초록 ▼

The workpiece-carrier spindle assembly comprises a stator (10) mounted on a slide (202), a spindle (50) supported by active magnetic bearings and rotated by an external electric motor (2) connected to the stator via a coupling (3) which filters the mechanical disturbances due to the excentricity of

The workpiece-carrier spindle assembly comprises a stator (10) mounted on a slide (202), a spindle (50) supported by active magnetic bearings and rotated by an external electric motor (2) connected to the stator via a coupling (3) which filters the mechanical disturbances due to the excentricity of the motor, and a chuck (5) fixed to the spindle (50). Additional means for detecting movements of the spindle assembly slide (202) include, in the servo-control plane of each of the radial beraings, two position detectors (216, 218: 215, 217) fixed to the stator (10) and facing two plane reference surfaces (211, 212) disposed parallel to the direction of slide displacement and delivering signals which are applied to means for selectively modifying the electric reference voltages applied to the servo-control loops of the magnetic bearings. The spindle assembly is applicable to machine tools for providing optical-quality machining.

대표청구항 ▼

A workpiece-carrier spindle assembly having active magnetic bearings for a very high precision machine tool, the assembly comprising a stator mounted on a slide for guidance along a predetermined direction, a spindle mounted inside the stator, a chuck fixed to the spindle, first and second radial ac

A workpiece-carrier spindle assembly having active magnetic bearings for a very high precision machine tool, the assembly comprising a stator mounted on a slide for guidance along a predetermined direction, a spindle mounted inside the stator, a chuck fixed to the spindle, first and second radial active bearings supporting the spindle and controlled from radial detectors for detecting the position of the rotor, an axial abutment constituted by an axial active magnetic bearing co-operating with a disk fixed to the spindle and controlled from at least one axial detector for detecting the position of the spindle, and an electric motor for rotating the spindle, wherein: the electric motor is external to the spindle assembly stator, is disposed behind the spindle and substantially in alignment therewith, the external motor has a smaller air gap than the air gap between the radial magnetic bearings and the spindle, the rotary drive communicated to the spindle by the external motor expressed in revolutions per second (Hz) lies outside the servo-control passband of the magnetic suspension system expressed in hertz, a flexible coupling device connects the outlet shaft of the external motor to the rear portion of the spindle while filtering mechanical disturbances due to the eccentricity of the motor, and the spindle assembly further includes additional means for detecting movements of the spindle assembly guide slide and means for selectively modifying the electrical reference voltages of the servo-control loops of the axial bearing and of the radial bearings as a function of the signals from said additional detection means, said additional means for detecting movements of the slide on which the workpiece-carrier spindle assembly is placed including two detectors in the servo-control plane of each of the radial bearings, said detectors being fixed to the spindle assembly stator and facing two plane reference surfaces disposed parallel to the displacement direction of said slide, said detectors delivering electrical signals proportional to variations in the distances between said detectors and said plane reference surfaces in order to control in real time the means for selectively modifying the reference voltages of the servo-control loops of the radial bearings of the workpiece-carrier spindle assembly as a function of said proximity variations between the detectors and the plane reference surfaces.