| 摘要 |
PURPOSE:To facilitate control of the thermal displacement of a main shaft so as to improve the machining accuracy by causing the thermal expansion to generate around a motor casing provided on the center in the width direction of a thrust bearing and also around a positioning pin to connect the motor casing with a supporting rest. CONSTITUTION:The space between a casing 7 and a supporting rest 5 being supported only through four places on a supporting flange 7d in hearing portions 7b, 7e, so as to minimize the contact area, the casing 7 is maintained to an uniform temperature as the heat transfer quantity is small. The supporting flange 7c is provided in a position conforming approximately to the vertical direction of a shaft center CT and the casing 7 is formed in a vertical objective shape against the shaft center CT with its deformation occurring uniformly without any strain against a Z axis. The expansion of a main shaft 9 in the Z axis direction occurs toward an arrow mark B to the right and toward an arrow mark A to the left around the center position in the width direction of the Z axis of a radial ball bearing 17 supporting a thrust, that is, around the installed position DP of a positioning pin 20, and the casing 7 also has the heat expansion generating around the positioning pin 20. The thermal displacement of the main shaft 9 need not take into consideration the heat expansion of the casing 7 but the pin installed position DP is to be considered as the basis.
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