JPH07175295A - Image forming device - Google Patents

Abstract

PURPOSE:To make an image quality constant by controlling the current value for electrifying a photoreceptor corresponding to the image output number of sheets. CONSTITUTION:A counting part 8 is made to count the image output number of sheets. A current detecting part 10 is made to read an electrification table 9 corresponding to the image output number of sheets counted by the counting part 8 for detecting the current value to be supplied to an electrifying unit 3 previously registered in the electrification table 9. A current control part 2 is made to control so as to supply the current corresponding to the current value detected by the current detecting part 10 to the electrifying unit 3 and to control the current made to flow to the electrifying unit 3 depending on the image output number of sheets.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a contact type charger that charges a photoreceptor by contact, and more particularly to stabilization of the charging potential of the photoreceptor.

[0002]

2. Description of the Related Art At present, there are non-contact type chargers for charging a photoconductor without contacting them, and contact type chargers for charging a photoconductor by contacting the same without any contact. The non-contact type charger can stabilize the charging potential of the photoconductor even if the electrostatic capacity of the photoconductor changes, but ozone is often generated. On the other hand, the contact type charger reduces the generation of ozone.

In the contact type charger, a constant current control method is generally used in which the charging current is controlled to be constant for reasons such as low manufacturing cost. In the contact type charger adopting the constant current control method, the amount of electricity required to keep the charging potential of the photosensitive member constant increases as the electrostatic capacity of the photosensitive member increases. A constant current value is set in advance according to the capacity.

[0004]

However, the electrostatic capacity of the photoconductor increases as the photoconductor fatigues. If the current value is adjusted to the initial electrostatic capacity of the photoconductor, the larger the number of output images, the lower the charging potential, causing problems such as background stains. Further, if the current value is adjusted to the electrostatic capacity after deterioration of the photoconductor, the charging potential becomes too high at the initial stage, which adversely affects the durability of the photoconductor.

The present invention has been made in order to solve the above drawbacks, and an image forming apparatus is obtained in which a current value for charging a photoconductor is controlled according to the number of output images to keep image quality constant. The purpose is to

[0006]

An image forming apparatus according to the present invention has a counting section, a charging table, a current detecting section, and a current control section, and the counting section counts the number of image outputs and charges the charging table. The number of images output and the current value sent to the charger are registered according to the number of images output, and the current detector reads the charging table based on the number of images output counted by the counter and sends the current value to the charger Then, the current control unit controls to send the current having the current value detected by the current detection unit to the charger.

[0007]

In the present invention, the counting section counts the number of output images. The current detection unit reads the charging table based on the number of output images counted by the counting unit, and detects the current value sent to the charger registered in the charging table in advance. The current controller controls the current of the current value detected by the current detector to be sent to the charger, and controls the current to be sent to the charger according to the number of output images.

[0008]

1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a layout diagram. As shown in the figure, the image forming apparatus according to the present invention includes a main controller 1, a current controller 2, a charger 3, an optical writer 4, a developing device 5, a transfer device 6, a static eliminator 7, a counter 8, The charging table 9 and the current detection unit 10 are provided.

The main controller 1 controls the entire image forming apparatus.
The current controller 2 has a DA converter 21 and a high voltage output device 22. The DA converter 21 converts the current value detected by the current detector 10 into an analog signal and sends it to the high voltage output unit 22. The high voltage output section 22 generates a current having the current value sent from the DA conversion section 21 and sends it to the charger 3. The charger 3 contacts the photoconductor 11 and applies a current generated by the high voltage output unit 22 to the photoconductor 11.
To charge the photoconductor 11. The optical writer 4 exposes the photoconductor 11 with a light image to form an electrostatic latent image on the photoconductor 11. The developing device 5 develops the electrostatic latent image on the photoconductor 11 with a toner. The transfer device 6 transfers the developed image onto the recording paper 13.
The static eliminator 7 neutralizes the photoconductor 11. The counting unit 8 is the recording paper 1
The number of output sheets of 3 is counted. The charging table 9 is the recording paper 13
The number of output sheets and the current value to be output corresponding to the number of output sheets are registered. Here, the number of output sheets and the current value corresponding to the number of output sheets are determined in advance by experiments or the like. The current detection unit 10 reads the charging table 9 based on the number of output sheets of the recording paper 13 counted by the counting unit 8 and detects the current value sent to the charger 3.

The operation of transferring an image to the recording paper 13 by the image forming apparatus having the above-mentioned structure will be described with reference to the layout diagram of FIG. 2 and the flowchart of FIG.

When image formation is started, the main controller 1 instructs the current detector 10 to detect the current value to be output. When the current detection unit 10 receives the instruction, it reads the charging table 9 and detects the current value corresponding to the output number "0" (step S).
1). The main controller 1 sends the current value detected by the current detector 10 to the current controller 2. The DA converter 21 of the current control unit 2 converts the sent current value into an analog signal, and the current control unit 2
To the high voltage output unit 22 of The high voltage output unit 22 generates a current of the current value sent from the DA converter 21, and supplies the generated current to the charger 3 (step S2).

Since the charger 3 is in contact with the photoconductor 11, it charges the surface of the photoconductor 11 to give the photoconductor 11 photosensitivity (step S3). When the photoconductor 11 rotates clockwise and the charged surface of the photoconductor 11 advances to the position of the optical writing unit 4, the optical writing unit 4 exposes the photoconductor 11 with an optical image. The photoconductor 11 is discharged by photoconduction and forms an electrostatic latent image. When the photoreceptor 11 further rotates and the formed electrostatic latent image advances to the developing device 5, the developing device 5 develops the electrostatic latent image with a toner. The transfer device 6 transfers the developed image onto the recording paper 13 (step S4). Thereafter, the cleaning unit 12 removes the excess toner on the surface of the photoconductor 11, and the charge removal unit 7 removes the charge on the photoconductor 11 (step S5).

When the charge removal is completed, the counting unit 8 causes the recording paper 13
The number of output sheets is counted up (step S6). Since the main control unit 1 gives an instruction to detect the current value every fixed number of sheets, when a constant reference number of sheets is counted from the start of counting or the previous detection of the current value (step S7),
The current detection unit 10 is instructed to detect the current value when the number of output sheets is counted. Upon receiving the instruction, the current detecting unit 10 reads the charging table 9 and detects the current value corresponding to the counted number of output sheets (step S8). The main controller 1 sends the current value detected by the current detector 10 to the current controller 2. The current control unit 2 generates a current of the sent current value and causes the generated current to flow in the charger 3 (step S9). The reference number can be freely set and changed.

When continuing (step S10), the operations from charging (step S3) to current generation (step S9) are repeated. As described above, the output of the recording paper 13 is repeated, the photoconductor 11 becomes fatigued, and the supplied current is increased as the electrostatic capacity of the photoconductor 11 increases, so that the charging voltage is kept constant and a good image is always produced. Obtainable.

In the above embodiment, the number of image output sheets and the current value to be sent to the charger 3 according to the number of image output sheets are registered in the charging table 9. The current value may be registered and the current detection unit 10 may detect the current value from the registered relational expression based on the number of output images.

Further, a detecting means for detecting the charging potential of the photoconductor 11 and a display means for displaying the charging potential detected by the detecting means may be provided so that the charging potential can be visually confirmed. As a result, the charged potential can be confirmed during maintenance work, and the maintenance work can be performed easily and reliably.

[0017]

As described above, the present invention counts the number of output images, detects the current value sent to the charger registered in advance in the charging table based on the counted number of output images,
The current of the detected current value is controlled to be sent to the charger, and the current sent to the charger is controlled according to the number of image output sheets.
Even if the photoconductor fatigues due to image output and the electrostatic capacity increases, the charging voltage of the photoconductor can be kept constant, and good images can always be formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a layout diagram.

FIG. 3 is a flowchart showing the operation of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main control part 2 Current control part 3 Charging device 4 Optical writing device 5 Developing device 6 Transfer device 7 Static eliminator 8 Counting part 9 Charging table 10 Current detection part 11 Photosensitive body 12 Cleaning part

Claims (1)

[Claims] 1. An image forming apparatus using a contact type charger that contacts and charges a photoconductor, comprising a counting section, a charging table, a current detecting section and a current control section, and the counting section is the number of image output sheets. The charging table registers the number of images output and the current value sent to the charger according to the number of images output, and the current detector reads the charging table based on the number of images output counted by the counter. An image forming apparatus, wherein the current value sent to the charger is detected, and the current controller controls to send the current having the current value detected by the current detector to the charger.