Manufacturing apparatus for impact absorber, impact absorber, and method for manufacturing impact absorber

Abstract

To reduce time required for processing while easily manufacturing an impact absorption body and achieving a length in an arbitrary axial direction, compared to a conventional processing method.SOLUTION: An apparatus (1) for manufacturing an impact absorption body includes: heating means (21) for heating a heated part as a part of a cylindrical body (2) between a first support (3) and a second support (4), and lowering a rotational torque required for plastic deformation of the heated part with respect to a rotational torque required for plastic deformation in non-heating; and moving means (M1) for relatively moving the first support (3) and the second support (4) with a rotational torque exceeding a rotational torque required for plastic deformation of the heated part and less than a rotational torque required for plastic deformation in non-heating.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a manufacturing apparatus for a shock absorber, a shock absorber, and a method for manufacturing a shock absorber, and more particularly to a manufacturing apparatus for a shock absorber that can be used in an automobile or the like to absorb shock during a collision, a shock absorber, and a method for manufacturing a shock absorber.

Background Art

[0002] In order to reduce the weight of automobiles and ensure collision safety, various lightweight and high-rigidity hollow shock absorbers have been developed. In particular, the development of a vehicle body structure in which axial crushing continues as long as possible without Euler buckling is required. Regarding such a shock absorber, the technique described in Patent Document 1 below is known. Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2011-58579) describes using an energy absorption structure using an inverted spiral type origami structure as a side member of an automobile. Patent Document 1 describes forming folds in advance on a cylindrical metal body, or forming notches or thin-wall processing so that it can be folded at the position of the fold line.

[0003] In addition, Non-Patent Document 1 and Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2011-104612) describe a technique called hydroforming in which a high-pressure fluid is introduced into a cylindrical tube disposed in a mold to expand and deform the tube along the inner surface of the mold to process the tube.

[0004] Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2018-187637) describes a technique in which a cylindrical body is sandwiched between molds (17, 27) of two supports, the portion between the molds (17, 27) is heated, and the supports are relatively moved (twisted) to form a fold line (concave and convex line) on the surface of the cylindrical body, and the two molds (17, 27) are shifted in the axial direction of the cylindrical body to form the fold line step by step.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-58579 (paragraphs "0021" to "0022", "0037") [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-104612 (paragraphs "0033" to "0041") [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-187637

[0006] [Non-Patent Document 1] "Application of Tube Hydroforming to Automotive Part Forming", Automotive Engineering, Vol. 57, No. 6, (2003), pages 23-28 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] (Problems of the Prior Art) When making folds, notches, thinning processes, etc. on a cylindrical metal body as described in Patent Document 1, when the number of fold lines increases, there is a problem that the processing becomes difficult. In particular, as the axial length of the tube becomes longer and the number of stages increases, the number of fold lines also increases dramatically, so there is a problem that the processing operation becomes troublesome with the processing method described in Patent Document 1. In the hydroforming method described in Non-Patent Document 1 and Patent Document 2, when trying to process a metal with high rigidity, it is necessary to make the pressure of the fluid extremely high, and there are also problems that the processing is difficult and the cost becomes high. In particular, as the axial length of the tube becomes longer, it becomes more difficult to apply the pressure required for the fluid, and pressure unevenness is likely to occur, and processing unevenness is also likely to occur. Therefore, in the hydroforming method, there is also a problem that only a tube with an axial length corresponding to the size of the manufacturing apparatus can be processed, and an impact absorber of an arbitrary size cannot be processed.

[0008] In the technique described in Patent Document 3, the problems in Patent Documents 1, 2, and Non-Patent Document 1 can be solved. However, in a technique such as that in Patent Document 3 where two molds (jigs) are shifted in the axial direction to gradually form a fold line, after processing one stage of the fold line and before processing the next stage of the fold line, it is necessary to remove (loosen) the mold, shift the cylindrical body in the axial direction, and then attach (tighten) the mold. Therefore, in Patent Document 3, there are problems that the number of steps required for processing one stage is large and the time required for processing becomes long. Also, in the technique described in Patent Document 3, at the time of processing the first stage, it is a mold corresponding to the cylindrical body before the fold line is formed, whereas after the second stage and later, the mold cannot be made to adhere to the material (cylindrical body) unless a mold corresponding to the cylindrical body after the fold line is formed is used. Therefore, it is necessary to change the mold between the first stage and after the second stage, and there is also a problem that the types of molds increase and the cost rises. Also, depending on the shape of the fold line, there is a problem that the production of the mold is not easy.

[0009] The technical problem of the present invention is to reduce the time required for processing while easily manufacturing a shock absorber and realizing an arbitrary axial length as compared with conventional processing methods.

Means for Solving the Problems

[0010] In order to solve the above technical problem, the manufacturing apparatus for a shock absorber according to the invention described in claim 1 is For a hollow cylindrical body extending in the axial direction, a first support body that supports an unprocessed portion of the cylindrical body, A second support body that is spaced apart from the first support body along the axial direction of the cylindrical body and supports an unprocessed portion of the cylindrical body, A heating means that heats a portion of the cylindrical body between the first support body and the second support body, which has a predetermined length in the axial direction, and reduces the rotational torque required for plastic deformation of the heated portion as compared with the rotational torque required for plastic deformation when not heated. Moving means for relatively moving the first support and the second support with a rotational torque that exceeds the rotational torque required for plastic deformation of the heated portion and is less than the rotational torque required for plastic deformation during non-heating. Control means for controlling the moving means to relatively move the first support and the second support along the circumferential direction of the cylindrical body, thereby the heated part forming , inclined with respect to the axial direction concavo-convex lines on the cylindrical body, the control means relatively moving the first support and the second support by a relative movement amount corresponding to the inclination angle of the concavo-convex lines with respect to the axial direction. and comprising 、 After plastically deforming the heated part by one stage, heating the position shifted by one stage along the axial direction of the cylinder body with the heating means and plastically deforming by the relative movement between the first support and the second support are repeated, thereby sequentially heating and plastically deforming the cylinder body, and the direction of the relative movement is made opposite between the odd-numbered stages and the even-numbered stages of the heated part th characterized by the above.

[0011] The invention according to claim 2 is an apparatus for manufacturing a shock absorber according to claim 1, heating means for heating the heated portion to a temperature at which the rotational torque required for plastic deformation of the heated portion is 1 / 3 times or less the rotational torque required for plastic deformation during non-heating, with respect to the rotational torque required for plastic deformation during non-heating. characterized by comprising the above.

[0012] To solve the above technical problem, the shock absorber according to claim 3 is characterized by being manufactured by the apparatus for manufacturing a shock absorber according to claim 1 or 2.

[0013] To solve the above technical problem, the method for manufacturing a shock absorber according to claim 4 supports an unprocessed portion of a hollow cylindrical body extending in the axial direction with a first support and a second support at intervals, heats a heated portion of a part of the cylindrical body between the first support and the second support with heating means to reduce the rotational torque required for plastic deformation of the heated portion with respect to the rotational torque required for plastic deformation during non-heating. According to the relative movement amount corresponding to the inclination angle of the concavo-convex line formed on the cylindrical body with respect to the axial direction, the first support body and the second support body are relatively moved with a rotational torque that exceeds the rotational torque required for plastic deformation of the heated portion and is less than the rotational torque required for plastic deformation during non-heating, thereby forming a concavo-convex line on the cylindrical body. It is characterized by this.

Effect of the Invention

[0014] According to the invention described in claims 1, 3, and 4, compared with the conventional processing method, the manufacturing of the shock absorber can be made easier, an arbitrary axial length can be realized, and the time required for processing can be reduced. According to the invention described in claim 2, it is easy to sufficiently ensure the difference in the rotational torque required for plastic deformation between the heated portion and other portions, the heated portion can be efficiently processed, plastic deformation of the non-heated portion can be suppressed, and it is easy to realize a shock absorber having the desired shape.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] Next, with reference to the drawings, examples which are specific examples of embodiments of the present invention will be described, but the present invention is not limited to the following examples. In the description using the following drawings, illustrations other than the members necessary for the description are appropriately omitted for ease of understanding.

EXAMPLE

[0017] FIG. 1 is an explanatory view of a manufacturing apparatus for a shock absorber according to Embodiment 1 of the present invention. In FIG. 1, a manufacturing apparatus 1 for a shock absorber according to Embodiment 1 of the present invention includes a first support portion 3 disposed on one end side of a cylindrical body 2 and a second support portion 4 disposed on the other end side. Each of the support portions 3 and 4 is arranged to support an unprocessed portion of the cylindrical body 2, that is, a portion where the concavo-convex line 31 described later is not formed. In Embodiment 1, as an example of the cylindrical body 2, a square iron pipe is used. The cylindrical body 2 is formed in a cylindrical shape extending in the axial direction, that is, a so-called pipe shape. Further, in Embodiment 1, although the cylindrical body 2 is arranged along the horizontal direction, it can be arbitrarily changed according to the installation environment of the manufacturing apparatus 1, such as being arranged along the gravity direction (vertical direction) or obliquely. Also, as an example, the cylindrical body 2 of Embodiment 1 uses a mild steel material made of steel, but the material is not limited to this, and other metals, alloys, resins, etc. can be used.

[0018] The first support portion 3 and the second support portion 4 are configured substantially the same as the upstream portion and the downstream portion described in Patent Document 3, for example, and various conventionally known configurations can be applied, so a detailed description is omitted. In Embodiment 1, instead of the handle 15 in Patent Document 3, a gear 15 as an example of a gear is formed on the outer periphery, but the configuration of the handle 15 in Patent Document 3 can also be adopted. In Example 1, drive is transmitted from a motor M1, which is an example of a moving means, to a gear 15 via a gear train (not shown). In Example 1, a plurality of gears including the motor M1 and the gear 15 are configured to be able to apply a predetermined torque to the cylindrical body 2 by relatively moving (rotating) the first support portion 3 with respect to the second support portion 4. In Example 1, a configuration in which the second support portion 4 is fixed and the first support portion 3 is rotated is illustrated, but the present invention is not limited thereto. It is also possible to adopt a configuration in which the first support portion 3 is fixed and the second support portion 4 is rotated, or a configuration in which both the first support portion 3 and the second support portion 4 are rotated.

[0019] The manufacturing apparatus 1 of the shock absorber according to Example 1 includes a heating device 21 as an example of a heating means. The heating device 21 according to Example 1 has a rail 22 extending along the axial direction of the cylindrical body 2 on the sides of the first support portion 3 and the second support portion 4. A slider 23 is supported by the rail 22 so as to be movable along the axial direction of the cylindrical body 2. A heating device main body 24 is supported by the slider 23. The heating device main body 24 has a coil-shaped (ring-shaped) heating portion 26 that surrounds the outer periphery of the cylindrical body 2. The heating portion 26 is configured to be able to non-contact heat a predetermined range (one stage of the processing target) of the cylindrical body 2 by electromagnetic induction heating (IH) when energized. A motor (not shown) for moving the slider 23 is disposed on the slider 23. The motor M1, the motor for the slider 23, and the heating device main body 24 are configured to be able to transmit and receive control signals to and from a controller C as an example of control means. The controller C has an input / output interface I / O for inputting and outputting signals to and from the outside. Further, the controller C has a ROM (Read Only Memory) in which programs, information, etc. for performing necessary processes are stored. Further, the controller C has a RAM (Random Access Memory) for temporarily storing necessary data. Further, the controller C has a CPU (Central Processing Unit) for performing processes according to programs stored in the ROM and the like. Therefore, the controller C of the first embodiment is constituted by an information processing device, a so-called computer device. Thus, the controller C can realize various functions by executing programs stored in the ROM and the like.

[0020] (Function of the controller C) The controller C has a function of executing a process according to an input signal from the signal output element and outputting a control signal to each of the control elements. That is, the controller C has the following functions.

[0021] FIG. 2 is an explanatory diagram of the rotational torque required for plastic deformation in the cylindrical body of the first embodiment, and is a diagram with time on the horizontal axis and torque on the vertical axis. The heating control means C1 controls the heating device 21 to control partial heating of the cylindrical body 2. The heating control means C1 of the first embodiment controls the heating device 21 to heat a portion surrounded by the heating portion 26 (that is, one stage of the object to be processed) in the cylindrical body 2 to 950° C. as an example of a predetermined temperature. In FIG. 2, an experiment was conducted on the value of the rotational torque required for plastic deformation of the mild steel used in the cylindrical body 2 of the first embodiment. In FIG. 2, in the experiment, since the mild steel repeats buckling and work hardening, the history (profile) of the rotational torque has a wavy result. In FIG. 2, when not heated (room temperature: 25° C.), the average rotational torque required for plastic deformation is about 1200 Nm, whereas at 950° C., the average rotational torque required for plastic deformation is about 350 Nm (less than 1 / 3 of that when not heated). Therefore, depending on the material used, the degree of reduction in rotational torque during heating may vary, or if the degree of reduction desired during heating (not 1 / 3, but 1 / 2 or 1 / 4, etc.) is different compared to when not heated, the temperature can be appropriately changed according to the material used and the desired degree of reduction in rotational torque. The heating control means C1 of Example 1 starts heating the cylinder body 2 with the heating device 21 before forming the uneven line (31), and ends the heating with the heating device 21 when the formation of the uneven line (31) is completed.

[0022] FIG. 3 is an explanatory view of the shock absorber. FIG. 3A is an explanatory view before processing, FIG. 3B is an explanatory view of the state after being processed in one stage, FIG. 3C is an explanatory view of the state after being processed in two stages, FIG. 3D is an explanatory view of the state after being processed in three stages, and FIG. 3E is an explanatory view of the state after being processed in four stages. The deformation control means C2 controls the motor M1 to relatively move (rotate) the first support portion 3 with respect to the second support portion 4 to deform the cylinder body 2. In FIG. 3, in the deformation control means C2 of Example 1, at the uneven line 31 to be formed, the first support portion 3 is rotated with respect to the second support portion 4 according to the inclination angle θ with respect to the outer side 32 extending in the axial direction of the cylinder body 2. In Example 1, when the inclination angle θ is 5° as an example, the first support portion 3 is rotated by 5°. Note that the deformation control means C2 of Example 1 rotates the first support portion 3 in the forward rotation direction when processing the odd-numbered stages (the first stage, the third stage, the fifth stage,...) of the cylinder body 2, and rotates the first support portion 3 in the reverse rotation direction when processing the even-numbered stages (the second stage, the fourth stage, the sixth stage,...). Therefore, the uneven line 31 is formed along a so-called reverse helix. Note that in Example 1, the first support portion 3 is rotated in the reverse direction for the odd-numbered and even-numbered stages so that the uneven line 31 is formed along a reverse helix, but it is not limited thereto. It is also possible to configure such that the first support portion 3 is rotated in the same direction for both the odd-numbered and even-numbered stages so that the uneven line is formed along a helix. It is also possible to change the inclination angle for each stage.

[0023] In addition, in the first embodiment, when the first support portion 3 is rotated, the motor M1, the gear train, the first support portion 3, etc. are configured such that a rotational torque of about 700 Nm acts on the cylindrical body 2. When the machining of one stage of the cylindrical body 2 is completed, the slider control means C3 moves the slider 23 by a predetermined length (one stage) along the axial direction of the cylindrical body 2.

[0024] (Operation of the first embodiment) In the manufacturing apparatus 1 of the shock absorber according to the first embodiment having the above configuration, when forming the concavo-convex line 31 on the cylindrical body 2, with both ends of the cylindrical body 2 supported by the support portions 3 and 4, a part of the cylindrical body 2 is heated by the heating device 21. Then, the first support portion 3 is rotated with respect to the second support portion 4. At this time, a rotational torque of about 700 Nm acts on the cylindrical body 2. That is, the rotational torque does not reach about 1200 Nm, which is the rotational torque required for plastic deformation when the cylindrical body 2 is not heated, and a torque exceeding about 350 Nm, which is the rotational torque required for plastic deformation of the heated portion, acts on the cylindrical body 2. Therefore, the non-heated portion does not plastically deform, and only the heated portion surrounded by the heating portion 26 plastically deforms. Thus, the concavo-convex line 31 is formed only on the heated portion (only one stage). Next, the heating portion 26 moves one stage along the axial direction of the cylindrical body 2, and the second-stage portion is heated. At this time, the processed first-stage portion is not heated, the temperature decreases, and the rotational torque required for plastic deformation returns. Therefore, the concavo-convex line 31 can be formed only on the second-stage portion. Similarly, the concavo-convex line 31 can be formed in the third stage and subsequent stages, and the shock absorber 41 having the concavo-convex line 31 formed on the cylindrical body 2 can be formed. Also, the number of stages can be arbitrarily increased, and the axial length can be arbitrarily changed.

[0025] Therefore, in the manufacturing apparatus 1 of the shock absorber according to the first embodiment, when shifting to the processing of the next stage after the processing of one stage, it is possible to shift to the next stage only by sliding the heating device 21 with respect to the cylindrical body 2. Therefore, compared with the technique described in Patent Document 3, it is possible to shorten the processes and time required when shifting to the next stage. Therefore, the overall processing time can also be shortened. Therefore, the manufacturing apparatus 1 of the shock absorber according to the first embodiment can reduce the time required for processing while easily manufacturing the shock absorber 41 and realizing an arbitrary axial length as compared with the conventional processing method. In particular, in the heating device 21 of the first embodiment, the heating unit 26 is arranged in a non-contact manner with respect to the cylindrical body 2, and the movement during the sliding of the heating device 21 can also be performed smoothly. Therefore, compared with the configuration in which the heating unit 26 is in contact with the cylindrical body 2, it is possible to shorten the processing time, and deformation, damage, etc. of the cylindrical body 2 due to the contact and separation between the cylindrical body 2 and the heating unit 26 are also suppressed.

[0026] Also, in the first embodiment, the heating unit is heated to a temperature at which the rotational torque required for plastic deformation is 1 / 3 or less compared to when not heated. Therefore, the difference in torque required between the portion of the processing target where the uneven line 31 is to be formed and the portion that is not the processing target is large. Therefore, only the portion to be processed can be efficiently processed, and plastic deformation of the portion that is not desired to be processed can be suppressed. Therefore, it is easier to realize the shock absorber 41 having the target shape. In addition, in the manufacturing apparatus 1 of the shock absorber according to the first embodiment, it was possible to heat to the target temperature of 950°C in about 30 seconds. That is, the processing time can also be performed in a very short time. Furthermore, the torque required during processing was about 700 Nm, but this can be realized with a significantly smaller amount of energy compared to the case of forming the uneven line 31 on the cylindrical body 2 by existing press processing. And the shock absorber 41 of the first embodiment manufactured in this way has the uneven line 31 formed along the reverse helix, and it is possible to obtain the shock absorber 41 in which the initial peak load is lowered and the crushing amount is large compared to the cylindrical body in which the uneven line 31 is not formed.

[0027] (Modification example) As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. For example, the shape of the heating unit 26 is not limited to a ring shape (annular shape), and can also be square or hexagonal. Further, although it is desirable that the heating unit 26 is non-contact, it is also possible to adopt a configuration in which heating is performed by contact. In addition, in the embodiment, the case of using the square cylindrical body 2 has been illustrated, but the present invention is not limited thereto. For example, it is also possible to use a polygonal cylindrical body such as a hexagonal cylinder or an octagonal cylinder, an elliptical cylinder, a circular cylinder, a cylinder having a star-shaped, trapezoidal, or rhombic cross section. When using a circular cylinder, since there is a risk of slipping between the mold and the circular cylinder when twisting, it is desirable to provide a portion that catches like a protrusion and a groove on the circular cylinder and the mold, and add a configuration in which the twisting force is easily transmitted.

[0028] Furthermore, in the embodiment, the cylindrical body 2 has been illustrated as a cylindrical body having the same inner diameter and outer diameter from one end side to the other end side, but the present invention is not limited thereto. It is also possible to use a cylindrical body in which the diameter increases from one end side to the other end side, that is, a so-called conical body (conical shell). In addition, it is also possible to use a cylindrical body in which the diameter periodically expands and contracts from one end side to the other end side, that is, a so-called bellows-shaped cylindrical body. In addition, in the first embodiment, a configuration has been illustrated in which an impact absorber 41 having an inverted spiral-shaped uneven line 31 is obtained by rotating the first support portion 3 in the reverse direction for each stage. However, the present invention is not limited thereto. It is also possible to manufacture an impact absorber in which a (forward) spiral-shaped uneven line is formed by rotating the first support portion 3 in the same direction for each stage.

[0029] Furthermore, in Example 1, the case where the heating range (the length of one stage) by the heating unit 26 is fixed was exemplified, but it is not limited to this. For example, the heating unit 26 may be configured such that the first heating unit and the second heating unit are arranged along the axial direction, and the first heating unit and the second heating unit can be individually controlled. When it is desired to shorten the length of one stage, only the first heating unit is used for heating. When it is desired to lengthen the length of one stage, both the first heating unit and the second heating unit are used for heating, so that the length of one stage can be adjusted in two steps. Also, by providing three or more heating units, it is possible to adjust the length of one stage in three or more steps. Therefore, it is possible to arbitrarily change the length of one stage for each shock absorber 41, and it is also possible to adopt a configuration in which the length of one stage is different for each stage within one shock absorber 41.

[0030] FIG. 4 is an explanatory view of Modification 1. FIG. 4A is an explanatory view of the state before processing, FIG. 4B is an explanatory view of the state after processing for one stage, and FIG. 4C is an explanatory view of the state after processing for two stages. In the above Example 1, each of the support portions 3 and 4 supports both end portions of the cylindrical body 2 and is configured not to move in the axial direction, but it is not limited to this. As shown in FIGS. 4A to 4C, each time processing for one stage is performed, the first support portion 3 can be moved one stage at a time in the axial direction. At this time, the first support portion 3 supports the unprocessed portion. Therefore, also in Modification 1, unlike Patent Document 3, it is not necessary to change the inner shape of the first support portion 3, and processing is possible while preventing an increase in the types of the first support portion (die).

[0031] FIG. 5 is an explanatory view of Modification 2. FIG. 5A is an explanatory view of the state before processing, FIG. 5B is an explanatory view of the state after processing for one stage, and FIG. 5C is an explanatory view of the state after processing for two stages. In FIG. 5, in Modification 2, in FIG. 5A at the stage before processing, the first support portion 3 and the second support portion 4 are arranged with an interval of two stages. As shown in FIGS. 5A to 5C, when processing for two stages is performed, it is also possible to move (shift) the first support portion 3 two stages in the axial direction.

[0032] FIG. 6 is an explanatory diagram of Modification Example 3. FIG. 6A is an explanatory diagram of the state before processing, and FIG. 6B is an explanatory diagram of the state after being processed by one step. In FIG. 6, in Modification Example 3, in FIG. 6A at the stage before processing, the first support portion 3 and the second support portion 4 are arranged with an interval of three steps (or more). As shown in FIGS. 6A and 6B, it is also possible to adopt a configuration in which processing is performed on a portion that is not adjacent to the support portions 3 and 4 along the cylindrical body 2. In addition, in the configurations illustrated in the first embodiment and Modification Examples 1 to 3, the position of the second support portion 4 does not have to be at the end of the cylindrical body 2, and it is also possible to set it at the central portion in the axial direction of the cylindrical body 2. Further, it is also possible to move the second support portion 4 in the axial direction as the processing progresses.

[0033] In addition, in the first embodiment, the case where mild steel is used as the cylindrical body 2 is illustrated, but it is not limited thereto. It is possible to use any material, such as any material for which the rotational torque decreases due to heating, aluminum, stainless steel, aluminum alloy, titanium alloy, etc.

Explanation of reference numerals

[0034] 1... Manufacturing apparatus of impact absorber, 2... Cylindrical body, 3... First support, 4... Second support, 21... Heating means, 31... Concavo-convex line, 41... Impact absorber, C... Control means, M1... Moving means.

Claims

1. With respect to a hollow cylindrical body extending in the axial direction, a first support for supporting an unprocessed portion of the cylindrical body, A second support spaced apart from the first support along the axial direction of the cylindrical body and supporting an unprocessed portion of the cylindrical body, Heating means for heating a heated portion that is a part of the cylindrical body between the first support and the second support and has a predetermined length in the axial direction, and reducing the rotational torque required for plastic deformation of the heated portion with respect to the rotational torque required for plastic deformation when not heated, Moving means for relatively moving the first support and the second support with a rotational torque that exceeds the rotational torque required for plastic deformation of the heated portion and is less than the rotational torque required for plastic deformation when not heated, Control means for controlling the moving means to relatively move the first support and the second support along the circumferential direction of the cylindrical body, thereby forming uneven lines inclined with respect to the axial direction on the heated portion of the cylindrical body. The control means relatively moves the first support and the second support by a relative movement amount corresponding to the inclination angle of the uneven lines with respect to the axial direction, comprising After plastically deforming the heated portion by one stage, heating the position shifted by one stage along the axial direction of the cylindrical body with the heating means and plastically deforming by relative movement of the first support and the second support, and repeating this process to sequentially heat and plastically deform the cylindrical body, The direction of the relative movement is opposite between the odd-numbered stages and the even-numbered stages of the heated portion A manufacturing apparatus for a shock absorber, characterized by this.

2. The heating means for heating the heated portion to a temperature at which the rotational torque required for plastic deformation of the heated portion is 1 / 3 times or less with respect to the rotational torque required for plastic deformation when not heated, The manufacturing apparatus for a shock absorber according to claim 1, characterized by comprising this.

3. An impact absorber, characterized by being manufactured by the manufacturing apparatus of the impact absorber according to claim 1 or 2.

4. Support an unprocessed portion of a hollow cylindrical body extending in the axial direction with a first support and a second support at intervals, Heat a heated portion of a part of the cylindrical body between the first support and the second support with heating means to reduce the rotational torque required for plastic deformation of the heated portion compared to the rotational torque required for plastic deformation when not heated, According to the relative movement amount corresponding to the inclination angle of the uneven line formed on the cylindrical body with respect to the axial direction, with a rotational torque that exceeds the rotational torque required for plastic deformation of the heated portion and is less than the rotational torque required for plastic deformation when not heated, by relatively moving the first support and the second support, an uneven line is formed on the cylindrical body A method for manufacturing an impact absorber, characterized by the above.

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