To provide a sliding friction resistance mechanism having high reliability and safety with a less change of a sliding friction resistance value with a temperature change.

When a carbon fiber 19 exposed to an abutment side is energized abutting on a rotor 11 on a driving part side, a top portion thereof has line pressure abutment thereon in the form of abutting on a number of lines. Thus, an oil film is cut into pieces to bring about linear-abutment operation in a narrower range which gives less influences to a change in the viscosity of oil due to a temperature change. The high degree sliding friction resistance mechanism is hardly influenced by the oil which becomes a highly viscous condition in a low temperature region, in particular.