To improve centering of a shaft by increasing the substantial fitting length of the outer peripheral wall of a block which abuts and fixes on/to the inner peripheral surface of a sealing case and the sealing case by providing a projecting part projecting to an oil holding part along the inner peripheral surface of the sealing case from the outer peripheral wall of the block.

In the abutting part of the outer peripheral wall of a block 16 and the inner peripheral surface of a sealing case 2, projecting parts 90 projecting to an oil tank 27 are formed along the inner peripheral surface of the sealing case 2. Because the contact surface length (substantial fitting length) of the outer peripheral wall of the conventional block 16 and the inner peripheral surface of the sealing case 2 can be increased by providing these plurality of projecting parts 90, the block 16 can be surely mounted on the sealing case 2. Thus, a centering work of a shaft 13 becomes easy and rigidity of the sealing case 2 itself can be improved.