JPS6339431Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to an axial piston pump.
In particular, the present invention relates to improvements in a variable displacement mechanism in a variable displacement rotary swash plate type axial piston pump.

An example of a conventional variable displacement rotary swash plate type axial piston pump is shown in FIG. This pump includes a housing 1, a rotating shaft 2 rotatably supported at one end of the housing 1,
A cylinder block 3 is housed in a housing 1 at an end opposite to the rotating shaft 2 so as to be slidably fixed thereto, and an appropriate number of cylinders 4 are bored in the cylinder block 3 parallel to the shaft. It is equipped with a piston 5 that is slidably inserted into the cylinder 4, and a swash plate 6 that is fixed to the tip of the rotating shaft 2 and has an inclined surface that is in constant sliding contact with the piston 5, and is integral with the rotating shaft 2. As the swash plate 6 rotates, the piston 5, which is always in sliding contact with the inclined surface of the swash plate 6, reciprocates within the cylinder hole 4 and discharges pressure oil. When changing the flow rate of the discharged oil, the cylinder block 3 is displaced relative to the housing 1 by moving the adjustment rod 9 back and forth, and the hollow part 5 is moved between the rear opening 4a of the cylinder hole 4 and the intermediate part of the piston 5.
By relatively changing the positional relationship with the relief port 10 bored so as to communicate with the cylinder hole 4,
capacity has been substantially changed.
In addition, in the figure, numeral 7 is a suction valve, and 8 is a discharge valve.

However, in the case of such conventional variable displacement rotary swash plate type axial piston pumps,
Since the structure is such that the discharge amount is changed by displacing the cylinder block as a whole, it is necessary to change the length of the discharge flow path in response to the displacement of the cylinder block, which results in a longer piston and a corresponding increase in equipment efficiency. This has the drawback of increasing the overall length, and also has the drawback of poor responsiveness since the entire cylinder block is displaced.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide an axial piston pump that is small in size and has excellent responsiveness in variable displacement control.

In order to achieve the above object, the present invention provides a control plate movable in the axial direction in the housing, which faces the cylinder hole and has a through hole into which the piston is slidably inserted. The capacity of the cylinder hole is changed by displacing it with respect to the relief port.

Embodiments of the present invention will be described below with reference to the drawings.

2 to 5 are diagrams showing an embodiment of the present invention. First, to explain the configuration, a cylinder block 3 is fixed by a fixing member 11 at a position opposite to the rotating shaft 2 in the housing 1, and the joint surface between the end surface of the cylinder block 3 and the inner wall surface of the housing 1 is O. It is sealed by rings 12 and 13. Therefore, the cylinder block 3 is the housing 1
It may be integrally molded with. A fixing plate 14 is fixed at a substantially central position within the housing 1 by a retaining ring 15 at right angles to the axis of the housing 1. A control plate 31 is disposed between the plate 14 and the cylinder block 3.
It is fitted to the inner circumferential surface of the cylinder so as to be slidable within a predetermined range along the axial direction. The control plate 31 is connected to the cylinder block 3 by a spring 32 which is mounted in a stored state with one end in contact with the fixed plate 14.
is biased in the direction of A communication hole 3 is provided in the center of the control plate 31 to communicate between both end surfaces.
A suitable number of holes 3 are formed through the fixing plate 14, and a communication hole 16 is similarly formed in the fixing plate 14. The control plate 31 is provided with through holes 41 located on the outer circumferential side of the communication hole 33 and facing the respective cylinder holes 4 of the cylinder block 3. The parts are slidably inserted. A control cylinder 92 is formed in the center of the cylinder block 3 and extends over the abutting wall of the housing 1, and a control piston 91 is slidably inserted into the control cylinder 92. The pressure of the discharge passage 81 is introduced into the control sill 92 via a pressure compensating valve 93, and the control piston 91 moves back and forth depending on the increase or decrease in the pressure, thereby causing the control plate 31 to interact with the spring 32. They are now working together to advance and retreat.

Two relief ports 10 are formed in the body of the piston 5 so as to face each other within the movement range of the control plate 31, allowing communication between the hollow portion 5a and the outer circumferential surface. A suction passage 71 is formed at the tip of the piston 5 so as to communicate between the inside of the housing 1 and the hollow part 5a of the piston 5, and a valve body 72 of the suction valve 7 is provided in this suction passage 71. . Valve body 7
2 is constantly biased by a compression spring 73 whose one end is locked to the piston 5 via a spring retainer 74, and is always trying to close the suction passage 71. It is designed to open due to the pressure of suction oil only during the stroke when the valve is drawn out from the cylinder. That is, the suction valve 7 is a check valve, as schematically shown in FIGS. 3 and 4, and the same applies to the discharge valve 8. A rod 51 is rotatably held at the tip of the piston 5, and the tip of the rod 51 is rotatably held by a reaction plate 62. The reaction plate 62 is rotatably supported on the inclined surface 61 of the swash plate 6 via a radial bearing 63 and a thrust bearing 64. The piston 5 is constantly urged toward the swash plate 6 by a compression spring 52 whose one end is locked to the fixed plate 14. Therefore, the piston 5 is pushed through the rod 51, the reaction plate 62, and the bearings 63, 64. It is designed to be in constant sliding contact with the inclined surface 61 of the swash plate 6.

In the figure, reference numeral 17 is an oil inlet hole formed in the side wall of the housing 1.

The operation of the rotary swash plate compressor configured as described above will be explained below.

When the rotating shaft 2 rotates, the swash plate 6 rotates and the reaction plate 62 swings in the axial direction, and this movement causes the piston 5 to reciprocate with a constant stroke. With this reciprocating movement, the oil that has entered the housing 1 from the oil inlet 17 is absorbed when the piston 5 moves from the lower position to the upper position in FIG.
When the piston 5 is pulled out from the cylinder 4 (hereinafter referred to as suction stroke), the valve body 72 of the suction valve 7 is pushed to open the suction passage 71, and the hollow part 5 of the piston 5
a and into the cylinder hole 4 communicating therewith. At this time, discharged oil, which will be described later, is prevented from flowing back into the cylinder hole 4 by the action of the discharge valve 8. Next, when the piston 5 moves from the upper position to the lower position in FIG. 3, that is, when the piston 5 is pushed into the cylinder hole 4 (hereinafter referred to as
This is called the compression stroke. ), the oil in the cylinder hole 4 and the hollow part 5a of the piston 5 is compressed, pushes the discharge valve 8, opens the discharge passage 81, and discharges the oil. At this time, the action of the suction valve 7 prevents oil from flowing backward from the suction path 71.

Control of the discharge amount is performed by displacing the control plate 31.

Now, assuming that the control plate 31 is in the position shown in FIG. 3, that is, in the position closest to the cylinder block 3, the relief port 10 is closed by the control plate 31 throughout the compression stroke. Therefore, oil will not escape into the housing 1 from the relief port 10 throughout the entire stroke. Therefore, in this case, the discharge amount is maximum.

On the other hand, when the control plate 31 is at the farthest position from the cylinder block 3 as shown in FIG. Since the piston 5 is opened, the entire amount of oil in the hollow portion 5a of the piston 5 and the cylinder hole 4 escapes into the housing 1 through the relief port 10 during the compression stroke. Therefore, in this case, the discharge amount is the minimum.

Maximum discharge state (Figure 3) and minimum discharge state (Figure 5)
The intermediate discharge state between the state shown in FIG. 4 is the state shown in FIG. In Figure 4, control plate 3
1 is located between the cylinder block 3 and the fixed plate 14. During the compression stroke of the piston 5, the relief port 10 is closed by the control plate 31 from the beginning to the middle of the stroke. Therefore, the oil in the hollow portion 5a of the piston 5 and the cylinder hole 4 pushes the discharge valve 8 and is discharged into the discharge passage 81. The escape port 10 is unblocked by the control plate 31 and opens into the housing 1 during the compression stroke. Therefore, the oil in the hollow portion 5a of the piston 5 and the cylinder hole 4 escapes into the housing 1 through the relief port 10 during the compression stroke. Therefore, the discharge amount is reduced from the maximum discharge amount by this escape amount. The oil that escaped into the housing 1 returns to the suction passage 7.
1 and compressed again.

In this way, the discharge amount can be adjusted by changing the position of the control plate 31. To change the position of the control plate 31, the control piston 91 may be actuated. In this embodiment, the discharge pressure is
When the value exceeds the set value (usually determined by the biasing force of the spring of this pressure compensation valve 93),
This pressure compensation valve 93 switches and operates to introduce the discharge pressure into the control cylinder 92 and control piston 9
1 is pushed out to the control plate 31 side. This pushing operation causes the control plate 31 to be displaced from the cylinder block 3 by a predetermined amount. Due to this displacement, the above-mentioned adjustment operation is performed, and the discharge pressure decreases. When the discharge pressure becomes equal to or less than the set value of the pressure compensation valve 93, the pressure compensation valve 93 returns to its original position, and the control cylinder 9
The oil in 2 is discharged, and the control piston 91 returns to its original state together with the control plate 31 by the biasing force of the spring 32.

As explained above, according to the present invention, a control plate is provided which faces the cylinder hole of the cylinder block and has a through hole into which the piston is slidably inserted, and this control plate is connected to the relief port of the piston. Since the cylinder capacity is relatively changed by displacing the piston, the piston length can be shortened and the entire pump can be made more compact, as well as improving responsiveness, compared to the case where the entire cylinder block is displaced. I can do it. In addition, since a fluid pressure cylinder/piston mechanism is used as a means for controlling the control plate, the operating pressure for controlling the control plate is not limited to the fluid pressure immediately after discharge as in the above embodiment, but can be adjusted as needed. The configuration is simple because it can be introduced from any appropriate location in the fluid pressure circuit that includes the invented axial piston pump. Furthermore, since the control cylinder/piston mechanism is disposed in the center surrounded by the cylinder hole of the cylinder block, the dead space of the cylinder block can be used effectively, which is effective in making the entire pump more compact.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing a conventional example, Fig. 2 is a longitudinal sectional view showing an embodiment of the present invention, and Figs. 3, 4, and 5 are various operating states for explaining its operation. FIG. DESCRIPTION OF SYMBOLS 1... Housing, 2... Rotating shaft, 3... Cylinder block, 4... Cylinder, 5... Piston, 5a... Hollow part, 6... Swash plate, 7... Suction valve, 8... Discharge valve , 10... Relief port, 14... Fixed plate, 17... Oil inlet, 31... Control plate, 32... Spring, 41...
Through hole, 91... control piston.

Claims (1)

[Scope of utility model registration request] a housing; a rotating shaft rotatably supported at one end of the housing; a cylinder block provided at an end of the housing opposite to the rotating shaft; The cylinder has a plurality of cylinder holes drilled in the cylinder hole, a piston slidably inserted into the cylinder hole, and an inclined surface that is in constant sliding contact with the tip of each piston, and is fixed to the rotating shaft. In the axial piston pump, the axial piston pump is equipped with a swash plate and is capable of sucking in, compressing, and discharging fluid by reciprocating the piston as the swash plate rotates, the piston being slidably inserted into the axial piston pump. A control plate having a hole formed opposite to the cylinder hole is provided in the housing so as to be movable within a predetermined range along the axial direction of the housing, and a control plate is provided in the body of the piston so as to communicate the inside of the piston with the inside of the housing. A control cylinder is provided in a central portion surrounded by the cylinder hole of the cylinder block, and a control piston is slidably inserted into the control cylinder. The control plate is inserted into the housing so that fluid pressure in the fluid pressure circuit can be introduced into the internal pressure chamber of the control cylinder, and the control piston is moved forward and backward depending on the increase or decrease in the fluid pressure, so that the control plate is inserted into the housing. An axial piston pump characterized in that the discharge amount is variably controlled by changing the relative position of the control plate and the relief port by moving and displacing the control plate in the axial direction.