Patent Description:
For example, Japanese Patent Application <CIT> discloses a sealed type battery that includes an electrode outside terminal, a sealing plate, and an electrical collector plate overlaid on the sealing plate. The electrode outside terminal includes a flange part and a columnar inserting part that protrudes in one direction from the flange part. A shape of a traverse cross section of the columnar inserting part is a hollow truck shape. On each of the sealing plate and the electrical collector plate, a penetration hole is formed into which the columnar inserting part is inserted. Here, to overlap the penetration hole of the sealing plate and the penetration hole of the electrical collector plate, the sealing plate and the electrical collector plate are overlaid, and the columnar inserting part is inserted into these penetration holes. Then, by caulking a tip end portion of the columnar inserting part, it is possible to fix the electrode outside terminal to the sealing plate.

For example, Japanese Patent <CIT> discloses a square secondary battery that includes an outside terminal, a cover, and an electrical collector plate overlaid on the cover. The outside terminal includes a terminal head part formed in a rectangular shape and includes a shaft part provided on a terminal head part and formed in an oval shape. On the cover, a penetration hole is formed into which a shaft part of the outside terminal is inserted. On the electrical collector plate, an opening hole is formed into which the shaft part is inserted. Here, to overlap the penetration hole and the opening hole, the cover and the electrical collector plate are overlaid. Then, the shaft part of the outside terminal is inserted into the penetration hole and the opening hole. Then, by caulking a tip end portion of the shaft part, it is possible to fix the outside terminal to the cover.

Anyway, on the electrode outside terminal disclosed by <CIT>, the columnar inserting part formed in the truck shape is caulked. On the outside terminal disclosed by <CIT>, the shaft part formed in the oval shape is caulked. As described above, if a member formed in the truck shape or the oval shape is caulked, a thickness of the caulked portion had been far from constant and had been varied. As the result, it happened that a caulking strength had not been secured.

United States Patent Application <CIT> discloses a secondary battery and a battery pack using the same. In the secondary battery of <CIT>, an insertion portion of a negative electrode terminal is inserted into through-holes provided in an outer insulating member, a sealing plate, an inner insulating member, and a terminal connection portion of a negative electrode collector, and the insertion portion is crimped. A countersunk hole is provided around the through-hole of the terminal connection portion. The insertion portion of the negative electrode terminal is radially expanded in the countersunk hole. A distal end of a thin portion provided at a distal end of the crimped part of the insertion portion and the edge of the countersunk hole are welded by application of a high energy beam, and a groove is provided on the outer peripheral side of the countersunk hole.

Furthermore <CIT> discloses a caulking method and resulting terminal-conductive member-sealing plate arrangement, wherein the caulked part is oval, the method being a two step process employing a caulking tool.

A manufacturing method for a secondary battery proposed here includes a first preparation step, a second preparation step, a first caulking step, and a second caulking step. At the first preparation step, a terminal formed in an oval like shape and having a cylindrical shaft part is inserted into an attachment hole formed on a sealing plate of a secondary battery that includes a case main body whose part is opened and includes the sealing plate provided at the opening of the case main body, so as to make the shaft part protrude from the sealing plate. At the second preparation step, a conductive member is arranged at a periphery of the attachment hole and on a surface at a side where the shaft part of the sealing plate protrudes. At the first caulking step, a caulking tool having a tip end part formed in an oval like shape and having a base end part formed in a complete round shape whose diameter is larger than the tip end part is used to insert the tip end part into the shaft part of the terminal, so as to make the base end part expand an inner diameter of a portion of the shaft part protruding from the sealing plate. At the second caulking step, the portion of the shaft part expanded at the first caulking step is pressed to be flat.

According to the manufacturing method for the secondary battery proposed here, it is possible by the tip end part formed in the oval like shape of the caulking tool to uniformly abut the inner circumferential surface of the shaft part formed in the oval like shape. Then, the base end part formed in the complete round shape of the caulking tool is abutted on the shaft part, to outwardly widen from a portion of the shaft part along the long diameter direction of the oval like shape, and thus it is possible to inhibit variation in the thicknesses of the caulked portion of the shaft part. Therefore, it is possible to secure the caulking strength for the terminal.

According to the manufacturing method for the secondary battery proposed here, the base end part might include a reduced diameter portion whose diameter becomes smaller toward the tip end part. At the first caulking step, the reduced diameter portion of the base end part might be used to expand the inner diameter of the portion of the shaft part protruding from the sealing plate.

The manufacturing method for the secondary battery proposed here might include a third caulking step for pressing to form a step on a peripheral edge part in a long diameter direction of the oval like shape of the expanded portion of the shaft part pressed to be flat at the second caulking step.

A secondary battery proposed herein but not forming part of the claimed invention includes a case main body whose part is opened, a sealing plate that is provided at the opening of the case main body, a terminal that is attached to the sealing plate, and a conductive member that is connected to the terminal. The terminal includes a caulked part that is caulked with respect to the conductive member and is formed in an oval like shape. The caulked part includes a long diameter part that is along a long diameter direction of the oval like shape, and a short diameter part that is along a short diameter direction of the oval like shape. A length of the long diameter part in the short diameter direction is longer than a length of the short diameter part in the long diameter direction.

Below, one embodiment of a herein disclosed secondary battery will be explained with drawings. The matters other than matters particularly mentioned in this specification, and required for practicing the present invention can be grasped as design matters of those skilled in the art based on the related art in the present field. The present disclosure can be implemented on the basis of contents disclosed in the present specification and a common general technical knowledge of this field. Incidentally, in the following accompanying drawings, the members/parts providing the same effect are given the same numerals and signs.

In the present specification, the "battery" is a term denoting an electric storage device capable of extracting the electric energy in general, and is a concept including a primary battery and a secondary battery. The term "secondary battery" means an electric storage device in general that can be repeatedly charged and discharged, and semantically covers a so-called storage battery, such as a lithium secondary battery, a nickel hydrogen battery, and a nickel cadmium battery. Below, a lithium ion secondary battery, which is one kind of the secondary battery, is taken as an example, and then the herein disclosed secondary battery will be described in details. However, the herein disclosed secondary battery is not restricted to the lithium ion secondary battery in accordance with the embodiment explained here.

<FIG> is a perspective view of a secondary battery <NUM> in accordance with the present embodiment. <FIG> is a cross sectional view of the secondary battery <NUM> at a II-II cross section of <FIG>. As shown in <FIG> and <FIG>, the secondary battery <NUM> includes an electrode body <NUM>, a case main body <NUM>, and a sealing plate <NUM>.

As shown in <FIG>, the electrode body <NUM> is a power generating element of the secondary battery <NUM>. The electrode body <NUM> includes a positive electrode sheet <NUM> as a positive electrode element, a negative electrode sheet <NUM> as a negative electrode element, and a sheet-shaped separator <NUM>. The separator <NUM> is arranged between the positive electrode sheet <NUM> and the negative electrode sheet <NUM>. In the electrode body <NUM>, the positive electrode sheet <NUM>, the negative electrode sheet <NUM>, and the separator <NUM> are laminated. The electrode body <NUM> in accordance with the present embodiment has a laminate type structure in which the positive electrode sheet <NUM> and the negative electrode sheet <NUM>, formed into predetermined shapes, are overlaid via the separator <NUM>.

The positive electrode sheet <NUM> includes, for example, a positive electrode collector foil that is formed in a rectangular shape, a positive electrode active material layer that is formed on both surfaces of the positive electrode collector foil, and a positive electrode collector tab 21a that protrudes from the positive electrode active material layer. The positive electrode collector foil is, for example, an aluminum foil. The positive electrode active material layer contains a positive electrode active substance. The positive electrode active substance, for example, in a lithium ion secondary battery, is a material like a lithium transition metal composite material that can release lithium ions at an electrically charging time and can absorb lithium ions at an electrically discharging time. However, in general, various materials other than the lithium transition metal composite material are proposed as the positive electrode active substance, and thus the positive electrode active substance is not particularly restricted. The positive electrode collector tab 21a is a part of the positive electrode collector foil and protrudes from the positive electrode active material layer. Here, the positive electrode collector tab 21a protrudes upward from the positive electrode active material layer. On the positive electrode collector tab 21a, the positive electrode active material layer is not formed.

The negative electrode sheet <NUM> includes, for example, a negative electrode collector foil that is formed in a rectangular shape, a negative electrode active material layer that is formed on both surfaces of the negative electrode collector foil, and a negative electrode collector tab 22a that protrudes from the negative electrode active material layer. The negative electrode collector foil is, for example, a copper foil. The negative electrode active material layer contains a negative electrode active substance. The negative electrode active substance, for example, in a lithium ion secondary battery, is a material like a natural graphite that can store lithium ions at an electrically charging time and can release lithium ions, stored at the electrically charging time, at an electrically discharging time. However, in general, various materials other than the natural graphite are proposed as the negative electrode active substance, and thus the negative electrode active substance is not particularly restricted. The negative electrode collector tab 22a is a part of the negative electrode collector foil and protrudes from the negative electrode active material layer. Here, the negative electrode collector tab 22a protrudes upward from the negative electrode active material layer. On the negative electrode collector tab 22a, the negative electrode active material layer is not formed.

The separator <NUM> is, for example, formed with a porous sheet (e.g., a film, a non-woven fabric, or the like) consisted of a resin, such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide.

In the present embodiment, the electrode body <NUM> is manufactured, in a state where a plurality of positive electrode collector tabs 21a are overlaid and a plurality of negative electrode collector tabs 22a are overlaid, by laminating the positive electrode sheet <NUM> and the negative electrode sheet <NUM> via the separator <NUM>.

As shown in <FIG>, the case main body <NUM> is a case including a space at the inside and a part of the case is opened. Here, the case main body <NUM> accommodates the electrode body <NUM> and, on the case main body <NUM>, an opening <NUM> is formed to accommodate the electrode body <NUM>. As shown in <FIG>, the case main body <NUM> is formed in a rectangular shape, but the shape of the case main body <NUM> is not particularly restricted. The case main body <NUM> is formed, for example, with aluminum or with aluminum alloy whose main component is aluminum, but even a material for forming the case main body <NUM> is not particularly restricted.

In the present embodiment, the case main body <NUM> might accommodate an electrolyte in addition to the electrode body <NUM>. As the electrolyte, it is possible to use a nonaqueous electrolyte in which a supporting salt is dissolved into a nonaqueous type solvent. As an example of the nonaqueous type solvent, it is possible to use carbonate type solvent, such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. As an example of the supporting salt, it is possible to use a fluorine-containing lithium salt, such as LiPF<NUM>.

The sealing plate <NUM> is a plate-shaped member provided on the opening <NUM> of the case main body <NUM>. The sealing plate <NUM> is formed in a rectangular shape (here, oblong rectangle shape) longer in a predetermined direction. Here, in a state where the sealing plate <NUM> is attached to the opening <NUM>, a peripheral edge part of the sealing plate <NUM> is joined to a rim of the opening <NUM> of the case main body <NUM>. It is preferable that this join is implemented, for example, by welding continuously without gaps and, for example, it is implemented by laser welding. The sealing plate <NUM> is formed, for example, with aluminum or with aluminum alloy whose main component is aluminum, but even a material for forming the sealing plate <NUM> is not particularly restricted.

In the present embodiment, as shown in <FIG>, an injection hole <NUM> and a gas exhaust valve <NUM> is provided on the sealing plate <NUM>. The injection hole <NUM> is a hole for injecting the electrolyte into the case main body <NUM> after the sealing plate <NUM> is attached to the case main body <NUM>. As shown in <FIG>, it is possible to fit a plug <NUM> into the injection hole <NUM>. By fitting the plug <NUM> into the injection hole <NUM>, the injection hole <NUM> is closed. The gas exhaust valve <NUM> is a thin-walled part that is configured to be broken so as to exhaust gas inside the case main body <NUM> to the outside of the case main body <NUM> when an internal pressure of the secondary battery <NUM> becomes equal to or more than a predetermined value.

The secondary battery <NUM> in accordance with the present embodiment includes a terminal <NUM>, a conductive member <NUM>, and a connecting member <NUM>. The terminal <NUM> is attached to the sealing plate <NUM>. Here, the terminal <NUM> includes a positive electrode terminal 50a that is connected to the positive electrode sheet <NUM> of the electrode body <NUM>, and includes a negative electrode terminal 50b that is connected to the negative electrode sheet <NUM> of the electrode body <NUM>. Here, the positive electrode terminal 50a and the negative electrode terminal 50b have the same shape and the same configuration. Below, in explanations common for the positive electrode terminal 50a and the negative electrode terminal 50b, a wording of terminal <NUM> would be used.

<FIG> is a plane view in which an attachment hole <NUM> of the sealing plate <NUM> is schematically shown. <FIG> shows a state in which the terminal <NUM> cut by a traverse cross section is inserted into the attachment hole <NUM>. In the present specification, the traverse cross section means a cross section cut in a horizontal direction. In the present embodiment, as shown in <FIG>, the attachment hole <NUM> is formed on the sealing plate <NUM>. The attachment hole <NUM> is formed in an oval like shape. Here, the oval means a curve geometrically similar to an egg shape, an ellipse shape, an oval shape. The oval like shape semantically contains an oval shape, a truck shape, an ellipse shape, an egg shape, and the like. In the present embodiment, a long diameter direction D11 of the oval like shape is the same as a longitudinal direction of the sealing plate <NUM>. A short diameter direction D12 of the oval like shape is the same as a shorter direction of the sealing plate <NUM>.

In the present embodiment, as shown in <FIG>, the terminal <NUM> is attached to the sealing plate <NUM> in a state of being inserted into the attachment hole <NUM>. Here, as shown in <FIG>, an outside insulating member <NUM> exists between a rim of the attachment hole <NUM> and the terminal <NUM>.

<FIG> is a view that schematically shows a caulked part <NUM> of the terminal <NUM>. <FIG> is a cross sectional view of the terminal <NUM> at a V-V cross section of <FIG>. <FIG> is a cross sectional view of the terminal <NUM> at a VI-VI cross section of <FIG>. In <FIG>, the upper and lower positions of <FIG> are reversed. In the present embodiment, as shown in <FIG>, the terminal <NUM> includes a head part <NUM>, a cylinder part <NUM>, and the caulked part <NUM>. The head part <NUM> is a portion arranged at the outside of the sealing plate <NUM> (here, a side opposite to the case main body <NUM>). The head part <NUM> is an approximately flat-plate shaped portion larger than the attachment hole <NUM>, and is arranged along an outside surface of the sealing plate <NUM>.

The cylinder part <NUM> is a portion that is inserted into the attachment hole <NUM> via the outside insulating member <NUM>. The cylinder part <NUM> protrudes downward from a central part of the head part <NUM>. The cylinder part <NUM> is, for example, a cylindrical portion that extends in an up and down direction. The caulked part <NUM> is a portion caulked with respect to the conductive member <NUM> of the terminal <NUM>. In other words, it can be said that the caulked part <NUM> is a portion caulked with respect to the sealing plate <NUM>. The caulked part <NUM> is provided at a lower end of the cylinder part <NUM> and protrudes to an outward of the cylinder part <NUM>. In the present embodiment, the cylinder part <NUM> and the caulked part <NUM> each is formed in a shape corresponding to the attachment hole <NUM>, and is formed here in an oval like shape as shown in <FIG>. In other words, the traverse cross section shapes of the cylinder part <NUM> and the caulked part <NUM> are oval like shapes. Here, an inner circumferential surface and an outer circumferential surface of the cylinder part <NUM> are formed in oval like shapes.

As shown in <FIG>, the outside insulating member <NUM> is attached over an region from an inner circumferential surface of the attachment hole <NUM> of the sealing plate <NUM> to a surface at the outside of the sealing plate <NUM> (in other words, a head part <NUM> side of the terminal <NUM>). In the present embodiment, the outside insulating member <NUM> includes a base part <NUM>, an insulation cylinder part <NUM>, and a side wall <NUM>. The base part <NUM> is a plate-shaped member that is attached to a portion of a surface at the outside of the sealing plate <NUM> around the attachment hole <NUM>. On the base part <NUM>, the head part <NUM> of the terminal <NUM> is arranged. The insulation cylinder part <NUM> is a cylindrical portion that protrudes from a bottom surface of the base part <NUM>. The insulation cylinder part <NUM> is a portion that is inserted into the attachment hole <NUM>. Into the insulation cylinder part <NUM>, the cylinder part <NUM> of the terminal <NUM> is inserted. The side wall <NUM> is standing from a peripheral edge of the base part <NUM>. The head part <NUM> of the terminal <NUM> is surrounded by the side wall <NUM> of the outside insulating member <NUM>.

The outside insulating member <NUM> is arranged between the sealing plate <NUM> and the terminal <NUM>, and secures insulation of them. In addition, the outside insulating member <NUM> secures the airtightness of the attachment hole <NUM> of the sealing plate <NUM>. In consideration of the perspective described above, it is preferable that the outside insulating member <NUM> consists of a material outstanding for a chemical resistant property or a weather resistant property. In this embodiment, PFA is used for the outside insulating member <NUM>. PFA is a copolymer with tetrafluoroethylene and perfluoroalkoxyethylene (Tetrafluoroethylene-Perfluoroalkylvinylether Copolymer). However, the material used for the outside insulating member <NUM> is not restricted to PFA.

As shown in <FIG>, the conductive member <NUM> is connected to the terminal <NUM>. Here, the conductive member <NUM> connected to the positive electrode terminal 50a is referred to as a positive electrode conductive member 55a, too. The conductive member <NUM> connected to the negative electrode terminal 50b is referred to as a negative electrode conductive member 55b, too. The conductive member <NUM> is arranged inside the case main body <NUM>. The conductive member <NUM> is arranged along a surface at an inner side of the sealing plate <NUM>, and is provided at a periphery of the attachment hole <NUM>. The conductive member <NUM> is a plate-shaped member. As shown in <FIG>, the conductive member <NUM> includes a penetration hole <NUM> and a groove <NUM>. The penetration hole <NUM> penetrates the conductive member <NUM>. Into the penetration hole <NUM>, the cylinder part <NUM> of the terminal <NUM> is inserted. The penetration hole <NUM> corresponds to a shape of the cylinder part <NUM>, and is here formed in an oval like shape. The groove <NUM> is formed at a portion of the conductive member <NUM> around the penetration hole <NUM>. The groove <NUM> is a groove dented upwardly from a bottom surface of the conductive member <NUM>. On the groove <NUM>, the caulked part <NUM> of the terminal <NUM> is arranged.

As shown in <FIG>, the connecting member <NUM> is connected to the conductive member <NUM>. The connecting member <NUM> is arranged at the inside of the case main body <NUM>, and is arranged along an inner side surface of the sealing plate <NUM>. Here, the connecting member <NUM> connected to the positive electrode conductive member 55a is referred to as a positive electrode connecting member 70a, too. The connecting member <NUM> connected to the negative electrode conductive member 55b is referred to as a negative electrode connecting member 70b, too. The positive electrode connecting member 70a is to connect the positive electrode terminal 50a and the positive electrode sheet <NUM>, and is connected to the positive electrode conductive member 55a and the positive electrode collector tab 21a. The negative electrode connecting member 70b is to connect the negative electrode terminal 50b and the negative electrode sheet <NUM>, and is connected to the negative electrode conductive member 55b and the negative electrode collector tab 22a.

In the present embodiment, the connecting member <NUM> includes a first plate part <NUM>, a second plate part <NUM>, and a step part <NUM>. The first plate part <NUM> is a portion arranged along a surface of the conductive member <NUM>, and is connected to the conductive member <NUM>. The first plate part <NUM> is a flat-plate shaped portion. The second plate part <NUM> is a portion arranged along a surface at an inner side of the sealing plate <NUM>. The second plate part <NUM> is a flat-plate shaped portion. The second plate part <NUM> of the positive electrode connecting member 70a is joined to the positive electrode collector tab 21a. The second plate part <NUM> of the negative electrode connecting member 70b is joined to the negative electrode collector tab 22a. The step part <NUM> is a portion standing from one end part of the first plate part <NUM> to one end part of the second plate part <NUM> and coupling the first plate part <NUM> and the second plate part <NUM>. In the present embodiment, the step part <NUM> is arranged along an end of the conductive member <NUM>.

In the present embodiment, inside insulating members <NUM> are provided between the conductive member <NUM> and the sealing plate <NUM>, and between the connecting member <NUM> and the sealing plate <NUM>. The conductive member <NUM> and the connecting member <NUM> are attached to the sealing plate <NUM> via the inside insulating member <NUM>.

The inside insulating member <NUM> includes a flat part <NUM>, a hole <NUM>, and a side wall <NUM>. The flat part <NUM> is a portion arranged along a surface at an inner side of the sealing plate <NUM>. The flat part <NUM> is a flat-plate shaped portion. The hole <NUM> is a hole provided correspondingly to the attachment hole <NUM> of the sealing plate <NUM>, into which the cylinder part <NUM> of the terminal <NUM> is inserted. In the present embodiment, the hole <NUM> is formed on the flat part <NUM> and penetrates the flat part <NUM>. The hole <NUM> is formed in a shape corresponding to the cylinder part <NUM>, and the hole here is formed in an oval like shape. The side wall <NUM> is extending downward from a peripheral edge part of the flat part <NUM>. The conductive member <NUM> and the connecting member <NUM> are surrounded by the side wall <NUM>.

The inside insulating member <NUM> is arranged inside the case main body <NUM>, and thus it is preferable that the inside insulating member <NUM> has a necessary chemical resistant property. In the present embodiment, PPS is used for the inside insulating member <NUM>. PPS is a polyphenylene sulfide resin. Incidentally, a material used for the inside insulating member <NUM> is not restricted to PPS.

Above, the secondary battery <NUM> in accordance with the present embodiment has been explained. Next, a manufacturing method for the secondary battery <NUM> will be described. Here, a method for caulking the terminal <NUM> and fixing to the sealing plate <NUM> will be explained according to a flowchart of <FIG>. In the present embodiment, as shown in <FIG>, the manufacturing method for the secondary battery <NUM> includes a first preparation step S11, a second preparation step S12, a first caulking step S13, a second caulking step S14, and a third caulking step S15.

<FIG> is a cross sectional view that shows the terminal <NUM> before caulking. <FIG>, <FIG> are cross sectional views respectively showing states of the terminal <NUM> during the first caulking step S13, the second caulking step S14, and the third caulking step S15. Incidentally, in <FIG>, drawings of the sealing plate <NUM>, the outside insulating member <NUM>, and the inside insulating member <NUM> are omitted. In the present embodiment, as shown in <FIG>, the terminal <NUM> includes a shaft part <NUM>. The shaft part <NUM> is a portion provided at the head part <NUM> (see <FIG>).

The shaft part <NUM> is a portion that can become the cylinder part <NUM> and the caulked part <NUM> after the terminal <NUM> is caulked, as shown in <FIG>. Here, by caulking the shaft part <NUM>, it is possible to fix the terminal <NUM> to the sealing plate <NUM>. In the shaft part <NUM>, a portion being caulked becomes the caulked part <NUM> and a portion being not caulked becomes the cylinder part <NUM>. In the present embodiment, the shaft part <NUM> is formed in a cylindrical shape. The shaft part <NUM> is formed in an oval like shape, and for more details, a shape of a traverse cross section of the shaft part <NUM> is the oval like shape. A shape of the inner circumferential surface of the shaft part <NUM> and a shape of the outer circumferential surface of the shaft part each is the oval like shape.

In the present embodiment, at the first preparation step S11 of <FIG>, as shown in <FIG>, the terminal <NUM> including the shaft part <NUM> is inserted into the attachment hole <NUM> formed on the sealing plate <NUM> to make the shaft part <NUM> protrude from the sealing plate <NUM>. In the present embodiment, at first, the outside insulating member <NUM> is inserted into the attachment hole <NUM> of the sealing plate <NUM>. Here, as shown in <FIG>, the insulation cylinder part <NUM> of the outside insulating member <NUM> is inserted into the attachment hole <NUM> to make the base part <NUM> of the outside insulating member <NUM> be attached to the outside surface of the sealing plate <NUM>. Then, as shown in <FIG>, the shaft part <NUM> of the terminal <NUM> is inserted into the insulation cylinder part <NUM> that has been inserted into the attachment hole <NUM>. At that time, as shown in <FIG>, the head part <NUM> of the terminal <NUM> is arranged on the base part <NUM> of the outside insulating member <NUM>, to induce a state where a part (here, tip end part) of the shaft part <NUM> (see <FIG>) protrudes to an inner side of the sealing plate <NUM>, in other words, to a case main body <NUM> side.

Next, at the second preparation step S12 of <FIG>, as shown in <FIG>, the conductive member <NUM> is arranged. Here, the conductive member <NUM> is arranged on a surface at a side where the shaft part <NUM> of the sealing plate <NUM> protrude at the periphery of the attachment hole <NUM>, in other words, on a surface at an inner side of the sealing plate <NUM>. In the present embodiment, at first, the inside insulating member <NUM> is arranged. Here, the hole <NUM> is formed on the inside insulating member <NUM>. To overlap this hole <NUM> with the attachment hole <NUM> of the sealing plate <NUM>, the inside insulating member <NUM> is arranged on the surface at the inner side of the sealing plate <NUM>. Then, the conductive member <NUM> is arranged on the surface at the inner side of the sealing plate <NUM> via the inside insulating member <NUM>. Here, to make the penetration hole <NUM> formed on the conductive member <NUM> be overlapped with the attachment hole <NUM> of the sealing plate <NUM> and the hole <NUM> of the inside insulating member <NUM>, the conductive member <NUM> is arranged. At that time, the conductive member <NUM> is arranged on the flat part <NUM> of the inside insulating member <NUM>.

Incidentally, in the present embodiment, the second preparation step S12 is performed after the first preparation step S11, but the second preparation step S12 might be performed before the first preparation step S11.

Although described above, as shown in <FIG>, the first caulking step S13 to the third caulking step S15 are performed in an order after the first preparation step S11 and the second preparation step S12 are performed. Here, at first, the first caulking step S13 of <FIG> is performed. At the first caulking step S13, as shown in <FIG>, an inner diameter of the shaft part <NUM> of the terminal <NUM> is expanded. At the first caulking step S13, a first caulking tool <NUM> is used.

<FIG> is a view showing the first caulking tool <NUM> and is a view in which the first caulking tool <NUM> is viewed from a tip end part <NUM> side. As shown in <FIG> and <FIG>, the first caulking tool <NUM> includes a tip end part <NUM> and a base end part <NUM>. As shown in <FIG>, the tip end part <NUM> is a portion that is inserted into the cylindrical shaft part <NUM> of the terminal <NUM>. The tip end part <NUM> has a shape corresponding to the inner circumferential surface of the shaft part <NUM>, and the shape here is an oval like shape as shown in <FIG>. A shape of a traverse cross section of the tip end part <NUM> is the oval like shape.

As shown in <FIG>, the base end part <NUM> is connected to the tip end part <NUM>. In other words, the tip end part <NUM> protrudes from the base end part <NUM>. As shown in <FIG>, the base end part <NUM> is formed in a complete round shape whose diameter is larger than the tip end part <NUM>. A shape of a traverse cross section of the base end part <NUM> is the complete round shape. Here, the phrase "whose diameter is larger than the tip end part <NUM>" means that it is larger than a long diameter of the tip end part <NUM> formed in the oval like shape. In the present embodiment, as shown in <FIG>, the base end part <NUM> includes a reduced diameter portion <NUM>. The reduced diameter portion <NUM> is a portion whose diameter is getting smaller toward the tip end part <NUM>. An outer circumferential surface of the reduced diameter portion <NUM> is an inclined surface that is inclined to a central axis of the base end part <NUM> more toward the tip end part <NUM>. Here, the reduced diameter portion <NUM> continues to the tip end part <NUM>.

In the present embodiment, the wording "complete round" semantically contains a case of a strictly complete round and a case where a little error is caused on the diameters. For example, it is possible to determine whether it is a strictly complete round or not, by measuring a complete round degree of the base end part <NUM>. In order to measure the complete round degree, for example, the base end part <NUM> is cut in a diameter direction into <NUM> equal sections or <NUM> equal sections. Then, regarding a distance between opposed two points of equally divided boundary points, for example, a micrometer is used to measure a plurality of such distances. The complete round degree is a numerical value obtained by dividing <NUM> into a difference between the maximum value and the minimum value among a plurality of distances regarding such two points. In the present embodiment, the complete round semantically contains a case where the complete round degree is <NUM> to <NUM>, preferably the complete round degree is <NUM> to <NUM>, or more preferably the complete round degree is <NUM> to <NUM>.

At the first caulking step S13 of <FIG>, as shown in <FIG>, the first caulking tool <NUM> is used to insert the tip end part <NUM> into the shaft part <NUM> of the terminal <NUM>, so as to make the base end part <NUM> expand an inner diameter of a portion of the shaft part <NUM> protruding from the sealing plate <NUM>. Here, the reduced diameter portion <NUM> of the base end part <NUM> is used to expand the inner diameter of the portion of the shaft part <NUM> protruding from the sealing plate <NUM>. Here, the tip end part <NUM> of the first caulking tool <NUM> is formed in an oval like shape, and thus the inner circumferential surface of the shaft part <NUM> is uniformly widen when the tip end part <NUM> was inserted into the oval-like-shaped shaft part <NUM>. Then, by the reduced diameter portion <NUM> of the base end part <NUM> formed in the complete round shape, it is expanded outwardly in a short diameter direction D12 (see <FIG>) of the oval like shape from a portion of the shaft part <NUM> along a long diameter direction D11 (see <FIG>) of the oval like shape, among the inner circumferential surface of the shaft part <NUM>. In the present embodiment, the outer circumferential surface of the reduced diameter portion <NUM> is an inclined surface, and the inner diameter of the shaft part <NUM> is expanded along the outer circumferential surface of the reduced diameter portion <NUM>.

Next, at the second caulking step S14 of <FIG>, as shown in <FIG>, the portion of the shaft part <NUM> expanded at the first caulking step S13 of <FIG> is pressed to be flat. At the second caulking step S14, a second caulking tool <NUM> different from the first caulking tool <NUM> is used. The second caulking tool <NUM> includes a flat surface <NUM>. The flat surface <NUM> is a surface being flat, and has a shape larger than the caulked part <NUM> of the terminal <NUM>, for example, has a shape which is one size larger than the attachment hole <NUM> (see <FIG>) formed on the sealing plate <NUM>. The flat surface <NUM> might be formed in a round shape, or might be formed in a rectangular shape.

At the second caulking step S14, the second caulking tool <NUM> is used to make the flat surface <NUM> push the expanded portion of the shaft part <NUM>. Then, the second caulking tool <NUM> is pushed toward the shaft part <NUM> side so as to make the flat surface <NUM> press the expanded portion of the shaft part <NUM>. Incidentally, the number of pressing operations at the second caulking step S14 might be <NUM>, or might be plural. By pressing with the second caulking tool <NUM>, the expanded portion of the shaft part <NUM> becomes to have a flat surface. This expanded portion will be the caulked part <NUM> of the terminal <NUM>. The caulked part <NUM> is formed in an oval like shape.

Next, at the third caulking step S15 of <FIG>, as shown in <FIG>, the expanded portion of the shaft part <NUM> pressed to be flat at the second caulking step S14 of <FIG> (hereinafter, referred to as caulked part <NUM>) is pressed to form a step 53d. The step 53d is, as shown in <FIG>, formed at a peripheral edge part of the both sides in the long diameter direction D11 of the oval like shape of the caulked part <NUM>. At the third caulking step S15 in accordance with the present embodiment, as shown in <FIG>, a third caulking tool <NUM> is used. The third caulking tool <NUM> includes a base end part <NUM>, and a first press part <NUM> and a second press part <NUM> that protrude downward from a base end part <NUM>. The first press part <NUM> and the second press part <NUM> are arranged in an opposed manner, correspondingly to the peripheral edge parts at the both sides in the long diameter direction D11 of the caulked part <NUM>. Although the illustrations are omitted, a bottom surface of the first press part <NUM> and a bottom surface of the second press part <NUM> each is formed in an U shape. Here, to make the U-shaped dented portions be opposed, the first press part <NUM> and the second press part <NUM> are arranged.

At the third caulking step S15, the third caulking tool <NUM> is used to make the first press part <NUM> and the second press part <NUM> press the peripheral edge parts at the both sides in the long diameter direction D11 of the caulked part <NUM>. At the peripheral edge parts in the long diameter direction D11 of the caulked part <NUM>, which are pressed by the first press part <NUM> and the second press part <NUM>, the steps 53d dented to the sealing plate <NUM> (see <FIG>) side are formed. The shape of this step 53d becomes the same as the shape of the bottom surface of the first press part <NUM> and as the shape of the bottom surface of the second press part <NUM>, and the shape here is an U shape as shown in <FIG>. Incidentally, the number of pressing operations performed at the third caulking step S15 might be <NUM>, or might be plural.

As described above, regarding the terminal <NUM> caulked through the first caulking step S13 to the third caulking step S15, the terminal <NUM> includes the caulked part <NUM> being caulked with respect to the conductive member <NUM> and being formed in an oval like shape, as shown in <FIG>. The caulked part <NUM> includes a long diameter part 53a being along the long diameter direction D11 of the oval like shape, and a short diameter part 53b being along the short diameter direction D12 of the oval like shape. In the present embodiment, there are two long diameter parts 53a. Two long diameter parts 53a configure the peripheral edge parts at both sides in the short diameter direction D12 of the caulked part <NUM>. There are two short diameter parts 53b, too. Two short diameter parts 53b configure the peripheral edge parts excluding the steps 53d of the peripheral edge parts at the both sides in the long diameter direction D11 of the caulked part <NUM>.

A length L1 in the short diameter direction D12 of the long diameter part 53a is longer than a length L2 in the long diameter direction D11 of the short diameter part 53b. Here, the length L1 of the long diameter part 53a means a maximum length in the short diameter direction D12 of the long diameter part 53a. In addition, the length L2 of the short diameter part 53b means a maximum length in the long diameter direction D11 of the short diameter part 53b.

A rate of a thickness T11 (see <FIG>) of the long diameter part 53a with respect to a thickness T12 (see <FIG>) of the short diameter part 53b is <NUM> to <NUM>, or preferably <NUM> to <NUM>. Here, the thickness T11 of the long diameter part 53a means an average thickness of two long diameter parts 53a. The thickness T12 of the short diameter part 53b means an average thickness of two short diameter parts 53b. In the present embodiment, a rate of the thickness T12 of the short diameter part 53b with respect to the thickness T11 of the long diameter part 53a is also <NUM> to <NUM>, or preferably <NUM> to <NUM>. Incidentally, when the rate of the thickness T11 of the long diameter part 53a with respect to the thickness T12 of the short diameter part 53b is within a range of <NUM> to <NUM>, the thickness T11 of the long diameter part 53a might be the same as the thickness T12 of the short diameter part 53b, or might be thinner or thicker than the thickness T12 of the short diameter part 53b.

Incidentally, in the present embodiment, after the first caulking step S13 to the third caulking step S15 of <FIG> are performed, the portion of the caulked part <NUM> on which the step 53d has been added at the third caulking step S15 is welded with the conductive member <NUM>. Here, at the first caulking step S13 to the third caulking step S15, in a case where an oil is used when the terminal <NUM> is caulked, it is preferable to remove the oil with an air blow device or the like before the welding with the caulked part <NUM> and the conductive member <NUM>.

From the above, in the present embodiment, as shown in <FIG>, the manufacturing method for the secondary battery <NUM> includes the first preparation step S11, the second preparation step S12, the first caulking step S13, and the second caulking step S14. At the first preparation step S11, as shown in <FIG>, the terminal <NUM> including the shaft part <NUM> cylindrically formed in the oval like shape is inserted into the attachment hole <NUM> formed on the sealing plate <NUM> of the secondary battery <NUM>, so as to make the shaft part <NUM> protrude from the sealing plate <NUM>. At the second preparation step S12, the conductive member <NUM> is arranged on a surface at a side where the shaft part <NUM> of the sealing plate <NUM> protrudes at the periphery of the attachment hole <NUM>. At the first caulking step S13, as shown in <FIG>, the first caulking tool <NUM>, including the tip end part <NUM> formed in the oval like shape as shown in <FIG> and including the base end part <NUM> formed in the complete round shape whose diameter is larger than the tip end part <NUM>, is used to insert the tip end part <NUM> into the shaft part <NUM> of the terminal <NUM>, so as to make the base end part <NUM> expand the inner diameter of the portion protruding from the sealing plate <NUM> among the shaft part <NUM>. At the second caulking step S14, as shown in <FIG>, the portion of the shaft part <NUM> expanded at the first caulking step S13 is pressed to be flat.

By doing this, as shown in <FIG>, it is possible with the tip end part <NUM> formed in the oval like shape of the first caulking tool <NUM> to uniformly abut the inner circumferential surface of the shaft part <NUM> formed in the oval like shape. Then, by making the base end part <NUM> formed in the complete round shape of the first caulking tool <NUM> abut the shaft part <NUM>, it is possible to outwardly widen from a portion of the shaft part <NUM> along the long diameter direction D11 of the oval like shape, and thus it is possible to inhibit variation in the thicknesses of the caulked portion of the shaft part <NUM>. Therefore, it is possible to secure the caulking strength of the terminal <NUM>.

In the present embodiment, as shown in <FIG>, the terminal <NUM> includes the caulked part <NUM> having been caulked in the oval like shape with respect to the conductive member <NUM>. The caulked part <NUM> includes the long diameter part 53a along the long diameter direction D11 of the oval like shape, and the short diameter part 53b along the short diameter direction D12 of the oval like shape. The length L1 in the short diameter direction D12 of the long diameter part 53a is longer than the length L2 in the long diameter direction D11 of the short diameter part 53b. Here, at the first caulking step S13 of <FIG>, as shown in <FIG>, by using the base end part <NUM> formed in the complete round shape of the first caulking tool <NUM>, the shaft part <NUM> formed in the oval like shape of the terminal <NUM> is expanded. At that time, a portion to become the long diameter part 53a is outwardly widened at first, and then a portion to become the short diameter part 53b is outwardly widened. As the result, the length L1 of the long diameter part 53a becomes longer than the length L2 of the short diameter part 53b. Thus, by using the base end part <NUM> formed in the complete round shape to expand the shaft part <NUM> formed in the oval like shape, it is possible to make the length L1 of the long diameter part 53a be longer than the length L2 of the short diameter part 53b.

In the present embodiment, the rate of the thickness T11 (see <FIG>) of the long diameter part 53a with respect to the thickness T12 (see <FIG>) of the short diameter part 53b is <NUM> to <NUM>. By doing this, it is possible to inhibit variation in the thicknesses of the caulked part <NUM>, and thus it is possible to secure the caulking strength.

Anyway, the applicant of the present application performed tests in which, with below-described Example <NUM> and Comparative Example <NUM> of manufacturing methods for the secondary battery <NUM>, the shaft part <NUM> of the terminal <NUM> was caulked and the rate (T11/T12) of the thickness T11 of the long diameter part 53a with respect to the thickness T12 of the short diameter part 53b was calculated.

The first caulking tool <NUM> as shown in <FIG> and <FIG>, in other words, the first caulking tool <NUM> whose tip end part <NUM> was formed in the oval like shape was used to caulk the terminal <NUM>.

The first caulking tool was used, in which the tip end part of the first caulking tool was formed in the complete round shape, to caulk the terminal <NUM>.

Incidentally, not only in Example <NUM> but also in the Comparative Example <NUM>, the procedure of the first preparation step S11, the second preparation step S12, the second caulking step S14, and the third caulking step S15 is the same. Here, the manufacturing method for Example <NUM> was performed on <NUM> terminals <NUM>, total <NUM> times. Then, for each of the plurality of terminals <NUM>, the rate of the thickness T11 of the long diameter part 53a with respect to the thickness T12 of the short diameter part 53b was calculated. Similarly, the manufacturing method of Comparative Example <NUM> was performed on <NUM> terminals <NUM>, total <NUM> times. Then, for each of the plurality of terminals <NUM>, the rate of the thickness T11 of the long diameter part 53a with respect to the thickness T12 of the short diameter part 53b was calculated. These results are shown in <FIG>.

While shown in <FIG>, in a case where the first caulking tool <NUM> including the oval-like-shaped tip end part <NUM> was used like as Example <NUM> to caulk the terminal <NUM>, the rate (T11/T12) was <NUM> to <NUM>. An average of the rates (T11/T12) in Example <NUM> was <NUM>. On the other hand, in the case where the first caulking tool including the complete-round-shaped tip end part was used like as Comparative Example <NUM> to caulk the terminal <NUM>, the rate (T11/T12) was <NUM> to <NUM>. An average of the rates (T11/T12) in Comparative Example <NUM> was <NUM>. From these things, it can be understood that, by using the first caulking tool <NUM> including the oval-like-shaped tip end part <NUM>, the value of the rate (T11/T12) can be closer to <NUM> and the variation in the thicknesses of the caulked part <NUM> of the terminal <NUM> can be inhibited.

In the present embodiment, as shown in <FIG>, the base end part <NUM> of the first caulking tool <NUM> includes the reduced diameter portion <NUM> whose diameter becomes smaller toward the tip end part <NUM>. At the first caulking step S13 of <FIG>, the reduced diameter portion <NUM> of the base end part <NUM> is used to expand the inner diameter of the portion of the shaft part <NUM> protruding from the sealing plate <NUM>. By doing this, the portion of the shaft part <NUM> protruding from the sealing plate <NUM> has the inner diameter being gradually expanded, depending on the diameter of the reduced diameter portion <NUM>. Thus, it is easy to expand the portion of the shaft part <NUM> protruding from the sealing plate <NUM>.

In the present embodiment, the manufacturing method for the secondary battery <NUM> includes, as shown in <FIG>, the third caulking step S15 (see <FIG>) for pressing the peripheral edge part in the long diameter direction D11 of the oval like shape, of the expanded portion of the shaft part <NUM> pressed to be flat at the second caulking step S14 of <FIG>, so as to form the step 53d. By doing this, the portion provided with the step 53d becomes in a pressed state, and thus it is possible to hardly form a gap between the portion of the shaft part <NUM> provided with the step 53d and the conductive member <NUM>. Therefore, it is possible to properly perform welding at the portion provided with the step 53d by welding with the conductive member <NUM>.

Claim 1:
A manufacturing method for a secondary battery (<NUM>), comprising:
a first preparation step (S11) for inserting a terminal (<NUM>) formed in an oval like shape and having a cylindrical shaft part (<NUM>) into an attachment hole (<NUM>) formed on a sealing plate (<NUM>) of a secondary battery (<NUM>) that comprises a case main body (<NUM>) whose part is opened and comprises the sealing plate (<NUM>) provided at the opening of the case main body (<NUM>), so as to make the shaft part (<NUM>) protrude from the sealing plate (<NUM>);
a second preparation step (S12) for arranging a conductive member (<NUM>) at a periphery of the attachment hole (<NUM>) and on a surface at a side where the shaft part (<NUM>) of the sealing plate (<NUM>) protrudes;
a first caulking step (S13) for using a caulking tool (<NUM>) having a tip end part (<NUM>) formed in an oval like shape and having a base end part (<NUM>) formed in a complete round shape whose diameter is larger than the tip end part (<NUM>), to insert the tip end part (<NUM>) into the shaft part (<NUM>) of the terminal (<NUM>), so as to make the base end part (<NUM>) expand an inner diameter of a portion of the shaft part (<NUM>) protruding from the sealing plate (<NUM>); and
a second caulking step (S14) for pressing the portion of the shaft part (<NUM>) expanded at the first caulking step (S13) to be flat.