| 摘要 |
PURPOSE:To increase a frictional coefficient between a rank arm and a crank pin by forming the film of triiron tetraoxide on the surface of the hole of the crank arm and the shaft part of the crank pin. CONSTITUTION:The surface of the shaft part 4 of a crank pin 3 is covered with triiron tetraoxide by the use of a previously known formation method for a triiron tetraoxide cover layer. And the crank pin 3 is put into a crank arm 1 under pressure with the aid of an ordinary putting in under pressure processing. A crank thus made retains a high frictional coefficient between the crank arm 1 and the crank pin 3, and strengthens coherence and also is able to increase twist torque without increasing the tightness degree of putting in under pressure between the two more than necessary. |
