JP4512435B2 - Axial swash plate piston pump - Google Patents

Description

  The present invention relates to an axial type swash plate type piston pump provided in a hydraulic excavator or the like, in which a piston shoe slidably contacting a cam plate provided on a swash plate has a static pressure pocket for storing lubricating oil.

  There exists a thing shown by patent document 1 as this kind of prior art. As a basic configuration, this prior art includes a drive shaft that is rotatably accommodated in a casing, and a rotor that is rotated by the drive shaft and has a plurality of cylinders. A piston is slidably disposed in each of the rotor cylinders, and a piston shoe that slides on a cam plate provided on a swash plate is provided at each end of the piston.

  FIG. 5 is a cross-sectional view showing a piston shoe constituting a main part of a conventional axial swash plate type piston pump described in Patent Document 1. As shown in FIG. Hereinafter, the piston shoe will be described with reference to FIG.

Piston shoes 13 is connected to the piston 9, and the spherical bearing 13A which is set to a smaller diameter than the diameter of the piston 9, and the disk portion 13B that slides the cam plate on which is not shown, as opposed to the spherical bearing 13A And a disk-shaped protrusion 13C formed on the disk portion 13B and set to a diameter DA. A static pressure pocket 30 set to a diameter DB for storing lubricating oil is formed on the side of the disk portion 13B facing a cam plate (not shown). Further, an auxiliary static pressure pocket 31 having a depth h and a width a having predetermined dimensions is formed on the outer peripheral side of the static pressure pocket 30.

Further, a drill hole 9a through which lubricating oil is guided along the axial direction is formed inside the piston 9, and the above-described piston 9 is provided on the spherical bearing 13A, the disc-shaped protrusion 13C, and the disk portion 13B of the piston shoe 13. A drill hole 13a is formed for guiding the lubricating oil guided to the drill hole 9a to the sliding surface 13B1 through the static pressure pocket 30 and the auxiliary static pressure pocket 31 of the disk portion 13B.

In the prior art provided with such a piston shoe 13, when the rotor rotates as the drive shaft is driven, each piston in the rotor slides by a stroke corresponding to the tilt angle of the swash plate. Pressure oil is sucked and discharged by sliding. During this time, the disk portion 13B of the piston shoe 13 shown in FIG. 5 connected to the end of the piston slides on a cam plate (not shown) provided on the swash plate. During the sliding of the disk portion 13B of the piston shoe 13, the lubricant guided to the static pressure pocket 30 and the auxiliary static pressure pocket 31 of the disk portion 13B is applied to the sliding portion of the disk portion 13B and the cam plate. Supplied. As a result, the piston shoe 13 can be smoothly slid.
Japanese Patent No. 2547643

  As described above, in the prior art disclosed in Patent Document 1, the sliding portion between the piston shoe 13 and a cam plate (not shown) is interposed via the static pressure pocket 30 and the auxiliary static pressure pocket 31 of the disk portion 13B of the piston shoe 13. By supplying the lubricating oil, the piston shoe 13 can be smoothly slid.

In the prior art described above above, the width a diameter DB and the auxiliary hydrostatic pockets 31 of the hydrostatic pockets 30 are formed in the disc portion 13B of the piston shoe 13, a disk-shaped protrusion 13 C diameter DA or the like of Although the magnitude relation has not been defined, the inventors have, for example, as shown in FIG. 5, in a state where the diameter DB of the hydrostatic pockets 30 is set smaller than the diameter DA of the disc-shaped protrusion 13C is When the piston shoe 13 is pressed against the cam plate with a large pressing force P through the piston 9 by the pressure of the pressure oil that slides the piston 9, the static pressure pocket 30 and the auxiliary static pocket 30 are compared with the pressing force P. It was confirmed that the reaction force N due to the pressure of the lubricating oil supplied to the pressure pocket 31 was significantly reduced.

  That is, the pressing ratio N / P becomes smaller than the desired value, and the wall surface facing the cam plate by forming the static pressure pocket 30 by the large pressing force P described above is deformed as shown by the broken line 30a in FIG. In addition, the entire wall surface that forms the auxiliary static pressure pocket 31 and faces the cam plate is crushed as indicated by a broken line 31a, and the step portion 30b that is positioned in the vicinity of the peripheral portion of the wall surface of the static pressure pocket 30 is provided. That is, the step portion 30b formed between the static pressure pocket 30 and the auxiliary static pressure pocket 31 is displaced in the cam plate direction, the step portion 30b comes into contact with the cam plate, and the deformed step portion 30b causes the static pressure. The present inventors have confirmed that a blocking portion 32 that prevents the flow of lubricating oil between the pocket 30 and the auxiliary static pressure pocket 31 may be formed.

Thus, when the static pressure pocket 30 or the auxiliary static pressure pocket 31 is deformed by the pressing force P and the closed portion 32 is formed by contacting the cam plate, the sliding surface 13B1 of the disk portion 13B of the piston shoe 13 and the cam Sufficient lubricating oil is not supplied to the sliding portion with the plate, and the frictional force between the disc portion 13B and the cam plate increases. As a result, the sliding failure of the piston shoe 13 is caused, and there is a concern that the sliding portion between the disc portion 13B and the cam plate is seized.

  The present invention has been made based on the above-mentioned confirmation by the present inventors. The purpose of the present invention is to provide at least a static pressure pocket in the disk portion of the piston shoe, and realize a good sliding operation of the piston shoe. It is an object to provide an axial type swash plate type piston pump that can be used.

To achieve the above object, the present invention provides a rotor having a plurality of cylinders rotated by a drive shaft, a piston slidably disposed in each of the cylinders of the rotor, and end portions of these pistons. A piston shoe slidably contacting a cam plate provided on a swash plate, the piston shoe being connected to the piston and having a diameter smaller than the diameter of the piston; A disk portion that slides on the cam plate; and a disk-shaped protrusion formed on the disk portion so as to face the spherical bearing. Lubricating oil is applied to a side of the disk portion that faces the cam plate. in axial type swash plate type piston pump with hydrostatic pockets for storing, the diameter of the hydrostatic pockets, the disc of said piston shoe Greater than the diameter of the protrusions, and characterized in that it is smaller than the diameter of the piston.

In the present invention configured as described above, since the diameter of the static pressure pocket is set larger than the diameter of the disk-like protrusion of the piston shoe, a large pressing force P is applied to the disk portion via the disk-like protrusion of the piston shoe. The position of the peripheral edge of the wall surface forming the static pressure pocket and facing the cam plate can be sufficiently separated from the position of the maximum deformation portion of the static pressure pocket. Therefore, it is possible to suppress the deformation in the above-described manner, so that a blocking portion that prevents the flow of the lubricating oil between the disk portion and the cam plate is not generated. Therefore, the lubricating oil guided to the static pressure pocket can be stably supplied to the sliding portion between the disc portion and the cam plate in spite of the large pressing force P applied to the disc portion, and the piston shoe can slide well. Operation can be realized.

  In addition, since the diameter of the static pressure pocket is set smaller than the diameter of the piston, the reaction force N caused by the lubricating oil guided to the static pressure pocket is set to an appropriate magnitude according to the pressing force P given through the piston. The desired pressing ratio N / P can be ensured.

According to the present invention, in the above invention, an auxiliary static pressure pocket connected to the static pressure pocket is provided, and the diameter of the spherical bearing of the piston shoe is set larger than the diameter of the disc-shaped protrusion of the piston shoe. The diameter of the auxiliary static pressure pocket is set larger than the diameter of the spherical bearing of the piston shoe and smaller than the diameter of the piston.

According to the present invention, in the above invention, the diameter of the spherical bearing of the piston shoe is set larger than the diameter of the disk-like protrusion of the piston shoe, and the diameter of the static pressure pocket is set to the spherical surface of the piston shoe. It is characterized by being set larger than the diameter of the bearing.

Further, the present invention is the above invention, wherein the static pressure pocket is provided with an annular auxiliary sliding portion slidably contacting the cam plate, and an inner diameter of the auxiliary sliding portion is set to be equal to that of the disc-shaped protrusion of the piston shoe. It is characterized by being set larger than the diameter and smaller than the diameter of the spherical bearing of the piston shoe.

In the present invention, the diameter of the static pressure pocket formed in the disk portion of the piston shoe is larger than the diameter of the disc-shaped protrusion of the piston shoe formed in the disk portion so as to face the spherical bearing, and is larger than the diameter of the piston. Because of the small setting, when a large pressing force is applied to the disk part via the disk-like projection of the piston shoe, deformation at the peripheral part of the wall surface forming the static pressure pocket can be suppressed to a small level. Therefore, the closed portion that prevents the oil flow is not generated, and therefore the lubricating oil can be stably supplied to the sliding portion between the disc portion and the cam plate. As a result, a good sliding operation of the piston shoe can be realized, and seizure of the sliding portion between the disc portion and the cam plate, which has been a concern in the past, can be prevented, and excellent durability can be secured.

  Hereinafter, the best mode for carrying out an axial swash plate type piston pump according to the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view showing the overall configuration of a first embodiment of an axial type piston pump according to the present invention. First, the basic configuration of the first embodiment of the present invention will be described with reference to FIG.

  In the first embodiment of the present invention, a drive shaft 3 is rotatably housed in a casing formed by a front casing 1 and a rear casing 2. The drive shaft 3 is rotatably supported by a rear bearing 4 provided on the rear casing 2 and a front bearing 5 provided on the front casing 1. The shaft spline 6 formed on the outer periphery of the drive shaft 3 is engaged with the hole spline 8 of the rotor 7 so that the rotor 7 rotates integrally with the rotation of the drive shaft 3.

  A plurality of cylinders are formed in the circumferential direction inside the rotor 7, and pistons 9 are arranged in these cylinders. A piston shoe 13 which will be described later constituting the main part of the present embodiment is connected to the end portions of these pistons 9.

  A valve plate 10 with which the rotor 7 slides is fixed to the rear casing 2, and a suction port 11 and a discharge port 12 are formed on the valve plate 10.

  A cradle 16 is fixed to the front casing 1, and a swash plate 14 is tiltably held by the cradle 16. The swash plate 14 is provided with a cam plate 15 with which the piston shoe 13 is in sliding contact. A servo plate 17 is connected to the swash plate 14, and the servo plate 17 is driven by a servo piston 18.

FIG. 2 is a cross-sectional view showing the piston shoe constituting the main part of the first embodiment of the present invention. The piston shoe 13 of this embodiment shown in FIG. 2 is also connected to the piston 9 in the same manner as the piston shoe 13 shown in FIG. 5 and has a spherical surface set to a diameter D0 smaller than the diameter D2 of the piston 9. A bearing 13A, a disk portion 13B having a sliding surface 13B1 that slides on the cam plate 15 shown in FIG. 1, and a disk portion 13B formed so as to face the spherical bearing 13A, are larger than the diameter D0 of the spherical bearing 13A. And a disc-shaped protrusion 13C set to a small diameter D5. On the side facing the cam plate 15 of the disk portion 13B, for example, a static pressure pocket 20 for storing lubricating oil, and a depth of a predetermined dimension arranged on the outer peripheral side of the static pressure pocket 20 and connected to the static pressure pocket 20 are provided. An auxiliary static pressure pocket 19 having a height h and forming a flat space is provided.

Further, a drill hole 9a through which the lubricating oil is guided along the axial direction is formed inside the piston 9, and the spherical bearing 13A of the piston shoe 13, the disc-shaped protrusion 13C, and the disk 13B have a drill hole of the piston 9. A drill hole 13a is formed for guiding the lubricating oil guided to 9a to the sliding surface 13B1 through the static pressure pocket 20 and the auxiliary static pressure pocket 19 of the disk portion 13B.

In the first embodiment, in particular, the diameter D1 of the static pressure pocket 20 is set to be larger than the diameter D5 of the disc-like protrusion 13c of the piston shoe 13 and smaller than the diameter D2 of the piston 9. Further, the diameter D3 of the auxiliary static pressure pocket 19 connected to the static pressure pocket 20 is set to be larger than the diameter D0 of the spherical bearing 13A of the piston shoe 13 and smaller than the diameter D2 of the piston 9.

  Even in the first embodiment, when the drive shaft 3 is driven, the rotor 7 rotates, and the pistons 9 in the rotor 7 slide by a stroke corresponding to the tilt angle of the swash plate 14, respectively. The pressure oil is sucked and discharged by sliding. During this time, the disk portion 13B of the piston shoe 13 connected to the end of the piston 9 slides on the cam plate 15 provided on the swash plate 14. During the sliding of the disk portion 13B of the piston shoe 13, the sliding portion between the sliding surface 13B1 of the disk portion 13B and the cam plate 15, the static pressure pocket 20 and the auxiliary static pressure pocket 19 of the disk portion 13B. The guided lubricant is supplied. Thereby, smooth sliding of the piston shoe 13 is performed.

This embodiment is particularly the diameter D1 of the hydrostatic pocket 20 formed in the disc portion 13B of the piston shoe 13, since it was set larger than a disc-shaped protrusion 13 C of diameter D5 of the piston shoe 13, the piston shoe 13 When a large pressing force P is applied to the disk portion 13 through the disc-shaped protrusion 13C, the position of the peripheral portion of the wall surface that forms the static pressure pocket 20 and faces the cam plate 15 is determined as the maximum deformation of the static pressure pocket 20. It can be sufficiently separated from the position of the portion, that is, from the position of the central portion of the static pressure pocket 20, and the deformation at the peripheral edge of the static pressure pocket 20 and the auxiliary static pressure pocket 19 are formed to face the cam plate 15. The deformation of the wall surface can be suppressed as shown by broken lines 20b and 19a in FIG. Thereby, it is possible to prevent a blocking portion that prevents the flow of the lubricating oil from occurring between the disk portion 13B and the cam plate 15.

  That is, the stepped portion 20 a between the static pressure pocket 20 and the auxiliary static pressure pocket 19 is not brought into contact with the cam plate 15, and the opening 21 can be secured between the stepped portion 20 a and the cam plate 15. it can.

  Accordingly, the lubricating oil guided to the static pressure pocket 20 can be supplied to the auxiliary static pressure pocket 19 through the opening 21 in spite of the large pressing force P applied to the disk portion 13B. Lubricating oil stored in the auxiliary static pressure pocket 19 can be stably supplied to the sliding portion between the sliding surface 13B1 of the disk portion 13 and the cam plate 15. Thereby, the favorable sliding motion of the piston shoe 13 can be realized, seizure of the sliding portion between the disk portion 13B and the cam plate 15 can be prevented, and excellent durability can be ensured.

  Since the diameter D1 of the static pressure pocket 20 and the diameter D3 of the auxiliary static pressure pocket 19 are set to be smaller than the diameter D2 of the piston 9, the reaction force by the lubricating oil guided to the static pressure pocket 20 and the auxiliary static pressure pocket 19 is set. N can be set to an appropriate magnitude according to the pressing force P applied through the piston 9, and a desired pressing ratio N / P can be ensured.

  In the first embodiment described above, the auxiliary static pressure pocket 19 is provided so as to form a flat space, but instead of being provided in this way, it is formed by a concave spherical wall surface having a large polar radius. You may make it the structure which provided the space.

  FIG. 3 is a cross-sectional view showing a piston shoe constituting the main part of the second embodiment of the present invention. In the second embodiment, the disk portion 13B of the piston shoe 13 does not include the auxiliary static pressure pocket 19 provided in the first embodiment, but includes only the static pressure pocket 22. In the second embodiment, the diameter D1 of the static pressure pocket 22 is set to be larger than the diameter D0 of the spherical bearing 13A of the piston shoe 13 and smaller than the diameter D2 of the piston 9. The other basic configuration is the same as that in the first embodiment described above, for example.

  In the second embodiment configured as described above, when a large pressing force P is applied to the disk portion 13B, the deformation at the peripheral edge portion of the wall surface that forms the static pressure pocket 22 and faces the cam plate 15 is shown in FIG. As shown by the broken line 22a, it can be kept small. Thereby, it is possible to prevent a blocking portion that prevents the flow of the lubricating oil from occurring between the disk portion 13B and the cam plate 15, and the lubricating oil stored in the static pressure pocket 22 is allowed to slide on the disk portion 13B. It can be stably supplied to the sliding portion between the surface 13B1 and the cam plate 15, the good sliding operation of the piston shoe 13 can be realized, and the same effect as in the first embodiment can be obtained.

FIG. 4 is a cross-sectional view showing a piston shoe constituting the main part of the third embodiment of the present invention. Also in the third embodiment, the disk portion 13B of the piston shoe 13 is not provided with the auxiliary static pressure pocket 19 provided in the first embodiment. In the third embodiment, an annular auxiliary sliding portion 24 slidably contacting the cam plate 15 is provided inside the static pressure pocket 23, and the inner diameter D4 of the auxiliary sliding portion 24 is set to a disc-like protrusion 13C of the piston shoe 13. Is set to be smaller than the diameter D0 of the spherical bearing 13A of the piston shoe 13. Other basic configurations are the same as those in the second embodiment described above, for example.

  In the third embodiment configured as described above, when a large pressing force P is applied to the disk portion 13, deformation at the peripheral edge portion of the wall surface that forms the static pressure pocket 23 and faces the cam plate 15, and auxiliary sliding The deformation of the portion 24 can be reduced as shown by the broken line 23a in FIG. Thereby, it is possible to prevent a blocking portion that prevents the flow of the lubricating oil from occurring between the disk portion 13B and the cam plate 15.

  The end surface of the auxiliary sliding portion 24 facing the cam plate 15 is pressed against the cam plate 15 by the pressing force P described above, that is, the entire end surface of the auxiliary sliding portion 24 is camped. Since it is held so as to be substantially parallel to the surface of the plate 15, a closed portion is not formed. That is, a minute gap is formed between the auxiliary sliding portion 24 and the cam plate 15 according to the reaction force N generated when the lubricating oil is guided to the static pressure pocket 23, and the lubricating oil passes through the gap. Inflow and outflow.

  Therefore, also in the third embodiment, the lubricating oil stored in the static pressure pocket 23 can be stably supplied to the sliding portion between the sliding surface 13B1 of the disk portion 13B and the cam plate 15, and the piston shoe 13 has a good quality. A sliding operation can be realized, and the same effect as in the second embodiment can be obtained.

It is sectional drawing which shows the whole structure of 1st Embodiment of the axial type swash plate type piston pump which concerns on this invention. It is sectional drawing which shows the piston shoe which comprises the principal part of 1st Embodiment of this invention. It is sectional drawing which shows the piston shoe which comprises the principal part of 2nd Embodiment of this invention. It is sectional drawing which shows the piston shoe which comprises the principal part of 3rd Embodiment of this invention. It is sectional drawing which shows the piston shoe which comprises the principal part of the conventional axial type swash plate type piston pump.

DESCRIPTION OF SYMBOLS 3 Drive shaft 7 Rotor 9 Piston 13 Piston shoe 13A Spherical bearing 13a Drill hole 13B Disk part 13B1 Sliding surface 13C Disc-shaped protrusion 14 Swash plate 15 Cam plate 19 Auxiliary static pressure pocket 20 Static pressure pocket 20a Step part 21 Opening part 22 Static Pressure pocket 23 Static pressure pocket

Claims (4)

A rotor that is rotated by a drive shaft and has a plurality of cylinders, a piston that is slidably disposed in each of the cylinders of the rotor, and a cam that is connected to each of the end portions of these pistons and is provided on a swash plate A piston shoe sliding on the plate,
The piston shoe is connected to the piston, a spherical bearing which is set to a smaller diameter than the diameter of the piston, and a disk portion slidably contacting the cam plate above, to the disk portion so as to face the spherical bearing In an axial type swash plate type piston pump having a disk-shaped projection formed and having a hydrostatic pocket for storing lubricating oil on the side of the disk portion facing the cam plate,
An axial type swash plate type piston pump characterized in that a diameter of the static pressure pocket is set larger than a diameter of the disk-like projection of the piston shoe and smaller than a diameter of the piston. In the invention of claim 1,
An auxiliary static pressure pocket connected to the static pressure pocket, the diameter of the spherical bearing of the piston shoe is set to be larger than the diameter of the disk-like protrusion of the piston shoe, and the diameter of the auxiliary static pressure pocket Is set larger than the diameter of the spherical bearing of the piston shoe and smaller than the diameter of the piston. In the invention of claim 1,
The diameter of the spherical bearing of the piston shoe is set larger than the diameter of the disc-shaped protrusion of the piston shoe, and the diameter of the static pressure pocket is set larger than the diameter of the spherical bearing of the piston shoe. Axial type swash plate type piston pump. In the invention of claim 3,
An annular auxiliary sliding portion that is in sliding contact with the cam plate is provided inside the static pressure pocket, and the inner diameter of the auxiliary sliding portion is larger than the diameter of the disc-shaped protrusion of the piston shoe, An axial type swash plate type piston pump characterized in that it is set smaller than the diameter of the spherical bearing.

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