DE102011011225A1 - slave cylinder - Google Patents

Abstract

In a slave cylinder for a hydraulic release system of a friction clutch of vehicles, the slave cylinder has a slave cylinder housing which is arranged concentrically to a transmission input shaft, a guide sleeve being arranged radially spaced in a longitudinal bore of the slave cylinder housing to form an annular pressure chamber and an annular piston axially in the pressure chamber is displaceably guided, which is provided with a seal on the pressure chamber side, failures or functional impairments due to swelling seals are reduced by arranging a limiting means on the pressure chamber side, which limits swelling of the seal in the axial direction.

Description

The invention relates to a slave cylinder for a hydraulic release system of a friction clutch of vehicles, wherein the slave cylinder has a slave cylinder housing which is arranged concentrically to a transmission input shaft, wherein a guide sleeve in a longitudinal bore of the slave cylinder housing radially spaced to form an annular pressure chamber is arranged and in the pressure chamber Annular piston is guided axially displaceable, which is provided on the pressure chamber side with a seal.

A generic slave cylinder is for example in the DE 196 81 324 A1 disclosed. Such slave cylinder belong to hydraulic clutch release systems, in which the slave cylinder z. By actuation of a master cylinder z. B. is actuated by means of a clutch pedal. Master cylinder and slave cylinder are connected by a hydraulic pressure line. The annular piston of the slave cylinder actuates a plate spring of the vehicle clutch via a release bearing. Generic release systems are known as Zentralausrücker (CSC = Concentric Slave Cylinder).

In manually operated clutches EPDM seals are used for the release system in the prior art, because brake fluid is usually used as the operating medium. Other seal materials are considered incompatible with this operating medium.

When using another medium or entry of a foreign substance (oil, grease and the like), there is a swelling and softening of the seals, and as a result to functional impairments. In the further course, a system failure often occurs due to clamping pistons or torn seals with subsequent leakage.

An object of the invention is therefore to reduce failures or functional impairments due to swelling seals.

This object is achieved by a slave cylinder for a hydraulic release system of a friction clutch of vehicles, wherein the slave cylinder has a slave cylinder housing which is arranged concentrically to a transmission input shaft, wherein a guide sleeve in a longitudinal bore of the slave cylinder housing radially spaced to form an annular pressure chamber is arranged and in Pressure chamber, an annular piston is axially displaceably guided, the pressure chamber side is provided with a seal, wherein pressure chamber side of the seal, a limiting means is arranged, which limits a swelling of the seal in the axial direction.

The guide sleeve may be a metal sleeve, which is connected to the slave cylinder housing made of a possibly reinforced plastic or may also be integrally connected to the slave cylinder housing. In the solution according to the invention there is a mechanical impediment to the physical swelling of the seal. This also causes a mechanical obstruction of the gap extrusion of the gap between slave cylinder piston and slave cylinder housing or guide sleeve. In the column extrusion, parts of the seal are pressed into a gap between the annular piston and the slave cylinder housing or annular piston and guide sleeve. Experiments have surprisingly shown that by a limiting means with respect to their axial extent encapsulated seals well withstand the attack of swelling media. As long as no space is available for swelling, the seals do not absorb the hydraulic fluid or any components contained therein as foreign matter, and therefore also show no reduction in hardness and are thus not damaged.

Preferably, the seal comprises a lip seal with sealing lips, which are arranged spread radially. The lip seal is attached either directly or by means of a seal carrier to the annular piston. The two sealing lips are pressed under pressurized pressure chamber to the wall of the longitudinal bore and the guide sleeve and seal the pressure chamber from the environment. The lip seal is made of a plastic or rubber such as EPDM.

The limiting means is in one embodiment, a ring which is arranged on the pressure chamber side of the lip seal and firmly connected to the annular piston or the seal carrier. The ring can be made of metal or plastic. The ring limits the expansion of the lip seal in the axial direction in the direction of the pressure chamber. For attachment to the slave cylinder piston or seal carrier, the ring preferably comprises a fastening part which is arranged in a circumferential annular groove of the lip seal, and an outer delimiting ring which extends radially outwards from the fastening part, and an inner delimiting ring extending from the fastening part extends radially inward. The inner mounting ring together with the outer mounting ring cover in one embodiment 50% to 95% of the radial width of the pressure chamber. The radial thickness of the ring is dimensioned so that obstructs the axial extent of the lip seal, but the sealing effect is maintained. The ring engages the lip seal together with the sealing ring carrier or the slave cylinder piston axial direction on both sides firmly and clamps this if necessary. By clamping is meant that the lip seal is compressed in the axial direction. The sealing lips of the lip seal are not fixed, so they can continue to develop their sealing effect.

The ring preferably comprises attachment means which protrude through openings of the lip seal and which are connected to the annular piston or the seal carrier. The attachment means in one embodiment are trunnions that extend axially. The pins are preferably formed integrally with the ring, for example by the ring is made together with the pins as an injection molded part in plastic. Alternatively, fastening bolts, screws or the like may also be provided here, which are screwed to the ring, welded, glued, glued or otherwise friction-positively or materially connected. The fastening means protrude through openings of the lip seal and are, for example, integral with the ring and frictionally or positively, for example by means of a snap connection, connected to the annular piston or the seal carrier.

In an alternative embodiment, it is provided that the sealing ring carrier has an elasticity in the radial direction, that a gap between the sealing ring carrier and the longitudinal bore of the slave cylinder housing is reduced so much that a depression of the lip seal is prevented in the gap.

In an alternative embodiment it is provided that the seal comprises an inner seal arranged in an inner annular groove and an outer seal arranged in an outer annular groove. The two side surfaces of the respective annular groove limit the expansion of the seals in the axial direction. The side surfaces of the ring groove thus together form the limiting means. Preferably, it is provided that the inner and outer seals each comprise a sealing base body and a sealing lip, wherein the sealing lip forms a V-shaped gap with the sealing base body.

The above-mentioned problem is also solved by a slave cylinder for a hydraulic release system of a friction clutch of vehicles, wherein the slave cylinder has a slave cylinder housing which is arranged concentrically to a transmission input shaft, wherein a guide sleeve in a longitudinal bore of the slave cylinder housing radially spaced to form an annular pressure chamber is and an annular piston is axially displaceably guided in the pressure chamber, the pressure chamber side is provided with a seal, wherein the seal is attached to a seal carrier which is connected by a snap connection with a piston body, wherein the seal carrier is made of a plastic whose surface at least partially provided with a metallic coating. In one embodiment of the invention, the piston body is made of polyamide. The piston body can be made with or without reinforcements. The metallic coating prevents water absorption and associated swelling of the piston body. The gap dimensions between the seal carrier and the slave cylinder housing are so low in a development that squeezing the seal into the gap is reliably avoided.

Parts of the surface of the seal carrier are provided in one embodiment of the invention with recesses. The recesses are arranged in particular on the piston body facing end side and the inside and outside of the seal carrier. The recesses cause a stiffening of the seal carrier, so that it can expand only to a lesser extent under the influence of swelling agents or thermal expansion.

Embodiments of the invention will be described with reference to FIGS 1 to 7 explained in more detail.

Showing:

1 a first embodiment of a slave cylinder according to the invention in a partial section;

2 a second embodiment of a slave cylinder according to the invention in a partial section;

3 a third embodiment of a slave cylinder according to the invention in a partial section;

4 a third embodiment of a slave cylinder according to the invention in a partial section;

5 the embodiment of the seal carrier according to the invention according to 4 in spatial representation;

6 the embodiment of the seal carrier according to the invention according to 4 in spatial representation;

7 the further embodiment of a seal carrier according to the invention in a spatial representation.

The 1 shows a section of a slave cylinder 1 in a partial section. This includes a slave cylinder housing 2 with a longitudinal bore 3 which has a substantially cylindrical inner surface 4 has, and a guide sleeve 5 with a likewise cylindrical outer surface 6 , Between the inner surface 4 the slave cylinder housing 2 and the outer surface 6 the guide sleeve 5 becomes an annulus 7 enclosed, in which an annular piston 8th is arranged. The ring piston 8th includes a piston body 9 as well as a seal 10 , The seal closes together with the slave cylinder housing 2 and the guide sleeve 5 a pressure room 11 one. The slave cylinder is arranged concentrically around a transmission input shaft, which in 1 only schematically with reference to a rotation axis 12 the transmission input shaft is shown. The radial direction is in 1 with a double arrow R, the axial direction marked with a double arrow A. The circumferential direction with respect to the axis of rotation 12 sticks out of the drawing plane. The directions of the 1 also apply to the 2 and 3 ,

The slave cylinder 1 is connected via a pressure line, not shown, with a master cylinder. The master cylinder comprises a master cylinder piston, with which a pressure chamber of the master cylinder is pressurized. The pressure chambers of master cylinder and slave cylinder are hydraulically connected to each other through the pressure line. If the master cylinder piston is moved by application of force, the slave cylinder piston is also moved. The master cylinder piston is coupled to a clutch pedal, in the manual actuation of the master cylinder piston is acted upon with a force. A movement of the master cylinder piston and the hydraulically coupled thereto slave cylinder piston takes place against the restoring force of the plate spring and possibly further return means of the vehicle clutch.

The seal 10 is a lip seal with an outer lip 13 and an inner lip 14 which are V-shaped radially spread apart from each other. The seal 10 is made of an elastomer, preferably EPDM or HNBR. The seal 10 includes, how out 2 to recognize a sealing foot 15 which is in a corresponding gasket holder 17 of the ring piston 8th (or the seal carrier 30 as in the embodiment of 2 ) intervene. The sealing foot 15 is radially outward and inward of the seal receiver 17 enclosed. The sealing lips 13 . 14 are in the range of a seal body 19 arranged.

Schematically represented in 1 is a release bearing 20 , whose bearing inner ring 21 with the piston body 9 is connected and its bearing outer ring 22 interacts with a plate spring, not shown, of the vehicle clutch. The slave cylinder housing 2 includes a flange part 23 for fastening the slave cylinder housing 2 on a clutch or transmission housing. Between the slave cylinder housing 2 and the bearing inner ring 21 is a biasing spring 24 arranged.

On the pressure room 11 facing side of the seal 10 is a ring 25 arranged, fixed to the piston body 9 connected is. The connection can be as in the embodiment of 2 shown in detail by means of webs or the like, which pass through openings in the seal 10 protrude and firmly with the ring piston 8th are connected, for example by a snap connection or the like. The ring 25 is wedge-shaped on average and lies with wedge surfaces 26 on the lips 13 . 14 the seal 10 at. The ring 25 limits an expansion of the seal 10 in the direction of the pressure chamber 11 If the seal 10 swells, thus expands, so hinders the ring 25 this at the sources, since a volume expansion in the axial direction is prevented. In the radial direction an expansion is possible. This causes the sealing lips in the radial direction more strongly to the inner surface 4 or outer surface 6 is pressed, which increases the sealing effect rather than impaired.

2 shows an alternative embodiment of the ring 25 , Compared to the embodiment of 1 the same or equivalent parts are provided with identical reference numerals and only where indicated for clarity again described. The ring 10 here comprises an annular fastening part 27 and a from the attachment part 27 radially outwardly and inclined in the axial direction extending outer boundary ring 28 and one from the attachment part 27 radially inwardly and inclined in the axial direction extending inner boundary ring 29 , The boundary rings 27 . 28 , correspond to the wedge surfaces 26 of the embodiment of 1 ,

The seal 8th is in the embodiment of 2 not directly with the ring piston 8th but is connected in a manner known per se by means of a seal carrier 30 on the ring piston 8th attached. The seal carrier comes with a snap connection with a circumferential snap hook 16 , which has a radially outwardly projecting circumferential collar 18 engages on the piston body 9 established. The seal carrier 30 includes a seal receiving part 31 and a connecting part 32 , The seal receiving part is in cross-section substantially U-shaped, thus forming an annular circumferential annular groove into which the seal 10 with to the cross-section substantially rectangular or trapezoidal sealing foot 15 protrudes. Radial inwards or outwards and in axial direction slightly inclined, the sealing lips close 11 and 12 at. Between the sealing lips 11 and 12 remains in a cross section in approximately semicircular and annular circumferential receiving space 33 in the fastening part 27 of the ring 25 protrudes. The recording room 33 forms an annular circumferential groove on an axial end face of the ring 25 , From the attachment part 27 extend radially inwardly or outwardly and axially in the direction of the pressure chamber 11 inclined their inner or outer boundary rings 28 . 29 , The two boundary rings 28 . 29 extend in the radial direction almost over the entire radial width b of the pressure chamber 11 , the height h of the ring 25 - Measured by the radially innermost part of the inner boundary ring 29 to the radially outermost part of the outer boundary ring 28 as in 2 sketched - is thus only slightly smaller than the value of the width b. The difference between the values h and b can be quite in the range of the gap between the annular piston 8th or seal carrier 30 and the annulus 7 lie.

The ring 25 is fixed to the seal carrier 30 connected. This is in 2 indicated by two dashed lines, the pins 34 Outline the ring with the ring 25 are connected, for example, integrally formed as a plastic part to these, and through openings or holes in the seal 10 protrude, wherein the bores extend substantially axially and starting from the receiving space 33 through the entire sealing foot 15 extend in the axial direction and with the seal carrier 30 are firmly connected. The connection of the pins 34 with the seal carrier 30 For example, this can be done by turning the pins 34 in corresponding holes of the seal carrier 30 protrude and glued or welded to these or alternatively by clip connections between the pin 34 and the seal carrier 30 , In a waiver of an independent seal carrier, for example, as in the embodiment of 1 shown, the connection of the ring takes place 25 directly with the ring piston 8th ,

As previously shown, the boundary rings 28 . 29 inclined in the axial direction, an angle α between the seal 10 facing side of the limiting ring, in 2 represented by the inner boundary ring 29 , with respect to the axial direction, for example through the axis of rotation 12 according to 1 is thus less than 90 °. Due to this inclination, swelling of the seal moves 10 in that the sealing lips move radially inwards or outwards, instead of only a corresponding tensile stress on the pins 34 build.

3 shows a further embodiment of the invention. Compared to the embodiments of the 1 and 2 the same or equivalent parts are provided with identical reference numerals and only where indicated for clarity again described. Stable a V-shaped lip seal, the sealing lips of a seal as in the 1 and 2 represented both on the inner surface 4 as well as on the outer surface 6 abut, is the seal 10 here divided into an inner seal 35 and an outer seal 36 , The inner seal 35 carries the inner sealing lip 14 , the outer seal 36 the outer sealing lip 13 , The sealing lips 13 and 14 each form a V-shaped gap with the sealing body.

The inner seal 35 is in an inner ring groove 37 arranged, according to the outer seal 36 in an outer annular groove 38 arranged. The ring groove 37 . 38 each have a front boundary surface 39 and a rear boundary surface 40 as well as a groove bottom 41 , The seals 35 . 36 are through the annular groove 37 . 38 Thus, each set in three directions and can each extend only to the effective area for the sealing effect. The inner seal 35 is thus fixed on both sides in the axial direction, and is at the bottom of the groove 41 the inner ring groove 37 set against expansion radially outward. In a swelling of the inner seal 35 An expansion thus takes place only radially inward.

Correspondingly reversed are the conditions in the outer seal 36 , This is also fixed in the axial direction on both sides and through the groove bottom 41 the outer ring groove 38 Also defined radially inward, so that an expansion in sources of the seal can only be done radially outward. The seals 35 and 36 can both directly on the piston body 9 of the ring piston 8th be arranged as well as on a seal carrier 30 as in 2 be arranged shown.

The limiting means, which is an extension of the seals 35 . 36 prevented in the axial direction, here is in each case the annular groove in which the seals 35 . 36 are arranged.

4 shows a further embodiment of the invention. 4 shows according to the representation of 2 and 3 a schematic diagram of a slave cylinder according to the invention 1 , The presentation of the 4 is essentially the same as the 2 , therefore, the same elements will not be described again. In contrast to the embodiment of 2 has the embodiment of 4 no ring 25 on. Instead, the gap dimensions of the seal carrier 30 opposite the annulus 7 or pressure chamber 11 so chosen that the seal 10 can not be pushed into the gap. The seal 10 can therefore no longer be pressed under pressure in the sealing gap, since the sealing ring carrier 30 is flexible and closes the sealing gap. Thus, a swollen, soft seal not damaged when pressurized.

The 5 and 6 show the embodiment of the seal carrier according to the invention 30 according to 4 in spatial representation. As can be seen, the snap hooks extend 16 only in each case over part of the circumference and are each arranged at 90 ° to each other, so each two snap hooks 16 are arranged opposite one another. The snap hooks 16 each comprise two radially extending legs 46 between which a traverse 47 is arranged, which is a hook strip 48 wearing. The hook strip 48 is triangular in cross section, so the cross section increases in the direction of the arrow 49 at. This allows the respective snap hook 16 over the covenant 18 be pushed and engages behind this in the manner of a snap connection, so that a positive connection between the piston body 9 and the seal carrier 30 will be produced. The seal carrier 30 is made of an unreinforced plastic, such as polyamide (PA). To further prevent water absorption, the seal carrier 30 provided with a metallic coating, which may be vapor-deposited, for example.

The seal 10 is made of silicone rubber. The abbreviation of this material is VMQ according to ISO or MVQ according to ASTM. Such plastics are offered under various trade names, for example "Silopren", "Silastik", "SE", "Blensil" or "silicone".

7 shows a development of the in the 5 and 6 illustrated seal carrier 30 , The piston body 9 facing annular end face 42 and the piston body 9 facing area 43 of the inner circumference and 44 the outer periphery of the seal carrier 30 are with recesses 45 Mistake. The recesses 45 are often arranged side by side, so that the entire circumference of the face 42 of the seal carrier with recesses 45 is provided. The piston body 9 facing area 43 the inner circumference and the area 44 the outer periphery of the seal carrier 30 are so with recesses 45 provided that these each form a circumferentially extending row. The recesses cause line-shaped elevations similar to corrugations in sheets over the seal carrier 30 extend. This results in a higher mechanical stability. The recesses 45 prevent the expansion of the seal carrier 30 by water absorption or thermal expansion.

LIST OF REFERENCE NUMBERS

1

slave cylinder

2

Slave cylinder housing

3

longitudinal bore

4

palm

5

guide sleeve

6

outer surface

7

annulus

8th

annular piston

9

piston body

10

poetry

11

pressure chamber

12

axis of rotation

13

outer sealing lip

14

inner sealing lip

15

sealing foot

16

snap hooks

17

seal Housing

18

Federation

19

seal body

20

release bearing

21

Bearing inner ring

22

Bearing outer ring

23

flange

24

biasing spring

25

ring

26

wedge surfaces

27

attachment portion

28

outer boundary ring

29

inner boundary ring

30

seal carrier

31

Seal receiving part

32

connecting part

33

accommodation space

34

spigot

35

inner seal

36

outer seal

37

inner ring groove

38

outer ring groove

39

front boundary surface

40

rear boundary surface

41

groove base

42

face

43

Area

44

Area

45

recess

46

leg

47

traverse

48

Hakenleiste

49

arrow

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19681324 A1 [0002]

Claims (10)

Slave cylinder ( 1 ) for a hydraulic release system of a friction clutch of vehicles, wherein the slave cylinder is a slave cylinder housing ( 2 ) concentric with a transmission input shaft ( 12 ), wherein a guide sleeve ( 5 ) in a longitudinal bore of the slave cylinder housing ( 2 ) radially spaced to form an annular pressure chamber ( 11 ) is arranged and in the pressure chamber ( 11 ) an annular piston ( 8th ) is guided axially displaceable, the pressure chamber side with a seal ( 10 ), characterized in that the pressure chamber side of the seal ( 10 ) a limiting means ( 25 . 26 . 27 . 28 . 29 . 37 . 38 ), which is a source of the seal ( 10 ) is limited in the axial direction. Slave cylinder ( 1 ) according to claim 1, characterized in that the seal ( 10 ) a lip seal with sealing lips ( 10 . 11 ), which are arranged spread radially and the lip seal ( 10 ) by means of a seal carrier ( 30 ) on the ring piston ( 8th ) is attached. Slave cylinder ( 1 ) according to claims 1 and 2, characterized in that the limiting means comprise a ring ( 25 ), the pressure chamber side of the lip seal ( 10 ) and fixed with the annular piston ( 8th ) or the seal carrier ( 30 ) connected is. Slave cylinder ( 1 ) according to one of claims 1 to 3, characterized in that the ring ( 25 ) a fastening part ( 27 ), which in a circumferential annular groove ( 33 ) of the lip seal ( 10 ) is arranged, as well as an outer boundary ring ( 28 ) extending from the mounting part ( 27 ) extends radially outward, and an inner boundary ring ( 29 ) extending from the mounting part ( 27 ) extends radially inwardly includes. Slave cylinder ( 1 ) according to claim 4, characterized in that the ring ( 25 ) Fastening means ( 34 ) through openings of the lip seal ( 10 ) and the with the ring piston ( 8th ) or the seal carrier ( 30 ) are connected. Slave cylinder ( 1 ) according to claim 5, characterized in that the fastening means pins ( 34 ) which extend axially. Slave cylinder ( 1 ) according to claim 1, characterized in that the seal ( 10 ) an inner seal ( 35 ), which are in an inner annular groove ( 37 ) is arranged, and an outer seal ( 36 ), which are in an outer annular groove ( 38 ) is arranged. Slave cylinder ( 1 ) according to claim 7, characterized in that the inner and outer seals ( 35 . 36 ) each have a sealing base body and a sealing lip ( 13 . 14 ), wherein the sealing lip ( 13 . 14 ) forms a V-shaped gap with the seal base body. Slave cylinder ( 1 ) for a hydraulic release system of a friction clutch of vehicles, wherein the slave cylinder is a slave cylinder housing ( 2 ) concentric with a transmission input shaft ( 12 ), wherein a guide sleeve ( 5 ) in a longitudinal bore of the slave cylinder housing ( 2 ) radially spaced to form an annular pressure chamber ( 11 ) is arranged and in the pressure chamber ( 11 ) an annular piston ( 8th ) is guided axially displaceable, the pressure chamber side with a seal ( 10 ), the gasket ( 10 ) on a seal carrier ( 30 ) is attached, which by means of a snap connection ( 16 ) with a piston body ( 9 ), characterized in that the seal carrier ( 30 ) consists of plastic whose surface is at least partially provided with a metallic coating. Slave cylinder ( 1 ) according to claim 9, characterized in that a part of the surface of the seal carrier ( 30 ) with recesses ( 45 ) is provided.

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