MAGNETIC BEARING SPINDLE APPARATUS

摘要

Formed in a spindle (2) is a cooling processing liquid passage (19) extending axially. Fixedly provided on a rear end of a housing (1) is a cylindrical cooling processing liquid supplying member (29) adapted to be inserted into the passage (19) with a gap therebetween. A radial spacing between an outer peripheral surface of the supplying member (29) and an inner peripheral surface of the passage (19) is made larger than a radial spacing between touchdown bearings (9) and the spindle (2) when the spindle (2) is supported in non-contact condition. Formed on the inner peripheral surface of the passage (19) is a spiral groove (21) to feed a cooling processing liquid forward over a distance from a rear end of the passage (19) which is longer than a distance, by which the supplying member (29) is inserted from the rear end of the passage (19) during rotation of the spindle (2). Formed in a rear end of the housing (1) is a processing liquid reservoir (32) communicating with a gap between the spindle (2) and the supplying member (29). Formed in the housing (1) is a drainage hole (33) communicating with the reservoir (32). Provided between the housing (1) and the spindle (2) is a labyrinth seal (28) for providing sealing between an area of the reservoir (32) in the housing (1) and an area forwardly thereof. Accordingly, it is possible to prevent failure of the entire magnetic bearing spindle apparatus.