JP2004240230A - Electrophotographic printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric current limit circuit for a rotating polygon mirror motor in which the heat generation and the burnout of a motor driving circuit and a rotating polygon mirror motor at the time of the lock of the rotating polygon mirror motor is prevented and the acceleration time of the rotating polygon mirror motor is kept equivalent to that of a conventional type. <P>SOLUTION: A plurality of limit values of electric current of the rotating polygon mirror motor are given and a control is performed to switch the limit values of the electric current according to the value of revolution of the rotating polygon mirror motor. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic printing device using a rotating polygon mirror motor.
[0002]
[Prior art]
An example of the prior art will be described with reference to FIG.
[0003]
When the rotating polygon mirror motor 3 is driven by connecting a constant voltage power supply, a large current flows through the rotating polygon mirror motor 3 when the rotating polygon mirror motor 3 starts and accelerates because the back electromotive force of the motor is small. Therefore, generally, the current flowing through the rotary polygon mirror motor 3 is detected by the current sensor 2 and compared with the reference voltage 12 by the comparator 13. If a current larger than the specified value flows, the operation of the motor drive circuit 1 is stopped. The motor is stopped, and control is performed so that the current flowing through the rotary polygon mirror motor 3 becomes equal to or less than a specified value. This control is used at the time of starting and accelerating the rotary polygon mirror motor 3. When the rotation speed of the rotary polygon mirror motor 3 increases and the back electromotive force increases, the current flowing through the rotary polygon mirror motor 3 decreases. 13 will not work.
[Non-patent document 1]
"Special Feature: Servo Circuit Technology for Brushless Motors", Transistor Technology SPECIAL No. 73, CQ Publishing Company, published in January 2001, p. 10-11
[0004]
[Problems to be solved by the invention]
When the value of the current to be limited in the circuit for limiting the current to the rotary polygon mirror motor is set to one, the value of the current to be limited is “acceleration time from the start of the rotary polygon mirror motor to the reaching of the specified number of revolutions”, The setting is made in consideration of “the current value when the rotating polygon mirror motor is rotating at the specified number of revolutions is not reduced”.
[0005]
Generally, in order to shorten the acceleration time of the rotary polygon mirror motor, the current limit value for the rotary polygon mirror motor is set to be high. Therefore, when the rotating polygon mirror motor is locked, a large current flows through the motor driving circuit and the rotating polygon mirror motor, and there is a problem that the motor driving circuit and the rotating polygon mirror motor generate heat and burn out.
[0006]
The present invention reduces the current limit value to the rotating polygon mirror motor when the rotating speed of the rotating polygon mirror motor is low, and reduces the current to the rotating polygon mirror motor when the rotating speed of the rotating polygon mirror motor increases. An object of the present invention is to provide a motor drive circuit and a control circuit for preventing heat generation and damage of the motor even when the rotary polygon mirror motor is locked without increasing the limit value and without deteriorating the acceleration characteristics of the rotary polygon mirror motor.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided an electrophotographic printing apparatus for forming a latent image on a photoreceptor by a laser beam generating means and a rotary polygon mirror for scanning the laser beam. It is characterized by having means for switching the current limit value of the rotary polygon mirror motor according to the number.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
[0009]
FIG. 1 shows a configuration in which there are two limit values of the current flowing through the rotary polygon mirror motor 3.
[0010]
The rotary polygon mirror motor 3 is driven by the motor drive circuit 1. The rotation speed of the rotary polygon mirror motor 3 is detected by a rotation detection FG sensor 4, amplified by an FG amplifier 5, and converted into a voltage by an F / V converter 6. The output of the F / V converter 6 is compared with the value of the reference voltage C7 by the comparator B8, and when the rotation speed of the rotary polygon mirror motor 3 becomes higher than the set rotation speed, a signal is output from the comparator B8. The output of the reference voltage A9 and the output of the reference voltage B10 are switched by the output of the comparator B8. When the rotation of the rotary polygon mirror motor 3 is low, the reference voltage A9 is selected, and when the rotation of the rotary polygon mirror motor 3 is high, the reference voltage B10 is selected.
[0011]
The comparator A11 compares the value of the reference voltage A9 or the reference voltage B8 with the value of the current sensor 2. When the output of the current sensor is larger than the reference voltage, the comparator A11 instructs the motor drive circuit 1 to stop the motor drive. give. When the reference voltage A9 is selected by the output of the comparator B8, the current limit value to the rotating polygon mirror 3 is low. When the reference voltage B10 is selected by the output of the comparator B8, the rotating polygonal mirror is rotated. The current limit to mirror 3 is higher.
[0012]
The motor drive circuit 1 and the rotary polygon mirror when the rotary polygon mirror motor 3 is locked to switch the value for limiting the current flowing through the rotary polygon mirror motor 3 according to the number of rotations of the rotary polygon mirror motor 3 according to the series of flows. Heat generation and smoke generation of the motor 3 can be prevented. Further, when the rotating polygon mirror motor 3 rotates, the current limit value to the rotating polygon mirror motor 3 is increased according to the number of rotations, so that the acceleration characteristics of the rotating polygon mirror motor 3 are prevented from being impaired.
[0013]
【The invention's effect】
As described above, according to the present invention, the limit value of the current flowing through the motor is switched according to the number of revolutions of the rotating polygon mirror motor. Heat generation and burnout can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of the present invention.
FIG. 2 is a block diagram illustrating an example of a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Motor drive circuit, 2 ... Current sensor, 3 ... Rotating polygon mirror motor, 4 ... Rotation detection FG sensor, 5 ... FG amplifier, 6 ... F / V conversion, 7 ... Reference voltage C, 8 ... Comparator B, 9 Reference voltage A, 10 Reference voltage B, 11 Comparator A, 12 Reference voltage, 13 Comparator.

Claims (1)

In an electrophotographic printing apparatus in which a latent image is formed on a photoreceptor by a laser beam generating means and a rotary polygon mirror that scans the laser beam, a current limit value of the rotary polygon mirror motor according to the number of rotations of the rotary polygon mirror motor. An electrophotographic printing apparatus, comprising: means for switching between (a) and (b).

Images