Electric storage device, electric storage apparatus, method for producing electric storage device, and method for producing cover plate

1. A method for producing an electric storage device, the device comprising:

an electrode assembly comprising a positive electrode plate and a negative electrode plate that are insulated from each other; and

a case that houses the electrode assembly and comprises a case body having an opening, and a cover plate configured to cover the opening of the case body,

the method comprising:

irradiating a seam between the cover plate and an opening edge of the case body with a laser, with the cover plate being placed on the opening edge of the opening of the case body,

wherein the case body comprises a step portion at the opening edge,

wherein the cover plate comprises a projection that is inserted into the opening of the case body,

wherein at least a portion of the projection opposes the step portion within the case body,

wherein the seam is irradiated with the laser at a position corresponding to the step portion in the laser irradiation step, and

wherein the step portion extends from an outer surface of the case body toward an inner surface of the case body such that the step portion is non-perpendicular to the inner surface of the case body to provide a gap between the cover plate and the opening edge of the opening of the case body.

2. The method for producing an electric storage device according to claim 1 , wherein the projection is formed by coining the cover plate from the outer surface of the case body toward the inner surface of the case body.

3. The method for producing an electric storage device according to claim 1 , wherein a circumference edge portion of the cover plate, which is placed on the opening edge of the case body, is subjected to a compression molding.

4. The method for producing an electric storage device according to claim 1 , wherein the projection is locally located in a vicinity of a circumference edge of the cover plate.

5. The method for producing an electric storage device according to claim 1 , wherein the projection includes an outer circumferential edge spaced at a distance from an inner surface of the opening edge.

6. The method for producing an electric storage device according to claim 1 , wherein the projection has a linear shape that extends along the opening edge of the case body.

7. The method for producing an electric storage device according to claim 1 , wherein the projection includes a tip in a projecting direction with an arcuate cross section.

8. The method for producing an electric storage device according to claim 1 , wherein the cover plate comprises a case inner side portion that is inserted into the opening of the case body, and a thin portion that is formed around a circumference edge of the cover plate and has a thickness smaller than the case inner side portion,

wherein the projection projects from the case inner side portion, and

wherein H2≧H1+H3−H0 is satisfied, when a dimension in a thickness direction of the case inner side portion is H0, a dimension in the thickness direction of the thin portion is H1, a dimension in a thickness direction of the projection is H2, and a height difference in a thickness direction of the step portion is H3.

9. A method for producing a cover plate configured to cover an opening of a case body that houses an electrode assembly comprising a positive electrode plate and a negative electrode plate that are insulated from each other, the method comprising:

forming a projection that opposes, within the case body, a step portion formed at an opening edge of the opening of the case body, with the cover plate being placed on the opening edge, by coining the cover plate at a corresponding position from an outer surface of the case body toward an inner surface of the case body, the step portion being non-perpendicular to the inner surface of the case body to provide a gap between the cover plate and the opening edge of the opening of the case body.

10. The method for producing a cover plate according to claim 9 , wherein a circumference edge portion of the cover plate, which is placed on the opening edge of the case body, is subjected to a compression molding.

11. The method for producing an electric storage device according to claim 1 , wherein the projection extends, in a first direction, linearly along the opening edge of the case body, and

wherein the projection includes a ridge that, in a second direction perpendicular to the first direction, protrudes from a linear portion of the cover plate toward inside of the case.