JPH02256884A - Piston pump with variable capacity - Google Patents

Abstract

PURPOSE:To facilitate fabrication and miniaturize the above pump by forming a semi-cylindrical tab having an arc-shaped surface with the axis of tilting as the center to the yoke in such a way as protruding on both sides of a ring- shaped body, and by arranging a bearing surface to receive this arc-shaped surface at the inner wall of a pump housing. CONSTITUTION:A yoke 5 is fitted with protrusions in a single piece protruding up and down and to the left and right from the yoke body 51, wherein the upper protrusion 52 contacts the tip of an operational piston 16 on the back while the lower protrusion 53 receives the force of a yoke return spring 13 on the back through a spring receptacle 12. The front of the left and right protrusions 54 presents a tab 11 in the form of arc-shaped surface so that the yoke body 51 is supported by the housing 1 tiltably against the force of the operational piston 16 and spring 13. A circular slide bearing 10 is fixed by a pin to the inner wall of this housing 1, and the two tabs 11 are supported by an arc-shaped concave bearing surface of said bearing 10 with possibility of relative sliding. This accomplishes the intended yoke from a less number of parts, wherein the bearing slide surface is lessened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable displacement piston pump, and more specifically, to an operation for controlling the tilting angle of a yoke that gives a pump element a displacement depending on the tilting angle. The present invention relates to an improvement in a yoke support structure for a variable displacement piston pump having a piston, a yaw that applies a restoring spring force to the yoke to oppose the operating piston, and a return spring.

[Prior Art] In this type of variable displacement piston pump, an approach in which tilting of the yoke is supported by an arcuate slide bearing is disclosed in, for example, Japanese Utility Model Application No. 57-61185 or Japanese Patent Application Laid-open No. 63-90.
It is described in Publication No. 676, etc. In these conventional variable displacement piston pumps, the yoke itself is formed in a semicylindrical shape, and the entire front side of the yoke is an arcuate tilting sliding surface.

[Problems to be Solved by the Invention] In the conventional variable displacement piston pump described above, the entire front side of the yoke itself is an arcuate tilting sliding surface.
There is a drawback that the radius of the tilting shaft becomes larger and the sliding friction increases, resulting in a decrease in hysteresis in the increase/decrease in the discharge amount due to the tilting operation. In addition, in order to reduce this hysteresis, a passage structure must be used to guide part of the discharged pressure oil between the sliding surfaces, which increases the size of the pump due to the large tilting radius and complicates the structure. The increase in the number of man-hours required to process the pods has become a problem. In addition, conventionally, the bearings were installed integrally with the pump body housing, or both bearings were integrated and attached to the housing, so if the machining accuracy of the bearing surface is not good, hysteresis increases, and the pump body housing There were various problems such as the large number of man-hours required to process such large parts and the difficulty in surface treatment.

Therefore, an object of the present invention is to provide a variable displacement piston pump equipped with a yoke tilting support structure in which the sliding area of the bearing is small when the tilting movement of the yoke is supported by the circular arc surface slide bearing, and therefore hysteresis is reduced. The objective is to realize a compact structure that is easy to process and assemble with a minimum number of parts.

[Means for Achieving the Object] A variable displacement piston pump according to the invention according to claim 1 includes a yoke that provides a pump element with a displacement according to a tilting angle, and a tilting angle of the yoke is controlled. The device includes an operating piston and a yoke return spring that applies a restoring spring force to the yoke opposing the operating piston, wherein the yoke has a semi-cylindrical ear portion having an arcuate surface centered on a tilting axis. The annular main body is integrally formed with the pump main body so as to protrude from both sides thereof, and an arcuate concave bearing surface for receiving the arcuate surface is arranged on the inner wall surface of the pump main body housing.

In the variable displacement piston pump according to the second aspect of the invention, the slide bearings are separate bearing parts on both sides that are pivotally supported by the pump body housing.

[Function] In the variable displacement piston pump according to the invention as set forth in claim 1, the yoke has semicylindrical ears having a circular arc surface centered on the tilting axis that protrudes from both sides of the annular main body. 1. Since a circular concave bearing surface that receives the circular arc surface is arranged on the inner wall surface of the pump body housing, the shaft diameter of the tilting shaft can be reduced to the necessary minimum, and the sliding area of the bearing surface is reduced to reduce hysteresis. It is something.

Further, in the variable displacement piston pump according to the invention set forth in claim 2, in addition to the one set forth in claim 1, separate bearing parts are used as the slide bearings on both sides pivotally supported by the pump main body housing. , the difference in coaxial precision between the arcuate ears on both sides of the yoke is absorbed by the pivoting of separate bearing parts on both sides, thus reducing the resistance to the tilting movement of the yoke and suppressing the occurrence of hysteresis. be.

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

[Example] In Fig. 1, a variable displacement piston pump according to an example of the present invention uses a main body housing 1 made of aluminum alloy for weight reduction, and an end cover 2 made of cast iron. It may be made of aluminum to further reduce weight.

A cylinder block 4 and a slip retainer 8 are attached to a rotating shaft 3 rotatably supported by bearings on the main body housing 1 and end cover 2, and these cylinders are rotated by rotating the rotating shaft 3 with an external electric motor or the like. The block 4 and slipper retainer 8 are adapted to rotate together. The slipper retainer 8 can be tilted to follow the yoke 5, and presses each slipper 9, which is connected to the head of each piston 6 in the cylinder pro 4 with a universal joint structure, against the inclined sliding surface of the yoke 5. The piston 6 is caused to perform a stroke motion by rotating the piston 6 while it is still rotating.

The yoke 5 has arcuate ears 11 on both sides that are supported by arcuate slide bearings 10 shown by broken lines attached to the main body housing 1, and is tiltable about the center of the circle of the arcuate surface. The details of this yoke 5 are shown in 2A, 2B and 2.
As shown in Figure C, the yoke main body part 5 is circular.
Projections are integrally formed on the top, bottom, left and right from 1. The upper protrusion 52 is a part that comes into contact with the tip of the operating piston 16 on the back side, and the lower protrusion 53 is a part that receives the force of the yoke return spring 13 via the spring receiver 12 on the back side. Furthermore, the left and right protrusions 54 are portions that support the yoke body 51 in a tiltable manner to the pump body housing 1 against the force of the operating piston 16 and the spring 13, and the front side thereof becomes the arcuate ear portion 11. ing. FIG. 2C is a sectional view in which a part of the pump body housing side is added to the cross section taken along the line x--X in FIG.
0 is attached with a pin, and the both ear portions 11 are supported so as to be relatively slidable by the arcuate concave bearing surface of the bearing tO. In this case, as shown in FIG. 2A, the center oa of the annular yoke main body portion 51 and the arcuate surface ear portion 11
It is shifted in the vertical direction from the arc center Ob. The circular slide bearing 10 is attached to the shoulder portion 61 of the main body housing 1 with a pin 62, as shown in FIG. 3A. In this case the pin 62 may be part of the central portion as shown in Figures 3b and 3C. Like this - Bearing 1 with a wooden pin
If the central portion of the bearing 10 is rotatably attached to the housing shoulder 61, as shown in FIG.

The rear side of the cylinder block 4 is pressed against the pump end cover 2 via the boat plate 7, and each cylinder chamber in the cylinder block 4 is opened to the discharge boat 30 or the suction boat of the end cover 2 as the cylinder block 4 rotates. 31 in order.

A straight through hole 19 communicating into the housing 1 is bored in the end cover 2 at a position corresponding to the operating piston 16,
A control valve sleeve 15 is inserted into this through hole 19 from the back side of the pump. The tip of the control valve sleeve 15 protrudes into the housing 1, and is covered with the operating piston 16, which is a cylindrical cap part. Here, the inner diameter of the through hole 19 is smaller than the outer diameter of the operating piston 16.

An annular recess 33 having a diameter larger than the outer diameter of the operating piston 16 is provided at the opening edge of the through hole 19 on the inner surface of the housing so that the tail end of the operating piston 6 can be received and seated therein. It is being

The distal end surface of the control valve sleeve 15 is connected to the operating piston 16.
A pressurizing chamber 24 is formed between the inner surface of the tip of the operating piston and the inner surface of the tip of the operating piston. Inside the control valve sleeve 15, a pressure compensator spool 17 is slidably disposed together with a spacer disk 22 in a valve hole bored approximately along its central axis, and a spring receiver is attached to the end surface of the spool 17 on the rear side of the pump. It receives the spring force of the pressure regulating spring 2o via 18.

The pressure regulating spring 20 is housed in a case 14 and attached to the upper back surface of the end cover 2, and the initial deflection amount can be adjusted by a pressure regulating screw 21 attached to the case 14.

Passages 26, 27, and 28 are also bored in the control valve sleeve 15, and the passage 26 reaches the sleeve tip in the axial direction and communicates with the pressurizing chamber 24, as well as a bleed hole formed at a predetermined position in the middle of the sleeve tip. The passage 27 leads to a low pressure drain line in the body housing 1 and the passage 28 opens into a hole 29 .
communicates with the discharge boat 30 via a passage 32 in the end cover 2. Note that the bleed hole 29 is connected to the operating piston 1.
6 is moved toward the tip by the hydraulic pressure in the pressurizing chamber 24, and the yoke 5
When the operation piston 1 is raised to the position of approximately the discharge amount;
6 is pre-positioned to be interposed within the housing 1 at its tail end. In the figure, 31 is a drain hole.

The spool 17 receives discharge pressure through a passage 32.28 and a through hole in the spool on the end face on which the spacer 22 is disposed, and the other end receives discharge pressure through the passage 27 and another through hole in the spool to the housing. 1 and receives the spring force of the pressure regulating spring 20. Therefore, when the discharge pressure exceeds the set value by the pressure regulating spring 20, the spool 17 is displaced against the spring 20, thereby the passage 28 communicates with the passage 26, the discharge pressure is introduced into the pressurizing chamber 24, and the operating piston 1
6 is displaced to rotate the yoke 5 in a direction where its tilt angle decreases (stands up).

The control valve sleeve 15 further has a maximum discharge amount adjusting mechanism at its tip, and in the example shown in FIG. It is designed to be locked with a lock nut 25. It goes without saying that the retraction limit of the operating piston 16 determines the maximum tilt angle of the yoke 5, and therefore the maximum discharge amount is set.

FIG. 4 shows the control valve sleeve 15 removed from the through hole 19. In this case, when the case 14 is first removed from the end cover 2 and then the sleeve 15 is pulled out, the operating piston 16 is pushed back by the spring 13 via the yoke 5 and moves back together with the sleeve 15. When the sleeve 15 is further pulled out, the tail end of the operating piston 16 enters the annular recess and the operating piston 15 is seated. When the sleeve 15 is pulled out, the operating piston 16 remains seated as shown in FIG. It will be left behind, and in this state it will wait for the sleeve 15 to be reinserted and returned. Furthermore, even if the operating piston 16 is dislodged internally due to an impact or the like during this time, it can be easily restored by hand because the thickness of the end face cover 2 is not so thick. The removed sleeve 15 is then adjusted as desired, such as by increasing the amount of protrusion of the screw 23 at the tip and decreasing the maximum discharge amount set value, as shown in FIG. All you have to do is return it to . As a method for adjusting the maximum discharge amount setting, for example, as shown in FIG. Various modifications are possible, such as intervening in the.

[Effects of the Invention] As described above, according to the present invention, the tilting support structure of the yoke can be constructed with a small number of parts, and can be realized with a bearing having a small sliding area, which does not require precision machining. Since the bearing sliding surface is integrated into the yoke and bearing parts, the number of man-hours required for machining large parts such as the pump end cover and main body housing can be reduced, improving machining efficiency.Also, the bearing parts can be made as separate parts on both the left and right sides of the main body. When the pump is pivoted to the housing, the tilting movement of the yoke becomes smoother, and a compact pump with no hysteresis in the variable discharge characteristics is obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2A is a rear view of the yoke, FIG. 2B is a side view of the yoke, and FIG.
Figure C is a cross-sectional view of the X-X line cross section of Figure 2A with a cross section of the pump body housing added, Figure 3A is a side view showing an example of an arcuate slide bearing, and Figures 3B and 3C are arcuate surfaces. Side view and rear view showing another example of a slide bearing, No. 4
The figure is a cross-sectional view of the main part showing how the sleeve is removed, Figure 5 is a cross-sectional view of the main part when the maximum discharge rate setting is decreased, and Figure 6 is a cross-sectional view showing another example of the maximum discharge rate setting adjustment mechanism. be. (Explanation of symbols of main parts) 1: Pump body housing, 2: Pump end cover 3
2 rotating shaft, 4; cylinder block, 5: yoke, 6: piston, 10: arcuate surface slide bearing, 11: arcuate surface ear, 13: yoke return spring, 14: case, 15:
Control valve sleeve, 16: Operation piston, 17: Pressure convencer spool, 19: Through hole, 20: Pressure regulating spring,
21: Pressure adjustment screw, 23: Maximum discharge rate setting adjustment screw, 2
5: lock nut, 30: discharge boat, 31: adult boat, 33: annular recess.

Claims (2)

[Claims] 1. A variable pump having a yoke that provides a displacement volume to the pump element according to a tilting angle, an operating piston that controls the tilting angle of the yoke, and a yoke return spring that provides a restoring spring force to the yoke that opposes the operating piston. In the displacement piston pump, the yoke has semi-cylindrical ears having an arcuate surface centered on the tilting axis and integrally protrudes from both sides of the annular main body, and is attached to the inner wall surface of the pump main body housing. A variable displacement piston pump characterized in that a slide bearing having a bearing surface having an arcuate concave surface for receiving the arcuate surface is provided. 2. 2. The variable displacement piston pump according to claim 1, wherein the slide bearing comprises separate bearing parts on both sides that are pivotally supported on the pump body housing.