Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1989-08-01
1991-11-26
Ip, Paul
Electricity: motive power systems
Induction motor systems
Primary circuit control
318773, 318783, H02P 126
Patent
active
050685872
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a spindle drive control apparatus in a machine tool which can rotate the spindle motor at a high speed with a high power and which can rotate the spindle motor at a superlow speed (for example, about 0.5 rpm) with high torque. That is, it relates to a spindle drive control apparatus for a machine tool which can handle both high speed heavy duty cutting machining and drilling and contouring by a single spindle motor.
BACKGROUND ART
In a machine tool, when controlling the angular position of the spindle or spindle motor, that is, when drilling or contouring during C-axis control, it is necessary that the spindle be rotated smoothly at a superlow speed and have a high torque. Further, for normal cutting machining etc. high speed rotation and a high cutting power are required.
Therefore, in the past, two motors were provided for driving the spindle. One was the spindle motor for rotating the spindle at a high speed for cutting machining etc. The other was a C-axis control motor having a detector. This C-axis control motor had an output shaft affixed to a worm. A worm gear engaged with the worm was affixed to the spindle. In this way, during C-axis control, the C-axis control motor was driven to rotate the spindle at a superlow speed. To switch to normal cutting machining etc. after this, the above-mentioned C-axis control motor had to be retracted to a retraction position and the spindle motor driven.
However, as mentioned above, two types of motors had to be provided and, further, worm gears, retraction mechanisms, etc. were necessary. Therefore, the apparatus can not be said to have been the best in space or cost.
DISCLOSURE OF THE INVENTION
Therefore, the present invention has an object to resolve these problems by the provision of a spindle drive control apparatus for a machine tool which uses a single spindle motor and which can be applied to both high speed rotational machining and superlow speed rotational machining.
In view of the above object, the present invention provides a spindle drive control apparatus for a machine tool characterized by comprising a three-phase spindle motor which rotatingly drives a spindle of a machine tool, a rotational position detector which detects the rotational position of the said spindle, and a connection switching means which can switch the connection states of the phase windings of the three-phase spindle motor between a .DELTA. (delta) connection and Y (star) connection.
To rotate the spindle at high speed, the three-phase spindle motor is switched to the .DELTA. connection, and to rotate it at superlow speed, it is switched to the Y connection. When switched to the Y connection, the base speed becomes lower than the .DELTA. connection and the torque generated becomes larger by a corresponding amount.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of the constitution of the present invention;
FIG. 2 is a front view of a workpiece along the arrow line II of FIG. 1;
FIG. 3 is a schematic view of switching the connections of motor windings; and
FIG. 4 is a view explaining the mode of operation of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Below, the present invention will be explained in further detail based on the embodiments shown in the attached drawings. Referring to FIG. 1, a spindle 50 axially supported through a bearing 52 by a spindle head housing 54 of the machine tool is rotatingly driven by a three-phase spindle motor 60 (three phase induction motor). That is, a belt 64 is stretched over a pulley 62 provided on the output shaft of the spindle motor 60 and another pulley 66 provided on the spindle 50 so as to rotatingly drive the spindle 50. This position of angular rotation and rotational speed are detected by a known pulse encoder or other positional detector 68.
At the end of the spindle 50 is mounted a workpiece W through a chuck 56. The workpiece W is machined by a tool 58. When cutting the outer circumference of the workpiece W etc., the spindle 50 is rotate
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Kono Shinichi
Nakamura Kosei
Numai Kazuhisa
Fanuc Ltd.
Ip Paul
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