Piston assembly and fluid pressure cylinder

Abstract

The utility model provides a piston assembly and a fluid pressure cylinder. A piston assembly (14) and a fluid pressure cylinder (10) are provided with a piston rod (50) extending in the axial direction, a piston (48) attached to the outer peripheral portion of the piston rod (50), and a caulking portion (70) connecting the piston (48) and the piston rod (50) by crushing the tip of the piston rod (50), the piston rod (50) having a shaft hole (74) penetrating the center portion in the axial direction, and a seal member (54) sealing the shaft hole (74). The caulking part (70) has a stopper (76) that protrudes toward the shaft hole (74) and prevents the seal member (54) from falling off.

Description

Technical Field

[0001] The utility model relates to a piston assembly and a fluid pressure cylinder. Background Art

[0002] A piston assembly for a fluid pressure cylinder has a piston rod and a piston mounted on the outer peripheral portion of the piston rod. Depending on the type of piston assembly, there may be a case where the piston and the piston rod are connected integrally by riveting the piston rod.

[0003] In the piston assembly, a technique of making the piston rod into a hollow tubular shape has been proposed (Japanese Utility Model Laid-Open No. 61-1703).

[0004] In the case of achieving high-speed operation and high-frequency operation of the fluid pressure cylinder, as described in Japanese Utility Model Laid-Open No. 61-1703, it is effective to make the piston rod into a hollow tubular shape to reduce the weight. Such a piston rod has a sealing member in the hollow portion to prevent leakage of the fluid in the cylinder chamber.

[0005] The sealing member reciprocates together with the piston rod. Therefore, in the case of high-speed operation of the fluid pressure cylinder, a large acceleration is applied to the sealing member. If the fixing of the sealing member is insufficient, the sealing member may fall off from the piston rod. On the other hand, in the structure as described in Japanese Utility Model Laid-Open No. 61-1703, there is a problem that the weight of the sealing member and the fixing structure increases, and thus the weight of the piston rod increases. Summary of the Utility Model

[0006] The purpose of the utility model is to solve the above technical problems.

[0007] One aspect of the following utility model is a piston assembly, comprising: a piston rod extending in the axial direction; a piston mounted on the outer peripheral portion of the piston rod; and a riveting portion that crushes the tip of the piston rod to connect the piston and the piston rod. The piston rod has: a shaft hole axially penetrating the central portion of the piston rod; and a sealing member inserted into the shaft hole to seal the shaft hole. The riveting portion has a stopper that protrudes toward the shaft hole and prevents the sealing member from falling off.

[0008] Another view is a fluid pressure cylinder, comprising: a cylinder tube; a head cover that seals the top end of the cylinder tube; a rod cover that seals the base end of the cylinder tube; and a piston assembly, at least a part of which is received inside the cylinder tube. The piston assembly includes: a piston rod that extends axially and passes through the rod cover; a piston that is mounted on the outer periphery of the piston rod and slides inside the cylinder tube; and a riveting portion that crushes the top end of the piston rod to connect the piston to the piston rod. The piston rod has: an axial hole that axially penetrates the central portion of the piston rod; and a sealing member that is inserted into the axial hole to seal the axial hole. The riveting portion has a stopper that protrudes toward the axial hole and prevents the sealing member from falling off.

[0009] The above structure can fix the sealing member to the piston rod with sufficient strength without increasing the weight of the hollow tubular piston rod.

[0010] The above objects, features, and advantages should be easily understood from the following description of the embodiments with reference to the drawings. Description of the Drawings

[0011] Figure 1 is a cross-sectional view of the fluid pressure cylinder according to an embodiment of the present invention.

[0012] Figure 2A is Figure 1 a cross-sectional view of the process of installing a piston on the piston rod of, Figure 2B is Figure 2A a cross-sectional view of the process of installing the sealing member on the piston rod of, Figure 2C is a cross-sectional view of the process of riveting the top end portion of the piston rod. Detailed Description of the Embodiments

[0013] As Figure 1 shown, the fluid pressure cylinder 10 according to an embodiment of the present invention includes a cylinder body 12 and a piston assembly 14. The piston assembly 14 performs a protruding action and a pulling-in action by the supply / discharge of fluid to / from the cylinder body 12. The fluid pressure cylinder 10 is used in an automated manufacturing line of a factory or the like.

[0014] The cylinder body 12 of the fluid pressure cylinder 10 has: a cylinder tube 16, a head cover 18, and a rod cover 20. The cylinder tube 16 is a cylindrical member having a cylinder chamber 22 that axially penetrates inside. The head cover 18 is mounted on the top end side (head side) of the cylinder tube 16, and the rod cover 20 is mounted on the base end side (rod side). The top end of the cylinder chamber 22 is sealed by the head cover 18, and the base end is sealed by the rod cover 20.

[0015] The head cover 18 has: a head-side port 24, a central hole 26, and a first shock absorber 28. The head-side port 24 opens on the outer peripheral surface of the head cover 18. The head-side port 24 is connected to a pipe for supplying / discharging fluid. The central hole 26 is formed inside the head cover 18. The head-side port 24 communicates with the central hole 26. The central hole 26 is a hole formed at the center of the head cover 18 and opens toward the cylinder chamber 22. The top end of the central hole 26 is sealed by an end wall 18a of the head cover 18. The first shock absorber 28 is installed so as to project from the base end of the head cover 18 toward the cylinder chamber 22. The first shock absorber 28 is a cylindrical member made of an elastic member such as rubber or an elastomer, for example. When the piston assembly 14 moves toward the top end, the first shock absorber 28 mitigates the impact caused by the collision between the piston assembly 14 and the head cover 18.

[0016] The rod cover 20 mainly has: a rod-side port 32, an insertion through-hole 34, a second shock absorber 36, and a sliding portion 38. The rod-side port 32 opens on the outer peripheral surface of the rod cover 20. The insertion through-hole 34 is formed inside the rod cover 20. The rod-side port 32 communicates with the insertion through-hole 34. The rod-side port 32 is connected to a pipe for supplying / discharging fluid. The rod-side port 32 communicates with the cylinder chamber 22 via the insertion through-hole 34. The insertion through-hole 34 extends in the axial direction along the center of the rod cover 20 and penetrates the rod cover 20 in the axial direction. The insertion through-hole 34 allows the piston rod 50 of the piston assembly 14 to pass through. The insertion through-hole 34 has a diameter larger than the outer diameter of the piston rod 50, thereby forming a rod-side flow path 40 for fluid to flow between the piston rod 50. The rod-side flow path 40 is a flow path connecting the cylinder chamber 22 and the rod-side port 32 and supplies / discharges fluid to / from the base end of the cylinder chamber 22. The second shock absorber 36 mitigates the impact caused by the collision between the piston assembly 14 and the rod cover 20.

[0017] The sliding portion 38 is provided in the insertion through-hole 34. The sliding portion 38 is located at the base end side compared to the rod-side port 32. The sliding portion 38 has: a guide member 42, a rod gasket 44, and a snap ring 46. The guide member 42 slidably abuts against the outer peripheral surface of the piston rod 50 to guide the displacement direction of the piston assembly 14 in the axial direction. The rod gasket 44 is disposed adjacent to the base end of the guide member 42. The rod gasket 44 closes the gap between the piston rod 50 and the insertion through-hole 34 to prevent fluid from leaking along the gap between the piston rod 50 and the insertion through-hole 34. The snap ring 46 is fitted into a groove of the insertion through-hole 34. The snap ring 46 prevents the rod gasket 44 from coming off the piston rod 50.

[0018] The piston assembly 14 mainly has: a piston 48, a piston rod 50, a riveted portion 70, and a sealing member 54. The piston 48 is installed on the outer periphery of the top end portion of the piston rod 50. The outer peripheral portion of the piston 48 can be in close contact with and slide on the inner peripheral surface of the cylinder tube 16. The piston 48 hermetically and liquid-tightly divides the cylinder chamber 22 into a first pressure chamber 22a on the top end side and a second pressure chamber 22b on the base end side.

[0019] The piston 48 is not particularly limited, but is constructed to connect the first block 48a and the second block 48b. The piston 48 is also equipped with a magnet 56, a gasket 58 and a guide ring 62. The first block 48a has a first receiving groove 52a and a second receiving groove 52b. The first receiving groove 52a is located near the top of the first block 48a and accommodates the guide ring 62. The guide ring 62 slides with the inner circumferential surface of the cylinder tube 16 to prevent uneven wear of the gasket 58. The second receiving groove 52b is located at the base end compared to the first receiving groove 52a. The second receiving groove 52b accommodates the annular gasket 58. The gasket 58 is in close contact with the inner circumferential surface of the cylinder tube 16 so as to be able to slide. The gasket 58 prevents the fluid from leaking along the gap between the piston 48 and the cylinder tube 16.

[0020] The second block 48b contacts the base end of the first block 48a. The second block 48b has a third receiving groove 52c. The third receiving groove 52c is an annular recess. The third receiving groove 52c receives a magnet 56. The magnet 56 contacts the first block 48a. The magnet 56 is used to detect the position of the piston 48.

[0021] The piston rod 50 is a cylindrical member extending slenderly in the axial direction. The piston rod 50 is formed of metal such as stainless steel. The piston rod 50 is not limited to metal, and can also be formed of materials such as resin. The base end of the piston rod 50 passes through the insertion hole 34 of the rod cover 20 and protrudes outward from the base end of the rod cover 20.

[0022] like Figure 2C As shown, a reduced diameter portion 60 for mounting the piston 48 is provided at the outer peripheral portion of the top end portion of the piston rod 50. The portion of the piston rod 50 other than the reduced diameter portion 60 is referred to as the main body 64. The outer diameter of the reduced diameter portion 60 is smaller than the outer diameter of the main body 64. A step portion 66 is formed between the reduced diameter portion 60 and the main body 64. The piston 48 has a through hole 68 that passes through the first block 48a and the second block 48b along the center. The through hole 68 has an inner diameter through which the reduced diameter portion 60 of the piston rod 50 can be inserted. The inner diameter of the through hole 68 has a smaller size than the main body 64 of the piston rod 50. Therefore, the piston 48 is fixed to the piston rod 50 without exceeding the step portion 66.

[0023] At the top end of the piston rod 50, a riveting portion 70 is formed. The riveting portion 70 is formed by crushing the top end of the piston rod 50 toward the base end side in the axial direction. The top end of the piston rod 50 is deformed in a manner of being radially pressed and expanded. The deformed portion is the riveting portion 70. At the top end portion of the through hole 68 of the piston 48, a tapered portion 72 with a diameter gradually increasing toward the top end is formed. The riveting portion 70 enters the tapered portion 72 in a manner of filling the tapered portion 72 of the through hole 68. The riveting portion 70 prevents the piston 48 from falling off toward the top end side by protruding radially outward in the tapered portion 72. In addition, the piston 48 is pressed toward the stepped portion 66 by the riveting portion 70 and the tapered portion 72. Thus, the piston 48 is fixed relative to the piston rod 50 without wobbling.

[0024] The piston rod 50 has a shaft hole 74 extending in the axial direction at the center portion. As Figure 1 shown, the shaft hole 74 penetrates from the top end to the base end of the piston rod 50. The shaft hole 74 reduces the kinetic energy of the piston rod 50 by lightening the piston rod 50. Thus, the high-speed operation and high-frequency operation of the fluid pressure cylinder 10 are facilitated.

[0025] As Figure 2C shown, the shaft hole 74 has a small-diameter portion 74a and a large-diameter portion 74b. The small-diameter portion 74a occupies most of the shaft hole 74 and has a first inner diameter. The large-diameter portion 74b has a second inner diameter larger than the first inner diameter. The large-diameter portion 74b is axially disposed in a range overlapping with the piston 48. The large-diameter portion 74b is located on the top end side of the small-diameter portion 74a, and a part thereof overlaps with the riveting portion 70. At the boundary between the small-diameter portion 74a and the large-diameter portion 74b, a stepped portion 74c with a change in the inner diameter of the shaft hole 74 is formed.

[0026] The large-diameter portion 74b is for inserting the sealing member 54. The sealing member 54 is a sphere made of an elastic material such as rubber or an elastomer, for example. The sealing member 54 prevents the leakage of the fluid passing through the shaft hole 74 by being in close contact with the large-diameter portion 74b or the stepped portion 74c. In addition, the material of the sealing member 54 is not limited to rubber or an elastomer, and may also be a metal such as resin or steel. The shape of the sealing member 54 is not limited to spherical, and may also be a cylindrical shape or the like, for example.

[0027] The sealing member 54 has an outer diameter substantially the same as the second inner diameter of the large-diameter portion 74b and is larger than the first inner diameter of the small-diameter portion 74a. The stepped portion 74c prevents the displacement of the sealing member 54 toward the base end side by abutting against the base end side of the sealing member 54. The deformed portion caused by the riveting portion 70 abuts against the top end side of the sealing member 54.

[0028] The riveting portion 70 forms a stopper 76 that protrudes toward the shaft hole 74. The stopper 76 abuts against the top end side of the sealing member 54 by protruding toward the inside of the shaft hole 74. The stopper 76 has an inner diameter smaller than the outer diameter of the sealing member 54, thereby preventing the sealing member 54 from falling off toward the top end side. Moreover, the stopper 76 presses the sealing member 54 against the stepped portion 74c to fix the sealing member 54 so as not to wobble in the axial direction. The sealing member 54 is held clamped between the stepped portion 74c and the stopper 76.

[0029] The fluid pressure cylinder 10 of the present embodiment is configured as described above. Hereinafter, with reference to Figures 2A to 2C a method for manufacturing the piston assembly 14 will be described.

[0030] As Figure 2A shown, a cylindrical piston rod 50 having a shaft hole 74 is prepared. The piston rod 50 is manufactured by processing a hollow tubular material. A hollow tubular material cut to a prescribed length is prepared, and a part of the top end side thereof is processed by cutting or the like to form a reduced diameter portion 60 on the outer peripheral portion and a large diameter portion 74b on the inner peripheral portion. Through the above processes, the piston rod 50 is manufactured. Such a manufacturing method can manufacture the piston rod 50 by performing a minimum amount of processing on a general-purpose pipe material, and thus can be produced at low cost.

[0031] Next, as shown in the figure, the piston 48 is mounted on the outer peripheral surface of the reduced diameter portion 60 of the piston rod 50. That is, the second block 48b is inserted into the reduced diameter portion 60 from the top end side. Thereafter, the first block 48a is mounted on the top end side of the second block 48b.

[0032] Next, as Figure 2B shown, the sealing member 54 is inserted into the large diameter portion 74b of the piston rod 50. The movement of the sealing member 54 toward the base end side is restricted by the stepped portion 74c.

[0033] Next, as Figure 2C shown, the top end portion of the piston rod 50 is compressed toward the base end side in the axial direction, and a riveting process is performed to deform the top end portion of the piston rod 50 so as to expand toward the inner peripheral side and the outer peripheral side. Thereby, the riveting portion 70 is formed, and the sealing member 54 and the piston 48 are fixed so as not to fall off from the piston rod 50.

[0034] The piston assembly 14 of the present embodiment as described above can reliably prevent the sealing member 54 from falling off from the piston rod 50 even when moving at high speed. In addition, since the fixing of the sealing member 54 to the piston rod 50 is completed simultaneously with the riveting process of the piston 48, the manufacturing man-hours can be suppressed, and thus the manufacturing cost can be suppressed.

[0035] Regarding the above content, the following supplementary notes are also disclosed.

[0036] (Supplementary Note 1)

[0037] One view is that the piston assembly 14 includes: a piston rod 50 that extends along the axial direction; a piston 48 that is mounted on the outer peripheral portion of the piston rod; and a riveting portion 70 that crushes the top end of the piston rod to connect the piston and the piston rod. The piston rod has: a shaft hole 74 that axially penetrates the central portion of the piston rod; and a sealing member 54 that is inserted into the shaft hole to seal the shaft hole. The riveting portion has a stopper 76 that protrudes toward the shaft hole and prevents the sealing member from falling off.

[0038] The above piston assembly fixes the sealing member through the riveting portion, thereby being able to combine the sealing member and the piston rod with sufficient strength without increasing the weight. In addition, the structure is simplified, and it can be manufactured with a small amount of man-hours, so the mass productivity is excellent.

[0039] (Supplementary Note 2)

[0040] In the piston assembly described in Supplementary Note 1, it may also be that the shaft hole has a small-diameter portion and a large-diameter portion. The small-diameter portion has a first inner diameter, and the large-diameter portion is located at the top end of the small-diameter portion and has a second inner diameter larger than the first inner diameter. The sealing member has an outer diameter larger than the first inner diameter and is inserted into the large-diameter portion. This piston assembly can prevent the sealing member from moving toward the proximal end side through the small-diameter portion, and can simplify the fixing structure of the sealing member.

[0041] (Supplementary Note 3)

[0042] In the piston assembly described in Supplementary Note 2, it may also be that the sealing member is clamped by a step portion 74c at the boundary between the large-diameter portion and the small-diameter portion and the stopper, and is in close contact with the inner peripheral surface of the shaft hole. The sealing member of this piston assembly can reliably seal the shaft hole.

[0043] (Supplementary Note 4)

[0044] In the piston assembly described in any one of Supplementary Notes 1 to 3, it may also be that the sealing member is spherical or cylindrical. This piston assembly uses the sealing member as an elastic material, so as to be able to exhibit high sealing performance.

[0045] (Supplementary Note 5)

[0046] Another view is a fluid pressure cylinder 10, comprising: a cylinder tube 16; a head cover 18 that seals the top end of the cylinder tube; a rod cover 20 that seals the base end of the cylinder tube; and a piston assembly, at least a part of which is received inside the cylinder tube. The piston assembly includes: a piston rod that extends axially and passes through the rod cover; a piston that is mounted on the outer periphery of the piston rod and slides inside the cylinder tube; and a riveting portion that crushes the top end of the piston rod to connect the piston to the piston rod. The piston rod has: an axial hole that axially penetrates the central portion of the piston rod; and a sealing member that is inserted into the axial hole to seal the axial hole. The riveting portion has a stopper that protrudes toward the axial hole and prevents the sealing member from falling off.

[0047] The above-mentioned fluid pressure cylinder can lighten the weight of the piston rod, so it is very suitable for high-speed operation and high-frequency operation.

[0048] In addition, the present utility model is not limited to the above content, and various structures can be adopted without departing from the gist of the present utility model.

Claims

1. A piston assembly, characterized in that: The piston assembly (14) comprises: A piston rod (50) extending in an axial direction; a piston (48) mounted on the outer periphery of the piston rod; and a rivet portion (70) which compresses the top end of the piston rod to connect the piston to the piston rod, The piston rod has: an axial hole (74) which axially penetrates the central portion of the piston rod; and a sealing member (54) inserted into the shaft hole to seal the shaft hole, The rivet portion has a stopper (76) which protrudes toward the shaft hole and prevents the sealing component from falling off.

2. The piston assembly according to claim 1, characterized in that: The shaft hole has a small diameter portion and a large diameter portion, the small diameter portion has a first inner diameter, and the large diameter portion is located at the top end of the small diameter portion and has a second inner diameter larger than the first inner diameter. The sealing member has an outer diameter larger than the first inner diameter and is inserted into the large diameter portion.

3. The piston assembly according to claim 2, characterized in that: The sealing member is sandwiched by a step portion (74c) at a boundary between the large diameter portion and the small diameter portion and the stopper, and is in close contact with the inner peripheral surface of the shaft hole.

4. The piston assembly according to any one of claims 1 to 3, characterized in that: The sealing member is in a spherical shape or a cylindrical shape.

5. A fluid pressure cylinder comprising: Cylinder tube (16); A head cover (18) which seals the top end of the cylinder tube; a rod cover (20) which seals the base end of the cylinder tube; and A piston assembly, at least a portion of which is accommodated in the cylinder tube, characterized in that: The piston assembly comprises: A piston rod extending axially and inserted through the rod cover; a piston mounted on the outer periphery of the piston rod and sliding inside the cylinder tube; and A rivet portion that crushes the top end of the piston rod to connect the piston to the piston rod, wherein the piston rod has: an axial hole, the axial hole axially penetrating a central portion of the piston rod; and a sealing member, the sealing member being inserted into the shaft hole to seal the shaft hole; The rivet portion has a stopper that protrudes toward the shaft hole and prevents the sealing component from falling off.

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