 is lowered. The brake fluid discharged into the reservoir 44 is pressurized by a pump 45 driven by the car's engine or a specially provided external motor, and is discharged into the pressure side piping 9 of the brake master cylinder 5 via the check valve 46. be done. When the deceleration signal disappears due to a decrease in brake fluid pressure, the three-way solenoid valve 28
returns to the non-operating position and the brake fluid pressure stops decreasing.
However, since the two-way solenoid valve 29 remains in operation for a period of time determined by the off-delay time circuit 27 (for example, 0.09 steps), the brake fluid pressure is maintained constant. Then, if the wheels are still in the recovery state (the state in which the wheel speed is accelerated from the state where the wheel speed has been decelerated toward the vehicle body speed) and an acceleration signal is generated by the acceleration signal generator 25, that signal is sent to the OR circuit 26. Since the two-way solenoid valve 29 continues to be energized via the brake fluid pressure, the brake fluid pressure continues to be maintained. When the acceleration signal disappears (if no acceleration signal is generated, when the signal from the OFF delay reduction circuit 27 disappears), the two-way solenoid valve 29 becomes inactive, and the brake master cylinder 5, brake device 12,
16, the brake fluid pressure increases. Even in the process of lowering and increasing the brake fluid pressure by the brake fluid pressure control device 1, the brake fluid pressure of the brake device 16 is controlled via the auxiliary brake fluid pressure limiting valve 14, so the fluid pressure change occurs only once. This is done according to the characteristics shown in Figure 4.
During such work, the hydraulic pressure from the master cylinder 5 is directly supplied to the brake devices 7 and 8 of the front right wheel 1 and the rear left wheel 4, so the rotational speed of each wheel 1 and 4 is zero. It is in a complete skid state.

However, since the other wheels 2 and 3 are prevented from skidding by the above-described operation, the steering performance and directional stability of the vehicle are guaranteed without being extremely degraded. Next, the action of the auxiliary brake fluid pressure control valve 14 when it starts to skid in the event of excessive braking will be described.

As is clear from the above description of the operation of the anti-skid device, when the lower wheel speed is used as the control signal, the deceleration of the wheel with the higher wheel speed is not used as skid control information. Therefore, if there is a large difference in the brake fluid pressure between the left front wheel 2 and the right rear wheel 3 that are subject to control, causing skid, the wheels with high wheel speeds will not be able to properly control the brake fluid, and the brake fluid will not be able to adequately control the wheels. can't get power. However, if the auxiliary brake fluid pressure control valve 14 is provided between the brake fluid pressure control device 10 and the rear wheel brake device 16, the relationship between the front wheel brake fluid pressure and the rear wheel brake fluid pressure will be different from that of the auxiliary brake fluid pressure control valve 14. Since the inlet 31 is connected to the front wheel brake device 12 and the outlet 32 is connected to the rear wheel brake device 16, the characteristics shown in Fig. 4 are obtained, and the brake fluid is
While Po is lower, the same pressure is applied to the front and rear wheels, but when it is higher than Po, the brake fluid pressure of the rear wheels is kept lower than that of the front wheels. Therefore, the ratio of the braking forces generated at the front wheels and the rear wheels becomes the dashed-dotted line C in FIG. In other words, if rB is the friction coefficient of the road surface that just starts to skid due to the brake fluid pressure Po, it will be a constant value on a low friction road surface of French B or less, but on a road surface with a friction coefficient higher than that, it will rise to the right. The curve C, which is a straight line and shows the ratio of the braking forces applied by the brake device of the present invention, can be approximated to the curve A showing the ratio of the braking forces that the wheels receive from the road surface. The position of point B on the dashed-dotted line C and the size of the opening to the right of it are optimized depending on the compression load of the compression spring 41 of the auxiliary brake fluid pressure control valve 14 and the pressure receiving area ratio of the large diameter portion and the small diameter portion of the piston 33. Just design it. However, as shown in FIG. 1, it is difficult to completely approximate the solid line a with the dashed line C due to the structure of the auxiliary brake fluid pressure control valve. Therefore, when it is necessary to choose between making the front wheels or the rear wheels skid faster,
Normally, the load on the front wheels is greatly distributed compared to the load on the rear wheels,
Since the braking force on the front wheels is large and the braking force on the rear wheels is small, it is desirable to strengthen the skid head direction on the front wheels in order to improve braking efficiency and stabilize maneuverability.
The auxiliary brake fluid pressure control valve in the above embodiments may be a variable load valve that detects the load distribution of each wheel and controls the fluid pressure in accordance with the load. As is clear from the above description, the present invention provides the following effects. ■ One front wheel and one rear wheel are designed to prevent skids,
The remaining wheels are supplied with brake fluid pressure from the master cylinder, so even if the remaining wheels skid during braking, the above 10,000 front and rear wheels are prevented from skidding. Therefore, the maneuverability of the vehicle is ensured, and even if the brake fluid pressure supplied to one of the front and rear wheels is loosened more than necessary due to the operation of the brake fluid pressure control device, the remaining wheels will not be in a skid state. Since the braking force is ensured even when the vehicle is in use, it is possible to prevent the braking distance from increasing unnecessarily.

■ Furthermore, the brake fluid pressure supplied to one front wheel and the rear wheel is controlled based on the smaller of the wheel speeds of both wheels, and the brake fluid pressure supplied to the rear wheel is further controlled according to a predetermined relationship. Since the pressure has been reduced by the brake system, the ratio of the braking force applied to the brake devices of these two wheels can be approximated to the ratio of the braking force applied from the road surface, and the appropriate brake force can be applied according to the friction coefficient of the road surface. This prevents both wheels from skidding, ensuring maneuverability and shortening the flaking distance.

■ In order to ensure vehicle maneuverability and shorten braking distance, one brake pressure control device can control the brake pressure for one front wheel and one rear wheel, compared to control for all wheels. As a result, the structure and capacity of the control device can be made small and 4-capacity, which is economical, and the installation space can be reduced and the weight can be reduced.

In particular, there is no need to provide any adjustment mechanism in the system to which the remaining wheels belong, making it possible to further reduce the size and weight.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between the coefficient of friction between the wheel tire and the road surface and the ratio of the braking force in front and back, Fig. 2 is an overall schematic diagram showing one embodiment of the present invention, and Fig. 3 is a diagram showing the relationship between the coefficient of friction between the wheel tire and the road surface. 4 is a characteristic diagram of the auxiliary brake fluid pressure control valve 14. 1, 2... Front wheel, 3, 4... Rear wheel, 5
...Brake master cylinder, 7, 8, 12,
16... Flake device, 10... Brake fluid pressure control device, 14... Auxiliary brake fluid pressure control valve, 17, 1
8...Wheel speed detector, 10...Electronic control device, 20, 21...Converter, 22...
...low wheel speed selection circuit, 23...differentiator, 2
4...Deceleration signal generator, 25...
Acceleration signal generator, 27... Off delay time limit circuit, 28, 29... Solenoid valve, 30... Body, 33... Piston, 41...・・Compression spring, 44・・・Reservoir, 45・・・Pump, 46・
·····non-return valve. Hair - figure hair 2 figure hair 3 figure Qin. Figure 4

Claims (1)

[Claims] 1 A brake system that is separated into two systems: one brake system that is connected to the front wheel of one of the left and right wheels and the rear wheel brake system of one of the left and right wheels, and the other brake system that is connected to the brake system of the remaining wheels. A wheel speed detector is provided for detecting the rotational speed of only one front wheel and one rear wheel associated with the one brake system and transmitting an electric signal proportional to the rotational speed, and a wheel speed detector is provided for detecting the speed of these wheels. The lower wheel speed selection circuit selects the smaller of the output signals of the brake, and based on the selected signal, a control signal is sent to control brake pressure reduction according to the skid condition of the wheels. In the vehicle anti-skid device that operates a pressure control device to control only the brake fluid pressure of the one brake system, the brake fluid pressure control device and a rear wheel brake device belonging to the one brake system are connected to each other. An auxiliary brake fluid pressure control valve is interposed between them to reduce the brake fluid pressure supplied to the brake system of the rear wheel in a predetermined relationship, and the brake fluid pressure of the other brake system is directly applied to the brake system of the remaining wheels. An anti-skid device for vehicles designed to be supplied to