JP2006070777A - Swash plate type variable displacement piston pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid generation of galling and abnormal wear by preventing shortage of oil films of a case and a control piston, with respect to the control piston which is slidably inserted into the case and cannot be rotated by contacting a swash plate. <P>SOLUTION: The control piston 41 is inserted into a bore 27 provided in the case 12 so as to be slidable in the axial center direction. A spherical face 32 of a tip part of the control piston 41 is formed to be width across flat and engaged with an opening part 44 of the swash plate 43. An axial center hole 45 is bored on the control piston 41 in the axial center direction, and a through hole 47 is bored on the outer peripheral face of the control piston 41 approximately orthogonal to the axial center hole 45. On the outer peripheral face, a plurality of oil grooves (not illustrated) are formed in the axial center direction at even intervals in the circumferential direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydraulic piston pump that supplies pressure fluid to various actuators to operate these actuators, and further relates to a swash plate type variable displacement piston pump used as a hydraulic power source for industrial machines such as machine tools.

  Conventionally, in a machine tool having a small installation space, the pump pressure and discharge flow rate are controlled to reduce the size and effectively use the output of the driving electric motor. Conventionally, as an example of this type of variable displacement piston pump, for example, as shown in FIG. 4, a variable displacement piston pump 10 has a body 11 and a case 12 integrally formed by a screw member (not shown). The case 12 is provided with a shaft (shaft member) 16 that is rotatably supported by a ball bearing 14 and a needle bearing 15. A spline 16 a is formed on the shaft 16, and the cylinder barrel 18 rotates together with the shaft 16 by being coupled to a spline groove 16 b formed on the inner peripheral surface of the cylinder barrel 18.

An odd number of bores 19 are formed on the same circumference around the rotation axis of the cylinder barrel 18, and an odd number of pistons 20 are slidably inserted into the bore 19. A head portion 21 that is one end portion of the piston 20 protrudes from the opening of the bore 19 and is slidably abutted on the surface of the swash plate 23 via a shoe 22.
The swash plate 23 is in contact with a plain bearing 24 coupled to the body 11. The elastic force of the spring 28 acts on the swash plate 23 via the needle bearing 17, the barrel holder 29, and the shoe holder 30. The inclination angle θ of the swash plate 23 changes as the sliding bearing 24 slides. The rear end of the swash plate 23 is normally urged so that the inclination angle θ is maximized by the elastic force of the spring member 25 for tilting, and a control disposed on the opposite side of the spring member 25. The piston (piston member) 26 controls the swash plate 23 until it reaches the minimum inclination angle θ against the urging force of the spring member 25. Then, by operating the control piston 26, the required inclination angle θ is given to the swash plate 23 to control the discharge capacity of the pump. The control piston 26 is slidably fitted into a bore 27 formed in the case 12.

In the variable displacement piston pump 10 configured as described above, the piston 20 built in the cylinder barrel 18 that rotates in synchronization with the shaft 16 is pressed by the spring member 25 and the control piston 26, and has an inclination angle θ, for example. By engaging and sliding on the outer peripheral surface of the swash plate 23, the fluid reciprocates along the axial direction of the shaft 16 to discharge the pressure fluid to an actuator (not shown) (see, for example, Patent Document 1).
JP 2002-202048 A

However, in a swash plate type variable displacement piston pump configured so that one end of the control piston is engaged with the swash plate and cannot rotate, the control piston repeats sliding in a state where the oil film is cut, galling, There was a problem that abnormal wear occurred.
The present invention has been made in order to solve the above-described problem. Even in a swash plate type variable displacement piston pump configured such that one end portion of the control piston is engaged with the swash plate and cannot rotate, And a swash plate type variable displacement piston pump capable of preventing the occurrence of oil film breakage.

In order to achieve the above object, the present invention provides a piston member that is slidably inserted axially into a cylinder barrel that is rotatably supported together with a shaft member,
A swash plate member tilted by the piston member and engaged with one end of the piston member;
In the swash plate type variable displacement piston pump with
Concave portions provided in the axial direction at equal intervals on the outer peripheral surface of the piston member;
An axial hole formed in the axial direction in communication with the through hole;
A through hole formed in the radial direction in communication with the recess;
Have
Oil in the swash plate type variable displacement piston pump is supplied from the shaft hole to the outer peripheral surface of the piston member through the through hole.
According to the present invention, since the oil in the pump is always guided to the outer peripheral surface of the piston member, it is possible to prevent the occurrence of oil film breakage with respect to the outer peripheral surface of the piston member even during full flow full cut-off switching. In addition, seizure of the constituent members of the swash plate type variable displacement piston pump and occurrence of abnormal wear can be prevented.

  In the present invention, since the oil in the pump is always guided to the outer peripheral surface of the piston member, it is possible to prevent the occurrence of oil film breakage on the outer peripheral surface of the piston member even during full flow full cut-off switching. It is possible to prevent seizure of the constituent members of the variable displacement piston pump and occurrence of abnormal wear.

A swash plate type variable displacement piston pump 40 according to an embodiment of the present invention will be described in detail with reference to the drawings. 1, the same components as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.
In FIG. 1, a control piston (piston member) 41 slidably inserted into a bore 27 has an engaging portion in which a spherical surface 32 at one end is formed to have a two-sided width as shown in FIGS. 42 is provided. The engaging portion 42 is engaged with an opening 44 formed in the swash plate 43. Therefore, since the engaging part 42 is engaged with the opening part 44, the control piston 41 can be displaced in the axial direction but cannot be rotated.

The control piston 41 has a hole (axial hole) 45 drilled in the axial direction from the engagement portion 42 side and a small hole 46 inserted into the other end of the control piston 41. Yes. A through hole 47 is formed in the hole 45 in the radial direction, and a hole 48 is formed from one side of the engaging portion 42.
Further, a plurality of oil grooves (recesses) 49 are formed in the circumferential direction on the outer peripheral surface of the control piston 41 at equal intervals in the axial direction. Therefore, in the swash plate type variable displacement piston pump 40, the oil stored in the pump 40 is led out from the hole 45 to the oil groove 49 through the through hole 47 and the hole 48. Therefore, oil is supplied between the outer peripheral surface of the control piston 41 and the inner peripheral surface of the bore 27.
For this reason, in the case of the swash plate type variable displacement piston pump 40, it is possible to prevent the oil film from being cut off against the control piston 41 even during the full flow full cut-off switching which makes the pump displacement variable.

  In this case, the oil groove 49 may be formed spirally on the outer peripheral surface of the control piston 41 continuously in the axial direction. Furthermore, the shape of the oil groove 49 may of course be formed in a V-shaped cross-section, a U-shape and a quadrangular shape.

It is a top view which shows the principal part enlarged structure which shows the engagement state of the control piston and swash plate of the swash plate type variable displacement piston pump which concerns on embodiment of this invention. It is sectional drawing of the II-II line of FIG. It is an external view of the control piston of FIG. It is a longitudinal cross-sectional view which shows schematic structure of the conventional swash plate type variable displacement piston pump.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 40 Swash plate type variable displacement piston pump 11 Body 12 Case 13 Main body 16 Shaft 17 Needle bearing 18 Cylinder barrel 19, 27 Bore 20 Piston 22 Shoe 23, 43 Swash plate 26, 41 Control piston 34 Inclined surface 42 Engagement part 44 Opening 45 holes (axial hole)
47 Through hole 49 Oil groove

Claims (1)

A piston member slidably inserted in the axial direction into a cylinder barrel rotatably supported with the shaft member;
A swash plate member tilted by the piston member and engaged with one end of the piston member;
In the swash plate type variable displacement piston pump with
Concave portions provided in the axial direction at equal intervals on the outer peripheral surface of the piston member;
An axial hole formed in the axial direction in communication with the through hole;
A through hole formed in the radial direction in communication with the recess;
Have
The oil in the swash plate type variable displacement piston pump is supplied from the shaft hole to the outer peripheral surface of the piston member through the through hole.

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