JPH0143344Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is a master cylinder for operating wheel brakes, clutches, etc. of automobiles, in particular, a piston is slid into a cylinder hole in a cylinder body, and the cylinder body includes: This piston is fitted with a bearing that slidably supports the rod portion protruding from the rear end of the piston, and is fitted with a circlip that presses the rear end surface of the bearing.

BACKGROUND ART Such a master cylinder is disclosed in Japanese Utility Model Publication No. 148958/1983.

Problems to be Solved by the Invention In the master cylinder disclosed in the above publication, the inner circumferential edge of the circlip that presses the rear end face of the bearing faces the outer circumferential surface of the rod portion of the piston. In particular, during contraction, the inner periphery of the rod may come into contact with and damage the outer periphery of the rod, and such damage can damage the lip of the sealing member of the bearing when the rod slides, causing oil leakage. becomes.

This invention was made in consideration of these points,
To provide a simple and effective master cylinder capable of protecting the outer peripheral surface of a rod part from a circlip when the circlip contracts.

Means for Solving the Constituent Problems of the Invention In order to achieve the above object, the present invention includes a rear end of the bearing that supports the outer circumferential surface of the rod portion, and that supports the inner circumferential surface of the circlip. It is characterized in that opposing annular extensions are provided that protrude to provide a space for attaching and detaching the circlip.

Function: The bearing supports the piston rod over a wide area in the form of an annular extension, which improves the stability of the piston operation.

When the circlip is retracted to remove it from the cylinder body during disassembly of the master cylinder, the inner peripheral edge of the circlip is received by the annular extension of the bearing and is prevented from coming into contact with the outer peripheral surface of the rod portion of the piston.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is an assembly of a master cylinder and a negative pressure booster, and a mounting flange 2a formed at the rear end of the cylinder body 2 of the master cylinder M is connected to a negative pressure booster. It is configured by being connected to the front surface of the booster shell 3 of the booster B with bolts 4.

The master cylinder M is configured in a tandem type by sliding a pair of front and rear pistons 6 and 7 into the cylinder hole 5 of the cylinder body 2. The inside of the cylinder hole 5 is divided into a pair of independent front and rear hydraulic chambers 8, 9 by both pistons 6, 7, and when the rear piston 7 is advanced, hydraulic pressure is generated in both hydraulic chambers 8, 9, and by these hydraulic pressures. Corresponding wheel brakes (not shown) can be activated.

The rear piston 7 has a rod portion 7a that extends rearward and penetrates the front wall of the booster shell 3.
An output rod 10 in the booster shell 3 is connected to the rod portion 7a.

The cylinder body 2 is provided with a bearing device hole 11 that has a larger diameter than the cylinder hole 5 and is connected to the rear end thereof, and a bearing 12 that slidably supports the rod portion 7a is mounted in the bearing device hole 11 with an O-ring. A circlip 14, which is fitted through the bearing 13 and comes into contact with the rear end surface of the bearing 12 to prevent it from coming off, is locked to the inner circumferential wall of a positioning cylinder 15, which will be described later.

A sealing member 16 is mounted on the inner circumferential surface of the bearing 12 and is in close contact with the outer circumferential surface of the rod portion 7a.

Further, an annular extension 12a is provided at the rear end of the bearing 12 so as to increase the effective width of the bearing surface. The extension portion 12a is connected to the circlip 14.
It has an attachment/detachment space a and faces the inner circumferential surface thereof.

The positioning cylinder part 15 is provided so as to protrude from the rear end surface of the cylinder body 2 so as to surround the rod part 7a, and has a hollow part 15a having a larger diameter than the bearing mounting hole 11 and continuous to the rear end. A rear seal member 17 is attached to the rear end of the positioning cylinder part 15 so as to close the hollow part 15a in close contact with the outer peripheral surface of the rod part 7a.
This is done by elastically fitting an annular hook 19 formed on one side of the outer periphery of the rear seal member 17 into an annular groove 18 formed on the outer periphery of the rear seal member 17 .

The annular groove 18 is formed in such a size that an annular passage 20 remains on one side of the annular hook part 19 fitted therein, and the annular passage 20 and the hollow part 15a are connected to each other.
A through hole 21 is bored in the positioning cylinder portion 15 to provide communication therebetween.

On the other hand, a positioning recess 22 is formed on the front surface of the booster shell 3 in correspondence with the positioning cylinder part 15, and a rear seal member 17 is formed in the recess 22.
The positioning cylinder part 15 is fitted together with this. This restricts the connection position of master cylinder M and negative pressure booster B. At that time, the rear seal member 17
are adapted to come into close contact with the inner circumferential wall and end wall of the positioning recess 22.

Further, a groove 23 is formed in the lower part of the front surface of the booster shell 3 facing the mounting flange 2a to open the annular passage 20 to the atmosphere.

Next, the operation of this embodiment will be explained. When the negative pressure booster B is operated, the output rod 10 is boosted and moves forward, and the rear piston 7 is moved forward via the rod portion 7a.
advance.

At this time, the bearing 12 supports the rod portion 7a over a wide range by forming the annular extension 12a, thereby improving the stability of the operation of the rear piston 7.

On the other hand, the front seal member 16 slides on the outer peripheral surface of the rod portion 7a to prevent leakage of hydraulic oil from the cylinder hole 5, and the rear seal member 17 also slides on the outer peripheral surface of the rod portion 7a.
It slides into contact with the outer peripheral surface of the booster shell 3 to prevent leakage of negative pressure from the booster shell 3.

In the unlikely event that the front seal member 16 is damaged and the hydraulic oil in the cylinder hole 5 leaks from the damaged part, the oil will first leak into the hollow part 1 of the positioning cylinder part 15.
5a and then from the through hole 21 to the annular passage 2
0 and the concave groove 23 to the outside naturally,
Oil is prevented from accumulating in the hollow portion 15a and entering the booster shell 3.

Further, if the rear seal member 17 is damaged and the negative pressure inside the booster shell 3 leaks from the damaged part to the hollow part 15a, the air in the atmosphere will immediately leak into the groove 23, the annular passage 20, and the through hole. 21 into the hollow portion 15a and eliminates the negative pressure, leakage negative pressure is prevented from acting on the back surface of the front seal member 16 and causing oil leakage from the front seal member 16.

In this case, the through hole 2 is placed on the circumference of the positioning cylinder 15.
Even if the positions of 1 and the groove 23 are shifted from each other, since they communicate through the annular passage 20, there will be no problem with the outflow of hydraulic oil and the inflow of air.

When the positioning cylinder part 15 of the master cylinder M is pulled out from the positioning recess 22 of the negative pressure booster B in order to separate the master cylinder M and the negative pressure booster B for maintenance, the rear seal member 17 is connected to the positioning cylinder part 15. Therefore, it escapes from the positioning recess 22 together with the cylindrical portion 15. In this way, the rear seal member 17 and the rod portion 7 are connected not only when the master cylinder M and the negative pressure booster B are separated, but also when they are connected.
Since unnecessary sliding contact with the rod portion 7a is avoided, there is no risk that the lip of the rear seal member 17 will be damaged by the rod portion 7a.

Further, when the master cylinder M is disassembled, when the circlip 14 is contracted to be removed from the cylinder body 2, the inner peripheral edge of the circlip 14 is received by the annular extension 12a of the bearing 12, and the rear piston 7
Since the rod portion 7a is prevented from coming into contact with the outer circumferential surface of the rod portion 7a, the outer circumferential surface of the rod portion 7a will not be damaged.

Effects of the invention As described above, according to the invention, in order to increase the effective width of the bearing surface of the bearing that supports the rod portion of the piston, an annular extension is provided protruding from the rear end of the bearing, and the annular extension is connected to the circlip. Since the attachment/detachment space is provided on the inner periphery and the rods are opposed to each other, the annular extension functions to protect the rod from the inner periphery of the circlip, thereby preventing damage to the outer periphery of the rod when the circlip contracts. I can do it. That is, since the extension part of the bearing is effectively used to protect the rod part, no special protection member is required and the structure is simple.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional side view of one embodiment of the present invention;
The figure is an enlarged view of the main part. a... Detachment space, 2... Cylinder body, 5...
Cylinder hole, 6, 7... Piston, 7a... Rod part, 12... Bearing, 12a... Annular extension part, 1
4...Circlip.

Claims (1)

[Scope of utility model registration request] The piston is slid into the cylinder hole of the cylinder body, and the cylinder body is fitted with a bearing that slidably supports the rod portion protruding from the rear end of the piston, and a circlip that presses the rear end surface of the bearing. In the locked master cylinder,
A master cylinder characterized in that a rear end of the bearing is provided with an annular extension projecting from the inner circumferential edge of the circlip to support the outer circumferential surface of the rod portion and facing the inner circumferential edge of the circlip with a space for attaching and detaching the circlip. .