JPH05197246A - Image stabilizing method for full-color copying machine - Google Patents

Abstract

PURPOSE:To provide an image stabilizing method for a full-color copying machine capable of obtaining a stable full-color image without color difference on every sheet. CONSTITUTION:When a power is supplied, a preliminary operation processing for warming up a fixing device is executed (S1), and when a temperature is <=70 deg.C, a test mode is applied (S2), and the initialization in a memory is performed (S3). At this time, toner images (monochromatic color) are formed on the surfaces A and B of a photosensitive body (S4). The toner images formed on the surfaces A and B of the photosensitive body are respectively detected by a photosensor so as to perform an arithmetic operation and calculate density DA and density DB (S5). In the case that the density DB is low as compared with the density DA regarded as the reference (S6), a potential correction and a light quantity correction with reference to a difference between the density and the density DB is performed so as to increase a processing condition on the surface B of the photosensitive body (S7 and S8). In the case that the density DB is higher than the density DA, the potential correction and the light quantity correction with reference to the difference between the density DA and the density DB are performed so as to decrease the processing condition on the surface B of the photosensitive body (S9 and S10).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full color copying machine, and more particularly to an image stabilizing method applied to an image fixing device of a full color copying machine.

[0002]

2. Description of the Related Art A conventional full-color copying machine using a transfer intermediate develops and transfers yellow (Y), magenta (M), and cyan (C) in that order, and transfers Y, M, and C on the transfer belt.
A combined image of is formed. Since the image alignment is required here, the peripheral length of the photosensitive member needs to be an integral multiple of the peripheral length of the transfer belt, and in consideration of the size of the apparatus, it is practically twice. That is, when the photosensitive belt makes one round, the Y image is developed on the first half of the photosensitive belt in which the transfer belt makes two rounds, and the M image is developed on the next half of the transfer belt, and the M image is developed once. Transferred onto the Y image on the belt. The C image is developed on the next half circumference of the photosensitive member, and is transferred onto the Y and M images of the transfer belt, which has completed one round.

[0003]

FIG. 7 shows a photosensitive member portion of a constitutional example of the conventional full-color copying machine described above. As shown in the figure, the leading edge of the first Y image of the continuous copy is X. The photoconductor 34 rotates in the direction of the arrow, and when it makes a half turn, the leading edge of the M image is set to Y. Further, a C image is formed in the next half circle. If the surface of the photoconductor 31 in the range from X to Y in the clockwise direction, that is, the surface of the photoconductor 31 in the shaded area is the D surface, and the surface of the photoconductor in the range from Y to X in the clockwise direction is the E surface, continuous copying is performed. When the toner colors Y, M, and C are used, In this way, the combination of D side and E side changes for each sheet.

However, on the D side and the E side of the photoconductor (black-and-white copy, single-color copy, etc. are almost no problem).
If a slight difference in sensitivity or a difference in density occurs, the color of each sheet changes. The factors that cause the difference in sensitivity between the surfaces D and E and the difference in toner adhesion are (a) the difference in fatigue between the surfaces D and E,
(B) Temperature difference between D surface and E surface due to temperature distribution inside the machine, (c)
There are differences in the photosensitive film thickness between the D surface and the E surface during the manufacture of the photoconductor, (d) pre-exposure during the photoconductor device, and the like. For example, if the halftone density of the D side is slightly higher than that of the E side, yellow cyan is used for the first, third, fifth, ... Copies formed by a combination of the D side, the E side, and the D side. The second copy, the fourth copy, the sixth copy ... formed by the combination of the E side, the D side, and the E side ... wins with magenta, and the appearance differs depending on the original, but the greenish image is even on the odd number. There is a problem that a magenta-like image is formed with one sheet.

In view of the above-mentioned problems in the conventional full-color copying machine, the present invention provides an image stabilizing method for a full-color copying machine which can obtain a stable full-color image with no color difference for each number of sheets.

[0006]

According to the present invention, a fixing device of a copying machine is preliminarily operated to determine whether the temperature of the fixing device is equal to or higher than a predetermined temperature, and based on the determination result, the temperature is a predetermined temperature. If the following is set, the fixing device is set to a predetermined mode to initialize the memory, and when the memory is initialized, toner images are formed on both surfaces of the photoconductor of the fixing device, and the formed toner image is detected and detected. Calculate the density of both sides by processing the results,
This is achieved by an image stabilizing method of a full-color copying machine, which compares the densities on both sides with one of the calculated densities as a reference and controls the charging potential of the photoconductor based on the comparison result.

[0007]

According to the image stabilizing method of the full-color copying machine of the present invention, the fixing device of the copying machine is preliminarily operated, and it is judged whether or not the temperature of the fixing device is equal to or higher than a predetermined temperature. If the temperature is lower than a predetermined temperature, the fixing device is set to a predetermined mode to initialize the memory, and when the memory is initialized, a toner image is formed on both surfaces of the photoconductor of the fixing device, and the formed toner image is detected. Then, the detection result is arithmetically processed to calculate the densities on both sides, the densities on both sides are compared with one of the calculated densities as a reference, and the charging potential of the photoconductor is controlled based on the comparison result.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image stabilizing method for a full color copying machine according to the present invention will be described below with reference to the drawings.

FIG. 1 is a flow chart for explaining an embodiment of the image stabilizing method of the present invention.

FIG. 2 shows an example of the structure of a full color copying machine using the image stabilizing method of FIG.

First, the full color copying machine of FIG. 2 will be described.

A full-color copying machine (hereinafter referred to as a copying machine) 10 shown in FIG. 2 includes a document mounting table 11, an exposure optical system 12, a sheet-shaped photosensitive member 13, developing tanks 14a to 14c for each color component, and a sheet-shaped sheet. Transfer intermediate body (transfer belt) 15, paper cassettes 16a and 16b for each size, charging charger 17, transfer rollers 18a and 18
b, the fixing device 20.

Further, the exposure optical system 12 includes a light source lamp 12a for irradiating the original 21 placed on the original placing table 11 with light, and a reflected light from the original 21 as shown by a chain line in FIG.
It is provided with a plurality of reflecting mirrors 12b leading to the upper part, an image forming lens 12c arranged on the optical path, and a color separation filter 12d having color filters of three primary colors (red, green, blue).

The photoconductor 13 is rotatably driven by two rollers 22a and 22b, and developing tanks 14a to 14c are arranged near the center of the upper surface of the photoconductor 13 in a non-contact state.
A charging charger 17 or the like is arranged on the side of the first roller 22a of the photoconductor 13, and a cleaning mechanism 23 for removing toner remaining on the photoconductor 13 is provided on the lower surface of the photoconductor 13 on the side of the first roller 22a. It is arranged.

The transfer belt 15 includes three rollers 24a to 24c.
The second roller of the photoconductor 13 is driven to rotate by
It is arranged on the 22b side. The second roller 22b side of the photoconductor 13 is pressed against one side of the transfer belt 15, and the transfer roller 18a is arranged on the back side of the transfer belt 15 at the position where the photoconductor 13 is pressed. This transfer belt
A transfer roller 18b is arranged on the lower surface of 15.

Next, the operation of the color copying machine having the above structure will be briefly described.

First, a document 21 placed on the document table 11
The light source 12a irradiates the light and scans it several times.
Through the imaging lens 12c and the color separation filter 12d,
The optical image is decomposed into color components.

The color separation filter 12 is divided into several scans.
Each optical machine image for each color component transmitted through each color filter of d is
The photoconductor uniformly charged by the charger 17 in order.
Imagewise exposed to 13. The latent image for each color component created in order here is a developing tank 14 having a developer of a complementary color (yellow, magenta, cyan) of each color filter of the color separation filter 12d.
After being developed with the developers a to 14c and visualized, they are sequentially transferred to the transfer belt 15 by the transfer roller 18a.

In this manner, by superposing the toner images for each color component on the transfer belt 15, one completed color toner image is created. This color toner image is taken out from one of the paper feed cassettes 16a and 16b, and is transferred by the transfer roller 18b to the recording medium 25 that is brought into close contact with the lower surface of the transfer belt 15. After this, the transfer belt 15 is separated from the recording medium 25, and the transfer belt 15 is passed through the conveying path 26 and fixed.
The color image introduced into 20 and transferred onto the recording medium 25 is fixed.

FIG. 3 is a block diagram showing the control unit of the copying machine of FIG.

The control unit of FIG. 3 is connected to an output amplification unit 28 for amplifying the output from the photosensor, a main control unit 29 connected to the output amplification unit 28, and a main control unit 29. It is configured by the charging output control unit 30.

The main control unit 29 has a central processing unit (hereinafter referred to as CPU) 31, as shown in FIG.
A random access memory (hereinafter referred to as RAM) 32 connected to the CPU 31 and a read only memory (hereinafter referred to as ROM) 33 connected to the CPU 31 are included.

The control of the entire copying machine is performed by the CPU 31 which constitutes the main control section 29 of the control section.
The processing program is stored in the RAM 32 in advance. The temperature of the fixing device is input to the CPU 31, and
The detection result of the toner concentration detection sensor is input.

The toner concentration detection sensor detects the toner image formed on the A surface and B surface of the photoconductor 13 and outputs the result to the CPU 31.

The CPU 31 calculates the density difference between the A surface and the B surface of the photoconductor 13 based on the detected value, and controls the density of the B surface with the A surface as a reference. , The charging potential of the charger (see the characteristic table in FIG. 5),
The exposure amount of the copy lamp (see the characteristic table of FIG. 6) is set and the set value is output to the charging output control unit 30.

Inside the copying machine, the density difference between the A side and the B side of the photoconductor 13 is detected in advance, and A is detected based on the detected amount.
As a means for making a difference in charging potential between the surface B and the surface B, a photosensor P1 is provided in the vicinity of the photoconductor 13 as shown in FIG. 2 so that the amount of toner image formed on the photoconductor 13 can be detected. Keep it. Further, the toner image on the transfer belt 15 after being transferred may be detected by the photo sensor P2.

The detection processing by the photosensor will be described below.

First, the surface A of the photoconductor 13 is charged, exposed and developed, and the amount of toner attached is detected by the photo sensor P1.

Next, the surface B of the photoconductor 13 is charged, exposed and developed, and the amount of toner attached is detected by the photosensor P1. At this time, the exposure is a halftone level exposure. The developing color may be any one of Y, M, and C (provided that the same color is detected on the A side and the B side).

Next, regarding the feedback method to the charging potential, for example, when it is detected that the density of the A surface is higher than that of the B surface, when the correction is not applied, the charging potentials of Y, M, and C are respectively changed. It is assumed that V _Y , V _M , and V _C.

In this correction, in case of A side, B side and A side,
Charging potential V _Y, V _M + α, and V _C, when the B side A side B side, the charge potential V _Y -α, V _M, as V _C-.alpha., the potential correction amount alpha so as not to substantially image difference It can be adjusted.

As shown in FIG. 3, the outputs of the photosensors P1 and P2 are output to the main control section through the output amplification section 28.
It is sent to 29 for processing.

Next, as shown in FIG. 5, the correction potential α is determined according to the sensor output difference between the A surface and the B surface. This relationship, that is, the potential correction amount α and the light amount correction amount β shown in FIGS.
The relationship is stored in the RAM 32 in advance, and the charging is controlled through the charging output control unit 30 of FIG.

The image stabilizing method of the full-color copying machine of this embodiment will be described below with reference to the flow chart of FIG.

The processing procedure shown in FIG. 1 is executed based on the program stored in the ROM 33 of FIG.

First, when the power of the copying machine is turned on, the fixing device is warmed up and preliminary operation processing is performed (step S1), and it is determined whether the temperature T of the fixing device is 70 ° C. or higher (step S1). S2), if the temperature T is 70 ° C. or lower, the test mode is entered because it is left unused for a long time. In the test mode, the inside of the memory is initialized and the correction condition before the power is turned on is cleared (step S3). At that time, a toner image (one color) is formed on the surfaces A and B of the photoconductor 13 (step S4). The formed toner image is a thin uniform density image when the surface potential of the photoconductor 13 is 200 volts (V). The formed toner image is detected by a photo sensor on each of the A surface and the B surface of the photoconductor 13, and the detection results are arithmetically processed to calculate the density D _A and the density D _B (step S5). The difference between the density D _A and the density D _B is calculated based on the density D _{A of the} calculated data (photoreceptor A
Surface reference) (step S6). Concentration D _B relative density D _A
Is low, the potential correction / light amount correction of the difference between the density D _A and the density D _B moves in the direction of increasing the process condition of the surface of the photoconductor B (steps S7 and S8). Further, if the concentration is high D _B relative density D _A, the difference position of the potential correction-amount correction of the density D _A and the density D _B moves in a direction to lower the process conditions of the photosensitive member B surface (step S9, S10) ..

By the above, the potential correction and the light amount correction amount are set and stored. After that, the copying process starts.

In step S2, the fixing temperature is 70.degree.
If it is greater than or equal to the above, density D _A = density D in step S6
_In the case of _B , each is left for a short time immediately after being used, and the correction conditions before power-on are maintained to start the copying process.

[0039]

According to the image stabilizing method of the full-color copying machine of the present invention, the fixing device of the copying machine is preliminarily operated to judge whether the temperature of the fixing device is equal to or higher than a predetermined temperature, and based on the judgment result. If the temperature is equal to or lower than a predetermined temperature, the fixing device is set to a predetermined mode to initialize the memory, and when the memory is initialized, a toner image is formed on both surfaces of the photoconductor of the fixing device.
The formed toner image is detected, the detection result is arithmetically processed to calculate the densities on both sides, the densities on both sides are compared using one of the calculated densities as a reference, and the charging potential of the photoconductor is determined based on the comparison result. Since it is controlled, a stable full-color image with no color difference for each number of sheets can be obtained.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining an embodiment of an image stabilizing method for a full color copying machine according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a full-color copying machine using the image stabilizing method of FIG.

3 is a block diagram showing a configuration example of a control unit of the copying machine of FIG.

4 is a block diagram showing a configuration example of a main control unit in FIG.

5 is an explanatory diagram of charging potential characteristics of the charging charger of FIG.

FIG. 6 is an explanatory diagram of an exposure amount characteristic of the copy lamp of FIG.

FIG. 7 is an explanatory diagram of a photoconductor of a conventional full-color copying machine and its peripheral devices.

[Explanation of symbols]

S1 Stage of preliminary operation process of fixing device S2 Stage of determining temperature of fixing device S3 Test mode setting and memory initialization stage S4 Toner image forming stage S5 Density calculation stage of formed toner image S6 Density difference calculating stage S7, S8 Density Comparison and density difference potential correction / light amount correction step S9, S10 Density comparison and density difference potential correction / light amount correction step 10 Full color copying machine 11 Original platen 12 Exposure optical system 13 Sheet-shaped photoconductors 14a-14c Developing tanks for each color component 15 Transfer belts 16a, 16b Paper cassettes for each size 17 Charging chargers 18a, 18b Transfer rollers 20 Fixers

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 15/20 109 21/00 117

Claims (1)

[Claims] 1. A fixing device of a copying machine is preliminarily operated to determine whether the temperature of the fixing device is equal to or higher than a predetermined temperature, and if the temperature is equal to or lower than the predetermined temperature based on the determination result. Set the fixing device to a predetermined mode to initialize the memory,
When the memory is initialized, a toner image is formed on both surfaces of the photoconductor of the fixing device, and the formed toner image is detected,
Arithmetically processing the detection results to calculate the densities of the both surfaces, comparing the densities of the both surfaces with one of the calculated densities as a reference, and controlling the charging potential of the photoconductor based on the comparison results. An image stabilizing method for a full-color copying machine, characterized by: