GB2222213A

GB2222213A - Hydraulic cylinder

Info

Publication number: GB2222213A
Application number: GB8910982A
Authority: GB
Inventors: Hans-Dieter Reinartz; Helmut Steffes
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1988-05-16
Filing date: 1989-05-12
Publication date: 1990-02-28
Anticipated expiration: 2009-05-12
Also published as: GB8910982D0; GB2222213B; DE3816608A1; FR2631395B1; FR2631395A1

Description

A H.D.Reinartz 137-91 / ú9 2 2 2 13 1 HYDRAULIC CYLINDER The invention is

related to a hydraulic cylinder, in particular to a master cylinder for the actuation of a hydraulic clutch of automotive vehicles, being comprised of a plastic cylinder housing and of a plastic piston.

A master cylinder, in particular for the actuation of hydraulic clutches of automotive vehicles, is known from the German patent application P 3331834.4, with a housing made of plastic and provided with a flange accommodating a piston slidable within a bore by means of an actuating rod and sealed from bore by means of a seal arrangement and with a valve arrangement actuatable by the piston, the valve arrangement connecting a compensating chamber with a pressure chamber thtrough a duct closable upon actuation of the valve arrangement in the released position of the master cylinder.

It is proposed in the aforementioned German patent application to firmly surround the shell surface of the housing by a metal sleeve in the vicinity of the piston seal, to fabricate the flange of metal to superimpose it on the housing and urge it against a stop at housing by the sleeve.

The present invention seeks to provide an improved construction and reduce cost of manufacture. The invention seeks to largely avoid metal components and employ plastics components 2 instead.

Other aspects of construction which refinements of the invention may provide are as follows.

Mounting of the internals of the hydraulic cylinder may be simplified, particularly during mass production. Components of the construction may be introduced from one side into the open cylinder housing. Threaded connections may be avoided. Time may be saved during mounting.

A conicity of the interior space is required for the manufacture of plastic bodies having tubular, sleeve or cylindrical shape in order to be able smoothly to extract the tool from the injection moulded element. Such conicity may have a detrimental effect on the functioning of the cylinder, especially in case of elevated overall axial lengths.

In addition, the accumulation of plastic material stages involve the risk of undesired deformations in the course of solidification. In practice, dimples may form and warping may occur.

The present invention may involve the reduction of detrimental effect of the aforementioned manufacturing techniques structure and on the operation of a cylinder.

The present invention may enable reduction of the length of the piston to the very minimum under injection moulding technique aspects even whilst maintaining the stroke unvaried.

An improvement relative to the state-of-the-art design according to the German patent application P3331834.4 is that the piston is guided at one position instead of two.

Guidance at two positions has the disadvantage 3 on the hydraulic 3 that a smooth running of the piston cannot be guaranteed. As a matter of fact, force components occur when the piston is guided at two positions which are no longer directed along the axis of the piston. These force components lead to inconvenience during operation and to premature wear.

The metal flange 41 and the metal cup 36 shown in the German patent application previously mentioned may be avoided by a construction in accordance with the present invention.

According to the invention there is provided a hydraulic cylinder comprising a plastics cylinder housing and a plastics piston, characterised in that a substantially sleeve-shaped guide element made of plastics is for guidance of the piston positioned within the cylinder housing by at least one compression spring.

An assembly comprising the guide element and other components, such as seals and a disc with preferably radially disposed hydraulic ducts, may be accommodated in the cylinder housing and may be positoned by at least one compression spring.

A compact design results in that the cylinder housing may have a smaller diameter position forming a pressure chamber in which hydraulic pressure can be built up in the event of the forward movement of the piston and a portion having a larger diameter in which the components of the assembly including the guide element are arranged coaxially.

Particular ease of mounting can be achieved by providing a first compression spring inside the assembly and a second compression spring outside the hydraulic cylinder and by arranging that both compression springs co-operate to position the 4 assembly.

In a preferred embodiment, a hydraulic cylinder mounted in the automotive vehicle is proposed whose set-up is characterised by the following procedure of mounting in the vehicle: first mounting step: biasing without play of the components of the assembly including the guide element within the cylinder housing by means of the first compression spring, second mounting step: retaining the components of the assembly including the guide element by the second compression spring and by a sheet or plate steel cup while the hydraulic cylinder is mounted on the bulkhead of the automotive vehicle.

It is furthermore proposed that a pressure discharge body with metal thread is fixed to the cylinder housing in particular by the acoustic method, that is to say, by ultrasonic irradiation.

An especially simple set-up of the master cylinder is achieved in that a cup shape element is proposed which performs the function of a check valve for preventing fluid flow to and from a fluid reservoir.

In the interest of an uncomplicated securement of the piston rod to the piston, it is proposed that the piston rod is secured to the piston by means of a rubber element.

In order that the invention and its various other preferred featurs may be understood more easily, an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawing, the single figure of which shows an axial cross section through a hydraulic cylinder constructed in accordance with the invention.

i In the drawing, a cylinder housing 1 and piston 2 are made of plastics. A sleeve-shaped guide element 3, also made of plastics, to guide the piston is disposed in the interior of the housing. The cylinder housing has a portion having a smaller internal diameter and d portion having a larger internal diameter. The portion having the smaller diameter consists substantially of a pressure chamber 4. Pressure is built up in the chamber 4 when the piston 2 moves to the left. Hydraulic fluid is conveyed through connection 5 to a slave cylinder.

In the portion of the cylinder housing having the larger diameter, an assembly of individual components is accommodated.

The assembly comprises the following components arranged coaxially with respect to one another:- a valve cup 6, a ring-shaped and corrugated disc 7 furnished with radially disposed ducts 8, a seal 9, and a guide element 3. The components of the assembly are subjected to the pressure of a compression spring 10 which, too, is arranged coaxially and which transmits its force to the assembly through a shaped ring 11.

A second compression spring is located outside the cylinder and is identified by reference numeral 12. The compression spring 12 exerts a force on a sheet or plate steel cup 13 which acts through a shoulder 14 of the guide elment 3 on the components of the assembly. It will be appreciated that the assembly is kept together by the two compression springs 10, 12.

Mounting of the master cylinder automotive vehicle proceeds as follows:

First of all, the components of the assembly in the 6 inclusive of the guide element will be biased without any play within the cylinder housing by means of the compression spring 10. Subsequently, the components of the assembly including the guide element will simultaneously be held together, on one hand, by means of the spring 12 and the sheet or plate steel cup 13 and, on the other hand, the whole hydraulic cylinder will be mounted on the bulkhead of the vehicle.

The operation of the master cylinder is as follows:

Hydraulic fluid from a reservoir, the drawing, is already present through the hydraulic fluid connection 16, the duct 21, the radial ducts 8 provided in the corrugated disc 7, the slots 17 of the piston and in the pressure chamber 4.

When force is exerted on the push rod 15 as a result of pedal depression, then the piston 2 moves to the left, the edge 18 of the piston moves over the radially diposed ducts 8 in the corregated disc 7. Under the effect of the pressure forming within the chamber 4, the sealing lips of the cup 6 sealingly adhere to the.shaft of the piston.

The cup 6, thus, performs a valve function. It shuts off the connection between the reservoir and the pressure chamber 4 at the beginning of the pressure surge.

In the event of a continued movement of the piston 2 to the left, the pressure in the pressure chamber 4 increases, hydraulic fluid is forced through the connection 5 to the consumer, for example to a slave cylinder. The connection 5 is formed in a connecting body or pressure discharge body 20. The body 20 is provided with a metal not shown in N 7 thread for connecting a hydraulic line. The body 20 is secured to the plastic cylinder housing by the acoustic method, that is to say, by ultrasonic irradiation. The piston rod 15 is retained on the piston 2 by means of a rubber element 19.

8

Claims

CLAIMS:

1. A hydraulic cylinder comprising a plastics cylinder housing and a plastics piston, characterised in that a substantially sleeve-shaped guide element made of plastics is for guidance of the piston positioned within the cylinder housing by at least one compression spring.

2. A hydraulic cylinder as claimed in claim 1, characterised in that an assembly comprising the guide element and other components, such as seals and a disc with hydraulic ducts, is accommodated in the cylinder housing and is positioned by said at least one compression spring.

3. A hydraulic cylinder as claimed in claim 2, characterised in that the hydraulic ducts extend radially.

4. A hydraulic cylinder as claimed in any one of the preceding claims, characterised in that the cylinder housing has a portion having a smaller diameter forming a pressure chamber in which hydraulic pressure is built up in the event of the forward movement of the said piston and a portion having a larger diameter in which the components of the assembly including the guide element are arranged coaxially.

5. A hydraulic cylinder as claimed in any one of the preceding claims, characterised in that a first one of the compression springs is provided inside the assembly and a second compression spring outside the hydraulic cylinder and in that both compression springs are arranged to co-operate to position the assembly.

6. A hydraulic cylinder as claimed in claim 5, mounted in an automotive vehicle, characterised in the following mounting steps, the components of the 11 9 assembly including the guide element within the cylinder housing are biased without Play by means of the first compression spring, the components of the assembly including the guide element are retained by the said second compression spring and by a sheet or plate steel cup while the hydraulic cylinder is mounted on the bulkhead of the automotive vehicle.

7. A hydraulic cylinder as claimed in any one of the preceding claims, characterised in that a connecting body with a metal thread is fixed to the cylinder housing.

8. A hydraulic cylinder as claimed in claim 7, characterised in that the connecting body is fixed to the cylinder housing by the acoustic method, that is to say, by ultrasonic irradiation.

9. A hydraulic cylinder as claimed in any one of the preceding claims, characterised in that a cup shaped element performs the function of a check valve for preventing fluid flow to and from a fluid reservoir.

10. A hydraulic cylinder as claimed in any one of the preceding claims, characterised in that a piston rod is secured to the piston by means of a rubber element.

11. A hydraulic cylinder substantially as described herein with reference to the drawing.

Published 1990 at The Patent OMce, State House. 66.7 L High Ho3burn. LondonWClR4TP. Purther copies May be obtainedfronIT119 Pgt,6=02106Sales Branch, St Mary Cray, Orpington. Kart BR5 3RD. Printed by Multiplex techniques ltd. St MAXY Cray. Kent, Con- V87