First opening is formed of a thermoplastic resin material and an insulating holder (30) having (31), and the connecting ring having a second opening formed of a thermoplastic resin material (41) (40), first opening (31) and the second opening is inserted so as to extend over the (41), while being formed from a metal material having a higher melting point of the thermoplastic resin material melting, insulating holder (30) and and a coupling part (80) having a rigidity higher than the rigidity of the connecting ring (40), welded to each of at least a partial portion in contact with the coupling part (80) of the insulating holder (30) and the connecting rings (40) and has a bonded portion formed Te.