WO2014079428A1

WO2014079428A1 - Slave cylinder

Info

Publication number: WO2014079428A1
Application number: PCT/DE2013/200250
Authority: WO
Inventors: Philippe Wagner
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2012-11-22
Filing date: 2013-10-28
Publication date: 2014-05-30
Also published as: DE112013005612A5; IN2015DN03092A; DE112013005612B4; CN104797837A; EP2923101A1; CN104797837B; DE102013221840A1

Abstract

The invention relates to a slave cylinder having a housing (1) which is arranged concentrically around a transmission input shaft and consists of a plastics main material, and having an annular piston (3) which is axially movable therein, is able to be subjected to a pressure of a pressure medium and is operatively connected to a release bearing (7), wherein a stop is provided on the housing (1), said stop limiting a stroke of the piston (3) in the direction of the release bearing (7), and the stop (a) consists according to the invention at least partially of a metal sleeve and/or of a second plastics material different from the plastics material of the main body of the housing (1) or interacts therewith.

Description

slave cylinder

The invention relates to a slave cylinder of a release system for clutch or brake systems of a motor vehicle according to the preamble of the first claim.

Generic concentric slave cylinders (CSCs) or CSCs are used in hydraulic clutch systems in the functional chain between the clutch pedal and the clutch, and have a housing designed as an annular cylinder, which is arranged around a clutch or transmission input shaft an axially displaceable annular piston is guided, which carries a release bearing which is supported on a clutch, an energy accumulator designed as a helical compression spring surrounds the piston ,

For example, such a slave cylinder is known from DE 1 1 2005 000 619 T5, which comprises a plastic body which defines an annular bore in which an annular piston is slidably mounted. The piston is sealed to the bore by an annular seal. Between the seal and the closed end of the bore, a pressure chamber is defined, in which a pressure medium is introduced. The pressure medium comes from a master cylinder, which can be actuated by a clutch pedal. The piston of the slave cylinder acts on a release bearing, by which in turn the clutch is actuated. In its fully outwardly depressed position, the piston contacts a circlip located on the housing which limits the piston stroke. The retaining ring has a circular cross-section and is seated in a groove in the outer circumference of the radially inwardly located wall region of the piston, which limits the pressure chamber inwards.

The disadvantage of these solutions is that the maximum pull-out force is "relatively" low, especially at high temperatures when the coupling overheats, due to the fact that the positive-locking connection on the plastic housing causes local stress concentrations which reduce the maximum pull-out force In- reduced wall of the housing over the connection. In addition, the force is also dependent on the connection to the housing at the circlip.

As a result, there is a risk that the slave cylinder pushes too far, because overheating of the clutch and consequent overfilling of the hydraulic system, the plate spring tongues of the clutch bulge in the unengaged state of the clutch from the release bearing. The preload spring built into the slave cylinder feeds the piston so that additional hydraulic fluid from the pressure chamber can enter the system through the sniffer bore and damage the system.

The task is to develop a slave cylinder, which has a reliable stop for the piston stroke and absorbs a high impact force, even at high temperatures.

This object is solved by the characterizing features of the first claim.

Advantageous embodiments emerge from the subclaims.

The slave cylinder is preferably formed in the form of a CSC and has a housing arranged concentrically about a transmission input shaft made of plastic and an axially movable annular piston, which with a pressure of a pressure medium

can be acted upon and is operatively connected to a release bearing, wherein the housing is provided a stop which limits a stroke of the piston towards the release bearing and the stop according to the invention at least partially from a plastic material of a base body of the housing different plastic material and / or a metallic sleeve.

The metallic sleeve is preferably attached by encapsulation with plastic on the housing and is molded in particular as an insert in the manufacture of the housing from the plastic and is thereby integrated into the housing.

To ensure the required strength, the sleeve is made of steel or aluminum. It has one or more openings / holes through which the plastic the base material of the housing is sufficient so that a good clamping of the sleeve is ensured in the housing.

To form the stop, the sleeve is facing radially outward

Edge area provided. This can be done after assembly of the piston by a forming process e.g. be generated by a radially outward beading and in this case even without further components form the stop for the piston.

Alternatively, the radially outwardly facing edge region of the sleeve may be spaced from an end face of the housing facing it, whereby a groove-like recess is formed. In this recess, a conventional snap ring may then be arranged, which forms the stop for the piston in connection with the sleeve.

Preferably, the substantially cylindrical wall portion of the sleeve is arranged radially inwardly of the piston, so that the running surface of the piston is not affected.

Alternatively, the stop may also be made from the second plastic material that differs from the plastic material of the main body of the housing via a two-component injection molding process and have a radially outwardly facing edge region which serves as a stop or which is spaced from the end face of the housing facing thereon, wherein then in the recess formed thereby also a snap ring is arranged, which forms the stop for the piston in conjunction with the second plastic material The second plastic material has higher strength properties than the base material of the housing. Furthermore, it is advantageous if the second plastic material has a high temperature resistance. To achieve the required properties of the second plastic material, this may be fiber-reinforced or contain other strength-increasing additives.

Since the existing of metallic material (especially steel) existing sleeve or the second plastic material has a higher strength than the plastic of the housing (especially at high temperatures), it is possible to produce a much higher impact force, since it can be assumed that the sleeve will not be the weak spot. Due to the fixed connection between sleeve and housing via the bore matrix, the maximum impact force will depend on the complete wall thickness of the housing. The use of a positive connection with a snap ring or a clip ensures both when sending a stopper from a metallic sleeve (in particular a steel sleeve) as well as a second plastic material made of a high-strength plastic, the inclusion of higher forces than in a conventional plastic housing, since the stress concentration on the steel ring or on radially outwardly facing paragraph of the second plastic material is much less critical.

The invention will be described below with reference to embodiments and associated

Drawings explained in more detail. Show it:

FIG. 1 shows the region of a housing arranged radially on the inside, in which a steel sleeve is arranged,

2 shows the slave cylinder with the integrated steel sleeve which has been flanged,

3 shows the slave cylinder with a steel sleeve and a snap ring as a stop,

Figure 4 shows a portion of a housing made of a plastic material which is combined with a second plastic material by a 2K injection molding process.

FIG. 1 shows an end of a radially inner first wall region 1.1 of a plastic housing 1 of a slave cylinder. In the non-designated inner diameter of the first wall portion 1.1, a steel sleeve 2 is used, which has a plurality of openings 2.1 and the end face 1.2 of the first wall portion 1 .1 projects beyond a crimping 2.2. The steel sleeve 2 was molded with plastic to the housing 1, wherein the plastic flows into the openings 2.1 and thereby an intimate connection between the housing 1 and steel sleeve 2 is produced, which withstands high loads in the axial direction.

After injection molding of the steel sleeve 2, the piston 3 is mounted with the piston seal 4 in the annular space 5 of the housing 1, which is formed by the first wall portion 1 .1 and a second wall portion 1 .3 of the housing 1 according to Figure 2. In the annular space 5 opens a pressure medium bore 6, so that between the first wall portion 1 .1, second wall portion 1.3 and piston seal 4, a pressure chamber D is formed. After assembly of the piston 3 the flaring region 2.2 is deformed radially outward, so that it protrudes circumferentially beyond the outer diameter 1 .1 'of the first wall region 1.1 by a region a. Known manner, the piston 3 acts upon pressurization of the pressure chamber D on a release bearing 7 and it is a preload spring 8 is provided.

The region a forms a stop a for a radially inner end region 3.1 of the piston 3, by which it is ensured that no pressure medium can escape from the pressure chamber D even at high temperatures.

In contrast to FIG. 2, the steel sleeve 2 according to FIG. 3 has no flaring region 2.2. It is only provided a collar 2.3, which is axially spaced from the end face 1.2 of the first wall portion 1.1 and the radially does not protrude beyond the outer diameter of the first wall portion 1 .1 ', so that the piston 3 and the piston seal 4 mounted in the annular space 5 can be. Between the end face 1.2 of the first wall portion 1 .1, the collar 2.3 and the outer diameter 1 .1 ', a groove N is formed, in which after the assembly of piston 3 and piston seal 4, a snap ring 9 is inserted and, like the crimping 2.2 in Fig. 2 over the outer diameter 1.1 'of the first wall portion 1 .1 to a region (stop) a protrudes circumferentially, and thus forms a stop a for the radially inner end portion 3.1 of the piston 3, which is also ensured that the piston 3 is held by the stopper a even at high pressures and temperatures and thus can escape from the pressure chamber D no pressure medium even at high temperatures. The stop formed by the snap ring 9 a cooperates in this case with the collar 2.3 of the sleeve 2, because the snap ring 9 is by the front side 3.1 of the piston 3 at a high pressure in the pressure chamber D in the groove N against the collar 2.3 and thus pressed against the steel sleeve 2. Because the steel sleeve 2 is substantially stronger than the plastic of the housing 1, higher axial forces can also be absorbed with this solution.

An end region of the first wall region 1 .1 of a housing 1 made of plastic with a second plastic material 10 injection-molded in the 2K injection molding process is shown in FIG.

The radially outwardly facing edge region is formed by a collar 10. 1 of the second plastic material 10, which is spaced from a facing end face 1 .2 of the housing 1. In the resulting groove N a snap ring 9 is arranged, which protrudes radially beyond the outer diameter 1.1 'of the first wall region 1 .1 and thereby forms a stop a which, in conjunction with the collar 10.1 and thus with the second plastic material 10, limits the stroke of the piston 3 (not shown here).

LIST OF REFERENCE NUMBERS

1 . casing

1 .1 first wall area

1 .1 'outer diameter

1 .2 front side

1 .3 second wall area

2. steel sleeve

2.1 breakthroughs

2.2 Flaring area

2.3 Federation

3rd piston

3.1 frontal area of the piston

4. Piston seal

5. annulus

6. Pressure fluid hole

7. Release bearing

8. preload spring

9th snap ring

10. second plastic material

10.1 Bund a stop

D pressure chamber

N groove

Claims

P121297-10 WO 2014/079428 PCT / DE2013 / 200250 - 8 patent claims

1 . Slave cylinder with a concentrically arranged around a transmission input shaft housing (1) made of a plastic material and an axially movable annular piston (3) which is acted upon by a pressure of a pressure medium and with a release bearing (7) is in operative connection, wherein the housing (1) a stop (a) is provided which limits a stroke of the piston (3) in the direction of the release bearing (7), characterized in that the stop (a) at least partially made of a metallic sleeve and / or from a the plastic material of the main body of the housing (1) distinguishing second plastic material (10) consists or interacts with these.

2. slave cylinder according to claim 1, characterized in that the metallic sleeve is fixed by molding with plastic on the housing (1).

3. slave cylinder according to claim 1 or 2, characterized in that the metallic sleeve is a steel sleeve (2) or consists of aluminum and one or more openings (2.1) / has holes through which the plastic from the base material of the housing (1) enough.

4. slave cylinder according to one of claims 1 to 3, characterized in that the sleeve has a radially outwardly facing edge region.

5. slave cylinder according to claim 4, characterized in that the radially outwardly facing edge region after assembly of the piston (3) is produced by a forming process.

6. slave cylinder according to claim 4 or 5, characterized in that the radially outwardly facing edge region is a crimping region (2.2) which is flanged.

7. slave cylinder according to one of claims 4 to 6, characterized in that the radially outwardly facing edge region in the form of a collar (2.3) is formed, P121297-10

WO 2014/079428 PCT / DE2013 / 200250

- 9 - of a referring thereto end face (1 .2) of the housing (1) is objected and in the recess / groove formed thereby (N) a snap ring (9) is arranged, which in connection with the sleeve the stop (a ) forms for the piston (3).

8. slave cylinder according to one of claims 3 to 7, that a substantially cylindrical wall portion of the sleeve, in which the apertures are located radially inwardly of the piston (3) is arranged.

9. slave cylinder according to claim 1, characterized in that the stop (a) from the of the plastic material of the base body of the housing (1) different second plastic material (10) is made via a two-component injection molding and has a radially outwardly facing edge region which serves as stop (a).

10. slave cylinder according to claim 1 or 9, characterized in that the radially outwardly facing edge region by a collar (10.1) of the second plastic material (10) is formed, which is spaced from an assigning end face (1.2) of the housing (1) and that in the recess / groove (N) formed thereby a snap ring (9) is arranged, which forms in connection with the second plastic material (10) the stop (a) for the piston (3).