Piston-cylinder arrangement for a release unit, in particular for a master cylinder of a hydraulic clutch actuation device

Abstract

Piston-cylinder arrangement for a release unit, in particular for a master cylinder of a hydraulic clutch actuation device, comprising a cylinder (2) designed as a housing, which spans an annular pressure chamber (3) in which a piston (4, 10, 15) is mounted so as to be axially movable, wherein the piston (4, 10, 15) is sealed off from the pressure chamber (3) by means of a seal (5, 13, 14, 17) surrounding the piston (4, 10, 15), wherein the seal (5, 13, 14, 17) which can be pressurised on both sides and extends radially to the cylinder (2) is held by a support ring (6, 16) which radially encloses the piston (4, 10, 15), wherein the support ring (6, 16) has a support back which engages radially in the seal (5, 13, 14, 17). (7), characterized in that the seal (5, 13, 14, 17) extends symmetrically on both sides of the support back (7) and that the support ring (6, 16) is fastened to the piston (4, 10, 15) by an interference fit.

Description

[0001] The invention relates to a piston-cylinder arrangement for a release unit, in particular for a master cylinder of a hydraulic clutch actuation device, comprising a cylinder designed as a housing, which spans an annular pressure chamber in which a piston is mounted so as to be axially movable, wherein the piston is sealed off from the pressure chamber by means of a seal surrounding the piston.

[0002] Hydraulic master cylinders, such as those used in hydraulic clutch actuation systems in vehicles, consist of a cylinder designed as a housing. This housing spans an annular pressure chamber in which a piston is mounted for axial movement. To seal the piston against the hydraulic medium in the pressure chamber, the piston is provided with at least one seal. Elastomer seals pressurized on one side are used as seals. This seals the pressure or hydraulic fluid only in the direction of the pressure chamber. If pressure is applied to the back of the seal, a lifting of one seal leg from the seal raceway is generated, which is generally referred to as overflow.To prevent overflow, a radial preload must be applied to the seal, ensuring sealing in the depressurized state and preventing overflow of the seal when pressure builds up. This design requires increased design effort.

[0003] DE 10 2011 080 924 A1 discloses a master cylinder with a seal that extends radially to the cylinder and is held by a support ring that radially surrounds the piston. The support ring has a support back that radially engages the seal.

[0004] The invention is based on the object of providing a piston-cylinder arrangement which has a seal which can be pressurised on both sides and which nevertheless reliably prevents overflow of the seal.

[0005] According to the invention, this object is achieved in that the seal, which can be pressurized on both sides and extends radially to the cylinder, is held by a support ring radially enclosing the piston, wherein the support ring has a support back that engages radially with the seal. Such a support ring with the support back creates additional axial and radial rigidity of the seal, thereby reliably preventing overflow. Furthermore, the seal is very compact, has a low coefficient of friction, and requires only a small amount of installation space.

[0006] In a particularly simple production process, the support ring and the seal are connected to each other by vulcanization.

[0007] According to the invention, the seal expands symmetrically on both sides of the support backing. This symmetrical seal design ensures the seal functions the same regardless of which side the hydraulic fluid flows against the seal. Overflow is prevented in all cases.

[0008] In one embodiment, the support ring has a W-shaped cross-section into which the seal is symmetrically inserted. This W-shaped cross-section ensures particularly stable positioning of the seal while simultaneously providing reliable sealing against the pressure chamber.

[0009] In a particularly cost-saving design, the support ring consists only of the support back, which is secured in a groove in the piston. This allows for particularly simple installation of the support ring.

[0010] In one embodiment, the piston is formed in at least two parts, with the support ring, designed as a support back, being attached between the two parts of the piston. This simplifies the assembly of the support ring on the piston.

[0011] In one variant, the support ring is attached to the piston by force-fitting, form-fitting, and / or material-fitting means. In each case, an interference fit is present, resulting in a reliable connection between the support ring and the piston.

[0012] In one embodiment, the seal is radially preloaded against the cylinder. This radial preload creates a reliable seal even at ambient pressure when the seal is installed in the cylinder. This seal is supported by the support ring when fluid pressure is applied to the seal.

[0013] In one variant, the support ring is made of metal, plastic, or a sintered ring. Particularly cost-effective materials are used, which are selected depending on the application.

[0014] The invention permits numerous embodiments. Some of these are explained in more detail with reference to the figures shown in the drawing.

[0015] They show: Fig. 1 an embodiment of a piston-cylinder arrangement according to the invention, Fig. 2 a first embodiment of a seal according to piston-cylinder arrangement in Fig. 1, Fig. 3 a fluid flow direction which is applied to the seal according to Fig. 2 attacks, Fig. 4 a schematic representation of a formed part for a support ring according to Fig. 2, Fig. 5 shows a further embodiment of the seal according to the piston-cylinder arrangement according to Fig. 1, Fig. 6 another embodiment of the seal according to the piston-cylinder arrangement according to Fig. 1.

[0016] Identical features are marked with the same reference symbols.

[0017] In Fig. Figure 1 shows a master cylinder 1 of a hydraulic clutch actuation device of a vehicle, in which the cylinder 2 is designed as a housing. The cylinder 2 defines an annular pressure chamber 3 containing a hydraulic medium. A piston 4 is moved axially within the pressure chamber 3.

[0018] The piston 4 is sealed from the pressure chamber 3 by an annular seal 5, which radially surrounds the piston 4 and in Fig. 2. The seal 5 is mounted on a support ring 6, which, for example, has a W-shaped cross-section and a radial support back 7 in the center, which projects into the seal 5. The attachment between the piston 4 and the support ring 6 is achieved by an interference fit, which is generally referred to as a force-fitting connection. However, a material and / or form-fitting connection can also be used. A sealing leg 8, which is formed symmetrically around the support back 7, has a radial preload towards the cylinder 2 when installed at ambient pressure and thus creates a seal against the pressure chamber 3. By flowing against the sealing waist 9 formed centrally on the sealing leg 8, the contact pressure of the sealing leg 8 against the cylinder 2 increases.The support back 7 partially creates additional axial and radial rigidity of the seal 5, which increases the positional accuracy of the seal 5 when subjected to hydraulic fluid flow. The support ring 6, as such, is responsible for the axial positioning of the seal 5. Furthermore, this area can also simply ensure the force transmission between the seal 5 with the support ring 6 and the piston 4 for assembly.

[0019] Due to this symmetrical design of the seal 5 and in particular the use of the support back 7 to stabilize the seal 5, this seal 5 is suitable to be exposed to a fluid flow of the hydraulic medium on both sides ( Fig. 3).

[0020] In Fig. Figure 4 shows a formed part for forming the w-like support ring 6, which can be easily manufactured in at least one step of a forming process. Alternatively, the support ring 6 can also be designed as a plastic injection-molded part, a turned part, or a sintered part.

[0021] However, an asymmetric design of the pressurizable seal 5 in the axial direction is also conceivable, depending on the requirements. The attachment between the piston 4 and the support ring 6 can alternatively be achieved via an axial transition fit, provided that a corresponding seal between the piston 4 and the support ring 6 is enabled by the seal 5. A positive or material-fit connection is also conceivable as a further attachment option.

[0022] In Fig. 5 shows a multi-part piston 10 with the assembled seal 5, in which the support ring consists solely of the support back 7, wherein the support back 7 is pressed between two parts 11, 12 of the piston 10 and engages radially into the described symmetrical seal 5. Assembly is carried out in such a way that the two parts 11, 12 of the piston 10 are mounted with two seal halves 13, 14. In the next step, the parts 11, 12 of the piston 10 are joined to the seal halves 13, 14 and the support back 7 by means of a force-locking connection.

[0023] According to Fig.6 features a one-piece piston 15 with a support ring 16, with the support ring 16, designed as a support back, engaging in a circumferential groove of the piston 15. During assembly, the seal 17 is slipped over the piston 15 and pushed into the appropriate position. In a next step, the slotted support ring 16 is mounted on the piston 15. The support ring 16 is fixed in position by the piston geometry and the circumferential force of the support ring 16.

[0024] By means of this described arrangement, a piston-cylinder arrangement is provided, the seal of which can be pressurized with the hydraulic medium on both sides without overflow occurring. List of reference symbols 1 master cylinder 2 cylinders 3 Pressure chamber 4 pistons 5 Seal 6 support ring 7 Support back 8 sealing legs 9 Sealing waist 10 pistons 11 Piston part 12 Piston part 13 Seal half 14 Seal half 15 pistons 16 Support ring 17 Seal

Claims

[1] Piston-cylinder arrangement for a release unit, in particular for a master cylinder of a hydraulic clutch actuation device, comprising a cylinder (2) designed as a housing, which spans an annular pressure chamber (3) in which a piston (4, 10, 15) is mounted so as to be axially movable, wherein the piston (4, 10, 15) is sealed off from the pressure chamber (3) by means of a seal (5, 13, 14, 17) surrounding the piston (4, 10, 15), wherein the seal (5, 13, 14, 17) which can be pressurised on both sides and extends radially to the cylinder (2) is held by a support ring (6, 16) which radially encloses the piston (4, 10, 15), wherein the support ring (6, 16) has a radially engaging in the seal (5, 13, 14, 17) supporting back (7), characterized by that the seal (5, 13, 14, 17) expands symmetrically on both sides of the support back (7) and that the support ring (6, 16) is attached to the piston (4, 10, 15) by an interference fit. [2] Piston-cylinder arrangement according to claim 1, characterized by that the support ring (6, 16) and the seal (5, 13, 14, 17) are connected to each other by vulcanization. [3] Piston-cylinder arrangement according to claim 1 or 2, characterized by that the support ring (6) has a w-like cross-section into which the seal (5) is inserted symmetrically. [4] Piston-cylinder arrangement according to claim 1 or 2, characterized by that the support ring (16) consists only of the support back, which is fastened in a groove of the piston (15). [5] Piston-cylinder arrangement according to claim 4, characterized by that the piston (10) is formed in at least two parts, wherein the support ring formed as a support back (7) is fastened between the two parts (11, 12) of the piston (10). [6] Piston-cylinder arrangement according to at least one of the preceding claims, characterized bythat the support ring (6, 17) is fastened to the piston (4, 10, 15) in a force-fitting and / or form-fitting and / or material-fitting manner. [7] Piston-cylinder arrangement according to at least one of the preceding claims, characterized by that the seal (5, 13, 14, 17) is preloaded radially against the cylinder (2). [8] Piston-cylinder arrangement according to at least one of the preceding claims, characterized by that the support ring (6, 16) consists of metal or plastic or a sintered part.

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