JPH07168401A - Image forming device - Google Patents

Abstract

PURPOSE:To stabilize process control at the time of reading a black toner patch by operating the process control so that toner patch density may be specified density and keeping the patch density constant in the case of forming a base patch with color toner. CONSTITUTION:A sensor for detecting the toner patch image density faces an intermediate transfer body 10, and the previously decided color toner patch is formed on a photoreceptor 7, and the developed toner patch density is read. The black toner patch is transferred on the color toner patch so as to obtain (base density output) - (black toner patch density output) = (black process control DATA output). Namely, by operating the process control before forming the black toner patch and keeping the density constant, a process control DATA error is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and when a light-absorbing toner (black) is detected on a light-absorbing base material, a member for reflecting light is provided between the base material and the member. Regarding the case.

[0002]

2. Description of the Related Art Conventionally, an optical sensor for reading a toner patch density for use in process control is monitored on a transfer intermediate, and it is easy to read a color toner patch. However, when trying to read the black toner patch, the transfer intermediate was kneaded with carbon black in order to have conductivity, so that it could not be distinguished from the base material, and process control could not be performed. Therefore, conventionally, a color toner layer is provided on the base material so that the black toner patch can be read.
In the known technique, as shown in JP-A-1-360177, there is a technique in which a toner layer is provided on a base to measure high density and low density, but high density and low density are stacked and measured. There was nothing to do.

[0003]

According to the conventional method, when the color toner layer on the base material is not stable, or when the color toner patch density is not sufficiently obtained when detecting the black toner patch, the black toner patch is used. When the density is detected, the output does not show a true value due to the fluctuation of the base density. Further, if the black toner patch and the transfer intermediate base cannot be distinguished from each other, a noise component of the base may be picked up to detect a high density.

[0004]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and according to the image forming apparatus of claim 1, a full-color copying machine using process control, wherein black toner is used. When the process control is performed by the method, a base patch with color toner is created on the surface of the transfer intermediate, and then a patch with black toner is created and read. The image forming apparatus is characterized in that the density of the base patch is kept constant by operating the process control so that the toner patch density becomes.

According to the image forming apparatus of the second aspect, the color toner patch density (color toner process control sensor output voltage)> black toner patch density (black toner process control sensor output voltage) is satisfied. The image forming apparatus according to claim 1, wherein the toner patch density is kept constant.

According to the image forming apparatus of the third aspect, the color toner patch density is set so that the color toner patch density (the output voltage of the process control sensor of the color toner) can be used to the maximum extent of the dynamic range of the process control sensor. The image forming apparatus according to claim 1, wherein the image forming apparatus is kept constant at a saturated position.
According to the image forming apparatus of claim 4, when the color toner patch cannot be kept at a constant density, the developing device is automatically switched to another color to keep the base density constant, and the developing device is switched. Even if the base density cannot be kept constant, the image forming apparatus according to claim 1, wherein the base layer is composed of two or more colors and the density is kept constant.

According to the image forming apparatus of the fifth aspect, the surface potential of the photoconductor when the color toner patch density is created by the process control is different from the surface potential when the process control is performed during copying. The image forming apparatus according to claim 1, wherein

According to the image forming apparatus of the sixth aspect, the patch density is saturated by creating the color toner patch density with three colors of Y, M and C without operating the process control. The image forming apparatus according to claim 1.

According to the image forming apparatus of claim 7, the image forming apparatus is a full-color copying machine using process control, and when performing process control with black toner,
In a method in which a base patch with color toner is created on the surface of the transfer intermediate, and then a patch with black toner is created and read, the black toner patch length <color toner length, and the black toner patch is inside the color toner patch. The image forming apparatus is characterized by making it possible to distinguish a transfer intermediate (black) and a black toner patch.

According to the image forming apparatus of claim 8, when the color toner patch and the black toner patch cannot be distinguished, the read patch density data is not adopted for the process control. It is a device.

According to the image forming apparatus of claim 9, the image forming apparatus is a full-color copying machine using process control, and when performing process control with black toner,
In the method that creates a base patch with color toner on the surface of the transfer intermediate, and then creates and reads a patch with black toner, cuts off the place where the black toner patch density is lower than the process control sensor output, An image forming apparatus characterized by preventing noise.

[0012]

According to the image forming apparatus of the present invention, when the density of the color toner patch of the base fluctuates (base density)-
(Black toner patch density) is the process control DAT
Since it is A, it is necessary to keep the base concentration constant. The process control DATA error can be eliminated by moving the process control before making a black toner patch to keep the density constant.

According to the image forming apparatus of the second aspect, when the color toner patch density width (base sensor output) becomes narrower than the black toner patch density width (sensor output width), the black toner patch density becomes maximum (sensor output). MIN)
At this time, the output of the black sensor reaches a peak above the color toner patch density, so the color toner patch density can be kept constant by setting the color toner patch sensor range wider than the black toner patch sensor range.

According to the image forming apparatus of claim 3, since the density of the color toner patch is saturated in the image forming apparatus 1.7, it is stable if the process control is performed on the basis of the surface potential (-400 V) at the time of saturation. It becomes easy to KEEP the base concentration.

According to the image forming apparatus of the fourth aspect, a color toner patch is usually formed with one color, but there are cases where the base density cannot be kept constant, such as when the developer life is approaching. Therefore, when the base density cannot be maintained, the density can be maintained by automatically switching to another color (Y → M → C). Further, when the color toner patch density cannot be maintained for one color, the base density can be maintained automatically by using two or more colors. According to the image forming apparatus of claim 5, in the process control at the time of copying, the density of the toner patch is changed (the surface potential is changed to make the order of the density) so that the density can be learned at the initial stage of the developer. Go. Therefore, the surface potential for forming the reference patch is used where the developer characteristic (V-D curve) lies. However, in the case of controlling the color toner patch density, it is necessary to use a potential higher than the surface potential during copying in order to control the saturation density. Therefore, when the reference patch of the toner patch density is made, the surface potential is higher at the time of copying, and by using the surface potential where the V-D curve is saturated, the process control can be accurately controlled.

According to the image forming apparatus of the sixth aspect, the color toner patch is made up of three colors, and the toner patch density is increased until the output of the process control sensor is saturated, thereby eliminating the base density control. It will be possible.

According to the image forming apparatus of the seventh aspect, when the color toner patch length is made longer than the black toner patch length, the sensor output waveform becomes transfer intermediate output → color toner patch output → black toner patch output → color toner patch. Output → transfer intermediate output, and the output of the transfer intermediate and the output of the black toner patch can be distinguished. Therefore, it becomes possible to extract only the black toner patch output DATA as the process control DATA.

According to the image forming apparatus of claim 8, when the black toner patch portion is accidentally protruded from the color toner patch portion, the sensor output waveform is: transfer intermediate output → color. Toner patch output → black toner patch output → transfer intermediate output (there may be the case in reverse)) Since it cannot be distinguished from the transfer intermediate output DATA, the sensor output DAT of the black toner patch at this time
By not adopting A, it is possible to prevent noise from entering.

According to the image forming apparatus of the ninth aspect, in the seventh aspect, when the black toner is peeled off to the black toner patch portion due to an accident, a transfer intermediate appears in that portion. Toner patch sensor output DAT
The noise of the output of the transfer intermediate is included in A. Therefore, by cutting off the transfer intermediate output from the sensor output DATA of the black toner patch portion, it is possible to prevent the mixing of noise.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details will be described below based on the embodiments of the present invention shown in the drawings. Needless to say, the present invention should not be limited to these examples.

A color copying machine according to an embodiment of the present invention is
As shown in FIG. 1, a transparent document placing table 1 is provided on the upper surface of the machine frame. An exposure optical system 2 is arranged below the original placing table 1, and the exposure optical system 2 illuminates an original 13 placed on the original placing table 1 with light. , A plurality of reflecting mirrors 2b for guiding the reflected light from the original 13 onto the photoconductor 7 as shown by a chain line, an imaging lens 2c arranged on the optical path, and red, green, and blue. And a color separation filter 2d having color filters of three primary colors. On the optical axis of the exposure optical system 2, a belt-shaped photoconductor 7 made of an organic photoconductor (OPC), which is irradiated with a light image subjected to exposure scanning, is arranged.
Paper feed cassettes 8 and 9 containing transfer paper 19 are disposed on the paper input side. The paper feed rollers 23 and 24 are provided on the upper surfaces of the paper feed cassettes 8 and 9, respectively.
Are provided, and these paper feed rollers 23 and 24 are
The transfer paper 19 is discharged from the paper feed cassettes 8 and 9 and sent out toward the intermediate transfer body 10. A timing roller 25 is provided on the delivery side of the paper feed rollers 23 and 24 in the direction of the intermediate transfer body 10. The timing roller 25 is rotated in synchronization with the intermediate transfer body 10. It has become. The intermediate transfer member 10 is rotatably driven by the first to third rollers 18a, 18b, and 18c, and is in pressure contact with the driving roller 15 that rotatably drives the photosensitive member 7. A transfer charger 21 is provided on the back surface side of the intermediate transfer body 10 at the portion where the drive roller 15 is pressed, and a transfer charger 21 is provided on the front surface side of the intermediate transfer body 10 at the installation portion of the third roller 18c. A transfer roller 22 is provided. The peeling plate 20, the transport belt 11, and the fixing device 12 are arranged in this order on the delivery side of the transfer roller 22.
Photoreceptor 7 irradiated with reflected light from the exposure optical system 2
Are driven to rotate by the driven roller 14 and the drive roller 15. A charger 16 for charging the photosensitive member 7 and a discharge lamp 26 for discharging the photosensitive member 7 are provided on the outer peripheral side of the photosensitive member 7 on the side of the driven roller 14, and the photosensitive member 7 in the vicinity of the charger 16 is disposed. A cleaning device 17, which is a cleaning unit that removes the toner remaining on the photoconductor 7, is disposed below. Then, in this cleaning device 17,
For example, a cleaning blade 17a made of urethane or the like
17a are provided, and the cleaning blades 17a and 17a are pressed against the photoconductor 7 to scrape off, for example, toner remaining on the photoconductor 7. Further, near the center above the photoconductor 7, a black and white developing tank 3 and color developing tanks 4 to 6 are arranged in a non-contact state with the photoconductor 7. In the developing tanks 4 to 6, color developers of yellow, magenta, and cyan are individually stored.

Next, the operation of the color copying machine having the above construction will be described below. First, the copy mode is executed by pressing a copy start switch (not shown). This copy mode has a copy cycle in which yellow, magenta, and cyan are developed and transferred to the intermediate transfer body 10. When the copy mode is executed, first,
The yellow copy cycle will be executed. That is, the original 13 placed on the original placing table 1 is irradiated with light from the light source lamp 2a, and exposure scanning is performed. The reflected light from the original 13 is incident on the color separation filter 2d through the reflecting mirrors 2b ... And the imaging lens 2c, and is separated into color components by the color separation filter 2d. The light for each color component transmitted through each color filter of the color separation filter 2d in the above exposure scanning is applied to the photoconductor 7 that is uniformly charged by the charging charger 16, and the photoconductor 7 is exposed at the A1 portion. . As a result, a yellow electrostatic latent image corresponding to the image of the document 13 is formed on the photoconductor 7. After that, each of the electrostatic latent images is visualized by being developed with the developer supplied from the developing magnet roller at the portion opposite to the developing tank 4 having the yellow developer which is the complementary color of the color separation filter 2d. It becomes a toner image. Then, this toner image is transferred to the intermediate transfer member 10 by the transfer charger 21. When the above yellow copy cycle is completed, the photoconductor 7 is cleaned by the cleaning device 17 and discharged by the discharge lamp 26. And
The magenta and cyan toner images are transferred to the intermediate transfer member 10 in the same copy cycle as described above. When each copy cycle described above is executed, the toner image for each color component is transferred to the same position on the intermediate transfer body 10 by the transfer charger 21, and the toner for each color component is completed. One toner image is formed. On the other hand, the transfer papers 19 accommodated in the paper feed cassettes 8 and 9 are fed one by one to the timing roller 25 by the paper feed rollers 23 and 24, and the timing roller 25 is synchronized with the intermediate transfer body 10 to transfer papers. 19 is conveyed between the intermediate transfer body 10 and the transfer roller 22. Transferred paper 1
The toner image of the intermediate transfer member 10 is transferred by the transfer roller 22 and then the intermediate transfer member 1 is transferred by the peeling plate 20.
It is separated from 0 and is introduced into the fixing device 12 by the conveyor belt 11. Then, the color toner image is fixed on the transfer paper 19 and then discharged to the outside, whereby one copy mode is completed.

Next, the image density automatic control function will be described. In a full-color copying machine, if the density balance of yellow, magenta, and cyan is destroyed for some reason, it is very difficult for the user to make adjustments. If it cannot be adjusted, it will be a service call. This is a function developed to keep the image density constant in order to eliminate it. The following items can be cited as the causes of the concentration imbalance.

Deterioration of the developer with the number of copies.

· Decrease in transfer efficiency due to environmental changes.

A decrease in the surface potential of the photoconductor due to environmental changes.

(4) Changes in developer characteristics due to environmental changes.

It is natural to design to prevent these balance changes as much as possible, but it is necessary to correct the changes because the photoreceptor potential and the developer characteristics change due to environmental changes and the like. As the sensor, an infrared sensor is installed at a position where the toner adhesion amount on the intermediate transfer member can be read. Toner patch (yellow, magenta, and cyan pattern of 2 × 3 cm) is created on the intermediate transfer member at a constant surface potential at the initial installation of the main body, and the sensor output value at that time is CP.
Let U remember. The main body has a fixing temperature of 100 when the power is on.
When the temperature is below ℃, when the power is left on for more than 2 hours,
This function works automatically. First, an image patch having a certain constant surface potential is created, its density is measured, and it is compared with the initially stored value. When it is different from this value, the grid potential of the main charger is changed and the transfer belt is rotated until the initial image density becomes the same, and the surface potential of the photoconductor is determined. This operation is performed for each of yellow, magenta, and cyan to determine the conditions for the next copy. Further, the following method was used in order to minimize the reading error. That is, the data of 5 mm at the front and rear ends of the patch to be created is ignored. This is because when developing, the amount of toner adhered to the front and rear ends is less than or equal to the surface potential amount due to the influence of the lines of electric force of the electrostatic latent image.
This is to ignore the range of influence. The measurement data is measured every 10 msec in one patch, and the average of the measured values is used as the measurement value, and for the change due to the life of the measuring part like noise and the temperature characteristic, another reference sensor is additionally provided, The white patch is always read, and the current of the light emitting element is determined by the value. Furthermore, when the surface potential is changed by this mechanism, if only the potential is changed, the color balance of yellow, magenta, and cyan will be greatly deviated. Figure 6
When the surface potential is changed by a γ curve (a copy density curve with respect to the original density is called a γ curve) as shown in FIG. The ideal γ curve is best when the curves for each color are the same. On the other hand, when the light amount is changed, the γ curve moves like B.
Further, when the surface potential and the light amount are changed at the same time, the γ curve moves like D. A relational expression of the surface potential, the light amount, and the C point was found so as to eliminate the change of the C point at the rising portion of the γ curve, and the process was designed so that the C point does not change even if the surface potential is changed. In other words, because of this formula, even if the density correction mechanism works, the point C of each color does not move and only the density is corrected.

The details of the present invention will be described with reference to a full-color copying machine CX7700 (modified) in which an optical sensor (photointerrupter) is mounted toward the surface of the transfer intermediate for use in process control on the transfer intermediate. To do. In addition, copy operation, professional

Set control

[Gamma control] is as described above.

1) Structure of transfer belt Binder resin (polycarbonate, polyimide, etc.)
Is heated to the melting temperature and carbon black (φ0.1 to
0.1 μm) is added to the binder resin, and 1 to 20% w
The control is performed so that it becomes t. Then, the molten state is stretched into a film or a tube. The transfer belt used in this experiment is made of polycarbonate resin and has a thickness of 150 μm and a surface electric resistance value of 10 ⁶ to 10 ¹⁰ Ω.
/ □ was used.

2) How to make a toner patch The sensor for detecting the toner image density is an intermediate transfer member 10.
A predetermined color toner patch is formed on the photoconductor 7 and the density of the developed toner patch is read. Then, the black toner patch is transferred onto the color toner patch, and base density output-black toner patch density output = black process control DATA output.

The relationship between the color toner patch density (thickness) on the transfer intermediate and the sensor output is shown in FIG. Also,
FIG. 3 shows the relationship between the density of the black toner patch on the color toner patch and the sensor output. As an actual movement, assuming that the patch density output of the toner patch A read by the sensor is AD (V), the sensor for detecting the toner image density on the intermediate transfer body 10 monitors. When the reference value in the initial _stage of the developer is AD _INI (V), the process control works so that it becomes AD _INI (V) during life.

A color NEW developer is added to form a color toner patch at a surface potential of -300V, and a reference value AD _INI (V) at the initial stage of the developer is stored. Then, before the timing of performing the process control of the black developer, a color toner patch is formed with a surface potential of −300 V, and the sensor output at that time is compared with the reference value AD _INI (V). On the other hand, when the same value cannot be obtained, the surface potential is automatically shaken so that the same color toner patch density can be obtained.

If the relationship of color toner patch density (color toner process control sensor output voltage)> black toner patch density (black toner process control sensor output voltage) is maintained, the sensor output of FIG. 4 is obtained. Density (Proton sensor output voltage of color toner) <
When the density is reversed to the black toner patch density (black toner process control sensor output voltage), the black toner patch output bottoms out as shown in FIG. 5, and the original sensor output cannot be obtained. Therefore, the dynamic range D (V) of the black toner patch is measured from FIG. 3 and the reference value AD _INI (V) is set to an output higher than the D (V) to prevent the black toner patch output from reaching a peak. In the figure, the dynamic range of the black toner patch is 3.0 (V), so the reference value AD _INI (V)
Is -200 so that the surface potential becomes higher than 3.0 (V).
Determine to V or higher.

A color NEW developer is put in, and the reference value AD _INI (V) at the initial stage of the developer is stored by using the surface potential −400 V at which the color toner patch density is saturated in FIG.
Then, a color toner patch is formed with a surface potential of −400 V before the timing of performing the process control of the black developer, and the sensor output at that time is compared with the reference value AD _INI (V). On the other hand, when the same value cannot be obtained, the surface potential is automatically shaken so that the same color toner patch density can be obtained. The base toner patch becomes stable by using the saturation region where the density is stable.

The YELLOW toner patch was made with the YELLOW developer, and the black toner patch was put on the YELLOW toner patch. However, the YELLOW developer became extremely tired by continuing to make a YELLOW single color copy, and the YELLOW toner patch density was the standard. When the value falls below the value AD _INI (V), the developer for forming the color toner patch is changed to MAGENTA (C
Switch to YAN) to maintain the base concentration. Or
Insufficient density by creating a color toner patch with two layers of YELLOW plus MAGENTA (CYAN) (reference value A
( _Below D _INI (V)).

The process control of the color developer is V
-Use the middle of the lying D curve (where the relationship between surface potential and ID is linear). In this example, a color NEW developer is added and the color toner patch is applied with a surface potential of −150 V.
The reference value AD _INI (V) in the initial stage of the developer was stored. However, since the relationship between the surface potential and the ID is different between the sleeping portion of the V-D curve and the saturated concentration range, the reference value A
When the density correction from D _INI (V) is applied, excess or deficiency occurs in the surface potential correction in some cases. Therefore, in order to obtain a more actual measured value, when the color toner patch density correction is performed, the reference value T at the initial stage of the developer is set to −400 V which is different from the surface potential (surface potential in the saturation density range) during the copying process.
_Memorize P _INI (V) at the same time as AD _INI (V). Then, before performing the black toner process control, the reference value TP
Correct the color toner patch density based on _INI (V).

Surface potential of color toner patch is -400V
By making three layers of YELLOW, MAGENTA, and Cyan so that the thickness of the toner patch is three times that of a single color, the sensor output saturates, and there is a sufficient margin even if the density decreases due to the fatigue of the developer. Color toner patch density control is not performed, surface potential is -400
Creating a three-color toner patch with V fixed eliminates complicated control.

Black toner patch length <color toner patch length, and if the black toner patch is formed inside the color toner patch, signal waveforms as shown in FIGS. 4 and 5 are obtained, and the color toner patch density output is obtained in the valley. The generated signal is selected as the black toner patch density output, and the transfer intermediate (black) and the black toner patch can be distinguished. Although the toner patch length depends on the process speed and the sensor sensitivity, in this example, the process speed is 184 mm / sec, the sensor response time is 130 μsec, and the color toner patch length is 10
When the black toner patch length is 5 mm or more, the transfer intermediate output → color toner patch output → black toner patch output → color toner patch output → transfer intermediate output can be detected.

When the surface potential application time t for making a black toner patch is inputted into the machine in advance and the relation of t <t _BK is satisfied as compared with the black toner patch sensor output reading time t _BK , the black at this time is obtained. The toner patch sensor output value is not used for process control.

In FIG. 3, even if the black toner patch is MAX, it does not fall below 0.1V. Therefore, when the output value of the black toner patch sensor is below 0.1V, it is cut off.

Others The present invention is not limited to the embodiments described above and shown in the drawings, and it is needless to say that the present invention can be appropriately modified and implemented without departing from the scope of the invention.

[0044]

According to the image forming apparatus of the first aspect,
When the color toner patch density of the base fluctuates, (base density)-(black toner patch density) becomes the process control DATA, so it is necessary to keep the base density constant. The process control DATA error can be eliminated by moving the process control before making a black toner patch to keep the density constant.

According to the image forming apparatus of the present invention, when the color toner patch density width (base sensor output) becomes narrower than the black toner patch density width (sensor output width), the black toner patch density becomes maximum (sensor output). MIN)
At this time, the output of the black sensor reaches a peak above the color toner patch density, so the color toner patch density can be kept constant by setting the color toner patch sensor range wider than the black toner patch sensor range.

According to the image forming apparatus of the third aspect, since the density of the color toner patch is saturated in the image forming apparatus 1.7, it is stable if the process control is performed on the basis of the surface potential (-400 V) at the time of saturation. It becomes easy to KEEP the base concentration.

According to the image forming apparatus of the fourth aspect, a color toner patch is normally formed with one color, but there are cases in which the base density cannot be kept constant, such as when the developer life is approaching. Therefore, when the base density cannot be maintained, the density can be maintained by automatically switching to another color (Y → M → C). Further, when the color toner patch density cannot be maintained for one color, the base density can be maintained automatically by using two or more colors. According to the image forming apparatus of claim 5, in the process control at the time of copying, the density of the toner patch is changed (the surface potential is changed to make the order of the density) so that the density can be learned at the initial stage of the developer. Go. Therefore, the surface potential for forming the reference patch is used where the developer characteristic (V-D curve) lies. However, in the case of controlling the color toner patch density, it is necessary to use a potential higher than the surface potential during copying in order to control the saturation density. Therefore, when the reference patch of the toner patch density is made, the surface potential is higher at the time of copying, and by using the surface potential where the V-D curve is saturated, the process control can be accurately controlled.

According to the image forming apparatus of the sixth aspect, the color toner patch is formed with three colors, and the toner patch density is increased until the output of the process control sensor is saturated, thereby eliminating the base density control. It will be possible.

According to the image forming apparatus of the seventh aspect, when the color toner patch length is made longer than the black toner patch length, the sensor output waveform becomes transfer intermediate output → color toner patch output → black toner patch output → color toner patch. Output → transfer intermediate output, and the output of the transfer intermediate and the output of the black toner patch can be distinguished. Therefore, it becomes possible to extract only the black toner patch output DATA as the process control DATA.

According to the image forming apparatus of the eighth aspect, in the seventh aspect, when the black toner patch portion is accidentally protruded from the color toner patch portion, (sensor output waveform is transfer intermediate output → color Toner patch output → black toner patch output → transfer intermediate output (there may be the case in reverse)) Since it cannot be distinguished from the transfer intermediate output DATA, the sensor output DAT of the black toner patch at this time
By not adopting A, it is possible to prevent noise from entering.

According to the image forming apparatus of the ninth aspect, in the seventh aspect, when the black toner is peeled off to the black toner patch portion due to an accident, a transfer intermediate appears in that portion. Toner patch sensor output DAT
The noise of the output of the transfer intermediate is included in A. Therefore, by cutting off the transfer intermediate output from the sensor output DATA of the black toner patch portion, it is possible to prevent the mixing of noise.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a copying machine according to the present invention.

FIG. 2 is a correlation diagram between a color toner patch density and a sensor output on a transfer intermediate according to the present invention.

FIG. 3 is a correlation diagram between a black toner patch density on a color toner patch and a sensor output according to the present invention.

FIG. 4 is a correlation diagram between sensor output and time when color toner patch density> black toner patch density.

FIG. 5 is a correlation diagram between sensor output and time when color toner patch density <black toner patch density.

FIG. 6 is a correlation diagram between copy density and document density.

[Explanation of symbols]

 1 Original Placement Table 2 Exposure Optical System 2a Light Source Lamp 2b Reflecting Mirror 2c Imaging Lens 2d Color Filter 3 Black and White Developing Tank 4 Color Developing Tank 5 Color Developing Tank 6 Color Developing Tank 7 Photoreceptor 8 Paper Feeding Cassette 9 Supply Paper cassette 10 Intermediate transfer member 11 Conveyor belt 12 Fixing device 13 Original document 14 Followed roller 15 Drive roller 16 Charging charger 17 Cleaning device 17a Cleaning blade 18a First roller 18b Second roller 18c Third roller 19 Transfer paper 20 Separation plate 21 Transfer charger 22 Transfer Roller 23 Paper Feed Roller 24 Paper Feed Roller 25 Timing Roller 26 Static Elimination Lamp

Front page continuation (72) Inventor Tadashi Kawabata 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (9)

[Claims] 1. A full-color copying machine using process control, wherein when performing process control with black toner, a base patch with color toner is created on the surface of the transfer intermediate, and then a patch with black toner is created. In the reading method, when creating a base patch with color toner, operate the process control so that the density of the toner patch becomes a predetermined density,
An image forming apparatus characterized in that the density of a base patch is kept constant. 2. The color toner patch density is kept constant so that the relationship of color toner patch density (color toner process control sensor output voltage)> black toner patch density (black toner process control sensor output voltage) is satisfied. The image forming apparatus according to claim 1. 3. The color toner patch density (output voltage of the process control sensor of the color toner) is kept constant at a place where the color toner patch density is saturated so that the dynamic range of the process control sensor can be utilized to the maximum extent. The image forming apparatus according to claim 1. 4. When the color toner patch cannot be kept at a constant density, the developing device is automatically switched to another color so as to keep the base density constant, and the base density is kept constant even if the developing device is switched. 2. The image forming apparatus according to claim 1, wherein when the color density cannot be maintained, the base layer is composed of two or more colors to keep the density constant. 5. The image according to claim 1, wherein the surface potential of the photoconductor when the color toner patch density is created by the process control is different from the surface potential when the process control is performed at the time of copying. Forming equipment. 6. The image forming apparatus according to claim 1, wherein the patch density is saturated by creating the color toner patch density with three colors of Y, M and C without operating the process control. 7. A full-color copying machine using process control, wherein when performing process control with black toner, a base patch with color toner is created on the surface of the transfer intermediate, and then a patch with black toner is created. Black toner patch length <
An image forming apparatus characterized in that a color toner length and a black toner patch are formed inside a color toner patch so that a transfer intermediate (black) and a black toner patch can be distinguished from each other. 8. The image forming apparatus according to claim 7, wherein when the color toner patch and the black toner patch cannot be distinguished, the read patch density data is not adopted for the process control. 9. A full-color copying machine using process control, wherein when performing process control with black toner, a base patch with color toner is created on the surface of the transfer intermediate, and then a patch with black toner is created. In the reading method, the image forming apparatus is characterized in that a portion lower than the output of the process control sensor where the black toner patch density is saturated is cut off to prevent noise.