JP2016133074A - Variable displacement swash-plate hydraulic pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an operating force generated when a tilting actuator tilts a swash plate, and achieve overall downsizing, weight reduction, and cost reduction.SOLUTION: A hydrostatic bearing oil groove 13 cut out along a convex curved surface 12C for introducing hydraulic oil from a discharge passage 3B is provided in a leg section 12A of a swash plate 12. A protrusion fitting groove 14 cut out along the concave curved surface 12C to be continuous with the other end surface 13C of the hydrostatic bearing oil groove 13 and having a smaller dimension H3 than a depth dimension H1 of the hydrostatic bearing oil groove 13 is provided in the leg section 12A. Furthermore, a protrusion extending along a tilting support surface 4A of a swash-plate support member 4 in a state of protruding to the protrusion fitting groove 14 and the hydrostatic bearing oil groove 13 from the tilting support surface 4A, and slidably fitted into the protrusion fitting groove 14 is provided on the tilting support surface 4A. With this configuration, the protrusion 15 is fitted into the protrusion fitting groove 14 and a projected net area difference is generated between two end surfaces 13B and 13C in a length direction of the hydrostatic bearing oil groove 13.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a variable displacement swash plate type hydraulic pump suitably used for construction machines such as a hydraulic excavator, a hydraulic crane, and a wheel loader.

  In general, a variable displacement swash plate hydraulic pump is used as a hydraulic pump that constitutes a hydraulic power source in a construction machine such as a hydraulic excavator.

  In this variable displacement swash plate hydraulic pump according to the prior art, a pair of legs are provided on the back side of the swash plate and projecting convexly toward the swash plate support member. A pair of tilt support surfaces are provided corresponding to the pair of leg portions and formed in a concave curved shape to support the swash plate so as to tilt through the leg portions. The leg portion is formed with an oil groove for a hydrostatic bearing that keeps the space between the leg portion and the tilt support surface of the swash plate support member in a lubricated state by pressure oil introduced from the supply / discharge passage of the casing. (For example, refer patent document 1).

Japanese Patent Laid-Open No. 2003-3951

  By the way, in the variable displacement swash plate hydraulic pump according to the prior art, the pressure of the pressure oil discharged from the cylinder by the piston becomes a hydraulic reaction force, and the swash plate is pressed to the swash plate support member side through this piston. The resultant force of the pressing reaction force by the piston acts at a position deviated from the tilt center of the swash plate. As a result, the force with which the piston presses the swash plate acts as a swinging moment in the direction of tilting the swash plate. When the swash plate is tilted in the same direction as the swing moment by the tilt actuator, the swash plate can be tilted with a small operating force by the swing moment acting in the same direction. However, when the swash plate is tilted in the direction against the swinging moment by the tilting actuator, a large operating force is required for the swinging moment acting in the reverse direction.

  As a result, the tilting actuator must set the performance (output) according to the operating force required when tilting the swash plate in the direction against the swinging moment. For this reason, the tilting actuator is increased in size, and there is a problem that the variable capacity swash plate hydraulic pump is hindered from being reduced in size, weight, and cost.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to reduce the operating force when the swash plate is tilted by the tilt actuator, thereby reducing the overall size, weight, and cost. It is an object of the present invention to provide a variable displacement swash plate type hydraulic pump that can be realized.

  A variable displacement swash plate hydraulic pump according to the present invention is provided with a cylindrical casing having a pump chamber inside and a pair of supply / exhaust passages provided on one side in the axial direction, and the casing on the other side of the pump chamber. A swash plate support member, a rotary shaft extending in the axial direction in the pump chamber of the casing and rotatably supported by the casing, and provided in the casing so as to rotate integrally with the rotary shaft and spaced apart in the circumferential direction A cylinder block having a plurality of cylinders extending in the axial direction, a plurality of pistons removably fitted in the cylinders of the cylinder block, and projecting end sides of the pistons protruding from the cylinders. A plurality of mounted shoes, a swash plate whose front side is a smooth surface for slidably guiding each shoe and whose rear side is supported to be tiltable by the swash plate support member, and a casing are provided. A tilt actuator that tilts and drives the swash plate by supplying and discharging a tilt control pressure from the outside, and on the back side of the swash plate, the swash plate support member is sandwiched by the rotation shaft. A pair of leg portions having convex curved surfaces projecting in a convex curve shape is provided, and the swash plate support member is formed in a concave curved shape corresponding to the convex curved surface of the pair of leg portions. A pair of tilting support surfaces for tiltably supporting the swash plate via the legs are provided.

  In order to solve the above-described problem, a feature of the configuration adopted by the present invention is that at least one leg portion of the pair of leg portions provided on the swash plate is notched along the convex curved surface. An oil groove for hydrostatic bearings through which pressure oil from each of the supply / discharge passages is guided is provided, and at least one of the pair of leg portions is continuously provided from a groove end position of the oil groove for the hydrostatic bearing. Protrusion fitting grooves that are notched along the convex curved surfaces of the leg portions and have shallower dimensions than the hydrostatic bearing oil grooves are provided, and the pair of swash plate support members At least one of the tilt support surfaces is provided along the tilt support surface in a state of projecting from the tilt support surface toward the protrusion fitting groove and / or the hydrostatic bearing oil groove. Protrusions that extend slidably fit into the projection fitting grooves of the leg portions, In that by being fitted into the protrusion fitting groove it was configured to have a difference in pressure receiving area in the longitudinal direction of both ends of the electrostatic pressure bearing oil groove.

  According to the present invention, it is possible to reduce the operating force when the swash plate is tilted by the tilt actuator, and it is possible to reduce the size, weight, and cost of the variable displacement swash plate hydraulic pump.

It is sectional drawing which shows the variable capacity | capacitance type | mold swash plate type hydraulic pump by the 1st Embodiment of this invention in the state in which the top dead center of the piston was an upper side and the bottom dead center became the lower side. It is sectional drawing which looked at the variable displacement type swash plate type hydraulic pump from the direction of arrows II-II in FIG. It is a perspective view shown in the state which assembled | attached the swash plate support member and the swash plate. It is a disassembled perspective view in the state which decomposed | disassembled the swash plate support member and the swash plate. It is sectional drawing of the principal part expansion which looked at the fitting state of the inclination support surface of a swash plate support member, and the convex curve surface of the leg part of a swash plate from the arrow VV direction in FIG. FIG. 3 is a cross-sectional view of a variable displacement swash plate hydraulic pump according to a second embodiment of the present invention as viewed from the same position as in FIG. 2. It is a disassembled perspective view shown in the state which decomposed | disassembled the swash plate support member and swash plate in FIG. It is a disassembled perspective view which shows the state which decomposed | disassembled the swash plate supporting member which has the circular arc-shaped groove | channel by the 3rd Embodiment of this invention, the oil groove for static pressure bearings, and the circular arc-shaped convex part. It is sectional drawing of the principal part expansion which looked at the swash plate support member and swash plate in FIG. 8 from the same position as FIG. It is a disassembled perspective view in the state which decomposed | disassembled the swash plate support member which has the circular arc-shaped groove by the 4th Embodiment of this invention, the oil groove for static pressure bearings, and an arc-shaped convex part.

  Hereinafter, a configuration of a variable displacement swash plate hydraulic pump according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  1 to 5 show a variable displacement swash plate hydraulic pump according to a first embodiment of the present invention.

  In FIG. 1, a variable displacement swash plate hydraulic pump 1 (hereinafter referred to as a hydraulic pump 1) discharges pressure oil used in various actuators (not shown) mounted on, for example, a construction machine. The hydraulic pump 1 is illustrated so that a top dead center of a piston 8 described later is positioned on the upper side and a bottom dead center is positioned on the lower side. The hydraulic pump 1 is configured as a hydraulic pump whose pressure oil discharge direction is determined in advance. The hydraulic pump 1 includes a casing 2, a swash plate support member 4, a rotating shaft 5, a cylinder block 6, a cylinder 7, a piston 8, a shoe 9, a valve plate 11, a swash plate 12, a hydrostatic bearing oil groove 13, and a protrusion, which will be described later. The fitting groove 14, the protrusion 15, the tilting actuators 16 and 17, etc. are included.

  The casing 2 is formed as a cylindrical body that becomes an outer shell of the hydraulic pump 1. The casing 2 includes a cylindrical casing body 2A, and a front casing 2B and a rear casing 2C in which both ends of the casing body 2A are closed, and the inside thereof is a pump chamber 2D. The casing body 2A may be formed integrally with either the front casing 2B or the rear casing 2C.

  As shown in FIG. 2, the rear casing 2C located on one side of the casing body 2A is provided with a suction passage 3A and a discharge passage 3B constituting a pair of supply / discharge passages. The suction passage 3A is connected to a hydraulic oil tank (not shown) serving as a supply source of hydraulic oil, and the discharge passage 3B is connected to a discharge pipe (none of which is shown) extending toward the control valve device. . Further, a swash plate support member 4 described later is provided on the front casing 2B located on the other side of the casing body 2A so as to face the back side of the swash plate 12.

  The swash plate support member 4 is provided on the front casing 2B side which is the other side of the casing 2 in the pump chamber 2D. As shown in FIGS. 2 and 4, the swash plate support member 4 is integrally formed with a pair of tilt support surfaces 4 </ b> A and 4 </ b> B with a rotation shaft 5 described later interposed therebetween. The tilt support surfaces 4A and 4B of the swash plate support member 4 support a swash plate 12 described later in a tiltable (swingable) manner.

  The tilt support surfaces 4A and 4B of the swash plate support member 4 are formed in a concave curved shape corresponding to the convex curved surfaces 12C and 12D of the leg portions 12A and 12B constituting the swash plate 12. The swash plate support member 4 guides the swash plate 12 so as to be tiltable (slidable) in directions indicated by arrows A and B in FIG. Further, as shown in FIG. 2, the swash plate support member 4 is provided with a shaft insertion hole 4C located between the tilt support surfaces 4A and 4B, and the shaft insertion hole 4C has a rotating shaft. 5 is inserted with a gap.

  Here, the tilt support surfaces 4A and 4B of the swash plate support member 4 are, as shown in FIG. 4, intermediate portions in the length direction with respect to the one end edges 4A1 and 4B1 and the other end edges 4A2 and 4B2 in the length direction. Is formed as a concave curved surface that becomes the deepest portions 4A3, 4B3. The tilt support surfaces 4A and 4B are fitted so that the convex curved surfaces 12C and 12D of the legs 12A and 12B constituting the swash plate 12 can tilt (slide). A protrusion 15 described later is provided on the tilt support surface 4A located on the high pressure side (pressure oil discharge side) of 4A and 4B.

  The rotating shaft 5 is provided to extend in the axial direction in the pump chamber 2D of the casing 2, and the rotating shaft 5 is rotatably supported by the front casing 2B and the rear casing 2C via bearings. The other end of the rotating shaft 5 is a protruding end 5A protruding in the axial direction from the front casing 2B, and a motor such as an engine is connected to the protruding end 5A via a power transmission mechanism (not shown). Is done.

  The cylinder block 6 is provided in the casing 2 so as to rotate integrally with the rotary shaft 5, and the cylinder block 6 includes a plurality of cylinders 7 (FIG. 1, FIG. 2) extending in the axial direction and spaced apart in the circumferential direction. 1 each is shown). Generally, the number of cylinders 7 provided in the cylinder block 6 is set to an odd number, for example, 7 or 9.

  The piston 8 is slidably inserted into each cylinder 7 of the cylinder block 6. Each piston 8 reciprocates in the cylinder 7 as the cylinder block 6 rotates, and repeats the suction stroke and the discharge stroke.

  The shoe 9 is provided on each piston 8. Specifically, each shoe 9 is swingably attached to an end portion of a piston 8 that protrudes from the cylinder 7 of the cylinder block 6 in the axial direction of the rotary shaft 5.

  The shoe presser 10 holds each shoe 9 against the swash plate 12. As shown in FIG. 1, the shoe presser 10 presses the shoes 9 toward a smooth surface 12E of a swash plate 12 described later so that each shoe 9 draws an annular locus on the smooth surface 12E of the swash plate 12. It compensates for sliding displacement.

  The valve plate 11 is positioned in the casing 2 and is fixed between the rear casing 2C and the cylinder block 6. The valve plate 11 slidably contacts the end face of the cylinder block 6 to rotatably support the cylinder block 6 that rotates integrally with the rotary shaft 5. Further, a pair of supply / discharge ports 11A, 11B having an eyebrow shape are formed in the valve plate 11 so as to draw a circle, and these supply / discharge ports 11A, 11B are formed in the suction passage 3A and the discharge passage 3B of the rear casing 2C. Communicated with.

  The supply / discharge ports 11 </ b> A and 11 </ b> B of the valve plate 11 intermittently communicate with the cylinders 7 when the cylinder block 6 rotates. At this time, the piston 8 reciprocating in each cylinder 7 sucks the hydraulic oil into each cylinder 7 through the suction passage 3A and the supply / discharge port 11A in the suction stroke. Further, in the discharge stroke by the piston 8, the pressure oil that is in a high pressure state in each cylinder 7 is discharged from the discharge passage 3B via the supply / discharge port 11B.

  Thereby, the force with which the piston 8 presses the swash plate 12 via the shoe 9 differs between the suction passage 3 </ b> A side for sucking hydraulic oil and the discharge passage 3 </ b> B side for discharging pressure oil. Moreover, the pressing force at this time varies depending on the position of each piston 8 in the cylinder block 6. Therefore, when the hydraulic pump 1 is in operation, as shown in FIG. 5, a swinging moment C is generated with respect to the swash plate 12, and this swinging moment C causes the swash plate 12 to move in the direction indicated by the arrow B (the tilt angle is It acts to tilt in the direction of decreasing).

  The swash plate 12 is provided in the casing 2 so as to be tiltable via a swash plate support member 4. On the back side of the swash plate 12, as shown in FIGS. 3 and 4, a pair of leg portions 12A and 12B projecting in a convex curve toward the tilting support surfaces 4A and 4B of the swash plate support member 4 are provided. Is provided.

  The leg portions 12A and 12B of the swash plate 12 are disposed so as to sandwich the rotating shaft 5, and are slidably fitted to the tilt support surfaces 4A and 4B of the swash plate support member 4 having a concave curved shape. Is. That is, the leg portions 12A and 12B are formed as arcuate semi-cylindrical bodies having convex curved surfaces 12C and 12D that are slidably fitted to the tilt support surfaces 4A and 4B of the swash plate support member 4, respectively. The convex curved surfaces 12C and 12D of the leg portions 12A and 12B made of the semi-cylindrical body are fitted to the tilt support surfaces 4A and 4B of the swash plate support member 4 with the oil film interposed therebetween. , 4B and substantially the same curved surface.

  Specifically, the convex curved surfaces 12C and 12D are convex curved shapes in which the intermediate portion in the length direction becomes the top portions 12C3 and 12D3 with respect to the curved one end edges 12C1 and 12D1 and the other end edges 12C2 and 12D2. Is formed to protrude. The leg 12A is fitted so that its convex curved surface 12C can slide on the tilt support surface 4A. On the other hand, the leg 12B is fitted so that its convex curved surface 12D can slide on the tilt support surface 4B. Here, among the leg portions 12A and 12B, a hydrostatic bearing oil groove 13 described later is provided on the convex curved surface 12C of the leg portion 12A located on the pressure oil discharge side (high pressure side).

  On the other hand, the surface side (cylinder block 6 side) of the swash plate 12 is a smooth surface 12E for slidably guiding the shoes 9 as shown in FIGS. In addition, a through hole 12F that extends through the plate thickness direction (axial direction of the casing 2) is provided at the center position of the swash plate 12, and the through hole 12F is located between the leg portions 12A and 12B. Thus, the rotating shaft 5 is inserted with a gap. The swash plate 12 is tilted in directions indicated by arrows A and B in FIG. 1 by using tilt actuators 16 and 17 described later. The discharge capacity (pressure oil discharge flow rate) of the hydraulic pump 1 is variably controlled according to the tilt angle of the swash plate 12.

  Next, the configuration of the hydrostatic bearing oil groove 13, the protrusion fitting groove 14, and the protrusion 15 which are characteristic portions of the present invention will be described.

  The hydrostatic bearing oil groove 13 is a convex curved surface of the leg portion 12A that is pressed by the piston 8 in the discharge stroke that has received the pressure of the pressure oil, out of the pair of leg portions 12A and 12B provided on the swash plate 12. 12C. The hydrostatic bearing oil groove 13 is notched deep along the convex curved surface 12C of the leg portion 12A, and the pressure oil is guided from the discharge passage 3B through the oil guide passage 18 to be described later. The space between the convex curved surface 12C of 12A and the tilt support surface 4A of the swash plate support member 4 is maintained in a lubricated state.

  As shown in FIGS. 4 and 5, the hydrostatic bearing oil groove 13 is centered on the top 12C3 of the convex curved surface 12C provided on the leg 12A formed as a semi-cylindrical body, and both of the semi-cylindrical bodies. It is formed as a long groove extending a certain length toward the end edges 12C1 and 12C2. The hydrostatic bearing oil groove 13 is formed as a concave groove extending with a certain width dimension so that, for example, a rectangular or U-shaped cross section is continuous. The length of the hydrostatic bearing oil groove 13 is set to a dimension capable of communicating with an oil guide passage 18 described later even when the swash plate 12 has the maximum tilt angle.

  Here, in the hydrostatic bearing oil groove 13, the depth dimension from the convex curved surface 12C to the groove bottom 13A is set to the dimension H1. In the hydrostatic bearing oil groove 13, the groove end position on the arrow A direction side in FIG. 5 becomes one end face 13 B, and this one end face 13 B has a larger area due to the depth dimension H 1.

  On the other hand, in the hydrostatic bearing oil groove 13, the groove end position on the arrow B direction side in FIG. 5 is the other end face 13 </ b> C, and the other end face 13 </ b> C is connected (continuous) to the protrusion fitting groove 14 described later. Thus, the depth dimension H2 is smaller than the depth dimension H1 at the one end face 13B (H2 <H1). Thereby, the other end surface 13C has a smaller pressure receiving area than the one end surface 13B.

  In addition, although each end surface 13B and 13C is extended and formed in the radial direction so that it may become substantially perpendicular | vertical with respect to the convex curved surface 12C, it is good also as a structure inclined with respect to the convex curved surface 12C. The hydrostatic bearing oil groove 13 may have a cross-sectional shape other than a rectangular shape or a U-shape, such as a triangular shape or a pentagonal shape.

  The hydrostatic bearing oil groove 13 formed in this way is maintained in a lubrication state by the pressure oil supplied from the discharge passage 3B via the oil guide passage 18, and the swash plate support member 4 It can function as a hydrostatic bearing with respect to the tilt support surface 4A.

  The protrusion fitting groove 14 is provided on the convex curved surface 12 </ b> C of the leg portion 12 </ b> A together with the hydrostatic bearing oil groove 13. The protrusion fitting groove 14 extends in a circular arc shape from the position of the hydrostatic bearing oil groove 13 along the convex curved surface 12C, and a protrusion 15 described later is slidably fitted therein.

  Here, the protrusion fitting groove 14 is formed as a rectangular groove having the same width as the hydrostatic bearing oil groove 13, and is continuous from the other end surface 13 </ b> C serving as the groove end position of the hydrostatic bearing oil groove 13, It is notched along the convex curved surface 12C of the leg 12A. The depth dimension of the protrusion fitting groove 14 is set to a dimension H3 shallower than the entire depth dimension H1 of the hydrostatic bearing oil groove 13. Thus, the depth dimension of the other end face 13C of the hydrostatic bearing oil groove 13 is set to a dimension H2 that is shallower by the depth dimension H3 of the protrusion fitting groove 14 than the entire depth dimension H1 ( H2 = H1-H3).

  The protrusion 15 is provided on one tilt support surface 4 </ b> A facing the leg portion 12 </ b> A of the swash plate 12 among the pair of tilt support surfaces 4 </ b> A and 4 </ b> B provided on the swash plate support member 4. The protrusion 15 is fitted in the protrusion fitting groove 14 on the leg portion 12A side, so that the pressure oil guided from the discharge passage 3B is sealed in the hydrostatic bearing oil groove 13, and this pressure oil leaks to the outside. It is a thing which suppresses doing.

  In this case, the protrusion 15 extends along the tilt support surface 4A in a state of projecting from the tilt support surface 4A toward the protrusion fitting groove 14 and the hydrostatic bearing oil groove 13, and the protrusion 12 of the leg portion 12A is fitted. The groove 14 is slidably fitted.

  Further, the protrusion 15 is a protrusion that protrudes in a rectangular shape and extends in an arc shape along the tilt support surface 4A so that the protrusion 15 fits into the protrusion fitting groove 14 with a slight gap that does not leak pressure oil. Is formed. Furthermore, the protrusion 15 is provided to extend from the other end edge 4A2 of the tilt support surface 4A to the vicinity of the deepest portion 4A3.

  Thereby, the protrusion 15 can seal the hydrostatic bearing oil groove 13 by being fitted into the protrusion fitting groove 14 while allowing the swash plate 12 to tilt. Thereby, the protrusion 15 can give the pressure receiving area difference to the both ends of the length direction of the oil groove 13 for hydrostatic bearings by applying the pressure by pressure oil to the one end surface 13B and the other end surface 13C.

  The pair of tilting actuators 16 and 17 drives the swash plate 12 to tilt. As shown in FIG. 1, each of the tilting actuators 16 and 17 is located on the radially outer side of the cylinder block 6 and is formed in the cylinder holes 16A and 17A in the casing body 2A, and slides into the cylinder holes 16A and 17A. Tilt pistons 16C and 17C that are movably inserted and define hydraulic chambers 16B and 17B between the cylinder holes 16A and 17A, and for supplying and discharging tilt control pressure into the hydraulic chambers 16B and 17B. Control pressure passages 16D and 17D formed in the casing body 2A are included.

  The tilting actuators 16 and 17 are disposed at positions opposed to each other in the radial direction of the cylinder block 6 with respect to the casing body 2A, and the tilting pistons 16C and 17C drive the swash plate 12 in the directions indicated by arrows A and B. To do. That is, the tilt control pressure is supplied and discharged from the outside to the hydraulic chambers 16B and 17B of the tilt actuators 16 and 17 through the control pressure passages 16D and 17D shown in FIG. Note that pressure oil discharged from the discharge passage 3B can be used as the tilt control pressure supplied to the tilt actuators 16 and 17.

  Here, as shown in FIG. 1, when the tilting piston 17C of the tilting actuator 17 extends from the cylinder hole 17A and the tilting piston 16C of the tilting actuator 16 contracts into the cylinder hole 16A by the tilt control pressure. The swash plate 12 is driven to tilt in the direction indicated by the arrow A (the positive direction in which the tilt angle of the swash plate 12 increases) by the tilting piston 16C. On the other hand, when the tilting piston 16C extends from the cylinder hole 16A and the tilting piston 17C contracts into the cylinder hole 17A, the swash plate 12 is moved by the tilting piston 17C in the direction indicated by the arrow B (the tilt angle of the swash plate 12). Tilt is driven in the opposite direction).

  The oil guide passage 18 is provided in the casing 2 (see FIG. 2). One side of the oil guide passage 18 in the length direction is connected to the discharge passage 3B on the rear casing 2C side. On the other hand, the other side in the length direction of the oil guide passage 18 is branched into the deepest portion 4A3 of the tilt support surface 4A of the swash plate support member 4 and the deepest portion 4B3 of the tilt support surface 4B on the front casing 2B side. It is open. Accordingly, the oil guide passage 18 can supply the pressure oil discharged to the discharge passage 3B to the hydrostatic bearing oil groove 13 and the like.

  The variable displacement swash plate hydraulic pump 1 according to the first embodiment has the above-described configuration. Next, the tilting operation of the swash plate 12 will be described.

  First, when the discharge capacity of the hydraulic pump 1 is increased, the tilt piston 17C of the tilt actuator 17 is extended, and the tilt piston 16C of the tilt actuator 16 is contracted. As a result, the swash plate 12 is driven to tilt in the direction of arrow A in FIG. 1 so that the tilt angle becomes large.

  On the other hand, when the discharge capacity of the hydraulic pump 1 is decreased, the tilt piston 16C of the tilt actuator 16 is extended, and the tilt piston 17C of the tilt actuator 17 is contracted. As a result, the swash plate 12 is tilted in the direction indicated by the arrow B in FIG. 1 so that the tilt angle becomes small.

  Here, in the variable displacement swash plate type hydraulic pump 1, the piston 8 that receives the pressure of the pressure oil discharged from the cylinder 7 to the discharge passage 3 </ b> B as a hydraulic reaction force causes the swash plate 12 to be swash plate through the shoe 9. Press toward the support member 4 side. At this time, a moment (oscillation moment C in FIG. 5) that causes the swash plate 12 to tilt (swing) is generated by the force of each piston 8 pressing the swash plate 12. When the swash plate 12 is tilted in the same direction as the swinging moment C acts by the tilting actuators 16 and 17, the swinging moment C acting in the same direction can be tilted with a small operating force. . However, when the swash plate 12 is tilted in the direction against the swinging moment C by the tilting actuators 16 and 17, a large operating force is required for the swinging moment C acting in the reverse direction.

  However, according to the first embodiment, the leg portion 12A of the swash plate 12 is notched deep in the groove depth along the convex curved surface 12C, and the hydrostatic bearing from which the pressure oil from the discharge passage 3B is guided. An oil groove 13 is provided. Further, the leg portion 12A of the swash plate 12 is notched along the convex curved surface 12C continuously from the other end surface 13C which is the groove end position of the hydrostatic bearing oil groove 13, and the hydrostatic bearing oil groove 13 is obtained. The protrusion fitting groove 14 having a dimension H3 shallower than the depth dimension H1 is provided. Further, the tilt support surface 4A of the swash plate support member 4 extends along the tilt support surface 4A in a state of projecting from the tilt support surface 4A toward the protrusion fitting groove 14 and the hydrostatic bearing oil groove 13. A protrusion that extends and is slidably fitted in the protrusion fitting groove 14 of the leg 12A is provided. Accordingly, the protrusion 15 can be fitted in the protrusion fitting groove 14, so that the pressure receiving area difference can be provided between both end faces 13 </ b> B and 13 </ b> C in the length direction of the hydrostatic bearing oil groove 13.

  That is, in the hydrostatic bearing oil groove 13, the area of the one end face 13B is set to be large by the large depth dimension H1, and the area of the other end face 13C is set to be small by the small depth dimension H2. In this configuration, when the pressure oil is supplied to the hydrostatic bearing oil groove 13, the pressure oil pressure acts on the end faces 13B and 13C. In this case, the swash plate 12 acts so that the pressure is tilted in the direction indicated by the arrow A due to the pressure receiving area difference between the large one end surface 13B and the small other end surface 13C.

  Thus, even when the swinging moment C is applied to the swash plate 12, the pressure oil is received by the one end face 13B, so that the swash plate 12 is moved in the direction of arrow A against the swinging moment C. A pressing force can be applied.

  As a result, the tilting actuators 16 and 17 that tilt the swash plate 12 tilt the swash plate 12 in the direction of the swinging moment C when tilting the swash plate 12 in a direction against the swinging moment C. In any case, the swash plate 12 can be tilted with a small operating force. Thereby, since the tilting actuators 16 and 17 can be reduced in size, the variable displacement swash plate hydraulic pump 1 can be reduced in size, weight, and cost.

  Next, FIG. 6 and FIG. 7 show a second embodiment of the present invention. The feature of this embodiment is directed to, for example, a bi-tilting hydraulic pump used in a hydraulic closed circuit. For this reason, the protrusion fitting grooves are provided in a pair of legs provided on the swash plate so as to be point-symmetric with respect to the rotation axis, and the protrusions are also point-symmetric with respect to the rotation axis. The swash plate support member is provided on each of the pair of tilt support surfaces. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 6, the variable displacement swash plate hydraulic pump 21 (hereinafter referred to as the hydraulic pump 21) according to the second embodiment can switch the discharge direction of the pressure oil according to the tilt direction of the swash plate 24 described later. It is configured as a tilting hydraulic pump. The hydraulic pump 21 includes the swash plate support member 4, the rotary shaft 5, the cylinder block 6, the cylinder 7, the piston 8, the shoe 9, the valve plate 11, the tilting actuators 16 and 17, and a casing 22 and a swash plate 24 described later. The hydrostatic bearing oil grooves 25 and 26, the protrusion fitting grooves 27 and 28, and the protrusions 29 and 30 are configured.

  The casing 22 according to the second embodiment is composed of a casing body 22A, a front casing 22B, and a rear casing 22C in substantially the same manner as the casing 2 according to the first embodiment. However, the casing 22 according to the second embodiment is different from the casing 2 according to the first embodiment in that a pair of supply / discharge passages 23A and 23B is provided in the rear casing 22C. Here, the supply / discharge passage 23 </ b> A and the supply / discharge passage 23 </ b> B are configured to selectively drive a tilting angle of a swash plate 24, which will be described later, from a position of zero angle in one direction and the other direction. The suction passage for sucking in and the discharge passage for discharging the pressure oil can be switched to each other.

  The swash plate 24 according to the second embodiment is substantially the same as the swash plate 12 according to the first embodiment. The leg portions 24A and 24B, the convex curved surfaces 24C and 24D (one end edges 24C1 and 24D1, the other end edge 24C2). 24D2, top 24C3, 24D3), smooth surface 24E, and through-hole 24F. However, in the swash plate 24 according to the second embodiment, the tilt angle is set larger than the swash plate 12 according to the first embodiment to a position where the hydraulic oil suction side and the discharge side can be reversed. Is different.

  The first hydrostatic bearing oil groove 25 according to the second embodiment is provided on the convex curved surface 24C of the leg portion 24A in the same manner as the hydrostatic bearing oil groove 13 according to the first embodiment. A bottom 25A, one end surface 25B, and the other end surface 25C are included.

  On the other hand, the second hydrostatic bearing oil groove 26 is formed on the convex curved surface 24D of the leg portion 24B so as to be point-symmetric with the first hydrostatic bearing oil groove 25 with respect to the axis of the rotary shaft 5. The groove bottom 26A, one end surface 26B, and the other end surface 26C are provided.

  The first protrusion fitting groove 27 is a rectangular groove having the same width as that of the first hydrostatic bearing oil groove 25, similarly to the protrusion fitting groove 14 according to the first embodiment. Along with the first hydrostatic bearing oil groove 25, it is provided on the convex curved surface 24C of the leg 24A. The first protrusion fitting groove 27 is a slidably fitted first protrusion 29 to be described later, and is connected to the first hydrostatic bearing oil groove 25 so as to be continuous with the first static pressure bearing oil groove 25. From the other end face 25C of the pressure groove oil groove 25 to the other end edge 24C2 of the convex curved face 24C, the arc extends along the convex curved face 24C.

  The second protrusion fitting groove 28 is a leg portion together with the second hydrostatic bearing oil groove 26 so as to be point-symmetric with the first protrusion fitting groove 27 with respect to the axis of the rotary shaft 5. 24B is provided on the convex curved surface 24D. The second protrusion fitting groove 28 is formed as a rectangular groove having the same width as that of the second hydrostatic bearing oil groove 26. The second protrusion fitting groove 28 is slidably fitted with a second protrusion 30 described later, and the second static pressure so as to be continuous with the second hydrostatic bearing oil groove 26. From the one end surface 26B of the bearing oil groove 26 to the one end edge 24D1 of the convex curved surface 24D, the arc extends along the convex curved surface 24D.

  The first protrusion 29 is provided on the tilt support surface 4 </ b> A of the swash plate support member 4. Similar to the projection 15 according to the first embodiment, the first projection 29 is fitted into the first projection fitting groove 27 on the leg portion 24A side, whereby the first hydrostatic bearing oil groove. 25, both end faces 25B and 25C in the length direction have a pressure receiving area difference.

  The first protrusion 29 protrudes in a rectangular shape so as to fit into the first protrusion fitting groove 27 with a slight gap that does not leak pressure oil, and in an arc shape along the tilt support surface 4A. It is formed as an elongated ridge. Further, the first protrusion 29 is provided so as to extend from the other end edge 4A2 of the tilt support surface 4A to the vicinity of the deepest portion 4A3. Thus, the first protrusion 29 seals the first hydrostatic bearing oil groove 25 while allowing the swash plate 24 to be tilted, so that the first end face 25B and the other end face 25C are made of pressure oil. Pressure can be applied.

  The second protrusion 30 is provided on the tilt support surface 4 </ b> B of the swash plate support member 4 so as to be point-symmetric with the first protrusion 29 with respect to the axis of the rotation shaft 5. The second projection 30 is fitted into the second projection fitting groove 28 on the leg portion 24B side, whereby pressure is received on both end faces 26B and 26C in the length direction of the second hydrostatic bearing oil groove 26. It gives an area difference.

  The second protrusion 30 protrudes in a rectangular shape so as to fit into the second protrusion fitting groove 28 with a slight gap that does not leak pressure oil, and in an arc shape along the tilt support surface 4B. It is formed as an elongated ridge. The second protrusion 30 is provided so as to extend from one end edge 4B1 of the tilting support surface 4B to the vicinity of the deepest portion 4B3. As a result, the protrusion 30 seals the second hydrostatic bearing oil groove 26 while allowing the swash plate 24 to tilt, thereby applying pressure by pressure oil to the one end face 26B and the other end face 26C. Can be made.

  As shown in FIG. 6, the first oil guide passage 31 is connected to the supply / discharge passage 23 </ b> A on one side in the length direction, and communicates with the first hydrostatic bearing oil groove 25 on the other side. The support member 4 opens to the deepest part 4A3 of the tilt support surface 4A. Thereby, the first oil guide passage 31 can supply the pressure oil flowing through the supply / discharge passage 23 </ b> A to the first hydrostatic bearing oil groove 25.

  The second oil guide passage 32 is tilted and supported by the swash plate support member 4 so that one side in the length direction is connected to the supply / discharge passage 23B and the other side communicates with the second hydrostatic bearing oil groove 26. It opens to the deepest part 4B3 of the surface 4B. Accordingly, the second oil guide passage 32 can supply the pressure oil flowing through the supply / discharge passage 23B to the second hydrostatic bearing oil groove 26.

  Thus, according to the second embodiment, the first hydrostatic bearing oil groove 25, the second hydrostatic bearing oil groove 26, the first protrusion fitting groove 27, and the second protrusion fitting groove. 28, the first protrusion 29 and the second protrusion 30 are provided so as to be point-symmetric with respect to the rotation axis 5. Thus, even with the bi-tilt hydraulic pump 21 that can selectively tilt the swash plate 24 in one direction and the other direction with the tilt angle as a reference to switch the discharge direction of the pressure oil. A pressing force that opposes the swinging moment C can be applied to the swash plate 24, and the tilting actuator that tilts the swash plate 24 can be downsized.

  Next, FIG. 8 and FIG. 9 show a third embodiment of the present invention. A feature of this embodiment is that a hydrostatic bearing is provided in which at least one of the pair of legs provided on the swash plate is notched along a convex curved surface and pressure oil is guided from each supply / discharge passage. An oil groove is provided, and at least one of the pair of leg portions protrudes from the convex curved surface toward the tilt support surface of the swash plate support member and extends from the groove end position of the hydrostatic bearing oil groove to the convex curved surface. Protrusions extending along the swash plate support member are provided, and at least one of the tilt support surfaces provided on the swash plate support member is cut along the tilt support surface so that the protrusions on the leg can slide. Protrusion fitting grooves are provided to be fitted to the protrusions, and the protrusions are configured to have a pressure receiving area difference at both ends in the longitudinal direction of the oil groove for hydrostatic bearings by being fitted into the protrusion fitting grooves. . Note that in the third embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 8, the hydrostatic bearing oil groove 41 according to the third embodiment is provided on the convex curved surface 12 </ b> C of the leg portion 12 </ b> A of the swash plate 12. The hydrostatic bearing oil groove 41 is formed as a long groove extending a certain length toward both end edges 12C1 and 12C2 of the semi-cylindrical body with the top portion 12C3 of the convex curved surface 12C as the center. The hydrostatic bearing oil groove 41 is formed, for example, as a concave groove extending so that a rectangular or U-shaped cross section is continuous, and the depth dimension from the convex curved surface 12C to the groove bottom 41A is shown in FIG. Thus, the dimension H4 is set. In the hydrostatic bearing oil groove 41, an end portion on the arrow A direction side is one end surface 41B, and an end portion on the arrow B direction side is the other end surface 41C.

  Here, the hydrodynamic groove 41 for the hydrostatic bearing has a large dimension H6 by extending the depth dimension H4 (diameter dimension) of the one end face 41B to the outside in the radial direction by the height dimension H5 of the protrusion 42 described later. (H6 = H4 + H5). As a result, an end face having a dimension H6 larger than the depth dimension H4 of the other end face 41C can be formed on one end side of the hydrostatic bearing oil groove 41 (H6> H4).

  The hydrostatic bearing oil groove 41 is supplied with pressure oil from the discharge passage 3 </ b> B through the oil guide passage 18, and maintains a lubrication state by this pressure oil, and the tilt support surface 4 </ b> A of the swash plate support member 4. It can function as a hydrostatic bearing.

  The protrusion 42 is provided on the convex curved surface 12 </ b> C of the leg portion 12 </ b> A together with the hydrostatic bearing oil groove 41. The protrusion 42 is formed as a protrusion protruding from the position of the hydrostatic bearing oil groove 41 toward the tilt support surface 4A and extending in an arc shape along the convex curved surface 12C of the leg portion 12A. The protrusion 42 is slidably fitted into a protrusion fitting groove 43 described later, and is a convex curved surface of a leg portion 12A that forms a semi-cylindrical body with one end face 41B that is a groove end position of the oil groove 41 for hydrostatic bearings. Between the one end edge 12 </ b> C <b> 1 of 12 </ b> C, for example, it protrudes into a rectangular cross section with the same width as the hydrostatic bearing oil groove 41.

  Here, the protrusion 42 is provided so as to be continuous with the one end surface 41 </ b> B of the hydrostatic bearing oil groove 41. The end surface 42A of the protrusion 42 has a radial height dimension H5 (protrusion dimension). As a result, the protrusion 42 can increase the depth dimension H4 (radial dimension) of the one end face 41B that receives pressure by the height dimension H5 of the end face 42A.

  The protrusion fitting groove 43 is provided on the tilt support surface 4 </ b> A of the swash plate support member 4. The protrusion fitting groove 43 extends in an arc shape along the tilt support surface 4A, and the protrusion 42 of the leg 12A is slidably fitted therein. The protrusion fitting groove 43 is provided to extend from one end edge 4A1 of the tilting support surface 4A to the vicinity of the deepest portion 4A3.

  Therefore, the protrusion fitting groove 43 seals the pressure oil introduced from the discharge passage 3B into the hydrostatic bearing oil groove 41 by fitting the protrusion 42, and the pressure oil leaks to the outside. Can be suppressed. Thereby, the pressure by pressure oil can be made to act on the one end surface 41B and the other end surface 41C by sealing the oil groove 41 for hydrostatic bearings.

  Thus, according to the third embodiment, it is possible to obtain substantially the same operational effects as those of the first embodiment. In particular, according to the third embodiment, the hydrostatic bearing oil groove 41 has an area on the one end face 41B side set to be large by a large depth dimension H6, and an area of the other end face 41C is set to be a small depth dimension H4. It is set small. Thereby, the swash plate 12 can be pressed against the swash plate 12 in a direction against the swinging moment C due to the area difference between the large one end surface 41B and the small other end surface 41C (pressure difference area).

  Next, FIG. 10 shows a fourth embodiment of the present invention. The feature of this embodiment is directed to, for example, a bi-tilting hydraulic pump used in a hydraulic closed circuit. Therefore, the protrusion fitting grooves are respectively provided on the pair of tilt support surfaces provided on the swash plate support member so as to be point-symmetric with respect to the rotation axis, and the protrusions are also pointed with respect to the rotation axis. It is set as the structure each provided in a pair of leg part provided in the swash plate so that it may become symmetrical. Note that in the fourth embodiment, the same components as those in the third embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 10, a swash plate 51 according to the fourth embodiment includes leg portions 51A and 51B, convex curved surfaces 51C and 51D, a smooth surface 51E, and a through hole 51F. Compared with the swash plate 12 according to the third embodiment, the swash plate 51 according to the fourth embodiment has a larger tilt angle to a position where the hydraulic oil suction side and the discharge side can be reversed. It is different in point.

  Similar to the hydrostatic bearing oil groove 41 according to the third embodiment, the first hydrostatic bearing oil groove 52 according to the fourth embodiment is provided on the convex curved surface 51C of the leg 51A. The bottom 52A, one end surface 52B, and the other end surface 52C are configured.

  On the other hand, the second hydrostatic bearing oil groove 53 is formed on the convex curved surface 51D of the leg 51B so as to be point-symmetric with the first hydrostatic bearing oil groove 52 with respect to the axis of the rotary shaft 5. The groove bottom 53A, one end surface 53B, and the other end surface 53C are provided.

  The first protrusion 54 according to the fourth embodiment protrudes from the convex curved surface 51C of the leg 51A toward the tilting support surface 4A, like the protrusion 42 according to the third embodiment, and the leg 51A It is formed as a ridge extending in an arc shape along the convex curved surface 51C.

  The second protrusion 55 has a convex curved surface 51D of the leg portion 51B together with the second hydrostatic bearing oil groove 53 so as to be point-symmetric with the first protrusion 54 with respect to the axis of the rotating shaft 5. Is provided. The second protrusion 55 is formed in the same manner as the first protrusion 54 except for the installed direction.

  The first protrusion fitting groove 56 according to the fourth embodiment is provided on the tilt support surface 4A of the swash plate support member 4 in the same manner as the protrusion fitting groove 43 according to the third embodiment. The first protrusion fitting groove 56 extends in an arc shape along the tilt support surface 4A, and the first protrusion 54 of the leg 51A is slidably fitted therein.

  The second protrusion fitting groove 57 is provided on the tilt support surface 4B of the swash plate support member 4 so as to be point-symmetric with the first protrusion fitting groove 56 with respect to the axis of the rotating shaft 5. Yes. The second protrusion fitting groove 57 is formed in the same manner as the first protrusion fitting groove 56 except for the installed direction.

  Thus, according to the fourth embodiment, the first hydrostatic bearing oil groove 52, the second hydrostatic bearing oil groove 53, the first protrusion 54, the second protrusion 55, and the first protrusion. The fitting groove 56 and the second protrusion fitting groove 57 are provided so as to be point-symmetric with respect to the rotating shaft 5. Thus, even with a bi-tilt hydraulic pump that can selectively tilt the swash plate 51 in one direction and the other direction and switch the discharge direction of the pressure oil with reference to the position where the tilt angle is zero, A pressing force that opposes the swinging moment C can be applied to the swash plate 51, and the tilt actuator that tilts and drives the swash plate 51 can be reduced in size.

  In the first embodiment, a case where the swash plate support member 4 is provided separately from the casing 2 is illustrated. However, the present invention is not limited to this, and the tilt support member may be formed integrally with the front casing of the casing. This configuration can be similarly applied to other embodiments.

  1,21 Hydraulic pump (variable displacement swash plate hydraulic pump), 2,22 casing, 2D pump chamber, 3A suction passage (supply / discharge passage), 3B discharge passage (supply / discharge passage), 4 swash plate support member, 4A, 4B Tilt support surface, 5 Rotating shaft, 6 Cylinder block, 7 Cylinder, 8 Piston, 9 Shoe, 11 Valve plate, 12, 24, 51 Swash plate, 12A, 12B, 24A, 24B, 51A, 51B Leg, 12C , 12D, 24C, 24D, 51C, 51D Convex curved surface, 12E, 24E Smooth surface, 13, 41 Oil groove for hydrostatic bearing, 14, 43 Protrusion fitting groove, 15, 42 Protrusion, 16, 17 Tilt actuator, 18 oil guide passage, 23A, 23B supply / discharge passage, 25, 52 first hydrostatic bearing oil groove, 26, 53 second hydrostatic bearing oil groove, 27 , 56 First projection fitting groove, 28, 57 Second projection fitting groove, 29, 54 First projection, 30, 55 Second projection, 31 First oil guide passage, 32 Second guide Oil passage, H1, H2, H3, H4, H5, H6 dimensions

Claims (6)

A cylindrical casing having a pump chamber inside and a pair of supply / exhaust passages provided on one side in the axial direction, a swash plate support member provided on the other side of the pump chamber of the casing, and a pump chamber of the casing A rotating shaft that extends in the axial direction and is rotatably supported by the casing, and a plurality of cylinders that are provided in the casing so as to rotate integrally with the rotating shaft and extend in the axial direction and spaced apart in the circumferential direction. A cylinder block, a plurality of pistons inserted into the cylinders of the cylinder block so as to be able to reciprocate, a plurality of shoes mounted on the protruding end sides of the pistons protruding from the cylinders, A swash plate that is a smooth surface that slidably guides the shoe and whose back side is tiltably supported by the swash plate support member, and a tilt control pressure that is provided on the casing and is supplied and discharged from the outside. Ri swash plate and a tilting actuator for tilting drive,
On the back surface side of the swash plate, a pair of legs having a convex curved surface protruding in a convex curved shape toward the swash plate support member across the rotation shaft is provided,
The swash plate support member is formed in a concave curved shape corresponding to the convex curved surface of the pair of leg portions, and a pair of tilt support members that tiltably support the swash plate via the leg portions. In the variable displacement swash plate hydraulic pump configured to provide a surface,
At least one of the pair of legs provided on the swash plate is provided with an oil groove for a hydrostatic bearing that is notched along the convex curved surface and into which the pressure oil from each supply / discharge passage is guided. Provided,
At least one leg portion of the pair of leg portions is notched along the convex curved surface of the leg portion continuously from the groove end position of the hydrostatic bearing oil groove. Protrusion fitting grooves with dimensions shallower than the depth dimension are provided,
At least one tilt support surface of the pair of tilt support surfaces provided on the swash plate support member is provided with the protrusion fitting groove and / or the hydrostatic bearing oil groove from the tilt support surface. Provided with a protrusion that extends along the tilt support surface in a state of projecting toward the protrusion, and is slidably fitted into the protrusion fitting groove of the leg,
The variable displacement swash plate hydraulic pump characterized in that the protrusion is configured to have a pressure receiving area difference at both ends in the length direction of the hydrostatic bearing oil groove by being fitted into the protrusion fitting groove. .   The protrusion fitting grooves are provided in the pair of leg portions provided in the swash plate so as to be point-symmetric with respect to the rotation axis, and the protrusions are also point-symmetric with respect to the rotation axis. The variable displacement swash plate hydraulic pump according to claim 1, wherein the variable displacement swash plate hydraulic pump is provided on each of the pair of tilt support surfaces provided on the swash plate support member. The pair of legs provided on the swash plate is formed by an arc-shaped semi-cylindrical body,
The hydrostatic bearing oil groove is formed as a long groove extending a certain length toward both end edges of the semi-cylindrical body with the top of the semi-cylindrical body as the center,
The variable displacement swash plate hydraulic pump according to claim 1, wherein the protrusion fitting groove is formed between a groove end position of the hydrostatic bearing oil groove and an end edge of the semi-cylindrical body. A cylindrical casing having a pump chamber inside and a pair of supply / exhaust passages provided on one side in the axial direction, a swash plate support member provided on the other side of the pump chamber of the casing, and a pump chamber of the casing A rotating shaft that extends in the axial direction and is rotatably supported by the casing, and a plurality of cylinders that are provided in the casing so as to rotate integrally with the rotating shaft and extend in the axial direction and spaced apart in the circumferential direction. A cylinder block, a plurality of pistons inserted into the cylinders of the cylinder block so as to be able to reciprocate, a plurality of shoes mounted on the protruding end sides of the pistons protruding from the cylinders, A swash plate that is a smooth surface that slidably guides the shoe and whose back side is tiltably supported by the swash plate support member, and a tilt control pressure that is provided on the casing and is supplied and discharged from the outside. Ri swash plate and a tilting actuator for tilting drive,
On the back surface side of the swash plate, a pair of legs having a convex curved surface protruding in a convex curved shape toward the swash plate support member across the rotation shaft is provided,
The swash plate support member is formed in a concave curved shape corresponding to the convex curved surface of the pair of leg portions, and a pair of tilt support members that tiltably support the swash plate via the leg portions. In the variable displacement swash plate hydraulic pump configured to provide a surface,
At least one of the pair of legs provided on the swash plate is provided with an oil groove for a hydrostatic bearing that is notched along the convex curved surface and into which the pressure oil from each supply / discharge passage is guided. Provided,
At least one leg of the pair of legs protrudes from the convex curved surface toward the tilt support surface of the swash plate support member and extends from the groove end position of the hydrostatic bearing oil groove to the convex curved surface. Provided with a protrusion extending along the
At least one tilt support surface of the pair of tilt support surfaces provided on the swash plate support member is cut along the tilt support surface and the projection of the leg portion is slidably fitted. Protrusion fitting groove to be fitted,
The variable displacement swash plate hydraulic pump characterized in that the protrusion is configured to have a pressure receiving area difference at both ends in the length direction of the hydrostatic bearing oil groove by being fitted into the protrusion fitting groove. .   The protrusion fitting grooves are respectively provided on the pair of tilt support surfaces provided on the swash plate support member so as to be point-symmetric with respect to the rotation axis, and the protrusions are also based on the rotation axis. 5. The variable displacement swash plate hydraulic pump according to claim 4, wherein the variable displacement swash plate hydraulic pump is provided on each of the pair of legs provided on the swash plate so as to be point-symmetric. The pair of legs provided on the swash plate is formed by an arc-shaped semi-cylindrical body,
The hydrostatic bearing oil groove is formed as a long groove extending a certain length toward both end edges of the semi-cylindrical body with the top of the semi-cylindrical body as the center,
The variable displacement swash plate hydraulic pump according to claim 4, wherein the protrusion is formed between a groove end position of the hydrostatic bearing oil groove and an end edge of the semi-cylindrical body.

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