Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1988-06-08
1990-03-13
Tolin, Gerald P.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
361419, 363141, H05K 720
Patent
active
049087347
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a control unit in which a plastic case houses power components such as the transistors of an inverter and a smoothing capacitor that are used in an AC motor control apparatus or the like.
2. Description of the Related Art
A control apparatus for an AC motor which drives the spindle of a machine tool uses the circuitry shown in FIG. 4. In order to house this control apparatus in a case 10, it is necessary to have terminals for the illustrated three-phase power supply 14, 15, 16, terminals 18, 19, 20 for feeding current to an AC motor, a ground terminal 26, and terminals 28, 30, T.sub.2 -2 for a thermostat 32. Principal components such as an electromagnetic contactor 34 rectifying diode 36 smoothing capacitor 38 regenerative transistor 40 transistor inverter 42 and filter 44 are disposed inside the case 10, and a number of control elements such as resistors, capacitors, fuses and diodes are disposed in the case 10 and connected to control lines 46.
Control components of this kind are fixed to a mounting board by tightening screws, and conductive portions are connected by soldering, after which the components are accommodated within the case 10, which is made of metal. In this case, it is necessary to mount a number of components which differ in size, and assembly is carried out manually by a skilled worker. A problem that results is poor operating efficiency. Furthermore, since the case is made of metal, the case is heavy and high in cost. Since the sizes of the circuit components differ depending upon the current capacity of the motor, cases of different size must be fabricated. The result is poor productivity.
SUMMARY OF THE INVENTION
The present invention has been devised in order to solve the foregoing problems and its object is to provide a control unit in which cost can be reduced by improving upon the case for the control apparatus.
In accordance with the present invention, there is provided a control unit including a plastic case having a bottom portion provided at predetermined locations with ribs and a plurality of mounting holes of the same size and an upper portion provided with a predetermined number of engaging members, a plurality of power components such as transistors housed in said case and fixed at the mounting holes by screws and each being provided at an upper portion with energizing terminals of the same size, a printed circuit board having a back side on which there is formed a circuit pattern which contacts the energizing terminals of the power components and a front side on which circuit components such as resistors are disposed, the printed circuit board being fixed to the case by inserting the engaging members of the case in engaging holes formed in the board, and heat radiating fins selected to have a predetermined heat capacity and fixed to the case so as to be freely attachable and detachable.
Thus, in the control unit of the present invention, the bottom of the plastic case is provided with mounting holes at positions which are changed depending upon the sizes of the power components, the power components are fixed to the case by screws of the same size, the energizing terminals of each of the power components have a common size, and the case and printed circuit board are fixed by the engaging holes of the printed circuit board and the engaging members of the case. As a result, there is obtained a control unit which is light in weight and capable of being assembled automatically by a robot. In addition, by suitably selecting the power components and the heat radiating fins and then attaching them to the case, control units having a variety of current capacities can be realized using the same case.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating the general construction of a control unit having a case according to the present invention;
FIG. 2 is a view of the bottom of the case illustrated in FIG. 1;
FIG. 3 is a view illustrating power components mounted inside the
REFERENCES:
patent: 3940665 (1976-02-01), Seki
patent: 4015173 (1977-03-01), Nitsche
patent: 4177499 (1979-12-01), Volkmann
patent: 4399486 (1983-08-01), Petsch
patent: 4587593 (1986-05-01), Liautaud
patent: 4712160 (1987-12-01), Sato
Fanuc Ltd.
Tolin Gerald P.
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