JPH0511562A - Color balance adjusting device for electrophotographic device - Google Patents

Abstract

PURPOSE:To stabilize the adjustment of image density by a control means by allowing a detection means to detect toner adhesive amount based on a difference from the part of a transfer means, where a toner image is not formed. CONSTITUTION:In a color balance adjusting device 50 constituted of an infrared sensor 26 for detecting the toner adhesive amount of the toner image formed on an intermediate transfer body 21 and an automatic adjusting device 51 which adjusts the image density by correcting the light quantity of an exposing optical system 14 based on the toner adhesive amount, the toner adhesive amount is detected by the infrared sensor 26 based on the difference from the part where the toner image is not formed on the intermediate transfer body 21. Namely, for example, the density (y) of yellow toner and the density (t) of a surface where the toner does not adhere on the intermediate transfer body 21 are detected, and density (y') is calculated as the difference between the density (y) and the density (t). When the density (y') is larger than a reference value AD, lamp voltage (x) is increased, and when it is smaller than the value AD, the lamp voltage (x) is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color balance adjusting device for an electrophotographic apparatus such as a copying machine.

[0002]

2. Description of the Related Art Electrophotographic devices such as full-color copying machines
The process is designed to enable all color reproduction with three color toners of yellow, magenta and cyan. Also, the most important point in such full color reproducibility is
To maintain the gray balance by always setting the gradations of yellow, magenta, and cyan to the same level. By doing so, it is possible to reproduce all colors with toners of three colors of yellow, magenta, and cyan. If this breaks down, the copy itself becomes a reddish or bluish copy.

However, each developer is different in the number of times it is copied by monochromatic copying or the like, that is, fatigue is different, and the optical system is exposed to light more than the initial state due to dust adhesion due to long-term use. Is changing. For this reason, at the time of installation, a serviceman adjusts the gradation of the image, so there are few problems. It is very difficult to maintain the same gradation.

Therefore, in recent years, in order to reduce the stability in this life and the troublesomeness of the initial adjustment, the density of the reference image formed on the intermediate transfer member is always read,
An electrophotographic apparatus has been proposed which is provided with a color balance adjusting device which feeds back the exposure amount at the time of image formation of each color image of yellow, magenta, and cyan to maintain color balance.

[0005]

However, in the above-mentioned conventional color balance adjusting apparatus, the contamination of the optical system and the deterioration of the developer can be sufficiently detected and the automatic adjustment can be performed. In terms of image quality stability, it is insufficient.

That is, in order to feed back the amount of optical light, it is necessary to make the reference image density extremely thin, and by doing so, it is necessary to make it easier to detect dirt on the optical system and fatigue of the developer. However, when the reference image density is made extremely low as described above, the detection value includes the surface state value (noise) of the transfer intermediate as shown in the following items at the time of detection.

Glossiness (small unevenness) Scratch (large unevenness) Angle with sensor In addition, the value of each of the above noises greatly changes due to scratches caused by the cleaner and printing durability such as toner filming. For this reason, there is a problem in that the color balance cannot be maintained due to a large noise with respect to the toner adhesion amount that is originally desired to be detected, and as a result, the accuracy of the color balance adjusting device deteriorates.

[0008]

In order to solve the above-mentioned problems, a color balance adjusting device for an electrophotographic apparatus of the present invention has a plurality of color toners and a transfer means for transferring a toner image onto a transfer paper. A color balance adjustment including a detection unit that detects the toner adhesion amount of the toner image formed on the transfer unit, and an adjustment unit that adjusts the image density by correcting the light amount of the exposure optical system based on the toner adhesion amount. In the device,
The following measures are taken.

That is, the detection of the toner adhesion amount by the detection means is performed with a difference from the portion of the transfer means where the toner image is not formed.

[0010]

According to the above construction, the toner adhesion amount of the transfer means detected by the detection means is detected as a difference from the portion of the transfer means where the toner image is not formed. Therefore, even if the surface state of the transfer unit on which the toner image is formed changes due to printing durability, the toner adhesion amount is always detected based on the surface state of the transfer unit, so that the control unit can stabilize the image density adjustment. Can be converted.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a color copying machine as an electrophotographic apparatus including an embodiment of a color balance adjusting apparatus according to the present invention, FIG. 2 is a characteristic diagram showing characteristics of the infrared sensor of FIG. 1, and FIG. FIG. 4 is a block diagram showing the electrical configuration of the color balance adjusting apparatus of FIG. 1, and FIG. 4 is a flowchart showing the operation of the color copying machine of FIG. 1 when adjusting yellow.

In FIG. 1, a transparent original placing table 11 for placing an original P on the upper surface of the machine frame is an opaque metal plate 12.
Further, an opaque document pressing plate 13 for pressing the document P on the document mounting table 11 is provided on the document mounting table 11 so as to be opened and closed. For example, a document size or the like is printed on the upper surface of the sheet metal 12, and at least one of the lower surface of the sheet metal 12 and the lower surface of the document pressing plate 13 is formed as a gray surface by printing in gray.

An exposure optical system 14 for scanning an image of the original P is arranged below the original table 11, and the exposure optical system 14 has a home position below the metal plate 12 in the sub scanning direction. Movable and transparent document holder 1
Light source lamp 1 for illuminating the lower surface of the document P via
4a, a plurality of reflecting mirrors 14b for guiding the light reflected by the original P to the exposure position A on the photoconductor 16 as shown by the dashed line in the figure, and a color filter of three primary colors of red, green and blue. The color separation filter 14c and the imaging lens 14d are included.

The photosensitive member 16 is formed in a belt shape and is rotatable in the counterclockwise direction in the drawing by a driven roller 17 and a driving roller 18, and a charging charger 19 is arranged upstream of the exposure position A. Further, in the present embodiment, yellow, magenta, and cyan are adopted as an example of the first, second, and third colors for forming a color image, and therefore, downstream of the exposure position A, sequentially, Yellow developing tank 20Y, magenta developing tank 20M, cyan developing tank 20
Cy is arranged, and further, a black developing tank 20B for performing black-and-white copying or four-color copying, and an intermediate transfer body 21 as a transfer means for intermediately transferring the toner image on the photoconductor 16. A cleaning unit 22 and a discharge lamp 23 are arranged.

The intermediate transfer member 21 is a black film in which carbon is dispersed in polycarbonate, is formed in a belt shape like the photosensitive member 16, and has first to third rollers 24a-2.
4c can rotate in the clockwise direction in the figure, and
The transfer roller 25 is pressed against the photoconductor 16. An infrared sensor 26 as a detection unit used for color balance adjustment in the present embodiment is arranged downstream of the transfer roller 25, and the third roller 24c transfers the toner image on the intermediate transfer member 21 to the transfer paper 27. Is pressed against a transfer roller 28. As the infrared sensor 26, a sensor that detects only a wavelength of 750 nm or more is selected. FIG. 2 shows an example of characteristics of the infrared sensor 26.

The transfer paper 27 is preset in the cassette 30 at the lower right of the drawing, is conveyed to the position of the timing roller 33 by the paper feed rollers 31 and 32, and is aligned with the toner image on the intermediate transfer member 21. It is conveyed by 33 to the position of the transfer roller 28. The transfer paper 27 on which the toner image has been transferred is fixed by the conveyance belt 34 to the fixing device 35.
The toner image is conveyed to the fixing device 35, and the toner image is fixed by the fixing device 35 and then discharged. Therefore, the image of the original P is copied onto the transfer paper 27 by the process of charging-exposure-developing-transfer.

The toner density y measured by the infrared sensor 26 is input to the automatic adjustment device 51 as described later, and the lamp voltage x of the light source lamp 14a is determined to automatically adjust the color balance of yellow, magenta and cyan. Has the function of adjusting.

In the above-described structure, when performing normal color copying, the image of the original P is scanned three times and separated into three colors by the color separation filter 14c, and the electrostatic latent image of each color is formed on the photoconductor. 16 is formed. The electrostatic latent images of the respective colors on the photoconductor 16 are the yellow developing tank 20Y and the magenta developing tank 20 which are the complementary colors of the respective colors of the color separation filter 14c.
Each of the toner images is made visible by the M and cyan developing tanks 20Cy, and each toner image is transferred onto the intermediate transfer member 21. still,
When performing normal color copying, the black developing tank 20
B, the infrared sensor 26 is not used, and in the case of black-and-white copying, only the black developing tank 20B is used.

In FIG. 3, an automatic adjusting device 51 constitutes an example of an adjusting means, and in order to enable a color balance adjusting operation as described later, a toner density y is inputted from an infrared sensor 26 and a machine is used. The reference value A ₀ stored after the adjustment of the main body is set, and the comparison circuit 52 for comparing these values and the memory for storing the optimum lamp voltage values x _y · x _m · x _c for each of yellow, magenta, and cyan And 53. The automatic adjustment device 51 further
Color During balancing, with appropriate modifications to the lamp voltage x of the light source lamp 14a based on the difference output from the comparator circuit 52, the normal image forming time, the ramp voltage value x _y · stored lamp voltage x in the memory 53 An exposure voltage control circuit 54 is provided to control the exposure voltage to be x _m · x _c .

Next, with reference to FIG. 4, an operation for adjusting yellow in the color copying machine configured as described above will be described.

First, the copying machine is set to the color balance adjustment mode manually or automatically, for example, every 1000 normal copying. Here, when the lower surface of the sheet metal 12 is printed in gray, the light source lamp 14a does not move and illuminates the lower surface of the sheet metal 12, while when the lower surface of the document pressing plate 13 is printed in gray. Light source lamp 14a
Moves to illuminate the lower surface of the document pressing plate 13. Therefore, the light source lamp 14a illuminates the gray surface which is one of the lower surface of the metal plate 12 and the lower surface of the document pressing plate 13.

In step S1 shown in FIG. 4, the voltage x is applied for a predetermined time to turn on the light source lamp 14a, and in step S2, the blue filter of the color separation filter 14c is selectively arranged in the optical path. , The yellow developing tank 20Y is selectively driven. Therefore, the light illuminated by the light source lamp 14a and reflected by the gray surface, which is the lower surface of the sheet metal 12 or the document pressing plate 13, is passed through the blue film of the color separation filter 14c to the photoconductor 1.
An electrostatic latent image corresponding to the gray surface is formed on the photoconductor 16 by being guided to the exposure position A on the photoconductor 6. Then, the electrostatic latent image on the photoconductor 16 is visualized by toner in the yellow developing tank 20Y, and this toner is transferred to the intermediate transfer body 21.
At this time, the transfer paper 27 is not conveyed.

At the subsequent step S4, the intermediate transfer member 2
The density y of the yellow toner on 1 and the density t of the surface on which the toner is not attached are detected by the infrared sensor 26, and the density y ′ (= y
-T) is calculated. Then, in step S5,
The comparator circuit 52 compares the density y ′ with the reference value A ₀ . When the density y ′ is larger than the reference value A ₀ , the process branches to step S6, the lamp voltage x is increased by a predetermined value a (for example, about 1V), and the process returns to step S1.
When the density y ′ is smaller than the reference value A ₀ , step S7
And the lamp voltage x is decreased by a predetermined value a (for example, about 1 V), and the process returns to step S1.

The above reference value A ₀ means that the image quality is adjusted by a service person or the like when the machine is installed, and yellow, magenta,
After matching the gradation of each color of cyan, in the above operation,
The yellow image density y ₀ when the developer is not fatigued and the intermediate transfer member 21 is not changed, and the intermediate transfer member 2
The value A ₀ obtained from the density t _{0 of the} area where the toner does not adhere to ₁ is stored. Further, this value is different for each color, and is described in the following description assuming that the magenta reference value is B ₀ and the cyan reference value is C ₀ .

When the density y'matches the reference value A ₀ by repeating the processing of steps S1 to S5 in this way, the lamp voltage x at the time of matching is determined to be the yellow lamp voltage _xy (step S8), and the memory is stored. The data is stored in 53 (step S9).

When the yellow lamp voltage _xy is determined and stored in this way, magenta and cyan are similarly processed by using the stored reference values B ₀ and C ₀ , and magenta and cyan are processed. Each lamp voltage x _m · x _{c of} is determined and stored. The lamp voltage x _y · x _m · x _c adjusted and stored in this way is used as a center value during normal copying. Further, by using this feedback system, it is possible to always obtain a stable image with good color balance regardless of the surface property of the intermediate transfer member 21.

[0027]

As described above, in the color balance adjusting apparatus for an electrophotographic apparatus according to the present invention, the amount of toner adhered by the detecting means is detected with a difference from the portion of the transfer means where the toner image is not formed. It is a composition.

Thus, the toner adhesion amount can be detected on the basis of the surface condition of the transfer device. Therefore, even when the surface condition of the transfer device on which the toner image is formed changes due to printing, the control device can be used. With this, it is possible to stabilize the adjustment of the image density due to, and it is possible to provide an excellent electrophotographic apparatus that always maintains the stability of the full-color image quality.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing characteristics of an infrared sensor that constitutes the color copying machine.

FIG. 3 is a block diagram showing an electrical configuration of a color balance adjusting device that constitutes the color copying machine.

FIG. 4 is a flowchart showing an operation when adjusting yellow of the color copying machine.

[Explanation of symbols]

 14 Exposure Optical System 21 Intermediate Transfer Body (Transfer Means) 26 Infrared Sensor (Detection Means) 51 Automatic Adjustment Device (Adjustment Means) 50 Color Balance Adjustment Device

Claims (1)

Claim: What is claimed is: 1. A detection unit that has a plurality of color toners and a transfer unit that transfers a toner image onto a transfer sheet, and that detects a toner adhesion amount of the toner image formed on the transfer unit. In the color balance adjusting device comprising an adjusting unit for adjusting the image density by correcting the light amount of the exposure optical system based on the toner adhesion amount, the toner image of the transfer unit is detected by detecting the toner adhesion amount by the detecting unit. A color balance adjusting device for an electrophotographic apparatus, which is performed with a difference from a portion not formed.