Roller, separation device, image reading apparatus, and recording apparatus

A roller comprising:

• an elastic body portion that is provided on an outer circumferential surface of a shaft, wherein the elastic body portion includes:
• an inner circumferential portion which serves as the shaft side;
• an outer circumferential portion which serves as an outer circumferential side with respect to the inner circumferential portion;
• a space portion between the inner circumferential portion and the outer circumferential portion;
• and
• a plurality of joining portions which join the inner circumferential portion and the outer circumferential portion to each other in the space portion and define a plurality of sub-space portions,
• wherein at least a portion of each of the joining portions has a curved shape, and
• wherein the joining portions are each joined to the inner circumferential portion and the outer circumferential portion such that connecting portions between the joining portions and the inner circumferential portion and connecting portions between the joining portions and the outer circumferential portion do not form acute angles in the space portion, and
• wherein an area of one joining portion is less than an area of one sub-space portion when viewed along a rotational axis of the roller, and
• wherein a connecting portion between a first joining portion of the joining portions and the inner circumferential portion and a connecting portion between a second joining portion, which is adjacent to the first joining portion, of the joining portions and the outer circumferential portion are provided on the same straight line extending in a radial direction of the roller from a center of the roller.

A roller comprising:

• an elastic body portion that is provided on an outer circumferential surface of a shaft, wherein the elastic body portion includes:
• an inner circumferential portion which serves as the shaft side;
• an outer circumferential portion which serves as an outer circumferential side with respect to the inner circumferential portion;
• a space portion between the inner circumferential portion and the outer circumferential portion;
• and
• a plurality of joining portions which join the inner circumferential portion and the outer circumferential portion to each other in the space portion and define a plurality of sub-space portions,
• wherein at least a portion of each of the joining portions has a curved shape,
• wherein the joining portions are each joined to the inner circumferential portion and the outer circumferential portion such that connecting portions between the joining portions and the inner circumferential portion and connecting portions between the joining portions and the outer circumferential portion do not form acute angles in the space portion,
• wherein the sub-space portion has two inner circumferential portion corner portions that are formed at the connecting portions between the joining portions and the inner circumferential portions and two outer circumferential portion corner portions that are formed at the connecting portions between the joining portions and the outer circumferential portions, and at least one of the two inner circumferential portion corner portions has a right angle, and
• wherein a connecting portion between a first joining portion of the joining portions and the inner circumferential portion and a connecting portion between a second joining portion, which is adjacent to the first joining portion, of the joining portions and the outer circumferential portion are provided on the same straight line extending in a radial direction of the roller from a center of the roller.