JP2017048690A - Water pressure rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency of a water pressure rotating machine.SOLUTION: A piston pump 100 includes a cylinder block 2 to which a shaft 1 is connected, a plurality of cylinders 2b formed in the cylinder block 2, a piston 6 slidably inserted into the cylinder 2b, a shoe 8 connected to an end of the piston 6, a swash plate 9 with which the shoe 8 is brought into slidable contact, and a coating layer 20 provided on a concave spherical surface 8a of one of the piston 6 and the shoe 8 so as to slide with a convex spherical surface 6a of the other. The coating layer 20 has a communication area A1 in which a first communication hole 6c can be communicated with a second communication hole 8c, a lubrication groove 20b having one end 20c opened to a storage chamber 19 and the other end 20d extended toward the communication area A1, and an isolation area A3 isolating the communication area A1 from the lubrication groove 20b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hydraulic rotating machine.

  As a hydraulic rotating machine, for example, a piston pump as in Patent Document 1 is known. Patent Document 1 discloses a hydraulic axial piston pump having a shoe that is in sliding contact with a piston.

JP-A-8-247021

  As disclosed in Patent Document 1, in a piston pump using water with poor lubricity as a working fluid, if the lubricity of the sliding surface between the piston and the shoe deteriorates, the frictional resistance of the sliding surface increases, and the pump There is a risk that the efficiency of the system will decrease.

  The present invention has been made in view of the above problems, and an object thereof is to improve the lubricity of the sliding surface between the piston and the shoe and to improve the efficiency of the hydraulic rotating machine.

  1st invention is provided in the concave spherical surface part of any one of a piston and a shoe, the coating layer which slides with the other convex spherical surface part, the 1st communicating hole provided in a piston, and the 2nd provided in a shoe. A communication hole, a storage chamber for storing the cylinder block, and a covering layer in which the first communication hole and the second communication hole can communicate with each other; one end opening into the storage chamber and the other end in the communication region And a separation region that separates the communication region and the lubrication groove from each other.

  In the first invention, a lubricating groove that opens to the accommodation chamber is formed in the coating layer provided on the concave spherical surface portion. For this reason, water flows in from the accommodation chamber through the lubrication groove, and a water lubrication film is formed between the coating layer and the convex spherical surface portion. In addition, the coating layer is provided with an isolation region that separates the communication groove where the first communication hole and the second communication hole communicate with the lubricating groove. For this reason, it is suppressed that pressurized water leaks from the connection part of a 1st communicating hole and a 2nd communicating hole to a lubricating groove.

  The second invention is characterized in that the lubricating groove extends over the semi-concave spherical surface of the coating layer centering on the communication region.

  In the second invention, when the hydraulic rotating machine is operated, the lubricating groove is formed so as to reach the semi-concave spherical surface of the coating layer on which the pressing force acts. For this reason, it becomes possible to supply water through the lubricating groove to the sliding surface of the portion where the pressing force acts, and the slidability of this portion can be improved. As a result, the volumetric efficiency of the hydraulic rotating machine can be improved.

  According to a third aspect of the present invention, the depth of the lubricating groove decreases from one end to the other end.

  The fourth invention is characterized in that the width of the lubricating groove becomes narrower from one end to the other end.

  In the third and fourth inventions, the cross-sectional area of the lubricating groove gradually decreases as it goes from one end to the other end. For this reason, water is retained in the lubricating groove by capillary action, and a water lubricating film is easily formed between the sliding surface and the convex spherical surface portion. As a result, the slidability between the piston and the shoe is improved, and the volumetric efficiency of the hydraulic rotating machine can be improved.

  The fifth invention is characterized in that a plurality of lubrication grooves are provided, and the coating layer further has a connection groove for connecting adjacent lubrication grooves.

  In 5th invention, the water which flows in from the end of a lubrication groove is distributed to an adjacent lubrication groove through a connection groove. For this reason, water flows uniformly into each lubricating groove, and a lubricating film of water is formed between the sliding surface and the convex spherical surface portion without being biased to one place. As a result, the slidability between the piston and the shoe is improved, and the volumetric efficiency of the hydraulic rotating machine can be improved.

  In the present invention, the lubricity of the sliding surface between the piston and the shoe can be improved, and the efficiency of the hydraulic rotating machine can be improved.

It is sectional drawing of the hydraulic rotating machine which concerns on embodiment of this invention. It is an enlarged view of the joint part of the piston and the shoe of the hydraulic rotating machine according to the embodiment of the present invention. It is an enlarged view of a shoe of a hydraulic rotating machine concerning an embodiment of the present invention. It is the figure seen from the arrow A direction of FIG. It is an enlarged view of the joint part of the piston and shoe of the hydraulic rotating machine which concerns on the modification of embodiment of this invention. It is an enlarged view of a shoe of a hydraulic rotating machine concerning a modification of an embodiment of the present invention. It is the figure seen from the arrow B direction of FIG.

  Hereinafter, with reference to FIGS. 1-4, the hydraulic rotating machine 100 which concerns on embodiment of this invention is demonstrated.

  The hydraulic rotating machine 100 is a hydraulic rotating machine that uses water as a working fluid. The hydraulic rotary machine 100 functions as a piston pump capable of supplying pressurized water by rotating the shaft 1 and reciprocating the piston 6 by power from the outside, and the water fluid supplied from the outside The piston 6 reciprocates due to the pressure and the shaft 1 rotates, thereby functioning as a piston motor capable of outputting a rotational driving force. The hydraulic rotary machine 100 may function only as a piston pump, or may function only as a piston motor.

  In the following description, the case where the hydraulic rotating machine 100 is used as a piston pump is illustrated, and the hydraulic rotating machine 100 is simply referred to as “piston pump 100”.

  As shown in FIG. 1, the piston pump 100 includes a shaft 1 that is rotated by a power source, a cylinder block 2 that is connected to the shaft 1 and rotates together with the shaft 1, and a case 3 that houses the cylinder block 2. The case 3 includes a case main body 3a that is open at both ends, a front cover 4 that seals one open end of the case main body 3a and the shaft 1 is inserted, and the other open end of the case main body 3a is sealed to the shaft 1 An end cover 5 for accommodating the end portion.

  A power source is connected to one end 1 a of the shaft 1 that protrudes to the outside through the insertion hole 4 a of the front cover 4. The end portion 1 a of the shaft 1 is rotatably supported by the insertion hole 4 a of the front cover 4 via the first bush 16. The other end 1 b of the shaft 1 is accommodated in an accommodation recess 5 a provided in the end cover 5 and is rotatably supported via a second bush 17.

  The cylinder block 2 has a through hole 2a through which the shaft 1 passes, and is splined to the shaft 1 through the through hole 2a. Thereby, the cylinder block 2 rotates as the shaft 1 rotates. The cylinder block 2 is rotatably supported by the case 3 via a slide bearing 15 and is accommodated in an accommodation chamber 19 formed in the case 3. The interior of the storage chamber 19 is filled with water.

  In the cylinder block 2, a plurality of cylinders 2 b having openings on one end face are formed in parallel with the shaft 1. The plurality of cylinders 2 b are formed with a predetermined interval in the circumferential direction of the cylinder block 2. A cylindrical piston 6 is inserted into the cylinder 2b so as to freely reciprocate.

  The piston 6 is formed with a hollow portion 6b extending in the axial direction and a first communication hole 6c having one end opened in the hollow portion 6b and extending in the axial direction. The volume chamber 7 is defined by the hollow portion 6b of the piston 6 and the inner wall of the cylinder 2b. One end of the piston 6 projects from the opening of the cylinder 2b, and a convex spherical surface 6a is formed at the end. The volume chamber 7 and the convex spherical surface portion 6a communicate with each other through the first communication hole 6c.

  Water is guided to the volume chamber 7 through a supply passage 10 formed in the end cover 5. The water in the volume chamber 7 is discharged through a discharge passage 11 formed in the end cover 5.

  The piston pump 100 includes a shoe 8 that is rotatably connected to a convex spherical portion 6 a provided at an end of the piston 6 and that is in sliding contact with the convex spherical portion 6 a, and a swash plate 9 that is in sliding contact with the shoe 8 as the cylinder block 2 rotates. And a valve plate 18 interposed between the cylinder block 2 and the end cover 5.

  The shoe 8 is formed through a concave spherical surface portion 8 a that receives the convex spherical surface portion 6 a formed at the end portion of each piston 6, a circular flat plate portion 8 b that is in sliding contact with the swash plate 9, and the axial center of the shoe 8. A second communication hole 8c.

  A coating layer 20 that is coated with a resin material such as polyetheretherketone is formed on the inner surface of the concave spherical surface portion 8a. The concave spherical surface portion 8 a is in sliding contact with the outer surface of the convex spherical surface portion 6 a of the piston 6 through the sliding surface 20 a of the coating layer 20. The shoe 8 can be displaced at any angle with respect to the convex spherical portion 6a. The configuration of the coupling portion between the piston 6 and the shoe 8 will be described in detail later.

  The flat plate portion 8b of the shoe 8 that is in sliding contact with the swash plate 9 is provided with a coating layer 21 that is coated with a resin material such as polyetheretherketone.

  The resin material of the coating layers 20 and 21 is not limited to polyether ether ketone, but water such as polyacetal, polyamide, polyphenylene sulfide, polyamide imide, polyether imide, polyimide, polytetrafluoroethylene, phenol resin, or the like having poor lubricity. Even if it is a case where it is used as a working fluid, what kind of resin may be sufficient if it is resin with abrasion resistance. Thus, the coating layers 20 and 21 coated with a resin material that can ensure lubricity even when the working fluid is water are provided on the sliding portion, so that seizure occurs even when water is used as the working fluid. Etc. can be suppressed.

  The swash plate 9 is fixed to the inner wall of the front cover 4 and has a sliding contact surface 9 a inclined from a direction perpendicular to the axis of the shaft 1. The flat plate portion 8b of the shoe 8 is in surface contact with the sliding contact surface 9a via the coating layer 21.

  The valve plate 18 is a disk member with which the base end surface of the cylinder block 2 is in sliding contact, and is fixed to the end cover 5. In the valve plate 18, a supply port 18 a that connects the supply passage 10 and the volume chamber 7 and a discharge port 18 b that connects the discharge passage 11 and the volume chamber 7 are formed.

  Next, with reference to FIGS. 2 to 4, the structure of the coupling portion between the piston 6 and the shoe 8 will be described. FIG. 2 is an enlarged cross-sectional view showing a joint portion between the piston 6 and the shoe 8. FIG. 3 is a cross-sectional view of the shoe 8 before being coupled to the piston 6. 4 is a view as seen from the direction of arrow A in FIG.

  As shown in FIG. 2, the piston 6 and the shoe 8 are coupled to connect the first communication hole 6 c and the second communication hole 8 c. The coating layer 21 is supplied with water pressurized in the volume chamber 7 through the first communication hole 6c and the second communication hole 8c. For this reason, the coating layer 21 always contains water, water acts as a lubricant, and the frictional resistance on the sliding surface between the shoe 8 and the swash plate 9 is reduced.

  Further, as shown in FIGS. 2 to 4, a lubricating groove 20b is provided on the sliding surface 20a of the covering layer 20 that is in sliding contact with the convex spherical surface portion 6a.

  The lubrication groove 20b is formed such that one end 20c opens into the storage chamber 19 and the other end 20d extends toward the connection portion between the first communication hole 6c and the second communication hole 8c. Since the lubrication groove 20b is open to the accommodation chamber 19, water flows from the accommodation chamber 19 through the lubrication groove 20b between the sliding surface 20a and the convex spherical surface portion 6a of the coating layer 20, and lubricates the water. A film is formed. As described above, the water lubrication film is formed between the sliding surface 20a and the convex spherical surface portion 6a, whereby the frictional resistance on the sliding surface between the piston 6 and the shoe 8 is reduced.

  In order to improve the slidability between the piston 6 and the shoe 8, it is desirable to provide the lubricating groove 20b over the entire sliding surface 20a. However, when the lubrication groove 20b communicates with the second communication hole 8c, the water pressurized in the volume chamber 7 flows out into the storage chamber 19 through the first communication hole 6c, the second communication hole 8c, and the lubrication groove 20b. End up. Even if the lubricating groove 20b is formed so as not to open to the second communication hole 8c, when the shoe 8 is tilted with respect to the piston 6 as the swash plate 9 is tilted, the first communication hole 6c communicates. If the lubrication groove 20b is provided at the position where the pressure is applied, the water pressurized in the volume chamber 7 flows out into the storage chamber 19 through the first communication hole 6c and the lubrication groove 20b.

  Thus, if the water pressurized by the volume chamber 7 flows out into the storage chamber 19 through the lubrication groove 20b, the volumetric efficiency of the piston pump 100 will fall. For this reason, the lubrication groove 20b is formed at a position not communicating with the first communication hole 6c and the second communication hole 8c even when the shoe 8 is tilted with respect to the piston 6 as the swash plate 9 is tilted. The

  Specifically, as shown in FIGS. 2 to 4, the coating layer 20 includes a communication region A1 in which the first communication hole 6c and the second communication hole 8c can communicate, and a lubrication region in which the lubrication groove 20b is provided. A2 and an isolation region A3 that separates the communication region A1 and the lubrication region A2.

  The communication area A1 is a range in which the first communication hole 6c and the second communication hole 8c can communicate with each other when the shoe 8 is inclined with respect to the piston 6 as the swash plate 9 is tilted. This is a region surrounded by a first circle C1 having a first diameter D1 centered on 8c. The first diameter D1 is set based on the overlapping range of the opening end of the first communication hole 6c and the opening end of the second communication hole 8c, that is, the diameter of the first communication hole 6c and the diameter of the second communication hole 8c. Is done.

  The lubrication region A2 is a region extending from the open end 8d of the concave spherical portion 8a to the vicinity of the communication region A1, and includes most of the semi-concave spherical surface of the sliding surface 20a centering on the communication region A1. The semi-concave spherical surface of the sliding surface 20a is a portion where a relatively large pressing force acts when the shoe 8 is pressed against the piston 6 when the piston pump 100 is operated. The convex spherical surface is centered on the communication region A1. It is a concave spherical surface surrounded by a second circle C2 having a second diameter D2 corresponding to the diameter of the portion 6a.

  As shown in FIG. 4, a plurality of lubricating grooves 20b are provided radially in the lubricating region A2 with the second communication hole 8c as the center. These lubricating grooves 20b are formed to extend over the semi-concave spherical surface of the sliding surface 20a. For this reason, it becomes possible to supply water through the lubricating groove 20b to the sliding surface 20a where the relatively large pressing force acts, and the frictional resistance of this portion can be reduced and the slidability can be improved.

  Further, as shown in FIGS. 2 and 3, the lubricating groove 20b provided in the lubricating region A2 is formed so that the depth gradually decreases from the one end 20c to the other end 20d. As shown in FIG. 4, the lubricating groove 20b is formed so that the width gradually decreases from the one end 20c to the other end 20d. That is, the lubricating groove 20b is formed so that the cross-sectional area gradually decreases from the one end 20c toward the other end 20d.

  As described above, the lubricating groove 20b is formed to have a smaller cross-sectional area as it is away from the one end 20c that opens in the storage chamber 19, so that water is easily retained in the lubricating groove 20b by capillary action. As a result, particularly in the lubricating region A2, the formation of a water lubricating film between the sliding surface 20a and the convex spherical surface portion 6a is promoted.

  The isolation region A3 is a region surrounded by the third circle C3 having the third diameter D3 and the first circle C1 having the first diameter D1, and includes the first communication hole 6c and the second communication hole 8c that open to the communication region A1. In order to block communication with the lubricating groove 20b provided in the lubricating region A2.

  When the third diameter D3 is set to be larger, the isolation region A3 is enlarged, the blocking property between the communication region A1 and the lubrication region A2 is improved, and pressurized water from the connection portion between the first communication hole 6c and the second communication hole 8c. Leakage is suppressed. On the other hand, since the lubrication area A2 becomes narrow, the slidability between the piston 6 and the shoe 8 is lowered. For this reason, the magnitude | size of the 3rd diameter D3 is set in consideration of the balance of interruption | blocking property and sliding property.

  As described above, the sliding surface 20a is provided with the lubrication region A2 where the lubrication groove 20b is provided, and the isolation region A3 separating the communication region A1 and the lubrication region A2. For this reason, it is possible to improve the slidability between the piston 6 and the shoe 8 and to suppress the leakage of pressurized water from the connection portion between the first communication hole 6c and the second communication hole 8c. As a result, the volumetric efficiency of the piston pump 100 can be improved.

  The sliding surface 20a is provided with a connection groove 20e that connects adjacent lubricating grooves 20b. Water flowing from one end 20c of the lubricating groove 20b is distributed to the adjacent lubricating groove 20b through the connecting groove 20e. For this reason, water flows uniformly into each lubricating groove 20b, and a water lubricating film is formed between the sliding surface 20a and the convex spherical surface portion 6a without being biased to one place. By providing the connection grooves 20e at a plurality of locations, the lubrication grooves 20b and the connection grooves 20e may be formed in a mesh shape on the sliding surface 20a.

  Next, a method for connecting the shoe 8 to the piston 6 will be described.

  The shoe 8 is coupled to the piston 6 so as to cover the convex spherical portion 6 a of the piston 6. Specifically, the convex spherical surface portion 6a of the piston 6 is inserted into the concave spherical surface portion 8a of the shoe 8 with the open end 8d as shown in FIG. Then, the open end 8d is drawn (crimped) from the outside in the radial direction in a state where the convex spherical portion 6a is inserted into the concave spherical portion 8a. As shown in FIG. 2, the concave spherical surface portion 8a is deformed into a shape along the convex spherical surface portion 6a, and the convex spherical surface portion 6a can be slidably supported by the concave spherical surface portion 8a.

  Here, when the opening end portion 8d is drawn from outside in the radial direction, the coating layer 20 provided on the concave spherical surface portion 8a is also contracted and deformed. When the coating layer 20 contracts, the internal stress increases and part of the coating layer 20 may be damaged. However, the coating layer 20 is provided with a plurality of lubrication grooves 20b. During drawing, the width of the lubrication grooves 20b is narrowed, so that an increase in internal stress is alleviated. Thus, by providing the lubricating groove 20b, it is possible to prevent the coating layer 20 from being damaged when the opening end portion 8d is drawn.

  Next, the operation of the piston pump 100 will be described.

  When the shaft 1 is rotationally driven by power from the outside and the cylinder block 2 rotates, the flat plate portion 8b of each shoe 8 slides with respect to the swash plate 9, and each piston 6 corresponds to the tilt angle of the swash plate 9. The cylinder 2b reciprocates with the stroke amount. The volume of each volume chamber 7 is increased or decreased by the reciprocation of each piston 6.

  Water is guided to the volume chamber 7 which is enlarged by the rotation of the cylinder block 2 through the supply passage 10 of the end cover 5 and the supply port 18 a of the valve plate 18. The water sucked into the volume chamber 7 is increased in pressure by the reduction of the volume chamber 7 due to the rotation of the cylinder block 2, and is discharged through the discharge port 18 b of the valve plate 18 and the discharge passage 11 of the end cover 5. As described above, in the piston pump 100, the suction and discharge of water are continuously performed as the cylinder block 2 rotates.

  Further, in the piston pump 100, while the piston pump 100 is operating, the pressurized water in the volume chamber 7 is supplied to the coating layer 21 through the first communication hole 6c and the second communication hole 8c. For this reason, the coating layer 21 is always in a state containing water, and the shoe 8 and the swash plate 9 are prevented from being seized.

  In the piston pump 100, the water in the storage chamber 19 is supplied to the coating layer 20 through the lubrication groove 20b while the piston pump 100 is operating. For this reason, a lubricating film of water is formed between the sliding surface 20a and the convex spherical surface portion 6a, and seizure of the piston 6 and the shoe 8 is suppressed.

  According to the above embodiment, there exist the effects shown below.

  In the piston pump 100, water flows from the storage chamber 19 between the sliding surface 20a of the coating layer 20 and the convex spherical surface portion 6a through the lubricating groove 20b, and a lubricating film of water is formed. For this reason, the slidability between the piston 6 and the shoe 8 can be improved. Further, the lubricating groove 20b is a sliding surface so as not to communicate with the first communication hole 6c and the second communication hole 8c even when the shoe 8 is tilted with respect to the piston 6 as the swash plate 9 is tilted. 20a. For this reason, the leakage of the pressurized water from the connection part of the 1st communicating hole 6c and the 2nd communicating hole 8c can be suppressed. As a result, the volumetric efficiency of the piston pump 100 can be improved.

  Next, a modification of the piston pump 100 according to the embodiment of the present invention will be described with reference to FIGS.

  In the above embodiment, the convex spherical portion 6 a is provided at the end of the piston 6, and the concave spherical portion 8 a is provided at the shoe 8. Instead of this, a configuration may be adopted in which a concave spherical portion 36a is provided at the end of the piston 6 and a convex spherical portion 38a is provided in the shoe 8.

  In the modification, the open end portion 36d of the piston 6 is drawn from the outside in the radial direction, whereby the concave spherical portion 36a is deformed into a shape along the convex spherical portion 38a, and the convex spherical portion 36a is deformed by the concave spherical portion 36a. Can be slidably supported. The concave spherical surface portion 36a is provided with a coating layer 40, and the coating layer 40 has a communication region A1, a lubrication region A2, and an isolation region A3, as in the above embodiment. The lubrication region A2 is provided with the lubrication groove 40b as in the above embodiment.

  Other configurations and functions are the same as those of the above-described embodiment, and thus description thereof is omitted. Also in the modified example, the same effect as the above-described embodiment is obtained.

  Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be described together.

  The piston pump 100 includes a cylinder block 2 to which the shaft 1 is coupled and rotating together with the shaft 1, a plurality of cylinders 2b formed in the cylinder block 2 and arranged at predetermined intervals in the circumferential direction of the cylinder block 2, and a cylinder 2b A piston 6 that is slidably inserted into the cylinder 2b and divides the volume chamber 7 inside the cylinder 2b, a shoe 8 that is rotatably connected to the end of the piston 6, a swash plate 9 that is in sliding contact with the shoe 8, and a piston 6 And the cover layers 20 and 40 that slide on the other convex spherical surface portions 6a and 38a, the piston 6 and the volume chamber 7 and the end portions. A first communication hole 6c that communicates with the first communication hole, a second communication hole 8c that is provided in the shoe 8 and is connected to the first communication hole 6c, and a storage chamber 19 that houses the cylinder block 2. The covering layers 20 and 40 have a communication region A1 in which the first communication hole 6c and the second communication hole 8c can communicate, one end 20c and 40c opening into the storage chamber 19, and the other end 20d and 40d facing the communication region A1. It has the lubrication groove | channels 20b and 40b extended, and isolation | separation area | region A3 which separates communication area | region A1 and lubrication groove | channels 20b and 40b, It is characterized by the above-mentioned.

  In this configuration, water flows from the storage chamber 19 between the sliding surfaces 20a and 40a of the coating layers 20 and 40 and the convex spherical surfaces 6a and 38a through the lubricating grooves 20b and 40b, thereby forming a lubricating film of water. Is done. For this reason, the frictional resistance at the contact surface between the piston 6 and the shoe 8 can be reduced, and the slidability between the piston 6 and the shoe 8 can be improved. Further, the lubrication grooves 20b and 40b are slid so as not to communicate with the first communication hole 6c and the second communication hole 8c even when the shoe 8 is inclined with respect to the piston 6 as the swash plate 9 is inclined. It is formed on the moving surfaces 20a and 40a. For this reason, the leakage of the pressurized water from the connection part of the 1st communicating hole 6c and the 2nd communicating hole 8c can be suppressed. As a result, the volumetric efficiency of the piston pump 100 can be improved.

  Further, the lubricating grooves 20b and 40b are formed so as to extend over the semi-concave spherical surfaces of the coating layers 20 and 40 centering on the communication area A1.

  In this configuration, when the piston pump 100 is operated, the shoe 8 is pressed against the piston 6 so that a relatively large pressing force acts on the semi-concave spherical surface surrounded by the second circle C2 having the second diameter D2. Thus, lubricating grooves 20b and 40b are formed. For this reason, it becomes possible to supply water to the sliding surfaces 20a and 40a of the part where a relatively large pressing force acts through the lubricating grooves 20b and 40b, and the slidability of this part can be improved. As a result, the volumetric efficiency of the piston pump 100 can be improved.

  Further, the lubrication grooves 20b and 40b are characterized in that the depth decreases from the one end 20c and 40c toward the other end 20d and 40d.

  Further, the lubrication grooves 20b and 40b are characterized in that the width becomes narrower from the one end 20c and 40c toward the other end 20d and 40d.

  In these configurations, the cross-sectional areas of the lubricating grooves 20b and 40b gradually decrease from the one end 20c and 40c toward the other end 20d and 40d. For this reason, water is retained in the lubricating grooves 20b and 40b by capillary action, and a water lubricating film is easily formed between the sliding surfaces 20a and 40a and the convex spherical portions 6a and 38a. As a result, the slidability between the piston 6 and the shoe 8 is improved, and the volumetric efficiency of the piston pump 100 can be improved.

  A plurality of the lubricating grooves 20b and 40b are provided, and the coating layers 20 and 40 further include connection grooves 20e and 40e that connect the adjacent lubricating grooves 20b and 40b.

  In this configuration, water flowing in from the one ends 20c and 40c of the lubricating grooves 20b and 40b is distributed to the adjacent lubricating grooves 20b and 40b through the connection grooves 20e and 40e. For this reason, water flows uniformly into each of the lubricating grooves 20b, 40b, and a lubricating film of water is formed between the sliding surfaces 20a, 40a and the convex spherical portions 6a, 38a without being biased to one place. The As a result, the slidability between the piston 6 and the shoe 8 is improved, and the volumetric efficiency of the piston pump 100 can be improved.

  The embodiment of the present invention has been described above. However, the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  In the above embodiment, the case where the piston pump 100 is a fixed capacity type in which the tilt angle of the swash plate 9 is fixed has been described. Instead of this, the piston pump 100 may be a variable displacement type capable of changing the tilt angle of the swash plate 9.

  Moreover, in the said embodiment, the resin material is used as a material of the coating layers 20 and 40. FIG. Instead, carbon fiber, glass fiber, ceramic fiber, or DLC (Diamond Like Carbon) may be used as a material.

  DESCRIPTION OF SYMBOLS 100 ... Piston pump (hydraulic rotary machine), 1 ... Shaft, 2 ... Cylinder block, 2b ... Cylinder, 3 ... Case, 6 ... Piston, 6a, 38a ... Convex Spherical surface part, 6c ... 1st communicating hole, 7 ... Volume chamber, 8 ... Shoe, 8a, 36a ... Concave spherical surface part, 8c ... 2nd communicating hole, 8d, 36d ... Open end, 9 ... swash plate, 19 ... storage chamber, 20, 40 ... coating layer, 20a, 40a ... sliding surface, 20b, 40b ... lubrication groove, 20c, 40c .. One end, 20d, 40d ... the other end, 20e, 40e ... connection groove, A1 ... communication region, A2 ... lubrication region, A3 ... isolation region, D1 ... first diameter , D2 ... second diameter, D3 ... third diameter, C1 ... first circle, C2 ... second circle, C3 ... third circle

Claims (5)

A cylinder block connected with a shaft and rotating together with the shaft;
A plurality of cylinders formed in the cylinder block and arranged at predetermined intervals in the circumferential direction of the cylinder block;
A piston that is slidably inserted into the cylinder and defines a volume chamber inside the cylinder;
A shoe rotatably connected to an end of the piston;
A swash plate in sliding contact with the shoe;
A coating layer provided on one of the concave spherical portions of the piston and the shoe and sliding with the other convex spherical portion;
A first communication hole provided in the piston and communicating the volume chamber and the end;
A second communication hole provided in the shoe and connected to the first communication hole;
A storage chamber for storing the cylinder block;
The coating layer is
A communication region in which the first communication hole and the second communication hole can communicate with each other;
A lubrication groove having one end opened in the storage chamber and the other end extending toward the communication region;
A hydraulic rotating machine comprising an isolation region separating the communication region and the lubricating groove.   2. The hydraulic rotating machine according to claim 1, wherein the lubrication groove is formed to extend over a semi-concave spherical surface of the coating layer with the communication region as a center.   3. The hydraulic rotating machine according to claim 1, wherein the lubrication groove has a depth that decreases from the one end toward the other end. 4.   4. The hydraulic rotating machine according to claim 1, wherein the lubricating groove has a width that decreases from the one end toward the other end. 5. A plurality of the lubricating grooves are provided,
The hydraulic rotating machine according to any one of claims 1 to 4, wherein the coating layer further includes a connection groove that connects the adjacent lubrication grooves.

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