Trapezoidal protrusions, which protrude to the inside of a region, are provided on a right-side part and a left-side part of a mounting member. Holding sections, which extend in a circumferential direction, are formed in lateral surfaces of the trapezoidal protrusions. The holding sections include first holders which are opened to an upper side, and a second holder that is opened to a lower side. The first holders, and the second holder are respectively provided with second protrusions which protrude into a groove in a plural number, and can maintain the cable in a groove. First protrusions are respectively provided on rear-side ends to guide lead-out of the cable from the mounting member.