JPH10149009A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus capable of appropriately controlling image density by minimizing a load applied to cleaning. On the surface of a photoconductor, a pattern 21 for measuring and controlling the toner concentration having a length equal to or less than half the length of the cleaning blade in the photoconductor longitudinal direction is formed. A large number of the patterns 21 are formed in a row in the longitudinal direction of the photoconductor 1, and the large number of the patterns 2
1, and is detected by a photo sensor 22 provided in correspondence with 1. The pattern 21 includes Y, M, C,
The image is formed so as to be shifted for each Bk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly to a pattern (toner image) for measuring and controlling toner density formed on an image carrier. The present invention relates to a toner density control technique based on the detection result of (1).

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile or the like utilizing an electrophotographic process, an electrostatic latent image is formed by performing image exposure (light writing) on a uniformly charged photosensitive member surface. I do. The electrostatic latent image is developed with a toner in a developing section to obtain a visualized toner image. This toner image is transferred onto a sheet and fixed as described below. By the way, in order to keep the density of this toner image constant and maintain the image quality,
The toner density control is being performed.

[0003] The most common method of toner density control is to form a pattern in a non-image area of a photoreceptor, detect the amount of reflected light from the pattern, compare it with a reference value obtained in advance, and determine the reference value. The toner density is controlled by adjusting the charging potential, adjusting the amount of light, adjusting the developing bias, and the like so as to approach the values. For example, JP-A-55-90981
In this publication, a developing density detector is provided on a part of the photoreceptor having a smooth image forming surface, and toner replenishment is controlled in accordance with the amount of reflected light from the detected part, thereby keeping the toner density constant. A technique for obtaining a clear image with an appropriate density has been proposed.

Japanese Unexamined Patent Publication No. Sho 59-195684 discloses a device for maintaining the size of a reference density plate image formed on a photosensitive member substantially constant even when the photographing magnification is changed. In addition, there is proposed a technique for preventing waste of toner due to excessively large reference density plate image formation, increase in load on the cleaning device, and reduction in toner supply control density.

[0005]

However, the above-mentioned 2)
In any of the prior arts including the related art, since the solid measurement and control pattern images were formed at the same position in the longitudinal direction of the image carrier, the solid transfer was always performed at the same position on the cleaning blade or the cleaning brush. The pattern image was input, and the cleaning was a heavy load.

In the case of one-color development such as a black-and-white image, a pattern image forms only one pattern at a time, but in the case of four-color development, a color image forms patterns for four colors, Alternatively, in order to control the gradation, several patterns with different densities are created for one color. Therefore, when a pattern image is formed at the same position, the cleaning load is further increased compared to a monochrome image machine. It has become big. As a result, there is a problem that the cleaning device is quickly consumed and cleaning failure easily occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of appropriately controlling the image density while minimizing the load required for cleaning.

[0008]

In order to achieve the above object, the present invention is directed to an image bearing member for carrying a toner image obtained by visualizing an electrostatic latent image, and an image bearing member on the image bearing member. A cleaning device having a toner removing member such as a cleaning blade or a cleaning brush for removing toner, a toner density measuring means for measuring the density of a toner on an image carrier, and detecting the density of a control pattern; Control means for controlling the toner density based on the density detection result by the means, wherein the pattern is formed by changing the position in the longitudinal direction of the image carrier, and the length of the pattern is changed by the toner removing member. Of the image carrier length in the longitudinal direction
/ 2 or less.

According to a second aspect of the present invention, there is provided an image carrier for carrying a toner image obtained by visualizing an electrostatic latent image, and a cleaning blade or a cleaning brush for removing residual toner on the image carrier. A cleaning device having a toner removing member, a toner density detecting means for detecting the density of a pattern for measuring and controlling the toner density on the image carrier, and a control for controlling the toner density based on the density detection result by the toner density detecting means And a plurality of toner concentration detecting means provided in the longitudinal direction of the image carrier.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an image forming unit (around a photoconductor) of a color copying machine according to an embodiment of the present invention. The drum-shaped photoconductor 1 rotates in a counterclockwise direction as indicated by an arrow A. Around the photoreceptor 1, a charger 2, a Bk (black) developing device 3, a C (cyan) developing device 4, an M (magenta) developing device 5, a Y (yellow) developing device 6, a static eliminator 7 before cleaning, A cleaning device 8, a neutralizing lamp 9, and an intermediate transfer belt 10 are arranged. Further, the intermediate transfer belt 10 rotates clockwise as indicated by an arrow B, and transfers the toner image formed on the photoconductor 1. Around the intermediate transfer belt 10, a paper transfer device 11,
An intermediate transfer belt cleaning device 12 and a lubricity imparting agent application device 13 are provided.

In the vicinity of the photoreceptor 1 and in the vicinity of the downstream side of the charger 2, there is an optical writing system schematically indicated by the symbol L.
Color scanner (not shown) (color image reading device)
Thus, data read for each color separation of blue, green, and red is converted into an optical signal, and optical writing corresponding to the original image is performed, thereby forming an electrostatic latent image on the photoconductor 1. . In addition, a toner density detecting device 15 including a large number of photo sensors is arranged around the photoconductor 1 and near the downstream side of the Y developing device 6 as described later with reference to FIG.

Next, a series of image forming processes in the image forming unit configured as described above will be described. When the image data read by the color scanner is formed using any one of the Bk developing device 3, the C developing device 4, the M developing device 5, and the Y developing device 6, for example, the Bk developing device 3 will be described. The photosensitive drum 1 is rotated in the direction of the arrow A, and performs the optical writing on the photosensitive member 1 charged by the charger 2 as described above to form an electrostatic latent image.
Causes the toner to adhere (develop), thereby visualizing the electrostatic latent image. Then, the visualized toner image on the photoconductor 1 is indicated by an arrow B.
The image is transferred onto the intermediate transfer belt 10 rotating in the direction (intermediate transfer).

After the intermediate transfer, the photosensitive member 1 is neutralized by a pre-cleaning static eliminator 7 and then cleaned by a cleaning device 8.
Then, the transfer residual toner is removed, and the charge is further removed by the charge removing lamp 9.

The toner image transferred onto the intermediate transfer belt 10 is transferred (paper transfer) onto transfer paper by a paper transfer unit 11. Then, the transfer residual toner on the intermediate transfer belt 10 is removed by the intermediate transfer belt cleaning device 12.
This series of operations is repeated.

On the other hand, if the image data read by the color scanner is not formed into a toner image unless a plurality of developing units among the developing units 3, 4, 5, and 6 are used, for example,
A case in which an image is formed by the types of developing devices will be described.
First, a portion to be developed by the Bk developing device 3 is read by a color scanner, and is written on the photoreceptor 1 to form an electrostatic latent image. Then, the electrostatic latent image is developed by the Bk developing device 3,
Intermediate transfer is performed on the intermediate transfer belt 10. Next, the portion developed by the C developing device 4 is read by a color scanner, and is similarly developed on the photoconductor 1 and intermediately transferred onto the intermediate transfer belt 10. Hereinafter, M and Y are similarly intermediate-transferred onto the intermediate transfer belt 10. Then, the intermediate transfer belt 10
Above, the toner images that have been intermediately transferred in the order of Bk, C, M, and Y and are superimposed are transferred onto transfer paper by the paper transfer unit 11. The transfer residual toner is removed by the intermediate transfer belt cleaning device 12. This series of operations is repeated.

The image forming apparatus shown in the present embodiment is provided with a process control means for forming a latent image on the photosensitive member 1 with the toner density, the charging potential on the photosensitive member 1 and the developing bias. In this case, the laser light power is controlled. The process control means detects a pattern (toner image) for measuring and controlling the toner density formed on the non-image area of the photoreceptor 1 by the toner density detecting device 15 based on the toner density and the charge. The potential, the developing bias, and the laser beam power are controlled.

FIG. 2 is a perspective view of the photosensitive member showing the size of a pattern (toner image) for toner concentration measurement and control, and FIG. 3 is a perspective view of the photosensitive member showing an actual pattern arrangement. The laser beam power at the time of writing on the photoreceptor 1 is divided into 10 levels from PW1 to PW10 from high to low power, and a pattern for density and measurement control is set to 10 per color.
Create pieces. The size of each pattern 21 is 30 mm × 20 mm as shown in FIG.
As shown in FIG. 3, ten patterns 21-1 to 21-10 are formed on one row in the longitudinal direction of the photoconductor 1. This pattern 21 is formed in each color of Bk, C, M, and Y.

FIG. 4 is a diagram showing a pattern and a photosensor provided to face the pattern. The toner density detecting device 15 includes ten patterns 21-1 to 21-21.
Corresponding to -10, ten photosensors 22-1 to 22-10 each including a light emitting element and a light receiving element are provided. Then, the respective patterns 21-1 to 21-10 are detected by the respective photo sensors 22-1 to 22-10. Specifically, light is emitted from the light emitting portion of the photo sensor 22 to the pattern 21, the reflected light is received by the light receiving portion, and the level is detected. That is, if the amount of reflected light is large, the toner density is low, and if the amount of reflected light is small, the toner density is high.

The process control means (not shown) includes:
As described above, each process is controlled based on the pattern density detection result of the toner density detection device 15. The control by the process control is performed once per 150 cumulative copies and when the fixing temperature is lower than 100 ° C. after the main switch is turned on. Separately, the developing units 3 and 3 are provided based on the output of the photo sensor 22.
The toner concentrations in 4, 5, and 6 are also controlled. This is to supply toner into the developing units 3, 4, 5, and 6 based on the detection result of the photo sensor 22-1 when forming the pattern 21-1 of the highest density PW1. Yes, usually, Bk, C, M,
All the colors of Y are formed, and the toner density is controlled.

FIG. 5 is a diagram showing a state in which each color pattern is formed with a shift, and FIG. 6 is a diagram showing a state in which patterns are formed so that the order of density is alternated. When the pattern 21 of all colors of Bk, C, M, and Y is formed in the non-image area every time copying is performed, as shown in FIG. 5, the pattern 21 is not always formed at the same position. , Bk, C,
Images are formed with M and Y shifted. When ten patterns 21 are formed, as shown in FIG.
An image is formed alternately at a position having a high density.

Referring again to FIG. 2, the length of the pattern 21 in the longitudinal direction of the photoconductor is 30 mm, and the length of the cleaning blade of the cleaning device 8 in the longitudinal direction of the photoconductor is, for example, as follows.
345 mm. The length of the pattern 21 may be smaller than that, but the length of the pattern 21 is set to be equal to or less than half the length of the cleaning blade (or cleaning brush). As described above, in the embodiment of the present invention, the length of the pattern 21 is set to be equal to or less than half the length of the cleaning blade and the image is formed by changing the position in the longitudinal direction of the photoconductor. It is possible to prevent the input of the untransferred toner density measurement and control pattern 21 continuously at the same position in the hand direction and reduce the load on cleaning.

[0022]

According to the first aspect of the present invention, the length of the toner concentration measurement and control pattern in the longitudinal direction of the image carrier is determined by the length of the toner removing member such as a cleaning blade or a cleaning brush in the longitudinal direction of the image carrier. Since the image is formed by changing the length to less than half of the length and changing the position in the longitudinal direction of the image carrier, the toner removal member is used for measuring and controlling the toner density which is not transferred continuously at the same position in the longitudinal direction of the image carrier. Can be prevented, and the load on the cleaning can be reduced.

According to the second aspect of the present invention, when a plurality of patterns for measuring and controlling the toner density are prepared, the plurality of patterns are formed in the longitudinal direction of the image carrier and provided in the longitudinal direction of the image carrier. By detecting with the density detecting means, it is possible to prevent continuous input of an untransferred pattern at the same position in the longitudinal direction of the image carrier. Therefore, the load on the cleaning can be reduced, and the cleaning time can be shortened.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming unit of a color copying machine according to an embodiment of the present invention.

FIG. 2 is a perspective view of the photoconductor showing the size of a pattern for toner density measurement and control.

FIG. 3 is a perspective view of a photoconductor showing an actual pattern arrangement.

FIG. 4 is a diagram showing a pattern for measurement and control and a photo sensor provided to face the pattern.

FIG. 5 is a diagram illustrating a state in which each color pattern is shifted and formed.

FIG. 6 is a diagram illustrating a state in which a pattern is formed so that the order of density is alternated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Bk developing device 4 C developing device 5 M developing device 6 Y developing device 7 Static eliminator before cleaning 8 Cleaning device 9 Static elimination lamp 10 Intermediate transfer belt 11 Paper transfer device 12 Intermediate transfer belt cleaning device 15 Toner density Detecting device 21 Pattern 22 Photo sensor

Claims (2)

[Claims] 1. A cleaning device having an image carrier for carrying a toner image obtained by visualizing an electrostatic latent image, and a toner removing member such as a cleaning blade or a cleaning brush for removing residual toner on the image carrier. And a toner density detecting means for detecting the density of a pattern for measuring and controlling the toner density on the image carrier, and a control means for controlling the toner density based on the density detection result by the toner density detecting means. Is configured to form an image by changing the position in the longitudinal direction of the image carrier, and the length thereof is set to 以下 or less of the length of the toner removing member in the longitudinal direction of the image carrier. An image forming apparatus. 2. A cleaning device having an image carrier for carrying a toner image obtained by visualizing an electrostatic latent image, and a toner removing member such as a cleaning blade or a cleaning brush for removing residual toner on the image carrier. And a toner density detecting means for detecting the density of the pattern for measuring and controlling the toner density on the image carrier, and a control means for controlling the toner density based on the density detection result by the toner density detecting means, An image forming apparatus comprising a plurality of density detecting means provided in a longitudinal direction of an image carrier.