Turning – Process of turning
Reexamination Certificate
1999-10-21
2002-10-15
Tsai, Henry (Department: 3722)
Turning
Process of turning
C082S047000, C082S118000, C279S004020
Reexamination Certificate
active
06463835
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for controlling a motor-driven chucking device in which a chuck of a machine tool is driven to open or close by a driving motor. More particularly, the present invention relates to a method and apparatus for controlling a motor-driven chucking device in which a chuck is driven to open or close by a spindle motor for driving a main spindle.
2. Description of the Related Art
A chuck for grasping a workpiece is mounted on the spindle nose of a machine tool, such as a lathe. There is a publicly known chucking device in which the open-close operation of the gripping jaws of the chuck is carried out by a hydraulic cylinder. However, the chucking device using a hydraulic cylinder to drive the gripping jaws has an unfavorably short open-close stroke of the gripping jaws and therefore needs to adjust the position of the gripping jaws or to change them in order to grip workpieces much different in diameter from those which are expected to be held by the gripping jaws. The position adjustment or the change of the gripping jaws requires a problematic operation and causes the operating efficiency and the availability factor of the machine tool to reduce unfavorably.
There has heretofore been another type of chucking device in which gripping jaws are driven to open or close by a servo-motor as disclosed in Japanese Utility Model Application Post-Exam Publication No. 63-38968 (1988). In this chucking device, the position of the gripping jaws is detected indirectly with a sensor, and the open position of the gripping jaws at the time of initiating gripping or ungripping is controlled to an appropriate position according to the size of workpieces.
In the conventional chucking device in which the gripping jaws are driven to open or close by a servo-motor, the open position of the gripping jaws can be controlled, but the workpiece gripping force cannot be controlled. It is also impossible for the conventional chucking device to effect delicate control by combining together the closing side position (gripping position) of the gripping jaws and the driving torque of the servo-motor, or control such that travel speeds of the gripping jaws are changed from one to another according to the position of the gripping jaws.
SUMMARY OF THE INVENTION
Under these circumstances, an object of the present invention is to provide a method and apparatus for controlling a motor-driven chucking device in which a chuck of a machine tool is driven to open or close by a driving motor, which are capable of delicately controlling the workpiece gripping force, the travel speed of the gripping jaws, and so forth.
To attain the above-described object, the present invention provides a method of controlling a motor-driven chucking device in which gripping jaws of a chuck supported by a frame provided on a body of a machine tool are opened or closed by a torque controllable driving motor to grip a workpiece. The control method includes the steps of inputting a set value for gripping force with which the gripping jaws grip the workpiece, and opening or closing the gripping jaws by controlling the rotation of the driving motor according to the set value for the gripping force.
Preferably, the above-described control method further includes the step of converting the driving torque of the driving motor and the gripping force of the chuck to each other.
The above-described control method preferably includes the step of stopping the movement of the gripping jaws when the driving torque of the driving motor has reached a value corresponding to the set value for the gripping force.
The above-described control method preferably includes the step of selecting or changing the set value for the gripping force in response to a command from an NC machining program.
Preferably, the driving motor used in the above-described control method is capable of controlling the position and travel speed of the gripping jaws, and the control method further includes the steps of inputting a set value for the gripping diameter of the workpiece, and controlling the position and travel speed of the gripping jaws by controlling the rotation of the driving motor according to the set value for the gripping diameter.
The above-described control method preferably includes the steps of converting the driving torque of the driving motor and the gripping force of the chuck to each other, and converting the rotational position of the driving motor and the position of the gripping jaws to each other.
The above-described control method preferably includes the step of outputting a gripping signal confirming that the workpiece has been gripped when the driving torque of the driving motor has reached a value corresponding to the set value for the gripping force and the gripping jaws have stopped at a position within a predetermined range from the set value for the gripping diameter.
The above-described control method preferably includes the step of selecting or changing at least one of the set value for the gripping force and the set value for the gripping diameter in response to a command from an NC machining program.
In addition, the present invention provides a method of controlling a motor-driven chucking device in which gripping jaws of a chuck supported by a frame provided on a body of a machine tool are opened or closed by a position controllable driving motor to grip a workpiece. The control method includes the steps of inputting a gripping operation initiating position of the gripping jaws, inputting a set value for the gripping diameter of the workpiece, and moving the gripping jaws to open or close between the gripping operation initiating position and the set value for the gripping diameter by controlling the rotation of the driving motor.
Preferably, the above-described control method further includes the step of selecting or changing at least one of the gripping operation initiating position and the set value for the gripping diameter in response to a command from an NC machining program.
In addition, the present invention provides a method of controlling a motor-driven chucking device in which gripping jaws of a chuck supported by a frame provided on a body of a machine tool are opened or closed by a position and speed controllable driving motor to grip a workpiece. The control method includes the steps of inputting a set value for a speed change position at which a travel speed of the gripping jaws is to be changed, and changing the travel speed of the gripping jaws to a low speed by controlling the rotation of the driving motor when the position of the gripping jaws has exceeded the set value for the speed change position in a direction for gripping the workpiece.
Preferably, the above-described control method further includes the step of selecting or changing the set value for the speed change position in response to a command from an NC machining program.
In addition, the present invention provides a method of controlling a motor-driven chucking device in which gripping jaws of a chuck supported by a frame provided on a body of a machine tool are opened or closed by a position controllable driving motor to grip a workpiece. The control method includes the steps of inputting a gripped portion dimension of a workpiece having a known gripped portion dimension, gripping the workpiece, whose gripped portion dimension has been input, with the gripping portions of the gripping jaws of the chuck, and making the present diametrical position data concerning the gripping portions coincide with position data corresponding to the gripped portion dimension.
In the above-described control method, the chuck is preferably provided on a main spindle rotatably supported by a headstock of the machine tool.
Preferably, the driving motor used in the above-described control method rotates and positions the main spindle about the axis of the main spindle, and the control method further includes the steps of bringing the main body part of the chuck into a locked sta
Ogawa Toru
Segawa Yasunori
Armstrong Westerman & Hattori, LLP
Hitachi Seiki Co., Ltd.
Tsai Henry
LandOfFree
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