WO2017110641A1

WO2017110641A1 - Cylinder device

Info

Publication number: WO2017110641A1
Application number: PCT/JP2016/087325
Authority: WO
Inventors: 靖久小俣; 裕一小林; 拓馬須貸
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2015-12-25
Filing date: 2016-12-15
Publication date: 2017-06-29
Also published as: JP2019031986A

Abstract

Provided is a cylinder device which satisfies specifications required for each portion and which enables a piston rod to be manufactured at low cost. A cylinder device is provided with: a hollow cylinder in which an operating fluid is sealed; a piston inserted in a slidable manner in the cylinder; a rod guide provided at the opening of the cylinder; and a piston rod which has on one end side thereof a piston mounting section connected to the piston, and which has on the other end side thereof a vehicle body-side mounting section extending through a rod guide to the outside of the cylinder and mounted to the vehicle body side. The piston rod is formed by joining a piston mounting member which has a piston mounting section, and a vehicle body-side mounting member which has a vehicle body-side mounting section. The hardness of the vehicle body-side mounting member is higher than that of the piston mounting member.

Description

Cylinder device

The present invention relates to a cylinder device in which, for example, a piston rod that is expanded and contracted from the inside of a cylinder is constituted by a plurality of members.

A cylinder device typified by a hydraulic cylinder or a hydraulic shock absorber has a cylindrical cylinder, a piston slidably fitted in the cylinder, one end side connected to the piston in the cylinder, and the other end side a rod guide. And a piston rod protruding from the cylinder so as to be extendable and contractable. In order to reduce the weight of the cylinder device, it is known that the piston rod is constituted by a plurality of members including, for example, a hollow rod (see, for example, Patent Document 1).

JP 2012-172344 A

An object of the present invention is to provide a cylinder device that satisfies specifications suitable for each part of a piston rod and can be manufactured at low cost.

A cylinder device according to an embodiment of the present invention includes a cylindrical cylinder in which a working fluid is sealed, a piston that is slidably inserted into the cylinder, a rod guide that is provided in an opening of the cylinder, and a piston that is coupled to the piston. A piston rod having a piston attachment portion on one end side, extending to the outside of the cylinder via a rod guide, and having a vehicle body side attachment portion attached to the vehicle body side on the other end side. The piston rod is formed by joining a piston mounting member having a piston mounting portion and a vehicle body side mounting member having a vehicle body side mounting portion. The hardness of the vehicle body side mounting member is larger than the hardness of the piston mounting member.

The piston rod has a piston mounting portion on one end side, and a vehicle body side mounting portion that protrudes out of the cylinder and is mounted on the vehicle body side, for example, on the other end side. Since a lateral force or the like acts on the vehicle body side mounting portion outside the cylinder, it is preferable that the rod is hard. On the other hand, since the piston mounting portion is located in the cylinder and connected (fixed) to the piston, it is difficult to receive a lateral force or the like from the outside. Further, the piston mounting portion needs to be subjected to screw processing, caulking processing, or the like in order to connect (fix) the piston. From the viewpoint of ease of processing, it is better that the piston mounting portion has a lower hardness.

According to one embodiment of the present invention, specifications suitable for each part of the piston rod can be satisfied, and the piston rod can be manufactured at low cost.

It is a longitudinal section showing the hydraulic shock absorber by a 1st embodiment. It is a front view of the principal part fracture | rupture which expands and shows the piston and piston rod in FIG. It is sectional drawing which shows process (I), (II), (III) which manufactures a piston rod. It is sectional drawing which shows the manufacturing process (I), (II), (III) of the piston rod following FIG. It is sectional drawing which shows process (I), (II), (III) which manufactures the piston rod by 2nd Embodiment. It is sectional drawing which shows the manufacturing process (I), (II), (III) of the piston rod following FIG. It is sectional drawing which shows the piston rod by 3rd Embodiment. It is sectional drawing which shows process (I), (II), (III) which manufactures the piston rod by 4th Embodiment. It is sectional drawing which shows the manufacturing process (I), (II), (III) of the piston rod following FIG.

Hereinafter, a cylinder device according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 9 of the accompanying drawings, taking as an example a case where the cylinder device is configured as a hydraulic shock absorber that buffers vibrations of a vehicle.

Here, FIG. 1 to FIG. 4 show the first embodiment. A hydraulic shock absorber 1 as a cylinder device constitutes a suspension device for a vehicle together with a suspension spring (not shown) made of, for example, a coil spring. In the following description, one end side in the axial direction of the hydraulic shock absorber 1 is described as a “lower end” side, and the other end side in the axial direction is described as an “upper end” side.

The hydraulic shock absorber 1 includes an outer cylinder 2, an inner cylinder 4, a piston 6, a rod guide 9, a rod seal 10, a piston rod 11, and the like. The bottomed cylindrical outer cylinder 2 constitutes the outer shell of the hydraulic shock absorber 1. The outer cylinder 2 is closed by welding the bottom cap 3 at the lower end side, which is one end side, and is open at the upper end side, which is the other end side. In addition, a plurality of caulking portions 2A that are bent radially inward by, for example, partial caulking are provided at the upper end portion of the outer cylinder 2. The upper end side opening of the outer cylinder 2 is closed by a rod guide 9 and a rod seal 10 which will be described later.

The inner cylinder 4 is provided coaxially in the outer cylinder 2 and constitutes a multi-cylinder cylinder together with the outer cylinder 2. The inner cylinder 4 is attached by fitting the lower end side to the outer peripheral side of the bottom valve 5, and the upper end side is closed by a rod guide 9 described later. The inner cylinder 4 defines an annular reservoir chamber A between the inner cylinder 4 and the outer cylinder 2, and gas is sealed in the reservoir chamber A together with a working liquid (hereinafter referred to as oil liquid). This gas may be atmospheric pressure air or compressed nitrogen gas. The bottom valve 5 is located on the lower end side of the inner cylinder 4 and is provided between the bottom cap 3 and the inner cylinder 4.

The piston 6 is slidably inserted (inserted) into the inner cylinder 4. The piston 6 defines the inside of the inner cylinder 4 in two chambers (that is, a bottom side oil chamber B and a rod side oil chamber C). A plurality of

oil passages

6A and 6B are formed in the piston 6 so that the bottom side oil chamber B and the rod side oil chamber C can communicate with each other. In these

oil passages

6A and 6B, the working liquid (oil liquid) flows from one chamber to the other chamber among the oil chambers A and B in the inner cylinder 4 (cylinder) by the movement of the piston 6. It constitutes a passage that allows this.

On the upper surface of the piston 6, a disk valve 7 constituting a reduction-side damping valve is provided. When the piston 6 slides downward along the inner cylinder 4 during the reduction stroke of the piston rod 11, which will be described later, the reduction-side disk valve 7 moves from the bottom side oil chamber B toward the rod side oil chamber C. A predetermined damping force is generated by applying a resistance force to the oil liquid flowing through the passage 6A.

Further, a disk valve 8 constituting an extension-side damping valve is provided on the lower surface of the piston 6. When the piston 6 slides upward along the inner cylinder 4 during the extension stroke of the piston rod 11, the extension-side disc valve 8 is moved from the rod-side oil chamber C toward the bottom-side oil chamber B. A predetermined damping force is generated by applying a resistance force to the oil flowing through the inside.

The upper end side (opening end side) of the outer cylinder 2 and the inner cylinder 4 is closed by a rod guide 9 and a rod seal 10. Here, the rod guide 9 is a guide member that slidably guides a later-described displacement of a piston rod 11 in the axial direction. The rod guide 9 is formed as a cylindrical body having a predetermined shape by forming, cutting, or the like, for example, a metal material or a hard resin material, and the upper end side (opening end side) of the outer cylinder 2 and the inner cylinder 4. Is provided to be fitted.

The rod seal 10 is provided between the upper surface of the rod guide 9 and the caulking portion 2A of the outer cylinder 2. The rod seal 10 has a metallic annular plate 10A as a core, and an elastic seal material such as rubber is integrally formed on the annular plate 10A by means of, for example, baking. The rod seal 10 seals (seal) between the outer cylinder 2 and the piston rod 11 in a liquid-tight and air-tight manner when the inner circumference thereof is in sliding contact with the outer circumference side of the piston rod 11.

The piston rod 11 extends in the inner cylinder 4 in the axial direction. The piston rod 11 is connected to the piston 6 at one end in the axial direction (the lower end in FIG. 1), and the upper end extends to the outside of the outer cylinder 2 and the inner cylinder 4 via the rod guide 9. Here, the piston rod 11 is composed of a total of three members including a piston mounting member 12, a hollow cylinder member 13, and a vehicle body side mounting member 14.

The piston mounting member 12, the hollow cylinder member 13, and the vehicle body side mounting member 14 are made of steel materials such as carbon steel having different materials (hardness and / or strength which are mechanical properties). And the piston attachment member 12 and the hollow cylinder member 13 are integrated by the joining part 15 which used joining means, such as friction welding, for the end surface which mutually opposes. Furthermore, the hollow cylinder member 13 and the vehicle body side mounting member 14 are similarly integrated with a joint portion 16 using joint means such as friction welding at opposite end surfaces.

The piston mounting member 12 is formed using a steel material such as S15C (carbon steel for mechanical structure), for example, and has a bottomed cylindrical boss portion 12A and a downward direction from the boss portion 12A so as to be coaxial with the boss portion 12A. It is comprised by the rod part 12B as a protruding piston attaching part. The piston mounting member 12 is formed with a bottomed cylindrical boss portion 12A and a rod portion 12B using means such as cold forging.

The rod portion 12B of the piston mounting member 12 is formed to have a smaller diameter than the boss portion 12A, and the piston 6 is connected to the outer peripheral side of the piston mounting member 12 by a nut 17 in an inserted state. That is, a male screw 12C is formed on the outer periphery on the lower side of the rod portion 12B, and a nut 17 is screwed to the male screw 12C. The nut 17 prevents the piston 6 and the

disk valves

7 and 8 from being removed from the rod portion 12B of the piston mounting member 12, and is fixed in a rotating state.

Here, the boss portion 12A of the piston mounting member 12 has a cylindrical portion 12A1 as shown in FIGS. As shown in FIG. 3, the boss portion 12 A has a cylindrical portion 12 A 1 whose opening end side is joined to the axial end surface of the hollow cylindrical member 13 by a joining portion 15. As shown in FIGS. 3 (I) and 3 (II), the joining portion 15 is joined by friction welding or the like in a state where the opening side end surface of the cylindrical portion 12A1 is abutted against the axial end surface of the hollow cylindrical member 13. It is formed by joining using means.

The hollow cylinder member 13 is formed using a steel material (for example, a carbon steel for mechanical structure such as S30C or a steel pipe such as STKM) having a hardness higher than that of the piston mounting member 12, and a slide on which the rod seal 10 slides. A moving contact member is formed. For this reason, the hollow cylindrical member 13 is subjected to a heat treatment as will be described later and then subjected to a polishing process to prevent damage to the rod seal 10. By forming the hollow cylinder member 13 to be harder than the piston mounting member 12, durability and life as a sliding contact member can be improved.

Further, an annular groove 13A is provided on the outer peripheral side of the hollow cylinder member 13 as shown in FIG. The annular groove 13A is formed by machining using a means such as groove rolling at a position separated by a predetermined dimension from the joint 15 (or the mounting position of the piston 6) with the piston mounting member 12. Has been. An annular stopper 19 described later is fitted and fixed in the annular groove 13A.

The vehicle body side mounting member 14 is formed with a Vickers hardness of 250 Hv or more, for example, using a steel material (for example, carbon steel for machine structure such as S45C) having a hardness of the hollow cylinder member 13 or more. Accordingly, the hardness of the piston mounting member 12, the hollow cylinder member 13, and the vehicle body side mounting member 14 is piston mounting member 12 <hollow cylinder member 13 ≦ vehicle body side mounting member 14, and the vehicle body side mounting member 14 is the hardest material. Is formed. The hollow cylinder member 13 has a hardness equal to or lower than that of the vehicle body side mounting member 14, and is harder than the piston mounting member 12.

The vehicle body-side mounting member 14 protrudes upward from the boss portion 14A so as to be coaxial with the boss portion 14A formed in a disk shape with a radial dimension equal to the outer diameter of the hollow cylinder member 13. It is comprised by the axial part 14B as a vehicle body side attaching part. The shaft portion 14B is formed with a smaller diameter than the boss portion 14A, and a male screw 14C is formed on the outer peripheral side thereof (see FIGS. 1 and 2). When a fastening nut (not shown) or the like is screwed to the male screw 14C, the vehicle body side mounting member 14 of the piston rod 11 is prevented from being pulled out to the vehicle body (not shown) side of the vehicle, and in a non-rotating state. Fixed. In addition, the bottom cap 3 side of the outer cylinder 2 is attached to the wheel (not shown) side of the vehicle.

Here, as shown in FIGS. 2 to 4, the boss portion 14 A of the vehicle body side mounting member 14 is joined to the axial end surface of the hollow cylindrical member 13 by the joint portion 16 at the outer peripheral side of the lower surface. As shown in FIGS. 3 (I) and (II), the joint portion 16 is a joint such as friction welding in a state in which the end face of the vehicle body side mounting member 14 abuts against the axial end face of the hollow cylinder member 13. It is formed by joining using means.

The hardness of the joining

parts

15 and 16 and the vicinity thereof is increased as compared with other parts by performing joining work in a pressurized state using, for example, a friction welding machine (not shown), for example, 450 HV or more. May be Vickers hardness. For this reason, by applying heat treatment (particularly tempering treatment) to the

joint portions

15 and 16 and the vicinity thereof as described later, a local increase in hardness can be suppressed, and the toughness is recovered and the steel structure is restored. To stabilize.

As shown in FIG. 1, the piston rod 11 is provided with a rebound stopper 18 via an annular stopper 19. The annular stopper 19 is inserted into the outer peripheral side of the piston rod 11, and is fixed to the annular groove 13A of the hollow cylindrical member 13 using means such as plastic flow or caulking. The rebound stopper 18 is supported from below by an annular stopper 19 in a state of being inserted into the outer peripheral side of the piston rod 11. The rebound stopper 18 abuts, for example, the lower surface side of the rod guide 9 when the piston rod 11 is fully extended, and the rebound stopper 18 is elastically bent and deformed, thereby reducing the impact at the stroke end in the extension stroke. it can.

The hydraulic shock absorber 1 according to the first embodiment has the above-described configuration. Next, the manufacturing process of the piston rod 11 will be described with reference to FIGS. 3 (I) to (III) and FIGS. 4 (I) to (I). This will be described with reference to III).

The piston rod 11 is composed of a total of three members including a piston mounting member 12, a hollow cylinder member 13, and a vehicle body side mounting member 14. Among these, the vehicle body side mounting member 14 is a cylindrical body 14 'as a material. This cylindrical body 14 'is a member before the boss portion 14A and the shaft portion 14B (vehicle body side mounting portion) are formed on the vehicle body side mounting member 14, and is a steel material having a hardness higher than that of the hollow cylindrical member 13 (for example, (Carbon steel for machine structure such as S45C).

As shown in FIGS. 3 (I) and 3 (II), the end surface on the one side in the axial direction of the hollow cylindrical member 13 has an end surface on the opening side of the cylindrical portion 12A1 of the boss portion 12A of the piston mounting member 12 as a friction welding machine ( It joins in the position of the junction part 15 using joining means, such as not shown. Further, the end surface of the cylindrical body 14 ′ is joined to the end surface on the other axial side of the hollow cylindrical member 13 at the position of the joint portion 16 by using a joining means such as a friction welding machine. Note that both the

joints

15 and 16 may be formed simultaneously by friction welding, one of which may be formed first, and the other may be formed thereafter. Moreover, when joining

parts

15 and 16 are formed using joining means, such as friction welding, a burr | flash will generate | occur | produce around it.

Therefore, a deburring process is performed as shown in FIG. In this case, for example, a burr portion generated around the

joints

15 and 16 on both ends of the hollow cylindrical member 13 is applied by applying a predetermined tool 20 (for example, a cutting tool for deburring) from the outer peripheral side thereof. Scraped off. During such a deburring process, the workpiece (ie, the piston rod 11 comprising the piston mounting member 12, the hollow cylindrical member 13 and the cylindrical body 14 ') is rotated via a chuck (not shown) or the like, and the friction welding is performed. The joint burr produced by projecting outside the

joints

15 and 16 is removed so as to be scraped off by the tool 20.

Thus, the joint 15 between the piston mounting member 12 and the hollow cylinder member 13 is processed so that the outer peripheral surface thereof has a uniform surface shape. Further, the joint 16 between the hollow cylinder member 13 and the vehicle body side mounting member 14 is also processed so that the outer peripheral surface thereof has a uniform surface shape. Such a deburring process may be performed on both the

joints

15 and 16 at the same time, one of which may be deburred first, and then the other may be deburred.

Next, FIGS. 4 (I) and (II) show the heat treatment process of the piston rod 11. Among these, FIG. 4 (I) shows a quenching process, and the hollow cylinder member 13 is subjected to quenching treatment by high frequency induction heating over the quenching ranges L1 and L2. The hollow cylindrical member 13 is quenched by quenching with water or oil after induction heating the portions of the quenching ranges L1 and L2 with high frequency. In this case, the end portion of the cylindrical body 14 '(the boundary portion with the joint portion 16) is also included in the quenching range L1. The quenching range L2 is a range for quenching the joint 15 between the piston mounting member 12 and the hollow cylinder member 13. The part of the range L3 among the hollow cylinder members 13 is a non-processed part which is not quenched, and is located between the quenched ranges L1 and L2.

In the range L3 where the quenching process is not performed, the annular groove 13A shown in FIGS. 1 and 2 is formed in the hollow cylindrical member 13 by post-processing, so that the quenching process by high frequency is excluded. That is, the portion corresponding to the range L3 of the hollow cylindrical member 13 is excluded from the range in which the rebound stopper 18 is slidably contacted with the rod seal 10 because the rebound stopper 18 is attached together with the annular stopper 19 via the annular groove 13A. For this reason, the part of the range L3 becomes a part which does not require a surface hardening process etc.

FIG. 4 (II) shows a tempering step, and the hollow cylinder member 13 is tempered over the tempering range L4. The tempering treatment is a treatment for recovering toughness and stabilizing the structure of a steel material that contains martensite and has become hard but brittle and has an unstable structure by the above-described quenching process. In this case, the tempering range L4 includes the entire length of the hollow cylindrical member 13, the end of the boss portion 12A of the piston mounting member 12 (portion including at least the cylindrical portion 12A1), and the end of the cylindrical body 14 '(joint portion 16). And a boundary range). The tempering range L4 is set longer than the total range of the quenching ranges L1, L2 and the range L3, as shown in the following formula 1.

FIG. 4 (III) is a post-processing step performed after the tempering process, for example, plastic processing by cutting and rolling. Thereby, a male screw 12C is formed on the rod portion 12B of the piston mounting member 12. Further, the hollow cylindrical member 13 is formed with an annular groove 13A for attaching the rebound stopper 18. Furthermore, the boss portion 14A and the shaft portion 14B are formed in the vehicle body side mounting member 14 (that is, the cylindrical body 14 ') at this stage, and the male screw 14C is formed on the outer peripheral side of the shaft portion 14B.

Next, to the piston rod 11 manufactured in this manner, the piston 6 and the

disk valves

7 and 8 are inserted and attached to the rod portion 12B of the piston mounting member 12, and in this state, the nut 17 is attached to the male screw 12C. , And the piston 6 and the

disk valves

7 and 8 are secured to the rod portion 12B in a locked state (see FIG. 2).

Further, after the nut 17 is screwed onto the male screw 12C, the rod portion 12B of the piston mounting member 12 is subjected to caulking or the like for loosening the nut 17. In some cases, laser welding or the like for stopping (loosening) the nut 17 is performed between the rod portion 12 B and the nut 17. Since the material of the piston mounting member 12 uses, for example, S15C having a low carbon content, it is possible to suppress the occurrence of cracks due to welding. On the other hand, a rebound stopper 18 is attached to the annular groove 13 A of the hollow cylinder member 13 via an annular stopper 19.

Next, in this state, the piston rod 11 is inserted into the inner cylinder 4 together with the piston 6 and the like. Thereafter, the upper end side (opening end side) of the outer cylinder 2 and the inner cylinder 4 is closed by the rod guide 9 and the rod seal 10. At this time, the oil liquid is sealed in the bottom side oil chamber B and the rod side oil chamber C in the inner cylinder 4, and in the reservoir chamber A between the outer cylinder 2 and the inner cylinder 4 together with the oil liquid Gas is sealed.

In the assembled state of the hydraulic shock absorber 1 according to the first embodiment, the bottom cap 3 side is attached to the vehicle wheel side. Further, on the projecting end side of the piston rod 11, the shaft portion 14B of the vehicle body side mounting member 14 is fastened to the vehicle body side with a nut or the like via a male screw 14C. As a result, when vibration is generated while the vehicle is running, the piston rod 11 is expanded and contracted, and a damping force is generated by the

disk valves

7 and 8 of the piston 6 to attenuate the vibration at this time.

That is, when the piston rod 11 is in the reduction stroke, the pressure in the bottom side oil chamber B is higher than that in the rod side oil chamber C. Then, it circulates into the rod side oil chamber C through the disc valve 7 and generates a damping force. An amount of oil corresponding to the volume of the piston rod 11 entering the inner cylinder 4 flows into the reservoir chamber A from the bottom side oil chamber B via the bottom valve 5, and in the reservoir chamber A. The gas enclosed inside is compressed to absorb the ingress volume of the piston rod 11.

On the other hand, when the piston rod 11 is in the extension stroke, the pressure in the rod-side oil chamber C is higher than that in the bottom-side oil chamber B, so that the pressure oil in the rod-side oil chamber C is the oil passage 6B of the piston 6. Then, it circulates into the bottom side oil chamber B through the disk valve 8, and a damping force is generated. Then, an amount of oil corresponding to the advancing volume of the piston rod 11 that has advanced from the inner cylinder 4 flows into the bottom-side oil chamber B from the reservoir chamber A through the bottom valve 5.

By the way, the piston rod 11 has one side (lower end side) in the length direction formed of a piston mounting member 12, and the other side (upper end side) in the length direction protrudes outside the cylinder (outer cylinder 2, inner cylinder 4). A vehicle body side mounting member 14 is provided. The vehicle body side mounting member 14 and the piston mounting member 12 have different required specifications (for example, bending strength, tensile strength, and hardness as mechanical properties). That is, the vehicle body side mounting member 14 is required to increase its strength by making the material hard because a lateral force or the like acts outside the cylinder. On the other hand, since the piston mounting member 12 is located in the inner cylinder 4 and connected (fixed) to the piston 6, it is difficult to receive a lateral force or the like from the outside. Further, the piston mounting member 12 needs to be subjected to processing of the male screw 12C and caulking for loosening of the nut 17 in order to connect (fix) the piston 6, and has a lower hardness from the viewpoint of ease of processing. Is good.

Therefore, in the first embodiment, the piston rod 11 is constituted by a total of three members including the piston mounting member 12, the hollow cylinder member 13, and the vehicle body side mounting member 14, and these piston mounting member 12, hollow cylinder member 13, and The vehicle body side mounting member 14 is formed using steel materials such as carbon steel having different materials (hardness and / or strength which are mechanical properties). The piston mounting member 12 and the hollow cylinder member 13 are integrated with each other at their end faces facing each other by a joint portion 15 using means such as friction welding, and the hollow cylinder member 13 and the vehicle body side mounting member 14 are similarly connected to each other. Opposing end faces are integrated by a joint 16 using means such as friction welding.

The material hardness of the piston mounting member 12, the hollow cylinder member 13, and the vehicle body side mounting member 14 is piston mounting member 12 <hollow cylinder member 13 ≦ vehicle body side mounting member 14, and the vehicle body side mounting member 14 is formed to be the hardest. Yes. The hollow cylinder member 13 has a hardness equal to or lower than that of the vehicle body side mounting member 14, and is harder than the piston mounting member 12. In this case, since the hardness of the material is substantially proportional to the tensile strength, the piston mounting member 12 <the hollow cylinder member 13 ≦ the vehicle body side mounting member 14 is also provided for the tensile strength. Further, since there is a relationship that is substantially proportional to the shear strength, the piston mounting member 12 <the hollow cylinder member 13 ≦ the vehicle body side mounting member 14 is also obtained with respect to the shear strength. Although the hardness of the material is in the above-described size relationship, the hollow cylinder member 13 is quenched, so the hardness relationship after the heat treatment may be different from the vehicle body side mounting member 14 depending on the case. Is harder. Further, with respect to the amount of carbon, the piston mounting member 12 <the hollow cylinder member 13 ≤ the vehicle body side mounting member 14. More specifically, for example, the piston mounting member 12 uses S15C, the hollow cylinder member 13 uses S25C, the vehicle body side mounting member 14 uses S35C, etc., so that the hardness is piston mounting member 12 <hollow cylinder member 13 ≦ vehicle body side mounting member. 14 can be used.

As a result, the piston mounting member 12 that does not easily receive a lateral force or the like from the outside does not require high screw strength for the male screw 12C and the like, and can reduce the hardness. Therefore, the boss portion 12A and the rod portion 12B can be connected by means such as cold forging. It can be formed, and the material cost can be reduced. Further, since the piston mounting member 12 that does not require high screw strength can be reduced in hardness, when the nut 17 is screwed onto the male screw 12C and the caulking process for loosening is performed, for example, on the rod portion 12B side. The amount of deformation (elastic deformation and plastic deformation) between the male screw 12C and the nut 17 increases.

As a result, the rod portion 12B of the piston mounting member 12 stabilizes the residual axial force applied to the piston 6 and the

disk valves

7 and 8 between the nut 17 and the caulking performed to suppress variation in damping force characteristics. The processing effect is stabilized. Moreover, the piston mounting member 12 is made of, for example, carbon steel for machine structure such as S15C, and can be lower in hardness than the

other members

13 and 14, so that the nut 17 can be stopped (loosened) by laser welding or the like. When joining to the rod part 12B by this, since the amount of carbon is low, it can suppress that the crack by welding arises.

The piston mounting member 12 and the hollow cylinder member 13 are integrated by a joint portion 15 using means such as friction welding on the end face sides facing each other. Since the piston mounting member 12 that does not require high screw strength or the like can be reduced in hardness, the hardness of burrs generated around the joint portion 15 by friction welding can be suppressed to a low level, and the deburring process is performed. Workability and workability can be improved.

Since the hollow cylinder member 13 provided between the piston mounting member 12 and the vehicle body side mounting member 14 can be formed as a long hollow rod, the piston rod 11 can be significantly reduced in weight. The hollow cylinder member 13 is made of, for example, carbon steel for mechanical structure such as S30C, or a steel pipe such as STKM, and can be formed to be harder than the piston mounting member 12, so that the toughness as a hollow rod can be ensured. Moreover, since the hollow cylindrical member 13 as the sliding contact member with which the rod seal 10 is brought into sliding contact is subjected to surface treatment by subjecting the outer peripheral surface thereof to heat treatment as described above, and then subjected to polishing or the like, the rod seal 10 is worn. Damage can be suppressed for a long time.

Further, since a lateral force or the like acts on the vehicle body side mounting member 14 outside the outer cylinder 2, the material can be made harder by using carbon steel for mechanical structure such as S45C, and the strength is increased. be able to. Furthermore, the vehicle body side attachment member 14 can reduce the processing cost of the vehicle body side attachment member 14 by making the joining end surface of the boss | hub part 14A with respect to the hollow cylinder member 13 solid.

Therefore, according to the first embodiment, the piston rod 11 can be formed as a hollow rod, and the overall weight can be reduced. The piston mounting member 12 and the vehicle body side mounting member 14 that are frictionally joined to both ends of the hollow cylindrical member 13 can satisfy the specifications required for each part, and the piston rod 11 can be manufactured at low cost. can do.

In the heat treatment step shown in FIGS. 4 (I) and (II), a portion (hollow) including both

joints

15 and 16 of the hollow cylindrical member 13 and where the rebound stopper 18 is attached together with the annular stopper 19 via the annular groove 13A. After performing quenching in a range excluding the portion corresponding to the range L3 of the cylindrical member 13, the hollow cylindrical member 13 is tempered over a tempering range L4 including the ranges L1, L2, and L3.

Thereby, a local decrease in hardness can be suppressed in the vicinity of the abutting surface of the hollow cylindrical member 13 and the

joint portions

15 and 16. Further, in the case of quenching only, there was a local increase in hardness on the joint 16 side of the hollow tube member 13 and the vehicle body side mounting member 14, but by tempering after quenching, the vicinity of the joint 16 The portion can be suppressed to, for example, a Vickers hardness of 450 HV or less (250 HV or more). For this reason, it is possible to suppress a decrease in tensile strength due to a local decrease in hardness and to suppress embrittlement due to a local increase in hardness.

Next, FIG. 5 and FIG. 6 show a second embodiment. The feature of the second embodiment resides in that a bottomed cylindrical boss portion and a shaft portion are formed in advance on the vehicle body side attachment member before performing friction welding. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

The piston rod 31 employed in the second embodiment is composed of three members: a piston mounting member 32, a hollow cylinder member 33, and a vehicle body side mounting member 34, in substantially the same manner as the piston rod 11 described in the first embodiment. It is configured. Among these, the piston mounting member 32 has a boss portion 32A, a rod portion 32B, and a male screw 32C, and these are configured in the same manner as the piston mounting member 12 described in the first embodiment. The hollow cylinder member 33 is configured as a sliding contact member in the same manner as the hollow cylinder member 13 described in the first embodiment. The length (axial direction) of the hollow cylinder member 33 is the length of a cylinder portion 34A1 which will be described later. It is shorter by the length.

Further, the vehicle body side mounting member 34 includes a boss portion 34A formed in a bottomed cylindrical shape with a radial direction dimension equal to the outer diameter of the hollow cylindrical member 33 using a steel material such as S45C (carbon steel for machine structure), for example. , And a shaft portion 34B as a vehicle body side mounting portion protruding upward from the boss portion 34A so as to be coaxial with the boss portion 34A. However, the boss portion 34A of the vehicle body side attachment member 34 is different from the vehicle body side attachment member 14 described in the first embodiment in that it has a cylindrical portion 34A1.

The piston mounting member 32 and the hollow cylinder member 33 are integrated by the joint part 35 similar to the joint part 15 described in the first embodiment, and the hollow cylinder member 33 and the vehicle body side mounting member 34 are the first part. They are integrated by a joint portion 36 similar to the joint portion 16 described in the embodiment. However, in this case, the boss portion 34A of the vehicle body side mounting member 34 is joined to the axial end surface of the hollow tubular member 33 by the joining portion 36 at the opening end side of the tubular portion 34A1.

The hardness of the piston mounting member 32, the hollow cylinder member 33, and the vehicle body side mounting member 34 is the piston mounting member 32 <the hollow cylinder member 33 ≦ the vehicle body side mounting member 34, and the vehicle body side mounting member 34 is formed to be the hardest. The hollow cylinder member 33 has a hardness equal to or lower than that of the vehicle body side mounting member 34 and is harder than the piston mounting member 32. In this case, since the hardness of the material is substantially proportional to the tensile strength, the piston mounting member 32 <the hollow cylinder member 33 ≦ the vehicle body side mounting member 34 is also provided for the tensile strength.

The piston rod 31 according to the second embodiment has the above-described configuration. Next, the manufacturing process of the piston rod 31 will be described with reference to FIGS. 5 (I) to (III) and FIGS. 6 (I) to (III). ) Will be described.

As shown in FIGS. 5 (I) and (II), the end surface on the one side in the axial direction of the hollow cylinder member 33 has an end face on the opening side of the cylinder portion 32A1 of the boss portion 32A of the piston mounting member 32. It joins in the position of the junction part 35 using joining means, such as not shown. Further, the end surface of the boss 34A (cylinder 34A1) of the vehicle body side mounting member 34 is located at the position of the joint 36 by using a joining means such as a friction welding machine. Be joined. Note that both of the

joint portions

35 and 36 may be formed by friction welding at the same time, either one may be formed first, and the other may be formed thereafter. Further, when the joining

portions

35 and 36 are formed using joining means such as friction welding, burrs are generated around the joining

portions

35 and 36.

Therefore, a deburring process is performed as shown in FIG. In this case, the burr portions generated around the

joint portions

35 and 36 on both ends of the hollow cylindrical member 33 are scraped by applying a predetermined tool 20 (for example, a cutting tool for deburring) from the outer peripheral side thereof. It is. During the deburring process, the workpiece (ie, the piston rod 31 including the piston mounting member 32, the hollow cylindrical member 33, and the vehicle body side mounting member 34) is rotated via a chuck (not shown) or the like, and the friction Bonding burrs produced by protruding to the outside of the

bonding portions

35 and 36 by pressure welding are removed so as to be scraped off by the tool 20.

Thus, the joint portion 35 between the piston mounting member 32 and the hollow cylinder member 33 is processed so that the outer peripheral surface thereof has a uniform surface shape. Further, the joint portion 36 between the hollow cylinder member 33 and the vehicle body side mounting member 34 is also processed so that the outer peripheral surface thereof has a uniform surface shape. Such a deburring process may be performed on both of the

joint portions

35 and 36 at the same time, either one of which may be deburred first, and then the other may be deburred.

Next, FIGS. 6 (I) and (II) show the heat treatment process of the piston rod 31. Among these, FIG. 6 (I) shows a quenching process, and the hollow cylindrical member 33 is subjected to quenching treatment by high frequency induction heating over the quenching ranges L5 and L6. The hollow cylindrical member 33 is quenched by quenching with water or oil after induction heating the portions of the quenching ranges L5 and L6 with high frequency. In this case, in the vehicle body side mounting member 34, the open end side of the cylinder portion 34A1 of the boss portion 34A is included in the quenching range L5. The quenching range L6 is a range for quenching the joint portion 35 between the piston mounting member 32 and the hollow cylinder member 33. The part of the range L7 among the hollow cylinder members 33 is a non-processed part which is not quenched, and is positioned between the quenched ranges L5 and L6.

In the range L7 where the quenching process is not performed, the annular groove 33A shown in FIG. 6 (III) is formed in the hollow cylindrical member 33 by post-processing, so that the quenching process by high frequency is excluded. The rebound stopper 18 is attached to the annular groove 33A of the hollow cylinder member 33 via the annular stopper 19 in the same manner as the annular groove 13A of the hollow cylinder member 13 described in the first embodiment. For this reason, the portion corresponding to the range L7 of the hollow cylindrical member 33 is excluded from the range in which the rod seal 10 is in sliding contact. For this reason, the part of the range L7 becomes a part which does not require a surface hardening process etc.

FIG. 6 (II) shows a tempering process, and the hollow cylindrical member 33 is tempered over the tempering range L8. The tempering treatment is a treatment for recovering toughness and stabilizing the structure of a steel material that contains martensite and has become hard but brittle and has an unstable structure by the above-described quenching process. In this case, the tempering range L8 includes the entire length of the hollow cylindrical member 33, the end portion of the boss portion 32A of the piston mounting member 32 (a portion including at least the cylindrical portion 32A1), and the boss portion 34A of the vehicle body side mounting member 34 (at least And a long range extending to the cylindrical portion 34A1). The tempering range L8 is set longer than the total range of the quenching ranges L5, L6 and the range L7, as shown in the following formula 2.

FIG. 6 (III) is a post-processing step performed after the tempering process, for example, plastic processing by cutting and rolling. As a result, the male screw 12 C is formed on the rod portion 32 B of the piston mounting member 32. Further, the hollow cylindrical member 33 is formed with an annular groove 33A for attaching the rebound stopper 18. Furthermore, a male screw 34 C is formed on the outer peripheral side of the shaft portion 34 B of the vehicle body side mounting member 34.

Next, to the piston rod 31 manufactured in this way, the piston 6 and the

disk valves

7 and 8 are inserted and attached to the rod portion 32B of the piston attachment member 32. In this state, the nut 17 is attached to the male screw 32C. , And the piston 6 and the

disc valves

7 and 8 are secured to the rod portion 32B in a locked state (see FIG. 2).

Further, after the nut 17 is screwed onto the male screw 32C, the rod portion 32B of the piston mounting member 32 is subjected to caulking or the like for loosening the nut 17. In some cases, laser welding or the like for stopping (loosening) the nut 17 is performed between the rod portion 32 B and the nut 17. Since the material of the piston mounting member 32 has a low carbon content, it is possible to suppress the occurrence of cracks due to welding. On the other hand, the rebound stopper 18 is attached to the annular groove 33 A of the hollow cylinder member 33 via the annular stopper 19.

Thus, also in the second embodiment configured as described above, the piston rod 31 can be formed as a hollow rod, and the overall weight can be reduced, and the same effect as in the first embodiment can be obtained. Can do. The piston mounting member 32 and the vehicle body side mounting member 34 that are provided by frictional joining to both ends of the hollow cylindrical member 33 can satisfy the specifications required for the respective parts, and the piston rod 31 can be manufactured at low cost. can do.

In the heat treatment step shown in FIGS. 6 (I) and (II), a portion (hollow) that includes both the

joint portions

35 and 36 of the hollow cylindrical member 33 and the rebound stopper 18 is attached together with the annular stopper 19 via the annular groove 33A. After performing quenching to a range excluding the portion corresponding to the range L7 of the cylindrical member 33, the hollow cylindrical member 33 is tempered over a tempering range L8 including the ranges L5, L6, and L7.

Thereby, in the vicinity of the abutting surfaces of the hollow cylindrical member 33 and the

joint portions

35 and 36, a local decrease in hardness can be suppressed. Further, by performing tempering after the quenching treatment, the vicinity of the joint portion 36 can be suppressed to, for example, a Vickers hardness of 450 HV or less (250 HV or more). For this reason, it is possible to suppress a decrease in tensile strength due to a local decrease in hardness and to suppress embrittlement due to a local increase in hardness.

Next, FIG. 7 shows a third embodiment. A feature of the third embodiment resides in that an annular groove for a rebound stopper is formed in advance in a hollow cylindrical member serving as a sliding contact member of the piston rod before heat treatment. Note that in the third embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

The piston rod 41 employed in the third embodiment has a hollow cylinder member 42 between the piston mounting member 12 and the vehicle body side mounting member 14 in substantially the same manner as the piston rod 11 described in the first embodiment. It is set as the structure to provide. The hollow cylinder member 42 is configured in substantially the same manner as the hollow cylinder member 13 described in the first embodiment, and both end sides thereof are joined to the piston attachment member 12 and the vehicle body side attachment member 14 by

joint portions

15 and 16. .

However, in this case, an annular groove 42A for the rebound stopper 18 is formed in advance before heat treatment (or before the hollow cylindrical member 42 is joined between the piston mounting member 12 and the vehicle body side mounting member 14). This is different from the first embodiment. For this reason, in the heat treatment process of the piston rod 41, the quenching process is performed in the range L9 including the hollow cylindrical member 42 and the

joint portions

15 and 16 on both ends. The quenching range L9 includes at least the cylindrical portion 12A1 of the boss portion 12A of the piston mounting member 12 and the end portion of the boss portion 14A of the vehicle body side mounting member 14 (boundary portion with the joint portion 16). In addition, when welding the receiving member of a rebound stopper, since the annular groove 42A is not processed, quenching can be performed without dividing the portion to be quenched and the portion not to be quenched.

Further, in the heat treatment step of the piston rod 41, after performing the quenching process in the range L9 including the hollow cylindrical member 42 and the

joints

15 and 16 on both ends, the tempering process is performed over a range L10 larger than the range L9. The tempering range L10 includes the entire length of the hollow cylindrical member 42 and the

joint portions

15 and 16 on both end sides, a part of the boss portion 12A of the piston mounting member 12 (including at least the cylindrical portion 12A1), and the vehicle body side mounting member 14. The end portion of the boss portion 14A (the boundary portion with the joint portion 16) is included.

Thus, also in the third embodiment configured as described above, the piston rod 41 can be formed as a hollow rod, and the overall weight can be reduced, and the same effect as in the first embodiment can be obtained. Can do. In particular, in the third embodiment, an annular groove 42A for the rebound stopper 18 is formed in advance in the hollow cylindrical member 42 before performing the heat treatment as described above.

For this reason, in the heat treatment step including the hollow cylindrical member 42, for example, it is not necessary to remove the peripheral portion of the annular groove 42A from the quenching range L9, and the quenching process can be efficiently performed over the entire length of the hollow cylindrical member 42. That is, in the first embodiment, quenching is performed in the two ranges L1 and L2, but in this embodiment, the joint portion 15 on the vehicle body side mounting member 14 side is connected to the joint portion 15 on the piston mounting member 12 side. Up to 16, the quenching process can be performed smoothly over the entire length of the hollow cylindrical member 42, that is, without interrupting the quenching process in the middle of the hollow cylindrical member 42.

Next, FIG. 8 and FIG. 9 show a fourth embodiment. The feature of the fourth embodiment is that the piston rod is composed of two members, a piston mounting member and a vehicle body side mounting member. Note that in the fourth embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

The piston rod 51 employed in the fourth embodiment is composed of two members, a piston mounting member 52 and a vehicle body side mounting member 53. Of these, the piston mounting member 52 has a boss portion 52A and a rod portion 52B (piston mounting portion) in substantially the same manner as the piston mounting member 12 described in the first embodiment. A male screw 52C is formed on the rod portion 52B of the piston mounting member 52 as shown in FIG. 9 (III), and a nut 17 (see FIG. 2) is screwed onto the male screw 52C. In this case, the piston mounting member 52 is provided with a rod portion 52B protruding from one axial side of the boss portion 52A, and a cylindrical portion 52A1 extending short in the axial direction from the other axial side of the boss portion 52A. .

As the vehicle body side mounting member 53, a cylindrical body 53 ′ that is a material thereof is used similarly to the vehicle body side mounting member 14 described in the first embodiment. This cylindrical body 53 ′ is a member before the boss portion 53 A and the shaft portion 53 B (vehicle body side mounting portion) are formed on the vehicle body side mounting member 53, as shown in FIG. It is formed using a steel material having a great hardness (for example, carbon steel for mechanical structure such as S45C). However, the vehicle body side mounting member 53 in this case is different from the first embodiment in that it has a hollow cylindrical portion 53C.

The cylinder portion 53C of the vehicle body side attachment member 53 corresponds to the hollow cylinder member 13 described in the first embodiment. For example, the vehicle body side attachment member is made of a steel material such as S45C (carbon steel for machine structure). The third embodiment is different from the first embodiment in that it is formed integrally with a cylindrical body 53 'of 53 (that is, formed using the same steel material).

Here, as shown in FIGS. 8 (I) to (II), the opening side end surface of the cylindrical portion 53C of the cylindrical body 53 ′ that is the material of the vehicle body side mounting member 53 is the opening side end surface of the piston mounting member 52. On the other hand, it is joined by the joining portion 54. The joining portion 54 is formed by joining both ends using a joining means such as friction welding in a state where the end face of the cylindrical portion 53C is abutted against the opening-side end face of the piston mounting member 52.

The piston rod 51 according to the fourth embodiment has the above-described configuration. Next, the manufacturing process of the piston rod 51 will be described with reference to FIGS. 8 (I) to (III) and FIGS. 9 (I) to (III). ) Will be described.

As shown in FIGS. 8 (I) and (II), the vehicle body side mounting member 53 uses a joining means such as a friction welding machine in which the end surface of the piston mounting member 52 is connected to the opening side end surface of the cylindrical portion 53C of the cylindrical body 53 '. Are joined at the position of the joining portion 54. Thus, when the joining part 54 is formed using joining means such as friction welding, burrs are generated around the joining part 54.

Therefore, a deburring process is performed as shown in FIG. 8 (III). In this case, the burr part generated around the joint 54 is scraped off by applying a predetermined tool 20 (for example, a cutting tool for deburring) from the outer peripheral side. During such a deburring process, the workpiece (ie, the piston rod 51 including the piston mounting member 52 and the vehicle body side mounting member 53) is rotated via a chuck (not shown) or the like, and is joined by the friction welding. Bonding burrs generated by projecting to the outside of 54 are removed so as to be scraped off by the tool 20.

Next, FIGS. 9 (I) and (II) show the heat treatment process of the piston rod 51. Among these, FIG. 9 (I) shows a hardening process, and the cylindrical part 53C of the vehicle body side mounting member 53 is subjected to a hardening process by high-frequency induction heating over the hardening ranges L11 and L13. The cylindrical portion 53C of the vehicle body side mounting member 53 is quenched by quenching with water or oil after induction heating the portions of the quenching ranges L11 and L13 with high frequency. In this case, the end portion of the cylinder portion 53C (the boundary portion with the joint portion 54) is included in the quenching range L13. A portion in the range L12 in the cylindrical portion 53C of the vehicle body side attachment member 53 is a non-processing portion that is not quenched.

In the non-quenching range L12, the annular groove 53D shown in FIG. 9 (III) is formed in the cylindrical portion 53C by post-processing, and therefore, quenching by high frequency is excluded. That is, the portion corresponding to the range L12 of the cylindrical portion 53C is excluded from the range in which the rebound stopper 18 is attached to the rod seal 10 through the annular groove 53D through the annular groove 53D. For this reason, the part of the range L12 becomes a part which does not require a surface hardening process etc.

FIG. 9 (II) shows the tempering process, and the tempering process is performed on the cylindrical portion 53C of the vehicle body side mounting member 53 over the tempering range L14. In this case, the tempering range L14 is a long range including the entire length of the cylinder portion 53C of the vehicle body side mounting member 53 and the end portion of the piston mounting member 52 (boundary portion with the joint portion 54). The tempering range L14 is set longer than the total range of the quenching ranges L11, L12, and L13, as shown in the following equation (3).

FIG. 9 (III) shows a post-processing step performed after the tempering process, for example, plastic processing by cutting and rolling. Thereby, an annular groove 53D for attaching the rebound stopper 18 is formed in the cylinder portion 53C of the vehicle body side attachment member 53. Further, a male screw 52C is formed on the rod portion 52B of the piston mounting member 52. Furthermore, the boss portion 53A and the shaft portion 53B are formed on the vehicle body side mounting member 53 (that is, the cylindrical body 53 ') at this stage, and the male screw 53E is formed on the outer peripheral side of the shaft portion 53B. The male screw 53E may be the same as the male screw 14C shown in FIGS.

Thus, also in the fourth embodiment configured as described above, the piston rod 51 can be formed as a hollow rod, and the overall weight can be reduced, and the same effect as in the first embodiment can be obtained. Can do. And the piston attachment member 52 and the vehicle body side attachment member 53 can satisfy the specifications required for the respective parts, and the piston rod 51 can be manufactured at low cost.

Particularly, in the fourth embodiment, the piston rod 51 is composed of two members, a piston mounting member 52 and a vehicle body side mounting member 53. For this reason, the piston rod 51 can be manufactured by forming the joint portion 54 (friction joint portion) at one location between the piston mounting member 52 and the vehicle body side mounting member 53, thereby simplifying the manufacturing process. be able to.

In the first embodiment, the boss portion 14A and the shaft portion 14B of the vehicle body side mounting member 14 are formed after the heat treatment on the columnar body 14 'that is the material of the vehicle body side mounting member 14. Was described as an example. However, the present invention is not limited to this. For example, in a state where the boss portion 14A and the shaft portion 14B (vehicle body side mounting portion) are first formed on the vehicle body side mounting member 14, the end surface side of the boss portion 14A is attached to the piston. It is good also as a structure joined to the end surface of the member 52. FIG. This is the same for the fourth embodiment. Further, in the fourth embodiment, the cylindrical portion 53C is integrally provided on the vehicle body side mounting member 53 side, but the cylindrical portion 53C may be integrally provided on the piston mounting member 52 side. In this case, since the hardness of the vehicle body side attachment member 53 side and the cylinder portion 53C may be the same, it is preferable to provide the cylinder portion 53C integrally on the vehicle body side attachment member 53 side.

In the first embodiment, a shock absorber using a multi-cylinder cylinder including the outer cylinder 2 and the inner cylinder 4 has been described as an example. However, the present invention is not limited to this, and may be applied to a cylinder device such as a shock absorber composed of a single cylinder. This also applies to the second to fourth embodiments.

Further, in each of the above embodiments, a shock absorber attached to a vehicle such as an automobile has been described as an example as a representative example of the cylinder device. However, the present invention is not limited to this. For example, the present invention may be applied to a shock absorber used in various machines, structures, buildings, or the like serving as vibration sources, or a cylinder device such as a hydraulic cylinder or a pneumatic cylinder.

Next, the forms included in each of the above embodiments will be described. In other words, the piston rod has a sliding contact member between the piston mounting member and the vehicle body side mounting member, in which a seal member provided on the inner peripheral side of the rod guide is in sliding contact. The contact member is hollow, and the hardness of the sliding contact member and the piston mounting member is configured such that sliding contact member> piston mounting member.

Thereby, since the sliding contact member can be formed as a long hollow rod, the piston rod can be significantly reduced in weight. The sliding contact member is made of, for example, carbon steel for mechanical structure such as S30C or steel tube such as STKM, and can be formed to be harder than the piston mounting member, so that toughness as a hollow rod can be ensured. In addition, the sliding contact member with which the seal member (rod seal) is in sliding contact is mirror-finished by applying a polishing process after the outer peripheral surface is heat-treated, thus suppressing wear and damage of the rod seal over a long period of time. Can do.

Further, the material hardness of the vehicle body side mounting member and the sliding contact member is configured such that the vehicle body side mounting member ≧ the sliding contact member. Since a lateral force or the like is applied to the vehicle body side mounting member outside the cylinder, the material can be made hard by using, for example, carbon steel for mechanical structure such as S45C, and the strength can be increased. The sliding contact member has a hardness equal to or lower than that of the vehicle body side mounting member and is larger than the piston mounting member 12. Thereby, durability and lifetime of a sliding contact member can be improved.

The piston rod is configured such that the vehicle body side mounting member having a hollow end surface and the sliding contact member having a hollow end surface are joined. For this reason, the vehicle body side mounting member can increase the bonding strength by making the bonding end surface of the sliding contact member hollow.

Although several embodiments of the present invention have been described above, the above-described embodiments of the present invention are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof. In addition, any combination or omission of each constituent element described in the claims and the specification is possible within a range where at least a part of the above-described problems can be solved or a range where at least a part of the effect is achieved. It is.

This application claims priority based on Japanese Patent Application No. 2015-253901 filed on Dec. 25, 2015. The entire disclosure including the specification, claims, drawings and abstract of Japanese Patent Application No. 2015-253901 filed on Dec. 25, 2015 is incorporated herein by reference in its entirety.

1 hydraulic shock absorber (cylinder device), 2 outer cylinder (cylinder), 4 inner cylinder (cylinder), 6 piston, 9 rod guide, 11, 31, 41, 51 piston rod, 12, 32, 52 piston mounting member, 12B , 32B, 52B Rod part (piston mounting part) 13, 33, 42 Hollow cylinder member (sliding contact member) 14, 34, 53 Car body side mounting member, 14B, 34B, 53B Shaft part (car body side mounting part) , 15, 16, 35, 36, 54 joints

Claims

A cylinder device,
A cylindrical cylinder filled with a working fluid;
A piston slidably inserted into the cylinder;
A rod guide provided at an opening of the cylinder;
A piston rod having a piston mounting portion connected to the piston on one end side, extending to the outside of the cylinder via the rod guide and having a vehicle body side mounting portion mounted on the vehicle body side on the other end side;
With
The piston rod is formed by joining a piston mounting member having the piston mounting portion and a vehicle body side mounting member having the vehicle body side mounting portion,
The cylinder device has a hardness that is greater than a hardness of the piston mounting member.
The cylinder device according to claim 1,
The piston rod has a sliding contact member between the piston mounting member and the vehicle body side mounting member, in which a seal member provided on the inner peripheral side of the rod guide comes into sliding contact.
The sliding contact member is hollow;
The cylinder device in which the hardness of the sliding contact member is larger than the hardness of the piston mounting member.
The cylinder device according to claim 2,
The cylinder device, wherein a hardness of a material of the vehicle body side mounting member is equal to or more than a hardness of a material of the sliding contact member.
The cylinder device according to claim 1,
The vehicle body side mounting member has a hollow end surface, and the piston mounting member has a hollow end surface.
A cylinder device,
A cylindrical cylinder filled with a working fluid;
A piston slidably inserted into the cylinder;
A rod guide provided at an opening of the cylinder;
A piston rod having a piston mounting portion connected to the piston on one end side, extending to the outside of the cylinder via the rod guide and having a vehicle body side mounting portion mounted on the vehicle body side on the other end side;
With
The piston rod is formed by joining a piston mounting member having the piston mounting portion and a vehicle body side mounting member having the vehicle body side mounting portion,
The carbon amount of the vehicle body side mounting member is larger than the carbon amount of the piston mounting member.
The cylinder device according to claim 5,
The piston rod has a sliding contact member between the piston mounting member and the vehicle body side mounting member, in which a seal member provided on the inner peripheral side of the rod guide comes into sliding contact.
The sliding contact member is hollow;
The amount of carbon of the sliding contact member is greater than the amount of carbon of the piston mounting member.