Inner ring and pipe joint

An inner ring comprising:

• a bulge portion formed at one axial end portion such that an outer circumferential surface thereof projects toward a radially outer side, and to be press-fitted into an end portion of a tube;
• a press-fitting portion formed at another axial end portion and to be press-fitted into an end portion of a joint body;
• and
• a cylindrical body portion formed between the bulge portion and the press-fitting portion and having a constant outer diameter over an entirety in an axial direction, the outer diameter being smaller than an outer diameter of the press-fitting portion, wherein
• a fluid flow passage is formed inside an inner circumferential surface of the inner ring,
• the inner ring includes a tapered surface formed at the another axial end portion of the inner circumferential surface such that a diameter thereof gradually increases from the one axial side toward the another axial end thereof in a state before the press-fitting portion is press-fitted into the end portion of the joint body,
• the press-fitting portion includes a primary sealing portion and a secondary sealing portion located radially outward of the primary sealing portion,
• an annular groove having an arc cross-sectional shape is formed between the primary sealing portion and the secondary sealing portion,
• a deformation starting point, which serves as a starting point from which the inner circumferential surface is deformed due to the press-fitting portion receiving external force from the joint body when the press-fitting portion is press-fitted into the end portion of the joint body, is located at a point of intersection of the inner circumferential surface and a virtual tangent line K which is tangent to the annular groove and extends in a radial direction of the inner circumferential surface, and
• a diameter increase starting point of the tapered surface is located in a range from the deformation starting point to a position, on the inner circumferential surface, corresponding to another axial end of an outer circumferential surface of the body portion.