JPH01289752A - Hydraulic servo unit - Google Patents

Abstract

PURPOSE:To aim at the shortening of axial length of a booster cylinder by fitting a booster piston in a simulator piston free of slide motion in a device where the simulator piston adjoining to a hydraulic power source chamber is fitted in the booster cylinder. CONSTITUTION:A tandem type master cylinder M where a hydraulic booster B is connected to the rear is fitted with each of operating pistons 4, 6 in front and in the rear of a cylinder hole 3, and a piston rod 10 of the operating piston 6 is oiltightly pierced through a guide member 11 and extended to the side of the hydraulic booster B. In this case, a guide cylinder 29 and a simulator piston 30 are fitted in a cylinder hole 28 of the hydraulic booster B, and a front part of this piston 30 is fitted in the cylinder 29. Then, a booster piston 43 is fitted in different diametral cylinder hole parts 41, 42 of the simulator piston 30, and an output hydraulic chamber 47 and a reaction chamber 48 are partitioned each between a large diametral part 43b of this piston 43, a receiving cylinder 32 and a stepped part 30b of the simulator piston 30.

Description

Detailed Description of the Invention A1 Object of the Invention (1) Industrial Field of Application The present invention is directed to a master cylinder in which a booster cylinder is coupled to the rear end of a cylinder body of a master cylinder, and the booster cylinder has a hydraulic power supply connected to a hydraulic pressure supply source. A simulator piston facing the hydraulic chamber is slidably engaged with the simulator piston so that it is held in a retracted position when the hydraulic pressure supply source is normal, and the booster piston and the simulator are movable in the axial direction relative to the simulator piston. A resilient means for urging the booster piston rearward is interposed between the piston and the output hydraulic chamber formed facing the rear side of the booster piston, and an input hydraulic chamber communicating with the hydraulic pressure supply source. An inlet valve connected to the operating member and opened in response to the forward movement of the valve piston slidably fitted to the booster piston with respect to the booster piston is interposed, and an outlet communicating with the output hydraulic chamber and the oil tank. The present invention relates to a hydraulic booster in which an outlet valve is interposed between the chamber and the chamber and the outlet valve is closed in response to the forward motion of the valve piston relative to the booster piston.

(2) Conventional technology Conventionally, such hydraulic boosters have been developed, for example, in the
It is known from Publication No. 187 and the like.

(3) Problems to be Solved by the Invention By the way, in the above conventional device, the simulator piston is slidably fitted into the inner surface of the booster cylinder, and the booster piston is slidably fitted into the inner surface of the booster cylinder. Since the simulator piston and the booster piston are disposed side by side in the axial direction, the booster cylinder must be formed long in the axial direction.Moreover, when the brake is operated when the oil pressure of the oil pressure supply source fails, It is necessary to push the booster piston while sliding it on the booster cylinder, resulting in a loss of pedal force due to sliding friction.

The present invention has been made in view of the above circumstances, and is a hydraulic booster that reduces the axial length of the booster cylinder as much as possible and suppresses the loss of pedal force when the hydraulic pressure supply source fails. The purpose is to provide a power device.

B0 Configuration of the Invention (1) Means for Solving the Problems According to the present invention, the booster piston is slidably fitted into the simulator piston.

(2) Effect According to the above configuration, the booster piston and the simulator
Since the Tavistones are arranged so that at least a portion thereof overlaps in the axial direction, the axial length of the booster cylinder can be shortened, and the booster piston does not slip relative to the booster cylinder.

(3) Embodiment Below, an embodiment of the present invention will be explained with reference to the drawings. First, in FIG. A hydraulic booster B is connected to the rear part, and a bushing rod 1 as an operating member linked and connected to the brake pedal P moves forward in response to the depression operation of the brake pedal P, so that the boosting operation of the hydraulic booster B is performed. This occurs, and braking oil pressure is generated in the master cylinder M accordingly.

The master cylinder M is a tandem type master cylinder, and the cylinder body 2 is provided with a cylinder hole 3 whose front end is closed, and one hydraulic chamber is formed between the cylinder hole 3 and the front end wall. The working piston 4 on the front side and the working piston 6 on the rear side forming the other hydraulic chamber 5 between the working piston 4 and the working piston 6 on the rear side are slidably fitted, and the working piston 4 on the front side A spring (not shown) is interposed between the working piston 4 on the front side and the working piston 6 on the rear side. A spring 7 is interposed to urge the piston 6 rearward. Therefore, by pressing the rear working piston 6 forward, the volumes of the front hydraulic chamber and the rear hydraulic chamber 5 are contracted, and braking oil pressure is output from these hydraulic chambers 5.

At the rear of the cylinder body 2, a connecting cylinder part 9 which forms a stepped part 8 between the cylinder hole 3 and the cylinder hole 3 is provided to protrude coaxially with the cylinder hole 3. On the other hand, a front end portion of a piston rod 10 extending rearward is fixed to the operating piston 6, and a guide member 11 is fixed to the rear portion of the cylinder body 2 to guide the movement of the piston rod 10. This guide member 11 is
A fitting cylinder part 11a that fits into the rear end of the cylinder hole 3, and a part 11b that extends outward in the radial direction from the rear end of the fitting cylinder part 11a are composed of a part 11b. 11b is fitted into the connecting cylinder portion 9 in an oil-tight manner and is brought into contact with the stepped portion 8. Moreover, with the abutment receiver's portion 11b in contact with the stepped portion 8, a retaining ring 22 that engages with the outer circumferential edge of the abutment receiver’s portion 11b is fitted onto the inner surface of the connecting cylinder portion 9, thereby causing the guide member 11 to move into the cylinder. It is fixed to the main body 2. Also piston rod 10
penetrates the guide member 11 in an oil-tight and movable manner and extends toward the hydraulic booster B side.

A replenishment oil chamber 12 is provided between the guide member 11 and the operating piston 6.
The cylinder body 2 is provided with an oil passage 15 that communicates an oil reservoir 14 in an oil tank 13 formed in the upper part of the cylinder body 2 with the supply oil chamber 12. Further, a cup seal 16 that slides into contact with the inner surface of the cylinder hole 3 is fitted to the operating piston 6, and the cup seal 16 and the operating piston 6 are used to supply oil when the pressure in the hydraulic chamber 5 is lower than that in the supply oil chamber 12. It is configured to allow flow of hydraulic oil from the oil chamber 12 to the hydraulic chamber 5.

A valve mechanism 18, which is driven to open and close by a stopper pin 17, is provided at the front of the operating piston 6 to open and close the hydraulic chamber 5 and the supply oil chamber 1.
The valve mechanism 1 is arranged to communicate and cut off the
8 is pressed by a stopper pin 17 to open the valve when the actuating piston 6 returns to the retraction limit. The stopper pin 17 has a long hole 1 that is elongated in the axial direction and is bored in the piston rod 10.
The stopper pin 17 is inserted into the piston rod 10 perpendicularly to the axis of the piston rod 10, and both ends of the stopper pin 17 protrude from the outer surface of the piston rod 10. It is fixed to a shaped holder 20. Furthermore, the holder 20 is biased in the direction of contacting the guide member 11 by a spring 21 interposed between the holder 20 and the actuating piston 6, so that the stopper pin 17 is substantially fixed to the cylinder body 2. Become.

A booster cylinder 24 of a hydraulic booster B is coaxially joined to the rear end of the cylinder body 2, and the cylinder body 2 and the booster cylinder 24 are connected by bolts 25.

That is, a flange 26 provided at the front end of the booster cylinder 24 and a flange 27 provided at the rear end of the cylinder body 2 are coupled by bolts 25.

A cylinder hole 28 is bored in the booster cylinder 24 coaxially with the cylinder hole 3 of the master cylinder M, and a guide cylinder 29 is slidably fitted into the cylinder hole 28. The front part of the guide cylinder 29 has a stepped part 29a that comes into contact with the rear end of the connecting cylinder part 9 in the cylinder body 2.
A small diameter cylindrical portion 29b coaxially protrudes through the connecting cylindrical portion 9, and the small diameter cylindrical portion 29b is fitted into the connecting cylindrical portion 9 in an oil-tight manner. In addition, a cylindrical similitarviston 3 is provided in the cylinder hole 28.
0 is slidably fitted to this simulator piston 3.
A small diameter cylindrical portion 30a that slidably fits into the guide cylindrical body 29 is coaxially connected to the front portion of the cylinder 0 via a step portion 30b. Moreover, a spring 3 is provided between the guide cylinder 29 and the simulator piston 30, which generates a spring force in the direction of separating the two from each other.
1 is reduced. Further, a cylinder 32 is oil-tightly fitted into the rear end of the simulator piston 30, and the cylinder 32 is in contact with the rear end of the simulator piston 30.
The rear end of the booster cylinder 24 is engaged with a regulating collar 33 that extends radially inward. Thus, when the simulator piston 30 is at the retraction limit, the simulator piston 30 and the receiver tube 32 are substantially integrated.

An annular hydraulic pressure source hydraulic chamber 34 is formed between the booster cylinder 24, the guide cylinder 29, and the simulator piston 30 so as to face the front surface of the cylinder piston 30. An inlet oil passage 35 communicating with the oil pressure source oil pressure chamber 34 is bored. Moreover, the spring 31 is housed in the hydraulic source hydraulic chamber 34, and the hydraulic pressure introduced into the hydraulic source hydraulic chamber 34 and the spring 31
As a result, the simulator piston 30 is urged rearward, and the guide cylinder 29 is urged forward. Further, an annular oil chamber 36 is formed between the guide cylinder 29 and the booster cylinder 24, and an outlet oil passage 37 that communicates the oil chamber 36 with an oil tank (not shown) is bored in the booster cylinder 24. Furthermore, the small diameter cylindrical portion 30 of the simulator piston 30
An annular oil passage 38 is formed between the guide cylinder 29 and the annular oil passage 38 , and an oil passage 39 that communicates the annular oil passage 38 with the oil chamber 36 is bored in the guide cylinder 29 .

The simulator piston 30 is provided with a first cylinder hole 41 at the front 081 and a second cylinder hole 42 having a larger diameter than the first cylinder hole 41 and coaxially connected to the first cylinder hole 41. A booster piston 43 is slidably fitted into the first and second cylinder holes 41,42. That is, the booster piston 43 includes a small diameter portion 43a that is slidably fitted into the first cylinder hole 41;
At the rear end of the small diameter portion 43a, a second
It is basically formed in a cylindrical shape and has a large diameter portion 43b that slides into cylinder hole portion 43. Also booster piston 43
The rear end portion extends rearwardly through the receiver tube 32 in an oil-tight and movable manner. A retaining ring 44 is fitted on the outer surface of the rear end of the booster piston 43.
4 is disposed between the bearing member 45 and the bearing cylinder 32 such that at least a portion thereof protrudes outward in the axial direction of the booster cylinder 24 when the simulator piston 30 is at its retraction limit. A return spring 46 is compressed. Therefore, the booster piston 43 is urged rearward.

An annular output hydraulic pressure chamber 47 is defined between the large diameter portion 43b of the booster piston 43 and the receiver tube 32, and therefore the output hydraulic pressure chamber 47 is formed facing the back surface of the booster piston 43. become. Further, an annular reaction force chamber 48 is defined between the large diameter portion 43b of the booster piston 43 and the stepped portion 30b of the simulator piston 30.
will be in front of the

Connected to the reaction force chamber 48 are four accumulators that together with the return spring 46 constitute a resilient means RB and urge the booster piston 43 rearward. attached to. This accumulator 49 includes a bottomed cylindrical mounting body 50 that is screwed onto the booster cylinder 24, a bottomed cylindrical cylinder body 51 that is screwed onto the mounting body 50 in an oil-tight manner, and An oil chamber 52 is formed between the body 50 and the closed end, and a spring chamber 5 is formed between the cylinder body 51 and the closed end.
3 and a piston 54 that is oil-tightly and slidably fitted into the cylinder body 51, and a spring 5 that is housed in the spring chamber 53 to bias the piston 54 in a direction that contracts the oil chamber 52.
It consists of 5.

Moreover, the pressure receiving area of the piston 54 facing the oil chamber 52 is set smaller than the pressure receiving area of the booster piston 43 facing the reaction force chamber 48. Further, the accumulator 49 is attached to the booster cylinder 24 so that its oil chamber 52 is located below the oil sump 14 of the oil tank 13.

The mounting body 50 is screwed onto the booster cylinder 24 with a seal member 56 interposed between it and the outer surface of the booster cylinder 24, and an oil chamber 5 is provided at the closed end of the mounting body 50.
An oil passage 57 leading to the booster cylinder 24 is bored.
an oil passage 58 that communicates the oil passage 57 with the reaction force chamber 48;
is drilled.

An annular input hydraulic chamber 60 whose axial ends are oil-tightly sealed is formed between the intermediate portion of the small diameter portion 43a of the booster piston 43 and the inner surface of the first cylinder hole portion 41 of the simulator piston 30. The input hydraulic pressure chamber 60 is connected to the small diameter cylindrical portion 30a of the piston 30 regardless of the forward movement of the booster piston 43.
A communication hole 61 is bored to communicate with the. Further, an annular recess is provided on the outer surface of the small diameter portion 43a of the booster piston 43 on the front side of the input hydraulic pressure chamber 60 to form an annular outlet chamber 62 whose axial ends are sealed.
A communication hole 63 is provided in the small diameter cylindrical portion 30a of the simulator piston 30 so that the outlet chamber 62 is always communicated with the annular oil passage 38 regardless of the operation of the booster piston 43.

Therefore, the outlet chamber 62 is constantly communicated with the oil tank.

The booster piston 43 has a small-diameter cylinder hole 64 on the front side and a large-diameter cylinder hole 65 on the rear side coaxially bored, and the small-diameter cylinder hole 64 has a valve piston connected to the bushing rod l. 66 is slidably fitted. On the other hand, the rear end of a piston rod 10 coaxially connected to the working piston 6 in the master cylinder M is inserted into the front end of the simulator piston 30 facing the front end of the booster piston 43.
A boost chamber 67 facing the rear end of 0 is defined by the connecting cylinder portion 9, the guide member 11, the guide cylinder 29, the simulator piston 30, the booster piston 43, and the valve piston 66, and hydraulic pressure is introduced into the boost chamber 67. As a result, the actuating piston 6 moves forward.

A connecting rod 8 is fitted in a large-diameter cylinder hole 65 of the booster piston 43 in an oil-tight and slidable manner, and the front end of this connecting rod 68 is connected to the rear end of the valve piston 66. Further, the front end of the bushing rod 1 is connected to the rear end of the connecting rod 8. Moreover, booster piston 4
A retaining ring 69 is fitted onto the inner surface of the rear end portion of the valve 3 to abut against the rear end of the connecting rod 68 to restrict the backward limit of the connecting rod 8, that is, the valve piston 66. Furthermore, booster piston 4
A spring 71 that urges the valve piston 66 rearward is compressed between a retaining ring 70 fitted on the inner surface of the front end of the valve 3 and the front end of the valve piston 66.

The valve piston 66 has a boost chamber 6 open at its front end.
An oil supply passage 73 is coaxially bored and communicates with the booster piston 43 , the valve piston 66 , and the connecting cylinder 8 . Further, the booster piston 43 has the annular chamber 7.
An oil passage 75 is bored through which the output oil pressure chamber 4 communicates with the output oil pressure chamber 47. Therefore, the boost chamber 67 and the output hydraulic pressure chamber 47 are always in communication via the oil supply passage 73.

Between the valve piston 66 and the booster piston 43, there is an inlet valve 76 that communicates and blocks communication between the input hydraulic chamber 60 and the oil supply passage 73, and an inlet valve 76 that communicates with and blocks the input hydraulic chamber 60 and the oil supply passage 73.
Outlet valve 77 that performs shutoff, reaction force chamber 48 and oil supply path 7
An on-off valve 78 is provided for communicating and blocking communication between the three.

The inlet valve 76 includes an annular recess 79 that communicates with the oil supply path 73 and is provided on the outer surface of the intermediate portion of the valve piston 66, and an input hydraulic chamber 6.
The annular recess 79 is relatively long in the axial direction of the valve piston 66, and the inlet valve hole 80 is connected to the booster piston 43. 43 along the radial direction.

The inlet valve 76 opens when the inlet valve hole 80 communicates with the annular recess 79 , and when the valve piston 66 is at its retracting limit with respect to the booster piston 43 , the inlet valve hole 80 opens from the annular recess 79 . The positions of the annular recess 79 and the inlet valve hole 80 are set such that the valve piston 66 is in the forward position and the valve is in the closed state, and the valve piston 66 is in the forward position and the valve is in the closed state.
The valve opens when the valve moves forward.

The outlet valve 77 has a first outlet valve hole 81 that communicates with the oil supply path 73 and is bored in the valve piston 66, and a second outlet valve hole 82 that communicates with the outlet chamber 62 and is bored in the booster piston 43. Both outlet valve holes 81 and 82 are bored along the radial direction of the valve piston 66 and the booster piston 43 at mutually corresponding positions. In this Yamaguchi valve 77, when the valve piston 66 is at the retraction limit with respect to the booster piston 43, the first and second outlet valve holes 81, 82 communicate with each other and are slightly opened. When the forward movement of the valve piston 66 relative to the booster piston 43 starts, the inlet valve 76 closes before it opens.

The on-off valve 78 includes the annular recess 79 and a valve hole 83 that communicates with the reaction force chamber 48 and is bored in the booster piston 43. In this on-off valve 78, when the valve piston 66 is at the retracting limit with respect to the booster piston 43, the valve hole 83 communicates with the annular recess 79 and is slightly open. When forward operation is started, the outlet valve 77 closes before it closes.

Next, the operation of this embodiment will be explained. When the brake pedal P is not actuated, the valve piston 66 is held at the retracting limit with respect to the booster piston 43 by the spring force of the spring 71, and the booster piston 43 is held at the retracting limit by the spring force of the spring 71. 46 holds the simulator piston 30 at the retract limit. In this state, the inlet valve 76 is closed, and the outlet valve 77 and on-off valve 78 are open, so the boost chamber 67, output hydraulic pressure chamber 47, and reaction force chamber 48 are at atmospheric pressure. . Therefore, the actuating piston 6 of the master cylinder M is retracted by the spring 7 to the retracting limit.

When the brake pedal P is depressed to brake the automobile in this state, the valve piston 66 is pushed forward by the brake pedal P via the bushing rod 1 and the connecting rod 68. In response to the forward movement of the valve piston 66 relative to the booster piston 43, the on-off valve 78 first closes, the outlet valve 77 closes, and then the inlet valve 76 opens. For this reason, the input hydraulic chamber 60 and the boost chamber 67 communicate with each other,
By introducing the working hydraulic pressure into the boost chamber 67, the working piston 6 receives the hydraulic pressure on its back and moves forward, and the master cylinder M
boost operation is started.

At the beginning of such boosting operation, the valve piston 6
6 moves forward until the inlet valve 76 is opened, hydraulic pressure is supplied to the boost chamber 67 and the working piston 6 is moved forward, so this is compared to a case where the working piston is pressed and operated by a booster piston. Therefore, the operating piston 6 can be pressed and operated quickly regardless of the friction of the seal between the booster piston 43 and the simulator piston 30, and the initial operation of the operating piston 6 can be made smooth.

By the way, when the inlet valve 76 is opened, as described above, hydraulic pressure is supplied to the boost chamber 67 and also to the output hydraulic chamber 47, and the booster piston 43 also receives hydraulic pressure on its back surface, so that the valve piston 66 Since it moves forward relative to the inlet valve 76, the inlet valve 76 is closed and the outlet valve 77 is opened. Therefore, the population dialect 7
The working piston 6 moves forward due to the hydraulic pressure acting on the boost chamber 67 before the valve 6 closes and the outlet valve 77 opens, and the output hydraulic pressure of the master cylinder M becomes as shown by the characteristic lines P and -P shown in FIG. Elephants are increasing rapidly. As a result, the play in each part up to the brake terminal a is immediately removed.

After the output oil pressure reaches Pl, the valve piston 66 moves forward in response to the depression of the brake pedal P, so that the valve piston 66 moves forward relative to the booster piston 43, and the booster piston 43 moves forward relative to the valve piston 66. The opening and closing of the inlet valve 76 and the outlet valve 77 are alternately repeated. Therefore, the oil pressure in the boost chamber 67 and the amount of forward movement of the operating piston 6 also increase in accordance with the amount of forward movement of the valve piston 66, and the output oil pressure of the master cylinder M changes in accordance with the stroke, as shown by characteristic lines P and -P□. and increase.

By the way, when the valve piston 66 moves forward, the booster piston 4 moves forward by the hydraulic pressure in the output hydraulic chamber 47.
3 is a reaction force chamber 4 in front of the return spring 46 while contracting it.
When the booster piston 43 moves forward, the opening/closing valve 78 is closed and the reaction force chamber 48 is in a sealed state. For this reason, reaction force chamber 4
8 presses the piston 54 while contracting the spring 55 in the accumulator 49. Therefore, the booster piston 43 moves forward while receiving a reaction force from the spring 55 and a reaction force from the return spring 46 on its front side.

When the stepped portion 43b of the booster piston 43 comes into contact with the stepped portion 30b of the simulator piston 30 as the booster piston 43 moves forward, the forward movement of the booster piston 43 is blocked.

Therefore, from then on, only the valve piston 66 moves forward with the inlet valve 76 kept open by the depression force of the brake pedal P. However, when the oil pressure in the boost chamber 67 becomes greater than the depression force of the brake pedal P, the valve piston 66 is pushed back and the inlet valve 76 is closed. Furthermore, rake pedal P
If you continue to press the button, the valve piston 66 will move forward again and the inlet valve 76 will open. By repeating this kind of action,
The hydraulic pressure in the boost chamber 67 is the characteristic line P in Fig. 2! -P, increases rapidly. When the depression force of the brake pedal P becomes larger than the oil pressure (supplied oil pressure) in the boost chamber 67, the valve piston 66 moves forward at once. However, since the front end of the large diameter portion 68a of the connecting rod 68 connected to the valve piston 66 comes into contact with the rear end of the large diameter cylinder hole 65 of the booster piston 43, the characteristic line P3 Pa in FIG.
As shown in , the valve piston 66 moves forward only slightly and stops.
Stroke operation stops.

Moreover, since the forward and backward movement of the valve piston 660 is a minute movement that causes the inlet valve 76 to open or close, it does not impair the operational feeling.

Brake pedal P to release the operation of master cylinder M
When released, the spring 71 causes the valve piston 66 to first close the inlet valve 76 and then open the outlet valve 77. As a result, the hydraulic pressure in the boost chamber 67 is released and the actuating piston 6 retreats to the retraction limit, and the hydraulic pressure in the output hydraulic pressure chamber 47 and the reaction force chamber 48 is released, so that the booster piston 43 has its rear end supported by the return spring 46. quickly retreats to the retraction limit where it abuts the cylinder 32.

In such a hydraulic booster, the characteristic lines P and − in FIG.
Pz is the hydraulic pressure that presses the booster piston 43 forward by the hydraulic pressure of the output hydraulic chamber 47, the backward urging force by the resilient means RB, that is, the spring force that urges the booster piston 43 backward by the return spring 46, and the reaction force. It is determined by the balance with the reaction force by the force chamber 48, and the range in which the output oil pressure of the master cylinder M corresponds to the stroke can be arbitrarily set by adjusting the loads of the return spring 46 and the spring 55. Moreover, in order to correspond to the stroke until the output oil pressure of the master cylinder M increases, it is necessary to increase the loads of the return spring 46 and the spring 55, but most of this load is transferred to the accumulator 4.
9, the load on the return spring 46 can be made relatively small. Therefore, the return spring 46 can be made relatively small and its installation space can be reduced, contributing to miniaturization of the hydraulic booster B. Even if the load on the accumulator 49 is increased, the pressure receiving area of the piston 54 facing the oil chamber 52 is made smaller than the pressure receiving area of the booster piston 43 facing the reaction force chamber 48, so that the pressure of the spring 55 can be increased. The load is also relatively small, so the accumulator 49 can also be relatively small.

Also, assume that a hydraulic failure occurs in the hydraulic power supply source in this hydraulic booster. In this case, since the oil pressure in the oil pressure source oil pressure chamber 34 decreases, the simulator piston 30
It is held at the retraction limit only by the spring force. Therefore, when the brake pedal P is depressed to perform a braking operation, the valve piston 66 moves forward while contracting the spring 71, and after the connecting rotor 8 comes into contact with the booster piston 43,
The booster piston 43 moves forward while contracting the spring 31, and the front end of the booster piston 430 touches the operating piston 6.
The actuating piston 6 is pressed forward by contacting the rear end of the piston rod 10 connected to the piston rod 10, and an output hydraulic pressure is generated in the master cylinder M.

During this time, the booster piston 43 tries to compress the return spring 46, but the compressive force causes the simulator piston 30, which is in a substantially free state, to advance. Further, after the simulator piston 30 comes into contact with the guide cylinder 29, the booster piston 43 moves relatively forward, and the forward action of the valve piston 66 and the booster piston 43 continues until the booster piston 43 comes into contact with the simulator piston 30. As a result, sufficient output oil pressure can be obtained from the master cylinder M, and sufficient braking oil pressure can be obtained even in the event of oil pressure failure.

By the way, when the brake is operated in such a state where the hydraulic power source fails, only the simulator piston 30 slips with respect to the booster cylinder 24, and the booster piston 43 does not slip. Therefore, loss of brake pedal P depression force due to sliding friction can be suppressed to a small level.

Moreover, the booster piston 43 is the simulator piston 3
Since the simulator piston 30 and the booster piston 43 are arranged so that at least a portion thereof overlaps in the axial direction, the axial length of the booster cylinder 24 is reduced by that amount. Can be shortened.

Further, since the return spring 46 interposed between the simulator piston 30 and the booster piston 43 is arranged so that a part thereof projects outward in the axial direction of the booster cylinder 24, there is no space for storing the return spring 46. The booster cylinder 24 can be shortened in the axial direction by
Together with the axial shortening due to the fitting of the booster piston 43 to the simulator piston 30, the axial length of the booster simulator 24 can be further shortened.

When such a hydraulic booster and an anti-lock brake device are mounted on a vehicle, the kick bank phenomenon of the anti-lock brake device can be alleviated. That is, an increase in oil pressure in the boost chamber 67 due to kickback causes an increase in oil pressure in the output oil pressure chamber 47, and the booster piston 43
This is because the outlet valve 77 moves forward and the outlet valve 77 opens.

C1 Effects of the Invention As described above, according to the present invention, since the booster piston is slidably fitted into the cylinder piston, the booster piston and the simulator piston are arranged so that at least a portion thereof overlaps in the axial direction. As a result, the axial length of the booster cylinder can be shortened, and the loss of pedal force when the oil pressure of the oil pressure supply source fails can be suppressed.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional side view of the embodiment of the present invention, and FIG. 2 is an output characteristic diagram of the device of the present invention.

Claims (1)

[Claims] A booster cylinder is connected to the rear end of the cylinder body of the master cylinder, and the booster cylinder has a simulator piston whose front face faces a hydraulic chamber connected to a hydraulic power supply source, and is designed to be held in a retracted position when the hydraulic power supply source is normal. A resilient means for urging the booster piston rearward is interposed between the booster piston and the simulator piston, which are slidably fitted and movable relative to the simulator piston in the axial direction, A booster piston of a valve piston is connected to an operating member and slidably fitted to the booster piston between an output hydraulic chamber formed facing the back of the booster piston and an input hydraulic chamber communicating with a hydraulic pressure supply source. An inlet valve that opens when the valve piston moves forward relative to the booster piston is interposed between the output hydraulic pressure chamber and an outlet chamber communicating with the oil tank, and an outlet valve that closes when the valve piston moves forward relative to the booster piston. A hydraulic booster in which a booster piston is slidably fitted into a simulator piston.