JPH09254759A - Antiskid brake control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce consumption of brake liquid at ABS control, improve responsiveness for fall of MCY pressure (master cylinder pressure), simplify a system, and furthermore reduce cost. SOLUTION: When wheels have a tendeny to be locked, respective hold valves 10, 12, 14, 16 are closed so as to hold brake liquid pressure of respective wheel cylinders 6, 7, 8, 9. Simultaneously a second opening/closing valve 41 is closed and a third opening/closing valve 42 is opened, and MCY pressure is lowered due to outflow to a large diameter chamber 41. Further the hold valve of a wheel having a tendency to be locked is opened, the brake liquid is discharged to the liquid chamber 4b of the MCY 4 and the large diameter chamber 41, and the brake liquid pressure is reduced. At pressure increase of ABS, the second opening/closing valve is opened and the third opening/closing valve 42 is closed, and the MCY pressure is raised by output of a brake booster 3. Only at this time brake liquid is exhausted to a reservoir 5, and hence the consumption is small. Further, because output of the booster 3 is controlled by control of an electromagnetic selector valve 23, the ABS control is effectively performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an anti-skid brake control system (hereinafter, also referred to as ABS) in a hydraulic brake system for automobiles, etc. It belongs to the technical field of a pumpless ABS that does not have a pump for returning to the wheel cylinder when pressure is increased.

[0002]

2. Description of the Related Art When a vehicle is braked, the braking wheels may be locked, resulting in unstable steering and a long braking distance. For this reason, anti-skid control (hereinafter Various ABSs that perform (also referred to as ABS control) have been proposed. When this ABS detects that the wheels tend to lock during braking, the braking force of the wheels is weakened to eliminate the locking tendency, and then the braking force is increased again to stabilize the steering of the vehicle. The brake control is performed so that the braking distance is as short as possible.

By the way, in the ABS applied to the hydraulic brake system, when the wheel lock tendency is detected, a part of the brake fluid in the brake cylinder is discharged to the sump to reduce the brake fluid pressure and the wheel is recovered. The pump supplies the brake fluid from the sump to the brake cylinder again to reincrease the brake fluid pressure. However, the ABS using such a pump not only has a complicated structure but also uses an expensive pump.
Inevitably, the entire system is expensive.

Therefore, a pump-less ABS that does not use a pump has been conventionally proposed. FIG. 7 is a diagram schematically showing such a pumpless ABS. In the figure, 1 is ABS, 2 is a brake pedal, 3 is a brake booster composed of a negative pressure booster, 4 is a tandem master cylinder, 5 is a reservoir of the master cylinder 4, and 6 to 9 are front, rear, left and right brakes respectively. The first to fourth wheel cylinders 10, 10 are first normally-open holding valves that are electromagnetic valves arranged in the passage between the master cylinder 4 and the first wheel cylinder 6, and 11 is the first holding valve 10. A first check valve that is arranged in parallel with the first wheel cylinder 6 and allows only the flow of brake fluid from the first wheel cylinder 6 toward the master cylinder 4;
Reference numeral 12 is a normally open second holding valve composed of an electromagnetic valve arranged in a passage between the master cylinder 4 and the second wheel cylinder 7, and 13 is a second wheel cylinder arranged in parallel with the second holding valve 12. A second check valve that allows only the flow of the brake fluid from 7 to the master cylinder 4, and a normally open third check valve 14 that is an electromagnetic valve disposed in the passage between the master cylinder 4 and the third wheel cylinder 8. The holding valve, 15 is arranged in parallel with the third holding valve 14, and the third wheel cylinder 8 is provided.
From the master cylinder 4 to the master cylinder 4, the third check valve 16 allows the master cylinder 4 to flow.
And a fourth wheel cylinder 9, a normally open fourth holding valve consisting of a solenoid valve, 17 is a fourth holding valve 16
A fourth valve that is arranged in parallel with the fourth wheel cylinder 9 and allows only the flow of the brake fluid from the fourth wheel cylinder 9 toward the master cylinder 4.
A check valve, 18 is a normally closed first pressure reducing valve which is an electromagnetic valve disposed in a passage between the first wheel cylinder 6 and the reservoir 5 of the master cylinder 4, and 19 is a second wheel cylinder 7 and the reservoir 5. Normally closed second pressure reducing valve formed of a solenoid valve disposed in the passage between the third wheel cylinder 8 and the reservoir 5, and normally closed third pressure reduction valve formed of a solenoid valve disposed in the passage between the third wheel cylinder 8 and the reservoir 5. Pressure reducing valve, 21 is the fourth wheel cylinder 9
Normally closed fourth pressure reducing valve composed of a solenoid valve disposed in the passage between the reservoir 5 and the reservoir 5, 22 is a negative pressure source, 23 is an atmosphere supply to the brake booster 3, and a negative pressure supply of the negative pressure source 22. It is an electromagnetic switching valve including an electromagnetic valve for switching control. Each electromagnetic switching valve 6, 7, 8, 9, 10, 12, 14, 16, 23 is connected to an electronic control unit (not shown) for ABS control,
When the electronic control unit detects the lock tendency of the wheels based on the wheel speed from a wheel speed sensor (not shown), the electronic control unit performs switching control.

FIG. 8 is a sectional view of a negative pressure booster which constitutes the brake booster 3. In the figure, 24 is an input shaft, 25 is a valve plunger, 26 is a valve body, 27 is a front shell, 28 is a rear shell, 29 is a power piston member and a diaphragm, and the space formed by both shells 27 and 28 is two chambers. The power piston 30 is connected to the negative pressure source 22 in the normal state by the electromagnetic switching valve 23, and is connected to the atmosphere when necessary. The first chamber 31 is introduced with a predetermined negative pressure when not operating. Atmosphere is introduced at the time of brake operation, and when necessary, the second chamber is connected to the negative pressure source 22 by the electromagnetic switching valve 23. The second chamber 32 selectively switches the second chamber to the first chamber or the electromagnetic switching valve 23. Switching control valve, 33 is a valve body of the switching control valve 32, 34 is a first valve seat of the switching control valve 32 provided in the valve plunger 25, and 35 is a second valve of the switching control valve 32 provided in the valve body 26. seat, 36 is a first passage connecting the second chamber 31 and the switching control valve 32, 37
Is a second passage connecting the first chamber 30 and the switching control valve 32,
38 is an output shaft, 39 is a reaction disc, and 40 is a return spring.

In this ABS 1, as shown in FIG. 7, when the brake is not operated, the first to fourth holding valves 10, 12,
14, 16 are respectively set to the communication position I, the first to fourth pressure reducing valves 18, 19, 20, 21 are set to the shut-off position I, respectively, and the electromagnetic switching valve 23 is set to the first chamber 30 of the brake booster 3. Connected to the negative pressure source 22 and the second chamber 31
Is set to a first position I for connecting to the atmosphere, and the switching control valve 32 has a valve body 33 seated on a first valve seat 34 and slightly separated from a second valve seat 35 as shown in FIG. . Therefore, the negative pressure from the negative pressure source 22 is introduced into the first chamber 30 through the electromagnetic switching valve 23, and further the second passage 3
7, and is introduced into the second chamber 31 through the gap between the valve element 33 and the second valve seat 35 and the first passage 36.

When the brake pedal 2 is depressed to normally apply the brake, the input shaft 24 and the valve plunger 25 move forward, the valve body 33 is seated on the second valve seat 35, and then the first valve seat 34 is closed. Move away from 33. As a result, the atmosphere is introduced into the second chamber through the electromagnetic switching valve 23, the gap between the first valve seat 34 and the valve body 33, and the first passage 36.
Then, a pressure difference occurs between the second chamber 31 and the first chamber 30, the power piston 29 operates due to this pressure difference, and the brake booster 3 causes the output shaft 3 via the valve body 26.
8 to output. The master cylinder 4 operates by the output of the brake booster 3 to generate a master cylinder pressure (hereinafter, also referred to as MCY pressure), and the MCY pressure causes the first to fourth holding valves 10, 12, 14, 16 respectively. It is supplied as brake fluid pressure to the first to fourth wheel cylinders 6, 7, 8 and 9 through which the normal brake operates.

When the brake pedal 2 is released, the input shaft 24 and the valve plunger 25 are retracted, the first valve seat 34 is seated on the valve body 33, and the valve body 33 is separated from the second valve seat 35. As a result, the air in the second chamber 31 is allowed to flow through the first passage 3
6, the gap between the first valve seat 34 and the valve body 33, the second passage 3
7, the first chamber 30, and the electromagnetic switching valve 23 to pass the negative pressure source 2
2 and the negative pressure is introduced into both the first and second chambers 30 and 31. Therefore, the second chamber 31 and the first chamber 30
The pressure difference between and disappears, and the valve body 26, the power piston 29, and the output shaft 38 are all retracted by the spring force of the return spring 40, returning to the initial non-actuated position shown in FIG. Therefore, the MCY pressure of the master cylinder 4 and the brake fluid pressure (hereinafter, also referred to as WCY pressure) of the first to fourth brake cylinders 6, 7, 8 and 9 disappears, and the normal brake is released.

During normal braking, when the electronic control unit determines that at least one of the wheels tends to lock due to the wheel speed from a wheel speed sensor (not shown), the first to fourth holding valves 10, 12, 14, 16 are provided. To shut off position II. As a result, the WCY pressures of the first to fourth wheel cylinders 6, 7, 8 and 9 do not increase any more and are in the holding state. At the same time, the electromagnetic switching valve 23 is also switched to the second position II so that the atmosphere is introduced into the first chamber 30 and the air in the second chamber 31 is discharged to the negative pressure source 22 so that the pressure difference between the chambers 30 and 31 is reduced. Get smaller. As a result, the output of the brake booster 3 is reduced, so that the MCY pressure of the master cylinder 4 is reduced.

First to fourth wheel cylinders 6, 7,
Even if the WCY pressures of 8 and 9 are held, the first to fourth pressure reducing valves 18, 19, 20 are applied to the wheels for which it has been determined that the lock tendency has not been resolved and the WCY pressure needs to be reduced.
The pressure reducing valve corresponding to the wheel of 21 is switched to the communication position II. As a result, the WCY pressure of the corresponding wheel cylinder among the first to fourth wheel cylinders 6, 7, 8 and 9 is reduced. When it is determined that the wheel lock tendency has been eliminated, the pressure reducing valve switched to the communication position II is switched to the shutoff position I, the holding valve corresponding to the wheel is switched to the communication position I, and the electromagnetic switching valve 23 is switched to the first position I. As a result, the MCY pressure of the master cylinder 4 is supplied to the wheel cylinder corresponding to that wheel, and the WCY pressure of that wheel cylinder is increased. When it is determined that the wheel becomes the lock tendency again, the WCY pressure of the wheel cylinder is maintained by controlling the holding valve of the wheel, the pressure reducing valve of the wheel and the electromagnetic switching valve 23 as described above. Depressurization and pressure increase are controlled. In this way, the ABS control is performed on the wheel determined to have the lock tendency.

When it is judged that the locking tendency of the wheels has been completely eliminated, the ABS control is released, and the holding valves of the remaining wheels are also switched to the communication position I so that the respective wheel cylinders 6, 7, 8 are released. , 9 are canceled. As a result, the MCY pressure is applied to each wheel cylinder 6, 7,
8 and 9, the WCY pressure is increased.

The first to fourth check valves 1
1, 13, 15, 17 are wheel cylinders 6, 7, 8, 9 when the brake pedal 2 is released during ABS control.
Is for immediately releasing the WCY pressure of the above into the master cylinder 4.

[0013]

However, in such a pumpless ABS, the brake fluid of the wheel cylinder is discharged to the reservoir 5 of the master cylinder 4 through the pressure reducing valve when the pressure is reduced in the ABS control. The discharged brake fluid must be supplemented with brake fluid from the master cylinder 4. For this reason, the brake fluid in the master cylinder 4 is consumed, and the brake pedal 2 makes an extra stroke during ABS control, resulting in poor operation feeling of the brake pedal 2.

Therefore, it is conceivable to increase the capacity of the master cylinder 4 to suppress the extra stroke of the brake pedal 2 in anticipation of the consumption of the brake fluid during the ABS control. However, if the capacity is increased, the master is inevitably used. Cylinder 4
There is a problem that the size becomes large.

Further, since the MCY pressure is reduced only by reducing the output of the brake booster 3 by switching the electromagnetic switching valve 23 during the ABS control, the reduction of the MCY pressure is delayed. Therefore, the WCY pressure of the wheel cylinder may be rapidly increased when the ABS control is increased, and the wheel may tend to be locked again at an early stage, which makes it difficult to properly perform the ABS control.

Furthermore, in the above-mentioned ABS, it is necessary to provide eight electromagnetic on-off valves, four check valves, and a discharge passage from each wheel cylinder to the reservoir, so that not only the system is complicated but also the system is complicated. , The cost is high.

The present invention has been made in view of the above problems, and an object thereof is to reduce the consumption of brake fluid during ABS control as much as possible without increasing the capacity of the master cylinder. An object of the present invention is to provide an anti-skid brake control system capable of suppressing an extra stroke and improving the response of a decrease in master cylinder pressure. Another object of the present invention is to provide an anti-skid brake control system capable of simplifying the system and further reducing the cost.

[0018]

In order to solve the above-mentioned problems, the invention of claim 1 provides a brake operating means and a switching control valve operated by the operation of the brake operating means to supply a pressure working fluid. The brake booster for boosting and outputting the operating force of the brake operating means, and the master cylinder for operating the master cylinder piston by the output of the brake booster to generate the master cylinder pressure in the liquid chamber. A reservoir that stores the brake fluid of the master cylinder, a brake cylinder that generates the braking force of the wheels by supplying the master cylinder pressure as the brake fluid pressure, and a larger diameter than the master cylinder piston. A large-diameter piston that receives the output of the brake booster, a large-diameter chamber defined by the large-diameter piston, and A first opening / closing valve that is provided in a passage that connects the liquid chamber of the cylinder and the brake cylinder and that is formed of a solenoid valve having a communication position and a cutoff position and is set to a normal communication position; A second opening / closing valve that is provided in a passage that connects the liquid chamber and the large-diameter chamber, and includes an electromagnetic valve that has a shut-off position and a communication position and that is set to a normally shut-off position; and the reservoir of the master cylinder. A third opening / closing valve which is provided in a passage connecting to the large-diameter chamber and is formed of an electromagnetic valve having a communication position and a shut-off position and which is set to a normal communication position; and the first to third opening / closing valves. An electronic control device for controlling, wherein the electronic control device performs anti-skid brake control by controlling the first to third opening / closing valves when it is determined that the wheels tend to lock. It is.

The invention according to claim 2 further comprises an electromagnetic switching valve comprising an electromagnetic valve for controlling the supply / discharge of the pressure working fluid to / from the brake booster, wherein the electronic control device is the anti-skid brake. At the time of control, the electromagnetic switching valve is switched and controlled to control the output of the brake booster.

Further, in the invention of claim 3, the operation force of the brake operating means is boosted by the operation of the brake operating means and the operation of the brake operating means actuating the switching control valve to supply the pressure working fluid. And a brake booster that outputs the brake, a master cylinder that generates a master cylinder pressure in the liquid chamber by operating the master cylinder piston by the output of the brake booster, a reservoir that is held at atmospheric pressure, and the master cylinder. Pressure is supplied as brake fluid pressure to generate a wheel braking force, a large-diameter piston formed to have a larger diameter than the master cylinder piston and receiving the output of the brake booster, and the large-diameter piston. A large chamber defined by a piston and the brake cylinder during decompression control in anti-skid brake control. Is provided in a passage connecting the first pressure reservoir, which stores a brake fluid discharged from the master cylinder to a set pressure, and the fluid chamber of the master cylinder, and the brake cylinder, and connects a communication position and a blocking position. A solenoid valve provided in a passage connecting the brake cylinder and the first pressure reservoir, the solenoid valve having a first opening / closing valve that is set to a communication position at a normal time, and a solenoid valve having a cutoff position and a communication position; A second opening / closing valve set to the normal shut-off position, and a solenoid valve provided in the passage connecting the large diameter chamber and the reservoir and having a communicating position and a shut-off position. A third check valve, a first check valve provided in parallel with the third check valve and allowing only the flow of the brake fluid from the reservoir toward the large diameter chamber, and the first check valve. A second check valve provided in a passage connecting the pressure reservoir and the liquid chamber of the master cylinder, which allows only the flow of the brake fluid from the first pressure reservoir toward the liquid chamber, and the master cylinder. A fourth opening / closing provided in a passage that connects the liquid chamber and the large-diameter chamber, is composed of an electromagnetic valve having a shutoff position and a communication position, is set to a normally shutoff position, and is controlled by the electronic control unit. A valve and an electronic control unit for controlling the first to fourth opening / closing valves, and the electronic control unit controls the first to third opening / closing valves when it is determined that the wheels tend to lock. The feature of this is that anti-skid brake control is performed.

[0021] According to a fourth aspect of the present invention, the brake operating means and the switching control valve are operated by the operation of the brake operating means to supply the pressure working fluid, whereby the brake operating means is operated by the pressure working fluid. A brake booster that boosts the force and outputs it, a master cylinder that generates a master cylinder pressure in the liquid chamber by the master cylinder piston operating by the output of this brake booster, and a reservoir that is held at atmospheric pressure. , A first setting by storing the brake fluid discharged from the brake cylinder at the time of pressure reduction control in anti-skid brake control, and a brake cylinder that generates the braking force of the wheels by supplying the master cylinder pressure as brake fluid pressure Pressure reservoir for accumulating pressure, the liquid chamber of the master cylinder, and the blur. A first opening / closing valve, which is provided in a passage connecting to the cylinder and has a communication position and a shut-off position, and which is set to a normal communication position, connects the brake cylinder to the first pressure reservoir. A second opening / closing valve which is provided in the passage and is set to a normally closed position, and which comprises an electromagnetic valve having a blocking position and a communication position, and a first opening / closing valve and the first pressure reservoir. A second fluid lower than the first set pressure is connected to the connection passage and stores the brake fluid discharged from the brake cylinder during the pressure reduction control in the anti-skid brake control.
A second pressure reservoir accumulating at a set pressure, and a pressure reservoir switching valve that controls opening and closing of a second connection passage that connects the second pressure reservoir to the first connection passage based on at least the pressure of the brake cylinder. , Provided in a passage that connects the first and second pressure reservoirs to the liquid chamber of the master cylinder, and allows only the flow of brake fluid from the first and second pressure reservoirs toward the liquid chamber. The first check valve and the brake fluid that is provided on the first pressure reservoir side of the first connection passage from the second connection passage connection position and flows from the second opening / closing valve toward the first pressure reservoir. A second check valve that allows only a flow, and a passage that connects the first and second pressure reservoirs with the liquid chamber of the master cylinder are provided with the first and second check valves. A third check valve provided in a passage between the force reservoirs and allowing only a flow of the brake fluid from the second pressure reservoir toward the first pressure reservoir, and controlling the first and second opening / closing valves And an electronic control unit for controlling the first and second on-off valves when it is determined that the wheels are in a locking tendency. The electronic control unit performs anti-skid brake control. .

Further, according to the invention of claim 5, the operation force of the brake operating means is boosted by the operation of the brake operating means and the operation of the brake operating means actuating the switching control valve to supply the pressure working fluid. And a brake booster that outputs the brake, a master cylinder that generates a master cylinder pressure in the liquid chamber by operating the master cylinder piston by the output of the brake booster, a reservoir that is held at atmospheric pressure, and the master cylinder. Pressure is supplied as brake fluid pressure to generate a wheel braking force, a large-diameter piston formed to have a larger diameter than the master cylinder piston and receiving the output of the brake booster, and the large-diameter piston. A large chamber defined by a piston and the brake cylinder during decompression control in anti-skid brake control. Is provided in a passage connecting the first pressure reservoir that stores the brake fluid discharged from the first set pressure to the first set pressure, the fluid chamber of the master cylinder, and the brake cylinder, and the communication position and the cutoff position. A first opening / closing valve which is formed of a solenoid valve having a normal position and is set in a communication position at the normal time; and an electromagnetic valve which is provided in a passage connecting the brake cylinder and the first pressure reservoir and has a cutoff position and a communication position. A second opening / closing valve which is formed of a valve and is set to a normally closed position, the second opening / closing valve and the first opening / closing valve.
Is connected to the first connection passage with the pressure reservoir and stores the brake fluid discharged from the brake cylinder during the pressure reduction control in the anti-skid brake control, so that the second set pressure lower than the first set pressure is accumulated. A second pressure reservoir, a pressure reservoir switching valve that controls opening and closing of a second connection passage that connects the second pressure reservoir to the first connection passage based on at least the pressure of the brake cylinder, and the large diameter chamber A third on-off valve which is provided in a passage connecting to the reservoir and which is composed of an electromagnetic valve having a communication position and a cutoff position and which is set to a normal communication position;
A first check valve, which is provided in parallel with the third opening / closing valve and permits only the flow of the brake fluid from the reservoir toward the large diameter chamber, and the first and second pressure reservoirs and the master cylinder. A second check valve provided in a passage connecting to the liquid chamber and allowing only the flow of brake fluid from the first and second pressure reservoirs toward the liquid chamber; and the liquid chamber of the master cylinder. A fourth opening / closing valve which is provided in a passage connecting to the large diameter chamber and which is formed of an electromagnetic valve having a shutoff position and a communication position and which is set to a normally shutoff position; and the first to fourth on / off valves. And an electronic control unit for controlling, wherein the electronic control unit performs anti-skid brake control by controlling the first to third opening / closing valves when it is determined that the wheels tend to lock. It is characterized.

Further, in the invention of claim 6, the pressure reservoir switching valve is acted on one side by the pressure of the brake cylinder and on the other side by the pressure of the brake fluid discharged from the second on-off valve. And a passage opening / closing valve that is controlled by the control piston to control opening / closing of the second connection passage.

According to a seventh aspect of the present invention, the pressure reservoir switching valve has a control piston in which the pressure of the brake cylinder acts on one side and a set spring force of a spring acts on the other side, and the control piston. And a passage opening / closing valve for controlling the opening / closing of the second connection passage.

The invention according to claim 8 further comprises pressure detecting means for detecting the pressure of the brake cylinder, wherein the pressure reservoir switching valve is provided in the second connecting passage and has an electromagnetic shutoff position and a communicating position. The electronic control unit comprises a fifth opening / closing valve which is a valve and is set to a normally closed position, and the electronic control unit is configured to operate the fifth opening / closing valve based on an output signal of the pressure detecting means.
It is characterized by controlling the on-off valve of.

[0026]

In the ABS according to the invention of claim 1 configured as described above, the electronic control unit sets the first and third opening / closing valves to the shut-off position when it determines that the wheels tend to lock. The second on-off valve is set to the communication position. As a result, the brake fluid pressure of the brake cylinder is maintained at the fluid pressure at that time. At the same time, the brake fluid in the fluid chamber of the master cylinder is introduced into the large-diameter chamber, the master cylinder pressure is reduced to be equal to the fluid pressure of the large-diameter chamber, and then the holding state is established. In that case, since both the solenoid valves of the second and third on-off valves are operated, the master cylinder pressure rapidly drops. Therefore, the responsiveness of the system is improved, and
BS control will be performed more appropriately. Also,
At this time, since the hydraulic pressure in the large diameter chamber acts on the large diameter piston,
Since the output of the brake booster is suppressed, the hydraulic pressure in the large diameter chamber, that is, the master cylinder pressure becomes a value lower than the master cylinder pressure generated first.

Further, when the electronic control unit determines that the wheels still tend to lock even if the brake fluid pressure in the brake cylinder is held, the electronic control unit sets the first opening / closing valve to the communicating position to perform the ABS control. As a result, the brake fluid in the brake cylinder corresponding to the wheel that tends to lock is discharged into the fluid chamber and the large-diameter chamber of the master cylinder, and the brake fluid pressure is reduced. At this time, since the brake fluid in the brake cylinder is not directly discharged to the reservoir, the brake fluid is not consumed. When the brake fluid pressure in the brake cylinder becomes equal to the master cylinder pressure and the fluid pressure in the large diameter chamber, the brake fluid pressure is not reduced any further and is held.

When the electronic control unit determines that the wheel lock tendency has been eliminated and the wheel speed has recovered to the predetermined speed, the second control is performed.
And the third opening / closing valve is set to the communication position. As a result, the booster liquid in the large diameter chamber is discharged to the reservoir, so that the output of the booster booster rises and the master cylinder pressure rises. As a result, the brake fluid pressure in the brake cylinder is increased again. At this time, the brake fluid is consumed by the amount introduced from the brake cylinder into the large diameter chamber. However, the consumption amount of the brake fluid is smaller than that when the brake fluid in the brake cylinder is directly discharged to the reservoir when the brake fluid pressure is reduced as in the conventional ABS described above. Therefore, the increase in the stroke of the brake operating means is suppressed,
The operation feeling of the brake operating means is improved. Moreover, when the large-diameter piston returns to the non-actuated position when the brake is released, the large-diameter chamber becomes negative pressure, so that brake fluid is introduced from the reservoir into the large-diameter chamber, further reducing brake fluid consumption. To be done.

Particularly, in the second aspect of the invention, the electronic control unit controls the output of the brake booster by controlling the electromagnetic switching valve during the ABS control. As a result, the master cylinder pressure is reduced more effectively and more quickly when the master cylinder pressure is reduced during ABS control.

Further, in the invention of claim 3, when the ABS control is started when the tendency of the wheel lock is detected,
Although the pressure of the brake cylinder is held as in the invention of 1, the second opening / closing valve is switched to the communication position when the lock tendency is not resolved even if the brake cylinder pressure is held. As a result, the brake fluid in the brake cylinder is discharged to the first pressure reservoir, the brake fluid pressure in the brake cylinder is reduced, and
Is accumulated in the pressure reservoir. When it is determined that the wheel lock tendency has been eliminated, the second opening / closing valve is switched to the shutoff position and the first opening / closing valve is switched to the communication position. As a result, the brake fluid pressure in the brake cylinder is increased. At this time, during the master cylinder pressure increasing control in the ABS pressure increasing control, the fourth on-off valve is alternately and repeatedly controlled between the shut-off position and the communication position. During communication between the large-diameter chamber and the liquid chamber of the master cylinder, the master cylinder pressure is increased by the effective diameter of the large-diameter piston, so that the master cylinder pressure is less increased. Therefore, the master cylinder pressure can be easily controlled, which is favorable. Further, since the control of the brake booster can be deleted during the ABS control, the responsiveness in the ABS control is improved.

Further, in each of the fourth and fifth aspects of the invention, the fourth on-off valve alternates between the shut-off position and the communication position during the master cylinder pressure increase control during the ABS control pressure increase control. Is repeatedly controlled to switch. During communication between the large-diameter chamber and the liquid chamber of the master cylinder, the master cylinder pressure is increased by the effective diameter of the large-diameter piston, so that the master cylinder pressure is less increased. Therefore, it becomes easier to control the master cylinder pressure, which is favorable.

Further, in each of the inventions of claims 4 and 6 to 8, as in the invention of claim 3, when the brake cylinder pressure is held at the time of starting the ABS control, the lock tendency is still not resolved, The second on-off valve is switched to the communication position. At this time, since the pressure of the brake cylinder is large and the pressure reservoir switching valve closes the second connection passage, the brake fluid is discharged to the first pressure reservoir, and the brake fluid pressure of the brake cylinder is reduced. The first pressure reservoir accumulates pressure. When the brake fluid pressure of the brake cylinder becomes lower than the set pressure of the first pressure reservoir, the pressure reservoir switching valve opens the second connection passage, so that the brake fluid is discharged to the second pressure reservoir and the brake fluid of the brake cylinder is released. The pressure is further reduced and the second pressure reservoir accumulates pressure.

When it is judged that the locking tendency of the wheels has been eliminated, the second opening / closing valve is switched to the shut-off position, the first opening / closing valve is switched to the communicating position, and the master cylinder pressure is introduced into the brake cylinder. , The master cylinder pressure is increased. At this time, if it is determined that the master cylinder pressure needs to be controlled, the output of the brake booster is controlled by the electromagnetic switching valve to control the master cylinder pressure. When the master cylinder pressure becomes lower than the set pressure of the first pressure reservoir due to the control of the master cylinder pressure by controlling the electromagnetic switching valve or the reduction of the operation input of the brake operating means, the pressure accumulated in the first pressure reservoir is reduced. Is returned to the liquid chamber of the master cylinder. In the inventions of claims 4 and 6 to 8,
Since the brake fluid stored in the first pressure reservoir during the S control is returned to the master cylinder, the fluid amount loss during the ABS control is reduced.

Further, in the invention of each of claims 5 to 8, the same pressure reduction control as the ABS control in the invention of claim 4 is performed, and the ABS in claim 3 is also performed.
The same master cylinder pressure control as the control master cylinder pressure control is performed. According to the inventions of claims 5 to 8,
Similar to the invention of claim 4, the loss of the amount of brake fluid at the time of ABS control can be reduced, and like the ABS of claim 3, the electromagnetic switching valve can be deleted and the control of the brake booster can be deleted. Responsiveness is improved.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of an embodiment of an anti-skid brake control system according to the present invention. The same components as those of the conventional ABS described above are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, the ABS 1 of this embodiment is a cylinder housing 4a of a tandem master cylinder 4.
In, the large diameter portion 4e having a diameter larger than the diameter of the liquid chamber forming portion 4d forming the liquid chambers 4b and 4c of the master cylinder 4 is provided adjacent to the brake booster 3. A large-diameter piston 4h larger than the diameters of the primary piston 4f and the secondary piston 4g of the master cylinder 4 is slidably fitted in the large-diameter portion 4e. The large-diameter piston 4h is formed integrally with the primary piston 4f, and the output shaft 38 of the brake booster 3 can come into contact with the end portion thereof. The large-diameter piston 4h defines a large-diameter chamber 4i corresponding to the large-diameter chamber of the present invention in the large-diameter portion 4e.

Further, in the passage connecting the large diameter chamber 4i and the reservoir 5, there is provided a normally open second opening / closing valve 41 which is an electromagnetic valve having a communication position I and a shutoff position II. A normally closed third on-off valve 42, which is an electromagnetic valve having a shutoff position I and a communication position II, is provided in a passage connecting the large diameter chamber 4i and the liquid chamber 4b. These second
The third on-off valves 41 and 42 are connected to the electronic control device described above.

By the way, the diameter of the large-diameter chamber 4i has a decompression ability when the MCY pressure is reduced by the brake fluid in the fluid chamber 4b of the master cylinder 4 flowing into the large-diameter chamber 4i at the start of ABS control, as will be described later. When the WCY pressure is maintained after decompression in the ABS control, the electromagnetic switching valve 23 is controlled to increase the output of the brake booster 3 to reduce the M
It is determined by the balance with the return ability when raising the CY pressure to return it to the original level as much as possible.

The other structure of this embodiment is the same as the conventional ABS except that the first to fourth pressure reducing valves 18, 19, 20, 21 in the above-mentioned conventional ABS are omitted. In that case, the first to fourth holding valves 10, 12, 14, 16 constitute a first opening / closing valve of the present invention.

In the ABS of this embodiment constructed as described above, each solenoid valve is set in the state shown in FIG. 1 when it is not operating, and the brake booster 3 is in the non-operating state shown in FIG. . Therefore, the large diameter chamber 4i is
It communicates with the reservoir 5 via the on-off valve 41 and is shut off from the liquid chamber 4b.

When the normal brake is actuated and released by depressing the brake pedal 2, the large-diameter piston 4h moves forward, the brake fluid in the large-diameter chamber 4i is discharged to the reservoir 5, and the large-diameter piston 4h retreats. The ABS is the same as the above-described conventional ABS except that the brake fluid is introduced from the reservoir 5 into the large-diameter chamber 4i.

At least one of the wheels during normal braking
If it is determined that one has a lock tendency, the first to fourth
The holding valves 10, 12, 14, 16 are all switched to the shutoff position II, the first opening / closing valve 41 is switched to the shutoff position II, and the second opening / closing valve 42 is switched to the communication position I. As a result, the first to fourth wheel cylinders 6, 7, 8 and 9 are shut off from both liquid chambers 4b and 4c of the master cylinder 4 and their WCY pressures are maintained. The large diameter chamber 4i is blocked from the reservoir 5 and communicates with the liquid chamber 4b.

Therefore, the brake fluid in the fluid chamber 4b flows into the large-diameter chamber 4i, and the hydraulic pressure in the large-diameter chamber 4i rises.
Of the large chamber 4i decreases until it is balanced with the increasing hydraulic pressure of the large chamber 4i, and the MCY pressure of the liquid chamber 4c also decreases equally to the MCY pressure of the liquid chamber 4b via the secondary piston 4g. At the same time, the electromagnetic switching valve 23 is switched, and the output of the brake booster 3 decreases as in the conventional ABS described above, so the MCY pressure further decreases. In that case, the MCY pressure is rapidly reduced by the switching control of the first and second on-off valves 41, 42, and is also performed by the output reduction of the brake booster 3, so that the responsiveness is the reduction of the output of the brake booster 3. Better than when alone.

First to fourth wheel cylinders 6, 7,
Even if the WCY pressures of 8 and 9 are held, the lock tendency is not resolved yet, and for the wheels determined to require reduction of the WCY pressure, the first to fourth holding valves 10, 12, 14,
The holding valve corresponding to the wheel of 16 is switched to the communication position I. As a result, the brake fluid of the corresponding wheel cylinder among the first to fourth wheel cylinders 6, 7, 8 and 9 is discharged into the fluid chambers 4b and 4c and the large diameter chamber 4i of the master cylinder, and the WCY pressure of that wheel cylinder is reduced. Is decompressed. At this time, since the brake fluid in the wheel cylinder is not discharged to the reservoir 5, the brake fluid is not consumed.

When it is determined that the wheel speed of the wheel which has the tendency to lock has recovered to the predetermined speed, the holding valve of the wheel is also closed again.
Switched to II, and the first to fourth holding valves 10, 12, 1
All 4 and 16 are set to the shut-off position II, and the WCY pressures of the first to fourth wheel cylinders 6, 7, 8 and 9 are both held. Then, in this holding state, the electromagnetic switching valve 23 is switched to the first position I, the output of the brake booster 3 is increased, and the MCY pressure of the master cylinder 3 is increased as much as possible and then returned.

First to fourth wheel cylinders 6, 7,
When the WCY pressures of 8 and 9 are in this holding state, if it is determined that the locking tendency of the wheel that had the locking tendency has been eliminated, that wheel of the first to fourth holding valves 10, 12, 14, 16 The holding valve is switched to the communication position I, and the WCY pressure of the wheel cylinder of the wheel is increased. At this time, the electromagnetic switching valve 23 is controlled according to this pressure increase, and the MCY pressure is increased. However, if the MCY pressure increases even if it is insufficient, the second on-off valve 42 is switched to the shutoff position I and the first on-off valve 41 is switched to the communication position I to raise the MCY pressure. In that case, the first and second on-off valves 4
When the MCY pressure rises due to the switching of 1, 42, the electromagnetic switching valve 23 may be simultaneously controlled so that the MCY pressure rises due to this control.

On the other hand, since the large-diameter chamber 4i communicates with the reservoir 5, the brake fluid in the large-diameter chamber 4i is stored in the reservoir 5.
Is discharged. Therefore, the brake fluid discharged from the wheel cylinder of the wheel that tends to lock when the WCY pressure is reduced to the large diameter chamber 4i is consumed.

Considering this consumption amount, on a road surface having a low friction coefficient (hereinafter, also referred to as a low μ road), the above-mentioned MCY pressure return ability is not insufficient when the ABS control is held after depressurization. Liquid consumption is small. Further, although the brake fluid is relatively consumed on the road surface having a high friction coefficient (hereinafter, also referred to as a high μ road), the brake fluid is still consumed on the high μ road.
Since the pressure reduction of the S control is small, the amount of the brake fluid discharged from the wheel cylinder to the large diameter chamber 4i at this time is small.

It should be noted that at the time of the second pressure reduction in the ABS control, the holding valve is set to the communication position II, the second opening / closing valve 42 is set to the shutoff position I, and the first opening / closing valve 41 is set to the communication position I, Further, by controlling the electromagnetic switching valve 23 to reduce the output of the brake booster 3, the brake fluid in the reservoir 5 can be made to flow into the large diameter chamber 4i through the first opening / closing valve 41 to replenish the consumed amount. By controlling the solenoid valves 10, 12, 14, 16, 23, 41, 42 in this manner, the degree of freedom in devising to compensate the consumption of the brake fluid is increased.

When it is determined that the wheel locking tendency is completely eliminated, each solenoid valve 10, 12, 14, 16, 23, 41, 42 is shown in FIG. 1 as in the conventional ABS control described above. Deactivated.

According to the ABS of this example, the ABS
Only when the WCY pressure in the control is increased, the brake fluid of the two wheel cylinders 8 and 9 discharged to the large diameter chamber 4i is consumed, so that the first to the first ABSs as in the conventional ABS described above are consumed. 4 wheel cylinders 10, 12, 14, 1
The amount of brake fluid consumed can be reduced as compared with the case where the brake fluid of No. 6 is directly discharged to the reservoir 5. Therefore, an increase in the stroke of the brake pedal 2 can be suppressed, and the operation feeling of the brake pedal 2 is improved. Moreover, since it is not necessary to increase the capacity of the liquid chambers 4b and 4c of the master cylinder 4, it is possible to prevent the master cylinder from increasing in size.

Further, according to this example, since the decrease of the MCY pressure during the ABS control is directly controlled by the second and third opening / closing valves 41 and 42 which are electromagnetic valves, the MCY pressure can be quickly decreased. it can. Therefore, it is possible to improve the responsiveness of the decrease in the MCY pressure. This allows
The ABS control can be performed even more appropriately.

Further, according to this example, the discharge passages from the pressure reducing valves 18, 19, 20, 21 and the wheel cylinders 6, 7, 8, 9 used in the conventional ABS to the reservoir 5 can be eliminated. The system can be simplified and the cost can be reduced.

In the above example, the electromagnetic switching valve 23, which is a two-position four-way electromagnetic valve, is used to control the output of the brake booster 3 during ABS control, but the present invention is not limited to this. Instead, by combining an appropriate number of two-position two-way solenoid valves having a communication position and a shut-off position, it is possible to achieve a function substantially similar to the function of the electromagnetic switching valve 23. Also, the electromagnetic switching valve 2
3 can be omitted.

Further, in the present invention, the master cylinder 4 may be a single master cylinder. Further, in the present invention, the primary piston and the large-diameter piston are integrally provided, but they may be provided separately.

Further, the present invention relates to the above-mentioned first to fourth pressure reducing valves 18, 19, 20, 21 in the conventional ABS.
A pressure reducing valve corresponding to a required wheel (for example, a front wheel or a drive wheel) and a discharge passage to the reservoir 5 in which the pressure reducing valve is provided may be provided.

FIG. 2 is a diagram showing another example of the embodiment of the present invention. The same components as those of the conventional ABS shown in FIG. 7 and the example shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 2, in this embodiment, the normally closed first to fourth pressure reducing valves 18, 19, 2 in the conventional ABS shown in FIG. 7 are used.
The return passage from 0, 21 to the reservoir 5 of the master cylinder 4 is deleted. Then, the first pressure reservoir 4
3 is connected to the first and second pressure reducing valves 18 and 19, and the first pressure reservoir 43 contains the brake fluid discharged from the first and second wheel cylinders 6 and 7 during the pressure reduction in the ABS control. 1 and 2nd pressure reducing valve 18,1
It is stored via 9 and is maintained at a predetermined pressure higher than atmospheric pressure. Further, the first pressure reservoir 43 is connected to the liquid chamber 4c of the master cylinder 4 via a fifth check valve 44.

Similarly, the second pressure reservoir 45 is connected to the third and fourth pressure reducing valves 20 and 21, and the second pressure reservoir 45 has a third pressure reducing pressure during ABS control.
The brake fluid discharged from the fourth wheel cylinders 8 and 9 is stored through the third and fourth pressure reducing valves 20 and 21 and is maintained at a predetermined pressure higher than atmospheric pressure. Further, the second pressure reservoir 45 is connected to the liquid chamber 4b of the master cylinder 4 via a sixth check valve 46.

In contrast to the ABS shown in FIG. 7, in this example, a large diameter chamber 4i is provided in the master cylinder 4 as in the example shown in FIG. In this case, the seal 47 provided on the housing of the master cylinder 4 prevents pressure leakage in the large diameter chamber 4i. The large diameter chamber 4i is connected to the reservoir 5 of the master cylinder 4. Then, in the connection passage between the large diameter chamber 4i and the reservoir 5, the communication position I and the blocking position II
A normally open fourth on-off valve 48 composed of an electromagnetic valve set with and is provided, and a seventh check valve 49 for blocking only the flow of the brake fluid from the large diameter chamber 4i to the reservoir 5 is provided. It is provided in parallel with the 4 on-off valve 48. The seventh check valve 49 prevents the large diameter chamber 4i from becoming negative pressure when the primary piston of the master cylinder 4 slides. The large-diameter chamber 4i may be connected to a reservoir, which is provided separately from the reservoir 5 of the master cylinder 4 and is maintained at atmospheric pressure. In addition, the large diameter chamber 4i of the master cylinder 4 and the master cylinder 4
In the connection passage between the liquid chamber 4b and the shutoff position I and the communication position I
Normally closed fifth on-off valve 50 consisting of a solenoid valve with I and I set
Is provided.

Further, in this example, the electromagnetic switching valve 23 of the ABS shown in FIG. 7 is deleted, and the ABS control by the control of the brake booster 3 is not performed. Therefore,
The brake booster 3 is adapted to perform only normal brake control by depressing the brake pedal 2. Other configurations in the ABS of this example are the same as the ABS shown in FIG. 7. In the ABS of this example configured in this way,
First, at the time of normal braking, it is the same as the above-mentioned conventional one, and the description thereof will be omitted.

Next, the ABS control will be described. First, at the start of the ABS control when the tendency of the wheels to be locked is detected,
First to fourth holding valves 10, 12, 14, 16 and fourth
The on-off valves 48 are set to the shutoff positions II, respectively, and the WCY pressures of the wheel cylinders 6, 7, 8 and 9 do not increase any more and are held. At this time, the fourth on-off valve 48
Even if the pedal input increases, the primary piston 4f does not move forward and the master cylinder 4
The MCY pressure in each liquid chamber 4b, 4c of
The pressure at the start of S control is maintained.

Even if the WCY pressure is held, the first to fourth pressure reducing valves 18, 19, 2 are applied to the wheels for which it has been determined that the lock tendency has not been eliminated and the WCY pressure needs to be reduced.
The pressure reducing valve corresponding to the wheel of 0, 21 is in the communication position II
Is switched to. As a result, the brake fluid of the corresponding wheel cylinder among the first to fourth wheel cylinders 6, 7, 8 and 9 is discharged to the reservoirs 43 and 45,
The WCY pressure of the wheel cylinder is reduced. When it is determined that the locking tendency of the wheel has been eliminated, the pressure reducing valve switched to the communication position II is switched to the shutoff position I, and the holding valve corresponding to the wheel is switched to the communication position I. As a result, the WCY pressure of the wheel cylinder corresponding to the holding valve is increased.

At this time, the MCY pressure of the master cylinder 4 is immediately reduced to near the WCY pressure of the wheel cylinder, but the fifth opening / closing valve 50 alternates between the shut-off position II and the communication position I by, for example, duty control. The switching control is repeatedly performed. At this time, when the large diameter chamber 4i and the liquid chamber 4b communicate with each other, the MCY pressure is increased by the effective diameter of the large diameter piston 4h, and the increase in MCY pressure is reduced. Easier to do. Moreover, since the fifth on-off valve 50 is repeatedly switched and controlled, M
The CY pressure is increased more slowly. Then, the boosting force due to the output of the brake booster 3 becomes the limit and M
When the CY pressure cannot be increased, the fourth on-off valve 48 is alternately and repeatedly controlled between the communication position I and the cut-off position II by, for example, duty control, so that the primary piston 4f of the master cylinder 4 is changed. Is gradually advanced to gradually increase the MCY pressure. Thus, the fourth
The reason why the opening / closing valve 48 is repeatedly switched and controlled so that the MCY pressure is slowly increased is that the MCY pressure is not changed to the normal master cylinder diameter by simply switching the fourth opening / closing valve 48 to the communication position I. Since the pressure is increased according to the output of No. 3, this increase is too large and the MCY pressure and W
This is because the difference from the CY pressure becomes large. Especially,
Because the pedal input is large during sudden braking,
Since the pressure increase of the MCY pressure becomes extremely large, the repeated switching control of the fourth opening / closing valve 48 becomes more effective and more appropriate in the pressure increase of the ABS control. Whether the repeated switching control of the fourth on-off valve 48 is performed according to the wheel speed when the decrease in the wheel speed during pressure increase is small, or
Alternatively, it is carried out by various methods such as starting a certain control from the start of increasing the pressure.

ABS disappears when the locking tendency of the wheels is completely eliminated.
When the control ends and the brake pedal 2 is released, MCY
Since the pressure drops, the first and second pressure reservoirs 43,
The brake fluid of 45 is the fifth and sixth check valves 44 and 46, and the fluid chambers 4c and 4 of the master cylinder 4, respectively.
It is returned to the reservoir 5 via b.

Other functions of the ABS of this example are the same as those of the conventional ABS described above and the example ABS shown in FIG.
Further, according to the ABS of this example, the control of the brake booster 3 can be deleted during the ABS control, so that the responsiveness in the ABS control is improved.

FIG. 3 is a diagram showing still another example of the embodiment of the present invention. The same components as those of the above-described conventional ABS and each of the above-described examples are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 3, in this example, the normally-closed first to fourth pressure reducing valves 18, 19, 2 in the conventional ABS shown in FIG. 7 are used.
The return passage from 0, 21 to the reservoir 5 of the master cylinder 4 is deleted. In addition, the first pressure reservoir 43
To the first and second pressure reducing valves 18 and 19, and to the first and second
Eighth check valve 51 that allows only the flow of brake fluid from the pressure reducing valves 18, 19 to the first pressure reservoir 43
The brake fluid discharged from the first and second wheel cylinders 6 and 7 at the time of pressure reduction in the ABS control is connected to the first pressure reservoir 43 via the first and second pressure reducing valves 18 and 19. The set pressure (for example, 30
kg / cm ² ) is designed to accumulate pressure. Further, the first pressure reservoir 43 is connected to the liquid chamber 4c of the master cylinder 4 via the fifth check valve 44.

Further, the third pressure reservoir 52 allows the first pressure reservoir 43 only the flow of the brake fluid from the third pressure reservoir 52 toward the first pressure reservoir 43.
Is connected via a check valve 53,
It is connected to the first and second pressure reducing valves 18 and 19 via a first mechanical valve 54. The first mechanical valve 54 is a ball valve 55 that controls communication and disconnection between the first and second pressure reducing valves 18, 19 and the third pressure reservoir 52.
And a stepped piston 56 including a small diameter portion that receives the WCY pressure of the second wheel cylinder 7 and a large diameter portion that receives the pressure of the brake fluid discharged from the first and second pressure reducing valves 18 and 19. There is. In the ball valve 55, the WCY pressure of the second wheel cylinder 7 is set to the first and second pressure reducing valves 18,
When the brake fluid pressure discharged from 19, that is, the pressure of the first pressure reservoir 43 is higher than a predetermined pressure (for example, ^{2 to 3} kg / cm ² ) or more, it is closed to close the first and second pressure reducing valves 18 and 19 and the third pressure reservoir 52. And the WCY pressure of the second wheel cylinder 7 is cut off and the brake fluid pressure discharged from the first and second pressure reducing valves 18 and 19, that is, the first pressure reservoir 4
When the pressure is higher than the pressure of 3 by a predetermined pressure and lower than the pressure, open it first.
The second pressure reducing valves 18 and 19 and the third pressure reservoir 52 are set to communicate with each other. Therefore, the set pressure (for example, 3 kg / cm ² ) lower than the pressure accumulated in the first pressure reservoir 43 is accumulated in the third pressure reservoir 52.

Similarly, in the passage connecting the liquid chamber 4b of the master cylinder 4 and the third and fourth wheel cylinders 8 and 9, the second pressure reservoir 45 is provided with the third and fourth pressure reducing valves 2.
0, 21 is connected via a tenth check valve 57 that allows only the flow of brake fluid from the third and fourth pressure reducing valves 20, 21 to the second pressure reservoir 45.
Brake fluid discharged from the third and fourth wheel cylinders 8 and 9 at the time of pressure reduction in the ABS control is passed through the third and fourth pressure reducing valves 20 and 21 and the tenth check valve 57 to the second pressure reservoir 45. Is stored as a predetermined pressure (for example, 30 kg / cm ² ) higher than the atmospheric pressure. Further, the second pressure reservoir 45 is connected to the liquid chamber 4b of the master cylinder 4 via the sixth check valve 46.

Further, the first pressure reservoir 58 allows the second pressure reservoir 45 only the flow of the brake fluid from the fourth pressure reservoir 58 toward the second pressure reservoir 45.
The first check valve 59 is connected, and the third and fourth pressure reducing valves 20, 21 are connected via the second mechanical valve 60. The second mechanical valve 60 includes a ball valve 61 that controls communication and disconnection between the third and fourth pressure reducing valves 20 and 21 and the fourth pressure reservoir 58, and a small diameter that receives the WCY pressure of the fourth wheel cylinder 9. And a stepped piston 62 including a large diameter portion that receives the pressure of the brake fluid discharged from the third and fourth pressure reducing valves 20 and 21. In the ball valve 61, the WCY pressure of the fourth wheel cylinder 9 is set to the third and fourth pressure reducing valves 2.
A predetermined pressure (for example, ^{2 to 3} kg / cm ² ) from the brake fluid pressure discharged from 0,21, that is, the pressure of the second pressure reservoir 45.
When it is higher than the above, close the third and fourth pressure reducing valves 20, 21.
And the fourth pressure reservoir 58 are shut off, and the WCY pressure of the fourth wheel cylinder 9 is set to the third and fourth pressure reducing valves 20, 2.
When the brake fluid pressure discharged from No. 1, that is, the pressure higher than the pressure of the second pressure reservoir 45 by a predetermined pressure, the pressure is set to open so that the third and fourth pressure reducing valves 20, 21 and the fourth pressure reservoir 58 communicate with each other. Has been done. Therefore, a predetermined pressure (for example, 3 kg / cm ² ) lower than the pressure accumulated in the third pressure reservoir 45 is accumulated in the fourth pressure reservoir 58. The other configuration of this example is the same as the ABS system of FIG. 7.

The operation of this example configured as described above will be described. First, the action during normal braking is the same as in the above-mentioned examples and the conventional example. Next, the ABS control will be described. First, when the ABS control in which the wheel lock tendency is detected is started, the first to fourth holding valves 10, 12, 14, 1
6 is set to the shut-off position II, and the WCY pressures of the wheel cylinders 6, 7, 8 and 9 do not increase any more and are in the holding state. At this time, each pressure reducing valve 18, 19, 2
0, 21 are set to the shutoff position I, and each pressure reducing valve 18,
Since the pressure on the output side of 19, 20, 21 is atmospheric pressure, the WCY pressure of each wheel cylinder 7, 9 causes the stepped piston 5 of the first and second mechanical valves 54, 60 to move.
The ball valves 55 and 61 are closed by 6,62.

Even if the WCY pressure is maintained, the lock tendency is not resolved yet and it is determined that the WCY pressure needs to be reduced.
Pressure reducing valve 18, 19, 2 corresponding to the wheel of 0, 21
0 and 21 are switched to the communication position II. This allows
Of the first to fourth wheel cylinders 6, 7, 8 and 9, the brake fluid of the corresponding wheel cylinder is the pressure reducing valve 18,1.
Emitted from 9, 20, 21. At this time, the pressure reducing valve 18,
The pressure of the brake fluid discharged from 19, 20, 21 is the first
And the stepped pistons 56, 62 of the second mechanical valves 54, 60 are acted on. However, initially, this pressure is lower than the WCY pressures of the second and fourth wheel cylinders 7, 9, so that the ball The valves 55 and 61 are kept closed. Therefore, the pressure reducing valves 18, 19, 20,
The brake fluid discharged from 21 is discharged to the first and second pressure reservoirs 43 and 45. As a result, the WCY pressure of the wheel cylinders 6, 7, 8 and 9 is reduced and the first and second pressure reservoirs 43 and 45 are accumulated.

The WCY pressure of the wheel cylinders 6, 7, 8 and 9 becomes lower than the high set pressure (eg, 30 kg / cm ² ) of the first and second pressure reservoirs 43 and 45, that is, the WCY pressure is reduced by the pressure reducing valve 18, When the pressure becomes lower than the pressure of the brake fluid discharged from 19, 20, 21 by a predetermined pressure (for example, ^{2 to 3} kg / cm ² ),
The stepped pistons 56, 62 move upward, and the ball valves 55, 61 open. As a result, the brake fluid discharged from the pressure reducing valves 18, 19, 20 and 21 is discharged to the third and fourth pressure reservoirs 5.
Stored in the second and third pressure reservoirs 52,
In 58, a pressure lower than the high set pressure (eg, 30 kg / cm ² ) accumulated in the first and second pressure reservoirs 43, 45 is accumulated. Therefore, the WCY pressure of the wheel cylinders 6, 7, 8 and 9 is further reduced.

When it is judged that the locking tendency of the wheels has been eliminated, the pressure reducing valves 18, 19, 2 switched to the communication position II.
The valves 0, 21 are switched to the shut-off position I, and the holding valves 10, 12, 14, 16 corresponding to the wheels are switched to the communication position I. As a result, the holding valve 10, 12, 1
The MCY pressure of the master cylinder 4 is introduced into the wheel cylinders 6, 7, 8 and 9 corresponding to 4 and 16 to increase the WCY pressure.

At this time, when it is judged that the MCY pressure needs to be controlled, the electromagnetic switching valve 23 is on / off controlled by, for example, duty control, and the brake booster 3 is controlled.
Is controlled to control the MCY pressure.

For example, if a vehicle has a road surface with a high coefficient of friction (high μ
When changing from a road) to a road surface having a low friction coefficient (low μ road), the MCY pressure is controlled by the control of the electromagnetic switching valve 23, or the pedal input of the brake pedal 2 is reduced. And a second pressure reservoir 43,
When the pressure becomes lower than the set pressure of 45, the pressure accumulated in the first and second pressure reservoirs 43, 45 is returned to the liquid chambers 4b, 4c of the master cylinder 4 via the fifth and sixth check valves 44, 46.

ABS disappears when the wheel locking tendency is completely eliminated.
When the control ends and the brake pedal 2 is released, MCY
Since the pressure drops, the first and second pressure reservoirs 43,
The brake fluid in No. 45 passes through the fifth and sixth check valves 44, 46, respectively, and the brake fluid in the third and fourth pressure reservoirs 52, 58 respectively goes in the ninth and tenth.
It is returned to the reservoir 5 via the check valves 53 and 59 and the fifth and sixth check valves 44 and 46, and further via the liquid chambers 4c and 4b of the master cylinder 4, respectively. Another function of the ABS of this example is the above-mentioned conventional AB.
Same as S.

According to the ABS of this example, since the brake fluid stored in the first and second pressure reservoirs 43, 45 is returned to the master cylinder 4 during ABS control, it is possible to reduce the fluid amount loss during ABS control. You can

In this example, each pressure reducing valve 18, 19, 20,
It is supposed that two pressure reservoirs for storing the brake fluid discharged from 21 are provided for each system like the first to fourth pressure reservoirs 43, 45, 52, 58 with different set pressures. 3 pressurized reservoirs per system
It is also possible to provide more than one set pressure and different set pressures. In that case, the mechanical valve is replaced by the WC instead of the ball valves 55, 61 and the stepped pistons 56, 62.
Two or more corresponding to two or more pressure reservoirs excluding the input port and the pressure reservoir of the maximum set pressure by the spool that operates according to the pressure difference between the Y pressure and the pressure of the brake fluid discharged from the pressure reducing valve. It can be configured by a spool valve that controls to sequentially switch communication with the output port of the. Of course, it goes without saying that the mechanical valve may have another structure.

FIG. 4 is a diagram showing still another example of the embodiment of the present invention. The same components as those of the above-described conventional ABS and each of the above-described examples are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 4, in this example, in addition to the ABS of the example shown in FIG. 3, the large diameter chamber 4i shown in FIG. 49
A normally closed fifth opening / closing valve 50 including an electromagnetic valve is provided, and the electromagnetic switching valve 23 is deleted. The other configuration of this example is the same as the ABS of FIG.

In the ABS of the present embodiment constructed as described above, the pressure reducing control of the ABS control is the same as the pressure reducing control of the ABS control in the ABS of FIG. 3, and the MCY pressure control of the master cylinder 4 of the ABS control is performed. This is the same as the MCY pressure control of the ABS control in the ABS of FIG. Further, the other control and the normal brake in the ABS control of this example are the same as the other control and the normal brake in the conventional ABS control.

According to this example, the loss of the amount of brake fluid during ABS control can be reduced as in the case of the ABS shown in FIG. 3, and the electromagnetic switching valve 23 is eliminated as in the case of the ABS shown in FIG. Control can be deleted, and the responsiveness in ABS control is improved.

FIG. 5 is a diagram showing still another example of the embodiment of the present invention. The same components as those of the above-described conventional ABS and each of the above-described examples are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, instead of the first and second mechanical valves 54, 60 having stepped pistons 56, 62 in the ABS of the example shown in FIG. 4, a first piston having a control piston 63 as shown in FIG. A second mechanical valve 66 having a mechanical valve 64 and a control piston 65 is provided. These control pistons 63 and 65 are
Second or fourth wheel cylinder 7, 9 on one side respectively
WCY pressure is applied and spring 7 is applied to the other side.
A spring force of 3,74 is applied. The spring forces of these springs 73 and 74 are set such that the WCY pressures of the second and fourth wheel cylinders 7 and 9 are set pressures of the first and second pressure reservoirs 43 and 45 (eg, 30 kg /
predetermined pressure (for example in ^{cm 2), 2kg / cm 2} ) the opening pressure plus (e.g.,
32 kg / cm ² ) is preferably set equal to the force applied to the other side of each control piston 63, 65, but it can be set arbitrarily in relation to the force due to this valve opening pressure.

Then, the WCY of the second wheel cylinder 7
When the force exerted by the pressure on the control piston 63 is equal to or greater than the set spring force of the spring 73, the control piston 63
Moves downward to close the ball valve 55 to shut off the first and second pressure reducing valves 18, 19 and the third pressure reservoir 52, and the force applied to the control piston 63 by the WCY pressure of the second wheel cylinder 7 is applied. When the spring force is lower than the set spring force, the control piston 63 moves upward to open the ball valve 55 to open the first and second pressure reducing valves 18 and 19 and the third pressure reservoir 5.
2 is connected. Similarly, when the force applied by the WCY pressure of the fourth wheel cylinder 9 acting on the control piston 65 is equal to or greater than the set spring force of the spring 74, the control piston 65 moves downward to close the ball valve 61 and close the third valve. And the fourth pressure reducing valves 20, 21 and the fourth pressure reservoir 5
8 and the fourth wheel cylinder 9 W
When the force applied to the control piston 65 by the CY pressure is lower than this set spring force, the control piston 65 moves upward to open the ball valve 61 and open the third and fourth pressure reducing valves 20, 21 and the fourth pressure reservoir 58. Is designed to be connected.

As a result, while the force applied to the control pistons 63, 65 by the WCY pressure of the second and fourth wheel cylinders 7, 9 is larger than the set spring force, the pressure reducing valves 18, 19, 20, 21 are operated by the pressure reducing valves 18, 19, 20, 21. The discharged brake fluid is stored in the first and second pressure reservoirs 43 and 45, respectively, and the first and second pressure reservoirs 43 and 45 are accumulated. Further, when the forces applied to the control pistons 63, 65 by the WCY pressures of the second and fourth wheel cylinders 7, 9 are smaller than the set spring forces, respectively,
The brake fluid discharged from each pressure reducing valve 18, 19, 20, 21 is supplied to the third and fourth pressure reservoirs 52, 58, respectively.
Is stored in the third and fourth pressure reservoirs 52 and 58.

According to the ABS of this example, the opening / closing control of the mechanical valve is performed by the difference between the force by the WCY pressure of the wheel cylinder and the set spring force of the spring, that is, the WCY pressure of the wheel cylinder and the set pressure of the pressure reservoir of the maximum set pressure. Therefore, the operation becomes more reliable than the ABS shown in FIG. AB in this example
The other effects of S are the same as the effects of ABS in FIG.

FIG. 6 is a diagram showing still another example of the embodiment of the present invention. The same components as those of the above-described conventional ABS and each of the above-described examples are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, instead of the first and second mechanical valves 54 and 60 in the ABS of the example shown in FIG. 4,
As shown in FIG. 6, normally-closed sixth and seventh on-off valves 67, 7 made of solenoid valves having a shut-off position I and a communication position II set.
0 is provided. Further, in this example, the first to fourth pressure switches 68, 69, 71, 7 for detecting the WCY pressures of the first to fourth wheel cylinders 6, 7, 8, 9 respectively.
2 are provided. Then, each WCY pressure has a maximum set pressure, that is, the first and second pressure reservoirs 43,
When the pressure is higher than the set pressure of 45, the first to fourth pressure switches 68, 69, 71, 72 do not output the pressure detection signal, and the sixth and seventh opening / closing valves 67, 70 are held in the shutoff position I. It is like this. Further, when each WCY pressure becomes equal to or lower than the set pressure of the first and second pressure reservoirs 43 and 45,
The sixth and seventh opening / closing valves 67, 70 are generated by the pressure detection signals from the first to fourth pressure switches 68, 69, 71, 72.
Can be switched to the communication position II. As a result, the brake fluid discharged from the first to fourth pressure reducing valves 18, 19, 20, 21 is stored in the third and fourth pressure reservoirs 52, 58, respectively, and the third and fourth pressure reservoirs 52, 58 are Accumulates pressure.

According to the ABS of the present embodiment thus constructed, the sixth and seventh opening / closing valves 67 and 70, which are electromagnetic valves, are used in place of the mechanical valves.
As the seventh on-off valves 67, 70, for example, on-off valves of the same type such as the first to fourth on-off valves 18, 19, 20, 21 can be used. Therefore, the number of valves can be reduced, the cost can be reduced, and the configuration can be simplified. Other operational effects of this example are the same as the operational effects of the ABS of the example shown in FIG.

In each of the above-mentioned embodiments, a negative pressure booster is used for the brake booster 3, but the present invention is not limited to this.
Other pressure working fluids such as hydraulic pressure, compressed air, etc. can also be used.

[0094]

As is apparent from the above description, according to the ABS of the first aspect of the invention, the brake fluid in the brake cylinder discharged to the large diameter chamber is discharged only when the brake fluid pressure is increased in the ABS control. Since the brake fluid is consumed, it is possible to reduce the consumption amount of the brake fluid as compared with the case where the brake fluid in the brake cylinder is directly discharged to the reservoir when the brake fluid pressure is reduced as in the conventional ABS described above. . Therefore, an increase in the stroke of the brake operating means can be suppressed, and the operation feeling of the brake operating member is improved. Moreover, since the capacity of the liquid chamber of the master cylinder is not increased, it is possible to prevent the master cylinder from increasing in size.

Further, according to the first aspect of the invention, since the decrease of the master cylinder pressure during the ABS control is directly controlled by the solenoid valve, the master cylinder pressure can be decreased rapidly and the responsiveness of the system is improved. Can be improved. This makes it possible to perform the ABS control more appropriately.

Further, according to the invention of claim 1, the conventional AB
Since the pressure reducing valves, the check valves, and the discharge passages from the wheel cylinders to the reservoir used in S can be deleted, the system can be simplified and the cost can be reduced.

In particular, according to the second aspect of the invention, since the output of the brake booster is also controlled during the ABS control, the master cylinder pressure can be reduced more effectively and more quickly during the ABS control. can do. Further, according to the invention of claim 3, the control of the brake booster can be eliminated during the ABS control, so that the responsiveness in the ABS control is improved.

Further, according to the inventions of claims 3 and 5, when the large diameter chamber of the master cylinder and the liquid chamber of the master cylinder are in communication, the master cylinder pressure is increased by the effective diameter of the large diameter piston. Therefore, the increase in the master cylinder pressure can be reduced. As a result, the master cylinder pressure can be easily controlled and the master cylinder pressure can be improved.

Further, according to the inventions of claims 4, 6, 7 and 8, since the brake fluid stored in the first pressure reservoir is returned to the master cylinder during the ABS control, the fluid during the ABS control is obtained. Volume loss can be reduced.

Further, according to the inventions of claims 5 to 8, the loss of the amount of brake fluid at the time of ABS control can be reduced, and the solenoid switching valve can be eliminated to eliminate the control of the brake booster. , ABS response is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an embodiment of an anti-skid brake control system according to the present invention.

FIG. 2 is a diagram showing another example of the embodiment of the present invention.

FIG. 3 is a diagram showing still another example of the embodiment of the present invention.

FIG. 4 is a diagram showing still another example of the embodiment of the present invention.

FIG. 5 is a diagram showing still another example of the embodiment of the present invention.

FIG. 6 is a diagram showing still another example of the embodiment of the present invention.

FIG. 7 is a diagram showing an example of a conventional ABS.

FIG. 8 is a cross-sectional view showing an example of a negative pressure booster used in a conventional ABS.

[Explanation of symbols]

1 ... ABS, 2 ... Brake pedal, 3 ... Brake booster, 4 ... Master cylinder, 4b, c ... Liquid chamber, 4f ... Primary piston, 4g ... Secondary piston, 4h ... Large diameter piston, 4i ... Large diameter chamber, 5 ... Reservoir, 6 ... First wheel cylinder, 7 ... Second wheel cylinder, 8 ... Third
Wheel cylinder, 9 ... 4th wheel cylinder, 10 ...
1st holding valve, 12 ... 2nd holding valve, 14 ... 3rd holding valve, 1
6 ... Fourth holding valve, 22 ... Negative pressure source, 23 ... Electromagnetic switching valve, 2
4 ... Input shaft, 29 ... Power piston, 30 ... First chamber, 3
1 ... 2nd chamber, 32 ... Switching control valve, 41 ... 2nd on-off valve, 4
2 ... 3rd on-off valve, 43 ... 1st pressure reservoir, 44 ... 5th
Check valve, 45 ... Second pressure reservoir, 46 ... Sixth
Check valve, 47 ... Seal, 48 ... Fourth on-off valve, 5
0 ... Fifth on-off valve, 52 ... Third pressure reservoir, 54, 64
... 1st mechanical valve, 55, 61 ... Ball valve, 56,
62 ... Stepped piston, 58 ... Fourth pressure reservoir, 60,
66 ... Second mechanical valve, 63 ... Control piston, 6
7 ... 6th on-off valve, 70 ... 7th on-off valve, 68 ... 1st pressure switch, 69 ... 2nd pressure switch, 71 ... 3rd pressure switch, 72 ... 4th pressure switch, 73, 74 ... Spring

Claims (8)

[Claims] 1. A brake operating means, and a brake doubler that operates by operating the brake operating means to actuate a switching control valve to supply a pressure working fluid to boost and output the operating force of the brake operating means. Force device, a master cylinder that generates a master cylinder pressure in the fluid chamber by operating the master cylinder piston by the output of the brake booster, a reservoir that stores the brake fluid in the master cylinder, and the master cylinder pressure is the brake fluid. A brake cylinder that generates a braking force for the wheels by being supplied as pressure, a large-diameter piston that has a larger diameter than the master cylinder piston, and receives the output of the brake booster, and a partition formed by this large-diameter piston. The large diameter chamber and the passage connecting the liquid chamber of the master cylinder to the brake cylinder. A first opening / closing valve that is provided and that is formed of an electromagnetic valve having a communication position and a shut-off position and is set to the normal communication position is provided in a passage that connects the liquid chamber of the master cylinder and the large diameter chamber. A second opening / closing valve which is an electromagnetic valve having a shutoff position and a communication position and is set to the normally shutoff position; and a communication position which is provided in a passage connecting the reservoir of the master cylinder and the large diameter chamber. A third opening / closing valve which is formed of an electromagnetic valve having a shutoff position and is set to a normally open communication position; and an electronic control device for controlling the first to third opening / closing valves, the electronic control device comprising: An anti-skid brake control system, characterized in that anti-skid brake control is performed by controlling the first to third opening / closing valves when it is determined that the wheels tend to lock. 2. An electromagnetic switching valve comprising an electromagnetic valve for switching control of supply / discharge of the pressure working fluid to / from the brake booster, wherein the electronic control unit controls the electromagnetic switching valve during the anti-skid brake control. 2. The anti-skid brake control system according to claim 1, wherein the output of the brake booster is controlled by switching control. 3. A brake operating means, and a brake doubler for boosting and outputting an operating force of the brake operating means by operating a switching control valve by operating the brake operating means to supply a pressure working fluid. Force device, a master cylinder that operates the master cylinder piston by the output of this brake booster to generate a master cylinder pressure in the fluid chamber, a reservoir held at atmospheric pressure, and the master cylinder pressure as the brake fluid pressure. A brake cylinder that generates a braking force for the wheels by being supplied, a large-diameter piston that has a larger diameter than the master cylinder piston, and receives the output of the brake booster, and a partition formed by this large-diameter piston Large-diameter chamber and brake discharged from the brake cylinder during pressure reduction control in anti-skid brake control A first pressure reservoir that stores a liquid at a set pressure by storing liquid, and a solenoid valve that is provided in a passage that connects the liquid chamber of the master cylinder and the brake cylinder, and has a communication position and a cutoff position. A normal shutoff position, which includes a first opening / closing valve set to a normal communication position and a solenoid valve provided in a passage connecting the brake cylinder and the first pressure reservoir and having a shutoff position and a communication position. A second opening / closing valve set to, and a passage that connects the large diameter chamber and the reservoir,
A third opening / closing valve which is composed of an electromagnetic valve having a communication position and a shutoff position and is set to the normal communication position, and a brake fluid which is provided in parallel with the third opening / closing valve and which is directed from the reservoir toward the large diameter chamber. Of a brake fluid that is provided in a passage connecting the first pressure reservoir and the fluid chamber of the master cylinder, the first check valve allowing only the flow of the brake fluid from the first pressure reservoir to the fluid chamber. A second check valve that allows only the flow of the fluid, and a passage that connects the liquid chamber of the master cylinder and the large diameter chamber,
A fourth on-off valve, which is an electromagnetic valve having a shut-off position and a communication position, is set to a normally-off position and is controlled by the electronic control unit, and electronic control for controlling the first to fourth on-off valves The anti-skid brake control is characterized in that the electronic control device performs anti-skid brake control by controlling the first to third opening / closing valves when it is determined that the wheels tend to lock. system. 4. The brake operating means and the switching control valve actuated by the operation of the brake operating means to supply the pressure working fluid, thereby boosting the operating force of the brake operating means by the pressure working fluid. A brake booster that outputs, a master cylinder that operates the master cylinder piston by the output of the brake booster to generate a master cylinder pressure in the liquid chamber, a reservoir that is held at atmospheric pressure,
The master cylinder pressure is supplied as the brake fluid pressure to generate a braking force for the wheels, and the brake fluid discharged from the brake cylinder during the pressure reduction control in the anti-skid brake control is stored to make the first set pressure. Is provided in a passage connecting the first pressure reservoir for accumulating in the master cylinder, the liquid chamber of the master cylinder and the brake cylinder, and includes a solenoid valve having a communication position and a cutoff position, and is set to a normal communication position. A first opening / closing valve, the brake cylinder, and the first
A second on-off valve, which is provided in a passage connecting to the pressure reservoir and has a shut-off position and a communication position, and which is set to a normally shut-off position, the second on-off valve and the first shut-off valve. It is connected to a first connection passage to a pressure reservoir and stores brake fluid discharged from the brake cylinder during pressure reduction control in anti-skid brake control, so that a second set pressure lower than the first set pressure is accumulated. Two pressure reservoirs, a pressure reservoir switching valve that controls opening and closing of a second connection passage that connects the second pressure reservoir to the first connection passage based on at least the pressure of the brake cylinder, and the first and second pressure reservoir switching valves. Brake fluid that is provided in a passage that connects the pressure reservoir and the liquid chamber of the master cylinder and that is directed from the first and second pressure reservoirs to the liquid chamber. A first check valve that permits flow only, is provided in the first pressure reservoir side of the second connecting passage connecting position of the first connecting passage, the second
A second check valve that allows only the flow of brake fluid from the open / close valve to the first pressure reservoir, and a passage that connects the first and second pressure reservoirs to the fluid chamber of the master cylinder. A third check valve provided in a passage between the first and second pressure reservoirs and allowing only a flow of the brake fluid from the second pressure reservoir toward the first pressure reservoir; An electronic control device for controlling a second on-off valve, wherein the electronic control device controls the first and second on-off valves when it determines that the wheels tend to lock, thereby performing anti-skid brake control. Anti-skid brake control system characterized by performing. 5. A brake operating means, and a brake doubler for boosting and outputting an operating force of the brake operating means by operating a switching control valve to supply a pressure working fluid by operating the brake operating means. Force device, a master cylinder that generates a master cylinder pressure in the fluid chamber by operating the master cylinder piston by the output of the brake booster, a reservoir held at atmospheric pressure, and the master cylinder pressure as the brake fluid pressure. A brake cylinder that generates a braking force for the wheels by being supplied, a large-diameter piston that is formed to have a larger diameter than the master cylinder piston, and receives the output of the brake booster, and a partition formed by this large-diameter piston Large-diameter chamber and brake discharged from the brake cylinder during pressure reduction control in anti-skid brake control A solenoid valve provided in a passage connecting the first pressure reservoir, which stores a liquid to a first set pressure by accumulating the liquid, and the liquid chamber of the master cylinder, and the brake cylinder, and has a communication position and a cutoff position. And a solenoid valve provided in a passage connecting the brake cylinder and the first pressure reservoir, the solenoid valve having a shut-off position and a communication position. It is connected to a second opening / closing valve that is set to the shutoff position and a first connection passage between the second opening / closing valve and the first pressure reservoir, and is discharged from the brake cylinder during pressure reduction control in antiskid brake control. A second pressure reservoir for accumulating a second set pressure lower than the first set pressure by storing the brake fluid, and at least based on the pressure of the brake cylinder. And a pressure reservoir switching valve that controls opening and closing of a second connection passage that connects the second pressure reservoir to the first connection passage, and a passage that connects the large-diameter chamber and the reservoir, and shuts off the communication position. A third opening / closing valve which is formed of a solenoid valve having a position and which is normally set to the communicating position; The first check valve to allow,
A first passage is provided in a passage connecting the first and second pressure reservoirs to the liquid chamber of the master cylinder, and allows only a flow of brake fluid from the first and second pressure reservoirs toward the liquid chamber. A check valve of No. 2 and a solenoid valve provided in a passage connecting the liquid chamber of the master cylinder and the large diameter chamber, and having a shut-off position and a communication position. An on-off valve and an electronic control device for controlling the first to fourth on-off valves are provided, and the electronic control device controls the first to third on-off valves when it is determined that the wheels tend to lock. An anti-skid brake control system characterized by performing anti-skid brake control. 6. A control piston, wherein the pressure reservoir switching valve has one side on which the pressure of the brake cylinder acts and the other side on which the pressure of the brake fluid discharged from the second on-off valve acts. The anti-skid brake control system according to claim 4 or 5, wherein the anti-skid brake control system comprises a mechanical valve including a passage opening / closing valve controlled by the control piston to control opening / closing of the second connection passage. 7. The pressure reservoir switching valve includes a control piston, on one side of which the pressure of the brake cylinder acts and on the other side of which a set spring force of a spring acts, and a control piston controlled by the control piston. The anti-skid brake control system according to claim 4 or 5, wherein the anti-skid brake control system comprises a mechanical valve including a passage opening / closing valve that controls opening / closing of the two connection passages. 8. A pressure detecting means for detecting the pressure of the brake cylinder is provided, and the pressure reservoir switching valve is an electromagnetic valve provided in the second connection passage and having a cutoff position and a communication position. 6. A fifth opening / closing valve which is set to a position, wherein the electronic control unit controls the fifth opening / closing valve based on an output signal of the pressure detecting means. Anti-skid brake control system.