Method for forming constriction in cylindrical member

Abstract

Provided is a method for forming a constriction in a cylindrical member that suppresses fluctuation in the shape of a constriction formation section caused by the elasticity of the cylindrical member and thereby makes it possible to accurately form a constriction of a target size. The present invention includes a constriction formation step for sequentially pressing a first processing roller and a second processing roller that have different outer circumferential shapes and can rotate a cylindrical member around a rotational axis that is parallel to a cylindrical shaft against the outer circumferential surface of the rotating cylindrical member between a mandrel and a mandrel head to form a constriction. At the constriction formation step, the first processing roller and the second processing roller are each pressed against the cylindrical member along a perimeter of 200–1000 mm in addition to the circumferential length of the cylindrical member.

Description

Method for forming a constriction on a cylindrical member

[0001] The present invention relates to a method for forming a constriction on the outer peripheral surface of a cylindrical member.

[0002] For example, as a power storage system, the development of a sodium-sulfur battery (hereinafter referred to as a NaS battery), which is a secondary battery that utilizes the reaction between sodium and sulfur, is underway. This NaS battery has, for example, a β-alumina solid electrolyte tube inserted inside a cylindrical positive electrode container made of aluminum or the like, sulfur is filled in the space between the positive electrode container and the β-alumina solid electrolyte tube, and sodium is filled inside the β-alumina solid electrolyte tube.

[0003] Then, for example, in a high-temperature environment of 300°C or higher, the ionic conductivity of the β-alumina solid electrolyte is increased, and sodium and sulfur are reversibly reacted through the solid electrolyte, so that charging and discharging are repeatedly performed.

[0004] In such a NaS battery, when charging and discharging are repeated, for example, as the temperature changes between 100°C and 300°C, the internal pressure of the positive electrode container also fluctuates greatly. As a damper for absorbing such fluctuations in the internal pressure of the positive electrode container, a constriction (recess) extending in the circumferential direction is formed on the outer peripheral surface of the cylindrical positive electrode container. By forming such a constriction, it is possible to prevent the positive electrode container from being damaged when it expands, for example, in the longitudinal direction.

[0005] Conventionally, when forming a constriction on the outer peripheral surface of a cylindrical member such as the positive electrode container of a NaS battery, a cylindrical mandrel is inserted inside the cylindrical member, and then a processing roller that rotates together with the cylindrical member is pressed against the outer peripheral surface of the rotating cylindrical member and pushed in the radial direction to form a constriction, which is a long groove recessed so as to extend in the circumferential direction of the cylindrical member (see, for example, Patent Documents 1 and 2).

[0006] Japanese Patent Application Laid-Open No. 8-132145, Patent No. 3429658

[0007] However, in conventional methods for forming a constriction in a cylindrical member, if the constriction is formed using two processing rollers, and the processing rollers are immediately removed from the cylindrical member after processing, the elastic force of the cylindrical member will cause it to try to return to its original shape, making it impossible to form a constriction of the desired dimensions.

[0008] Furthermore, if the processing rollers were immediately removed from the cylindrical member after processing with the two processing rollers, there was a problem in that the roundness of the cylindrical member after necking would decrease, and cracks were likely to occur in the formed neck.

[0009] This invention was proposed in view of the above-mentioned problems, and aims to provide a method for forming a constriction in a cylindrical member that can accurately form a constriction of a desired size by suppressing shape fluctuations of the constriction-forming portion due to the elastic force of the cylindrical member.

[0010] To solve the above problems, a method for forming a constriction in a cylindrical member according to one embodiment of the present invention proposes the following means: (1) A method for forming a constriction in a cylindrical member according to embodiment 1 of the present invention is a method for forming a constriction in a cylindrical member that is hollow cylindrical in shape and forms a constriction that is recessed inward along the circumferential direction, comprising a clamping step of clamping the cylindrical member between a first clamp equipped with a cylindrical mandrel inserted into the hollow interior from one open end of the cylindrical member and a second clamp equipped with a cylindrical mandrel head inserted into the hollow interior from the other open end of the cylindrical member, and the first clamp and the second clamp together with the cylindrical member around the cylindrical axis The process includes a rotation step of rotating the cylindrical member and a constriction-forming step of sequentially pressing a first processing roller and a second processing roller, which have different outer circumferential shapes and allow the cylindrical member to rotate around a rotation axis parallel to the cylindrical axis, against the outer circumferential surface of the rotating cylindrical member between the mandrel and the mandrel head to form the constriction, wherein the constriction-forming step presses the first processing roller and the second processing roller against the cylindrical member for a circumference in the range of 200 mm to 10,000 mm in addition to the circumference of the cylindrical member.

[0011] (2) Embodiment 2 of the present invention is the method for forming a constriction in a cylindrical member according to Embodiment 1, wherein the outer diameter of the cylindrical member is in the range of 75 mm or more and 95 mm or less.

[0012] (3) Embodiment 3 of the present invention is a method for forming a constriction in a cylindrical member according to Embodiment 2, wherein in the constriction forming step, after processing the cylindrical member, the first processing roller and the second processing roller are pressed against the cylindrical member for a period of 0.2 seconds to 5.0 seconds.

[0013] (4) A fourth aspect of the present invention is the method for forming a constriction in a cylindrical member according to the second aspect, wherein in the constriction forming step, after processing the cylindrical member, the first processing roller and the second processing roller are pressed against the cylindrical member, respectively, while the cylindrical member rotates in a range of 2 to 32 rotations.

[0014] (5) Embodiment 5 of the present invention is the method for forming a constriction in a cylindrical member according to Embodiment 2, wherein in the constriction forming step, the rotational speed of the cylindrical member is 230 rpm or more and 250 rpm or less.

[0015] (6) Embodiment 6 of the present invention is a method for forming a constriction in a cylindrical member according to any one of embodiments 1 to 5, wherein the insertion length of the mandrel into the cylindrical member is longer than that of the mandrel head.

[0016] (7) Embodiment 7 of the present invention is a method for forming a neck of a cylindrical member according to any one of embodiments 1 to 6, wherein the cylindrical member is made of a metal including aluminum.

[0017] (8) Embodiment 8 of the present invention is a method for forming a constriction in a cylindrical member according to any one of embodiments 1 to 7, wherein a fitting member that can be fitted onto the mandrel head is formed on the surface of the mandrel facing the mandrel head.

[0018] (9) Embodiment 9 of the present invention is a method for forming a constriction in a cylindrical member according to any one of embodiments 1 to 8, wherein the cylindrical member in which the constriction is formed is a battery case for a sodium-sulfur battery.

[0019] According to the present invention, it is possible to provide a method for forming a constriction in a cylindrical member that suppresses shape fluctuations of the constriction-forming portion due to the elastic force of the cylindrical member, and enables the accurate formation of a constriction of the desired dimensions.

[0020] This is a cross-sectional view showing an example of a NaS battery in a charged state. This is a perspective view showing an example of a constriction forming apparatus used in the method for forming a constriction in a cylindrical member according to this embodiment. This is a schematic configuration diagram of the constriction forming apparatus (cylindrical member processing apparatus) as seen from the side. This is a flowchart showing the constriction forming method for a cylindrical member according to one embodiment of the present invention in steps. This is an explanatory diagram showing a jig for inserting a mandrel. This is a cross-sectional view showing (a) a constriction (intermediate formed body) formed by the first processing roller and (b) a constriction formed by the second processing roller.

[0021] The following describes a method for forming a constriction in a cylindrical member according to one embodiment of the present invention, with reference to the drawings. The embodiments described below are provided specifically to better illustrate the spirit of the invention and do not limit the present invention unless otherwise specified. In addition, the drawings used in the following description may be enlarged for convenience to make the features of the present invention easier to understand, and the dimensional ratios of each component may not be the same as in reality.

[0022] [Sodium-Sulfur Battery (NAS Battery)] First, we will describe a sodium-sulfur battery (NAS battery), which is an example of the application of a constricted cylindrical member formed by the method for forming a constriction in a cylindrical member of one embodiment.

[0023] Figure 1 is a cross-sectional view showing an example of a NaS battery in a charged state. The NaS battery 50 comprises a positive electrode container 53 made of a constricted cylindrical member, a solid electrolyte tube 55 housed inside the positive electrode container 53, and an outer container (battery container) 51 that houses the positive electrode container 53 and the solid electrolyte tube 55.

[0024] An annular insulating member 57 is positioned on the upper part of the positive electrode container 53, and this annular insulating member 57 is fitted between the inner circumferential surface of the positive electrode container 53 and the outer circumferential surface of the solid electrolyte tube (sodium housing) 55. An electrode cap 59 is positioned on top of this annular insulating member 57. In other words, in this embodiment, the electrode cap 59 is positioned at the opening of the positive electrode container 53, thereby creating an airtight seal inside the positive electrode container 53.

[0025] When the NaS battery 50 is charged, the solid electrolyte tube 55 is filled with pure sodium (metallic sodium) 65. A sulfur electrode 67, made of graphite felt impregnated with sulfur, is placed in the space between the positive electrode container 53 and the solid electrolyte tube 55. A positive electrode terminal 61 is connected to the upper end of the positive electrode container 53, and a negative electrode terminal 62 is placed on the electrode cap 59.

[0026] The positive electrode container 53 can be any cylindrical member with a constriction, manufactured by the method for forming a constriction in a cylindrical member of this embodiment, described later, with one open end closed. A constriction 53a is formed near the open end, with a recess that curves inward (towards the center) encircling the outer surface.

[0027] The positive electrode container 53 may be entirely made of, for example, an aluminum alloy. The outer casing (battery container) 51 covering the outer surface of the positive electrode container 53 is made of, for example, nickel-containing stainless steel. The solid electrolyte tube (sodium housing) 55 is made of β-alumina. Furthermore, the annular insulating member 57 is made of α-alumina, and the electrode cap 59 is made of aluminum or the like. In addition, the positive electrode terminal 61 and the negative electrode terminal 62 are made of aluminum or the like.

[0028] In this configuration, the NaS battery 50 is designed so that charging and discharging occur when sodium (Na) filled inside the solid electrolyte tube 55 and sulfur (S) placed outside the solid electrolyte tube 55 react through the solid electrolyte tube 55 made of β-alumina.

[0029] That is, 2Na + XS → Na ２ S Ｘ (Discharge), Na ２ S Ｘ →The reversible reaction of 2Na + XS (charge) allows for repeated charging and discharging. Here, sodium polysulfide (Na) is produced by the reaction. ２ S Ｘ The sodium 65 will be present inside the sulfur electrode 67 as described above. Therefore, in the discharge state, there is no sodium 65 inside the solid electrolyte tube 55, resulting in a hollow state, while in the charge state, the inside of the solid electrolyte tube 55 is filled with sodium 65.

[0030] The positive electrode container 53 of such a NaS battery 50 is subjected to stress that causes it to expand and contract along its longitudinal direction (vertical direction in Figure 1) due to the charging and discharging process described above and changes in the external temperature environment. Therefore, the constriction 53a acts as a damper that allows for this expansion and contraction of the positive electrode container 53 due to temperature changes, thereby preventing damage to the positive electrode container 53.

[0031] The following describes one embodiment of a method for forming a constriction in a cylindrical member that can be suitably used as a positive electrode container for a NaS battery as described above. Figure 2 is a perspective view showing an example of a constriction forming apparatus (cylindrical member processing apparatus) used in the method for forming a constriction in a cylindrical member of this embodiment. Figure 3 is a schematic configuration diagram of the constriction forming apparatus (cylindrical member processing apparatus) viewed from the side.

[0032] The constriction forming device (cylindrical member processing device) 10 comprises a first clamp 11, a second clamp 12, and a processing roller device 19.

[0033] The first clamp 11 includes a work stopper 13 that contacts one end We1 of the cylindrical member W during processing and biases the cylindrical member W toward the second clamp 12, a rotatable cylindrical mandrel 14 extending from one end We1 of the cylindrical member W, and a mandrel stopper 15 that adjusts the position of the mandrel 14 along a direction perpendicular to the cylindrical axis of the mandrel 14.

[0034] The second clamp 12 includes a mandrel head 16, a workpiece stopper 17 that contacts the other end We2 of the cylindrical member W during processing and biases the cylindrical member W toward the first clamp 11, and a rotating device (motor) 18 that rotates the workpiece stopper 17.

[0035] During the necking process, the cylindrical member W is held between the first clamp 11 and the second clamp 12. Then, by rotating the work stopper 17 with the rotating device (motor) 18, the cylindrical member W, whose other end We2 is in contact with the work stopper 17, rotates around its cylindrical axis.

[0036] Furthermore, a fitting projection (fitting member) 21 is formed at the center of the circular end face of the mandrel 14 facing the mandrel head 16. Also, a recess 22 capable of receiving the fitting projection 21 is formed at the center of the circular end face of the mandrel head 16 facing the mandrel 14.

[0037] During the necking process, the ends of the mandrel 14 and the mandrel head 16 come into close proximity, and the fitting of the fitting projection 21 and the recess 22 prevents misalignment of the central axes of the mandrel 14 and the mandrel head (core metal) 16.

[0038] Furthermore, in this embodiment, the mandrel 14 is formed to be longer in the direction of the cylindrical axis than the mandrel head 16. The ratio of the lengths of the mandrel 14 and the mandrel head 16 in the direction of the cylindrical axis is adjusted according to the position where a constriction is formed in the cylindrical member W. That is, the position where the mandrel 14 and the mandrel head 16 face each other is the position where a constriction is formed in the cylindrical member W.

[0039] The processing roller device 19 is composed of a first processing roller 24 and a second processing roller 25 with different outer peripheral shapes, and a sliding pedestal 26 that supports these first processing roller 24 and second processing roller 25. The first processing roller 24 and the second processing roller 25 are driven rollers that are driven by contacting the outer peripheral surface Wf of the rotating cylindrical member W. Incidentally, these first processing roller 24 and second processing roller 25 may be configured to rotate by rotating means such as a motor.

[0040] The first processing roller 24 forms, for example, a constriction (intermediate forming body) such that a cross-section perpendicular to the circumferential direction forms, for example, a trapezoid with respect to the cylindrical member W. Further, the second processing roller 25 performs further constriction processing on the constriction (intermediate forming body) having a trapezoidal cross-section formed by the first processing roller 24, and forms a constriction such that a cross-section perpendicular to the circumferential direction forms, for example, a trapezoid with a curved bottom.

[0041] Thus, in the constriction forming device 10 of the present embodiment, by sequentially pressing the first processing roller 24 and the second processing roller 25 with different outer peripheral shapes against the outer peripheral surface Wf of the rotating cylindrical member W, a constriction having a target cross-sectional shape is formed on the cylindrical member W.

[0042] The sliding pedestal 26 of the constriction forming device 10 slides in a direction orthogonal to the cylindrical axis of the cylindrical member W. Thereby, between a neutral position where neither the first processing roller 24 nor the second processing roller 25 contacts the outer peripheral surface Wf of the cylindrical member W, a first processing position where only the first processing roller 24 contacts the outer peripheral surface Wf of the cylindrical member W, and a second processing position where only the second processing roller 25 contacts the outer peripheral surface Wf of the cylindrical member W, the first processing roller 24 and the second processing roller 25 are moved.

[0043] In the constriction forming device 10 of the present embodiment, by controlling the holding time at the processing positions of the first processing roller 24 and the second processing roller 25 and the circumferential length in contact with the cylindrical member W, a constriction with a target dimension can be accurately formed on the outer peripheral surface of the cylindrical member W.

[0044] FIG. 4 is a flowchart showing step by step a method for forming a constriction of a cylindrical member according to an embodiment of the present invention. In the method for forming a constriction of the cylindrical member of the present embodiment, a constriction forming device (cylindrical member processing device) 10 having the above-described configuration is used.

[0045] First, the mandrel 14 and the mandrel head 16 are set in the constriction forming device 10 such that they have a diameter smaller by 10% or less than the inner diameter of the cylindrical member W which is the workpiece.

[0046] The cylindrical member W may have, for example, an outer diameter in the range of 75 mm or more and 95 mm or less, a thickness in the range of 1.0 mm or more and 2.0 mm or less, and a length in the range of 400 mm or more and 600 mm or less. In the present embodiment, a cylindrical member W made of an aluminum alloy having an outer diameter of 85 mm, a thickness of 1.3 mm, and a length of 500 mm is used.

[0047] Next, the mandrel 14 is inserted into the hollow interior from the open end on the one end We1 side of the cylindrical member W. When inserting the cylindrical member W onto the mandrel 14, it is preferable to attach an insertion jig 29 to the tip of the mandrel 14, for example, as shown in FIG. 5. By using such an insertion jig 29, the mandrel 14 can be smoothly guided into the hollow portion of the cylindrical member W, and damage to the mandrel 14 can be prevented.

[0048] Next, the mandrel head 16 is inserted into the hollow interior from the open end on the other end We2 side of the cylindrical member W. As a result, the fitting protrusion 21 of the mandrel 14 fits into the recess 22 of the mandrel head 16 inside the cylindrical member W. The opposing portion between the mandrel 14 and the mandrel head 16 becomes the position for forming a constriction on the cylindrical member W.

[0049] Then, by biasing the mandrel stopper 15 and the work stopper 17 against one end We1 and the other end We2 of the cylindrical member W, respectively, the cylindrical member W is clamped between the first clamp 11 and the second clamp 12 (clamping step S1).

[0050] Next, the rotating device (motor) 18 is operated to rotate the cylindrical member W around its cylindrical axis via the work stopper 17 (rotation process S2). In this rotation process S2, by maintaining an appropriate clearance between the inner surface of the cylindrical member W and the outer surface of the mandrel 14 and the outer surface of the mandrel head 16, it is possible to prevent the cylindrical member W from rotating eccentrically with respect to the mandrel 14.

[0051] The rotational speed of the cylindrical member W from the rotational process S2 to the next constriction formation process S3 can be set to a range of, for example, 230 rpm or more and 250 rpm or less. In this embodiment, the rotational speed of the cylindrical member W is set to 240 rpm.

[0052] Next, a constriction is formed in the cylindrical member W at a predetermined constriction formation position (constriction formation step S3). At this time, the constriction formation position of the cylindrical member W should be set in a range of 10 mm to 100 mm along the length direction of the cylindrical member W from the open end on the other end We2 side of the cylindrical member W (the other open end). Such a constriction formation position is determined by the formation position of the constriction 53a in the positive electrode container 53 of the NaS battery 50 in Figure 1.

[0053] In the constriction formation process S3, first, the sliding base 26 of the constriction formation device 10 is slid to move the first processing roller 24 to a position where it contacts the outer circumferential surface Wf of the cylindrical member W. As a result, the first processing roller 24 rotates in response to the rotation of the cylindrical member W. In this embodiment, the constriction formation position by the first processing roller 24 and the second processing roller 25 is set to a position 34 mm from the other end We2 of the cylindrical member W.

[0054] Then, the sliding base 26 is slid further, and the first processing roller 24 is pressed against the inside of the cylindrical member W at a predetermined processing rate. As a result, a constriction (intermediate forming body) V1 is formed on the cylindrical member W, such that the cross section perpendicular to the circumferential direction is, for example, trapezoidal, as shown in Figure 6(a).

[0055] When forming the constriction (intermediate formation) V1 with the first processing roller 24, the first processing roller 24 is pressed against the cylindrical member W with a circumference in the range of 200 mm to 10,000 mm, in addition to the circumference of the cylindrical member W. For example, in the case of a cylindrical member W with an outer diameter of 85 mm, the first processing roller 24 should be pressed against the cylindrical member W with a circumference of approximately (85 mm × 3.14) + 1,000 mm = 1,267 mm. This means that after the constriction (intermediate formation) V1 has been formed on the first processing roller 24 (after processing), the first processing roller 24 is continued to be pressed against the cylindrical member W with a circumference of an additional 1,000 mm.

[0056] Furthermore, when pressing the first processing roller 24 against the cylindrical member W, after the formation of the constriction (intermediate forming body) V1 on the cylindrical member (after processing), the first processing roller 24 may be pressed against the cylindrical member W for a further period of 0.2 seconds to 5.0 seconds.

[0057] Furthermore, in order to maintain the roundness of the cylindrical member W when forming the constriction (intermediate forming body) V1, it is also preferable to press the first processing roller 24 against the cylindrical member W for a further 10.0 seconds or more after the formation (processing) of the constriction (intermediate forming body) V1.

[0058] Furthermore, when pressing the first processing roller 24 against the cylindrical member W, after the formation of the constriction (intermediate forming body) V1 on the cylindrical member (after processing), the first processing roller 24 may be pressed against the cylindrical member W while the cylindrical member W rotates in a range of 2 to 32 rotations.

[0059] In this way, after the formation of the constriction (intermediate forming body) V1 on the cylindrical member (after processing), the first processing roller 24 is further pressed against the cylindrical member W for a predetermined circumference, predetermined time, and predetermined number of rotations. This prevents the shape of the formed constriction (intermediate forming body) V1 from changing due to the shape restoration caused by the elastic force of the aluminum alloy constituting the cylindrical member W. As a result, a constriction (intermediate forming body) V1 with the dimensions specified in the design can be formed on the cylindrical member W.

[0060] Next, the sliding base 26 is slid in the opposite direction to the processing direction of the first processing roller 24, thereby separating the first processing roller 24 from the cylindrical member W. Next, the second processing roller 25 is moved to the position where the constriction (intermediate forming body) V1 of the cylindrical member W is formed. As a result, the second processing roller 25 rotates in a manner driven by the rotation of the cylindrical member W.

[0061] Then, the sliding base 26 is slid further and placed on top of the constriction (intermediate formation) V1 formed by the first processing roller 24, and the second processing roller 25 is pressed against it at a predetermined processing rate. As a result, a constriction V2 is formed in the cylindrical member W, as shown in Figure 6(b), with a cross section perpendicular to the circumferential direction, for example, forming a trapezoid with a curved bottom.

[0062] When forming the constriction V2 (final processed form) with the second processing roller 25, the second processing roller 25 is pressed against the cylindrical member W with a circumference in the range of 200 mm to 10,000 mm, in addition to the circumference of the cylindrical member W. For example, in the case of a cylindrical member W with an outer diameter of 85 mm, the second processing roller 25 should be pressed against the cylindrical member W with a circumference of approximately (85 mm × 3.14) + 1,000 mm = 1,267 mm. This means that after the constriction V2 is formed on the second processing roller 25 (after processing), the second processing roller 25 is continued to be pressed against the cylindrical member W with a circumference of an additional 1,000 mm.

[0063] Furthermore, when pressing the second processing roller 25 against the cylindrical member W, after the formation of the constriction V2 in the cylindrical member (after processing), the second processing roller 25 may be pressed against the cylindrical member W for a further period of 0.2 seconds to 5.0 seconds.

[0064] Furthermore, in order to maintain the roundness of the cylindrical member W when forming the constriction V2, it is also preferable to press the second processing roller 25 against the cylindrical member W for a further 10.0 seconds or more after the formation of the constriction V2 (after processing).

[0065] Furthermore, when pressing the second processing roller 25 against the cylindrical member W, after the formation of the constriction V2 in the cylindrical member (after processing), the second processing roller 25 can also be pressed against the cylindrical member W while the cylindrical member W rotates in a range of 2 to 32 rotations.

[0066] In this way, after the formation of the constriction V2 (final processed form) on the cylindrical member (after processing), the second processing roller 25 is further pressed against the cylindrical member W for a predetermined circumference, predetermined time, and predetermined number of rotations. This prevents the shape of the formed constriction V2 from changing due to the elastic force of the aluminum alloy constituting the cylindrical member W restoring its shape. As a result, a constriction V2 with the dimensions specified in the design can be accurately formed on the cylindrical member W.

[0067] In this embodiment, the constriction of the cylindrical member W is formed in two stages using the first processing roller 24 and the second processing roller 25. However, the method is not limited to this, and the constriction can also be formed in multiple stages using three or more processing rollers. In this case as well, after the formation of the constriction is complete (after processing), each processing roller can be pressed against the cylindrical member W for a predetermined circumference, a predetermined time, and a predetermined number of rotations to suppress the change in the shape of the constriction due to the elastic force of the cylindrical member W.

[0068] According to the method for forming a constriction in a cylindrical member of this embodiment, after the formation of the constriction is complete (after processing), by continuing to press the first processing roller and the second processing roller against the cylindrical member W for a predetermined circumference, predetermined time, and predetermined number of rotations, it is possible to suppress changes in the shape of the constriction due to the elastic force of the cylindrical member W, and to form a constriction in the cylindrical member W according to the design dimensions.

[0069] Although one embodiment of the present invention has been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0070] According to the present invention's method for forming a constriction in a cylindrical member, a cylindrical member can be obtained in which a constriction is formed with high precision and minimal error when forming a constriction along the circumferential direction of the cylindrical member. A cylindrical member with such a constriction can be preferably used in a battery container equipped with a buffer function that allows for thermal expansion and contraction. Therefore, it has industrial applicability.

[0071] 10... Narrowing device (cylindrical member processing device) 11... First clamp 12... Second clamp 13, 17... Work stopper 14... Mandrel (core metal) 15... Mandrel stopper 16... Mandrel head (core metal) 18... Rotating device (motor) 19... Processing roller device 24... First processing roller 25... Second processing roller 26... Sliding base W... Cylindrical member V1... Narrowing (intermediate forming body) V2... Narrowing

Claims

1. A method for forming a constriction in a cylindrical member having a hollow cylindrical shape, wherein the constriction is formed inward along the circumferential direction, comprising: a clamping step of clamping the cylindrical member between a first clamp equipped with a cylindrical mandrel inserted into the hollow interior from one open end of the cylindrical member and a second clamp equipped with a cylindrical mandrel head inserted into the hollow interior from the other open end of the cylindrical member; a rotation step of rotating the cylindrical member together with the first and second clamps around the cylindrical axis; and a constriction forming step of sequentially pressing a first processing roller and a second processing roller, which have different outer peripheral shapes and are rotatable around a rotation axis parallel to the cylindrical axis of the cylindrical member, against the outer peripheral surface of the rotating cylindrical member between the mandrel and the mandrel head to form the constriction. The constriction forming step is a method for forming a constriction in a cylindrical member, wherein, in addition to the circumference of the cylindrical member, the first processing roller and the second processing roller are pressed against the cylindrical member for a circumference in the range of 200 mm to 10,000 mm.

2. The method for forming a constriction in a cylindrical member according to claim 1, wherein the outer diameter of the cylindrical member is in the range of 75 mm or more and 95 mm or less.

3. The method for forming a constriction in a cylindrical member according to claim 2, wherein, in the constriction forming step, after processing the cylindrical member, the first processing roller and the second processing roller are further pressed against the cylindrical member for a range of 0.2 seconds to 5.0 seconds.

4. The method for forming a constriction in a cylindrical member according to claim 2, wherein, in the constriction forming step, after processing the cylindrical member, the first processing roller and the second processing roller are pressed against the cylindrical member, respectively, while the cylindrical member rotates in a range of 2 to 32 rotations.

5. The method for forming a constriction in a cylindrical member according to claim 2, wherein in the constriction forming step, the rotation speed of the cylindrical member is 230 rpm or more and 250 rpm or less.

6. The method for forming a constriction in a cylindrical member according to any one of claims 1 to 5, wherein the insertion length of the mandrel into the cylindrical member is longer than that of the mandrel head.

7. The method for forming a constriction in a cylindrical member according to any one of claims 1 to 5, wherein the cylindrical member is made of a metal including aluminum.

8. A method for forming a constriction in a cylindrical member according to any one of claims 1 to 5, wherein a fitting member that can be fitted onto the mandrel head is formed on the surface of the mandrel facing the mandrel head.

9. The method for forming a constriction in a cylindrical member according to any one of claims 1 to 5, wherein the cylindrical member having the constriction formed is a battery case for a sodium-sulfur battery.

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