| 摘要 |
A device for driving the main shaft of a machine tool, in which the dimension of the device is small, occurrence of vibrations and noises can be controlled and a region of operation from rotation at low speed to rotation at high speed is wide. This device comprises a main shaft (42) rotatably supported in a main shaft housin (40), a variable speed driving motor (48) having a winding change-over mechanism and provided formed therein with a through-hole (44) extending in the axial direction, a coupling member (50) for directly coupling the main shaft (42) to the output shaft (46) which are coaxially arranged with each other, and ceramic bearings (52) for journally supporting the output shaft (46). The variable speed driving motor (48) includes a winding for low speed rotation and another winding for high speed rotation, which are changed over by the winding change-over mechanism, whereby the motor (48) is rotated at speeds different from each other. The coupling member (50) directly connects the main shaft (42) to the output shaft (46) to thereby transmit the rotational output of the variable speed driving motor (48) directly to the main shaft (42). The ceramic bearings (52) are held by the motor casing (49) of the variable speed driving motor (48) to thereby journally support the output shaft (46) without causing a seizure even during rotation at high speed. Further, the variable speed driving motor (48) has a liquid cooled construction. |
