Double tilting swash plate pump

Abstract

A double tilting swash plate pump (1) according to an embodiment includes a casing (3) that accommodates a cylinder block (5) and a swash plate (7) and that has a first flow path (3a) and a second flow path (3b). The swash plate (7) includes: a first convex surface (73A) and a second convex surface (73B) that are cylindrical surfaces; a first pocket (74A) and a second pocket (74B) that are formed in the first convex surface (73A) and the second convex surface (73B); and a first notch (75A) and a second notch (75B) that are cut out from the first pocket (74A) and the second pocket (74B). The casing (3) includes: a third flow path (3c) and a fourth flow path (3d) that communicate the first flow path (3a) and the second flow path (3b) to the first pocket (74A) and the second pocket (74B); and a communication path (3e) that communicates the first notch (75A) and the second notch (75B) when the swash plate (7) is positioned at a neutral position.

Description

Double tilting swash plate pump

[0001] The present disclosure relates to a bi-directional tilting swash plate pump in which a swash plate can be swung in both directions from a neutral position.

[0002] Bi-directional tilting swash plate pumps, in which the swash plate can oscillate in both directions from a neutral position, are known. In such bi-directional tilting swash plate pumps, it is important to have a neutral characteristic that minimizes the discharge flow rate when the swash plate is in the neutral position.

[0003] In a double tilt type swash plate pump, it is structurally difficult to maintain the tilt angle of the swash plate at 0 degrees in the neutral position. Therefore, to improve the neutral characteristics, a neutral valve such as that disclosed in Patent Document 1 is sometimes used.

[0004] JP 2018-31463 A

[0005] However, the use of a neutral valve increases costs.

[0006] Therefore, an object of the present disclosure is to provide a double tilt type swash plate pump that can obtain good neutral characteristics without using a neutral valve.

[0007] From a first aspect, the present disclosure provides a compressor including: a rotating shaft; a cylinder block fixed to the rotating shaft, the cylinder block having a plurality of pistons inserted into a plurality of cylinder bores; a swash plate sliding on shoes attached to heads of the plurality of pistons; and a casing accommodating the cylinder block and the swash plate, the casing including a casing body supporting the swash plate so that the swash plate can swing, and a valve cover having first flow passages communicating with some of the plurality of cylinder bores and second flow passages communicating with other some of the plurality of cylinder bores. The swash plate has an insertion hole through which the rotating shaft is inserted, the insertion hole being formed on both sides of the insertion hole. a first convex surface and a second convex surface which are cylindrical surfaces centered on the oscillation axis of the swash plate and are located at a position corresponding to the axial direction of the swash plate, a first pocket formed in the first convex surface, a second pocket formed in the second convex surface, a first notch cut from the first pocket in the extension direction of the oscillation axis, and a second notch cut from the second pocket in the extension direction of the oscillation axis, wherein the casing includes a third flow path which connects the first flow path with the first pocket, a fourth flow path which connects the second flow path with the second pocket, and a communicating path which connects the first notch and the second notch when the swash plate is located in a neutral position.

[0008] From a second aspect, the present disclosure provides a hydraulic engine comprising: a rotating shaft; a cylinder block fixed to the rotating shaft, the cylinder block having a plurality of pistons inserted into a plurality of cylinder bores; a swash plate that slides on shoes attached to heads of the pistons; and a casing that houses the cylinder block and the swash plate, the casing including a casing body that supports the swash plate so that the swash plate can swing, and a valve cover having first flow passages that communicate with some of the plurality of cylinder bores and second flow passages that communicate with other some of the plurality of cylinder bores, the swash plate having first convex surfaces and second convex surfaces that are cylindrical surfaces centered on a swing axis of the swash plate and are located on both sides of an insertion hole through which the rotating shaft is inserted. a first pocket formed in the first convex surface, and a second pocket formed in the second convex surface, the casing including a first notch extending so as to intersect with the contour of the first pocket in the extension direction of the oscillation shaft, a second notch extending so as to intersect with the contour of the second pocket in the extension direction of the oscillation shaft, a third flow path connecting the first flow path with the first pocket, and a fourth flow path connecting the second flow path with the second pocket, and the swash plate including connecting passages connecting a portion of the first notch located outside the contour of the first pocket and a portion of the second notch located outside the contour of the second pocket when the swash plate is positioned in a neutral position.

[0009] According to the present disclosure, a double tilt type swash plate pump is provided that can obtain good neutral characteristics without using a neutral valve.

[0010] 1 is a cross-sectional view of a double tilt type swash plate pump according to an embodiment of the present invention; FIG. 2 is a perspective view of a swash plate; and FIG. 3 is a cross-sectional view of a modified double tilt type swash plate pump.

[0011] FIG. 1 shows a double-reversible swash plate pump 1 according to one embodiment. The swash plate pump 1 is an axial piston pump that includes a hollow casing 3 and a rotating shaft 2 extending from the inside to the outside of the casing 3. One end of the rotating shaft 2 (the left end in FIG. 1 ) is connected to a prime mover such as an engine or an electric motor. In this embodiment, a valve plate 4, a cylinder block 5, and a swash plate 7 are housed within the casing 3. However, the valve plate 4 can be omitted.

[0012] For ease of explanation, the axial direction of the rotating shaft 2 will be referred to as the front-to-rear direction (the left side of Figure 1 is the front and the right side is the rear), the extension direction of the swing shaft 9 (see Figure 2) of the swash plate 7, which will be described later, will be referred to as the up-to-down direction (the upper side of Figure 1 is the upside and the lower side is the downside), and the direction perpendicular to these will be referred to as the left-to-right direction.

[0013] The casing 3 includes a container-shaped casing body 3A that opens rearward and has a bottom wall 31 and a peripheral wall 32, and a valve cover 3B that closes the opening of the casing body 3A. The rotating shaft 2 penetrates the bottom wall 31 of the casing body 3A. In this embodiment, the rotating shaft 2 also penetrates the valve cover 3B, but the rotating shaft 2 does not have to penetrate the valve cover 3B. Bearings 21, 22 that rotatably support the rotating shaft 2 are held in the bottom wall 31 of the casing body 3A and the valve cover 3B, respectively.

[0014] The valve plate 4 is attached to the front surface of the valve cover 3B. The valve plate 4 is provided with a first port 41 and a second port 42, which are arc-shaped and face in opposite directions.

[0015] The rotating shaft 2 is rotated in one direction, and the swash plate 7 is swung in both directions from a neutral position by the servo piston 8. When the swash plate 7 is swung in one direction from the neutral position, the first port 41 becomes the suction port and the second port 42 becomes the discharge port, and when the swash plate 7 is swung in the opposite direction from the neutral position, the second port 42 becomes the suction port and the first port 41 becomes the discharge port.

[0016] The valve cover 3B is provided with a first flow passage 3a communicating with the first port 41 and a second flow passage 3b communicating with the second port 42. The first flow passage 3a and the second flow passage 3b open to the outer peripheral surface or rear surface of the valve cover 3B, and these openings form external connection ports. Depending on the direction of swing of the swash plate 7 from the neutral position, one of the first flow passage 3a and the second flow passage 3b becomes an intake passage, and the other becomes a discharge passage.

[0017] The cylinder block 5 is fixed to the rotary shaft 2, and rotates together with the rotary shaft 2 to slide against the valve plate 4. The cylinder block 5 has a plurality of cylinder bores 51 that open forward around the periphery of the rotary shaft 2. A plurality of pistons 61 are inserted into each of the cylinder bores 51.

[0018] The cylinder block 5 is also provided with cylinder ports 52 for connecting each of the cylinder bores 51 to the first port 41 or the second port 42. As the cylinder block 5 rotates, some of the cylinder bores 51 communicate with the first flow path 3a through the corresponding cylinder ports 52 and first port 41, and some of the cylinder bores 51 communicate with the second flow path 3b through the corresponding cylinder ports 52 and second port 42.

[0019] A plurality of shoes 62 are attached to the heads of the pistons 61. In this embodiment, the shoes 62 slide on the swash plate 7 via annular shoe plates 63 attached to the swash plate 7. However, the shoe plates 63 may be omitted, and the shoes 62 may slide directly on the swash plate 7. The shoes 62 are held down by a holding plate so as to maintain contact with the shoe plates 63.

[0020] The swash plate 7 is supported by the bottom wall 31 of the casing body 3A so as to be swingable around the swing shaft 9 shown in Fig. 2. The bottom wall 31 of the casing body 3A may be divided into a bottom wall main body that is continuous with the peripheral wall 32 and a support base that is fixed to the bottom wall main body and swingably supports the swash plate 7.

[0021] 2, the swash plate 7 has an insertion hole 70 through which the rotary shaft 2 is inserted. The swash plate 7 includes an elongated central portion 71 extending across the insertion hole 70, and a first shoulder portion 72A and a second shoulder portion 72B provided on either side of the central portion 71 in the width direction of the central portion 71. The pivot shaft 9 of the swash plate 7 described above extends in the width direction of the central portion 71, i.e., in the direction in which the first shoulder portion 72A and the second shoulder portion 72B are aligned.

[0022] 1, the swash plate 7 further includes a lever portion 76 extending from the first shoulder portion 72A toward the servo piston 8. The servo piston 8 extends in the left-right direction (a direction perpendicular to the plane of the paper in FIG. 1) and is held by the casing main body 3A so as to be slidable in the left-right direction. The casing main body 3A also has a pair of pressure chambers formed therein for moving the servo piston 8 axially. The servo piston 8 moves in one direction or the other in the axial direction depending on the pressure difference between the pair of pressure chambers.

[0023] A slider 81 is engaged with the servo piston 8 so as to be slidable in the front-rear direction. The slider 81 is engaged with the tip of the lever portion 76 so as to be rotatable about an axis parallel to the oscillation axis 9 of the swash plate 7. When the servo piston 8 moves in one axial direction, the swash plate 7 is oscillated in one direction via the slider 81, and when the servo piston 8 moves in the other axial direction, the swash plate 7 is oscillated in the opposite direction via the slider 81.

[0024] 2, the first shoulder portion 72A and the second shoulder portion 72B of the swash plate 7 have a first convex surface 73A and a second convex surface 73B, respectively, which are cylindrical surfaces centered on the pivot shaft 9. In other words, the centers of curvature of the first convex surface 73A and the second convex surface 73B are the pivot shaft 9. The first convex surface 73A and the second convex surface 73B are located on both sides of the insertion hole 70 in the width direction of the central portion 71.

[0025] Meanwhile, the bottom wall 31 of the casing body 3A has a pair of concave surfaces 33, 34 that are in surface contact with the first convex surface 73A and the second convex surface 73B and slide against the first convex surface 73A and the second convex surface 73B. Similar to the first convex surface 73A and the second convex surface 73B, the concave surfaces 33, 34 are also cylindrical surfaces centered on the oscillation shaft 9.

[0026] A first pocket 74A extending in a direction perpendicular to the oscillation axis 9 is formed in the first convex surface 73A. In this embodiment, the first pocket 74A is a D-cut groove. That is, the first pocket 74A has a flat bottom and a pair of side surfaces whose height decreases from the center to both ends. However, the shape of the first pocket 74A can be changed as needed.

[0027] Furthermore, a first notch 75A is formed in the first convex surface 73A, cutting from the first pocket 74A in the extension direction of the oscillation shaft 9. In this embodiment, the first notch 75A is cut upward from the first pocket 74A, but the first notch 75A may be cut downward from the first pocket 74A. In this embodiment, the first notch 75A is located in the center of the first pocket 74A in the left-right direction, but the position of the first notch 75A in the left-right direction can be changed as appropriate.

[0028] Similarly, a second pocket 74B extending in a direction perpendicular to the oscillation axis 9 is formed in the second convex surface 73B. In this embodiment, the second pocket 74B is a D-cut groove. That is, the second pocket 74B has a flat bottom and a pair of side surfaces whose height decreases from the center to both ends. However, the shape of the second pocket 74B can be changed as needed.

[0029] Additionally, a second notch 75B is formed in the second convex surface 73B, the second notch 75B being cut from the second pocket 74B in the extension direction of the oscillation shaft 9. In this embodiment, the second notch 75B is cut downward from the second pocket 74B, but the second notch 75B may be cut upward from the second pocket 74B. Additionally, in this embodiment, the second notch 75B is located in the center of the second pocket 74B in the left-right direction, but the position of the second notch 75B in the left-right direction can be changed as appropriate.

[0030] 1, the valve cover 3B and the casing body 3A are provided with a third flow passage 3c that connects the first flow passage 3a to the first pocket 74A and a fourth flow passage 3d that connects the second flow passage 3b to the second pocket 74B. When the first flow passage 3a serves as the discharge passage, high discharge pressure is introduced into the first pocket 74A via the third flow passage 3c, and when the second flow passage 3b serves as the discharge passage, high discharge pressure is introduced into the second pocket 74B via the fourth flow passage 3d. This reduces the pressing force of the swash plate 7 against the bottom wall 31 of the casing body 3A.

[0031] Furthermore, a communication passage 3e is provided in the bottom wall 31 of the casing body 3A. The communication passage 3e communicates with the first notches 75A and the second notches 75B when the swash plate 7 is in the neutral position. That is, both ends of the communication passage 3e open at positions corresponding to the first notches 75A and the second notches 75B on the pair of concave surfaces 33, 34.

[0032] In the swash plate pump 1 configured as described above, when the swash plate 7 is in the neutral position, the first flow path 3a and the second flow path 3b are connected via the third flow path 3c, the first pocket 74A, the first notch 75A, the connecting passage 3e, the second notch 75B, the second pocket 74B, and the fourth flow path 3d. This keeps the discharge flow rate at or near zero. Therefore, good neutral characteristics can be achieved without using a neutral valve.

[0033] The first notches 75A and the second notches 75B are cut out from the first pockets 74A and the second pockets 74B in the extending direction of the pivot shaft 9. Therefore, when the swash plate 7 is in the neutral position, both ends of the communication passages communicating with the first notches 75A and the second notches 75B are blocked by the first convex surfaces 73A and the second convex surfaces 73B of the swash plate 7 when the swash plate 7 pivots from the neutral position, thereby releasing the communication between the first flow passage 3a and the second flow passage 3b.

[0034] <Modifications> The present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present disclosure.

[0035] For example, as shown in FIG. 3, a modified double tilt type swash plate pump 1A may be configured such that, contrary to the above embodiment, the first notch 75A and the second notch 75B are provided in the bottom wall 31 of the casing body 3A and the communicating passage 3e is provided in the swash plate 7.

[0036] More specifically, the first notch 75A extends so as to intersect with the contour of the first pocket 74A in the extension direction of the pivot shaft 9, and the second notch 75B extends so as to intersect with the contour of the second pocket in the extension direction of the pivot shaft 9. The communication passage 3e communicates with a portion of the first notch 75A located outside the contour of the first pocket 74A and a portion of the second notch 75B located outside the contour of the second pocket 74B when the swash plate 7 is in the neutral position.

[0037] 3, the first notch 75A extends from a position overlapping with the upper part of the first pocket 74A to a position above the first pocket 74A, but the first notch 75A may extend from a position overlapping with the lower part of the first pocket 74A to a position below the first pocket 74A. Similarly, in FIG. 3, the second notch 75B extends from a position overlapping with the lower part of the second pocket 74B to a position below the second pocket 74B, but the second notch 75B may extend from a position overlapping with the upper part of the second pocket 74B to a position above the second pocket 74B.

[0038] 3, as in the previous embodiment, the discharge flow rate is kept at or near zero when the swash plate 7 is in the neutral position, thereby achieving favorable neutral characteristics without using a neutral valve. Meanwhile, in FIG. 3, the first notches 75A and the second notches 75B extend in the direction of the pivot shaft 9. Therefore, when the swash plate 7 is in the neutral position, both ends of the communication passage 3e communicating with the first notches 75A and the second notches 75B are blocked by the concave surfaces 33 and 34 of the casing body 3A when the swash plate 7 pivots from the neutral position, thereby disabling communication between the first flow passage 3a and the second flow passage 3b.

[0039] <Summary> In a first aspect, the present disclosure provides an engine including: a rotating shaft; a cylinder block fixed to the rotating shaft, the cylinder block including a plurality of pistons inserted into a plurality of cylinder bores; a swash plate sliding on shoes attached to heads of the plurality of pistons; and a casing accommodating the cylinder block and the swash plate, the casing including a casing body supporting the swash plate so as to be able to swing, and a valve cover having first flow passages communicating with some of the plurality of cylinder bores and second flow passages communicating with other some of the plurality of cylinder bores. The swash plate is provided with an insertion hole inserted through the rotating shaft. a first convex surface and a second convex surface, which are cylindrical surfaces centered on the oscillating axis of the swash plate and are located on either side of a hole; a first pocket formed in the first convex surface; a second pocket formed in the second convex surface; a first notch cut from the first pocket in the extension direction of the oscillating axis; and a second notch cut from the second pocket in the extension direction of the oscillating axis, wherein the casing includes a third flow path connecting the first flow path with the first pocket, a fourth flow path connecting the second flow path with the second pocket, and a communicating passage connecting the first notch and the second notch when the swash plate is located in a neutral position.

[0040] According to the above configuration, when the swash plate is in the neutral position, the first and second flow passages communicate with each other via the third flow passage, the first pocket, the first notch, the communication passage, the second notch, the second pocket, and the fourth flow passage. This allows the discharge flow rate to be kept at or near zero. This allows for excellent neutral characteristics to be achieved without using a neutral valve. Because the first and second notches are cut out from the first and second pockets in the direction of the pivot shaft, when the swash plate is in the neutral position, both ends of the communication passages communicating with the first and second notches are blocked by the first and second convex surfaces of the swash plate when the swash plate pivots from the neutral position, thereby disabling communication between the first and second flow passages.

[0041] In a second aspect, the present disclosure provides an engine including, from a second aspect, a rotating shaft, a cylinder block fixed to the rotating shaft and having a plurality of pistons inserted into a plurality of cylinder bores, a swash plate sliding on shoes attached to heads of the plurality of pistons, and a casing accommodating the cylinder block and the swash plate, the casing including a casing body supporting the swash plate so that the swash plate can oscillate, and a valve cover having first flow passages communicating with some of the plurality of cylinder bores and second flow passages communicating with other some of the plurality of cylinder bores, wherein the swash plate has first convex surfaces and a second convex surface which are cylindrical surfaces centered on an oscillating axis of the swash plate and are located on both sides of an insertion hole through which the rotating shaft is inserted. and a second convex surface, a first pocket formed in the first convex surface, and a second pocket formed in the second convex surface, the casing including a first notch extending so as to intersect with the contour of the first pocket in the extension direction of the oscillation shaft, a second notch extending so as to intersect with the contour of the second pocket in the extension direction of the oscillation shaft, a third flow path connecting the first flow path with the first pocket, and a fourth flow path connecting the second flow path with the second pocket, and the swash plate including connecting passages connecting with a portion of the first notch located outside the contour of the first pocket and a portion of the second notch located outside the contour of the second pocket when the swash plate is positioned in a neutral position.

[0042] According to the above configuration, when the swash plate is in the neutral position, the first and second flow passages communicate with each other via the third flow passage, the first pocket, the first notch, the communication passage, the second notch, the second pocket, and the fourth flow passage. This allows the discharge flow rate to be kept at or near zero. This achieves favorable neutral characteristics without using a neutral valve. Because the first and second notches extend in the direction of the pivot shaft, when the swash plate is in the neutral position, both ends of the communication passages communicating with the first and second notches are blocked by concave surfaces of the casing that slide against the first and second convex surfaces of the swash plate when the swash plate pivots from the neutral position, thereby disabling communication between the first and second flow passages.

[0043] As a third aspect, in the first or second aspect, for example, the first pocket and the second pocket may extend in a direction perpendicular to the oscillation axis.

Claims

1. A device comprising: a rotating shaft; a cylinder block fixed to the rotating shaft, with a plurality of pistons inserted into a plurality of cylinder bores; a swash plate sliding against shoes attached to the heads of the plurality of pistons; and a casing accommodating the cylinder block and the swash plate, the casing including a casing body supporting the swash plate so that the swash plate can oscillate, and a valve cover having a first passage communicating with some of the plurality of cylinder bores and a second passage communicating with other some of the plurality of cylinder bores, wherein the swash plate includes a first convex surface and a second convex surface which are cylindrical surfaces centered on the oscillation axis of the swash plate and are located on both sides of an insertion hole through which the rotating shaft is inserted, a first pocket formed in the first convex surface, a second pocket formed in the second convex surface, a first notch cut from the first pocket in the extension direction of the oscillation axis, and a second notch cut from the second pocket in the extension direction of the oscillation axis, a third flow path that connects the first flow path with the first pocket, a fourth flow path that connects the second flow path with the second pocket, and a connecting passage that connects the first notch and the second notch when the swash plate is positioned in a neutral position.

2. A device comprising: a rotating shaft; a cylinder block fixed to the rotating shaft and having a plurality of pistons inserted into a plurality of cylinder bores; a swash plate sliding on shoes attached to the heads of the plurality of pistons; and a casing accommodating the cylinder block and the swash plate, the casing including a casing body supporting the swash plate so that the swash plate can oscillate, and including a valve cover having first flow passages communicating with some of the plurality of cylinder bores and second flow passages communicating with other some of the plurality of cylinder bores, wherein the swash plate includes a first convex surface and a second convex surface which are cylindrical surfaces centered on the oscillation axis of the swash plate and are located on both sides of an insertion hole through which the rotating shaft is inserted, a first pocket formed in the first convex surface, and a second pocket formed in the second convex surface, a second notch extending in the extension direction of the oscillating shaft so as to intersect with the contour of the second pocket; a third flow path connecting the first flow path to the first pocket; and a fourth flow path connecting the second flow path to the second pocket; and the swash plate includes a communication passage connecting a portion of the first notch located outside the contour of the first pocket and a portion of the second notch located outside the contour of the second pocket when the swash plate is positioned in a neutral position.

3. A double tilt type swash plate pump according to claim 1 or 2, wherein the first pocket and the second pocket extend in a direction perpendicular to the oscillation axis.

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