JPS63268980A - Axial piston pump - Google Patents

Abstract

PURPOSE:To ensure a long lifetime by decentering the hydraulic seal part of a valve plate in such a way as to agree to the direction of the resultant moment of a cylinder block pressing moment and a cylinder block overturning moment. CONSTITUTION:A valve plate 21 having an intake port 22 and a delivery port 23 is made to have a hydraulic seal part C' slidably contacted by the slide face B of a cylinder block 9. The center of an inner seal part 24A is dislocated by a distance (a) and that of an outer seal part 24B is also dislocated by a distance (b). As a result, the point of application comes to X', thereby causing the resultant moment direction of a cylinder block pressing force and moment and a cylinder block overturning moment to the point of opening force application X', and enabling the maintenance of a hydraulic balance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an axial piston pump with improved hydraulic balance between a cylinder block and a valve plate sliding surface.

[Conventional technology]

A conventional axial piston pump is shown in FIGS. 5 to 10.

In the drawing, reference numeral 1 denotes a pump housing, and a lid 2 is fixed to one end of the pump housing 1, and an end cap 3 is fixed to the other end of the pump housing 1. The lid body 2 and the end cap 3 are each formed with shaft support portions 4 and 5, and a shaft 8 is supported by these shaft support portions 4 and 5 via bearings 6 and 7.

A cylinder block 9 is attached to the shaft 8 by spline connection, and the cylinder block 9 has a plurality of cylinder bores 10 provided at predetermined intervals in the circumferential direction, and pistons 11 are fitted into these cylinder bores 10. has been done.

The tip of the piston 11 is made into a spherical surface, and this spherical portion 12
A shoe 13 is swingably provided. These shoes 1
The flat portion 13A of No. 3 is in sliding contact with the swash plate surface 14A of the rocker cam 14. Shoes 13 are held together by shoe retainers 15. The rear surface of the cylinder block 9 is a sliding surface B with respect to the valve plate 16, and the sliding surface B is a spherical surface. The valve plate 16 is held by the end cap 3, and the valve plate 16 is formed with a suction port 17 and a discharge port 18, and the suction port 17 is connected to a suction port 19 formed in the end cap 3. Furthermore, the discharge ports 18 each communicate with discharge ports 20 formed in the end cap 3.

The rotation of the shaft 8 causes the cylinder block 9 to rotate, and the shoe 13 connected to the piston 11 slides on the swash plate surface 14A, causing the piston 11 to reciprocate within the cylinder bore 10, thereby drawing suction. It performs a discharge stroke and constitutes a hydraulic pump.

As shown in FIG. 7, the hydraulic seal portion C of the valve plate 16 is formed concentrically with the suction and discharge ports 17° and 18 on the inner and outer sides of the suction port 17 and the discharge port 18, and the seal portion pressurized oil (Cylinder block 5)
The point of action of the force pushing back is X.

The force of pressing the cylinder block 9 by the cylinder bore 10 to the piston 11 acts on a point Y on the sliding surface B of the cylinder block 9, and the hydraulic balance is maintained at these points X and Y.

However, the cylinder block 9 has cylinder bores 10~
In addition to force, the piston 11 exerts a prying force F from the swash plate surface 14A to the piston 11, and ΣF acts on the cylinder block 9 as a whole on the piston 11 on the discharge side.

``This ΣF acts on the driving spline portion 8a of the cylinder block 9 to the shaft 8, and it is generally desirable that the supporting forces ΣF and ΣF' of the shaft 8 be on the same line of action at the center of the spline engagement length. In many cases, these cannot be made the same due to the relationship with other component devices.

Therefore, if the line of action is deviated by 6g, a cylinder block overturning moment of ΣF×Δg will be generated in the cylinder block 9.

[Problem that the invention seeks to solve]

Conventionally, the design has been made to make the cylinder block overturning moment relatively small, but with higher pressure and compactness, the cylinder block overturning moment has increased.

In response to such a cylinder block overturning moment, the resultant force of the hydraulic balance between the cylinder block 9 and the valve plate 16 cannot achieve sufficient balance at the point of action This often resulted in poor efficiency and shortened lifespan.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its object is to ensure that the direction of the composite moment Mo of the cylinder block pressing moment MP and the cylinder block overturning moment MFr coincides with the point of application X' of the separating force. To provide an axial piston pump that maintains hydraulic balance, eliminates contact between a cylinder block and a valve plate only on the outer circumferential side, and has a sufficient lifespan.

(Means and operations for solving the problem) In order to achieve the above object, the present invention provides a cylinder block that rotates due to rotational drive of a shaft, and a sliding surface of this cylinder block that is in sliding contact with a suction port and a discharge port. An axial piston, which is equipped with a valve plate having a port and which moves a piston reciprocatingly into a cylinder bore by sliding a shoe connected to the piston on a swash plate surface as the cylinder block rotates, thereby performing suction and discharge strokes. In the pump, the direction of the opening force (point of application It has been decided.

Then, a composite moment M of the cylinder block pressing moment MP and the cylinder block overturning moment MPr
The direction of o is made to coincide with the point of application of the opening force X' to maintain hydraulic balance.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

In the description of the axial piston pump according to the present invention, the other components except the valve plate are the same as those of the conventional axial piston pump described above, so the description will be simplified by giving the same reference numerals as those of these components.

A suction port 22 and a discharge boat 23 are formed in the valve plate 21 of the axial piston pump according to the present invention, as shown in FIG. A hydraulic seal portion C' is formed which slides into contact with the hydraulic seal portion C'.

This hydraulic seal part C' is connected to the suction and discharge boats 22 and 23.
Inner inner seal portion 24A and suction/discharge boat 22
．． 23 outer outer seal portion □24B.

The inner seal portion 24A is formed with its machining center O' shifted by a distance a toward the piston bottom dead center A with respect to the center 0 of the cylinder block, and the outer seal portion 24B is formed with its machining center O'' is the distance from the center O of the cylinder block 9 to the piston top dead center mouth side,! It is formed by shifting by lIb.

Therefore, the seal area on the piston top dead center port side is larger than the seal area on the piston bottom dead center side, and the boat part consisting of the suction and discharge boats 22 and 23, and the hydraulic seal part C'
The point of application of the separating force due to the pressure oil is X' (see Figure 2).

That is, the opening force is a force that attempts to lift the cylinder block 9 due to the pressure acting on the hydraulic seal portion C'.

Conventional axial piston pump valve plate 16
On the spherical surface of Figure 10, p and p.

There is a pressure distribution like this.

This pressure distribution exists over the high pressure side half circumference (shaded area) of the valve plate 16.

Therefore, the separation force F due to the pressure distribution p, P. .

Fl also exists on the high pressure side half circumference, and the center of gravity of this separation force distribution is located at the point of action X shown in FIG.

On the other hand, when the seal area on the piston top dead center opening side of the hydraulic seal portion C' of the valve plate 21 is larger than the seal area on the piston bottom dead center A side as in the present invention, the position of the center of gravity of the opening force is at point X. ', and this X' becomes the point of action.

By moving the point of action from X to X' in this way,
Cylinder block pressing force F1 pressing moment 11vlP from cylinder bore 10 to piston 11 and cylinder block overturning moment MF acting on the piston top dead center mouth side
The resultant direction of r coincides with the point of application X' of the separation force, and hydraulic balance can be maintained.

That is, the cylinder block pressing force F is calculated when high pressure P acts on the cylinder bore 10 having a diameter dp as shown in FIG. 9 (N is the number of pistons 11 (the number of cylinder bores IO)).
), and this pressing force F acts on the cylinder block 9-valve plate 21.

Moreover, the average value FP of this pressing force F acts on point Y in FIG. The force FP at this time and the area FPX with a distance fIY between the point Y where the force FP acts and the center of the cylinder block 9
ΩY is cylinder block pressing moment MP.

Tilting moment MF acting on the cylinder block 9
r(FrxΔg) and piston pressing moment Mp (
Fp XRp ) acts as shown in FIG.

The direction in which the composite moment Pr of these moments M and Mp acts is Mo. As shown in FIG. 4, the direction of this resultant moment (Fo
By adjusting the seal width to an appropriate size,
Cylinder block tilting moment MFr and opening force Fv
It is possible to balance the supporting moment due to

In other words, the direction of the opening force Fv (point of application X') is determined by eccentrically setting the hydraulic seal portion C' of the valve plate 21 so as to match the direction of the composite moment MQ of the moment MP due to the pressing force and the moment MPr due to the prying force. It is.

〔Effect of the invention〕

As described in detail above, the axial piston pump according to the present invention includes a cylinder block that rotates due to rotational drive of a shaft, and a valve plate with which the sliding surface of the cylinder block is in sliding contact and has a suction boat and a discharge boat. In an axial piston pump, the piston is reciprocated into the cylinder bore by sliding a shoe connected to the piston into sliding contact with the swash plate surface as the cylinder block rotates, thereby performing the suction and discharge processes.The cylinder block pressing moment MP and the cylinder block overturning moment MFr, and the direction of the opening force (point of application X') is determined by making the hydraulic seal portion C' of the valve plate eccentric. It is.

Therefore, the direction of the composite moment MQ of the cylinder block pressing moment MP and the cylinder block overturning moment MPr coincides with the point of application X' of the opening force, and the hydraulic balance is maintained. Since there is no contact only on the outer circumference side, a sufficient life can be obtained.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of one embodiment of the present invention, Fig. 2 is a sectional view taken along the line Figure IV-IV
5 is a longitudinal sectional view of a conventional axial piston pump, FIG. 6 is a sectional view taken along line Vl-IV in FIG. 5, and FIG. 7 is a sectional view taken along line ■-■ in FIG. 6. Figure 8 is a cross-sectional view taken along the line ■-■ in Figure 6, Figure 9 is an explanatory diagram of the cylinder block pressing force and cylinder block overturning moment, and Figure 10 is a cross-sectional view taken along the line X-X in Figure 7. It is. 8 is a shaft, 9 is a cylinder block, 10 is a cylinder bore, 11 is a piston, 13 is a shoe, 14A is a swash plate surface, and 21 is a valve plate.

Claims (1)

[Claims] The cylinder block is equipped with a cylinder block that rotates due to rotational drive of a shaft, and a valve plate that has a suction port and a discharge port in sliding contact with the sliding surface of the cylinder block. In an axial piston pump in which the piston reciprocates in the cylinder bore by sliding on the surface and thereby performs the suction and discharge strokes, the piston is moved in the direction of the composite moment M_o of the cylinder block pressing moment M_p and the cylinder block overturning moment M_F_r. An axial piston pump characterized in that the direction of the opening force (point of action X') is determined by eccentrically setting the hydraulic seal portion C' of the valve plate.