Hydraulic assembly pressure accumulator

Abstract

To further improve a pressure accumulator of a liquid pressure assembly of a vehicle brake device, especially improve the behavior of a pressure accumulator at a cut-off border portion of a medium between a fluid chamber and an accumulation chamber.SOLUTION: In a pressure accumulator (34) of a liquid pressure assembly of a vehicle brake device equipped with a piston (44) and a packing sealing the piston (44) with respect to a piston guide (42), the packing is configured to include an elastomer ring (64) held by the piston (44). A layer ring (66) is provided, which is held by the piston (44) and is pressed against the piston guide (42) by the elastomer ring (64).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a pressure accumulator for a hydraulic assembly of a vehicle braking system, comprising a piston and a packing sealing the piston against a piston guide, the packing being configured to comprise an elastomer ring carried by the piston. [Background technology]

[0002] It is known that in vehicle brake systems, for example in passenger cars or trucks, hydraulic assemblies are used to distribute hydraulic fluid to several associated vehicle brakes. Furthermore, for this purpose, it is known to provide one or more pressure accumulators in the vehicle brake system, particularly in the hydraulic assembly itself, for controlling the brake pressure in the vehicle brakes. These pressure accumulators are used, among other things, to improve the response characteristics of the associated brakes. These accumulators have a piston that is movably displaceable by a piston guide. The piston separates a fluid chamber side, where the brake fluid is located, from a reservoir chamber side, where a pretensionable element, such as a gas cushion and / or a mechanical spring, is located. These pressure accumulators are also known, among other things, as low-pressure accumulators. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to further improve such pressure accumulators of hydraulic assemblies of vehicle brake systems, in particular to improve the behavior of the pressure accumulator at the media separation boundary between the fluid chamber and the accumulator chamber. [Means for solving the problem]

[0004] According to the present invention, there is provided a pressure accumulator for a hydraulic assembly of a vehicle brake system, comprising a piston and a packing sealing the piston against a piston guide, the packing being configured such that the packing comprises an elastomer ring held by the piston, and further comprising a layer ring held by the piston and pressed against the piston guide by the elastomer ring. By layer ring, it is understood that the ring forms a "layer" between the piston guide and the elastomer ring, i.e., the ring thickness in the radial region between the piston guide and the elastomer ring is smaller than the ring width in the axial direction. This means that the ring is relatively thin in the radial direction and relatively wide in the axial direction, i.e., the ring is thinner in the radial direction than its length in the axial direction, particularly in this region.

[0005] The solution according to the invention transmits the pretension of the elastomer ring to the layer ring, so that the contact force transmitted by the elastomer ring is reproduced in the sealing gap between the layer ring and the piston guide. This allows for lower friction between the packing and the piston guide compared to conventional O-ring packings. Therefore, the effect of a low-friction lip packing can be achieved in terms of the formation of a lubricating film on the piston guide, without the disadvantages of a lip packing. Therefore, for a conventional lip packing, higher dimensional requirements would have to be imposed on the retention of the packing on the piston than are necessary for the solution according to the invention. The layer ring according to the invention is preferably made of a material that is less elastic than the elastomer ring, in particular its modulus of elasticity (E module) being greater than that of the elastic ring. Preferably, the layer ring has a resistance of 500 N / mm. 2 Above 700N / mm 2 The elastomer ring preferably has an E module of 100 N / mm 2 Below, especially 70N / mm 2 It has the following E modules:

[0006] In a further advantageous embodiment of the solution of the present invention, the layer ring has an L-shaped cross section and is provided with retaining legs facing the piston. The retaining legs are used to securely fix the layer ring of the present invention on the piston. This ensures a precise relative position between the elastomer ring and the layer ring, particularly over the entire service life of the pressure accumulator of the present invention. Such a layer ring preferably also has sealing legs that abut against the piston guide, forming the aforementioned layer between the elastomer ring and the piston guide. The advantageous retaining legs of the present invention are preferably held in the piston in a piston groove. An elastomer ring is also preferably present in this piston groove, where the retaining legs are particularly advantageously pressed axially against the side wall of the piston groove by the elastomer ring.

[0007] Alternatively, the layer ring may be preferably T-shaped in cross section and have retaining legs directed toward the piston, which allows the retaining legs to be wider in the axial direction than in an L-shaped layer ring, which provides further advantages in terms of the frictional and sliding properties of the sealing device between the piston and the piston guide.

[0008] Preferably, the retaining legs are arranged on the side of the elastomer ring facing the reservoir chamber of the piston. This holds the layer ring on the reservoir chamber side of the elastomer ring, so that the layer ring is drawn in when the piston moves into the reservoir chamber and pushed out when the piston moves out. This supports the particularly advantageous effect of the layer ring with respect to the formation of a lubricating film, which is similar to that of a lip seal. When the piston moves in, a lubricating film is drawn in and formed by the hydraulic fluid, and when the piston moves out, this lubricating film is pushed out again.

[0009] Furthermore, the layer ring according to the invention is preferably made of plastic, where plastic in the present invention exclusively refers to thermoplastic and thermosetting plastics, which is used in particular to distinguish it from metals or other non-plastic materials.

[0010] In other respects, the elastomer ring according to the invention is preferably designed asymmetrically in cross section, which in particular ensures that the lubricating film between the piston and the piston guide does not form with the same strength or thickness in the two radial directions of the piston's movement. Rather, the asymmetric sealing also results in an asymmetric contact pressure profile for controlling the amount of leakage during the piston's reciprocating movement.

[0011] In this case, the elastomer ring is preferably configured with a steeply inclined sealing flank from its contact area with the layer ring toward the piston's fluid chamber. By steeply inclined sealing flank is meant a flank angle between the sealing flank surface and the piston guide of between 12° and 45°, in particular between 15° and 30°, in cross section. The steeply inclined sealing flank serves to displace hydraulic fluid from the piston guide when the piston leaves the reservoir chamber.

[0012] Additionally or alternatively, the asymmetric elastomer ring is configured with a flat sealing flank extending from its contact area with the layer ring toward the piston reservoir chamber. By flat sealing flank is meant a flank angle between the surface of the sealing flank and the piston guide, in cross section, of between 0° and 10°, in particular between 2° and 8°. The flat sealing flank is used to selectively remove a certain amount of hydraulic fluid from the piston guide when the piston enters the reservoir chamber.

[0013] The elastomer ring of the pressure accumulator according to the invention is preferably held in the piston by a piston groove, which can be manufactured to relatively loose tolerances, thereby reducing manufacturing costs.

[0014] Furthermore, in the pressure accumulator according to the invention, the piston is also made of plastic, in particular of fiber-reinforced plastic, which further reduces production costs. At the same time, the solution according to the invention ensures that such pistons are sufficiently free from wear, in particular that the wear of the piston surface does not expose glass fibers. Otherwise, additional guide rings or the like would be required to prevent wear, which would entail a large structural length for the piston.

[0015] Next, an embodiment of the solution according to the invention will be explained in more detail with the aid of the accompanying schematic drawings. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a hydraulic circuit diagram of a vehicle brake device having an internal pressure accumulator. [Figure 2] FIG. 1 shows a longitudinal section through a first pressure accumulator according to the state of the art. [Figure 3] FIG. 1 shows a longitudinal section of a second pressure accumulator according to the state of the art. [Figure 4] 1 is a longitudinal sectional view of a first embodiment of a pressure accumulator according to the present invention. FIG. [Figure 5] FIG. 4 is a longitudinal sectional view of a second embodiment of a pressure accumulator according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] FIG. 1 shows an example of a vehicle braking system 10, as commonly used and conventionally used in modern automobiles. The vehicle braking system 10 includes four wheel brakes 12, with both wheel brakes 12 shown on the left side of FIG. 1 associated with the front wheels of each vehicle, and both wheel brakes 12 shown on the right side of FIG. 1 associated with the rear wheels of each vehicle. Alternative arrangements are possible. The vehicle braking system 10 also includes a number of hydraulic lines 14 to which various functional assemblies are connected. These assemblies include a brake actuator 16, which includes a brake master cylinder, a brake booster, and a brake pedal; a main on-off valve 18; a switching valve 20; a damper 22; a reverse pump 24; a motor 26; an intake valve 28; a discharge valve 30; a check valve 32; and a pressure accumulator 34. The pressure accumulator 34 is connected to the associated hydraulic line 14 to conduct fluid between the discharge valve 30 and the check valve 32. The pressure accumulators are adapted so that the hydraulic fluid or brake fluid conveyed from the brake actuators 16 to the wheel brakes 12 and present in these accumulators can be quickly drained again from the wheel brakes 12 by means of, in particular, the drain valves 30 .

[0018] 2 and 3 show two embodiments of a conventional pressure accumulator 34. Each has an aluminum housing 36, which defines a cylindrical fluid chamber 38 therein. The fluid chamber 38 is defined by an end wall 40 and a cylindrical piston guide 42, in which a piston 44 is slidably supported. The piston 44 thus separates the reservoir chamber 46 from the fluid chamber 38. A metal coil spring 48 is arranged in the reservoir chamber 46 and is supported at its end by a metal cover 50, which thus urges the piston 44 toward the fluid chamber 38. The fluid chamber 38 is conductively connected to the remaining hydraulic line 14 by a line 52. The fluid chamber 38 is thereby filled with the brake fluid also present in the hydraulic line 14.

[0019] The pistons 44 are furthermore sealed against the piston guide 42 by means of a seal 54, which in the embodiment according to Fig. 2 is provided in the form of an O-shaped elastomer ring in cross section. In contrast, in the embodiment according to Fig. 3, the seal 56 is configured as a V-shaped elastomer ring, which forms a lip seal with one of its sealing legs in the piston guide 42. The elastomer ring is supported in each associated piston 44 in a piston groove 58, which is rectangular in cross section and extends around the circumference of the piston. In this case, in the embodiment according to Fig. 3, each piston 44 requires two guide rings 60 made of a harder plastic than the elastomer ring in its axial end region, which results in a longer axial length of the piston 44 than in the embodiment according to Fig. 2.

[0020] 4 and 5 each show an embodiment of a pressure accumulator 34 according to the invention, which has a housing 36, a fluid chamber 38, an end wall 40, a piston guide 42, a piston 44, an accumulation chamber 46, a spring 48, a cover 50 and a tube 52 corresponding to the embodiment according to FIGS. 2 and 3.

[0021] However, in these embodiments, unlike the previous embodiment, a seal is formed between the piston 44 and the piston guide 42. In both embodiments, this seal is provided by a layer ring 66 made of plastic, positioned radially outward from the elastomer ring 64, which is held by the piston 44 and pressed against the piston guide 42 by the elastomer ring 64.

[0022] In the embodiment according to Fig. 4, the layer ring 66 is configured L-shaped in cross section with a retaining leg 68 facing the piston 44 and a sealing leg 70 extending parallel to the piston guide 42. The sealing leg 70 starts from the retaining leg 68 and faces the fluid chamber 38. The embodiment according to Fig. 5 shows a layer ring 66 that is T-shaped in cross section and has, in addition to the sealing leg 70 and the retaining leg 68, a sliding leg 72 facing parallel to the piston guide 42 towards the reservoir chamber 46. The sliding leg 72 is thus likewise located between the outer periphery of the piston 44 and the piston guide 42 and, like the sealing leg 70, prevents wear of the piston material as the piston 44 reciprocates inside the piston guide 42.

[0023] The elastomer ring 64, which thus presses the layer ring 66 against the piston guide 42, thus forms a sealing connection between the piston 44 and the piston guide 42 and simultaneously prevents wear at the piston guide 42. In this case, the elastomer ring 64 is asymmetrically configured in cross section, i.e., has sealing flanks with different inclinations toward the layer ring 66, i.e., the sealing flanks are not radially axially symmetrical in cross section. The elastomer ring 64 is configured with a steeply inclined sealing flank 74 from its contact area with the layer ring 66 toward the fluid chamber or fluid chamber 38, and a flat sealing flank 76 from its contact area with the layer ring 66 toward the reservoir chamber or reservoir chamber 46. The flat sealing flank 76 has a flank angle 78 of 10° between its surface and the piston guide 42, as viewed in cross section. The steeply inclined sealing flank 74 thus has a flank angle 80 of 25°.

[0024] The elastomer ring 64, like the packings 54 and 56, is fixedly held on the piston 44 by means of a piston groove 58. Due to the sealing and simultaneously anti-friction effect of the elastomer ring 66, the piston groove 58 can be manufactured with relatively loose dimensional tolerances. It is therefore possible, in particular, for the piston 44 according to FIGS. 4 and 5 to be manufactured from fiber-reinforced plastic. [Explanation of symbols]

[0025] 10 Vehicle braking system 12 Wheel brakes 14 Hydraulic pipe 16 Brake actuator 18 Main shut-off valve 20 Switching valve 22 Damper 24 Reverse pump 26 Motor 28 Suction valve 30 Discharge valve 32 Check valve 34 Pressure Accumulator 36 Housing 38 Fluid chamber 40 End Wall 42 Piston guide 44 Piston 46 Accumulation chamber 48 Spring 50 Cover 52 tube 54 Packing (Elastomer ring O-shaped) 56 Packing (elastomer ring V-shaped) 58 Piston groove 60 Guide Ring 62 Packing according to the present invention 64 Elastomer Ring 66-layer ring 68 Holding leg 70 Sealing legs 72 Sliding legs 74 Steep Sealing Flank 76 Flat Sealed Legs 78 Flank angle 80 flank angle

Claims

1. A pressure accumulator (34) for a hydraulic assembly of a vehicle brake system (10) comprising a piston (44) and a packing sealing the piston (44) against a piston guide (42), the packing being configured to include an elastomer ring (64) retained by the piston (44), a layer ring (66) held by the piston (44) and pressed against the piston guide (42) by the elastomer ring (64); The elastomer ring (64) is held in the piston (44) by a piston groove (58), A pressure accumulator in which the retaining legs (68) of the layer ring (66) are pressed axially against the side walls of the piston groove (58) by the elastomer ring (64).

2. 2. The pressure accumulator according to claim 1, wherein the layer ring (66) is configured L-shaped in cross section and has the retaining legs (68) directed towards the piston (44).

3. 2. The pressure accumulator according to claim 1, characterized in that the layer ring (66) is configured T-shaped in cross section and has the retaining legs (68) directed towards the piston (44).

4. 4. The pressure accumulator according to claim 2 or 3, characterized in that the retaining legs (68) are arranged on the side of the elastomer ring (64) that faces the storage chamber side of the piston (44).

5. Pressure accumulator according to any one of claims 1 to 4, characterized in that the layer ring (66) is made of plastic.

6. 6. Pressure accumulator according to claim 1, characterized in that the elastomer ring (64) is configured asymmetrically in cross section.

7. 7. The pressure accumulator according to claim 1, wherein the elastomer ring (64) is configured with a steeply inclined sealing flank (74) from its abutment area with the layer ring (66) to the fluid chamber side of the piston (44).

8. 8. The pressure accumulator according to claim 1, wherein the elastomer ring (64) is configured with a flat sealing flank (76) from its abutment area with the layer ring (66) to the accumulation chamber side of the piston (44).

9. Pressure accumulator according to any one of claims 1 to 8, characterized in that the piston (44) is made from plastic, in particular from fiber-reinforced plastic.

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