Electron beam welding device and sodium–sulfur battery manufacturing method

Abstract

The present invention provides an electron beam welding device comprising: a chamber for accommodating a pair of workpieces butted against each other and keeping the workpieces in a vacuum atmosphere; an electron beam radiation device for radiating an electron beam toward a groove portion of the workpieces accommodated inside the chamber; a holding device for pressing the workpieces upward from below the workpieces and holding the workpieces in a manner allowing rotation in the circumferential direction; and a cooling jig for cooling the workpieces while pressing the workpieces downward from above the workpieces and holding the workpieces in a manner allowing rotation in the circumferential direction, wherein the cooling jig comprises, inside a metal body portion, a cooling channel for circulating cooling water for cooling the workpieces, and is formed such that the ratio (S / V) of the channel surface area S (units: cm2) of the cooling channel to the volume V (units: cm3) of the body portion is between 100% and 170%.

Description

Electron beam welding device and method for manufacturing sodium-sulfur batteries

[0001] The present invention relates to an electron beam welding apparatus and a method for manufacturing a sodium-sulfur battery.

[0002] A sodium-sulfur battery, for example, has a bottomed cylindrical part made of a solid electrolyte such as β-alumina placed inside a metal container on the positive electrode side, which serves as a storage case, with sodium as the negative electrode active material housed inside the bottomed cylindrical part and sulfur as the positive electrode active material housed outside. During discharge, sodium-sulfur batteries generate electricity as ionized sodium permeates the solid electrolyte and reacts with sulfur to produce sodium polysulfide, while charging is achieved by the reverse reaction, which produces sodium and sulfur.

[0003] Electron beam welding is used to weld the metal parts that make up such sodium-sulfur batteries. Electron beam welding is a welding method in which an electron beam accelerated by high voltage is irradiated onto the welding portion of a pair of workpieces that are butted together, causing the workpieces to weld, vaporize, and rapidly solidify, resulting in a weld.

[0004] Patent Document 1 describes an electron beam welding method in which an electron beam is applied substantially perpendicularly to a joint portion of two or more workpieces and the two or more workpieces and the electron beam are rotated relative to each other to weld and join the workpieces. Patent Document 2 describes an electron beam welding method in which a spatter prevention cover is provided in a chamber to prevent backflow of metal vapor, such as spatter, toward the electron beam irradiation device, and workpieces are welded and joined while preventing backflow of metal vapor from the welded portion of the workpieces toward the electron beam irradiation device.

[0005] JP 2007-14980 A JP 7-227683 A

[0006] In general, electron beam welding causes less thermal deformation and welding distortion to the workpiece than conventional welding methods, and can achieve high-quality welding, making it an effective means for assembling parts such as sodium-sulfur batteries, which require high welding precision.

[0007] However, irradiation of the electron beam during electron beam welding can cause abnormal heating of the welded portion of the workpiece. To prevent such abnormal heating of the workpiece, a cooling jig is attached to the jig that holds the workpiece during welding. However, depending on the structure of the cooling jig, the cooling effect of the workpiece may not be sufficient. As a result, abnormal heating occurs in the welded portion of the workpiece, and the heat may affect the yield of the workpiece.

[0008] In view of the above problems, the present invention provides an electron beam welding apparatus and a method for manufacturing a sodium-sulfur battery that can improve the cooling efficiency of a workpiece and reduce the thermal influence of electron beam welding on the workpiece.

[0009] The present inventors have conducted extensive research to solve the above problems and have created the present invention, which is exemplified below.

[0010] [Aspect 1] In one embodiment, the present invention provides a cooling jig that includes a chamber for accommodating a pair of workpieces butted together and holding them in a vacuum atmosphere; an electron beam irradiation device for irradiating an electron beam toward grooves of the workpieces accommodated in the chamber; a holding device for pressing the workpieces from below upward and holding the workpieces rotatably in a circumferential direction; and a cooling jig for pressing the workpieces from above downward and cooling the workpieces while holding the workpieces rotatably in the circumferential direction, the cooling jig having a cooling flow path within a metal main body for circulating cooling water for cooling the workpieces, and a volume V (unit: cm) of the main body. 3 ) relative to the flow channel surface area S (unit: cm 2 In one embodiment, the present invention provides an electron beam welding apparatus in which the volume v (unit: cm ) of the cooling flow passage is set to a value of 100 to 170%. 3 ) relative to the flow channel surface area S (unit: cm 2) is 100 to 350%. [Aspect 3] In one embodiment, the present invention is the electron beam welding apparatus according to Aspect 1 or 2, wherein the cooling flow path includes a spiral-shaped flow path that spirals from a central axis extending in the vertical direction of the cooling jig toward the outer periphery. [Aspect 4] In one embodiment, the present invention is the electron beam welding apparatus according to any one of Aspects 1 to 1, wherein the cooling flow path is arranged so that the water depth increases as it approaches the outer periphery from the central axis extending in the vertical direction of the cooling jig. [Aspect 5] In one embodiment, the present invention is the electron beam welding apparatus according to Aspect 1, wherein the cooling flow path is arranged so that the water depth increases as it approaches the outer periphery from the central axis extending in the vertical direction of the cooling jig. 2 The electron beam welding apparatus according to any one of Aspects 1 to 4 further includes a cooling water flow control device for controlling the amount of cooling water so that the amount of cooling water is 5 to 8 L / min when the cooling jig is pressed against the workpiece. 2 When the flow channel surface area is 160 to 400 cm 2The electron beam welding apparatus according to any one of Aspects 1 to 5 is configured so as to achieve the above. [Aspect 7] In one embodiment, the present invention is the electron beam welding apparatus according to any one of Aspects 1 to 6, wherein the electron beam irradiation device includes a control device for controlling the current value of the electron beam, and one or both of the holding device and the cooling jig include a control device for controlling the rotation speed of the workpiece. [Aspect 8] In one embodiment, the present invention is the electron beam welding apparatus according to any one of Aspects 1 to 7, further including a laser ablation device for irradiating a groove portion of the workpiece with a laser and polishing the groove. [Aspect 9] In one embodiment, the present invention is the electron beam welding apparatus according to any one of Aspects 1 to 8, further including an inspection device capable of determining the quality of the welding state of the workpiece, the inspection device including an inspection chamber for accommodating the workpiece, a vacuum pump capable of evacuating the inspection chamber, a measurement unit for measuring the evacuation time required to reach a predetermined vacuum level after evacuation begins in the inspection chamber with the workpiece accommodated therein, and a judgment unit for judging the quality of the welding state of the workpiece based on the measurement result of the measurement unit. [Aspect 10] In one embodiment, the present invention is the electron beam welding apparatus according to any one of Aspects 1 to 8, wherein a plurality of electron beam irradiation devices are arranged in the height direction of the chamber.[Aspect 11] In one embodiment, the present invention relates to a method for manufacturing a sodium-sulfur battery including a positive electrode side body portion for accommodating a positive electrode and a negative electrode, a positive electrode side bottom lid joined to a lower end of the positive electrode side body portion via a first weld, a positive electrode ring metal fitting joined to an upper end of the positive electrode side body portion via a second weld, a positive electrode terminal joined to the upper end of the positive electrode ring metal fitting via a third weld, a negative electrode ring metal fitting that is electrically insulated from the positive electrode ring metal fitting by an insulating ring and is disposed more inwardly than the positive electrode ring metal fitting, and a negative electrode side top lid joined to the upper end of the negative electrode ring metal fitting via a fourth weld, A method for manufacturing a sodium-sulfur battery includes: a first welding step of welding a first groove portion using the electron beam irradiation device according to any one of Aspects 1 to 10 to form a first weld; a second welding step of welding a second groove portion between a positive electrode side body portion and a positive electrode ring fitting using the electron beam irradiation device to form a second weld; a third welding step of welding a third groove portion between the positive electrode ring fitting and a positive electrode terminal using the electron beam irradiation device to form a third weld; and a fourth welding step of welding a fourth groove portion between the negative electrode ring fitting and a negative electrode side upper lid using the electron beam irradiation device to form a fourth weld. [Aspect 12] In one embodiment, the present invention provides a method for manufacturing a sodium-sulfur battery according to Aspect 11, wherein the second groove portion and the fourth groove portion are located at different heights, and the second welding step and the fourth welding step are performed simultaneously using a plurality of electron beam irradiation devices. [Aspect 13] In one embodiment, the present invention relates to the method for manufacturing a sodium-sulfur battery according to Aspect 11 or 12, wherein the first to fourth welding steps are performed under conditions of a welding speed of 1 to 5 m / min and a beam current of 50 to 80 mA. [Aspect 14] In one embodiment, the present invention relates to the method for manufacturing a sodium-sulfur battery according to any one of Aspects 11 to 13, wherein the weld width of the first groove portion is 2.0 mm or more and the weld depth is 2.0 mm or more. [Aspect 15] In one embodiment, the present invention relates to the method for manufacturing a sodium-sulfur battery according to any one of Aspects 11 to 14, wherein the weld width of the second groove portion is 2.0 mm or more and the weld depth is 1.5 mm or more.[Aspect 16] In one embodiment, the present invention relates to a method for manufacturing a sodium-sulfur battery according to any one of Aspects 11 to 15, wherein the third groove portion has a weld width of 1.0 mm or more and a weld depth of 2.0 mm or more. [Aspect 17] In one embodiment, the present invention relates to a method for manufacturing a sodium-sulfur battery according to any one of Aspects 11 to 16, wherein the fourth groove portion has a weld width of 2.0 mm or more and a weld depth of 2.0 mm or more. [Aspect 18] In one embodiment, the present invention relates to a method for manufacturing a sodium-sulfur battery according to any one of Aspects 11 to 17, wherein the first to fourth groove portions have a plurality of ribs arranged along the circumferential direction.

[0011] According to the present invention, it is possible to provide an electron beam welding apparatus and a method for manufacturing a sodium-sulfur battery that can improve the cooling efficiency of a workpiece and reduce the thermal influence on the workpiece due to electron beam welding.

[0012] FIG. 2( a ) is a schematic partial cross-sectional view illustrating an electron beam welding apparatus according to an embodiment of the present invention. FIG. 2( b ) is a schematic cross-sectional view of a cooling jig according to an embodiment of the present invention, and FIG. 2( b ) is a schematic plan view of a cooling channel provided in the cooling jig according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a sodium-sulfur battery according to an embodiment of the present invention. FIGS. 4( a ) to 4 ( f ) are schematic cross-sectional views illustrating a method for assembling a sodium-sulfur battery according to an embodiment of the present invention. FIG. 5( a ) is a schematic cross-sectional view illustrating a sodium-sulfur battery according to an embodiment of the present invention before welding the second groove portion and the fourth groove portion of the sodium-sulfur battery according to an embodiment of the present invention. FIG. 5( b ) is a schematic cross-sectional view illustrating the configuration of a negative electrode side upper lid provided with a rib according to an embodiment of the present invention, and FIGS. 5( c ) and 5 ( d ) are schematic cross-sectional views illustrating a state in which the negative electrode ring metal fitting and the negative electrode side upper lid are butted together via the rib. FIG. 6 is a schematic diagram illustrating an example of a sodium-sulfur battery production line using an electron beam welding apparatus according to an embodiment of the present invention. Fig. 7 is a schematic diagram showing an inspection device for inspecting a sodium-sulfur battery after completion of the fourth welding step of the present invention. Figs. 8(a) to 8(c) are schematic cross-sectional views showing cooling jigs with different cooling channel shapes. Fig. 9 is a schematic diagram illustrating a test method for evaluating the influence of temperature on the inside of a sodium-sulfur battery during electron beam welding.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0014] 1, an electron beam welding apparatus 10 according to an embodiment of the present invention includes a chamber 1 for accommodating a workpiece W and maintaining it in a vacuum atmosphere, an electron beam irradiation device 2 for irradiating an electron beam toward a groove portion B of the workpiece W accommodated in the chamber 1, a holding device 3 for pressing the workpiece W from below upward and holding the workpiece W rotatably in the circumferential direction, and a cooling jig 4 for pressing the workpiece W from above downward and cooling the workpiece W while holding the workpiece W rotatably in the circumferential direction. Note that in FIG. 1, the workpiece W is a component of a sodium-sulfur battery, and an example will be described in which the workpiece W is a component of a sodium-sulfur battery, and the groove portion B between a pair of workpieces Wa and Wb that are butted together is welded.

[0015] A vacuum atmosphere is maintained inside the chamber 1. The workpiece W is transported into the chamber 1 by a transport mechanism such as a transport conveyor (not shown) and held in a holding device 3. The holding device 3 is disposed at the bottom of the chamber 1. The holding device 3 includes a holding portion 31 that holds the workpiece W, and a shaft portion 32 connected to the holding portion 31. The shaft portion 32 is configured to push up the workpiece W held by the holding portion 31 to an electron beam irradiation position within the chamber 1 and to rotate the workpiece W in a circumferential direction.

[0016] The cooling jig 4 is disposed at the top of the electron beam welding apparatus 10 so as to face the holding device 3. The cooling jig 4 is a jig for cooling the workpiece W to prevent the workpiece W from being abnormally heated by the heat during welding. The cooling jig 4 is configured to be able to press the workpiece W from above to below. In addition, a guide roller (not shown) that rotates the workpiece W in a circumferential direction around its axis in conjunction with the rotation mechanism of the holding device 3 may be connected to the bottom of the cooling jig 4. The cooling jig 4 may be configured so that the workpiece W can be rotated in the circumferential direction via this guide roller.

[0017] 2(a), the cooling jig 4 includes a metal cooling plate 41 for cooling the workpiece W while pressing it, a metal main body 42 arranged on the cooling plate 41, a seal plate 43, a regulating plate 44, a bellows 48, and a water supply pipe 47. The cooling plate 41 and the main body 42 may be made of stainless steel, chromium steel, or the like to improve cooling efficiency and ensure strength. It is particularly preferable that the cooling plate 41 be made of copper, which has high electrical conductivity.

[0018] A main body 42 is disposed on the cooling plate 41, and includes a cooling flow path 421 through which cooling water for cooling the workpiece is circulated. A sealing plate 43 is disposed on the cooling flow path 421 to prevent leakage of the cooling water. A ring-shaped restricting plate 44 is disposed above the sealing plate 43 and the main body 42 to restrict the pressure of the cooling jig 4 against the workpiece W. A bellows 48, which is a thin pipe made of stainless steel or the like and formed into a bellows shape, is connected to the center of the restricting plate 44. The bellows 48 has a double-pipe structure and includes a flow path for the cooling water discharged from the cooling flow path 421 and a water supply pipe 47 located on the inner periphery of the flow path for the cooling water to flow into the cooling flow path 421. The water supply pipe 47 is inserted through the center of the sealing plate 43.

[0019] As shown in FIG. 2( b), the cooling channel 421 is preferably configured as a spiral-shaped channel that spirals from a central axis X extending in the vertical direction of the cooling jig 4 toward the outer periphery. By providing such an elongated, spiral-shaped cooling channel 421 in the main body 42, the contact surface area between the metal portion of the main body 42 and the cooling channel 421 is increased, thereby improving the cooling efficiency of the cooling jig 4. Furthermore, according to the configuration shown in FIG. 2( b), the channel shape is spiral, so the length of the cooling channel 421 is sufficiently long. As a result, the main body 42 is cooled more efficiently. The shape of the cooling channel 421 is not limited to the shape shown in FIG. 2( b). For example, the cooling channel 421 may have a shape in which multiple concentric cooling channels are connected to each other.

[0020] In order to improve the cooling efficiency of the cooling jig 4 that cools the workpiece W, it is necessary to sufficiently cool the main body 42 that contacts the cooling plate 41 that cools the workpiece W by the cooling flow path 421. The larger the contact area between the metal parts that make up the main body 42 and the cooling flow path 421 formed in the main body 42, the more improved the cooling capacity of the main body 42 by the cooling flow path 421. Therefore, the volume V (unit: cm) of the main body 42 of the cooling jig 4 is 3 ) and the flow path surface area S (unit: cm ) of the cooling flow path 421 through which the cooling water flows. 2 It is important to adjust the ratio (S / V) of the total amount of the hydroxyl group to the total amount of the hydroxyl group within an appropriate range.

[0021] According to an embodiment of the present invention, the cooling jig 4 is formed so that the ratio (S / V) of the flow path surface area S of the cooling flow path 421 to the volume V of the main body 42 is 100 to 170%. As a result, a large area is secured for heat exchange between the main body 42 and the cooling water that cools the main body 42, thereby improving cooling efficiency. In this specification, the "volume V of the main body 42" refers to the volume of the metal portion that constitutes the main body 42. This volume V of the main body 42 does not include spaces such as screw holes and recesses disposed within the main body 42 to connect the main body 42 to the adjacent cooling plate 41, regulating plate 44, and sealing plate 43. In addition, in this specification, the "flow path surface area S" refers to the surface area calculated by the sum of the side and bottom surfaces of the cooling flow path 421 that contribute to cooling the main body 42, and does not include the surface area of ​​the top surface of the cooling flow path 421 that contacts the sealing plate 43.

[0022] If the ratio (S / V) of the flow path surface area S of the cooling flow path 421 to the volume V of the main body 42 is too small, the cooling capacity may be insufficient. On the other hand, if the ratio (S / V) is too large, the rigidity of the main body 42 may be insufficient against the upward thrust of the workpiece W from the holding device 3. According to one embodiment of the present invention, the ratio (S / V) of the flow path surface area S of the cooling flow path 421 to the volume V of the main body 42 is preferably 100 to 170%, more preferably 100 to 150%, and even more preferably 110 to 130%.

[0023] The cooling capacity of the cooling flow path 421 may not be sufficiently increased by simply increasing the volume of the cooling flow path 421. Therefore, in addition to the above ratio (S / V), the volume v (unit: cm 3 ) of the cooling channel 421 relative to the channel surface area S (unit: cm 2 ) in an appropriate range, the cooling capacity of the cooling jig 4 can be further improved. The ratio (S / v) of the flow path surface area S of the cooling flow path 421 to the volume v of the cooling flow path 421 is 100 to 350%, preferably 150 to 300%, more preferably 200 to 300%, and even more preferably 250 to 290%.

[0024] 2(a), the cooling flow passages 421 may be arranged so that the water depth increases as the distance from the central axis X approaches the outer periphery of the main body 42. The "water depth" of the cooling flow passages 421 refers to the distance between the upper end of the cooling flow passage 421 that contacts the seal plate 43 and the deepest position of the cooling flow passage 421. As shown in the example of FIG. 2(a), the water depth of the cooling flow passage 421a that is closest to the central axis X of the cooling flow passage 421 and the water depth of the cooling flow passage 421b that is adjacent to the outer periphery of the cooling flow passage 421a may be approximately the same, but the water depth of the cooling flow passage 421c that is closest to the outer periphery of the main body 42 is deeper than the cooling flow passages 421a and 421b.

[0025] According to one embodiment of the present invention, the water depth of the cooling flow passage 421c closest to the outer periphery of the main body 42 is formed to be deeper than the water depth of the cooling flow passage 421a closer to the center of the main body 42. Therefore, the bottom surface of the cooling flow passage 421c closest to the outer periphery of the main body 42 is positioned close to the position close to the outer periphery of the workpiece W that is irradiated with the electron beam, so that the workpiece W is cooled more efficiently.

[0026] The cooling water enters the cooling flow passage 421 via the water supply pipe 47 and flows from the center of the cooling flow passage 421 toward the outer periphery. The outermost cooling flow passage 421c has a flow passage 421d formed therein, which is connected to the inside of a bellows 48 formed above the cooling flow passage 421. The cooling water in the cooling flow passage 421c flows into the bellows 48 via the flow passage 421d. The cooling water that has flowed into the bellows 48 circulates and is supplied to the water supply pipe 47 again.

[0027] If the pressure-receiving area of ​​the workpiece W pressed by the cooling jig 4 through the cooling plate 41 is too large, the cooling plate 41 for cooling the workpiece W may become indented due to the effects of thermal expansion, etc., resulting in uneven cooling and reduced cooling capacity. Deformation, etc. may also shorten the life of the cooling jig 4. Conversely, if the pressure-receiving area of ​​the workpiece W is too small, the cooling capacity of the workpiece W may decrease, and the holding of the cooling jig 4 may become unstable, making it difficult to apply a stable pressing force to the workpiece W.

[0028] The pressure-receiving area of ​​the workpiece W pressed by the cooling jig 4 is 25 to 30 cm 2 , preferably 26 to 30 cm 2 It is preferable to adjust the contact area between the cooling plate 41 and the workpiece W so that the contact area between the cooling plate 41 and the workpiece W is equal to or less than the surface area of ​​the cooling plate 41. Here, the "pressure-receiving area" refers to the surface area of ​​the portion where the workpiece W and the cooling plate 41 are in direct contact with each other and which receives the pressing force from the cooling plate 41. In the example of FIG. 2( a), this refers to the surface area of ​​the ring-shaped bottom surface 410 of the cooling plate 41 which abuts against the workpiece W.

[0029] In particular, in welding of the joints of the sodium-sulfur battery described later, the pressure-receiving area of ​​the workpiece pressed by the cooling jig 4 is 25 to 30 cm 2 When the flow path surface area S of the cooling flow path 421 is 160 to 400 cm 2 , preferably 200 to 400 cm 2 , more preferably 300 to 380 cm 2 It is preferable that the flow path surface area S of the cooling flow path 421 of the main body 42 is adjusted so that:

[0030] In order to adjust the cooling capacity according to the amount of heat generated at the weld zone by electron beam irradiation, it is preferable to appropriately adjust the amount of cooling water flowing through the cooling flow path 421. Therefore, the electron beam welding apparatus 10 according to one embodiment of the present invention preferably includes a cooling water volume control device 400 for controlling the amount of cooling water. As shown in FIG. 1 , the cooling water volume control device 400 may include, for example, a flow meter 401, a thermometer 402, and a controller 403 for controlling a pump that discharges cooling water. The cooling water volume control device 400 may be configured to control the amount of cooling water supplied to the cooling jig 4 by adjusting the opening of the pump and valve based on the relationship between the temperature of the cooling water returned from the cooling flow path 421 to the bellows 8 and a predetermined cooling water volume. While a lower cooling water temperature is preferable in terms of cooling effectiveness, a sufficient cooling effect can be obtained even at a temperature of 20 to 30°C. Furthermore, the cooling capacity of the cooling jig 4 increases as the amount of cooling water increases. To suppress abnormal heating of the weld zone during electron beam welding, the cooling water volume control device 400 is preferably configured to control a pressure-receiving area of ​​25 to 30 cm. 2 At this time, it is preferable to control the amount of cooling water so that the amount of cooling water is 5 to 8 L / min, more preferably 6 to 8 L / min, and even more preferably 7 to 8 L / min.

[0031] 1, an electron beam irradiation device 2 for irradiating an electron beam onto a workpiece W is disposed on the side of a chamber 1. Preferably, a plurality of electron beam irradiation devices 2 are disposed at different positions in the height direction of the chamber 1 that holds the workpiece W. By using a plurality of electron beam irradiation devices 2, a plurality of portions to be welded on the workpiece W can be simultaneously welded, thereby shortening the welding processing time.

[0032] The electron beam irradiation device 2 may further include a laser ablation device 5 for irradiating the groove B1 of the workpiece W with laser light and polishing the groove B. The laser ablation device 5 may be disposed on the side of the chamber 1. The laser ablation device 5 is a device for melting and evaporating deposits adhering to the surface of the groove B, which will be the part to be welded, with laser light and removing them before the electron beam irradiation by the electron beam irradiation device 2.

[0033] For example, when a sodium-sulfur battery described below is used as the workpiece W and a positive electrode side body portion, which is a positive electrode container of the sodium-sulfur battery, and a positive electrode side bottom lid are welded together, sulfur, which serves as a positive electrode active material contained in the positive electrode side body portion, may adhere to the end surface of the positive electrode side body portion. If electron beam welding is performed with sulfur still adhering to the end surface of the positive electrode side body portion, the adhesion between the positive electrode side body portion and the positive electrode side bottom lid may be impaired.

[0034] According to the electron beam welding apparatus 10 of the embodiment of the present invention, before irradiating the workpiece W with an electron beam, impurities such as sulfur adhering to the surface of the groove B of the workpiece W are removed by a laser beam, thereby cleaning the surface of the groove B of the workpiece W. This improves the adhesion of the weld, enabling electron beam welding with high joint reliability.

[0035] The output of the laser beam from the laser ablation device 5 is arbitrary. For example, when welding the positive electrode side body portion and the positive electrode side bottom cover of a positive electrode container constituting a sodium-sulfur battery, it is preferable to adjust the output of the laser beam so that the change in the overall length of the positive electrode container before and after treatment is 0.10 mm or less, preferably 0.04 mm or less, and so that the surface roughness Ra (JIS B0601:2013) of the end face after irradiation with the laser beam is 5.0 or less, more preferably Ra is 3.2 or less.

[0036] For example, the laser output of the laser ablation device 5 can be set to 8.0 to 10.0 W, more preferably 9.0 to 10.0 W, the pulse period can be set to 30 to 50 μs, more preferably 35 to 45 μs, the laser movement speed can be set to 3000 to 9000 mm / s, more preferably 4000 to 6000 mm / s, more preferably 4000 to 5000 mm / s, and the focal depth can be set to −4 to 4 mm, more preferably −2 to 2 mm.

[0037] There are no particular limitations on the method of irradiating the workpiece W with laser light. Any laser pattern can be selected, such as an oscillating pattern, a step pattern, or a circle pattern. Among these, by using a circle pattern in which the laser light is irradiated along the circumferential direction of the end face of the workpiece W, the efficiency of removing foreign matter by irradiating the workpiece with laser light is particularly good.

[0038] Furthermore, the electron beam irradiation device 2 preferably includes a control device 23 for controlling the current value of the electron beam in accordance with the electron beam welding conditions, and one or both of the holding device 3 and the cooling jig 4 preferably include a control device 24, 440 for controlling the rotation speed of the workpiece W. By controlling the rotation speed of the workpiece W and the beam current value and / or beam welding output (beam power) within appropriate ranges by the control devices 23, 24, 430, the welding speed, weld depth, and weld width of the weld when electron beam welding the groove portion B of the workpiece W can be adjusted to be appropriate.

[0039] For example, in electron beam welding, when the workpiece W is rotated and the electron beam is irradiated onto the groove B, the control device 23 may irradiate the electron beam continuously over one or more revolutions around the outer periphery of the workpiece W, thereby partially overlapping the irradiated portions of the electron beam. In this case, spattering in the overlapping portions may cause unevenness on the surface, which may result in poor welding.

[0040] Therefore, it is preferable that the control device 23 controls the beam current value and / or the beam welding output of the electron beam so as to gradually increase the power density of the electron beam from the welding start point. Furthermore, it is preferable that the control device 23 controls the beam current value and / or the beam welding output of the electron beam so as to gradually decrease the power density of the electron beam toward the welding end point. As a result, the occurrence of welding defects such as irregularities formed on the surface of the weld is suppressed.

[0041] Although not limited to the following, it is preferable that the control device 23 controls the beam current value and / or beam welding output of the electron beam so that the electron beam is irradiated at a power density of 5 to 15%, more preferably 7 to 10%, of that in normal operation at the welding start point, and gradually increases the power density of the electron beam to the normal operation level in 0.1 to 1 s, more preferably 0.4 to 0.6 s. Furthermore, it is preferable that the control device 23 controls the beam current value and / or beam welding output of the electron beam so that the power density of the electron beam is gradually decreased 0.1 to 1 s, more preferably 0.4 to 0.6 s, before the welding end point is reached, so that the electron beam is irradiated at a power density of 5 to 15%, more preferably 7 to 10%, of that in normal operation at the welding end point.

[0042] The control device 24, 440 for controlling the rotation speed of the workpiece W is preferably configured to control the rotation speed of the workpiece W in accordance with the power density of the electron beam required for welding, the welding speed, the welding depth of the weld of the workpiece W, and the like. For example, there is a relationship between the welding depth of the weld and the welding output of the electron beam, such that the deeper the welding depth, the higher the welding output is required. There is also a relationship between the welding speed of the electron beam and the welding output, such that the higher the welding speed, the higher the welding output is required. Furthermore, welding with a high welding output may generate volatile components that contaminate the weld. The control device 24, 440 may be configured to control the rotation speed of the workpiece W based on a predetermined relationship between the welding speed and welding output of the electron beam. For example, when performing electron beam welding of sodium-sulfur batteries, as described below, the control device 24, 440 is preferably configured to control the rotation speed of the workpiece W so that the electron beam welding output is 1 to 4 kW, preferably 2 to 3 kW, and the welding speed is preferably 2 to 6 m / min, preferably 3 to 5 m / min.

[0043] (Sodium-sulfur battery) The configuration of a sodium-sulfur battery suitable for electron beam welding using the electron beam welding apparatus 10 shown in FIG. 1 is shown in FIG. 3. The sodium-sulfur battery 100 includes a positive electrode side body portion 61 for accommodating a positive electrode and a negative electrode, a positive electrode side bottom cover 64 joined to the lower end of the positive electrode side body portion 61 via a first weld p1, a positive electrode ring fitting 62 joined to the upper end of the positive electrode side body portion 61 via a second weld p2, a positive electrode terminal 63 joined to the upper end of the positive electrode ring fitting 62 via a third weld p3, a negative electrode ring fitting 21 positioned more inward than the positive electrode ring fitting 62 while being electrically insulated from the positive electrode ring fitting 62 by an insulating ring 40, and a negative electrode side upper cover 22 joined to the upper end of the negative electrode ring fitting 21 via a fourth weld p4. A negative electrode terminal 29 is provided on the upper surface of the negative electrode side upper cover 22. The negative electrode side upper cover 22 and the negative electrode terminal 29 can be provided as an integrally molded product, for example.

[0044] Metals such as aluminum or aluminum alloys can be used as materials for the positive electrode side body portion 61, the positive electrode side bottom cover 64, the positive electrode ring metal fitting 62, the positive electrode terminal 63, the negative electrode ring metal fitting 21, and the negative electrode side top cover 22. For example, an aluminum alloy A3003 as specified in JIS H4000:2014 can be suitably used. Furthermore, the electron beam welding apparatus 10 according to the embodiment of the present invention can be suitably used for joining metal parts, such as the joining between the positive electrode side body portion 61 and the positive electrode side bottom cover 64, the joining between the positive electrode side body portion 61 and the positive electrode ring metal fitting 62, the joining between the positive electrode ring metal fitting 62 and the positive electrode terminal 63, and the joining between the negative electrode ring metal fitting 21 and the negative electrode side top cover 22.

[0045] The insulating ring 40 is preferably made of aluminum oxide such as α-alumina. The insulating ring 40 is joined to the outer periphery of the upper end of a bottomed tubular (typically cylindrical) solid electrolyte 50. The solid electrolyte 50 is preferably made of one or both of β-alumina and β"-alumina. The insulating ring 40 and the solid electrolyte 50 can be joined by glass.

[0046] A bottomed cylindrical anode container 26 (typically cylindrical) is provided inside the bottomed cylindrical solid electrolyte 50, and contains the anode active material 7. A small hole 26a is provided at the bottom of the anode container 26. The anode container 26 can be made of high chromium steel, stainless steel (e.g., SUS304), an aluminum alloy, or SPCC (cold-rolled steel plate). A bottomed cylindrical safety tube 70 is provided outside the anode container 26 and inside the solid electrolyte 50. The safety tube 70 can be made of aluminum or an aluminum alloy. For example, an aluminum alloy A3003 as specified in JIS H4000:2014 can be suitably used.

[0047] Additionally, sulfur 6 as a positive electrode active material is contained within a space (positive electrode space) 28 surrounded by the positive electrode side body 61 and the positive electrode side bottom lid 64 outside the bottomed tubular solid electrolyte 50. Because sulfur 6 is an insulator, a positive electrode current collector 27 is generally provided to ensure electrical continuity between the positive electrode and the negative electrode and reduce the internal resistance of the battery. The positive electrode current collector 27 may be a member made of a felt material made of conductive carbon fiber and / or graphite fiber. The positive electrode current collector 27 is impregnated with sulfur 6 as a positive electrode active material and is disposed so as to abut against both the inner circumferential surface of the positive electrode side body 61 and the outer circumferential surface of the bottomed tubular solid electrolyte 50, thereby ensuring electrical continuity between the positive electrode and the negative electrode and reducing the internal resistance of the battery.

[0048] An inert gas such as argon, helium, or neon is sealed in the space 37 inside the negative electrode container 26 as a pressure (negative electrode side pressure) generating source, and nitrogen gas is sealed in the positive electrode space 28 as a pressure (positive electrode side pressure) generating source.

[0049] During discharge, sodium 7 molten in the anode container 26 is supplied into the safety tube 70 through the small hole 26a due to the pressure of the inert gas, filling the safety tube 70. The overflowing sodium 7 is then supplied to the space (anode space) 38 between the solid electrolyte 50 and the safety tube 70. Some of the sodium 7 supplied between the solid electrolyte 50 and the safety tube 70 has released electrons to the external circuit through the anode terminal 29 in the anode space 38, becoming sodium ions. These sodium ions then pass through the solid electrolyte 50 and enter the cathode space 28, where they react with sulfur 6 and electrons supplied from the external circuit through the cathode terminal 63 to produce sodium polysulfide. This allows a voltage of, for example, about 1.8 to 2.3 V to be generated.

[0050] During charging, when a voltage is applied from an external circuit through the positive electrode terminal 63 and the negative electrode terminal 29, the sodium polysulfide releases electrons to the external circuit through the positive electrode terminal 63 to generate sulfur and sodium ions, and the generated sodium ions permeate (pass) the solid electrolyte 50 and move to the negative electrode space 38. The sodium ions that have moved to the negative electrode space 38 move inward, over the upper end of the safety tube 70, and then move through the small hole 26a into the negative electrode container 26. They then react with electrons supplied from the external circuit through the negative electrode terminal 29 to become electrically neutral (becoming sodium 7), thereby converting electrical energy into chemical energy.

[0051] The following method can be used to seal the inert gas in the anode can 26. First, the anode can 26 is inverted so that the small hole 26a is at the top, and heated and melted sodium 7 is injected into the anode can 26 through the small hole 26a. The sodium 7 is cooled and solidified. Next, the anode can 26 is turned upside down and placed in the solid electrolyte 50. Subsequently, the opening of the solid electrolyte 50 is sealed under an inert gas atmosphere, and the sodium 7 is melted by heating. At this time, the molten sodium moves to the bottom of the anode can 26, and the inert gas moves to the top instead. In this way, the inert gas is sealed in the upper part of the anode can 26. Using an inert gas as the gas to be sealed in the anode can 26 prevents the material constituting the anode can 26 from reacting with the sealed gas and consuming it, thereby preventing a decrease in the pressure of the inert gas.

[0052] A preferred method for sealing nitrogen gas in the positive electrode space 28 is to place solid sodium azide, such as in pellet form, in the positive electrode space 28 during battery assembly, and then generate nitrogen gas by thermal decomposition after the positive electrode space 28 is sealed. Electron beam welding, which has high joining reliability, can be performed in a vacuum during battery assembly.

[0053] The positive electrode side body portion 61 may have a constriction 21 a. The constriction 21 a provides the positive electrode side body portion 61 with a spring effect, which can mitigate expansion and contraction of the positive electrode side body portion 61 due to thermal changes. After the positive electrode solidifies, the portion where the positive electrode current collector 27 is present is fixed with sulfur or sodium polysulfide and becomes immobile, so the constriction 21 a must be located above the position where the positive electrode current collector 27 is housed.

[0054] The manufacturing process of such a sodium-sulfur battery includes: a first welding step of welding a first groove B1 between the positive electrode side body portion 61 and the positive electrode side bottom cover 64 using an electron beam irradiation device 2 to form a first welded portion p1; a second welding step of welding a second groove B2 between the positive electrode side body portion 61 and the positive electrode ring metallic member 62 using an electron beam irradiation device 2 to form a second welded portion p2; a third welding step of welding a third groove B3 between the positive electrode ring metallic member 62 and the positive electrode terminal 63 using an electron beam irradiation device 2 to form a third welded portion p3; and a fourth welding step of welding a fourth groove B4 between the negative electrode ring metallic member 21 and the negative electrode side upper cover 22 using an electron beam irradiation device 2 to form a fourth welded portion p4.

[0055] Although the first welding step, the second welding step, the third welding step, and the fourth welding step may each be performed separately, it is preferable to perform the second welding step and the fourth welding step simultaneously using multiple electron beam irradiation devices 2. For example, the second groove portion B2 between the positive electrode side body portion 61 and the positive electrode ring fitting 62 and the fourth groove portion B4 between the negative electrode ring fitting 21 and the negative electrode side upper cover 22 are arranged at different heights. Therefore, by arranging multiple electron beam irradiation devices 2 at different heights corresponding to the second groove portion B2 and the fourth groove portion B4, respectively, the second welding step and the fourth welding step can be performed simultaneously. As a result, the equipment for the welding process can be made smaller, and the welding time can be shortened.

[0056] The electron beam welding process can be performed, for example, as follows. First, as shown in FIG. 4( a), the positive electrode side body 61 is erected so that the constricted portion 21a of the positive electrode side body 61 faces downward. Positive electrode current collectors 27a, 27b, 27c, and 27d, made of conductive felt material made of carbon fiber and / or graphite fiber, are placed on the inner circumferential surface and opening of the positive electrode side body 61. A positive electrode side bottom cover 64 to be joined to the positive electrode side body 61 is placed on the positive electrode current collector 27c. Then, as shown in FIG. 4( b), a first groove B1 between the positive electrode side body 61 and the positive electrode side bottom cover 64 is welded using an electron beam irradiation device 2 to form a first weld p1 (first welding step). It is preferable to clean the end surfaces of the positive electrode side body 61 and / or the positive electrode side bottom cover 64 using a laser ablation device 5 before the first welding step.

[0057] Next, as shown in FIG. 4( c), the positive electrode side body 61 is stood upright with the positive electrode side bottom cover 64 facing downward, and the solid electrolyte 50 with the negative electrode ring fitting 21 and the positive electrode ring fitting 62 joined thereto is placed inside the positive electrode side body 61 so as to face the positive electrode current collector 27 disposed on the inner circumferential surface of the positive electrode side body 61. Then, as shown in FIG. 4( d), the second groove B2 between the positive electrode side body 61 and the positive electrode ring fitting 62 is welded using the electron beam irradiation device 2 to form a second weld p2 (second welding step). At this time, the fourth groove B4 between the negative electrode ring fitting 21 and the negative electrode side top cover 22 is welded using the electron beam irradiation device 2 to form a fourth weld p4 (fourth welding step).

[0058] As shown in Fig. 4(e), the positive electrode terminal 63 is placed on the positive electrode ring fitting 62. Then, as shown in Fig. 4(f), the third groove portion B3 between the positive electrode ring fitting 62 and the positive electrode terminal 63 is welded using the electron beam irradiation device 2 to form a third weld portion p3 (third welding step).

[0059] In the first to fourth welding steps, welding is preferably performed under conditions of a welding speed of 1 to 5 m / min, more preferably 2 to 3 m / min, a beam current of 50 to 80 mA, more preferably 60 to 70 mA, and a beam welding output of 1 to 4 kW, more preferably 2 to 3 kW.

[0060] Furthermore, it is preferable that welding be performed so that the weld width of the first groove portion B1 is 2.0 mm or more, more preferably 3.0 mm or more, and the weld depth is 2.0 mm or more, more preferably 4.5 mm or more. Furthermore, it is preferable that welding be performed so that the weld width of the second groove portion B2 is 2.0 mm or more, more preferably 3.0 mm or more, and the weld depth is 1.5 mm or more, more preferably 3.5 mm or more. Furthermore, it is preferable that welding be performed so that the weld width of the third groove portion B3 is 1.0 mm or more, preferably 2.0 mm or more, more preferably 3.0 mm or more, and the weld depth is 2.0 mm or more, more preferably 3.0 mm or more. Furthermore, it is preferable that welding be performed so that the weld width of the fourth groove portion B4 is 2.0 mm or more, more preferably 3.0 mm or more, and the weld depth is 2.0 mm or more, more preferably 4.0 mm or more.

[0061] The upper limit of the weld width of the first groove portion B1 is not particularly limited as long as sufficient adhesion by electron beam welding is ensured, but is preferably 5.0 mm or less, more preferably 4.0 mm or less. The weld depth of the first groove portion B1 is not particularly limited as long as it does not penetrate the positive electrode side body portion 61 and the positive electrode side bottom cover 64, but is preferably 6.0 mm or less, more preferably 5.0 mm or less. The upper limit of the weld width of the second groove portion B2 is not particularly limited as long as sufficient adhesion by electron beam welding is ensured, but is preferably 5.0 mm or less, more preferably 4.0 mm or less. The weld depth of the second groove portion B2 is not particularly limited as long as it does not penetrate the positive electrode side body portion 61 and the positive electrode ring fitting 62, but is preferably 6.0 mm or less, more preferably 5.0 mm or less. The upper limit of the weld width of the third groove portion B3 is not particularly limited as long as sufficient adhesion can be ensured by electron beam welding, but is preferably 5.0 mm or less, more preferably 4.0 mm or less. The weld depth of the third groove portion B3 is not particularly limited as long as it does not penetrate the positive electrode ring metal fitting 62 and the positive electrode terminal 63, but is preferably 4.5 mm or less, more preferably 4.0 mm or less. The upper limit of the weld width of the fourth groove portion B4 is not particularly limited as long as sufficient adhesion can be ensured by electron beam welding, but is preferably 5.0 mm or less, more preferably 4.0 mm or less. The weld depth of the fourth groove portion B4 is not particularly limited as long as it does not penetrate the negative electrode ring metal fitting 21 and the negative electrode side upper cover 22, but is preferably 6.0 mm or less, more preferably 5.0 mm or less.

[0062] The weld width (bead width) refers to the maximum width of the weld, and the weld depth refers to the maximum depth from the surface of the weld. The weld depth can be measured by observing the cross sections of the first to fourth welds p1 to p4 in a cross section passing through the axis of the workpiece and along the longitudinal direction.

[0063] In the first to fourth welding steps, it is preferable that multiple ribs 221 be arranged along the circumferential direction in the first to fourth groove portions B1 to B4. By arranging multiple ribs 221 between the welded members, a certain gap is formed between the welded members. For example, as shown in FIG. 5( b), a rib 221 protruding outward from the outer periphery of the negative electrode side upper cover 22 is provided on the lower part of the negative electrode side upper cover 22. As shown in FIG. 5( c), four ribs 221 are provided along the circumferential direction of the negative electrode side upper cover 22. The number of ribs 221 is not particularly limited. The number of ribs 221 is, for example, 3 to 10, preferably 4 to 8. As shown in FIG. 5( d), the rib 221 of the negative electrode side upper cover 22 and the negative electrode ring fitting 21 abut via the rib 221. As shown in FIG. 5( e ), in the area where the rib 221 of the negative electrode side upper lid 22 is not formed, a gap is provided between the rib 221 of the negative electrode side upper lid 22 and the negative electrode ring metal fitting 21 .

[0064] 5(a) is a schematic diagram showing the assembled state of the sodium-sulfur battery before the second welding step and the fourth welding step are simultaneously performed. A certain gap is formed in the second groove portion B2 and the fourth groove portion B4 by a rib 221 disposed between the positive electrode side body portion 61 and the positive electrode ring fitting 62 and a rib 221 disposed between the negative electrode ring fitting 21 and the negative electrode side upper lid 22. This gap allows air inside the sodium-sulfur battery to be discharged to the outside of the sodium-sulfur battery.

[0065] 5(a) is held by the holding device 3 and cooling jig 4 in the chamber 1 of the electron beam welding apparatus 10 of FIG. 1, and when the atmosphere in the chamber 1 is maintained at a vacuum state, the air in the sodium-sulfur battery is drawn into the chamber 1 and pushed out of the sodium-sulfur battery. Then, while the holding device 3 and cooling jig 4 press the sodium-sulfur battery, the electron beam irradiation device 2 irradiates the second groove portion B2 and the fourth groove portion B4 with an electron beam. This melts the rib 221, so that the positive electrode side body portion 61 and the positive electrode ring metal fitting 62, and the negative electrode ring metal fitting 21 and the negative electrode side upper cover 22 are tightly fixed together.

[0066] As described above, according to the embodiment of the present invention, by arranging a plurality of ribs 221 along the circumferential direction in the first to fourth groove portions B1 to B4, which become the first to fourth welded portions, it is possible to more reliably evacuate the sodium-sulfur battery.

[0067] 6 is a schematic diagram illustrating an example of a sodium-sulfur battery manufacturing line using an electron beam welding apparatus according to an embodiment of the present invention. A flat transport pallet 102 containing sodium-sulfur batteries is placed on a transport conveyor 101 constituting a transport mechanism. The transport pallet 102 is provided so as to be able to be carried into and out of chambers 103, 104, and 105 by the transport conveyor 101. Electron beam irradiation devices 201, 202, 203, and 204 are provided in the chambers 103, 104, and 105, respectively, for performing electron beam welding on the sodium-sulfur batteries. Inspection devices 110 and 111 may be provided downstream of the electron beam irradiation devices 201, 202, 203, and 204 to perform inspections after the electron beam welding process performed by the electron beam irradiation devices 201, 202, 203, and 204. After the sodium-sulfur batteries are subjected to electron beam welding processing by the electron beam irradiation devices 201, 202, 203, and 204 and undergo predetermined inspections, a sleeve tube for housing the sodium-sulfur batteries is attached to the exterior casing 106. A thermal mica sheet, a fireproof carbon sheet, and an insulating mica sheet are wrapped around the outer periphery of the sleeve tube, and a heat-insulating and / or insulating plate material is adhesively fixed to the bottom surface of the sleeve tube.

[0068] 7 is a schematic diagram showing an inspection device 113 for inspecting a sodium-sulfur battery after the fourth welding step of the present invention is completed. This inspection device 113 can be used as a device for inspecting whether or not a welding hole has occurred in the fourth welded portion welded in the fourth welding step.

[0069] That is, this inspection device 113 is an inspection device 113 capable of determining whether the welding condition of the workpiece W is good or bad, and is equipped with an inspection chamber 1130 for accommodating the workpiece W, a vacuum pump 1132 capable of evacuating the inspection chamber 1130, a vacuum gauge 1131 connected to the inspection chamber 1130, a measurement unit 1133 for measuring the evacuation time required to reach a predetermined vacuum level from the start of evacuation when the workpiece W is accommodated in the inspection chamber 1130, and a judgment unit 1134 for judging whether the welding condition of the workpiece W is good or bad based on the measurement results of the measurement unit 1133.

[0070] The measurement unit 1133 and the determination unit 1134 are configured with a general-purpose computer 1135 or the like capable of performing various calculation processes. The computer 1135 may be equipped with a storage device (not shown) or the like that stores the calculation results and past inspection results of the measurement unit 1133 and the determination unit 1134. As the vacuum gauge 1131, for example, an electric resistance type vacuum gauge such as a Pirani vacuum gauge is suitably used. The measurement unit 1133 is connected to the vacuum pump 1132 and the vacuum gauge 1131.

[0071] When the workpiece W to be inspected is placed in the inspection chamber 1130, evacuation is performed by a vacuum pump 1132. The pressure during evacuation is measured by a vacuum gauge 1131. If a weld hole has occurred in the workpiece W to be inspected, the evacuation time required to reach a predetermined vacuum level inside the inspection chamber 1130 will be longer than usual.

[0072] Therefore, in this inspection, the inspection chamber 1130 is evacuated, and the measurement unit 1133 measures the evacuation time required to reach a predetermined vacuum level after evacuation begins. If the evacuation time exceeds the specified time, the judgment unit 1134 provisionally judges the workpiece W to be defective (first judgment process). Furthermore, the judgment unit 1134 compares the evacuation time of the workpiece W provisionally judged to be defective with the evacuation time of the previous workpiece W measured immediately before (second judgment process). If the difference between the evacuation time of the workpiece provisionally judged to be defective in the second judgment process and the evacuation time of the previous workpiece W measured immediately before is equal to or greater than a threshold, the judgment unit 1134 judges that a weld hole has occurred in the workpiece W and finally judges the workpiece W to be defective. Note that the comparison of the evacuation time in the second judgment process is not limited to the previous workpiece W, but can also be made with workpieces several works before that. According to the inspection device 113 of the embodiment of the present invention, defective products due to welding of the workpiece W can be easily detected, and even if the workpiece W is repeatedly determined to be defective, false detection of the defective product can be prevented by comparing the vacuum exhaust time with that of the previous workpiece W.

[0073] (Cooling Jig) Three cooling jigs were prepared as shown in Figures 8(a), 8(b), and 8(c). The pressure-receiving area of ​​the cooling jig 4a in Figure 8(a) was 32.2 cm 2 , the flow path surface area S (unit: cm ) of the cooling flow path 421 a formed in the main body 42 a 2 ) is 50 cm 2 , the volume v of the cooling flow path 421a (unit: cm 3 ) is 60 cm 3 , the cooling water flow rate is 1.7 L / min, and the volume V of the main body 42a (unit: cm 3 ) is 358 cm 3 and the flow path surface area S (unit: cm) of the cooling flow path 421a with respect to the volume V of the main body 42a. 2 ) ratio (S / V) is 14%, and the volume v (unit: cm 3 ) of the cooling flow passage 421a relative to the flow passage surface area S (unit: cm 2 The pressure-receiving area of ​​the cooling jig 4b in FIG. 8(b) was 32.2 cm 2, the flow path surface area S (unit: cm 2 ) is 85cm 2 , the volume v of the cooling flow path 421b (unit: cm 3 ) is 101 cm 3 , the cooling water flow rate is 5.0 L / min, and the volume V of the main body 42b (unit: cm 3 ) is 317 cm 3 and the flow path surface area S (unit: cm) of the cooling flow path 421b with respect to the volume V of the main body 42b. 2 ) ratio (S / V) is 27%, and the volume v (unit: cm 3 ) relative to the flow channel surface area S (unit: cm 2 The ratio (S / v) of the pressure-receiving area of ​​the cooling jig 4 in FIG. 8(c) was 28.8 cm 2 , the flow path surface area S (unit: cm 2 ) is 359 cm 2 , the volume v of the cooling channel 421 (unit: cm 3 ) is 130 cm 3 , the cooling water flow rate is 7.0 L / min, and the volume V of the main body 42 (unit: cm 3 ) is 288 cm 3 and the flow path surface area S (unit: cm ) of the cooling flow path 421 with respect to the volume V of the main body 42. 2 ) ratio (S / V) is 125%, and the volume v (unit: cm 3 ) of the cooling channel 421 relative to the channel surface area S (unit: cm 2 The ratio (S / v) of the total solubility of the cellulose derivatives to the total solubility of the cellulose derivatives was 276%.

[0074] To evaluate the thermal impact of electron beam welding on the inside of the sodium-sulfur battery, a temperature measuring device T1 was connected to the positive electrode side body part 61 of the sodium-sulfur battery, and a temperature measuring device T2 was connected to the positive electrode ring metal fitting 62, and the temperature change between the positive electrode ring metal fitting 62 and the solid electrolyte 50 was measured when the positive electrode side body part 61 and the positive electrode ring metal fitting 62 were electron beam welded together in the first welding step, as shown in Figure 9. The welding conditions were a beam current of 72 mA, a lens current of 660 mA, and a welding speed of 3 m / min for the electron beam irradiation device.

[0075] In the cooling jig 4a shown in FIG. 8(a), the maximum temperature change ΔT between T1 and T2 due to electron beam welding was 109°C, whereas in the cooling jig 4b shown in FIG. 8(b), the maximum temperature change ΔT between T1 and T2 due to electron beam welding was approximately 90°C. On the other hand, in the cooling jig 4 shown in FIG. 8(c), the maximum temperature change ΔT between T1 and T2 due to electron beam welding was 77°C, and the cooling effect of the workpiece W was the highest compared to the configurations of FIGS. 8(a) and 8(b). Thus, the electron beam welding apparatus according to the embodiment of the present invention can improve the cooling efficiency of the workpiece W and reduce the thermal impact on the interior of the workpiece W due to electron beam welding. As a result, the occurrence of defective workpieces W caused by abnormal heating of the workpiece W due to electron beam welding can be reduced.

[0076] 1: Chamber 2: Electron beam irradiation device 3: Holding device 4: Cooling jig 4a: Cooling jig 4b: Cooling jig 5: Laser ablation device 6: Sulfur 7: Sodium 8: Bellows 10: Electron beam welding device 21: Negative electrode ring metal fitting 22: Negative electrode side upper lid 23: Control device 24: Control device 26: Negative electrode container 26a: Small hole 27: Positive electrode current collector 28: Positive electrode space 29: Negative electrode terminal 31: Holding part 32: Shaft part 37: Space 38: Negative electrode space 40: Insulating ring 41: Cooling plate 42: Main body part 43: Seal plate 44: Regulating plate 47: Water supply pipe 48: Bellows 50: Solid electrolyte 61: Positive electrode side body part 62: Positive electrode ring metal fitting 63: Positive electrode terminal 64: Positive electrode side bottom lid 70: Safety tube 100: Sodium-sulfur battery 101: Transport conveyor 102: Transport pallet 103: Chamber 104: Chamber 105: Chamber 106: Exterior 110: Apparatus 111: Apparatus 113: Inspection device 201: Electron beam irradiation device 202: Electron beam irradiation device 203: Electron beam irradiation device 204: Electron beam irradiation device 221: Rib 400: Cooling water amount control device 410: Bottom surface 421: Cooling flow path 430: Control device 440: Cooling water amount control device 440: Control device 1130: Inspection chamber 1131: Vacuum gauge 1132: Vacuum pump 1133: Measurement unit 1134: Determination unit 1135: Computer

Claims

1. A method for manufacturing a vacuum chamber for holding a pair of workpieces butted together in a vacuum atmosphere; an electron beam irradiation device for irradiating an electron beam toward the grooves of the workpieces housed in the chamber; a holding device for pressing the workpieces from below upward and holding the workpieces rotatably in the circumferential direction; and a cooling jig for pressing the workpieces from above downward and cooling the workpieces while holding the workpieces rotatably in the circumferential direction, the cooling jig having a cooling flow path within a metal main body for circulating cooling water to cool the workpieces, and a volume V (unit: cm) of the main body. 3 ) relative to the flow channel surface area S (unit: cm 2 ) is 100 to 170%.

2. The volume v of the cooling channel (unit: cm 3 ) relative to the flow channel surface area S (unit: cm 2 2. The electron beam welding device according to claim 1, wherein the ratio (S / v) of the total number of electrodes is 100 to 350%.

3. An electron beam welding device according to claim 1, wherein the cooling flow path includes a spiral-shaped flow path that rotates from a central axis extending in the vertical direction of the cooling jig toward the outer periphery.

4. An electron beam welding device according to claim 1, wherein the cooling flow path is arranged so that the water depth increases from the central axis extending in the vertical direction of the cooling jig toward the outer periphery.

5. The pressure-receiving area of ​​the workpiece pressed by the cooling jig is 25 to 30 cm 2 2. The electron beam welding apparatus according to claim 1, further comprising a cooling water flow rate control device for controlling the amount of cooling water so that the amount of cooling water is 5 to 8 L / min when 6. The cooling flow path has a pressure-receiving area of ​​the workpiece pressed by the cooling jig of 25 to 30 cm 2 When the flow path surface area is 160 to 400 cm 2 2. The electron beam welding apparatus according to claim 1, wherein the welding is performed in a manner such that:

7. An electron beam welding apparatus as described in claim 1, wherein the electron beam irradiation device is equipped with a control device for controlling the current value of the electron beam, and one or both of the holding device and the cooling jig are equipped with a control device for controlling the rotation speed of the workpiece.

8. The electron beam welding apparatus according to claim 1, further comprising a laser ablation device for irradiating the groove portion of the workpiece with a laser and polishing the groove portion.

9. An electron beam welding apparatus according to claim 1, further comprising an inspection device capable of determining whether the welding condition of the workpiece is good or bad, the inspection device comprising: an inspection chamber for accommodating the workpiece; a vacuum pump capable of evacuating the interior of the inspection chamber; a measurement unit for measuring the evacuation time required to reach a predetermined vacuum level from the start of evacuation while the workpiece is accommodated in the inspection chamber; and a judgment unit for judging whether the welding condition of the workpiece is good or bad based on the measurement results of the measurement unit.

10. The electron beam welding apparatus according to claim 1, wherein a plurality of the electron beam irradiation devices are arranged in the height direction of the chamber.

11. A method for manufacturing a sodium-sulfur battery comprising: a positive electrode side body portion for accommodating a positive electrode and a negative electrode; a positive electrode side bottom lid joined to the lower end of the positive electrode side body portion via a first weld; a positive electrode ring metal fitting joined to the upper end of the positive electrode side body portion via a second weld; a positive electrode terminal joined to the upper end of the positive electrode ring metal fitting via a third weld; a negative electrode ring metal fitting positioned more inward than the positive electrode ring metal fitting and electrically insulated from the positive electrode ring metal fitting by an insulating ring; and a negative electrode side top lid joined to the upper end of the negative electrode ring metal fitting via a fourth weld, the method comprising: a first welding step of welding a first groove portion between the positive electrode side body portion and the positive electrode side bottom lid using the electron beam irradiation device according to any one of claims 1 to 10 to form the first weld; a second welding step of welding a second groove portion between the positive electrode side body portion and the positive electrode ring metallic member using the electron beam irradiation device to form the second welded portion; a third welding step of welding a third groove portion between the positive electrode ring metallic member and the positive electrode terminal using the electron beam irradiation device to form the third welded portion; and a fourth welding step of welding a fourth groove portion between the negative electrode ring metallic member and the negative electrode side upper lid using the electron beam irradiation device to form the fourth welded portion.

12. The method for manufacturing a sodium-sulfur battery according to claim 11, wherein the second groove portion and the fourth groove portion are located at different height positions, and the second welding step and the fourth welding step are carried out simultaneously using a plurality of the electron beam irradiation devices.

13. The method for manufacturing a sodium-sulfur battery according to claim 11, wherein the first to fourth welding steps are performed at a welding speed of 1 to 5 m / min and a beam current of 50 to 80 mA.

14. The method for manufacturing a sodium-sulfur battery according to claim 11, wherein the weld width of the first groove portion is 2.0 mm or more and the weld depth is 2.0 mm or more.

15. The method for manufacturing a sodium-sulfur battery according to claim 11, wherein the second groove portion has a weld width of 2.0 mm or more and a weld depth of 1.5 mm or more.

16. The method for manufacturing a sodium-sulfur battery according to claim 11, wherein the third groove portion has a weld width of 1.0 mm or more and a weld depth of 2.0 mm or more.

17. The method for manufacturing a sodium-sulfur battery according to claim 11, wherein the fourth groove portion has a weld width of 2.0 mm or more and a weld depth of 2.0 mm or more.

18. A method for manufacturing a sodium-sulfur battery according to claim 11, wherein a plurality of ribs are arranged along the circumferential direction of the first to fourth groove portions.

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