Pipe joint

Abstract

A pipe joint includes: an inner ring having a bulge portion to be press-fitted into an end portion of the tube; a joint body having an inner circumference into which an end portion of the inner ring is to be press-fitted, and having an external thread portion on an outer circumference thereof; and a union nut having an internal thread portion to be tightened to the external thread portion, and configured to press the end portion of the tube when the internal thread portion is tightened to the external thread portion. The bulge portion has a tapered portion configured to generate a surface pressure between the tube and the tapered portion by pressing by the union nut. An outer circumferential surface of the tapered portion has a concave surface portion formed in a concave surface shape in an axial cross-sectional view.

1 . A pipe joint comprising:
 an inner ring having a bulge portion formed on one axial side so as to project toward a radially outer side, the bulge portion being for press-fitting into an end portion of a tube;   a joint body having an inner circumference into which an end portion on another axial side of the inner ring is to be press-fitted in a state where the bulge portion is press-fitted into the end portion of the tube, the joint body having an external thread portion on an outer circumference thereof; and   a union nut having an internal thread portion to be tightened to the external thread portion, and configured to press the end portion of the tube toward the other axial side when the internal thread portion is tightened to the external thread portion, wherein   the bulge portion has a tapered portion formed so as to be tapered from a middle portion in an axial direction thereof toward the one axial side and configured to generate a surface pressure between the tube and the tapered portion by pressing by the union nut, and   an outer circumferential surface of the tapered portion has a concave surface portion formed in a concave surface shape in an axial cross-sectional view.   
     
     
         2 . The pipe joint according to  claim 1 , wherein the concave surface portion is formed over an entire axial length of the outer circumferential surface of the tapered portion. 
     
     
         3 . The pipe joint according to  claim 1 , wherein the outer circumferential surface of the tapered portion has a convex surface portion formed in a convex surface shape on the one axial side with respect to the concave surface portion in the axial cross-sectional view. 
     
     
         4 . A pipe joint comprising:
 an inner ring having a bulge portion formed on one axial side so as to project toward a radially outer side, the bulge portion being for press-fitting into an end portion of a tube;   a joint body having an inner circumference into which an end portion on another axial side of the inner ring is to be press-fitted in a state where the bulge portion is press-fitted into the end portion of the tube, the joint body having an external thread portion on an outer circumference thereof, and   a union nut having an internal thread portion to be tightened to the external thread portion, and configured to press the end portion of the tube toward the other axial side when the internal thread portion is tightened to the external thread portion, wherein   the bulge portion has a tapered portion formed so as to be tapered from a middle portion in an axial direction thereof toward the one axial side and configured to generate a surface pressure between the tube and the tapered portion by pressing by the union nut, and   a diameter D of one axial end of an outer circumferential surface of the tapered portion and an inner diameter d of a non-deformed portion, of the tube, that does not become deformed even when the bulge portion is press-fitted satisfy a relationship of 1.0d ≤D≤1.4d.