JPH05323780A - Color image recording method and device therefor - Google Patents

Abstract

PURPOSE:To reproduce a color image with a proper image density, without loosing color balance even if an image density is lowered among the developers of each color, regardless of the fact that a toner concentration is almost a prescribed value. CONSTITUTION:When a color balance detecting circuit 63 detects the fact that the color balance is abnormal, regardless of the fact that the toner concentration is almost the prescribed value, a second CPU 60 reads the color of toner to be forcibly consumed and a developing bias changing value, from a second lock-up table T2, and executes processing for forcibly consuming the toner, based on the data obtained by the reading.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention employs a developing method for developing an electrostatic latent image by using a two-component developer composed of toner and carrier, and a method and apparatus for recording a color image of a plurality of colors. In particular, the present invention relates to a color image recording method and apparatus for controlling the toner charge amount in order to obtain an appropriate color balance.

[0002]

2. Description of the Related Art In a developing device that visualizes an electrostatic latent image on an image bearing member by using a two-component developer composed of toner and carrier, the weight mixing ratio of toner and carrier in the two-component developer ( Hereinafter, this is referred to as toner concentration T _C ) has a great influence on the developability. For example, if the toner density of the two-component developer is lower than the proper value, the density of the developed image will be low. On the contrary, if the toner density becomes too high, the density of the developed image becomes too high and the so-called fog increases. Therefore, the recorded image on the transfer material transferred from the image carrier becomes unsuitable.

Therefore, in order to always obtain an image having a preferable density, the toner density of the two-component developer is set to an appropriate level,
At the same time, it is necessary to keep the appropriate level constant during development. Therefore, conventionally, there has been proposed a two-component developer concentration control method in which the toner concentration of the two-component developer is maintained constant by controlling the toner supply amount. This density control method detects change events such as magnetic permeability change and volume change of two-component developer, change of image density after development, and color change of two-component developer due to toner and carrier having different colors. Thus, the toner concentration is detected, and the toner replenishment amount is controlled based on the detected toner concentration, so that the toner concentration is maintained at an appropriate level.

However, in the method of detecting a change event as described above, stable operation for a long period of time has been difficult due to reasons such as erroneous detection and difficulty in compensating for deterioration of the surface of the photosensitive member over time.

As a solution to this problem, Japanese Patent Laid-Open No. 57-1366 has been proposed.
No. 69 “Two-component developer concentration control device” is introduced. This "two-component developer concentration control device" is a detection level that should detect the volume of the two-component developer in the developing device so that the developing effect in the recording device can be stably and appropriately maintained for a long period of time. With a plurality of, separately, by optically detecting the developed image of the reference image formed on the photosensitive surface to detect the developing performance, or the density of the recorded image,
In response to this, by switching and setting a plurality of detection levels by the central processing unit, the toner concentration of the two-component developer is controlled in order to avoid carrier replenishment as much as possible and to keep the developing performance as constant as possible. It is composed. For the time being, the above-mentioned object was achieved.

[0006]

However, the contents of the original document to be image-recorded often have variations in blackening rate due to differences in image density and image density, and blackening of line drawings, character images, low-density originals, etc. When a developing operation is executed to continuously form an image of original contents having a low rate, the predetermined image density corresponding to the toner density cannot be obtained even though the toner density is constant, and the toner The phenomenon that the correspondence between the density and the image density is broken occurs. It was also found that this phenomenon is likely to occur in the case of a color electrostatic recording device in which a color image can be reproduced by using a two-component developer of various colors.

Then, when the cause of occurrence of such a phenomenon was considered, the following findings were found.

That is, as a result of analyzing the phenomenon common to the above two examples, the developing sleeve and the stirring means in the developing device are continuously driven to rotate within the developing time during the image forming process in the electrostatic recording apparatus. However, it has been found that this stirring time, in other words, the residence time of the two-component developer in the toner hopper, is commonly related. That is, in the former example, since the original is of low density, the toner consumption amount per unit time is smaller than usual, and the toner retention time becomes longer accordingly. In the latter example, the toner consumption amount of the two-component developer for each color is different, and the residence time of the toner is also different for each color.

Considering that the phenomenon of the above example occurs even when the toner density is constant, it can be presumed that the phenomenon is not caused by the so-called spent toner in which the toner component is attached around the carrier and the toner charge amount is reduced. However, since it is related to the toner retention time, that is, the toner charge amount is expected to continue to increase as the toner retention time increases, and the chance of friction between the toner and the carrier increases. It is considered that the toner charge amount out of the range affects the image density. This phenomenon will be described below.

FIG. 12A is a diagram showing a transition of toner consumption of each color corresponding to the number of copies in a color image forming apparatus for recording a color image with a two-component developer of a plurality of colors, and FIG. 12C is a diagram showing the toner charge amount of each color corresponding to the number of copies in the color image forming apparatus, and FIG. 12C shows the optical image density (CD) corresponding to the number of copies in the color image forming apparatus. It is a figure.

Here, the optical image density (CD) means a constant exposure part formed on the photosensitive drum by irradiation from the scanning optical system based on an image signal corresponding to the reflected light from the standard density plate. It is the image density corresponding to the reflected light from the standard toner image developed under the electrostatic process condition.

FIG. 12A shows an example of copying a certain color original document, and the solid line BK shows the transition of the toner consumption amount according to the number of copies of black toner, specifically, A4 paper. Average consumption of 80 mg per sheet, 300
It consumes about 240g per 0 sheets. The solid line Y indicates the transition of the toner consumption amount according to the number of copies of the yellow toner, and specifically, the average toner consumption amount is 50 mg per sheet,
Consume about 150g per 3000 sheets. The solid line C shows the transition of the toner consumption amount according to the number of copies of the cyan toner. Specifically, the average consumption is 50 mg per sheet, and about 150 g per 3000 sheets. The solid line M shows the transition of the toner consumption amount according to the number of copies of the magenta toner. Specifically, the average consumption is 10 mg per sheet, and about 30 g per 3000 sheets. These show that the amount of consumption differs depending on the color of the developer.

The above is an ideal case in which the development characteristics of each color do not change even after copying 3000 sheets.

However, in a normal image recording apparatus,
Due to the demand for simplification of control, the developing sleeve and the stirring means in the developing device are continuously driven to rotate within the developing time during the image forming process. Therefore, as described below, the charge amount of each color toner in the developing device varies due to the toner staying for a long time. An example thereof will be described below.

In FIG. 12B, the solid line BK shows the change in the toner charge amount Q / m according to the number of copies of black toner. From this, the toner charge amount is substantially constant regardless of the increase in the number of copies. It is presumed that this is because the toner density is controlled so that the toner is sequentially replenished according to the consumption, so that the toner that remains for a long time is small.

The solid line Y shows the transition of the toner charge amount Q / m according to the number of copies of the yellow toner, and the solid line C shows the toner charge amount Q / m according to the number of copies of the cyan toner.
From the above, the toner charge amount slightly increases with an increase in the number of copies, but gradually increases. It is presumed that this is because the toner concentration is controlled so that the toner is sequentially replenished according to the consumption, but the toner staying for a long time remains slightly beyond the allowable range.

The solid line M shows the transition of the toner charge amount Q / m according to the number of copies of magenta toner, and the toner charge amount extremely rises as the number of copies increases. It is presumed that this is because the toner concentration is controlled so that the toner is sequentially replenished according to the consumption, but a large amount of toner staying for a long time exceeds the allowable range and remains.
As described above, when each color developer is loaded, the difference in toner charge amount between the color developers is small and does not affect the developability, but as the copying is continued, each color developer is Due to the difference in the amount of toner consumed, there is a difference in the amount of toner that stays for a long time.
This shows that the toner charge amount differs between the color developers and the developability also varies.

The following phenomenon occurs due to the difference in toner charge amount between the color developers.

In FIG. 12C, the solid line BK shows the transition of the optical image density (CD) according to the number of copies of black toner. From now on, the optical image density (CD) is substantially constant regardless of the increase in the number of copies. That is, the developability is substantially constant. The solid line Y shows the transition of the optical image density (CD) according to the number of copies of the yellow toner, and the solid line C
Is the optical image density (C
D) of the optical image density (C
D) is slightly increased as the number of copies increases, but gradually rises. This indicates that the yellow and cyan toners are slight, but the developability is deteriorated. Solid line M is optical image density (CD) according to the number of magenta toner copies.
And the optical image density (CD) rises extremely as the number of copies increases. This indicates that magenta toner extremely reduces the developability.

As described above, in the image forming apparatus in which the stirring in each color developing device is continuously performed over the entire developing time, there is a difference in the consumption amount of each color developing agent, and each color developing existing in the developing device is different. Due to the difference in the stirring time of the agent, the developability is affected. Therefore, there is a problem in that the image density is reduced in the case of a single color reproduced by the image recording apparatus, and in color copying, a desired amount of each color toner is not developed and the color balance of the color image is disturbed.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the image density between the color developers regardless of maintaining the toner density substantially constant at a predetermined value. In this case, a color image can be reproduced with proper image density and without disturbing the color balance.

[0022]

To achieve the above object, the present invention provides a charging step for uniformly charging a latent image bearing member, an exposure step for imagewise exposing the latent image bearing member, and a predetermined color toner. And a developing step of developing with any one of a plurality of developing devices loaded with the developing device, wherein a plurality of color toner images are formed on the latent image carrier by repeating the charging, exposing and developing steps. In the recording method, a reference exposure for forming a reference exposure portion by performing image exposure based on a reference image density signal that changes the reflection density stepwise or continuously while the toner density is maintained substantially constant at a predetermined value. Process,
A process of developing the reference exposure unit with one of developing devices loaded with yellow toner, magenta toner, and cyan toner, and repeating the reference exposure / developing process, the yellow toner, the magenta toner, and the cyan toner. Based on the reference toner image forming step of forming the reference toner image of the color layer, the color balance detecting step of detecting the color balance of the reference toner image of the three-color layer, and the detection result in the color balance detecting step, And a color balance adjusting step including a toner consuming step of consuming color toner in at least one of the developing devices.

[0023]

In the present invention, basically, the latent image carrier is uniformly charged in the charging step, the latent image carrier is imagewise exposed in the exposing step, and a plurality of color toners are loaded in the developing step. By repeating the charging, exposing, and developing steps such as developing with any one of the developing devices, toner images of a plurality of colors are formed on the latent image carrier. Processing is performed. ..

That is, even if the toner density is maintained substantially constant at a predetermined value, for example, a reference image density signal that changes the reflection density stepwise or continuously every time a predetermined number of copies are made. A reference exposure step of performing image exposure to form a reference exposure portion based on the above is performed. And
Three-color layer consisting of yellow toner, magenta toner, and cyan toner by repeating the step of developing the reference exposure part with one of the developing devices loaded with yellow toner, magenta toner, and cyan toner, the reference exposure step, and the developing step. The reference toner image forming step of forming the reference toner image and the color balance detecting step of detecting the color balance of the reference toner images of the three color layers are sequentially executed. When it is detected in the color balance detecting step that the color balance of the reference toner images of the three color layers is out of order, in the color balance adjusting step, a plurality of developing devices are used to restore the color balance to the normal state. A toner consuming step of consuming the color toner in at least one of the developing devices is performed.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a color image recording apparatus according to an embodiment of the present invention. The color image recording apparatus 100 includes a photosensitive drum 1 which is a latent image carrier and a motor which rotates the photosensitive drum 1. Motor driver 1 for controlling M
0, encoder 11, four developing devices 20BK, 20C,
20M, 20Y, high-voltage power supply 40, transfer device 42, charger 4
1, first CPU 50, reading optical system 51, scanning optical system 5
2, optical system drive circuit 53, hopper drive circuit 54, second C
PU 60, color separation light detection means 61, decoder 62, color balance detection circuit 63, development bias circuits 64 and 4
1 for each of the developing devices 20BK, 20C, 20M, 20Y
Toner density detecting means 65BK, 65 provided respectively
It has C, 65M, and 65Y.

When a copy button (not shown) is pressed, the scanning optical system 52 is controlled under the control of the first CPU 50.
A light source emits light based on an image signal corresponding to the image density of the original image from the above to irradiate the photosensitive drum 1 with light, thereby forming an electrostatic latent image on the photosensitive surface of the photosensitive drum 1. Latent image development device 20BK, 20C, 20M, 20Y
The toner images of a plurality of colors are stacked (superposed) on the photoconductor drum 1 by sequentially developing with, and the transfer device 42 is discharge-driven based on the resist signal to transfer the toner images onto the transfer paper. After that, the transfer paper is fixed to form a reproducible image that can be stored. That is, black B
K, cyan C, magenta M, and yellow Y are used as basic colors, and other colors are reproduced by appropriately selecting and stacking these basic colors. In this case, the order of superposing the colors other than the basic color is cyan C, magenta M, and yellow Y in order from the lower layer. The toner images of a plurality of colors may be superposed on the transfer drum instead of on the photosensitive drum 1.

The photosensitive drum 1 uses a drum-shaped conductive support made of aluminum and having a diameter of 150 mm, and a thickness of 0.1 μm made of an ethylene vinyl acetate copolymer on the support.
m is an OPC photosensitive member formed by laminating an intermediate layer of m and a photosensitive layer having a film thickness of 35 μm. When the photosensitive layer is irradiated with light, the surface potential drops. Therefore, if the photosensitive drum 1 is previously uniformly charged to a predetermined potential and then the light based on the light and shade of the original image is irradiated, the surface potential of the photosensitive drum 1 becomes non-uniform, and a portion having a lowered potential is formed. be able to.
This is what is called an electrostatic latent image. The photoconductor drum 1 is not limited to this, and may have another structure such as a photoconductor made of amorphous silicon. Here, for convenience of description, the OPC photosensitive member described above will be described. The latent image carrier is not limited to the photosensitive drum 1, but may be a belt-shaped member.

The motor driver 10 is a circuit that mainly controls the drive of a main motor (not shown) that rotates the photosensitive drum 1. Based on a control signal from the first CPU 50, the motor driver 10 turns on the rotation speed and rotation of the main motor.・ Off control.

The encoder 11 generates a pulse signal having a predetermined width corresponding to the rotation phase of the photosensitive drum 1, and the first CP
Output to U50. As a result, the first CPU 50 detects the rotation phase of the photosensitive drum 1.

The reading optical system 51 includes a proof lamp (not shown) integrally formed with the first scanning mirror, and a second scanning mirror (V mirror) which moves at a speed ratio of 1/2 of that of the first scanning mirror.
The original is scanned while the optical path length in front of the lens is always kept constant. As a result, the reading optical system 51 forms an image of the reflected light from the document on the platen glass on the light receiving portion of the solid-state image sensor, and outputs the output signal from the solid-state image sensor to the optical system drive circuit 53 as an image information signal. To do.

When the scanning optical system 52 is an analog type,
A known scanning system is used. For example, although not shown, an illumination lamp integrally formed with the first scanning mirror, a second scanning mirror (V mirror) that moves at a speed ratio of 1/2 of the first scanning mirror, and the like, and an optical path in front of the lens The original is scanned while the length is always kept constant. A standard density plate corresponding to, for example, optical reflection density CD = 1.0 is provided at one lower end of the platen glass, and this is irradiated by an irradiation lamp,
After the standard latent image is formed on the photosensitive drum 1, it can be developed with toner. Further, the irradiation intensity can be adjusted by controlling a so-called CVR, which is a power source for lighting the illumination lamp.

As a so-called digital scanning optical system, a method using a similar reading scanning system or a method of storing image data forming a standard density portion in a memory and forming a standard latent image based on this data There is. In the case of the digital system, the scanning optical system 52 as an image exposing means for forming an electrostatic latent image is a laser scanning provided with a polygon mirror or the like for rotationally scanning the laser light from the semiconductor laser 52b modulated by the image signal. A fixed scanning system using a system, an LED array, or liquid crystal may be used.

Further, in the digital scanning optical system, there are an intensity modulation method and a pulse width modulation method as a light modulation method of a laser emitted from the scanning optical system. The intensity modulation method is a method of adjusting the irradiation intensity by adjusting a current conducted to, for example, a semiconductor laser, and the pulse width modulation method, for example, compares image data with a reference wave composed of a triangular wave and binarizes it. This is a method of adjusting the irradiation light amount (irradiation area per pixel). Either of the two modulation methods can be selected or used in combination when the standard latent image is formed, if necessary.

The optical system drive circuit 53 is a circuit including a circuit for controlling a mechanical system such as a polygon mirror, and an image processing circuit for processing an image signal from the reading optical system 51. For example, the optical reflection densities 0 to 1. Standard image density data that changes stepwise or continuously up to 0 is stored in a ROM, and a scanning optical system 5 is used to form a standard latent image based on this data.
Control 2 The RO storing standard image density data
M functions as a standard image signal generating means.

Developing devices 20BK, 20C, 20M, 20Y
Are loaded with two-component developers of black, cyan, magenta, and yellow, respectively, and the mechanical configurations are exactly the same except that the loaded two-component developers have different color components. That is, the developing devices 20BK, 20C, 20M, 2
As shown in FIG. 2, 0Y is a developing sleeve 20c including a magnet roller 20b having an N pole and an S pole in a developing tank 20a formed of a lower casing and an upper casing, and a pressure contact with the developing sleeve 20c. Member 20 made of a rigid member provided in the upper casing so that
d, screw-shaped first and second stirring rollers 20
e and 20f, and a scraper 20g for scraping the two-component developer from the developing sleeve 20c. The two-component developer is composed of toner and carrier, and the toner is attached to the carrier and conveyed to the position of the developing sleeve 20c.
The developing sleeve 20c conveys the developing sleeve 20c to a developing area, which is a position facing the photosensitive drum 1. Further, in order to replenish the developing tank 20a with new toner, the replenishment port 20h communicates with a toner hopper (not shown), and a toner conveying screw (not shown) driven by the hopper drive circuit 54 in response to the toner replenishment signal is provided. It is configured to include. In addition,
Instead of the regulating member 20d, a thin layer forming means including a magnetic rod or a magnetic plate may be provided.

The first stirring roller 20e has a shape that conveys the two-component developer toward the front side of the recording paper, and the second stirring roller 20f has a shape that conveys the two-component developer toward the back side of the recording paper. ing. In addition, the first and second stirring rollers 2
By providing a partition wall between 0e and 20f, the two-component developer can be smoothly circulated and locally retained. As a result, the two-component developer conveyed to the developing area can be replaced, and the developing conditions are stabilized.

The scraper 20g is rotatably supported by rollers and is provided so as to come into pressure contact with / separate from the developing sleeve 20c. At the time of pressure contact, the two-component developer which has passed through the developing area and consumed toner is removed from the developing sleeve 20c. Scrape.

To the developing sleeve 20c, a developing bias circuit 6 for applying a voltage having an AC bias component and a DC bias component via a protective resistor in order to prevent fogging of an image.
4 are provided.

The developing bias circuit 64 includes the developing sleeve 2
The toner in the two-component developer conveyed to the developing area by 0c is moved by receiving an electrostatic force by the electric field created by the electrostatic latent image formed on the surface of the photosensitive drum 1.
An AC power supply for applying an AC bias for causing toner to vibrate between the developing sleeve 20c and the photoconductor 1 in the developing area, and a high-voltage DC power supply for applying a DC bias are provided. In this way, the developing bias circuit 64 generates an oscillating electric field between the developing sleeve 20c and the photosensitive drum 1,
Since the toner particles vibrate between the developing sleeve 20c and the photoconductor drum 1, the two-component developer and the photoconductor drum 1 do not come into contact with each other efficiently and clearly.
It is possible to form a toner image on the toner particles. The developing bias circuit 64 can change the developing bias according to a control signal from the second CPU 60.

Developing devices 20BK, 20C, 20M, 20Y
Toner density detecting means 65BK, 65
C, 65M, and 65Y detect the change in the magnetic permeability of the two-component developer, so that the corresponding developing devices 20BK, 20C, and
The toner concentration in the two-component developer loaded in 20M and 20Y is detected, but the toner concentration may be detected by detecting the volume level of the two-component developer. Here, for convenience of explanation, the toner concentration detecting means for detecting the toner concentration based on the change in magnetic permeability will be described.

The high voltage power supply circuit 40 is a circuit for applying a predetermined high voltage to the transfer device 42 and the charging device 41, and is a second CP.
Under the control of U60, the initial charging potential of the photoconductor drum 1 can be changed by changing the voltage value applied to the charger 41.

As shown in FIG. 3, the reference toner images of the three-color layers are formed one by one with the gray density levels 1 to 6 corresponding to the gray density levels of 6 gradations. In this case, if the toner charge amount of each color is appropriate,
As shown in FIG. 4, the toner adhesion amount per color increases as the gray density level increases, but in any of gray density levels 1 to 6, cyan toner C and magenta The amounts of the toner M and the yellow toner Y attached are equal to each other, and appear as gray to human eyes. However, when the toner adhesion amount of each color is different in the reference toner image of the three-color layer, the color balance is lost and the desired color cannot be reproduced. The details will be described later.

Therefore, under the control of the CPU 60, the color separation light detection means 61, the decoder 62, and the color balance detection circuit 63 check whether or not the color balance is lost.

The color-separated light detecting means 61 photoelectrically converts the color-separated light from the reference toner image of the three-color layer and outputs it. For example, a tungsten lamp is used as a light source, and a light-receiving portion including three photosensors is used. And a configuration in which three photosensors are provided with color filters of blue B, green G, and red R on the front surface, and color reflected light reflected by a reference toner image of three color layers is projected by a tungsten lamp. Filters B, G, and R are color-coded, and the separated light is received by each photosensor and output as blue, green, and red signals. In this case, the color separation light detection means 61 sequentially outputs color separation signals for all three color layer reference toner images of gray density level 1 to gray density level 6. The color separation light detecting means 61 is not limited to this, and uses three color LEDs of B (blue), G (green) and R (red) as a light source, and the above three color colors on the front surface of the light receiving portion. It is also possible to omit the filter. Further, the color separation light detection means 61 uses a tungsten lamp as a light source,
A configuration may be adopted in which blue, green, and red color filters are provided on the entire surface of a single photosensor, the color filters are switched to sequentially obtain separated light of each color, and the single photosensor receives the separated light. Further, a configuration in which a single photosensor is used by using three color LEDs of B (blue), G (green), and R (red) as light sources may be used. When a white light source is used, the color filter for receiving light is the color of the color toner used, that is, cyan,
You may use the color filter of each color of magenta and yellow. This is because the detection accuracy improves as the spectral characteristics of the toner and the spectral characteristics of the color filter come closer to each other.

The decoder 62 performs white level correction and black level correction on the analog electric signal reflecting the density of each color from the color separation light detection means 61, and then converts it into a 2-bit digital electric signal, for example. It is output to the color balance detection circuit 63 as a blue code I _B , a green code I _G , and a red code I _R , which will be described later.

The color balance detection circuit 63, as shown in FIG. 3, is a toner adhesion amount of each color corresponding to each gray density level when the color balance is proper (this toner adhesion amount is the 2-bit digital electric signal). (Which is the same standard as the above) is stored, and the stored contents are compared with the signals (blue code I _B , green code I _G , red code I _R ) from the decoder 62 to obtain the color balance. Is abnormal, and if abnormal, it is determined what color the gray is biased, and the determination result is output to the CPU 60.

FIG. 5 shows the relationship between the color balance state and the contents of the blue code I _B , the green code I _G , and the red code I _R in gray density level 3 and gray density level 6.
It is the figure which illustrated about. In FIG. 5, the contents of the blue code I _B , the green code I _G , and the red code I _R , that is, the density level of each color is expressed by 2 bits, “00” indicates no density, and “01” and “10”. ,
The higher the numerical value is "11", the higher the density is.

In the case C1, the reference toner images of the second and third levels are reddish and are visible to human eyes. This indicates that the adhered amount of the cyan toner C is smaller than the adhered amounts of the magenta toner M and the yellow toner Y. In this case, if the attached amounts of the magenta toner M and the yellow toner Y are appropriate, the attached amount of the cyan toner C is smaller than the appropriate value, and the charged amount of the cyan toner C is likely to exceed the appropriate value. ..

In the case C2, the reference toner images of the levels 2 to 6 are reddish and are visible to the human eye. This indicates that the amount of the cyan toner C attached is smaller than that of the case C1. In this case, it is highly possible that the charge amount of the cyan toner C further exceeds the appropriate value.

In the case C3, the reference toner images of the second and third levels are bluish and are visible to the human eye. This indicates that the adhesion amount of the yellow toner Y is smaller than the adhesion amounts of the magenta toner M and the cyan toner C. In this case, if the attached amounts of the magenta toner M and the cyan toner C are appropriate, the attached amount of the yellow toner Y is smaller than the appropriate value, and the charge amount of the yellow toner Y is likely to exceed the appropriate value. ..

In the case C4, the reference toner images of levels 2 to 6 are bluish and are visible to the human eye. This indicates that the adhesion amount of the yellow toner Y is smaller than that of the case C3. In this case, it is highly possible that the charge amount of the yellow toner Y further exceeds the appropriate value.

In case C5, the reference toner images of the second and third levels are greenish and are visible to human eyes. This is because the attached amount of magenta toner M is yellow toner Y and cyan toner C.
It shows that it is less than. In this case, if the attached amounts of the yellow toner Y and the cyan toner C are appropriate, the attached amount of the magenta toner M is smaller than the appropriate value, and the charged amount of the magenta toner M is likely to exceed the appropriate value. ..

In the case C6, the reference toner images of the levels 2 to 6 are greenish and are visible to human eyes. This indicates that the adhesion amount of the magenta toner M is smaller than that of the case C5. In this case, it is highly possible that the charge amount of the magenta toner M exceeds the proper value.

In case C7, the reference toner images of the second and third levels are yellowish and are visible to human eyes. This indicates that the adhered amounts of the magenta toner M and the cyan toner C are small. In this case, if the adhesion amount of the yellow toner Y is proper, the adhesion amounts of the magenta toner M and the cyan toner C are smaller than the proper values, and the charge amounts of the magenta toner M and the cyan toner C exceed the proper values. There is a high possibility.

In the case C8, the reference toner images of levels 2 to 6 are yellowish and are visible to human eyes. This indicates that the adhered amounts of the magenta toner M and the cyan toner C are smaller than those of the case C7. In this case, it is highly possible that the charge amounts of the magenta toner M and the cyan toner C further exceed the appropriate values.

In the case C9, the reference toner image of the second to third levels is magenta and is visible to the human eye. This indicates that the adhered amounts of the yellow toner Y and the cyan toner C are small. In this case, if the adhering amount of the magenta toner M is appropriate, the adhering amounts of the yellow toner Y and the cyan toner C are smaller than the appropriate values, and the yellow toner Y
Also, it is highly possible that the charge amount of cyan toner C exceeds an appropriate value.

In the case C10, the reference toner image of levels 2 to 6 is magenta and is visible to the human eye. This is because the amount of adhered yellow toner Y and cyan toner C is case C9.
It is shown that it is less than that of. In this case, it is highly possible that the charge amounts of the yellow toner Y and the cyan toner C further exceed the appropriate values.

In the case C11, the reference toner image of the second and third levels has a cyan color and is visible to the human eye. This indicates that the adhered amounts of the yellow toner Y and the magenta toner M are small. In this case, if the adhesion amount of the cyan toner C is proper, the adhesion amounts of the yellow toner Y and the magenta toner M are smaller than the proper values, and the charge amounts of the yellow toner Y and the magenta toner M exceed the proper values. There is a high possibility.

In the case C12, the reference toner image of the second to sixth levels has a cyan color and is visible to the human eye. This is because the adhesion amount of the yellow toner Y and the magenta toner M is C1.
It is shown that it is smaller than that of 1. In this case, there is a high possibility that the charge amounts of the yellow toner Y and the magenta toner M will exceed the proper values.

In the case C13, a reference toner image of 2 to 6 levels appears as gray in human eyes. This indicates that the adhered amount of each color toner is substantially uniform and is an appropriate amount. In this case, the charge amount of each color toner is an appropriate value.

In the color image recording method and apparatus according to the present invention, the color balance detection circuit 63 has the case C.
1 to C13 is determined and the data of the cases C1 to C13 is output to the second CPU 60. In the case of the cases C1 to C12, the second CPU 60 outputs a second lookup table described later. With reference to T2, a developing bias control signal for forcibly consuming toner of a color having a high toner charge amount is output.

The causes of the phenomena of cases C1 to C13 are considered to be based on all of the factors that determine the toner adhesion amount, but the main cause is the fluctuation of the developing performance of the developing device having each color toner. , The fluctuation of the conditions for forming the standard latent image of each color.

Here, since it can be defined that the standard latent image forming conditions for the respective colors are substantially equal, it can be understood that the variation in the developing performance of the former developing device is the main cause. The color of the reference toner image is deviated from gray and has a tint when the development performance of each color toner deteriorates and an amount of adhering color toner that is less than the proper adhering amount appears, and the color of the color toner is a complementary color. This is because it looks dark.

Regarding the decrease in the developability of the toner having a small amount of adhesion, if it is detected that the toner concentration is maintained at a substantially standard level, the toner charge amount increases and the toner and the carrier are separated. The adhesion becomes too large,
It can be presumed that even if the development electric field is appropriate, the development cannot be performed in an appropriate amount.

The first CPU 50, which controls the image forming process in sequence, has a built-in image forming program for executing the image forming process, and the image forming process is executed by a start signal issued in response to the pressing of the copy button. The program is started to execute the image forming process.

[0067] The 2CPU60 the first look-up table T1 associates in a one-to-one relationship data between the image density CD and the toner concentration T _c in the proper charge amount of toner,
Case C1 showing the state of color balance shown in FIG.
To C13, a second lookup table T2 in which developing bias control data are associated with each other in a one-to-one relationship, and an image density control program including a toner density determination program and a color balance control program
It is stored on the OM 60a.

The toner density determination program determines whether or not the toner density of each color detected by each of the toner density detecting means 65BK, 65C, 65M, and 65Y is below a predetermined value, and the toner density is below a predetermined value. This is a program for transmitting a toner density NG signal to the first CPU 50 when there is a color that has become negative and a toner density OK signal to the first CPU 50 when there is no color whose toner density has fallen below a predetermined value. The first
The CPU 50 has a toner density determination result register R1 for setting the toner density NG signal or the toner density OK signal received from the second CPU 60 for each color. The signal in this toner density determination result register R1 is the toner density N.
Regarding the color of the G signal, by controlling the hopper drive circuit 54 and rotating the toner replenishing roller 27R of the corresponding color, the toner in the toner hopper 27 is replenished to the developing tank and the toner density is maintained constant. The color balance control program, when the color balance becomes abnormal even though the toner density is kept almost constant at a predetermined value,
This program detects this and forcibly consumes toner of a certain color in order to restore the color balance to normal. In this embodiment, for the color forcibly consuming the toner, the developing bias circuit 64 increases the developing bias of the color so that the toner charge amount of the color is rapidly reduced. However, the present invention is not limited to this, for example, by changing the electrostatic process conditions of other modes such as increasing the initial charging potential, the amount of toner charge is rapidly reduced, or the electrostatic process conditions are not changed at all. Alternatively, the toner may be forcibly consumed.

The first CPU 50 has a first counter CT1 for counting the number of copies and a second counter CT2.
The first counter CT1 counts the number of continuous copies at the time of continuous copying by the detection signal from the paper discharge sensor and the like, and the second counter CT2 copies the timing indicating the execution of the color balance control program. The number of copies, that is, the total number of copies after the previous toner charge amount control is performed, is counted. Specifically, the color balance control program is executed every time 1000 copies are made. This is because the toner charge amount control can be sufficiently dealt with practically by intermittent control, and the toner forming the reference toner image is removed by the cleaner for cleaning the photoconductor drum 1 and used for normal copying. This is because it is not possible to save toner.

Next, the image recording operation in the first embodiment will be described with reference to the flow charts of FIGS. 6 is a main flow executed by the first CPU 50, and FIG. 7 is a color balance control flow executed by the second CPU 60. The power is turned on by pressing the main switch (not shown). As a result, the first CPU 50 and the second CPU 60 are activated (step F-1 in FIG. 6).

The first CPU 50 is the first motor driver 1
By driving 0, the main motor is started, and the first and second stirring rollers 20e, 20f of the developing devices 20BK, 20C, 20M, 20Y are connected to this drive system to stir the two-component developer of each color. To do. Further, the heater of the fixing device is heated to a predetermined temperature. Further, the first CPU 50 connects the photosensitive drum 1 to the drive system of the main motor to rotate the photosensitive drum 1, and charges the photosensitive drum 1 with a charger 41 and a static eliminator (not shown) to repeat the static elimination. Pre-processing such as adjusting the image forming process conditions is performed. Further, in the pre-processing, the number of continuous copies A set by the user by a predetermined button operation is set in the first counter CT1 (step F-2).

By the way, as described above, the second CPU 60
Indicates that the toner density detection signals of the respective colors from the toner density detection means 65BK, 65C, 65M, and 65Y are always in the set range based on the toner density determination program 7.5.
(Wt%) ± 0.5 (wt%) or less,
Judgment is made by referring to the first look-up table T1. When the value is below the set range, the toner density NG signal is output.
It is transmitted to the toner concentration determination result register R1 of the PU 50.

Therefore, the first CPU 50 reads the signal of each color set in the toner density determination result register R1 (step F-3), and determines whether or not the color of the toner density NG signal exists (step F-). 4). As a result, if the color of the toner density NG signal exists, the toner of that color is replenished (step F-5) and the process proceeds to step (F-6). On the other hand, if the toner density OK signal is obtained for all the colors, the process immediately proceeds to step (F-6) to judge whether the countdown value in the second counter CT2 is “0”, and thus the total is obtained. It is determined whether or not the count value of the number of copies reaches the total number of copies 1000, which is related to the setting. As a result, if the total number of copies has not reached 1000, the process proceeds to step (F-9). If the total number of copies reaches 1000, the first CPU 5
For 0, the second counter CT2 is set to "1000" which is the set value of the total number of copies (step F-7),
An image density control interrupt is generated and a color balance control command signal is output to the second CPU 60 (step F-8).

Therefore, the second CPU 60 is connected to the first CPU 5
In response to the color balance control command signal from 0, the scanning optical system 52 is activated and six standard electrostatic latent images corresponding to gray density levels 1 to 6 are formed on the photosensitive drum 1.
The layers are sequentially formed on top (step F-81 in FIG. 7). Then, the developing devices 20C, 20M and 20Y are sequentially driven to visualize the standard electrostatic latent image of each density as a toner image to form a toner image (step F-82). In this case, in the first rotation of the photosensitive drum 1, a standard electrostatic latent image of each density is uniformly charged, and then standard latent image information is written to form a visible image as a cyan toner image. In the second rotation, the standard electrostatic latent image of each density is uniformly charged, and then the standard latent image information (the same) is written to form a visible image as a magenta toner image. The standard electrostatic latent image of each density is uniformly charged, then the standard latent image information (the same) is formed by writing, and this is visualized as a yellow toner image, thereby superimposing three colors. Toner images are formed, and six three-layer standard toner images corresponding to gray density levels 1 to 6 as shown in FIGS. 3 and 4 are formed. Next, the second CPU 60 controls the color separation light detection means 61, the decoder 62, and the color balance detection circuit 63 to execute the color balance detection processing (step F-83).

Then, it is determined whether or not the color balance detection result output from the color balance detection circuit 63 corresponds to the case C13 shown in FIG. 5, that is, whether or not the color balance is normal. (Step F
-84). As a result, the color balance is cases C1 to C.
If any of 12 is abnormal and it is abnormal, it is determined whether the toner forced consumption flag F is set, that is, whether the color balance is currently being corrected (step F-85). As a result, if the toner forced consumption flag F is not set and the color balance is not currently being corrected, the toner forced consumption flag F is set (step F-86). Then, the control data corresponding to the detection result (one of cases C1 to C12) from the color balance detection circuit 63 is read from the second lookup table T2, and the toner is forcibly consumed for the color indicated by the control data. (Step F-87). In this case, the electrostatic latent image is formed on the entire surface of the photoconductor drum 1 by so-called solid development. Further, when performing solid development, the development bias is increased. As a result, the consumption speed of the toner is increased, and it is possible to quickly normalize the color balance. Note that cases C2, C4, C6, C
Cases C1, C3, C5, C7, C9, and C1 when the toner adhesion amount is relatively large, such as 8, C10, and C12.
The developing bias is changed to a higher value as compared with the case where the toner adhesion amount is relatively small as in No. 1. In addition, the step (F-
In 87), solid development is executed several times.

After the toner is forcibly consumed in step (F-87), it is confirmed in step (F) whether or not the toner charge amount of the color for which the toner is forcibly consumed is reduced and the color balance is normalized. Return to F-81). When it is determined in step (F-85) that the toner forcible consumption flag F is set, the toner is forcibly consumed as described above, but the toner consumption is insufficient. Since it means that the color balance has not been normalized yet, the step (F-86) is skipped and the process proceeds to the step (F-87).

When it is determined in step (F-84) that the color balance is normal, it is determined whether the toner forced consumption flag F is set (step F-88). As a result, if the toner forced consumption flag F is set, it means that the color balance has been normalized as a result of the toner forced consumption. Therefore, the toner forced consumption flag F is set to end the toner forced consumption processing. Reset (step F-89) and return. on the other hand,
If the toner forced consumption flag F is reset, it means that the color balance is normal from the beginning, and it is not necessary to perform the toner forced consumption processing, and therefore the process directly returns.

Therefore, the first CPU 50 executes the image forming process based on the image forming program (FIG. 6).
Step F-9). Then, the countdown value of the continuous copy number of the first counter CT1, the second counter CT2
The countdown value of the total number of copies of 1 is subtracted by 1 (step F-10), and it is determined whether or not the countdown value of the number of continuous copies of the first counter CT1 is "0" to determine whether the number of continuous copies relating to the setting is continuous. Number of copies A
(Step F-11), and when the countdown value of the first counter CT1 is "0" and the continuous copy number A has been reached, the process ends. On the other hand, if the number of continuous copies A has not been reached, the process returns to step (F-3) to make continuous copies for that number.

Next, the second to fifth embodiments will be described with reference to FIGS. 8 to 11. Since FIGS. 8 to 11 have many parts in common with FIG. 7, only the differences will be briefly described. To do. [Second Embodiment] If it is known in advance how much toner should be consumed to reduce the amount of toner whose toner charge amount has become too large and the developability to be recovered, it is necessary to force toner for color balance adjustment. The consumption may be performed once each time a predetermined number of copies are made (for example, 1000 to 5000 sheets). In this case, as shown in FIG. 8, in the toner forced consumption process of step (F-87), a predetermined amount of toner or more is forcibly consumed, and thereafter, as shown in FIG. You can return without returning to 81). [Third Embodiment] If it is known in advance how much toner should be consumed to reduce the amount of toner whose toner charge amount has become too large and the developability to be recovered, it is necessary to force toner for color balance adjustment. The consumption is performed once each time a predetermined number of copies are made (for example, 1000 to 5000 sheets), and thereafter, new toner is forcibly supplied to the developing device for the color for which toner forcible consumption has been performed. The deterioration of the developer (increase in the toner charge amount) may be efficiently recovered. In this case, as shown in FIG. 9, in the toner forced consumption process of step (F-87), a predetermined amount of toner or more is forcibly consumed, and further, in step (F-87a). It is sufficient to replenish the toner, and then return without returning to step (F-81) as shown in FIG. [Fourth Embodiment] If the color balance is not restored even after the forced toner consumption for the color balance adjustment is performed a predetermined number of times (for example, three times), there is no prospect of recovery even if the toner forced consumption is further performed. As a developer exchange,
Alternatively, a message to that effect may be displayed so that the developing device can be replaced.

The operation in this case is as shown in FIG. That is, when it is determined in step (F-84) that the color balance is not normal, it is determined whether the toner forced consumption number N has reached the set number N ₀ (step F-8a). As a result, if the set number N ₀ has not been reached, the process proceeds to step (F-85). After the forced toner consumption processing in step (F-87) is performed through steps (F-85) to (F-86), the toner forced consumption number N is incremented by 1 (step F-87).
a) Return to step (F-81). On the other hand, in step (F-84a), the number N of forced toner consumptions is equal to the number N
_When it is determined that the number has reached ₀ , it is determined that there is no prospect of recovery as described above, and a message to that effect is displayed so that the developer or the developing device may be replaced (step F-84).
b) Return. [Fifth Embodiment] If the color balance is not restored even after the toner is forcibly consumed for adjusting the color balance a predetermined number of times (for example, three times), the developing condition may be changed.

The operation in this case is as shown in FIG. That is, when it is determined in step (F-84) that the color balance is not normal, it is determined whether the toner forced consumption number N has reached the set number N ₀ (step F-8a). As a result, if the set number N ₀ has not been reached, the process proceeds to step (F-85). After the forced toner consumption processing in step (F-87) is performed through steps (F-85) to (F-86), the toner forced consumption number N is incremented by 1 (step F-87).
a) Return to step (F-81). On the other hand, in step (F-84a), the number N of forced toner consumptions is equal to the number N
_When it is determined that the number has reached ₀ , the developing conditions are changed (step F-84c) and the process returns. Here, as a mode of changing the developing condition, a change of the charging potential to the photoconductor,
Image exposure intensity can be changed (pulse width is changed during pulse width modulation), development bias can be changed, development sleeve rotation speed can be changed. These development conditions can be changed independently or in any combination. You may change it. Needless to say, the change of the developing condition should be changed so as to improve the developability.

[0082]

As described above, according to the image recording method and apparatus of the present invention, the image density decreases between the color developers regardless of maintaining the toner density at a predetermined value substantially constant. Even if the error occurs, by forcibly consuming the toner of the color whose image density has decreased,
In addition, it is possible to reproduce a color image without disturbing the color balance.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an image recording apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a detailed configuration of a developing device.

FIG. 3 is a diagram showing reference toner images of three color layers corresponding to six gradation density levels formed on a photosensitive drum.

FIG. 4 is a schematic diagram showing a toner layered state of the reference toner image of the three-color layer shown in FIG.

FIG. 5 is a diagram showing a relationship between densities of respective colors forming a reference toner image of three color layers and a color balance state.

FIG. 6 is a flowchart showing an image recording operation common to each embodiment.

FIG. 7 is a flowchart showing a color balance control operation in the first embodiment.

FIG. 8 is a flowchart showing a color balance control operation in the second embodiment.

FIG. 9 is a flowchart showing a color balance control operation in the third embodiment.

FIG. 10 is a flowchart showing a color balance control operation in the fourth embodiment.

FIG. 11 is a flowchart showing a color balance control operation in the fifth embodiment.

FIG. 12A is a diagram showing the relationship between the number of copies for each color used for color image formation and the amount of toner consumed, and FIG. 12B is the number of copies for each color used for color image formation. FIG. 6 is a diagram showing the relationship with the toner charge amount, and FIG. 7C is a diagram showing the relationship between the number of copies and the image density for each color used for color image formation.

[Explanation of symbols]

1 photoconductor drum 20BK, 20C, 20M, 20Y developing device 50 first CPU 54 hopper drive circuit 60 second CPU 61 color separation light detection means 62 decoder 63 color balance detection circuit 64 development bias circuit 65BK, 65C, 65M, 65Y toner density detection means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location G03G 15/01 113 A H04N 1/29 G 9186-5C (72) Inventor Kunihisa Yoshino Hachioji City, Tokyo 2970 Ishikawacho Konica Stock Company

Claims (8)

[Claims] 1. A developing device of any one of a plurality of developing devices for charging a latent image carrier uniformly, an exposing process for exposing the latent image carrier to an image, and a plurality of developing devices respectively loaded with toners of a predetermined color. In a color image recording method of forming a toner image of a plurality of colors on the latent image carrier by repeating the charging, exposing and developing steps, the toner density is maintained substantially constant at a predetermined value. A reference exposure step of forming a reference exposure portion by performing image exposure on the basis of a reference image density signal in which the reflection density changes stepwise or continuously, and the reference exposure portion is set to yellow toner, magenta toner, and The reference toner of the three-color layer including the yellow toner, the magenta toner and the cyan toner is obtained by repeating the step of developing with any one of the developing devices loaded with cyan toner and the reference exposure / developing step. -A reference toner image forming step of forming an image, a color balance detecting step of detecting the color balance of the reference toner images of the three color layers, and a plurality of developing devices based on the detection result of the color balance detecting step. A color image recording method comprising a color balance adjusting step including a toner consuming step of consuming at least one color toner in a developing device. 2. A charging device for uniformly charging the latent image carrier, an exposing process for exposing the latent image carrier to an image, and a developing device selected from a plurality of developing devices respectively loaded with toners of a predetermined color. In a color image recording method of forming a toner image of a plurality of colors on the latent image carrier by repeating the charging, exposing and developing steps, the toner density is maintained substantially constant at a predetermined value. A reference exposure step of performing image exposure to form a reference exposure portion based on a reference image density signal in which the reflection density changes stepwise or continuously; The reference toner of the three-color layer including the yellow toner, the magenta toner and the cyan toner is obtained by repeating the step of developing with any one of the developing devices loaded with cyan toner and the reference exposure / developing step. -A reference toner image forming step of forming an image, a color balance detecting step of detecting the color balance of the reference toner images of the three color layers, and a plurality of developing devices based on the detection result of the color balance detecting step. A color having a color balance adjusting step including a toner consuming step of consuming at least one color toner in the developing device and a toner replenishing step of replenishing the color toner consumed in the toner consuming step Image recording method. 3. A developing device of any one of a plurality of developing devices for respectively charging a latent image carrier with a uniform charging process, an exposure process for exposing the latent image carrier with an image. In a color image recording method of forming a toner image of a plurality of colors on the latent image carrier by repeating the charging, exposing and developing steps, the toner density is maintained substantially constant at a predetermined value. A reference exposure step of forming a reference exposure portion by performing image exposure on the basis of a reference image density signal in which the reflection density changes stepwise or continuously, and the reference exposure portion is set to yellow toner, magenta toner, and The reference toner of the three-color layer including the yellow toner, the magenta toner and the cyan toner is obtained by repeating the step of developing with any one of the developing devices loaded with cyan toner and the reference exposure / developing step. -A reference toner image forming step of forming an image, a color balance detecting step of detecting the color balance of the reference toner images of the three color layers, and a plurality of developing devices based on the detection result of the color balance detecting step. When the number of executions of the color balance adjusting step including a toner consuming step of consuming color toner in at least one of the developing devices and the toner consuming step based on the detection result of the color balance detecting step reaches a predetermined number. And a display step of displaying that the developer should be replaced. 4. A developing device, which is any one of a plurality of developing devices for charging a latent image carrier uniformly, an exposing process for exposing the latent image carrier to an image, and a developing device for loading a predetermined color toner, respectively. In a color image recording method of forming a toner image of a plurality of colors on the latent image carrier by repeating the charging, exposing and developing steps, the toner density is maintained substantially constant at a predetermined value. A reference exposure step of forming a reference exposure portion by performing image exposure on the basis of a reference image density signal in which the reflection density changes stepwise or continuously, and the reference exposure portion is set to yellow toner, magenta toner, and The reference toner of the three-color layer including the yellow toner, the magenta toner and the cyan toner is obtained by repeating the step of developing with any one of the developing devices loaded with cyan toner and the reference exposure / developing step. -A reference toner image forming step of forming an image, a color balance detecting step of detecting the color balance of the reference toner images of the three color layers, and a plurality of developing devices based on the detection result of the color balance detecting step. When the number of executions of the color balance adjusting step including a toner consuming step of consuming color toner in at least one of the developing devices and the toner consuming step based on the detection result of the color balance detecting step reaches a predetermined number. And a step of changing an image forming condition in at least one of the charging, exposing and developing steps. 5. The color separation detection step detects color separation light from a reference toner image of a three-color layer formed on the latent image carrier. Alternatively, the color image recording method according to claim 3 or 4. 6. The color balance detecting step detects color separation light from a reference toner image transferred onto a recording material body, claim 1, or claim 2, or claim 3, or The color image recording method according to claim 4. 7. The toner consuming step comprises depositing toner on the latent image carrier, claim 1, claim 2, claim 3, claim 4, claim 5, or claim 5. Or the color image recording method according to claim 6. 8. A latent image carrier, charging means for uniformly charging the latent image carrier, image exposing means for exposing the latent image carrier to an image, at least a yellow toner, a magenta toner,
In a color image recording apparatus provided with a developing device in which cyan toner is individually loaded, yellow toner, magenta toner, and cyan toner are formed on the latent image carrier while the toner density is maintained substantially constant at a predetermined value. And a standard image signal generating means for generating a standard image signal for forming a three-color reference toner image, and the reflected light from the three-color reference toner image is separated into blue, green and red components and detected. A color image including: a color separation light detecting unit for driving the color separation light detecting unit; and a color balance control unit for driving at least one of the developing devices based on a detection signal from the color separation light detecting unit to consume toner. Recording device.