JPH09286321A - Closed center type hydraulic pressure booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the load of a pump from increasing and use an engine- driven pump as a hydraulic pressure source for a closed center type hydraulic pressure booster. SOLUTION: When accumulated pressure of an accumulator 11 for operation hydraulic pressure which accumulates operation hydraulic pressure for operating a brake booster 1 is equivalent to or less than a prescribed pressure, a piston 37 is in an inoperative condition, a pressure release valve 43 is closed, and a valve passage 42 and a reservoir connecting hole 41 are shut down. Hydraulic fluid which is discharged from a pump 10 is supplied to the accumulator 11 for operation hydraulic pressure, and the accumulated pressure rises. When the accumulated pressure of an accumulator 11 for operation hydraulic pressure exceeds prescribed pressure, the piston 37 moves to the left against the spring force of a controlling spring 38 by the operation of the accumulated pressure. Therefore, the pressure release valve 43 is opened, and the valve passage 42 and the reservoir connecting hole 41 are connected. Therefore, the hydraulic fluid discharged from the pump 10 is returned to a reservoir 15, and the pump 10 is kept under no-load operating condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a hydraulic booster that boosts an operating force of an operating member by hydraulic fluid pressure of hydraulic fluid and outputs the boosted force. The present invention belongs to the technical field of a hydraulic pressure source for generating hydraulic fluid used in an apparatus.

[0002]

2. Description of the Related Art For example, in a brake or a clutch of a vehicle such as an automobile, various hydraulic boosters are used which boost the operating force of an operating member by hydraulic pressure of hydraulic fluid and output the boosted force. As such a hydraulic booster, there are a closed center type hydraulic booster and an open center type hydraulic booster.

In the closed center type hydraulic booster, when not operating, the control valve shuts off the power chamber from the pump side and communicates with the reservoir, and the hydraulic pressure of the accumulator in which the pump discharge pressure is stored is Set to the state where the control valve is also introduced, and when operating, the control valve shuts off the power chamber from the reservoir and communicates with the pump side, and also introduces the hydraulic pressure from the pump introduced to this control valve into the power chamber It is a hydraulic booster designed to be set in a closed state.

This conventional closed center type hydraulic booster uses a motor-driven pump and an accumulator that stores the hydraulic fluid pressure, which is the discharge pressure of the pump, as a hydraulic pressure source for generating hydraulic fluid pressure. There is. By driving the pump with a motor, the accumulator always stores a predetermined hydraulic pressure required for the brake, and the predetermined hydraulic pressure stored in the accumulator is used when the brake is activated to ensure that the brake is applied. It is designed to be used.

Further, in the open center type hydraulic booster, when the control valve shuts off the power chamber from the pump side and communicates with the reservoir, the hydraulic fluid discharged from the pump is controlled by the control valve. The working fluid is returned to the reservoir again through the circulating fluid.At the time of operation, the control valve shuts off the power chamber from the reservoir and communicates with the pump side, and squeezes the working fluid discharged from the pump. Is a hydraulic booster which is configured to generate a hydraulic pressure and set the hydraulic pressure introduced into the power chamber.

In this conventional open center type hydraulic booster, the hydraulic pressure source for generating the working hydraulic pressure is generally shared with the hydraulic pressure source of the power steering system. It uses a drive pump. Then, the pump is constantly driven by the engine to constantly circulate the hydraulic fluid so that the hydraulic fluid is returned from the reservoir to the reservoir again through the control valve of the hydraulic booster and the power steering system. The control valve of the pressure booster squeezes the hydraulic fluid discharged from the pump to generate hydraulic pressure, and the generated hydraulic pressure ensures that the brake is applied.

[0007]

By the way, in the closed center type hydraulic booster, in order to always accumulate a predetermined hydraulic pressure in the accumulator, a pressure detection device such as a pressure switch for detecting the pressure of the accumulator is used. Means are provided. The pressure detecting means is activated when the accumulated pressure of the accumulator becomes equal to or lower than a predetermined pressure, the control device drives the motor by the activation signal, and the operation is stopped when the accumulated pressure of the accumulator exceeds the prescribed pressure, and the operation is stopped. The signal causes the control device to stop driving the motor. As a result, a predetermined hydraulic pressure can be constantly stored in the accumulator.

However, in the hydraulic pressure source in such a closed center type hydraulic booster, not only a dedicated motor for driving the pump is necessary, but also pressure detection for controlling this motor. Special parts such as a means and a control device are required, resulting in a large number of parts and high cost.

Therefore, it is conceivable that the pump is driven by the engine like the engine-driven pump in the above-mentioned open center type hydraulic booster so that a dedicated motor is not required.

However, when the pump is driven by the engine, the pump is always driven during engine operation. In the case of the open center type hydraulic booster, the hydraulic fluid is circulated, so even if the pump is constantly driven, the load on the pump is hardly applied. In the case of a booster, if the pump is constantly driven, the accumulated pressure in the accumulator becomes extremely large, which causes a problem that the load on the pump increases.

The present invention has been made in view of the above problems, and an object thereof is to prevent an increase in the load of the pump even if an engine-driven pump is used as the hydraulic pressure source. A closed center type hydraulic booster capable of using an engine-driven pump as a hydraulic pressure source.

[0012]

In order to solve the above-mentioned problems, the invention of claim 1 comprises a reservoir for storing a hydraulic fluid,
A pump that sucks and discharges the hydraulic fluid from the reservoir, a hydraulic fluid accumulator that stores the discharge pressure of the pump as hydraulic fluid pressure, an input shaft that operates when an operating force is transmitted, and the hydraulic fluid accumulator during operation. The power chamber to which the working hydraulic pressure stored in the power chamber is supplied, the power piston that is actuated by the working hydraulic pressure in the power chamber to boost and output the operating force, and the working hydraulic pressure accumulator during operation. And a control valve for selectively controlling the hydraulic fluid pressure in the power chamber to be discharged to the reservoir when the hydraulic fluid pressure is not supplied to the power chamber. In a closed center type hydraulic booster in which the control valve is operated, the pump is a pump driven by an engine, and Flop and passage pump load control device is provided in between the hydraulic fluid pressure accumulator,
This pump load control device closes when the accumulated pressure of the hydraulic fluid accumulator is less than or equal to a predetermined pressure to shut off between the pump and the reservoir, and when the accumulated pressure of the hydraulic fluid accumulator exceeds the predetermined pressure. Is provided with a normally-closed pressure relief valve that opens to communicate between the pump and the reservoir to release the pump discharge pressure to the reservoir.

According to a second aspect of the present invention, the pump load control device is provided in a housing and slidably in the housing, the accumulated pressure of the hydraulic fluid accumulator acts, and the hydraulic fluid accumulator is provided. A valve control piston that operates when the accumulated pressure exceeds the predetermined pressure to open the pressure relief valve, a pump connection port formed in the housing and connected to the discharge side of the pump, and a pump connection formed in the housing A reservoir connection port connected to the mouth and connected to the reservoir, wherein the pressure relief valve is provided in a passage that connects the pump connection port and the reservoir in the housing. .

Further, the invention of claim 3 further comprises a second pressure lower than the predetermined pressure for controlling the operation of the pressure relief valve of the pump load control device while being connected to the pump.
A control fluid pressure accumulator for storing a predetermined pressure of the control fluid pressure accumulator, and a passage portion of the passage between the pump load control device and the hydraulic fluid pressure accumulator, the accumulated pressure of the control fluid pressure accumulator being the second predetermined value. A pressure accumulation control device for controlling the pressure is provided.

According to a fourth aspect of the present invention, the pump load control device is further provided in a housing and slidably in the housing, and the accumulated pressure of the hydraulic fluid accumulator acts in a direction to open the pressure relief valve. With the stored pressure of the control hydraulic pressure accumulator is actuated in the direction of closing the pressure relief valve, and a valve control piston that operates when the accumulated pressure of the hydraulic fluid accumulator exceeds the predetermined pressure to open the pressure relief valve. A normally closed control hydraulic pressure relief valve that is provided in the housing and is opened by the operation of the valve control piston to release the accumulated pressure of the control hydraulic pressure accumulator to the reservoir, and is connected to the pump formed in the housing. A pump connection port and a reservoir formed on the housing and connected to the pump connection port and the reservoir. A pressure relief valve is provided in a passage that connects the pump connection port and the reservoir in the housing, and the pressure accumulation control device slides in the housing. A hydraulic pressure control piston that is disposed so as to be actuated when the accumulated pressure of the control hydraulic pressure accumulator acts and the accumulated pressure of the control hydraulic pressure accumulator reaches the second predetermined pressure; It is characterized in that it is provided with a normally open hydraulic pressure control valve which is closed by the operation of the hydraulic pressure control piston and shuts off a passage connecting the pump and the control hydraulic pressure accumulator.

[0016]

According to the inventions of claims 1 and 2 thus constructed, the pump is driven by the engine, and the discharge pressure of the pump is accumulated in the hydraulic fluid accumulator. When the accumulated pressure of the hydraulic fluid accumulator exceeds a predetermined pressure, the normally closed pressure relief valve opens to communicate between the pump and the reservoir, and the pump discharge pressure is discharged to the reservoir and becomes zero. As a result, when the accumulated pressure of the hydraulic fluid accumulator exceeds the predetermined pressure, the pump is put into a no-load operation state and an increase in the load of the pump is prevented.

Particularly, in the inventions of claims 3 and 3,
The operation of the pressure relief valve is also controlled by the accumulated pressure of the control hydraulic accumulator that stores the second predetermined pressure lower than the predetermined pressure. As a result, the pressure relief valve is more fully operated, and the pump is more reliably brought into the no-load operation state.

[0018]

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 in which a hydraulic booster according to the present invention is applied to a brake booster, and FIG. 2 is a partially enlarged view of FIG.

As shown in FIG. 1, a brake booster 1 to which the hydraulic booster of this embodiment is applied is provided with a front housing portion 2
The housing 2 includes a housing 2a and a rear housing portion 2b. An input shaft 3 connected to a brake pedal (not shown) is liquid-tightly and slidably penetrated through the rear housing portion 2b. A power piston 4 is provided in the front housing portion 2a so as to be liquid-tight and slidable.
The tip end portion 3a is fitted in a liquid-tight manner so as to be slidable.
Further, an output shaft 5 that operates by transmitting the output of the power piston 3 to a piston of a master cylinder (not shown) is brought into contact with the front end of the power piston 4, and a return spring 6 is provided.
And retained by the retainer 7. Further, a power chamber 8 is formed in the housing between the front housing portion 2a and the rear housing portion 2b, and the power chamber 8 is facing the rear end of the power piston 4.

Further, a control valve 9 is provided between the front housing part 2a and the rear housing part 2b. As shown in detail in FIG. 2, the control valve 9 includes a supply passage 1 that connects a power chamber 8 and a hydraulic fluid accumulator 11 that stores a discharge pressure of a pump 10 driven by an engine E.
2, the supply passage 1 formed in the front housing 2a
Poppet type valve body 13 provided with a ball valve provided in 2a
Of the valve seat member 14 having the first valve seat 14a on which the valve body 13 can be seated, which is also provided in the supply passage 12a, and the passage connecting the power chamber 8 and the reservoir 15 to the rear housing 2b. And a second valve seat 17b formed in the discharge passage 16 and having an axial through hole 17a forming a part of the discharge passage 16 and a second valve seat 17b formed around the opening end of the axial through hole 17a. Member 17 and valve body 13
Is constituted by a first valve spring 18 which constantly urges the valve seat 14a toward the first valve seat 14a, and a second valve spring 19 which constantly urges the tubular member 17 away from the valve body 13. In that case, the tubular member 17 is the rear housing 2
It is fitted so as to be liquid-tight and slidable on the cylindrical protrusion 20 formed in b. Inner hole 20a of this cylindrical protrusion 20
Constitutes a part of the discharge passage 16.

This control valve 9 has a valve body 13 having a first valve seat 14 as shown in FIG. 2 when the brake booster 1 is not operated.
The second valve seat 17b is separated from the valve body 13 while being seated on a. Therefore, the power chamber 8 is disconnected from the hydraulic fluid accumulator 11 when not in operation, and communicates with the reservoir 15 via the clearance between the valve body 13 and the second valve seat 17b and the discharge passage 16. There is.
Further, when the brake booster 1 is operated, the tubular member 17 moves to the left, the second valve seat 17b is seated on the valve body 13, and the valve body 13 is separated from the first valve seat 14a. ing. Therefore, the power chamber 8 is shut off from the reservoir 15 at the time of this operation, and the valve body 13 and the first
It communicates with the hydraulic fluid accumulator 11 through a gap between the valve seat 14a and the supply passage 12a. The hydraulic pressure in the power chamber 8 acts on the valve body 13 in the same direction as the urging force of the first valve spring 18 via the passage 21 formed in the front housing part 2.

Further, a lever support member 22 is fixed to the rear end of the power piston 4, and this lever support member 22 is provided.
The one end of the lever 23 is swingably supported by the first support pin 24. The other end of the lever 23 is swingably supported by the tubular member 17 by a second support pin 25. Further, an axial long hole 23a is formed near the one end of the lever 23, and an engaging pin 3b protruding leftward and rightward from the input shaft 3 is fitted into the long hole 23a.
The engagement pin 3b can be engaged with both side walls of the elongated hole 23a. In that case, the first support pin 24 and the engagement pin 3b
The distance between and is set to be always smaller than the distance between the engagement pin 3b and the second support pin 25 regardless of whether the brake booster 1 is operated or not. Also,
Between the retainer portion 23b of the lever 23 and the step portion on the rear end side of the input shaft 3, there is provided a spring 26 that always urges the lever 23 to the left when the lever 23 is placed in FIG. Then, normally, as shown in the figure, the retainer portion 23b is brought into contact with the step portion of the input shaft 3 on the front end portion 3a side by the urging force of the spring 26.

Further, a travel limiter 27 is provided at the tip portion 3a of the input shaft 3. The travel limiter 27 is formed in the front end portion 3a, and the chamber 2 is formed by inserting the front end portion 3a into the hole 4a at the rear end portion of the power piston 4.
8 and the power chamber 8, a ball valve 29, a valve seat 30 on which the ball valve 29 can be seated, and the ball valve 29.
A normally open opening / closing valve 32 including a spring 31 for constantly urging the valve seat 30 toward the valve seat 30, and a push pin slidably fitted in the same passage and pressing the ball valve 29 to control opening / closing of the opening / closing valve 32. And 33.

The travel limiter 27 presses the retainer portion 23b of the lever 23 when the retainer portion 23b pushes the push pin 33 leftward in FIGS. 1 and 2, and pushes the push pin 33 leftward. The pin 33 pushes the ball valve 29 away from the valve seat 30 to open the opening / closing valve 32, whereby the power chamber 8 and the chamber 28 are formed in the axial groove 33a formed on the outer peripheral surface of the pressing pin 33 and Communication is performed through the open / close valve 32. Thus, when the power chamber 8 and the chamber 28 are in communication with each other, the input shaft 3 becomes axially movable relative to the power piston 4. Also, the retainer part 2
When 3b does not press the pressing pin 33, the pressing pin 33 does not press the ball valve 29 at all. Therefore, at this time, the ball valve 29 is seated on the valve seat 30 by the urging force of the spring 31 to close the opening / closing valve 32, and the power chamber 8 is closed.
The chamber 28 is closed and the chamber 28 is sealed. When the chamber 28 is thus sealed, the input shaft 3 cannot move axially relative to the power piston 4.

Further, in the pump discharge passage 34 between the pump 10 and the hydraulic fluid accumulator 11, a pump load control device 35 for controlling the accumulated pressure of the hydraulic fluid accumulator 11 is provided. This pump load control device 35
Is a housing 36, a piston 37 slidably and liquid-tightly slidable in the housing 36, and a pressure accumulation of the working hydraulic pressure accumulator 11 is applied to one surface, and the piston 37 is used for accumulating the working hydraulic pressure accumulator 11. A control spring 38 that constantly urges in a direction opposite to the direction of action of
A pump connection port 39 connected to the pump 10 side of the pump discharge passage 34, an accumulator connection port 40 connected to the hydraulic fluid pressure accumulator 11 side of the pump discharge passage 34 and always communicating with the pump connection port 39, and a reservoir 15. The reservoir connection port 41 to be connected and the L-shaped valve passage 42 formed in the piston rod 37a of the piston 37.
And a normally closed pressure relief valve 43 provided between the reservoir connection port 41 and the valve passage 42.

In this case, when the accumulated pressure of the hydraulic fluid accumulator 11 is equal to or lower than a predetermined pressure, the spring force of the control spring 38 causes the piston 37 to move by the spring force and the discharge pressure from the pump 10 acting on the piston rod 37a.
When the accumulated pressure of the hydraulic pressure accumulator 11 is larger than the force of pushing the piston 37 to the left due to the accumulated pressure of the hydraulic fluid accumulator 11, and when the accumulated pressure of the hydraulic fluid accumulator 11 exceeds a predetermined pressure, the aforementioned combined force is activated. It is set to be smaller than the force that pushes the piston 37 due to the accumulated pressure of the hydraulic pressure accumulator 11.

Therefore, the hydraulic fluid accumulator 1
When the accumulated pressure of 1 is less than or equal to the predetermined pressure, the piston 37 is held at the illustrated position, the pressure relief valve 43 is closed, the valve passage 42 and the reservoir connection port 41 are shut off, and
When the accumulated pressure of the hydraulic fluid accumulator 11 exceeds a predetermined pressure, the piston 37 moves to the left against the spring force of the control spring 38, the pressure relief valve 43 is opened, and the valve passage 42 and the reservoir connection port 41. And are communicated with each other.

A check valve 44 permits only the flow of the hydraulic fluid from the pump 10 to the hydraulic fluid accumulator 11.

In the brake booster 1 of the present embodiment thus constructed, the pump 1 is operated when the engine E is operated.
0 is driven, in which case pump 1 is running while engine E is running.
The drive of 0 is continuously performed. The hydraulic fluid in the reservoir 15 discharged from the pump 10 by driving the pump 10 passes through the pump discharge passage 34, the pump connection port 39, the accumulator connection port 40, the pump discharge passage 34, and the check valve 44, and the hydraulic fluid accumulator. Then, the hydraulic fluid pressure accumulator 11 is stored.

The accumulated pressure of the hydraulic fluid accumulator 11 acts on the piston 37. However, while the accumulated pressure of the hydraulic fluid accumulator 11 is below a predetermined pressure, the piston 37 does not move to the left due to this accumulated pressure and the pressure relief valve. 43 is held closed. As the accumulated pressure of the hydraulic fluid accumulator 11 increases, the load on the pump 10 also increases.
Then, when the predetermined pressure is exceeded, the piston 37 moves to the left, the pressure relief valve 43 opens, and the pump connection port 39 and the reservoir connection port 41 are connected via the valve passage 42. Therefore, the hydraulic fluid discharged from the pump 10 is directly returned to the reservoir 15 and circulated between the reservoir 15, the pump 10 and the pressure relief valve 43. As a result, the pump 10 is put into a no-load operation state, and the load of the pump 10 is prevented from being greatly increased.

In this state, when the brake is not operated, the input shaft 3 is in the retracted limit position shown in FIGS. 1 and 2, so that the control valve 9 is in the inactive state. Therefore, the power chamber 8 is cut off from the hydraulic fluid pressure accumulator 11 and communicated with the reservoir 15. For this reason, the hydraulic pressure from the hydraulic fluid accumulator 11 is introduced from the seated position of the valve body 13 and the first valve seat 14a to a position closer to the hydraulic fluid accumulator 11 but is not supplied into the power chamber 8. , The power piston 4 does not operate.

When the brake is operated, the input shaft 3 is moved forward (leftward) by depressing the brake pedal. Then, first, the engaging pin 3b comes into contact with the side wall of the elongated hole 23a to rotate the lever 23 clockwise around the first support pin 24.
The tubular member 17 moves forward to seat the second valve seat 17b on the valve body 13 and separate the valve body 13 from the first valve seat 14a.
Therefore, the power chamber 8 is shut off from the reservoir 15 and communicates with the hydraulic fluid pressure accumulator 11, and the hydraulic pressure from the hydraulic fluid pressure accumulator 11 is supplied into the power chamber 8. The hydraulic pressure in the power chamber 8 acts on the power piston 4, so that the power piston 4 advances and generates an output. Then, this output operates a master cylinder (not shown) via the output shaft 5, and the brake is applied by the brake fluid pressure generated by the master cylinder.
The hydraulic pressure in the power chamber 8 also acts on the input shaft 3 in the backward direction.

As the power piston 4 advances, the lever 2
3 rotates counterclockwise about the engagement pin 3b, and as a result, the tubular member 17 retracts (moves to the right), and the gap between the valve body 13 and the first valve seat 14a becomes smaller. . And
When the hydraulic pressure in the power chamber 8 becomes a pressure corresponding to the pedal effort of the brake pedal, the forward movement of the input shaft 3 is stopped, and the first and second valve seats 14a and 17b are both in the neutral position where they are seated on the valve body 13, The hydraulic pressure in the chamber 8 is maintained at a pressure corresponding to the brake pedal depression force. Therefore, the output of the power piston 4 becomes a magnitude of the output at this time, that is, a magnitude obtained by multiplying the depression force of the brake pedal. In this way, the brake fluid pressure becomes a magnitude that doubles the pedaling force of the brake pedal.

When the depression of the brake pedal is released to release the brake operation, the input shaft 3 retracts. Then, the engagement pin 3 b moves the lever 2 around the first support pin 24.
3 is rotated counterclockwise, and the tubular member 17 retracts. As a result, the second valve seat 17b is separated from the valve body 13 and the power chamber 8 communicates with the reservoir 15. Therefore, the hydraulic pressure in the power chamber 8 is discharged to the reservoir 15 and the pressure in the power chamber 8 is increased. descend. Therefore, the power piston 4 retracts, and at this time, the lever 23 rotates clockwise around the second support pin 25. When the rear end of the lever support member 22 at the rear end of the power piston 3 comes into contact with the rear housing 2b as shown in FIG. 1, the power piston 3 is in the retracted limit, that is, the inoperative position, and accordingly, the input shaft 3 and the tubular shape are The member 17 is also in the inoperative position. In this way, the brake booster 1 stops outputting, the master cylinder is deactivated, and the brake is released.

When the brake is operated, the pedal force of the brake pedal is greatly increased, the tubular member of the control valve 9 and the valve body 13 are largely moved, and the front end 13a of the valve body 13 is moved forward.
When it abuts the facing wall 2a _{1 of} b, the valve body 13 will not advance any further. Therefore, the gap between the valve body 13 and the first valve seat 14a does not become larger, and the rotation of the lever 23 in the clockwise direction by the force from the input shaft 3 is stopped. As a result, the hydraulic pressure in the power chamber 8 becomes the same as the hydraulic fluid pressure accumulator 11 and does not rise any further, and the brake booster 1 is in the full load state.
In such a full load state of the brake booster 1, the hydraulic pressure in the power chamber 8 is constant, so the movement of the power piston 4 due to the hydraulic pressure in the power chamber 8 is stopped. After the brake booster 1 is in the full load state, when the depression force of the brake pedal further increases, only the input shaft 3 moves with respect to the power piston 4. Therefore, the pressing pin 33 is not pressed by the retainer portion 23b of the lever 23, so that it does not press the ball valve 29, and the ball valve 29 is seated on the valve seat 30. That is, the opening / closing valve 32 is closed. When the on-off valve 32 is closed, the chamber 28 is shut off from the power chamber 8,
It becomes a sealed state. As a result, the input shaft 3 becomes immovable relative to the power piston 4, so that the pedal effort of the brake pedal acts on the input shaft 3 directly on the power piston 4, and the power piston 4 is further operated by this pedal effort. Like Therefore, the output of the power piston 4 is increased by the increase of the pedaling force.

When the accumulated pressure of the hydraulic fluid accumulator 11 is consumed by the brake operation and becomes less than a predetermined pressure, the piston 37 of the pump load control device 35 moves rightward to the inoperative position shown in the figure. Therefore, the pressure relief valve 43 is closed and the hydraulic fluid from the pump 10 is sent to the hydraulic fluid accumulator 11 in the same manner as described above, and the accumulated pressure of the hydraulic fluid accumulator 11 rises. When the accumulated pressure of the hydraulic fluid accumulator 11 exceeds a predetermined pressure, the piston 37 is moved leftward to open the pressure relief valve 43, and the pump 10 is in a no-load operation state as described above. In this way, even if the accumulated pressure of the hydraulic fluid accumulator 11 is consumed, the hydraulic fluid accumulator 11 can always accumulate a predetermined hydraulic pressure during engine operation.

When the accumulated pressure of the hydraulic fluid accumulator 11 is far below the predetermined pressure and the fluid pressure required for braking cannot be obtained, the stroke of the brake pedal is increased so that the input shaft 3 moves. Since it greatly moves forward, the tubular member 17 and the valve body 13 largely move via the lever 23, and the front end 13a of the valve body 13 comes into contact with the facing wall 2a ₁ of the front housing 2b, and the tubular body 17
And do not move any further. In this state, further input shaft 3
When the lever is moved forward, the lever 23 rotates counterclockwise around the second support pin 25, so that the power piston 4 is pushed forward through the first support pin 24, and the power piston 4 moves forward and outputs. To do. Therefore, the master cylinder is actuated and the brake is applied by the output of the power piston 4. At this time, the brake ratio is determined by the lever ratio of the lever 23 [(distance between the first support pin 24 and the second support pin 25) / (distance between the engagement pin 3b and the second support pin 25)]. Since the pedaling force of is boosted and is transmitted to the power piston 4, the power piston 4 produces an output in which the pedaling force is boosted by the lever ratio. As described above, even if the hydraulic fluid pressure accumulator 11 does not accumulate pressure, the brake can be reliably applied by the force obtained by multiplying the pedal effort of the brake pedal by the lever ratio.

By the way, according to the closed center type brake booster 1 of this embodiment, the normally closed pressure relief valve 43 is provided in the pump discharge passage 34 between the pump 10 and the hydraulic fluid accumulator 11. At the same time, the opening and closing of the pressure relief valve 43 is controlled by the accumulated pressure of the accumulator.
Therefore, the engine prevents the load of the pump 10 from becoming unnecessarily large even if the pump 10 is continuously driven during engine operation. As a result, the engine-driven pump 10 can be used as the hydraulic pressure source of the closed center type brake booster 1.

Further, since the pressure relief valve 43 is constituted by the piston 37 controlled by the accumulated pressure of the hydraulic fluid accumulator 11, the piston rod 37a of this piston 37 and the housing 36, the pump load control device 3
The structure of 5 can be simplified.

Furthermore, since the pump 10 can be driven by the engine E, a dedicated motor or the like for driving the pump 10 such as the conventional closed center type brake booster 1 is not required, and the number of parts is reduced. Therefore, the cost can be reduced.

In this example, the pump 10 and the hydraulic fluid accumulator 11 are connected through the pump load control device 35. However, the pump 10 and the hydraulic fluid accumulator 11 are connected to the pump load control device 35. It is also possible to bypass 35 and connect it. In this case, the accumulator connection port 40 provided in the housing 36 of the pump load control device 35 becomes unnecessary.

FIG. 3 is a view similar to FIG. 1, showing another embodiment of the hydraulic booster of the present invention. The same components as those of the example shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the brake booster 1 shown in FIG. 1, only the hydraulic fluid pressure accumulator 11 is provided, but in the brake booster 1 of this example, as shown in FIG. 3, the hydraulic fluid pressure accumulator 11 is provided. In addition, a control hydraulic pressure accumulator 45 is provided. The control fluid pressure accumulator 45 is formed smaller than the working fluid pressure accumulator 11, and a predetermined pressure (hereinafter, referred to as a second predetermined pressure) stored in the control fluid pressure accumulator 45 is stored in the working fluid pressure accumulator 11. It is set much smaller than the pressure. The accumulated pressure of the control fluid pressure accumulator 45 acts on the surface of the piston 37 opposite to the surface of the piston 37 on which the accumulated pressure of the working fluid pressure accumulator 11 acts via the control fluid pressure accumulator connection port 46 formed in the housing 36. It is supposed to be done.
In the case of this example, the spring force of the spring 38, the pressure receiving area of the piston rod 37a on which the pump discharge pressure acts, the pressure receiving area of the piston 37 on which the accumulated pressure of the control hydraulic pressure accumulator 45 acts, and the accumulated pressure of the hydraulic fluid accumulator 11 are: The acting pressure receiving area of the piston 37 is set so that the piston 37 operates when the accumulated pressure of the hydraulic fluid accumulator 11 exceeds a predetermined pressure.

Further, the pump load control device 35 of this example is
A normally-closed first passage that controls the opening and closing of the passage in the housing 36 that communicates between the control fluid pressure accumulator connection port 46 and the second reservoir connection port 47 connected to the reservoir 15 to release the accumulated pressure of the control fluid pressure accumulator 45. 2 Pressure relief valve 48
Are provided (hereinafter, the accumulator connection port 40 is referred to as a hydraulic fluid accumulator connection port 40, and the reservoir connection port 41 is referred to as a first reservoir connection port 41).

Further, in the brake booster 1 of this embodiment, the pump discharge passage 34 between the hydraulic fluid pressure accumulator connection port 40 of the pump load control device 35 and the check valve 44 is provided.
The accumulator pressure accumulation control device 49 provided in the. The accumulator pressure accumulation control device 49 includes a housing 50, a valve piston 51 slidably arranged in the housing 50, and a pump load control device connection port 52 connected to the hydraulic fluid pressure accumulator connection port 40.
A hydraulic fluid pressure accumulator connection port 53 that is constantly connected to the pump load control device connection port 52 and is connected to the hydraulic fluid pressure accumulator 11; and a control accumulator connection port 5 that is connected to the control fluid pressure accumulator 45.
4, an L-shaped valve passage 55 formed in the valve piston 51, a normally-open pressure accumulation control valve 56 provided between the control accumulator connection port 54 and the valve passage 55,
It is composed of a spring 57 that constantly urges the valve piston 51 in a direction in which the pressure accumulation control valve 56 opens.

In this case, the spring force of the spring 57 is such that when the accumulated pressure of the control fluid pressure accumulator 45 exceeds the second predetermined pressure, the valve piston 51 is moved by this second predetermined pressure to close the pressure accumulation control valve 56. Is set to Therefore, when the accumulated pressure in the control hydraulic pressure accumulator 45 is equal to or lower than the second predetermined pressure, the valve piston 51 is held at the position shown in the figure, the accumulated pressure control valve 56 is opened, and the valve passage 55 and the control accumulator connection port 54 are communicated with each other. In addition, when the accumulated pressure of the control fluid pressure accumulator 45 exceeds the second predetermined pressure, the valve piston 51 moves to the left against the spring force of the spring 57 to close the accumulated pressure control valve 56 and close the valve passage 55. The control accumulator connection port 54 is cut off.

In the brake booster 1 of the present embodiment thus constructed, the pump 1 is stopped before the engine E is driven, and pressure is stored at least in the control hydraulic accumulator 45. Absent. Therefore, the valve piston 51 of the accumulator pressure accumulation control device 49 is
Due to the spring force of the spring 57, the illustrated pressure accumulation control valve 56
Is held in the open position. When the engine E is operated and the pump 10 is driven in this state in the same manner as in the above-described example, if the accumulated pressure in the hydraulic fluid accumulator 11 exceeds the first predetermined pressure, the pump load control device 35 Since the piston 37 moves to the left and the first pressure relief valve 43 is open, the hydraulic fluid in the reservoir 15 discharged from the pump 10 returns to the reservoir 15 again through the first pressure relief valve 43 as described above. , Ie simply circulating.

When the accumulated pressure in the hydraulic fluid accumulator 11 is equal to or lower than the first predetermined pressure, the piston 37 does not move and both the first and second pressure relief valves 43 and 48 are closed. Therefore, the reservoir 1 discharged from the pump 10
The hydraulic fluid 5 is pump discharge passage 34, pump connection port 3
It is sent to the pump load control device connection port 52 of the accumulator pressure accumulation control device 49 through the accumulator connection port 40 and the pump discharge passage 34.

The hydraulic fluid sent to the pump load control device connection port 52 is first supplied to the control hydraulic pressure accumulator 45 through the valve passage 55, the open pressure accumulation control valve 56, and the control accumulator connection port 54. The control fluid pressure accumulator 45 accumulates pressure. At this time, the accumulated pressure of the control hydraulic pressure accumulator 45 acts on the surface of the piston 37 opposite to the surface on which the accumulated pressure of the hydraulic fluid accumulator 11 acts. When the accumulated pressure of the control hydraulic pressure accumulator 45, that is, the discharge pressure of the pump 10 becomes higher than the accumulated pressure of the hydraulic fluid accumulator 11, the hydraulic fluid sent to the pump load control device connection port 52 opens the check valve 44 to open the hydraulic fluid accumulator 11. Is also supplied to the accumulator 11 to increase the accumulated pressure in the hydraulic fluid accumulator 11.

When the accumulated pressure of the control fluid pressure accumulator 45 exceeds the second predetermined pressure, the piston 51 of the accumulator accumulated pressure control device 49 is moved leftward by the pressure, and the accumulated pressure control valve 56 is closed. Therefore, the hydraulic fluid is not supplied to the control fluid pressure accumulator 45, and the control fluid pressure accumulator 4 is supplied.
Accumulator for hydraulic fluid 1
1, the hydraulic fluid is continuously supplied, and the accumulated pressure of the hydraulic fluid pressure accumulator 11 continues to increase.

When the accumulated pressure of the hydraulic fluid accumulator 11 exceeds the first predetermined pressure, the piston 37 operates for the spring force of the control spring 38, the force of the pump discharge pressure acting on the piston rod 37a, and the control fluid pressure acting on the piston 37. It moves to the left against the force due to the accumulated pressure of the accumulator 45. The second pressure relief valve 48 is opened immediately by only slightly moving the piston 37 to the left, so that the accumulated pressure of the control hydraulic pressure accumulator 45 is rapidly discharged to the reservoir. Therefore, the piston 37 has no resistance due to the accumulated pressure of the control fluid pressure accumulator 45, so that the piston 37 moves to the left quickly and reliably,
The first pressure relief valve 43 is opened quickly and reliably. Therefore, the hydraulic fluid in the reservoir 15 discharged from the pump 10 is circulated through the first pressure relief valve 43 and returned to the reservoir 15 as described above. This allows
The pump 10 is in no-load operation, and the pump discharge pressure becomes zero.

Since the pump discharge pressure becomes 0, the hydraulic pressure acting on the valve piston 51 of the accumulator pressure accumulation control device 49 also becomes 0, so that the valve piston 5
1 moves to the right to return to the inoperative position shown, and the pressure accumulation control valve 56
Opens. In this state, the brake operation is performed, and when the accumulated pressure of the hydraulic fluid accumulator 11 becomes equal to or lower than the first predetermined pressure, the piston 37 moves to the right and returns to the inoperative position illustrated.
As a result, the first and second pressure relief valves 43 and 48 are both closed. Thereafter, the hydraulic fluid accumulator 1 described above
Similar to the case where the accumulated pressure of 1 is the first predetermined pressure, the accumulated pressure of both accumulators 11 and 45 is restarted. In this way, the hydraulic pressure accumulator 11 always accumulates a hydraulic pressure exceeding the first predetermined pressure, and the load on the pump 10 is prevented from increasing.

According to the brake booster 1 of this example, the operation of the piston 37 is also controlled by the accumulated pressure of the control hydraulic pressure accumulator 45 and the second relief valve 48. The operation becomes quicker and more reliable than the example of FIG. 1 described above, and the reliability is further improved. As a result, when the accumulated pressure of the hydraulic fluid accumulator 11 exceeds the first predetermined pressure, the first pressure relief valve 43 surely and completely opens, so that the pump discharge pressure does not remain and the load of the pump 10 is reduced. You will definitely be able to get rid of it.

Since the operation for braking the brake booster 1 in this example is the same as that in the example shown in FIG.
The description is omitted.

In this example, the pump 10 and the hydraulic fluid accumulator 11 are connected through the pump load control device 35 and the accumulator pressure accumulation control device 49, but the pump 10 and the hydraulic fluid accumulator 11 are connected. Can be connected by bypassing at least one of the pump load control device 35 and the accumulator pressure accumulation control device 49. In this case, at least one of the accumulator connection port 40 provided in the housing 36 of the pump load control device 35 and the hydraulic fluid accumulator connection port 53 provided in the housing 50 of the accumulator pressure accumulation control device 49 becomes unnecessary.

In each of the above-described examples, the case where the hydraulic booster of the present invention is applied to the closed center type brake booster 1 using a lever is explained. The present invention is not limited to the above, and can be applied to all other closed center type brake boosters 1 that do not use a lever.

The hydraulic booster of the present invention can also be applied to other hydraulic boosters such as a clutch booster other than the brake booster.

[0058]

As is apparent from the above description, according to the hydraulic booster of the closed center type according to the first to fourth aspects of the invention, when the accumulated pressure of the hydraulic fluid accumulator exceeds a predetermined pressure, the pump Since the discharge pressure is set to 0, the pump can be put into a no-load operation state if a hydraulic pressure exceeding a predetermined pressure necessary for operating the hydraulic booster is stored in the hydraulic pressure accumulator. Therefore, even if the pump is continuously driven during engine operation, it is possible to prevent the load on the pump from increasing more than necessary. This allows
An engine driven pump can be used as a hydraulic pressure source of a closed center type hydraulic booster. Further, since the pump can be driven by the engine, a dedicated motor or the like for driving the pump such as the conventional closed center type hydraulic booster is not required, so that the number of parts can be reduced and the cost can be reduced. Can be reduced.

In particular, according to the second aspect of the invention, since the pressure relief valve of the pump load control device is operated and controlled by the valve control piston, the structure of the pump load control device can be simplified.

Further, according to the inventions of claims 3 and 4,
Since the operation of the pressure relief valve is controlled by the accumulated pressure of the hydraulic pressure accumulator and the accumulated pressure of the control hydraulic pressure accumulator, the pressure relief valve can be operated more completely. Therefore, if the hydraulic pressure exceeding the predetermined pressure is stored in the hydraulic fluid accumulator, the pump can be brought into the no-load operation state quickly and more reliably. Thereby, the reliability of the pump load control device is further improved.

Further, according to the invention of claim 4, the pressure relief valve of the pump load control device is controlled by the valve control piston, and the hydraulic pressure control valve of the pressure accumulation control device is controlled by the hydraulic pressure control piston. Therefore, both the pump load control device and the pressure accumulation control device can be simplified in structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an embodiment in which a hydraulic booster according to the present invention is applied to a brake booster.

FIG. 2 is a partially enlarged sectional view of the brake booster in FIG.

FIG. 3 is a cross-sectional view showing another example of the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Closed center type brake booster, 3 ... Input shaft, 4 ... Power piston, 8 ... Power chamber, 9 ... Control valve, 1
0 ... Pump, 11 ... Hydraulic fluid accumulator, 35 ...
Pump load control device, 36 ... Housing, 37 ... Piston, 38 ... Control spring, 43 ... Pressure relief valve, 45 ...
Accumulator for control hydraulic pressure, 49 ... Accumulator pressure accumulation control device, 50 ... Housing, 51 ... Valve piston,
56 ... Accumulation control valve, 57 ... Spring

Claims (4)

[Claims] 1. A reservoir for storing hydraulic fluid, a pump for sucking and discharging the hydraulic fluid from the reservoir, a hydraulic fluid accumulator for storing the discharge pressure of the pump as hydraulic fluid pressure, and an operation when an operating force is transmitted. An input shaft, a power chamber to which the hydraulic fluid pressure stored in the hydraulic fluid pressure accumulator is supplied during operation, and a power that is actuated by the hydraulic fluid pressure in the power chamber to boost and output the operating force. A control for selectively controlling the piston and the hydraulic fluid pressure stored in the hydraulic fluid pressure accumulator when operating to supply the hydraulic fluid pressure to the power chamber and discharging the hydraulic fluid pressure in the power chamber to the reservoir when not operating. And a valve, wherein the control valve is actuated by actuation of the input shaft, wherein the pump is an engine. A pump load control device is provided in a passage between the pump and the hydraulic fluid accumulator, and the pump load control device is configured such that the accumulated pressure of the hydraulic fluid accumulator is equal to or less than a predetermined pressure. When it is closed, it shuts off between the pump and the reservoir, and when the accumulated pressure of the hydraulic fluid accumulator exceeds the predetermined pressure, it opens to communicate between the pump and the reservoir to reduce the pump discharge pressure. A closed center type hydraulic booster comprising a normally-closed pressure relief valve that is released to the reservoir. 2. The pump load control device is provided in a housing and slidably in the housing, the accumulated pressure of the hydraulic fluid accumulator acts, and the accumulated pressure of the hydraulic fluid accumulator is the predetermined pressure. A valve control piston that operates when exceeding and opens the pressure relief valve;
The pressure relief valve includes a pump connection port formed in the housing and connected to a discharge side of the pump, and a reservoir connection port formed in the housing and connected to the pump connection port and the reservoir. The closed center type hydraulic booster according to claim 1, wherein the hydraulic booster is provided in a passage that connects the pump connection port and the reservoir in the housing. 3. A control hydraulic accumulator which is connected to the pump and stores a second predetermined pressure lower than the predetermined pressure, for controlling the operation of the pressure relief valve of the pump load control device, and the passage. Of these, a pressure accumulation control device that is provided in a passage portion between the pump load control device and the hydraulic fluid accumulator and that controls the accumulated pressure of the control hydraulic pressure accumulator to the second predetermined pressure is provided. The closed center type hydraulic booster according to claim 1. 4. The pump load control device is further provided in a housing and slidably provided in the housing, and the accumulated pressure of the hydraulic fluid pressure accumulator acts in a direction to open the pressure relief valve and the control fluid. The accumulated pressure of the pressure accumulator is actuated in the direction of closing the pressure relief valve,
A valve control piston that operates when the accumulated pressure of the hydraulic fluid accumulator exceeds the predetermined pressure to open the pressure relief valve; and an accumulator for control hydraulic pressure that is provided in the housing and is opened by the operation of the valve control piston. A normally closed control hydraulic pressure relief valve for releasing the stored pressure of the reservoir to the reservoir, a pump connection port formed in the housing and connected to the pump, and connected to the pump connection port formed in the housing and connected to the reservoir. The pressure relief valve is provided in a passage that connects the pump connection port and the reservoir in the housing, and the pressure accumulation control device is provided in the housing and in the housing. The control fluid pressure accumulator is slidably disposed and the accumulated pressure of the control fluid pressure accumulator is applied to the control fluid pressure accumulator. A hydraulic pressure control piston which operates when the accumulated pressure of the hydraulic pressure reaches the second predetermined pressure, and which connects the pump and the control hydraulic pressure accumulator provided in the housing and closed by the operation of the hydraulic pressure control piston. 4. A closed center type hydraulic booster according to claim 3, further comprising a normally open hydraulic pressure control valve for shutting off the passage.