JP7693201B2 - Shock absorber manufacturing apparatus, shock absorber, and method for manufacturing shock absorber - Google Patents

Description

Article 30, paragraph 2 of the Patent Law applied. Transactions of the Japan Society of Mechanical Engineers, Vol. 87, No. 895, The Japan Society of Mechanical Engineers

The present invention relates to an apparatus for manufacturing shock absorbers, shock absorbers, and methods for manufacturing shock absorbers, and in particular to an apparatus for manufacturing shock absorbers that can be used in automobiles and the like to absorb shock during collisions, shock absorbers, and methods for manufacturing shock absorbers.

In order to reduce the weight of automobiles and ensure their collision safety, various lightweight and highly rigid hollow shock absorbers have been developed, and in particular, there is a demand for the development of a vehicle body structure that allows axial collapse to continue for as long as possible without Euler buckling. The technology described in the following Patent Document 1 is known regarding such shock absorbers.
Patent Document 1 (JP 2011-58579 A) describes the use of an energy absorbing structure using an inverted spiral origami structure as a side member of an automobile. Patent Document 1 describes the construction of a cylindrical metal body by pre-creasing the metal body, cutting out notches, or thinning the metal body so that the metal body can be folded at the fold line.

Non-Patent Document 1 and Patent Document 2 (JP Patent Publication 2011-104612 A) describe a technology called hydroforming, in which a high-pressure fluid is introduced into a cylindrical tube placed inside a mold, causing the tube to expand and deform so that it fits the inner surface of the mold, thereby processing the tube.

Patent document 3 (JP Patent Publication 2018-187637A) describes a technology in which a cylinder is sandwiched between two support dies (17, 27), the part between the dies (17, 27) is heated, and the supports are moved (twisted) relative to one another to form fold lines (uneven lines) on the surface of the cylinder, and the two dies (17, 27) are shifted in the axial direction of the cylinder to form the fold lines in stages.

JP 2011-58579 A ("0021" to "0022", "0037") JP 2011-104612 A ("0033" to "0041") JP 2018-187637 A

"Application of Tube Hydroforming to Automotive Parts Forming", Automotive Technology, Vol. 57, No. 6, (2003), pp. 23-28

(Problems with the Prior Art)
When folding, notching, thinning, etc. a cylindrical metal body as described in Patent Document 1, as the number of folding lines increases, there is a problem that the processing becomes difficult. In particular, as the axial length of the tube increases and the number of stages increases, the number of folding lines also increases dramatically, so there is a problem that the processing work 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 processing metals with high rigidity, the fluid pressure must be very high, which makes processing difficult and expensive. In particular, the longer the axial length of the tube, the more difficult it becomes to apply the necessary pressure to the fluid, and pressure unevenness is more likely to occur, which also makes processing uneven. Therefore, the hydroforming method can only process tubes with an axial length that corresponds to the size of the manufacturing device, and there is also a problem that it is not possible to process shock absorbers of any size.

The technology described in Patent Document 3 can solve the problems in Patent Documents 1 and 2 and Non-Patent Document 1. However, in the technology of Patent Document 3, in which two dies (jigs) are shifted in the axial direction to form fold lines in stages, after processing the fold lines of one stage, it is necessary to remove (loosen) the die, shift the cylinder in the axial direction, and then attach (tighten) the die before processing the fold lines of the next stage. Therefore, in Patent Document 3, there are many steps required to process one stage, and there is a problem that the time required for processing is long. In addition, in the technology described in Patent Document 3, the die corresponding to the cylinder before the fold lines are formed is used when processing the first stage, whereas in the second stage and after, a die corresponding to the cylinder after the fold lines are formed must be used to make the die adhere to the material (cylinder). Therefore, there is a problem that the die needs to be changed between the first stage and the second stage and after, which increases the number of types of dies and increases costs. In addition, there is also a problem that it is not easy to manufacture the die depending on the shape of the fold lines.

The technical objective of the present invention is to make it easier to manufacture shock absorbers and achieve any axial length while reducing the time required for processing, compared to conventional processing methods.

In order to solve the above technical problem, the manufacturing apparatus for the shock absorber of the present invention described in claim 1 comprises:
a first support for supporting an unmachined portion of a hollow cylinder extending in an axial direction of the cylinder;
a second support spaced apart from the first support along an axial direction of the cylinder and supporting an unmachined portion of the cylinder;
a heating means for heating a heated portion, the heated portion being a part of the cylindrical body between the first support and the second support, the heated portion having a predetermined length in the axial direction, to reduce a rotational torque required for plastic deformation of the heated portion relative to a rotational torque required for plastic deformation when the heated portion is not heated;
a moving means for relatively moving the first support and the second support with a rotational torque that exceeds a rotational torque required for plastic deformation of the heated portion and is less than a rotational torque required for plastic deformation in a non-heated state;
a control means for controlling the moving means to relatively move the first support and the second support along a circumferential direction of the cylindrical body, thereby forming an uneven line inclined with respect to the axial direction in the heated portion of the cylindrical body, the control means relatively moving the first support and the second support by a relative movement amount corresponding to an inclination angle of the uneven line with respect to the axial direction;
Equipped with
After the heated portion is plastically deformed by one stage, a step is repeated in which a position shifted by one stage along the axial direction of the cylindrical body is heated by the heating means and plastically deformed by relative movement between the first support and the second support, thereby successively heating and plastically deforming the cylindrical body, and
The direction of the relative movement is opposite between the odd-numbered stages and the even-numbered stages of the heated portion.
It is characterized by:

The present invention relates to a manufacturing apparatus for an impact absorber, comprising:
the heating means for heating the heated portion to a temperature at which a rotational torque required for plastic deformation of the heated portion is 1/3 or less of a rotational torque required for plastic deformation when not heated;
The present invention is characterized by comprising:

In order to solve the above technical problem, the shock absorber of the invention described in claim 3 is:
The shock absorber is manufactured by the shock absorber manufacturing apparatus according to claim 1 or 2.

In order to solve the above technical problem, the manufacturing method of the impact absorber of the invention described in claim 4 comprises the steps of:
An unmachined portion of an axially extending hollow cylinder is supported by a first support and a second support at a distance from each other;
A heated portion of a part of the cylindrical body between the first support and the second support is heated by a heating means, and a rotational torque required for plastic deformation of the heated portion is reduced compared to a rotational torque required for plastic deformation when the heated portion is not heated;
The present invention is characterized in that the uneven lines are formed on the cylindrical body by moving the first support and the second support relative to each other 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, depending on an amount of relative movement that corresponds to an inclination angle of the uneven lines formed on the cylindrical body with respect to the axial direction.

According to the invention as set forth in claims 1, 3 and 4, it is possible to easily manufacture a shock absorber and realize any axial length while reducing the time required for processing, as compared with conventional processing methods.
According to the invention described in claim 2, it is easy to sufficiently ensure the difference in rotational torque required for plastic deformation between the heated portion and the other portions, the heated portion can be processed efficiently, and plastic deformation of the non-heated portions can be suppressed, making it easy to realize an impact absorber of the desired shape.

FIG. 1 is an explanatory diagram of a manufacturing apparatus for a shock absorber according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining the rotational torque required for plastic deformation in the cylindrical body of Example 1, in which the horizontal axis represents time and the vertical axis represents torque. FIG. 3 is an explanatory diagram of an impact absorber, with FIG. 3A being an explanatory diagram before processing, FIG. 3B being an explanatory diagram of the state after one stage has been processed, FIG. 3C being an explanatory diagram of the state after two stages have been processed, FIG. 3D being an explanatory diagram of the state after three stages have been processed, and FIG. 3E being an explanatory diagram of the state after four stages have been processed. 4A is an explanatory diagram of the first modified example, FIG. 4A being an explanatory diagram of the state before machining, FIG. 4B being an explanatory diagram of the state after one stage machining, and FIG. 4C being an explanatory diagram of the state after two stages machining. 5A is an explanatory diagram of the second modified example, FIG. 5A being an explanatory diagram of the state before machining, FIG. 5B being an explanatory diagram of the state after one stage machining, and FIG. 5C being an explanatory diagram of the state after two stages machining. 6A and 6B are explanatory diagrams of the third modified example, in which FIG. 6A is an explanatory diagram of the state before machining, and FIG. 6B is an explanatory diagram of the state after one stage of machining.

Next, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.
In the following description using the drawings, illustrations of components other than those necessary for the description are omitted as appropriate to facilitate understanding.

FIG. 1 is an explanatory diagram of a manufacturing apparatus for a shock absorber according to a first embodiment of the present invention.
1, the manufacturing apparatus 1 for manufacturing an impact absorber according to the first embodiment of the present invention has a first support part 3 arranged on one end side of a cylindrical body 2, and a second support part 4 arranged on the other end side. Each support part 3, 4 is arranged so as to support an unprocessed part of the cylindrical body 2, i.e., a part on which a later-described uneven line 31 is not formed.
In Example 1, a square-tubular iron pipe is used as an example of the cylindrical body 2. The cylindrical body 2 is formed in a cylindrical shape extending in the axial direction, that is, in a pipe shape. In Example 1, the cylindrical body 2 is arranged along the horizontal direction, but it can be arranged along the direction of gravity (vertical direction), obliquely, or the like, depending on the installation environment of the manufacturing device 1, etc. In Example 1, a mild steel material made of steel is used as an example of the cylindrical body 2, but the material is not limited to this, and other metals, alloys, resins, etc. can be used.

The first support portion 3 and the second support portion 4 are configured in substantially the same manner as the upstream portion and downstream portion described in, for example, Patent Document 3, and various conventionally known configurations can be applied, so detailed description will be omitted. Note that in Example 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 the first embodiment, a drive is transmitted to the gear 15 from a motor M1 as an example of a moving means via a gear train (not shown). In the first embodiment, a plurality of gears including the motor M1 and the gear 15 move (rotate) the first support part 3 relative to the second support part 4, so that a predetermined torque can be applied to the cylindrical body 2. Note that, in the first embodiment, a configuration in which the second support part 4 is fixed and the first support part 3 is rotated is exemplified, but this is not limited thereto. It is also possible to fix the first support part 3 and rotate the second support part 4, or to rotate both the first support part 3 and the second support part 4.

The manufacturing apparatus 1 of the impact absorber of the first embodiment has a heating device 21 as an example of a heating means. The heating device 21 of the first embodiment has a rail 22 extending along the axial direction of the cylindrical body 2 on the side of the first support part 3 and the second support part 4. A slider 23 is supported on 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 on the slider 23. The heating device main body 24 has a coil-shaped (ring-shaped) heating part 26 surrounding the outer periphery of the cylindrical body 2. The heating part 26 is configured to be able to heat a predetermined range of the cylindrical body 2 (one stage of the processing target) in a non-contact manner by electromagnetic induction heating (IH) when electricity is applied.
The slider 23 is provided with a motor (not shown) for moving 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 a control means. The controller C has an input/output interface I/O for inputting and outputting signals from and to the outside. The controller C also has a ROM (read-only memory) in which programs and information for performing necessary processing are stored. The controller C also has a RAM (random access memory) for temporarily storing necessary data. The controller C also has a CPU (central processing unit) for performing processing according to the programs stored in the ROM or the like. Therefore, the controller C of the first embodiment is configured with an information processing device, a so-called computer device. Therefore, the controller C can realize various functions by executing programs stored in the ROM or the like.

(Functions of 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.

FIG. 2 is a diagram for explaining the rotational torque required for plastic deformation in the cylindrical body of Example 1, in which the horizontal axis represents time and the vertical axis represents torque.
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 the part of the cylindrical body 2 surrounded by the heating part 26 (i.e., one stage of the processing object) 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 material used in the cylindrical body 2 of Example 1. In Fig. 2, the experiment results in a wavy history (profile) of the rotational torque because the mild steel material repeats buckling and work hardening.
In Fig. 2, the average rotational torque required for plastic deformation is about 1200 Nm when not heated (room temperature: 25°C), while the average rotational torque required for plastic deformation at 950°C is about 350 Nm (less than 1/3 when not heated). Therefore, if the degree of decrease in rotational torque when heated differs depending on the material used, or the degree of decrease (not 1/3, but 1/2 or 1/4) when heated is different from that when not heated, the temperature can be appropriately changed depending on the material used and the desired degree of decrease in rotational torque. The heating control means C1 of the first embodiment starts heating the cylindrical body 2 with the heating device 21 before forming the uneven line (31), and ends heating with the heating device 21 when the formation of the uneven line (31) is completed.

FIG. 3 is an explanatory diagram of an impact absorber, with FIG. 3A being an explanatory diagram before processing, FIG. 3B being an explanatory diagram of the state after one stage has been processed, FIG. 3C being an explanatory diagram of the state after two stages have been processed, FIG. 3D being an explanatory diagram of the state after three stages have been processed, and FIG. 3E being an explanatory diagram of the state after four stages have been processed.
The deformation control means C2 controls the motor M1 to move (rotate) the first support portion 3 relative to the second support portion 4, thereby deforming the cylindrical body 2. In FIG. 3, the deformation control means C2 of the first embodiment rotates the first support portion 3 relative to the second support portion 4 according to the inclination angle θ of the concave-convex line 31 to be formed with respect to the outer side 32 extending in the axial direction of the cylindrical body 2. In the first embodiment, when the inclination angle θ is 5°, for example, the first support portion 3 is rotated by 5°. Note that the deformation control means C2 of the first embodiment rotates the first support portion 3 in the forward direction when machining odd-numbered stages (first stage, third stage, fifth stage, ...) of the cylindrical body 2, and rotates the first support portion 3 in the reverse direction when machining even-numbered stages (second stage, fourth stage, sixth stage, ...). Therefore, the concave-convex line 31 is formed along a so-called reverse spiral. In the first embodiment, the first support portion 3 is rotated in the opposite directions for the odd-numbered stages and the even-numbered stages so that the concave-convex line 31 is formed along a reverse spiral, but this is not limited to this. It is also possible to configure the first support portion 3 to be rotated in the same direction for both the odd-numbered stages and the even-numbered stages so that the concave-convex line is formed along a spiral. It is also possible to change the inclination angle for each stage.

In the first embodiment, the motor M1, the gear train, the first support portion 3, etc. are configured so that when the first support portion 3 is rotated, 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 along the axial direction of the cylindrical body 2 by a predetermined length (one stage).

(Function of Example 1)
In the manufacturing apparatus 1 of the impact absorber of the first embodiment having the above-mentioned configuration, when forming the uneven line 31 on the cylindrical body 2, a part of the cylindrical body 2 is heated by the heating device 21 while both ends of the cylindrical body 2 are supported by the support parts 3 and 4. Then, the first support part 3 is rotated relative to the second support part 4. At this time, a rotational torque of about 700 Nm acts on the cylindrical body 2. That is, a torque acts on the cylindrical body 2 that does not reach about 1200 Nm, which is the rotational torque required for plastic deformation when not heated, and exceeds about 350 Nm, which is the rotational torque required for plastic deformation of the heated part. Therefore, the non-heated part does not plastically deform, and only the heated part surrounded by the heated part 26 plastically deforms. Therefore, the uneven line 31 is formed only on the heated part (only one stage).
Next, the heating unit 26 moves one step along the axial direction of the cylindrical body 2, and the second step is heated. At this time, the processed first step is not heated, so the temperature drops and the rotational torque required for plastic deformation returns. Therefore, the uneven lines 31 can be formed only in the second step.
In the same manner, the uneven lines 31 can be formed on the third and subsequent stages, and it is possible to form a shock absorber 41 having the uneven lines 31 formed on the cylindrical body 2. Furthermore, the number of stages can be increased as desired, and the axial length can be changed as desired.

Therefore, in the shock absorber manufacturing apparatus 1 of Example 1, when moving to the processing of the next stage after processing one stage, it is possible to move to the next stage simply by sliding the heating device 21 relative to the cylindrical body 2. Therefore, compared to the technology described in Patent Document 3, it is possible to reduce the steps and time required to move to the next stage. Therefore, the overall processing time can also be reduced. Therefore, compared to conventional processing methods, the shock absorber manufacturing apparatus 1 of Example 1 can reduce the time required for processing while easily manufacturing the shock absorber 41 and realizing any axial length.
In particular, in the heating device 21 of Example 1, the heating part 26 is disposed in a non-contact manner with the cylindrical body 2, and the heating device 21 can smoothly move when sliding. Therefore, compared to a configuration in which the heating part 26 is in contact with the cylindrical body 2, it is possible to shorten the processing time, and deformation and damage of the cylindrical body 2 due to contact and separation between the cylindrical body 2 and the heating part 26 are also suppressed.

In addition, in Example 1, the heated portion 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 the torque required between the portion to be processed where it is desired to form the uneven lines 31 and the portion not to be processed is large. Therefore, only the portion to be processed can be processed efficiently, and plastic deformation of the portion not to be processed can be suppressed. Therefore, it is easier to realize the shock absorber 41 in the desired shape.
In addition, in the impact absorber manufacturing device 1 of Example 1, it was possible to heat the material to the target temperature of 950°C in about 30 seconds. In other words, it is possible to perform the processing in a very short time. Furthermore, the torque required during processing was about 700 Nm, which can be achieved with a significantly smaller amount of energy than when attempting to form the unevenness lines 31 on the cylindrical body 2 by conventional press processing.
The impact absorber 41 of Example 1 manufactured in this manner has uneven lines 31 formed along an inverted spiral, and compared to a cylinder that does not have uneven lines 31 formed, it is possible to obtain an impact absorber 41 with a lower initial peak load and a larger amount of crushing.

(Example of change)
Although the embodiments of the present invention have been described in detail above, 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 may be a square or hexagonal shape. In addition, although it is preferable that the heating unit 26 is non-contact, it may be configured to heat by contact.
In the embodiment, the case where the cylinder 2 is a square cylinder is illustrated, but the present invention is not limited to this. For example, it is possible to use a polygonal cylinder such as a hexagonal cylinder or an octagonal cylinder, an elliptical cylinder, a cylindrical cylinder, a cylinder having a star-shaped cross section, a trapezoidal cross section, a diamond-shaped cross section, etc. When using a cylinder, since there is a risk of slipping between the die and the cylinder during twisting, it is desirable to provide a structure in which the cylinder and the die have hooking parts such as protrusions and grooves to easily transmit the twisting force.

Furthermore, in the embodiment, the cylindrical body 2 is exemplified as a cylindrical body having the same inner and outer diameters from one end side to the other end side, but is not limited to this. It is also possible to use a cylindrical body whose diameter increases from one end side to the other end side, a so-called pyramidal (pyramidal) cylindrical body. In addition, it is also possible to use a cylindrical body whose diameter periodically expands and contracts from one end side to the other end side, a so-called bellows-shaped cylindrical body.
In addition, in the first embodiment, the shock absorber 41 having the inverted spiral concave-convex line 31 formed thereon is obtained by rotating the first support portion 3 in the opposite direction for each stage, but the present invention is not limited to this. It is also possible to manufacture a shock absorber having a (forward) spiral concave-convex line formed thereon by rotating the first support portion 3 in the same direction for each stage.

Furthermore, in the first embodiment, the range (length of one stage) heated by the heating unit 26 is fixed, but this is not limited to the above. 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 are individually controllable. When it is desired to shorten the length of one stage, heating is performed only by the first heating unit, and when it is desired to lengthen the length of one stage, heating is performed by both the first heating unit and the second heating unit, so that the length of one stage can be adjusted in two stages. In addition, by providing three or more heating units, it is also possible to adjust the length of one stage in three or more stages. Therefore, it is possible to arbitrarily change the length of one stage for each shock absorber 41, and it is also possible to configure the length of one stage to be different for each stage within one shock absorber 41.

4A is an explanatory diagram of the first modified example, FIG. 4A being an explanatory diagram of the state before machining, FIG. 4B being an explanatory diagram of the state after one stage machining, and FIG. 4C being an explanatory diagram of the state after two stages machining.
In the above-mentioned embodiment 1, the support parts 3 and 4 support both ends of the cylindrical body 2 and do not move in the axial direction, but the present invention is not limited to this. As shown in Figs. 4A to 4C, it is also possible to configure the first support part 3 to move in the axial direction by one step each time one step is processed. At this time, the first support part 3 supports the unprocessed part. Therefore, in the modified example 1, unlike Patent Document 3, it is not necessary to change the inner shape of the first support part 3, and processing is possible while preventing an increase in the number of types of the first support part (mold).

5A is an explanatory diagram of the second modified example, FIG. 5A being an explanatory diagram of the state before machining, FIG. 5B being an explanatory diagram of the state after one stage machining, and FIG. 5C being an explanatory diagram of the state after two stages machining.
In Figure 5, in modified example 2, in Figure 5A, which is the pre-machining stage, the first support part 3 and the second support part 4 are arranged with a distance of two steps between them, and as shown in Figures 5A to 5C, when machining of the two steps is performed, it is also possible to move (shift) the first support part 3 in the axial direction by two steps.

6A and 6B are explanatory diagrams of the third modified example, in which FIG. 6A is an explanatory diagram of the state before machining, and FIG. 6B is an explanatory diagram of the state after one stage of machining.
In Figure 6, in modified example 3, in Figure 6A, which is the pre-processing stage, the first support portion 3 and the second support portion 4 are arranged with a gap of three stages (or more), and as shown in Figures 6A and 6B, it is also possible to perform processing on the portions along the cylindrical body 2 that are not adjacent to the support portions 3 and 4.
In the configurations illustrated in Example 1 and Modifications 1 to 3, the position of the second support portion 4 does not have to be the end portion of the cylindrical body 2, and may be the central portion in the axial direction of the cylindrical body 2. Also, the second support portion 4 may be moved in the axial direction as the machining progresses.

In addition, in the first embodiment, a case where mild steel is used as the cylindrical body 2 is illustrated, but the present invention is not limited to this. Any material that reduces the rotational torque when heated, such as aluminum, stainless steel, aluminum alloy, titanium alloy, etc., can be used.

1...Shock absorber manufacturing apparatus,
2...cylindrical body,
3...first support,
4...second support,
21... heating means,
31... Uneven line,
41...shock absorber,
C...control means,
M1... Means of transportation.

Claims (4)

a first support for supporting an unmachined portion of a hollow cylinder extending in an axial direction of the cylinder;
a second support spaced apart from the first support along an axial direction of the cylinder and supporting an unmachined portion of the cylinder;
a heating means for heating a heated portion, the heated portion being a part of the cylindrical body between the first support and the second support, the heated portion having a predetermined length in the axial direction, to reduce a rotational torque required for plastic deformation of the heated portion relative to a rotational torque required for plastic deformation when the heated portion is not heated;
a moving means for relatively moving the first support and the second support with a rotational torque that exceeds a rotational torque required for plastic deformation of the heated portion and is less than a rotational torque required for plastic deformation in a non-heated state;
a control means for controlling the moving means to relatively move the first support and the second support along a circumferential direction of the cylindrical body, thereby forming an uneven line inclined with respect to the axial direction in the heated portion of the cylindrical body, the control means relatively moving the first support and the second support by a relative movement amount corresponding to an inclination angle of the uneven line with respect to the axial direction;
Equipped with
After the heated portion is plastically deformed by one stage, a step is repeated in which a position shifted by one stage along the axial direction of the cylindrical body is heated by the heating means and plastically deformed by relative movement between the first support and the second support, thereby successively heating and plastically deforming the cylindrical body, and
The direction of the relative movement is opposite between the odd-numbered stages and the even-numbered stages of the heated portion.
1. An apparatus for manufacturing an impact absorber comprising: the heating means for heating the heated portion to a temperature at which a rotational torque required for plastic deformation of the heated portion is 1/3 or less of a rotational torque required for plastic deformation when not heated;
2. The impact absorber manufacturing apparatus according to claim 1, further comprising: A shock absorber manufactured by the shock absorber manufacturing apparatus according to claim 1 or 2. An unmachined portion of an axially extending hollow cylinder is supported by a first support and a second support at a distance from each other;
A heated portion of a part of the cylindrical body between the first support and the second support is heated by a heating means, and a rotational torque required for plastic deformation of the heated portion is reduced compared to a rotational torque required for plastic deformation when the heated portion is not heated;
a rotational torque that exceeds a rotational torque required for plastic deformation of the heated portion and is less than a rotational torque required for plastic deformation when not heated, according to an amount of relative movement that corresponds to an inclination angle of the uneven line formed on the cylindrical body with respect to the axial direction, thereby forming an uneven line on the cylindrical body.

Images