JPH082005Y2 - Master cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a master cylinder that fixes a seal on the body side and a return port on the piston side to generate two systems of hydraulic pressure.

[Prior Art] Conventionally, as a master cylinder having a structure in which a seal is fixed on the cylinder body side and a return port is provided on the piston side, for example, that shown in FIG. 3 is known.

In FIG. 3, reference numeral 1 is a cylinder body, and a secondary guide bush 3 having cup seals 17 and 18 arranged on both sides of a cylinder hole 2 opened on the right side of the cylinder body 1, a plastic guide spacer 4, and A primary guide bush 5 in which a cup seal 9 and a seal 10 are arranged on both sides is incorporated, and a case 7 is screwed into a screw portion 6 formed on the inner circumference of the opening of the cylinder body 1 to prevent the retainer from falling off.

A primary piston 8 is slidably incorporated in the guide bush 5, and a through hole that connects the inner circumference and the outer circumference.
11 is provided, and the outer peripheral surface of the guide bush 5 is communicated with the tank connection port 13 through a liquid passage 12 which is a cylindrical gap formed between the case 7 and the spacer 4. A cylindrical hole is formed on the liquid chamber A side of the primary piston 8, a return port 14 is provided in the cylindrical hole portion, and a return spring 15 is further incorporated therein.

On the other hand, a secondary piston 16 is slidably incorporated in the secondary guide bush 3, and a through hole 19 is provided to connect the inner circumference and the outer circumference. The through hole 19 communicates with the tank connection port 20. Further, a return port is provided in a cylindrical hole portion formed on the liquid chamber B side of the secondary piston 16.
21 is provided and a return spring 22 is incorporated.

In the master cylinder having such a structure, when the primary piston 8 advances due to the brake operating force,
Pressurization of the primary liquid chamber A is started from the position where the return port 14 crosses the cup seal 9, and at the same time, the secondary piston 16 also advances due to the pressurization of the primary liquid chamber A, and the return port 21 passes the cup seal 17. Pressurization of the secondary liquid chamber B is simultaneously started from the open position.

On the other hand, when the brake operation force is released, the secondary piston 16 and the primary piston 8 retract due to the spring force of the return springs 22 and 15, and the return ports 21 and 14
Return over the cup seals 17,9 and return ports 21,1
4 and the guide bushes 3, 5 through the through holes 19, 11 for the liquid chambers B, A
Communicates with the tank side and releases pressure to the tank side.

Looking at the guide bush 3 provided on the secondary side, the cup seal 17 for sealing the secondary hydraulic pressure is provided on the left side.
And a cup seal 18 for sealing the primary hydraulic pressure on the right side. Further, in order to prevent the guide bush 3 from moving to the right due to the secondary hydraulic pressure, a part of the guide bush 3 on the right end face is arranged. At the same time, the projection 3a is formed, and at the same time, the cup portion of the cup seal 18 is divided into upper and lower parts so as to surround the projection 3a. The movement is blocked.

[Problems to be solved by the invention] However, in such a conventional guide bush positioning structure for the secondary side in the master cylinder, a guide having cup seals 18 and projections 3a for receiving the primary hydraulic pressure is provided at a plurality of positions. Since the shape of the bush 3 is complicated and the parts cost is high, and the guide bush 3 and the cup seal 18 have to be aligned and assembled, there is a problem that the assembly work is complicated.

The present invention has been made in view of such conventional problems, and a master cylinder capable of simplifying processing and assembling by simplifying the secondary side seal structure assembled and fixed in the cylinder body and achieving cost reduction. The purpose is to provide.

[Means for Solving the Problem] First, according to the present invention, a primary side and a secondary side sealing members are fixedly arranged by guide bushes in a cylinder hole in a cylinder body, and a primary piston provided with a return port is provided in the sealing member. The target is a master cylinder with a structure in which a secondary piston is slidably provided.

With regard to the master cylinder having such a structure, in the present invention, the cylinder hole opening on the secondary side has a plug closing structure, the outer circumference of the guide bush on the secondary side has a stepped cylindrical shape, and it becomes a part for incorporating the guide bush. The cylinder hole has a stepped hole shape, and the stepped cylindrical shape of the bush and the stepped hole shape of the cylinder hole are fitted together to prevent movement of the guide bush due to hydraulic pressure.

[Operation] In the master cylinder of the present invention having such a configuration, the guide bush need only have a simple shape such that the outer circumference is a stepped cylindrical shape, and the secondary hydraulic pressure is received by a normal cup seal. Further, the primary hydraulic pressure only needs to be received by the O-ring, and the seal structure on the secondary side can be made extremely simple, so that the cost of parts and the number of assembly steps can be reduced.

Further, since the movement of the guide bush toward the primary side is blocked by the contact with the stepped portion of the cylinder hole, the O-ring can be used for the seal on the primary side without any problem, and the seal structure can be simplified.

FIG. 1 is a sectional view showing an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a cylinder body, and a cylinder hole 24 is formed so as to penetrate in the axial direction of the cylinder body 1. A guide bush mounting hole 26 is formed on the right side of the cylinder hole 24, and the seal holder 2 is inserted in the guide bush mounting hole 26.
8, cup seal 30, guide bush 32 and O-ring 34
Are sequentially assembled, and the cap member 36 is attached from the outside, and the cap member is attached to the booster mounting flange 38 of the cylinder body 1.
The underside of 36 is fitted. The final assembling and fixing of the cap member 36 is realized by assembling and fixing the master cylinder to a negative pressure booster (not shown).

A primary piston 40 is slidably incorporated in the guide bush 32, and the primary piston 40 has a return port 42 in the cylindrical portion at the tip, and the return port 42 is located immediately after the cup seal 30 at the piston initial position shown in the figure. ing. The guide bush 32 is provided with a liquid passage 4 which communicates the inner circumference with the outer circumference, and the liquid passage 44 passes from a stepped groove 46 on the flange end face through a liquid passage 48 formed in the upper axial direction of the cylinder body 1 to connect the tank. It communicates with 50.

On the other hand, on the secondary side, which is the left side of the cylinder hole 24,
A plug mounting screw hole 52, a guide bush mounting hole 54, an O-ring mounting hole 56, and a piston slide hole 58 are formed in order of decreasing diameter.

The guide bush 60 is incorporated into the stepped hole portion 90 composed of the guide bush mounting hole 54 and the O-ring mounting hole 56,
The guide bush 60 has a stepped portion 92 corresponding to the stepped hole portion 90, an O-ring 62 is incorporated in the ring mounting hole 56 side, and a cup seal 64 is incorporated in the opposite side. The secondary side is closed by attaching the plug 66 to the screw hole.

A secondary piston 70 having cylindrical portions on both sides is slidably incorporated in the guide bush 60. The secondary piston 70 is provided with a return port 72 in the cylindrical portion on the side of the secondary liquid chamber B, and the return port 72 is located immediately after the cup seal 64 at the initial position shown. Also, the guide bush
60 has a liquid passage 74 that communicates the inner circumference and the outer circumference, and the liquid passage 74 communicates with the tank connection port 76.

Furthermore, a return spring 78 is incorporated between the plug 66 and the secondary piston 70, and
A return spring 80 is also installed between the 70 and the primary piston 40 via a retainer. The return spring 80 further presses and supports the rod member 82 on the secondary piston 70 side through a retainer, and the bottom of the cylindrical hole of the primary piston 40 contacts the right side of the rod member 82 by the stroke of the primary piston 40 when the primary side fails. The secondary piston 70 can be stroked integrally with the primary piston 40.

FIG. 2 shows the secondary side seal structure in the embodiment of FIG. 1 taken out, and the guide bush 60 has a large diameter on the side where the cup seal 64 is installed and a small diameter on the side where the O-ring 62 is installed. It has a cylindrical shape with an annular groove on the large diameter part.
84 is formed, and the liquid passage 74 is provided in the annular groove 84.

That is, the guide bush 60 basically has a simple stepped cylindrical shape as shown in the drawing, and the cup seal
As for the 64 and the O-ring 62, the cup seal used in the conventional master cylinder or a commercially available one can be used as it is.

Next, the operation of the above embodiment will be described.

First, the assembly of the secondary side of FIG. 1 will be described. The O-ring 62, the guide bush 60 and the cup seal 64 are externally attached to the cylinder body 1 with respect to the secondary piston 70.
When the assembly is inserted and the assembly is assembled from the left side of the cylinder hole 24 as shown in the drawing, the secondary piston 70
Is positioned by contacting the expanded portion of the rear end with the stepped portion of the piston slide hole 58, and the O-ring 62 is an O-ring mounting hole.
The guide bush 60 is pushed into the small diameter side of the guide bush 60, and the guide bush 60 is positioned by abutting against the stepped outer diameter shaped cylinder hole step, and in this state the cup seal 64 enters the specified position and finally The secondary spring assembly can be completed by inserting the return spring 78 and screwing in the plug 66.

As a result, assembling on the secondary side, particularly for assembling the seal structure, only needs to be considered in the axial direction.
Since the O-ring 62, the guide bush 60, and the cup seal 64 have no particular positional relationship around the axis, the assembly itself is extremely easy.

In the embodiment shown in FIG. 1, a fitting protrusion is provided on the outer diameter step portion corresponding to the cylinder hole step portion which prevents the guide bush 60 from moving to the right, and is fitted to the cylinder side. Since the guide bush 62 is fitted in the portion and is prevented from rotating, it is necessary to position the guide bush 62 around the axis for mounting the cylinder hole.

Next, in the assembled state as shown in FIG. 1, when the primary piston 40 moves forward by the brake operation and the secondary piston 70 also moves forward accordingly, and the brake hydraulic pressure is generated, the secondary hydraulic pressure is the cup seal. 64
Received by the guide bush 64 from the liquid passage 74 to the tank connection port
Leakage to the 76 side is prevented, and naturally, when the hydraulic pressure on the secondary fluid chamber B side becomes low, brake fluid is supplied from the tank side through the gap between the cup seal 64 and the secondary piston 70. On the other hand, the hydraulic pressure on the primary side is cut by the O-ring 62, and the O-ring 62 has a bidirectional hydraulic sealing function, so that the leakage of the primary hydraulic pressure to the tank connection port 76 side is always sealed. .

In the embodiment shown in FIG. 1, the guide bush 32 having exactly the same size and shape as the secondary side is used on the primary side, and therefore the cup seal 30 and the O-ring 34 are the same as those on the secondary side. Is used, and the O-ring 34 is supported by the cap member 36.

Further, in the embodiment of FIG. 1, the tank connection ports 50, 7
A nipple 86 is connected to 6 and a partition wall 88 is provided in the nipple 86 to supply the brake fluid by one hose connection from the reservoir tank which is separately arranged, and which secures the volume of the one-side chamber liquid on the primary side and the secondary side. Although the case where the nipple 86 is provided is taken as an example, it goes without saying that a reservoir tank having the same tank connection structure may be directly attached instead of the nipple 86.

[Advantages of the Invention] As described above, according to the present invention, in the secondary side seal structure, the guide bush may have a simple shape such that the outer circumference is a stepped cylindrical shape, and the secondary hydraulic pressure is a normal cup. Only the seal needs to be received, and the primary hydraulic pressure need only be received by the O-ring. Since the seal structure on the secondary side can be made extremely simple, the cost of parts and the number of assembly steps can be reduced. Also, since the movement of the guide bush toward the primary side is blocked by the step contact of the bush outer diameter part with the cylinder hole step, even if an O ring is used for the primary side seal, the O ring will not collapse. The primary side hydraulic pressure can be reliably sealed.

[Brief description of drawings]

 1 is a sectional view of an embodiment showing an embodiment of the present invention; FIG. 2 is an explanatory view of a secondary side seal structure of the present invention: FIG. 3 is an explanatory view of a conventional technique. 1: Cylinder body 24: Cylinder hole 26,54: Guide bush mounting hole 32,60: Guide bush 28: Seal retainer 30,64: Cup seal 34,62: O-ring 36: Cap member 38: Booster mounting flange 40: Primary Piston 42,72: Return port 44,74: Liquid passage 46: End groove 48: Liquid passage 50,76: Tank connection port 52: Plug mounting screw hole 58: Piston slide hole 70: Secondary piston 78,80: Return spring 82 : Rod member 84: Annular groove 86: Nipple 88: Partition wall 90: Stepped hole 92: Stepped part

Claims (1)

[Scope of utility model registration request] 1. A primary side and a secondary side cup seals 30, 64 are fixedly arranged in a cylinder hole 24 of a cylinder body 1 by guide bushes 32, 60, and return ports 42, 72 are provided in the guide bushes 32, 60. In the master cylinder in which the primary piston 40 and the secondary piston 70 are slidably provided, a plug 66 for closing the cylinder hole opening on the secondary side is provided, and the guide bush 60 on the secondary side is provided.
A stepped hole portion 90 composed of a guide bush mounting hole 54 and an O-ring mounting hole 56 is formed in the cylinder hole 24 which is the built-in portion of
A master cylinder characterized in that a stepped portion 92 that fits into the stepped hole portion 90 is formed on the outer periphery of the guide bush 60.