JPS5879452A - Motor-driven equipment - Google Patents

Abstract

PURPOSE:To enhance the shielding effect of a motor-driven equipment and to suppress the spark noise of the device by combining a toroidal coil, a through condenser and conductive paint. CONSTITUTION:When a drive motor of a drive unit (b) is rotated, spark noise generated between a commutator and motor brushes 9, 9' is suppressed through a motor frame metal 6, conductive paint coated on the inner surface of a non- conductive case 1, a shielding circuit made of a metal plate 3, and a power source via condensers 4, 4' through toroidal choke coils 10, 10' to motor brushes 9, 9' in an electric circuit.

Description

[Detailed Description of the Invention] The present invention suppresses electrical noise caused by sparks generated between a commutator and brushes, and prevents the electrical noise from having an adverse effect on radio equipment such as televisions and radios, and NC devices. With the goal.

Conventionally, as a method for preventing spark noise in electric equipment, a structure has been adopted in which a metal layer is formed using metal plating or metal foil over the entire inner surface of a non-conductive case to prevent spark noise from radiating to the outside. However, it has the disadvantage of poor workability and is not suitable for mass production in terms of man-hours.

The present invention aims to eliminate the above-mentioned conventional drawbacks, and one embodiment thereof will be described below with reference to the accompanying drawings.

In Figures 1 and 2, a is a drive unit that generates power, a power supply unit that supplies DC power to b), and C is a clutch unit d that has a mechanism that partially disconnects the power source with torque.
This is a deceleration unit that transmits decelerated power to.

A concave locking portion 2 is provided on a part of the inner surface of the non-conductive coos 1, and a feedthrough capacitor 4.times.4' is attached to a metal plate 3 having a thickness that fits into the locking portion 2.

As shown in FIG. 2 The metal plate 3 fitted into the locking part 2 and the motor frame metal part 6 are electrically connected by a conductive paint 6. The power cord 7 is connected to the motor through the terminals of the feed-through capacitors 4, 4' and toroidal choke coils 10, 10' embedded in the resin part 8 of the motor frame at the position closest to the motor brushes 9, 9'. It is connected to the brushes 9, 9'.

In the above configuration, when the electric motor of the drive unit b is rotated, the spark noise generated between the commutator and the motor brushes 9'9' is suppressed by coating the motor frame metal part 6 and the inner surface of the non-conductive case 1. Conductive paint6. This is suppressed by a shield circuit consisting of a metal plate 3 and an electric circuit that supplies power from the power source to the motor brushes 9, 9' via feedthrough capacitors 4, 4', toroidal choke coils 10, 10', and to the motor brushes 9, 9'. As a result, the spark noise radiated to the outside had the characteristics shown in FIG. 6. As is clear from a comparison with FIG. 4, it can be seen that the above configuration eliminates most of the spark noise.

In the above embodiment, an electric circuit using a toroidal coil and a feedthrough capacitor and a shield circuit made of conductive paint were used together, but the material of the conductive paint was made of a conductive reflective material. By coating the entire inner surface, the toroidal coil can be omitted.

In short, it is sufficient to have a circuit configuration based on the conductivity of the conductive paint and shielding properties due to the reflective property.

In the electrical circuit diagram shown in Figure 3, 4 and 4' are feed-through capacitors, 6 is conductive paint, 9 and 9' are motor brushes, 10 and 10' are toroidal choke coils, and 1
1 is an electric motor, 12 is a bridge diode, 13 is a capacitor, 14 is a varistor, and 15 is an AC power terminal.

As described above, according to the present invention, the combination of the toroidal coil, the feedthrough capacitor, and the conductive paint can enhance the shielding effect and suppress spark noise.
Its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view of an electric screwdriver according to an embodiment of the present invention, FIG. 1(b) is a sectional view taken along line A-A', and FIG. FIG. 2 (0)) is a sectional view of the main part showing the connection between the plate and the motor frame, FIG. 3 is an electric circuit diagram of the electric screwdriver according to the same embodiment, and FIG. FIG. 6 is a graph showing the electrical noise measurement results of an electric screwdriver that does not implement the present invention. 1... Non-conductive case, 2... Locking part, 3... Metal plate, 4, 4',...
,,Feedthrough capacitor, 5 ,,,,,, Conductive paint, 9
, 9' 0. ．． 1. , motor brush, 10 , 10
' , , , , , Chalk , 6 , , , , Frame. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Fig. 3 Fig. 4 Mr. Shuubai Shodai 1 (Koshi) No. 554 Competent Knight's Lustful Relative' (MνJr)

Claims (4)

[Claims] (1) an electric motor, a non-conductive case surrounding the electric motor, and a power connection section provided in the non-conductive case to which a power cord connected to the electric motor is fixed;
A choke coil connected between the brush of the electric motor and the power source and near the brush, a feed-through capacitor connected between the choke coil and the power source, and a feed-through capacitor that holds the feed-through capacitor and connects at least the electric motor and the power source. An electric device that has a metal plate that shields the connection part and electrically connects the metal plate and the frame of the electric motor. (2) The electric device according to claim 1, wherein the metal plate is clamped by fitting into a locking portion provided on the inner surface of the cover. (3) The above metal plate and electric motor frame are:
On the inner surface of the non-conductive case, conductive paint is applied between the locking part where the metal plate and the inner surface of the valve-facing conductive wire contact and the part where the electric motor frame and the inner surface of the non-conductive case contact. The electric device according to claim 1, wherein the electrical connection is made by applying a conductive paint to the metal plate and the frame of the electric motor. (4) The electric device according to claim 1, wherein the choke coil is a toroidal choke coil.