A high-precision image control method that can be conducted frequently without time or labor. The coil includes a segmented annular base ring conductor including a plurality of capacitances disposed between the segments, and at least one arcuate conductor symmetrically connected at each end to the base ring, one end terminating in direct contact with the base ring, the other end electrically connected to the base ring via two of the capacitive electrical connections. The engine assembly normally projects toward the passenger compartment at upper and lower parts thereof.