Rotary swashplate type hydraulic pump

Abstract

To provide a rotary swash plate-type hydraulic pump which can be formed in compact.SOLUTION: A rotary swash plate-type hydraulic pump includes: a casing; a cylinder block disposed in the casing in a manner of being not relatively rotatable and provided with a plurality of cylinder bores; a plurality of pistons each inserted to each of the plurality of cylinder bores; and a rotary swash plate housed in the casing rotatably around an axis and reciprocating the pistons. The casing includes an annular suction passage to which each of the plurality of cylinder bores is connected, and the suction passage is formed at a side closer to the other side in an axial direction than the cylinder block of the casing in a manner of being overlapped with the plurality of cylinder bores.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a swash plate type hydraulic pump that reciprocates a plurality of pistons by rotating a swash plate.

Background Art

[0002] As a piston pump, for example, a swash plate type piston pump as disclosed in Patent Document 1 is known. In the piston pump of Patent Document 1, when the swash plate rotates, the piston reciprocates. As a result, pressurized oil is discharged from the piston pump.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the piston pump of Patent Document 1, the suction port is connected to the cylinder chamber through a plurality of suction chambers. The plurality of suction chambers are formed in the cylinder block. Therefore, the cylinder block becomes large, leading to an increase in the size of the swash plate type piston pump.

[0005] Therefore, an object of the present invention is to provide a swash plate type hydraulic pump that can be formed compactly.

Means for Solving the Problems

[0006] The rotary swashplate hydraulic pump of the present invention comprises a casing, a cylinder block disposed within the casing so as not to rotate relative to it and having a plurality of cylinder bores formed thereon, a plurality of pistons inserted into each of the plurality of cylinder bores, and a rotary swashplate housed within the casing so as to be rotatable about an axis and causing each of the pistons to reciprocate, wherein the casing includes an annular intake passage through which each of the plurality of cylinder bores is connected, the intake passage is formed in the casing axially away from the cylinder block and overlaps the plurality of cylinder bores when viewed in the axial direction.

[0007] According to the present invention, the intake passage is formed in the casing axially away from the cylinder block and overlaps with the plurality of cylinder bores when viewed axially. Therefore, the intake passage can be formed compactly in the radial direction. This makes it possible to form a compact rotary swashplate hydraulic pump. Furthermore, since the intake passage is formed in an annular shape when viewed axially and is arranged to overlap with the plurality of cylinder bores, the portion of the casing on the axially away side from the cylinder block can be widely used for the intake passage. Therefore, the flow area of ​​the intake passage can be secured. This makes it possible to reduce power loss in the working fluid flowing through the intake passage.

[0008] The rotary swashplate hydraulic pump of the present invention comprises a casing, a cylinder block disposed within the casing so as not to rotate relative to it and having a plurality of cylinder bores formed therein, a plurality of pistons inserted into each of the plurality of cylinder bores, and a rotary swashplate housed within the casing so as to be rotatable about an axis and causing each of the pistons to reciprocate, wherein the casing includes a discharge passage connected to each of the plurality of cylinder bores, and the discharge passage is formed in an annular shape so as to surround the plurality of cylinder bores.

[0009] According to the present invention, the discharge passage is formed in an annular shape. Therefore, it is possible to easily form a discharge passage that connects to multiple cylinder bores. Furthermore, the discharge passage surrounds the multiple cylinder bores from the outside. Therefore, the cylinder bores can be cooled from the outside by the working fluid flowing through the discharge passage. [Effects of the Invention]

[0010] According to the present invention, a rotary swashplate type hydraulic pump can be made compact. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing a rotary swashplate type hydraulic pump according to an embodiment of the present invention. [Figure 2] Figure 1 shows a cross-sectional view of a rotary swashplate type hydraulic pump cut along the cutting line II-II. [Figure 3] Figure 1 shows a cross-sectional view of a rotary swashplate type hydraulic pump cut along the cutting line III-III. [Figure 4] Figure 1 shows a cross-sectional view of a rotary swashplate type hydraulic pump cut along the cutting line IV-IV. [Figure 5] Figure 1 shows a cross-sectional view of a rotary swashplate type hydraulic pump cut along the cutting line VV. [Figure 6] This is an enlarged cross-sectional view showing a magnified view of region X shown in Figure 3. [Modes for carrying out the invention]

[0012] Hereinafter, a rotary swashplate type hydraulic pump 1 according to an embodiment of the present invention will be described with reference to the aforementioned drawings. Note that the concept of direction used in the following description is for convenience of explanation and does not limit the orientation of the invention's configuration to that direction. Furthermore, the rotary swashplate type hydraulic pump 1 described below is merely one embodiment of the present invention. Therefore, the present invention is not limited to this embodiment, and additions, deletions, and modifications are possible without departing from the spirit of the invention.

[0013] <Rotating swashplate type hydraulic pump> The rotary swashplate hydraulic pump (hereinafter referred to as "pump") 1 shown in Figure 1 is installed in various machines such as construction machinery such as shovels and cranes, industrial machinery such as forklifts, agricultural machinery such as tractors, and hydraulic machinery such as presses. In this embodiment, pump 1 is a rotary swashplate type variable displacement hydraulic pump. Pump 1 comprises a casing 11, a cylinder block 12, a rotary swashplate 13, a plurality of pistons 14, and a variable displacement mechanism 15. Pump 1 also comprises a plurality of intake check valves 16, a plurality of discharge check valves 17, and a linear actuator 18. Pump 1 discharges working fluid when driven by a drive source (e.g., an engine, an electric motor, or both).

[0014] <Casing> The casing 11 houses the cylinder block 12, the rotating swash plate 13, the multiple pistons 14, and the variable displacement mechanism 15. The casing 11 includes an intake passage 21 and a discharge passage 22, which will be described in detail later. The casing 11 is a cylindrical member that extends along a predetermined axis L1.

[0015] <Cylinder Block> The cylinder block 12 is positioned within the casing 11 so as not to rotate relative to it. More specifically, the cylinder block 12 is fixed to the casing 11. In this embodiment, the cylinder block 12 is integrally formed with the axially intermediate portion of the casing 11. However, the cylinder block 12 may be a separate component from the casing 11. If it is a separate component, the cylinder block 12 is fixed to the casing 11 by, for example, press-fitting, spline coupling, key coupling, fastening, or joining. The cylinder block 12 has a plurality of cylinder bores 12b that open at one end face 12a. The one end face 12a is the end face on one side in the axial direction of the cylinder block 12. The cylinder block 12 has a plurality of spool holes 12c, a plurality of communication passages 12d, and a shaft insertion hole 12e. The cylinder block 12 has the same number of cylinder bores 12b and spool holes 12c. In this embodiment, the cylinder block 12 has nine cylinder bores 12b and spool holes 12c formed therein. However, the number of cylinder bores 12b and spool holes 12c is not limited to nine.

[0016] Each of the cylinder bores 12b is arranged circumferentially with spacing around the axis L1. The cylinder bores 12b extend axially from one end face 12a to the other end face 12f. The other end face 12f is the end face on the other side of the cylinder block 12 in the axial direction. The cylinder bore 12b has an intake port 12g on the other end face 12f of the cylinder block 12.

[0017] Each of the spool holes 12c is circumferentially spaced around the axis L1. Each of the spool holes 12c is disposed radially inward of the cylinder bore 12b. More specifically, the cylinder block 12 has a shaft insertion hole 12e around the axis L1 on one end surface 12a as will be described later. The spool holes 12c are spaced apart from each other around the shaft insertion hole 12e. Also, the spool holes 12c are associated with each of the cylinder bores 12b. The spool holes 12c are disposed radially inward with respect to the corresponding cylinder bores 12b. The spool holes 12c have discharge ports 12i on the other end surface 12f of the cylinder block 12. The spool holes 12c are for discharging a part of the volume of the cylinder bores 12b. For example, the diameter of the spool holes 12c is smaller than the diameter of the cylinder bores 12b.

[0018] Each of the communication passages 12d connects the corresponding cylinder bore 12b and the spool hole 12c. The communication passages 12d extend in the radial direction. The communication passages 12d are located on the other end surface 12f side in the cylinder block 12.

[0019] The shaft insertion hole 12e is formed along the axis L1 in the cylinder block 12. The shaft insertion hole 12e axially penetrates the cylinder block 12 from one end surface 12a to the other end surface 12f.

[0020] <Swash plate> The rotating swash plate 13 includes a swash plate-side inclined surface 13a. The rotating swash plate 13 is housed within the casing 11 so as to be rotatable around the axis L1. More specifically, the rotating swash plate 13 is housed within the casing 11 on one side in the axial direction. The rotating swash plate 13 extends along the axis L1. The rotating swash plate 13 is supported by the casing 11 so as to be rotatable about the axis L1. The rotating swash plate 13 is positioned to face one end face 12a of the cylinder block 12. One end portion of the rotating swash plate 13 protrudes from the axial end face of the casing 11, i.e., from one end of the casing 11. One end portion of the rotating swash plate 13 is connected to the aforementioned drive source on the axial side. The rotating swash plate 13 is then rotationally driven by the drive source. By rotating, the rotating swash plate 13 causes the piston 14, which will be described in detail later, to reciprocate. In this embodiment, the rotating swash plate 13 is integrally formed with a disc portion having a rotating swash plate-side inclined surface 13a and a rotatably supported shaft portion; however, the disc portion and the shaft portion may be formed separately.

[0021] The swash plate-side inclined surface 13a is a surface formed on the other end side of the swash plate 13. The swash plate-side inclined surface 13a faces one end face 12a of the cylinder block 12. The swash plate-side inclined surface 13a is tilted toward one end face 12a of the cylinder block 12 about a first orthogonal axis L2. The first orthogonal axis L2 is an axis perpendicular to axis L1. In this embodiment, the tilt angle of the swash plate-side inclined surface 13a is fixed.

[0022] <Piston> Multiple pistons 14 are inserted into each of the cylinder bores 12b of the cylinder block 12. That is, the cylinder block 12 has the same number of pistons (9 pistons in this embodiment) 14 as the cylinder bore 12b. Each of the pistons 14 reciprocates within the cylinder bore 12b as the rotating swash plate 13 rotates. More specifically, the piston 14 is in contact with the rotating swash plate side inclined surface 13a, and the rotating swash plate side inclined surface 13a slides relative to the piston 14. When the rotating swash plate 13 rotates, the piston 14 reciprocates within the cylinder bore 12b with a stroke amount corresponding to the tilt angle of the rotating swash plate side inclined surface 13a. In this embodiment, the piston 14 is in contact with the rotating swash plate side inclined surface 13a via a shoe 23. Each of the shoes 23 is pressed against the rotating swash plate side inclined surface 13a by a retaining plate 24. As a result, when the rotating swash plate 13 rotates, the piston 14 is made to reciprocate in one axial direction and the other via the shoe 23.

[0023] <Variable Capacitance Mechanism> As shown in Figure 1, the variable displacement mechanism 15 includes a plurality of spools 25, a plurality of springs 26, and a swash plate rotation shaft 27. In this embodiment, the variable displacement mechanism 15 includes the same number of spools 25 and springs 26 as the number of spool holes 12c, i.e., nine spools 25 and springs 26. The variable displacement mechanism 15 adjusts the effective stroke length S of each piston 14. In this embodiment, the variable displacement mechanism 15 changes the effective stroke length S of the piston 14 by adjusting the opening and closing of the cylinder bore 12b. By changing the effective stroke length S, the variable displacement mechanism 15 changes the discharge capacity of the pump 1.

[0024] More specifically, the variable displacement mechanism 15 adjusts the opening and closing of the cylinder bore 12b between the tank 19 and the spool hole 12c and the suction passage 21 as the piston 14 strokes from bottom dead center to top dead center (i.e., during the discharge stroke of the pump 1). This allows the variable displacement mechanism 15 to adjust the effective stroke length S of each piston 14. However, the variable displacement mechanism 15 is not limited to adjusting the effective stroke length S of all pistons 14. The top dead center is the point where the piston 14 is furthest to the other axial direction, and the bottom dead center is the point where the piston 14 is furthest to the one axial direction.

[0025] <Spool> Each of the spools 25 is positioned to correspond to each of the cylinder bores 12b. The spools 25 open and close the corresponding cylinder bores 12b. More specifically, the spools 25 open and close the space between the corresponding cylinder bores 12b and the tank 19 by reciprocating motion. The spools 25 adjust the opening and closing of the space between the cylinder bores 12b and the tank 19 during the discharge process. Each of the spools 25 is biased by a spring 26 towards a swash plate rotation shaft 27, which will be described later.

[0026] <Swashplate rotation axis> The swash plate rotation shaft 27 rotates in conjunction with the rotating swash plate 13. The rotation of the swash plate rotation shaft 27 also causes each of the spools 25 to reciprocate. This opens and closes the gap between the cylinder bore 12b and the tank 19. In this embodiment, the communication passage 12d is opened and closed. Furthermore, the swash plate rotation shaft 27 can change the open and closed positions of each of the spools 25. The open and closed positions of each spool 25 are the positions where each spool 25 begins to open the communication passage 12d and the positions where it closes.

[0027] More specifically, the swash plate rotation shaft 27 has a swash plate rotation shaft side inclined surface 27a. The swash plate rotation shaft 27 is inserted through the shaft insertion hole 12e of the cylinder block 12 and extends along the axis L1. One axial end of the swash plate rotation shaft 27 protrudes from the shaft insertion hole 12e toward the rotating swash plate 13. The one axial end of the swash plate rotation shaft 27 is connected to the rotating swash plate 13 in a manner that prevents relative rotation. Therefore, the swash plate rotation shaft 27 rotates around the axis L1 in conjunction with the rotating swash plate 13. The other axial end of the swash plate rotation shaft 27 also protrudes from the shaft insertion hole 12e toward the intake passage 21, which will be described later.

[0028] The swash plate rotation axis side inclined surface 27a is located in the axial middle portion of the swash plate rotation axis 27. The swash plate rotation axis side inclined surface 27a is positioned to face the other end of the cylinder block 12. More specifically, the swash plate rotation axis side inclined surface 27a faces each of the discharge ports 12i of the spool hole 12c. The swash plate rotation axis side inclined surface 27a is tilted about a second orthogonal axis L3 which is parallel to the first orthogonal axis L2. The second orthogonal axis L3 is also an axis perpendicular to the axis L1. In this embodiment, the swash plate rotation axis side inclined surface 27a is tilted in the same direction as the rotation swash plate side inclined surface 13a, i.e., clockwise about the second orthogonal axis L3. The tilt angle of the swash plate rotation axis side inclined surface 27a is fixed. The other axial end of the spool 25, which is biased by the spring 26, abuts against the swash plate rotation axis side inclined surface 27a. The inclined surface 27a on the swash plate rotation axis side slides and rotates relative to the spool 25. Therefore, when the swash plate rotation axis 27 rotates, the spool 25 reciprocates in the spool hole 12c with a stroke corresponding to the tilt angle of the inclined surface 27a on the swash plate rotation axis side.

[0029] The swash plate rotation axis side inclined surface 27a can move forward and backward in the axial direction. By moving forward and backward, the swash plate rotation axis side inclined surface 27a adjusts the opening and closing of the space between the cylinder bore 12b and the tank 19. More specifically, by moving forward and backward, the swash plate rotation axis side inclined surface 27a adjusts the opening and closing position of the spool 25. A linear actuator 18 is connected to the other end of the swash plate rotation axis 27 in the axial direction. The linear actuator 18 may be either an electric or hydraulic linear actuator. The swash plate rotation axis side inclined surface 27a can move forward and backward by the linear actuator 18 so as to approach and move away from the other end face 12f of the cylinder block 12. This makes it possible to change the dead center position of the spool 25 in the cylinder bore 12b (more specifically, the axial position of the dead center). For example, by moving forward in one direction in the axial direction, the dead center position of the spool 25 in the cylinder bore 12b shifts to one side in the axial direction. On the other hand, as the inclined surface 27a on the swash plate rotation axis side retracts in the other direction in the axial direction, the dead center position of the spool 25 in the cylinder bore 12b shifts in the other direction in the axial direction. Therefore, the opening and closing position of the spool 25 in the cylinder bore 12b can be shifted in the axial direction.

[0030] The effective stroke length S of the piston 14 is the range of stroke from which the working fluid can be discharged from the cylinder bore 12b. Therefore, the effective stroke length S of the piston 14 can be changed by shifting the opening and closing position of the spool 25 in the axial direction. Consequently, the discharge capacity in the cylinder bore 12b can be changed by moving the swash plate rotation axis side inclined surface 27a forward and backward in the axial direction.

[0031] <Suction passage> As shown in Figures 1 to 3, the intake passage 21 has a plurality of intake ports 21a, a plurality of intake-side annular portions 21b, a plurality of communication portions 21c, and a communication chamber 21d. The intake passage 21 is formed in the casing 11 axially away from the cylinder block 12. The intake passage 21 is connected to the tank 19 and also to the cylinder bore 12b (see Figure 1). Working fluid is drawn from the tank 19 to the cylinder bore 12b through the intake passage 21.

[0032] The intake passage 21 is formed in an annular shape when viewed in the axial direction. Here, the intake passage 21 is formed in an annular shape centered on the axis L1. The intake passage 21 surrounds the swash plate rotation axis 27. The intake passage 21 overlaps each of the cylinder bores 12b when viewed in the axial direction. The intake passage 21 is connected to the cylinder bores 12b from the axial direction. More specifically, the intake passage 21 overlaps each of the intake side openings 12g of the cylinder bores 12b when viewed in the axial direction. The intake passage 21 is connected to the cylinder bores 12b through these intake side openings 12g.

[0033] The intake passage 21 also overlaps with each of the spool holes 12c when viewed in the axial direction. More specifically, the intake passage 21 overlaps with each of the outlets 12i of the spool holes 12c when viewed in the axial direction. Each of the outlets 12i is connected to the tank 19 via the intake passage 21.

[0034] Multiple intake ports 21a are connected to the tank 19 (see Figure 1). As shown in Figure 2, two intake ports 21a are formed on the outer circumferential surface of the casing 11. Note that the number of intake ports 21a formed on the casing 11 is not limited to two, but may be one or three or more. Each of the intake ports 21a is formed on the outer circumferential surface of the casing 11, on the other end in the axial direction. Multiple intake ports 21a are arranged at equal intervals in the circumferential direction when viewed in the axial direction. In this embodiment, two intake ports 21a are arranged at a 180-degree interval.

[0035] As shown in Figures 2 and 3, the intake-side annular portion 21b is formed in an annular shape when viewed in the axial direction. Here, the intake-side annular portion 21b is formed in an annular shape centered on the axis L1. As shown in Figure 3, the intake-side annular portion 21b extends to the other end face 12f of the cylinder block 12. In this embodiment, the other end face 12f of the cylinder block 12 faces the intake-side annular portion 21b (i.e., the intake passage 21). The intake-side annular portion 21b overlaps each of the cylinder bores 12b when viewed in the axial direction. More specifically, when viewed in the axial direction, the intake-side annular portion 21b overlaps each of the intake-side ports 12g of the cylinder bores 12b, and each of the intake-side ports 12g of the cylinder bores 12b faces the intake-side annular portion 21b. In this embodiment, at a position adjacent to the other end face 12f, the outer diameter portion of the intake-side annular portion 21b extends to the radially outward side of the cylinder bores 12b. The inner diameter portion of the intake-side annular portion 21b is formed to match the shape of the cylinder bore 12b. Multiple passage portions 21e are formed in the intake-side annular portion 21b at equal intervals in the circumferential direction when viewed in the axial direction. Each of the passage portions 21e is arranged to correspond to each of the intake ports 21a. In this embodiment, two passage portions 21e are formed in the intake-side annular portion. The intake-side annular portion 21b is connected to each of the intake ports 21a via each of the passage portions 21e. The outer and inner diameters of the intake-side annular portion 21b are formed to be the same diameter in the portion on the other side in the axial direction, and the diameter decreases radially inward as it proceeds from the axial middle portion toward one side in the axial direction. Therefore, the inhaled working fluid can be smoothly guided into the cylinder bore 12b.

[0036] Each of the connecting portions 21c is connected to the intake-side annular portion 21b. The casing 11 has the same number of connecting portions 21c as there are spool holes 12c. However, the number of connecting portions 21c is not limited to the same number as the spool holes 12c. Each of the connecting portions 21c extends from the intake-side annular portion 21b toward the spool holes 12c when viewed in the axial direction. More specifically, the connecting portions 21c are arranged radially so as to extend radially outward from the discharge port 12i of the spool holes 12c.

[0037] The communication chamber 21d is formed in an annular shape when viewed in the axial direction. More specifically, the communication chamber 21d is an annular shape centered on axis L1 and is located around the swash plate rotation axis 27. The communication chamber 21d is positioned inside the intake-side annular portion 21b so as to overlap each of the spool holes 12c. More specifically, the communication chamber 21d is positioned inside the intake-side annular portion 21b so as to overlap the discharge port 12i of the spool holes 12c. The outer diameter portion of the communication chamber 21d is formed to be tangent to the spool holes 12c when viewed in the axial direction. The communication chamber 21d is connected to the communication portion 21c and, via the communication portion 21c, is connected to the intake-side annular portion 21b.

[0038] <Discharge passage> As shown in Figures 1, 4, and 5, the discharge passage 22 has a discharge-side annular portion 22a, a plurality of discharge-side branch portions 22b, a discharge port 22c, and a confluence portion 22d. The discharge passage 22 is formed in the axial middle portion of the casing 11. The discharge passage 22 is formed in an annular shape as shown in Figure 5. More specifically, the discharge passage 22 is formed in an annular shape in the casing 11 and surrounds a plurality of cylinder bores 12b from the outside. In this embodiment, the discharge passage 22 is formed with a larger diameter than the suction passage 21 (see dotted line in Figure 2). Here, at least the outermost diameter of the discharge passage 22 is formed with a larger diameter than the outermost diameter of the suction passage 21. The discharge passage 22 is connected to each of the cylinder bores 12b. The pump 1 discharges the working fluid through the discharge passage 22 and the discharge port 22c.

[0039] The discharge-side annular portion 22a is formed in an annular shape when viewed in the axial direction, as shown in Figure 5. Here, the discharge-side annular portion 22a is formed in an annular shape centered on the axis L1. The discharge-side annular portion 22a surrounds multiple cylinder bores 12b from the outside. The discharge-side annular portion 22a is formed with a larger diameter than the intake-side annular portion 21b (see the dotted line in Figure 2). The discharge-side annular portion 22a is formed in the casing 11 on one side in the axial direction from the communication passage 12d. More specifically, multiple discharge check valves 17, which will be described in detail later, are arranged between the discharge-side annular portion 22a and the intake-side annular portion 21b in the axial direction.

[0040] Multiple discharge-side branch sections 22b extend from each of the cylinder bores 12b toward the discharge-side annular section 22a. The same number of discharge-side branch sections 22b are formed in the casing 11 as there are cylinder bores 12b. Each discharge-side branch section 22b corresponds to each of the cylinder bores 12b. Each discharge-side branch section 22b extends radially outward from the corresponding cylinder bore 12b. Furthermore, each discharge-side branch section 22b extends radially and then bends to extend axially toward the discharge-side annular section 22a. The discharge-side branch sections 22b are connected in the discharge-side annular section 22a at positions that are equally spaced from each other in the circumferential direction.

[0041] The discharge port 22c discharges the working fluid. In this embodiment, there is one discharge port 22c in the casing 11. However, there may be multiple discharge ports 22c. The discharge port 22c is connected, for example, to a hydraulic actuator. The discharge port 22c is formed on the outer circumferential surface of the casing 11 in the axial middle portion. In this embodiment, the discharge port 22c is positioned 90 degrees circumferentially relative to each of the two suction ports 21a when viewed in the axial direction. That is, in the circumferential direction around the axis L1, the positions of the discharge port 22c and the suction ports 21a are different. Note that in Figure 1, for the sake of explanation, the discharge port 22c and one of the suction ports 21a are positioned at the same location in the circumferential direction.

[0042] The confluence section 22d connects the discharge-side annular section 22a and the discharge port 22c. The confluence section 22d is positioned so that the pulsations of the working fluid discharged from each of the multiple cylinder bores 12b cancel each other out. More specifically, the confluence section 22d is connected to one of the discharge-side branch sections 22b at the same position in the circumferential direction around the axis L1 in the discharge-side annular section 22a. Here, the same position is not limited to exactly the same position. For example, it is sufficient if at least a part of each of the confluence section 22d and the discharge-side branch sections 22b overlap each other radially. The working fluid flowing from the discharge-side branch sections 22b connected at the same position flows directly to the confluence section 22d. On the other hand, the working fluid led from each of the other eight discharge-side branch sections 22b to the discharge-side annular section 22a branches and flows clockwise and counterclockwise in the discharge-side annular section 22a before converging at the confluence section 22d. As a result, the pulsations of the working fluid cancel each other out when they merge. Note that the position of the merging section 22d is not limited to the above description. For example, there may be multiple discharge ports 22c and merging sections 22d in the casing 11. For example, each of the merging sections 22d is connected to several of the discharge-side branch sections 22b at the same position in the circumferential direction around axis L1. The remaining discharge-side branch sections 22b are arranged so as not to be located at a position offset by 180 degrees from the merging section 22d.

[0043] <Intake check valve> Each of the intake check valves 16 is provided in each of the cylinder bores 12b, as shown in Figure 1. That is, in this embodiment, there are the same number of intake check valves 16 as there are cylinder bores 12b, i.e., 9 valves. More specifically, each of the intake check valves 16 is inserted into the cylinder bore 12b from the other side in the axial direction. In this embodiment, as shown in Figure 3, one end of the intake check valve 16 is inserted into the intake port 12g. The other end of each intake check valve 16 protrudes from the intake port 12g of the cylinder bore 12b into the intake passage 21, or more specifically, the intake annular portion 21b. An internal passage 16b is formed in the intake check valve 16, as shown in Figure 6. The intake annular portion 21b is connected to the cylinder bore 12b via the internal passage 16b. Each internal passage 16b of the intake check valve 16 opens into each of the communication portions 21c. Therefore, the intake-side annular portion 21b is always connected to the spool hole 12c.

[0044] As shown in Figure 1, the intake check valve 16 opens and closes between the intake-side annular portion 21b and the cylinder bore 12b by a check valve body 16a. More specifically, the intake check valve 16 opens and closes the inner passage 16b by the check valve body 16a. This allows the intake check valve 16 to open and close between the intake passage 21 and the cylinder bore 12b. The check valve body 16a moves in the axial direction. The check valve body 16a extends in the axial direction, with the portion on the other side of the axial direction protruding from the cylinder bore 12b. A spring 16c is provided on the protruding portion of the check valve body 16a, and the spring 16c biases the check valve body 16a in the closing direction. Here, the spring 16c is located upstream of the valve seat 16d of the intake check valve 16. By opening and closing, the intake check valve 16 allows a unidirectional flow of working fluid from the intake passage 21 to the cylinder bore 12b and prevents reverse flow. Therefore, during the intake process when the piston 14 moves from top dead center to bottom dead center, the working fluid flows from the intake passage 21 to the cylinder bore 12b. On the other hand, during the discharge process when the piston 14 moves, the flow of the working fluid from the intake passage 21 to the cylinder bore 12b is stopped.

[0045] <Discharge check valve> Each of the multiple discharge check valves 17 is provided for each of the cylinder bores 12b, as shown in Figure 4. That is, in this embodiment, there are nine discharge check valves 17, the same number as the discharge-side branch portions 22b. More specifically, each of the nine discharge check valves 17 is provided for each of the discharge-side branch portions 22b of the discharge passage 22. In this embodiment, each discharge check valve 17 is inserted into the portion extending radially from the outer circumferential surface of the casing 11 to each discharge-side branch portion 22b. The discharge check valves 17 open and close the discharge passage 22. More specifically, the discharge check valves 17 open and close the discharge-side branch portion 22b (more precisely, the portion extending radially) with the check valve body 17a. This allows the discharge check valves 17 to open and close the discharge passage 22 at a position away from the discharge-side annular portion 22a. Therefore, the opening and closing operation of the discharge check valve 17 is suppressed from being affected by the working fluid introduced into the discharge-side annular portion 22a from the other cylinder bore 12b.

[0046] The check valve body 17a moves radially in a different direction from the check valve body 16a. The check valve body 16a extends radially, and a spring 17b is provided on its radially outer portion. Here, the spring 17b is located downstream of the valve seat 17c of the discharge check valve 17. The check valve body 17a opens the discharge passage 22 during the discharge stroke. Therefore, the discharge check valve 17 allows a unidirectional flow of working fluid from the cylinder bore 12b to the discharge annular portion 22a (or discharge port 22c) during the discharge stroke. On the other hand, the discharge check valve 17 prevents flow in the reverse direction. Therefore, during the suction stroke, the flow of working fluid from the cylinder bore 12b to the discharge port 22c is stopped.

[0047] <Pump operation> The operation of pump 1 will now be explained. When the rotating swash plate 13 is driven by the drive source, each piston 14 reciprocates in the cylinder bore 12b accordingly. As a result, each piston 14 draws working fluid into the cylinder bore 12b from the intake passage 21 via the intake check valve 16 during the intake process. More specifically, during the intake process, the working fluid is drawn from the intake port 21a through the passage 21e to the intake-side annular portion 21b. Subsequently, the working fluid is guided from the intake-side annular portion 21b to the cylinder bore 12b via the intake check valve 16. In this embodiment, working fluid is drawn into the intake-side annular portion 21b from two intake ports 21a. Therefore, variations in the distance between each cylinder bore 12b and the nearest intake port 21a are suppressed. This suppresses variations in power loss in the working fluid distributed to each cylinder bore 12b. This suppresses the malfunction of the suction check valve 16 due to insufficient suction power.

[0048] Each piston 14 discharges working fluid from the cylinder bore 12b through the discharge check valve 17 and the discharge passage 22 during the discharge process. More specifically, during the discharge process, when the working fluid in the cylinder bore 12b is pressurized by the piston 14, the discharge check valve 17 eventually opens the discharge passage 22. This guides the working fluid from the cylinder bore 12b through the discharge-side branch 22b to the discharge-side annular section 22a. In the discharge-side annular section 22a, the working fluid is divided from each of the discharge-side branch 22b in a clockwise and counterclockwise direction when viewed axially. The divided working fluid then merges at the discharge port 22c and is discharged from the discharge port 22c.

[0049] Furthermore, in pump 1, the swash plate rotation shaft 27 rotates in conjunction with the rotation of the rotating swash plate 13, causing each of the spools 25 to reciprocate in sync with the corresponding piston 14 in the spool hole 12c. As a result, the communication passage 12d opens during the suction stroke of each piston 14, and closes during the discharge stroke of each piston 14. This allows communication between the cylinder bore 12b and the communication passage 12d until the communication passage 12d is closed during the discharge stroke (i.e., until the piston 14 moves the open stroke length S2). Until the communication passage 12d is closed, the discharge of working fluid from the cylinder bore 12b to the discharge port 22c is restricted. Therefore, the effective stroke length S of each piston 14 is shorter than the actual stroke length S1 by the amount of the open stroke length S2, and pump 1 discharges working fluid with a discharge capacity corresponding to the effective stroke length S. In pump 1, the inclined surface 27a on the swash plate rotation axis side is moved axially by the linear actuator 18, thereby changing the opening and closing position of the spool 25. This changes the effective stroke length S of each piston 14, and thus increases or decreases the discharge capacity of pump 1.

[0050] In the pump 1 of this embodiment, the intake passage 21 is formed in the casing 11 axially away from the cylinder block 12 and overlaps with a plurality of cylinder bores 12b when viewed axially. Therefore, the intake passage 21 can be formed compactly in the radial direction. This allows the pump 1 to be made compact. Furthermore, since the intake passage 21 is formed in an annular shape when viewed axially and is arranged to overlap with a plurality of cylinder bores 12b, the portion of the casing 11 on the axially away side from the cylinder block 12 can be widely used for the intake passage 21. Therefore, the flow area of ​​the intake passage 21 can be secured. This reduces power loss in the working fluid flowing through the intake passage 21.

[0051] Furthermore, in the pump 1 of this embodiment, the spool hole 12c is connected to the suction passage 21. Therefore, there is no need to provide a new passage connected to the spool hole 12c. This allows the casing 11 to be made compact.

[0052] Furthermore, in the pump 1 of this embodiment, the communication chamber 21d is formed inside the suction-side annular portion 21b. Therefore, the inside of the suction-side annular portion 21b can be effectively utilized.

[0053] Furthermore, in the pump 1 of this embodiment, two suction ports 21a are formed on the outer circumferential surface of the casing 11. Therefore, variations in the shortest path from either of the suction ports 21a to each cylinder bore 12b can be suppressed. This reduces power loss in the working fluid flowing through the suction passage 21.

[0054] Furthermore, in the pump 1 of this embodiment, the discharge passage 22 is formed in an annular shape. Therefore, the pulsations of the working fluid discharged from each of the nine cylinder bores 12b can cancel each other out. This makes it possible to suppress the generation of pulsations in the discharged working fluid.

[0055] Furthermore, in the pump 1 of this embodiment, the discharge passage 22 is offset axially from the suction passage 21. Therefore, the discharge passage 22 and the suction passage 21 can be partially overlapped when viewed axially. This allows the pump 1 to be made compact in the radial direction.

[0056] Furthermore, in the pump 1 of this embodiment, the discharge passage 22 surrounds the nine cylinder bores 12b from the outside. Therefore, the cylinder bores 12b can be cooled from the outside by the working fluid flowing through the discharge passage 22.

[0057] Furthermore, in the pump 1 of this embodiment, the discharge passage 22 is formed with a larger diameter than the suction passage 21. That is, the suction passage 21 is positioned to overlap with the discharge passage 22 when viewed in the axial direction, or to be radially inward from it. Therefore, the suction passage 21 is formed compactly in the radial direction. This allows the casing 11 to be formed compactly.

[0058] Furthermore, in the pump 1 of this embodiment, each of the multiple discharge-side branch sections 22b extends from each of the multiple cylinder bores 12b toward the discharge-side annular section 22a. Therefore, the discharge-side annular section 22a can be formed radially outward from the multiple cylinder bores 12b.

[0059] Furthermore, in the pump 1 of this embodiment, the discharge-side branch portion 22b extends radially from the cylinder bore 12b and then bends to extend axially in one direction toward the discharge-side annular portion 22a. Therefore, the discharge-side annular portion 22a can be formed axially away from the radially extending portion of the discharge-side branch portion 22b. This ensures the strength of the pump 1.

[0060] Furthermore, in the pump 1 of this embodiment, the discharge check valve 17 is positioned between the discharge-side annular portion 22a and the suction-side annular portion 21b in the axial direction. Therefore, the discharge-side annular portion 22a and the suction-side annular portion 21b are formed separately. Thus, the strength of the pump 1 can be ensured.

[0061] Furthermore, in the pump 1 of this embodiment, the discharge port 22c is positioned so that the pulsations of the working fluid discharged from each of the multiple cylinder bores 12b cancel each other out. Therefore, the pulsations of the working fluid discharged from the pump 1 can be suppressed.

[0062] Furthermore, in the pump 1 of this embodiment, the discharge passage 22 is formed in an annular shape. Therefore, the pulsations of the working fluid discharged from each of the multiple cylinder bores 12b can cancel each other out. This makes it possible to suppress the generation of pulsations in the discharged working fluid. In addition, the discharge passage 22 surrounds the multiple cylinder bores 12b from the outside. Therefore, the working fluid flowing through the discharge passage 22 can cool the cylinder bores 12b from the outside.

[0063] <Other Embodiments> The pump 1 of this embodiment does not necessarily need to have a variable displacement mechanism 15. The variable displacement mechanism 15 only needs to be able to change the effective stroke length S of at least one piston 14. Also, the shapes of the suction passage 21 and discharge passage 22 in the pump 1 are merely examples and may have other shapes. For example, the suction passage 21 and discharge passage 22 do not necessarily both need to be annular; at least one of the suction passage 21 and discharge passage 22 may be annular. The other of the suction passage 21 and discharge passage 22 may be formed individually for each cylinder bore 12b. Furthermore, the suction passage 21 does not necessarily need to have a communication chamber 21d; each of the communication portions 21c may be connected to each of the discharge ports 12i. Moreover, in the discharge passage 22, the discharge side branch portion 22b does not necessarily need to be bent. For example, the discharge side annular portion 22a may be formed radially outward of the discharge side branch portion 22b. [Explanation of Symbols]

[0064] 1. Rotary swashplate hydraulic pump 11 Casing 12 Cylinder Block 12a One end face 12b Cylinder bore 12c spool hole 12f Other end surface 13. Rotating swashplate 14 pistons 15 Variable Capacitance Mechanism 19 tanks 21 Suction passage 21a Inhalation port 21b Intake side annular portion 21c Communication part 21d Communication room 22 Discharge passage 22a Discharge side annular section 22b Discharge side branch section 22c discharge port 25 spools 27 Swashplate rotation axis

Claims

1. Casing and, A cylinder block is arranged within the casing in a manner that prevents relative rotation, and in which a plurality of cylinder bores are formed. Multiple pistons inserted into each of the aforementioned multiple cylinder bores, A rotating swash plate is housed within the casing so as to be rotatable around its axis, and causes each of the pistons to reciprocate. The system includes a variable displacement mechanism that changes the effective stroke length of at least one of the plurality of pistons, The casing includes an annular intake passage through which each of the plurality of cylinder bores is connected. The variable displacement mechanism includes a plurality of spools that open and close the space between the cylinder bore and the tank, The cylinder block includes a plurality of spool holes into which each of the plurality of spools is inserted. A rotary swashplate hydraulic pump, wherein each of the plurality of spool holes is located inside the plurality of cylinder bores and connected to the intake passage.

2. The aforementioned intake passage has an intake-side annular portion, a plurality of communication portions, and a communication chamber. The intake-side annular portion is formed in an annular shape and is arranged to overlap the plurality of cylinder bores when viewed in the axial direction. Each of the aforementioned multiple communication portions is connected to the intake-side annular portion, The rotary swashplate type hydraulic pump according to claim 1, wherein the communication chamber is arranged inside the suction-side annular portion so as to overlap the plurality of spool holes when viewed in the axial direction, and is connected to the suction-side annular portion via the plurality of communication portions.

3. The rotary swashplate type hydraulic pump according to claim 1 or 2, wherein the suction passage has a plurality of suction ports for drawing in working fluid.

4. The casing includes a discharge passage to which each of the plurality of cylinder bores is connected. The rotary swashplate type hydraulic pump according to any one of claims 1 to 3, wherein the discharge passage is formed in an annular shape.

5. The rotary swashplate type hydraulic pump according to claim 4, wherein the discharge passage is offset in the axial direction with respect to the suction passage.

6. The rotary swashplate type hydraulic pump according to claim 4 or 5, wherein the discharge passage surrounds the plurality of cylinder bores from the outside.

7. The rotary swashplate type hydraulic pump according to claim 6, wherein the discharge passage is formed to have a larger diameter than the suction passage.

8. The discharge passage has a discharge-side annular portion and a plurality of discharge-side branch portions. The discharge-side annular portion is formed in an annular shape and surrounds the plurality of cylinder bores from the outside. The rotary swashplate hydraulic pump according to claim 6 or 7, wherein each of the plurality of discharge-side branch sections extends from each of the plurality of cylinder bores toward the discharge-side annular section.

9. The rotary swashplate type hydraulic pump according to claim 8, wherein each of the plurality of discharge-side branch sections extends radially outward from the cylinder bore and is further bent to extend axially toward the discharge-side annular section.

10. Each of the aforementioned multiple discharge-side branch sections is further provided with a plurality of discharge check valves that allow a unidirectional flow of working fluid from the cylinder bore to the discharge-side annular section and prevent reverse flow, The rotary swashplate type hydraulic pump according to claim 8 or 9, wherein each of the plurality of discharge check valves is positioned in the axial direction between the discharge-side annular portion and the suction passage.

11. The discharge passage includes a discharge port for discharging working fluid and a confluence portion connecting the discharge-side annular portion and the discharge port. The rotary swashplate hydraulic pump according to claim 9 or 10, wherein the confluence section is positioned such that the pulsations of the working fluid discharged from each of the multiple cylinder bores cancel each other out.

12. Casing and, A cylinder block is arranged within the casing in a manner that prevents relative rotation, and in which a plurality of cylinder bores are formed. Multiple pistons inserted into each of the aforementioned multiple cylinder bores, A rotating swash plate is housed within the casing so as to be rotatable around its axis, and causes each of the pistons to reciprocate. The system includes a variable displacement mechanism that changes the effective stroke length of at least one of the plurality of pistons, The casing includes a discharge passage connected to each of the plurality of cylinder bores and an annular intake passage connected to each of the plurality of cylinder bores, The discharge passage is formed in an annular shape so as to surround the plurality of cylinder bores, The variable displacement mechanism includes a plurality of spools that open and close the space between the cylinder bore and the tank, The cylinder block includes a plurality of spool holes into which each of the plurality of spools is inserted. A rotary swashplate hydraulic pump, wherein each of the plurality of spool holes is located inside the plurality of cylinder bores and connected to the intake passage.

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