An ultrasonic weld is provided in a cover component, is formed protruding from the cover component, and is provided so that it can join the cover component and the body component together by being fixed to the body component with ultrasonic welding. A locking mechanism is provided so that it can join the cover component and the body component together via engaging portions that engage with each other. The locking mechanism includes a first engaging portion provided in the cover component, and a second engaging portion that is provided in another component fixed to the body component, and that can engage with the first engaging portion. Thus, it is possible to decrease the number of components, and also reduce equipment costs and production control costs.