JP2013181561A - Shock absorber, and method of manufacturing rod - Google Patents

Abstract

The present invention provides a technique capable of suppressing destruction with time of a bonded portion of a rod.
A cylindrical cylinder, a cylindrical piston that divides a space in the cylinder, one end supports the piston in the cylinder, and the other end projects from the opening of the cylinder. A piston rod that reciprocates in the direction of the center line of the piston, the piston rod being joined by friction welding or welding of at least two members made of steel to at least one of the two members In addition, the quenching process is performed in a range not including the joining part of the two members, and the tempering process is performed on the part subjected to the quenching process and the range including the joining part.
[Selection] Figure 6

Description

  The present invention relates to a shock absorber and a method for manufacturing a rod.

A suspension device (suspension) of a vehicle such as an automobile is provided with a shock absorber in order to appropriately reduce vibration transmitted from the road surface to the vehicle body during traveling and improve riding comfort and steering performance.
For example, the hydraulic shock absorber described in Patent Document 1 is configured as follows. That is, the cylinder (damper tube) is composed of a double cylinder of an inner cylinder (inner cylinder) on which the piston slides and an outer cylinder (outer cylinder) provided outside the inner cylinder, and is inserted into the inner cylinder. A piston valve device configured by mounting a damping force generation valve or the like on the piston rod; and a bottom valve device configured by a damping force generation valve or the like and provided at the bottom. When the hydraulic shock absorber is compressed, a compression damping force is generated by the oil of the piston rod entering volume that enters the inner cylinder. Damping force is generated.

JP 2002-227900 A

A piston valve device of a shock absorber is configured by attaching a piston, a valve, and the like to a rod (piston rod) and fixing them with a male screw and a nut formed at the tip of the rod. In order to reduce the weight of the rod, it is also conceivable to manufacture the rod using a hollow steel pipe. When manufacturing a rod using a hollow steel pipe, this hollow steel pipe and the member which comprises the front-end | tip part in which an external thread is formed are joined, for example by friction welding or welding. When a member joined by friction welding or welding is used for a rod that reciprocates between the inside and outside of the cylinder, if the hardness of the joined portion joined by friction welding or welding is too high, the joining portion will be destroyed over time. There is a fear.
An object of this invention is to provide the buffering device which can suppress the time-dependent destruction of the joining site | part in a rod.

  For this purpose, the present invention provides a cylindrical cylinder, a cylindrical dividing member for dividing the space in the cylinder, one end portion supporting the dividing member in the cylinder, and the other A rod that protrudes from an opening of the cylinder and reciprocates in the direction of the center line of the cylinder, and the rod is joined by friction welding or welding of at least two members made of steel, The at least one member of the two members is subjected to a quenching process in a range not including the joint part of the two members, and the part including the quenching process and the range including the joint part A shock absorber characterized by being subjected to a tempering treatment.

Here, the hardness of the joining part of the rod is preferably Vickers hardness Hv450 or less by performing the tempering treatment. As a result, it is possible to more reliably suppress the aging destruction of the bonded portion.
The rod may be joined by friction welding or welding a cylindrical member and a member having a cylindrical portion and a columnar portion. Thereby, a rod can be reduced in weight easily.

  From another point of view, the present invention is such that one end supports a member that divides the space in the cylinder in the cylinder, and the other end projects from the opening of the cylinder. A method of manufacturing a rod that reciprocates in a linear direction, wherein at least two members made of steel are joined by friction welding or welding, and the two members are connected to at least one of the two members The rod manufacturing method is characterized in that a quenching process is performed in a range not including the joint part, and a tempering process is performed on the part subjected to the quenching process and the range including the joint part.

Here, by performing the tempering treatment, it is preferable that the hardness of the joining portion is Vickers hardness Hv450 or less. As a result, it is possible to more reliably suppress the aging destruction of the bonded portion.
Further, the cylindrical member and the member having a cylindrical part and a columnar part may be joined by friction welding or welding. Thereby, a rod can be reduced in weight easily.

  ADVANTAGE OF THE INVENTION According to this invention, the time-dependent destruction of the joining site | part in a rod can be suppressed.

It is a figure which shows schematic structure of the suspension apparatus which concerns on embodiment. It is a figure which shows schematic structure of the hydraulic shock absorber which concerns on this Embodiment. It is a figure which shows the flow of the oil at the time of the compression stroke of a hydraulic shock absorber. It is a figure which shows the flow of the oil at the time of the expansion stroke of a hydraulic shock absorber. It is a figure which shows the process in which a piston rod is manufactured. It is a figure which shows the process in which a piston rod is manufactured.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of a suspension device 1 according to the present embodiment.
As shown in FIG. 1, the suspension device 1 includes a hydraulic shock absorber 100 described later, and a spring 30 disposed outside the cylinder 110 and the piston rod 200 of the hydraulic shock absorber 100.

  The piston rod 200 is a rod-shaped member in which a cylindrical member and a member having a part of a columnar part and a cylindrical part are joined as will be described later. A piston 141 (see FIG. 2), which will be described later, is attached to one end side, and a nut 21 is attached to the other end side in the center line direction. Hereinafter, the center line direction of the cylinder and the column of the piston rod 200 may be simply referred to as “center line direction”.

  The suspension device 1 is attached to the outer periphery of the cylinder 110 and supports the lower end portion of the spring 30, and the suspension device 1 is attached to the outer periphery on the other end side in the center line direction of the piston rod 200. And an upper spring seat 32 that supports the portion. A lower seat rubber 35 is interposed between the lower end portion of the spring 30 and the lower spring seat 31, and an upper seat rubber 36 is interposed between the upper end portion of the spring 30 and the upper spring seat 32.

The suspension device 1 includes a wheel side mounting portion 40 provided at a lower portion of the cylinder 110. On the other hand, a bolt 33 for attaching the suspension device 1 to the vehicle body is attached to the upper spring seat 32.
The suspension device 1 also includes a bump rubber 41 that is press-fitted into the outer periphery of the piston rod 200 protruding from the cylinder 110, and a bump rubber cup 42 that is disposed on the outer periphery of the bump rubber 41.

  The suspension device 1 has an upper end mounted on the outer periphery of the bump rubber cup 42 and a lower end mounted on the lower spring seat 31, and a bellows-like dust cover 50 covering the outer periphery of the cylinder 110 and the piston rod 200 therebetween. It has. The lower end of the dust cover 50 is fastened to the lower spring seat 31 with, for example, a fastening ring and a screw (not shown).

  In addition, the suspension device 1 is arranged in the vertical direction on the upper end side of the piston rod 200, and is disposed inside a plurality of (two in this embodiment) mount rubbers 61 that absorb vibration and inside the plurality of mount rubbers 61. A cylindrical mount collar 62 and an upper washer 63 sandwiching a plurality of mount rubbers 61 from above and below are provided. The upper mount rubber 61 among the plurality of mount rubbers 61 is inserted into a recess formed in the upper spring seat 32 so as to be recessed from the upper end thereof. The lower mount rubber 61 is covered at its upper end and outer periphery by a mount rubber cup 65 disposed below the upper spring seat 32.

FIG. 2 is a diagram showing a schematic configuration of the hydraulic shock absorber 100 according to the present embodiment.
As shown in FIG. 2, the hydraulic shock absorber 100 includes a thin-cylindrical outer cylinder 111, a thin-cylindrical inner cylinder 112 accommodated in the outer cylinder 111, and one end in the center line direction of the outer cylinder 111. And a cylinder 110 having a bottom lid 113 for closing the part.

Further, the hydraulic shock absorber 100 supports the piston 141 with a later-described piston 141 inserted into the inner cylinder 112 so as to be movable in the center line direction, and one end portion (lower end portion in FIG. 2) in the center line direction. A piston rod 200 and a rod guide 125 that is disposed inside the outer cylinder 111 and guides the piston rod 200 are provided.
The piston 141 is in contact with the inner periphery of the inner cylinder 112, and a space in which the liquid (oil in this embodiment) in the inner cylinder 112 is sealed is a first end on the one end side in the center line direction from the piston 141. The oil chamber is divided into an oil chamber Y1 and a second oil chamber Y2 on the other end side of the piston 141 in the center line direction. The piston 141 is formed with a first oil passage 141a and a second oil passage 141b which are holes penetrating in the center line direction.

In addition, the hydraulic shock absorber 100 includes a bump stopper cap 70 that allows the piston rod 200 to reciprocate and is attached to the other end of the outer cylinder 111 in the center line direction.
Further, the hydraulic shock absorber 100 is provided on the inner side of the bump stopper cap 70 and on the opposite side of the piston 141 with respect to the rod guide 125, so that the liquid in the cylinder 110 leaks and foreign matter enters the cylinder 110. An oil seal 129 is provided.

The hydraulic shock absorber 100 includes a first valve device 130 disposed at one end portion in the center line direction of the inner cylinder 112 and a second valve disposed at one end portion of the piston rod 20 in the center line direction. Device 140.
The first valve device 130 includes a valve body 131 in which a first oil passage 131a and a second oil passage 131b, which are holes penetrating in the center line direction, and a first oil passage 131a formed in the valve body 131. A first valve 132 that closes one end portion in the center line direction and a second valve 133 that closes the other end portion in the center line direction of the second oil passage 131b formed in the valve body 131 are provided.
The second valve device 140 includes a piston 141, a first valve 142 that closes one end of the first oil passage 141 a formed in the piston 141 in the center line direction, and a second oil formed in the piston 141. And a second valve 143 that closes the other end of the channel 141b in the center line direction.

  In the cylinder 110, the length of the outer cylinder 111 in the center line direction is longer than the length of the inner cylinder 112, and the inner cylinder 112 is disposed concentrically with the outer cylinder 111. That is, one end of the inner cylinder 112 in the center line direction is supported by one end of the outer cylinder 111 in the center line direction via the valve body 131 and the bottom cover 113 of the first valve device 130. . On the other hand, the other end of the inner cylinder 112 in the center line direction is supported by the rod guide 125. Thus, the inner cylinder 112 is arranged concentrically with the outer cylinder 111 so that the gap between the outer periphery of the inner cylinder 112 and the inner periphery of the outer cylinder 111 is constant in the center line direction. A reservoir chamber R is formed by the outer periphery of the inner cylinder 112 and the inner periphery of the outer cylinder 111. In the hydraulic shock absorber 100 of the present embodiment, the interior of the reservoir chamber R is partitioned into an oil chamber in which oil is sealed and a gas chamber in which air, inert gas, and the like are sealed. As shown in FIG. 2, the first valve device 130 separates the first oil chamber Y <b> 1 and the reservoir chamber R by a valve body 131.

Next, the behavior of the hydraulic shock absorber 100 configured as described above will be described.
First, the behavior of the hydraulic shock absorber 100 during the compression stroke will be described.
FIG. 3 is a diagram illustrating the flow of oil during the compression stroke of the hydraulic shock absorber 100.
When the piston rod 200 moves toward one end side in the center line direction (downward in FIG. 3) with respect to the cylinder 110 as indicated by a white arrow, the pressure in the first oil chamber Y1 is moved by the movement of the piston 141. Rise. Then, the oil in the first oil chamber Y1 opens the second valve 143 that closes the second oil passage 141b of the second valve device 140, and flows into the second oil chamber Y2 above the second valve device 140 ( (See arrow A). The oil flow from the first oil chamber Y1 to the second oil chamber Y2 is throttled by the second valve 143 and the second oil passage 141b to obtain a damping force during the compression stroke of the hydraulic shock absorber 100.

  The oil in the first oil chamber Y1 opens the first valve 132 that closes the first oil passage 131a, and flows into the reservoir chamber R formed between the inner cylinder 112 and the outer cylinder 111 (see arrow B). ). The oil flow from the first oil chamber Y1 to the reservoir chamber R is throttled by the first valve 132 and the first oil passage 131a to obtain a damping force during the compression stroke of the hydraulic shock absorber 100.

Next, the behavior during the expansion stroke of the hydraulic shock absorber 100 will be described.
FIG. 4 is a diagram illustrating the flow of oil during the extension stroke of the hydraulic shock absorber 100.
When the piston rod 200 moves to the other end side in the center line direction (upward in FIG. 4) with respect to the cylinder 110 as indicated by a white arrow, the volume of oil is insufficient in the first oil chamber Y1. As a result, negative pressure is obtained. Thereby, the oil in the second oil chamber Y2 opens the first valve 142 that closes the first oil passage 141a of the second valve device 140, and flows into the first oil chamber Y1 (see arrow C). The oil flow from the second oil chamber Y2 to the first oil chamber Y1 is throttled by the first valve 142 and the first oil passage 141a of the second valve device 140, and the damping force during the expansion stroke of the hydraulic shock absorber 100 Get.

  Further, when the piston rod 200 moves toward the other end side in the center line direction with respect to the cylinder 110 (upward in FIG. 4), the oil in the reservoir chamber R becomes the second of the valve body 131 of the first valve device 130. The second valve 133 that closes the oil passage 131b is opened, and flows into the first oil chamber Y1 (see arrow D). The oil flow from the reservoir chamber R to the first oil chamber Y1 is throttled by the second valve 133 and the second oil passage 131b of the first valve device 130 to obtain a damping force during the expansion stroke of the hydraulic shock absorber 100. .

Next, the piston rod 200 will be described.
As shown in FIG. 2, the piston rod 200 is joined to a cylindrical member 210 which is a cylindrical member, and both ends of the cylindrical member 210 in the center line direction, and a partly cylindrical portion and a cylinder are joined. A first mixing member 220 and a second mixing member 230 which are mixing members having a shape-like portion. In FIG. 3, the first mixing member 220 is joined to the lower end (one end) of the cylindrical member 210, and the second mixing member 230 is joined to the upper end (the other end) of the cylindrical member 210. ing.

The cylindrical member 210 is a thin cylindrical member made of carbon steel. For the cylindrical member 210, for example, a structural steel pipe such as STKM (carbon steel pipe for mechanical structure) is used.
The first mixing member 220 is a member made of carbon steel, and includes a first cylindrical portion 221 (see FIG. 5) that is a cylindrical portion, and a first cylindrical portion 222 (see FIG. 5) that is a columnar portion. Have The first cylindrical portion 221 is joined to one end portion of the cylindrical member 210 in the center line direction using the method described below. The first cylindrical portion 222 is formed with a male screw for fixing the piston 141, the first valve 142, the second valve 143 and the like together with the nut. For example, the first mixing member 220 can be formed by forging.

  The second mixing member 230 is a member made of carbon steel, and a second cylindrical portion 231 (see FIG. 5) that is a cylindrical portion and a second cylindrical portion 232 (see FIG. 5) that is a cylindrical portion. Have The second cylindrical portion 231 is joined to the other end portion in the center line direction of the cylindrical member 210 by using the method described below. The second cylindrical portion 232 is formed with a male screw for fixing the mount rubber 61, the mount collar 62, the upper washer 63 and the like together with the nut 21. For example, the second mixing member 230 may be formed by forging.

  In FIG. 2, the first mixing member 220 is joined to the lower end portion of the cylindrical member 210, and the second mixing member 230 is joined to the upper end portion of the cylindrical member 210. May be joined to the upper end portion of the cylindrical member 210, and the second mixing member 230 may be joined to the lower end portion of the cylindrical member 210.

Next, a method for manufacturing the piston rod 200 will be described.
5 and 6 are diagrams illustrating a process of manufacturing the piston rod 200. FIG. 5 and 6, one end side in the center line direction is shown on the left side, and the other end side in the center line direction is shown on the right side.
First, the first mixing member 220 before molding the male screw is placed on one end side in the center line direction of the cylindrical member 210, and the second mixing member 230 before molding the male screw is placed on the center of the cylindrical member 210. It arrange | positions at the other edge part side of a line direction (refer Fig.5 (a)). The cylindrical member 210 and the first mixing member 220 are friction-welded, and the cylindrical member 210 and the second mixing member 230 are friction-welded.

  That is, in a state where the cylindrical member 210 is fixed, the first mixing member 220 in which the first columnar portion 222 is supported by the jig is rotated in one rotation direction with the center line as the rotation center. And while rotating the 1st mixing member 220, the end surface of the one end part side of the cylindrical member 210 and the end surface of the other end part side of the 1st cylindrical part 221 of the 1st mixing member 220 match. Then, the first mixing member 220 is moved in the center line direction (see FIG. 5B). And a high pressure is applied when both end surfaces contact and frictional heat is added, and the cylindrical member 210 and the 1st mixing member 220 are joined (refer FIG.5 (c)). Due to this friction welding, a first outer portion projecting outward from the outer peripheral surface of the cylindrical member 210 and the first mixing member 220 is formed in the first bonding portion 225 which is a bonding portion between the cylindrical member 210 and the first mixing member 220. A protruding portion 226 and a first inner protruding portion 227 protruding inward from the inner peripheral surface of the first cylindrical portion 221 of the cylindrical member 210 and the first mixing member 220 are formed (see FIG. 5D).

  On the other hand, with the cylindrical member 210 fixed, the second mixing member 230, in which the second columnar portion 232 is supported by the jig, is rotated in the other rotation direction with the center line as the rotation center. And while rotating the 2nd mixing member 230, the end surface of the other end part side of the cylindrical member 210 and the end surface of the 1st end part side of the 2nd cylindrical part 231 of the 2nd mixing member 230 match. Then, the second mixing member 230 is moved in the center line direction (see FIG. 5B). And a high pressure is applied when both end surfaces contact and frictional heat is added, and the cylindrical member 210 and the 2nd mixing member 230 are joined (refer FIG.5 (c)). Due to this friction welding, a second outer portion projecting outward from the outer peripheral surface of the cylindrical member 210 and the second mixing member 230 is formed in the second bonding portion 235 which is a joint portion between the cylindrical member 210 and the second mixing member 230. A protruding portion 236 and a second inner protruding portion 237 protruding inward from the inner peripheral surface of the second cylindrical portion 231 of the cylindrical member 210 and the second mixing member 230 are formed (see FIG. 5D).

Note that the above-described friction welding between the cylindrical member 210 and the first mixing member 220 and the friction welding between the cylindrical member 210 and the second mixing member 230 may be performed simultaneously, or one of them may be friction welding. After that, the other may be friction-welded. When not performed simultaneously, the rotation direction of the second mixing member 230 may be the same as the rotation direction of the first mixing member 220.
Further, the joining of the cylindrical member 210 and the first mixing member 220 and the joining of the cylindrical member 210 and the second mixing member 230 are not limited to friction welding, and may be joined by welding. At that time, welding of the cylindrical member 210 and the first mixing member 220 and welding of the cylindrical member 210 and the second mixing member 230 may be performed at the same time, or after welding one of them, the other May be welded.

  After joining the cylindrical member 210 and the first mixing member 220, the first outer protrusion 226 is removed by, for example, cutting (see FIG. 6A). Moreover, after joining the cylindrical member 210 and the 2nd mixing member 230, the 2nd outer side protrusion part 236 is removed by cutting, for example (refer Fig.6 (a)). The removal of the first outer protrusion 226 and the removal of the second outer protrusion 236 may be performed simultaneously, or after removing either one, the other may be removed.

  After removing the first outer protrusion 226 and the second outer protrusion 236, the cylindrical member 210 of the piston rod 200 is quenched as shown in FIG. 6B. That is, after the cylindrical member 210 is heated, it is rapidly cooled in water or oil. The cylindrical member 210 is subjected to a quenching process because the cylindrical member 210 reciprocates (moves) in the center line direction while contacting the rod guide 125 and the oil seal 129 during the compression stroke and the expansion stroke of the hydraulic shock absorber 100. ) (See FIGS. 3 and 4) to increase the hardness and strength so as to withstand repeated contact forces. Therefore, it is necessary to quench the portion of the cylindrical member 210 that comes into contact with the rod guide 125 and the oil seal 129 during the compression stroke and the expansion stroke of the hydraulic shock absorber 100. 3 and 4, in the hydraulic shock absorber 100 according to the present embodiment, the first joint portion 225 and the second joint portion 235 at both ends of the cylindrical member 210 are not covered, that is, the first It is sufficient to quench the portion between the first joint portion 225 and the second joint portion 235 (inside the first joint portion 225 and inside the second joint portion 235). Therefore, in the quenching process according to the present embodiment, as shown in FIG. 6B, the position where the predetermined length α is entered from the inner end 225 a of the first joint 225 to the inside, and the second joint 235. A quenching process is performed between the inner end portion 235a and a position having a predetermined length β inside. And by this hardening process, the hardness of the cylindrical member 210 becomes Vickers hardness Hv450 or more. The predetermined length α and the predetermined length β may be the same length or may be different.

  After the cylindrical member 210 of the piston rod 200 is quenched, the piston rod 200 is tempered. That is, the piston rod 200 is heated and held for a certain time, and then slowly cooled. The reason why the piston rod 200 is tempered is to mainly impart toughness to the steel hardened by the quenching process, but in the tempering process according to the present embodiment, in addition to the part subjected to the quenching process, Tempering treatment is also performed on the first joint 225 and the second joint 235. That is, as shown in FIG. 6C, a tempering process is performed on a range including the cylindrical member 210, the first cylindrical portion 221 of the first mixing member 220, and the second cylindrical portion 231 of the second mixing member 230. . And by this tempering process, hardness becomes Vickers hardness Hv450 or less. In other words, in the manufacturing method according to the present embodiment, the hardness of the portion of the cylindrical member 210 that has become the Vickers hardness Hv450 or more by the quenching process is reduced to the Vickers hardness Hv450 or less by the tempering process, and the friction. The hardness of the 1st junction part 225 and the 2nd junction part 235 which became Vickers hardness Hv450 or more by pressure welding or welding is made Vickers hardness Hv450 or less by a tempering process.

Then, male threads are formed by rolling, for example, on the first cylindrical portion 222 of the first mixing member 220 and the second cylindrical portion 232 of the second mixing member 230, which are both ends of the piston rod 200.
In this way, the piston rod 200 is manufactured.

The piston rod 200 manufactured by the manufacturing method described above has the following advantages.
That is, a portion of the cylindrical member 210 that reciprocates (moves) in the center line direction while contacting the rod guide 125 and the oil seal 129 during the compression stroke and the expansion stroke of the hydraulic shock absorber 100 is subjected to quenching and tempering treatment. It is strong enough to withstand repeated contact forces.
Also, when the cylindrical member 210 and the first mixing member 220 are friction welded or welded, the first joint 225 formed, and when the cylindrical member 210 and the second mixed member 230 are friction welded or welded. Since the formed second joint portion 235 is tempered and has a Vickers hardness of Hv450 or less, it is possible to suppress the occurrence of aging fracture (hydrogen brittle fracture, delayed fracture, and cracking). . That is, if the tempering process is not performed and the friction welded or welded state remains, the hardness of the first joint portion 225 and the second joint portion 235 may exceed the Vickers hardness Hv450, and aging failure may occur. Will increase. On the other hand, in the piston rod 200 according to the present embodiment, the tempering process is performed after the friction welding or welding, and the hardness becomes Vickers hardness Hv450 or less, so that the secular change failure is less likely to occur. . And since the tempering process is performed to make the hardness of the first joint part 225 and the second joint part 235 Vickers hardness Hv450 or less, the part subjected to the quenching process is performed simultaneously with the tempering process. The number of steps can be reduced as compared with the case where the tempering process is performed only for the joint portion 225 and the second joint portion 235.

  In the above-described embodiment, the first joint 225 formed when the cylindrical member 210 and the first mixing member 220 are friction welded or welded, the cylindrical member 210 and the second mixing member 230, Although tempering is performed on both of the second joint portion 235 formed at the time of friction welding or welding, the present invention is not particularly limited to such a mode. A tempering process may be performed on one of the first joint 225 and the second joint 235. Compared with the case where the tempering treatment is not performed, the joint portion subjected to the tempering treatment can be made less likely to cause aging damage.

DESCRIPTION OF SYMBOLS 1 ... Suspension device, 100 ... Hydraulic shock absorber, 110 ... Cylinder, 125 ... Rod guide, 129 ... Oil seal, 200 ... Piston rod, 210 ... Cylindrical member, 220 ... First mixing member, 230 ... Second mixing member

Claims (6)

A cylindrical cylinder;
A cylindrical partition member for partitioning the space in the cylinder;
A rod whose one end supports the partition member in the cylinder, the other end projects from the opening of the cylinder, and reciprocates in the direction of the center line of the cylinder;
With
The rod is joined by friction welding or welding of at least two members made of steel, and is hardened within a range not including the joining portion of the two members with respect to at least one of the two members. A shock absorber characterized in that a tempering treatment is performed on a region that has been subjected to the treatment and that includes the portion subjected to the quenching treatment and the range including the joining portion.   2. The shock absorber according to claim 1, wherein the hardness of the joint portion of the rod is Vickers hardness Hv450 or less by performing the tempering process.   3. The rod according to claim 1, wherein the rod is joined by friction welding or welding of a cylindrical member and a member having a cylindrical portion and a columnar portion. Shock absorber. A rod manufacturing method in which one end supports a member that partitions the space in the cylinder in the cylinder, and the other end projects from the opening of the cylinder and reciprocates in the direction of the center line of the cylinder. There,
Joining at least two steel members by friction welding or welding;
Quenching treatment is performed for at least one member of the two members in a range not including the joint portion of the two members,
A method for producing a rod, comprising performing a tempering process on a region including the quenching process and a range including the joining part.   The method for manufacturing a rod according to claim 4, wherein the tempering treatment is performed so that the hardness of the joint portion is set to Vickers hardness Hv450 or less.   6. The method for manufacturing a rod according to claim 4, wherein the cylindrical member and the member having a cylindrical portion and a columnar portion are joined by friction welding or welding.

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