| 摘要 |
PURPOSE:To prevent the occurrence of a powder lock phenomenon during operation of a clutch and to enable lowering of drag torque, by a method wherein a plurality of partitions serving to check the flow, in the circumferential direction, of magnetic powder placed in an annular groove, are locatd in the annular groove formed in a labyrinth member. CONSTITUTION:When a yoke 14 is excited with an exciting coil 16 energized, a magnetic circuit B is formed, a gap 32 between an inner peripheral friction surface 18 and an outer peripheral friction surface 30 is filled with a powder material 36 through a magnetic force, and rotation of a crank shaft 4 is transferred to an output shaft 6. When a current is disconnected and the yoke 14 is brought in a non-exciting condition, a magnetic circuit B is eliminated, and the powder material 36 is brought in a condition in which it adheres in a laminar manner to the inner peripheral friction surface 18. When an engine is brought to a stop and the crank shaft 4 stops its turning, the powder material 36 on the inner peripheral friction surface 18 drops due to the gravity, and enters annular grooves 66 and 70 in labyrinth members 20 and 22. The flow of the powder material 36 in the circumferential direction is checked by partitions 68, the powder material is prevented from dropping on the inner peripheral friction surface 18, and both, powder lock phenomenon and drag phenomenon can be prevented from occurring due to deviation of the powder material 36 during non-rotation and rotation at a low speed of the crank shaft 4. |
