Patent ID: 8420188

Claim:
A passenger compartment antenna device for a vehicle electronic key system, the passenger compartment antenna device comprising: a first resin member having a hollow rectangular tube shape including at least two inner wall surfaces and comprising a polyamide resin that exhibits a first hygroscopic expansion coefficient, wherein the first resin member forms a case for the passenger compartment antenna; and a second resin member having a rectangular tube shape including at least two outer wall surfaces and comprising a polybutylene terephthalate resin that exhibits a second hygroscopic expansion coefficient; wherein the first hygroscopic expansion coefficient is larger than the second hygroscopic expansion coefficient when measured under usage environment conditions of the passenger compartment antenna device, and wherein the at least two inner wall surfaces of the first resin member and the at least two outer wall surfaces of the second resin member come into contact with each other and define at least a first fitting surface and a second fitting surface; and wherein at least the first and second fitting surfaces include a plurality of recess-projection engagement structures spaced apart from each other in a circumferential direction that is orthogonal to the longitudinal direction of the first and second resin members, and wherein the first recess-projection engagement structure is arranged near a middle portion of the passenger compartment antenna device and comprises at least two through holes disposed in at least one of the walls of the first resin member and at least two projections disposed on at least one of the outer wall surfaces of the second resin member so as to respectively engage with the at least two through holes; and wherein the second recess-projection engagement structure is disposed on the first and second resin members and comprises at least two recesses disposed at an end of at least one of the walls of the first resin member so as to form a rectangular projection between the recesses and at least two projections formed on at least one of the outer wall surfaces of the second resin member so as to respectively engage with the at least two recesses of the first resin member.