BEARING PRELOAD HYDRAULIC CIRCUIT, MAIN SPINDLE DEVICE AND METHOD FOR PRELOAD OF ROLLER BEARING

摘要

PROBLEM TO BE SOLVED: To prolong the life of a bearing by heightening a preload performance. ;SOLUTION: When pressure is removed from a return oil hydraulic chamber Ra and hydraulic oil is supplied to preload rear and front hydraulic chambers Rb and Rc, the heavy preload of a fixed position is realized, and when pressure is removed from the hydraulic chambers Ra and Rb and hydraulic oil is supplied to the hydraulic chamber Rc, the middle preload of a fixed position is set, and when pressure is removed from the hydraulic chambers Ra and Rc and hydraulic oil is supplied to the hydraulic chamber Rb (δ2δ1), the low preload of a fixed position is set. Also, when hydraulic oil is supplied to the hydraulic chambers Ra and Rb and pressure is removed from the hydraulic chamber Rc, constant pressure preload is set. In this case, when pressure inside a bearing is higher than set hydraulic pressure PD containing the force of a preload spring 17, a rear piston member 9 is moved to a front side to shorten an outer ring span L, thereby suppressing an increase in preload. The pressure receiving area A2 of the hydraulic chamber Rb is set larger than the pressure receiving area A1 of the hydraulic chamber Ra.;COPYRIGHT: (C)2000,JPO