The principal axis device null which circulates the coolant inside the principal axis

摘要

PURPOSE:To increase a limit speed due to seizure of a bearing and to improve machining precision, by providing a means which cools a bearing from its inner ring side in a way that cooling liquid is circulated from an external cooling liquid source to the interior of a main spindle for recovery. CONSTITUTION:The outer ring size of a front bearing 12 is cooled by a cooling liquid flow passage means situated to a static housing 14 to support an outer ring. A cooling liquid feed source is a cooling liquid source 66, being equal as a flow passage means to a helical cooling liquid passage 68 or having a plurality of flow passages formed in a longitudinal direction. Lubricating oil additionally serving as cooling is fed between the outer and the inner ring of the front bearing 12. A part of cooling liquid flowing in an annular space 76 flows in a plurality of bearing cooling liquid lines 86 (outbound) disposed at an equal angle in the vicinity of the front bearing 12. The line 86 is communicated at the front end part of a main spindle 10 to a bearing cooling liquid return line (inbound) 88 having the large position size of a radial position through a communicating passage. This constitution recovers cooling liquid, cooling the bearing 12 from its inside, to the cooling liquid source 66.