Sliding shoe for a piston of a piston machine, piston machine with sliding shoe

Abstract

The invention relates to a sliding shoe for a working piston of a hydrostatic piston machine, having a sliding side, at which an unloading recess is configured, in which a hydrostatic pressure field can be configured, and which is bordered by a sealing web, the apex or top surface of which can slide against an inclined surface of the piston machine. Furthermore, a hydrostatic piston machine is disclosed, having at least one such sliding shoe, which bears against the inclined surface.

Description

Technical Field

[0001] The present invention relates to a sliding boot and a piston machine having the sliding boot. Background Technology

[0002] The hydrostatic axial piston press of this class has a cylinder-piston unit, each having a working piston arranged axially in a cylinder and capable of axial displacement therein. This working piston, for example, has a piston head received in a concave notch of a sliding shoe. Through this piston head, the working piston is supported on an inclined surface or plane of the axial piston press, particularly on the swashplate. During operation, the sliding shoe transmits the supporting force of the working piston to the swashplate. Due to mechanical stress in the sliding support area, the swashplate and sliding shoe can wear, and even the sliding shoe can break.

[0003] To eliminate or at least mitigate this risk, the slipper is lubricated into a swashplate rolling surface in the region of its sliding surface and subjected to hydrostatic unloading. This is achieved through a pressure medium channel, typically located in the center, extending from a concave notch in the slipper towards its sliding surface. Through this channel, lubricating or pressure medium is fed into the unloading recess of the sliding surface, thereby creating a hydrostatic unloading pressure field there.

[0004] The applicant's document DE 10 2015 208 886 A1 discloses a sliding shoe having a lubricating medium channel leading to a sliding surface. In this respect, unloading recesses in the form of circumferential grooves are concentrically constructed and separated by sealing webs. Pressure medium is guided radially outward from the pressure medium channel to the circumferential grooves. The sealing webs prevent the pressure medium from continuing to flow without resistance, thus creating a defined pressure unloading field. The sliding surface, arranged at the sealing webs, here seals and slides against the swashplate.

[0005] Document DE 102 35 813 B4 illustrates a similar sliding boot and a method for manufacturing a sliding surface for the sliding boot, the sliding surface being characterized by a sealed web and a notch.

[0006] Document DE 196 01 721 C2 illustrates a sliding boot with a multi-piece structure designed to reduce its weight.

[0007] Document GB 983 310 discloses a sliding shoe with unloading notches configured in different ways. These unloading notches vary from spiral configurations to radially outward meandering configurations to labyrinthine configurations.

[0008] The common feature of the aforementioned sliding shoes is that the unloading notch or groove in the sliding surface of the sliding shoe has a substantially rectangular cross-section.

[0009] In contrast, document EP 1 409 196 B1 shows an unloading notch in the sliding surface of a sliding shoe, which has a fully circumferential cutout, i.e., a recess, on its radially outer side. This unloading notch either has an edge face that is vertically positioned relative to the sliding surface, or it slopes downwards toward the sliding surface, such that the maximum diameter of the unloading notch exists at the sliding surface.

[0010] The pressure medium for the pressure field of the unloading notch originates from the working space of the corresponding working piston, wherein the aforementioned pressure medium channel fluidly connects the unloading notch to the working space. This allows the unloading pressure field to withstand pressure fluctuations in the working space as the working piston extends and retracts.

[0011] Especially during intake, when the working piston extends during pump operation, the pressure can drop so drastically in the working space and through the pressure medium passage and also in the unloading notch that the pressure medium transitions into the vapor phase.

[0012] The common feature of the aforementioned sliding shoes is that the vaporized pressure medium accumulates in the contact area of ​​the circumferential edges of the sealing web, i.e., at the sliding surface. Then, if a vapor explosion occurs due to subsequent pressure increases, the consequence is cavitation damage, especially to the circumferential edges of the sealing web. Consequently, the circumferential edges, and gradually even the additional area of ​​the sliding surface of the sealing web, are damaged, thereby shortening the sealing gap and negatively impacting the sealing function. Over time, the sealing web can completely corrode, losing its sealing function. This is accompanied by the slipper losing hydrostatic unloading and lubrication, which can lead to indirect damage to the swashplate and even machine failure. Summary of the Invention

[0013] In contrast, the objective of this invention is to provide a sliding shoe for the working piston of a piston machine, particularly a radial or axial piston machine, which is better protected from corrosion due to cavitation at the sealing web. Furthermore, a piston machine in which corrosion due to cavitation in the sliding surface region of the sliding shoe is reduced should be provided.

[0014] A sliding shoe for a slidingly supported hydrostatic piston press has a sliding side, on which, particularly at the center or concentrically with the longitudinal axis of the sliding shoe, an unloading recess is constructed, in which a hydrostatic pressure field can be formed. The unloading recess is surrounded by a sealing web, particularly on the outer periphery. That is, the sealing web forms the edge surface of the unloading recess. The apex or top surface of the sealing web can slide against the inclined surface, particularly the planar surface, of the piston press. According to the invention, the edge surface of the unloading recess is configured at the sealing web such that, at this edge surface, during the prescribed operation of the piston press, the pressure medium of the pressure field containing a greater proportion of vapor, or the vapor phase, can be guided away from the top surface, in which the sliding shoe rotates around the axis of rotation spaced apart from it.

[0015] In this way, the potential explosion of the vapor-containing phase or vapor phase does not occur at or in the top surface, but more precisely, within the sliding shoe. Therefore, the associated corrosion no longer involves the top surface, sliding surface, or sealing surface of the sealing web, thus better protecting the sealing web from cavitation.

[0016] Preferably, a pressure medium passage is provided, which extends through the sliding shoe from the unloading recess toward the receiving portion of the piston head for the working piston. Through this pressure medium passage, pressure medium from the hydrostatic working space can be applied to the unloading recess during piston machine operation.

[0017] In one extended scheme, the edge surface is configured such that the phase containing more vapor or the vapor phase can be guided away by means of dynamic forces generated by operation (e.g., especially centrifugal force and / or centripetal force and gravity).

[0018] The piston machine is preferably configured as an axial piston machine, wherein the inclined surface of the swashplate has a constant or adjustable angle. Here, multiple working pistons are housed in cylinder bores of cylinders that are rotatable about a rotation axis, the cylinder bores being arranged on the pitch circle (Teilkreis), and the working pistons are supported at the swashplate by their respective sliding shoes.

[0019] Preferably, the sliding shoe or unloading notch has a longitudinal axis that extends orthogonally to the sliding side.

[0020] In one extended embodiment, away from the apex or top surface of the sealing web, the unloading recess has a base that widens radially, particularly about the longitudinal axis.

[0021] In one extended scheme, the edge face is configured such that the direction has a component that enters into the sliding shoe, particularly parallel to the longitudinal axis.

[0022] In one extended scheme, the edge face is configured such that the direction has, in particular, a radially outward component about the longitudinal axis.

[0023] In one extended scheme, the hindcut is formed at the sealing web by the edge face.

[0024] In one extended embodiment, particularly in a cross section opened by a longitudinal axis, an acute angle is formed by edge faces and surfaces or planes that open radially outward about the longitudinal axis, with the top surface located within the surface or plane.

[0025] In order to reduce mechanical stress in the edge areas of the top surface, sealing surface, or sliding surface, in one extension, a transition portion from the top surface to the edge surface is provided, which has, in particular, a right angle, a chamfer, or a radius in the cross section opened by the longitudinal axis.

[0026] In order to reliably aggregate a phase containing a large amount of vapor or a vapor phase, in one extended scheme, the unloading notch configuration has an aggregation section away from the top surface.

[0027] Preferably, for this purpose, the gathering section is recessed relative to the remaining unloading notch.

[0028] Alternatively, a collection cavity can be constructed in the sliding shoe away from the top surface, into which the unloading notch flows.

[0029] The unloading notch can be configured as a solid or a ring-shaped body.

[0030] In the first case, in one extended embodiment, the unloading notch is configured as a disc opening into the interior of the sliding shoe, the disc having a disc bottom and a fan-shaped, unfolding disc edge. In the second case, in one extended embodiment, the unloading notch is configured as a disc edge with a fan-shaped, unfolding disc edge.

[0031] In one extended scheme, the clustered section is formed at least partially by the edge of the disc.

[0032] In order to better form and control the pressure field of the hydrostatic pressure, in an extended embodiment, the sliding shoe has at least one additional unloading notch on the sliding side that is concentric or parallel to the aforementioned unloading notch and / or at least one additional sealing web that is concentric or parallel to the aforementioned sealing web.

[0033] In order to fluidly connect multiple unloading notches, in one extension scheme, at least one additional sealing web has a local recess on its top surface, which is formed in particular by a flat radial groove.

[0034] The smaller the flow resistance of the localized sinkhole or the larger the cross-section of the sinkhole, the weaker the sealing function of the associated sealing web, and in most cases, it may even lose its sealing function, thus retaining only a supporting function. The sealing web then becomes the supporting web.

[0035] The piston press according to the invention has at least one sliding shoe configured according to any of the above-described embodiments. A piston or working piston is coupled to this sliding shoe, which is supported on an inclined surface by the sliding side of the sliding shoe for achieving the stroke. The piston press is preferably an axial piston press having a swashplate with a constant or adjustable angle. Here, a plurality of working pistons are provided, axially movable, housed in cylinder bores of a cylinder barrel rotatable about a rotation axis, the cylinder bores being arranged on the pitch circle. The working pistons are supported on the swashplate by their respective sliding shoes. Attached Figure Description

[0036] Embodiments of the sliding shoe and axial piston mechanism according to the invention are illustrated in more detail in the accompanying drawings. They show: Figure 1 A partial perspective view from below of a first embodiment of the sliding boot. Figure 2 A bottom view of the second embodiment of the sliding boot. Figure 3 The cross-section of the third embodiment of the sliding boot, and Figure 4 according to Figure 3 A magnified diagram showing the details of the sliding boot. Detailed Implementation

[0037] according to Figure 1 The first embodiment of the sliding boot 1 has a substantially cylindrical collar portion 2, according to Figure 1 The head of the working piston of a piston machine, especially an axial piston machine (not shown), can be inserted into the collar from the rear and above. A base 6, radially widening about the longitudinal axis 4 of the sliding shoe 1, abuts the collar 2. This base 6 has a sliding surface 8 that extends circumferentially and annularly around the longitudinal axis 4. Here, the sliding surface 8 is configured to abut against the swashplate of the axial piston machine (not shown), thereby allowing the working piston to be supported at the swashplate. An unloading recess 10 is recessed at the center relative to the annular sliding surface 8, into which a pressure medium passage 12 converges in the center of the region of the longitudinal axis 4. This pressure medium passage penetrates the sliding shoe 1 to a spherical receiving portion in the collar 2, into which the piston head can be inserted. Pressure medium from a hydrostatic working space, defined by the working piston, is supplied to the unloading recess 10 through the pressure medium passage 12.

[0038] Since the principle and structure of the sliding shoe have been fully disclosed in the prior art, this specification focuses on details related to understanding the invention.

[0039] according to Figure 1 The sliding surface 8 is also the top surface of the sealing web 16, which surrounds and seals the pressure field that can be constructed in the unloading recess 10 relative to the surrounding environment. Here, a seal is achieved when the sliding shoe 1, with its sliding surface 8, abuts against the swashplate of the axial piston machine during operation. The unloading recess 10 has an outer peripheral edge surface 14, which is constructed at the inner periphery of the sealing web 16. According to the invention, the edge surface 14 is configured such that, according to the third embodiment… Figure 3 and Figure 4 This will more accurately describe the configuration scheme.

[0040] Figure 2 A second embodiment of the sliding shoe 101 is shown, which is consistent with the embodiment according to Figure 1 The difference in the first embodiment lies particularly in that the sealing web 16, having a sliding surface 8, and the unloading recess 10 are arranged concentrically, alternatingly. Here, only the sealing web 16 is configured to have a completely planar sliding surface 8. The sealing webs 16', 16" and 16'" each have sliding surfaces 8', 8" and 8'" respectively, each having two recesses arranged diagonally. These recesses are constructed as flat grooves 18', 18" and 18'". Here, flat groove 18' is offset by 90° relative to flat groove 18" and the latter is further offset by 90° relative to flat groove 18'".

[0041] according to Figure 2 Pressure medium is applied to the central unloading recess 10'" through the pressure medium channel 12. This unloading recess is fluidly connected to the unloading recess 10" via the flat groove 18'". As mentioned above, the sealing web 16 does not have such a flat groove, therefore, among all the sealing webs 16, 16', 16" and 16'", this sealing web has the greatest sealing capacity. Then, since the pressure medium arriving at the full sealing gap of the sealing web 16 remains in the outermost unloading recess 10', which is connected to the surrounding environment via the flat groove 18', the pressure medium can flow out from the internal space of the piston machine housing (not shown). Therefore, the strongest unloading pressure field is generated radially within the unloading recesses 10, 10" and 10'" of the sealing web 16. Here, all the sealing surfaces or top surfaces 8, 8', 8" and 8'" abut against the planar swashplate and are simultaneously the support surface and the sliding surface.

[0042] According to the evidence shown Figure 2 In the embodiments, the sealing web 16 also has an edge surface 14 according to the configuration of the present invention, which will now be described in more detail.

[0043] Figure 3 A cross-section is shown of a third embodiment of the sliding boot 201 according to the present invention. This sliding boot is substantially the same as that according to... Figure 1 The sliding shoe 201 is configured similarly to the other sliding shoe, but has a slightly narrower sealing web 16 in the radial direction and a pressure medium passage 12 with a larger diameter. The sliding shoe 201 slides against the swashplate 20 of the axial piston mechanism according to the invention (not shown) with its sliding surface, or rather, the top surface 8 of the sealing web 16. This axial piston mechanism has a drive shaft with a rotation axis 22, around which the sliding shoe 201, along with another identically constructed sliding shoe (not shown), rotates during operation. Correspondingly, the centrifugal force F... F The centripetal force F acts on the sliding shoe 201 and the pressure medium carried by the sliding shoe. P To counteract this centrifugal force, the centripetal force is transmitted from the piston head (not shown) of the working piston, housed in the sliding shoe, to the sliding shoe 201, thereby causing the sliding shoe to maintain its orbital path.

[0044] During operation, pressure medium from the hydrostatic working space is supplied to the pressure medium passage 12 through the central bore of the working piston, which is bounded by the working piston. Accordingly, the pressure medium passage 12 and the unloading recess 10 are loaded with pressure medium. In the illustrated embodiment, the unloading recess 10 has a disc shape, with a disc bottom 24 and a disc edge 26. With respect to the axis of rotation 22, the disc edge has a circumferential region 26a on the outer side during operation and a circumferential region 26i on the inner side during operation. The disc edge 26 is radially bounded circumferentially by an edge surface 14, which is also a section of the inner surface of the sealing web 16. The base of the disc edge 26 is deeper than that of the disc bottom 24. Furthermore, the edge surface 14 has a larger diameter about the longitudinal axis 4 towards this base than in the region of the top surface of the sealing web 16, or the sliding surface 8. Therefore, the edge surface 14 is positioned radially outward at an acute angle to the sliding surface 8 about the longitudinal axis 4 of the sliding shoe 201.

[0045] Figure 4 Showing according to Figure 3 A magnified view of detail A. The top surface, or sliding surface 8, of the sealing web 16 transitions into the edge surface 14 via a transition portion, which is in the form of a cylindrical outer peripheral surface 28. In this way, the acute angle between the edge surface 14 and the sealing surface 8 is "blunted," and the transition portion is configured as a right angle, thereby reducing the mechanical stress in the sliding pair—the swashplate 20 and the sliding surface 8.

[0046] The disc edge 26 has a gathering section 30, which is also constructed circumferentially and forms the apex region of the disc edge 26. As mentioned above, during the operation of the axial piston machine, a phase containing more vapor or a vapor phase of the pressure medium can be generated in the unloading notch 10. If an explosion occurs, there is a threat of cavitation. Since, in principle, when the sliding shoes 1; 101; 201 are surrounding, the liquid phase of the pressure medium, due to its higher density, is radially outward about the axis of rotation 22, that is, according to Figure 3 The vapor accumulates in the outer region 26a, while the lower-density phase containing more vapor or the vapor phase accumulates in the inner region 26i. Here, the risk of cavitation is greatest.

[0047] To prevent this corrosion, according to the invention, the unloading recess 10, configured to cooperate with the sealing web 16, is positioned such that the edge face 14 is placed at an acute angle to the sliding surface 8 as described above. Furthermore, accumulation sections 30 are provided in the relative interiors of the sliding shoes 1; 101; 201. Due to the forces acting during operation, especially centrifugal force and the slope of the edge face 14, the vapor phase critical for cavitation accumulates in the area of ​​the accumulation section 30, i.e., away from the areas threatened by cavitation in the transition section 28 and the sealing surface 8. In this way, the sliding shoes 1; 101; 201 are protected from corrosion by guiding the vapor phase away from the aforementioned areas.

[0048] List of reference numerals 1; 101; 201 Sliding boot 2. Collar 4. Vertical axis 6. Base 8; 8', 8" 8'" Top surface 10; 110, 10', 10", 10'" Unloading notch 12 Pressure Medium Channel 14 Edge surfaces 16; 16', 16" and 16'" Sealed web 18; 18', 18" and 18'" flat grooves 20 Slope 22 Rotation axis 24. Bottom of the plate 26, 26i, 26a: Disc edge, inner area, outer area 28. Transition Section 30 cluster sections F F Centrifugal force F P Centripetal force.

Claims

1. A sliding shoe for a working piston of a hydrostatic piston press, having a sliding side with an unloading recess (10; 110) formed thereon, in which a hydrostatic pressure field can be formed, and the unloading recess is surrounded by a sealing web (16), the top surface (8) of which can slide against an inclined surface (20) of the piston press, characterized in that, The edge face (14) of the unloading notch (10; 110) is configured at the sealing web (16) such that the vapor-containing phase of the pressure medium of the pressure field can be guided away from the top surface (8) at the edge face. The edge surface (14) and the top surface form an acute angle that opens radially outward about the longitudinal axis (4) of the sliding shoe (1; 101; 201). The unloading notch (10) is configured as a disc, which has a bottom (24) and an edge (26, 26a, 26i). Compared with the bottom (24), the base of the edge (26) is deeper. The unloading notch (10; 110) is configured to have an accumulation section (30) away from the top surface (8), in which a phase containing more vapor can accumulate. The aggregation section (30) is recessed in the axial direction relative to the remaining unloading notch.

2. The sliding shoe according to claim 1, wherein, The edge face (14) of the unloading notch (10; 110) is configured at the sealing web (16) such that the pressure medium vapor of the pressure field can be directed away from the top surface (8) at the edge face.

3. The sliding shoe according to claim 1, wherein, Away from the top surface (8), the unloading recess (10; 110) has a base that is radially widened.

4. The sliding shoe according to claim 1 or 2, wherein, The edge surface (14) forms a back cut at the sealing web (16).

5. The sliding boot according to claim 1 or 2, having a transition portion (28) from the top surface (8) to the edge surface (14), the transition portion having a right angle or a chamfer.

6. The sliding shoe according to claim 1 or 2, having at least one additional unloading notch (10', 10", 10'"), said at least one additional unloading notch being concentric with the aforementioned unloading notch (110).

7. The sliding boot according to claim 6, having at least one additional sealing web (16', 16", 16'"), said at least one additional sealing web being concentric with the aforementioned sealing web (16).

8. The sliding boot according to claim 7, having a partial recess (18', 18", 18'") of the top surface (8', 8", 8'"), the recess being formed by a flat radial groove.

9. A piston machine having at least one sliding shoe (1; 101; 201) configured according to any one of claims 1-8, and having a piston coupled to said sliding shoe, said sliding shoe being supported by a sliding side on an inclined surface (20) for achieving a stroke.

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