PURPOSE: To facilitate the fitting work, and secure the sealing at the time of positioning an outer edge of a plunger cover at a front edge of a case for support and of fitting an electromagnetic switch to a front bracket by fitting the outer edge of the plunger cover in a notch groove of the front surface of the front bracket.

CONSTITUTION: Multiple projections are provided in a rear end of an outer edge of a plunger cover, and insertion holes corresponding to the projections are provided in a front edge of a case, and the projections are inserted into the insertion holes to position an outer edge of the plunger cover at a front end of the case for support, and fitting of the outer edge of the plunger cover to a front bracket is thereby facilitated.