Method for forming constriction in cylindrical member

Abstract

Provided is a method for forming a constriction in a cylindrical member with which it is possible to prevent a fluctuation of the wall thickness of a constriction forming part and the decrease in the roundness of the cross section of the cylindrical member without damaging the inner circumferential surface of the cylindrical member. The present invention comprises: a step for clamping a cylindrical member between a first clamp provided with a columnar mandrel inserted from one open end of the cylindrical member into the hollow interior and a second clamp provided with a columnar mandrel head inserted from the other open end of the cylindrical member into the hollow interior; a rotation step for causing the cylindrical member to rotate about the cylinder axis together with the first clamp and the second clamp; and a constriction formation step for pressing a processing roller, which is capable of rotating about a rotation axis parallel to the cylinder axis of the cylindrical member, against the outer circumferential surface of the rotating cylindrical member, and forming a constriction, between the mandrel and the mandrel head. The clearance between the inner circumferential surface of the cylindrical member and the outer circumferential surface of the mandrel is set to 10% or less of the inner diameter of the cylindrical member.

Description

Method for forming a constriction on a cylindrical member

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

[0002] For example, as a power storage system, 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] And, for example, by increasing the ionic conductivity of the β-alumina solid electrolyte in a high-temperature environment of 300°C or higher and causing sodium and sulfur to reversibly react through the solid electrolyte, 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 core metal called a 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 Laid-Open No. 8-132145 Patent No. 3429658

[0007] However, conventional methods for forming a constriction in cylindrical members have a problem in that the mandrel inserted to prevent the cylindrical member from collapsing adheres tightly to the inner surface of the cylindrical member after constriction, making it difficult to remove the mandrel from the cylindrical member after constriction, and thus the inner surface of the cylindrical member is easily damaged.

[0008] On the other hand, if the clearance between the inner surface of the cylindrical member and the outer surface of the mandrel is made too large in order to facilitate the removal of the mandrel after necking, there are problems such as the cylindrical member deforming during necking, which reduces the roundness of the cross-section, and the wall thickness of the formed neck becoming more variable.

[0009] This invention has been proposed in view of the above problems, and aims to provide a method for forming a constriction in a cylindrical member that can prevent variations in the wall thickness of the constricted portion and a decrease in the roundness of the cross-section of the cylindrical member without damaging the inner circumferential surface of the cylindrical member.

[0010] To solve the above problems, the following means are proposed for forming a constriction in a cylindrical member according to one embodiment of the present invention. (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 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; a rotation step of rotating the cylindrical member together with the first clamp and the second clamp around the cylindrical axis; and a constriction forming step of pressing a processing roller, which allows 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 clearance between the inner circumferential surface of the cylindrical member and the outer circumferential surface of the mandrel is set to 10% or less of the inner diameter of the cylindrical member.

[0011] (2) Embodiment 2 of the present invention is a method for forming a constriction in a cylindrical member according to Embodiment 1, wherein the inner diameter of the cylindrical member is formed to be larger than the outer diameter of the mandrel by a range of 0.1 mm or more and 2.0 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 1 or 2, wherein the insertion length of the mandrel into the cylindrical member is longer than that of the mandrel head.

[0013] (4) Embodiment 4 of the present invention is a method for forming a constriction in a cylindrical member according to any one of embodiments 1 to 3, wherein the cylindrical member is made of a metal including aluminum.

[0014] (5) Embodiment 5 of the present invention is a method for forming a constriction in a cylindrical member according to any one of embodiments 1 to 4, wherein the processing roller consists of a first processing roller and a second processing roller having different outer peripheral shapes, and in the constriction forming step, the constriction is formed by sequentially pressing the first processing roller and the second processing roller against the outer peripheral surface of the cylindrical member.

[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 cylindrical member in which the constriction is formed is a battery case for a sodium-sulfur battery.

[0016] According to the present invention, it is possible to provide a method for forming a constriction in a cylindrical member that prevents variations in the wall thickness of the constricted portion and a decrease in the roundness of the cross-section of the cylindrical member, without damaging the inner circumferential surface of the cylindrical member.

[0017] 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) viewed from the side. This is a flowchart showing the step-by-step method for forming a constriction in a cylindrical member according to one embodiment of the present invention. This is a cross-sectional view illustrating the clearance when a mandrel and a mandrel head are inserted into a cylindrical member. This is an explanatory diagram showing a jig for inserting the mandrel. This is a cross-sectional view showing (a) a constriction (intermediate forming body) formed by the first processing roller and (b) a constriction formed by the second processing roller.

[0018] 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.

[0019] [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.

[0020] 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.

[0021] 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.

[0022] When the NaS battery 50 is charged, the solid electrolyte tube 55 is filled with pure 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 will be filled with sodium 65.

[0027] 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.

[0028] 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.

[0029] The constriction forming device (cylindrical member processing device) 10 comprises a first clamp 11, a second clamp 12, and a processing roller device 19.

[0030] 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.

[0031] The second clamp 12 includes a mandrel head (core metal) 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The processing roller device 19 consists of a first processing roller 24 and a second processing roller 25, which have different outer circumference shapes, and a sliding base 26 that supports the first processing roller 24 and the second processing roller 25. The first processing roller 24 and the second processing roller 25 are driven rollers that move by contacting the outer circumference Wf of a rotating cylindrical member W. The first processing roller 24 and the second processing roller 25 may also be configured to be rotated by a rotating means such as a motor.

[0037] The first processing roller 24 forms a constriction (intermediate forming body) on the cylindrical member W, for example, such that the cross section perpendicular to the circumferential direction is, for example, trapezoidal. The second processing roller 25 further constricts the trapezoidal constriction (intermediate forming body) formed by the first processing roller 24, so that the cross section perpendicular to the circumferential direction is, for example, trapezoidal with a curved bottom.

[0038] 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 having different outer peripheral shapes against the outer peripheral surface Wf of the rotating cylindrical member W, a constriction having the target cross-sectional shape is formed on the cylindrical member W.

[0039] The sliding pedestal 26 of the constriction forming device 10 slides in a direction orthogonal to the cylindrical axis of the cylindrical member W. As a result, the first processing roller 24 and the second processing roller 25 are moved between a neutral position where neither of them 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.

[0040] FIG. 4 is a flowchart showing step by step the constriction forming method of a cylindrical member according to an embodiment of the present invention. In the constriction forming method of the cylindrical member of the present embodiment, the constriction forming device (cylindrical member processing device) 10 having the above-described configuration is used.

[0041] First, the mandrel 14 and the mandrel head 16 having a diameter smaller by 10% or less than the inner diameter of the cylindrical member W, which is the workpiece, are set in the constriction forming device 10. In the present embodiment, for example, a cylindrical member W made of an aluminum alloy, having a length of 500 mm, an inner diameter r1 of 84.6 mm, and a wall thickness of 1.3 mm, is used.

[0042] As a result, as shown in FIG. 5, when the mandrel 14 and the mandrel head 16 are inserted into the cylindrical member W, the clearance Δt between the inner peripheral surface Wr of the cylindrical member W and the outer peripheral surface 14f of the mandrel 14 and the outer peripheral surface 16f of the mandrel head 16 is set to at least 10% or less of the inner diameter r1 of the cylindrical member W.

[0043] For example, the inner diameter r1 of the cylindrical member W may be larger than the outer diameter r2 of the mandrel 14 and the outer diameter r2 of the mandrel head 16 in the range of 0.1 mm or more and 2.0 mm or less.

[0044] As an example, the inner diameter r1 of the cylindrical member W was set to 84.6 mm, the outer diameters r2 of the mandrel 14 and the mandrel head 16 were set to 84.2 mm, and the clearance Δt was set to 0.2 mm.

[0045] When using the cylindrical member W with an inner diameter r1 of 84.6 mm, the optimal range of the clearance Δt may be, for example, in the range of 0.05 mm to 0.5 mm, more preferably in the range of 0.2 mm to 0.4 mm.

[0046] Next, the mandrel 14 thus selected 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, for example, an insertion jig 29 to the tip of the mandrel 14 as shown in FIG. 6. By using such an insertion jig 29, the mandrel 14 can be smoothly guided into the hollow portion of the cylindrical member W, preventing damage to the mandrel 14.

[0047] When inserting the cylindrical member W onto such a mandrel 14, as described above, by setting the clearance Δt to at least 10% or less of the inner diameter r1 of the cylindrical member W, the cylindrical axis of the mandrel 14 and the cylindrical axis of the cylindrical member W coincide, and when the cylindrical member W is rotated, the cylindrical member W does not rotate eccentrically with respect to the mandrel 14.

[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. Thereby, inside the cylindrical member W, the fitting protrusion 21 of the mandrel 14 fits into the recess 22 of the mandrel head 16. Such an opposing portion between the mandrel 14 and the mandrel head 16 becomes the position where the constriction of the cylindrical member W is formed.

[0049] Then, by biasing the work stopper 15 and the work stopper 17 against the 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 step S2). In this rotation step S2 as well, by keeping the clearance Δt between the inner circumferential surface Wr of the cylindrical member W and the outer circumferential surface 14f of the mandrel 14 and the outer circumferential surface 16f of the mandrel head 16 to at least 10% or less of the inner diameter r1 of the cylindrical member W, it is possible to prevent the cylindrical member W from rotating eccentrically with respect to the mandrel 14.

[0051] Next, the sliding base 26 of the constriction forming device 10 is slid to first 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 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.

[0052] Then, the sliding base 26 is slid further, pressing the first processing roller 24 toward 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 7(a).

[0053] 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 and moving the second processing roller 25 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.

[0054] 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 7(b), where the cross section perpendicular to the circumferential direction is, for example, a trapezoid with a curved bottom (constriction formation step S3).

[0055] In this way, the constriction V2 formed in two stages by the first processing roller 24 and the second processing roller 25 is formed such that its bottom surface V2e maintains the thickness of the cylindrical member W, while the inclined sides V2s extending toward this bottom surface are thinner than the thickness of the cylindrical member W.

[0056] 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 be formed in one step using a single processing roller, or in multiple stages using three or more processing rollers.

[0057] As described above, according to the method for forming a constriction in a cylindrical member of this embodiment, as shown in Figure 5, when the mandrel 14 and mandrel head 16 are inserted into the cylindrical member W, the clearance Δt between the inner circumferential surface Wr of the cylindrical member W and the outer circumferential surface 14f of the mandrel 14 and the outer circumferential surface 16f of the mandrel head 16 is set to at least 10% or less of the inner diameter r1 of the cylindrical member W. This suppresses snagging when inserting or removing the cylindrical member W from the mandrel 14 and mandrel head 16, thereby preventing damage to the inner circumferential surface Wr of the cylindrical member W due to friction.

[0058] Furthermore, by setting the clearance Δt to 10% or less, the change in thickness (uneven thickness) during necking is stabilized, and a neck with a stable and stable wall thickness over the entire length in the circumferential direction can be formed on the cylindrical member W.

[0059] Furthermore, by setting the clearance Δt to 10% or less, it is possible to prevent deterioration of the roundness along the circumferential direction and to form a stable, less dimensionally variable constriction in the cylindrical member W.

[0060] 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.

[0061] 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.

[0062] 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 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 around a cylindrical axis together with the first and second clamps; and a constriction forming step of pressing a processing roller, which allows 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. A method for forming a constriction in a cylindrical member, wherein the clearance between the inner circumferential surface of the cylindrical member and the outer circumferential surface of the mandrel and the outer circumferential surface of the mandrel head is set to 10% or less of the inner diameter of the cylindrical member.

2. The method for forming a constriction in a cylindrical member according to claim 1, wherein the inner diameter of the cylindrical member is formed to be larger than the outer diameter of the mandrel and the outer diameter of the mandrel head by a range of 0.1 mm to 2.0 mm.

3. The method for forming a constriction in a cylindrical member according to claim 1 or 2, wherein the insertion length of the mandrel into the cylindrical member is longer than that of the mandrel head.

4. The method for forming a constriction in a cylindrical member according to claim 1 or 2, wherein the cylindrical member is made of a metal including aluminum.

5. The method for forming a constriction in a cylindrical member according to claim 1 or 2, wherein the processing roller consists of a first processing roller and a second processing roller having different outer peripheral shapes, and in the constriction forming step, the constriction is formed by sequentially pressing the first processing roller and the second processing roller against the outer peripheral surface of the cylindrical member.

6. The method for forming a constriction in a cylindrical member according to claim 1 or 2, wherein a fitting member that can be fitted onto the mandrel head is formed on the surface of the mandrel facing the mandrel head.

7. The method for forming a constriction in a cylindrical member according to claim 1 or 2, wherein the cylindrical member having the constriction formed is a battery case for a sodium-sulfur battery.

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