Fluid working machine

Abstract

The fluid working machine comprises: a cylinder (11) having a housing portion (11a) for containing a fluid; a piston (21) that reciprocates in the cylinder (11); and a crankshaft (26) that performs a rotational motion in conjunction with the reciprocating motion of the piston (21). The piston (21) has an opposing recess (56) provided in an opposing portion (52) facing a sliding surface (29) of the crankshaft (26) to which fluid is supplied from the housing portion (11a) via the communication path (54). A facing recess (56) is provided in the facing portion (52) such that a center-of-gravity position of a force acting on the piston (21) from a fluid in the facing recess (56) is located upstream in a rotational direction of the crankshaft (26) when viewed from a central axis of the piston (21).

Description

Technical Field

[0001] The present disclosure relates to a fluid working machine that performs energy conversion between a fluid and a machine. Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2011-99350 discloses a radial pump motor that supplies fluid (oil) to a sliding surface via a passage through a piston that reciprocates in a cylinder provided around a rotation axis. Summary of the invention

[0003] Problems to be solved by the present invention

[0004] Oil entrained by the sliding surface of the rotating shaft usually enters between the piston and the rotating shaft (called "dynamic pressure effect"). However, when the rotating shaft rotates at a high speed, there is a case where some of the oil entrained by the sliding surface does not enter between the piston and the rotating shaft, but pushes the piston from the side. In this case, the piston may tilt relative to the cylinder, which may cause the piston to contact the rotating shaft.

[0005] The present disclosure is mainly directed to this point, and its purpose is to prevent the piston from tilting when the rotary shaft rotates.

[0006] Means used to solve problems

[0007] According to one aspect of the present disclosure, a fluid working machine is provided, which includes: a cylinder having a shell part for accommodating a fluid; a piston, which reciprocates in the cylinder due to the pressure of the fluid; and a rotating shaft, which performs a rotating motion in combination with the reciprocating motion of the piston, wherein a plurality of cylinders and pistons are arranged in the circumferential direction of the rotating shaft in the fluid working machine, and the piston includes: a communicating path, which is connected to the shell part; and a relative recess, which is arranged in a relative part of a sliding surface facing the rotating shaft, and the fluid is supplied to the relative recess from the shell part via the communicating path, and the relative recess is arranged in the relative part so that when viewed from the central axis of the piston, the center of gravity position of the force acting on the piston from the fluid in the relative recess is located upstream of the rotating shaft in the rotation direction.

[0008] The opposing recess may include a first recess having a rectangular shape through which the central axis passes, and a second recess that is smaller than the first recess and connected to the first recess at an upstream side in the rotation direction.

[0009] In addition, the width of the first recess in the longitudinal direction along the rotation direction may be greater than the width of the second recess in the longitudinal direction.

[0010] In addition, the planar shape of each of the first recess and the second recess may be a rectangle, and the second recess may be connected to the first recess at the center of the first recess in the lateral direction.

[0011] In addition, the width of the second recess in the lateral direction may be smaller than the width of the first recess in the lateral direction.

[0012] In addition, the communication path may be provided such that the communication path passes through the piston along the center axis, and the second recessed portion may be located upstream of the communication path in the rotational direction.

[0013] In addition, the width of the first recess in the longitudinal direction along the rotation direction may be greater than the width of the communication path in the longitudinal direction.

[0014] In addition, the center of the bottom surface of the first recess may coincide with the center of the communication path. In addition, the position of the second recess may be the same as the position of the bottom surface of the first recess in the axial direction of the piston.

[0015] In addition, the opposing recess may be a recess having a rectangular planar shape, and the center position of the recess may be located upstream of the rotation axis in the rotation direction when viewed from the center axis of the piston.

[0016] Effects of the Invention

[0017] According to the present disclosure, it is possible to prevent the piston from tilting when the rotary shaft rotates. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a schematic diagram showing the configuration of a fluid working machine 1 according to one embodiment.

[0019] Figure 2 2 is a schematic diagram showing the internal structure of the cylinder 11 and the piston 21 .

[0020] Figure 3 2 is a schematic diagram showing the opposing recessed portion 56 of the piston 21 .

[0021] Figure 4A and Figure 4B Each is a schematic diagram showing a configuration of a piston 121 according to a comparative example.

[0022] Figure 5 2 is a schematic diagram showing the internal configuration of a piston 21 according to a modified example.

[0023] Figure 6 is a schematic diagram showing the opposing recessed portion 66 according to a modified example.

[0024] Description of Reference Numerals

[0025] 1Fluid working machine

[0026] 11 to 14 cylinders

[0027] 11a Shell part

[0028] 21 to 24 pistons

[0029] 26 Crankshaft

[0030] 29 Sliding surface

[0031] 52 Relative part

[0032] 54 Connectivity Path

[0033] 56 Relative concave part

[0034] 57 First recess

[0035] 58 Second recess

[0036] 66 Relative concave part

[0037] 67 recess

[0038] C2 Center axis DETAILED DESCRIPTION

[0039] <Structure of Fluid Working Machine>

[0040] The construction of a fluid working machine according to one embodiment will be described below. In the following description, a hydraulic pump motor is described as an example of a fluid working machine, but the fluid working machine is not limited to a hydraulic pump motor. A fluid working machine, also known as a fluid machine, is generally a device that converts energy between a fluid and a machine. Liquids such as water and oil and gases such as air and gas are used as fluids. Depending on the properties of the fluid such as density and viscosity, applications such as low-speed rotation, high-speed rotation, etc. vary.

[0041] Figure 1 1 is a schematic diagram showing a configuration of a fluid working machine 1 according to one embodiment. Here, the fluid working machine 1 is mounted on a vehicle such as a truck. For example, the fluid working machine 1 transmits the generated power to the driving wheels of the vehicle.

[0042] The fluid working machine 1 includes cylinders 11, 12, 13 and 14, a first supply path 16, a second supply path 18, pistons 21, 22, 23 and 24, a crankshaft 26, and valve units 31, 32, 33 and 34. Although four cylinders and four pistons are provided, the number of cylinders and pistons is not limited thereto and may be three or five or more.

[0043] The cylinders 11 to 14 are arranged in the circumferential direction of the crankshaft 26. The cylinders 11 to 14 are arranged counterclockwise at equal intervals (specifically, at 90 degree intervals) along the circumferential direction.

[0044] The first supply path 16 is a flow path connecting the cylinders 11 to 14 to the first chamber 17 storing the high-pressure fluid. The first supply path 16 is branched so that the fluid can be supplied to the cylinders 11 to 14. The second supply path 18 is a flow path connecting the cylinders 11 to 14 to the second chamber 19 storing the low-pressure fluid. The second supply path 18 is also branched so that the fluid can be supplied to the cylinders 11 to 14.

[0045] The pistons 21 to 24 are arranged in the circumferential direction of the crankshaft 26, and reciprocate in the cylinders 11 to 14. The pistons 21 to 24 reciprocate due to the pressure of the fluid supplied to the cylinders 11 to 14. By reciprocating the pistons 21 to 24, the crankshaft 26 in contact with the pistons 21 to 24 rotates.

[0046] The crankshaft 26 is a rotating shaft that performs a rotational motion in combination with the reciprocating motion of the pistons 21 to 24. The crankshaft 26 includes a shaft member 27 and a cam member 28. The shaft member 27 is an axial portion of the crankshaft 26. The rotation center C1 of the shaft member 27 is located at a position where the center axis C2 of the pistons 21 to 24 intersects. The cam member 28 is eccentrically disposed relative to the outer periphery of the shaft member 27. The pistons 21 to 24 are in contact with the outer peripheral surface of the cam member 28. With this configuration, the reciprocating motion of the pistons 21 to 24 is converted into the rotational motion of the shaft member 27 via the cam member 28.

[0047] The valve units 31 to 34 regulate the flow of the high-pressure fluid in the first chamber 17 and the low-pressure fluid in the second chamber 19 to the cylinders 11 to 14. Each of the valve units 31 to 34 regulates the flow of the fluid to the corresponding cylinder 11 to 14. For example, the valve unit 31 regulates the flow of the fluid into the cylinder 11.

[0048] In the above description, the crankshaft 26 is rotated by reciprocating the pistons 21 to 24 due to the pressure of the fluid supplied to the cylinders 11 to 14. However, the present disclosure is not limited thereto. For example, the crankshaft 26 coupled to the transmission of the vehicle may rotate, and its rotation may reciprocate the pistons 21 to 24, thereby supplying the fluid in the cylinders 11 to 14 to the first chamber 17 or the second chamber 19.

[0049] <Detailed structure of cylinder and piston>

[0050] The configuration of each of the cylinders 11 to 14 is the same, and the configuration of each of the pistons 21 to 24 is the same. Hereinafter, the cylinder 11 and the piston 21 will be used as an example, and the detailed configurations of the cylinder 11 and the piston 21 will be described in detail.

[0051] Figure 21 is a schematic diagram showing the internal configuration of the cylinder 11 and the piston 21. The cylinder 11 includes a housing portion 11a that contains a fluid. As described above, the fluid is supplied to the housing portion 11a via the valve unit 31. The fluid in the housing portion 11a applies pressure to the upper surface of the piston 21 (specifically, the upper surface 51a of the main body portion 50 of the piston 21). Here, the fluid contained in the housing portion 11a is oil.

[0052] The piston 21 reciprocates in the cylinder 11 due to the pressure of the fluid in the housing portion 11A. Here, the piston 21 reciprocates in the cylinder 11 by receiving the pressure from the fluid. Figure 2 The piston 21 reciprocates in the direction of the arrow shown. The piston 21 includes a main body member 50 , a facing portion 52 , a communication path 54 , and a facing recess 56 .

[0053] The main body member 50 is formed in a columnar shape. The upper surface 51a of the main body member 50 is located in the housing portion 11a of the cylinder 11. The upper surface 51a receives the pressure from the fluid in the housing portion 11a. By receiving the pressure from the fluid, the upper surface 51a causes the piston 21 to move in a Figure 2 A gap is formed between the outer peripheral surface 51b of the main body member 50 and the inner wall surface 11b of the cylinder 11.

[0054] The opposing portion 52 is an opposing portion of the sliding surface 29 of the cam member 28 facing the crankshaft 26. The opposing portion 52 is a lower portion of the piston 21 and is integral with the main body member 50. Here, unlike the columnar main body member 50 which is a columnar shape, the opposing portion 52 has a rectangular parallelepiped shape. An opposing surface 53 which is a lower surface of the opposing portion 52 is a curved surface so as to be parallel to the sliding surface 29 of the cam member 28.

[0055] The communication path 54 is a flow path provided in the piston 21 and communicates with the housing portion 11a of the cylinder 11. The communication path 54 is provided so as to pass through the piston 21 along the center axis C2. Specifically, the communication path 54 is provided so as to pass through the center of the body member 50 and the opposing portion 52.

[0056] The opposing recess 56 is provided on the central portion of the opposing surface 53 of the opposing portion 52. The opposing recess 56 is communicated with the communication path 54. The fluid is supplied from the housing portion 11a to the opposing recess 56 via the communication path 54. Since the pressure of the fluid in the housing portion 11a is higher than the pressure of the fluid in the opposing recess 56, the fluid in the housing portion 11a is supplied to the opposing recess 56. Specifically, when the high-pressure fluid is supplied from the first chamber 17 ( Figure 1) is supplied to the housing portion 11a, the fluid in the housing portion 11a is supplied to the relative recess 56. The oil as the fluid supplied to the relative recess 56 forms an oil film on the sliding surface 29, thereby reducing the friction between the piston 21 and the cam member 28. That is, the oil supplied to the relative recess 56 serves as lubricating oil between the piston 21 and the cam member 28.

[0057] The force (hereinafter referred to as the reaction force) from the oil existing between the relative recess 56 and the sliding surface 29 acts uniformly on the entire bottom surface 56a of the relative recess 56. By receiving the reaction force, the piston 21 Figure 2 Therefore, the piston 21 reciprocates relative to the cylinder 11 due to the reaction force and the pressure from the fluid in the housing portion 11a.

[0058] The relative recess 56 is not symmetrically arranged with respect to the central axis C2 of the piston 21. Specifically, the relative recess 56 is formed on the relative surface 53 so that when viewed from the central axis C2 of the piston 21, the center of gravity position of the reaction force acting on the entire bottom surface 56a (the center of gravity position may be referred to as the center position of the total reaction force acting on the bottom surface 56a) is located upstream of the crankshaft 26 in the rotation direction (in the vicinity of the crankshaft 26). Figure 2 The center of gravity is located on the left side of the central axis C2). Figure 2 In the equation, the reaction force acting on the center of gravity is expressed as reaction force F. Figure 2 In the figure, for convenience of explanation, the reaction force acting on the position other than the center of gravity of the bottom surface 56a is not shown.

[0059] The following will refer to Figure 3 The specific configuration of the opposing recessed portion 56 is described. Figure 3 2 is a schematic diagram showing the opposing recess 56 of the piston 21, and is a view of the opposing surface 53 viewed from the sliding surface 29. Figure 3 As shown, the opposite recess 56 has a first recess 57 and a second recess 58 .

[0060] The first recess 57 is formed to be recessed from the opposing surface 53 to a predetermined depth. The first recess 57 is communicated with the communication path 54 at the bottom surface 56a. The first recess 57 is formed at a position where the center axis C2 of the piston 21 passes. The first recess 57 is arranged so that the center of the bottom surface 56a coincides with the center of the communication path 54 (i.e., the center axis C2). Therefore, the center portion of the bottom surface of the first recess 57 is communicated with the communication path 54.

[0061] like Figure 3As shown, the planar shape of the first recess 57 is a rectangle. The first recess 57 is formed to be larger than the communication path 54. The width L1 in the longitudinal direction and the width L3 in the lateral direction of the first recess 57 along the rotation direction are larger than the width (in other words, diameter) of the communication path 54 in the longitudinal direction.

[0062] The second recessed portion 58 is located upstream of the communication path 54 in the rotation direction (at Figure 3 The second recess 58 is connected to the first recess 57 at one end in the longitudinal direction. The bottom surface of the second recess 58 and the bottom surface of the first recess 57 form the above-mentioned bottom surface 56a. In other words, the position of the bottom surface of the second recess 58 is the same as the position of the bottom surface of the first recess 57 in the axial direction of the piston 21 (see FIG. Figure 2 Since the second recess 58 is connected to the first recess 57, the relative recess 56 does not have a symmetrical shape with respect to the central axis C2 of the piston 21, and the center of gravity position of the reaction force acting on the relative recess 56 also deviates from the central axis C2 of the piston 21 (see Figure 2 ).

[0063] The planar shape of the second recess 58 is a rectangle, in the same manner as the first recess 57. Figure 3 As shown, the second recess 58 is connected to the first recess 57 at the center of the first recess 57 in the lateral direction. Specifically, the second recess 58 is located at the same position as the communication path 54 in the lateral direction. In this way, the reaction force acting on the opposite recess 56 is centered in the lateral direction, thereby stabilizing the behavior of the piston 21 during movement.

[0064] The size of the second recess 58 is smaller than that of the first recess 57. Specifically, the width L2 of the second recess 58 in the longitudinal direction (the direction along the rotation direction) is smaller than the width L1 of the first recess 57 in the longitudinal direction. More specifically, the width L2 of the second recess 58 in the longitudinal direction is smaller than half of the width L1 of the first recess 57 in the longitudinal direction. In addition, the width L4 of the second recess 58 in the lateral direction is smaller than the width L3 of the first recess 57 in the lateral direction. More specifically, the width L4 of the second recess 58 in the lateral direction is smaller than half of the width L3 of the first recess 57 in the lateral direction. By adjusting the width L2 of the second recess 58 having the above-mentioned shape in the longitudinal direction, the position of the center of gravity of the reaction force acting on the relative recess 56 can be easily adjusted without changing the shape of the first recess 57.

[0065] Since the center of gravity of the reaction force acting on the relative recess 56 is offset upstream from the central axis of the piston 21 in the rotation direction, the piston 21 can be prevented from contacting the sliding surface 29 of the crankshaft 26 when the crankshaft 26 rotates. Figure 4A and Figure 4B The comparative example shown describes this embodiment in detail.

[0066] Figure 4A and Figure 4B Each is a schematic diagram showing the configuration of a piston 121 according to a comparative example. Figure 4A As shown, the relative recess 156 of the piston 121 of the comparative example is symmetrically arranged with respect to the central axis of the piston 121. Therefore, the center of gravity position of the reaction force acting on the relative recess 156 coincides with the central axis of the piston 121. In the piston 121 of the comparative example, since the structure other than the relative recess 156 is the same as the above-mentioned piston 21, its detailed description is omitted. Normally, the oil entrained by the sliding surface 29 of the crankshaft 26 enters between the relative portion 52 and the sliding surface 29 (dynamic pressure effect). However, in the comparative example, when the crankshaft 26 rotates at a high speed, a portion of the oil entrained by the sliding surface 29 does not enter between the relative portion 52 and the sliding surface 29 of the piston 121, but pushes the side wall of the relative portion 52 from the side. In this case, as Figure 4B As shown, the piston 121 pushes the side wall of the opposite part 52 from the side ( Figure 4B The force P shown in FIG. 1 is caused to tilt relative to the cylinder 11. Therefore, the tilted piston 121 contacts the sliding surface 29 of the crankshaft 26, causing wear on the piston 121 and the sliding surface 29.

[0067] In contrast, in the present embodiment, the relative recess 56 is formed so that when viewed from the center axis of the piston 21, the center of gravity position of the reaction force from the oil in the relative recess 56 acting on the piston 21 is located upstream of the crankshaft 26 in the rotation direction. In this case, since the reaction force is more likely to act on the upstream side of the center axis C2 of the piston 21 in the rotation direction, the upstream side of the piston 21 in the rotation direction is more likely to be lifted due to the reaction force (i.e., the piston 21 is slightly tilted relative to the cylinder 11). Therefore, even if the crankshaft 26 rotates at a high speed, the oil entrained by the sliding surface 29 easily enters between the relative portion 52 of the piston 21 and the sliding surface 29, so that the relative portion 52 can be prevented from being pushed from the side. Therefore, since the inclination of the piston 21 is suppressed, the contact of the piston 21 with the sliding surface 29 can be suppressed.

[0068] (Variation Example)

[0069] Figure 5 2 is a schematic diagram showing the internal configuration of a piston 21 according to a modified example. Figure 6 is a schematic diagram showing the opposing recessed portion 66 according to a modified example.

[0070] The opposing recess 56 of the piston 21 has a first recess 57 and a second recess 58 (see Figure 3). On the other hand, Figure 6 As shown, the relative recess 66 of the piston 21 according to the modified example is a recess 67 having a rectangular planar shape. Here, the recess 67 has the same configuration as the first recess 57 of the relative recess 56 described above. Specifically, the planar shape of the recess 67 is a rectangle.

[0071] On the other hand, the center position of the recess 67 is different from the center position of the first recess 57. When viewed from the center axis C2 of the piston 21, the center position of the recess 67 is located upstream of the crankshaft in the rotation direction. That is, the center position of the recess 67 is displaced from the center of the communication path 54. Therefore, the center position of the relative recess 66 is displaced from the center of the communication path 54.

[0072] Also in the modified example, when viewed from the central axis C2 of the piston 21, the center of gravity position ( Figure 5 The position where the reaction force F acts in the rotation direction is located upstream of the crankshaft 26. Therefore, since the reaction force is more likely to act on the upstream side of the center axis C2 of the piston 21 in the rotation direction, the upstream side of the piston 21 in the rotation direction is more likely to be lifted due to the reaction force. Therefore, since the oil entrained by the sliding surface 29 easily enters between the opposing portion 52 of the piston 21 and the sliding surface 29, the piston 21 is prevented from tilting, thereby preventing the opposing portion 52 from being pushed from the side.

[0073] In the above description, the recess 67 has the same shape as the first recess 57, but is not limited thereto. For example, the width of the recess 67 in the longitudinal direction may be greater than the width of the first recess 57 in the longitudinal direction. In this case, the width of the recess 67 in the lateral direction may be less than the width of the first recess 57 in the lateral direction.

[0074] <Effects of this embodiment>

[0075] The piston 21 of the fluid working machine 1 of the above-mentioned embodiment has: a communication path 54, which is communicated with the housing portion 11a; and a relative recess 56, which is provided in the relative portion 52 and faces the sliding surface 29 of the crankshaft 26. Fluid (oil) is supplied to the relative recess 56 from the housing portion 11a via the communication path 54. The relative recess 56 is provided in the relative portion 52 so that when viewed from the central axis of the piston 21, the center of gravity position of the reaction force from the oil in the relative recess 56 acting on the bottom surface 56A of the relative recess 56 is located upstream of the rotation axis in the rotation direction. In the above-mentioned configuration, since the reaction force is more likely to act on the upstream side of the central axis C2 of the piston 21 in the rotation direction, the upstream side of the piston 21 in the rotation direction is more likely to be lifted due to the reaction force. Therefore, even if the crankshaft 26 rotates at a high speed, the oil entrained by the sliding surface 29 easily enters between the relative portion 52 and the sliding surface 29 of the piston 21, so that the relative portion 52 can be prevented from being pushed from the side. Therefore, since the inclination of the piston 21 is suppressed, the contact of the piston 21 with the sliding surface 29 can be suppressed.

[0076] The present disclosure is explained based on exemplary embodiments. The technical scope of the present disclosure is not limited to the scope explained in the above-mentioned embodiments, and various changes and modifications can be made within the scope of the present disclosure. For example, all or part of the present device can be constructed with any unit that is functionally or physically dispersed or integrated. In addition, new exemplary embodiments generated by any combination of them are included in the exemplary embodiments of the present disclosure. In addition, the effect of the new exemplary embodiment brought about by the combination also has the effect of the original exemplary embodiment.

Claims

1. A fluid working machine, comprising: a cylinder having a housing portion for containing a fluid; a piston that reciprocates in the cylinder due to the pressure of the fluid; as well as a rotating shaft that performs a rotating motion in combination with the reciprocating motion of the piston, wherein A plurality of the cylinders and the pistons are arranged in the fluid working machine in the circumferential direction of the rotating shaft. The piston comprises: a communication path communicating with the housing portion; and a relative recessed portion provided in an opposite portion of the sliding surface facing the rotating shaft and to which the fluid is supplied from the housing portion via the communicating path, and The opposing recess is provided in the opposing portion such that the position of the center of gravity of the force acting on the piston from the fluid in the opposing recess is located upstream of the rotation axis in the rotation direction when viewed from the center axis of the piston.

2. The fluid working machine according to claim 1, wherein: The relative recess comprises: a first recess having a rectangular shape through which the central axis passes; and A second recessed portion that is smaller than the first recessed portion and is connected to the first recessed portion on an upstream side in the rotation direction.

3. The fluid working machine according to claim 2, wherein: The width of the first recess in the longitudinal direction along the rotation direction is greater than the width of the second recess in the longitudinal direction.

4. The fluid working machine according to claim 2, wherein: The first recess and the second recess each have a rectangular planar shape, and The second recess is connected to the first recess at the center of the first recess in the lateral direction.

5. The fluid working machine according to claim 4, wherein: The width of the second recess in the lateral direction is smaller than the width of the first recess in the lateral direction.

6. The fluid working machine according to claim 2, wherein: The communication path is arranged such that the communication path passes through the piston along the central axis, and The second recessed portion is located upstream of the communication path in the rotation direction.

7. The fluid working machine according to claim 6, wherein: The width of the first recessed portion in the longitudinal direction along the rotation direction is larger than the width of the communication path in the longitudinal direction.

8. The fluid working machine according to claim 2, wherein: The center of the bottom surface of the first recess coincides with the center of the communication path.

9. The fluid working machine according to claim 2, wherein: The position of the second recess is the same as the position of the bottom surface of the first recess in the axial direction of the piston.

10. The fluid working machine according to claim 1, wherein: The relative recess is a recess having a rectangular planar shape, and When viewed from the central axis of the piston, the center position of the recessed portion is located upstream of the rotation axis in the rotation direction.

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