Machine tool
First Claim
1. A machine tool comprising a spindle device carrying a tool element attached to the forward end of a rotor spindle drivingly rotatable as supported by a control-type magnetic bearing device, working force calculating means for calculating a working force acting on the tool element upon the tool element coming into contact with a workpiece based on exciting current of a magnetic bearing of the magnetic bearing device, and discriminating means for discerning whether the contact of the tool element with the workpiece is normal or abnormal based on variations in the working force;
- wherein the discriminating means determines the rate of increase of the working force, compares the increase rate of the working force with a predetermined reference increase rate and construes the contact of the tool element with the workpiece as abnormal when the working force increase rate has exceeded the reference increase rate.
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Accused Products
Abstract
A machine tool comprises a spindle device carrying a tool element attached to the forward end of a rotor spindle drivingly rotatable as supported by a control-type magnetic bearing device, a working force calculating unit for calculating a working force acting on the tool element upon the tool element coming into contact with a workpiece based on exciting current of a magnetic bearing of the bearing device, and a discriminating unit for discerning whether the contact of the tool element with the workpiece is normal or abnormal based on variations in the working force.
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Citations
7 Claims
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1. A machine tool comprising a spindle device carrying a tool element attached to the forward end of a rotor spindle drivingly rotatable as supported by a control-type magnetic bearing device, working force calculating means for calculating a working force acting on the tool element upon the tool element coming into contact with a workpiece based on exciting current of a magnetic bearing of the magnetic bearing device, and discriminating means for discerning whether the contact of the tool element with the workpiece is normal or abnormal based on variations in the working force;
wherein the discriminating means determines the rate of increase of the working force, compares the increase rate of the working force with a predetermined reference increase rate and construes the contact of the tool element with the workpiece as abnormal when the working force increase rate has exceeded the reference increase rate. - View Dependent Claims (2, 3)
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4. A machine tool comprising a spindle device carrying a tool element attached to the forward end of a rotor spindle drivingly rotatable as supported by a control-type magnetic bearing device, working force calculating means for calculating a working force acting on the tool element upon the tool element coming into contact with a workpiece based on exciting current of a magnetic bearing of the magnetic bearing device, and discriminating means for discerning whether the contact of the tool element with the workpiece is normal or abnormal based on variations in the working force;
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wherein the control-type magnetic bearing device comprises two radial magnetic bearings arranged respectively at positions spaced apart from each other axially of the spindle for supporting the rotor spindle radially thereof, two radial displacement detecting means arranged respectively at positions spaced apart from each other axially of the spindle for detecting radial displacement of the rotor spindle at their respective positions, and radial control means for controlling the two radial magnetic bearings based on the outputs of the two radial displacement detecting means; wherein the two radial magnetic bearings each comprise a pair of first electromagnets and a pair of second electromagnets arranged respectively on two radial axes orthogonal to each other in a plane perpendicular to the axis of the rotor spindle;
the two radial displacement detecting means each comprise a pair of first position sensors arranged axially adjacent to the pair of first electromagnets for detecting the position of the rotor spindle with respect to a first radial direction, a first subtracter for determining the displacement of the rotor spindle in the first radial direction by calculating the difference between the outputs of the pair of first position sensors, a pair of second position sensors arranged axially adjacent to the pair of second electromagnets for detecting the position of the rotor spindle with respect to a second radial direction, and a second subtracter for determining the displacement of the rotor spindle in the second radial direction by calculating the difference between the outputs of the pair of second position sensors; and
the radial control means comprises a first radial direction controller for controlling the attraction of the first electromagnets based on the output of the first subtracter, and a second radial direction controller for controlling the attraction of the second electromagnets based on the output of the second subtracter. - View Dependent Claims (5, 6, 7)
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Specification