Dynamic seal assembly having valve and diaphragm functions

Abstract

The invention relates to a sealing assembly (2) comprising a piston (4) having a longitudinal axis L, the piston comprising at least two radial piston walls (10, 11), i.e. a first and a second radial piston wall, relative to the longitudinal axis L, between which a recess (12) is formed, and a seal (3) which is received in the recess (12), wherein a first sealing lip (8) extends radially outward beyond the radial piston walls (10, 11), characterized in that the first radial piston wall (10) extends radially outward less than the second radial piston wall (11), and a second sealing lip (9) rests sealingly against the first radial piston wall (10) and seals with said wall into a space (13) at a pressure below a predetermined limit pressure p G , at which pressure the bypass line (5) within the piston (4) extends at least partially around the recess (12), wherein the second sealing lip (9) pivots radially inward at a pressure above the predetermined limit pressure p G , so that the space (13) is opened.

Description

Technical Field

[0001] This invention relates to a sealing assembly for pistons used in hydraulic systems, particularly for pistons in the hydraulic internal circuits of transmissions. Such pistons are pressurized by fluid to, for example, actuate a shift fork in a transmission or also actuate a disengagement bearing of a clutch. The invention also relates to disengagement systems incorporating such sealing assemblies. Background Technology

[0002] DE 10 2013 012 044 A1 discloses a sealing assembly including a sealing ring having at least one first sealing lip, the first sealing lip having at least one channel groove for guiding two spaces that are sealed and separated from each other. The first sealing lip, in an elastically pre-tensioned state, contacts the surface of the machine element to be sealed and is disposed on a facet of the sealing ring on the side of the sealing ring facing the first space to be sealed. A second sealing lip is disposed on the facet of the sealing ring on the other side of the second space to be sealed. The second sealing lip is designed as a valve lip to limit relative overpressure in the first space to be sealed relative to the second space to be sealed. At least one sealing flange is disposed axially between the first and second sealing lips, the sealing flange being distributed to the surface to be sealed at a radial distance adjacent to the sealing flange in the unpressurized state of the sealing assembly.

[0003] The second sealing lip forms a static seal in the statically placed sealing assembly. In the unpressurized state of the sealing assembly, i.e., when there is almost no pressure difference between the spaces to be sealed, the valve lip reliably seals the medium against the surfaces to be sealed. Therefore, the medium to be sealed cannot travel from the first space to be sealed through the passage groove to the second space to be sealed, because that space is sealed by the valve lip. According to the prior art, targeted, i.e., limited leakage may occur. However, above a certain pressure, this known seal breaks down again.

[0004] Furthermore, DE 10 2017 108 030 A1 discloses a switching module for an automatic transmission, which has a cylinder assembly consisting of two cylinder components for disengaging two shift forks. The two cylinder components are arranged axially aligned with each other and connected to each other via a plastic intermediate piece. Each cylinder is equipped with a piston capable of axial displacement by means of hydraulic fluid. Each piston has a basic cylindrical shape, wherein a radial sealing ring seals the piston against the inner surface of the cylinder at its front end. However, with this type of seal, leakage can occur even under low pressure.

[0005] The object of the present invention is to provide a sealing assembly for a piston in a hydraulic system, particularly for a piston in a hydraulic circuit of a transmission in a motor vehicle, the sealing assembly reliably achieving a sealing function up to a predetermined limit pressure and a limited leakage flow from the predetermined limit pressure allowing the discharge of hydraulic fluid and air. Summary of the Invention

[0006] This objective is achieved through the following sealing components and disconnection system.

[0007] One embodiment of the sealing assembly has the following:

[0008] - A piston having a longitudinal axis L, the piston having at least two radial piston walls relative to the longitudinal axis L, namely a first radial piston wall and a second radial piston wall, a groove being formed between the first radial piston wall and the second radial piston wall.

[0009] - A seal, received in a recess, having a first sealing lip extending radially outward beyond the radial piston wall.

[0010] The first radial piston wall extends less radially outward than the second radial piston wall, and the second sealing lip is seated sealingly against the first radial piston wall at a pressure below a predetermined limit acting on it, and together with the first radial piston wall seals the inlet space. A bypass line within the piston extends at least partially around a groove from the inlet space. The second sealing lip is positioned above a predetermined limit pressure p. G Under pressure, it pivots radially inward, thus opening up the access space.

[0011] Using this sealing assembly, two spaces with different pressures can be sealed against each other until the ultimate pressure p is reached. G Because the two sealing lips sit abutting against the respective wall seals below a certain ultimate pressure. Above the ultimate pressure, the second sealing lip slopes inward, i.e., into the interior of the groove, thereby creating a passage between the second sealing lip and the first radial piston wall. This passage allows hydraulic fluid and air to permeate into the inlet space and flow from the inlet space into the bypass line. The bypass line preferably extends around the edge of the groove to the region of the second radial piston wall, allowing fluid to flow outward from this region. Therefore, from the predetermined ultimate pressure p G A certain amount of fluid circulates around the seal in the groove and a limited leakage occurs.

[0012] Ultimate pressure p GFor example, the second sealing lip can be defined by the geometry of its shape and / or by the choice of material forming it, at pressures above which the second sealing lip pivots or tilts. Specifically, the thinner and longer the second sealing lip, the lower the limiting pressure required to open the inlet space for fluid. The same applies to materials: the softer and more elastic the material, the higher the limiting pressure p. G The lower.

[0013] On the other hand, the limited leakage flow flowing outward through the bypass line, i.e., the flow rate per unit time, exceeds the ultimate pressure p. G The extent of leakage flow can be determined by the geometry of the bypass lines. Therefore, the determining factors for limiting leakage flow are specifically the number of bypass lines, and the width and depth of one or more bypass lines. The more lines there are and the greater the depth or width, the greater the limited leakage flow of hydraulic fluid to the outside.

[0014] As mentioned above, the first radial piston wall extends less radially outward than the second radial piston wall. The purpose is to create a gap between the second radial piston wall and the housing, which, when using a sealing assembly, radially surrounds the second radial piston wall, allowing hydraulic fluid to permeate through this gap to the second radial piston wall. If the pressure of the hydraulic fluid is sufficiently high, i.e., exceeding a predetermined limit pressure p... G Then the second radial sealing lip pivots, as already mentioned, and allows access into the access space and thus into one or more bypass lines.

[0015] According to a preferred embodiment of the sealing assembly, the first radial piston wall has a flattened radial outer end and the second radial piston wall has a similarly flattened radial outer end, wherein the radial distance between the radial outer ends is A>0. The larger this radial distance A is, the more hydraulic fluid can penetrate to the second sealing lip and act on it according to the opening or pivoting of the second sealing lip. The radial distance is also a method for determining the magnitude of the leakage flow.

[0016] The radial distance A between the radially outer ends of the radial piston wall can, for example, be less than 1 / 3 of the radial extension of the groove. This means that the radial distance A is small compared to the depth of the groove and therefore small compared to the radial expansion of the radial piston wall. This particularly ensures that below a predetermined limit pressure p... G At the same time, the sealing components ensure a complete seal against the hydraulic fluid.

[0017] In an advantageous embodiment of the sealing assembly according to the invention, a bypass line extends from the inlet space to the radially outer end of the second radial piston wall. Therefore, the bypass line surrounds the entire recess from the inlet space to the radially outer end of the second radial piston wall. When the sealing assembly is in use, the second radial piston wall defines the sealing assembly to the outside, i.e., to the environment, meaning that leakage flow of hydraulic fluid can escape to the outside in the region of the radially outer end of the second radial piston wall. This ensures pressure above the ultimate pressure p. G Limited leakage.

[0018] Regarding the predetermined ultimate pressure p G In practice, this can be, for example, between 0.2 bar and 5 bar, and include both values. This means that if the pressure of the hydraulic fluid in the space or chamber at least partially defined in the axial direction by the first radial piston wall rises above said value when using the sealing assembly according to the invention, the second sealing lip pivots and hydraulic fluid permeates into the access space.

[0019] In the sealing assembly according to the invention, the second sealing lip is preferably formed as a single piece with the seal. In other words, in this embodiment, the second sealing lip is an integral part of the seal. Therefore, the second sealing lip is subjected to pressures above a predetermined limit p. G The tilting or pivoting occurs by bending or warping the second sealing lip relative to the rest of the seal, which may also be referred to below as the sealing body. Alternatively, the second sealing lip may be formed separately and hinged to the sealing body via a connecting device.

[0020] According to a preferred embodiment of the invention, the piston is formed about a longitudinal axis L. This means that the sealing assembly can be inserted into the cylindrical opening of the housing and can slide relative to the inner wall of the housing in an axial direction relative to the longitudinal axis to actuate the clutch disengagement bearing or one or more disengagement forks or shift forks (in the case of an internal gear shifter). In other words, the sealing assembly according to the invention is suitable in this case for forming part of a concentric driven cylinder or an internal transmission shifting mechanism.

[0021] The bypass line of the sealing assembly can extend from the access space to the region between the second radial piston wall and the first sealing lip. This means that the bypass line still terminates within the groove of the sealing assembly according to the invention. Leakage flow occurring above the ultimate pressure thus flows into the aforementioned region and can then pass between the second radial piston wall and the housing it is guided to, and flow outward. The first sealing lip seals this region in the axial direction, preventing hydraulic fluid from flowing back in the direction of the first radial piston wall. According to an alternative embodiment, the bypass line, or one of a plurality of bypass lines, can also extend axially outside the second radial piston wall and thus direct the leakage flow directly to the outside.

[0022] As already mentioned, two or more bypass lines may also be present in the sealing assembly according to the invention, particularly to increase leakage flow. Multiple bypass lines may have different geometries / sizes and / or different routes to adapt leakage flow to various requirements.

[0023] The present invention also relates to a disconnection and engagement system having a housing having a first space and a second space defined axially by a sealing assembly according to the above embodiment. The piston of the sealing assembly is mounted such that it can be displaced axially within the housing, and the first space is designed to be pressurized by hydraulic fluid during operation. The sealing assembly seals the first space, which serves as a fluid space during operation, and the fluid space is actuated by hydraulic fluid to actuate the disconnection and engagement system from the second space, which can be opened toward the clutch side. In this disconnection and engagement system, a first sealing lip is seated against the wall of the housing. When the hydraulic fluid is below a limit pressure p... G When the pressure is applied to the first space, the piston slides within the housing along the longitudinal axis L, wherein two sealing lips seal and separate the first space from the second space. If the pressure of the hydraulic fluid exceeds the predetermined limit pressure p... G The second sealing lip opens by pivoting into the access space, while the first sealing lip remains seated sealingly against the housing. In this way, only specific, desired leakage flows can enter the second space through the bypass line.

[0024] The sealing assembly according to the invention and the disconnection / engagement system therein receiving the sealing assembly have the advantage of a short axial design, thus requiring less axial space. Furthermore, the assembly of the sealing assembly within the housing is simplified because there is only one radial sealing edge formed by a first radial sealing lip. Finally, limited leakage of hydraulic fluid can be achieved more precisely than in embodiments where the leakage path extends through the seal, i.e., the seal body, because in such cases only a small deformation effect acts on the cross-section of the bypass line, whereas with a leakage path through the seal, the elastomeric material of the seal can affect the cross-section of the leakage path. Attached Figure Description

[0025] The invention will now be described by way of non-limiting example with reference to the accompanying drawings. In the drawings:

[0026] Figure 1 The cross-section shows the pressure below the predetermined limit pressure p. G Exemplary embodiments of the sealing assembly of the present invention in a state of [condition], and [other conditions].

[0027] Figure 2 This shows that when the pressure is higher than the predetermined limit pressure p G In the state Figure 1 The implementation method. Detailed Implementation

[0028] Figure 1 An embodiment of the sealing assembly according to the invention is shown in longitudinal section. Reference numeral 1 shows the housing surrounding the sealing assembly according to the invention, which is generally indicated by reference numeral 2 and defines the hydraulic disconnect engagement device 100. The sealing assembly 2 is designed here to rotate symmetrically about its longitudinal axis L, wherein only one half of the sealing assembly 2 located above the longitudinal axis L is shown in the figure.

[0029] The sealing assembly 2 includes a seal 3 and a piston 4, which can slide axially relative to the longitudinal axis L within the housing 1. The sealing assembly 2 seals the first space 6 against the second space 7. For this purpose, the seal 3 includes a plurality of protrusions 3a that are sealingly connected to the piston 4. In practice, hydraulic fluid is applied to the first space 6 to displace the piston 4 against the second space 7. In this way, the piston 4 can actuate a disengagement bearing or several disengagement forks or shift forks (not shown in the figure) to open or close the clutch or engage or disengage a gear.

[0030] The seal 3 includes a first sealing lip 8 and a second sealing lip 9. As can be seen, the first sealing lip 8 sits against the housing 1 or the inner wall of the housing 1, and thus seals the two spaces 6, 7 against each other. The second sealing lip 9, extending from the seal 3 against the first radial piston wall 10, is pre-tensioned against the first radial piston wall 10, and the pressure of the hydraulic fluid in the first chamber 6 is below a predetermined limit pressure p. G This ensures that no fluid can penetrate into the second space 7.

[0031] As can be seen in the figure, the first radial piston wall 10 extends almost to the housing 1 in the radial direction, creating a small distance A. This radial distance A allows fluid to penetrate into the second sealing lip 9. The second radial piston wall 11 extends further toward the housing 1 in the radial direction than the first radial piston wall 10. In the illustrated embodiment, the first radial piston wall 10 has a flattened radial end 10a, while the second radial piston wall 11 has a similarly flattened radial end 11a. The radial distance A corresponds to the difference between the radial end 11a and the radial end 10a.

[0032] The first radial piston wall 10 and the second radial piston wall 11 define the groove 12 of the piston 4, and the seal 3 is fitted into the groove. As already mentioned, Figure 1 A state is shown in which the pressure of the hydraulic fluid in the first chamber 6 is less than a predetermined limit pressure p. G In this state, fluid or air can penetrate into the groove 12 through a radial distance A, but only to the second sealing lip 9. Below the predetermined limit pressure p... G This seals the entry space 13 defined by the seal 3, the second sealing lip 9, and the first radial piston wall 10. In this way, fluid cannot penetrate into the bypass line 5 branching from the entry space 13. As can be seen, in the illustrated embodiment, the bypass line 13 extends around the groove 13 inside the piston 4 to the region of the upper radial end 11a of the second radial piston wall 11.

[0033] Now refer to Figure 2 According to an embodiment of the sealing assembly 2 of the present invention, the pressure of the hydraulic fluid in the first space 6 exceeds a predetermined limit pressure p. G In this state, the second sealing lip 9 pivots into the interior of the access space 13, thereby disengaging the second sealing lip itself from the first radial piston wall 10 and allowing hydraulic fluid to flow into and from the access space 13 to the bypass line 5. As indicated by the two arrows in the upper left of the figure, fluid flows between the housing 1 and the second radial piston wall 11 into the second chamber 7. In this way, a defined leakage flow can be achieved.

[0034] List of reference numerals

[0035] 1. Shell

[0036] 2 Sealing components

[0037] 3. Seals

[0038] 3a Protrusion

[0039] 4 Pistons

[0040] 5. Bypass pipeline

[0041] 6 First Space

[0042] 7 Second Space

[0043] 8 First sealing lip edge

[0044] 9 Second sealing lip edge

[0045] 10 First radial piston wall

[0046] 10a Radial outer end

[0047] 11 Second radial piston wall

[0048] 11a Radial outer end

[0049] 12 grooves

[0050] 13 Entering the space

[0051] 100 Hydraulic disconnect coupling device

Claims

1. A sealing assembly (2) comprising: - A piston (4) having a longitudinal axis L, the piston having at least two radial piston walls (10, 11) relative to the longitudinal axis L, namely a first radial piston wall and a second radial piston wall, a groove (12) being formed between the first radial piston wall and the second radial piston wall. - A seal (3), which is received in the groove (12) and has a first sealing lip (8) extending radially outward beyond the radial piston walls (10, 11). Its features are, The first radial piston wall (10) extends radially outward less than the second radial piston wall (11), and the second sealing lip (9) is below the predetermined limit pressure p acting on the second sealing lip. G The piston (4) is sealed against the first radial piston wall (10) and together with the first radial piston wall, seals the entry space (13). A bypass line (5) within the piston (4) extends from the entry space at least partially around the groove (12), wherein the second sealing lip (9) is at a pressure higher than the predetermined limit pressure p. G Under pressure, it pivots radially inward, causing the access space (13) to open, and hydraulic fluid flows from the access space into the bypass line.

2. The sealing assembly (2) according to claim 1, characterized in that, The first radial piston wall (10) has a flattened radial outer end (10a) and the second radial piston wall (11) has a flattened radial outer end (11a), wherein there is a radial distance A>0 between the radial outer ends (10a, 11a).

3. The sealing assembly according to claim 2, characterized in that, The radial distance A is less than 1 / 3 of the radial range of the groove (12).

4. The sealing assembly (2) according to claim 2, characterized in that, The bypass line (5) extends from the access space (13) to the radial outer end (11a) of the second radial piston wall (11).

5. The sealing assembly (2) according to any one of claims 1 to 4, characterized in that, The predetermined ultimate pressure p G Between 0.2 bar and 5 bar, and including both values.

6. The sealing assembly according to any one of claims 1 to 4, characterized in that, The second sealing lip (9) and the sealing element (3) are formed as one piece.

7. The sealing assembly (2) according to any one of claims 1 to 4, characterized in that, The bypass line (5) extends from the access space (13) to the area between the second radial piston wall (11) and the first sealing lip (8).

8. The sealing assembly (2) according to any one of claims 1 to 4, characterized in that, There are two or more bypass lines (5).

9. A disconnection system (100) having a housing (1) having a first space (6) and a second space (7) defined in an axial direction by a sealing assembly (2) according to any one of claims 1 to 8, wherein the piston (4) of the sealing assembly (2) is displaceably mounted in the housing (1) in the axial direction, and the first space (6) is designed to be pressurized by hydraulic fluid during operation.

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