JPH021705B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid device for preventing wheel locking.

Conventionally, various anti-skid devices for vehicles have been developed as brake devices for vehicles to perform more effective and safe braking action on any road surface. In these anti-skid devices, the skid condition of the wheels is evaluated by a control unit, and based on this evaluation, the brake pressure supplied to the brake cylinder of the wheel brake device is reduced, increased, or held constant. One type of such a system is, for example, as shown in Japanese Patent Publication No. 52-21663, which includes a control unit that detects the skid state of a wheel and generates a pressure relief control signal, and a control unit that receives the pressure relief control signal, and an actuator that reduces the brake pressure of the wheel brake device,
The actuator includes a cut valve that blocks a passage connecting the master cylinder and the brake cylinder of the wheel brake device, a pressure chamber provided between the cut valve and the brake cylinder, and a variable pressure chamber that is movably disposed inside the housing. a servo piston that partitions a low pressure chamber that is constantly in communication with a low pressure source; a hydraulic plunger that opens and closes the cut valve and increases or decreases the volume of the pressure chamber by movement of the servo piston; a solenoid valve that switches from a connection position between the transformation chamber and the low pressure source to a connection position between the transformation chamber and the high pressure source; a spring provided in the low pressure chamber and urging the servo piston in a direction in which the cut valve opens; It is known to have the following.

By the way, this type of anti-skid device is controlled as follows.

That is, first, when reducing the brake pressure in the brake cylinder of the wheel brake device, the solenoid valve is switched in response to a pressure release control signal from the control unit to introduce high pressure gas into the variable pressure chamber.
The cut valve is shut off by retracting the servo piston and the hydraulic plunger against the urging force of the main spring, and the volume within the pressure chamber is increased by retracting the servo piston and the hydraulic plunger. Second, when the brake pressure in the brake cylinder is to be increased again, the pressure build-up control signal generated from the control unit switches the solenoid valve to discharge the high-pressure gas in the variable pressure chamber to the low-pressure source side, thereby increasing the biasing force of the main spring. This moves the servo piston and hydraulic plunger forward to reduce the volume within the pressure chamber. Thirdly, when maintaining the brake pressure in the brake cylinder, a pressure holding control signal from the control unit switches the solenoid valve to interrupt the introduction of high pressure gas into the variable pressure chamber and the discharge of high pressure gas from the variable pressure chamber. However, the volume of the pressure chamber is kept constant.

By the way, when the vehicle is running on a low-friction road surface such as a frozen road surface, the wheels may skid and move toward lock due to the action of relatively low brake pressure, and the pressure release control signal may take a relatively long time. Occurs continuously.

This occurs because the friction coefficient of the road surface is small and the resistance that the tires receive from the road surface is small.

Therefore, in the above-mentioned type of anti-skid device, if the hydraulic plunger and the servo piston can be brought into contact and separated from each other, even if the hydraulic plunger retreats until the brake pressure in the brake cylinder becomes zero and stops at that position, High-pressure gas is still supplied to the variable pressure chamber, and the servo piston continues to retreat, causing the hydraulic plunger and servo piston to separate, often resulting in so-called servo piston overstroke. Once this overstroke occurs, the rotation of the wheel Even if a pressure build-up control signal is generated in the control unit due to recovery and the servo piston moves forward, the hydraulic plunger will not move forward and the brake pressure will not increase until the servo piston comes into contact with the hydraulic plunger and cancels the overstroke. Since the brake pressure does not increase, the brake pressure is actually too relaxed.

In addition, in the case where the hydraulic plunger and the servo piston are integrally provided, even if the brake pressure in the brake cylinder becomes zero, high pressure gas is still supplied to the variable pressure chamber, and the hydraulic plunger and the servo piston are connected. If you continue to move backwards, the brake pressure in the brake cylinder becomes negative, and therefore,
Even when the pressure charging control signal is transmitted to the solenoid valve, a process of reducing the negative pressure is first required, and the brake pressure does not increase immediately.

In this way, the anti-skid device of the above type is
When controlling the brake pressure, the brake was actually loosened too much, which increased the control distance and was dangerous.

In an attempt to solve these problems,
In an example in which a valve is provided that shuts off the passage connecting the switching valve and the pressure transformation chamber by the movement of the hydraulic plunger away from the servo piston (see Japanese Patent Application Laid-open No. 47-43673), if negative pressure is generated on the brake cylinder side of the cut valve, An example of installing a valve that communicates the brake cylinder side with the master cylinder side (Japanese Patent Laid-Open No. 53
-Refer to Publication No. 57369), but in the former case, even if the switching valve switches to communicate the variable pressure chamber with the low pressure source, the valve overcomes the spring force that biases it in the valve closing direction. Since the hydraulic plunger does not open until a pressure difference is created, the hydraulic plunger does not move forward immediately in response to switching of the switching valve, and as a result, the above-mentioned problem cannot be reliably solved. Also, in the latter case,
Since the hydraulic fluid on the master cylinder side is supplied until there is no negative pressure on the brake cylinder side, there is a drawback that the amount of operation of the master cylinder suddenly increases, making the driver feel uneasy.

The present invention was made in view of the above-mentioned problem, and prevents the pressure release control signal from being transmitted to the solenoid valve more than necessary to prevent the servo piston from retracting excessively, thereby increasing the braking distance. An object of the present invention is to provide an anti-skid device that can prevent skidding.

According to the present invention, the above objects include: a control unit that detects a skid state of a wheel and generates a pressure relief control signal; an actuator that receives the pressure relief control signal and reduces the brake pressure of a wheel brake device; The actuator includes a cut valve that blocks a passage communicating between the master cylinder and the brake cylinder of the wheel brake device, a pressure chamber provided between the cut valve and the brake cylinder, and a pressure chamber movably disposed inside the housing. a servo piston that partitions a variable pressure chamber and a low pressure chamber that is constantly in communication with a low pressure source; a hydraulic plunger that opens and closes the cut valve and increases or decreases the volume of the pressure chamber by movement of the servo piston; and the pressure release control signal. a solenoid valve that is switched from a connection position between the transformation chamber and the low pressure source to a connection position between the transformation chamber and the high pressure source in response to the change in pressure; and a spring for biasing the hydraulic plunger, wherein the control unit controls the brake pressure confined between the cut valve and the brake cylinder when the pressure release control signal is generated. a transducer that generates an output signal for the time required to make the pressure zero by the movement of the hydraulic plunger; and a transducer for emitting an output signal for the replaced time, and a time period for which the pressure relief control signal is emitted from the transducer. This is accomplished by an anti-skid device including a limiter that limits transmission beyond the solenoid valve.

To be more specific, in Fig. 1, the horizontal axis is the retraction amount S of the hydraulic plunger, and the vertical axis is the brake pressure P in the brake cylinder.As shown in the pressure characteristic curve obtained experimentally, the brake pressure P is 40Kg/ ^cm2 ,
When the brake pressure P is 60Kg/cm ² and 100Kg/cm ² , the retreat amount S of the hydraulic plunger required to reduce the brake pressure P to zero is approximately 20mm, 30mm, and 36mm, respectively. There is a substantially proportional relationship with the amount of retraction S of the hydraulic plunger required to reduce the pressure to zero. Further, the relationship between the time for transmitting the pressure release control signal to the electromagnetic valve and the amount of retraction S of the hydraulic plunger is also approximately proportional. Therefore, according to the present invention,
Even if the pressure relief control signal continues to be generated beyond the time output from the converter, the limiter prevents the control signal from being transmitted to the solenoid valve, so the moment the brake pressure reaches zero High pressure gas is no longer introduced into the variable pressure chamber, and the servo piston no longer moves back. In this way, the servo piston is prevented from retracting excessively and separating from the hydraulic plunger, or from retracting the hydraulic plunger in a way that creates negative pressure on the brake cylinder side, so that it responds to the brake pressure charge control signal. This makes it possible to immediately increase the brake pressure, thereby preventing an increase in the braking distance.

Hereinafter, details of the present invention will be explained based on illustrated embodiments.

FIG. 2 is a brake circuit diagram including an anti-skid device according to a first embodiment of the present invention. In the figure, an anti-skid device 1 consists of a control unit 2 and an actuator 3. The master cylinder 4 has a known structure, and the brake pedal 5
driven by. A first hydraulic pressure generating chamber (not shown) therein is connected via a pipe 6 to a brake cylinder of a front wheel brake device (not shown). A piping 7 is connected to a second hydraulic pressure generating chamber (not shown) of the master cylinder 4, and the piping is connected to the actuator 3.

A cylinder 9 containing a cut valve 8 is installed in the actuator 3. The cut valve 8 is composed of a sphere 10 and a valve seat 11, and the valve chamber 11 is formed in a protrusion 13 provided on the inner wall of the cylinder hole 12 of the cylinder 9, and the sphere 10 is movably inserted into the cylinder hole 12. and is constantly pressed toward the valve seat 11 by the spring 14. An inlet port 15 of the cylinder 9 is connected to a pipe 7, and an outlet port 16 of the cylinder 9 is connected via a pipe 17 to brake cylinders 20, 21 of brake devices for rear wheels 18, 19. The cut valve 8 moves the sphere 1 in response to the retreat of the hydraulic plunger 22.
0 seats on the valve seat 11, communication between the master cylinder 4 and the brake cylinders 20 and 21 is cut off. Further, a pressure chamber 23 having a variable volume is provided in the cylinder hole 12 on the left side of the cut valve 8 and is in constant communication with the brake cylinders 20 and 21. The right end side of the hydraulic plunger 22 can come into contact with the sphere 10, and the left end side can freely protrude from an opening 24 provided at the left end of the cylinder 9, and comes into contact with a servo piston 25, which will be described later. The hydraulic plunger 22 is movably inserted into the cylinder hole 12 so as to open and close the cut valve 8 and increase/decrease the volume of the pressure chamber 23 by movement of the servo piston 25.

A housing 26 is attached to the outer periphery of the left end of the cylinder 9, and a servo piston 25 is fitted into the housing 26, which divides the inside into two chambers, a variable pressure chamber 27 and a low pressure chamber 28. Servo piston 25 is movable within housing 26 . 2
9 is a sealing member, and the sealing member 29 maintains airtightness between the variable pressure chamber 27 and the low pressure chamber 28. Further, a spring 31 is stretched between the lower surface 30 of the housing 26 and the servo piston 25 in the low pressure chamber 28 . The spring 31 constantly presses the servo piston 25 in the direction of the protrusion 32 of the housing 26 and presses the hydraulic plunger 22 to the right via the servo piston 25. The sealing member 33 fits into a groove provided in the cylinder 9, and maintains airtightness between the variable pressure chamber 27 and the atmosphere surrounding the actuator 3, which is a high pressure source. Further, the sealing member 33' performs liquid-tight sealing between the pressure chamber 23 and the variable pressure chamber 27, and fits into a groove provided in the cylinder 9.

Opening 3 provided on the transformer chamber 27 side of the housing 26
4 is connected to a solenoid valve 36 via a pipe 35. The solenoid valve 36 has a demagnetized position a and an energized position b.
At the degaussing position a, the piping 35 and the piping 37 are connected as shown. The piping 37 is connected to the engine intake manifold 39, which is a low pressure source, via a check valve 38.
is connected to. At the excitation position b, communication between the piping 35 and the piping 37 is cut off, and the piping 35 is connected to the atmosphere, which is a high pressure source.

On the other hand, an opening 40 provided on the low pressure chamber 28 side of the housing 26 is connected to a pipe 37 via a pipe 41 (although the intermediate route is omitted in the figure), and the low pressure chamber 28 is always in communication with the intake manifold 39.

The control unit 2 has the following configuration. That is, 42 is a pressure gauge, and the pressure gauge 42
is provided in the pipe 17, and is connected to the brake cylinder 2.
The brake pressure P within 0.21 is measured and a voltage V proportional to the brake pressure P is constantly output. 4
3 is a memory device, and the memory device 43 is connected to the arithmetic circuit 4.
When the pressure release control signal Y from 4 is output,
The output voltage V ₁ of the pressure gauge 42 is stored and output at any time. Although not shown, the calculation circuit 44 is connected to a wheel speed detector provided near the rear wheels 18 and 19, calculates wheel rotation speed, wheel deceleration, wheel slip rate, etc., and calculates the wheel deceleration, wheel slip rate, etc. etc. exceeds a predetermined reference value, a pressure relief control signal Y is output. 45 is a converter, and the converter 4
5 generates an output 1 for a predetermined time T set according to the magnitude of the output voltage V ₁ from the time when the pressure relief control signal Y is input. This set value T is the time required to retreat the hydraulic plunger 22 in order to reduce the brake pressure P to zero when the pressure release control signal Y is generated, and for example, when the anti-skid device 1 is installed. This is determined depending on the type of vehicle and the experimental results shown in Figure 1.
The AND circuit 46 has one input terminal connected to the output terminal of the converter 45, the other input terminal connected to the output terminal of the arithmetic circuit 44, and a set value T output by the converter 45.
It acts as a limiter to restrict the pressure relief control signal Y from the arithmetic circuit 44 from being transmitted to the solenoid valve beyond the time period of . The output terminal of the AND circuit 46 is
Connected to one end of the OR circuit 47, and also connected to one end of the NOT circuit 4.
8 to one input end of the AND circuit 49. Further, the other input terminal of the AND circuit 49 is connected to the output terminal of the arithmetic circuit 44 . Reference numeral 50 denotes a pulse generating circuit, and the pulse generating circuit 50 outputs 0 while the input is 0, and repeats outputs of 1 and 0 in short cycles while the input is 1. The output terminal of this pulse generating circuit 50 is connected to the other input terminal of the OR circuit 47. The output end of the OR circuit 47 is connected to a current amplifier 51. the output end of the current amplifier 51;
That is, the output end of the control unit 2 is connected to the solenoid valve 3.
6 solenoid 52. Depending on whether the output of the OR circuit 47 is 0 or 1, in other words, depending on whether the energization to the solenoid 52 is interrupted
6, it can be switched between a demagnetized position a and an excitation position b.

Next, the operation of the anti-skid device 1 according to the first embodiment will be explained.

FIG. 2 shows the anti-skid device 1 in its inoperative state. That is, the output of the arithmetic circuit 44 is 0, the outputs of the AND circuit 46, the AND circuit 49, the pulse generation circuit 50, the OR circuit 47, and the current amplifier 51 are all 0, and the solenoid valve 36 is in the demagnetized position a. For this reason, the variable pressure chamber 27 and the low pressure chamber 28 are both connected to an intake manifold 39 through pipes 35 and 41, respectively. Therefore, the servo piston 25 is pushed against the housing 2 by the biasing force of the spring 31.
6, the hydraulic plunger 22 advances to open the cut valve 8, thereby communicating the master cylinder 4 with the brake cylinders 20, 21 of the wheel brake devices for the rear wheels 18, 19.

First, we will discuss the case where the driver applies the brakes while the vehicle is traveling on a high friction road surface such as a dry asphalt road surface.

When applying brakes with relatively low hydraulic pressure,
The wheel shows no tendency to lock, the solenoid valve 36 is in the degaussed position a shown, the cut valve 8 is in the open state, while the pipe 7, the inlet port 15 of the cylinder 9, the outlet port 16 and the pipe 17 are sequentially passed through. The brake pressure fluid is transmitted to the brake cylinders 20, 21 of the rear wheels 18, 19, and on the other hand, the brake pressure fluid is transmitted to the front wheel side brake cylinder via the piping 6, thereby applying the brakes.

If you apply brakes with fairly high hydraulic pressure,
Since the wheels 18, 19 exhibit a locking tendency, the arithmetic circuit 44 of the control unit 2 generates a pressure relief control signal Y and transmits this control signal Y to the memory 43. Therefore, when the pressure release control signal Y is generated, the memory 43, which until then had always inputted the instantaneous brake pressure P in the brake cylinders 20, 21 using the pressure gauge 42 but did not output any output, A voltage V ₁ proportional to the brake pressure P is stored and output. In response to this output voltage V ₁ , the converter 45 continuously generates an output 1 for a predetermined time T that is preset according to the magnitude of the voltage V ₁ from the time when the pressure relief control signal Y is generated. do.
Since both of its two inputs are 1, the AND circuit 46 outputs 1, and the OR circuit 47 also outputs 1.
Incidentally, when the AND circuit 46 is outputting 1,
The outputs of AND circuit 49 and pulse generation circuit 50 are both 0.

Current amplifier 51 receives output 1 of OR circuit 47
The solenoid 52 of the solenoid valve 36 is energized and excited via the solenoid 52 of the solenoid valve 36. Therefore, the solenoid valve 36 is switched to the excitation position b, the communication between the variable pressure chamber 27 and the intake manifold 39 is cut off, and the atmosphere is introduced into the variable pressure chamber 27. Then, the pressure in the variable pressure chamber 27 becomes higher than the pressure in the low pressure chamber 28, and the servo piston 25 retreats to the left against the biasing force of the spring 31. As the piston 25 retreats, the hydraulic plunger 22 receiving hydraulic pressure from the master cylinder 4 also retreats, and the cut valve 8 is shut off. Thereafter, when the atmosphere is further introduced into the variable pressure chamber 27, the servo piston 25 and the hydraulic plunger 22 are further retreated, and the volume of the pressure chamber 23 is increased. Therefore, the brake fluid pressure supplied to the brake cylinders 20, 21 is reduced, the rotation of the wheels 18, 19 is restored, and locking is prevented. Thereafter, the arithmetic circuit 44 eliminates the pressure relief control signal Y. This disappearance of pressure relief control signal Y occurs before the time when the output of transducer 45 switches to zero. This is because the tires receive a large amount of resistance from the road surface because the vehicle is running on a high-friction road surface, and the rotation of the wheels recovers before the brake pressure P is reduced to zero. Therefore, the AND circuit 49
And the output of the pulse generating circuit 50 remains at 0. When the control signal Y disappears, the solenoid valve 36 is switched to the demagnetized position a by the spring force. As a result, the pressure in the variable pressure chamber 27 decreases again to the pressure in the intake manifold 39, the servo piston 25 moves to the right due to the tension of the main spring 31, the volume of the pressure chamber 23 decreases, and the brake fluid pressure decreases. increase From then on,
The above-described brake pressure control such as decreasing and increasing the brake fluid pressure is repeated.

Next, a case will be described in which the brakes are applied while the vehicle is running on a low-friction road surface.

In this case, the vehicle may tend to lock up even when the brakes are applied with relatively low hydraulic pressure.

At this time, the arithmetic circuit 44 outputs the pressure relief control signal Y.
occurs. Then, similar to the brake pressure control when driving on a high-friction road surface described above, the converter 45 continues output 1 for a predetermined time T set in accordance with the magnitude of the brake pressure P when the control signal Y is generated. The brake pressure P is reduced to zero by switching the solenoid valve 36 to position b to reliably prevent the wheels 18 and 19 from locking.

However, when the vehicle travels on this low-friction road surface, the pressure release control signal Y continues to be generated for a long time. For this reason,
After the hydraulic plunger 22 shuts off the cut valve 8,
It retreats together with the servo piston 25 until the hydraulic pressure in the brake cylinders 20, 21 drops to zero. After that, the pressure release control signal Y continues to be generated, but when the brake pressure P becomes zero and the hydraulic plunger 22 stops moving backward, the output of the converter 45 switches to 0, and the output of the AND circuit 46 becomes 0. Therefore, the output of the NOT circuit 48 and the arithmetic circuit 4
Both outputs of 4 become 1, and the pulse generating circuit 50 is activated to repeat outputs of 1 and 0 in short cycles.
Therefore, the output of the OR circuit 47 is repeated as 1 and 0, and this output is transmitted to the solenoid 52 via the current amplifier 51. As a result, the solenoid valve 36 is switched between the energized position b and the demagnetized position a even in short periods, and the pressure transformation chamber 27 becomes high pressure and low pressure every short period. Therefore, the servo piston 25 repeats minute retreat and minute advance, and the servo piston 25 approaches the hydraulic plunger 22.

After that, when the rotation of wheels 18 and 19 is restored,
The arithmetic circuit 44 eliminates the pressure relief control signal Y.
Then, the two inputs of the AND circuit 49 become 0, and the outputs of the AND circuit 49, pulse generation circuit 50, OR circuit 47, and current amplifier 51 become 0.
Therefore, the solenoid valve 36 is switched to the demagnetizing position a. Therefore, the variable pressure chamber 27 communicates with the intake manifold 39, the pressure within the variable pressure chamber 27 decreases, and the servo piston 25 moves forward to the right due to the tension of the spring 31. At this time, the hydraulic plunger 22 is immediately moved to the right by the servo piston 25 because the energization to the solenoid valve 36 has been intermittent in short cycles to keep the servo piston 25 within a minute fluctuation and suppress overstroke. is pushed forward. As a result, the volume inside the pressure chamber 23 quickly decreases,
Brake pressure P increases quickly.

Thereafter, the above-described brake pressure control is repeated every time the pressure release control signal Y occurs or disappears.

After repeating a series of brake pressure controls on a high-friction road surface or a low-friction road surface, when the driver stops depressing the brake pedal 5 due to reasons such as the vehicle stopping or decreasing to an appropriate traveling speed, the main spring 31 Due to the force, the hydraulic plunger 22 and the servo piston 25 move further to the right, the cut valve 8 is opened, and the master cylinder 4 and the brake cylinders 20 and 21 communicate with each other. Therefore, the brake pressure fluid that has been supplied to the brake cylinders 20 and 21 is returned to the master cylinder 4 side, and the brake is released.

In this way, in the anti-skid device according to this embodiment, the solenoid valve 36 is activated in response to the pressure relief control signal Y.
The time during which is energized and switched to excitation position b is
The pressure P in the brake cylinders 20 and 21 is reduced so as not to exceed a predetermined time T necessary for reducing the brake pressure P to zero when the pressure release control signal Y is generated, and If the control signal Y is still being generated even after time T has elapsed, the pulse generating circuit 50 is activated to turn on and off the energization to the solenoid valve 36 at short intervals, thereby moving the servo piston 25 close to the hydraulic plunger 22. Therefore, overstroke of the servo piston 25 can be suppressed, necessary brake pressure can be quickly obtained, and the braking distance does not increase.

Next, an anti-skid device according to a second embodiment of the present invention will be described with reference to FIG.

In FIG. 3, parts corresponding to those in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the first embodiment in that brake pressure holding control is possible.

That is, the actuator 3' is provided with a solenoid valve 53 in addition to the solenoid valve 36. This solenoid valve 53
has a demagnetized position C and an excitation position d. At the degaussing position c, as shown in the figure, the solenoid valve 3 is connected via the piping 54.
6, and is also connected to the intake manifold 39 via piping 55 and check valve 38. At the excitation position d, communication between the piping 54 and the piping 55 is cut off.

In addition, in the control unit 2',
The output terminal of the AND circuit 46 is directly connected to the input terminal of the current amplifier 51, and the pressure release control signal Y output terminal and the pressure holding control signal H output terminal of the arithmetic circuit 44 are respectively connected to the input terminal of the OR circuit 56. The output terminal of the OR circuit 56 is connected to the front current amplifier 5.
It is connected to the solenoid 58 of the electromagnetic valve 53 via 7.

Depending on whether the output of the OR circuit is 0 or 1, that is, depending on whether or not energization to the solenoid 58 is cut off, the solenoid valve 53 can be switched between a demagnetized position c and an excitation position d.

Therefore, brake pressure control by brake operation when driving on a low-friction road surface will be described below.

When pressure release control signal Y occurs, OR circuit 5
6 becomes 1, the solenoid 58 is energized via the current amplifier 57, the solenoid valve 53 is switched to the energized position d, and communication between the pipes 54 and 55 is cut off. Further, the memory device 43 stores and outputs a voltage V ₁ proportional to the brake pressure P when the control device Y generates the voltage V 1 , and the converter 45 outputs the voltage V ₁
The output 1 is continuously generated for a predetermined time T set in advance according to the magnitude of the output. Therefore, at the same time that the control signal Y is generated, the output of the AND circuit 46 becomes 1.
Therefore, the solenoid valve 36 is switched to the excitation position b via the current amplifier 51. Therefore, the atmosphere is introduced into the variable pressure chamber 27, the hydraulic plunger 22 shuts off the cut valve 8, and moves back further to the left together with the servo piston 25.

In this case, while the pressure release control signal Y continues to be generated for a long period of time, the brake pressure P in the brake cylinders 20, 21 becomes zero due to the retreat of the hydraulic plunger 22, and when the hydraulic plunger 22 stops retreating, the corresponding A predetermined time T after the control signal Y is generated
lapses, the output of the converter 45 becomes 0. Therefore, the output of the AND circuit 46 becomes 0, the solenoid 52 of the solenoid valve 36 is demagnetized, and the solenoid 52 of the solenoid valve 36 is demagnetized.
is switched to position a. On the other hand, since the arithmetic circuit 44 is still generating the pressure relief control signal Y,
The solenoid 58 is excited via the OR circuit 56 and the current amplifier 57, and the solenoid valve 53 is in the d position.
Therefore, when the predetermined time T for reducing the brake pressure P to zero has elapsed while the pressure release control signal Y is being generated, the variable pressure chamber 27 is closed to the atmosphere and the intake manifold 3.
9, and the servo piston 25 remains in contact with the hydraulic plunger 22.

Thereafter, when the rotation of the wheels 18 and 19 is restored and the pressure release control signal Y from the arithmetic circuit 44 disappears, the solenoid valve 53 is switched to the degaussing position C, and the atmosphere in the pressure conversion chamber 27 is forced into the intake manifold 39. Inhaled. The servo piston 25 is pushed rightward by the spring 31 and moves forward. At this time, since the hydraulic plunger 22 is in contact with the servo piston 25, it moves forward immediately, the volume inside the pressure chamber 23 decreases, and the brake pressure P immediately increases.

After that, the pressure holding control signal H is sent from the arithmetic circuit 44.
When this occurs, the solenoid 58 is energized via the OR circuit 56 and the current amplifier 57, the solenoid valve 53 is switched to the energized position d, and the connection between the transformation chamber 27 and the intake manifold 39 is cut off. 25 is stopped in the right direction, the volume of the pressure chamber 23 becomes constant, and the brake pressure P becomes constant.

Thereafter, when the pressure holding control signal H disappears, the variable pressure chamber 27 is connected to the intake manifold 39 again, and the brake pressure P increases. Thereafter, when the pressure holding control signal H is generated again, the brake pressure P becomes constant. In this way, when the brake pressure P increases step by step and the pressure release control signal Y is generated again,
For a time T set according to the magnitude of the brake pressure P when the control signal Y is generated,
sets the output to 1, and the brake pressure P decreases in the same way as described above.

Thereafter, the above-described brake pressure control process is repeated.

In this way, in the anti-skid device according to the second embodiment, in response to the pressure release control signal Y, the solenoid valve 3
6 is energized and switched to the excitation position b so that it does not exceed a predetermined time T necessary to bring the brake pressure P to zero when the pressure release control signal Y is generated, Brake cylinder 20,2
1, and if the control signal Y is still generated after the elapse of the time T, the attached solenoid valve 53 is switched to the excitation position d, thereby communicating the pressure change chamber 27 and the intake manifold 39. Therefore, the servo piston 25 and the hydraulic plunger 22 remain in contact with each other and stand still when the brake pressure P is zero. Therefore, there is no overstroke of the servo piston 25, the necessary brake pressure can be quickly obtained, and the braking distance is not increased.
Further, since the servo piston 25 is stationary, the hydraulic plunger 22 does not even make slight fluctuations, and there is no pulse pressure to the brake cylinders 20, 21 at all, so that there is no adverse effect on brake pressure control.

The present invention is not limited to the two embodiments described above, but can be modified based on the technical idea of the present invention.

For example, the hydraulic plunger 22 and the servo piston 25 may be provided integrally.

In addition, the predetermined time T required to bring the brake pressure P to zero when the pressure release control signal Y is generated.
is not limited to the value determined based on the characteristic curve shown in the first figure obtained from experimental results, but may be changed depending on the type of vehicle to which the anti-skid device 1 is installed.

Further, the actuator 1 may be provided for each wheel 18, 19 to independently control both wheels 18, 19, or a wheel speed detector and an actuator may be provided on the front wheel side, respectively, to perform four-wheel independent control.

As is clear from the above, the present invention eliminates the brake pressure trapped between the cut valve and the brake cylinder when a pressure release signal is generated by the transformer by moving the hydraulic plunger. The pressure release control signal is replaced with the time required to reach the solenoid valve, and the limiter restricts the pressure relief control signal from being transmitted to the solenoid valve beyond this replaced time, thereby preventing excessive movement of the servo piston. As a result, the pressure can be increased quickly after the brake pressure is released, and an increase in the braking distance can be prevented.

[Brief explanation of drawings]

FIG. 1 is a characteristic curve of the brake pressure in the brake cylinder with respect to the amount of retraction of the hydraulic plunger, and FIGS. 2 and 3 are diagrams showing a first embodiment and a second embodiment of the present invention, respectively. 2, 2'...Control unit, 3, 3'...
...Actuator, 8...Cut valve, 22...
... Hydraulic plunger, 25 ... Servo piston, 2
7...Transformer chamber, 28...Low pressure chamber, 36...Solenoid valve, 42...Pressure gauge, 43...Memory device, 44...
Arithmetic circuit, 45... converter, 46... AND circuit,
50... Pulse generation circuit, 53... Solenoid valve.

Claims (1)

[Claims] 1. A control unit that detects a skid state of a wheel and generates a pressure relief control signal, and an actuator that receives the pressure relief control signal and reduces the brake pressure of the wheel brake device, and the actuator is connected to a master cylinder. a cut valve that blocks a passage communicating between the cut valve and the brake cylinder of the wheel brake device; a pressure chamber provided between the cut valve and the brake cylinder; and a pressure chamber movably arranged inside the housing and constantly communicating with the variable pressure chamber and a low pressure source a servo piston that separates the pressure chamber from the low pressure chamber; a hydraulic plunger that opens and closes the cut valve and increases or decreases the volume of the pressure chamber by movement of the servo piston; a solenoid valve that switches from a connection position with a source to a connection position between the transformation chamber and a high pressure source; and a solenoid valve provided in the low pressure chamber that biases the hydraulic plunger in a direction in which the cut valve opens with the servo piston interposed therebetween. In the anti-skid device having a spring, the control unit is configured to reduce the brake pressure trapped between the cut valve and the brake cylinder by moving the hydraulic plunger when the pressure release control signal is generated. a transducer that emits a replacement output signal for the replacement time required to make the pressure zero, and the pressure relief control signal is transmitted to the solenoid valve beyond the time that the output signal is emitted from the converter. an anti-skid device;