JP2894374B2 - Loss stroke reduction mechanism of hydraulic booster - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic booster used for a brake booster or the like, and more particularly, to a hydraulic booster provided with a loss stroke reducing mechanism for reducing a loss stroke at the initial operation of an input shaft. Related to the device.

2. Description of the Related Art Conventionally, as a hydraulic booster having a loss stroke reducing mechanism, a power piston slidably provided in a housing, a power chamber formed in a rear portion of the power piston in the housing, and An input shaft slidably penetrated from the rear side of the power piston in the housing, and provided over the power piston and the distal end of the input shaft, and the hydraulic pressure according to the input applied to the input shaft is set to the above-described value. A control valve for supplying to the power chamber; and a reaction force piston slidably provided on the outer periphery of the input shaft, retracted with respect to the input shaft by hydraulic pressure in the power chamber, and abutting against a stopper provided on the input shaft. A spring that is elastically mounted between the power piston and the reaction piston and holds the reaction piston at a forward position separated from the stopper by a predetermined elastic repulsion; That a stopper for restricting the free retraction of the input shaft relative to the power piston in contact with Oite the housing person is known (JP-A-2-6
0871). In the hydraulic booster disclosed in the above publication, when the input shaft is advanced, a hydraulic pressure according to the input applied to the input shaft is supplied to the power chamber by the control valve, whereby the power piston is advanced. Boosting action is performed. At this time, the hydraulic pressure supplied to the power chamber acts on the input shaft to give a reaction force to the input shaft,
Acting on the reaction force piston, the reaction force piston is retracted with respect to the input shaft against the spring. Before the reaction force piston comes into contact with the stopper provided on the input shaft, the hydraulic pressure acts only on the input shaft with a relatively small pressure receiving area, so the output increases at a large boost ratio, and the reaction force piston If the two are integrated by contacting the stopper provided on the shaft, the pressure receiving area increases, and the output increases at a small boost ratio. A good operation feeling is secured by such a large boost ratio at the beginning of the operation. When the input to the input shaft is released from the operating state of the hydraulic booster, the hydraulic pressure supplied to the power chamber is discharged, and the power piston retreats. , A large flow passage area of the discharge passage in the control valve can be secured.
When the power piston is on the verge of the retreat end, first, the stopper provided on the input shaft contacts the housing to restrict retraction, and then the power piston is retracted to the retreat end position. With respect to. In other words, in the non-operating state, the input shaft is positioned at the forward position with the free retraction with respect to the power piston being restricted by the stopper abutting on the housing. Can be.

However, in the conventional hydraulic booster, the reaction piston and the stopper are arranged in series in the axial direction of the input shaft. The dimension in the direction was large. In view of such circumstances, the present invention provides a loss stroke reduction mechanism capable of reducing the axial dimension of a hydraulic booster by providing a reaction force piston and a stopper so as to overlap in the axial direction. Things.

That is, according to the present invention, there is provided a conventional hydraulic booster having the above-described structure, wherein the reaction piston is slidably fitted to a housing while maintaining liquid tightness. One end of the force piston faces the power chamber, the other end faces the low pressure side, and further, a slit is formed on the power chamber side of the reaction force piston, and a stopper provided on the input shaft passes through the slit to the housing. This is what can be abutted.

According to the above arrangement, the reaction force piston is slidably provided on the outer periphery of the input shaft, and is slidably fitted to the housing while maintaining the liquid tightness. Is facing the low pressure side. Therefore, when hydraulic pressure is introduced into the power chamber, the reaction force piston is retracted with respect to the input shaft against the resilience of the spring, and contacts the stopper provided on the input shaft to change the boosting ratio. I will be. On the other hand, a slit is formed in the reaction force piston on the power chamber side, and a stopper provided on the input shaft inside the reaction force piston can penetrate the slit and contact the housing.
Therefore, in the non-operation state, the input shaft can be positioned at the forward position with respect to the power piston by the stopper abutting on the housing, so that the loss stroke at the initial operation of the input shaft can be reduced. Since the reaction force piston and the stopper are arranged so as to overlap in the axial direction of the input shaft, the axial size of the hydraulic booster can be reduced as compared with the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, a bore 2 is formed in a housing 1 of a hydraulic booster, and a cylindrical portion 3A is formed in the bore 2 at the right rear portion. The formed power piston 3 is slidably fitted. A push rod 4 provided at the left end of the power piston 3 is slidably projected outside the housing 1 while maintaining liquid tightness, and its tip is linked with a piston of a master cylinder (not shown). The opening at the right end of the bore 2 is sealed by a plug 5 constituting a part of the housing 1, and the plug 5 is integrally fixed to the housing 1 by a nut 6 screwed to the housing 1. A power chamber 8 into which pressure oil is introduced is formed between the plug 5 and the power piston 3, and a spring 10 is provided in a low-pressure chamber 9 formed on the power piston 3 on a side opposite to the power chamber 8. The power piston 3 is normally held at a non-operating position shown in FIG. The low-pressure chamber 9 housing the spring 10 communicates with a reservoir (not shown) via a passage 11 formed in the housing 1. An input shaft 17 interlocked with a brake pedal (not shown) is slidably penetrated through a plug 5 constituting a part of the housing 1, and the left end of the input shaft 17 and the cylindrical shape of the power piston 3 are formed. The control valve 18 is provided over the inside of the part 3A. The control valve 18 includes a first valve seat 20 formed on a plate 19 provided in the cylindrical portion 3 </ b> A of the power piston 3, and a spring 21.
Of the first valve seat 20 from the side opposite to the power chamber 8 due to the repulsive force of
A ball valve 22 that is seated on the input shaft 17, an annular pin 23 that is provided at the distal end of the input shaft 17 and separates the ball valve 22 from the first valve seat 20, and is further formed at the distal end of the annular pin 23. And a second valve seat 24 on which the ball valve 22 is seated. The plate 19 includes retainers 56, 5
6 'and the power piston 3 are fixed to the power piston 3 by fixing screws 58 screwed to the cylindrical portion 3A.
In the non-operating state shown in the drawing, the ball valve 22 is seated on the first valve seat 20 by the repulsive force of the spring 21, and the power chamber 8 formed on the right side of the first valve seat 20 and the pressure chamber 2 formed on the left side.
Communication with 9 is cut off. The pressure chamber 29 communicates with a pump (not shown) through a supply passage 30, and the pump constantly supplies a predetermined pressure of oil to the pressure chamber 29. The supply passage 30 includes a radial passage 31 formed in the power piston 3, an annular groove 32 formed in the outer peripheral surface of the power piston 3, a radial passage 33 formed in the housing 1, and a passage 33. And a conduit (not shown) for connecting to the pump. Also,
In the non-operating state shown in FIG.
The valve seat 24 is separated from the ball valve 22 seated on the first valve seat 20, and in this state, the power chamber 8 is connected to the discharge passage 38.
Through the reservoir. This discharge passage 38
Are formed in the shaft of the annular pin 23, the passage 41 formed in the shaft of the shim 40 interposed between the annular pin 23 and the input shaft 17, and the shaft 39 of the input shaft 17. A passage 42, a passage 43 formed in the plug 5, and a passage 44 formed in the housing 1 are provided.
4 is connected to the above-described passage 11 so that the discharge passage 3
8 communicates with a reservoir (not shown). Further, the left end of the ball valve 22 constituting the control valve is slidably penetrated through the collar 48 while maintaining liquid tightness, and a balance chamber 49 is formed on the left side of the collar 48. The balance chamber 49 is formed in a communication passage 50 formed in the power piston 3.
The ball valve 22 communicates with the power chamber 8 through a through hole 51 formed in the plate 19, and the pressure receiving area of the ball valve 22 on the balance chamber 49 side is reduced from the area of the inner diameter of the first valve seat 20 to the second valve seat 24. , Ie, larger than the pressure receiving area of the ball valve 22 on the power chamber 8 side. By setting such a pressure receiving area, the input shaft 17
When the ball pin 22 is separated from the first valve seat 20 by advancing the annular pin 23 and the pressure in the power chamber 8 is thereby increased, the ball valve 22 is seated on the second valve seat 22 of the annular pin 23. The ball valve 22 is separated from the second valve seat 24 to prevent liquid leakage. However, the plug 5 constituting a part of the housing 1 has a cylindrical guide portion 5A projecting into the cylindrical portion 3A of the power piston 3 at the left end thereof.
A reaction force piston 55 is slidably fitted to the guide portion 5A, and the reaction force piston 55 is
Are slidably supported. The input shaft 17 is slidably fitted to the shaft of the reaction force piston 55, so that the reaction force piston 5 supported by the guide portion 5A is provided.
5, the input shaft 17 is slidably supported. A flange portion 55A extending radially outward is formed at the left end of the reaction force piston 55, and an outer peripheral portion of the flange portion 55A and a retainer 56 provided in the cylindrical portion 3A of the power piston 3 are formed. A spring 57 is interposed therebetween to normally hold the reaction force piston 55 at a non-operating position shown in FIG. In this state, the reaction force piston 5
5 is located at a forward position with respect to the input shaft 17 and is separated from a stepped stopper 17A provided on the input shaft 17.
As will be described later in detail, when the acting force of the oil pressure in the power chamber 8 applied to the reaction force piston 55 exceeds the set load of the spring 57, the reaction force piston 55 resists the spring 57 and Then, it is retracted and comes into contact with the stopper 17A. As a result, before the reaction piston 55 comes into contact with the stopper 17A, the reaction piston 55
Is applied to the power piston 3 via the spring 57 and the retainer 56 while the reaction force piston 55 contacts the stopper 17A. Since the reaction force is transmitted to the input shaft 17 as a reaction force, the reaction force piston 55
The boost ratio can be changed before and after contact with 7A.
Further, the spring 57 and the retainer 56 are disposed in a gap formed between the outer periphery of the guide portion 5A and the inner periphery of the cylindrical portion 3A of the power piston 3. Therefore,
In the non-operating state shown in the drawing, the guide portion 5A, the sliding portion of the reaction force piston 55 with respect to the guide portion 5A, the sliding portion of the input shaft 17 with respect to the reaction force piston 55, and a spring for biasing the reaction force piston 55 57 are arranged in the radial direction while overlapping each other in the axial direction. As a result, for example, the axial size of the hydraulic booster is reduced as compared with the conventional device in which the sliding portion of the reaction piston 55 and the sliding portion of the input shaft 17 are arranged in series in the axial direction. be able to. Next, a description will be given of a loss stroke reduction mechanism at the initial stage of operation of the input shaft 17. A step 17B having a reduced diameter at the distal end is formed at the distal end of the input shaft 17, and the distal end of the input shaft 17 is further extended from the distal end. A radially inner flange portion 61 formed at the right end of the cylindrical stopper member 61
A, the flange portion 61A of the cylindrical stopper member 61 is brought into contact with the step portion 17B. The cylindrical stopper member 61 is fixed to the input shaft 17 by press-fitting the annular member 62 between the outer periphery of the input shaft 17 on the distal end side of the step portion 17B and the inner periphery of the cylindrical stopper member 61. At the same time, the liquid tightness between them is maintained. As shown in FIG. 2, stoppers 61 </ b> B protruding outward in the radial direction are formed integrally at the left end of the cylindrical stopper member 61 at positions opposed to each other in the radial direction.
The reaction force piston 55 is projected outward from a shaft portion of the reaction force piston 55 via a diametrical slit 55B formed in a flange portion 55A of the reaction force piston 55. Then, the above-described shim 40 and the annular pin 23 are sequentially inserted into the cylindrical stopper member 61, and a spring 63 is elastically mounted between the annular pin 23 and the plate 19. The stopper 61B is in contact with the left end surface of the guide portion 5A to restrict the input shaft 17 from retreating. On the other hand, the left end of the retainer 56 is extended to a right side position adjacent to the stopper 61B, so that the retracting of the input shaft 17 can be restricted by the retainer 56 when the power piston 3 is retracted. By the way, the outer side in the radial direction of the power chamber 8 formed in the bore 2 is kept liquid-tight by a seal member 66 provided on the outer periphery of the plug 5 and a seal member 67 provided on the outer periphery of the power piston 3. ing. On the other hand, the space between the radially inner side of the power chamber 8 and the discharge passage 38 is sealed by the following four sealing means. That is, the gap between the reaction force piston 55 communicating with the power chamber 8 and the guide portion 5A is sealed by the seal member 68 provided on the inner periphery of the guide portion 5A, and the cylindrical stopper member 61 communicating with the power chamber 8 is provided. The gap between the annular pin 23 is sealed by a seal member 69 provided on the outer periphery of the annular pin 23. Further, the gap between the cylindrical stopper member 61 communicating with the power chamber 8 and the reaction force piston 55 is a relatively long sliding surface in the axial direction between the annular member 62 and the reaction force piston 55 and the input shaft 17. 70. The space between the discharge passage 38 and the atmosphere is sealed by seal members 71 and 72 provided on the inner and outer circumferences of the plug 5. In the above configuration, in a non-operating state in which the depression of a brake pedal (not shown) is released, the annular pin 23 is urged rightward by a spring 63 mounted between the annular pin 23 and the plate 19, and the ball valve The power chamber 8 is separated from the reservoir 22 and communicates with the reservoir via the discharge passage 38. In this state, when the input shaft 17 is advanced by depressing the brake pedal, the second valve seat 24 formed at the distal end of the annular pin 23 comes into contact with the ball valve 22 and the discharge passage 38 and the power chamber 8 And the ball valve 22 is separated from the first valve seat 20 against the spring 21 by the annular pin 23 (point A in FIG. 3), so that the ball valve 22 is always introduced into the pressure chamber 29. The pressurized oil is introduced into the power chamber 8 through a gap between the outer circumference of the annular pin 23 and the inner circumference of the plate 19. When pressure oil is introduced into the power chamber 8, the power piston 3 is advanced leftward against the spring 10, and the reaction piston 55 is displaced rightward against the spring 57. In the early stage of the operation, the reaction force piston 55 is
Thus, the input shaft 17 is kept separated from the stopper 17A. In this state, the acting force of the hydraulic pressure in the power chamber 8 applied to the reaction force piston 55 is received by the power piston 3 via the spring 57, the retainer 56 and the fixing screw 58, and the acting force is applied to the input shaft 17. It is not transmitted. Therefore, the reaction force transmitted to the driver via the input shaft 17 is obtained by the oil pressure in the power chamber 8 directly acting on the input shaft 17, and the pressure receiving area of the input shaft 17 at this time is relatively small. The output increases at a large boost ratio (see the straight line B in FIG. 3). When the hydraulic pressure in the power chamber 8 rises and the leftward movement of the power piston 3 proceeds, and a substantial braking action is performed, the reaction piston 5
5 comes into contact with the stopper 17A of the input shaft 17 (C in FIG. 3).
point). As a result, the acting force applied to the reaction force piston 55 is transmitted to the input shaft 17 via the stopper 17A, so that the boosting ratio decreases, and thereafter, the output increases at a small boosting ratio (the straight line in FIG. 3). D). In addition, the resistance from the seal portion applied to the input shaft 17 when the brake pedal is depressed is determined by the sliding surface 70 between the reaction force piston 55 and the input shaft 17 and the seal member 71 provided on the inner periphery of the plug 5. Is the resistance given by Since the sealing means between the power chamber 8 and the discharge passage 38, which is particularly high in pressure, is used as the sliding surface 70, the resistance of the sealing portion applied to the input shaft 17 is reduced as compared with the case where a rubber sealing member is provided therebetween. It can be made sufficiently small, so that the operation feeling at the initial stage of depression of the brake pedal can be made light. Furthermore, since the seal members 68 and 71 must ensure communication between the passage 42 formed in the input shaft 17 and the passage 43 formed in the plug 5 even when the input shaft 17 moves forward and backward, the input shaft It is necessary to dispose it in the axial direction by more than the amount of movement of the actuator 17. On the other hand, the sliding surface 70
It is necessary to form the sliding surface 70 in the axial direction in order to obtain a sufficient sealing action. Since the sliding surface 70 is formed long in the axial direction, it is possible to prevent the axial dimension of the hydraulic booster from increasing. Next, when the depression of the brake pedal is released from the above-described brake operation state and the annular pin 23 is displaced rightward by the spring 63, the ball valve 22 is seated on the first valve seat 20. The communication with the power room 8 is cut off. Following this, the annular pin 23
When the second valve seat 24 is separated from the ball valve 22, the power chamber 8 communicates with the reservoir through the discharge passage 38, so that the oil pressure in the power chamber 8 decreases and the power piston 3 is retracted to the right. . At this time, the retraction of the input shaft 17 is regulated by the stopper 61B of the cylindrical stopper member 61 integral with the input shaft 17 abutting on the retainer 56 integral with the power piston 3. The seated ball valve 22 and the second valve seat 24 of the annular pin 23 are largely separated from each other to secure a large flow passage area therebetween. When the right end of the power piston 3 is shortly before contacting the plug 5, the cylindrical stopper member 6 contacting the retainer 56
The first stopper 61B comes into contact with the guide portion 5A. When the power piston 3 retreats by a predetermined distance from this state and the right end thereof comes into contact with the plug 5 and stops, the stopper 61B of the cylindrical stopper member 61
With respect to the annular pin 23
Ball valve 22 having the second valve seat 24 seated on the first valve seat 20
To a position close to. Therefore, when the brake pedal is depressed next time, the second valve seat 24 is immediately seated on the ball valve 22 to cut off the communication between the power chamber 8 and the reservoir, so that the loss stroke at the initial stage of depressing the brake pedal can be reduced. . In addition, the sealing member 68
May be provided on the outer periphery of the right end of the reaction force piston 55 instead of being provided on the inner periphery of the guide portion 5A, or the sliding surface between the guide portion 5A and the reaction force piston 55 may be omitted by omitting the seal member 68. May be used as sealing means. Furthermore,
Instead of using the sliding surface 70 as a sealing means, a sealing member can be provided here.

As described above, according to the present invention, since the reaction force piston and the stopper are arranged so as to overlap in the axial direction, the axial size of the hydraulic booster is smaller than that of the prior art. Can be shortened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, taken along line II of FIG. 2;

FIG. 2 is a front view showing an assembled state of a reaction force piston 55 and a cylindrical stopper member 61 shown in FIG.

FIG. 3 is a characteristic diagram of a hydraulic booster.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Housing 3 ... Power piston 5 ... Plug (housing) 8 ... Power room 17 ... Input shaft 18 ... Control valve 55 ... Reaction force piston 55A ... Flange part 55B
... Slit 57 ... Spring 61 ... Cylindrical stopper member 61B
… Stopper

Claims (1)

(57) [Claims] 1. A power piston slidably provided in a housing, a power chamber formed in a rear part of the power piston in the housing, and an input slidably penetrating the housing from a rear side of the power piston. A control valve that is provided across the shaft, the power piston, and a tip end of the input shaft, and supplies a hydraulic pressure corresponding to an input applied to the input shaft to the power chamber; A reaction force piston that is movably provided, retreats with respect to the input shaft by the hydraulic pressure in the power chamber, and contacts a stopper provided on the input shaft, and is elastically mounted between the power piston and the reaction force piston. A spring for holding a reaction force piston at a forward position separated from the stopper by a predetermined elasticity, and an input provided to the input shaft and abutting on the housing in a non-operating state to input power to the power piston. In a hydraulic booster provided with a stopper for restricting free retraction of the shaft, the reaction force piston is slidably fitted to the housing while maintaining liquid tightness, and one end of the reaction force piston is connected to the power chamber. The other end faces the low pressure side, and a slit is formed on the power chamber side of the reaction force piston, and a stopper provided on the input shaft can pass through the slit to be able to contact the housing. The loss stroke reduction mechanism of the hydraulic booster.