Shoes and axial piston pumps

Abstract

This provides a shoe that can reduce wear with a simple configuration. [Solution] A shoe 6 according to one embodiment is used in a swash plate type axial piston pump and includes a disc portion 61 and a support portion 65. The disc portion 61 includes a sliding surface 62 facing the swash plate of the axial piston pump and an outer peripheral surface 63 facing radially outward. The support portion 65 includes a concave spherical surface 66 that protrudes from the disc portion 61 in the opposite direction to the direction of the sliding surface 62 and engages with the head 51 of the piston 5. Between the sliding surface 62 and the outer peripheral surface 63, a curved surface 64 is formed that curves away from the extension surface of the sliding surface 62 as it extends radially outward.

Description

Technical Field

[0007]

[0001] The present disclosure relates to shoes used in a swash plate type axial piston pump, and an axial piston pump including the shoes.

Background Art

[0002] A swash plate type axial piston pump includes a rotating shaft, a cylinder block fixed to the rotating shaft, a plurality of pistons slidably held in the cylinder block, and a plurality of shoes respectively attached to the heads of the plurality of pistons.

[0003] For example, Patent Document 1 discloses a shoe that slides on a swash plate. The shoe includes a disk portion having a sliding surface facing the swash plate, and a support portion protruding in a direction opposite to the direction in which the sliding surface faces from the disk portion. The support portion has a concave curved surface into which the head of the piston fits.

[0004] In the shoe of Patent Document 1, in order to prevent contact between the shoe and the swash plate and reduce wear of the shoe, four slits are provided in the outer peripheral side portion of the disk portion, thereby dividing the outer peripheral side portion into four shoe pieces. Further, each shoe piece is provided with a pocket recessed from the sliding surface, and each pocket and the concave curved surface are communicated by a communication hole.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] <00000——31>However, the shape of the shoe of Patent Document 1 is complicated.

[0007] Therefore, the present disclosure aims to provide a shoe that can reduce wear with a simple configuration. [Means for solving the problem]

[0008] This disclosure provides a shoe for use in a swash plate type axial piston pump, comprising: a disc portion including a sliding surface facing the swash plate of the axial piston pump and an outer peripheral surface facing radially outward; and a support portion including a concave spherical surface that protrudes from the disc portion in the opposite direction to the direction of the sliding surface and engages with the head of the piston of the axial piston pump, wherein a curved surface is formed between the sliding surface and the outer peripheral surface, which curves away from the extension of the sliding surface as it extends radially outward.

[0009] This disclosure also provides an axial piston pump comprising a shoe and a swash plate facing the sliding surface of the shoe.

[0010] This disclosure provides an axial piston pump comprising a shoe and a swash plate facing the sliding surface of the shoe, wherein the curved surface of the shoe is smoothly connected to the sliding surface and the outer peripheral surface. [Effects of the Invention]

[0011] According to this disclosure, a shoe is provided that can reduce wear with a simple configuration. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of a swashplate type axial piston pump including a shoe according to one embodiment. [Figure 2] This is a cross-sectional view of the shoe. [Figure 3] This is a cross-sectional view of the modified shoe. [Modes for carrying out the invention]

[0013] Figure 1 shows a swashplate type axial piston pump 1 including a shoe 6 according to one embodiment.

[0014] The axial piston pump 1 includes a hollow casing 2 and a rotating shaft 11 extending from the inside to the outside of the casing 2. The rotating shaft 11 is rotated by a prime mover such as an electric motor or an engine. Inside the casing 2 are a valve plate 3, a cylinder block 4, a swash plate 71, and a support base 72.

[0015] For the sake of explanation, the axial direction of the rotating shaft 11 will be referred to as the front-rear direction (one end located outside the casing 2 is forward, and the other end is backward), and the two directions perpendicular to the axial direction of the rotating shaft 11 will be referred to as the up-down direction (the upper side of Figure 1 is upward, and the lower side is downward) and the left-right direction.

[0016] Casing 2 includes a container-shaped casing body 21 that opens backward and a valve cover 22 that closes the opening of the casing body 21. The rotating shaft 11 passes through the bottom of the casing body 21. Bearings 12 and 13 that rotatably support the rotating shaft 11 are held in the bottom of the casing body 21 and the valve cover 22, respectively.

[0017] The valve plate 3 is mounted on the front surface of the valve cover 22. The valve plate 3 is provided with two arc-shaped ports, a first port 31 and a second port 32, facing opposite directions. In Figure 1, the first port 31 is depicted as the upper top dead center and the second port 32 as the lower bottom dead center, but the actual positions of the first port 31 and the second port 32 are on both sides of the rotation axis 11 in the left-right direction perpendicular to the distance between the top dead center and the bottom dead center. The top dead center is the position where the piston 5 is most retracted, and the bottom dead center is the position where the piston 5 is most advanced.

[0018] For example, when the rotating shaft 11 rotates in one direction, the first port 31 is the suction port and the second port 32 is the discharge port. In the rotation direction of the rotating shaft 11, the first port 31, which is the suction port, is located on the downstream side of the top dead center and on the upstream side of the bottom dead center, and the second port 32, which is the discharge port, is located on the downstream side of the bottom dead center and on the upstream side of the top dead center.

[0019] Alternatively, when the rotating shaft 11 rotates in both directions, when the rotating shaft 11 rotates in one direction, the first port 31 is the suction port and the second port 32 is the discharge port, and when the rotating shaft 11 rotates in the reverse direction, the second port 32 is the suction port and the first port 31 is the discharge port.

[0020] The valve cover 22 is provided with a first flow path 2a communicating with the first port 31 and a second flow path 2b communicating with the second port 32. The first flow path 2a and the second flow path 2b open to the outer peripheral surface or the rear surface of the valve cover 22, and these openings form external connection ports. When the rotating shaft 11 rotates in one direction as described above, the first flow path 2a is the suction path and the second flow path 2b is the discharge path.

[0021] The cylinder block 4 is fixed to the rotating shaft 11 and slides on the valve plate 3 by rotating together with the rotating shaft 11. The cylinder block 4 is provided with a plurality of cylinder bores 41 opening forward around the rotating shaft 11. A plurality of pistons 5 are respectively inserted into these cylinder bores 41. That is, the pistons 5 are slidably held by the cylinder block 4.

[0022] In addition, the cylinder block 4 is provided with cylinder ports 42 extending from each cylinder bore 41 to the valve plate . Some of these cylinder ports 42 communicate with the first port 31 and some others communicate with the second port 32.

[0023] A plurality of shoes 6 are respectively attached to the head of the piston 5. In the present embodiment, the shoe 6 slides on the swash plate 71 via an annular shoe plate 73 attached to the swash plate 71. However, the shoe plate 73 may be omitted, and the shoe 7 may slide directly on the swash plate 71. The shoe 6 is pressed by a pressing plate 74 so that the state of contact with the shoe plate 73 is maintained.

[0024] The swash plate 71 is supported by a support base 72 provided at the bottom of the casing body 21 so as to be swingable about a swing axis extending in the left - right direction.

[0025] Next, referring to FIG. 2, the shape of the shoe 6 will be described in detail. The shoe 6 includes a disk portion 61 and a support portion 65. The disk portion 61 includes a sliding surface 62 facing the swash plate 71 and an outer peripheral surface 63 facing the radially outer side. The support portion 65 projects from the disk portion 61 in a direction opposite to the direction in which the sliding surface 62 faces.

[0026] In the present embodiment, since the shoe 6 slides on the swash plate 71 via the shoe plate 73 as described above, the sliding surface 62 faces the swash plate 71 via the shoe plate 73. However, when the shoe 7 slides directly on the swash plate 71, the sliding surface 62 may face the swash plate 71 in a state of surface contact with the swash plate 71.

[0027] The support portion 65 is columnar with a smaller diameter than the disk portion 61 and includes a concave spherical surface 66 that fits with the head 51 of the piston 5. The piston 5 is provided with a through - hole 52 extending along the center line of the piston 5. The working fluid flowing into the cylinder bore 41 described above is supplied to the shoe 6 through the through - hole 52 and used as a lubricant.

[0028] A circular recess 82 with a diameter similar to that of the through hole 52 is provided at the center of the concave spherical surface 66, and a circular recess 81 with a diameter between the diameter of the piston head 51 and the diameter of the recess 82 is provided at the center of the sliding surface 62. The disc portion 61 is provided with a communication hole 83 that extends along the center line of the disc portion 61 and connects the recess 81 and the recess 82. Furthermore, the sliding surface 62 is provided with two concentric annular grooves 84 and 85 on the outside of the recess 81.

[0029] Between the sliding surface 62 and the outer peripheral surface 63 of the disc portion 61, a curved surface 64 is formed that curves away from the extended surface of the sliding surface 62 as it extends radially outward. In this embodiment, the curved surface 64 is smoothly connected to the sliding surface 62 and the outer peripheral surface 63. That is, the distance from the sliding surface 62 to the center of curvature of the curved surface 64 in the axial direction of the disc portion 61, and the distance from the outer peripheral surface 63 to the center of curvature of the curved surface 64 in the radial direction of the disc portion 61, are equal to the radius of curvature R of the curved surface 64.

[0030] For example, the width of the curved surface 64 in the radial direction of the disc portion 61 is 1% or more and 15% or less of the radius of the disc portion 61. The width of the curved surface 64 in the radial direction of the disc portion 61 may also be 5% or more and 10% or less of the radius of the disc portion 61. In this embodiment, the width of the curved surface 64 in the radial direction of the disc portion 61 is equal to the radius of curvature R of the curved surface 64.

[0031] The specific dimensions of the shoe 6 are as follows, for example: The diameter of the disc portion 61 is 20 mm or more and 30 mm or less, and the thickness of the disc portion 61 is 3 mm or more and 5 mm or less. The diameter of the support portion 65 is 15 mm or more and 20 mm or less, and the height of the support portion 65 is 8 mm or more and 12 mm or less. The radius of curvature R of the curved surface 64 may be 0.5 mm (5% of the radius of the disc portion 61 when the diameter of the disc portion 61 is 20 mm) or more and 1.5 mm (10% of the radius of the disc portion 61 when the diameter of the disc portion 61 is 30 mm), or it may be 0.1 mm (1% of the radius of the disc portion 61 when the diameter of the disc portion 61 is 20 mm) or more and 2.3 mm (15% of the radius of the disc portion 61 when the diameter of the disc portion 61 is 30 mm).

[0032] In the shoe 6 with the configuration described above, wear on the shoe 6 can be reduced by a simple configuration in which a curved surface 64 is formed between the sliding surface 62 and the outer peripheral surface 63.

[0033] <Variation> This disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure.

[0034] For example, the curved surface 64 does not necessarily have to be smoothly connected to the sliding surface 62 and the outer peripheral surface 63. As shown in Figure 3, the radius of curvature R of the curved surface 64 may be set to be large, and the distance from the sliding surface 62 to the center of curvature of the curved surface 64 in the axial direction of the disc portion 61, and the distance from the outer peripheral surface 63 to the center of curvature of the curved surface 64 in the radial direction of the disc portion 61, may be smaller than the radius of curvature R of the curved surface 64. However, if the curved surface 64 is smoothly connected to the sliding surface 62 and the outer peripheral surface 63 as in the above embodiment, the wear of the shoe 6 can be further reduced.

[0035] <Summary> In a first aspect, the present disclosure provides a shoe for use in a swash plate type axial piston pump, comprising: a disc portion including a sliding surface facing the swash plate of the axial piston pump and an outer peripheral surface facing radially outward; and a support portion including a concave spherical surface that protrudes from the disc portion in the opposite direction to the direction of the sliding surface and engages with the head of the piston of the axial piston pump, wherein a curved surface is formed between the sliding surface and the outer peripheral surface, which curves away from the extension of the sliding surface as it extends radially outward.

[0036] According to the above configuration, shoe wear can be reduced with a simple configuration that forms a curved surface between the sliding surface and the outer surface.

[0037] In a second embodiment, in the first embodiment, for example, the width of the curved surface in the radial direction of the disc portion may be 1% or more and 15% or less of the radius of the disc portion.

[0038] In a third embodiment, in the first embodiment, for example, the width of the curved surface in the radial direction of the disc portion may be 5% or more and 10% or less of the radius of the disc portion.

[0039] In a fourth embodiment, in any of the first to third embodiments, the curved surface may smoothly connect to the sliding surface and the outer peripheral surface.

[0040] In a fifth aspect, the present disclosure provides an axial piston pump comprising a shoe according to any of the first to third aspects and a swash plate facing the sliding surface of the shoe.

[0041] In a sixth aspect, the present disclosure provides an axial piston pump comprising a shoe according to any of the first to third aspects and a swash plate facing the sliding surface of the shoe, wherein the curved surface of the shoe is smoothly connected to the sliding surface and the outer circumferential surface. [Explanation of symbols]

[0042] 1. Axial piston pump 5 pistons 51 Head 6 Shoe 61 Disc section 62 Sliding surface 63 Outer surface 64 Curved surface 65 Support part 66 Concave spherical surface 71 Swash plate

Claims

1. A shoe used in a swashplate type axial piston pump, The disc portion includes a sliding surface facing the swash plate of the axial piston pump and an outer peripheral surface facing radially outward, The disc portion includes a support portion that protrudes in the opposite direction to the direction in which the sliding surface faces, and which includes a concave spherical surface that engages with the head of the piston of the axial piston pump, A shoe has a curved surface formed between the sliding surface and the outer circumferential surface, which curves away from the extended surface of the sliding surface as it extends radially outward.

2. The shoe according to claim 1, wherein the width of the curved surface in the radial direction of the disc portion is 1% or more and 15% or less of the radius of the disc portion.

3. The shoe according to claim 1, wherein the width of the curved surface in the radial direction of the disc portion is 5% or more and 10% or less of the radius of the disc portion.

4. The shoe according to any one of claims 1 to 3, wherein the curved surface is smoothly connected to the sliding surface and the outer peripheral surface.

5. A shoe according to any one of claims 1 to 3, A swash plate facing the sliding surface of the shoe, An axial piston pump equipped with [a specific feature].

6. A shoe according to any one of claims 1 to 3, The shoe comprises a swash plate facing the sliding surface of the shoe, An axial piston pump in which the curved surface of the shoe is smoothly connected to the sliding surface and the outer peripheral surface.

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