Variable displacement type swash plate type axial piston pump

Abstract

To provide a variable displacement type swash plate type axial piston pump having a throttle portion in which pressure fluid to be discharged from an action chamber into a main body is throttle-controlled, the throttle portion being capable of being easily manufactured.SOLUTION: In a control cylinder 25, a discharge groove 32 is formed in a recessed manner in the surface in linkage with a discharge hole 31. In the state that active force based on pressure fluid in the action chamber active in opposition to a swash plate and spring force of a spring perform approximately balancing action to minimize the inclination angle of the swash plate, the contraction portion is constructed by the discharge groove 32 and a control piston 24 to contraction-control the pressure fluid which flows from the action chamber into the discharge hole 31 and is discharged into the body. An opening of the contraction portion has an area based on a depth size L of the discharge groove 32 in the direction approximately perpendicular to the surface of the control cylinder 25 and the width size of the discharge groove 32 in the direction approximately perpendicular to the depth size L.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a variable displacement swash plate type axial piston pump in which multiple pistons are arranged in a cylinder block so that they can slide back and forth in the axial direction, the amount of reciprocation of the pistons is set by a tiltable swash plate, and the tilt angle of the swash plate is adjusted by a control piston that is movable axially. [Background technology]

[0002] In this type of variable displacement swash plate type axial piston pump, multiple pistons are arranged in a cylinder block so that they can reciprocate axially, and a tiltable swash plate is used to set the amount of reciprocation of each piston. The tilt angle of the swash plate is adjusted by the opposing pressure of the control piston and the spring force of a spring acting on the swash plate, and the pistons slide back and forth with the rotation of the cylinder block to suck and discharge the pressurized fluid. The control piston fits into a control cylinder to define a working chamber into which the pressurized fluid is introduced, and the acting force based on the pressurized fluid introduced into the working chamber is used as the pressing force of the control piston to press the swash plate in the direction of decreasing the tilt angle. The control cylinder is formed with a discharge hole (communication hole) that discharges the pressurized fluid in the working chamber into the main body (housing), and when the acting force based on the pressurized fluid in the working chamber acting against the swash plate and the spring force of the spring are approximately balanced to minimize the tilt angle of the swash plate, a part of the discharge hole is covered by the rear end of the control piston, forming a throttle section that throttles and controls the pressurized fluid discharged from the working chamber into the main body. The discharge hole is formed in a generally sector shape in plan view, which prevents the opening area of ​​the throttle portion from suddenly changing due to axial movement of the control piston. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 58-6971 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in such conventional variable displacement swash plate type axial piston pumps, the throttling section that throttles and controls the pressurized fluid discharged from the working chamber into the main body is composed of the control piston and the discharge hole, so if the control cylinder that processes and forms the discharge hole is particularly thick, there is a problem that the hole processing is cumbersome and time-consuming to manufacture.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a variable displacement swash plate type axial piston pump in which a throttle portion for throttling and controlling the pressure fluid discharged from the working chamber into the main body can be easily manufactured. [Means for solving the problem]

[0006] In order to achieve this object, the present invention takes the following measures: a cylinder block housed within the main body and engaged with the rotary shaft in the direction of rotation; a plurality of pistons arranged in the cylinder block so as to be capable of reciprocating axially; a plurality of working chambers defined by the pistons and the cylinder block for drawing in and discharging fluid; a tiltable swash plate with which the tips of the pistons protruding from the cylinder block come into sliding contact to set the amount of reciprocating movement of each piston; a control piston movable in the axial direction for pressing the swash plate in a direction decreasing the tilt angle; a control cylinder which fits the control piston to define a working chamber into which pressure fluid is introduced to press the control piston; a discharge hole formed in the control cylinder for discharging the pressure fluid in the working chamber into the main body; and a spring which applies a spring force to the swash plate in a direction increasing the tilt angle of the swash plate against the pressure. The control cylinder has a discharge groove formed as a recess in its surface connected to the discharge hole. When the force based on the pressurized fluid in the working chamber acting against the swash plate and the spring force of the spring are approximately balanced to minimize the tilt angle of the swash plate, a throttling section is formed by the discharge groove and the control piston and throttles and controls the pressurized fluid flowing from the working chamber through the discharge hole and discharged into the main body. The throttling section has an opening with an area based on the depth dimension of the discharge groove in a direction approximately perpendicular to the surface of the control cylinder and the width dimension of the discharge groove in a direction approximately perpendicular to this depth dimension. Effect of the Invention

[0007] As described above in detail, the invention described in claim 1 provides a control cylinder with a discharge groove formed as a recess in the surface thereof connected to the discharge hole, and a throttle portion for throttling and controlling the pressure fluid flowing from the working chamber through the discharge hole to the main body when the force based on the pressure fluid in the working chamber acting against the swash plate and the spring force of the spring are approximately balanced to minimize the tilt angle of the swash plate, the throttle portion being formed by the discharge groove and the control piston, the opening area of ​​which is based on the depth dimension of the discharge groove in a direction approximately perpendicular to the surface of the control cylinder and the width dimension of the discharge groove in a direction approximately perpendicular to this depth dimension. Therefore, since the discharge groove constituting the throttle portion is formed as a recess in the surface of the control cylinder, it is less affected even if the control cylinder is thick, and it can be manufactured more easily than a conventional pump in which the throttle portion is formed by the control piston and the discharge hole.

[0008] In the invention described in claim 1, the throttle portion has an opening area based on the depth dimension of the discharge groove in a direction substantially perpendicular to the surface of the control cylinder and the width dimension of the discharge groove in a direction substantially perpendicular to this depth dimension. Therefore, the depth dimension and width dimension can be easily set, and the optimal opening area according to the application can be easily obtained. [Brief description of the drawings]

[0009] [Figure 1] 1 is a vertical sectional view of a variable displacement swash plate type axial piston pump according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a main part A in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line BB in FIG. 2. [Figure 4] 3 is a view taken along the arrow C in FIG. 2. [Diagram 5] FIG. 5 is a view corresponding to FIG. 4 and showing another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Fig. 1, reference numeral 1 denotes a main body, which is composed of a cylindrical housing 2 with a closed front end and an open rear end, and a rear cover member 3 that closes the rear end opening of the housing 2. Reference numeral 4 denotes a rotating shaft, which passes through the inside of the main body 2 and is rotatably supported by a radial ball bearing 5 arranged at the front end of the housing 2 and a radial roller bearing 6 arranged at the rear cover member 3, with its tip protruding outside from the front end of the housing 2 and coupled to an electric motor (not shown).

[0011] A swash plate 7 is supported inside the main body 1 so as to be tiltable, and tilts at a certain angle with respect to a line perpendicular to the axis of the rotary shaft 4. A cylinder block 8 is housed inside the main body 1, and engages with the rotary shaft 4 at its own axis through spline engagement in the rotational direction, and is driven to rotate by the rotary shaft 4. The cylinder block 8 has a plurality of piston holes 9 formed at equal intervals in the circumferential direction radially outward from the axis. Each piston hole 9 opens on one end face of the cylinder block 8 facing the swash plate 7. A piston 10 is inserted into each piston hole 9 of the cylinder block 8 so as to be able to reciprocate in the axial direction, and defines a working chamber 11 together with the cylinder block 8. The tip of each piston 10 is formed into a spherical convex portion, and a shoe 12 is pivotally attached so as to be able to pivot. The shoe 12 of each piston 10 slides against the swash plate 7, and the swash plate 7 sets the amount of reciprocation of each piston 10 based on the angle of tilt.

[0012] Each shoe 12 is pressed against the swash plate 7 by the spring force of a spring 13 housed in the axis of the cylinder block 8 via a pin 14, a retainer 15, and a retainer plate 16. The volume of the working chamber 11 increases as each piston 10 moves leftward in Fig. 1 and takes in fluid, and the volume decreases as each piston 10 moves rightward in Fig. 1 and discharges pressurized fluid. Connecting holes 17 are connected to each working chamber 11, and the connecting holes 17 open at equal intervals in the circumferential direction on one end face of the cylinder block 8 opposite the other end face.

[0013] Reference numeral 18 denotes a disc-shaped valve plate that slides against the other end face of the cylinder block 8, and it forms suction ports 19 through which the fluid sucked in through each connecting hole 17 flows into each working chamber 11, and discharge ports 20 through which the discharged pressurized fluid flows. The suction ports 19 and discharge ports 20 are semicircular and arranged symmetrically about the axis of the valve plate 18. The valve plate 18 is spigot-fitted onto the outer periphery of the radial roller bearing 6, and is arranged inside the main body 1 concentrically with the rotating shaft 4. The spring force of the spring 13 is applied to the valve plate 18 via the cylinder block 8, and the valve plate 18 is pressed against the rear cover member 3. Reference numeral 21 denotes a cylindrical pin member that protrudes in the axial direction from the inner surface of the rear cover member 3, and engages with the valve plate 18 to prevent it from rotating.

[0014] Reference numeral 22 denotes a fluid suction passage and 23 a discharge passage for pressurized fluid, both of which are formed in rear cover member 3, with suction passage 22 connected to suction port 19 and discharge passage 23 connected to discharge port 20. Reference numeral 24 denotes a control piston which is fitted axially movably into a cylindrical control cylinder 25 which protrudes axially from the inner surface of rear cover member 3 and presses swash plate 7 in the direction decreasing the tilt angle. Reference numeral 26 denotes a spring which is arranged behind swash plate 7 inside main body 1 and applies a spring force to swash plate 7 in the direction increasing the tilt angle against the pressure of control piston 24.

[0015] Reference numeral 27 denotes a working chamber for introducing the pressurized fluid, which is defined by fitting the control piston 24 into the control cylinder 25. Reference numeral 28 denotes a flow hole for circulating the pressurized fluid introduced into the working chamber 27, which is formed axially through the axis of the control cylinder 25. Reference numeral 29 denotes a pressure regulating valve provided in the rear cover member 3, which introduces the pressurized fluid into the working chamber 27 through the flow hole 28 when the pressure in the discharge passage 23 reaches the cutoff pressure. The control piston 24 presses the swash plate 7 with an acting force based on the pressurized fluid introduced into the working chamber 27. Reference numeral 30 denotes a rod-shaped maximum discharge rate adjusting member, which is inserted through the inside of the flow hole 28 and screwed into the rear cover member 3, and is provided so that its axial tip can freely advance and retreat into the working chamber 27 by rotating it from the outside and can freely abut against the inner surface of the control piston 24 facing the working chamber 27, thereby regulating the maximum tilt angle of the swash plate 7 to set the maximum discharge rate of the pump.

[0016] Reference numeral 31 denotes a discharge hole formed in the control cylinder 25, which discharges the pressurized fluid in the working chamber 27 to the inside of the main body 1. Two discharge holes 31 are provided at diametrically symmetrical positions at the approximate middle of the axial direction of the control cylinder 25, and penetrate between the surface of the control cylinder 25 and the flow hole 28. Reference numeral 32 denotes a discharge groove, which is connected to the rear cover member 3 side of the discharge hole 31 and is formed as a recess in the surface of the control cylinder 25. As shown in FIG. 2 to FIG. 4, the discharge groove 32 is formed in a substantially V-shape in which the width dimension W gradually decreases from the connecting side with the discharge hole 31 toward the tip side (the rear cover member 3 side) in a plan view from the surface of the control cylinder 25. In addition, the discharge groove 32 is formed in an inclined shape in which the depth dimension L gradually decreases from the connecting side with the discharge hole 31 toward the tip side (the rear cover member 3 side) in a cross section approximately perpendicular to the surface of the control cylinder 25.

[0017] Reference numeral 33 denotes a throttle portion formed by the discharge groove 32 and the rear end 24R of the control piston 24, which throttles and controls the pressure fluid flowing from the working chamber 27 through the communication hole 28 and the discharge hole 31 and discharged into the main body 1 when the acting force based on the pressure fluid in the working chamber 27 acting against the swash plate 7 and the spring force of the spring 26 are approximately balanced to minimize the tilt angle of the swash plate 7 (the state shown in FIG. 1). The throttle portion 33 is an opening of a substantially triangular shape with an area S based on the depth dimension L of the discharge groove 32 in a direction approximately perpendicular to the surface of the control cylinder 25 and the width dimension W of the discharge groove 32 in a direction approximately perpendicular to the depth dimension L at the position where the rear end 24R of the control piston 24 and the discharge groove 32 overlap.

[0018] Next, the operation of this configuration will be described. 1 shows the state in which the discharge pressure of the discharge passage 23 reaches the cutoff pressure set by the pressure regulating valve 29, and the acting force based on the pressurized fluid in the working chamber 27 acting against the swash plate 7 and the spring force of the spring 26 are approximately balanced to minimize the tilt angle of the swash plate 7. The pressurized fluid is introduced into the working chamber 27 through the flow hole 28 by the pressure regulating valve 29, and the pressurized fluid in the working chamber 27 is throttled and controlled by the flow throttle section 33 through the flow hole 28 and the discharge hole 31, and is discharged into the main body 1.

[0019] In this state, the tilt angle of the swash plate 7 is at a minimum, so the amount of reciprocating movement of each piston 10 is approximately zero. As a result of the rotation of the cylinder block 8 accompanying the rotational drive of the rotary shaft 4, the pistons 10 do not reciprocate, and the volume of each working chamber 11 does not increase or decrease. As a result, the amount of pressurized fluid discharged from the discharge passage 23 is approximately zero.

[0020] In this state, when the discharge pressure of the discharge passage 23 falls below the cutoff pressure set by the pressure regulating valve 29, the pressurized fluid in the working chamber 27 flows through the communication hole 28 and is discharged to the low pressure side from the pressure regulating valve 29, the pressure in the working chamber 27 falls, and the swash plate 7 is biased by the spring force of the spring 26 to push the control piston 24 and tilt to the right in Figure 1, maximizing the tilt angle. At this time, the discharge hole 31 and discharge groove 32 are blocked by the control piston 24.

[0021] When the tilt angle of the swash plate 7 is at its maximum, the amount of reciprocating movement of each piston 10 is at its maximum, and fluid is drawn into the working chamber 11, whose volume increases with the rotation of the cylinder block 8, through the suction passage 22 and the suction port 19. Meanwhile, the pressurized fluid in the working chamber 11, whose volume decreases with the rotation of the cylinder block 15, flows through the discharge port 20 and is discharged from the discharge passage 23. In this way, a pump operates by continuously drawing in and discharging fluid as the cylinder block 8 rotates. When the rotation of the rotary shaft 4 is stopped, the pump operation stops.

[0022] In this operation, the control cylinder 25 has a discharge groove 32 formed as a recess on its surface connected to the discharge hole 31, and when the force based on the pressure fluid in the working chamber 27 acting against the swash plate 7 and the spring force of the spring 26 are approximately balanced to minimize the tilt angle of the swash plate 7, a throttle section 33 for throttling and controlling the pressure fluid flowing from the working chamber 27 through the discharge hole 31 and discharged into the main body 1 is formed by the discharge groove 32 and the control piston 24, and the throttle section 33 has an opening with an area S based on the depth dimension L of the discharge groove 32 in a direction approximately perpendicular to the surface of the control cylinder 25 and the width dimension W of the discharge groove 32 in a direction approximately perpendicular to the depth dimension L. Therefore, since the discharge groove 32 constituting the throttle section 33 is formed as a recess on the surface of the control cylinder 25, it is less affected even if the thickness between the surface of the control cylinder 25 and the flow hole 28 is thick, and it can be manufactured more easily than a conventional pump in which the throttle section is formed by a control piston and a discharge hole.

[0023] Further, the throttle portion 33 has an opening with an area S based on the depth dimension L of the discharge groove 32 in a direction substantially perpendicular to the surface of the control cylinder 25 and the width dimension W of the discharge groove 32 in a direction substantially perpendicular to the depth dimension L. Therefore, the depth dimension L and the width dimension W can be easily set, and therefore the optimal opening area S according to the application can be easily obtained.

[0024] Furthermore, the discharge groove 32 is formed in a generally V-shape with a width dimension W gradually decreasing from the connecting side with the discharge hole 31 toward the tip side (rear cover member 3 side) when viewed from above the surface of the control cylinder 25, and is formed in an inclined shape with a depth dimension L gradually decreasing from the connecting side with the discharge hole 31 toward the tip side (rear cover member 3 side) when viewed from a cross section generally perpendicular to the surface of the control cylinder 25. Therefore, the area S of the opening of the throttle portion 33 gradually increases and decreases according to the axial position of the control piston 24, so that the function of suppressing sudden pressure fluctuations in the working chamber 27 can be well maintained.

[0025] FIG. 5 shows another embodiment of the present invention. The same parts as in the first embodiment are given the same reference numerals and their explanation is omitted, and only the different parts are explained. The discharge groove 34 constituting the throttle portion is formed in an elliptical shape when viewed from the surface of the control cylinder 25, with the long diameter of the ellipse being disposed in the axial direction of the control cylinder 25 and the short diameter of the ellipse being disposed in a direction perpendicular to the axial direction of the control cylinder 25. Also, the discharge groove 34 is formed in an inclined shape in a cross section generally perpendicular to the surface of the control cylinder 25, with the depth dimension gradually decreasing from the connecting side with the discharge hole 31 toward the tip side (the rear cover member 3 side).

[0026] The pump is operated in the same manner as in the first embodiment. With this operation, the discharge groove 34 constituting the throttling portion is formed as a recess in the surface of the control cylinder 25, so that it is less affected even if the thickness dimension between the surface of the control cylinder 25 and the flow hole 28 (shown in Figure 1) is thick, and it can be manufactured more easily than conventional pumps in which the throttling portion is composed of a control piston and a discharge hole.

[0027] Also, the throttle portion has an opening area based on the depth dimension of the discharge groove 34 in a direction substantially perpendicular to the surface of the control cylinder 25 and the width dimension W1 of the discharge groove 34 in a direction substantially perpendicular to this depth dimension. Therefore, the depth dimension and width dimension can be easily set, and the optimal opening area according to the application can be easily obtained, as in the first embodiment.

[0028] Furthermore, the discharge groove 34 is formed in an elliptical shape when viewed from the surface of the control cylinder 25, and is formed in an inclined shape in which the depth dimension gradually decreases from the connecting side with the discharge hole 31 toward the tip side (the rear cover member 3 side) when viewed in a cross section substantially perpendicular to the surface of the control cylinder 25. Therefore, the area of ​​the opening of the throttling portion gradually increases and decreases according to the axial position of the control piston 24, so that the function of suppressing sudden pressure fluctuations in the working chamber can be well maintained, as in the first embodiment.

[0029] In the above embodiment, the discharge grooves 32, 34 are formed in a substantially V-shape or ellipse shape when viewed from the surface of the control cylinder 25, but may be formed in a substantially U-shape. Also, the discharge grooves 32, 34 are formed in an inclined shape in which the depth dimension gradually decreases from the connecting side with the discharge hole 31 toward the tip side (the rear cover member 3 side) when viewed in a cross section substantially perpendicular to the surface of the control cylinder 25, but it goes without saying that the discharge grooves 32, 34 may be formed in a flat shape when viewed in a cross section substantially perpendicular to the surface of the control cylinder 25. [Explanation of symbols]

[0030] 1: Main unit 4: Rotation axis 7: Swash plate 8: Cylinder block 10: Piston 11: Working chamber 24: Control piston 25: Control cylinder 26: Spring 27: Action chamber 31: Discharge hole 32, 34: Discharge groove 33: Squeezing section

Claims

[Claim 1] The hydraulic system comprises a cylinder block housed within the main body and engaged with the rotary shaft in the direction of rotation, a plurality of pistons arranged in the cylinder block so as to be capable of reciprocating in the axial direction, a plurality of working chambers defined by the pistons and the cylinder block for drawing in and discharging fluid, a tiltable swash plate with which the tips of the pistons protruding from the cylinder block come into sliding contact to set the amount of reciprocating movement of each piston, a control piston movable in the axial direction for pressing the swash plate in a direction decreasing the tilt angle, a control cylinder which fits the control piston to define an operating chamber into which pressure fluid is introduced to press the control piston, a discharge hole formed in the control cylinder for discharging the pressure fluid in the operating chamber into the main body, and a control piston. a spring which applies a spring force to the swash plate in a direction increasing the tilt angle of the swash plate against the pressure of the ton; a discharge groove which is recessed into the surface of the control cylinder and connected to the discharge hole; a throttling section which throttles and controls the pressurized fluid flowing from the working chamber through the discharge hole and discharged into the main body when the force based on the pressurized fluid in the working chamber acting against the swash plate and the spring force of the spring are approximately balanced to minimize the tilt angle of the swash plate, and which is constituted by the discharge groove and the control piston; and

Images