Fluid working machine

Abstract

To suppress an inclination of a piston when a rotating shaft rotates.SOLUTION: A fluid working machine comprises: a cylindrical 11 having an accommodation part 11a for accommodating fluid; a piston 21 which performs a reciprocation motion in the cylinder 11 by the pressure of the fluid; and a crankshaft 26 which performs a rotation motion in conjunction with the reciprocation motion of the piston 21. The piston 21 has: a communication path 54 communicating with the accommodation part 11a; and an opposing recess 56 formed at an opposing part 52 opposing a slide face 29 of the crankshaft 26, and supplied with the fluid from the accommodation part 11a via the communication path 54. The opposing recess 56 is formed at the opposing part 52 such that a gravity center position of a force acting on the piston 21 from the fluid in the opposing recess 56 is located at an upstream side in a rotation direction of the crankshaft 26 when viewed from a center axis of the piston 21.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fluid-working machine that performs energy conversion between a fluid and a machine. [Background technology]

[0002] The following Patent Document 1 discloses a radial pump motor that supplies a fluid (oil) to a sliding surface via a through passage that penetrates a piston that reciprocates in a cylinder arranged around a rotating shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-99350 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the oil that is drawn around by the sliding surface of the rotating shaft usually gets in between the piston and the rotating shaft (this is called the dynamic pressure effect). However, when the rotating shaft rotates at high speeds, some of the oil drawn around by the sliding surface may not get between the piston and the rotating shaft, and may instead push the piston from the side. In this case, the piston may tilt relative to the cylinder, causing it to come into contact with the rotating shaft.

[0005] The present invention has been made in consideration of these points, and has an object to suppress tilting of the piston when the rotating shaft rotates. [Means for solving the problem]

[0006] In one aspect of the present invention, there is provided a fluid-working machine comprising a cylinder having a storage portion for storing a fluid, a piston that reciprocates within the cylinder due to the pressure of the fluid, and a rotating shaft that rotates in conjunction with the reciprocating motion of the piston, wherein the cylinders and pistons are arranged in multiple locations circumferentially of the rotating shaft, the piston has a communicating passage communicating with the storing portion, and an opposing recess provided in an opposing portion facing the sliding surface of the rotating shaft, to which the fluid is supplied from the storing portion via the communicating passage, and the opposing recess is provided in the opposing portion so that the center of gravity of the force acting on the piston from the fluid in the opposing recess is located upstream in the rotational direction of the rotating shaft as viewed from the central axis of the piston.

[0007] The opposing recess may also have a rectangular first recess through which the central axis passes, and a second recess that is smaller than the first recess and is connected to the first recess on the upstream side in the rotation direction.

[0008] Furthermore, a width of the first recess in a longitudinal direction along the rotation direction may be greater than a width of the second recess in the longitudinal direction.

[0009] The first recess and the second recess may each have a rectangular planar shape, and the second recess may be connected to the first recess at the center of the first recess in the short side direction.

[0010] The width of the second recess in the short side direction may be smaller than the width of the first recess in the short side direction.

[0011] The communication passage may be provided so as to pass through the piston along the central axis, and the second recess may be located upstream of the communication passage in the rotational direction.

[0012] Furthermore, a width of the first recess in a longitudinal direction along the rotation direction may be greater than a width of the communication passage in the longitudinal direction.

[0013] The opposing recess may be a single recess having a rectangular planar shape, and a center position of the recess may be located upstream in the rotation direction of the rotation shaft as viewed from a central axis of the piston. Effect of the Invention

[0014] According to the present invention, it is possible to suppress tilting of the piston when the rotating shaft rotates. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of a fluid working machine 1 according to one embodiment. [Diagram 2] 2 is a schematic diagram showing the internal configuration of a cylinder 11 and a piston 21. FIG. [Diagram 3] 2 is a schematic diagram showing an opposing recess 56 of the piston 21. FIG. [Figure 4] 4 is a schematic diagram showing a configuration of a piston 121 according to a comparative example. FIG. [Diagram 5] 10 is a schematic diagram showing an internal configuration of a piston 21 according to a modified example. FIG. [Figure 6] 13 is a schematic diagram showing an opposing recess 66 according to a modified example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <Configuration of fluid working machines> A configuration of a fluid working machine according to one embodiment will be described. In the following description, a hydraulic pump motor will be taken 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 is also called a fluid machine, and is generally a device that converts energy between a fluid and a machine. As the fluid, liquids such as water or oil, or gases such as air or gas are used, and applications such as low-speed rotation and high-speed rotation vary depending on the properties of the fluid, such as density and viscosity.

[0017] 1 is a schematic diagram showing the configuration of a fluid working machine 1 according to one embodiment. The fluid working machine 1 is mounted on a vehicle such as a truck. The fluid working machine 1 transmits generated power to drive wheels of the vehicle, for example.

[0018] The fluid working machine 1 has cylinders 11, 12, 13, 14, a first supply passage 16, a second supply passage 18, pistons 21, 22, 23, 24, a crankshaft 26, and valve units 31, 32, 33, 34. Although four cylinders 11-14 and four pistons 21-24 are provided, the present invention is not limited to this, and the numbers of cylinders and pistons may be three or five or more.

[0019] The cylinders 11 to 14 are arranged in the circumferential direction of the crankshaft 26. The four cylinders 11 to 14 are arranged at equal intervals (specifically, at 90 degree intervals) along the circumferential direction.

[0020] The first supply path 16 is a flow path that connects a first chamber 17 that contains a high-pressure fluid to the cylinders 11 to 14. The first supply path 16 branches so that the fluid can be supplied to the four cylinders 11 to 14. The second supply path 18 is a flow path that connects a second chamber 19 that contains a low-pressure fluid to the cylinders 11 to 14. The second supply path 18 also branches so that the fluid can be supplied to the four cylinders 11 to 14.

[0021] The pistons 21-24 are arranged in the circumferential direction of the crankshaft 26, and reciprocate inside the cylinders 11-14. The pistons 21-24 reciprocate due to the pressure of the fluid supplied to the cylinders 11-14. The reciprocating motion of the pistons 21-24 rotates the crankshaft 26 in contact with the pistons 21-24.

[0022] The crankshaft 26 is a rotating shaft that rotates in conjunction with the reciprocating motion of the pistons 21-24. The crankshaft 26 has a shaft portion 27 and a cam portion 28. The shaft portion 27 is the shaft portion of the crankshaft 26. The center of rotation C1 of the shaft portion 27 is located at the position where the central axes C2 of the four pistons 21-24 intersect. The cam portion 28 is provided eccentrically on the outer periphery of the shaft portion 27. The pistons 21-24 contact the outer periphery of the cam portion 28. With this configuration, the reciprocating motion of the pistons 21-24 is converted into the rotational motion of the shaft portion 27 via the cam portion 28.

[0023] The valve units 31-34 regulate the flow of high-pressure fluid in the first chamber 17 and low-pressure fluid in the second chamber 19 to the cylinders 11-14. Each of the valve units 31-34 regulates the flow of fluid to the corresponding cylinders 11-14. For example, the valve unit 31 regulates the flow of fluid to the cylinder 11.

[0024] In the above description, the pistons 21-24 reciprocate due to the pressure of the fluid supplied to the cylinders 11-14, thereby rotating the crankshaft 26. However, this is not limited to the above, and for example, the pistons 21-24 may reciprocate as the crankshaft 26 connected to the vehicle transmission rotates, thereby supplying the fluid in the cylinders 11-14 to the first chamber 17 or the second chamber 19.

[0025] <Detailed structure of cylinder and piston> The cylinders 11 to 14 have the same configuration, and the pistons 21 to 24 have the same configuration. In the following, the detailed configurations of the cylinder 11 and the piston 21 will be described by taking the cylinder 11 and the piston 21 as an example.

[0026] FIG. 2 is a schematic diagram showing the internal configuration of the cylinder 11 and the piston 21. As shown in FIG. The cylinder 11 has a storage portion 11a that stores a fluid. As described above, the fluid is supplied to the storage portion 11a via the valve unit 31. The fluid in the storage portion 11a exerts pressure on the upper surface of the piston 21 (specifically, the upper surface 51a of the main body portion 50 of the piston 21). The fluid stored in the storage portion 11a is oil in this embodiment.

[0027] The piston 21 reciprocates in the cylinder 11 due to the pressure of the fluid in the accommodation portion 11a. Here, the piston 21 receives pressure from the fluid and reciprocates in the direction of the arrow shown in Fig. 2. The piston 21 has a main body portion 50, an opposing portion 52, a communication passage 54, and an opposing recess 56.

[0028] The main body 50 is formed in a cylindrical shape. An upper surface 51a of the main body 50 contacts the accommodation portion 11a of the cylinder 11. The upper surface 51a receives pressure from the fluid in the accommodation portion 11a. When the upper surface 51a receives pressure, the piston 21 moves downward in FIG. 2. A gap is formed between an outer peripheral surface 51b of the main body 50 and an inner wall surface 11b of the cylinder 11.

[0029] The facing portion 52 is a portion that faces the sliding surface 29 of the cam portion 28 of the crankshaft 26. The facing portion 52 is the lower portion of the piston 21, and is integrated with the main body portion 50. Unlike the cylindrical main body portion 50, the facing portion 52 here is a rectangular parallelepiped. The facing surface 53, which is the lower surface of the facing portion 52, is curved so as to be parallel to the sliding surface 29 of the cam portion 28.

[0030] The communication passage 54 is a flow path provided in the piston 21, and communicates with the accommodation portion 11a of the cylinder 11. The communication passage 54 is provided so as to penetrate the piston 21 along the central axis C2. Specifically, the communication passage 54 is provided so as to penetrate the center of the main body portion 50 and the opposing portion 52.

[0031] The facing recess 56 is a recess provided on the central side of the facing surface 53 of the facing portion 52. The facing recess 56 is in communication with the communication passage 54. A fluid is supplied from the accommodation portion 11a through the communication passage 54 to the facing recess 56. Since the pressure of the fluid in the accommodation portion 11a is higher than the pressure of the fluid in the facing recess 56, the fluid in the accommodation portion 11a is supplied to the facing recess 56. Specifically, when a high-pressure fluid is supplied from the first chamber 17 (FIG. 1) to the accommodation portion 11a, the fluid in the accommodation portion 11a is supplied to the facing recess 56. The oil, which is the fluid supplied to the facing recess 56, forms an oil film on the sliding surface 29 and reduces friction between the piston 21 and the cam portion 28. That is, the oil supplied to the facing recess 56 functions as a lubricant between the piston 21 and the cam portion 28.

[0032] A force (hereinafter referred to as a reaction force) from the oil present between the opposing recess 56 and the sliding surface 29 acts uniformly on the entire bottom surface 56a of the opposing recess 56. The piston 21 receives this reaction force and moves upward in FIG. 2. Therefore, the piston 21 reciprocates relative to the cylinder 11 due to this reaction force and the pressure from the fluid in the accommodation portion 11a.

[0033] Incidentally, the opposing recess 56 is not disposed symmetrically with respect to the central axis C2 of the piston 21. Specifically, the opposing recess 56 is formed on the opposing surface 53 such that the center of gravity of the reaction force acting on the entire bottom surface 56a (the center of gravity can also be said to be the center of all the reaction forces acting on the bottom surface 56a) is located upstream in the rotation direction of the crankshaft 26 as viewed from the central axis C2 of the piston 21. In FIG. 2, the reaction force acting on the center of gravity is designated as reaction force F. For ease of explanation, reaction forces acting on places other than the center of gravity of the bottom surface 56a are not shown in FIG. 2.

[0034] A specific configuration of the opposing recess 56 will be described below with reference to FIG. 3 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. The opposing recess 56 has a first recess 57 and a second recess 58, as shown in FIG.

[0035] The first recess 57 is formed so as to be recessed a predetermined depth from the opposing surface 53. The first recess 57 communicates with the communication passage 54 at a bottom surface 56a. The first recess 57 is formed at a position through which the central axis C of the piston 21 passes. Therefore, the center of the bottom surface of the first recess 57 communicates with the communication passage 54.

[0036] The planar shape of the first recess 57 is rectangular as shown in Fig. 3. The first recess 57 is formed larger than the communication passage 54. The longitudinal width L1 and lateral width L3 of the first recess 57 along the rotational direction are larger than the longitudinal width (in other words, the diameter) of the communication passage 54.

[0037] The second recess 58 is located upstream of the communication passage 54 in the rotation direction (at one end in the longitudinal direction shown in FIG. 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 bottom surface 56a described above. Since the second recess 58 is connected to the first recess 57, the opposing recess 56 is not symmetrical with respect to the central axis C2 of the piston 21, and the center of gravity of the reaction force acting on the opposing recess 56 is also shifted from the central axis C2 of the piston 21 (see FIG. 2).

[0038] The second recess 58 has a rectangular planar shape similar to the first recess 57. As shown in Fig. 3, the second recess 58 is connected to the first recess 57 at the center of the first recess 57 in the short side direction. Specifically, the second recess 58 is located at the same position as the communication passage 54 in the short side direction. As a result, the reaction force acting on the opposing recess 56 is located at the center in the short side direction, and the behavior of the piston 21 when it moves is stable.

[0039] 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 (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 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 the width L3 of the first recess 57 in the lateral direction. By adjusting the width L2 in the longitudinal direction of the second recess 58 having the above-mentioned shape, it becomes easier to adjust the center of gravity of the reaction force acting on the opposing recess 56 without changing the shape of the first recess 57.

[0040] By shifting the center of gravity of the reaction force acting on the opposing recess 56 upstream in the rotation direction from the central axis of the piston 21, it is possible to prevent the piston 21 from coming into contact with the sliding surface 29 of the crankshaft 26 when the crankshaft 26 rotates. This will be described in detail below in comparison with a comparative example shown in Fig. 4.

[0041] Fig. 4 is a schematic diagram showing the configuration of piston 121 according to a comparative example. Opposing recess 156 of piston 121 of the comparative example is provided symmetrically with respect to the central axis of piston 121 as shown in Fig. 4(a). Therefore, the position of the center of gravity of the reaction force acting on opposing recess 156 coincides with the central axis of piston 121. Since the configuration of piston 121 of the comparative example other than opposing recess 156 is similar to that of piston 21 described above, detailed description will be omitted. Usually, the oil drawn by the sliding surface 29 of the crankshaft 26 enters between the opposing portion 52 and the sliding surface 29 (dynamic pressure effect). However, in the comparative example, when the crankshaft 26 rotates at high speed, part of the oil drawn by the sliding surface 29 does not enter between the opposing portion 52 of the piston 121 and the sliding surface 29, but presses the side wall of the opposing portion 52 from the side. In this case, the force pressing the side wall of the opposing portion 52 from the side (force P shown in FIG. 4(b)) causes the piston 121 to tilt with respect to the cylinder 11 as shown in FIG. 4(b). Then, the tilted piston 121 comes into contact with the sliding surface 29 of the crankshaft 26, causing wear of the piston 121 and the sliding surface 29.

[0042] In contrast, in this embodiment, the opposing recess 56 is formed so that the center of gravity of the reaction force acting on the piston 21 from the oil in the opposing recess 56 is located upstream of the rotation direction of the crankshaft 26 as viewed from the central axis of the piston 21. In this case, the reaction force is more likely to act upstream of the central axis C2 of the piston 21 in the rotation direction, so that the upstream side of the rotation direction of the piston 21 is more likely to float due to the reaction force (i.e., the piston 21 is slightly inclined with respect to the cylinder 11). As a result, even when the crankshaft 26 rotates at a high speed, the oil that is dragged around by the sliding surface 29 is more likely to enter between the opposing portion 52 of the piston 21 and the sliding surface 29, so that the opposing portion 52 can be prevented from being pushed sideways. As a result, the piston 21 is prevented from tilting, and therefore the piston 21 can be prevented from contacting the sliding surface 29.

[0043] (Modification) Fig. 5 is a schematic diagram showing an internal configuration of the piston 21 according to a modified example. Fig. 6 is a schematic diagram showing an opposing recess 66 according to a modified example.

[0044] The opposing recess 56 of the piston 21 described above has a first recess 57 and a second recess 58 (see FIG. 3). In contrast, the opposing recess 66 of the piston 21 according to the modified example is a single recess 67 having a rectangular planar shape, as shown in FIG. 6. The recess 67 here has the same configuration as the first recess 57 of the opposing recess 56 described above. Specifically, the planar shape of the recess 67 is rectangular.

[0045] On the other hand, the center position of the recess 67 is different from the center position of the first recess 57. The center position of the recess 67 is located upstream in the rotation direction of the crankshaft as seen from the central axis C2 of the piston 21. In other words, the center position of the recess 67 is shifted from the center of the communication passage 54. As a result, the center position of the opposing recess 66 is shifted from the center of the communication passage 54.

[0046] Even in this modified example, the center of gravity of the force acting on the piston 21 from the fluid in the opposing recess 66 (the position where the reaction force F acts in FIG. 5) is located upstream in the rotational direction of the crankshaft 26 as viewed from the central axis C2 of the piston 21. For this reason, the reaction force is more likely to act upstream in the rotational direction of the central axis C2 of the piston 21, so that the upstream side of the rotational direction of the piston 21 is more likely to float due to the reaction force. As a result, the oil swept around by the sliding surface 29 is more likely to enter between the opposing portion 52 of the piston 21 and the sliding surface 29, so that it is possible to prevent the opposing portion 52 from being pushed sideways and causing the piston 21 to tilt.

[0047] In the above description, the recess 67 has the same shape as the first recess 57, but is not limited to this. For example, the longitudinal width of the recess 67 may be greater than the longitudinal width of the first recess 57. In this case, the lateral width of the recess 67 may be smaller than the lateral width of the first recess 57.

[0048] <Effects of this embodiment> The piston 21 of the fluid working machine 1 of the embodiment described above has a communication passage 54 communicating with the accommodation portion 11a, and an opposing recess 56 that is provided in the opposing portion 52 facing the sliding surface 29 of the crankshaft 26 and to which a fluid (oil) is supplied from the accommodation portion 11a via the communication passage 54. The opposing recess 56 is provided in the opposing portion 52 so that the center of gravity of the reaction force acting from the oil in the opposing recess 56 to a bottom surface 56a of the opposing recess 56 is located upstream of the central axis of the piston 21 in the rotation direction of the rotation shaft. In the above configuration, a reaction force is likely to act on the upstream side in the rotation direction of the central axis C2 of the piston 21, so that the upstream side in the rotation direction of the piston 21 is likely to float due to the reaction force. As a result, even when the crankshaft 26 rotates at high speed, the oil circulated by the sliding surface 29 is likely to enter between the opposing portion 52 of the piston 21 and the sliding surface 29, so that the opposing portion 52 is prevented from being pushed sideways. As a result, the piston 21 is prevented from tilting, so that the piston 21 is also prevented from contacting the sliding surface 29.

[0049] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0050] 1 Fluid-operated machines 11~14 cylinders 11a Storage section 21~24 Piston 26 Crankshaft 29 Sliding surface 52 Opposing part 54 Communication path 56 Opposite recess 57 First recess 58 Second recess 66 Opposite recess 67 Recess C2 center axis

Claims

1. A cylinder having a container for containing a fluid; a piston that reciprocates within the cylinder due to the pressure of the fluid; a rotating shaft that rotates in conjunction with the reciprocating motion of the piston; A fluid working machine comprising: a plurality of the cylinders and the pistons arranged in a circumferential direction of the rotating shaft, The piston is A communication passage communicating with the storage portion; a counter recess provided in a portion facing the sliding surface of the rotating shaft, the counter recess receiving the fluid from the storage portion through the communication passage; a fluid-working machine, wherein the opposing recess is provided in the opposing portion so that the center of gravity of a force acting on the piston from the fluid in the opposing recess is located upstream in the rotational direction of the rotation shaft as viewed from a central axis of the piston.

2. The opposing recessed portion is A rectangular first recess through which the central axis passes; a second recess portion that is smaller than the first recess portion and is connected to the first recess portion on the upstream side in the rotation direction; 2. A fluid-working machine according to claim 1.

3. A width of the first recess in a longitudinal direction along the rotation direction is larger than a width of the second recess in the longitudinal direction. A fluid-working machine according to claim 2.

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

5. The width of the second recess in the short side direction is smaller than the width of the first recess in the short side direction. A fluid-working machine according to claim 4.

6. The communication passage is provided to pass through the piston along the central axis, The second recess is located upstream of the communication passage in the rotation direction. A fluid-working machine according to claim 2.

7. A width of the first recess in a longitudinal direction along the rotation direction is larger than a width of the communication passage in the longitudinal direction. A fluid-working machine according to claim 6.

8. The facing recess is a single recess having a rectangular planar shape, A center position of the recess is located upstream of a central axis of the piston in a rotation direction of the rotation shaft.

2. A fluid-working machine according to claim 1.

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