Swash plate type hydraulic rotary machine

Abstract

To suppress uneven wear of a shoe.SOLUTION: A swash plate type hydraulic motor 1 includes a rotary shaft 6, a rotor 7 which rotates integrally with the rotary shaft 6 and in which a plurality of cylinders 8 are formed, a plurality of pistons 9 which are reciprocatably inserted into the cylinders 8 of the rotor 7, a plurality of shoes 15 which are provided at tips of the plurality of pistons 9, and a swash plate 11 on which the plurality of shoes 15 slide. A sliding surface 16 opposed to the swash plate 11 in the shoe 15 has an annular flat surface 16B abutting on the swash plate 11, and a curved inclined surface 16B inclined in the direction for separating from the swash plate 11 toward the outer peripheral direction of the shoe 15 from the outer peripheral edge of the flat surface 16C.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a swash plate type hydraulic rotary machine that is suitably used as a hydraulic motor or a hydraulic pump. [Background technology]

[0002] Construction machinery such as hydraulic excavators are equipped with a hydraulic pump as a hydraulic pressure source, a hydraulic motor (swing motor) that rotates the upper rotating body, a hydraulic motor (travel motor) that drives the lower traveling body, etc. These hydraulic pumps and hydraulic motors are variable displacement or fixed displacement swash plate hydraulic rotary machines.

[0003] A swash plate type hydraulic rotary machine generally comprises a rotating shaft rotatably mounted within a casing, a rotor formed with a plurality of cylinders mounted within the casing so as to rotate integrally with the rotating shaft, a plurality of pistons reciprocally inserted into the cylinders of the rotor, a plurality of shoes respectively mounted at the tips of the pistons, and a swash plate along which the plurality of shoes slide.

[0004] Generally, a circular recess (hydrostatic pocket) is formed on the sealing surface of the shoe that contacts the swash plate. During operation of a swash plate-type hydraulic rotary machine, hydraulic oil is supplied between the recess of the shoe and the swash plate, and as the shoe rotates on the swash plate, hydraulic oil in the casing is drawn into the sliding surface between the shoe and the swash plate. This forms an oil film between the shoe and the swash plate, allowing the shoe to slide on the swash plate while floating slightly (several micrometers to several tens of micrometers) above the swash plate. A shoe with arc-shaped pads on both the inner and outer peripheries of the sealing surface has also been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-151897 Summary of the Invention [Problem to be solved by the invention]

[0006] During operation of a swash plate-type hydraulic rotary machine, the shoes may tilt relative to the swash plate due to factors such as centrifugal force acting on the shoes and the tilting motion of the swash plate. The shoe in Patent Document 1 has a seal surface that protrudes longer than the pad. Therefore, when the shoes tilt, the outer periphery of the seal surface or the outer periphery of the outer pad comes into partial contact with the swash plate (uneven contact). This results in uneven wear of the shoes, shortening their lifespan.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide a swash plate type hydraulic rotary machine that is capable of suppressing uneven wear of the shoes. [Means for solving the problem]

[0008] The present invention provides a swash plate type hydraulic rotating machine comprising: a rotating shaft rotatably mounted within a casing; a rotor formed with a plurality of cylinders mounted within the casing so as to rotate integrally with the rotating shaft; a plurality of pistons reciprocally inserted into the cylinders of the rotor; a plurality of shoes respectively mounted at the tips of the pistons; and a swash plate against which the plurality of shoes slide; wherein the sliding surface of the shoe facing the swash plate has a flat, annular surface that abuts against the swash plate, and an inclined surface that slopes from the outer periphery of the flat surface toward the outer periphery of the shoe, away from the swash plate. [Effects of the Invention]

[0009] According to the present invention, uneven wear on the outer periphery of the shoe can be suppressed even when the shoe is tilted while floating above the swash plate. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a swash plate type hydraulic motor according to an embodiment of the present invention. [Figure 2]FIG. 2 is a perspective view showing the shoe according to the first embodiment alone. [Figure 3] 3 is a front view of the shoe as seen from the direction of arrows III-III in FIG. 2. [Figure 4] 4 is a cross-sectional view of the shoe as seen from the direction of arrows IV-IV in FIG. 3. [Figure 5] FIG. 3 is an enlarged cross-sectional view showing an outer peripheral edge portion of the shoe. [Figure 6] FIG. 4 is a cross-sectional view showing a state in which the shoe is inclined relative to the swash plate. [Figure 7] FIG. 4 is a characteristic diagram showing the relationship between the radial position of the shoe and the oil film pressure between the shoe and the swash plate according to the first embodiment. [Figure 8] FIG. 10 is a characteristic diagram showing the relationship between the radial position of the shoe and the oil film pressure between the shoe and the swash plate according to a comparative example. [Figure 9] FIG. 5 is a cross-sectional view of a shoe according to a second embodiment taken in the same position as in FIG. 4. [Figure 10] FIG. 3 is an enlarged cross-sectional view showing an outer peripheral edge portion of the shoe. [Figure 11] FIG. 4 is a front view of a shoe according to a third embodiment, taken in a position similar to that of FIG. 3. [Figure 12] 12 is a cross-sectional view of the shoe as seen from the direction of arrows XII-XII in FIG. 11. [Figure 13] FIG. 3 is an enlarged cross-sectional view showing an outer peripheral edge portion of the shoe. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a swash plate type hydraulic rotary machine according to the present invention will be described in detail below with reference to the accompanying drawings, taking a swash plate type hydraulic motor as an example.

[0012] 1 to 7 show a first embodiment of the present invention. In Fig. 1, a variable displacement swash plate hydraulic motor 1 serving as a swash plate hydraulic rotary machine is supplied with pressure oil from a hydraulic source (not shown) such as a hydraulic pump to rotate a rotary shaft 6 (described later).

[0013] The casing 2 forms the outer shell of the swash plate type hydraulic motor 1. The casing 2 includes a cylindrical casing main body 3 with a bottom and a rear casing 4 fixed to the casing main body 3. One axial side (left side in FIG. 1) of the casing main body 3 forms a front bottom portion 3A. The other axial side (right side in FIG. 1) of the casing main body 3 is closed by the rear casing 4. A swash plate support member 10 that supports a swash plate 11 (described later) so that the swash plate 11 can tilt is provided on the front bottom portion 3A side of the casing main body 3.

[0014] The valve plate 5 is disposed within the casing 2 and fixed to the rear casing 4. The valve plate 5 is configured as a switching valve plate that switches the supply / discharge direction of pressure oil to / from a cylinder 8 (described later), and has a pair of supply / discharge ports 5A, 5B that extend in an eyebrow shape around the rotary shaft 6. The supply / discharge ports 5A, 5B are connected to a hydraulic pump and a tank (neither of which are shown), which serve as a hydraulic source, via supply / discharge passages, hydraulic piping, etc., formed in the rear casing 4.

[0015] The rotating shaft 6 is rotatably disposed within the casing 2. One axial side of the rotating shaft 6 is rotatably attached to the front bottom 3A of the casing main body 3 via a bearing or the like. The other axial side of the rotating shaft 6 is rotatably attached to the rear casing 4 via a bearing. One side of the rotating shaft 6 forms a protruding end 6A that protrudes outward from the front bottom 3A of the casing main body 3. The rotating shaft 6 constitutes the output shaft of the swash plate hydraulic motor 1, and the protruding end 6A side of the rotating shaft 6 can be connected to, for example, a travel reducer or a swing reducer (neither of which are shown) of a hydraulic excavator.

[0016] The rotor (cylinder block) 7 is provided in the casing 2 so as to rotate integrally with the rotary shaft 6. The rotor 7 is formed as a thick-walled cylinder surrounding the rotary shaft 6. The rotor 7 has a plurality of cylinders 8 (only two are shown in FIG. 1 ) that extend axially and are equally spaced circumferentially. One axial side of the rotor 7 is an end face 7A that faces the swash plate 11. A cylindrical protrusion 7B that protrudes toward the swash plate 11 is integrally formed at the center of the end face 7A of the rotor 7. A spherical guide 13, which will be described later, is fitted onto the outer periphery of the cylindrical protrusion 7B so as to be relatively displaceable in the axial direction.

[0017] A stepped shaft hole 7C is formed on the inner periphery of the rotor 7, passing through the inner periphery of the cylindrical protrusion 7B in the axial direction. The shaft hole 7C is splined to the outer periphery of the rotary shaft 6. The rotor 7 is connected to the rotary shaft 6 via the shaft hole 7C so as to rotate integrally with the rotary shaft 6, and is also connected to the spherical guide 13 so as to rotate integrally with the rotary shaft 6. Furthermore, the other axial side of the rotor 7 forms a concave spherical sliding surface 7D that slidably abuts against the valve plate 5.

[0018] A plurality of cylinders 8 are provided at equal intervals around the rotor 7. Each of the cylinders 8 is formed as a bottomed hole with a uniform inner diameter over its entire length. One side of each of the cylinders 8 forms an open end 8A that opens to one end surface 7A of the rotor 7. Meanwhile, the other side of each of the cylinders 8 intermittently communicates with the supply and discharge ports 5A, 5B of the valve plate 5 via a cylinder port 8B.

[0019] The pistons 9 are respectively inserted and fitted into the multiple cylinders 8 of the rotor 7 so as to be able to reciprocate. The pistons 9 are formed as cylindrical rods inserted into the cylinders 8 with a small gap between them. The pistons 9 are driven in the axial direction so as to repeatedly reciprocate within the cylinders 8 by pressure oil supplied to the cylinders 8 from one of the supply and discharge ports 5A, 5B of the valve plate 5. The base ends of the pistons 9 are slidably inserted and fitted into the cylinders 8, and the tip ends of the pistons 9 protrude from the open end 8A of the cylinders 8 to the outside of the rotor 7.

[0020] A concave spherical portion 9A is formed at the tip (protruding end) of the piston 9, and a convex spherical portion 15C of a shoe 15 (described later) is attached to the concave spherical portion 9A so that it can swing. An oil hole 9B is formed in the center of the piston 9, passing through the piston 9 in the axial direction. When the swash plate type hydraulic motor 1 is in operation, some of the hydraulic oil (pressurized oil) supplied into the cylinder 8 is supplied to the shoe 15 as lubricating oil through the oil hole 9B of the piston 9.

[0021] The swash plate support member 10 is disposed inside the casing 2 and fixed to the front bottom portion 3A of the casing body 3. The swash plate support member 10 is provided with a pair of tilt support portions 10A that face each other across the rotary shaft 6. Each of the pair of tilt support portions 10A has a concave curved surface that supports the swash plate 11 so that it can tilt.

[0022] The swash plate 11 is tiltably mounted within the casing 2 and constitutes the variable displacement unit of the swash plate-type hydraulic motor 1. A smooth (flat) sliding surface 11A is formed on the front surface (rotor 7 side) of the swash plate 11, and shoes 15 attached to the tips of the pistons 9 slide on the sliding surface 11A of the swash plate 11. A shaft insertion hole 11B is formed in the center of the swash plate 11, and a rotating shaft 6 is inserted through the shaft insertion hole 11B. Both sides of the rotating shaft 6 sandwiching the swash plate 11 are rotatably engaged with tilt support portions 10A of the swash plate support member 10. The swash plate 11 is tilted while supported by the swash plate support member 10 (tilt support portions 10A) by being pushed by a tilt actuator (not shown) attached to the casing 2, changing the angle between the sliding surface 11A of the swash plate 11 and the rotating shaft 6.

[0023] The retainer 12 is disposed between a shoe 15 attached to the tip of the piston 9 and a spherical guide 13, and holds the shoe 15 slidably against the sliding surface 11A of the swash plate 11. The retainer 12 is formed as an annular plate surrounding the rotary shaft 6, and the spherical guide 13 is slidably fitted to the inner periphery of the retainer 12. The retainer 12 is formed with shoe insertion holes 12A, the same number as the number of shoes 15, spaced equally apart in the circumferential direction. Step portions 15B of the shoes 15 are inserted into these shoe insertion holes 12A. The retainer 12 is biased toward the sliding surface 11A of the swash plate 11 by the spherical guide 13 and a spring member 14. The retainer 12 holds the shoes 15 inserted into the shoe insertion holes 12A in a state pressed against the sliding surface 11A.

[0024] The spherical guide 13 is provided between the cylindrical protrusion 7B of the rotor 7 and the inner periphery of the retainer 12. The spherical guide 13 is formed as a cylindrical body with a spherical outer periphery, and is attached to the cylindrical protrusion 7B so as to be displaceable in the axial direction. The spherical outer periphery of the spherical guide 13 is fitted to the inner periphery of the retainer 12 so as to be able to swing (slide). The inner periphery of the spherical guide 13 is spline-connected to the rotating shaft 6, and the spherical guide 13 rotates integrally with the rotating shaft 6.

[0025] The spring member 14 is located on the outer periphery of the rotary shaft 6 and is provided between the cylindrical protrusion 7B of the rotor 7 and the spherical guide 13. The spring member 14 is formed, for example, by stacking a plurality of disc springs in the axial direction, and biases the rotor 7 and the spherical guide 13 in opposite directions. The spring member 14 presses the sliding surface 7D of the rotor 7 against the valve plate 5, and also presses each shoe 15 against the sliding surface 11A of the swash plate 11 via the spherical guide 13 and the retainer 12.

[0026] Next, the shoe 15 according to this embodiment will be described with reference to FIGS.

[0027] The shoes 15 are attached to the tips of the pistons 9 so as to be able to swing. Each shoe 15 is integrally formed with a disk-shaped portion 15A, a disk-shaped stepped portion 15B having a smaller diameter than the disk portion 15A, and a convex spherical portion 15C protruding from the stepped portion 15B. The disk portion 15A is formed in a disk shape with a larger diameter than the shoe insertion hole 12A of the retainer 12, and has a sliding surface 16 that faces the sliding surface 11A of the swash plate 11. The stepped portion 15B and the convex spherical portion 15C are inserted into the shoe insertion hole 12A of the retainer 12, and the convex spherical portion 15C is attached to the concave spherical portion 9A of the piston 9 so as to be able to swing.

[0028] A linear oil hole 15D is formed in the center of shoe 15, penetrating axially from disc portion 15A to convex spherical portion 15C. A portion of the hydraulic oil (pressurized oil) supplied into cylinder 8 is guided through oil hole 9B of piston 9 through oil hole 15D, and this hydraulic oil is supplied as lubricant between sliding surface 16 of shoe 15 and sliding surface 11A of swash plate 11. Shoe 15 rotates together with rotating shaft 6, rotor 7, and piston 9, and slides smoothly on sliding surface 11A of swash plate 11, tracing a ring-shaped path centered on rotating shaft 6.

[0029] The sliding surface 16 of the shoe 15 is formed on the surface of the disk portion 15A that faces the sliding surface 11A of the swash plate 11. As shown in Figures 2 to 4, the sliding surface 16 has a hydrostatic pocket 16A and a seal surface 16F, which includes a flat surface 16B and a curved inclined surface 16C. A chamfered portion (C-chamfered portion) 16D with an inclination angle of 45° is formed around the entire periphery on the outer circumferential side of the sliding surface 16.

[0030] The hydrostatic pocket 16A is located at the center of the sliding surface 16. The hydrostatic pocket 16A is circular, centered on the axial center A of the shoe 15, and is surrounded from the outer periphery by the flat surface 16B of the sealing surface 16F. As a result, the hydrostatic pocket 16A is located on the inner periphery of the flat surface 16B and is formed as a circular recess that is recessed into the flat surface 16B. The oil hole 15D of the shoe 15 opens into the hydrostatic pocket 16A, and the hydraulic oil discharged through the oil hole 15D to the swash plate 11 side is supplied to the hydrostatic pocket 16A.

[0031] The flat surface 16B constituting the sealing surface 16F is located radially outward of the hydrostatic pocket 16A and is formed as an annular flat surface surrounding the hydrostatic pocket 16A from the outside in the radial direction. The inner peripheral edge 16B1 of the flat surface 16B is circular with a radius R1 centered on the axial center A of the shoe 15. When the axial center A of the shoe 15 is perpendicular to the sliding surface 11A of the swash plate 11, the flat surface 16B abuts (surface-contacts) against the sliding surface 11A of the swash plate 11 as a hydrostatic bearing. By surrounding the hydrostatic pocket 16A from the outer periphery, the flat surface 16B seals the hydraulic oil supplied to the hydrostatic pocket 16A and prevents the hydraulic oil supplied between the sliding surface 11A of the swash plate 11 and the sliding surface 11A of the shoe 15 from leaking to the outside.

[0032] The hydraulic oil supplied to the hydrostatic pocket 16A generates a hydraulic reaction force on the shoe 15 in a direction that moves it away from the sliding surface 11A of the swash plate 11. This hydraulic reaction force causes the shoe 15 to float slightly (for example, several μm to several tens of μm) above the sliding surface 11A of the swash plate 11, and an oil film is formed between the sliding surface 11A of the swash plate 11 and the flat surface 16B of the shoe 15 (sliding surface 16). As a result, the sliding surface 11A of the swash plate 11 and the flat surface 16B of the shoe 15 (sliding surface 16) are appropriately lubricated, allowing the shoe 15 to slide smoothly on the sliding surface 11A of the swash plate 11. At this time, the thrust of the piston 9 that presses the shoe 15 against the swash plate 11 is set to be slightly (for example, several percent) larger than the hydraulic reaction force acting on the shoe 15 by the hydraulic oil supplied to the hydrostatic pocket 16A.

[0033] The curved inclined surface 16C, which serves as an inclined surface, is formed in an annular shape on the outer periphery of the flat surface 16B and constitutes a sealing surface 16F together with the flat surface 16B. The curved inclined surface 16C slopes from the outer periphery of the flat surface 16B toward the outer periphery of the shoe 15, away from the swash plate 11, and intersects with the chamfered portion 16D. The inner periphery of the curved inclined surface 16C forms an annular boundary portion 16E between the flat surface 16B and the curved inclined surface 16C. This boundary portion 16E is circular with a radius R2 and centered on the axial center A of the shoe 15. Note that in FIG. 3, boundary portion 16E between the flat surface 16B and the curved inclined surface 16C is illustrated as a circle centered on the axial center A of the shoe 15 to clearly show it. However, in reality, boundary portion 16E between the flat surface 16B and the curved inclined surface 16C is smoothly continuous to an extent that it cannot be illustrated. On the other hand, outer peripheral edge 16C1 of curved inclined surface 16C is circular with radius R3 from axial center A of shoe 15 and intersects with chamfered portion 16D. As shown in Fig. 5, curved inclined surface 16C is formed as a continuous inclined surface having a curved surface shape that includes a circle or an ellipse from boundary portion 16E with flat surface 16B toward outer peripheral edge 16C1.

[0034] Here, when the swash plate type hydraulic motor 1 is in operation, and the shoe 15 slides on the sliding surface 11A of the swash plate 11 around the rotary shaft 6, hydraulic oil is supplied to the hydrostatic pocket 16A of the shoe 15, and hydraulic oil filled in the casing 2 is drawn between the sliding surface 11A of the swash plate 11 and the sliding surface 16 of the shoe 15. As a result, pressure is generated by an oil film between the sliding surface 11A of the swash plate 11 and the sliding surface 16 of the shoe 15, and the shoe 15 slides on the sliding surface 11A while floating slightly (several μm to several tens of μm) above the sliding surface 11A of the swash plate 11. At this time, due to factors such as the centrifugal force acting on the shoe 15 and the tilting action of the swash plate 11, the sliding surface 16 of the shoe 15 will tilt relative to the sliding surface 11A of the swash plate 11, and there is a risk that part of the outer peripheral edge of the sliding surface 16 will come into contact (partial contact) with the sliding surface 11A of the swash plate 11.

[0035] When the shoe 15 is tilted relative to the sliding surface 11A of the swash plate 11, the curved inclined surface 16C formed on the outer periphery of the sliding surface 16 of the shoe 15 comes into contact with the sliding surface 11A before the chamfered portion 16D formed on the outer periphery of the shoe 15 comes into contact with the sliding surface 11A. This increases the contact area between the curved inclined surface 16C and the sliding surface 11A, reducing the contact pressure compared to when the edge of the chamfered portion 16D comes into contact with the sliding surface 11A, thereby reducing the frictional force between the shoe 15 and the swash plate 11.

[0036] 6, when the shoe 15 slides on the sliding surface 11A of the swash plate 11 in the direction of arrow B, the hydraulic oil in the casing 2 flows into the gap between the curved inclined surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11, creating a wedge effect. As a result, the gap between the sliding surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11 widens at the front side in the direction of travel (the direction of arrow B) and narrows at the rear side in the direction of travel. This wedge effect increases the pressure of the oil film between the entire sliding surface 16 of the shoe 15 and the sliding surface 11A of the swash plate 11, thereby reducing the frictional force caused by contact between the sliding surface 11A of the swash plate 11 and the curved inclined surface 16C of the shoe 15.

[0037] Here, on the sliding surface 16 of the shoe 15, the radius R1 of the inner peripheral edge 16B1 of the flat surface 16B (the inner peripheral radius of the flat surface 16B), the radius R2 of the boundary portion 16E between the flat surface 16B and the curved inclined surface 16C, and the radius R3 of the outer peripheral edge 16C1 of the curved inclined surface 16C (the outer peripheral radius of the curved inclined surface 16C) are set to satisfy the relationship given by the following equation 1.

[0038]

number

[0039] Thus, it is desirable to locate the boundary 16E between the flat surface 16B and the curved inclined surface 16C at the radially intermediate position of the flat surface 16B or closer to the outer periphery (closer to the curved inclined surface 16C) than the intermediate position. That is, if the boundary 16E were located closer to the inner periphery (closer to the hydrostatic pocket 16A) than the radially intermediate position of the flat surface 16B, the area of ​​the flat surface 16B would be reduced, reducing the sealing performance and the hydraulic reaction force acting on the shoe 15 by the hydraulic oil supplied to the hydrostatic pocket 16A. On the other hand, if the boundary 16E were located farther outward than the radially intermediate position of the flat surface 16B, the sealing performance of the flat surface 16B would be improved, but the frictional force between the flat surface 16B and the sliding surface 11A of the swash plate 11 would increase. Taking these factors into consideration, the boundary 16E between the flat surface 16B and the curved inclined surface 16C is located at the radially intermediate position of the flat surface 16B or closer to the outer periphery than the intermediate position.

[0040] Furthermore, the distance h between the outer circumferential edge 16C1 of the curved inclined surface 16C and the flat surface 16B in the direction perpendicular to the flat surface 16B (the direction toward the axial center A of the shoe 15) is set to a maximum of 100 μm (100 μm or less), which is larger than the thickness (e.g., several tens of μm) of the oil film formed between the sliding surface 11A of the swash plate 11 and the flat surface 16B. If the distance h exceeds 100 μm, the angle between the curved inclined surface 16C and the sliding surface 11A of the swash plate 11 becomes large, and the hydraulic oil flowing between them does not become a laminar flow. Therefore, when the shoe 15 slides on the sliding surface 11A of the swash plate 11, it is difficult for the hydraulic oil to flow between the curved inclined surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11, and the wedge effect does not increase the pressure of the oil film. Furthermore, if the distance h exceeds 100 μm, the area of ​​the flat surface 16B will be reduced, reducing the sealing performance and reducing the hydraulic reaction force acting on the shoe 15 by the hydraulic oil supplied to the hydrostatic pocket 16A. Taking these factors into consideration, the distance h between the outer peripheral edge 16C1 of the curved inclined surface 16C and the flat surface 16B is set to a maximum of 100 μm.

[0041] The swash plate type hydraulic motor 1 according to this embodiment has the shoes 15 as described above, and the operation of the swash plate type hydraulic motor 1 will be described below.

[0042] Hydraulic oil (pressurized oil) discharged from a hydraulic pump (not shown) is supplied to a supply / discharge passage (not shown) formed in the rear casing 4. This pressurized oil is supplied to and discharged from a plurality of cylinders 8 formed in the rotor 7 through supply / discharge ports 5A and 5B of the valve plate 5, and a plurality of pistons 9 repeatedly reciprocate within each of the cylinders 8.

[0043] At this time, the piston 9 presses the shoe 15 axially toward the sliding surface 11A of the swash plate 11 by the hydraulic oil supplied to the cylinder 8. Meanwhile, part of the hydraulic oil supplied to the cylinder 8 is supplied to a hydrostatic pocket 16A formed on the sliding surface 16 of the shoe 15 through an oil hole 9B in the piston 9 and an oil hole 15D in the shoe 15. The hydraulic oil supplied to the hydrostatic pocket 16A generates a hydraulic reaction force on the shoe 15 in a direction moving it away from the sliding surface 11A of the swash plate 11. This hydraulic reaction force causes the shoe 15 to float slightly above the sliding surface 11A of the swash plate 11, and an oil film is formed between the sliding surface 11A of the swash plate 11 and the flat surface 16B of the shoe 15 (sliding surface 16).

[0044] As a result, the sliding surface 11A of the swash plate 11 and the flat surfaces 16B of the shoes 15 are appropriately lubricated, and the shoes 15 slide on the sliding surface 11A of the swash plate 11, tracing a ring-shaped path centered on the rotary shaft 6. As the shoes 15 slide on the sliding surface 11A of the swash plate 11, the pistons 9 reciprocate within the cylinders 8, applying a rotational force to the rotor 7 about the rotary shaft 6. This rotational force of the rotor 7 rotates the rotary shaft 6, which in turn drives a mechanical element connected to the protruding end 6A of the rotary shaft 6.

[0045] When the shoe 15 slides on the sliding surface 11A of the swash plate 11 around the rotary shaft 6 during operation of the swash plate-type hydraulic motor 1, hydraulic oil is supplied to the hydrostatic pocket 16A of the shoe 15, and hydraulic oil filled in the casing 2 is drawn between the sliding surface 11A of the swash plate 11 and the sliding surface 16 of the shoe 15. This generates pressure due to an oil film between the sliding surface 11A of the swash plate 11 and the sliding surface 16 of the shoe 15, and the shoe 15 slides on the sliding surface 11A while floating slightly (several μm to several tens of μm) above the sliding surface 11A of the swash plate 11. At this time, the sliding surface 16 of the shoe 15 is tilted relative to the sliding surface 11A of the swash plate 11 due to factors such as the centrifugal force acting on the shoe 15 and the tilting motion of the swash plate 11.

[0046] In contrast, the sliding surface 16 of the shoe 15 in this embodiment has a flat surface 16B that abuts (is in surface contact with) the sliding surface 11A of the swash plate 11 when the axial center A of the shoe 15 is perpendicular to the sliding surface 11A of the swash plate 11, and a curved inclined surface 16C that slopes from the outer periphery of the flat surface 16B toward the outer periphery of the shoe 15 in a direction away from the swash plate 11. As a result, when the shoe 15 is tilted relative to the sliding surface 11A of the swash plate 11, the curved inclined surface 16C contacts the sliding surface 11A before the chamfered portion 16D formed on the outer periphery of the shoe 15. Therefore, the contact area between the curved inclined surface 16C and the sliding surface 11A is increased, and the contact pressure between them can be reduced, compared to when the edge of the chamfered portion 16D contacts the sliding surface 11A.

[0047] Furthermore, as shown in FIG. 6, when the shoe 15 slides on the sliding surface 11A of the swash plate 11 in the direction of arrow B, hydraulic oil filled in the casing 2 flows between the curved inclined surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11, creating a wedge effect. As a result, the gap between the sliding surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11 widens at the front side in the direction of travel (the direction of arrow B) and narrows at the rear side in the direction of travel. This wedge effect increases the pressure of the oil film between the entire sliding surface 16 of the shoe 15 and the sliding surface 11A of the swash plate 11, thereby reducing the frictional force caused by contact between the sliding surface 11A of the swash plate 11 and the curved inclined surface 16C of the shoe 15. As a result, uneven wear of the sliding surface 16 of the shoe 15 is prevented, extending the life of the shoe 15 and enabling the swash plate-type hydraulic motor 1 to operate stably for a long period of time.

[0048] Next, the results of a comparison between the oil film pressure generated between the sliding surface 16 of the shoe 15 and the swash plate 11 in this embodiment and the oil film pressure generated between the sliding surface 102 of the shoe 101 and the swash plate 11 in a comparative example will be explained with reference to Figures 7 and 8.

[0049] 7 shows the relationship between the oil film pressure generated between the sliding surface 16, which includes the hydrostatic pocket 16A, the flat surface 16B, and the curved inclined surface 16C, and the swash plate 11 when the shoe 15 according to this embodiment slides on the swash plate 11 (sliding surface 11A) in the direction of arrow B, and the shape of the sliding surface 16. In this case, the radius R1 of the inner peripheral edge 16B1 of the flat surface 16B is set to R1 = 10.3 mm, the radius R2 of the boundary portion 16E between the flat surface 16B and the curved inclined surface 16C is set to R2 = 13.4 mm, the radius R3 of the outer peripheral edge 16C1 of the curved inclined surface 16C is set to R3 = 16.0 mm, and the distance h between the outer peripheral edge 16C1 of the curved inclined surface 16C and the flat surface 16B is set to h = 0.3 μm.

[0050] 8 shows the relationship between the oil film pressure generated between the sliding surface 102, which has a hydrostatic pocket 102A and a flat surface (sealing surface) 102B, and the shape of the sliding surface 102, when a shoe 101 according to a comparative example slides on the swash plate 11 (sliding surface 11A) in the direction of arrow B. In this case, the diameter of the disk portion 101A is set equal to the diameter of the disk portion 15A of the shoe 15, and the radius R1 of the inner peripheral edge 102B1 of the flat surface 102B is set to R1 = 10.3 mm. The outer peripheral edge of the flat surface 102B intersects with a chamfered portion (C-chamfered portion) 102C formed on the outer peripheral edge of the sliding surface 102 and having an inclination angle of 45°.

[0051] 7, in this embodiment, the oil film pressure generated between the sliding surface 16 of the shoe 15 and the swash plate 11 increases from a pressure value P1 in the range of the curved inclined surface 16C (between the outer peripheral edge 16C1 of the curved inclined surface 16C and the boundary 16E) on the front side in the traveling direction (direction of arrow B) of the shoe 15, and reaches a maximum pressure value P3 at the position of the boundary 16E. In addition, the oil film pressure decreases to a pressure value P2 in the range of the flat surface 16B (between the boundary 16E and the inner peripheral edge 16B1 of the flat surface 16B), and maintains the pressure value P2 in the range of the hydrostatic pocket 16A (between the inner peripheral edge 16B1 on the front side in the traveling direction of the flat surface 16B and the inner peripheral edge 16B1 on the rear side in the traveling direction). Then, on the rear side of the direction of travel of the shoe 15 (direction of arrow B), the oil film pressure decreases from pressure value P2 in the range of the flat surface 16B (between boundary portion 16E and inner peripheral edge 16B1 of the flat surface 16B), and decreases to pressure value P1 in the range of the curved inclined surface 16C (between boundary portion 16E and outer peripheral edge 16C1 of the curved inclined surface 16C).

[0052] As described above, when the shoe 15 of this embodiment slides on the sliding surface 11A of the swash plate 11 in the direction of arrow B, hydraulic oil flows into the gap between the curved inclined surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11 due to a wedge effect at the front of the traveling direction, increasing the oil film pressure. As a result, as shown in Fig. 6, the gap between the sliding surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11 widens at the front of the traveling direction (the direction of arrow B) and narrows at the rear of the traveling direction. As a result, the wedge effect increases the oil film pressure between the entire sliding surface 16 of the shoe 15 and the sliding surface 11A of the swash plate 11, reducing the frictional force caused by contact between the sliding surface 11A of the swash plate 11 and the sliding surface 16 of the shoe 15.

[0053] 6, even if the shoe 15 is tilted relative to the sliding surface 11A of the swash plate 11, the curved inclined surface 16C formed on the outer periphery of the sliding surface 16 contacts the sliding surface 11A before the chamfered portion 16D formed on the outer periphery of the shoe 15. Therefore, the contact area between the curved inclined surface 16C and the sliding surface 11A is increased, and the contact pressure between them can be reduced, compared to when the edge of the chamfered portion 16D contacts the sliding surface 11A.

[0054] 8, the oil film pressure generated between the sliding surface 102 of the shoe 101 and the swash plate 11 in the comparative example increases from pressure value P1 in the range of the flat surface 102B (between the chamfered portion 102C and the inner circumferential edge 102B1 of the flat surface 102B) at the front side of the shoe 101 in the direction of travel (arrow B direction) and maintains pressure value P2 in the range of the hydrostatic pocket 102A (between the inner circumferential edge 102B1 of the flat surface 102B at the front side in the direction of travel to the inner circumferential edge 102B1 of the flat surface 102B at the rear side in the direction of travel of the shoe 101 (arrow B direction)).The oil film pressure then decreases to pressure value P1 in the range of the flat surface 102B (between the inner circumferential edge 102B1 of the flat surface 102B and the chamfered portion 102C) at the rear side of the shoe 101 in the direction of travel (arrow B direction).

[0055] Thus, when the shoe 101 of the comparative example slides on the sliding surface 11A of the swash plate 11 in the direction of arrow B, the oil film pressure between the flat surface 102B and the sliding surface 11A of the swash plate 11 is low, resulting in a large frictional force between the flat surface 102B and the sliding surface 11A of the swash plate 11. Furthermore, if the sliding surface 102 of the shoe 101 is tilted relative to the sliding surface 11A of the swash plate 11, the chamfered portion 102C on the outer periphery of the shoe 101 comes into contact with the sliding surface 11A of the swash plate 11. In this case, the edge of the chamfered portion 102C comes into contact with the sliding surface 11A of the swash plate 11, narrowing the contact area between them and increasing the contact pressure. This can result in uneven wear of the sliding surface 102 and shortening the life of the shoe 101.

[0056] Thus, in the embodiment, in the swash plate type hydraulic motor 1, which comprises a rotating shaft 6 rotatably arranged within the casing 2, a rotor 7 arranged within the casing 2 so as to rotate integrally with the rotating shaft 6 and having a plurality of cylinders 8 formed thereon, a plurality of pistons 9 inserted reciprocally into the plurality of cylinders 8 of the rotor 7, a plurality of shoes 15 respectively provided at the tips of the plurality of pistons 9, and a swash plate 11 on which the plurality of shoes 15 slide, the sliding surface 16 of the shoe 15 facing the swash plate 11 has an annular flat surface 16B that abuts against the swash plate 11, and an inclined surface (curved inclined surface 16C) that inclines from the outer peripheral edge of the flat surface 16B toward the outer periphery of the shoe 15 in a direction away from the swash plate 11.

[0057] With this configuration, when the shoe 15 tilts relative to the sliding surface 11A of the swash plate 11, the curved inclined surface 16C contacts the sliding surface 11A before the outer periphery of the shoe 15. This increases the contact area between the curved inclined surface 16C and the sliding surface 11A, reducing the contact pressure between them compared to when only the outer periphery of the shoe 15 contacts the sliding surface 11A. Furthermore, when the shoe 15 slides on the sliding surface 11A of the swash plate 11, hydraulic oil in the casing 2 flows between the curved inclined surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11, creating a wedge effect. As a result, the gap between the sliding surface 16C of the shoe 15 and the sliding surface 11A of the swash plate 11 becomes wider at the front and narrower at the rear in the direction of travel. This creates a wedge effect that increases the pressure of the oil film between the entire sliding surface 16 of the shoe 15 and the sliding surface 11A of the swash plate 11. As a result, the frictional force caused by contact between the sliding surface 11A of the swash plate 11 and the curved inclined surface 16C of the shoe 15 is reduced, preventing uneven wear of the sliding surface 16 of the shoe 15 and extending the life of the shoe 15.

[0058] In this embodiment, the inclined surface is formed by a curved inclined surface 16C having a curved surface shape that includes a circle or an ellipse. With this configuration, when the shoe 15 is inclined relative to the sliding surface 11A of the swash plate 11, the curved inclined surface 16C contacts the sliding surface 11A before the outer circumferential edge of the shoe 15. Because the curved inclined surface 16C has a curved surface shape that includes a circle or an ellipse, the contact area between the curved inclined surface 16C and the sliding surface 11A is further increased, and the contact pressure between them can be reduced, compared to when the outer circumferential edge of the shoe 15 contacts the sliding surface 11A.

[0059] In the embodiment, when the inner radius of the flat surface 16B is R1, the radius of the annular boundary portion 16E located between the flat surface 16B and the curved inclined surface 16C is R2, and the outer radius of the curved inclined surface 16C is R3, Meets TIFF2026007654000003.tif1160.

[0060] This configuration allows the boundary 16E between the flat surface 16B and the curved inclined surface 16C to be located at the radially central position of the flat surface 16B or slightly outward from the central position. This allows the area of ​​the flat surface 16B to be larger than, for example, when the boundary 16E is located closer to the inner periphery than the radially central position of the flat surface 16B, thereby maintaining good sealing performance of the flat surface 16B. Furthermore, compared to when the boundary 16E is located farther outward from the radially central position of the flat surface 16B, the area of ​​the flat surface 16B is prevented from becoming too large, thereby preventing an increase in friction between the flat surface 16B and the sliding surface 11A of the swash plate 11, thereby ensuring smooth sliding of the shoe 15.

[0061] In this embodiment, the distance h between the flat surface 16B and the outer circumferential edge 16C1 of the curved inclined surface 16C in the direction perpendicular to the flat surface 16B is set to a maximum of 100 μm. This configuration reduces the angle at which the curved inclined surface 16C intersects with the sliding surface 11A of the swash plate 11, facilitating laminar flow of hydraulic oil between them. This increases the oil film pressure due to a wedge effect generated when hydraulic oil flows between the curved inclined surface 16C and the sliding surface 11A of the swash plate 11, lifting the shoe 15 from the sliding surface 11A of the swash plate 11. Furthermore, increasing the area of ​​the flat surface 16B improves sealing performance, ensuring a sufficient hydraulic reaction force acting on the shoe 15 from the hydraulic oil supplied to the hydrostatic pocket 16A.

[0062] 9 and 10 show a second embodiment of the present invention. The feature of this embodiment is that the inclined surface of the sliding surface is formed as a linearly continuous inclined surface. In this embodiment, the same components as those in the first embodiment are given the same reference numerals, and their description will be omitted.

[0063] In the drawings, the shoe 21 according to this embodiment, like the shoe 15 according to the first embodiment, is integrally formed of a disk portion 21A, a disk-shaped stepped portion 21B, and a convex spherical portion 21C, and an oil hole 21D is formed in the center of the shoe 21. The disk portion 21A has a sliding surface 22 that faces the sliding surface 11A of the swash plate 11. However, the sliding surface 22 has a linear inclined surface 22C formed on the outer periphery, which differs from the shoe 15 in that it has a curved inclined surface 16C.

[0064] The sliding surface 22 of the shoe 21 is formed on the surface of the disk portion 21A that faces the sliding surface 11A of the swash plate 11. The sliding surface 22 has a hydrostatic pocket 22A and a sealing surface 22F, which is configured to include a flat surface 22B and a linearly inclined surface 22C. The hydrostatic pocket 22A and the flat surface 22B have the same configuration as the hydrostatic pocket 16A and the flat surface 16B of the shoe 15 in the first embodiment, and the inner peripheral edge 22B1 of the flat surface 22B is circular with a radius R1 centered on the axial center A of the shoe 21. A chamfered portion 22D with an inclination angle of 45° is formed around the entire circumference on the outer periphery of the disk portion 21A relative to the sliding surface 22.

[0065] The linear inclined surface 22C is an annular inclined surface formed on the outer periphery of the flat surface 22B and constitutes a sealing surface 22F together with the flat surface 22B. The linear inclined surface 22C slopes from the outer periphery of the flat surface 22B toward the outer periphery of the shoe 21, away from the swash plate 11, and intersects with the chamfered portion 22D. The inner periphery of the linear inclined surface 22C forms an annular boundary portion 22E between the flat surface 22B and the linear inclined surface 22C. This boundary portion 22E is circular and has a radius R2 centered on the axial center A of the shoe 21. Meanwhile, the outer periphery 22C1 of the linear inclined surface 22C forms a circle with a radius R3 from the axial center A of the shoe 21 and intersects with the chamfered portion 22D. The linear inclined surface 22C is formed as a continuously inclined surface that extends linearly from the boundary portion 22E with the flat surface 22B toward the outer periphery 22C1.

[0066] Here, the radius R1 of the inner peripheral edge 22B1 of the flat surface 22B (the inner peripheral radius of the flat surface 22B), the radius R2 of the boundary portion 22E between the flat surface 22B and the linearly inclined surface 22C, and the radius R3 of the outer peripheral edge 22C1 of the linearly inclined surface 22C (the outer peripheral radius of the linearly inclined surface 22C) are set to satisfy the relationship given by the above-mentioned mathematical expression 1. In addition, the distance h between the outer peripheral edge 22C1 of the linearly inclined surface 22C and the flat surface 22B in the direction perpendicular to the flat surface 22B is set to be equal to or greater than the thickness of the oil film formed between the sliding surface 11A of the swash plate 11 and the flat surface 22B, and is set to a maximum of 100 μm.

[0067] The shoe 21 according to the second embodiment has the above-described configuration, and the same effects as those of the first embodiment can be obtained in this embodiment. That is, when the shoe 21 is tilted relative to the sliding surface 11A of the swash plate 11, the linear inclined surface 22C contacts the sliding surface 11A before the chamfered portion 22D of the shoe 21. Therefore, compared to when the edge of the chamfered portion 22D of the shoe 21 contacts the sliding surface 11A, the contact area between the linear inclined surface 22C and the sliding surface 11A is increased, and the contact pressure between them can be reduced.

[0068] Furthermore, when the shoe 21 slides on the sliding surface 11A of the swash plate 11, hydraulic oil flows between the linearly inclined surface 22C of the shoe 21 and the sliding surface 11A of the swash plate 11, widening the gap between the sliding surface 22C of the shoe 21 and the sliding surface 11A of the swash plate 11 at the front and narrowing the gap at the rear in the direction of travel. This creates a wedge effect, increasing the pressure of the oil film between the entire sliding surface 22 of the shoe 21 and the sliding surface 11A of the swash plate 11. This reduces the frictional force caused by contact between the sliding surface 11A of the swash plate 11 and the linearly inclined surface 22C of the shoe 21, preventing uneven wear of the sliding surface 22C of the shoe 21 and extending the life of the shoe 21.

[0069] 11 to 13 show a third embodiment of the present invention. This embodiment is characterized in that an outer peripheral pad is provided on the outer peripheral side of the flat surface, and a pad inclined surface is formed on the protruding end surface of the outer peripheral pad. In this embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0070] In the drawings, the shoe 31 of this embodiment, like the shoe 15 of the first embodiment, is integrally formed with a disc portion 31A, a disc-shaped stepped portion 31B, and a convex spherical portion 31C, and an oil hole 31D is formed in the center of the shoe 31. The disc portion 31A has a sliding surface 32 that faces the sliding surface 11A of the swash plate 11. The sliding surface 32 has a hydrostatic pocket 32A and a sealing surface 32F, which includes a flat surface 32B and a curved inclined surface 32C. However, this differs from the shoe 15 of the first embodiment in that an inner peripheral pad 33 is disposed on the inner periphery of the flat surface 32B, and an outer peripheral pad 35 is formed on the outer periphery of the flat surface 32B.

[0071] The sliding surface 32 of the shoe 31 is formed on the surface of the disk portion 31A that faces the sliding surface 11A of the swash plate 11. The sliding surface 32 has a hydrostatic pocket 32A and a seal surface 32F, which includes a flat surface 32B and a curved inclined surface 32C. A chamfered portion 32D with an inclination angle of 45° is formed around the entire outer periphery of the disk portion 31A.

[0072] An inner peripheral edge 32B1 of the flat surface 32B is circular with a radius R1 centered on the axial center A of the shoe 31. An inner peripheral edge of the curved inclined surface 32C forms an annular boundary portion 32E located between the flat surface 32B and the curved inclined surface 32C, and this boundary portion 32E is circular with a radius R2 centered on the axial center A of the shoe 31. An outer peripheral edge 32C1 of the curved inclined surface 32C is circular with a radius R3 from the axial center A of the shoe 31, and forms the inner peripheral edge of an outer peripheral annular groove 36 between the outer peripheral pad 35 and the flat surface 32B. Here, the radius R1 of the inner peripheral edge 32B1 of the flat surface 32B (the inner peripheral radius of the flat surface 32B), the radius R2 of the boundary portion 32E between the flat surface 32B and the curved inclined surface 32C, and the radius R3 of the outer peripheral edge 32C1 of the curved inclined surface 32C (the outer peripheral radius of the curved inclined surface 32C) are set to satisfy the relationship given by the above mathematical expression 1.

[0073] The inner pad 33 is located within the hydrostatic pocket 32A and is provided on the inner circumferential side of the flat surface 32B. The inner pad 33 is composed of four pad pieces 33A arranged concentrically with the flat surface 32B around the axial center A of the shoe 31. The four pad pieces 33A have equal arc shapes, and oil passages 33B connecting the inner and outer circumferential sides of the inner pad 33 are formed between adjacent pad pieces 33A. The inner pad 33 protects the flat surface 32B from cavitation erosion, which occurs when hydraulic oil is supplied to the hydrostatic pocket 32A through the oil hole 31D of the shoe 31. An inner annular groove 34 is provided between the flat surface 32B and the inner pad 33 and is concentric with the flat surface 32B. The inner annular groove 34 is connected to the hydrostatic pocket 32A via the oil passages 33B of the inner pad 33.

[0074] The outer pad 35 is provided on the outer peripheral side of the flat surface 32B, surrounds the flat surface 32B, and protrudes toward the swash plate 11. The outer pad 35 is composed of four pad pieces 35A arranged concentrically with the flat surface 32B around the axial center A of the shoe 31. The four pad pieces 35A have the same arc shape, and an oil passage 35B that connects the inner and outer peripheral sides of the outer pad 35 is formed between adjacent pad pieces 35A.

[0075] A pad inclined surface 35C is formed on each of the protruding end surfaces of the four pad pieces 35A constituting the outer peripheral pad 35. The pad inclined surface 35C is formed as a curved inclined surface continuing to the curved inclined surface 32C of the sliding surface 32, specifically, as shown in Fig. 13, when an imaginary line C continuing to the curved inclined surface 32C of the sliding surface 32 is drawn, the curved inclined surface 35C is formed as a curved inclined surface that coincides with the imaginary line C. An outer peripheral edge 35D of the pad inclined surface 35C intersects with the chamfered portion 32D of the shoe 31, and the distance h between the outer peripheral edge 35D and the flat surface 32B is set to a maximum of 100 µm.

[0076] When the sliding surface 32 of the shoe 31 is inclined relative to the sliding surface 11A of the swash plate 11, the outer pad 35 contacts the swash plate 11 before the flat surface 32B, thereby protecting the flat surface 32B. At this time, the curved pad inclined surface 35C formed on the protruding end surface of the pad piece 35A constituting the outer pad 35 increases the contact area between the pad inclined surface 35C and the sliding surface 11A, thereby reducing the contact pressure therebetween.

[0077] The outer peripheral annular groove 36 is provided between the flat surface 32B and the outer peripheral pad 35. The outer peripheral annular groove 36 is disposed concentrically with the flat surface 32B and communicates with the outer peripheral edge of the shoe 15 through the oil passage 35B of the outer peripheral pad 35. As a result, when the shoe 15 slides on the sliding surface 11A of the swash plate 11 during operation of the swash plate type hydraulic motor 1, the hydraulic oil filled inside the casing 2 is introduced into the outer peripheral annular groove 36 through the oil passage 35B of the outer peripheral pad 35.

[0078] The shoe 31 according to the third embodiment has the above-described configuration, and this embodiment also achieves the same effects as the first embodiment. Furthermore, in this embodiment, when the shoe 31 is tilted relative to the sliding surface 11A of the swash plate 11, the outer pad 35 contacts the swash plate 11 before the flat surface 32B, thereby protecting the flat surface 32B. In this case, the protruding end surfaces of the four pad pieces 35A constituting the outer pad 35 each have a curved pad inclined surface 35C that connects to the curved inclined surface 32C of the sliding surface 32. This increases the contact area between the pad inclined surface 35C and the sliding surface 11A, thereby reducing the contact pressure between them. As a result, uneven wear of the outer pad 35 is prevented, and the outer pad 35's effect of protecting the flat surface 32B can be maintained for a long period of time.

[0079] In the third embodiment, a curved inclined surface 32C is formed on the outer circumferential side of the flat surface 32B of the sliding surface 32, and a curved pad inclined surface 35C continuing to the curved inclined surface 32C is formed on the protruding end surface of the pad piece 35A constituting the outer circumferential pad 35. However, the present invention is not limited to this, and for example, a linear inclined surface may be formed on the outer circumferential side of the flat surface 32B, and a linear pad inclined surface continuing to the linear inclined surface may be formed on the protruding end surface of the pad piece 35A constituting the outer circumferential pad 35.

[0080] Furthermore, while the first embodiment exemplifies shoe 15 having convex spherical portion 15C attached to concave spherical portion 9A of piston 9, the present invention is not limited to this and can be applied to, for example, a shoe having a concave spherical portion attached to a convex spherical portion formed on the tip of a piston. The same applies to shoe 21 according to the second embodiment and shoe 31 according to the third embodiment.

[0081] Furthermore, in the embodiment, the swash plate type hydraulic rotating machine has been described by taking as an example a variable displacement swash plate type hydraulic motor 1. However, the present invention is not limited to this, and may be applied to, for example, a fixed displacement swash plate type hydraulic motor, or a variable displacement or fixed displacement swash plate type hydraulic pump. [Explanation of symbols]

[0082] 2 Casing 6 Rotation Axis 7 rotor 8 cylinders 9 pistons 11 Swash plate 15,21,31 shoe 16, 22, 32 sliding surface 16B,22B,32B flat surface 16C, 32C curved inclined surface (inclined surface) 22C Straight inclined surface (inclined surface) 35 Outer pad 35C Pad Incline

Claims

1. a rotating shaft rotatably provided within the casing; a rotor provided in the casing so as to rotate integrally with the rotary shaft and having a plurality of cylinders; a plurality of pistons reciprocatably inserted into the plurality of cylinders of the rotor; a plurality of shoes respectively provided at the tips of the plurality of pistons; a swash plate on which the plurality of shoes slide, A swash plate type hydraulic rotary machine characterized in that the sliding surface of the shoe facing the swash plate has a flat annular surface that abuts against the swash plate and an inclined surface that inclines from the outer periphery of the flat surface toward the outer periphery of the shoe in a direction away from the swash plate.

2. 2. The swash plate type hydraulic rotary machine according to claim 1, wherein the inclined surface is formed as a curved inclined surface having a curved surface shape including a circular shape or an elliptical shape.

3. 2. The swash plate type hydraulic rotary machine according to claim 1, wherein the inclined surface is formed as a linearly continuous inclined surface.

4. When the inner radius of the flat surface is R1, the radius of the annular boundary portion located between the flat surface and the inclined surface is R2, and the outer radius of the inclined surface is R3, 4. The swash plate type hydraulic rotary machine according to claim 1, 2 or 3, wherein the following is satisfied:

5. 4. The swash plate type hydraulic rotary machine according to claim 1, wherein a distance between the flat surface and an outer periphery of the inclined surface in a direction perpendicular to the flat surface is set to a maximum of 100 μm.

6. An annular outer pad is provided on the outer periphery of the flat surface, surrounding the flat surface and protruding toward the swash plate.

2. The swash plate type hydraulic rotary machine according to claim 1, wherein a pad inclined surface is formed on a protruding end surface of the outer peripheral pad facing the swash plate, the pad inclined surface being continuous with the inclined surface.

Images