Vibration damper with a hydraulic end stop

Abstract

Vibration damper (1) with a hydraulic end stop (27; 29), comprising a cylinder (3) filled with damping medium in which a piston rod (5) is guided axially movably, wherein a first piston (9) is arranged on the piston rod (5), which divides the cylinder (3) into a working chamber (11; 13) on the piston rod side and a working chamber (11; 13) further away from the piston rod, wherein a pressure cylinder (29) is arranged in at least one of the working chambers (13), into which a second piston (27) arranged on the piston rod (5) moves depending on the stroke, wherein the pressure cylinder (29) is formed by a sleeve (39) separate from the cylinder (3), which forms an annular space (51) with the cylinder (3), which represents a connecting channel to a further working chamber (59), through which the damping medium from the working chamber (11; 13) on the piston rod side or further away from the piston rod13) is displaced, wherein the pressure cylinder (29) has at least one wall region (75) which is radially movable in the direction of the cylinder (3) and narrows the cross-section of the annular space (51) depending on the pressure level inside the pressure cylinder (29), characterized in that the pressure cylinder (29) is formed by a rigid support (39) and an elastic insert (79), wherein the rigid support (39) has at least one window-like opening (81) which is covered by the elastic insert (79) and the elastic insert (79) is arranged inside the pressure cylinder (29).

Description

[0001] The invention relates to a vibration damper with a hydraulic end stop according to the preamble of patent claim 1.

[0002] DE 10 2019 206 510 A1 discloses a vibration damper with a hydraulic end stop. A separate pressure cylinder is arranged within a cylinder. A second cylinder, attached to the piston rod, engages with the cylinder depending on the stroke, thereby displacing damping medium from the pressure cylinder against the retraction movement. The pressure cylinder is designed as a rigid body with respect to the compressive forces that occur. The use of a pressure relief valve is optionally provided.

[0003] Between the pressure cylinder and the cylinder, there is an annular space that serves as a drainage channel for the damping medium displaced from a working chamber remote from the piston rod toward a bottom valve. The achievable damping force is stroke-dependent due to the additional piston in conjunction with the pressure cylinder, and speed-dependent due to the valves present on a conventional first piston and the second piston.

[0004] From the generic document DE 10 2004 008 956 A1, a hydraulic tension stop is known which has a radially elastic pressure cylinder which, when a piston rod-side displacer is moved in above a defined working pressure, carries out an expansion movement which is supported by a working cylinder.

[0005] FR 1 194 935 A describes a vibration damper with a pressure cylinder in the working chamber remote from the piston rod. The pressure cylinder is formed by an elastomer element that influences the function of a piston valve upon contact with the piston valve.

[0006] DE 26 19 176 A1 discloses a gas spring that has a pressure cylinder with a radially elastic sealing attachment in the working chamber remote from the piston rod. The sealing attachment interacts with a piston rod section as a displacer within the pressure cylinder.

[0007] In the design of a vibration damper according to DE 11 2016 000 630 T5, a pressure cylinder is arranged within a working chamber remote from the piston rod, which has a smaller inner diameter than an elastic sealing ring of a displacer on a piston rod.

[0008] The object of the present invention is to improve the adaptability of the damping force characteristic to a target function.

[0009] The problem is solved by patent claim 1.

[0010] With the function of narrowing the annular space, it acts like an additional damping valve, so that in addition to the damping valves on the first and second pistons, a third valve is available for designing a damping force characteristic curve of the vibration damper.

[0011] The elastic insert can be clamped or vulcanized. Furthermore, a wide variety of applications can be achieved with a standardized rigid carrier and the associated inserts.

[0012] Depending on the pressure level, the size of the window-like opening and the elasticity of the support, a required expansion of the pressure cylinder or reduction of the annular space cross-section can be achieved.

[0013] The elastic insert is pushed through the opening.

[0014] The invention will be explained in more detail with reference to the following description of the figures.

[0015] It shows: Fig. 1 Longitudinal section through a vibration damper with hydraulic end stop Fig. 2 Detail of the Fig. 2 Fig. 3 and 4 Cross section of the printing cylinder from Fig. 2 Fig. 5 Inventive variant of the vibration damper with an elastic insert within the pressure cylinder Fig. 6 Alternative to Fig. 5

[0016] The invention is described using the example of a vibration damper 1 in the design of a twin-tube vibration damper, but the invention is not limited to this design.

[0017] The vibration damper 1 comprises a cylinder 3 completely filled with a damping medium, in which a piston rod 5 is guided for axial movement. A piston rod guide 7 closes one end of the cylinder 3. A first piston 9 is attached to the piston rod 5, the nominal diameter D1 of which is adapted to the inner diameter Z1 of the cylinder 3 and which divides the cylinder 3 into a working chamber 11; 13 on the piston rod side and a working chamber 11; 13 remote from the piston rod. The first piston 9 has a damping valve 15, which generates a damping force during a retraction movement, and a damping valve 17, which generates a damping force during an extension movement of the piston rod 5.

[0018] In this figure, an optionally usable rebound stop 19 is arranged in the piston rod-side working chamber 11. This rebound stop spring 21 is supported on the piston rod guide 7. In the direction of the piston 9, the rebound stop spring 21 has a spring plate 23, which, depending on the stroke, comes into operative connection with a drive ring 25 on the piston rod 5.

[0019] Furthermore, a second piston 27 is attached to the piston rod 5, which plunges into a pressure cylinder 29 with a pressure chamber 31 depending on the stroke. (see also Fig. 2). The second piston 27 has at least one throttle opening 33 through which the damping medium displaced by the second piston 27 from the pressure chamber 31 can flow into the working chamber 13 remote from the piston rod. To avoid extreme damping force jumps, the pressure cylinder 29 has at least one inlet slope 35, which can also be designed in combination with a throttle groove 37. The pressure cylinder 29 represents a separate component with respect to the cylinder 3 and has an inner diameter Z2 that is smaller than the inner diameter Z1 of the cylinder 3. Consequently, the second piston 27 also has a smaller nominal diameter D2 than the first piston 9.

[0020] The pressure cylinder 29 has a sleeve 39 and a base 41, with the base 41 resting on a support base 43 of a base 45. The base 45, in turn, rests with its annular web 47 on a base valve body 49, which defines the end of the cylinder 3. Between the inner wall of the cylinder 3 and the outer wall of the pressure cylinder 29 or the sleeve 39, there is an annular space 51, which provides a flow connection between the working chamber 13, remote from the piston rod, and the base valve body 49. For this purpose, the base 45 has at least one passage opening 53 radially outside the sleeve 39 of the pressure cylinder 29. This design of the pressure cylinder is by no means mandatory for the use of the invention. It is also possible to use a pressure cylinder 29 in which the sleeve 39 and the base 45 form a single structural unit, for example in the form of a plastic or even a cast or forged part.Furthermore, different designs of the pressure cylinder for fastening within the cylinder 3 would also be possible for the use of the invention.

[0021] The base valve body 49 comprises a damping valve 55, which becomes active when flow from the working chamber 13 remote from the piston rod passes through, allowing the volume displaced by the piston rod 5 to pass through. In addition, the base valve body 49 has a check valve 57, which opens when flow originates from a compensation chamber 59 into the working chamber 13 remote from the piston rod, without generating any significant damping force. The compensation chamber 59 is delimited by a container tube 61 enclosing the cylinder 3, which, together with an outer wall of the cylinder 3, forms the annular space, which is partially filled with damping medium and partially with a gas. The base valve body 49 rests on a base 63 of the container tube 61.The bottom 63 of the container tube 61, the container tube 61, and the piston rod guide 7 form a tensioning chain for the cylinder 3, the base 45, and the base valve body 49, since the cylinder 3 is axially supported on the annular web 47 of the base 45. Thus, the base 45 is axially fixed in both directions.

[0022] Between the pressure cylinder 29 and the base 45 there is a holding connection 65, which is designed within a cross-section 67 delimited by the sleeve 39. The cross-section 67 is determined by the outer contour of the sleeve 39. In the Fig. 1, the retaining connection 65 is formed by a riveted joint. A rivet 69 connects these two parts centrally within the base 41 and the support base 43.

[0023] During a compression movement of the piston rod 5 within a certain magnitude, only the first piston 9, or the damping valve 15 for the retraction direction, is active. The second piston 35 is then always located axially outside the pressure cylinder 29. If this comfort range is exceeded, the second piston 27 retracts into the pressure cylinder 29, reducing the volume of the pressure chamber 31 and displacing damping medium from the pressure chamber 31 into the working chamber 13 remote from the piston rod, so that both the first and the second piston 9; 27 with their damping valves 13; 33 generate a significantly greater damping force, since both damping valves 13; 33 are hydraulically connected in parallel. The annular chamber 51 then acts as a flow connection between the working chamber 13 remote from the piston rod and the compensation chamber 59, which functionally also represents a working chamber of the vibration damper 1.

[0024] Especially in the context of Fig. 2, Fig. 3 and Fig. 4 that the pressure cylinder 29 has at least one wall region 75 which is designed to be radially movable in the direction of the cylinder 3 and which narrows the cross-section of the annular space 51 depending on the pressure level within the pressure cylinder 29. The effect that the pressure cylinder 29 is designed to be radially elastic is utilized in that the radially elastic wall region 75 is formed by a partial reduction in the wall thickness of the pressure cylinder 29. The cross-section of the annular space 51 thus acts like a third damping valve 77 in addition to the damping valves 15; 33 on the first and second pistons 9; 27. The effect of the throttle cross-section depends on the pressure level within the pressure cylinder, i.e., depends on the retraction speed of the second piston 27 into the pressure cylinder 29. The third damping valve 77 ensures a further progression in the damping force characteristic curve of the vibration damper. This progression can, for example,be used to slightly reduce the damping force provided by the second piston 27 in order to achieve an increase in driving comfort, but on the other hand to have additional damping force available with the third damping valve 77 for particularly critical driving situations.

[0025] In this design, the radially elastic wall area extends over the entire stroke range of the second piston 27. Consequently, the maximum radial expansion is possible at the moment the second piston plunges into the pressure cylinder 29. If the vibration damper is shortened further, the supporting force of the vehicle suspension spring increases. Consequently, the damping force could be reduced.

[0026] In addition to the possibility of reducing the wall thickness, the pressure cylinder 29 can also be formed from a rigid support and an elastic insert 79, as also shown in Fig. 3 is shown in principle. In the version of the pressure cylinder 29 according to Fig. 5, the elastic insert 79 is arranged within the pressure cylinder 29. The rigid support or sleeve 39 has at least one window-like opening, which is covered by the elastic insert 79 in the direction of the annular space 51. When the second piston 27 plunges into the pressure cylinder 29, the pressure increases. Since the pressure within the pressure cylinder 29 is higher than in the annular space 51 due to the valve design of the damping valves 15; 33 and the damping valve 55 on the base valve body 49, the sleeve-shaped elastic insert 79 deforms and expands via the window-like openings 81 into the annular space 51, the cross-section of which is thereby reduced. Several openings 81 can be used, which are designed axially outside the stroke range of the piston 27. Thus, the radially elastic region 75 of the pressure cylinder is also arranged axially outside a stroke range of the second piston 27.Consequently, the expansion force acting on the elastic region is also constant at constant pressure within the pressure cylinder 29. The reduction of the cross-section in the annular space 51 is thus independent of the stroke position of the second piston 27 within the pressure cylinder 29. This design of the second pressure cylinder 29 can also be useful for adapting the damping characteristics of the vibration damper to a target specification.

[0027] The execution according to Fig. 6 follows the construction principle Fig. 5. In an alternative embodiment, the elastic insert 79 is arranged on an outer surface 83 of the pressure cylinder 29. The elastic insert 79 can be mounted like a shrink tube.

[0028] Both in the Fig. 5 and in the Fig.6, the pressure cylinder 29 is equipped with a pressure relief valve 85 in the discharge direction to the compensation chamber 59. This pressure relief valve 85 can optionally be designed for a limit pressure at the damping valve 33 of the second piston 27, but also for a maximum expansion force of the pressure cylinder 29 in order to set a minimum cross-section of the annular chamber 51. Reference symbol 1 vibration damper 3 cylinders 5 Piston rod 7 Piston rod guide 9 first piston 11 piston rod side working chamber 13 Working space remote from the piston rod 15 Damping valve 17 Damping valve 19 Pull stop 21 Rebound stop spring 23 spring plates 25 Driving ring 27 second piston 29 printing cylinders 31 Printing room 33 Throttle opening 35 inlet slope 37 Throttle groove 39 sleeve 41 Floor 43 Support floor 45 bases 47 Ringsteg 49 Bottom valve body 51 Annular space 53 Passage opening 55 Damping valve 57 Check valve 59 Compensation space 61 Container pipe 63 Floor 65 Holding connection 67 Cross section 69 rivet 71 cones 73 rivet head 75 wall area 77 third valve 79 elastic insert 81 window-like opening 83 outer surface 85 Pressure relief valve

Claims

[1] Vibration damper (1) with a hydraulic end stop (27; 29), comprising a cylinder (3) filled with damping medium, in which a piston rod (5) is guided so as to be axially movable, wherein a first piston (9) is arranged on the piston rod (5), which divides the cylinder (3) into a working chamber (11; 13) on the piston rod side and a working chamber (11; 13) remote from the piston rod, wherein a pressure cylinder (29) is arranged in at least one of the working chambers (13), into which a second piston (27) arranged on the piston rod (5) moves in a stroke-dependent manner, wherein the pressure cylinder (29) is formed by a sleeve (39) which is separate from the cylinder (3) and which forms an annular chamber (51) with the cylinder (3) which represents a connecting channel to a further working chamber (59), via which the damping medium is discharged from the working chamber (11; 13) on the piston rod side or remote from the piston rod.13), wherein the pressure cylinder (29) has at least one wall region (75) which is designed to be radially movable in the direction of the cylinder (3) and narrows the cross section of the annular space (51) depending on the pressure level within the pressure cylinder (29), ; characterized by in that the printing cylinder (29) is formed by a rigid support (39) and an elastic insert (79), wherein the rigid support (39) has at least one window-like opening (81) which is covered by the elastic insert (79) and the elastic insert (79) is arranged within the printing cylinder (29). [2] Vibration damper according to claim 1, characterized by that the pressure cylinder (29) is equipped with a pressure relief valve (85) in the discharge direction.

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