CN110005657B

CN110005657B - Hydraulic cylinder

Info

Publication number: CN110005657B
Application number: CN201811517787.3A
Authority: CN
Inventors: B.阿尔诺德; F.维茨贝格尔; M.容克; N.恩格勒特
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-12-13
Filing date: 2018-12-12
Publication date: 2023-05-30
Anticipated expiration: 2038-12-12
Also published as: CN110005657A; DE102017222552A1

Abstract

A hydraulic cylinder is disclosed having a cylinder housing in which a piston with a piston rod is slidingly guided. The piston rod is guided out of the cylinder housing through the housing opening. A sealing element is arranged in the housing opening, said sealing element surrounding the piston rod. The sealing element has at least one pressure groove on the side of the outer surface of the sealing element, which pressure groove is fluidically connected to a region between the sealing element and the piston rod, wherein the region is arranged at the height of the pressure groove as seen in the longitudinal direction. Alternatively or additionally, the piston may have a piston seal surrounding the piston. The piston seal may have a pressure groove at its inner surface, which is then fluidically connected to the region between the piston seal and the cylinder housing at the level of the pressure groove, as seen in the longitudinal direction.

Description

Hydraulic cylinder

Technical Field

The present invention relates to a hydraulic cylinder.

Background

Hydraulic cylinders or hydraulic cylinders (Hydrozylinder) are known from the prior art, which have a cylinder liner with a head and a bottom. A piston is slidingly guided in the cylinder sleeve, which separates a first pressure chamber from a second pressure chamber. At least one piston rod extends from the piston, through the head, and extends outwardly.

A hydraulic cylinder is known from DE 10 2013 212 224, in which a gap sleeve is provided in the region of the head, said gap sleeve surrounding the piston rod. The slit sleeve forms a slit seal with the piston rod. The gap sleeve is acted upon radially inward by adjacent pressure chambers at the outer surface of the gap sleeve locally with pressure medium. The inner surface of the gap sleeve is likewise acted upon by a pressure medium, wherein the pressure acting on the inner surface decreases linearly as seen in the longitudinal direction and as seen in the direction from the inside outwards. The gap sleeve disadvantageously involves a metal part which is precise and produced at high cost. The metal part is extremely sensitive to pressure deformation.

Alternatively to the slit sleeve, an elastomer seal is provided, but the piston rod disadvantageously rubs against the elastomer seal. Furthermore, the elastomeric seals have relatively high wear.

Disclosure of Invention

In contrast, the invention is based on the following task: a hydraulic cylinder is achieved which is cost-effective and has relatively little or no friction and has relatively little or no wear.

This object is achieved by a hydraulic cylinder having a cylinder housing and a piston rod. The piston rod is guided from the cylinder housing through a housing opening, wherein an annular sealing element is arranged in the housing opening between the piston rod and the cylinder housing, which sealing element surrounds the piston rod, and/or wherein the piston rod extends away from a piston guided in the cylinder housing, which piston is surrounded by an annular piston seal. According to the invention, at least one pressure groove is provided, which is delimited by the outer surface of the sealing element and which is connected by a fluid path to a pressure region delimited by the inner surface of the sealing element, wherein the pressure region is located radially inside the pressure groove as seen from the pressure groove, and/or at least one pressure groove is provided, which is delimited by the inner surface of the piston seal and which is connected by a fluid channel to a region delimited by the outer surface of the piston seal, wherein the region is located radially outside the pressure groove as seen from the pressure groove.

The invention also relates to other advantageous developments.

According to the invention, a cylinder, in particular a hydraulic cylinder, is provided having a cylinder housing. The piston rod is guided from the cylinder housing through the housing opening. An annular sealing element is preferably arranged between the piston rod and the cylinder housing in the housing opening. The sealing element may enclose the piston rod. In addition, it can be provided that the piston rod extends away from a piston guided in the cylinder housing, which can be surrounded by an annular piston seal, which is arranged, for example, on the piston. At least one pressure groove (Drucktsche) is advantageously provided. The pressure groove may furthermore be defined by an outer surface of a sealing element surrounding the piston rod. The pressure groove may be connected by a fluid path to a sealing area defined by the inner surface of the sealing element. Furthermore, the pressure groove may be sealed, for example. The sealing region is located radially inside the pressure groove, as seen from the pressure groove. The sealing regions and the pressure grooves may thus be arranged, for example, in rows one after the other, seen in the radial direction. The sealing area is preferably defined by the sealing element and the piston rod. Alternatively or additionally, a pressure groove may be provided, which is delimited by an inner surface of a piston seal surrounding the piston. The pressure groove may then be further connected by a fluid path to a sealing area defined by an outer surface of the piston seal. The sealing regions are then preferably arranged radially outside the pressure groove, as seen from the pressure groove, wherein the pressure groove and the sealing regions can be arranged in rows, as seen in the radial direction. The sealing area is preferably defined by the sealing element and by the cylinder housing.

This solution has the advantage that the sealing elements and/or the piston seals are substantially pressure-balanced in the region of their pressure grooves. Depending on the configuration of the pressure grooves and the number of pressure grooves, it is also possible, for example, to carry out a substantially complete pressure relief of the piston seal and/or the sealing element. If a gap seal is provided between the sealing element and the piston rod or between the piston seal and the cylinder housing, the gap seal can be formed by a corresponding embodiment of the at least one pressure groove or of the at least one respective pressure groove. The pressure groove can thus advantageously form a small gap, for example, with a defined leakage, wherein it is unnecessary to produce the sealing element and/or the piston seal precisely and at a high cost. In practice, the sealing element on the inner diameter and/or the piston seal on the outer diameter can be made less accurately, for example from an advantageous plastic, without thereby adversely affecting the gap seal. The gap seal can be set exactly as already explained above, due to the at least one pressure groove.

The pressure grooves described below may relate to pressure grooves for sealing sleeves and/or for piston seals. If a pressure tank is explained, the explanation also applies to a plurality or all of the pressure tanks.

The pressure groove is preferably sealed as seen in both longitudinal directions of the hydraulic cylinder. The pressure groove can thus be positively limited in the longitudinal direction. The sealing is preferably achieved by means of an additional sealing element. The pressure groove for the sealing element is then arranged between the outer surface of the sealing element, the inner surface of the cylinder housing or the inner surface of the head of the cylinder housing and the additional sealing element.

In a further embodiment of the invention, the or each pressure groove may be configured annularly and surround the sealing element and/or the piston seal. The pressure groove can be defined by two sealing elements in the form of sealing rings, seen in the longitudinal direction of the sealing sleeve and/or of the piston seal. In the case of a sealing element, the sealing ring may surround the sealing element at the outer periphery. In the case of a piston seal, the sealing ring can be arranged radially inside the piston seal.

In a further embodiment of the invention, it can be provided that the pressure groove is connected to the pressure region during the sealing of the sealing element by a fluid channel formed in the sealing element, which is extremely simple in terms of installation technology. Alternatively or additionally, it can be provided that the pressure groove is connected to the pressure region during the sealing of the piston by a fluid channel formed in the sealing of the piston. Furthermore, it is technically simple to design the fluid channel as a radial bore or a radial channel, which can be produced in a simple manner. It is furthermore conceivable to provide a plurality of fluid channels or fluid paths for the pressure tank, in order to provide an extremely rapid pressure equalization between the pressure in the pressure tank and the pressure in the pressure region. The plurality of fluid paths are preferably arranged on a partial circle (Teilkreis), i.e. are distributed uniformly in the circumferential direction and may be identically configured, which results in a uniform pressure loading of the sealing element and/or of the piston seal on the pressure groove. The fluid path is configured, for example, as a pore-forming star (Bohrungssterm).

In a preferred embodiment of the invention, a plurality of pressure grooves can be provided in the sealing element. Alternatively or additionally, a plurality of pressure grooves may be provided in the piston seal. In this way, different pressure levels can be formed in the pressure tank, for example, in order to set one or the sealing gap more precisely. Preferably, the plurality of pressure grooves are arranged in rows as seen in the longitudinal direction. This advantageously results in, for example, a substantially linear pressure drop being able to be produced over the pressure groove in the pressure region between the sealing element and the piston rod. The same applies to the pressure area between the piston seal and the cylinder housing. The linear or non-constant pressure profile in the sealing gap, seen from the inside to the outside in the longitudinal direction, can thus be compensated by one or more pressure chambers opposite the pressure region. For example, the expansion of the sealing element and/or of the piston seal, which is due to the linear pressure profile in the sealing gap, can be compensated for by a stepped pressure profile in the pressure groove or chamber, which resists the expansion. It is conceivable to provide a sealing element, in particular in the form of a common sealing ring, between the two pressure grooves, which is extremely simple in terms of equipment technology.

In a preferred manner, the sealing element has an annular recess, in particular cut out from the outer surface, for the sealing ring or for the individual sealing rings, so that the sealing rings can be fixed in a simple manner in terms of installation. Alternatively or additionally, it can be provided that the piston seal has an annular recess, in particular undercut from the inner surface, for the sealing ring or for the respective sealing ring. The sealing element with the sealing ring and/or the piston seal with the sealing ring can then form a unit which can be installed in a simple manner.

Preferably, the sealing element in the cylinder housing is inserted into an annular groove that opens radially inwards. It is conceivable to provide the annular groove in the cylinder head or in the guide sleeve of the hydraulic cylinder. The sealing element can then protrude radially inwards from the open annular groove. Alternatively or additionally, it may be provided that the piston seal in the piston is inserted into a radially outwardly open annular groove and protrudes radially outwardly from said annular groove. The sealing element and/or the piston seal is/are securely fastened in the hydraulic cylinder or in the piston by the annular groove.

The sealing element and/or the piston seal relates, for example, to a slit sleeve. The sealing element and/or the piston seal is preferably in particular, for example, configured as a hollow cylinder.

Drawings

Preferred embodiments of the invention are further explained below with the aid of the schematic drawings. The drawings show:

fig. 1 is a partial view of a hydraulic cylinder according to an embodiment in a longitudinal section in the region of its outlet opening;

fig. 2 is a partial view of a hydraulic cylinder according to a further embodiment in a longitudinal section in the region of the piston of the hydraulic cylinder; and

fig. 3 shows a part of the sealing element in a longitudinal section.

List of reference numerals:

1. a hydraulic cylinder;

2. a piston rod;

4. an outlet opening;

6. a cylinder housing;

8. an annular groove;

10; 54. a slit sleeve;

12 14, 16, 18;42 44, 46, 48; 56. a pressure tank;

20 50 sealing rings;

22. a fluid channel;

24, a step of detecting the position of the base; 52. a pressure region;

26. the pressure drops;

28. an end section;

30. a piston;

31. cylinder sleeve;

32 34 pressure chambers;

36. an outer surface;

38. an annular groove;

40. a piston seal;

58. a slit.

Detailed Description

Fig. 1 shows a hydraulic cylinder 1, which is shown schematically in dashed lines. The hydraulic cylinder has a piston rod 2 which protrudes from a cylinder housing 6 through an outlet opening 4. An annular groove 8 is hollowed out into the cylinder housing in the surface surrounding the piston rod 2. A sealing element in the form of a slit sleeve 10 is inserted into the annular groove. The slit sleeve is annular and surrounds the piston rod 2. The gap sleeve 10 defines

pressure grooves

12, 14, 16 and 18 with its outer surface. The pressure grooves are then each formed between the groove bottom of the annular groove 8 and the outer wall surface of the slot cover 10. The pressure grooves 12 to 18 are separated from each other by sealing rings 20, of which only one is provided with reference numerals for the sake of simplicity. The

pressure grooves

12 and 18 of the respective side face are then delimited laterally by sealing rings 20. The sealing rings 20 surround the gap sleeves 10 and are respectively placed into annular grooves on the outside of the gap sleeves 10. Furthermore, from each pressure channel 12 to 18, a fluid channel 22 extends radially inwards, of which only one is provided with reference numerals for the sake of simplicity. The respective pressure channel 12 to 18 is then fluidically connected to a section of the pressure region 24 between the piston rod 2 and the gap sleeve 10 via the respective fluid channel 22. If there is now a linear pressure drop in the pressure region 24, marked by the arrow 26, from the outside (p_2) to the inside (p_1), the pressure grooves 12 to 18 each have a mutually different pressure, the pressure groove 12 having the highest pressure, and the pressure in the following pressure grooves 14 to 18 each becoming smaller than the respective groove lying ahead in the longitudinal direction of the piston rod 2, viewed from the inside to the outside of the cylinder housing 6. Thus, a substantially linear pressure profile is produced by the plurality of pressure grooves 12 to 18 seen in the longitudinal direction. The innermost sealing ring 20, seen in the longitudinal direction, separates an end-side outer surface section of the gap sleeve 10 from the pressure groove 12. The outer surface section is fluidly connected to an inlet region arranged before said pressure region 24 and thus has a higher pressure than the adjacent pressure groove 12. The last sealing ring 20, which defines the pressure groove 18, separates an outer surface section of the gap housing 10 from the pressure groove 18. The outer surface section is then fluidically connected to the outlet region of the region 24 and is thus subjected to a minimum pressure.

Fig. 2 shows a piston 30, which is guided in a sleeve 31 (see fig. 1) of the hydraulic cylinder 1. The piston separates the first pressure chamber 32 from the second pressure chamber 34. An annular groove 38 is undercut into the outer surface 36 of the piston 30. Into which an annular piston seal 40 is fitted, which surrounds the piston 30. The piston seal 40 may be configured as a slit sleeve. The piston seal 40 defines with its inner surface a plurality of pressure grooves 42 to 48 arranged in rows along the longitudinal direction of the piston 30 and surrounding the piston 30. The pressure grooves 42 to 48 are each delimited from one another by a sealing ring 50, of which only one is provided with a reference number in fig. 2 for the sake of simplicity. The sealing rings 50 can each be inserted into a respective inner annular groove of the piston seal 40. From each pressure groove 42 to 48, a fluid channel 22 extends in the radial direction, wherein only one fluid channel is provided with reference numerals for the sake of simplicity. The fluid channel 22 is connected to a section of the pressure area 52 between the outer surface of the piston seal 40 and the cylinder jacket 31.

In the pressure chamber 34, depending on the operating state in fig. 2, a higher pressure (p_1) than in the pressure chamber 32 is present. A linearly decreasing pressure thus occurs in the pressure region 52, starting from the pressure chamber 34, in the longitudinal direction of the piston 30, as seen in the direction of the pressure chamber 32. The pressure grooves 42 to 48 thus form a substantially linear pressure profile in accordance with the embodiment in fig. 1. Furthermore, the piston seal 40 has an inner surface section on the side of the pressure chamber 34, which is delimited by the edge-side sealing ring 50 and is fluidically connected to the pressure chamber 34. The piston seal 40 has an inner surface section at its end section arranged on the side of the pressure chamber 32, which is delimited by an outer sealing ring 50 and is fluidically connected to the pressure chamber 32.

Another embodiment of a slit sleeve 54 is shown in fig. 3. This embodiment differs from fig. 1 in that it has only one pressure groove 56. The pressure groove is formed between the two sealing rings 20, seen in the longitudinal direction. The sealing ring 20 on the right in fig. 3 can furthermore be acted upon by the highest pressure by the gap 58 on its side facing away from the pressure groove 56.

A hydraulic cylinder is disclosed having a cylinder housing in which a piston with a piston rod is slidingly guided. The piston rod is guided out of the cylinder housing through the housing opening. A sealing element is arranged in the housing opening, said sealing element surrounding the piston rod. The sealing element has at least one pressure groove on the side of the outer surface of the sealing element, which pressure groove is fluidically connected to a region between the sealing element and the piston rod, wherein the region is arranged at the height of the pressure groove as seen in the longitudinal direction. Alternatively or additionally, the piston may have a piston seal that surrounds the piston. The piston seal may have a pressure groove on its inner surface, which is then fluidly connected to the region between the piston seal and the cylinder housing, as seen in the longitudinal direction, at the level of the pressure groove.

Claims

1. Hydraulic cylinder having a cylinder housing (6) and a piston rod (2), which is guided from the cylinder housing (6) via a housing opening (4), wherein an annular sealing element (10) is arranged in the housing opening between the piston rod (2) and the cylinder housing (6), which sealing element surrounds the piston rod (2), and/or wherein the piston rod (2) extends away from a piston (30) guided in the cylinder housing, which piston is surrounded by an annular piston seal (40), characterized in that at least one pressure groove (12, 14, 16, 18) is arranged, which is delimited by an outer surface of the sealing element (10), and which at least one pressure groove is connected by a fluid path to a pressure area delimited by an inner surface of the sealing element, wherein the pressure area is located radially inside the pressure groove as seen from the pressure groove (12, 14, 16, 18), and/or wherein at least one pressure groove (42, 44, 46, 48) is arranged, which pressure groove is delimited by a pressure groove (40) as seen from the outer surface of the pressure groove (40), and wherein the pressure groove (40) is delimited by a radial groove (52) is delimited by the pressure groove (52) and wherein the pressure groove (40) is delimited by the outer surface of the pressure groove (52, 14 16, 18;42 44, 46, 48;56 As seen in the longitudinal direction of the sealing element (10) and/or of the piston seal (40), are formed by two sealing rings (20; 50 As defined above).

2. The hydraulic cylinder according to claim 1, wherein the pressure groove (12, 14, 16, 18;42, 44, 46, 48; 56) is sealed seen in both longitudinal directions of the piston rod (2).

3. Hydraulic cylinder according to claim 1 or 2, wherein the pressure groove (12, 14, 16, 18;42, 44, 46, 48; 56) is configured annularly and surrounds the sealing element (10).

4. Hydraulic cylinder according to claim 1 or 2, wherein the pressure groove (12, 14, 16, 18) is connected to the pressure region (24) by a fluid channel (22) formed in the sealing element (10) in the case of the sealing element (10), and/or wherein the pressure groove (42, 44, 46, 48) is connected to the pressure region (52) by a fluid channel (22) formed in the piston seal (40) in the case of the piston seal (40).

5. Hydraulic cylinder according to claim 1 or 2, wherein a plurality of pressure grooves (12, 14, 16, 18) are provided in the case of a sealing element (10), and/or wherein a plurality of pressure grooves (42, 44, 46, 48) are provided in the case of a piston seal (40), each of which is connected to a configured pressure region (24; 52) by a fluid channel (22).

6. The hydraulic cylinder according to claim 5, wherein a plurality of pressure grooves (12, 14, 16, 18;42, 44, 46, 48) are arranged in a row.

7. The hydraulic cylinder according to claim 5, wherein a sealing ring (20; 50) is arranged between the two pressure grooves (12, 14, 16, 18;42, 44, 46, 48), respectively.

8. The hydraulic cylinder according to claim 7, wherein the sealing element (10) has an annular recess for the sealing ring or for each sealing ring (20), and/or wherein the piston seal (40) has an annular recess for the sealing ring or for each sealing ring (50).

9. Hydraulic cylinder according to claim 1 or 2, wherein the sealing element (10) in the cylinder housing (6) is fitted into and protrudes radially inwardly from an annular groove (8) which is open radially inwardly, and/or wherein the piston seal (40) in the piston (30) is fitted into and protrudes radially outwardly from an annular groove (38) which is open radially outwardly.

10. The hydraulic cylinder according to claim 1 or 2, wherein the sealing element and/or the piston seal is configured as a slit sleeve.