JPH0348060B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a master cylinder used in a hydraulic brake device or clutch device. More specifically, it is a master cylinder in which a piston guide is arranged and fixed inside the open end of the cylinder body, and is assembled by inserting the master cylinder open end into a booster that boosts the master cylinder operating force. This invention relates to an end insertion type master cylinder.

FIG. 1 is a conceptual cross-sectional view showing a conventional brake end insertion type tandem master cylinder. In the figure, reference numeral 1 denotes a cylinder body with an open end, and a primary piston 2 and a secondary piston 3 are disposed inside the body 1 to form a first pressure chamber 4 and a second pressure chamber 5. 6 is a primary return spring, and 7 is a secondary return spring. The cylinder body 1 is attached to the booster 8 by inserting its open end 1a into the recess 8a of the master cylinder operating force booster 8, and inserts the output rod 8b of the booster into the rear end recess of the primary piston 2. It is inserted and brought into contact with 2a. A piston guide 1 is provided inside the open end 1a of the cylinder body.
The guide 11 is fixed to the cylinder body 1 with one end abutting against the stepped portion 1b of the cylinder body and the other end abutting against the snap spring 12, and the primary piston 2 is slidably fitted inside. I've let it happen.
Both pressure chambers 4 and 5 have ports 12 and 13, respectively.
It communicates with a tank (not shown) via a. The tank further communicates with groove-shaped replenishment chambers 16 and 17 formed on the outer periphery of both pistons 2 and 3 via replenishment channels 14 and 15, and the replenishment chambers 16 and 17 each communicate with a communication path 18. , 19 to the back surfaces of the piston cups 20, 21 facing the first and second pressure chambers.

In the above master cylinder, the primary piston 2 is pushed leftward by the leftward movement of the output rod 8b of the booster, and the piston cup 2
0 blocks the port 12, and the liquid in the pressure chamber 4 is delivered to the brake system from the delivery port 22. Further, the secondary piston 3 is pushed to the left by the pressure in the pressure chamber 4, the piston cup 21 blocks the port 13, and the liquid in the pressure chamber 5 is sent out from the delivery port 23 to the brake system. Furthermore, when the master cylinder operating force from the output rod 8b is released, both pistons 2 and 3 are moved to the right by both return springs 6 and 7, and returned to the original position shown in the figure by both stoppers 24 and 25. . Furthermore, the output rod 8b
When the master cylinder operating force is suddenly released, the primary piston 2 suddenly moves to the right, the pressure in the first pressure chamber 4 decreases, and the replenishment fluid path 1
Liquid flows from a replenishing liquid chamber 16 connected to the tank via a replenishing liquid chamber 16 through a communication passage 18, passes over a piston cup 20, and is replenished into the first pressure chamber 4. Of course, the second pressure chamber 5 is also replenished with liquid from the replenishment liquid chamber 17. If such a replenishment liquid passage 14 and replenishment liquid chamber 16 were not provided, when the primary piston 2 rapidly moves to the right, the pressure inside the first pressure chamber 4 would drop and the inside of the chamber 4 would be under high negative pressure. However, in this case, the liquid cannot be replenished quickly and air may enter the tank. The replenishment liquid chamber 16 and the like are provided to eliminate this inconvenience.

However, in order to open the replenishment liquid passage in the cylinder as described above, the cylinder body must be lengthened accordingly. Therefore, if such an opening for the replenishment fluid passage is not formed on the inner circumferential surface of the cylinder, the overall length of the master cylinder can be shortened.
In an end insertion type master cylinder whose purpose is to shorten the total length, it is possible to further shorten the total length.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a master cylinder in which, in the case of a piston, particularly a tandem master cylinder, a replenishment fluid passage is formed without drilling or opening in the inner peripheral surface of the cylinder, thereby making it possible to shorten the overall length. be.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 2 is a sectional view showing a main part of an embodiment of a master cylinder according to the present invention. The illustrated master cylinder is an end insertion type tandem master cylinder for brakes, and the portions not shown have the same structure as in FIG. 1.

As shown in the figure, the master cylinder according to the present invention is
The open end 1a of the cylinder body 1 is inserted and assembled into the recess 8a of the booster 8 that boosts the master cylinder operating force, and the output rod 8b of the booster is inserted into the recess 2a of the primary piston. It is made by touching. A piston guide 11 is disposed inside the open end 1a of the cylinder body, and the piston guide 1
1 is fixed to the cylinder body 1 at one end portion located on the open end side. In this embodiment, an engaging portion 11a protruding radially outward is formed on the one end side portion of the piston guide, and the engaging portion 11a is connected to a stepped portion 1c formed inside the open end 1a of the cylinder body and a snap spring. It is clamped and fixed with locking means 12 such as the like. A liquid chamber 30 facing the other end surface 11c is formed at the other end of the piston guide, and the replenishment liquid path 14 is opened in the liquid chamber 30, particularly above the chamfer 1d of the stepped portion 1b. be. That is, conventionally, as shown in FIG. 1, one end surface (the end surface on the open end side) of the piston guide 11 was held in contact with the snap ring 12, and the other end surface was brought into contact with the stepped portion 1b of the cylinder body. In the invention, a protruding engagement portion 1 is provided on the open end side portion of the piston guide 11.
1a, and is fixed only at the open end side portion using this engaging portion 11a. Therefore, the other end surface 11c of the piston guide does not need to come into contact with the stepped portion 1b of the cylinder body as shown in FIG. 1, and the liquid chamber 30 can be formed facing this end surface 11c.
When the replenishment liquid passage 14 is opened to this liquid chamber 30, the liquid chamber 30 becomes the replenishment liquid chamber 1 formed in the piston of FIG.
It plays the role of 6. Therefore, according to the present invention, the replenishing liquid chamber 16 conventionally formed in the piston is no longer necessary, and the piston guide can be shifted to the left by that amount, thereby making it possible to shorten the overall length of the master cylinder.

As described above, in the master cylinder according to the present invention, the replenishment liquid chamber is defined on the end surface of the piston guide.
That is, this replenishment liquid chamber has a large cross section perpendicular to the axial direction. Therefore, even if the length in the axial direction is small, a sufficient volume is ensured, and as a result, the overall length of the master cylinder can be shortened.

Further, in the master cylinder according to the present invention, when the piston is assembled, the replenishment fluid path is opened on the outside of the chamfer that guides the piston cup without damaging it, so there is no risk of damaging the piston cup.

The present invention can be modified in various ways without departing from the gist thereof, and the means for fixing the piston guide at the one end portion located on the open end side thereof is not limited to that shown in the drawings, and various suitable means may be employed. obtain. Further, the present invention can be applied to master cylinders other than tandem types.

[Brief explanation of drawings]

FIG. 1 is a conceptual cross-sectional view showing a conventional master cylinder, and FIG. 2 is a conceptual cross-sectional view showing essential parts of an embodiment of the master cylinder according to the present invention. DESCRIPTION OF SYMBOLS 1... Cylinder body, 1a... Cylinder body opening end, 2... Piston, 11... Piston guide, 11
c... Piston guide other end surface, 14... Replenishment liquid path, 3
0...liquid chamber.

Claims (1)

[Claims] 1 Forming a hole in the end of the cylinder body that opens at the end and has a larger diameter than the piston sliding cylinder,
Further, a step formed at the boundary between the hole and the piston sliding cylinder is chamfered at the meeting portion of the piston sliding cylinder, and a piston guide is locked in the hole at a distance from the step. A master cylinder characterized in that a liquid chamber is formed between the piston guide and the stepped portion, and a replenishment liquid path communicating with the tank is opened in the stepped portion outside the chamfer.