A projection portion (145) protruding from a bottom surface 8141a) on a core portion side towards the center of the core portion (130) is formed in a core plate (140). A bond portion (142a) between a tube (132) and the core plate (140) is arranged closer to the center side of the core portion (130) than the bottom surface (141a) and at substantially the same position in a tube longitudinal direction X with respect to a push surface (143a) of a packing (150). Therefore, even when a load in a direction intersecting at right angles the tube longitudinal direction is applied to a formation portion of a fitting groove portion (143), the occurrence of a bending moment can be suppressed.