JPH08282470A - Brake assistor system - Google Patents

Abstract

PURPOSE: To boost brake pressure largely even when a pressure source goes in failure and stop a vehicle certainly in emergency with a minor pedaling force. CONSTITUTION: When the liquid pressure of an accumulator 5 sinks below a specified level, a pressure switch 13 is turned on. If in this condition, a brake pedal 2 is stamped, a pedal switch 14 is turned on. Accordingly an ECU 15 emits a control signal, and a selector valve 12 is changed over to the position II. Thereby a negative pressure from a vacuum tank 10 is applied to the pressure receiving surface of power piston 16 on its liquid pressure piston 17 side, so that the power piston 16 advances. Thereby the liquid pressure piston 17 is actuated to generate a brake liquid pressure, and brakes are applied. This brake pressure has a very larger value approx. equal to the brake pressure generated with the operation of a liquid pressure servo unit 3 while the pressure source is in normal function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake booster system for generating a large braking force by a fluid pressure, and in particular, it can generate a sufficiently large braking force even when the fluid pressure of a pressure source is lost. It is related to the brake booster system.

[0002]

2. Description of the Related Art For example, in an automobile, when a large braking force that cannot be obtained only by the driver's brake pedal force is required, or when the driver's brake pedal force is reduced, vacuum, compressed air or A brake booster system is used in which a large braking force can be obtained by using a pressure such as a hydraulic pressure.

Further, in such a brake booster system, if the fluid pressure of the pressure source fails, there is a possibility that a sufficient braking force cannot be obtained. For this reason, when the pressure source fails, the operating force of the brake operating member must be made much larger than in the normal case. Therefore, Japanese Patent Publication No. 6-29011 proposes a brake boosting system capable of obtaining a relatively large braking force even with a normal brake operating force when the pressure source fails.

FIG. 6 is a diagram showing the brake booster system disclosed in this publication. In the figure, 31 is a brake booster system, 32 is a brake pedal, 33 is a hydraulic booster, 34 is a master cylinder, 35 is a wheel cylinder, 36 is a pump, 37 is an accumulator, 38 is a booster, 39 is a boosting piston, Reference numeral 40 is an on-off valve.

As shown in FIG. 6, the pressure boosting piston 39 is a stepped piston, and the master cylinder pressure acts on the pressure receiving surface on the left large diameter portion of the piston.
The hydraulic pressure of a hydraulic pressure chamber (not shown) of the hydraulic booster 33 acts on the pressure receiving surface of the right side step portion.

When the brake is not operated, the booster piston 39
Is in the position shown and the on-off valve 40 is open. When the brake pedal 32 is depressed when the pressure source is normal,
The control valve of the hydraulic booster 33 is switched, the hydraulic fluid flows into the hydraulic fluid chamber, and the power piston (not shown) advances. As a result, the master cylinder 34 generates a brake fluid pressure, which is supplied to the pressure booster 38 and further supplied to the wheel cylinder 35 through the open / close valve 40 which is opened to operate the wheel cylinder 35. The brake works. At this time, the brake fluid pressure of the master cylinder 34 acts on the left large diameter portion pressure receiving surface and the right small diameter portion pressure receiving surface of the pressure boosting piston 39 of the pressure booster 38, and the hydraulic booster 33 operates on the right side step portion pressure receiving surface. Since the hydraulic pressure of the hydraulic chamber acts, the pressure boosting piston 39 does not move. Therefore, the on-off valve 40 is held open, and the brake fluid pressure of the master cylinder 34 is supplied to the wheel cylinder 35 as it is without being boosted by the booster 38.

When the pressure source fails, the brake pedal 32
Even if the user depresses, the hydraulic fluid does not flow into the hydraulic pressure chamber, and the power piston does not move forward depending on the hydraulic fluid. Further depressing the brake pedal 32 causes the power piston to move forward by pedaling force. As a result, the master cylinder 34 generates a brake fluid pressure, the brake fluid pressure is supplied to the pressure booster 38, and is further supplied to the wheel cylinder 35 through the open / close valve 40 that is open. At this time, the brake hydraulic pressure of the master cylinder 34 acts on the left large diameter portion pressure receiving surface and the right small diameter portion pressure receiving surface of the pressure boosting piston 39 of the pressure booster 38, but the hydraulic booster 33 operates on the right side step portion pressure receiving surface. Since the hydraulic pressure in the hydraulic chamber does not act, the pressure boosting piston 39 moves to the right and the on-off valve 40 closes. Therefore, the master cylinder 34 and the wheel cylinder 35 are disconnected. After the on-off valve 40 is closed, the brake fluid pressure of the master cylinder 34 is increased by the pressure booster 38 to a pressure increase ratio {(large diameter portion pressure receiving area).
/ (Small diameter portion pressure receiving area)} is increased, and the increased brake hydraulic pressure is supplied to the wheel cylinder 35. As a result, when the pressure source fails, a relatively large brake fluid pressure can be generated with a relatively small pedal effort.
In other words, the pedal effort can be reduced.

[0008]

By the way, in such a brake booster system 31, since the brake fluid pressure of the master cylinder 34 is increased by the pressure increasing piston 39, in order to obtain a large pressure increasing ratio, It is necessary to increase the diameter of the large diameter portion of the pressure piston 39. However, if the diameter of the large diameter portion of the booster piston 39 is increased, the amount of brake fluid supplied from the master cylinder 34 must also be increased. For this reason, the pedal stroke of the brake pedal 32 becomes large and the pedal feel becomes poor. Therefore, the diameter of the large diameter portion of the pressure boosting piston 39 cannot be increased so much that the pressure boosting ratio of the pressure booster 38 is limited. Therefore, in the brake booster system 31, when the pressure source fails, the brake fluid pressure cannot be increased to the same level as the brake fluid pressure when the pressure source is normal.

Further, since the brake fluid pressure cannot be greatly increased when the pressure source fails, there is a problem that a large pedaling force is required when the pressure source fails when the vehicle is stopped by sudden braking. is there.

The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to greatly increase the brake pressure even when the pressure source fails, and to rapidly brake. It is an object of the present invention to provide a brake booster system capable of reliably stopping the vehicle with a smaller pedal effort.

[0011]

In order to solve the above-mentioned problems, the invention of claim 1 provides a first pressure source for generating a first predetermined fluid pressure, a brake operating means for performing a brake operation,
A fluid pressure booster that outputs when the first predetermined fluid pressure is supplied by the operation of the brake operating means; and a master cylinder that operates by the output of the fluid pressure booster to generate a brake pressure. In a brake booster system including a brake cylinder that generates a braking force by supplying a brake pressure from a master cylinder, a second pressure source that generates a second predetermined fluid pressure and the second predetermined fluid pressure are supplied. To generate a brake pressure and supply the brake pressure to the brake cylinder, and the first predetermined fluid pressure of the first pressure source when the brake operating means is operated. Is less than or equal to a predetermined value, the second predetermined fluid pressure is supplied to the brake pressure generating means, and the first predetermined fluid pressure is the predetermined value. When the pressure exceeds the predetermined value, the supply / discharge control is performed so that the second predetermined fluid pressure is not supplied to the brake pressure generation means and the second predetermined fluid pressure supplied to the brake pressure generation means is discharged. It is characterized by having a valve.

According to a second aspect of the present invention, a first pressure source for generating a first predetermined fluid pressure, a brake operating means for performing a brake operation, and a first pressure source for operating the brake operating means are provided.
A fluid pressure booster that outputs when a predetermined fluid pressure is supplied, a master cylinder that operates by the output of this fluid pressure booster to generate brake pressure, and a brake pressure from this master cylinder are supplied. In a brake booster system including a brake cylinder that generates a braking force, a second pressure source that generates a second predetermined fluid pressure and a relay valve are provided, and the relay valve is switch-controlled to perform the second predetermined fluid. A pressure is supplied to operate to generate a brake pressure, and a brake pressure generating means for supplying the brake pressure to the brake cylinder, and a passage connecting the master cylinder and the brake cylinder are provided, The master cylinder is communicated with the brake cylinder and the brake pressure generating means is connected to the brake cylinder. A first position for disconnecting from the valve and a second position for connecting the master cylinder to the relay valve of the brake pressure generating means and disconnecting from the brake cylinder are set, and the first predetermined position of the first pressure source is set. A switching valve which is set to the first position when the fluid pressure exceeds a predetermined value and is set to the first position when the first predetermined fluid pressure of the first pressure source is equal to or lower than the predetermined value. It is characterized by being.

Further, according to the invention of claim 3, there is provided pressure detecting means for operating when the first predetermined fluid pressure of the first pressure source is equal to or lower than the predetermined value, and the pressure detecting means is the switching valve. And the switching valve is switch-controlled by an output signal from the pressure detecting means.

Further, the invention of claim 4 is provided with a passage for supplying the first predetermined fluid pressure of the first pressure source as pilot pressure to the switching valve, and the switching valve is switch-controlled by the pilot pressure. It is characterized by that.

[0015]

In the brake booster system according to the invention of claim 1 configured as described above, the first pressure source fails and the first predetermined fluid pressure is below a predetermined value, and the brake operating means is operated. Then, the switching valve is switched and the second predetermined fluid pressure of the second pressure source is supplied to the brake pressure generating means. As a result, the brake pressure generating means generates the brake pressure and also supplies the brake pressure to the brake cylinder to operate the brake. Since the brake pressure at this time is generated by the operation of the brake pressure generating means, it is increased to a pressure as large as that of the fluid pressure booster. In this way, since the brake fluid pressure is generated by the brake pressure generating means when the brake is activated when the pressure source fails,
Even when the first pressure source fails, the same large braking force as when the first pressure source is normal can be obtained. Therefore, not only the normal braking at the time of the failure of the first pressure source is performed almost as securely as at the time of the normal operation of the first pressure source, but also the pedal effort is reduced, and further, the stopping at the sudden braking is performed with a relatively small effort. It will be surely done.

According to the second aspect of the present invention, when the first pressure source fails and the first predetermined fluid pressure falls below a predetermined value, the switching valve switches, and the master cylinder and the relay valve of the brake pressure generating means. Are connected. Since the first pressure source has failed, the fluid pressure booster does not generate an output by the fluid pressure even if the brake operating means is operated, but when the brake operating means is operated by a predetermined amount, the fluid pressure boosting device is operated. The device produces an output by operating the brake operating means and operates the master cylinder. As a result, the master cylinder generates hydraulic pressure, and this hydraulic pressure is supplied to the relay valve of the brake pressure generating means. As a result, the second predetermined fluid pressure of the second pressure source is supplied to the brake pressure generating means, and the brake pressure generating means generates the brake pressure and supplies this brake pressure to the brake cylinder. The brake pressure at this time is also extremely large, which is almost the same as in the fluid pressure booster. Therefore, the invention of claim 2 also has the same effect as the invention of claim 1 described above.

Further, in the invention of claim 3, the switching valve can be switched by the output signal from the pressure detecting means. Further, in the invention of claim 4, the switching valve is switched by the disappearance of the pilot pressure.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a first embodiment of a brake booster system according to the present invention.

As shown in FIG. 1, the brake booster system 1 of the first embodiment has a brake pedal 2 and a hydraulic booster which is controlled by the brake pedal 2 and constitutes a fluid pressure booster of the present invention. The device 3, the pump 4 and the accumulator 5 that generate the first predetermined fluid pressure supplied to the hydraulic booster 3 and constitute the first pressure source of the present invention, and are operated by the hydraulic booster 3. A tandem master cylinder 6 of a two-brake system, a brake cylinder 7 to which brake fluid is supplied from the master cylinder 6, and a master cylinder 6
And a vacuum brake booster 9 which is arranged in a passage 8 of one of the brake systems between the brake cylinder 7 and constitutes a brake pressure generating means of the present invention, and a negative pressure source of the vacuum brake booster 9 (the second pressure source of the present invention). Equivalent to)
A vacuum tank 10 and a vacuum pump 11, a switching valve 12 that controls the negative pressure of the vacuum tank 10 to the vacuum brake booster 9, and an operation when the hydraulic pressure of the accumulator 5 drops below an extremely low predetermined value. The pressure switch 13 which constitutes the pressure detecting means of the present invention and the pedal switch 14 which is turned on when the brake pedal 2 is depressed.
And an electronic control unit (hereinafter referred to as ECU) 15 that outputs a control signal for switching the switching valve 12 when output signals are output from both the pressure switch 13 and the pedal switch 14.

The brake pedal 2, the hydraulic booster 3, the pump 4, the accumulator 5, the master cylinder 6 and the brake cylinder 7 constitute a conventionally known hydraulic brake booster system.

The vacuum brake booster 9 has a large-diameter power piston 16 on which negative pressure and atmospheric pressure act.
And a small-diameter hydraulic piston 17 that is actuated by the forward movement of the power piston 16 to generate a brake hydraulic pressure. The input / output characteristics of the vacuum brake booster 9 are determined so that the output thereof is equal to or less than the output of the master cylinder 6 when the hydraulic booster 3 is fully loaded when the pressure source of the hydraulic booster 3 is normal. Has been done. As a method of determining the input / output characteristics, there is a method of appropriately setting the diameter of the power piston 16, that is, the effective pressure receiving area and that of the hydraulic piston 17, or a method of limiting the negative pressure to be supplied to a predetermined amount. .

Further, the switching valve 12 is provided with a position I for connecting the vacuum brake booster 9 to the atmosphere and a position II for connecting the vacuum brake booster 9 to the vacuum tank 10, and is normally set to the position I. ing.

In the brake booster system 1 of the first embodiment constructed as described above, the power piston 16 and the hydraulic piston 17 of the vacuum brake booster 9 are in the illustrated non-operating position when the brake is not operating. Further, the switching valve 12 is set to the position I side, and the atmospheric pressure acts on both pressure receiving surfaces of the power piston 16.

When the pressure source of the hydraulic booster 3 is normal and the hydraulic pressure of the accumulator 5 exceeds a predetermined value, the pressure switch 13 does not turn on and does not generate an output signal. Therefore, the ECU 15 does not output the control signal, and the switching valve 12 is set to the position I shown in the figure. That is, the atmospheric pressure acts on both pressure receiving surfaces of the power piston 16.

When the brake pedal 2 is depressed in this state, the pedal switch 14 is turned on and an output signal is emitted.
However, the ECU 15 does not output the control signal because the output signal from the pressure switch 13 is not supplied. Therefore, the switching valve 12 is held at the position I, and the power piston 16 does not move forward. By depressing the brake pedal 2, the control valve (not shown) of the hydraulic booster 3 is switched, the hydraulic fluid flows into the hydraulic pressure chamber (not shown) of the hydraulic booster 3, and the power piston ( (Not shown) moves forward.
This causes the master cylinder 6 to generate brake fluid pressure,
The brake fluid pressure of one brake system is supplied to the brake cylinder 7 of that brake system, and the brake of that brake system operates. On the other hand, the brake fluid of the other brake system of the master cylinder 6 passes through the passage 8 and the fluid chamber 1 in front of the hydraulic piston 17 of the vacuum brake booster 9.
8 is supplied. As a result, the hydraulic piston 17 operates to generate brake hydraulic pressure, and this brake hydraulic pressure is supplied to the brake cylinder 7 of the other brake system to operate the brake of this brake system.

When the pressure source (pump 4 or accumulator 5) of the hydraulic booster 3 fails and the hydraulic pressure of the accumulator 5 drops abnormally below a predetermined value, the pressure switch 1
3 turns on and emits an output signal. When the brake pedal 2 is depressed in this state, the pedal switch 14 is turned on and an output signal is emitted. Therefore, since the ECU 15 is supplied with both the output signal from the pressure switch 13 and the output signal from the pedal switch 14, it outputs a control signal and the switching valve 12 is switched to the position II. As a result, a negative pressure from the vacuum tank 10 acts on the pressure receiving surface of the power piston 16 on the hydraulic piston 17 side.
6 moves forward. By the advance of this power piston 16,
The hydraulic piston 17 operates to generate a brake hydraulic pressure, and this brake hydraulic pressure is supplied to the brake cylinder 7 of the other brake system to operate the brake of this brake system. The brake pressure generated by the operation of the vacuum brake booster 9 is substantially the same as the brake pressure generated by the operation of the hydraulic booster 3 when the pressure source is normal. The brake fluid pressure generated in the master cylinder 6 by the pedaling force of the brake pedal 2 is supplied to the brake cylinder 7 of one brake system.

Brake boosting system 1 of the first embodiment
According to this, since the vacuum brake booster 9 is activated to generate the brake fluid pressure when the brake is activated when the pressure source fails, an extremely large braking force can be obtained. Therefore, not only can the normal braking at the time of pressure source failure be performed almost as securely as the normal braking at the time of normal pressure source, but also the pedal effort can be reduced, and the stopping at the sudden braking is comparatively small. You will be able to perform reliably with pedaling.

FIG. 2 is a diagram schematically showing a second embodiment of the present invention. The same components as those of the brake booster system of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the first embodiment described above, the switching valve 12 is switched based on the output signal of the pressure switch 13, but in the second embodiment, as shown in FIG. Since the second switching valve is provided in the second embodiment, the switching control of the second switching valve is referred to as the first switching valve in the second embodiment) by the hydraulic pressure of the accumulator 5. That is, the accumulator 5 and the pilot pressure introducing portion of the first switching valve 12 are connected via the passage 27, and the hydraulic pressure in the accumulator 5 is used as the pilot pressure for switching control of the first switching valve 12 through the passage 27. It acts on the 1-switching valve 12. Then, when the pressure source of the hydraulic booster 3 is normal, the first switching valve 12 is set to the position I by this pilot pressure and its output port is connected to the atmosphere. In the event of a failure, the first switching valve 12 is set to position II by a spring so that its output port is connected to the vacuum tank 10.

Further, since the first switching valve 12 is hydraulically controlled to be switched, the pedal switch 1 for detecting the brake operation is detected.
The second switching valve 19 which is switch-controlled by the output signal from 4
Is provided. In that case, when the brake pedal 2 is released, the second switching valve 19 is set to the position I by a spring to connect its output port to the atmosphere, and when the brake pedal 2 is depressed, the second switching valve 19 is moved from the pedal switch 14. The output signal is set to the position II so that its output port is connected to the first switching valve 12.

In the brake booster system 1 of the second embodiment thus constructed, when the pressure source of the hydraulic booster 3 is normal, it operates in the same manner as in the first embodiment. When the pressure source of the hydraulic booster 3 fails, the first switching valve 12 switches to the position II and its output port is connected to the vacuum tank 10. When the brake pedal 2 is depressed in this state, the second signal is output by the output signal from the pedal switch 14.
The switching valve 19 is switched to the position II, and its output port is connected to the first switching valve 12. As a result, the vacuum tank 1 is provided on the pressure receiving surface of the power piston 16 on the hydraulic piston 17 side.
Negative pressure from 0 acts. After that, the same operation as in the first embodiment is performed.

Also in the second embodiment, the same operational effect as in the first embodiment can be obtained. Further, in the second embodiment, the number of changeover valves is increased by one as compared with the first embodiment, but the pressure switch 13 and the ECU 15 are not necessary, so the number of parts is reduced.

FIG. 3 is a diagram schematically showing a third embodiment of the present invention. The same components as those of the brake booster system of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

While the vacuum brake booster 9 of the first embodiment described above does not have a relay valve, in this third embodiment, the vacuum brake booster 9'includes the relay valve 20 as shown in FIG. Have one.
That is, in this vacuum brake booster 9 ′, the relay valve 20 is switched by the hydraulic pressure from the master cylinder 6, and the negative pressure supply / discharge control to the power piston 16 is performed. The relay valve 20 is provided on the one side of the power piston 16 and is connected to the vacuum tank 10 by a switching valve 1
A position I which is connected via 2 and which communicates with the chamber 21 on the other side of the power piston 16 and the chamber 21 into which the atmospheric pressure is introduced at the normal time and the negative pressure from the vacuum tank 10 is introduced when the pressure source fails. Position to shut off between these two chambers 21 and 22
II, and three positions, that is, a position III that disconnects the chamber 22 from the chamber 21 and communicates with the atmosphere, are set to the position I in the normal state. This vacuum brake booster 9 '
Is arranged in the passage 8 and its input / output characteristics are set in the same manner as in the case of the vacuum brake booster 9 of the first embodiment described above.

In the brake booster system 1 of the third embodiment thus constructed, the switching valve 12 is set to the position I when the pressure source of the hydraulic booster 3 is normal.
The chamber 21 is in communication with the atmosphere. Therefore, when the pressure source is normal, the normal brake operates as in the first embodiment. At this time, the relay valve 20 is switched to the position III by the hydraulic pressure from the master cylinder 6 introduced into the liquid chamber 18, and the chamber 22 is cut off from the chamber 21 and communicates with the atmosphere. Because it communicates with the atmosphere,
No differential pressure is generated in the power piston 16, and the power piston 16 does not operate.

When the pressure source of the hydraulic booster 3 fails, the switching valve 12 is moved to the position II by the output signal from the pressure switch 13.
Is switched to. As a result, the vacuum from the vacuum tank 10 is introduced into the chamber 21. Since the chamber 21 and the chamber 22 communicate with each other via the relay valve 20, the negative pressure introduced into the chamber 21 is further introduced into the chamber 22. Therefore, no differential pressure is generated in the power piston 16 and the power piston 16 does not operate. In this state, the hydraulic booster 3 does not operate even if the brake pedal 2 is depressed, but when the brake pedal 2 is further depressed, the piston of the master cylinder 6 operates via the power piston to generate hydraulic pressure. To do. The hydraulic pressure of the master cylinder 6 is supplied to the hydraulic chamber 18 of the vacuum brake booster 9'through the passage, and the hydraulic pressure of the hydraulic chamber 18 causes the relay valve 2
0 is switched to position III. As a result, the chamber 21 and the chamber 22 are shut off and the atmosphere is introduced into the chamber 22, so that a differential pressure is generated in the power piston 16 and the power piston 16 moves forward. Due to the forward movement of the power piston 16, the hydraulic piston 17 operates to generate a brake hydraulic pressure in the hydraulic chamber 24. This brake fluid pressure is supplied to the brake cylinder 7, and the brake operates.

According to the third embodiment as well, it is possible to obtain the same effects as the first embodiment. Since the third embodiment includes the relay valve 20 for servo control, the output of the power piston 16 changes according to the hydraulic pressure of the master cylinder 6, that is, the pedal effort. Therefore, the brake fluid pressure of the brake cylinder 7 also changes according to the pedal effort, and it is possible to obtain the braking force according to the brake operation force of the driver.

FIG. 4 is a diagram schematically showing a fourth embodiment of the present invention. The same components as those of the brake boosting system of the first to third embodiments shown in FIGS. 1 to 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

In contrast to the vacuum brake booster 9'provided with the relay valve 20 of the third embodiment, which is arranged in the passage 8 of one brake system, in the fourth embodiment, as shown in FIG. As shown in FIG. 5, the vacuum brake booster 9'is arranged in parallel with the passage 8, and its input / output characteristics are set in the same manner as in the vacuum brake booster 9 of the first embodiment described above.

In the passage 8 of one brake system,
Switching valve 2 for selectively switching the master cylinder to the brake cylinder 7 or the vacuum brake booster 9 '.
3 is provided. The switching valve 23 is provided with a position I for connecting the master cylinder 6 and the brake cylinder 7 and a position II for connecting the master cylinder 6 and the liquid chamber 18 of the vacuum brake booster 9 ', and the position I is normally provided. Is set to. Further, a passage 25 connecting the liquid chamber 24 of the vacuum brake booster 9'and the brake cylinder 7 is provided with a shutoff position I and a communication position II, and is normally closed at the shutoff position I. An on-off valve 26 is provided. The switching valve 23 and the opening / closing valve 26 are switched and controlled by an output signal from the pressure switch 13.

In the brake booster system 1 of the fourth embodiment thus constructed, the switching valve 23 is set to the position I when the pressure source of the hydraulic booster 3 is normal.
The master cylinder 6 is connected to the brake cylinder 7 and is disconnected from the vacuum brake booster 9 '. Therefore, it operates in the same manner as the first to third embodiments.

When the pressure source of the hydraulic booster 3 fails, both the switching valve 23 and the opening / closing valve 26 are switched to the position II by the output signal from the pressure switch 13. As a result, the master cylinder 6 is disconnected from the brake cylinder 7, and the liquid chamber 1 of the vacuum brake booster 9'is also cut off.
8 is connected. The liquid chamber 24 of the vacuum brake booster 9'is connected to the brake cylinder 7. In this state, the hydraulic booster 3 does not operate even if the brake pedal 2 is depressed, but when the brake pedal 2 is further depressed, the piston of the master cylinder 6 operates via the power piston to generate hydraulic pressure. To do. The hydraulic pressure of the master cylinder 6 is supplied to the hydraulic chamber 18 of the vacuum brake booster 9'through the switching valve 23, and the hydraulic pressure of the hydraulic chamber 18 switches the relay valve 20 to the position III. As a result, the chamber 21 and the chamber 22 are disconnected from each other, and the atmosphere is introduced into the chamber 22, so that the power piston 1
6 moves forward. By the advance of this power piston 16,
The hydraulic piston 17 operates to generate brake hydraulic pressure in the hydraulic chamber 24. This brake fluid pressure is supplied to the brake cylinder 7 through the opening / closing valve 26, and the brake operates. According to the fourth embodiment as well, it is possible to obtain the same effects as those of the first to third embodiments.

FIG. 5 is a diagram schematically showing a fifth embodiment of the present invention. The same components as those of the brake boosting system of the first to fourth embodiments shown in FIGS. 1 to 4 described above are designated by the same reference numerals, and detailed description thereof will be omitted.

In the above-described fourth embodiment, the switching valve 23 and the on-off valve 26 are switched by the output signal from the pressure switch 13, but in the fifth embodiment, these switching is performed as shown in FIG. Pass the valve 23 and the on-off valve 26 through the passage 27.
The pilot pressure, which is the hydraulic pressure of the accumulator 5 introduced through the switch, is used for switching. That is, when the pressure source of the hydraulic booster 3 is normal, the switching valve 23 and the opening / closing valve 26 are both set to the position I by this pilot pressure, and when the pressure source of the hydraulic booster 3 fails. The switching valve 23 and the open / close valve 26 are both set to the position II by springs.

In the brake booster system of the fifth embodiment thus constructed, when the pressure source of the hydraulic booster 3 is normal, it operates in the same manner as in the third embodiment. When the pressure source of the hydraulic booster 3 fails, both the switching valve 23 and the opening / closing valve 26 are switched to the position II. Therefore, thereafter, the operation is similar to that of the fourth embodiment.

Also in the fifth embodiment, it is possible to obtain the same effects as those in the first to fourth embodiments. Further, according to the fifth embodiment, the pressure switch 13 is not required as compared with the fourth embodiment, so that the number of parts is reduced.

In each of the above embodiments, the hydraulic booster 2 is used.
Although the present invention is applied to a brake booster system including the above, the present invention is not limited to this, and a brake booster using another working fluid such as a negative pressure booster or an air-over hydraulic brake is used. It can also be applied to force systems.

[0048]

As is apparent from the above description, according to the brake booster system of the present invention, the brake fluid pressure is generated by the brake pressure generating means when the brake is operated when the first pressure source fails. Therefore, even when the first pressure source fails, the same large braking force as when the first pressure source is normal can be obtained. Therefore, even when the first pressure source fails, the same brake operation as the normal brake can be reliably performed, and the pedal effort can be reduced. Moreover, it is possible to reliably stop the vehicle with sudden braking with a comparatively small pedal effort.

[Brief description of drawings]

FIG. 1 is a first brake boosting system according to the present invention.
It is a figure which shows an Example typically.

FIG. 2 is a second brake boosting system according to the present invention.
It is a figure which shows an Example typically.

FIG. 3 is a third part of the brake booster system according to the present invention.
It is a figure which shows an Example typically.

FIG. 4 is a fourth part of the brake boosting system according to the present invention.
It is a figure which shows an Example typically.

FIG. 5 is a fifth part of the brake booster system according to the present invention.
It is a figure which shows an Example typically.

FIG. 6 is a diagram showing an example of a conventional brake booster system.

[Explanation of symbols]

1 ... Brake boost system, 2 ... Brake pedal, 3 ...
Hydraulic booster, 4 ... Pump, 5 ... Accumulator, 6 ...
Tandem master cylinder, 7 ... Brake cylinder, 8,
25, 27 ... Passage, 9, 9 '... Vacuum brake booster, 10 ... Vacuum tank, 11 ... Vacuum pump, 12 ... Changeover valve, 13 ... Pressure switch, 14 ... Pedal switch, 15
... ECU, 16 ... Power piston, 17 ... Hydraulic piston, 18 ... Liquid chamber, 19 ... Second switching valve, 20 ... Relay valve, 21 ... Negative pressure chamber, 22 ... Transformer chamber, 23 ... Switching valve, 24
… Liquid chamber, 26… Open / close valve

Claims (4)

[Claims] 1. A first pressure source that generates a first predetermined fluid pressure, a brake operating means that performs a brake operation, and a fluid that is output when the first predetermined fluid pressure is supplied by the operation of the brake operating means. It consists of a pressure booster, a master cylinder that operates by the output of this fluid pressure booster to generate a brake pressure, and a brake cylinder that generates a brake force by supplying the brake pressure from this master cylinder. In a brake booster system, a second pressure source that generates a second predetermined fluid pressure and a second pressure source that is operated to generate a brake pressure and supply the brake pressure to the brake cylinder. Brake pressure generating means for operating the brake operating means, and when the first predetermined fluid pressure of the first pressure source is less than or equal to a predetermined value when the brake operating means is operated, The second predetermined fluid pressure is supplied to the brake pressure generating means, and when the first predetermined fluid pressure exceeds the predetermined value, the second predetermined fluid pressure is not supplied to the brake pressure generating means. A brake booster system comprising: a switching valve that controls the supply and discharge so as to discharge the second predetermined fluid pressure supplied into the brake pressure generating means. 2. A first pressure source for generating a first predetermined fluid pressure, a brake operating means for performing a brake operation, and a fluid output when the first predetermined fluid pressure is supplied by the operation of the brake operating means. It consists of a pressure booster, a master cylinder that operates by the output of this fluid pressure booster to generate a brake pressure, and a brake cylinder that generates a brake force by supplying the brake pressure from this master cylinder. The brake booster system has a second pressure source for generating a second predetermined fluid pressure and a relay valve, and the relay valve is switch-controlled to operate by the supply of the second predetermined fluid pressure to operate the brake pressure. And a brake pressure generating means for supplying the brake pressure to the brake cylinder, the master cylinder and the brake. A first position which is provided in a passage connecting to the binder and which connects the master cylinder to the brake cylinder and shuts off the relay valve of the brake pressure generating means; and the master cylinder of the brake pressure generating means. A second position communicating with the relay valve and blocking the brake cylinder is set, and is set to the first position when the first predetermined fluid pressure of the first pressure source exceeds a predetermined value and the first position. A brake booster system comprising: a switching valve that is set to the first position when the first predetermined fluid pressure of the pressure source is equal to or lower than the predetermined value. 3. A pressure detecting means for operating when the first predetermined fluid pressure of the first pressure source is equal to or lower than the predetermined value is provided, and the pressure detecting means is connected to the switching valve, The brake booster system according to claim 1 or 2, wherein the switching valve is switch-controlled by an output signal from the pressure detecting means. 4. A passage is provided for supplying the first predetermined fluid pressure of the first pressure source as a pilot pressure to the switching valve, and the switching valve is switch-controlled by the pilot pressure. The brake booster system according to claim 1 or 2.