Motor output changeover control apparatus

Electricity: motive power systems – Induction motor systems – Primary circuit control

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Details

318772, 318778, 318729, H02P 126

Patent

active

050498002

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
This invention relates to a motor output changeover control apparatus used for the spindle motor of machine tools.
2. Background Art
The spindle motor of an ordinary machine tool comes equipped with a gear mechanism for the purpose of assuring a constant output over a wide range of speeds. By changing the rotational speed of the spindle connected to the spindle motor, a wide variety of cutting conditions can be realized using the machine tool.
A conventional spindle speed change mechanism for realizing a constant output over a wide range by gears uses a spindle motor having a single winding. As a consequence, the winding produces a large amount of heat and the speed change mechanism using gears is elaborate. In addition, the motor itself must have a large capacity.


DISCLOSURE OF THE INVENTION

The present invention solve the foregoing problems. An object of the present invention is to provide a motor output changeover control apparatus capable of obtaining a constant output of a spindle motor over a wide range by an AC motor having a low-speed winding and a high speed winding.
In accordance with the present invention, there is provided a motor output changeover control apparatus for an AC motor having a low-speed winding and a high-speed winding, the apparatus comprising winding changeover means for changing over a power line connection of the AC motor, and command means for issuing a power line changeover command to the winding changeover means based on a changeover request.
Thus, the winding changeover control apparatus of the invention is capable of stabilizing output characteristics over a wide range from high to low speed by changing over the power line connection of the AC motor. Moreover, since obtaining the constant output over a wide range can be realized by a single winding, it is possible to construct a spindle motor for a small-size machine tool. Thus there is provided a motor output changeover control apparatus which is very effective.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an embodiment of the present invention,
FIGS. 2(a) and (b) are views illustrating the winding arrangements of Y- and delta-connections of the winding of a spindle motor armature,
FIG. 3 is a view illustrating an example of a winding changeover sequence, and
FIG. 4 is a characteristic diagram illustrating an example of output characteristics with respect to rotational speed.


DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE FOR CARRYING OUT THE
INVENTION
An embodiment of the present invention will now be described in detail with reference to the drawings.
FIG. 1 is a block diagram illustrating an example of output changeover control of a motor performed by an AC spindle servo unit 1. A spindle motor 2 has its speed digitally controlled by a current signal pulse-width modulated by a transistorized inverter within the spindle servo unit 1. The spindle servo unit 1 includes a spindle changeover circuit 11. The spindle motor 2 is an AC motor having a low-speed winding and a high-speed winding, and the arrangement is such that winding changeover is possible by changing over the connections between terminals U, V, W and X, Y, Z of the power lines.
Numeral 3 denotes a programmable controller which outputs a changeover request signal to the spindle changeover circuit 11 in response to a speed detection signal, indicative of the speed of spindle motor 2, detected by the spindle servo unit 1. The arrangement is such that the programmable controller 3 forms the abovementioned changeover request signal in dependence upon changeover speed. The spindle changeover circuit 11 issues a power line changeover command to a relay circuit 4 based on the changeover request signal, and a command for changing over a ROM from a main ROM to a subordinate ROM. The power line changeover command is for alternately turning on and off electromagnetic contacts MC1, MC2 for winding changeover of the spindle motor 2.
FIGS. 2(a) and (b) illustrate a case in which the armature winding

REFERENCES:
patent: 3611082 (1971-10-01), Schmitz
patent: 3624471 (1971-11-01), Tapp
patent: 3860093 (1975-01-01), Mitsui et al.
patent: 4384243 (1983-05-01), Muskovac
patent: 4413218 (1983-11-01), Taylor et al.
patent: 4425539 (1984-01-01), Wills
patent: 4446415 (1984-05-01), Taylor et al.
patent: 4477760 (1984-10-01), Kuznetsov
patent: 4691155 (1987-09-01), Taylor et al.
patent: 4712054 (1987-12-01), Boldt
patent: 4736147 (1988-04-01), Shizhang

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