JPH0575037U - Hydraulic master cylinder for vehicle - Google Patents

Abstract

(57) [Summary] [Purpose] To make it possible to easily and accurately set the invalid stroke of a hydraulic master cylinder. [Structure] The piston guide 9 is screwed into the bearing hole 3a,
The front end surface 9a is abutted against the stepped portion 3c and attached. Front end face 9
The stepped portion 4b of the primary piston 4 is brought into contact with a, the retreat limit of the piston 4 is regulated, and an invalid stroke is set between the primary cup 12 and the relief port 21.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is a hydraulic master cylinder that hydraulically actuates the brakes and clutches of various vehicles such as four-wheeled vehicles, and in particular, the ineffective stroke until hydraulic pressure is generated in the hydraulic chamber in the cylinder hole, It relates to a structure for setting as accurately as possible.

[0002]

[Prior Art]

 2. Description of the Related Art As a hydraulic master cylinder for hydraulically operating a brake of an automobile, for example, there is one disclosed in Japanese Utility Model Publication No. 1-43343.

This hydraulic master cylinder is a tandem type in which the rear shaft of the primary piston is housed inside a hydraulic booster to shorten the cylinder body length, and a large diameter bearing hole continuous with the cylinder hole is formed. An annular piston guide is installed, and the primary piston is retained on the center axis of the cylinder hole by inserting the rear shaft through the annular piston guide installed in this bearing hole. The backward limit is regulated by the contact with the piston guide.

A primary cup that slides in a cylinder hole in a liquid-tight manner is mounted on the tip side of the primary piston, and when the primary piston is in the retracted limit, it is placed between the primary cup and the relief port. Invalid stroke is set.

[0005]

[Problems to be solved by the device]

 In such a configuration, the rear end of the cylinder body where the bearing hole opens serves as the machining reference surface, and the cylinder hole and the bearing hole are formed with this rear end of the body as the reference, but the piston guide is In addition to the manufacturing error of the piston guide itself and the circlip that prevents it from slipping when it is fixed in position, there are many steps such as the step between the cylinder hole and the bearing hole, and the circumferential groove into which the circlip fits. Due to manufacturing error, the above invalid stroke may not be set correctly.

The present invention has been made in view of such circumstances, and an object thereof is to provide a hydraulic master cylinder with a structure capable of accurately and easily obtaining a predetermined invalid stroke. It is in.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention inserts and holds a rear shaft of a piston inserted in a cylinder hole into an annular piston guide mounted in a large-diameter bearing hole continuous with the cylinder hole. In a vehicle hydraulic master cylinder in which a piston biased toward the bearing hole is brought into contact with the guide to regulate the retreat limit of the piston, the piston guide is screwed into the bearing hole. It is characterized in that the piston guide is mounted and brought into contact with the step portion of the cylinder hole and the bearing hole for positioning.

[0008]

[Action]

 With this configuration, the invalid stroke of the piston is determined by the position of the piston guide that is in contact with the stepped portion of the cylinder hole and the bearing hole, and affects the setting error of the invalid stroke such as the circlip for retaining. The existing factors are removed.

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

In the hydraulic master cylinder 1, a primary piston 4 and a secondary piston 5 are inserted in a cylinder hole 3 formed in a cylinder body 2 in a liquid-tight and movable manner. Between the cylinder hole 3 and the cylinder hole 3 is a tandem type that defines a first hydraulic chamber 6 and a second hydraulic chamber 7, and the rear end of the cylinder body 2 is screwed by a screw (not shown). It is attached to the front of the pressure booster 8.

On the rear side of the cylinder body 2, a large-diameter bearing hole 3a continuous with the cylinder hole 3 is provided with an opening at the rear end face, and an annular piston guide 9 is screwed into the bearing hole 3a. Has been done. The primary piston 4 has a small-diameter rear shaft 4a inserted through the piston guide 9 and is held on the cylinder center shaft, and further out of the rear seal member 10 to project into the negative pressure booster 8. The front end of a push rod 11 for pushing the primary and secondary pistons 4 and 5 toward the bottom of the cylinder hole 3 is inserted into the rear end.

A primary cup 12 is fitted to the tip of the primary piston 4, and a primary cup 13 and a secondary cup 14 are fitted to the tip and the rear end of the secondary piston 5. The chamber 6 and the second hydraulic chamber 7 are liquid-tightly sealed. A primary return spring 15 is compressed in the first hydraulic chamber 6, and a secondary return spring 16 is compressed in the second hydraulic chamber 7 with a set load lower than that of the primary return spring 15. The primary and secondary pistons 4 and 5 are urged in the bearing hole 3a direction by the elastic force of the return springs 15 and 16, and their retreat limit is set to the stepped portion 4b of the primary piston 4 and the piston guide 9. It is regulated by the contact with the front end surface 9a.

A reservoir 17 is attached to the mounting boss portion 2 a protruding upward from the cylinder body 2 so that the working fluid stored therein can be supplied to the cylinder hole 3 at any time. The interior of the mounting boss portion 2a is divided into two sub liquid storage chambers 18 and 19 by a partition wall 2b. The one sub-storage chamber 18 has a cylinder hole 3 in which the first hydraulic chamber 6 is provided via a communication hole 20 formed in the ridge 2c of the cylinder body 2 and a relief port 21 and a supply port 22. The sub storage chamber 19 on the other side communicates with the front side of the cylinder hole 3 in which the second hydraulic chamber 7 is provided via the relief port 23 and the supply port 24.

Sealing grooves 9b and 9c are provided on the inner and outer circumferences of the piston guide 9, and the secondary cup 25 and the O-ring 26 fitted in these sealing grooves 9b and 9c are respectively attached to the rear shaft of the primary piston 4. A liquid-tight seal is provided between 4a and the bearing hole 3a. The male screw 9d of the piston guide 9 is formed on the outer periphery of the rear portion, and is formed on the rear portion side of the bearing hole 3a, so that it is screwed into the screw 3b. A hexagonal tool hooking hole 9e as shown in FIG. 3 is provided in the rear end surface of the piston guide 9, and the piston guide 9 is rotated in a hexagonal cylindrical shape to be inserted into the tool hooking hole 9e. The bearing hole 3a is screwed or unscrewed with a tool (not shown).

Lubrication grooves 9 f, 9 f that connect the front end surface and the seal groove 9 b are provided on the inner peripheral surface of the piston guide 9, and a part of the hydraulic fluid is introduced into the secondary cup 25. Therefore, it is possible to prevent the pulling and the damage due to the sliding friction with the rear shaft 4a. The outer circumference of the front end surface 9a is cut into a C surface, and when the piston guide 9 is screwed in until it comes into contact with the step 3c of the cylinder hole 3 and the bearing hole 3a, the piston guide 9 and the bearing hole 3a A space for accumulating chips generated from the screw threads etc. is ensured so that the primary piston 4 can slide smoothly together with the lubricating grooves 9f, 9f.

The above-mentioned piston guide 9 is screwed into the bearing hole 3a by screwing the male screw 9d and the female screw 3b, and the front end surface 9a thereof is in the step portion 3c between the cylinder hole 3 and the bearing hole 3a. The screwing amount is regulated by abutting. The screw guide of the screwed piston guide 9 is restricted from pivoting in the pull-out direction by the contact between the front end surface 9a and the stepped portion 3c, so that the conventionally used circlip is omitted.

The pistons 4 and 5 are restricted in their backward movement limits when they are inoperative by the stepped portion 4b of the primary piston 4 contacting the front end surface 9a of the piston guide 9 screwed in this way. The distance from the retracted end position of the piston 4.5 until the respective primary cups 12 and 13 fully close the relief ports 21 and 23, that is, the ineffective stroke, is defined by the front end surface 9a of the piston guide 9 = the stepped portion 3c. I try to decide on the criteria.

In this embodiment, the piston guide 9 for supporting the primary piston 4 is screwed into the bearing hole 3a, and the front end surface 9a of the piston guide 9 is connected to the step between the cylinder hole 3 and the bearing hole 3a. By positioning by abutting against the portion 3c, the invalid stroke of each piston 4, 5 can be easily set based on this front end surface 9a = step portion 3c. Further, since the setting of the invalid stroke is not affected by the manufacturing error of the retaining circlip and the circumferential groove into which the circlip is fitted, the accuracy can be improved more than ever before. Moreover, in this embodiment, since the stepped portion 3c and the front end surface 9a of the piston guide 9 are the same surface, the manufacturing error of the piston guide 9 does not become a problem, and many factors which have an influence on the error of the invalid stroke are caused. Since it is removed, a higher precision void stroke is obtained.

Further, the piston guide 9 is restricted from pivoting in the pull-out direction by the contact between the front end surface 9a and the stepped portion 3c, so that the circlip and the circumferential groove that have been conventionally used can be omitted. Is advantageous to.

The present invention does not prevent the use of a circlip or a ring-shaped fixing nut as a means for preventing the piston guide from coming off more reliably. When these retaining members are used together, the retaining members do not affect the accuracy of the invalid stroke, as described above.

Further, the front end surface of the piston guide has an inner peripheral side piston contact portion that supports the piston, with respect to an outer peripheral side cylinder body contact portion that contacts the step portion of the cylinder hole and the bearing hole. It may be projected or recessed. In this case, the accuracy of the invalid stroke is affected by the manufacturing error of the piston guide, but as with the above-mentioned embodiment, since the manufacturing error due to the circlip and the circumferential groove is eliminated, the invalid stroke with higher accuracy than the conventional can get. Of these, in the structure in which the piston contact portion is recessed, a part of the piston can be accommodated in this recessed portion, so that the cylinder body length can be shortened.

The present invention is also applicable to a single type hydraulic master cylinder other than the tandem type shown in the embodiment.

[0023]

[Effect of the device]

 As described above, according to the structure of the present invention, the piston guide for restricting the retreat limit of the piston is screwed into the bearing hole of the cylinder body, and the piston guide is further connected to the step portion between the cylinder hole and the bearing hole. The ineffective stroke of the piston can be easily set by setting it to the predetermined position simply by making contact with. Since the invalid stroke set in this way does not affect the retaining member such as the circlip, which has been a cause of the error, it is possible to obtain a higher accuracy than before. Furthermore, since the piston guide does not loosen loosely, it is possible to reduce the cost by omitting the retaining member.

[Brief description of drawings]

FIG. 1 is an enlarged view of a main part of FIG.

FIG. 2 is a sectional front view of a hydraulic master cylinder showing an embodiment of the present invention.

FIG. 3 is a perspective view of the piston guide as viewed from the rear side.

4 is a perspective view of the piston guide of FIG. 3 viewed from the front side.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hydraulic master cylinder, 2 ... Cylinder body, 3 ... Cylinder hole, 3a ... Large diameter bearing hole continuing to the cylinder hole 3b ... Screws formed in the bearing hole 3a, 4 ... Primary piston, 4a ... Primary Rear shaft of piston, 4
b ... Stepped portion of primary piston 4, 5 ... Secondary piston, 8 ... Negative pressure booster, 9 ... Annular piston guide screwed into bearing hole 3a, 9a ... Front end surface of piston guide 9, 9d ... Male thread to be screwed with female thread 3b, 9e ... Tool mounting hole, 10 ... Rear seal member, 11 ... Push rod, 12, 13 ... Primary cup, 14, 25 ... Secondary cup, 21, 23 ... Relief port

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // B60T 11/20 7001-3H

Claims (1)

[Scope of utility model registration request] 1. A rear shaft of a piston inserted in a cylinder hole is inserted into and held by an annular piston guide mounted in a large-diameter bearing hole continuous with the cylinder hole, and the piston guide is provided with the bearing hole. In a hydraulic master cylinder for a vehicle in which a piston biased in a direction is brought into contact with the piston to regulate the backward movement limit of the piston, the piston guide is attached to the bearing hole by screwing, and the piston guide is attached. A hydraulic master cylinder for a vehicle, characterized in that it is positioned by abutting on a step portion of a cylinder hole and a bearing hole.