Variable displacement swash plate type hydraulic rotary machine

Abstract

To provide a variable displacement swash plate type hydraulic rotary machine capable of keeping lubricity between a swash plate and a control piston, suppressing floating of the control piston from the swash plate, and the swash plate of which can be made lightweight.SOLUTION: A control piston 18 of a tilt actuator 15 drives a swash plate 10 in a reclined position. A convex spherical surface part 21 of the control piston 18 is engaged with a concave spherical surface part 25 provided on the swash plate 10. The concave spherical surface part 25 has an escape part 26 and an engagement part 27. The engagement part 27 prevents the convex spherical surface part 21 of the control piston 18 and the concave spherical surface part 25 of the swash plate 10 from being released by abutment of a step part 23 of the control piston 18. The escape part 26 of the concave spherical surface part 25 has a pair of step groove parts 26A and a main body groove part 26B. A center axis X-X of the main body groove part 26B extends in a direction orthogonal to a virtual plane S-S including an oscillation center axis OA-OA of the swash plate 10 and a center axis OB-OB of a rotation axis 4.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a variable displacement swash plate type hydraulic rotary machine that is mounted on construction machinery such as a hydraulic excavator, a hydraulic crane, or a wheel loader and used as a hydraulic pump or a hydraulic motor. [Background technology]

[0002] For example, Patent Document 1 describes a variable displacement swash plate hydraulic rotary machine (hydraulic pump, hydraulic motor) that can adjust the discharge capacity of the hydraulic rotary machine by changing the angle of the swash plate. This variable displacement swash plate hydraulic rotary machine has control pistons (servo pistons) arranged in contact with both ends of the swash plate to change the angle of the swash plate. A spring force and a control pressure (hydraulic force) are applied to each control piston to generate thrust.

[0003] This adjusts the balance of the thrust of the control piston and controls the angle of the swash plate. Such control pistons are typically cylindrical or cylindrical. At least one of the contact points between the control piston and the swash plate may be spherical. Alternatively, a shoe may be disposed between the control piston and the swash plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 07-233781 Summary of the Invention [Problem to be solved by the invention]

[0005] The lubrication environment at the contact point between the swash plate and the control piston will now be explained. The casing of a hydraulic rotary machine is filled with a fluid (liquid such as hydraulic oil) that is pumped by the hydraulic rotary machine or a fluid (liquid such as hydraulic oil) that is pumped to the hydraulic rotary machine. At the contact point between the swash plate and the control piston, this fluid (liquid such as hydraulic oil) exists as a lubricating liquid (lubricating oil).

[0006] However, in conventional technology, lubricating fluid (hydraulic fluid such as hydraulic oil) is not actively supplied from outside between the swash plate and the control piston, so when the spring force and control pressure (hydraulic force) act on the control piston to press the swash plate, the lubricating fluid film (oil film) may break at the contact area, causing direct contact (metal-to-metal contact) at the contact area between the swash plate and the control piston, which may lead to wear.

[0007] Furthermore, in the prior art, the swash plate and the control piston are not fastened together. Therefore, when the swash plate repeatedly undergoes small oscillations or when the angle of the swash plate is rapidly reversed, the inertial force generated by the control piston can cause the control piston to lift off the swash plate. The lifted control piston can then collide with the swash plate, potentially causing wear at the contact point between the swash plate and the control piston. If wear progresses near the contact point between the control piston and the swash plate, it can become difficult to fine-tune the flow rate of the hydraulic rotary machine. Furthermore, wear debris can become trapped in the components, causing secondary wear and potentially contaminating the hydraulic fluid (hydraulic oil), resulting in various other problems.

[0008] On the other hand, for example, a communication hole may be provided in the control piston, and static pressure (hydraulic fluid such as hydraulic oil) may be supplied as a lubricating fluid between the swash plate and the control piston through the communication hole. However, in this case, when the control piston lifts off the swash plate as described above, a large amount of hydraulic fluid (hydraulic oil) may leak into the casing from that location, potentially degrading the performance of the hydraulic rotating machine (pump performance, motor performance). Furthermore, excessive pressure may be applied to the sealing member (oil seal) provided between the rotating shaft of the hydraulic rotating machine and the casing, potentially damaging the sealing member (oil seal).

[0009] Recently, hydraulic rotary machines have been required to adjust the angle of the swash plate quickly in order to reduce the energy consumption of hydraulic systems. Therefore, as the swash plate moves faster, the problems caused by the deterioration of the lubrication at the contact points between the control piston and the swash plate and the floating of the control piston become more pronounced. Furthermore, a heavy swash plate increases its inertia, which increases the time required to adjust the angle of the swash plate, so a lightweight swash plate is required.

[0010] An object of the present invention is to provide a variable displacement swash plate type hydraulic rotary machine that can ensure lubrication between the swash plate and the control piston, prevent the control piston from floating up from the swash plate, and reduce the weight of the swash plate. [Means for solving the problem]

[0011] The present invention is preferably a variable displacement swash plate type hydraulic rotary machine comprising: a rotary shaft rotatably provided within a casing; a cylinder block having a plurality of cylinders axially extending and spaced apart circumferentially, the cylinder block rotating integrally with the rotary shaft within the casing; a plurality of pistons reciprocally inserted into the plurality of cylinders; a plurality of shoes provided at each end of the plurality of pistons; a swash plate having a front surface that forms a smooth surface for slidably guiding the plurality of shoes and a back surface that is supported swingably relative to the casing; a control piston that presses the swash plate and a control cylinder into which the control piston is inserted, the tilt actuator for tilting the swash plate, the control piston having a convex spherical portion that engages with a concave spherical portion provided on the swash plate; a piston body having a tip end inserted into the control cylinder; a step portion connecting the convex spherical portion to the concave spherical portion of the swash plate, and a communicating hole for supplying hydraulic fluid between the convex spherical portion and the concave spherical portion of the swash plate; the concave spherical portion of the swash plate has a recess portion into which the step portion and the base end side of the piston body enter when the convex spherical portion of the control piston is engaged with the concave spherical portion; and an engagement portion that prevents the convex spherical portion of the control piston and the concave spherical portion of the swash plate from separating when the step portion of the control piston abuts against the recess portion; the recess portion has a pair of step grooves into which the step portion of the control piston enters when the convex spherical portion of the control piston is engaged with the concave spherical portion of the swash plate, and a main groove into which the base end side of the piston body enters between the pair of step grooves, and the central axis of the main groove extends in a direction perpendicular to an imaginary plane that includes the oscillation central axis of the swash plate and the central axis of the rotation shaft. [Effects of the Invention]

[0012] According to the present invention, lubrication between the swash plate and the control piston can be ensured, the control piston can be prevented from floating up from the swash plate, and the weight of the swash plate can be reduced. [Brief explanation of the drawings]

[0013] [Figure 1]1 is a longitudinal sectional view showing a variable displacement swash plate type hydraulic rotary machine according to an embodiment. [Figure 2] FIG. 2 is a front view showing the swash plate in FIG. [Figure 3] FIG. 2 is a side view showing the swash plate in FIG. [Figure 4] FIG. 10 is a cross-sectional view showing a state in which the control piston is being connected to the swash plate. [Figure 5] FIG. 5 is a front view showing the control piston and the swash plate as viewed from above in FIG. 4. [Figure 6] FIG. [Figure 7] 7 is a cross-sectional view of the concave spherical surface of the swash plate as viewed in the direction of arrow VII-VII in FIG. 6. [Figure 8] FIG. 4 is a side view showing the control piston. [Figure 9] FIG. 10 is a front view showing a swash plate according to a first modified example. [Figure 10] FIG. 10 is a front view showing a swash plate according to a second modified example. [Figure 11] FIG. 10 is a vertical cross-sectional view showing a variable displacement swash plate type hydraulic rotary machine according to a third modified example. [Figure 12] FIG. 12 is a side view showing the control piston in FIG. [Figure 13] 8 is a cross-sectional view taken in the same position as FIG. 7 and showing a concave spherical surface portion of a swash plate according to a fourth modified example. [Figure 14] FIG. 7 is a front view of a concave spherical portion according to a fifth modified example, taken in the same position as in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a variable displacement swash plate type hydraulic rotary machine according to an embodiment and a modified example will be described in detail with reference to the accompanying drawings, taking as an example a case where it is used as a hydraulic pump (variable displacement swash plate type hydraulic pump).

[0015] 1 to 8 show an embodiment. In Fig. 1, a variable displacement swash plate type hydraulic pump 1 (hereinafter referred to as hydraulic pump 1) includes a casing 2, a rotating shaft 4, a cylinder block 5, a plurality of pistons 7, a valve plate 8, a plurality of shoes 9, a swash plate 10, a cradle 11, a retainer 12, a retainer guide 13, a spring 14, and a tilting actuator 15. The hydraulic pump 1 is configured such that the rotating shaft 4 connected to a prime mover (an engine or electric motor serving as a drive source) of a hydraulic excavator, for example, is driven to rotate, and hydraulic oil in a plurality of cylinders 6 that is sucked from a tank is discharged as high-pressure oil.

[0016] The casing 2 is formed in a cylindrical (hollow) shape and constitutes the outer shell of the hydraulic pump 1. The casing 2 includes a cylindrical casing main body 2A with a bottom and a front casing 2B that closes the opening of the casing main body 2A. A cradle 11 is provided on the front casing 2B, which is located on one side (the right side in FIG. 1) of the casing 2, facing the rear surface of the swash plate 10.

[0017] Meanwhile, on the other side (left side in Fig. 1) of the casing body 2A, a pair of supply and discharge passages, i.e., an inflow passage 3A serving as a supply passage and an outflow passage 3B serving as a discharge passage, are provided, as shown by dashed lines in Fig. 1. One of the pair of supply and discharge passages, i.e., the inflow passage 3A, serves as a low-pressure side suction passage and is connected to a tank (not shown). The other of the pair of supply and discharge passages, i.e., the outflow passage 3B, serves as a discharge passage and is connected to a high-pressure side discharge pipe (not shown).

[0018] The rotating shaft 4 is rotatably provided in the casing 2. That is, the rotating shaft 4 extends in the axial direction within the casing 2 and is rotatably supported by the casing main body 2A and the front casing 2B via bearings 19, 19, respectively. In addition, an oil seal 20 serving as a sealing member is provided between the rotating shaft 4 and the front casing 2B.

[0019] One end of the rotating shaft 4 (the right end in FIG. 1) forms a protruding end 4A that protrudes axially from the front casing 2B. A prime mover such as an engine is connected to the protruding end 4A of the rotating shaft 4 via a power transmission mechanism (neither of which is shown). A male spline 4B is formed on the outer circumferential surface of the rotating shaft 4 at a portion that faces the cylinder block 5 in the radial direction. The male spline 4B is splined to a female spline 5A of the cylinder block 5.

[0020] The cylinder block 5 is disposed within the casing 2 so as to rotate integrally with the rotary shaft 4. To this end, the inner circumferential surface of the cylinder block 5 is formed with female splines 5A that are splined to male splines 4B of the rotary shaft 4. One end of the cylinder block 5, i.e., the right end facing the swash plate 10, is provided with a small-diameter end 5B that is smaller in diameter than the other portions. A retainer guide 13 is inserted into the small-diameter end 5B.

[0021] The cylinder block 5 has a plurality of axially extending cylinders 6 spaced apart circumferentially. Each cylinder 6 of the cylinder block 5 is formed with a cylinder port 6A that intermittently communicates with an intake port 8A and a discharge port 8B of a valve plate 8.

[0022] The multiple pistons 7 are inserted and fitted so as to be able to reciprocate (slide) within each cylinder 6 of the cylinder block 5. As the cylinder block 5 rotates, the pistons 7 reciprocate within the cylinder 6 between top dead center and bottom dead center, repeating intake and discharge strokes. Therefore, the pressure within each cylinder 6, which is connected to the high-pressure discharge port 8B, acts on the swash plate 10 via the pistons 7.

[0023] The piston 7 is formed as a cylindrical (or columnar) rod (rod body) overall. The tip end (left end in FIG. 1) of the piston 7 forms a flat surface 7A. Meanwhile, the base end (right end in FIG. 1) of the piston 7 forms a spherical recess 7B to which the spherical portion 9A of the shoe 9 is attached. The piston 7 is provided with an oil supply hole 7C that extends in the axial direction so as to penetrate between the flat surface 7A and the spherical recess 7B. The engagement portion between the spherical portion 9A of the shoe 9 and the spherical recess 7B of the piston 7, as well as the sliding portion between the shoe 9 and the swash plate 10, are lubricated by hydraulic oil supplied through the oil supply hole 7C.

[0024] The valve plate 8 is located inside the casing 2 and fixed to the other side of the casing main body 2A. That is, the valve plate 8 is provided between the casing main body 2A and the cylinder block 5. The valve plate 8 supports the cylinder block 5, which rotates integrally with the rotary shaft 4, so that the valve plate 8 can rotate together with the casing main body 2A. In this state, the valve plate 8 is in sliding contact with the end face of the cylinder block 5.

[0025] The valve plate 8 is formed with a pair of eyebrow-shaped supply and discharge ports, namely, a suction port 8A and a discharge port 8B. The suction port 8A is connected to the inlet passage 3A of the casing body 2A. The discharge port 8B is connected to the outlet passage 3B of the casing body 2A. The suction port 8A and the discharge port 8B of the valve plate 8 intermittently communicate with the cylinder ports 6A of each cylinder 6 as the cylinder block 5 rotates. During this time, the pistons 7 reciprocating within each cylinder 6 draw hydraulic oil into each cylinder 6 from the inlet passage 3A through the suction port 8A during their suction stroke, and then discharge the pressurized oil, which has become high-pressure within each cylinder 6, into the outlet passage 3B through the discharge port 8B during their discharge stroke.

[0026] A plurality of shoes 9 are attached to the protruding ends of the pistons 7 protruding from the cylinders 6 so as to be able to swing. Each shoe 9 has a spherical portion 9A that forms a spherical bearing, and the spherical portion 9A of each shoe 9 is attached to the spherical recess 7B of the piston 7. The shoes 9 are pressed against the smooth surface 10A of the swash plate 10 by the pressing force (hydraulic force) from the pistons 7 and are held in this state via a retainer 12 or the like. In this state, each shoe 9 rotates together with the rotating shaft 4, cylinder block 5, and pistons 7, sliding and displacing on the smooth surface 10A of the swash plate 10 to trace a ring-shaped circular locus.

[0027] The swash plate 10 is tiltably mounted within the casing 2 via a cradle 11. The front surface of the swash plate 10 is a smooth surface 10A that slidably guides each shoe 9. On the other hand, the rear surface of the swash plate 10 is tiltably supported by the cradle 11 on the casing 2 side. For this purpose, the rear surface of the swash plate 10 is provided with a pair of left and right legs 10C that protrude convexly toward the cradle sliding surface (not shown) of the cradle 11.

[0028] The legs 10C of the swash plate 10 are spaced apart from each other across the rotary shaft 4 and are slidably inserted into the cradle sliding surface of the cradle 11. The swash plate 10 is provided with a through-hole 10B extending in the thickness direction of the plate. The through-hole 10B is located between the pair of legs 10C and the rotary shaft 4 is inserted with a gap through it. The swash plate 10 is tilted in the directions of arrows A and B shown in FIG. 1 by a tilt actuator 15 (control piston 18). The discharge capacity (flow rate of pressure oil discharged) of the hydraulic pump 1 is variably controlled according to the tilt angle of the swash plate 10.

[0029] The cradle 11 is located around the rotary shaft 4 and fixed to the casing 2 (more specifically, the front casing 2B). The cradle 11 serves as a swash plate support (swash plate support) for the casing 2. The cradle 11 supports the swash plate 10 so that it can tilt (slide) in the directions indicated by arrows A and B in FIG. 1. The cradle 11 is formed with a shaft insertion hole 11A through which the rotary shaft 4 is inserted with a gap. The cradle 11 is integrally formed with a pair of cradle sliding surfaces on the left and right sides of the shaft insertion hole 11A (i.e., the rotary shaft 4). The cradle sliding surfaces of the cradle 11 support the swash plate 10 (legs 10C) so that it can tilt.

[0030] The retainer 12 is positioned between the protruding end of each piston 7 and each shoe 9, and the rotating shaft 4 is inserted through it. The retainer 12 abuts each shoe 9 against the smooth surface 10A of the swash plate 10. The retainer 12 is an annular plate as a whole, and has a through hole 12A formed in the center. The inner circumferential surface 12B of the through hole 12A is formed, for example, in a concave spherical or tapered shape. The inner circumferential surface 12B of the retainer 12 abuts against the outer circumferential surface 13A of a retainer guide 13, which is inserted onto the rotating shaft 4.

[0031] The retainer 12 holds each shoe 9 relative to the swash plate 10. To this end, the retainer 12 has a plurality of retaining holes 12C spaced apart in the circumferential direction for holding each shoe 9. The retainer 12 presses and holds each shoe 9 against the smooth surface 10A of the swash plate 10, thereby compensating for the sliding displacement of each shoe 9 along a circular path on the smooth surface 10A of the swash plate 10. In this case, the retainer 12 is biased toward the swash plate 10 (smooth surface 10A) by a spring 14 via a retainer guide 13.

[0032] The retainer guide 13 is provided between the retainer 12 and the cylinder block 5. That is, the retainer guide 13 is positioned between the cylinder block 5 and the retainer 12 and is inserted onto the rotary shaft 4. The outer peripheral surface 13A of the retainer guide 13 is formed into a convex spherical shape. The inner peripheral surface 12B of the retainer 12 abuts against the outer peripheral surface 13A of the retainer guide 13. The outer peripheral surface 13A of the retainer guide 13 presses the retainer 12 toward the swash plate 10.

[0033] The spring 14 is provided between the retainer guide 13 and the cylinder block 5 (small diameter end 5B). The retainer guide 13 constantly presses the retainer 12 toward the swash plate 10 by the spring force of the spring 14. In other words, the spring 14 applies an elastic force between the cylinder block 5 (small diameter end 5B) and the retainer guide 13 to the retainer guide 13 and the cylinder block 5 in directions that move them away from each other.

[0034] The tilt actuator 15 drives the tilt of the swash plate 10. The tilt actuator 15 is provided in the casing 2. The tilt actuator 15 includes a control cylinder 16 located radially outside the cylinder block 5 and formed in the casing main body 2A, and a control piston 18, also called a tilt piston (servo piston), slidably inserted into the control cylinder 16 and forming a hydraulic chamber 17 between the control cylinder 16 and the control piston 18.

[0035] The tilt actuators 15 are disposed in positions facing each other in the radial direction of the cylinder block 5 relative to the casing body 2A. The tilt actuators 15 drive the swash plate 10 to tilt in the directions of arrows A and B using a control piston 18. That is, a tilt control pressure is supplied to and discharged from a hydraulic chamber 17 of the tilt actuator 15 from an external source.

[0036] Due to this tilt control pressure, for example, when the control piston 18 of one tilt actuator 15 (e.g., the lower one in FIG. 1) extends from within the control cylinder 16 and the control piston 18 of the other tilt actuator 15 (e.g., the upper one in FIG. 1) contracts within the control cylinder 16, the swash plate 10 is driven to tilt in the direction of arrow A (i.e., the positive direction in which the tilt angle increases).

[0037] In contrast, when the control piston 18 of the other tilt actuator 15 (e.g., the upper one in Figure 1) extends from within the control cylinder 16 and the control piston 18 of one tilt actuator 15 (e.g., the lower one in Figure 1) retracts into the control cylinder 16, the swash plate 10 is driven to tilt in the direction of arrow B (i.e., the opposite direction in which the tilt angle becomes smaller).

[0038] The casing of a hydraulic pump is filled with a fluid (hydraulic oil) pumped by the hydraulic pump. This fluid (hydraulic oil) exists as a lubricant at the contact point between the swash plate and the control piston. However, in conventional technology, lubricant is not actively supplied between the swash plate and the control piston from the outside. Therefore, when the spring force and control pressure (hydraulic force) act on the control piston to press the swash plate, the lubricant film (oil film) at the contact point may break. This may cause metal-to-metal contact at the contact point between the swash plate and the control piston, leading to wear.

[0039] Furthermore, in the prior art, the swash plate and the control piston are not fastened together. Therefore, when the swash plate repeatedly undergoes small oscillations or when the angle of the swash plate is rapidly reversed, the inertial force generated in the control piston can cause the control piston to lift off the swash plate. The lifted control piston can then collide with the swash plate, potentially causing wear at the contact point between the swash plate and the control piston. If wear progresses near the contact point between the control piston and the swash plate, it can become difficult to fine-tune the flow rate of the hydraulic pump. Furthermore, wear debris can become trapped in the components, causing secondary wear and potentially contaminating the hydraulic oil, resulting in various other problems.

[0040] On the other hand, for example, a communication hole could be provided in the control piston, and static pressure (hydraulic oil) could be supplied as a lubricant between the swash plate and the control piston through this communication hole. However, in this case, when the control piston lifts off the swash plate as described above, a large amount of hydraulic oil could leak into the casing from that location, potentially reducing pump performance. Furthermore, excessive pressure could be applied to the sealing member (oil seal) between the rotating shaft of the hydraulic pump and the casing, potentially damaging the sealing member (oil seal).

[0041] Recently, hydraulic rotating machines such as hydraulic pumps and hydraulic motors are required to adjust the swash plate angle quickly in order to reduce the energy consumption of hydraulic systems. Therefore, as the swash plate moves faster, the problems caused by the deterioration of the lubrication at the contact points between the control piston and the swash plate and the floating of the control piston become more pronounced. Furthermore, a heavy swash plate increases its inertia, which increases the time required to adjust the swash plate angle, so a lightweight swash plate is required.

[0042] Therefore, in this embodiment, the hydraulic pump 1, which is a variable displacement swash plate type piston pump, employs the following configuration. Specifically, the control piston 18, which is a servo piston, has a convex spherical shape at the portion that contacts the swash plate 10. In other words, the control piston 18 has a convex spherical surface 21. A communication hole 24 is provided in the center of the control piston 18 to guide static pressure (hydraulic oil) between the control piston 18 and the swash plate 10. The portion of the swash plate 10 that contacts the control piston 18 has a concave spherical shape with the same diameter as the convex spherical surface 21 of the control piston 18. In other words, the swash plate 10 has a concave spherical surface 25 that engages with the convex spherical surface 21 of the control piston 18.

[0043] Furthermore, the concave spherical portion 25 of the swash plate 10 has a recess 26 that allows engagement and disengagement between the convex spherical portion 21 of the control piston 18 and the concave spherical portion 25 of the swash plate 10 when the control piston 18 is tilted. The recess 26 has a main body groove 26B into which a part of the piston main body 22, which serves as the rod portion of the control piston 18, enters.

[0044] The central axis XX of the main body groove 26B is aligned with the central axis O of the swash plate 10. A -O A and the central axis O of the rotation shaft 4 B -O B The swash plate 10 extends in a direction perpendicular to an imaginary plane SS including the swash plate 10. According to this embodiment, lubrication between the swash plate 10 and the control piston 18 can be ensured, lifting of the control piston 18 can be suppressed, assembly can be improved, and the swash plate 10 can be made smaller and lighter. These points will be explained in detail below.

[0045] As shown in FIG. 1, a hydraulic pump 1 as a variable displacement swash plate type hydraulic rotary machine includes a rotating shaft 4, a cylinder block 5, a plurality of pistons 7, a plurality of shoes 9, a swash plate 10, and a tilt actuator 15. The rotating shaft 4 is rotatably disposed within a casing 2. The cylinder block 5 has a plurality of cylinders 6 that are circumferentially spaced apart and extend in the axial direction. The cylinder block 5 rotates integrally with the rotating shaft 4 within the casing 2. The plurality of pistons 7 are respectively inserted into the plurality of cylinders 6 so as to be able to reciprocate. A plurality of shoes 9 are provided at each end of the plurality of pistons 7.

[0046] The swash plate 10 has a front surface 10A that slidably guides the shoes 9, and a rear surface 10B that is supported by a cradle 11 of the casing 2 so that the swash plate 10 can swing. A tilt actuator 15 drives the tilt of the swash plate 10. The tilt actuator 15 has a control piston 18 and a control cylinder 16. The control piston 18 presses the swash plate 10. The control piston 18 is inserted into the control cylinder 16.

[0047] The tilt actuator 15 tilts the swash plate 10 using a plurality of control pistons 18, more specifically, three control pistons 18. In this case, for example, two control pistons 18 are arranged on the discharge port 8B side of the valve plate 8 (upper side in FIG. 1), and one control piston 18 is arranged on the suction port 8A side of the valve plate 8 (lower side in FIG. 1).

[0048] As shown in FIGS. 1, 4, and 8, the control piston 18 has a convex spherical portion 21, a piston body 22, a stepped portion 23, and a communication hole 24. The convex spherical portion 21 is engaged with a concave spherical portion 25 provided on the swash plate 10. As shown in FIG. 2, the concave spherical portion 25 is provided on the outer diameter side of the swash plate 10, i.e., on the outer diameter side of the smooth surface 10A. The concave spherical portion 25 faces the cylinder block 5 in the radial direction across the cylinder block 5. The swash plate 10 is provided with multiple concave spherical portions 25, more specifically, three concave spherical portions 25. In this case, for example, two concave spherical portions 25 are arranged on the discharge port 8B side of the valve plate 8 (upper side in FIGS. 1 to 3), and one concave spherical portion 25 is arranged on the suction port 8A side of the valve plate 8 (lower side in FIGS. 1 to 3).

[0049] As shown in FIG. 1, the tip end side (left end side in FIG. 1) of the piston body 22 of the control piston 18 is inserted into the control cylinder 16. As shown in FIGS. 1, 4, and 8, a step portion 23 connects the base end side (right end side in FIG. 1) of the piston body 22 to the convex spherical portion 21. A communication hole 24 supplies hydraulic fluid between the convex spherical portion 21 and the concave spherical portion 25 of the swash plate 10. The communication hole 24 is located at the center of the control piston 18 and extends in the axial direction.

[0050] 2 to 7, the concave spherical portion 25 of the swash plate 10 has a relief portion 26 and an engagement portion 27. As shown in FIGS. 4 to 7, when the convex spherical portion 21 of the control piston 18 is engaged with the concave spherical portion 25, the step portion 23 of the control piston 18 and the base end side of the piston body 22 enter the relief portion 26. The engagement portion 27, with which the step portion 23 of the control piston 18 abuts, prevents the convex spherical portion 21 of the control piston 18 and the concave spherical portion 25 of the swash plate 10 from separating from each other.

[0051] That is, when the piston body 22 of the control piston 18 is inserted into the control cylinder 16 and the convex spherical portion 21 of the control piston 18 is displaced away from the concave spherical portion 25 of the swash plate 10, the step portion 23 of the control piston 18 comes into contact with the engaging portion 27 of the concave spherical portion 25. This prevents the convex spherical portion 21 of the control piston 18 from displacing further away from the concave spherical portion 25 of the swash plate 10.

[0052] 4 and 5, the recess 26 of the concave spherical surface portion 25 has a pair of stepped grooves 26A and a main body groove 26B. As shown in FIG. 4 and FIG. 5, the stepped portion 23 of the control piston 18 fits into the pair of stepped grooves 26A when the convex spherical surface portion 21 of the control piston 18 is engaged with the concave spherical surface portion 25 of the swash plate 10. The base end side of the piston main body 22 fits between the pair of stepped grooves 26A and the main body groove 26B when the convex spherical surface portion 21 of the control piston 18 is engaged with the concave spherical surface portion 25 of the swash plate 10.

[0053] As shown in FIG. 2, the central axis XX of the main body groove 26B is aligned with the central axis O of the swash plate 10. A -O A and the central axis O of the rotation shaft 4 B -O B The axis XX of the main body groove 26B extends in a direction perpendicular to an imaginary plane SS including the axis XX. Note that "perpendicular" includes not only completely perpendicular but also "almost perpendicular." In other words, "perpendicular" also includes cases where the angle between the central axis XX of the main body groove 26B and the imaginary plane SS deviates from 90° due to, for example, manufacturing errors, processing errors, etc. In other words, "perpendicular" allows for unavoidable deviations due to manufacturing errors, processing errors, etc.

[0054] 2 and 3, the relief portion 26 is disposed closer to the rotation axis 4 than the spherical center T of the concave spherical portion 25. That is, the relief portion 26 is disposed between the spherical center T of the concave spherical portion 25 and the rotation axis 4. In other words, the relief portion 26 is disposed between the spherical center T of the concave spherical portion 25 and the imaginary plane SS. Also, as shown in FIG. 4, the depth H1 of the stepped groove portion 26A is the same as or deeper than the depth H2 of the main body groove portion 26B.

[0055] As shown in FIG. 6, connection portion 26C between step groove portion 26A and main body groove portion 26B forms engagement portion 27 that protrudes toward spherical center T (FIG. 2) of concave spherical portion 25 to a position where the distance from the center T is smaller than the spherical radius R (FIG. 5) of convex spherical portion 21. That is, connection portion 26C between step groove portion 26A and main body groove portion 26B is a protruding engagement portion 27 that protrudes into concave spherical portion 25 to prevent convex spherical portion 21 of control piston 18 from slipping out. For this reason, as shown in FIG. 6, widthwise dimension D of paired step groove portions 26A is larger than the spherical diameter of concave spherical portion 25. Furthermore, in a direction perpendicular to the widthwise direction, the longest dimension C between paired step groove portions 26A and the periphery of concave spherical portion 25 is smaller than the spherical diameter of concave spherical portion 25.

[0056] The tilt angle (tilt angle) of the swash plate 10 provided with such concave spherical portions 25 is changed by the control pistons 18 connected to each concave spherical portion 25. That is, the tilt angle of the swash plate 10 is changed by the balance of the pressures (pressures in the hydraulic chambers 17) in the control cylinders 16 of the control pistons 18 located on the upper side and the control pistons 18 located on the lower side in FIG. 1 . At this time, the tilt angle of the swash plate 10 changes as the convexly curved legs 10C tilt along the cradle sliding surface of the cradle 11. This makes it possible to adjust the discharge flow rate of the hydraulic pump 1.

[0057] The control piston 18 has a convex spherical portion 21 that is pivotally connected to the concave spherical portion 25 of the swash plate 10. The control piston 18 also has a tapered piston body 22 that is inserted into the control cylinder 16. The tip of the piston body 22, located at the rear of the control cylinder 16, forms a cylinder inner surface contact portion 28 that contacts the inner surface of the control cylinder 16. That is, the cylinder inner surface contact portion 28 that contacts the inner surface of the control cylinder 16 is formed integrally with the piston body 22. A piston ring 29 is fitted in the vicinity of the cylinder inner surface contact portion 28.

[0058] A communication hole 24 for supplying static pressure (hydraulic oil) is provided in the center of the control piston 18. This allows hydraulic oil to be supplied between the concave spherical portion 25 of the swash plate 10 and the convex spherical portion 21 of the control piston 18. The concave spherical portion 25 of the swash plate 10 has a recess 26 that allows the concave spherical portion 25 to engage with and disengage from the convex spherical portion 21 of the control piston 18 when the control piston 18 is tilted. The recess 26 has a main body groove 26B that serves as a gap into which a portion of the piston main body 22 of the control piston 18 fits, and a pair of stepped grooves 26A formed near the ends of the main body groove 26B. The stepped portion 23 of the control piston 18 passes through the pair of stepped grooves 26A when the control piston 18 and the swash plate 10 are connected. The distance D (dimension D in the width direction) between the pair of stepped groove portions 26A is slightly larger than the diameter of the convex spherical portion 21 of the control piston 18.

[0059] 4 and 5, when the convex spherical portion 21 of the control piston 18 is engaged with the concave spherical portion 25 of the swash plate 10, the control piston 18 is tilted by a predetermined angle so that the convex spherical portion 21 of the control piston 18 enters the concave spherical portion 25 through the pair of stepped grooves 26A of the relief portion 26. At the same time, the neck portion of the control piston 18, i.e., the base end side of the control piston 18, enters the main body groove 26B. From this state, the tip end side of the control piston 18 (the portion 28 that contacts the cylinder inner surface) is moved clockwise in FIG. 4 around the convex spherical portion 21.

[0060] That is, the control piston 18 is moved in a direction in which the central axis of the control piston 18 and the central axis of the swash plate 10 become parallel (in a direction in which the inclination angle becomes smaller). As a result, the convex spherical portion 21 of the control piston 18 is fitted into the concave spherical portion 25 of the swash plate 10, and the stepped portion 23, which is the notched end face of the convex spherical portion 21, engages with the engaging portion 27 of the concave spherical portion 25 (i.e., the connecting portion 26C between the main groove portion 26B and the pair of stepped grooves 26A). As a result, the control piston 18 is not dislodged during sliding and is connected to the swash plate 10 so as to be able to swing freely.

[0061] The pair of step grooves 26A and main groove 26B are disposed closer to the central axis of the swash plate 10 than the center (spherical center T) of the concave spherical surface 25. That is, the pair of step grooves 26A and main groove 26B are disposed between the center (spherical center T) of the concave spherical surface 25 and the smooth surface 10A. The central axis XX of the main groove 26B is aligned with the oscillation central axis O of the swash plate 10. A -O A and the central axis O of the rotation shaft 4 B -O B The axis O of the rotary shaft 4 extends in a direction perpendicular to the imaginary plane SS including the axis O of the rotary shaft 4. B -O B is the central axis O of the swash plate 10. B -O B It also supports.

[0062] As described above, when engaging the control piston 18 with the swash plate 10 and when disengaging the control piston 18 from the swash plate 10, the control piston 18 needs to be tilted toward the pair of stepped grooves 26A and the main body groove 26B, as shown in Figure 4. On the other hand, when assembling the hydraulic pump 1, after engaging the control piston 18 with the swash plate 10, main components such as the cylinder block 5 and pistons 7 are arranged inside (inner diameter side, center side) of the swash plate 10. This prevents the control piston 18 from tilting toward the inside of the swash plate 10.

[0063] Therefore, by arranging the pair of stepped grooves 26A and the main body groove 26B between the center of the concave spherical surface 25 (spherical center T) and the cylinder block 5, it is possible to prevent the control piston 18 from falling off the swash plate 10 during assembly of the hydraulic pump 1. Although not shown, consider a case in which the pair of stepped grooves and the main body groove are arranged on the opposite side of the cylinder block from the center of the concave spherical surface (spherical center T), i.e., a configuration in which the center of the concave spherical surface (spherical center T) is located between the pair of stepped grooves and the main body groove and the cylinder block. In this case, the control piston may swing radially outward from the cylinder block during assembly of the hydraulic pump, which could cause the control piston to fall off the swash plate, thereby reducing assembly efficiency.

[0064] The central axis XX of the main body groove 26B is the same as the central axis O of the swash plate 10. A -O A and the central axis O of the rotation shaft 4 B -O B The axis O of the rotation shaft 4 extends in a direction perpendicular to the imaginary plane SS including the axis O of the rotation shaft 4. B -O B Although not shown in the figure, the central axis XX of the main body groove is aligned with the central axis O of the rotating shaft. B -O B If the grooves extend in a direction intersecting the center of the swash plate, the center-to-center distance between adjacent spherical recesses must be increased to prevent interference between the stepped grooves of the adjacent spherical recesses. This may result in an increase in the size of the swash plate. In other words, the center-to-center distance between adjacent spherical recesses cannot be minimized in order to reduce the weight of the swash plate.

[0065] In summary, static pressure (hydraulic oil) is supplied between the concave spherical surface 25 of the swash plate 10 and the convex spherical surface 21 of the control piston 18 through the communication hole 24 of the control piston 18. This ensures lubrication between the concave spherical surface 25 of the swash plate 10 and the convex spherical surface 21 of the control piston 18, thereby suppressing oil film breakdown and wear. Furthermore, the control piston 18 and the swash plate 10 are connected by a spherical joint between the convex spherical surface 21 and the concave spherical surface 25. In this case, the step portion 23 of the control piston 18 (i.e., the notched end surface of the convex spherical surface 21) engages with the engaging portion 27 of the concave spherical surface 25 (i.e., the connecting portion 26C between the main groove 26B and the pair of step grooves 26A). This prevents the control piston 18 from separating from (disengaging from) the swash plate 10 when the swash plate 10 oscillates (tilts) during operation of the hydraulic pump 1.

[0066] The pair of step grooves 26A and main body groove 26B are located closer to the rotary shaft 4 than the center of the concave spherical surface 25. This prevents the control piston 18 from moving away from (slipping out of) the swash plate 10 when assembling the hydraulic pump 1. Furthermore, the central axis XX of the main body groove 26B extends in a direction perpendicular to the imaginary plane SS. This allows the adjacent concave spherical surfaces 25 to be closer to each other, thereby reducing the weight of the swash plate 10.

[0067] The hydraulic pump 1 according to the embodiment has the above-described configuration, and its operation will now be described.

[0068] The hydraulic pump 1 converts the rotational motion of the rotating shaft 4 (cylinder block 5) into the motion of oil. When the rotating shaft 4 is driven to rotate by a prime mover such as an engine, the cylinder block 5 rotates integrally with the rotating shaft 4 within the casing 2. This causes multiple shoes 9 to slide and displace along the surface (smooth surface 10A) of the swash plate 10, tracing a ring-shaped trajectory, and in response, each piston 7 repeatedly reciprocates within each cylinder 6.

[0069] During one rotation of the cylinder block 5, each piston 7 repeatedly undergoes an intake stroke in which it slides from top dead center to bottom dead center within the cylinder 6, and a discharge stroke in which it slides from bottom dead center to top dead center. During the intake stroke of the piston 7, for example, hydraulic oil is drawn into the cylinder 6 from the inlet passage 3A side through the intake port 8A of the valve plate 8 and the cylinder port 6A. During the discharge stroke of the piston 7, the piston 7 converts the hydraulic fluid in each cylinder 6 into high-pressure oil and discharges it from the outlet passage 3B side through the cylinder port 6A and the discharge port 8B of the valve plate 8.

[0070] According to the embodiment, the control piston 18 has a communication hole 24 that supplies hydraulic oil (hydraulic fluid, lubricating oil) between the convex spherical surface portion 21 of the control piston 18 and the concave spherical surface portion 25 of the swash plate 10. Therefore, hydraulic oil (static pressure) can be supplied between the swash plate 10 and the control piston 18 through the communication hole 24 of the control piston 18. This ensures lubrication between the swash plate 10 and the control piston 18, thereby suppressing wear.

[0071] The concave spherical surface 25 of the swash plate 10 has an engaging portion 27. The step portion 23 of the control piston 18 abuts against the engaging portion 27, preventing the convex spherical surface 21 of the control piston 18 from separating from the concave spherical surface 25 of the swash plate 10. That is, when the control piston 18 tends to lift off the swash plate 10 due to its inertial force, the engaging portion 27 of the concave spherical surface 25 of the swash plate 10 abuts against the step portion 23 of the control piston 18. This prevents the control piston 18 from lifting off the swash plate 10 and prevents hydraulic oil from leaking into the casing 2 through a gap between the control piston 18 and the swash plate 10. This also improves the tracking ability of the control piston 18 and the swash plate 10. This allows for faster operation of the control piston 18 and the swash plate 10, thereby improving the speed of angle adjustment of the swash plate 10.

[0072] The recess 26 of the concave spherical surface 25 of the swash plate 10 has a pair of step grooves 26A and a main groove 26B. The central axis XX of the main groove 26B is aligned with the central axis O of the swash plate 10. A -O A and the central axis O of the rotation shaft 4 B -O B Therefore, the central axis XX of the main body groove is perpendicular to the central axis O of the rotating shaft. B -O B In comparison with a configuration in which the concave spherical portions 25 of the swash plate 10 extend in a direction intersecting the direction of the arrows, the concave spherical portions 25 of the swash plate 10 can be arranged closer to each other. In other words, the distance between adjacent concave spherical portions 25 can be reduced. This allows the area where the concave spherical portions 25 are provided to be smaller, and the weight of the swash plate 10 can be reduced.

[0073] According to the embodiment, the relief portion 26 is located closer to the rotary shaft 4 than the spherical center T of the concave spherical portion 25. Therefore, when inserting the convex spherical portion 21 of the control piston 18 into the concave spherical portion 25 of the swash plate 10, it is necessary to move (oscillate) the control piston 18 radially outward from the rotary shaft 4 side. In other words, when removing the convex spherical portion 21 of the control piston 18 from the concave spherical portion 25 of the swash plate 10, it is necessary to move (oscillate) the control piston 18 toward the rotary shaft 4 side. On the other hand, when assembling the hydraulic pump 1, which is a hydraulic rotary machine, the convex spherical portion 21 of the control piston 18 is inserted into the concave spherical portion 25 of the swash plate 10 to attach the control piston 18 to the swash plate 10, and then the cylinder block 5 is disposed inside the control piston 18.

[0074] Therefore, after the cylinder block 5 is disposed inside the control piston 18, the control piston 18 is less likely to move (oscillate) toward the rotary shaft 4. This makes it more difficult for the convex spherical portion 21 of the control piston 18 to come out of the concave spherical portion 25 of the swash plate 10. As a result, when assembling the hydraulic pump 1, it is possible to prevent the control piston 18 from coming out of the swash plate 10 (the control piston 18 from falling off the swash plate 10), making it easier to assemble the hydraulic pump 1.

[0075] 4, in the recess 26, the depth H1 of the stepped groove 26A is equal to or greater than the depth H2 of the main groove 26B. Conversely, the depth H2 of the main groove 26B is equal to or less than the depth H1 of the stepped groove 26A. By increasing the depth H2 of the main groove 26B, the convex spherical portion 21 of the control piston 18 can be more easily inserted into the concave spherical portion 25 of the swash plate 10 when the convex spherical portion 21 is engaged with the concave spherical portion 25 of the swash plate 10.

[0076] However, if the depth H2 of the main body groove 26B is deeper than the stepped groove 26A, the hydraulic oil supplied between the convex spherical portion 21 of the control piston 18 and the concave spherical portion 25 of the swash plate 10 through the communication hole 24 of the control piston 18 is likely to leak from the main body groove 26B during operation of the hydraulic pump 1. Therefore, by regulating the relationship between the depth H1 of the stepped groove 26A and the depth H2 of the main body groove 26B as described above, it is possible to ensure ease of installation of the control piston 18 and prevent hydraulic oil from leaking.

[0077] According to the embodiment, connection portion 26C between step groove portion 26A and main body groove portion 26B serves as engagement portion 27 that protrudes toward spherical center T to a position where the distance from the spherical center of concave spherical portion 25 is smaller than the spherical radius of concave spherical portion 25 and / or the spherical radius of convex spherical portion 21. Therefore, step portion 23 of control piston 18 can be brought into contact with connection portion 26C that serves as engagement portion 27.

[0078] According to this embodiment, the widthwise dimension D of the pair of stepped groove portions 26A is larger than the spherical diameter of the concave spherical portion 25. Furthermore, the longest dimension C, in a direction perpendicular to the widthwise direction, between the pair of stepped groove portions 26A and the periphery of the concave spherical portion 25 is smaller than the spherical diameter of the concave spherical portion 25. Therefore, the convex spherical portion 21 of the control piston 18 can be inserted between the pair of stepped groove portions 26A, and the pair of stepped grooves 26A (more specifically, the connection portion 26C between the stepped groove portion 26A and the main groove portion 26B) prevents the convex spherical portion 21 of the control piston 18 from slipping out of the concave spherical portion 25 of the swash plate 10.

[0079] In the above embodiment, the swash plate 10 is provided with three concave spherical portions 25. However, the present invention is not limited to this. For example, as shown in a first modified example in FIG. 9, the swash plate 10 may be provided with four concave spherical portions 25. That is, two concave spherical portions 25 may be arranged on the discharge port 8B side of the valve plate 8 and two concave spherical portions 25 may be arranged on the suction port 8A side of the valve plate 8. Furthermore, as shown in a second modified example in FIG. 10, the swash plate 10 may be provided with two concave spherical portions 25. That is, one concave spherical portion 25 may be arranged on the discharge port 8B side of the valve plate 8 and one concave spherical portion 25 may be arranged on the suction port 8A side of the valve plate 8.

[0080] In the embodiment, an example has been described in which the cylinder inner surface contact portion 28 formed integrally with the piston main body 22 of the control piston 18 slides on the inner surface of the control cylinder 16. However, the present invention is not limited to this, and for example, as in a third modified example shown in Figures 11 and 12, a cylinder inner surface contact portion 31 separate from the piston main body 22 of the control piston 18 may slide on the inner surface of the control cylinder 16.

[0081] That is, in the third modified example, the control piston 18 has a bottomed, cylindrical cylinder inner surface contact portion 31 connected to the piston main body 22 that slides against the inner surface of the control cylinder 16. The piston main body 22 has a distal end provided with a convex spherical engaging protrusion 32. The cylinder inner surface contact portion 31 also has a concave spherical engaging recess 33 that engages with the engaging protrusion 32 of the piston main body 22.

[0082] The engagement (connection) between these engaging protrusions 32 and engaging recesses 33 can be an engagement (connection) that can prevent separation between them, for example, an engagement (connection) by a spherical joint similar to that between the convex spherical portion 21 of the control piston 18 and the concave spherical portion 25 of the swash plate 10. In addition, the cylinder inner surface contact portion 31 is provided with another communication hole 34 that communicates with the communication hole 24 of the piston body 22. This communication hole 34 opens to the inner surface of the engaging recess 33.

[0083] According to the third modified example, the contact area (contact surface) between the control piston 18 (cylinder inner surface contact portion 31) and the inner surface of the control cylinder 16 can be increased, and the surface pressure can be reduced. This also contributes to suppressing wear. For example, even when a large output is required for the tilt actuator 15, such as a large hydraulic pump, the effect of suppressing wear can be more reliably obtained. Meanwhile, in the embodiment, the cylinder inner surface contact portion 28 is formed integrally with the piston main body 22 of the control piston 18, which makes it easier to insert the control piston 18 into the control cylinder 16 and improves workability.

[0084] In the above embodiment, the bottom surface of the concave spherical portion 25 of the swash plate 10 is formed as a uniform concave spherical surface. However, this is not limiting. For example, as shown in a fourth modification in FIG. 13, a hydraulic fluid pocket 35 for storing hydraulic fluid (hydraulic fluid, lubricating fluid) may be provided in the concave spherical portion 25 of the swash plate 10. That is, the hydraulic fluid pocket 35 serving as a hydrostatic pocket may be provided in the bottom surface of the concave spherical portion 25 constituting the spherical joint. In this case, hydraulic fluid (lubricating oil) supplied between the convex spherical portion 21 of the control piston 18 and the concave spherical portion 25 of the swash plate 10 through the communication hole 24 of the control piston 18 can be stored in the hydraulic fluid pocket 35. This allows hydraulic fluid (lubricating oil) to be actively supplied and maintained within the spherical joint, i.e., between the convex spherical portion 21 and the concave spherical portion 25.

[0085] As described above, according to the fourth modification, the hydraulic fluid pocket 35 is provided in the concave spherical portion 25 of the swash plate 10. Therefore, the hydraulic fluid pocket 35 improves the lubrication between the convex spherical portion 21 of the control piston 18 and the concave spherical portion 25 of the swash plate 10.

[0086] In the embodiment, the engaging portion 27 of the concave spherical portion 25, i.e., the connecting portion 26C between the main body groove 26B and the pair of stepped grooves 26A, is angular. In other words, in the embodiment, the angle between the main body groove 26B and the stepped groove 26A is 90°. However, this is not limiting, and for example, as in a fifth modified example shown in FIG. 14, the main body groove 26B and the pair of stepped grooves 26A may be connected by a curved (R-shaped) connecting portion 26C. Although not shown, the connecting portion may be chamfered.

[0087] In the embodiment, the hydraulic pump 1 is described as a single-tilt hydraulic pump in which the swash plate 10 is tilted to one side. However, the present invention is not limited to this, and may be applied to a double-tilt hydraulic pump in which the swash plate is tilted to both sides of a tilt angle of 0. This also applies to the modified example.

[0088] In the embodiment, the hydraulic pump 1 that converts the rotational motion of a cylinder block 5 into the motion of oil has been described as an example of a hydraulic rotating machine. However, the present invention is not limited to this, and may be used as other hydraulic rotating machines, such as a hydraulic motor that converts the motion of oil into the rotation of a cylinder block. For example, in the case of a hydraulic motor, hydraulic oil flows into and out of the cylinder block from a hydraulic source such as a hydraulic pump via a valve plate. This causes the pistons to reciprocate along a swash plate, converting the oil motion into the rotational motion of the cylinder block, thereby converting the oil motion into the rotational motion of a rotating shaft. This also applies to the modified example.

[0089] In the embodiment, the hydraulic pump 1 has been described as being applied to a hydraulic excavator. However, the invention is not limited to this, and may be applied to construction machinery other than hydraulic excavators, such as hydraulic cranes and wheel loaders. Furthermore, the invention is not limited to construction machinery, and may be widely applied as a variable displacement swash plate type hydraulic rotating machine used in various machinery, such as hydraulic pumps and hydraulic motors incorporated in industrial machinery or general machinery.

[0090] The above-described embodiments and modifications are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments and modifications is possible. [Explanation of symbols]

[0091] 1 Hydraulic pump (variable displacement swash plate type hydraulic rotary machine) 2 Casing 4 rotation axes 5 Cylinder block 6 cylinders 7 Pistons 9. Shoe 10 Swash plate 10A smooth surface 15 Tilt Actuator 16 Control cylinder 18 Control piston 21 Convex spherical part 22 Piston body 23 Step 24 Communication hole 25 Concave spherical part 26 Relief 26A Step groove 26B Body groove 26C Connection 27 Engagement part 35 Hydraulic fluid pocket XX Center axis of the body groove O A -O A Swash plate swing axis O B -O B Central axis of the rotating shaft SS Virtual Plane H1 Depth of step groove H2 Depth of the body groove D Width dimension of a pair of stepped grooves C: The longest dimension between the pair of stepped grooves and the periphery of the concave spherical surface

Claims

1. a rotating shaft rotatably provided within the casing; a cylinder block having a plurality of cylinders extending in an axial direction and spaced apart in a circumferential direction, the cylinder block rotating integrally with the rotary shaft within the casing; a plurality of pistons respectively inserted in the plurality of cylinders so as to be capable of reciprocating; a plurality of shoes provided at the respective ends of the plurality of pistons; a swash plate having a front surface that is a smooth surface for slidably guiding the plurality of shoes and a back surface that is supported so as to be swingable relative to the casing; a tilt actuator having a control piston that presses the swash plate and a control cylinder into which the control piston is inserted, and driving the swash plate to tilt; In a variable displacement swash plate type hydraulic rotary machine equipped with The control piston a convex spherical portion that engages with a concave spherical portion provided on the swash plate; a piston body portion whose tip side is inserted into the control cylinder; a step portion connecting a base end side of the piston body portion and the convex spherical portion; a communication hole for supplying hydraulic fluid between the convex spherical surface portion and the concave spherical surface portion of the swash plate, The concave spherical surface portion of the swash plate is a recess into which the step portion and the base end side of the piston main body enter when the convex spherical portion of the control piston is engaged with the concave spherical portion; an engaging portion that prevents the convex spherical portion of the control piston and the concave spherical portion of the swash plate from separating from each other when the step portion of the control piston abuts against the engaging portion, the relief portion includes a pair of stepped grooves into which the stepped portion of the control piston is fitted when the convex spherical portion of the control piston is engaged with the concave spherical portion of the swash plate, and a main body groove into which a base end side of the piston main body is fitted between the pair of stepped grooves, The central axis of the main body groove portion extends in a direction perpendicular to an imaginary plane including the swing central axis of the swash plate and the central axis of the rotation shaft. A variable displacement swash plate type hydraulic rotary machine characterized by the above.

2. the relief portion is disposed closer to the rotation axis than the center of the spherical surface of the concave spherical portion.

2. A variable displacement swash plate type hydraulic rotary machine according to claim 1.

3. The depth of the step groove portion is the same as or deeper than the depth of the main body groove portion.

2. A variable displacement swash plate type hydraulic rotary machine according to claim 1.

4. The connecting portion between the step groove portion and the main body groove portion is the engaging portion that protrudes toward the center of the spherical surface of the concave spherical surface portion to a position where the distance from the center of the spherical surface is smaller than the radius of the spherical surface.

2. A variable displacement swash plate type hydraulic rotary machine according to claim 1.

5. a widthwise dimension (D) of the pair of stepped groove portions is larger than a spherical diameter of the concave spherical portion; a longest dimension (C) between the pair of stepped groove portions and the periphery of the concave spherical portion in a direction perpendicular to the width direction is smaller than a spherical diameter of the concave spherical portion; 2. A variable displacement swash plate type hydraulic rotary machine according to claim 1.

6. A hydraulic fluid pocket for storing hydraulic fluid is provided in the concave spherical surface portion of the swash plate.

2. A variable displacement swash plate type hydraulic rotary machine according to claim 1.

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