JP2000046072A - Method and structure of coupling push rod with hydraulic piston in clutch booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution of a coupling part of a push rod with a hydraulic piston, suppress the costs, and prevent the generation of striking sounds when a clutch pedal is stamped and application of a shock to the pedal. SOLUTION: A power piston is operated by the air introduced into a pressure chamber of a power cylinder, and the output therefrom is transmitted to a piston 22 of a hydraulic cylinder via a push rod 16 coupled with the power piston. An inserting hole 22a is formed at the end face of the hydraulic piston 22, and a ring groove 22b is formed at the inner surface of the hole 22a, while a ring groove 16b is also formed at the outer circumferential surface of the forefront of the push rod 16. A wire ring 41 is simultaneously fitted in these grooves 16b and 22b, and the push rod 16 is coupled with the hydraulic piston 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clutch booster, and more particularly, to a push rod connected to a front surface of a power piston and a hydraulic piston to which an output of the power piston is transmitted via the push rod. The present invention relates to a connection structure and a method of connecting both.

A clutch booster generally includes a control valve which is switched by operating a clutch pedal to supply and discharge compressed air to and from a pressure chamber of a power cylinder, and a power piston which is operated by compressed air introduced into the pressure chamber. A push rod connected to the power piston to move forward and backward integrally, a piston of a hydraulic cylinder to which the output of the power piston is transmitted via the push rod, and a forward and backward movement through the hydraulic piston, And a push rod for operating the clutch for connecting and disconnecting the clutch by rotating the clutch outer lever.

The relationship between a conventional push rod 116 and a hydraulic piston 122 will be described with reference to FIG. The push rod 116 is fixed to the front side of the power piston 110 that divides the inside of the power cylinder 102 into a pressure chamber 112 and an atmosphere chamber 114, and moves forward and backward integrally.
The distal end of the push rod 116 extends through the push rod guide 128 housed in the housing 118 toward the hydraulic cylinder 104, and the distal end surface thereof is in contact with a concave portion on the end surface of the hydraulic piston 122. . Further, a rear end face of the clutch operating push rod 147 connected to a clutch outer lever (not shown) is in contact with a front side of the hydraulic cylinder 104.

[0004] When the clutch pedal (not shown) is depressed, the clutch booster sends the hydraulic pressure from the master cylinder to the hydraulic pressure chamber 124 of the hydraulic cylinder 104 via the passage 162 in the housing 118.
The control valve 106 is sent to the hydraulic chamber of the control valve 106 (not shown) through the internal passage 160.
, And compressed air is introduced into the pressure chamber 112 of the power cylinder 102 to operate the power piston 110. During this operation, first, the hydraulic piston 122 strokes by the hydraulic pressure introduced into the hydraulic pressure chamber 124 of the hydraulic cylinder 104, and the play on the clutch side (the right side in the drawing) with respect to the piston 122 is reduced. Then, the power piston 10 is stroked by the compressed air introduced through the control valve 106, the push rod 116 catches up with and contacts the hydraulic piston 122, and the stroke is further performed to operate the clutch.

[0005]

As described above, after the hydraulic piston 122 first strokes, the power piston 110 and the push rod 116 start the stroke with a delay, so that the push rod 116
Hydraulic piston 122 stroked ahead
There was a problem that a tapping sound was generated when the robot caught up with and came into contact. Further, the hydraulic piston 12 is not moved until the power piston 110 starts the stroke and the push rod 116 comes into contact with the hydraulic piston 122.
2 does not move, the hydraulic chamber 12 of the hydraulic cylinder 104 is moved by the stroke of the push rod 116.
4 decreases, and the hydraulic pressure in the hydraulic cylinder 104 increases. There has been a problem that this increase in hydraulic pressure is transmitted to the master cylinder and instantaneously shocks the clutch pedal.

FIG. 7 shows another example of a conventional clutch booster having a connection structure between a push rod and a hydraulic piston. This clutch booster has a built-in clutch wear adjusting function. ing. When the clutch booster is actually mounted on the clutch, the power piston 210 is located approximately in the middle of the power cylinder 202, and gradually moves backward (moves to the left in the drawing) as the clutch wears. Then, when the retracted power piston 210 presses the wear alarm switch 284, an alarm is issued.

In the example shown in FIG. 7, the spring 215 is disposed in the pressure chamber 212 so as to press the power piston 210 toward the hydraulic piston 222. And the power piston 210 is connected to the hydraulic piston 2
A clutch booster configured to bias in a direction away from the clutch 22 is also widely known. In the case of such a configuration, it is necessary to connect the hydraulic piston 222 and the push rod 216 on the power piston 210 side,
Normally, these two 216 and 222 are connected by a pin 286 as in the configuration of FIG.

In the above-described conventional configuration, the push rod 21
The connection between the hydraulic piston 222 and the hydraulic piston 222 is troublesome. In particular, as shown in FIG. 7, in the case where the housing 218 on the power cylinder 202 side and the body 220 of the hydraulic cylinder 204 are integrated, the push rod 216 is provided with the oil seal 270 of the push rod guide 228 or the like. After the cup seal 274 is fitted, the hydraulic piston 222 is connected with the pin 286, the pin 286 is prevented from being removed by the wiring 288, and then assembled into the housing 218 and assembled with the snap ring 280. There was a problem that assembly was poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a push rod and a hydraulic device of a clutch booster which do not generate a tapping sound or give a shock to a pedal when the clutch pedal is depressed. It is an object to provide a connection structure and a connection method with a piston. It is another object of the present invention to provide a connection structure and a connection method between a push rod and a hydraulic piston of a clutch booster, which has a simple structure, is easy to assemble, and is inexpensive.

[0010]

The coupling structure of the push rod and the hydraulic piston of the clutch booster according to the present invention operates the power piston by air introduced into the pressure chamber of the power cylinder, and outputs the power to the power piston. A clutch booster that transmits to the piston of the hydraulic cylinder via a push rod connected to the piston.Especially, a hole is formed in the end face of the hydraulic piston, and an annular While providing a groove, an annular groove is formed on the outer peripheral surface of the end of the push rod,
The push rod and the hydraulic piston are connected to each other via a wire that simultaneously engages in both of the annular grooves.

Further, the method for connecting the push rod and the hydraulic piston of the clutch booster according to the present invention is characterized in that a part is cut into an annular groove provided in an inner surface of a hole formed in an end surface of the hydraulic piston. Insert the substantially circular arc-shaped wiring, and then push a push rod having an annular groove on the outer peripheral surface through this wiring to spread it out. It is to be engaged with the groove.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a longitudinal sectional view of a clutch booster provided with a connection structure between a push rod and a hydraulic piston according to an embodiment of the present invention. The clutch booster includes a power cylinder 2 and a hydraulic cylinder. A cylinder 4 and a control valve 6 are provided.

The power cylinder 2 has a power piston 10 slidably fitted in a cylinder shell 8. The power piston 10 partitions the inside of the cylinder shell 8 into a pressure chamber 12 and an atmosphere chamber 14. ing. A push rod 16 is connected to the shaft center of the power piston 10 and moves forward and backward integrally. The power piston 10 is provided in the atmosphere chamber 14.
It is urged to the pressure chamber 12 side by a return spring 15 disposed inside, and is stopped at the inoperative position shown in FIG.

The connection structure between the power piston 10 and the push rod 16 will be described. At the center of the front surface of the power piston 10 (the direction in which the power piston 10 moves during operation, that is, the right side in FIG. 1 is referred to as the front), a push rod connecting portion 10a protruding in a cylindrical shape is formed. In the bottomed hole 10b of the shape connecting portion 10a,
The rear end of the push rod 16 is connected via the push rod holding member 11.

The push rod holding member 11 has a cup-shaped portion 11a and a flange 11b formed on the opening side (right side in the figure) as shown in an enlarged view in FIG. An annular groove 11c is provided on the inner peripheral surface of the portion 11a. A chamfered portion 11d is formed on a wall surface of the annular groove 11c on the opening side. On the other hand, an annular groove 16 a is also formed on the outer peripheral surface of the end of the push rod 16. The wiring 13 is simultaneously engaged in both the annular grooves 11c and 16a of the push rod holding member 11 and the push rod 16, thereby connecting the push rod 16 and the push rod holding member 11.

A female screw is formed on the inner peripheral surface of the bottomed hole 10 b of the power piston 10, and a male screw is formed on the outer peripheral surface of the push rod holding member 11. The push rod holding member 11 and the push rod 16 connected to the holding member 11 are fixed to the power piston 10 by being screwed into the bottom hole 10b. With the push rod holding member 11 screwed into the hole 10b of the power piston 10 as described above, the flange 11b of the push rod holding member 11 comes into contact with the distal end surface of the cylindrical connecting portion 10a of the power piston 10. ing.

In this embodiment, the push rod 1
6 and the structure of the connecting portion between the push rod holding member 11
Although the structure of the connecting portion between the distal end portion (the right side in FIG. 1) of the push rod 16 and the hydraulic piston 22 described later is the same as that of the conventional clutch booster, the present invention is not limited to such a structure. Similarly, it may be fixed by caulking or the like.

Further, a small cup seal 2 is provided on a sliding portion of the outer periphery of the power piston 10 with the cylinder shell 8.
1 and the wear ring 23 are fitted. By using such a small cup seal 21, the sliding resistance can be reduced without lowering the durability and airtightness of the seal member, and the operation feeling of the clutch pedal can be improved.

The hydraulic cylinder 4 is provided on a cylinder body 20 connected and fixed to a housing 18 for closing an opening of the cylinder shell 8. An O-ring 19 is interposed between the housing 18 and the cylinder body 20. Cylinder hole 20 of cylinder body 20
A hydraulic piston 22 is slidably disposed in a. The hydraulic piston 22 divides the inside of the cylinder hole 20a into a hydraulic chamber 24 on the power cylinder 2 side and an atmosphere chamber 26 on the distal end side. Liquid tightness and airtightness between 24 and 26 are maintained.

The push rod 16 connected to the power piston 10 extends through a guide portion (generally indicated by reference numeral 28) held at the center of the housing 18 to the hydraulic cylinder 4 side. The housing 18 has a recessed portion 18 protruding toward the atmosphere chamber 14 of the power cylinder 2 and having a through hole 18b formed in the bottom surface.
The guide portion 28 is accommodated in the concave portion 18c. The guide portion 28 includes an annular seal holding member 29, a liquid leakage preventing seal member 31 and an air suction preventing seal member 33 incorporated in annular concave portions formed at both ends of the inner surface of the seal holding member 29. ing. These two seal members 31, 33 are made of Y packing. Further, the seal holding member 29 is made of resin. The annular seal holding member 29 has an inner diameter substantially matching the outer diameter of the push rod 16 and an outer diameter substantially matching the inner diameter of the recessed portion 18c of the housing 18. The push rod 16 penetrates the inner periphery thereof while being fitted. An O-ring 37 is provided on the outer periphery of the seal holding member 29.
Are fitted to maintain liquid tightness and air tightness on the outer peripheral side of the guide portion 28.

The guide portion 28 is fixed by attaching a ring plate 39 to the entrance side of the recess 18 c of the housing 18 and pressing the ring plate 39 by the end of the cylinder body 20 fixed to the housing 18. Seal holding member 2
9 is prevented from falling off by the inner peripheral portion of the bottom surface of the concave portion 18c of the housing 18, while the seal member 3 for preventing liquid leakage is incorporated.
1 is prevented from falling off by the ring plate 39.

The distal end of the push rod 16 penetrating through the guide portion 28 is connected to a hydraulic piston 22 slidably fitted in the cylinder body 20.
An insertion hole 22a having an inner diameter slightly larger than the outer diameter of the push rod 16 is formed on the end surface of the hydraulic piston 22 on the power cylinder 2 side (see FIG. 3 showing a connecting portion in an enlarged manner). The tip of the push rod 16 is inserted into the hole 22a. An annular groove 22b is formed in the inner peripheral surface of the insertion hole 22a of the hydraulic piston 22.
On the other hand, an annular groove 16 b is also formed on the outer peripheral surface of the distal end of the push rod 16. A chamfered portion 22c is formed on the wall surface on the opening side (left side in FIG. 3) of the inner peripheral annular groove 22b of the hydraulic piston 22. A wire ring 41 is fitted in the annular grooves 22b and 16b, and engages with the push rod 16 and the hydraulic piston 22 at the same time to connect the two. The inclination angle of the chamfered portion 22c is set to an angle such that the push rod 16 comes out when a load equal to or more than a predetermined value is applied.

The wiring 41 has a shape in which a part of a substantially circular ring is cut and has a length of about three quarters in a free state. As shown in FIG. 4, the wiring 41 is slightly deformed, and the diameter D ₂ in the direction orthogonal to the diameter D ₁ (the vertical direction in FIG. 4) of the portion having the cut portion 41a is slightly shifted on both sides. It is enlarged. Therefore,
When this wiring 41 is fitted into both annular grooves 16b and 22b, it does not engage with the annular groove 22b of the hydraulic piston 22 over the entire circumference, but engages only at two places 41b and 41c on both sides. (See FIG. 5). As described above, the annular groove 22b of the hydraulic piston 22 is formed with the chamfered portion 22c at a predetermined angle, and the wiring 41 is not partially connected to the annular groove 22b of the hydraulic piston 22 but is formed in a part 41b, 41c. The push rod 16 does not come out of the hydraulic piston 22 with a pulling load less than a predetermined value. It can be removed from the hole 22a.

In the structure of this embodiment, when the push rod 16 is mounted on the hydraulic piston 22,
First, the wiring 41 is fitted into the annular groove 22b of the hydraulic piston 22, and then the push rod 16 is inserted into the insertion hole 22a of the hydraulic piston 22. The distal end 16c of the push rod 16 is tapered as shown in FIG. 3, and is inserted into the hole while pushing and expanding the wiring 41. Thereafter, when the annular groove 16b of the push rod 16 reaches the position of the wiring 41, The wiring 41 fits into the annular groove 16b.
As described above, the push rod 16 and the hydraulic piston 22 can be connected by a simple operation with a very simple structure, so that the cost can be reduced.

A push rod 47 for operating the clutch is in contact with the front surface (the end surface on the side of the atmosphere chamber 26) of the hydraulic piston 22. Further, the other end of the clutch operating push rod 47 is connected to a clutch outer lever (not shown).

The control valve 6 includes a housing 18
And, it is provided in valve holes 18a, 30a formed in a valve housing 30 fixed to the housing 18. A valve lifter 32 is provided in the valve hole 30a.
Are slidably fitted. On the housing 18 side of the valve lifter 32, a diaphragm 43 is provided.
It is clamped between the step on the inner surface of a and the annular retainer 45. The valve lifter 32 has a medium diameter portion 32 a slidably supported in a valve hole 30 a of the valve housing 30.
And a small-diameter portion 32c penetrating through the inside of the annular retainer 45, and a large-diameter portion 32b intermediate the small-diameter portion 32c. A seal member 49 is fitted around the outer periphery of the middle-diameter portion 32a. The inside of the valve holes 18a, 30a is partitioned into a hydraulic chamber 34, an exhaust chamber 35, and a variable pressure chamber 36 by the diaphragm 43 and the sealing member 49 on the outer periphery of the valve lifter 32.

The valve lifter 32 is constantly urged toward the hydraulic pressure chamber 34 by a spring 38 disposed in the variable pressure chamber 36. When the valve lifter 32 is not operated, the large diameter portion 32b hits the annular retainer 45 and stops. When the hydraulic pressure from the master cylinder is introduced into the
To move to the right in FIG. An axial and radial passage 32 d is formed in the valve lifter 32, and one end of the internal passage 32 d is connected to the variable pressure chamber 3.
Opened at the end on the 6th side, the other end is opened in the exhaust chamber 35, and is open to the atmosphere via an exhaust cover (not shown).

The valve hole 30 of the valve housing 30
a, the poppet valve 42
Are slidably disposed. This poppet valve 42
The head 42a faces the valve lifter 32 with a small diameter portion 30b formed in the valve hole 30a. A cap 44 is inserted into the opening side of the valve hole 30a, and is fixed by a retaining ring 46 so as not to fall out of the valve hole 30a. The small-diameter shaft portion 42b of the poppet valve 42 is slidably fitted on the inner peripheral surface of the cap 44 so that the poppet valve 42 is guided to move forward and backward. O-rings 48 and 50 are fitted on the outer peripheral surface of the shaft portion 42b of the poppet valve 42 sliding on the inner peripheral surface of the cap 44 and the outer peripheral surface of the cap 44 fitted on the inner peripheral surface of the valve hole 30a, respectively. Thus, the airtightness between the air pressure chamber 52 inside the valve hole 30a and the outside of the valve hole 30a is maintained.

A spring 54 is interposed between the back side (the right side in the figure) of the head 42a of the poppet valve 42 and the tip end surface of the cap 44 to urge the poppet valve 42 toward the valve lifter 32. When the control valve 6 is not operated, the head 42a of the poppet valve 42 urged by the spring 54 engages the small diameter portion 3 of the valve hole 30a.
0b is seated on a valve seat 56 formed on the side surface. When the poppet valve 42 is seated on the valve seat 56, an air tank (not shown) is provided through the compressed air supply port 58.
Is disconnected from the air pressure chamber 52 connected to the pressure change chamber 36. The poppet valve 42 is made of metal in the conventional configuration, but is made of resin in this embodiment. By making the poppet valve 42 resin, the weight can be reduced and the cost can be reduced.

The compressed air supply port 58 of the control valve 6 is connected to an air tank (not shown), and the variable pressure chamber 36 is connected to the supply port 30 of the valve housing 30.
The pressure chamber 12 is connected to the pressure chamber 12 of the power cylinder 2 via a pipe 66 and a pipe 66.

The hydraulic chamber 34 of the control valve 6 communicates with the hydraulic chamber 24 of the hydraulic cylinder 4 through a passage 60 formed in the housing 18. The hydraulic chamber 24 of the hydraulic cylinder 4 The opening 62 communicates with an inlet port 64 by a passage 62 formed at the end. Further, the inlet port 64 of the housing 18 is connected to an output pressure chamber of a master cylinder (not shown) operated by a clutch pedal.

The end (rear end) of the cylinder body 20 is connected to the hydraulic passage 6 formed in the housing 18.
0, 62, but the hydraulic fluid sent from the master cylinder is
Hydraulic chamber 24 and hydraulic chamber 34 of control valve 6
The passage grooves 20b and 20c are formed to supply the air to the air passage. The shape and size of these passage grooves 20b and 20c can be set as appropriate. In particular, it is preferable that the passage groove 20b on the master cylinder side has a sufficiently large passage area from the viewpoint of responsiveness. The passage groove 20c on the control valve 6 side preferably has a small sectional area so as to have an orifice effect, and may be a small slit or a small hole.

The operation of the clutch booster according to the above configuration will be described. When a clutch pedal (not shown) is depressed, the liquid in the output pressure chamber of the master cylinder
8 through the passage 62 and the passage groove 20 b of the cylinder body 20 from the inlet port 64 of the hydraulic cylinder 4.
Is sent to the hydraulic chamber 24 of the control valve 6 through the passage groove 20c and the passage 60. Therefore, the hydraulic piston 22 is pressed rightward in FIG. 1, but since the hydraulic piston 22 is connected to the push rod 16, only the hydraulic piston 22 does not make a stroke. In addition, the valve lifter 32 is moved rightward in the drawing by the hydraulic pressure introduced into the hydraulic chamber 34 of the control valve 6 via the diaphragm 43.

When the valve lifter 32 moves, first, the tip of the valve lifter 32 comes into contact with the head 42a of the poppet valve 42, and the passage 32 inside the valve lifter 32 is moved.
d is closed, and the valve lifter 32 further moves to move the poppet valve 42 away from the valve seat 56. When the poppet valve 42 is separated from the valve seat 56, the air pressure chamber 52 communicating with the compressed air supply port 58 and the variable pressure chamber 36 are connected. Then, the compressed air in the air tank is released from the air pressure chamber 52.
From the pressure chamber 12 of the power cylinder 2
Supplied to The compressed air supplied to the pressure chamber 12 moves the power piston 10 to the right in FIG. When the power piston 10 moves forward, the push rod 16 and the hydraulic piston 22
Move integrally to the right in FIG. 1 to move the clutch operating push rod 47 forward. As the clutch operating push rod 47 advances, the clutch outer lever operates to disengage the clutch.

Since the push rod 16 and the hydraulic piston 22 are connected and integrated as described above, when the power piston 10 and the push rod 16 make a stroke as in the conventional configuration shown in FIG. The tip of the piston 16 does not collide with the hydraulic piston 22 to generate a tapping sound. Further, since the hydraulic piston 22 does not make a stroke in advance, the volume of the hydraulic chamber 24 of the hydraulic cylinder 4 does not change during the stroke of the push rod 16, and no shock is transmitted to the clutch pedal. .

When the depression force on the clutch pedal is released, the pressure in the hydraulic chamber 34 of the control valve 6 decreases, and the valve lifter 32 returns to the state shown in FIG. Then, the internal passage 32d of the valve lifter 32 is opened, and the variable pressure chamber 36 is communicated with the exhaust chamber 35 via the internal passage 32d, and the air in the pressure chamber 12 of the power cylinder 2 flows through the pipe 66, the variable pressure chamber 36, and the internal passage. 32d, is discharged to the atmosphere via the exhaust chamber 35 and an exhaust cover (not shown). Then, the power piston 10, the push rod 16, the hydraulic piston 22, and the clutch operating push rod 47 return to the state of FIG. 1, the clutch outer lever returns, and the clutch is connected again.

[0037]

As described above, according to the connecting structure of the present invention, a hole is formed in the end face of the hydraulic piston, an annular groove is provided on the inner peripheral surface of the hole, and the outer peripheral portion of the end of the push rod is provided. Since the annular groove is formed on the surface, and the push rod and the hydraulic piston are connected via a wire that simultaneously engages in both annular grooves,
The structure can be simplified and the cost can be reduced.
The assemblability can be improved. In addition, since only the hydraulic piston does not precede the stroke when operating the clutch pedal, it is possible to prevent occurrence of a tapping sound and a shock to the clutch pedal. Further, according to the connecting method of the present invention, the push rod and the hydraulic piston can be connected by an extremely simple operation.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a clutch booster having a connection structure between a push rod and a hydraulic piston according to an embodiment of the present invention.

FIG. 2 is an enlarged longitudinal sectional view showing a coupling structure between a power piston and a push rod of the clutch booster.

FIG. 3 is an enlarged vertical sectional view showing an example of a connection structure between a push rod and a hydraulic piston.

FIG. 4 is a diagram showing an example of a wiring used for connecting a push rod and a hydraulic piston.

FIG. 5 is a diagram illustrating an engagement state of the wiring.

FIG. 6 is a cross-sectional view of a main part (a connection part between a push rod and a hydraulic piston) of a conventional clutch booster.

FIG. 7 is a view showing another example of a conventional clutch booster.

[Explanation of symbols]

 Reference Signs List 2 power cylinder 4 hydraulic cylinder 10 power piston 12 pressure chamber 16 push rod 16b annular groove of push rod 22 hydraulic piston 22a hole of hydraulic piston 22b annular groove of hydraulic piston 22c chamfer 41 wiring

Claims (5)

[Claims] 1. A clutch booster for operating a power piston by air introduced into a pressure chamber of a power cylinder and transmitting the output to a piston of the hydraulic cylinder via a push rod connected to the power piston. A hole is formed in the end surface of the rick piston, an annular groove is provided in the inner peripheral surface of the hole, and an annular groove is formed in the outer peripheral surface of the end portion of the push rod. A coupling structure between the push rod and the hydraulic piston of the clutch booster, wherein the push rod and the hydraulic piston are connected to each other. 2. The push rod of a clutch booster according to claim 1, wherein the annular groove of the hydraulic piston has a chamfer formed on a wall surface on the opening side of the hole. Connection structure with piston. 3. The clutch according to claim 1, wherein the wiring has a substantially arc shape with a part cut off. Connection structure. 4. The clutch according to claim 3, wherein the wiring has a deformed arc shape, and a portion protruding outward from a perfect circle is engaged with the annular groove of the hydraulic piston. Connection structure between push rod of booster and hydraulic piston. 5. A clutch booster for operating a power piston by air introduced into a pressure chamber of a power cylinder and transmitting the output to a piston of the hydraulic cylinder through a push rod connected to the power piston. In the method of connecting the hydraulic piston and the push rod, in the annular groove provided in the inner surface of the hole formed in the end surface of the hydraulic piston, insert a partially cut substantially arc-shaped wire ring, then, A clutch booster characterized in that a push rod having an annular groove on the outer peripheral surface is inserted into the wiring and pushed open, and then the wiring is inserted into the annular groove of the push rod and engaged with both annular grooves. Connection method between push rod and hydraulic piston.