Variable displacement piston device

Abstract

The utility model discloses a variable capacity piston device, even in the case where the supporting ball uses steel material, can fully ensure the wear resistance, load resistance, can realize the low cost. The structure of the utility model discloses a variable capacity piston device is characterized in that, have: cylinder barrel (110), it is supported in the casing (102) in the mode that can rotate with the shaft (104) together, a plurality of pistons (112) are inserted in the cylinder barrel (110) in the mode that can slide along the axial direction, the inclined plate (120) makes the stroke change of piston (112), and two supporting balls (130) support the inclined plate (120) as can rotate, and the supporting ball (130) uses the steel material of tempering temperature 500 DEG C or more, and the surface is implemented with soft nitriding treatment.

Description

Technical Field

[0001] This utility model relates to a variable capacity piston device for use in construction machinery, industrial machinery, etc. Background Technology

[0002] Variable capacity piston devices are sometimes used in construction machinery and industrial machinery. Specifically, examples include variable capacity piston pumps and variable capacity piston motors. One type, the swashplate variable capacity piston pump, can change the pump's capacity by tilting the swashplate (also known as a cyclone plate).

[0003] For example, Patent Document 1 discloses a variable capacity pump having "a cylinder and a swashplate, the cylinder being supported within a housing in a manner rotatable with a shaft, the swashplate being slidably in contact with the heads of a plurality of pistons inserted into the cylinder in a manner axially slidable, and being supported within the housing in a manner that prevents relative rotation with respect to the shaft." In the variable capacity pump of Patent Document 1, the swashplate is pressed by a drive device disposed in the housing, tilting about two ball bearings or cylindrical bodies forming an axis orthogonal to the axis of rotation of the shaft, thereby changing the tilt angle of the swashplate.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 2915559 Utility Model Content

[0007] Problems to be solved by the utility model

[0008] In the variable capacity pump of Patent Document 1, two balls are formed from a ceramic material containing "92-99.5% by weight of alumina (Al2O3) and the balance of unavoidable impurities such as SiO2, CaO2, MgO, and trace amounts of Na2O, K2O, and Fe". The hardness of typical bearing copper SUJ2 is around HV840, while the hardness of typical ceramics is a high level of around HV1600.

[0009] To machine (grind) high-hardness ceramics to the precision (ball diameter, sphericity, surface roughness, etc.) required for use as a ball supporting an inclined plate, special abrasive grains with a hardness higher than HV1600 are needed for extended processing. Therefore, while the ceramic balls used in Patent Document 1 are excellent from the perspective of wear resistance, they suffer from difficulties in mass production and high costs.

[0010] In view of this problem, the present invention aims to provide a variable capacity piston device that can fully ensure wear resistance and load resistance even when the support ball is made of steel, and can achieve low cost.

[0011] Solution for solving the problem

[0012] To address the aforementioned issues, the representative structural feature of the variable capacity piston device of this invention is that it comprises: a cylinder supported within a housing in a manner rotatable with a shaft; a plurality of pistons inserted into the cylinder in a manner slidable axially; a ramp plate that allows for variation in the piston stroke; and two support balls that support the ramp plate for rotation, the support balls being made of steel with a tempering temperature of 500°C or higher and having undergone soft nitriding treatment on their surface.

[0013] Preferably, the support ball has micro-pits formed by micro-shot peening.

[0014] The steel used for the support ball can be any one of high-speed tool steel, hot-rolled alloy tool steel, martensitic stainless steel, or molybdenum-based high-speed steel.

[0015] Preferably, the variable capacity piston device further comprises: two cylindrical bores formed in the inclined plate at positions opposite to the two support balls; and two ball guides housed in the cylindrical bores and supporting the support balls, the ball guides having a cylindrical outer peripheral surface and a concave spherical surface supporting the support balls, one or both of the ball guides being eccentric relative to the outer peripheral surface and capable of rotating within the cylindrical bores of the inclined plate.

[0016] Effects of the utility model

[0017] According to this invention, a variable capacity piston device can be provided, which can fully ensure wear resistance and load resistance even when the support ball is made of steel, and can achieve low cost. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating a variable-capacity piston pump, which is a variable-capacity piston device according to this embodiment.

[0019] Figure 2 This is a diagram illustrating the details of the inclined plate and the supporting ball.

[0020] Figure 3 This is a diagram illustrating the details of the inclined plate and supporting ball in a modified embodiment.

[0021] Figure 4 This is a diagram illustrating the spacing between a pair of cylindrical holes.

[0022] Explanation of reference numerals in the attached figures

[0023] D1, Axial; 100, Piston Pump; 102, Housing; 102a, Hemispherical Bore; 104, Shaft; 110, Cylinder; 112, Piston; 112a, Head; 114, Piston Slipper; 120, Inclined Plate; 120a, Through Hole; 122, Cylindrical Bore; 130, Support Ball; 140, Ball Guide; 142, Outer Peripheral Surface; 144, Concave Spherical Surface; 190, Spring Unit; 192, Spring; 194, Spring Seat Detailed Implementation

[0024] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in these embodiments are merely illustrative examples for ease of understanding of the invention and, unless specifically stated otherwise, do not limit the scope of the invention. Furthermore, in this specification and the accompanying drawings, elements having substantially the same function or structure are omitted from repeated description by using the same reference numerals; additionally, elements not directly related to the present invention are omitted from illustration or description.

[0025] Figure 1 This is a diagram illustrating a variable capacity piston pump (hereinafter referred to as piston pump 100) as a variable capacity piston device in this embodiment. Figure 1 (a) is a diagram illustrating the internal structure of the piston pump 100. Figure 1 (b) is Figure 1 (a) is a cross-sectional view of section AA. Furthermore, in this embodiment, a variable capacity piston is exemplified as a variable capacity piston device, but the present invention can also be applied to a variable capacity piston motor.

[0026] The piston pump 100 of this embodiment is a device that supplies fluids such as working oil to construction machinery or industrial machinery (not shown) through a discharge port (not shown). Figure 1 As shown in (a), the piston pump 100 of this embodiment has a housing 102. A cylinder 110 is disposed within the housing 102 and is supported so as to be able to rotate together with the shaft 104 (shaft).

[0027] A plurality of pistons 112 are inserted into the cylinder 110 and are capable of sliding along the axial direction D1 of the shaft 104. The plurality of pistons 112 are arranged in the circumferential direction of the cylinder 110 and reciprocate when the cylinder 110 is rotated, discharging working oil from the discharge port. In addition, the piston head 112a is mounted on a piston slide 114 that slides against the inclined plate 120.

[0028] The inclined plate 120 is supported within the housing 102 in a manner that is rotational but not relative to the shaft 104, and the stroke of the piston 112 is varied by tilting. Figure 1As shown in (b), the inclined plate 120 has an insertion hole 120a through which the shaft 104 is inserted.

[0029] In addition, such as Figure 1 As shown in (b), the inclined plate 120 is supported by two support balls 130 so that it can rotate. Furthermore, as... Figure 1 As shown in (a), the piston pump 100 is provided with a spring unit 190 for pressing the inclined plate 120. The spring unit 190 has a spring 192 and a spring seat 194.

[0030] The spring unit 190 is configured to generate a torque in the opposite direction (counterclockwise) to the clockwise torque generated on the inclined plate 120 with the support ball 130 as the fulcrum by the hydraulic pressure from the plurality of pistons 112. With this configuration, the inclined plate 120 tilts about the support ball 130 using the clockwise torque generated by the hydraulic pressure and the counterclockwise torque generated by the load of the spring unit 190.

[0031] Figure 2 This is a diagram illustrating the details of the inclined plate 120 and the support ball 130. Figure 2 (a) is a diagram showing the state in which the inclined plate 120 is supported by the support ball 130. Figure 2 (b) is the front view and sectional view of the ball guide 140.

[0032] like Figure 1 (b) and Figure 2 As shown in (a), hemispherical holes 102a are formed on the housing 102 at positions corresponding to the two support balls 130, respectively, to hold the support balls 130. In addition, "hemispherical hole" not only refers to a hole in the shape of bisecting the ball, but also includes several shapes that support a portion of the support ball 130 in a way that prevents it from falling off the support structure, allowing it to rotate.

[0033] Furthermore, two cylindrical holes 122 are formed in the inclined plate 120 at positions opposite to the two support balls 130. Two ball guides 140, which support the support balls 130, are housed in the two cylindrical holes 122. Thus, the inclined plate 120 is supported on the housing 102 via the support balls 130. Figure 2 As shown in (b), the two ball guides 140 have a cylindrical outer peripheral surface 142 and a concave spherical surface 144 that supports the support ball 130.

[0034] Furthermore, in this embodiment, the support ball 130 is made of steel with a tempering temperature of 500°C or higher. Examples of steel include high-speed tool steel (JIS G4403…SKH2 / SKH3 / SKH4 / SKH10 / SKH40 / SKH50 / SKH51 / SKH52 / SKH53 / SKH54 / SKH55 / SKH56 / SKH57 / SKH58 / SKH59), hot-rolled alloy tool steel (JIS G4404…SKD4 / SKD5 / SKD6 / SKD61 / SKD62), and martensitic stainless steel (JIS G4404…SKD4 / SKD5 / SKD6 / SKD61 / SKD62). G4303…SUS4303 / SUS410 / SUS410J1 / SUS410F2 / SUS416 / SUS420J1 / SUS420J2 / SUS420F / SUS420F2 / SUS431 / SUS440A / SUS440B / SUS440C / SUS440F), molybdenum-based high-speed steel (AISI…M1 / M2 / M10 / M50).

[0035] Furthermore, as a feature of this embodiment, the support ball 130 made of the aforementioned steel is subjected to soft nitriding treatment on its surface and has micro-pits formed based on micro-shot peening treatment.

[0036] Soft nitriding is a surface treatment process that involves combining nitrogen (N) with iron (Fe) on the surface of a metal to form a thin, hard Fe3N layer (shown in shaded area). In this embodiment, the steel used to support the ball was subjected to soft nitriding (salt bath soft nitriding) at a temperature of approximately 580°C for no more than 3 hours. The result is a compound layer (nitrided layer) with a hardness of HV900 or higher and a depth of less than 30 μm on the surface of the treated steel, while the hardness inside the ball is HV400 (≈HRC40) or higher. This soft nitriding treatment improves the wear resistance and load-bearing capacity of the support ball.

[0037] Here, by using steel with a tempering temperature of 500°C or higher as the material for the support ball 130, the decrease in hardness is minimal even after soft nitriding treatment. Therefore, even after soft nitriding treatment following heat treatment (quenching and tempering), the decrease in hardness of the support ball 130 can be prevented.

[0038] Micro-peening is a surface modification (surface shaping) process that uses particles with diameters of tens to hundreds of μm to penetrate (collide) a metal surface at high speeds of over 100 m / sec, creating micro-pits. Examples of particles used include steel particles, stainless steel particles, glass particles, ceramic particles, indium lead particles, tin particles, silver particles, molybdenum disulfide particles, tungsten disulfide particles, boron nitride particles, and fluoropolymer particles.

[0039] According to the piston pump 100 of this embodiment, by performing soft nitriding treatment on the steel that forms the support ball 130, sufficient wear resistance and load-bearing capacity required for supporting the inclined plate 120 can be ensured in the support ball 130. Furthermore, by performing micro-shot peening treatment on the support ball 130 based on the soft nitriding treatment, the hardness can be further improved through work hardening. In addition, by forming micro-pits on the surface of the support ball 130, the concave portions of the micro-pits serve as oil reservoirs, resulting in smooth flow.

[0040] As described above, the support ball 130 has a shorter processing time than ceramic balls, enabling mass production and thus higher productivity. Therefore, the support ball 130 of this embodiment has a lower cost compared to ceramic support balls. Furthermore, although the support ball 130 is made of steel, its wear resistance, load-bearing capacity, and durability are adequately ensured, enabling cost reduction of the variable capacity piston device.

[0041] Furthermore, the same wear resistance and load-bearing capacity can be achieved by performing soft nitriding and shot peening on the ball guide 140 instead of the support ball 130. However, the ball guide 140 is larger and has a larger surface area than the support ball 130. Additionally, if the ball guide 140 is treated, it would require treatment on both the housing 102 and the ramp 120, totaling four ball guides 140. This significantly increases the overall cost of the soft nitriding and shot peening treatments; therefore, it is preferable to treat the support ball 130.

[0042] (Modified example)

[0043] A variation of this embodiment will be described. Figure 3 This is a diagram illustrating the details of the inclined plate 120 and the support ball 130 in a modified embodiment. Figure 3 (a) is a diagram showing the state in which the inclined plate 120 is supported by the support ball 130. Figure 3 (b) is the front view and sectional view of the ball guide 140. Figure 3 (c) is a diagram showing the state in which the support ball 130 is removed from the inclined plate 120.

[0044] like Figure 1 (b) and Figure 3As shown in (a), hemispherical holes 102a are formed on the housing 102 at positions corresponding to the two support balls 130, respectively, to hold the support balls 130. Additionally, two cylindrical holes 122 are formed in the inclined plate 120 at positions opposite to the two support balls 130. Two ball guides 140 that support the support balls 130 are housed in the two cylindrical holes 122. Thus, the inclined plate 120 is supported on the housing 102 via the support balls 130. Furthermore, "hemispherical hole" refers not only to a hole shaped like a ball bisected, but also to several shapes that support a portion of the support ball 130 in a way that prevents it from detaching from the support structure, allowing it to rotate.

[0045] like Figure 3 As shown in (b), the two ball guides 140 have cylindrical outer peripheral surfaces 142 and concave spherical surfaces 144 that support the support ball 130. As a feature of the piston pump 100 of this embodiment, the center C2 of the concave spherical surface 144 of the ball guide 140 is eccentric relative to the center C1 of the outer peripheral surface 142. This eccentricity is set as t. Furthermore, the ball guide 140 is rotatable within the cylindrical bore 122 of the inclined plate 120.

[0046] Figure 4 This is a diagram illustrating the spacing between a pair of cylindrical holes 122. Figure 4 (a) to Figure 4 (e) illustrates a state in which the ball guide 140 is not contained in a pair of cylindrical holes 122. Figure 4 (f) to Figure 4 Example (j) illustrates a state in which a ball guide 140 supporting a support ball 130 is housed in a pair of cylindrical holes 122.

[0047] exist Figure 4 In the inclined plate 120 of (c), the spacing between a pair of cylindrical holes 122 is a predetermined interval L. That is, Figure 4 The spacing of the pair of cylindrical holes 122 in the inclined plate 120 of (c) did not deviate. In contrast, Figure 4 The inclined plate 120 of (a) deviated by a amount of "-2t" relative to the specified interval L. Figure 4 The inclined plate 120 of (b) deviates by a amount of "-t" relative to the specified interval L.

[0048] in addition, Figure 4 The inclined plate 120 of (d) deviates by a amount of "+t" relative to the specified interval L. Figure 4 The inclined plate 120 of (e) deviates by a amount of "+2t" relative to the specified interval L. Figure 4 (f) to Figure 4 The spacing of the pair of cylindrical holes 122 of (j) respectively corresponds to Figure 4 (a) to Figure 4 (e)

[0049] In such Figure 4 If the spacing between the pair of cylindrical holes 122, such as the inclined plate 120 in (c), does not deviate, then... Figure 4 As shown in (h), the center-to-center spacing of the support balls 130 supported on the ball guide 140 is also L. At this time, the rotation angle of the ball guide 140 in the cylindrical hole 122 is 0°, and the center-to-center spacing of the concave spherical surfaces 144 is also L.

[0050] In contrast, in such Figure 4 of (f), Figure 4 of (g), Figure 4 (i) and Figure 4 In the case where the spacing of a pair of cylindrical bores 122 is misaligned as in (j), the ball guide 140 housed in the pair of cylindrical bores 122 is pressed against the support ball 130 via the inclined plate 120 due to the hydraulic pressure of the plurality of pistons 112 and the load of the spring unit 190, and rotates within the cylindrical bore 122 in imitation of (pressing) the support ball 130.

[0051] As a specific example, in Figure 4 of (g), Figure 4 In (i), the spacing of the cylindrical holes 122 is L±t, but by rotating ±30° through the ball guide 140, the center spacing of the concave spherical surfaces 144 becomes L. Similarly, in Figure 4 of (f), Figure 4 In (j), the spacing of the cylindrical holes 122 is L±2t, but by rotating the ball guide 140 ±90°, the center spacing of the concave spherical surfaces 144 becomes L. Thus, the deviation in the spacing of a pair of cylindrical holes 122, i.e., the deviation in the spacing of a pair of spherical holes, is absorbed. Therefore, the supporting ball 130 and the concave spherical surface 144 can slide across the entire surface, improving the wear resistance of the supporting ball 130 and the inclined plate 120, preventing abnormal changes in performance (capacity) caused by changes in the support angle of the inclined plate due to wear, and preventing damage caused by significant wear.

[0052] It should be noted that, in this modified example, a structure is illustrated in which the concave spherical surfaces of the two ball guides 140, which are housed in the two cylindrical holes 122 formed in the inclined plate 120 and support the support ball 130, are eccentric relative to the outer peripheral surface, but this is not a limitation. For example, this invention can also be applied to a structure in which only the concave spherical surface of one of the two ball guides 140 is eccentric relative to the outer peripheral surface, and to two ball guides housed in the two cylindrical holes formed in the housing 102 and support the support ball.

[0053] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to these examples. It will be apparent to those skilled in the art that various modifications or alterations will be conceived within the scope of the claims, and these modifications or alterations naturally fall within the technical scope of the present invention.

[0054] Industrial availability

[0055] This invention can be used as a variable capacity piston device in construction machinery, industrial machinery, etc.

Claims

1. A variable capacity piston device, characterized in that, have: The cylinder barrel is supported within the housing in a manner that allows it to rotate with the shaft; Multiple pistons are inserted into the cylinder in a manner that allows them to slide axially. An inclined plate that causes the piston's stroke to change; as well as Two supporting balls support the inclined plate so that it can rotate. The support ball is made of steel with a tempering temperature of 500°C or higher, and its surface is subjected to soft nitriding treatment.

2. The variable capacity piston device according to claim 1, characterized in that, The support ball has micro-pits formed based on micro-shot peening treatment.

3. The variable capacity piston device according to claim 1, characterized in that, The steel used for the supporting ball is any one of high-speed tool steel, hot-rolled alloy tool steel, martensitic stainless steel, or molybdenum-based high-speed steel.

4. The variable capacity piston device according to any one of claims 1 to 3, characterized in that, The variable capacity piston device also features: Two cylindrical holes are formed on the inclined plate at positions opposite to the two supporting balls; and Two ball guides are received within the cylindrical bore and support the support balls. The ball guide has a cylindrical outer peripheral surface and a concave spherical surface that supports the supporting ball. One or both of the ball guides are eccentric relative to the outer peripheral surface and are capable of rotating within the cylindrical hole of the inclined plate.

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