PURPOSE: To eliminate the fluctuation of firing timing by providing the corresponding number of fixed magnetic poles with the rotary magnetic poles having the pole number corresponding with the number of cylinders while fixing the rotary magnetic poles to the rotary shaft to be driven by the engine thereby producing the magnetic rotary braking force to cancel the inertia of the rotary section.

CONSTITUTION: The rotary shaft 4 to be driven by an engine is supported rotatably by the bearing metals 2, 2 pressure inserted into the housing 1, while a space collar 7 applied at one end of the rotary shaft 4 through a washer 6 is fixed to the rotary shaft 4 through a roll pin 8 thus to limit the axial motion. The left end of the housing 1 is enlarged where a fixed magnetic pole 3 is fixed on the innercircumferential face while a rotary magnet pole 5 is fixed to the rotary shaft 4 while facing with said pole 3. In case of 4 cylinder engine, said poles 3, 5 are provided with two N and S poles alternatively with 90° angle. Consequently the rotary braking force is produced such that the inertia at the rotary section is cancelled at the firing by the magnetic rotary resistance of both poles 3, 5.