Patent ID: 8142257

Claim:
A detecting device for abnormal workpiece rotation in a non-circular workpiece grinding machine having a bed; a work head mounted on the bed and rotatably supporting a work spindle for supporting a workpiece with a non-circular portion thereon to be ground; a coupling member for coupling the work spindle with the workpiece to rotate the workpiece together with the work spindle in a predetermined angular phase relation; a wheel head rotatably carrying a grinding wheel and mounted on the bed to be movable back and forth in a direction intersecting with a rotational axis of the work spindle; a control device for controlling the rotation of the work spindle and the back and forth movement of the wheel head in a correlation according to profile data defining a finish shape of the non-circular portion and for varying the rotational speed of the work spindle in accordance with a grinding condition; the detecting device comprising: a sensor arranged to face a non-circular portion being ground with the grinding wheel for sensing a maximum diameter portion of the non-circular portion to detect that the maximum diameter portion is rotating in a detection phase section when the work spindle is rotating in a low speed rotational phase region in which the control device controls the work spindle to rotate at a low speed of the varying rotational speed; and abnormality judging means for judging that abnormal workpiece rotation is occurring, when the maximum diameter portion of the non-circular portion is not detected by the sensor with the work spindle rotating in the low speed rotational phase region.