Piston pump

Abstract

To suppress temperature rise in a cylinder block of a piston pump. [Solution] The piston pump (1) includes a cylindrical cylinder block (10) extending in an axial direction (X) and having a cylinder bore (11) passing therethrough in the axial direction, a valve plate (30) facing one axial end face (12) of the cylinder block, and a piston (20) housed in the cylinder bore. A cylindrical 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) around the axial direction. The valve plate has an intake port (60) through which a fluid (W) is drawn. A chamber (80) for housing the fluid is formed between the cylinder block and the ring. A first passage (90) connects the intake port and the chamber.

Description

[Technical Field]

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

[0002] For example, Patent Document 1 discloses various techniques for piston pumps. In this type of piston pump, a cylinder block having cylinder bores rotates relative to a valve plate having suction and discharge ports. When the cylinder bores communicate with the suction ports, the pistons in the cylinder bores move away from the valve plate, thereby drawing low-pressure fluid from the suction ports into the cylinder bores. When the cylinder bores communicate with the discharge ports, the pistons in the cylinder bores move toward the valve plate, thereby discharging high-pressure fluid from the cylinder bores to the discharge port. [Prior art documents] [Patent documents]

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

[0004] In a piston pump, a piston slides within a cylinder bore in a cylinder block, and frictional heat generated between the cylinder bore and the piston causes the temperature of the cylinder block to rise, which is undesirable as it can shorten the life of the piston pump.

[0005] An object of the present disclosure is to suppress a temperature rise in a cylinder block in a piston pump. [Means for solving the problem]

[0006] A first aspect of this disclosure relates to a piston pump (1). This piston pump (1) comprises a cylindrical cylinder block (10) extending in the axial direction (X) and having a cylinder bore (11) penetrating in 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) housed in the cylinder bore (11), wherein a cylindrical ring (50) is disposed on the outer circumference (Ra) of the cylinder block (10), and the cylinder block (10) is Together with the piston (20) and the ring (50), the valve plate (30) rotates relative to the valve plate (30) in the circumferential direction (T) around the axial direction (X). The valve plate (30) has an intake port (60) through which fluid (W) is drawn in. Between the cylinder block (10) and the ring (50), a chamber (80) is formed which the fluid (W) is contained, and a first passage (90) connects the intake port (60) and the chamber (80).

[0007] According to the first embodiment, the fluid (W) flows through the first passage (90) between the intake port (60) and the chamber (80). Since the fluid (W) flows into the chamber (80) between the cylinder block (10) and the ring (50), the cylinder block (10) can be cooled. In the piston pump (1), the temperature rise of the cylinder block (10) can be suppressed.

[0008] A second aspect of this disclosure relates to a piston pump (1) according to the first aspect. In this piston pump (1), the first passage (90) includes an inlet (95) through which the fluid (W) flows from the suction port (60) to the chamber (80), and an outlet (96) through which the fluid (W) flows out from the chamber (80) to the suction port (60), wherein the inlet (95) communicates with a position (60a) where the pressure (P) is relatively high in the suction port (60), and the outlet (96) communicates with a position (60b) where the pressure (P) is relatively low in the suction port (60).

[0009] According to the second aspect, the fluid (W) flows from a position (60a) in the suction port (60) where the pressure (P) is relatively high through the inlet portion (95) of the first passage (90) into the chamber (80), and flows out from the chamber (80) through the outlet portion (96) of the first passage (90) to a position (60b) in the suction port (60) where the pressure (P) is relatively low. By utilizing the difference in pressure (P) to promote the flow of the fluid (W), the cylinder block (10) can be cooled more effectively.

[0010] 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 chamber (80) includes a first chamber (80a), a second chamber (80b), and a third chamber (80c) that are arranged side by side in the circumferential direction (T) and that are separated from one another in the circumferential direction (T), the first chamber (80a) and the second chamber (80b) being communicated with each other by a first communication passage (110a), and the second chamber (80b) and the third chamber (80c) being communicated with each other by a second communication passage (110b).

[0011] According to the third embodiment, the fluid (W) flows in the circumferential direction (T) in the order of the first chamber (80a), the first connecting passage (110a), the second chamber (80b), the second connecting passage (110b), and the third chamber (80c). The cylinder block (10) can be cooled evenly in the circumferential direction (T).

[0012] A fourth aspect of the present disclosure relates to a piston pump (1) according to any one of the first to third aspects. In this piston pump (1), the first communication passage (110a) and the second communication passage (110b) are located at different positions in the axial direction (X).

[0013] According to the fourth embodiment, the fluid (W) flows in the circumferential direction (T) through the first chamber (80a), the first connecting passage (110a), the second chamber (80b), the second connecting passage (110b), and the third chamber (80c), and as it flows, it also begins to flow in the axial direction (X). The cylinder block (10) can be cooled evenly in the axial direction (X).

[0014] 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), 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 communication ports (91, 93) provided in a surface (31) of the valve plate (30) facing the one end face (12) in the axial direction (X), and communication passages (92, 94) provided in the valve plate (30) and communicating between the suction port (60) and the communication ports (91, 93), and when the opening (18) faces the communication ports (91, 93), the suction port (60) and the chamber (80) communicate with each other.

[0015] According to the fifth aspect, when the opening (18) faces the communication ports (91, 93), the fluid (W) can flow between the suction port (60) and the chamber (80) through the communication passages (92, 94) and the communication ports (91, 93) in the first passage (90).

[0016] 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 the 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).

[0017] According to the sixth aspect, the chamber (80) can be easily formed.

[0018] A seventh aspect of the present disclosure is directed to the piston pump (1) according to any one of the first to sixth 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).

[0019] According to the seventh aspect, in the swash plate type piston pump (1), it is possible to suitably suppress the temperature rise of the cylinder block (10). [Brief explanation of the drawings]

[0020] [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] Figure 10 shows a cross-sectional view of the cylinder block (10) and ring (50) according to the first embodiment, 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 cooling passage (90) according to the first embodiment as viewed from behind the valve plate (30). [Figure 13] FIG. 13 is a cross-sectional view showing the first cooling communication port (91) and the first cooling communication passage (92) in the cooling passage (90) according to the first embodiment. [Figure 14]FIG. 14 is a cross-sectional view showing the second cooling communication port (93) and the second cooling communication passage (94) in the cooling passage (90) according to the first embodiment. [Figure 15] FIG. 15 shows the distribution of the pressure (P) of the fluid (W) in the suction port (60) according to the first embodiment. [Figure 16] FIG. 16 shows the flow of the fluid (W) in the cooling passage (90) according to the first embodiment. [Figure 17] FIG. 17 shows a chamber (80) according to the second embodiment. [Figure 18] FIG. 18 shows a chamber (80) according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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).

[0025] (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.

[0026] 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).

[0027] (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).

[0028] 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).

[0029] (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.

[0030] 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.

[0031] (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).

[0032] The cylinder block (10) is cylindrical. More specifically, the cylinder block (10) is roughly 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 circumference 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).

[0033] 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.

[0034] The direction perpendicular to the axial direction (X), specifically around the axial direction (X) (axis (O)), is called the circumferential direction (T). The circumferential direction (T) is the relative rotational direction of the cylinder block (10) and ring (50) with respect to the valve plate (30), and the reverse direction. For convenience, in each figure, the direction of rotation within the circumferential direction (T) is indicated by the direction of the arrow. The radial direction perpendicular to the axial direction (X), with respect to the axis (O), is simply called the radial direction (R). The area outside the radial direction (R) is called the outer circumference side (Ra). The area inside the radial direction (R) is called the inner circumference side (Rb).

[0035] 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.

[0036] The cylinder bore (11) is disposed 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).

[0037] 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)).

[0038] 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)).

[0039] 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).

[0040] 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).

[0041] The recess (15) is partitioned in the axial direction (X) by the front sealing portion (17a) and the rear sealing portion (17b). The recess (15) is recessed on the inner circumference side (Rb) relative to the front sealing portion (17a) and the rear sealing portion (17b).

[0042] As shown in Figure 2, a connecting groove (16a) is provided on the outer circumferential surface of the partition wall (16) of the cylinder block (10). The connecting groove (16a) is recessed on the inner circumferential side (Rb) relative to the outer circumferential surface of the partition wall (16). The connecting groove (16a) extends in the circumferential direction (T) of the partition wall (16) and connects adjacent recesses (15) in the circumferential direction (T).

[0043] 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.

[0044] 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).

[0045] (piston) As shown in Figure 1, the piston (20) is housed in the cylinder bore (11). There are the same number of pistons (20) as there are cylinder bores (11) (9 in this example). The piston (20) includes a piston body (21) and a shoe (22). The piston body (21) is cylindrical and extends in the axial direction (X). The piston body (21) is liquid-tightly housed in the bore body portion (11a) of the cylinder bore (11). The piston body (21) slides axially (X) relative to the bore body portion (11a).

[0046] The shoe (22) is located at the rear end of the piston body (21). The shoe (22) constitutes the rear end (20a) of the piston (20). The rear end (20a) is an example of an end. The shoe (22) (the rear end (20a) of the piston (20)) is located behind the rear end of the cylinder bore (11) (the rear end face (13) of the cylinder block (10)). The piston (20) rotates relative to the housing (2).

[0047] (Valve plate) The valve plate (30) will be explained with reference to Figures 1, 6, and 7. Figure 6 shows the valve plate (30) as viewed from the front. Figure 7 shows the valve plate (30) as viewed from the rear.

[0048] 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)).

[0049] The valve plate (30) is positioned between the cylinder block (10) and the end cap (3) in the axial direction (X). The rear surface (31) of the valve plate (30) in the axial direction (X) faces the 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) is the surface facing the front end surface (one end surface) (12) of the cylinder block (10) in the axial direction (X). The 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).

[0050] A shaft through hole (33) for the drive shaft (4) is provided in the valve plate (30) in the axial direction (X). The front end of the drive shaft (4) is housed in a recess provided in the end cap (3).

[0051] 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). The space between the rear surface (31) of the valve plate (30) and the front end surface (12) of the cylinder block (10) is sealed in a liquid-tight manner.

[0052] As shown in Figures 6 and 7, the valve plate (30) has an intake port (60) and a discharge port (70). The intake port (60) and the discharge port (70) are located on the outer circumference (Ra) side of the through-hole (33). The intake port (60) and the discharge port (70) are spaced apart from each other in the circumferential direction (T).

[0053] As shown in Figure 7, the intake port (60) is located to the right of the axis (O). The intake port (60) is formed in an arc shape extending in the circumferential direction (T). The intake port (60) includes three intake side small ports (61) and an intake side notch (62). The three intake side small ports (61) are partitioned from each other and arranged in an arc shape extending in the circumferential direction (T). The intake side small ports (61) penetrate the valve plate (30) in the axial direction (X).

[0054] 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.

[0055] 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).

[0056] 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 in 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 suction side notch (62) may not be present.

[0057] 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.

[0058] 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).

[0059] As will be described in detail later, the valve plate (30) is provided with a cooling passage (90).

[0060] (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).

[0061] 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).

[0062] 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).

[0063] 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.

[0064] 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).

[0065] 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).

[0066] 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).

[0067] (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.

[0068] 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).

[0069] (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).

[0070] 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.

[0071] 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.

[0072] 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.

[0073] (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.

[0074] 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).

[0075] 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).

[0076] 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).

[0077] 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)).

[0078] 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.

[0079] 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).

[0080] 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.

[0081] (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).

[0082] 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).

[0083] (Inter-chamber passage) The inter-chamber passage (110) will be described with reference to FIG.

[0084] 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.

[0085] 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).

[0086] 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.

[0087] The inter-chamber passage (110) includes 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. The first inter-chamber passage (110a) is an example of a first communication passage. The second inter-chamber passage (110b) is an example of a second communication passage.

[0088] 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.

[0089] 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).

[0090] 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).

[0091] (cooling passage) The cooling passage (90) will be described with reference to Figures 12 to 14. Figure 12 shows the cooling passage (90) as seen from behind the valve plate (30). Figure 13 shows a cross-sectional view of the first cooling communication port (91) and the first cooling communication passage (92) of the cooling passage (90) taken along line XIII. Figure 14 shows a cross-sectional view of the second cooling communication port (93) and the second cooling communication passage (94) of the cooling passage (90) taken along line XIV. Figure 15 shows an example of the distribution of the pressure (P) of the fluid (W) in the suction port (60).

[0092] The piston pump (1) has a cooling passage (90). The cooling passage (90) is an example of a first passage. The cooling passage (90) is provided in the valve plate (30). The cooling passage (90) includes a first cooling communication port (91), a first cooling communication port (92), a second cooling communication port (93), and a second cooling communication port (94). The first cooling communication port (91) is an example of a communication port. The first cooling communication port (92) is an example of a communication port. The second cooling communication port (93) is an example of a communication port. The second cooling communication port (94) is an example of a communication port.

[0093] 12 and 13, the first cooling communication port (91) is provided on the rear surface (opposing surface) (31) of the valve plate (30). The first cooling communication port (91) is located slightly to the right of the bottom dead center (A) in the circumferential direction (T) (closer to the suction port (60)). The first cooling communication port (91) is located at approximately the same position in the circumferential direction (T) as the lowest small suction port (61) of the suction port (60). The first cooling communication port (91) is located on the outer circumferential side (Ra) of the suction port (60).

[0094] The first cooling communication port (91) does not penetrate the valve plate (30) in the axial direction (X). When viewed in the axial direction (X), the first cooling communication port (91) is formed in an arc shape extending in the circumferential direction (T). The first cooling 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). The first cooling communication port (91) is a groove extending in the circumferential direction (T) on the rear surface (31) of the valve plate (30).

[0095] The first cooling communication port (91) is located at approximately 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 first cooling communication port (91) when passing through the first cooling communication port (91).

[0096] The first cooling communication passage (92) is provided inside (34) of the valve plate (30). The first cooling communication passage (92) extends in the radial direction (R). The first cooling communication passage (92) connects the suction port (60) and the first cooling communication port (91). Specifically, the first cooling communication passage (92) connects the lowest suction-side small port (61) of the suction port (60) to the left end of the first cooling communication port (91) (the end on the discharge port (70) side in the circumferential direction (T)). The first cooling communication passage (92) connects the suction port (60) and the first cooling communication port (91).

[0097] Specifically, a first cooling vertical hole (91a) extending in the axial direction (X) is provided at the left end (the end on the discharge port (70) side in the circumferential direction (T)) of the first cooling communication port (91). The first cooling vertical hole (91a) is connected to the first cooling communication passage (92).

[0098] The outer peripheral end of the first cooling communication passage (92) opens into the outer peripheral surface of the valve plate (30) and is therefore closed by a plug (97).

[0099] The cooling passage (90) connects the suction port (60) and the chamber (80). When the opening (18) connected to the chamber (80) faces the first cooling communication port (91), the suction port (60) and the chamber (80) communicate with each other.

[0100] 12 and 14, the second cooling communication port (93) is provided on the rear surface (opposing surface) (31) of the valve plate (30). The second cooling communication port (93) is disposed in the circumferential direction (T) on the suction port (60) side, at a central position between the bottom dead center (A) and the top dead center (B). The second cooling communication port (93) is located in approximately the same position as the central suction-side small port (61) of the suction port (60) in the circumferential direction (T). The second cooling communication port (93) is located on the outer circumferential side (Ra) of the suction port (60).

[0101] The second cooling communication port (93) does not penetrate the valve plate (30) in the axial direction (X). When viewed in the axial direction (X), the second cooling communication port (93) is formed in an arc shape extending in the circumferential direction (T). The second cooling communication port (93) is a recess provided in the rear surface (31) of the valve plate (30) and recessed forward in the axial direction (X). The second cooling communication port (93) is a groove extending in the circumferential direction (T) on the rear surface (31) of the valve plate (30).

[0102] The second cooling communication port (93) is located at approximately 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 cooling communication port (93) when passing through the second cooling communication port (93).

[0103] The second cooling communication passage (94) is provided inside (34) of the valve plate (30). The second cooling communication passage (94) extends in the radial direction (R). The second cooling communication passage (94) connects the suction port (60) and the second cooling communication port (93). Specifically, the second cooling communication passage (94) connects the central suction side small port (61) of the suction port (60) to the central portion of the second cooling communication port (93) in the circumferential direction (T). The second cooling communication passage (94) connects the suction port (60) and the second cooling communication port (93) to each other.

[0104] More specifically, a second cooling vertical hole (93a) extending in the axial direction (X) is provided in the center in the circumferential direction (T) of the second cooling communication port (93). The second cooling vertical hole (93a) is connected to the second cooling communication passage (94).

[0105] The outer peripheral end of the second cooling communication passage (94) opens into the outer peripheral surface of the valve plate (30) and is therefore closed by a plug (98).

[0106] The cooling passage (90) connects the suction port (60) and the chamber (80). When the opening (18) connected to the chamber (80) faces the second cooling communication port (93), the suction port (60) and the chamber (80) communicate with each other.

[0107] The horizontal axis in Figure 15 represents the position in the circumferential direction (T) from the top dead center (B) of the suction port (60). The vertical axis in Figure 15 represents the pressure (P) of the fluid (W). As shown in Figure 15, the pressure (P) of the fluid (W) is lowest at the midpoint between the bottom dead center (A) and the top dead center (B) in the circumferential direction (T) of the suction port (60) (a position approximately 90° from the top dead center (B)). This is because the speed at which the piston (20) is retracted rearward in the cylinder bore (11) is the fastest.

[0108] 12, the cooling passage (90) includes an inlet portion (95) and an outlet portion (96). The inlet portion (95) is formed of a first cooling communication port (91) and a first cooling communication passage (92). The outlet portion (96) is formed of a second cooling communication port (93) and a second cooling communication passage (94).

[0109] The inlet (95) communicates with a position (60a) of the suction port (60) where the pressure (P) is relatively high (more specifically, a position slightly less than 180° from the top dead center (B)). The outlet (96) communicates with a position (60b) of the suction port (60) where the pressure (P) is relatively low (more specifically, a position approximately 90° from the top dead center (B)).

[0110] At the inlet 95, the fluid W flows from the suction port 60 into the chamber 80. At the outlet 96, the fluid W flows from the chamber 80 to the suction port 60.

[0111] (Fluid flow in cooling passages) Figure 16 shows the flow of the fluid (W) in the cooling passage (90) in a perspective view of the XVI cross section. For clarity, the valve plate (30) and the cylinder block (10) are separated in Figure 16. As shown in Figures 12 and 16, when the two openings (18) (communicating with the chamber (80)) arranged in the circumferential direction (T) face the first cooling communication port (91) and the second cooling communication port (93) in the cooling passage (90), a position (60a) in the suction port (60) where the pressure (P) is relatively high communicates with the inlet (95) of the cooling passage (90), and a position (60b) in the suction port (60) where the pressure (P) is relatively low communicates with the outlet (96) of the cooling passage (90).

[0112] The fluid W flows from the position 60a of the suction port 60 where the pressure P is relatively high through the inlet 95 of the cooling passage 90 into the chamber 80. Specifically, the fluid W flows from the position 60a of the suction port 60 where the pressure P is relatively high to the first cooling communication passage 92 of the cooling passage 90 and further to the first cooling communication port 91 of the cooling passage 90. The fluid W flows from the first cooling communication port 91 of the cooling passage 90 to the chamber 80 through the opening 18.

[0113] The fluid (W) flows through the inter-chamber passage (110) to the adjacent chamber (80) in the circumferential direction (T).

[0114] The fluid W flows from the chamber 80 through the outlet 96 of the cooling passage 90 to the position 60b of the suction port 60 where the pressure P is relatively low. Specifically, the fluid W flows from the chamber 80 through the opening 18 to the second cooling communication port 93 of the cooling passage 90. The fluid W flows from the second cooling communication port 93 of the cooling passage 90 to the second cooling communication passage 94 of the cooling passage 90 and further to the position 60b of the suction port 60 where the pressure P is relatively low.

[0115] (Action and effect) The fluid (W) flows between the suction port (60) and the chamber (80) through the cooling passage (90). The fluid (W) flows into the chamber (80) between the cylinder block (10) and the ring (50), thereby cooling the cylinder block (10). In the piston pump (1), a temperature rise in the cylinder block (10) can be suppressed.

[0116] In general, the fluid (W) drawn into the suction port (60) is cold. For example, the fluid (W) drawn into the suction port (60) is colder than the discharged drain liquid. The cold fluid (W) can be introduced from the suction port (60) through the cooling passage (90) into the chamber (80). The cold fluid (W) drawn into the suction port (60) can cool the cylinder block (10) more effectively than when drain liquid is used.

[0117] The fluid (W) flows from a position (60a) of relatively high pressure (P) in the intake port (60) through an inlet (95) of the cooling passage (90) into the chamber (80), and flows out from the chamber (80) through an outlet (96) of the cooling passage (90) to a position (60b) of relatively low pressure (P) in the intake port (60). By utilizing the difference in pressure (P) to promote the flow of the fluid (W), the cylinder block (10) can be cooled more effectively.

[0118] The fluid (W) flows in the circumferential direction (T) through the first chamber (80a), the first inter-chamber passage (110a), the second chamber (80b), the second inter-chamber passage (110b), and the third chamber (80c) in this order, thereby enabling the cylinder block (10) to be cooled evenly in the circumferential direction (T).

[0119] The fluid (W) flows in the circumferential direction (T) through the first chamber (80a), the first inter-chamber passage (110a), the second chamber (80b), the second inter-chamber passage (110b), and the third chamber (80c) in this order, and also flows in the axial direction (X). This allows the cylinder block (10) to be cooled evenly in the axial direction (X).

[0120] When two openings (18) (connected to the chamber (80)) arranged in the circumferential direction (T) face the first cooling communication port (91) and the second cooling communication port (93) in the cooling passage (90), the fluid (W) can flow between the intake port (60) and the chamber (80) via the first cooling communication passage (92) and the first cooling communication port (91) in the first passage (90) and the second cooling communication port (93) and the second cooling communication passage (94).

[0121] The chamber (80) can be simply formed by a recess (15) in the outer periphery (14) of the cylinder block (10).

[0122] The piston pump (1) includes a swash plate (40). In the swash plate type piston pump (1), the temperature rise of the cylinder block (10) can be suitably suppressed.

[0123] The chamber (80) is formed between the cylinder block (10) and the ring (50). A sufficient amount of fluid (W) can flow from the intake port (60) through the cooling passage (90) into the chamber (80), thereby sufficiently cooling the cylinder block (10).

[0124] Since the cooling passage (90) is provided in the valve plate (30), the cooling passage (90) can be easily configured.

[0125] 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 17 shows a chamber (80) according to the second embodiment.

[0126] 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).

[0127] 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).

[0128] The other configurations are the same as those in the first embodiment.

[0129] The chamber (80) can be simply formed by a recess (53) in the inner periphery (51) of the ring (50).

[0130] 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 embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted. Figure 18 shows a chamber (80) according to the third embodiment.

[0131] 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.

[0132] 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).

[0133] The other configurations are the same as those in the first embodiment.

[0134] 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.

[0135] <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.

[0136] The first cooling communication passage (92) and the second cooling communication passage (94) in the cooling passage (first passage) (90) may be formed as grooves provided in the front surface (32) (the end cap (3) side) of the valve plate (30). In this case, the first cooling vertical hole (91a) of the first cooling communication port (91) and the second cooling vertical hole (93a) of the second cooling communication port (93) penetrate the valve plate (30) in the axial direction (X).

[0137] The cylinder block (10) and the ring (50) may be constructed as a single unit.

[0138] The cylinder block (10) and the ring (50) are not limited to being cylindrical, but may be, for example, rectangular tubular.

[0139] The number of recesses (15) (recesses (53)) may be one.

[0140] The cooling passage 90 may be provided in a location other than the valve plate 30. The cooling passage 90 may be provided in the end cap 3 by running a pipe therethrough.

[0141] 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.

[0142] 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]

[0143] The present disclosure is applicable to piston pumps and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0144] X-axis direction Ra Outer circumference T circumferential direction W fluid P pressure 1 piston pump 10 Cylinder block 11 Cylinder bore 12 Front end surface (one end surface) 14 Outer periphery 15 recess 18 Aperture 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 60a position 60b position 80 Chamber 80a First Chamber 80b Second chamber 80c Third Chamber 90 Cooling passage (1st passage) 91 1st cooling communication port (communication port) 92 1st cooling communication path (communication path) 93 2nd cooling communication port (communication port) 94 2nd cooling communication path (communication path) 95 Inlet 96 Outlet 110a: First inter-chamber passage (first communication passage) 110b Second inter-chamber passage (second communication passage)

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 an intake port (60) through which a fluid (W) is drawn, A chamber (80) for accommodating the fluid (W) is formed between the cylinder block (10) and the ring (50), a first passage (90) that communicates the suction port (60) with the chamber (80); Piston pump.

2. The first passage (90) an inlet (95) through which the fluid (W) flows from the suction port (60) into the chamber (80); an outlet (96) through which the fluid (W) flows from the chamber (80) to the intake port (60); Including, The inlet (95) communicates with a position (60a) of the suction port (60) where the pressure (P) is relatively high, The outlet (96) communicates with a position (60b) in the suction port (60) where the pressure (P) is relatively low.

2. The piston pump according to claim 1.

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

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

4. the first communication passage (110a) and the second communication passage (110b) are located at different positions in the axial direction (X); 4. The piston pump according to claim 3.

5. 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) communication ports (91, 93) formed in a surface (31) of the valve plate (30) facing the one end surface (12) in the axial direction (X); a communication passage (92, 94) provided in the valve plate (30) and communicating between the suction port (60) and the communication port (91, 93); Including, When the opening (18) faces the communication opening (91, 93), the suction port (60) and the chamber (80) communicate with each other.

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

6. 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); 3. A piston pump according to claim 1 or 2, wherein the chamber (80) is formed in the recess (15, 53).

7. 3. The piston pump according to claim 1, further comprising a swash plate (40) that is inclined relative to the cylinder block (10) and that contacts an end (20a) of the piston (20) opposite the valve plate (30) in the axial direction (X).

Images