JP2753327B2 - Hydraulic booster - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic booster that is used in a brake booster or the like and performs servo control of an input and an output at a predetermined servo ratio. is there.

2. Description of the Related Art In general, a hydraulic booster is provided with a power piston slidably fitted in a housing and one end of the power piston as disclosed in Japanese Patent Application Laid-Open No. 61-94865. A power chamber into which a working hydraulic pressure is introduced, a control valve for switching and controlling the communication between the power chamber and a hydraulic pressure source or a reservoir,
An input shaft for operating the control valve and an output shaft connected to the power piston are provided. Then, by operating the input shaft and switching the control valve, hydraulic pressure from a hydraulic pressure source is introduced into the power chamber, and the power piston is operated by the hydraulic pressure to output from the output shaft. In this case, the hydraulic pressure booster performs so-called servo control for controlling the magnitude of the output of the output shaft in accordance with the magnitude of the input of the input shaft.

[Problems to be Solved by the Invention] By the way, in any of such conventional hydraulic boosters, the hydraulic booster is operated by switching the control valve by moving the input shaft forward by depressing a pedal or the like. It is designed to output for the first time. Therefore, conventionally, the hydraulic booster could not be automatically operated regardless of the operation of the input shaft.

However, when the hydraulic booster is used as a brake booster for a vehicle, the hydraulic booster can be automatically operated to automatically apply a brake depending on the driving condition of the vehicle. It is desired. In this case, when the conditions for activating the automatic brake such as obstacle avoidance or danger state avoidance are established, it is desired that the automatic brake be promptly applied in response to the condition. Also, for most drivers of vehicles, after the brake is applied by depressing the brake pedal, the vehicle decelerates and almost starts to stop, and the pedal depression tends to be slightly loosened. In many cases, it is not possible to obtain a firm feeling of braking, which means that the brakes are operated firmly until they stop.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic booster that can be operated automatically and as quickly as possible when automatic operation conditions are satisfied. That is.

Another object of the present invention is to provide a hydraulic booster that can provide a firm brake feeling when applied to a brake booster for a vehicle.

Means for Solving the Problems In order to solve the above-mentioned problems, the invention of claim 1 slidably slides in a hydraulic pressure source for generating hydraulic pressure, a reservoir for storing hydraulic fluid, and a hole in the housing. A power piston fitted thereto, a first power chamber into which the hydraulic pressure acting on the power piston is introduced, an input shaft slidably fitted into the power piston, and a power piston connected to the power piston. When the input shaft is not operated, the first power chamber communicates with the reservoir when the input shaft is not operated and is shut off from the hydraulic pressure source, and is activated when the input shaft moves forward toward the power piston. A hydraulic pressure booster having a control valve communicating with the hydraulic pressure source while shutting off the first power chamber from the reservoir, and further including a hydraulic pressure acting on the power piston. Power room, Normally, the second power chamber is communicated with the reservoir and is cut off from the hydraulic pressure source. When a predetermined operating condition is satisfied, the second power chamber is operated to cut off the second power chamber from the reservoir and the hydraulic pressure source. A switching valve communicating with the first power chamber, and the power piston includes a small-diameter portion where the hydraulic pressure of the first power chamber operates and a large-diameter portion where the hydraulic pressure of the second power chamber operates. It is characterized in that it is formed on a stepped piston.

Further, the invention according to claim 2 is characterized in that the switching valve has a second operating condition in which a predetermined output is obtained after the predetermined operating condition is established and the second power chamber is communicated with the hydraulic pressure source. When this happens, the second power chamber is shut off from both the hydraulic pressure source and the reservoir.

Further, the invention according to claim 3 is a hydraulic pressure source for generating hydraulic pressure, a reservoir for storing hydraulic fluid, a power piston slidably fitted in a hole of the housing, and the hydraulic pressure acting on the power piston. , An input shaft slidably fitted in the power piston, an output shaft connected to the power piston, and the first power source when the input shaft is not operated. A chamber communicates with the reservoir and is shut off from the hydraulic pressure source, and operates when the input shaft moves forward toward the power piston to shut off the first power chamber from the reservoir and reduce the hydraulic pressure. A hydraulic booster having a control valve communicating with a power source, further comprising: a second power chamber into which hydraulic pressure acting on the power piston is introduced; Through the orifice And a switching valve for disconnecting the second power chamber from the first power chamber and operating when a predetermined operating condition is satisfied, and for communicating with the hydraulic pressure source. Are provided, and
The power piston is formed as a stepped piston including a small-diameter portion on which the hydraulic pressure of the first power chamber operates and a large-diameter portion on which the hydraulic pressure of the second power chamber operates.

Further, a second switching valve and a pressure regulating valve which are connected in series with each other between the orifice and the first power chamber and are normally shut off and communicated with each other during operation are provided. It is characterized in that a third switching valve that is in communication and shuts off during operation is arranged in parallel.

The invention according to claim 5 is characterized in that a hydraulic pressure absorbing device is provided between the orifice and the second power chamber.

[Operation] In the hydraulic booster according to the first to fifth aspects of the present invention, the control valve is switched by the operation of the input shaft during the normal operation as in the prior art, so that the hydraulic pressure is reduced to the first pressure. The power piston is introduced into the power chamber, and the hydraulic pressure acts on the small diameter portion of the stepped piston, whereby the power piston operates.
In addition to this, when the predetermined condition is satisfied, the hydraulic pressure is directly introduced into the second power chamber simply by switching the switching valve.
This hydraulic pressure acts on the large-diameter portion of the stepped piston, so that the power piston operates. Therefore, the hydraulic booster immediately responds when the automatic operation condition is satisfied,
It will automatically and quickly operate regardless of the operation of the input shaft.

In particular, according to the second aspect of the present invention, when the second operating condition that a predetermined output is obtained after the automatic operation of the hydraulic pressure booster is satisfied, the hydraulic pressure of the second power chamber is set to the holding state. . Thus, when the hydraulic booster is applied to the brake booster, for example, when the hydraulic booster is applied to the brake booster, the vehicle is stopped by the stop signal from the speed sensor when the vehicle is stopped by the normal brake operation. The function of maintaining the operating state, such as functioning as a stop holding brake for holding the brake applied.

According to the third aspect of the present invention, the hydraulic pressure is introduced into the first power chamber by switching the control valve by the operation of the input shaft during the normal operation, and the hydraulic pressure is introduced into the small diameter portion of the stepped piston. , The power piston operates. At this time, the hydraulic pressure introduced into the first power chamber is also introduced into the second power chamber via the orifice, but the hydraulic pressure in the second power chamber is determined by the pressure of the hydraulic fluid from the first power chamber. Since the pressure is reduced by the orifice, the pressure rises later than the pressure rise in the first power chamber. Thus, even when the hydraulic pressure in the first power chamber does not increase when the input shaft stops at the intermediate load point, the hydraulic booster gradually outputs a predetermined amount by the hydraulic pressure in the second power chamber. As a result, the hydraulic booster has a post-effect.

Therefore, when this hydraulic pressure booster is used as a brake booster, after the brake is actuated by depressing the brake pedal, the vehicle starts decelerating and almost stops, and the driver's pedal depression tends to be loosened. Even so, the post-effect has a firm feeling of the brake, that is, the brake is operated firmly until the vehicle stops reliably.

Further, in the invention according to claim 4, when the second and third switching valves are not operated, the hydraulic pressure in the first power chamber is directly introduced into the second power chamber, and the second and third switching valves are not operated. At the time of operation, the hydraulic pressure of the first power chamber adjusted by the pressure regulating valve is introduced into the second power chamber. Therefore, the second
Since different hydraulic pressures are introduced into the power chamber, the output of the hydraulic booster due to the post-effect is changed.

Further, in the invention of claim 5, the second power chamber is connected to the second power chamber.
Since the hydraulic pressure introduced into the power chamber is further absorbed by the hydraulic pressure absorbing device by a predetermined amount, the increase in the hydraulic pressure of the second power chamber is further delayed. As a result, the post-effect of the hydraulic booster is more effectively performed.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing one embodiment of a hydraulic booster according to the present invention applied as a brake booster.

As shown in FIG. 1, the brake booster 1 includes a housing 2 formed in a substantially cylindrical shape. The housing 2 has a first hole 3 and a second hole 4 opened at the right end and the left end of the housing 2 respectively, and a third hole 5 communicating the first and second holes 3 and 4 coaxially. Has been established. The diameter of the second hole 4 is set to be larger than the diameter of the third hole 5.

A power piston 6 is disposed over the second and third holes 4,5. The power piston 6 has a first piston portion 7 sliding in the third hole 5 in a liquid-tight manner, and a second piston portion sliding in the second hole 4 in a liquid-tight manner and having a larger diameter than the first piston portion 7. 8
And In the power piston 6, fourth and fifth holes 9, 10 opening to the left and right ends, respectively, and a sixth hole 11, which communicates with the holes 9, 10, are formed coaxially. .

A plug 12 for closing the first hole 3 in a liquid-tight manner is fixed to the right end of the housing 2. Also, the middle part 13 of the plug 12
Is inserted into the third hole 5 in a liquid-tight manner, and the left end of the plug 12
14 protrudes into the fourth hole 9 of the power piston 6. Between the plug 12 and the power piston 6, a first power chamber 15
Are formed.

The plug 12 has a seventh hole 16 formed coaxially with the fourth to sixth holes 9 to 11. An input shaft 17 is slidably fitted in the seventh hole 16 in a liquid-tight manner. At the left end of the input shaft 17, a flange portion 18 is formed, and when the input shaft 17 retreats, that is, moves to the right, the right surface of the flange portion 18 is plugged.
By contacting the left end of 12, the input shaft 17 cannot move further to the right. This position is the retreat limit position of the input shaft 17. The flange portion 18 is disposed between a step portion 19 between the fourth hole 9 and the sixth hole 11 and a ring-shaped stopper member 20 attached to the power piston 6. When the piston 18 moves to the right with respect to the piston 6, the input shaft 17 is prevented from falling out of the power piston 6 by the flange portion 18 abutting on the retaining member 20. Therefore,
The flange portion 18 can move relative to the power piston 6 between the step portion 19 and the retaining member 20.
Further, a cylindrical member 21 is provided at the left end of the input shaft 17. On the other hand, the right end of the input shaft 17 is connected via a connecting member 22 to a brake pedal (not shown).

At substantially the center of the input shaft 17, an axial passage 24 communicating with the hole 23 of the cylindrical member 21 is formed.
A diametrical passage 25 communicating with the right end of is provided.
The passage 25 communicates with an annular groove 26 formed in the plug 12, and the annular groove 26 is a diametrical passage formed in the plug 12.
It communicates with an annular chamber 28 between the housing 2 and the plug 12 via 27. Further, the annular chamber 28 communicates with a reservoir 31 via a discharge port 29 and a discharge conduit 30 formed in the housing 2.

A valve body 33 having a ball 32 at the right end is slidably disposed in the sixth hole 11 of the power piston 6. The sixth hole 11
A cylindrical valve seat member 34 is fixedly mounted on the right end of the valve member 34. The ball 32 of the valve element 33 is seated on the valve seat member 34 by the urging force of the compression coil spring 35. A pressure chamber 37 is defined by a seal portion between the ball 32 and the valve seat member 34 and a seal member 36 for sealing the valve body 33. Further, the hole of the valve seat member 34
The left end of the cylindrical member 21 protrudes into 38, and the end face
Is in contact with

A compression coil spring is provided between the cylindrical member 21 and the valve seat member 34.
39 are arranged. This spring 39 is connected to the input shaft 17 and a cylindrical member.
21 is constantly biased in the direction in which the tubular member 21 moves away from the valve element 33, that is, rightward, and a leftward force is applied to the input shaft 17 so as to overcome the biasing force of the spring 39. If not, the input shaft 17 is set to the retreat limit position. When the input shaft 17 moves forward, that is, to the left with respect to the power piston 6 against the urging force of the spring 39, the left end of the tubular member 21 moves the valve body 33 to the left. 32 is separated from the valve seat member 34 so that the pressure chamber 37
And the first power chamber 15 communicate with each other. That is, the cylindrical member 21, the valve body 33 including the ball 32, and the valve seat member
The control valve 40 is constituted by 34.

The right end of the output shaft 41 is mounted in the fifth hole 10 of the power piston 6 by a ring-shaped retaining member 42 mounted on the power piston 6. This output shaft 41 is
A piston of a brake master cylinder (not shown) fixed to the left end of the housing 2 is operated.
The output shaft 41 and the power piston 6 are constantly attached to the right by a return spring 45 disposed between a plug 43 screwed into the housing 2 and a step 44 formed at the right end of the output shaft 41. It is being rushed. When a leftward force large enough to overcome the urging force of the spring 45 is not applied to the power piston 6, the right end of the power piston 6 abuts on the plug 12, and the power piston 6 is held at the retreat limit position. ing.

When both the power piston 6 and the input shaft 17 are at the retreat limit position, the flange portion 18 is located between the step portion 19 and the retaining member 20 at a position separated therefrom. That is, when the input shaft 17 is not operated, the input shaft 17 is held at a predetermined forward position away from the retaining member 20 with respect to the power piston 6 by its flange portion 18 abutting on the left end of the plug 12. Have been. In this held position, the left end of the cylindrical member 21 at the left end of the input shaft 17 is in contact with the ball 32.

A chamber 46 is formed between the power piston 6 and the output shaft 41. This chamber 46 communicates with the first power chamber 15 through a passage 47 formed in the power piston 6. Also the room
The left end of the valve body 33 faces inside 46. On the other hand, a second power chamber 48 is formed in the second hole 4 between the housing 2 and the power piston 6.

The pressure chamber 37 communicates via a passage 49 with an annular groove 50 provided on the outer periphery of the power piston 6 between the first piston section 7 and the second piston section 8. The groove 50 is provided through a hole 51 formed in the housing 2 and a filter 52 through a supply port 53.
Is in communication with The supply port 53 communicates with the accumulator 55 and the discharge side of the pump 56 through a supply conduit 54,
The suction side of 56 communicates with the reservoir 31. The pump 56 and the accumulator 55 constitute the hydraulic pressure source of the present invention. A check valve 57 is provided between the accumulator 55 and the pump 56 to allow the flow of the liquid in the direction from the pump 56 to the accumulator 55 but to prevent the flow of the liquid in the opposite direction.

Further, the housing 2 is provided with a first connection port 58 communicating with the first power chamber 15 and a second connection port 59 communicating with the second power chamber 48, respectively. The first connection port 58 is connected to the first port 61a of the three-port two-position switching valve 61 via the conduit 60. The second port 61b of the switching valve 61 is connected to a second connection port 59 via a conduit 62. Conduit 60 has an orifice
63 and a check valve 64 that allows only the flow of the liquid from the second connection port 59 to the first connection port 58 are provided in parallel. The second connection port 59 is connected to the reservoir 31 via a check valve 65. The check valve 65 is connected from the reservoir 31 to the second connection port.
Only the flow of liquid toward 59 is allowed. On the other hand, the third port 61c of the switching valve 61 is connected to the accumulator 55.

The switching valve 61 is formed of a solenoid valve, and is normally a first valve that connects the first port 61a and the second port 62b by a spring.
It is set to position I. When the predetermined operating condition is satisfied, the control device 66 excites the solenoid of the switching valve 61, so that the switching valve 61 is connected to the second port 61b and the third port 6b.
1c.

 Next, the operation of this embodiment will be described.

When the pump 56 is driven, the hydraulic fluid is supplied from the reservoir 31 to the check valve.
It is introduced into the accumulator 55 through 57 and into the pressure chamber 37 through the supply conduit 54, the supply port 53, the filter 52, the passage 51, the groove 50, and the passage 49. And the pressure chamber 37
And the accumulator 55 always maintain a constant hydraulic pressure.

In the normal state, since the switching valve 61 is set at the first position I, the first connection port 58 is connected to the second connection port 59 via the orifice 63.

In a state where the brake is not operated, in the brake booster 1, the input shaft 17, the power piston 6, and the output shaft 41 are all in the retreat limit positions. In this state, the ball 32 of the control valve 40 is seated on the valve seat member 34, and the tubular member 21 is seated on the ball 32. Therefore, the first
The power chamber 15 is isolated from the pressure chamber 37 and the reservoir 31. Therefore, a return spring is provided in the first power chamber 15.
It is maintained at a hydraulic pressure almost balanced with the spring force of 45.

When the brake pedal (not shown) is depressed for braking, the input shaft 17 moves to the left, the ball 32 immediately separates from the valve seat member 34, and the pressure fluid in the pressure chamber 37 is released from the first power chamber 15 Will be introduced. This pressure fluid causes the power piston 6 to move forward against the resilience of the spring 45, so that the output shaft 41
Is output to operate the piston of the master cylinder. Thereby, braking is performed. At this time, as the second piston portion 8 moves, the inside of the second power chamber 48 tends to become a negative pressure. However, since the hydraulic fluid in the atmospheric pressure state is sucked from the reservoir 31 through the check valve 65, The negative pressure does not occur in the second power chamber 48. Therefore, the power piston 6 can move smoothly without resistance.

Further, since the hydraulic pressure in the first power chamber 15 also acts on the input shaft 17, the force applied to the input shaft 17 by this hydraulic pressure is transmitted to the driver as a brake reaction force. With the movement of the power piston 6, the valve seat member 34 also moves to the left.
When the abutment with the ball 32, the communication between the pressure chamber 37 and the first power chamber 15 is cut off. For this reason, the pressurized liquid is not introduced into the first power chamber 15 any more, so that the movement of the power piston 6 stops. As a result, the pressurized liquid is introduced into the first power chamber 15 by the amount of depression of the brake pedal, that is, the amount corresponding to the input of the input shaft 17. Therefore, the output of the output shaft 41 is
It becomes the size according to the input of.

The pressure fluid in the first power chamber 15 is also introduced into the chamber 46 through the passage 47. Since the hydraulic pressure in this chamber 46 acts on the left end of the valve body 33, the first power chamber applied to the valve body 33
The force due to the hydraulic pressure in 15 is reduced and it does not move to the left. Thus, the spring force of the spring 35 does not need to be so large.

By the way, the hydraulic pressure in the first power chamber 15 is supplied from the first connection port 58 to the conduit 60, the orifice 63, the switching valve 61, and the second connection port 59.
, And is also introduced into the second power chamber 48. At this time, the pressure fluid that has passed through the orifice 63 tends to flow toward the reservoir 31, but the check valve 65 prevents the pressure fluid from flowing into the reservoir 31. As a result, the pressure fluid is introduced only into the second power chamber 48. The pressure in the second power chamber 48 is
Since the pressurized liquid is restricted by the orifice 63, the first power chamber 15
The pressure rises later than the internal pressure rise. Therefore, for example, when the input of the input shaft 17 is stopped at the intermediate load point and the valve seat member 34 comes into contact with the ball 32, the pressure in the first power chamber 15 no longer increases. However, since the pressure in the second power chamber 48 increases with a delay, the output of the output shaft 42 further increases even if the input of the input shaft 17 stops, and the braking force gradually increases by a predetermined amount. That is, a post-effect effect of the brake is performed. As a result, after the brake is actuated by depressing the brake pedal, the vehicle decelerates to almost stop, and even if the driver's pedal depression tends to loosen, the brake hydraulic booster 1 is effective thereafter. The action provides a firm feeling of the brake, that is, the brake is operated firmly until the vehicle stops.

When the depression of the brake pedal is released in order to release the brake operation, the input shaft 17 is largely retracted until the flange portion 18 contacts the power piston 6 with the retaining member 20. For this reason, the left end of the cylindrical member 21 is separated from the ball 32,
The first power chamber 15 communicates with the reservoir 31 to reduce its pressure. Therefore, the power piston 6 retreats due to the resilience of the spring 45, and accordingly, the hydraulic fluid in the first power chamber 15 is discharged to the reservoir 31 and the second power chamber 48
The pressure fluid inside is also discharged to the reservoir 31 via the switching valve 61, the check valve 64, and the first power chamber 15. At this time, the pressurized liquid in the second power chamber 48 mainly flows through the check valve 64 and is not affected by the orifice 63. In addition, since the cylindrical member 21 is largely separated from the ball 32 to form a large channel area, the pressure fluid in the first and second power chambers 15, 48 is quickly discharged to the reservoir 31. Therefore, the power piston 6 retreats quickly.

When the flange 18 contacts the left end of the plug 12, the input shaft
17 does not retreat any more, and only the power piston 6 retreats. Therefore, the flange portion 18 is separated from the retaining member 20. When the right end of the power piston 6 abuts on the plug 12, the retraction stops and the power piston 6 is in the retreat limit position.

In this state, the input shaft is at a predetermined position advanced with respect to the power piston 6, and the tip of the cylindrical member 21 is a ball.
It comes into contact with 32.

Next, based on various signals such as an overspeed signal or a stop signal from the speed sensor, a logical product of the speed signal from the speed sensor and the steering wheel angle signal, or an obstacle detection signal from the obstacle detection sensor, for example. , Switching valve
When the predetermined operating condition of 61 is satisfied, the controller 66 excites the solenoid of the switching valve 61. As a result, the switching valve 61 is switched to the second position II. As a result, the accumulator 55
Is introduced into the second power chamber 48 via the switching valve 61. Since this hydraulic pressure acts on the second piston portion 8, the power piston 6 advances, and the output shaft 41 outputs. With this output, the brake master cylinder operates and braking is automatically performed.

When the operation conditions of the switching valve are not satisfied by the automatic braking, the control device 66 releases the excitation of the solenoid.
The switching valve 61 is switched to the first position I. For this reason, the pressure fluid in the second power chamber 48 passes through the switching valve 61, the check valve 64, the first power chamber 15, the gap between the ball 32 and the cylindrical member 21 and the like as in the above-described normal case. Discharged to reservoir 31. Therefore, the power piston 6 returns to the original backward limit position by the spring 45, and the brake is released.

FIG. 2 is a sectional view similar to FIG. 1 showing another embodiment of the present invention. The same components as those in the above-described embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.

In this embodiment, a three-port three-position switching valve 61 'is used in place of the three-port two-position switching valve 61 of the above-described embodiment. Further, the first connection port 58 and the check valve 6 of the above-described embodiment are used.
4,75 and orifice 63 have been deleted.

The switching valve 61 'has a first port 61'a and a second port 61'b.
A first position I where all three ports are shut off, a second position II where all three ports are shut off to be in a neutral state, and a third position III where the third port 61'c and the second port 61'b communicate. Is set. The first port 61'a is connected to the reservoir 31, the second port 61'b is connected to the second connection port 59, and the third port 61'c is connected to the accumulator 55. The switching valve 61 'is normally connected to the first port 6
It is set to 1'a, and when a predetermined operating condition is satisfied, the control device 66 switches to the second position II or the third position III.

In this embodiment, when a predetermined first operation condition of the switching valve 61 'is satisfied, the control device 66 excites the solenoid and switches the switching valve 61' to the third position III. Thereby, the pressurized liquid of the accumulator 55 is introduced into the second power chamber 48. Since the hydraulic pressure in the second power chamber 48 acts on the second piston portion 8, the power piston 6 moves forward, and braking is performed.
When a predetermined braking force is obtained and a predetermined second operation condition is satisfied, the control device 66 switches the switching valve 61 to the second position II.
Accordingly, the second power chamber 48 is shut off from both the accumulator 55 and the reservoir 31, and the inside of the second power chamber 48 is maintained at the hydraulic pressure. When the second operating condition is not satisfied, the first
When the operating conditions are satisfied, the switching valve 61 'is moved to the third position II.
I, the braking force is further increased by further increasing the hydraulic pressure in the second power chamber 48, and if the first operating condition is not satisfied, the switching valve 61 'is switched to the first position I, The pressure fluid in the second power chamber 48 is discharged to the reservoir 33, and the brake is released. As described above, by providing the switching valve 61 'with the second position II for keeping the hydraulic pressure in the second power chamber 48 constant, the hydraulic pressure in the second power chamber 48 can be easily adjusted to a desired level. be able to. Also, by keeping the hydraulic pressure in the second power chamber 48 constant, the brake booster
For example, it is possible to provide a brake booster with a function as a stop holding brake that operates according to a stop signal from a speed sensor when a vehicle stops due to normal brake operation and holds a stopped vehicle while applying a brake. Become.

FIG. 3 is a diagram showing still another embodiment of the present invention.
Similarly, the same components as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted (in FIG. 3, only the main components are denoted by reference numerals). .

In this embodiment, a hydraulic pressure absorbing device 70 including second and third switching valves 67 and 68, a pressure regulating valve 69, a second accumulator and the like is further provided in the embodiment of FIG. That is, the second switching valve 67 and the pressure regulating valve 69 connected in series to the conduit 60 between the first connection port 58 and the orifice 63, and the third switching valve 68 are arranged in parallel. .
In this case, the second and third switching valves 67 and 68 are formed by two-port two-position valves. Normally, the second switching valve 67 is in the shut-off position I and the third switching valve 68 is in the communication position II. Is set. Further, a hydraulic pressure absorbing device 70 including an accumulator or the like is provided downstream of the orifice 63.

 The operation of this embodiment will be described.

In the illustrated normal state, the operation is almost the same as in FIG. In this case, when the input shaft 17 operates, the first power chamber
Since the pressure of the liquid flowing from 15 is absorbed by a predetermined amount by the hydraulic pressure absorbing device 70, the pressure rise in the second power chamber 48 is further delayed as compared with the embodiment of FIG. As a result, the after-effect of the brake is more effectively performed.

On the other hand, the second switching valve 67 is set to the communication position II, and the third switching valve 67
When the switch 68 is switched to the shut-off position I, the pressure fluid from the first power chamber 15 is introduced into the second power chamber 48 via the pressure regulating valve 69. The first power chamber 15 is controlled by the pressure regulating valve 69.
Is regulated, the maximum pressure introduced into the second power chamber 48 becomes smaller than in the normal state described above. Therefore, since the braking force in this case is weaker than that in the normal state, the final vehicle deceleration also becomes smaller. As described above, the final vehicle deceleration can be changed by the pressure adjusting valve 69.

On the other hand, the automatic braking operation by the switching valve 61 is the same as that of the embodiment of FIG.

In any of the above-described embodiments, it is clear that the present invention is applied to the brake booster. However, the present invention is applicable to other hydraulic boosters such as a clutch booster other than the brake booster. Needless to say, it can also be used.

[Effects of the Invention] As is clear from the above description, according to the hydraulic booster of each of the first to fifth aspects of the present invention, the input shaft can be operated only by switching the switching valve when predetermined conditions are satisfied. , The hydraulic booster can be operated automatically and promptly in response to the automatic operation condition when the automatic operation condition is satisfied.

In this case, the hydraulic pressure by the switching valve is applied to the large diameter portion of the stepped power piston, and the input shaft is exactly the same as before without any change. Even if the mounting space is small, the hydraulic booster can be easily mounted, and the input shaft is operated during normal operation of the hydraulic booster.
It is possible to prevent an operator's burden such as pedaling force from increasing.

In particular, according to the second aspect of the present invention, when the second operating condition that a predetermined output is obtained after the automatic operation of the hydraulic pressure booster is satisfied, the hydraulic pressure in the second power chamber is set to the holding state. For example, when a hydraulic pressure booster is applied to a brake booster, when the vehicle is stopped by a normal brake operation, the vehicle is operated by a stop signal from a speed sensor to apply a brake to the stopped vehicle. It is possible to provide the hydraulic booster with a function of maintaining the operating state, such as functioning as a stop holding brake for holding the vehicle in a stopped state.

Further, according to the third aspect of the invention, the orifice delays the increase in the hydraulic pressure of the second power chamber. Therefore, even if the input shaft stops and the hydraulic pressure of the first power chamber does not increase, the second orifice does not increase. (2) The output of the hydraulic booster can be gradually increased by a predetermined amount by the hydraulic pressure of the power chamber, so that the hydraulic booster can have a function of performing a post-effect. Therefore, when this hydraulic pressure booster is applied to a brake booster, after the brake is actuated by depressing the brake pedal, the vehicle decelerates and almost stops, and the driver's pedal depression tends to loosen. However, this post-effect provides a firm feeling of the brake, that is, the brake is firmly actuated until the vehicle stops reliably.

Further, according to the fourth aspect of the present invention, the second pressure regulating valve is used for the second operation.
Since different hydraulic pressures are introduced into the power chamber, it is possible to appropriately change the output by the post-effect of the hydraulic booster.

According to the fifth aspect of the present invention, the hydraulic pressure introduced into the second power chamber is absorbed by a predetermined amount by the hydraulic pressure absorbing device so that the increase in the hydraulic pressure of the second power chamber is further delayed, so that the hydraulic pressure is increased. The post-effect of the booster can be performed more effectively.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment in which a hydraulic booster according to the present invention is applied to a brake booster, FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention, and FIG. FIG. 7 is a longitudinal sectional view showing still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Brake booster (hydraulic booster), 2 ... Housing, 6 ... Power piston, 12 ... Plug (stopper means), 15 ... 1st power room, 17 ... Input shaft, 20 ... Retaining member, 31 ... Reservoir, 40 ... Control valve, 41 ... Output shaft, 48 ... Second power room, 55 ... Accumulator (hydraulic pressure source), 56 ... Pump (Liquid pressure source) , 61,61 '…… Switching valve

Claims (5)

(57) [Claims] 1. A hydraulic pressure source for generating hydraulic pressure, a reservoir for storing hydraulic fluid, a power piston slidably fitted in a hole of a housing, and the hydraulic pressure acting on the power piston is introduced. A first power chamber, an input shaft slidably fitted in the power piston, an output shaft connected to the power piston, and the first power chamber when the input shaft is not operated. The first power chamber communicates with the reservoir and is shut off from the hydraulic pressure source, and operates when the input shaft moves forward toward the power piston to disconnect the first power chamber from the reservoir and communicate with the hydraulic pressure source. A hydraulic booster provided with a control valve that performs a hydraulic operation. The hydraulic power booster further includes a second power chamber into which the hydraulic pressure acting on the power piston is introduced, and the second power chamber is normally communicated with the reservoir. Pressure source And a switching valve that is activated when predetermined operating conditions are satisfied to disconnect the second power chamber from the reservoir and communicate with the hydraulic pressure source. A hydraulic booster formed in a stepped piston comprising a small-diameter portion of the first power chamber on which hydraulic pressure acts and a large-diameter portion of the second power chamber on which hydraulic pressure acts. . 2. The switching valve according to claim 1, wherein said predetermined operating condition is satisfied and said second power chamber is communicated with said hydraulic pressure source. The hydraulic booster according to claim 1, wherein the second power chamber is shut off from both the hydraulic pressure source and the reservoir. 3. A hydraulic pressure source for generating hydraulic pressure, a reservoir for storing hydraulic fluid, a power piston slidably fitted in a hole of the housing, and the hydraulic pressure acting on the power piston is introduced. A first power chamber, an input shaft slidably fitted in the power piston, an output shaft connected to the power piston, and the first power chamber when the input shaft is not operated. The first power chamber communicates with the reservoir and is shut off from the hydraulic pressure source, and operates when the input shaft moves forward toward the power piston to disconnect the first power chamber from the reservoir and communicate with the hydraulic pressure source. A hydraulic booster provided with a control valve that performs the following operations. Further, a second power chamber into which the hydraulic pressure acting on the power piston is introduced, and an orifice formed in the first power chamber when the second power chamber is normally used. Communicated through And a switching valve that is shut off from the hydraulic pressure source and is activated when predetermined operating conditions are met to disconnect the second power chamber from the first power chamber and communicate with the hydraulic pressure source. Further, the power piston is formed as a stepped piston including a small-diameter portion where the hydraulic pressure of the first power chamber operates and a large-diameter portion where the hydraulic pressure of the second power chamber operates. A hydraulic booster. 4. A second switching valve and a pressure regulating valve which are connected in series between the orifice and the first power chamber and which are normally shut off and communicated during operation, are normally communicated with each other, and 4. The hydraulic booster according to claim 3, wherein a third switching valve that shuts off during operation is disposed in parallel. 5. The hydraulic booster according to claim 4, wherein a hydraulic pressure absorbing device is provided between the orifice and the second power chamber.