JPH0412697A - Electronic apparatus provided with motor - Google Patents

Abstract

PURPOSE:To improve the accuracy without enlarging the size of apparatus by connecting a DC motor through a first DC power supply circuit, isolated from a commercial power supply, with the commercial power supply thereby isolating the DC motor from a grounded frame while furthermore connecting the speed control circuit for the DC motor through a second DC power supply circuit, isolated from the commercial power supply, with the commercial power supply. CONSTITUTION:In a first DC power supply circuit 15, commercial source voltage is full-wave rectified through a diode bridge 22 and smoothed through a capacitor 23 to produce a DC voltage V1 for driving a DC motor 20. In a second power supply circuit 16, the first DC power supply circuit 15 is connected through a switching element 25 with the primary of an isolation transformer 24 having a secondary connected with a rectifying circuit 26 which produces a stabilized voltage VCC for driving the speed control circuit 18 for the DC motor 20. The DC motor 20 is isolated from the frame thereby isolated from the earth. Consequently, capacity of the second DC power supply 16 can be reduced resulting in reduction of size and improvement of reliability and performance of an electronic apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic device equipped with a motor suitable for a copying machine.

[Prior Art] Generally, DC motors are used in electronic devices equipped with motors suitable for copying machines and the like.

Conventionally, such a C motor is connected to a commercial power supply via a DC power circuit isolated from the commercial power supply, and the commercial power supply voltage is connected to a regulated DC voltage, for example 24V, for driving the motor via an isolation transformer. It was used as.

[Problems to be Solved by the Invention] However, since a relatively large power supply capacity is required to drive the C motor, the output capacity of the DC power supply circuit must be made considerably large. As a result, the volume of the DC power supply circuit increases, resulting in an increase in the size of the device and an increase in cost. Furthermore, the heat generated by the DC power supply circuit also increases, which impairs the performance and reliability of the device.

An object of the present invention is to solve the above-mentioned drawbacks, and to provide an electronic device equipped with a highly accurate motor without increasing the size of the device.

A DC motor is connected to the commercial power source through a first DC power circuit (not insulated from the commercial power source), and a second DC power source circuit (not insulated from the commercial power source) is connected to the commercial power source. A speed control circuit for controlling the speed of the DC motor is connected to the DC motor, and the DC motor is attached to a frame that is grounded via an insulating member.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a copying machine as an electronic device equipped with a motor. Reference numeral 1 denotes a document mounting table made of a transparent member such as glass, which is driven by a DC motor 20 (not shown) and moves back and forth in the direction of arrow a. to scan the original. A short-focus imaging element array 2 is disposed directly below the document placement table, and the document image placed on the document placement table is illuminated by an illumination lamp 13, and the reflected light image is transferred to the photosensitive drum 4 by the array 2. The top is exposed to slit light. Note that this photosensitive drum 4 is driven by a DC motor 20 and rotates in the direction of the arrow. Also 3
is a charger that uniformly charges 11 volts on a photosensitive drum 4 coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer.
Perform F-den.

The tram 4, which is uniformly charged by the charger 3, is subjected to image exposure by the element array 2, and an electrostatic image is formed. This electrostatic image is visualized by a developing device 5 using toner made of a resin or the like that softens and melts when heated. On the other hand, the recording paper P stored in the cassette S is the same
The photosensitive drum 4 is fed by a feeding roller 6 driven by a DC motor 20 and a pair of conveying rollers 7 that are rotated while being pressed against each other in the vertical direction in synchronization with the image on the photosensitive drum 4. sent to the top. Then, the toner image formed on the photosensitive drum 4 is transferred onto the recording paper P by the transfer discharger 8. Thereafter, the recording paper P separated from the photosensitive tram 4 by a known separating means is transported to a conveyance guide 9 which is also driven by the DC motor 20.
The image is guided to the fixing device 10, heated and fixed, and then discharged onto the tray 11. Note that after the toner image is transferred, residual toner on the photosensitive tram 4 is removed by a cleaner 12.

Here, FIG. 2 shows a control circuit for a DC motor 20 that drives the document placing table 1, photosensitive tram 4, and feeding roller 6 shown in FIG. 1, and 20 is a DC motor.

Reference numeral 21 denotes an outlet for plugging into a commercial power source, and this outlet 21 is connected to the first DC power circuit 15.

This first DC power supply circuit 15 is a diode bridge 22
and a smoothing capacitor 23, the commercial power supply voltage is full-wave rectified by the diode bridge 22, smoothed by the capacitor 23, and becomes a DC voltage Vl. Therefore, the first DC power supply circuit 15 is not insulated from the commercial power supply. This first
The DC power supply circuit 15 is connected to a second DC power supply circuit 16 so that its output voltage V1 is applied thereto, and this second DC power supply circuit 16 includes an isolation transformer 24 and a switching element 25 such as a transistor. are doing. The primary side of the isolation transformer 24 is connected to the first
is connected to the DC power supply circuit 15, and the secondary side is connected to the rectifier circuit 26.
A stabilized voltage VCC is output via the This voltage V
. C is isolated from the commercial power supply.

Further, the first DC power supply circuit 15 is connected to the motor circuit 17. That is, the motor circuit is a series circuit of the motor 20 and the switching element 29 with the flywheel diode 28 connected in parallel.

18 is a speed control circuit for controlling the speed of the DC motor 20, and this speed control circuit 18 is connected to the second DC power supply circuit 1.
A voltage Vcc from 6 is applied.

37 is a frequency generator for detecting the rotational speed of the DC motor 20, and is attached to the output shaft of the DC motor 20. The output of the frequency generator 37 is transmitted to the frequency-voltage converter 3
6, where it is converted into a voltage according to the frequency.

The difference between this voltage and a reference voltage from a reference voltage source 35 is amplified by an amplifier 34, and the eight amplified voltages are outputted to a comparator 32.

A triangular wave generator 33 compares this triangular wave with the output of the amplifier 34 in a comparator 32, and outputs a PWM waveform. The output of the comparator 32 turns on and off the switching element 29 of the motor circuit 17 via the photocoupler 30.

In this way, the duty ratio of the switching element 29 is controlled so that the rotation speed corresponds to the reference voltage 35, and the DC motor 20 is controlled to rotate at a constant speed.

FIGS. 3 and 4 show how the DC motor 20 is attached. Reference numeral 50 denotes a frame, which is made of a conductive member such as an iron plate. Furthermore, in the two-style power supply court system in the district, the frame 50 is grounded to the earth by attaching a ground wire. On the other hand, when power is supplied using a power supply cord including three types of ground wires, such as in America and Europe, the ground wires are connected to the frame 50. Motor 20 is attached to frame 50. The motor 20 contacts the frame 50 with an insulating member 51 in between, and the hiss 5 generated from an insulating material such as plastic
2 and 52'. Therefore, the motor 20 is mounted insulated from the frame 50 and is insulated from the ground.

Next, the installation of the DC motor 20 from the grounded frame 50 via the insulating member 51 will be described.

For boat fishing, the outer sheath of motors is now made of conductive metal, and if such a motor is mounted on a grounded frame, the motor outer sheath will also be grounded, and the motor shaft will also be grounded. Become.

(Usually bearings are not insulated.) Therefore, if a motor power source that is not insulated from the commercial power source is used, the safety standards in each diagram and the distance between the motor's internal windings, brushes, and other live parts and the outer jacket Creepage/clearance and dielectric strength requirements are required, leading to larger motors, lower performance, and higher costs.

Therefore, by attaching the motor 20 while insulating it with the insulating member 51, the requirements of the above-mentioned safety standards can be met, and a general DC motor can be used.

Furthermore, by driving the above-described DC motor 20 with the first DC power circuit 15 that is not insulated from the commercial power source, the capacity of the second DC power circuit 16 that is insulated from the commercial power source can be reduced.

Furthermore, the speed control circuit 18 including the frequency detection section is connected to the secondary side of the transformer 24 of the second DC power supply circuit 16 insulated from the commercial power supply, thereby smoothly complying with the safety standards shown in each figure.

[Other Embodiments] A second embodiment of the present invention will be explained using the control circuit shown in FIG. 5. Components in the figure that are the same as those in FIG. 2 are designated by the same numbers, and detailed explanation thereof will be omitted.

The motor circuit 17 includes a switching element 40 and a diode 4
1. A step-down DC-DC converter is constructed from the choke coil 42 and the capacitor 43 to step down the voltage (1) to the voltage (2)8. Then, the voltage vM becomes the voltage applied to the motor 20. Therefore, the reference voltage source controls the duty ratio of the switching element 40 and changes the voltage (2) so that the rotation speed corresponds to the reference voltage from 35.

In the above-mentioned embodiment, the rectified and smoothed commercial power supply is directly used as the driving power for the DC motor 20, so the voltage is as high as about 144 V in Japan, for example, and the DC motor 20 is also special. However, in this embodiment, since the voltage is stepped down and substituted, -
A C motor can be used for boat fishing, which is advantageous in terms of cost.

[Effects of the Invention] As detailed above, according to the present invention, the C motor is connected to the commercial power source via the first DC power circuit which is not insulated from the commercial power source, and the C motor is connected to the commercial power source. The above-mentioned D
A speed control circuit for controlling the speed of the DC motor is connected to the second motor, which is insulated from the commercial power supply because the DC motor is attached to a grounded frame via an insulating member.
The capacity of the DC power supply circuit can be reduced, and the device can be made smaller. Furthermore, the amount of heat generated can be reduced, the reliability and performance of the device can be improved, and the cost can also be reduced. By connecting the motor speed control circuit to the secondary side of the transformer 24 of the second DC power supply circuit 16, which is isolated from the commercial power supply, the safety standards shown in each figure can be obtained smoothly and without increasing costs. I can do something.

By attaching the motor to the frame in an insulated manner, the requirements of the above-mentioned safety standards can be met, and an ordinary DC motor can be used.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a copying machine as an electronic device equipped with a motor, according to an embodiment of the present invention, FIG. 2 is a control circuit diagram of a motor used in the device shown in FIG. 1, and FIG. 1, FIG. 4 is a sectional view of FIG. 3, and FIG. 5 is a motor control circuit diagram showing another embodiment of FIG. S2. 15... First DC power supply circuit 16... Second DC power supply circuit 17... Motor circuit 18... Motor speed control circuit 20... Motor 50... Frame 51... Insulation Element

Claims (2)

[Claims] (1) A first power source connected to a commercial power source that is not insulated from the commercial power source.
A second DC motor is connected to the commercial power supply through a DC power supply circuit, and a second DC motor is connected to the commercial power supply through a second DC power supply circuit.
An electronic device equipped with a motor, characterized in that a speed control circuit for controlling the speed of the DC motor is connected via a power supply circuit, and the DC motor is attached to a grounded frame via an insulating member. (2) The first DC power circuit has a bridge circuit and a smoothing capacitor, the second DC power circuit has an isolation transformer, and the motor is connected to the output end of the bridge circuit through the smoothing capacitor. 2. The electronic device according to claim 1, wherein the speed control circuit is connected to a secondary side of the isolation transformer.