JP2557708Y2 - Swash plate piston pump - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention is capable of reciprocating a stroke corresponding to a tilt angle of a swash plate in a bore of a cylinder block which rotates integrally with a rotary shaft and slides on a valve plate fixed to a casing. The bore is communicated with a suction passage and a discharge passage for hydraulic oil through a cylinder port provided in a cylinder block and a suction port and a discharge port penetrated through the valve plate. The present invention relates to a swash plate type piston pump that sucks and discharges hydraulic oil based on reciprocation of a piston in conjunction with the piston.

[0002]

2. Description of the Related Art In an axial piston pump disclosed in Japanese Patent Application Laid-Open No. Sho 62-13780, a cylinder block is slidably and non-rotatably supported on a rotating shaft supported in a casing and fixed on an end plate. The rear end face of the cylinder block is pressed against the valve plate. A piston is housed in each bore of the cylinder block surrounding the rotary shaft, and the tip of the piston is constantly pressed against the swash plate via the shoe. As a result, the piston reciprocates a stroke corresponding to the swash plate inclination angle.

[0003] At the rear end of the cylinder block, a cylinder port is formed for each bore, and the valve plate is provided with a long arcuate suction port and a discharge port corresponding to the motion trajectory of the cylinder port. Hydraulic oil is sucked and discharged through the port. A wedge-shaped notch is engraved on the side where the suction port and the discharge port overlap with the cylinder port on the sliding surface of the valve plate with respect to the cylinder block (hereinafter, referred to as the starting end).

In the piston pump disclosed in Japanese Utility Model Laid-Open Publication No. Sho 58-1772, the depth of the notch formed at the start end of each of the suction port and the discharge port of the valve plate is set at least equal to the length of the cylinder block in the rotation direction. ing.

In the piston pump disclosed in Japanese Patent Application Laid-Open No. 49-93902, notches are provided at the start end and the end of the discharge port of the valve plate, and an orifice is formed in a land between the suction port and the discharge port. The orifice communicates with the suction port inside the land.

[0006]

SUMMARY OF THE INVENTION In the case of a conventional piston pump having no notch at the start end of the suction port or the discharge port of the valve plate, the suction port is disconnected after the cylinder port is disconnected from the discharge port. (When the piston passes through the top dead center position), the cylinder port and the suction port pass directly through, and the high-pressure hydraulic oil remaining in the cylinder port flows back to the suction port for a moment, causing the cylinder port internal pressure to rise sharply. To decline. Also, after the communication of the cylinder port with the suction port is interrupted, the timing of the first communication with the discharge port (when the piston passes the bottom dead center position)
In this case, the high-pressure hydraulic fluid at the discharge port flows backward to the cylinder port for a moment, and the internal pressure of the cylinder port rapidly increases.

In the piston pumps of the above publications,
Prior to direct communication between the cylinder port and the suction port or the discharge port, the communication cross-sectional area between the cylinder port and the suction port or the discharge port is gradually increased through a wedge-shaped notch of the valve plate, and the pressure in the cylinder port is reduced. The pulsation and noise of the pump are reduced by preventing the pressure from changing suddenly.

However, as shown by the broken line in the graph of FIG. 5, even in the conventional piston pump having a notch in the valve plate, the pressure in the cylinder port cannot be ignored from the steady discharge pressure P ₁ when passing through the top dead center of the piston. It reached a stationary suction pressure P ₂ via a chute E _3. Also, when the piston passes through the bottom dead center, the pressure in the cylinder port becomes the steady suction pressure P ₂
It reached a stationary discharge pressure P ₁ via the overshoot E ₄ from. As long as the normal exhaust pressure P ₁ or constant suction pressure P ₂ from far off pressure fluctuations still exist, stable operation of the pump is inhibited, pulsation and noise is generated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a swash plate type piston pump in which pulsation and noise are reduced by alleviating a sudden change in pressure in a cylinder port when a discharge operation and a suction operation of a piston are switched. .

[0010]

According to the present invention, a wedge-shaped notch is provided on a sliding surface of a cylinder block with respect to a valve plate, the wedge-shaped notch being continuous with the starting end of each cylinder port in the rotation direction. A swash plate type piston pump is formed by providing a wedge-shaped notch that is continuous with the suction port and the discharge port with respect to the cylinder port on the side where the polymerization starts.

[0011]

The sharp end of the notch on the cylinder block side and the sharp end of the notch on the valve plate side overlap with each other as the suction port or the discharge port approaches the cylinder port due to the rotation of the cylinder block. Thereby, the suction port or the discharge port communicates with the cylinder port via the temporary passage formed by the notch on the cylinder block side and the notch on the valve plate side.

In this case, the overlapping surface of both notches has a substantially rhombic shape, and when the sharp end of the notch on the valve plate side directly overlaps the cylinder port to form a substantially triangular overlapping surface as in the conventional example. In comparison, the polymerization area is reduced. Therefore,
According to the present invention, the cross-sectional area of the temporary passage can be gradually increased from a state smaller than that of the conventional example. As a result, fluctuations in the internal pressure of the cylinder port are reduced, and pulsation and noise of the pump are suppressed.

[0013]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. As shown in FIG. 1, a rotary shaft 4 is rotatably supported between the casing 1 and the front cover 2 via bearings 5A and 5B, and a cylinder block 6 slides on the rotary shaft 4 via a spline 3. It is supported so as to be able to rotate relative to each other. A plurality of bores 7 are formed around the axis of the cylinder block 6 that rotates integrally with the rotating shaft 4, and each bore 7 accommodates a piston 10 so as to be slidable.

As shown in FIGS. 1 and 2 (a), a plurality of oblong cylinder ports 7a are formed in the rear end face 6a of the cylinder block 6, and each cylinder port 7a
“a” communicates with the respective bores 7. The rotation direction R of the cylinder block 6 is provided on the rear end face 6a of the cylinder block 6.
The notch 17 is engraved at the start end of each cylinder port 7a. As shown in FIGS. 2A, 3 and 4, the notch 17 is formed in a wedge-shaped groove having a V-shaped cross section. Therefore, the notch 17 is gradually deeper and wider as it goes from the tip to the cylinder port 7a side.

As shown in FIGS. 1 and 2 (b), a valve plate 9 is fixed to the inner end surface of the casing 1, and the valve plate 9
, The rear end face 6a of the cylinder block 6 is in sliding contact. The valve plate 9 is provided with a long arc-shaped suction port 9a corresponding to the movement trajectory of each cylinder port 7a of the cylinder block 6, and three short arc-shaped discharge ports 9b.
In the vicinity of the discharge port 9b of the valve plate 9, the cylinder block 6
In order to always receive the strong discharge pressure from the discharge stroke side cylinder port 7a, the strength of the valve plate 9 is secured by dividing the discharge port 9b into three.

As shown in FIGS. 2A and 2B, the length L ₁ of the notch 17 formed on the rear end face 6a of the cylinder block 6 is determined by the length of the discharge port 9b adjacent to the valve plate 9. Interval L
It is set to be larger than _{2 (L 2 <L 1)} . Therefore,
The notch 17 can communicate with both discharge ports 9b simultaneously across the connecting portion of the adjacent discharge ports 9b.

The sliding contact surface 9c of the valve plate 9 with respect to the cylinder block 6 has a notch 18 connected to the start end of each of the orbiting cylinder ports 7a and the start end of the suction port 9a that first overlaps, and three discharge ports 9b. A notch 19 is engraved on the leading end of the discharge port 9b located at the head. As shown in FIGS. 2B, 3 and 4, both notches 18 and 19 are formed in wedge-shaped grooves having a V-shaped cross section. Therefore, each notch 18, 19 becomes deeper and wider as it goes from the tip to the corresponding port 9a, 9b side. As shown in FIG. 4, the maximum depth d ₁ of the notch 17 provided on the cylinder block 6 is set to be substantially the same as the maximum depth d ₂ of each of the notches 18 and 19 provided on the valve plate 9. ing.

As shown in FIG. 1, a suction passage 8a and a discharge passage 8b are formed at the rear end of the casing 1 so as to communicate with a suction port 9a and a discharge port 9b of the valve plate 9, respectively. In conjunction with the rotation of the rotating shaft 4, each cylinder port 7a of the cylinder block 6 is sequentially connected to the suction port 9a and the discharge port 9b. Thereby, the hydraulic oil is sucked into the bore 7 from the suction passage 8a through the suction port 9a, and the hydraulic oil in the bore 7 is discharged to the discharge passage 8b through the discharge port 9b.

A swash plate 12 is supported on a swash plate guide 11 provided on the inner surface of the front cover 2 so as to be tiltable. The tilt angle of the swash plate 12 is controlled by a tilt control mechanism (not shown). A pressing spring 14 is interposed in a spline fitting portion at the tip of the cylinder block 6. Press spring 14
Spring force acts on the cylinder block 6 and also acts on the shoe retainer 16 via the pivot 15. As a result, each of the pistons 10
Are pressed against the swash plate 12.

The tip of a piston 10 is rotatably and irremovably connected to each shoe 13. Accordingly, each piston 10 reciprocates in a stroke corresponding to the tilt angle of the swash plate 12 in accordance with the rotation of the rotary shaft 4, and sucks hydraulic oil into the bore 7 and discharges hydraulic oil from the bore 7.

With the rotation of the rotary shaft 4, the rear end face 6a of the cylinder block 6 slides on the sliding surface 9c of the valve plate 9, and each cylinder port 7a communicates with the suction port 9a and the discharge port 9b. Repeat blocking.

As shown in FIGS. 3 and 4, when the cylinder port 7a and the suction port 9a (or the discharge port 9b) approach each other due to the circular movement of the cylinder port 7a accompanying the rotation of the cylinder block 6, the cylinder port 7
The sharp end of the notch 17 on the a side and the sharp end of the notch 18 (or 19) on the suction port 9a (or discharge port 9b) side are connected first. Thereby, the suction port 9a (or the discharge port 9b) and the cylinder port 7a communicate with each other via the temporary passage 20 formed by the notch 18 (or 19) and the notch 17, as shown in FIG.

As the overlapping area Q (hatched portion in FIG. 3) of the notch 17 and the notch 18 (19) gradually increases as the cylinder port 7a advances, the cross-sectional area of the temporary passage 20 at the narrowest portion also increases. Although it gradually increases, the change in the cross-sectional area of the passage in the narrowest portion is slow, so that the abrupt change of the hydraulic oil based on the pressure difference between the internal pressure of the cylinder port 7a and the pressure on the suction port 9a (or the discharge port 9b) side. Movement is suppressed.

In a configuration in which a wedge-shaped notch is formed only on the valve plate side and no notch is formed on the rear end surface of the cylinder block as in the conventional example, the notch on the valve plate side is immediately changed to the cylinder by the approach of the cylinder port. Connect to port.
In this case, the temporary passage connecting the suction port (or the discharge port) and the cylinder port is constituted only by the notch formed in the valve plate, and the overlap area between the notch and the cylinder port is substantially triangular.

In the case where the amount of entry of the sharp end of the conventional notch into the cylinder port region and the amount of entry of the sharp end of the notch 18 (or 19) into the notch 17 on the cylinder port 7a side in this embodiment are the same, The overlapping area Q of the diamond shape in the example is approximately half of the overlapping area of the triangular shape in the conventional example. Cylinder port 7a and ports 9a, 9b on valve plate 9 side
Such lowering of the overlapping area at the start of communication with the pressure suppresses pressure fluctuations in the cylinder port 7a as compared with the related art.

Therefore, as shown in FIG.
When There is switched from the discharge stroke to the suction stroke (when passing the top dead center), and the piston 10 even when it is switched to discharge stroke from the suction stroke (at the bottom dead center passage), a conventional example such as undershoot E ₃ Ya of overshoot E ₄ without causing the pressure in the cylinder port 7a is transitory steady discharge pressure P ₁ or constant suction pressure P ₂ stably and quickly. That is, there is no large fluctuation in the internal pressure fluctuation of the cylinder port 7a when switching between the suction operation and the discharge operation, and pulsation and noise can be reduced more than before.

Since the length L ₁ of the notch 17 formed on the cylinder block 6 side is set to be larger than the interval L ₂ between the discharge ports 9 b formed separately on the valve plate 9, three cylinder ports 7 a are formed. Even when the divided discharge ports 9b are located on the first (or second) discharge port 9b and are in direct communication with each other, the tip of the notch 17 is located next to the discharge port 9b. Or third) discharge port 9
Start communication with b. Therefore, the discharge oil from the cylinder port 7a is smoothly dispersed and discharged to the two discharge ports 9b, and the discharge pulsation is reduced.

[0028]

According to the present invention, as described in detail above, a wedge-shaped notch is provided on the sliding surface of the cylinder block with respect to the valve plate and connected to the starting end of each cylinder port in the rotation direction. The sliding contact surface of the cylinder port is provided with a wedge-shaped notch that is continuous with the polymerization start side of the suction port and the discharge port with respect to the cylinder port, so that the pressure in the cylinder port when the discharge operation and the suction operation of the piston are switched is abrupt. An excellent effect of reducing fluctuations and suppressing pulsation and noise is achieved.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

2A is a sectional view taken along line AA of FIG. 1, and FIG. 2B is a sectional view of FIG.
FIG. 4 is a cross-sectional view taken along line B.

FIG. 3 is an explanatory diagram showing a state of overlap between a notch on a valve plate side and a notch on a cylinder block side.

FIG. 4 is a cross-sectional view showing a superimposition state of a notch as viewed in a direction of line XX in FIG. 3;

FIG. 5 is a graph showing a measurement result of a pressure in a cylinder port with respect to a piston timing.

[Explanation of symbols]

1 casing, 4 rotating shafts, 6 cylinder blocks,
6a Rear end face, 7 bore, 7a Cylinder port, 8a
Suction passage, 8b discharge passage, 9 valve plate, 9a suction port, 9b discharge port, 9c sliding contact surface, 10 piston, 12 swash plate, 17 notch, 18 notch, 19
notch.

Claims (1)

(57) [Scope of request for utility model registration] 1. A piston, which rotates integrally with a rotating shaft and slides in contact with a valve plate fixed to a casing, accommodates a piston capable of reciprocating a stroke corresponding to a tilt angle of a swash plate. The bore communicates with a suction passage and a discharge passage for hydraulic oil through a cylinder port provided in the cylinder block and a suction port and a discharge port penetrated through the valve plate, and the piston is driven in conjunction with rotation of the rotating shaft. In a swash plate type piston pump for sucking and discharging hydraulic oil based on reciprocating motion, a wedge-shaped notch is provided on a sliding surface of a cylinder block with respect to a valve plate, the wedge-shaped notch being continuous with a rotation end of each cylinder port. A swash plate provided with a wedge-shaped notch on a sliding contact surface of a plate, which is connected to a polymerization start side of the suction port and the discharge port with respect to the cylinder port. Piston pump.