GB2212575A

GB2212575A - Master cylinder

Info

Publication number: GB2212575A
Application number: GB8825146A
Authority: GB
Inventors: Hermann Seip; Kurt Saalbach; Klaus Bergelin; Juergen Zoell; Josef Proels; Werner Englert
Original assignee: WILDEN GmbH; Alfred Teves GmbH
Current assignee: WILDEN GmbH; Continental Teves AG and Co oHG
Priority date: 1987-11-14
Filing date: 1988-10-27
Publication date: 1989-07-26
Anticipated expiration: 2008-10-27
Also published as: FR2623255B1; GB8825146D0; DE3738741A1; GB2212575B; FR2623255A1

Description

1 2 2 12 7 'S MASTER CYLINDER The invention relates to a master cylinder,

in particular for hydraulic clutch actuation in an automotive vehicle, of the kind including a housing in the lonctitudinal bore of which a pressure chamber is defined by a piston slidable by an operatinq rod, the piston being sealed against the longitudinal bore by means of a primary sealinq cup, and the pressure chamber being connected, in the release position and through a valve centrally arranged within the piston, to an intake chamber linked to a fluid reservoir via a fluid reservoir connection, a protective cap, a pressure connection and a secondary sealing cup which seals the longitudinal bore toward the outside.

A master cylinder of this kind is known from the publication of Messrs. FAG Kugelfischer, publ.

No. HB 49109 DA "Hydraulik fuer Fahrzeuge" (Hydraulic System for Vehicles). The arrangement described therein includes an aluminium housing in which a plastics piston is sealedly guided, upon the operation of which piston a hydraulic pressure is built up in a pressure chamber. In the release position, the pressure chamber is in direct connection, through a breathing hole, with a fluid reservoir which is linked to the master cylinder through a connecting element sealedly supported within the housinq and to an intake chamber through an intake port configured in the housing, the intake 2 chamber communicating with the pressure chamber through a valve which is centrally positioned within the piston and is open in the non-actuated condition.

In this known master cylinder, the comparatively high manufacturing costs have to be regarded as less advantageous these being due, apart from the utilisation of an expensive raw material, to the necessity of a mechanical finishing involving machining and to the employment of a plurality of components.

It is, therefore, an object of the present invention to provide a master cylinder of the kind referred to in the course of manufacture of which no is finishing of the housing will be required and the number of components necessary can be reduced.

According to the invention, there is provided a master cylinder, in particular for hydraulic clutch actuation in an automotive vehicle, of the kind includina a housing in the longitudinal bore of which a pressure chamber is defined by a piston slidable by an operating rod, the piston being sealed aqainst the longitudinal bore by means of a primary sealing cup), and the pressure chamber being connected, in the release position, throuah a valve centrally arranged within the piston, to an intake chamber linked to a fluid reservoir via a fluid reservoir connection, a protective cap, a pressure connection and a secondary sealing cup which seals the longitudinal bore toward the outside, characterised in that the longitudinal bore comprises three sections of different diametert the piston defining the pressure chamber in the first section of smallest diameter and the intake chamber in the second section of medium diameter, in that 1 c v t 1 3 the fluid reservoir connection is configured in one piece with the housing and is arranged in the transition range between The first and the second section and in that the link between the fluid reservoir connection and the pressure chamber, or the intake chamber is realised through a first, or a second slot which are formed in the wall of the' lonqitudinal bore.

In an embodiment of the object of the invention offering particular ease of assembly, it is envisaged that the longitudinal bore is closed by means of a closing element which limits the axial mobility of the piston in the release position, which is arranqed in the third section of the longitudinal bore and is axially retained by means of a self-locking plate.

An advantageous embodiment of the invention consists in that the operating rod presents a radial, preferably conically-shaped, expansion which interacts, in the release position, with a truncated cone-shaped annular surface configured at the closing element. This provision results in considerable advantages of tolerance with regard the idle travel existinq in the master cylinder.

An embodiment of the invention will now described by way of example with reference to accompanying drawings, in which:- Figure I shows an axial cross section of- a master cylinder according to this embodiment of the invention; Figure 2 shows an axial cross section of the housing of the master cylinder according to Figure 1; Figure 3 shows the view in the direction of the arrow W in Figure 2; to be the 4 Figure 4 shows the operating rod-side end of the master cylinder according to Figure 1, in a scaled-up view; Figure 5 shows a section on A-A in Figure 4.

The master cylinder shown in the drawing includes with a housing 1 preferably made of plastics material in the longitudinal bore 27 of which a piston 2 actuatable by an operating rod 5 is slidably guided. The longitudinal bore 27 is confiqured as a stepped bore being subdivided into a first section 8, a second section 11 and a third section 18, the first section 8 having the smallest and the third section 18 the largest diameter.

In the transition range between the first 8 and the second section 11, a fluid reservoir connection 9 is cast in at the housing 1 to form one piece with the latter, the fluid reservoir connection 9 serving to link, in the release position, a pressure chamber 14 defined in the first section 8 and an intake chamber 12 provided in the second section 11 to a fluid reservoir which is not shown in the drawinq. The aforementioned link is made through slots 23,24 (Figure 3) of different width which are configured in the wall of the longitudinal bore 27, are arranaed one behind the other in the direction of operation of the master cylinder and pass over from one to the other. The first slot 23 of narrower shape assumes the function of the known breathing hole and the second, expanded, slot 24 serves to establish the aforesaid link, ending up in a pressure fluid duct not shown in more detail which forms part of the fluid reservoir connection 9. A line (not illustrated) which leads to the clutch cylinder is connected to the pressure chamber 14 by means of a threaded bushing 13 cast in with the P1 1 t- 1 forming a is formed direction housing 1, sealed by a sealing ring 32 and pressure connection. A connection which by an intake duct 16 running in an axial within the piston 2 and an intake port 15 arranged at right angle to the latter and which is closable by means of a so-called Weihe valve 10 being centrally positioned in the piston 2 is provided for the purpose of balance of volumes between the pressure chamber 14 and the intake chamber 12. A primary sealing cup 3 seals the piston 2 against the first section 8 of the longitudinal bore 27 whereas sealing of the second section 11 toward the outside is realised by means of a secondary sealing cup 4 which is positioned at a guide section 6 of the piston.

The operating rod 5 which is connected to the piston 2 in an articulated manner presents a radial expansion 30 of conical shape at its end facing the piston 2, the expansion 30 abutting, in the release position, against a truncated cone-shaped annular surface 31 of a closina element 17 which is located in the third section 18 of the longitudinal bore 27. At its other end, the operating rod 5 is pivoted to a lever 20 being rotatably hinged to a pin 22 and forming part of an operating pedal 19 which is pretensioned in the release position by a return spring 21.

Due to the traction exerted by the return spring 21, the piston 2 is retained in its intiial position in which the front surface of its guide section 6 facing the closing element 17 is positioned at an axial distance from the closing element 17. The interior of the housing 1 is protected against the penetration of dust particles and the like by a protective cap 7 configured as a 1 6 bellows and retained in a radial groove 25 in the housing 1. At its other endr the protective cap 7 is in friction-contact connection with the operating rod 5.

As shown particularly in Figures 4 and 5 the closing element 17 is axially secured within the third section 18 of the longitudinal bore 27 by a self-locking plate or washer 26 which is pushed into recesses 28 in the housing. In the assembled condition, the locking plate 26 interacts with a aroove 29 which is configured in the closing element 17.

The node of operation of a hydraulic master cylinder according to this embodiment of the invention is as follows:

on actuating the operating pedal 19 against the force of the return spring 21, the operating rod 5 and the piston 2 will be slid to the left. As a consequence, and after the primary sealing cup 3 has moved beyond the range qf the first slot 23, the Weihe valve 10 will close,the pressure chamber 14 with respect to the intake chamber 12 filled with pressure fluid so that hydraulic pressure may build up in the pressure chamber 14, this pressure being conveyed to the clutch cylinder through the pressure connection.

When the clutching operation is ended, that is to say, when the operating pedal 19 is released, the piston 2 and the operating rod 5 will be shifted to the right under the effect of the pressure fluid which is supplied to the pressure chamber 14, that is, they will be shifted into the normal position until the piston 2 abuts against the closing element 17 by way of the expansion 30 of the operating rod 5. Since the piston 2 is retained in its final k 1 7 position at the stop in the housing by means of the return spring 21, a component group withdefined measurements will be created which renders superfluous an exact adjustment at the pedal.

8 secondary longitudinal characterise

Claims

CLAIMS:

1. A master cylindert in particular for hydraulic clutch actuation in an automotive vehicle, of the kind including a housing (1) in the longitudinal bore (27) of which a pressure chamber (14) is defined by a piston (2) slidable by an operating rod (5), the piston (2) being sealed against the longitudinal bore (27) by means of a primary sealing.cup (3), and the pressure chamber being connected, in the release position, through a valve (10) centrally arranged within the piston (2), to an intake chamber (12) linked to a fluid reservoir via a fluid reservoir connection (9), a protective cap (7), a pressure connection (13) and a sealina cup (4) which seals the bore (27) toward the outside, in that the longitudinal bore (27) comprises three sections (8,11,18) of different diameter, the piston (2) defining the pressure chamber (14) in the first section (8) of smallest diameter and the intake chamber (12) in the second section (11) of medium diameter, in that the fluid reservoir connection (9) is configured in one piece with the housing (1) and is arranged in the transition range between the first (8) and the second section (11) and in that the link between the fluid reservoir connection (9) and the pressure chamber (14), or the intake chamber (12) is realised through a first, or a second slot (23 or 24) which are formed in the wall of the longitudinal bore (27).

2. A master cylinder as claimed in claim 1, characterised in that the piston (2) is formed with a guide section (6) which bears the secondary sealing cup (4) and is guided in the second section 1 9 (11) of the longitudinal bore (27).

3. A master cylinder as claimed in claim 1 or 2, characterised in that the longitudinal bore (27) is closed by means of a closing element (17) which limits the axial mobility of the piston (2) in the release position.

4. A master cylinder as claimed in claim 3,, characterised in that the closing element (17) is arranged in the third section (18) of the longitudinal bore (27) and is axially retained by means of a self-locking plate or washer (26).

5. A master cylinder as claimed in claim 4, characterised in that the housing (1) is furnished with radial recesses (28) which accommodate the self-locking plate (26).

6. A master cylinder as claimed in claim 4, characterised in that the closing element (17) is formed with a radial groove (29) which is engaged by the self-locking plate (26). 20

7. A master cylinder as claimed in claim 1, characterised in that the first and second slots (23,24) are arranged one behind the other in the direction of operation and have different widths.

8. A master cylinder as claimed in claim 7, characterised in that the first slot (23) of narrower shape passes over to the second slot (24) of expanded shape.

9. A master cylinder as claimed in any one of the preceding claims, characterised in that the fluid reservoir connection (9) ends up in the second slot (24) which is configured open toward the second section (11).

10. A master cylinder as claimed in any one of the preceding claims. characterised in that the operating rod (5) presents a radial, preferably conically-shaped, expansion (30) which interacts, in the release position, with a truncated cone-shaped annular surface (31) configured at the closing element (17).

11. A master cylinder as claimed in any one of the preceding claims, characterised in that the pressure connection is formed by a threaded bushing (13) cast in with the housing (1) and sealed by means of a sealing ring (32).

12. A master cylinder as claimed in any one of the preceding claims, characterised in that the protective cap (7) is retained at one end in a radial groove (25) configured in the housing (1) and is in friction-contact connection with the o-perating rod (5) at the other end.

13. A master cylinder as claimed in any one of the preceding claims, characterised in that the housing (1) is made of plastics material.

14. A master cylinder as claimed in any one of the preceding claims, characterised in that the piston (2) is made of plastics material and is captive with the operating rod (5).

cylinder substantially reference to the accompanying

15. A master described with 25 drawings.

Pubbs [led 1989 at The Patent Office, State House. 66 7 1 1Lgh Holborn. London WC1R 4TP. Further copies maybe obtained from The Patent Oflice. Sales Branch, St Mary Cray. OrpingLor.. Kent BR5 3PM- printed by M,,11tIp.ex tecbr,1q7.ies ltd. St Mary Cray, Kent. Con. 1'87