Piston pump

Abstract

To suppress pulsation in a piston pump. [Solution] A piston pump (1) includes a cylinder block (10) having a cylinder bore (11) extending therethrough in an axial direction (X), a valve plate (30), and a piston (20). A ring (50) is disposed on the outer circumferential side (Ra) of the cylinder block. The cylinder block, together with the piston and ring, rotates relative to the valve plate in a circumferential direction (T). The valve plate has an intake port (60) and a discharge port (70). The intake port and the discharge port are spaced apart from each other in the circumferential direction. A chamber (80) is formed between the cylinder block and the ring. A first passage (90) connects the cylinder bore, which is moving from the intake port side to the discharge port side, to the chamber after the cylinder bore has finished communicating with the intake port and before it starts communicating with the discharge port.

Description

[Technical Field]

[0001] The present disclosure relates to piston pumps. [Background technology]

[0002] For example, Patent Document 1 discloses various piston pump technologies. In this type of piston pump, a cylinder block having cylinder bores rotates relative to a valve plate having suction ports and discharge ports. When the cylinder bores communicate with the suction ports, low-pressure fluid is drawn into the cylinder bores from the suction ports. When the cylinder bores communicate with the discharge ports, high-pressure fluid is discharged from the cylinder bores to the discharge ports. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-180154 Summary of the Invention [Problem to be solved by the invention]

[0004] When the cylinder bore is no longer connected to the intake port, the fluid in the cylinder bore is at low pressure. If the cylinder bore moves from the intake port to the discharge port, closing the connection to the intake port and opening the connection to the discharge port, high-pressure fluid may flow back from the discharge port into the cylinder bore. This backflow can cause pulsation, which is undesirable.

[0005] An object of the present disclosure is to suppress pulsation caused by fluid flowing back from the discharge port to the cylinder bore in a piston pump. [Means for solving the problem]

[0006] A first aspect of the present disclosure is directed to a piston pump (1). The piston pump (1) includes a cylindrical cylinder block (10) extending in an axial direction (X) and having a cylinder bore (11) passing through the axial direction (X), a valve plate (30) facing one end face (12) of the cylinder block (10) in the axial direction (X), and a piston (20) accommodated in the cylinder bore (11). A cylindrical ring (50) is disposed on an outer circumferential side (Ra) of the cylinder block (10). The cylinder block (10), together with the piston (20) and the ring (50), rotates relative to the valve plate (30) in a circumferential direction (T) around the axial direction (X). The valve plate (30) is configured to rotate in a direction perpendicular to the axial direction (X) when a fluid (W) is drawn in. The cylinder block (10) has a suction port (60) and a discharge port (70) through which the fluid (W) is discharged. The suction port (60) and the discharge port (70) are arranged apart from each other in the circumferential direction (T). A chamber (80) for accommodating the fluid (W) is formed between the cylinder block (10) and the ring (50). A first passage (90) is provided which connects the cylinder bore (11) with the chamber (80) after the cylinder bore (11) moving from the suction port (60) side to the discharge port (70) side has finished communicating with the suction port (60) and before the cylinder bore (11) starts communicating with the discharge port (70).

[0007] According to the first aspect, the fluid (W) is accommodated in the chamber (80) between the cylinder block (10) and the ring (50). After the cylinder bore (11) has finished communicating with the suction port (60) and before the cylinder bore (11) has started communicating with the discharge port (70), the fluid (W) is supplied from the chamber (80) to the cylinder bore (11) through the first passage (90).

[0008] The pressure in the cylinder bore (11) can be increased at a timing after the cylinder bore (11) has finished communicating with the suction port (60) and before the cylinder bore (11) starts communicating with the discharge port (70). Backflow of the fluid (W) from the discharge port (70) to the cylinder bore (11) can be suppressed, thereby suppressing pulsation caused by the backflow.

[0009] As described above, in the piston pump (1), pulsation caused by the fluid (W) flowing back from the discharge port (70) to the cylinder bore (11) can be suppressed.

[0010] A second aspect of the present disclosure is directed to the piston pump (1) according to the first aspect. The piston pump (1) has a second passage (100) that connects the discharge port (70) and the chamber (80).

[0011] According to the second embodiment, the fluid (W) can be replenished from the discharge port (70) through the second passage (100) to the chamber (80).

[0012] A third aspect of the present disclosure is directed to the piston pump (1) according to the first or second aspect. In this piston pump (1), the first passage (90) is provided in the valve plate (30).

[0013] According to the third aspect, the first passage (90) can be easily configured.

[0014] A fourth aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to third aspects. In this piston pump (1), the first passage (90) is provided with a throttle section (95) that reduces a passage area (S) of the first passage (90).

[0015] According to the fourth aspect, the fluid (W) flowing through the first passage (90) is reduced in pressure by the throttle portion (95), thereby making it possible to prevent a sudden increase in pressure in the cylinder bore (11).

[0016] A fifth aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to fourth aspects. In this piston pump (1), the cylinder bore (11) includes a first cylinder bore (11A) and a second cylinder bore (11B) arranged side by side in the circumferential direction (T), and the chamber (80) is arranged between the first cylinder bore (11A) and the second cylinder bore (11B) in the circumferential direction (T).

[0017] According to the fifth aspect, the layout of the chamber (80) becomes easier.

[0018] A sixth aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to fifth aspects. In this piston pump (1), the chamber (80) includes a first chamber (80a) and a second chamber (80b) arranged side by side in the circumferential direction (T) and partitioned from each other in the circumferential direction (T), and the first chamber (80a) and the second chamber (80b) communicate with each other via a third passage (110).

[0019] According to the sixth embodiment, the fluid (W) can be circulated in the circumferential direction (T) between the first chamber (80a) and the second chamber (80b) through the third passage (110).

[0020] A seventh aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to sixth aspects. In this piston pump (1), an opening (18) communicating with the chamber (80) is provided in the one end face (12) of the cylinder block (10), and the first passage (90) includes a first communication port (91) provided in a surface (31) of the valve plate (30) facing the one end face (12) in the axial direction (X), a second communication port (92) disposed apart from the first communication port (91) and provided in the facing surface (31), and a communication passage (93) provided in the valve plate (30) and communicating between the first communication port (91) and the second communication port (92), and when the cylinder bore (11) faces the first communication port (91) and the opening (18) faces the second communication port (92), the cylinder bore (11) and the chamber (80) communicate with each other.

[0021] According to the seventh aspect, when the cylinder bore (11) faces the first communication port (91) and the opening (18) faces the second communication port (92), the fluid (W) can be supplied from the chamber (80) to the cylinder bore (11) via the opening (18), the second communication port (92), the communication passage (93) and the first communication port (91).

[0022] An eighth aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to seventh aspects. In this piston pump (1), a recess (15, 53) is provided in the outer circumferential portion (14) of the cylinder block (10) or the inner circumferential portion (51) of the ring (50), and the chamber (80) is formed in the recess (15, 53).

[0023] According to the eighth aspect, the chamber (80) can be easily formed.

[0024] A ninth aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to eighth aspects. In this piston pump (1), the one end surface (12) of the cylinder block (10) is provided with an opening (18) communicating with the chamber (80), the opening (18) includes a first opening (18a), a second opening (18b), and a third opening (18c) arranged side by side in the circumferential direction (T), and a first pitch (Pa) between the first opening (18a) and the second opening (18b) and a second pitch (Pb) between the second opening (18b) and the third opening (18c) are different from each other.

[0025] According to the ninth aspect, it is possible to suppress noise caused by the pressure in the cylinder bore (11) increasing at a constant period.

[0026] A tenth aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to ninth aspects. The piston pump (1) includes a swash plate (40) that is inclined with respect to the cylinder block (10) and that contacts an end (20a) of the piston (20) on the side opposite to the valve plate (30) in the axial direction (X).

[0027] According to the tenth aspect, in the swash plate type piston pump (1), pulsation can be suitably suppressed.

[0028] An eleventh aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to tenth aspects. In this piston pump (1), a circumferential groove (121) is provided on an inner wall surface (120) of the cylinder bore (11), and a fourth passage (130) that connects the circumferential groove (121) and the chamber (80) is provided in the cylinder block (10).

[0029] According to the eleventh aspect, by sending the fluid (W) from the chamber (80) to the circumferential groove (121) via the fourth passage (130), the lubrication between the piston (20) and the inner wall surface (120) of the cylinder bore (11) can be improved.

[0030] A twelfth aspect of the present disclosure is directed to the piston pump (1) according to the eleventh aspect. The piston pump (1) includes a swash plate (40) that is inclined with respect to the cylinder block (10) and that contacts an end (20 a) of each piston (20) on the opposite side of the valve plate (30) in the axial direction (X), and the circumferential groove (121) is disposed closer to the swash plate (40) than a center (122) of each cylinder bore (11) in the axial direction (X).

[0031] According to the twelfth aspect, the piston (20) is pressed against the inner wall surface (120) of the cylinder bore (11) by the swash plate (40). Lubrication between the piston (20) and the inner wall surface (120) of the cylinder bore (11) is particularly required in an area close to the swash plate (40). By locating the circumferential groove (121) as close as possible to the swash plate (40), friction between the piston (20) pressed against the swash plate (40) and the inner wall surface (120) of the cylinder bore (11) can be reduced. [Brief explanation of the drawings]

[0032] [Figure 1]FIG. 1 is a cross-sectional view of a piston pump (1) according to a first embodiment, seen from the left. [Figure 2] FIG. 2 shows the cylinder block (10) according to the first embodiment as viewed from the left. [Figure 3] FIG. 3 shows the cylinder block (10) according to the first embodiment as viewed from the front. [Figure 4] FIG. 4 shows the cylinder block (10) according to the first embodiment as viewed from the rear. [Figure 5] FIG. 5 is a perspective view of the cylinder block (10) according to the first embodiment. [Figure 6] FIG. 6 shows the valve plate (30) according to the first embodiment as viewed from the front. [Figure 7] FIG. 7 shows the valve plate (30) according to the first embodiment as seen from the rear. [Figure 8] FIG. 8 is a perspective view of the ring (50) according to the first embodiment. [Figure 9] FIG. 9 shows the cylinder block (10) and the ring (50) according to the first embodiment as viewed from the front. [Figure 10] FIG. 10 is a cross-sectional view of the cylinder block (10) and the ring (50) according to the first embodiment, as viewed from the left. [Figure 11] FIG. 11 is a cross-sectional view of the cylinder block (10) and the ring (50) according to the first embodiment, as seen from the rear. [Figure 12] FIG. 12 shows the supply passage (90) and the refill passage (100) according to the first embodiment, as viewed from behind the valve plate (30). [Figure 13] FIG. 13 is a cross-sectional view of the supply passage (90) according to the first embodiment. [Figure 14] FIG. 14 is a cross-sectional view of the refill passage (100) according to the first embodiment. [Figure 15] FIG. 15 is a view corresponding to FIG. 11 according to the second embodiment, showing a cross-sectional view of the cylinder block (10) and the ring (50) as seen from the rear. [Figure 16]FIG. 16 is a view corresponding to FIG. 2 according to a third embodiment, showing the cylinder block (10) as viewed from the left. [Figure 17] FIG. 17 is a view corresponding to FIG. 10 according to the third embodiment, showing a cross-sectional view of the cylinder block (10) and the ring (50) as viewed from the left. [Figure 18] FIG. 18 is a view corresponding to FIG. 11 according to the third embodiment, showing a cross-sectional view of the cylinder block (10) and the ring (50) as seen from the rear. [Figure 19] FIG. 19 shows a chamber (80) according to a fourth embodiment. [Figure 20] FIG. 20 shows a chamber (80) according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications are possible within the scope of the technical concept of the present disclosure. Since the drawings are intended to conceptually explain the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary to facilitate understanding.

[0034] First Embodiment (piston pump) A piston pump (1) according to a first embodiment will be described. In the following description, with reference to Figure 1, the left is the front, the right is the rear, the front of the page is the left, the back of the page is the right, the top is the top, and the bottom is the bottom.

[0035] Figure 1 shows a cross-sectional view of the piston pump 1 as seen from the left. The piston pump 1 is a variable displacement axial piston pump. Note that a chamber 80, which will be described later, is not shown in Figure 1.

[0036] The piston pump (1) includes a housing (2), an end cap (3), a drive shaft (4), a cylinder block (10), a piston (20), a valve plate (30), a swash plate (40), and a ring (50).

[0037] (housing) As shown in Figure 1, the housing 2 is a hollow container. The front end of the housing 2 is an opening. The rear end wall of the housing 2 is provided with a through hole.

[0038] The housing (2) accommodates the drive shaft (4), the cylinder block (10), the pistons (20), the valve plate (30), the swash plate (40), and the rings (50).

[0039] (end cap) As shown in Fig. 1, the end cap (3) is a plate-like member with its thickness extending in the front-rear direction. The end cap (3) is fixed to the housing (2) so as to cover the front opening of the housing (2).

[0040] Although not shown, an intake pipe communicating with an intake port (60) described below and a discharge pipe communicating with a discharge port (70) described below may be connected to the end cap (3).

[0041] (drive shaft) As shown in Figure 1, the drive shaft 4 has an axis O extending in the front-rear direction. The drive shaft 4 passes through a through-hole at the rear of the housing 2 in the front-rear direction. The rear end of the drive shaft 4 is connected to the rotating shaft of an electric motor or an engine (not shown). The drive shaft 4 is rotated by the electric motor or the engine.

[0042] A bearing 5 is fixed in a through hole at the rear of the housing 2. The bearing 5 holds the drive shaft 4 relative to the housing 2. The drive shaft 4 rotates relative to the housing 2.

[0043] (cylinder block) The cylinder block (10) will be described with reference to Figures 1 to 5. Figure 2 shows the cylinder block (10) as seen from the left. Figure 3 shows the cylinder block (10) as seen from the front. Figure 4 shows the cylinder block (10) as seen from the rear. Figure 5 shows a perspective view of the cylinder block (10).

[0044] The cylinder block (10) is cylindrical. More specifically, the cylinder block (10) is substantially cylindrical. The axis (O) of the cylinder block (10) extends in the front-rear direction. The cylinder block (10) is spline-fitted to the outer periphery of the drive shaft (4). The axis (O) of the cylinder block (10) is coaxial with the axis (O) of the drive shaft (4). The cylinder block (10) rotates relative to the housing (2).

[0045] Hereinafter, the front-rear direction in which the axis (O) of the cylinder block (10) extends is referred to as the axial direction (X). The axis (O) of the cylinder block (10) extends in the axial direction (X). The axial direction (X) is the front-rear direction.

[0046] Of the directions perpendicular to the axial direction (X), the direction around the axial direction (X) (axial center (O)) is called the circumferential direction (T). The circumferential direction (T) is the relative rotation direction of the cylinder block (10) and the ring (50) with respect to the valve plate (30) and the reverse direction. For convenience, the rotation direction of the circumferential direction (T) is indicated by the arrow in each drawing. Of the directions perpendicular to the axial direction (X), the radial direction based on the axial center (O) is simply called the radial direction (R). The outside of the radial direction (R) is called the outer circumferential side (Ra). The inside of the radial direction (R) is called the inner circumferential side (Rb).

[0047] The cylinder block 10 has a plurality of (nine in this example) cylinder bores 11. The cylinder bores 11 penetrate the cylinder block 10 in the axial direction (X) from a front end face 12 to a rear end face 13. The front end face 12 is an example of one end face, and the rear end face 13 is an example of the other end face.

[0048] The cylinder bores (11) are arranged on the outer circumferential side (Ra) of the axis (O). The plurality of cylinder bores (11) are arranged at equal intervals along the circumferential direction (T).

[0049] 1, 3, and 4, the cylinder bore (11) includes a bore main body (11a) and a bore communication port (11b). The cross section of the bore main body (11a) (a cross section perpendicular to the extension direction of the cylinder bore (11); the same applies hereinafter) is circular. The bore main body (11a) defines a portion from the rear end of the cylinder bore (11) (the rear end surface (13) of the cylinder block (10)) to a portion slightly rearward of the front end of the cylinder bore (11) (a portion slightly rearward of the front end surface (12) of the cylinder block (10)).

[0050] The bore communication opening (11b) has a kidney-shaped or elliptical cross section that is short in the radial direction (R) and long in the circumferential direction (T). The cross-sectional area of ​​the bore communication opening (11b) is smaller than the cross-sectional area of ​​the bore main body (11a). The bore communication opening (11b) defines a section from the front end of the cylinder bore (11) (the front end surface (12) of the cylinder block (10)) to a portion slightly rearward of the front end of the cylinder bore (11) (a portion slightly rearward of the front end surface (12) of the cylinder block (10)).

[0051] As shown in FIG. 2, a plurality of recesses (15) (nine in this example) are provided in the outer peripheral portion (14) of the cylinder block (10). The recesses (15) are arranged at equal intervals in the circumferential direction (T). Adjacent recesses (15) in the circumferential direction (T) are separated by partition walls (16). The recesses (15) are recessed toward the inner peripheral side (Rb) with respect to the outer peripheral surface of the partition wall (16). The number of partition walls (16) is the same as the number of recesses (15) (nine in this example).

[0052] A front seal portion (17a) is provided over the entire circumference in the circumferential direction (T) at the front end of the outer circumferential portion (14) of the cylinder block (10). The outer circumferential surface of the front seal portion (17a) is flush with the outer circumferential surface of the partition wall (16). A rear seal portion (17b) is provided over the entire circumference in the circumferential direction (T) at the rear end of the outer circumferential portion (14) of the cylinder block (10). The outer circumferential surface of the rear seal portion (17b) is flush with the outer circumferential surface of the partition wall (16).

[0053] The recess (15) is defined in the axial direction (X) by the front seal portion (17a) and the rear seal portion (17b). The recess (15) is recessed toward the inner circumferential side (Rb) relative to the front seal portion (17a) and the rear seal portion (17b).

[0054] As shown in Fig. 2, a communication groove (16a) is provided in the outer peripheral surface of the partition wall (16) of the cylinder block (10). The communication groove (16a) is recessed inward (Rb) from the outer peripheral surface of the partition wall (16). The communication groove (16a) extends in the circumferential direction (T) of the partition wall (16) and connects the recesses (15) adjacent to each other in the circumferential direction (T).

[0055] As shown in Fig. 3, a plurality of openings 18 are provided in the front end surface 12 of the cylinder block 10. The number of openings 18 is the same as the number of recesses 15 (nine in this example). The openings 18 are disposed on the outer circumferential side (Ra) of the cylinder bores 11. As shown by the dashed lines in Fig. 2, the openings 18 penetrate the front seal portion 17a in the axial direction (X) and communicate with the recesses 15.

[0056] As shown in Figure 4, a cylindrical boss portion (19a) is provided in the center of the rear end face (13) of the cylinder block (10). The boss portion (19a) extends in the axial direction (X). The rear end of the boss portion (19a) is located rearward of the rear end face (13). A shaft through-hole (19b) for passing the drive shaft (4) penetrates the center of the cylinder block (10) in the axial direction (X) from the front end face (12) to the rear end of the boss portion (19a).

[0057] (piston) As shown in FIG. 1, the pistons (20) are accommodated in the cylinder bores (11). The number of pistons (20) is the same as the number of cylinder bores (11) (nine in this example). The pistons (20) include a piston body (21) and a shoe (22). The piston body (21) has a cylindrical shape extending in the axial direction (X). The piston body (21) is accommodated in the bore body portion (11a) of the cylinder bore (11) in a liquid-tight manner. The piston body (21) slides in the axial direction (X) relative to the bore body portion (11a).

[0058] The shoe (22) is provided at the rear end of the piston body (21). The shoe (22) constitutes the rear end portion (20a) of the piston (20). The rear end portion (20a) is an example of an end portion. The shoe (22) (the rear end portion (20a) of the piston (20)) is located rearward of the rear end of the cylinder bore (11) (the rear end surface (13) of the cylinder block (10)). The piston (20) rotates relative to the housing (2).

[0059] (Valve plate) The valve plate 30 will be described with reference to Figures 1, 6 and 7. Figure 6 shows the valve plate 30 as seen from the front, and Figure 7 shows the valve plate 30 as seen from the rear.

[0060] As shown in Fig. 1, the valve plate (30) is plate-shaped with its thickness oriented in the axial direction (X). The valve plate (30) is circular when viewed in the axial direction (X). The center of the valve plate (30) is coaxial with the axis (O) of the cylinder block (10) (hereinafter, the center of the valve plate (30) will be referred to as the axis (O)).

[0061] The valve plate (30) is disposed between the cylinder block (10) and the end cap (3) in the axial direction (X). A rear surface (31) of the valve plate (30) in the axial direction (X) faces a front end surface (one end surface) (12) of the cylinder block (10) in the axial direction (X). In other words, the rear surface (31) of the valve plate (30) faces the front end surface (one end surface) (12) of the cylinder block (10) in the axial direction (X). A front surface (32) of the valve plate (30) faces the end cap (3). The valve plate (30) does not rotate relative to the housing (2).

[0062] The valve plate (30) has a shaft through-hole (33) extending in the axial direction (X) for the drive shaft (4) to pass through. The front end of the drive shaft (4) is accommodated in a recess provided in the end cap (3).

[0063] The front end surface (12) of the cylinder block (10) slides in the circumferential direction (T) relative to the rear surface (31) of the valve plate (30). A liquid-tight seal is formed between the rear surface (31) of the valve plate (30) and the front end surface (12) of the cylinder block (10).

[0064] 6 and 7, the valve plate (30) has an inlet port (60) and a discharge port (70). The inlet port (60) and the discharge port (70) are disposed on the outer circumferential side (Ra) of the shaft through-hole (33). The inlet port (60) and the discharge port (70) are disposed apart from each other in the circumferential direction (T).

[0065] As shown in Figure 7, the suction port (60) is located to the right of the axis (O). The suction port (60) is formed in an arc shape extending in the circumferential direction (T). The suction port (60) includes three suction side small ports (61) and an suction side notch (62). The three suction side small ports (61) are separated from one another and arranged in an arc shape extending in the circumferential direction (T). The suction side small ports (61) penetrate the valve plate (30) in the axial direction (X).

[0066] The suction side notch (62) is connected to the left end of the uppermost small suction side port (61). The suction side notch (62) does not penetrate the valve plate (30) in the axial direction (X). The suction side notch (62) is a groove provided in the rear surface (31) of the valve plate (30). The suction side notch (62) is narrower than the small suction side port (61). The suction side notch (62) extends leftward toward the discharge port (70). The suction side notch (62) is intended to suppress pulsation.

[0067] As shown in Figure 7, the discharge port (70) is located to the left of the axis (O). The discharge port (70) is formed in an arc shape. The discharge port (70) includes three discharge-side small ports (71) and a discharge-side notch (72). The three discharge-side small ports (71) are separated from one another and arranged in an arc shape. The discharge-side small ports (71) pass through the valve plate (30) in the axial direction (X).

[0068] The discharge side notch (72) is connected to the right end of the small discharge side port (71) located at the bottom. The discharge side notch (72) does not penetrate the valve plate (30) in the axial direction (X). The discharge side notch (72) is a groove provided on the rear surface (31) of the valve plate (30). The discharge side notch (72) is narrower than the small discharge side port (71). The discharge side notch (72) extends rightward toward the suction port (60). The discharge side notch (72) serves to suppress pulsation. The discharge side notch (72) is shorter than the suction side notch (62). The suction side notch (62) may not be present.

[0069] A low-pressure fluid (W) is drawn into the suction port (60), and a high-pressure fluid (W) is discharged from the discharge port (70). The fluid (W) is, for example, hydraulic oil for hydraulic equipment.

[0070] The suction port (60) and the discharge port (70) of the valve plate (30) are located at the same position in the radial direction (R) as the cylinder bores (11) of the cylinder block (10). As will be described later, the cylinder bores (11) rotate in the circumferential direction (T) along the suction port (60) and the discharge port (70). When the cylinder bores (11) communicate with the suction port (60), a low-pressure fluid (W) is drawn into the cylinder bores (11) from the suction port (60). When the cylinder bores (11) communicate with the discharge port (70), a high-pressure fluid (W) is discharged from the cylinder bores (11) to the discharge port (70).

[0071] As will be described in detail later, the valve plate (30) is provided with a supply passage (90) and a refill passage (100).

[0072] (swash plate) The swash plate (40) will be described with reference to Figure 1. The swash plate (40) is disposed rearward of the cylinder block (10). The swash plate (40) is inclined with respect to the axis (O) of the cylinder block (10). The swash plate (40) is also inclined with respect to a vertical plane (L) that is perpendicular to the axis (O) of the cylinder block (10). The swash plate (40) is inclined with respect to the vertical plane (L) by an inclination angle (θ).

[0073] A spring 6 is interposed between the rear surface of the upper end of the swash plate 40 and the rear end wall of the housing 2. The spring 6 extends in the axial direction X. The spring 6 is biased so as to push the upper end of the swash plate 40 forward (so as to increase the inclination angle θ).

[0074] A rod (7) penetrates the end cap (3) in the axial direction (X). The rod (7) is movable back and forth in the axial direction (X). The rear end of the rod (7) contacts the front surface of the upper end of the swash plate (40). When the rod (7) pushes the upper end of the swash plate (40) rearward, the inclination angle (θ) decreases. In this way, the inclination angle (θ) of the swash plate (40) is adjusted by the spring (6) and the rod (7).

[0075] The swash plate 40 is held by the housing 2 and the end cap 3 via the spring 6 and the rod 7. The swash plate 40 does not rotate relative to the housing 2.

[0076] The shoe (22) at the rear end (20a) of the piston (20) in the axial direction (X) comes into contact with the front surface of the swash plate (40). In other words, the rear end (20a) of the piston (20) on the opposite side (rear) of the axial direction (X) from the (front) valve plate (30) comes into contact with the front surface of the swash plate (40).

[0077] The shoe (22) at the rear end (20a) of the piston (20) rotates (slides) in the circumferential direction (T) while contacting the front surface of the swash plate (40).

[0078] When the inclination angle (θ) of the swash plate (40) is changed, the amount of movement of the pistons (20) in the axial direction (X) changes, which in turn changes the amount of intake and discharge of the piston pump (1).

[0079] (ring) The ring (50) will be described with reference to FIGS. 1 and 8. FIG. 8 shows a perspective view of the ring (50). The ring (50) is cylindrical. More specifically, the ring (50) is cylindrical. The axis (O) of the ring (50) extends in the axial direction (X). The inner circumferential portion (51) of the ring (50) does not have any recesses. The inner circumferential portion (51) of the ring (50) has an inner circumferential surface (52) that is smooth.

[0080] The ring (50) is disposed on the outer periphery (Ra) of the cylinder block (10) in the radial direction (R). The axis (O) of the ring (50) is coaxial with the axis (O) of the cylinder block (10). The ring (50) is fixed to the outer periphery (14) of the cylinder block (10). The ring (50) rotates together with the cylinder block (10) relative to the housing (2).

[0081] (relative rotation) The cylinder block (10), together with the pistons (20) and rings (50), rotates in a circumferential direction (T) around the axial direction (X) relative to the valve plate (30) and the swash plate (40). The rotation direction of the cylinder block (10) is clockwise when viewed from rear to front (see FIG. 7). The cylinder bores (11) of the cylinder block (10) rotate in the circumferential direction (T) along the intake ports (60) and the discharge ports (70).

[0082] As shown in Figures 1 and 7, when the cylinder bore (11) reaches its lowest point, the piston (20) is at its bottom dead center (A), where it is pulled farthest to the rear. When the cylinder bore (11) reaches its highest point, the piston (20) is at its top dead center (B), where it is pushed farthest forward.

[0083] As described above, the suction port (60) and the discharge port (70) are spaced apart from each other in the circumferential direction (T). Between the suction port (60) and the discharge port (70) in the circumferential direction (T), there is a non-communicating region where neither the suction port (60) nor the discharge port (70) is present.

[0084] The cylinder bore (11) moving from the suction port (60) side to the discharge port (70) side passes through the lower non-communicating area (VA) on the bottom dead center (A) side. The cylinder bore (11) moving from the discharge port (70) side to the suction port (60) side passes through the upper non-communicating area (VB) on the top dead center (B) side.

[0085] (Chamber) The chamber (80) will be described with reference to Figures 9 to 11. Figure 9 shows the cylinder block (10) and the ring (50) as viewed from the front. Figure 10 shows the cylinder block (10) and the ring (50) as viewed from the left in a cross-sectional view taken along line X. Figure 11 shows the cylinder block (10) and the ring (50) as viewed from the rear in a cross-sectional view taken along line XI.

[0086] As shown in Figure 11, a chamber (80) is formed between the cylinder block (10) and the ring (50). The chamber (80) is formed in the recess (15) in the outer circumferential portion (14) of the cylinder block (10). More specifically, the chamber (80) is formed between the inner circumferential surface (52) of the ring (50) and the recess (15) in the outer circumferential portion (14) of the cylinder block (10). The chamber (80) contains a fluid (W).

[0087] The pressure of the fluid (W) in the chamber (80) is high, approximately the same as the discharge pressure.

[0088] As shown in Fig. 10, the inner peripheral surface (52) of the ring (50) and the outer peripheral surfaces of the front seal portion (17a) and the rear seal portion (17b) on the outer peripheral portion (14) of the cylinder block (10) are in contact with each other to define a chamber (80) in the axial direction (X). As shown in Fig. 11, the inner peripheral surface (52) of the ring (50) and the outer peripheral surface of the partition wall (16) on the outer peripheral portion (14) of the cylinder block (10) are in contact with each other to define a chamber (80) in the circumferential direction (T).

[0089] As shown in Fig. 11, there are a plurality of chambers (80). The number of chambers (80) is the same as the number of recesses (15) (nine in this example). The chambers (80) are arranged side by side in the circumferential direction (T). The chambers (80) (recesses (15)) are arranged between adjacent cylinder bores (11) in the circumferential direction (T).

[0090] As described above, as shown in Fig. 9, the front end surface (one end surface) (12) of the cylinder block (10) is provided with a plurality of openings (18). The openings (18) are disposed on the outer circumferential side (Ra) of the cylinder bores (11). As shown in Fig. 10, the openings (18) penetrate the front seal portion (17a) in the axial direction (X). The openings (18) communicate with the chamber (80) (recess (15)).

[0091] As shown in FIG. 11 , the openings 18 are located at the same positions as the chambers 80 (recesses 15) in the radial direction R. The number of openings 18 is the same as the number of chambers 80 (recesses 15) (nine in this example). When viewed in the axial direction X, the cross section of each opening 18 is circular. When viewed in the axial direction X, the cross section area of ​​each opening 18 is smaller than the cross section area of ​​each chamber 80 (recesses 15). The openings 18 are located at the center of each chamber 80 (recesses 15) in the circumferential direction T (at the midpoint between the partition walls 16 adjacent in the circumferential direction T). The intervals (pitch) between adjacent openings 18 in the circumferential direction T are equal to each other.

[0092] The chamber (80) and the opening (18) (which communicates with the chamber (80)) are arranged between the bore communication openings (11b) of the adjacent cylinder bores (11) in the circumferential direction (T).

[0093] As described above, as shown in FIG. 11, the outer peripheral surface of the partition wall 16 in the outer peripheral portion 14 of the cylinder block 10 is provided with a communication groove 16a (see also FIG. 2). The communication groove 16a is recessed toward the inner peripheral side (Rb) with respect to the outer peripheral surface of the partition wall 16. The communication groove 16a extends in the circumferential direction (T) of the partition wall 16 and communicates between the recesses 15 adjacent in the circumferential direction (T), i.e., between the chambers 80 adjacent in the circumferential direction (T). The specific arrangement of the communication groove 16a will be described later.

[0094] (supply passage) The supply passage (90) will be described with reference to Figures 12 and 13. Figure 12 shows the supply passage (90) as seen from the rear of the valve plate (30). Figure 13 shows the supply passage (90) in cross section taken along line XIII.

[0095] The piston pump (1) has a supply passage (90). The supply passage (90) is an example of a first passage. The supply passage (90) is provided in the valve plate (30). The supply passage (90) is located near the bottom dead center (A) of the valve plate (30). The supply passage (90) includes a first communication port (91), a second communication port (92), and a communication passage (93).

[0096] The first communication port (91) is provided in the rear surface (opposing surface) (31) of the valve plate (30). The first communication port (91) is arranged in a lower non-communicating area (VA) near the bottom dead center (A) of the rear surface (31) of the valve plate (30) in the circumferential direction (T). The first communication port (91) is arranged slightly to the right of the discharge notch (72) of the discharge port (70) (closer to the suction port (60) in the circumferential direction (T)). The first communication port (91) does not communicate with either the suction port (60) or the discharge port (70).

[0097] The first communication port (91) does not penetrate the valve plate (30) in the axial direction (X). The first communication port (91) has a circular shape when viewed in the axial direction (X). The first communication port (91) is a recess provided in the rear surface (31) of the valve plate (30) and recessed forward in the axial direction (X).

[0098] The first communication port (91) is located at approximately the same position in the radial direction (R) as the bore communication port (11b) of the cylinder bore (11) (see the two-dot chain line). The bore communication port (11b) of the cylinder bore (11) moving from the suction port (60) side to the discharge port (70) side passes through a lower non-communicating area (VA) near the bottom dead center (A). When passing through the first communication port (91), the bore communication port (11b) of the cylinder bore (11) faces the first communication port (91).

[0099] The second communication port (92) is provided on the rear surface (opposing surface) (31) of the valve plate (30). The second communication port (92) is disposed away from the first communication port (91) in the radial direction (R). The second communication port (92) is disposed on the outer circumferential side (Ra) of the first communication port (91) in the radial direction (R).

[0100] Like the discharge-side notch (72), the second communication port (92) is formed in an arc shape extending in the circumferential direction (T). A right end portion (92a) (an end portion on the suction port (60) side) of the second communication port (92) is located at approximately the same position as the first communication port (91) in the circumferential direction (T). A left end portion (92b) (an end portion on the discharge port (70) side) of the second communication port (92) is located to the left of the first communication port (91) in the circumferential direction (T) (closer to the discharge port (70)).

[0101] The second communication port (92) does not penetrate the valve plate (30) in the axial direction (X). The second communication port (92) has an arc shape extending in the circumferential direction (T) when viewed in the axial direction (X). The second communication port (92) is a recess provided in the rear surface (31) of the valve plate (30) and recessed forward in the axial direction (X). The second communication port (92) is a groove extending in the circumferential direction (T) on the rear surface (31) of the valve plate (30).

[0102] The second communication port (92) is located at the same position in the radial direction (R) as the opening (18) communicating with the chamber (80) (see the two-dot chain line). The opening (18) communicating with the chamber (80) faces the second communication port (92) when passing through the second communication port (92).

[0103] As described above, the openings 18 communicating with the chambers 80 are disposed in the circumferential direction T between the bore communication openings 11b of the adjacent cylinder bores 11. The leading opening 18 (chamber 80) is located to the left (closer to the discharge port 70 in the circumferential direction T) of the trailing bore communication opening 11b (cylinder bore 11).

[0104] Therefore, when the bore communication port (11b) of the cylinder bore (11) faces the first communication port (91), the opening (18) communicating with the chamber (80) faces the second communication port (92).

[0105] 12 and 13, the communication passage (93) is provided in the interior (34) of the valve plate (30). The communication passage (93) extends in the radial direction (R). The communication passage (93) connects the first communication port (91) to the right end (92a) (the end on the suction port (60) side) of the second communication port (92). The communication passage (93) connects the first communication port (91) to the second communication port (92).

[0106] More specifically, a vertical hole (92c) extending in the axial direction (X) is provided at the right end (92a) of the second communication port (92). The vertical hole (92c) is connected to the communication passage (93).

[0107] The left end (92b) of the second communication port (92) communicates with the communication passage (93) through a vertical hole (92c) in the right end (92a) of the second communication port (92).

[0108] The outer peripheral end of the communication passage (93) opens onto the outer peripheral surface of the valve plate (30) and is therefore closed by a plug (94).

[0109] A throttle portion (95) is provided in the communicating passage (93) of the supply passage (90). The throttle portion (95) reduces the passage area (S) of the communicating passage (93) in the supply passage (90). The passage area (S) is the area of ​​a cross section perpendicular to the extension direction of the communicating passage (93). Specifically, the throttle portion (95) reduces the passage diameter of the communicating passage (93). The throttle portion (95) is formed of a cylindrical body inserted into and fixed to the communicating passage (93).

[0110] The supply passage (90) connects the cylinder bore (11) with the chamber (80) after the cylinder bore (11) moving from the suction port (60) side to the discharge port (70) side has finished communicating with the suction port (60) and before it starts communicating with the discharge port (70).

[0111] Specifically, when the bore communication port (11b) of the cylinder bore (11) faces the first communication port (91) and the opening (18) communicating with the chamber (80) faces the second communication port (92), the cylinder bore (11) and the chamber (80) are connected to each other.

[0112] At this time, the fluid (W) contained in the chamber (80) flows sequentially through the opening (18), the left-side portion of the second communication port (92) (the portion closer to the discharge port (70)), the right end portion (92a) of the second communication port (92) (the end portion on the suction port (60) side), the vertical hole (92c) of the second communication port (92), the communication passage (93) (with the throttle portion (95) therein), the first communication port (91), the bore communication port (11b) of the cylinder bore (11), and the bore main body portion (11a) of the cylinder bore (11).

[0113] At this time, the bore communication port (11b) of the cylinder bore (11) does not communicate with either the suction port (60) or the discharge port (70).

[0114] (Replenishment passage) The refill passage (100) will be described with reference to Figures 12 and 14. Figure 12 shows the refill passage (100) as seen from the rear of the valve plate (30). Figure 14 shows the refill passage (100) in cross section along line XIV.

[0115] The piston pump (1) has a refill passage (100). The refill passage (100) is an example of a second passage. The refill passage (100) is provided in the valve plate (30). The refill passage (100) is located near the top dead center (B) of the valve plate (30). The refill passage (100) includes a refill communication port (101) and a refill communication passage (102).

[0116] The refilling communication port (101) is provided on the rear surface (opposing surface) (31) of the valve plate (30). The refilling communication port (101) is disposed in the vicinity of the top dead center (B) on the rear surface (31) of the valve plate (30) in the circumferential direction (T). The refilling communication port (101) is located at substantially the same position as the right end (end on the suction port (60) side) of the uppermost small discharge port (71) of the discharge port (70). The refilling communication port (101) is located on the outer circumferential side (Ra) of the discharge port (70).

[0117] The refill communication port (101) does not penetrate the valve plate (30) in the axial direction (X). When viewed in the axial direction (X), the refill communication port (101) is formed in an arc shape extending in the circumferential direction (T). The refill communication port (101) is a recess provided in the rear surface (31) of the valve plate (30) and recessed forward in the axial direction (X). The refill communication port (101) is a groove extending in the circumferential direction (T) on the rear surface (31) of the valve plate (30).

[0118] The refilling communication port (101) is located at the same position in the radial direction (R) as the opening (18) communicating with the chamber (80) (see the two-dot chain line). The opening (18) communicating with the chamber (80) faces the refilling communication port (101) when passing through the refilling communication port (101).

[0119] The refill communication passage (102) is provided in the interior (34) of the valve plate (30). The refill communication passage (102) extends in the radial direction (R). The refill communication passage (102) connects the discharge port (70) and the refill communication port (101). The refill communication passage (102) connects the discharge port (70) and the refill communication port (101).

[0120] More specifically, a refilling vertical hole (101a) extending in the axial direction (X) is provided in the center of the refilling communication port (101) in the circumferential direction (T). The refilling vertical hole (101a) is connected to the refilling communication passage (102).

[0121] The outer peripheral end of the refill communication passage (102) opens onto the outer peripheral surface of the valve plate (30) and is therefore closed by a plug (103).

[0122] The refill passage 100 connects the discharge port 70 to the chamber 80. When the opening 18, which is connected to the chamber 80, faces the refill communication port 101, the high-pressure fluid W in the discharge port 70 is refilled into the chamber 80 via the refill communication passage 102, the refill communication port 101, and the opening 18.

[0123] (Positional relationship between cylinder bore and chamber) The positional relationship between the cylinder bores (11) and the chambers (80) will be described with reference to Figure 11. The cylinder bores (11) include a first cylinder bore (11A), a second cylinder bore (11B), a third cylinder bore (11C), a fourth cylinder bore (11D), a fifth cylinder bore (11E), a sixth cylinder bore (11F), a seventh cylinder bore (11G), an eighth cylinder bore (11H), and a ninth cylinder bore (11I). These cylinder bores (11) are arranged in order in the circumferential direction (T).

[0124] The chambers (80) are arranged in the circumferential direction (T) between the first cylinder bore (11A) and the second cylinder bore (11B), between the second cylinder bore (11B) and the third cylinder bore (11C), between the third cylinder bore (11C) and the fourth cylinder bore (11D), between the fourth cylinder bore (11D) and the fifth cylinder bore (11E), between the fifth cylinder bore (11E) and the sixth cylinder bore (11F), between the sixth cylinder bore (11F) and the seventh cylinder bore (11G), between the seventh cylinder bore (11G) and the eighth cylinder bore (11H), between the eighth cylinder bore (11H) and the ninth cylinder bore (11I), and between the ninth cylinder bore (11I) and the first cylinder bore (11A).

[0125] (Inter-chamber passage) The inter-chamber passage (110) will be described with reference to Figure 2. The inter-chamber passage (110) is an example of a third passage.

[0126] The chamber (80) includes a first chamber (80a), a second chamber (80b), a third chamber (80c), a fourth chamber (80d), a fifth chamber, a sixth chamber, a seventh chamber, an eighth chamber, and a ninth chamber, which are not shown in Figure 2.

[0127] These chambers (80) are arranged side by side in the circumferential direction (T) and are separated from each other in the circumferential direction (T) by partition walls (16).

[0128] The inter-chamber passage 110 is formed by a communication groove 16a. The inter-chamber passage 110 (communication groove 16a) extends in the circumferential direction T of the partition wall 16 and connects the chambers 80 (recesses 15) adjacent to each other in the circumferential direction T.

[0129] The inter-chamber passages (110) include a first inter-chamber passage (110a), a second inter-chamber passage (110b), a third inter-chamber passage (110c), a fourth inter-chamber passage, a fifth inter-chamber passage, a sixth inter-chamber passage, a seventh inter-chamber passage, an eighth inter-chamber passage, and a ninth inter-chamber passage. Note that the fourth to ninth inter-chamber passages are not shown in Figure 2.

[0130] The first chamber (80a) and the second chamber (80b) communicate with each other through a first inter-chamber passage (110a). The second chamber (80b) and the third chamber (80c) communicate with each other through a second inter-chamber passage (110b). The third chamber (80c) and the fourth chamber (80d) communicate with each other through a third inter-chamber passage (110c). The same applies to the subsequent chambers and inter-chamber passages.

[0131] The first inter-chamber passage (110a) and the second inter-chamber passage (110b) are located at different positions in the axial direction (X). The second inter-chamber passage (110b) and the third inter-chamber passage (110c) are located at different positions in the axial direction (X). The first inter-chamber passage (110a) is located at the center of the partition wall (16) in the axial direction (X). The second inter-chamber passage (110b) is located at the front end of the partition wall (16) in the axial direction (X). The third inter-chamber passage (110c) is located at the rear end of the partition wall (16) in the axial direction (X).

[0132] The fourth inter-chamber passage and the seventh inter-chamber passage are located at the same position in the axial direction (X) as the first inter-chamber passage (110a). The fifth inter-chamber passage and the eighth inter-chamber passage are located at the same position in the axial direction (X) as the second inter-chamber passage (110b). The sixth inter-chamber passage and the ninth inter-chamber passage are located at the same position in the axial direction (X) as the third inter-chamber passage (110c). (Action and effect) A fluid (W) is accommodated in a chamber (80) between the cylinder block (10) and the ring (50). After the cylinder bore (11) has finished communicating with the suction port (60) and before the cylinder bore (11) has started communicating with the discharge port (70), the high-pressure fluid (W) is supplied from the chamber (80) to the cylinder bore (11) through the supply passage (90).

[0133] The pressure in the cylinder bore (11) can be increased at a timing after the cylinder bore (11) has finished communicating with the suction port (60) and before the cylinder bore (11) starts communicating with the discharge port (70). Backflow of the fluid (W) from the discharge port (70) to the cylinder bore (11) can be suppressed, thereby suppressing pulsation caused by the backflow.

[0134] As described above, in the piston pump (1), pulsation caused by the fluid (W) flowing back from the discharge port (70) to the cylinder bore (11) can be suppressed.

[0135] The chamber (80) is formed between the cylinder block (10) and the ring (50). A sufficient amount of fluid (W) can be accommodated in the chamber (80) compared to when the chamber (80) is formed in, for example, the valve plate (30). A sufficient amount of fluid (W) can be supplied from the chamber (80) to the cylinder bore (11) via the supply passage (90), thereby sufficiently increasing the pressure in the cylinder bore (11).

[0136] In comparison with the case where the chamber (80) is formed in, for example, the end cap (3), an increase in the axial dimension of the piston pump (1) can be suppressed.

[0137] High pressure fluid (W) can be replenished from the discharge port (70) through a refill passage (100) to the chamber (80).

[0138] Since the supply passage (90) is provided in the valve plate (30), the supply passage (90) can be easily configured.

[0139] The supply passage (90) is provided with a throttle portion (95). The throttle portion (95) reduces the passage area (S) of the supply passage (90). The throttle portion (95) reduces the pressure of the fluid (W) flowing through the supply passage (90), thereby suppressing a sudden increase in pressure in the cylinder bore (11).

[0140] The chamber (80) is disposed between the first cylinder bore (11A) and the second cylinder bore (11B) in the circumferential direction (T). The chamber (80) does not overlap with the first cylinder bore (11A) or the second cylinder bore (11B) in the circumferential direction (T). This facilitates the layout of the chamber (80).

[0141] Furthermore, the recess 15 (in the outer peripheral portion 14 of the cylinder block 10) that forms the chamber 80 does not overlap the first cylinder bore 11A or the second cylinder bore 11B in the circumferential direction T. In other words, the recess 15 is not aligned in a straight line with the first cylinder bore 11A or the second cylinder bore 11B in the radial direction R. This is advantageous in terms of ensuring the wall thickness of the cylinder block 10.

[0142] A fluid (W) can be circulated in the circumferential direction (T) between the first chamber (80a) and the second chamber (80b) through the inter-chamber passage (110).

[0143] When the cylinder bore (11) faces the first communication port (91) and the opening (18) faces the second communication port (92), the fluid (W) can be supplied from the chamber (80) to the cylinder bore (11) through the opening (18), the second communication port (92), the communication passage (93) and the first communication port (91).

[0144] The second communication port (92) is formed in an arc shape extending in the circumferential direction (T). Even if the opening (18) corresponding to the second communication port (92) is positioned offset in the circumferential direction (T) with respect to the cylinder bore (11) corresponding to the first communication port (91), the first communication port (91) and the second communication port (92) can be easily connected by the communication passage (93).

[0145] The chamber (80) can be simply formed by a recess (15) in the outer periphery (14) of the cylinder block (10).

[0146] The piston pump (1) includes a swash plate (40). In the swash plate type piston pump (1), pulsation can be suitably suppressed.

[0147] Second Embodiment A piston pump (1) according to a second embodiment will be described. In the following description, the same components as those in the above embodiment will be denoted by the same reference numerals, and detailed description thereof will be omitted. Figure 15 corresponds to Figure 11 and shows a cross-sectional view of the cylinder block (10) and the ring (50) as seen from the rear.

[0148] An opening 18 is provided in the front end surface (one end surface) 12 of the cylinder block 10. The opening 18 communicates with the chamber 80. The opening 18 communicates with the second communication port 92 of the supply passage 90 (see FIG. 12).

[0149] The openings 18 include a first opening 18a, a second opening 18b, a third opening 18c, a fourth opening 18d, a fifth opening 18e, a sixth opening 18f, a seventh opening 18g, an eighth opening 18h, and a ninth opening 18i. These openings 18 are arranged in order in the circumferential direction T.

[0150] The first pitch (Pa) between the first opening (18a) and the second opening (18b), the second pitch (Pb) between the second opening (18b) and the third opening (18c), the third pitch (Pc) between the third opening (18c) and the fourth opening (18d), the fourth pitch (Pd) between the fourth opening (18d) and the fifth opening (18e), the fifth pitch (Pe) between the fifth opening (18e) and the sixth opening (18f), the sixth pitch (Pf) between the sixth opening (18f) and the seventh opening (18g), the seventh pitch (Pg) between the seventh opening (18g) and the eighth opening (18h), the eighth pitch (Ph) between the eighth opening (18h) and the ninth opening (18i), and the ninth pitch (Pi) between the ninth opening (18i) and the first opening (18a) are different from one another.

[0151] It is sufficient that at least the first pitch (Pa) between the first opening (18a) and the second opening (18b) and the second pitch (Pb) between the second opening (18b) and the third opening (18c) are different from each other.

[0152] The other configurations are the same as those in the first embodiment.

[0153] This can suppress noise caused by the pressure in the cylinder bore (11) rising at a constant cycle, and in particular, can disperse high-frequency noise components to improve the tone quality.

[0154] Third Embodiment A piston pump (1) according to a third embodiment will be described. In the following description, the same components as those in the above-described embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 16 is a view equivalent to FIG. 2, showing the cylinder block (10) as viewed from the left. FIG. 17 is a view equivalent to FIG. 10, showing a cross-sectional view of the cylinder block (10) and the ring (50) taken along line XVII as viewed from the left. FIG. 18 is a view equivalent to FIG. 11, showing a cross-sectional view of the cylinder block (10) and the ring (50) taken along line XVIII as viewed from the rear.

[0155] The piston pump (1) includes a swash plate (40). The swash plate (40) is inclined with respect to the axis (O) of the cylinder block (10). A rear end (20a) of the piston (20) on the opposite side (rear) of the axial direction (X) from the (front) valve plate (30) contacts the front surface of the swash plate (40).

[0156] A circumferential groove (121) is provided on the inner wall surface (120) of the cylinder bore (11) (the bore main body (11a) of the cylinder bore (11)). The circumferential groove (121) is disposed closer to the swash plate (40) (rearward) than the center (122) of the cylinder bore (11) in the axial direction (X). More specifically, the circumferential groove (121) is disposed in a portion of the cylinder bore (11) that is approximately one-quarter of the way from the rear end (three-quarters of the way from the front end) in the axial direction (X). The circumferential groove (121) extends around the entire circumference as viewed in the axial direction (X).

[0157] The cylinder block (10) is provided with a groove passage (130). The groove passage (130) is an example of a fourth passage. The groove passage (130) connects the circumferential groove (121) and the chamber (80).

[0158] One end of the groove passage (130) opens into the inter-chamber passage (110) (more specifically, into the bottom surface of the communication groove (16a)). The other end of the groove passage (130) opens into the circumferential groove (121) on the inner wall surface (120) of the cylinder bore (11). The groove passage (130) extends in the radial direction (R). The inter-chamber passage (110) (communication groove (16a)) is located at the rear end of the partition wall (16) in the axial direction (X).

[0159] The other configurations are the same as those in the first embodiment.

[0160] By sending the fluid (W) from the chamber (80) through the groove passage (130) to the circumferential groove (121), the lubrication between the piston (20) and the inner wall surface (120) of the cylinder bore (11) can be improved.

[0161] The piston (20) is pressed against the inner wall surface (120) of the cylinder bore (11) by a radial force (F) in the radial direction (R) from the swash plate (40). Lubrication between the piston (20) and the inner wall surface (120) of the cylinder bore (11) is particularly required in an area close to the swash plate (40). By locating the circumferential groove (121) as close as possible to the swash plate (40), friction between the piston (20) pressed against the swash plate (40) and the inner wall surface (120) of the cylinder bore (11) can be reduced.

[0162] <Fourth embodiment> A piston pump (1) according to a fourth embodiment will be described. In the following description, the same components as those in the above embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted. Figure 19 shows a chamber (80) according to the fourth embodiment.

[0163] The inner peripheral portion (51) of the ring (50) is provided with a recess (53). The outer peripheral portion (14) of the cylinder block (10) is not provided with a recess. The outer peripheral portion of the cylinder block (10) has a smooth outer peripheral surface (14a).

[0164] The chamber (80) is formed in the recess (53) of the inner peripheral portion (51) of the ring (50). More specifically, the chamber (80) is formed between the recess (53) of the inner peripheral portion (51) of the ring (50) and the outer peripheral surface (14a) of the outer peripheral portion (14) of the cylinder block (10).

[0165] The other configurations are the same as those in the first embodiment.

[0166] The chamber (80) can be simply formed by a recess (53) in the inner periphery (51) of the ring (50).

[0167] Fifth Embodiment A piston pump (1) according to a fifth embodiment will be described. In the following description, the same components as those in the above embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted. Figure 20 shows a chamber (80) according to the fifth embodiment.

[0168] The cylinder block 10 has an outer circumferential portion 14 provided with a recess 15. The ring 50 has an inner circumferential portion 51 provided with a recess 53.

[0169] The chamber (80) is formed in both the recess (15) in the outer circumferential portion (14) of the cylinder block (10) and the recess (53) in the inner circumferential portion (51) of the ring (50). More specifically, the chamber (80) is formed in an area surrounded by the recess (15) in the outer circumferential portion (14) of the cylinder block (10) and the recess (53) in the inner circumferential portion (51) of the ring (50).

[0170] The other configurations are the same as those in the first embodiment.

[0171] The chamber 80 is formed by using both the recess 15 in the outer periphery 14 of the cylinder block 10 and the recess 53 in the inner periphery 51 of the ring 50. This allows the chamber 80 to be made larger. The chamber 80 can accommodate a larger amount of fluid W.

[0172] <Other embodiments> Although the embodiments and modifications have been described above, it will be understood that various modifications in form and details are possible without departing from the spirit and scope of the claims. Furthermore, elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate.

[0173] The communication passage (93) of the supply passage (first passage) (90) may be formed as a groove provided in the front surface (32) (on the end cap (3) side) of the valve plate (30). In this case, the vertical holes (92c) of the first communication port (91) and the second communication port (92) pass through the valve plate (30) in the axial direction (X). The same applies to the refill passage (second passage) (100) (the refill communication port (101) and the refill communication passage (102)).

[0174] The cylinder block (10) and the ring (50) may be constructed as a single unit.

[0175] The cylinder block (10) and the ring (50) are not limited to being cylindrical, but may be, for example, rectangular tubular.

[0176] The number of recesses (15) (recesses (53)) may be one.

[0177] The supply passage 90 and the refill passage 100 may be provided in a location other than the valve plate 30. The supply passage 90 and the refill passage 100 may be provided in the end cap 3 by running piping therethrough.

[0178] The piston pump (1) is not limited to a variable displacement type, and may be a fixed swash plate type, a rotating swash plate type, or a bent-axis type. In a bent-axis type piston pump, the axis of the drive shaft and the axis of the cylinder block are offset obliquely from each other.

[0179] The terms "first," "second," "third," etc. in the specification and claims are used to distinguish the terms to which these terms are attached, and do not limit the number or order of those terms. [Industrial Applicability]

[0180] The present disclosure is applicable to piston pumps and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0181] X-axis direction Ra Outer circumference T circumferential direction W fluid S aisle area Pa 1st pitch Pb 2nd pitch 1 piston pump 10 Cylinder block 11 Cylinder bore 11A First cylinder bore 11B Second cylinder bore 12 Front end surface (one end surface) 14 Outer periphery 15 recess 18 Aperture 18a 1st opening 18b 2nd opening 18c 3rd opening 20 pistons 20a Rear end (end) 30 Valve plate 31 Rear surface (opposite surface) 40 Swash plate 50 rings 51 Inner circumference 53 Recess 60 Intake port 70 Discharge port 80 Chamber 80a First Chamber 80b Second chamber 90 Supply passage (1st passage) 91 1st communication port 92 2nd communication port 93 Communication path 95 Constriction section 100 Replenishment aisle (2nd aisle) 110 Inter-chamber passage (third passage) 120 Inner wall 121 Circumferential groove 122 Central 130 Channel Access Path (4th Pathway)

Claims

1. a cylindrical cylinder block (10) extending in an axial direction (X) and having a cylinder bore (11) passing through the block in the axial direction (X); a valve plate (30) facing one end surface (12) of the cylinder block (10) in the axial direction (X); a piston (20) accommodated in the cylinder bore (11); Equipped with A cylindrical ring (50) is disposed on the outer circumferential side (Ra) of the cylinder block (10), the cylinder block (10), together with the piston (20) and the ring (50), rotates relative to the valve plate (30) in a circumferential direction (T) around the axial direction (X); The valve plate (30) has a suction port (60) through which a fluid (W) is sucked and a discharge port (70) through which the fluid (W) is discharged, the suction port (60) and the discharge port (70) are spaced apart from each other in the circumferential direction (T), A chamber (80) for accommodating the fluid (W) is formed between the cylinder block (10) and the ring (50), a first passage (90) that connects the cylinder bore (11) to the chamber (80) after the cylinder bore (11) moving from the suction port (60) side to the discharge port (70) has finished communicating with the suction port (60) and before the cylinder bore (11) starts communicating with the discharge port (70); Piston pump.

2. a second passage (100) communicating the discharge port (70) with the chamber (80); 2. The piston pump according to claim 1.

3. The first passage (90) is provided in the valve plate (30).

3. The piston pump according to claim 1 or 2.

4. the first passage (90) is provided with a throttle portion (95) that reduces a passage area (S) of the first passage (90); 3. The piston pump according to claim 1 or 2.

5. The cylinder bore (11) includes a first cylinder bore (11A) and a second cylinder bore (11B) arranged side by side in the circumferential direction (T), the chamber (80) is disposed between the first cylinder bore (11A) and the second cylinder bore (11B) in the circumferential direction (T).

3. The piston pump according to claim 1 or 2.

6. the chamber (80) includes a first chamber (80a) and a second chamber (80b) that are arranged side by side in the circumferential direction (T) and are partitioned from each other in the circumferential direction (T), The first chamber (80a) and the second chamber (80b) are in communication with each other through a third passage (110).

3. The piston pump according to claim 1 or 2.

7. an opening (18) communicating with the chamber (80) is provided in the one end surface (12) of the cylinder block (10); The first passage (90) a first communication port (91) provided in a surface (31) of the valve plate (30) facing the one end surface (12) in the axial direction (X); a second communication port (92) disposed at a distance from the first communication port (91) and provided on the opposing surface (31); a communication passage (93) provided in the valve plate (30) and communicating between the first communication port (91) and the second communication port (92); Including, When the cylinder bore (11) faces the first communication port (91) and the opening (18) faces the second communication port (92), the cylinder bore (11) and the chamber (80) communicate with each other.

3. The piston pump according to claim 1 or 2.

8. a recess (15, 53) is provided on an outer circumferential portion (14) of the cylinder block (10) or an inner circumferential portion (51) of the ring (50); The chamber (80) is formed in the recess (15, 53).

3. The piston pump according to claim 1 or 2.

9. an opening (18) communicating with the chamber (80) is provided in the one end surface (12) of the cylinder block (10); The opening (18) includes a first opening (18a), a second opening (18b), and a third opening (18c) arranged in sequence in the circumferential direction (T), a first pitch (Pa) between the first opening (18a) and the second opening (18b) and a second pitch (Pb) between the second opening (18b) and the third opening (18c) are different from each other; 3. The piston pump according to claim 1 or 2.

10. a swash plate (40) that is inclined with respect to the cylinder block (10) and that contacts an end (20a) of the piston (20) on the opposite side to the valve plate (30) in the axial direction (X), 3. The piston pump according to claim 1 or 2.

11. An inner wall surface (120) of the cylinder bore (11) is provided with a circumferential groove (121), The cylinder block (10) is provided with a fourth passage (130) that connects the circumferential groove (121) and the chamber (80).

3. The piston pump according to claim 1 or 2.

12. a swash plate (40) that is inclined with respect to the cylinder block (10) and that contacts an end (20a) of the piston (20) on the opposite side of the valve plate (30) in the axial direction (X), The circumferential groove (121) is disposed closer to the swash plate (40) than the center (122) of the cylinder bore (11) in the axial direction (X).

12. The piston pump of claim 11.

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