Electricity: electrical systems and devices – Miscellaneous
Patent
1988-07-08
1990-03-13
Tolin, Gerald P.
Electricity: electrical systems and devices
Miscellaneous
361399, 361412, 439 74, H02B 104
Patent
active
049087380
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a motor drive unit for accommodating electrical components used in controlling an AC motor.
2. Description of the Related Art
A motor drive circuit shown in the circuit diagram of FIG. 4, by way of example, is used as a control apparatus for an AC motor which drives the spindle or feed shaft of a machine tool. Electrical components such as an electromagnetic contactor A, rectifying diode B, smoothing capacitor C, regenerative transistor D, transistor bridge E and filter F, as well as electrical components such as a power resistor and fuse, are connected to a circuit extending from three-phase AC power supply terminals R, S, T shown in FIG. 4 to terminals U, V, W for feeding current to the AC motor.
The large electrical components among these components are connected to a mounting board by screws and are connected by using a cluster of wires, after which the components are housed in a metal case consisting of worked sheet metal.
In the control apparatus accommodated in the abovementioned metal case, the various electrical components which are each of a different shape are first fixed and then interconnected by the cluster of wires. Consequently, assembling the motor drive unit requires labor, and thus, automating the operation as by using an assembling robot involves many difficulties.
Furthermore, since the worked sheet-metal case is used as the external housing, problems arise in terms of cost and weight.
SUMMARY OF THE INVENTION
The present invention solves the aforementioned problems. An object is to provide a motor drive unit in which the control circuit and power circuit of a motor are mounted on individual plastic frames, and the components in the power circuit are interconnected by soldering or screw clamping using a wiring board. Thus, a metal case of worked plate metal and a wire cluster for wiring are no longer necessary.
In accordance with the present invention, there is provided a motor drive unit having a first frame made of synthetic resin for supporting a printed circuit board mounting control circuit components from among electrical components which drive and control an AC motor, a second frame made of synthetic resin for securing power circuit components from among said electrical components, and a connecting power distribution board having one surface on which components for connection by soldering are arranged and connected by soldering, and another surface on which components for connection by screws are connected by screws, these components being those from among the power circuit components, the connecting power distribution board being sandwiched between the two frames when the two frames are joined.
Thus, the motor drive unit of the present invention dispenses with the clustering of wires and the worked sheet-metal frame, simplifies the unit assembly operation and is more compact.
Further, in accordance with the invention, the power board sandwiched between the upper and lower frames allows the upper power circuit components to be connected by soldering and allows the electric circuitry of the lower power circuit components to be connected by screw clamping. As a result, operations requiring labor, namely the wiring of components and the clustering of wires, can be dispensed with to improve operating efficiency.
In accordance with the invention, the plastic upper and lower frames are joined into one. This makes it possible to dispense with the metal case of worked sheet metal so that cost and weight can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded, perspective view showing an embodiment of a motor drive unit according to the present invention;
FIG. 2 is a partial, exploded view illustrating an example of a method of mounting power circuit components on a power board according to the present invention;
FIG. 3 is a side elevational view of a floating nut according to the present invention; and
FIG. 4 is a circuit diagram showing an example of a motor drive unit for controlling
REFERENCES:
patent: 3631299 (1971-12-01), Meyer
patent: 4339628 (1982-07-01), Mancantonio
patent: 4444318 (1984-04-01), Alexander
patent: 4520425 (1985-05-01), Ito
Kanamori Yuji
Kobari Katsuo
Ota Naoto
Suzuki Naoyuki
Fanuc Ltd
Tolin Gerald P.
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