JP2007072093A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing the variance of image density. <P>SOLUTION: In the image forming apparatus, electrifying DC output is detected, for example, and developing DC output and laser beam quantity are controlled with the detected voltage as reference voltage, that means, any one of the electrifying DC output, the developing DC output and the laser beam quantity is set as reference so as to control the other output. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine using an electrophotographic process.

  In an image forming apparatus using an electrophotographic process, the image density is substantially determined by the charging potential of the photosensitive drum, the latent image potential of the latent image portion, and the developing potential during toner development.

  These depend on the DC component of the charging voltage, the DC component of the developing voltage, and the light amount of the optical element for latent image recording.

  Since the printing density of the image forming apparatus is required to be stable, each of the three outputs is controlled to have a predetermined value. For example, Japanese Patent Application Laid-Open No. H10-228688 describes a technique for controlling the charging voltage and the developing voltage to keep the image density appropriate.

  FIG. 3 shows a circuit for controlling the DC component of the charging output and the DC component of the development output to predetermined values.

  In FIG. 3, 1 is a photosensitive drum which rotates in the direction of the arrow. Reference numeral 2 denotes a charging roller, 3 denotes a developing sleeve, and 4 denotes a transfer roller. A recording paper (not shown) is passed between the photosensitive drum and the toner image on the photosensitive drum to transfer the toner image on the recording paper. 5 is a light for forming a latent image, 6 is a charging voltage generating circuit, 7 is a developing voltage generating circuit, 8 and 9 are error amplifiers, 10 is a reference voltage for charging output, and 11 is a reference voltage for developing voltage. R1, R2, R3, and R4 are resistors.

  The charging circuit will be described as a representative. The output of the charging voltage generation circuit 6 is applied to the charging roller 2 and the voltage divided by the resistors R1 and R2 is converted into a DC voltage through the low-pass filter LPF1. Is input to the error amplifier 8. A reference voltage of 10 is input to the other input terminal of the error amplifier 8, and an output of the error amplifier is input to a charging voltage generation circuit of 6. The charging voltage generation circuit 6 changes the DC voltage according to the output voltage of the error amplifier 8. Therefore, a constant voltage corresponding to the reference voltage of 10 is output as the DC voltage of the charging output.

The development circuit also operates in the same manner as charging.
Japanese Patent Laid-Open No. 5-2301

  However, in the above method, the output DC voltage varies due to variations in the reference voltage and variations in the resistance value. In addition, the light amount of the latent image recording optical element naturally varies.

  If these variations occur randomly, the printing density varies, which is inconvenient.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of effectively suppressing variations in print density.

  In order to solve these problems, the present invention uses one of these three outputs as a reference voltage for the other outputs.

  By so doing, it is possible to correlate the variations in each output, and it is possible to reduce the variation in print density by keeping the correlation between these outputs constant.

  That is, the technical contents of the present invention can solve the above-described problems by including the following configuration.

  (1) A development DC voltage detection circuit for detecting a DC component of the development voltage is provided, and the DC voltage of the charging voltage and / or the light quantity of the optical element for latent image recording are used with the output of the development DC voltage detection circuit as a reference voltage. An image forming apparatus characterized by controlling.

  (2) A charging DC voltage detection circuit for detecting a DC component of the charging voltage is provided, and the output voltage of the charging DC voltage detection circuit is used as a reference voltage to determine the DC voltage of the development voltage and / or the light quantity of the optical element for latent image recording. An image forming apparatus characterized by controlling.

  (3) A light amount detection circuit for detecting the light amount of the optical element for latent image recording is provided, and the DC voltage of the developing voltage and / or the DC component of the charging voltage are controlled using the output of the charging DC voltage detecting circuit as a reference voltage. An image forming apparatus characterized by that.

  According to the present invention, it is possible to effectively suppress variations in print density of the image forming apparatus.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 1 shows an embodiment of the present invention.

  In FIG. 1, 1 to 5 are the same as FIG.

  Reference numeral 12 denotes a charging output generation circuit, and the output is applied to the charging roller 2.

  The output is divided by resistors R5 and R6, and the divided potential is divided into a DC voltage by a low-pass filter LPF4 and input to the error amplifier 14.

  The output of the 13 development output generation circuit is applied to the 3 development sleeve.

  Further, the voltage is divided by the resistors R7 and R8, is divided into a DC voltage by the low-pass filter LPF3, and is input to the error amplifier 14.

  The output of the error amplifier 14 is input to 13 development output generation circuits.

  The output voltage of the development output generation circuit 13 changes its output DC voltage in accordance with the potential input from the error amplifier 14.

  Accordingly, the output DC voltage of the 13 development output generation circuit is equal to the DC voltage of the voltage divided by R7 and R8, and equal to the DC potential obtained by dividing the output of the 12 charge output generation circuit by R5 and R6. Be controlled.

  As a result, the development output DC voltage changes according to the charging output DC voltage.

  Even if the charging output DC voltage varies, the relationship between the charging output DC voltage and the development output DC voltage is kept constant, so that variations in printing density can be reduced.

[Other embodiments]
FIG. 2 shows another embodiment of the present invention.

  In FIG. 2, 1 to 5 are the same as FIG.

  The charging output generation circuit 12, the development output generation circuit 13, the error amplifier 14, and the resistors R5, R6, R7, and R8 are the same as those in FIG. Reference numeral 15 denotes a laser diode, and 16 denotes a laser diode light quantity adjustment circuit.

  In this embodiment, the same control is performed for the light intensity of the optical element for latent image recording, which is another parameter affecting the print density, and in this embodiment, the light intensity of the laser diode in this embodiment. The purpose is to further suppress variation.

  The output of the 12 charging output generation circuit is applied to the charging roller 2 and divided by the resistors R5 and R6, and is divided into a DC voltage by the low-pass filter LPF5.

  This voltage is input to the error amplifier 14 and also to the light amount adjustment circuit 16.

  The output DC voltage of the 13 development output generation circuit is controlled so that the DC voltage of the voltage divided by R7 and R8 is equal to the DC potential obtained by dividing the output of the 12 charge output generation circuit by R5 and R6. The

  The light quantity adjustment circuit 16 changes the light quantity of the laser diode 15 in accordance with the output of the low-pass filter LPF5.

  That is, the light quantity of the laser diode 15 is kept at an appropriate value according to the DC potential obtained by dividing the output of the charging output generation circuit by R5 and R6.

  By doing so, not only the development DC voltage but also the light amount of the optical element for latent image recording can be maintained at an appropriate value according to the charging DC voltage, and further, variations in print density can be suppressed.

  In all of these embodiments, the output DC voltage of the charging output generation circuit is described as a reference. Naturally, the output DC voltage of the charging output generation circuit and the latent image recording are based on the output DC voltage of the development output generation circuit. The output light voltage of the charging output generation circuit and the development output generation circuit may be controlled based on the light amount of the optical element for latent image recording.

The block diagram which shows the Example of this invention Block diagram showing another embodiment of the present invention Block diagram of conventional form

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Developing sleeve 4 Transfer roller 5 Light 6 and 12 for forming a latent image Charging voltage generation circuits 7 and 13 Development voltage generation circuits 8 and 9 and 14 Error amplifier 15 Laser diode 16 Light quantity adjustment circuit

Claims (3)

A development DC voltage detection circuit that detects a DC component of the development voltage is provided.
An image forming apparatus that controls a DC voltage of a charging voltage and / or a light amount of an optical element for recording a latent image using an output of the developing DC voltage detection circuit as a reference voltage. Equipped with a charging DC voltage detection circuit that detects the DC component of the charging voltage,
An image forming apparatus characterized by controlling a DC voltage of a developing voltage and / or a light quantity of an optical element for latent image recording using an output of the charging DC voltage detection circuit as a reference voltage. Provided with a light amount detection circuit for detecting the light amount of the optical element for latent image recording,
An image forming apparatus that controls a DC voltage of a developing voltage and / or a DC component of a charging voltage using an output of the charging DC voltage detection circuit as a reference voltage.

Images