JPS61244652A - Master cylinder - Google Patents

Abstract

PURPOSE:To prevent deformation of the thick walled end part of a rear sliding part due to void by providing a recessed part which is connected to a space part provided between both sliding parts, on the shaft center part of said rear sliding part of a synthetic resin piston having front and rear sliding parts. CONSTITUTION:The body part 14 of a synthetic resin piston 13 has a front sliding part 16 and a rear sliding part 17, and a slit type space part 18 is provided between both the sliding parts 16, 17. A recessed part 17A which is connected to the space part 18, is provided on the shaft center part, on the space part 18 side, of the rear sliding part 17. A recessed-faced engaging surface 17B for a push rod 33, the most recessed part of which is positioned at the shaft center part, is provided on the rear end surface of the rear sliding part 17. Due to the recessed part 17A, the wall thickness in the axial direction of the center part of the rear sliding part 17 between the recessed part 17A and the push-rod engaging surface 17B, can be greatly reduced, preventing a void from being created during a cooling process at the time of molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a master cylinder used in automobiles and the like, and particularly to a master cylinder whose piston is made of a synthetic resin material.

[Prior art]

As a master cylinder of this kind, Utility Model 58-151
There is one described in Publication No. 743.

[Problems with conventional technology]

The synthetic resin piston has a slit-like cavity, and the cavity constitutes a part of a passage connecting the hydraulic fluid reservoir and the hydraulic pressure chamber via a valve device, and the piston moves forward and backward. In the structure in which the above-mentioned valve device opens and closes, the rear portion having the bushing rod engagement surface is formed thickly, so voids are likely to occur in this rear portion during molding, and when such voids occur, the bushing rod While receiving repeated pushing force from the bushing rod, the engagement surface of the bushing rod deforms in the axial direction of the piston, resulting in dimensional deviations. As the amount of this deformation increases, the play stroke of the clutch or brake pedal connected to the bushing rod increases. However, there was a problem in that the driver's labor increased accordingly.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a master cylinder in which the medium-thick end portion of the bushing rod engaging portion of the piston does not undergo deformation due to voids.

[Means and steps for solving the problem] In order to achieve the above object, the present invention provides a rear sliding portion to which a bushing rod of a synthetic resin piston engages.

A concavity continuous to the slit-like space is provided in the axial center of the slit. , , [Example] In Fig. 1, ■ is the main body of the master cylinder,
It is molded using a synthetic resin material such as 66 nylon filled with glass fiber, and has a bottomed cylinder hole 2 that opens at one end (hereinafter referred to as the rear end) inside, and is located near the rear end of the outer wall. A mounting flange portion 3 is integrally formed to protrude from the mounting flange portion 3, and a reservoir mounting portion 5, which is the lower part of the hydraulic fluid reservoir 4, is provided in front and separated from the mounting flange portion 3 by a predetermined distance.
is integrally formed in a protruding manner and is surrounded by the reservoir mounting portion 5. At the top in the circumferential direction of the wall portion of the cylinder body l (which becomes the bottom of the reservoir 4), a potbelly hole 6 is formed. A small diameter portion (bottle hole) 6a of the cylinder body 6 and a through hole (bottle hole) 7 facing in the diametrical direction of the cylinder body are formed in the lower wall portion of the cylinder body 1.Mounting flange portion 3 A plurality of ribs 8 project radially from the outer wall of the cylinder body 1 and extend in the axial direction of the cylinder body 1.
The cylindrical part 9 is supported by the cylindrical part 9 and the central part in the longitudinal direction of the cylindrical part 9. The cylindrical part 9 is vertically sandwiched between the cylindrical part 9 and the mounting flange having a thick wall. 10, and the space formed between each rib 8 and the adjacent lip 8 is closed by a shield portion 10A formed integrally with the rib 8 at one end side of the lip 8. This shielding plate part 10A is to prevent water droplets and noise from being transmitted to the passenger compartment through the above-mentioned space when the master cylinder is attached to the body bag' □, and may be formed separately from the lip 8. be.

The cylinder body 1 is further provided with a discharge port 12 near the bottom of the cylinder hole, which communicates with a piping connection (not shown).

The cylinder body 1 slidably accommodates a piston 13 in its cylinder hole 2, and the piston 13 defines a hydraulic chamber A between it and the bottom (tip) of the cylinder hole 2. The piston 13 is made of synthetic resin, for example, is molded using carbon-filled 66 nylon, and as shown in FIG. It has a diameter reducing protrusion 15 with a step 15A. The body portion 14 of the piston 13 includes a front sliding portion 16, a rear sliding portion 17, and a slit-shaped predetermined hollow space 18 formed between the two sliding portions 16 and 17. On the side surface of the space 18, there is a recess 1 continuous to the space 18.
7A is formed at the axial center as shown in FIG. 3, and a concave bushing rod engagement surface 17B is formed on the rear end surface with the most concave bone located at the axial center, and a sealing member is fitted on the outer peripheral surface. A circumferential groove 17C is provided for mounting. This circumferential groove 1
7C is formed into a relatively large and deep groove. Also, the diameter-reducing protrusion of the piston 13! An axial through hole 19 communicating with the plate-shaped space 18 is formed in 5 . This piston 13 has a hole 20 fitted up to the stepped surface of the step 15A of the piston 13.
A return spring 21 stretched between the retainer 20 with a and the bottom of the cylinder hole 2 biases the cylinder body 1 toward the rear end (open end side), and in the non-operating state shown in the figure,
The illustrated position where the rear end surface is in pressure contact with the retaining fitting 22 fitted to the outer surface of the opening end of the cylinder body l, and the large diameter portion 6b of the pothole 6 opens toward the front end portion of the cavity "18". Reference numeral 23 denotes a regulating pin, which cooperates with the cavity 18 to regulate the maximum forward and backward movement distance of the piston 13, and is formed in the cylinder body 1 with the head 24 side facing downward. It is inserted into the cylinder hole 2 from the bottle hole 7, and the empty space 1
8 in the vertical direction and reaches into the pin hole a.゛A bag portion 25 that opens downward and a locking portion 26 with a claw that protrudes around the bag portion 25 are formed around the bottle hole 7 on the outer surface of the cylinder body 1, and the regulating pin 23 is A central thick part 2 formed on the side of the cylinder body 1 of the head 24
4a is press-fitted into the bag portion 25, and the claws of the locking portion 26 are press-fitted to the outer surface of the head 24, thereby being locked and held in the cylinder body 1 in an unusual and impossible-to-remove manner. ing. 2
7 is a sealing member.

28 is a valve member made of an elastic material, and a stem 29
The stem 29 has a hole 30 that opens at the other end and a hole 31 that communicates with the hole 30 and opens in the radial direction. is slidably inserted into the axial through hole 19 of the retainer 20 and is biased toward the regulating pin 23 side by the valve spring 32 interposed between the retainer 20 and the valve member 28, so that the other end side is pushed toward the regulating pin 23 side. 23 is press-fitted. The valve member 28 constitutes a shutoff valve M in which the end face of the diameter-reducing protrusion 15 of the piston 12 serves as a valve seat 15B, and the hole 31 is formed between the valve member 28 and the valve seat 1 in the illustrated non-operating state.
It is located at a position that opens toward the gap facing 5A. 33
is a bushing rod whose rear end is connected to a clutch pedal (not shown), and whose front end is inserted into the cylinder hole 2 and engaged with the bushing rod engagement surface 17B of the piston 12.

A boot 34 has a protrusion 35a projecting toward the inner surface, and is locked by engaging the protrusion 35a with the end surface of the stopper 22. The stopper 22 has a claw 37 and is fixedly held on the cylinder body 1 by engaging the claw 37 in a circumferential groove 36 formed on the outer surface of the rear end of the cylinder body 1. 38 and 39 are lip-shaped sealing members, and the sealing member 38 is fitted into a circumferential groove 17C formed in the rear sliding portion 17 of the piston 11 to seal between the cylinder body 1 and the sealing member 38. 39 is fitted into the base of the diameter-reducing protrusion 15 of the piston 12.

Reference numeral 40 denotes the main body of the hydraulic fluid reservoir 3, and the lower part thereof is inserted from above into an annular groove 41 that the reservoir mounting part 5 has, and is assembled to the reservoir mounting part 4. 42 is a lid of the reservoir 4, which is threadedly fitted onto the upper part of the reservoir body 40. The reservoir body 40 and the lid 42 are transparent bodies, and are made of, for example, 66 nylon. 42 is a diaphragm.

[Effect]

To briefly explain the operation of this master cylinder, in the non-operating state shown, the hydraulic fluid reservoir 4 and the hydraulic pressure chamber A are connected to the hole 6.
b - They communicate through a liquid passage consisting of a cavity 18, a stem 28, a hole 31, and a shutoff valve M. In this state, when the clutch pedal (not shown) is depressed, the bushing rod 33 is driven to the left in the figure, and as a result, the piston 13 moves in the same direction against the elasticity of the return spring 21. The movement causes the valve member 28 to sit on the valve seat 15A of the diameter-reducing protrusion 15, closing the shutoff valve M, shutting off the hydraulic pressure chamber A and the hydraulic fluid reservoir 4, and generating hydraulic pressure in the hydraulic pressure chamber A. The generated hydraulic pressure is discharged from the discharge port 12 to the outside of the cylinder body 1 through a piping connection (not shown), and is supplied to a tartarage operating cylinder (not shown) through piping connected to the piping connection.

In this embodiment, a recess 1 is provided in the rear sliding portion 17 of the piston 13.
7A, the distance between the recess 17A and the bushing rod retaining surface 17B, that is, the axial wall thickness of the central portion of the rear sliding portion 17, can be made significantly smaller than in the past. It is possible to prevent voids from occurring during the cooling process during molding.

Furthermore, in this embodiment, the circumferential groove 17C for fitting the sealing member 38 of the rear sliding part 17 is a deep groove, so the thickness in the radial direction of the central part of the rear sliding part 17 is also small. When the axial wall thickness is reduced as described above, the generation of voids can be completely eliminated.

〔Effect of the invention〕

As explained above, the present invention prevents the occurrence of voids in the rear sliding movement by providing a recess that is continuous with the slit-like cavity in the rearward moving part that the bushing rod of the piston engages with. Since this can be reliably prevented, the rear sliding portion will not deform even if it receives repeated pressing force from the bushing rod, and an increase in the play stroke of the bushing rod can be prevented.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, FIG. 2 is a plan view of a piston in the above embodiment, and FIG. FIG. 1- cylinder body, 2- cylinder hole, 13- piton, 15A... valve seat, 16- front sliding part, 17-...
Rear sliding part, 16A- recess, 18- empty space, 2 B
- Valve member, A - Hydraulic chamber, M. - Shutoff valve.

Claims (1)

[Claims] A synthetic resin piston is slidably inserted into a cylinder hole formed in a cylinder body to partition a hydraulic chamber, and the piston has a front sliding part and a rear sliding part equipped with a sealing member,
A slit-like space is formed between both sliding parts, and a protrusion protruding toward the inside of the cylinder hole is loosely fitted into the space,
A master cylinder in which a valve device disposed in a front sliding part can be opened and closed in response to movement of the piston, wherein a recess continuous to the void is provided in the axial center of the rear sliding part. .