Abstract: The magnetic bearing control device (1) has a motor drive circuit (13) provided with an inverter (13a) for driving the motor (4) capable of generating an electric power, the inverter being controlled by an inverter control circuit (14), and an over-speed detection circuit (17) for detecting the number of revolutions of the rotor (3) that is being rotated by the motor (4), the rotor being supported in non-contact manner by a magnetic bearing (5). When the over-speed detection circuit (17) detects that the rotor (3) is being rotated at a preset number of revolutions or more, the motor drive circuit (13) performs a switching operation of a switch portion 13c provided in the motor drive circuit (13) to separate the inverter (13a) from the motor (4) and connect the motor (4) to a regenerative circuit (13b), whereby the magnetic bearing (5) is driven and controlled, employing a regenerative electric power of the motor (4).

Abstract: A magnetic bearing device comprises a machine main body having position sensors for detecting the position of a rotary body and magnetic bearings for magnetically contactlessly supporting the rotary body, a controller for controlling the magnetic bearings based on the signals from the position sensors, a data processing computer installed at a location away from the controller, and modems for connecting the controller to the computer by communication lines.

Abstract: A machine tool comprises a spindle unit for raising a spindle on which a cutting tool is mounted by a magnetic force and supporting the spindle. The spindle unit carries out feedback control so as to maintain the spindle in its target position in the radial direction. A feeder for feeding the cutting tool to a work comprises a servo motor for moving the spindle unit relatively to the work. A feeding controller for controlling a feeding operation of the feeder controls the speed of rotation of the servo motor on the basis of feed speed data stored in a memory. The feed speed data comprises a first feed speed corresponding to the time when the cutting tool cuts through an end surface of the work crossing the direction of feeding and a second feed speed corresponding to the time of normal working and higher than the first feed speed.

Abstract: A spindle 2 is formed with a cooling-working fluid channel 19 axially extending therethrough. A housing 1 has fixed to the rear end thereof a tubular cooling-working fluid supply member 29 inserted in the fluid channel 19 with a clearance formed therearound. The radial spacing between the outer peripheral surface of the supply member 29 and the spindle inner peripheral surface defining the fluid channel 19 is made greater than the radial spacing between touchdown bearings 9 and the spindle 2 as supported contactlessly. The inner peripheral surface defining the fluid channel 19 is formed, over a range extending from the rear end of the channel and greater than the depth of insertion of the supply member 29, with helical grooves 21 for sending a cooling-working fluid forward when the spindle 2 is in rotation. A working fluid reservoir 32 communicating with the clearance between the spindle 2 and the supply member 29 is formed in a rear end interior portion of the housing 1.

Abstract: A magnetic bearing spindle device for machine tools comprises a spindle for mounting a tool element as changeably attached to a forward end thereof, a plurality of controllable magnetic bearings for contactlessly supporting the spindle, an electric motor for rotating the spindle as contactlessly supported by the magnetic bearings, a draw bar inserted through the spindle and axially movable for unclamping and clamping the tool element, state sensor switches for detecting the axial position of the draw bar to detect a state of having no tool element, an unclamping state or a clamping state, and a control unit for controlling the support of the spindle by the magnetic bearings and the rotation of the spindle by the motor based on the result of detection by the switches.

Abstract: A magnetic spindle device for machine tools has a spindle contactlessly supportable by a plurality of controllable magnetic bearings for mounting thereon a tool element which is automatically changeable for a tool element of different kind. The spindle device comprises a device for measuring the weight of the tool element by measuring the exciting currents of the magnetic bearing, and a device for changing over the control characteristics of the magnetic bearings based on the measured weight of the tool element.

Abstract: A magnetic bearing apparatus comprises a pair of radial magnetic bearings arranged on both sides in the axial direction of an axial magnetic bearing. A pair of first touchdown bearings are arranged at both ends of a spindle. Annular slide bearings are mounted as second touchdown bearings for receiving the spindle on inner peripheral parts of electromagnets in the axial magnetic bearing. The radial internal clearance between the slide bearing and the spindle is larger than the radial internal clearance between the first touchdown bearings and the spindle and is smaller than the radial internal clearance between the radial magnetic bearings and the spindle. Even if a central part of the spindle is deflected at the time of emergency stop, both the first touchdown bearings and the slide bearings receive the spindle, so that the load on the first touchdown bearings can be reduced.

Abstract: In a torque sensor, an oscillating voltage from an oscillator is applied to a torque detecting coil and a temperature compensating coil, and voltages from the torque detecting coil and the temperature compensating coil are input to a differential amplifier which produces a differential-amplified voltage for detection of a torque, wherein when the oscillator has ceased producing the oscillating voltage, a prescribed voltage is applied to a circuit through which the voltage from the torque detecting coil or the temperature compensating coil is input to the differential amplifier, thereby causing the differential amplifier to output a voltage shifted outside a prescribed range and thus detecting a failure of the oscillator.

Abstract: A torque sensor which includes two cylinders fixed to two shafts connected with each other through a torsion bar. The magnetic coupling state of the two cylinders is made variable corresponding to relative rotations of the two shafts. The magnetic coupling state thereof is detected by a coil impedance, which is indicative of a torque acting on the shafts. The two cylinders form at the opposite end edges thereof teeth provided with cutouts disposed circumferentially of the cylinders and are opposite to each other at portions of about half a width of each tooth. The two shafts are regulated by rotation so as to not put the teeth of the cylinders completely opposite or non-opposite to each other.

Abstract: A torque sensor according to this invention is so constructed that a plurality of magnetic cylinders mounted respectively to two shafts coupled via a torsion bar are able to be electromagnetically coupled variably to each other in accordance with the relative rotation of the two shafts, and the electromagnetic coupling state of a plurality of cylinders mounted to these two shafts is detected by the electromagnetic coupling detection coils. Components with elastic properties are used in the construction of the sensor so as to absorb the rattlings and thereby reduce the noise previously associated with these devices.

Abstract: A torque sensor which includes two cylinders fixed to two shafts connected with each other through a torsion bar. The magnetic coupling state of the two cylinders is made variable corresponding to relative rotations of the two shafts. The magnetic coupling state thereof is detected, which is indicative of a torque acting on the shafts. The two cylinders form at the opposite end edges thereof teeth provided with cutouts disposed circumferentially of the cylinders and are opposite to each other at portions of about half a width of each tooth. The two shafts are regulated by rotation so as to not put the teeth of the cylinders completely opposite or non-opposite to each other. This enlarges a rate of change in the magnetic coupling state, detecting the torque with high sensitivity, and reducing a lateral difference in the output.