Backlash eliminator
A backlash eliminator includes an input shaft ( 15 ) coupled to a driving motor ( 20 ) and having a drive gear ( 52 ); an output shaft ( 14 ) fixing a gear (W), as an object to be cut, thereon, and having a driven gear ( 42 ); and a stationary intermediate shaft ( 16 ) and a moving intermediate shaft ( 17 ) disposed parallel to the input shaft and the output shaft, and having large intermediate gears ( 62, 72 ) meshing with the drive gear, and small intermediate gears ( 63, 73 ) meshing with the driven gear, and a switching regulating valve ( 31 ) for pressing the moving intermediate shaft in its axial direction so that an output-side backlash elimination torque (Ts) between the driven gear and the small intermediate gear ( 73 ) acts in the same direction as the direction of generation of a cutting load torque (Tw) generated in the circumferential direction of the gear during machining of the gear.
1. A backlash eliminator adapted to eliminate backlash in a gear train using helical gears when a workpiece whose tooth profile is to be machined by a cutting tool is rotated by the gear train, the backlash eliminator comprising:
an input shaft coupled to a motor and having a drive gear;
an output shaft disposed parallel to the input shaft, and to which the workpiece is fixed coaxially with the output shaft, and having a driven gear; and
intermediate shafts disposed parallel to the input shaft and the output shaft, and each having a first intermediate gear meshing with the drive gear, and a second intermediate gear meshing with the driven gear, one of the intermediate shafts being supported to be stationary in an axial direction for positioning the output shaft in a rotating direction, and other of the intermediate shafts being supported to be movable in an axial direction for eliminating backlash between the other intermediate shaft and the output shaft; and
pressing means which presses the other intermediate shaft in the axial direction thereof in a switchable manner to exert a backlash eliminating force between the driven gear and the second intermediate gear in a direction identical with a direction of generation of a cutting load generated in a circumferential direction of the workpiece during machining of the workpiece,
wherein the other intermediate shaft is disposed such that a first clearance is formed between the casing and one end of the other intermediate shaft and a second clearance is formed between the casing and another end of the other intermediate shaft opposite to the first one end, and
the pressing means selectively supplies air to the first clearance and the second clearance to press the other intermediate shaft in the axial direction thereof in a switchable manner.