JPH10153909A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide various potentials based on a calculation result of a developing ability at the time of subsequent image formation by setting a toner concentration so that a developing ability of a developing device at an initial setting operation becomes an initial target developing ability. The present invention provides a copying machine that does not cause a problem such as a decrease in image gradation due to a change in the setting. SOLUTION: In an initial setting operation when a new developer is set in a developing device, a developing capability of the developing device is calculated, and an initial value set in advance in consideration of the calculated developing capability and a change in the developing capability over time. Based on the result of comparison with the target developing ability, the initial target toner density of the developing device is set so that the calculated developing ability becomes the initial target developing ability, and various potentials are determined based on the result of calculating the next developing ability. By the time, a main control unit 201 for controlling the toner density in the developing device to be the initial target toner density is provided.

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 such as a copying machine, a facsimile, and a printer. More specifically, the present invention relates to replenishing toner to a developing device so as to attain a target toner density based on the detection result of the toner density of the developing device. And an image forming apparatus that sets various potentials during image formation based on the potential of a reference pattern formed on an image carrier and the developing ability of a developing device calculated from a detection result of the amount of toner attached to the reference pattern. is there.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a facsimile, a printer, and the like, generally, an image carrier, such as a photosensitive drum, is rotated to charge the image carrier uniformly by a charging device. Writing an image on the image carrier by image exposure with an exposure device to form an electrostatic latent image,
The toner image on the image carrier formed by developing the electrostatic latent image with a developing device is transferred to a transfer material by a transfer device. And
In order to form a color image, the above-described image forming process is repeated for each color to form a plurality of color toner images on the image carrier, which are then collectively transferred to a transfer material, or a single color toner image is formed. A method of forming the image on an image carrier and sequentially transferring the image to a transfer material is employed.

In such an electrophotographic image forming apparatus, an electrostatic latent image of a patch pattern as a reference pattern is formed on an image carrier, developed by a developing device, and the surface potential of the patch pattern and its potential. 2. Description of the Related Art There has been known an image forming apparatus which employs a potential control method of calculating a developing capability of a developing device from a toner adhesion amount and determining various potentials such as a developing bias potential and a charging potential of an image carrier from the developing capability.

[0004] In particular, the present applicant has been able to perform accurate potential control in a short time, and at the same time, to change the environment of the developer,
As a potential control method capable of avoiding the influence on image reproduction due to aging, the potentials of a plurality of patch patterns formed on an image carrier and the toner adhesion amount are measured, and the plurality of sets of potentials and toner adhesion amounts are measured. Calculate a section where the relationship between the potential and the amount of toner attached linearly changes based on the data of the above, and obtain a linear approximation that linearly approximates the development characteristic from the data of the measured potential and the amount of toner attached in this section, A device that determines various potentials during image formation using this linear approximation formula has been proposed (see Japanese Patent Application No. 6-275869).

[0005]

In the image forming apparatus employing the above-described potential control method, when a new developer is set in the developing device, the toner charge amount of the developer is not a predetermined charge amount. In spite of the predetermined density, there is a possibility that the developing ability of the developing device deviates greatly from the target developing ability.

For example, when a new developer having a large toner charge is set in the developing device, the developing capability of the developing device becomes lower than the target developing capability. In this case, various potentials are set so as to increase the maximum value of the development potential (hereinafter, referred to as “maximum development potential”) corresponding to the target maximum amount of toner adhesion at the time of image formation. As the charge amount increases and the developing ability increases, the setting of various potentials is changed so as to gradually reduce the maximum developing potential. Also, for example,
When a new developer having a small toner charge amount is set in the developing device, the developing capacity becomes higher than the target developing capacity. In this case, various potentials are set so as to reduce the maximum developing potential, and when the toner charge amount decreases over time and the developing ability decreases,
The settings of various potentials are changed so as to increase the maximum developing potential.

However, if the maximum developing potential is largely changed by changing the setting of various potentials in order to obtain the optimum developing ability, the following problems may occur over time. For example, if the maximum developing potential set in accordance with the developing ability is too small, the developing potential for one of a plurality of gradations of the image becomes small. There is a problem that even if the potential on the image carrier slightly changes, the gradation disappears or the gradation largely changes. Conversely, if the maximum developing potential set according to the developing ability is too large, the problem of the gradation difference is eliminated, but it is necessary to increase the charging potential and the amount of exposure light for writing the latent image. In addition, the amount of charge passing through the photosensitive layer of the photoconductor as an image carrier increases, and the life of the photoconductor is shortened. Also, in the transfer process after development, the electric field formed between the high potential of the non-image area on the image carrier and the transfer charge on the intermediate transfer body and the transfer material increases, causing discharge breakdown and scattering the toner. Also, there may be a problem that the transfer becomes uneven.

In order to prevent the above-mentioned problem from occurring when the maximum developing potential is largely changed in accordance with the fluctuation of the developing ability, the present applicant sets the developing ability of the developing device at the time of the initial setting operation as a reference. An image forming apparatus has been proposed in which an allowable range of the developing capacity is set in advance and the setting of the target toner density in the toner replenishment control is changed so that the developing ability does not deviate from the upper and lower limits of the allowable range with the passage of time (Japanese Patent Application No. 2002-214568). Hei 7-321469). However, even if control is performed to change the setting of the target toner concentration over time as described above, from the time of the initial setting operation when a new developer is set to the time when the developing ability deviates from the upper and lower limits of the allowable range thereafter. In the meantime, various potentials are set according to the fluctuation of the developing ability, and the maximum developing potential becomes excessively large or small, which may cause a problem such as a decrease in the image gradation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device in which a new developer is set, even if the developing capability of the developing device deviates from a predetermined developing capability.
An object of the present invention is to provide an image forming apparatus which does not cause a problem such as a decrease in image gradation due to a change in setting of various potentials based on a calculation result of a developing ability at the time of image formation thereafter.

[0010]

In order to achieve the above object, according to the present invention, the toner density of a developing device is detected by a toner density detecting means, and the toner density in the developing device is determined based on the detection result. Is controlled to be the target toner density, and the developing ability of the developing device is calculated based on the potential of the reference pattern formed on the image carrier and the detection result of the toner adhesion amount. In an image forming apparatus that determines various potentials at the time of image formation based on an image forming apparatus, a developing capability of the developing device is calculated during an initial setting operation when a new developer is set in the developing device, and the calculated developing capability and the development over time are calculated. The initial target toner density of the developing device is set based on the result of comparison with the initial target developing ability set in advance in consideration of the change in the ability so that the calculated developing ability becomes the initial target developing ability. A control means for controlling the toner density in the developing device to the initial target toner density by the time of determining the various potentials based on the calculation result of the next developing ability is provided. .

In the image forming apparatus of the first aspect,
At the initial setting operation when a new developer is set in the developing device, the developing capability of the developing device is calculated, and the calculated developing capability and the initial target developing capability set in advance in consideration of the change in the developing capability over time are calculated. Compare. Based on the comparison result, the initial target toner density of the developing device is set so that the developing ability becomes the initial target developing ability. Then, by the time the various potentials are determined based on the calculation result of the next developing ability, the control is performed so that the toner density in the developing device becomes the initial target toner density. By controlling the toner concentration in the developing device to the initial target toner concentration in this manner, the developing capability of the developing device is set to the initial target developing capability. After the initial setting operation, the initial target developing capability is adjusted. Even if there is a change in the developing ability as considered in setting, the various potentials can be kept within appropriate ranges without greatly changing various potentials at the time of image formation determined based on the developing ability. .

According to a second aspect of the present invention, a toner is supplied to a developing device based on a comparison result between an output value of the toner density detecting means and a control reference value so that the toner density in the developing device becomes a target toner density. 2. The image forming apparatus according to claim 1, wherein the replenishment is controlled. After the initial target toner density is set at the time of the initial setting operation, while the toner is consumed from the developing unit or the toner is replenished to the developing unit, The toner adhesion amount is detected, and based on a comparison result between the toner adhesion amount and the initial target toner adhesion amount set according to the initial target developing ability, the toner adhesion amount is set to the initial target toner adhesion amount. The present invention is characterized in that an initial target toner density of a developing device is set.

In the image forming apparatus of the second aspect,
After the initial target toner concentration is set during the initial setting operation, the amount of toner adhering to the image carrier is detected while the toner is consumed from the developing device or the toner is supplied to the developing device. The detected toner adhesion amount is compared with an initial target toner adhesion amount set in accordance with the initial target developing ability. Based on the comparison result, the initial target toner density of the developing device is set so that the detected toner adhesion amount becomes the initial target toner adhesion amount.

According to a third aspect of the present invention, latent images of a plurality of reference patterns having different potentials are formed on an image carrier, and the plurality of latent images are developed by a developing device to form a toner image of the reference patterns. 3. The image according to claim 2, wherein the potential of the latent image of the reference pattern and the toner adhesion amount of the toner image are detected, and the developing capability of the developing device is calculated based on the plurality of sets of the detection results of the potential and the toner adhesion amount. In the forming apparatus, at the time of the initial setting operation, a toner adhesion amount of a toner image of an arbitrary one reference pattern selected from a plurality of reference patterns used for calculating the developing capacity is detected, and the toner adhesion amount and the initial amount are determined. An initial target toner density of a developing device is set based on a comparison result with an initial target toner adhesion amount set in accordance with a target developing ability so that the toner adhesion amount becomes the initial target toner adhesion amount. It is intended to.

In the image forming apparatus of the third aspect,
The amount of toner attached to the toner image of any one of the plurality of reference patterns selected from the plurality of reference patterns used for calculating the developing capacity is detected, and an initial target set in accordance with the amount of toner attached and the initial target developing capacity is detected. Compare the amount of toner adhesion. Based on the comparison result, the initial target toner density of the developing device is set so that the detected toner adhesion amount becomes the initial target toner adhesion amount.

According to a fourth aspect of the present invention, based on a comparison result between the output value of the toner density detecting means and a control reference value, the toner supplied to the developing device is adjusted so that the toner density in the developing device becomes the target toner density. 4. The image forming apparatus according to claim 3, wherein after the initial setting operation, the initial target toner density is set, and then the selected reference pattern is supplied while consuming toner from the developing unit or supplying toner to the developing unit. And detecting the toner adhesion amount of the toner image of the selected reference pattern, and controlling the output value of the toner density detection means when the detection result of the toner adhesion amount reaches the initial target toner adhesion amount. It is characterized in that it is newly set as a reference value.

In the image forming apparatus according to the fourth aspect,
At the time of the initial setting operation, after setting the initial target toner concentration, creating the selected reference pattern while consuming toner from the developing device or supplying toner to the developing device,
The toner adhesion amount of the toner image of the selected reference pattern is detected. Then, an output value of the toner density detecting means when the detection result of the toner adhesion amount becomes the initial target toner adhesion amount is newly set as a control reference value. Based on the comparison result between the newly set control reference value and the output value of the toner density detecting means, the toner supply to the developing device is controlled so that the toner density in the developing device becomes the initial target toner density.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the toner set when the detection result of the toner adhesion amount of the toner image of the selected reference pattern reaches the initial target toner adhesion amount. The control parameter of the toner density detecting means is changed so that the control reference value of the density detecting means falls within a predetermined suitable setting range. Here, the control parameter is a parameter that changes a detection characteristic indicating a relationship between an output value of the toner density detection unit and a toner density to be detected.

In the image forming apparatus according to the fifth aspect,
The control reference value of the toner density detecting means set when the detection result of the toner adhesion amount of the toner image of the selected reference pattern becomes the initial target toner adhesion amount falls within a predetermined suitable range. By changing the control parameter of the toner density detecting means, the comparison between the output value of the toner density detecting means and the control reference value can always be performed within the above-mentioned preferred setting range.

According to a sixth aspect of the present invention, a plurality of latent images of a reference pattern having different potentials are formed on an image carrier, and the plurality of latent images are developed by a developing device to form a toner image of the reference pattern. 2. The image according to claim 1, wherein the potential of the latent image of the reference pattern and the toner adhesion amount of the toner image are detected, and the developing capability of the developing device is calculated based on the detection results of the plurality of sets of potentials and the toner adhesion amount. In the forming apparatus, at the time of the initial setting operation, at least one of the two reference patterns having the maximum and minimum toner adhesion amounts is selected from the plurality of reference patterns used for calculating the developing capacity, and the selected reference pattern is selected. The potential of the latent image of the pattern and the amount of toner adhering to the toner image are detected, the developing capability of the developing device is calculated based on the detection result, and the calculated developing capability and changes in the developing capability over time are considered. Then, based on the result of comparison with the preset initial target developing ability, the initial target toner density of the developing device is set so that the calculated developing ability becomes the initial target developing ability. After controlling to the initial target toner density, a reference pattern is selected from the plurality of reference patterns so as to include two reference patterns with the maximum and minimum toner adhesion amounts, and the selected reference pattern is used. The developing ability is confirmed by using the following method.

In the image forming apparatus according to the sixth aspect,
At the time of the initial setting operation, at least one of the two reference patterns having the maximum and minimum toner adhesion amounts is selected from the plurality of reference patterns used for calculating the developing capacity, and the latent image of the selected reference pattern is selected. And the toner adhesion amount of the toner image. Then, the developing capability of the developing device is calculated based on the detection result. Based on a result of comparison between the calculated developing ability and an initial target developing ability set in advance in consideration of a change in the developing ability with time, the initial target of the developing device is set so that the calculated developing ability becomes the initial target developing ability. Set the toner density. And
After controlling the toner density in the developing device to be the initial target toner density, a reference pattern is selected from the plurality of reference patterns so that the toner adhesion amount includes two reference patterns of maximum and minimum, The developing ability is confirmed using the selected reference pattern.

According to a seventh aspect of the present invention,
In the image forming apparatus of the fourth, fifth or sixth embodiment, when the calculation result of the developing ability of the developing device over time after the initial setting operation is within the range of the predetermined target developing ability, The setting is changed by a predetermined constant value, and when the calculation result of the developing ability over time is out of the range of the predetermined target developing ability, the setting of the target toner density is the same as in the initial setting operation. In this case, the change is made based on the calculation result of the developing ability.

In the image forming apparatus of the present invention,
After performing the initial setting operation, if the calculation result of the developing ability of the developing device over time is within the range of the predetermined target developing ability, the setting of the target toner density is set in accordance with the deviation amount of the developing ability. Change not a value but a predetermined constant value.
On the other hand, when the calculation result of the developing ability over time is out of the range of the predetermined target developing ability, the setting of the target toner density is changed based on the calculation result of the developing ability as in the initial setting operation. I do.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic full-color copying machine (hereinafter referred to as a "color copying machine") as an image forming apparatus according to the present invention will be described below.
) Will be described. FIG. 2 is a schematic configuration diagram of the entire color copying machine according to the present embodiment, and FIG.
FIG. 3 is an enlarged view around a photosensitive drum and an intermediate transfer belt of the color copying machine. In FIG. 2, the color copying apparatus includes a color image reading device (hereinafter, referred to as a color scanner) 1 and a color image recording device (hereinafter, referred to as a color printer) 2.

First, the color scanner 1 forms an image of an original 3 on a color sensor 7 via an illumination lamp 4, a mirror group 5, and a lens 6, and converts color image information of the original into, for example, blue (Blue, It is read out for each color separation light of green (hereinafter, referred to as B), green (hereinafter, referred to as G), and red (Red, hereinafter, referred to as R) and converted into an electric image signal. And B, G, obtained by this color scanner 1,
Based on the color separation image signal intensity level of R, a color conversion process is performed in an image processing unit (not shown), and black (hereinafter, referred to as Bk), cyan (Cyan, hereinafter referred to as C),
Magenta (hereinafter referred to as M), yellow (Yel
low, hereinafter referred to as Y).

Next, in the color printer 2, the laser optical unit 8 converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the original image, and performs photosensitive writing as an image carrier. Body drum 9
To form an electrostatic latent image. The photosensitive drum 9 rotates counterclockwise as shown by the arrow, and around the photosensitive drum 9, a photosensitive member cleaning unit (including a pre-cleaning static eliminator) 1 is provided.
0, static elimination lamp 11, charging device 12, surface potential sensor 13 as surface potential measuring means, Bk developing device 14, C developing device 15, M developing device 16, Y developing device 17, image density measurement for detecting development density pattern A light reflection type optical sensor 18 and an intermediate transfer belt 19 as means are arranged. Each developing device has a developing sleeve (14a, 15a, 16a, 17a) that rotates by bringing a spike of developer into contact with the surface of the photosensitive drum 9 to develop an electrostatic latent image, and draws and agitates the developer. Developing paddle (14b, 1
5b, 16b, 17b) and toner concentration sensors (14c, 15c, 16c, 17c) as toner concentration measuring means for measuring the toner concentration of the developer.

Hereinafter, the outline of the copying operation will be described with an example in which the order of the developing operation (color toner image forming order) is Bk, C, M, and Y (however, the image forming order is not limited to this). ). When the copying operation is started, reading of the Bk image data is started at a predetermined timing by the color scanner 1, and light writing by a laser beam and formation of a latent image are started based on the image data (hereinafter, electrostatic image formation by the Bk image data). The latent image is called a Bk latent image, C, M, Y.
Are referred to as C latent image, M latent image and Y latent image, respectively).
Before the front end of the latent image reaches the developing position of the Bk developing device 14 so as to enable development from the front end of the Bk latent image, the rotation of the developing sleeve 14a is started to develop the Bk latent image with Bk toner. Thereafter, the developing operation of the Bk latent image area is continued,
When the rear end of the latent image passes the Bk developing position, the developer on the developing sleeve 14a is promptly cut off, and the developing operation is stopped. The developer is cut off by the developing sleeve 14.
This is performed by switching the rotation direction of “a” to a direction opposite to that during the developing operation. The switching of the Bk developing device 14 to the development inoperative state is completed at least before the leading end of the C latent image based on the next C image data arrives.

Next, the Bk toner image formed on the photosensitive drum 9 is transferred onto the surface of the intermediate transfer belt 19 driven at the same speed as the photosensitive drum 9 (hereinafter referred to as the photosensitive drum 9).
(Transfer of the toner image from the belt to the intermediate transfer belt 19 is referred to as belt transfer.) This belt transfer is performed by applying a predetermined bias voltage to the transfer bias roller 20a in a state where the photosensitive drum 9 and the intermediate transfer belt 19 are in contact with each other.

In the same operation, C, C are sequentially placed on the photosensitive drum 9.
M, Y toner images are formed (the order of Bk, C, M, Y is not limited to this), and the four-color superimposed belt transfer image is sequentially and accurately aligned on the intermediate transfer belt 19. And then transfer paper 24 by paper transfer unit 23
The paper transfer is performed collectively.

In the above-mentioned intermediate transfer belt unit, the intermediate transfer belt 19 includes the driving roller 21 and the transfer bias roller 2.
0 and a group of driven rollers, and is driven and controlled by a drive motor (not shown). At a predetermined position facing the surface of the intermediate transfer belt 19, a belt cleaning unit 22 is provided.
Are the inlet seal 22a, the cleaning blade 22b,
And a contact / separation mechanism 22c from the intermediate transfer belt 19. When cleaning is not required, the contact / separation mechanism 22c
Seal 22a and cleaning blade 2
2b is separated from the belt surface.

A paper transfer unit 23 is provided so as to face the portion of the intermediate transfer belt 19 wound around the drive roller 21. This unit 23
Paper transfer bias roller 23a, roller cleaning blade 23b, and mechanism 2 for contacting and separating from intermediate transfer belt 19
3c and the like. Although the paper transfer bias roller 23a is normally separated from the intermediate transfer belt 19, the four-color superimposed image formed on the belt 19 is
At the time of collective transfer to the transfer paper 24, the transfer is performed by the contact / separation mechanism 23c at a timing, and a predetermined bias voltage is applied to the roller 23a to transfer the image onto the transfer paper 24.

The transfer paper 24 is fed by a feed roller 25 and a registration roller 26 at the timing when the leading end of the four-color superimposed image on the surface of the intermediate transfer belt 19 reaches the paper transfer position. Then, the transfer paper 24 on which the four-color superimposed toner image is collectively transferred from the surface of the intermediate transfer belt 19 is conveyed to a fixing device 28 by a paper conveyance unit 27, and the fixing roller 28a and the pressure roller 2 are controlled to a predetermined temperature.
In step 8b, the toner image is fused and fixed, and is carried out to the copy tray 29 to obtain a full-color copy.

The photosensitive drum 9 after the belt transfer is
Photoconductor cleaning unit 10 (pre-cleaning static eliminator 10a, brush roller 10b, rubber blade 10c)
Then, the surface is cleaned, and the charge is uniformly removed by the charge removing lamp 11. After the transfer of the toner image onto the transfer paper 24, the surface of the intermediate transfer belt 19 is cleaned by pressing the cleaning unit 22 again by the contact / separation mechanism 22c.

The transfer paper cassettes 30, 31, 32,
Reference numeral 33 stores transfer papers of various sizes, which are fed and conveyed in the direction of the registration rollers 26 from the storage cassette of the size paper designated by the operation panel (not shown) at a certain timing. Reference numeral 34 denotes a manual paper feed tray for feeding OHP paper, thick paper, or the like.

The above is the description of the copy mode for obtaining four full colors. However, in the case of the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times. become. Further, in the case of the single color copy mode, only the developing device of the color is set in the developing operation (spring) until the predetermined number of sheets is completed, and the intermediate transfer belt 19 reciprocates while being in contact with the photosensitive drum 9. Direction, and the belt cleaning unit 22 performs a copying operation while keeping the belt cleaning unit 22 in contact with the intermediate transfer belt 19.

FIG. 1 is a block diagram of a control system of the present color copying machine. This control system includes a main control unit 201 as a control means and a plurality of peripheral control units. The main control unit 201 temporarily stores a CPU 202, a ROM 203 storing a control program and various data, and temporarily stores various data as a work area. And an I / O interface unit 205 for performing input / output with each peripheral control unit.

The main control unit 201 has an I / O
Via an interface unit 205, a laser optical system control unit 206, a power supply circuit 207, an optical sensor 18, toner concentration sensors 14c, 15c, 16c, 17c, a toner supply circuit 212, an intermediate transfer belt drive circuit 213, a surface potential sensor 13, and the like. It is connected. The laser optical system control unit 206 controls the laser optical unit 8 based on a command from the main CPU 202, and the power supply circuit 207 applies a high voltage to the charger 12 based on a command from the main CPU 202, and also controls the developing sleeve 14a. , 15
a, 16a and 17a are applied with a developing bias voltage, respectively. The optical sensor 18 optically detects the reflection density of the toner image on the photosensitive drum 9. The surface potential sensor 13 detects the surface potential of the photosensitive drum 9. The toner supply circuit 212 controls a toner supply motor of each toner supply unit based on a command from the main CPU 202 to supply toner of each color to each developing device.

FIG. 4 is a flowchart of a potential control routine performed by the main control unit 201. The potential control by the potential control routine is basically performed when the apparatus (copying machine) is started, but may be performed as needed, for example, every predetermined number of copies or every certain time. In the potential control routine of FIG. 4, the main control unit 201 first receives a signal from a fixing temperature sensor (not shown) that detects the fixing temperature of the fixing device 28 in order to distinguish the power-on state from the abnormality processing such as a jam. Fixing temperature is 100 ° C based on input signal
It is determined whether or not this is the case (step 501). Here, when the fixing temperature exceeds 100 ° C., it is determined that there is an abnormality, and the potential control is not performed. On the other hand, when the fixing temperature is 100
If the temperature is lower than ° C, the power supply circuit 207 supplies the photosensitive drum 9
The reference voltage is applied to the surface potential sensor 13 to calibrate the surface potential sensor 13 (step 502). This calibration value is used in subsequent potential calculations. Next, the main control unit 201 fetches the output value Vsg for the background portion of the photosensitive drum 9 from the optical sensor 18 so that the reflected light of the light emitted from the optical sensor 18 to the background portion of the photosensitive drum 9 becomes a constant value. Then, the light emission amount of the optical sensor 18 is adjusted (step 503).

Next, as shown in FIG. 5, electrostatic latent images 301, 302, 303, and patch patterns, which are reference patterns having N gradation densities, are provided at the center of the photosensitive drum 9 in the width direction.
Are created at predetermined intervals along the rotation direction of the photosensitive drum 9 (step 504). For example, 14 electrostatic latent images 301, 302,... 314 of a rectangular patch pattern having different gradation densities and each side being 40 mm are represented by one.
It is created at an interval of 0 mm. Hereinafter, a case where an electrostatic latent image of 14 patch patterns is created will be described.
Then, these electrostatic latent images 301, 302,.
The output value of the surface potential sensor 13 corresponding to the potential of the RAM 4 is read and converted into a surface voltage value using the calibration value.
04 (step 505). In this case, the main control unit 201 controls the electrostatic latent image 30 of the 14 patch patterns.
., 314 for four colors Bk, C, M, and Y are sequentially formed on the photosensitive drum 9 at predetermined intervals.

Next, the main controller 201 controls the electrostatic latent images 301 and 3 of the patch pattern for four colors on the photosensitive drum 9.
, 314 are developed for each color by a Bk developing unit 14, a C developing unit 15, an M developing unit 16, and a Y developing unit 17 to form a toner image of each color. The output value of the optical sensor 18 for the toner image is set to Vpi for each color.
It is stored in the RAM 204 as (i = 1 to 14) (step 506).

The main control unit 201 uniformly charges the photosensitive drum 9 by the charger 12 and changes the output of the laser optical unit 8 via the laser optical system control unit 206 to change the electrostatic latent image of the patch pattern. 301, 302, ...
.. 314 may be created, but the toner image of each patch pattern may be created by switching the developing bias voltage of each of the developing units 14 to 17 without operating the laser optical unit 8.

Next, the main control unit 201
The output value of the optical sensor 18 stored in the storage unit 4 is converted into a toner adhesion amount per unit area with reference to a table stored in the ROM 203 and stored in the RAM 204 (step 507).

FIG. 6 is a plot of the relationship between the measured data of the surface potential obtained in step 505 and the measured data of the amount of applied toner obtained in step 507 in each patch pattern on an XY plane. And the developing potential (the difference between the developing bias voltage Vb at the time of creating the patch pattern and the surface potential Vs of the photosensitive drum 9: V
b-Vs: unit (V)), and the toner adhesion amount per unit area (mg / cm ² ) is allocated on the Y axis. Normal,
As shown in FIG. 6, the infrared light reflection type sensor used as the optical sensor 18 shows a saturation characteristic in a large amount of toner attached to a large amount of toner, and the sensitivity in the large amount of toner is low. The measurement accuracy of the toner adhesion amount is also poor. Therefore, in order to accurately calculate a linear approximation formula (Y = a * X + b) that linearly approximates the true developing characteristic of the developing device, a high sensitivity section (high precision section) of the optical sensor 18 as shown in FIG. And measurement data of the development potential obtained from the output value of the surface potential sensor 13 and the optical sensor 1
The linear approximation formula is calculated using only the measurement data points in the section where the relationship with the toner adhesion amount obtained from the output value of FIG. 8 is a straight line (step 508), and the calculation accuracy of the linear approximation formula is increased. ing. Further, the RO data is set in advance so that the measurement data points in this section are denser than the other sections.
The light amount data used by the laser optical unit 8 when each patch pattern to be stored in the M203 is created is set to a desired value, so that, when the total number of measurement data is the same and the data intervals are equal, Then, the number of pieces of measurement data used for calculating the linear approximation expression is increased, and the calculation accuracy of the linear approximation expression is further improved.

When the toner image of each patch pattern is created by changing the developing bias voltage without operating the laser optical unit 8 as described above, the measured data points in the above-mentioned section are more than those in other areas. The data of the developing bias voltage stored in advance in the ROM 203 and applied when creating each patch pattern is set to a desired value so as to be dense.

To select the measurement data of the section from all the measurement data in step 508, for example, focusing on the measurement data of the toner adhesion amount calculated in step 507, 0.15 to 0.40 mg / cm ^What is necessary is to select a set of measurement data of the toner adhesion amount and the development potential between the ^two .

Next, a smoothing process is performed only on the effective measurement data selected in step 508 using a plurality of formulas shown in equation 1 (step 509), and smoothing is performed on the measurement data having a large measurement error. The linear approximation formula can be calculated with high accuracy without causing a deviation in the approximate straight line calculation as in the case where the process is used to calculate the linear approximation formula. Here, i ≦ n ≦ j, and the smoothing process is not performed on the measurement data at the end of the section.
Also, “′” is added to the measurement data after the smoothing process.

X '(n) = X (n-1) * 0.25 + X (n) * 0.5 + X
(n + 1) * 0.25 Y '(n) = Y (n-1) * 0.25 + Y (n) * 0.5 + Y (n + 1) *
0.25 X '(i) = X (i) X' (j) = X (j) Y '(i) = Y (i) Y' (j) = Y (j)

By applying the least-squares method to the measured data obtained in this way after the smoothing processing, a linear approximation of the developing characteristics of each of the developing units 14 to 17 is performed to obtain a linear approximation of the developing characteristics. Is obtained for each color (step 510). Various control potentials are calculated for each color based on the linear approximation formula. For the calculation of the least squares method, a plurality of equations shown in the following Expression 2 were used. Here, “′” indicating the measurement data after the smoothing process is omitted for convenience. K indicates the number of measurement data used for the calculation.

Xave = ΣXn / k Yave = ΣXn / k Sx = Σ (Xn-Xave) * (Xn-Xave) Sy = Σ (Yn-Yave) * (Yn-Yave) Sxy = Σ (Xn-Xave) * (Yn-Yave)

Then, a linear approximation formula calculated from the measured data of the surface potential of the patch pattern and the toner adhesion amount obtained from the surface potential sensor 13 and the optical sensor 18 is represented by Y =
When a * X + b, the coefficients a and b are expressed by the following equation 3 using the variables of the above equation 2.

## EQU3 ## a = Sxy / Sx b = Yave-a * Xave

The coefficient a may be determined by the following method. That is, since a plurality of continuous (for example, four) data sets are obtained from a plurality of sets of measurement data in the selected section, a linear regression is performed on each of the data sets, and among them, a linear regression is performed. It is also possible to select a value having a large value, a value in which the value of the gradient a is close to the average value, or a value having the largest correlation coefficient of the linear regression equation.

Next, the main control unit 201 uses the linear approximation formula calculated for each color in step 510 to set each control potential so that the value of Y becomes the required maximum toner adhesion amount Mmax. It is determined (step 511). As shown in FIG. 7, an image is obtained from the developing electric field (Vgp) necessary for obtaining the above Mmax and Vk (= -b / a: development start voltage) which is the X intercept of the calculated linear approximation. Vkp (developing potential: reference potential for setting various potentials during formation)
Vb−Vs) is determined by the following equation (4).

Vgp = Mmax / a Vkp = Vgp + Vk

Next, from the value of the developing electric field Vgp, R
Referring to the potential table as shown in FIG. 8 stored in the OM 203 (step 512), the charging potential (Vd)
The developing bias voltage (Vb) and the maximum exposure potential (Vl) are determined as target potentials (step 513). Then, the power supply circuit 207 is adjusted so that the charging potential of the photosensitive drum 9 by the charger 12 becomes the target potential Vd, and the amount of laser light emission (light emission power) by the laser optical system 8 becomes the target potential Vl. Adjustment, and each color developing device 13-1
7 are adjusted so that each of the developing bias voltages becomes the target voltage Vb (step 514).

Next, an example of control at the time of an initial setting operation when a new developer (hereinafter, referred to as "initial agent") is set in the developing device according to this embodiment will be described.

[Control Example 1] FIG. 9 is a flowchart showing one control example at the time of the initial setting operation. After the initial agent is set in the developing device of the present color copier, the control flow of FIG. 4 is executed. When the calculation of the approximate straight line in step 510 is completed, the control flow is temporarily interrupted and the control flow of FIG. 9 is executed.
First, the above-mentioned approximate straight line is obtained for the developing device in which the initial agent is set, and the inclination a of the approximate straight line is set as the developing capability a0 of the developing device in which the initial agent is set (step 601). Next, the maximum value a [max] and the minimum value a [min] of the range of the developing ability a0 and the desirable developing ability in the initial agent, which is the initial target developing ability set in advance in consideration of the change of the developing ability over time, are set. Is performed (step 602).
If the developing capacity a0 is larger than the maximum value a [max] or smaller than the minimum value a [min], the toner density control point of the toner density sensor (T sensor) is changed, thereby setting the initial target toner density. (Step 6
03). Then, the toner density in the developing device is adjusted to the level of the initial target toner density (step 604). Thereafter, the process is started from the patch pattern creation in step 504 in FIG. On the other hand, when the developing capacity a0 is between the maximum value a [max] and the minimum value a [min], the adjustment is not performed on the toner density sensor, but is executed from the calculation of the development potential in step 511 in FIG. 4 ( Step 605).

FIG. 10 is a graph showing the relationship between the toner concentration TC in the developing device and the developing ability a, and the relationship between the control voltage Vcnt of the toner concentration sensor and the toner concentration TC.
However, the absolute value of these relations varies depending on the conditions of the developing device (development gap, the amount of developer pumped, etc.), the mounting accuracy of the toner density sensor, the dispersion of the toner density sensor itself, etc., but the relative value (difference) Is the same.

When the initial developing ability of the developing device in which the initial agent is set is not the initial target developing ability, that is, when the developing ability is out of the target range, the central value (for example, the maximum value a [max] and the minimum value Then, a difference between the control voltage Vcnt0 and the intermediate control value a [min] is calculated, and a target control voltage Vcnt (actually, a difference between Vcnt0 and Vcnt0 ′) is obtained from the graph of FIG. Actually, instead of calculation, for example, a look-up table may be prepared in advance, and the control voltage Vcnt may be obtained with reference to the table. Thereby, the correction amount of the toner density sensor can be obtained.

As described above, according to the control at the time of the initial setting operation shown in FIG. 9, even when the developing ability of the developing device in which the initial agent is set is low, it is possible to set various potentials optimal for the subsequent image formation.
Since the changes in various potentials over time can be moderated, image quality such as grayscale collapse and highlight reproducibility differs with the grayscale reproduction adjustment value (γ adjustment) set during the initial setting operation A different impression can be prevented.

[Control Example 2] Next, another control example at the time of the initial setting operation will be described. A straight line Q in FIG. 11 indicates the developing ability of the developing device immediately after the initial agent is set, and a straight line P indicates the initial target developing ability. In FIG. 11, data in the calculation range used for calculating the developing capacity is indicated by black circles. If the initial target toner density is changed so that the toner adhesion amount at an arbitrary point A in this calculation range becomes the toner adhesion amount at the point A ′, the straight line Q becomes a straight line P and the developing unit The ability becomes the initial target developing ability.

FIG. 12 is a graph showing the relationship between the toner concentration TC, the toner adhesion amount M, and the control voltage Vcnt of the toner concentration sensor, showing the method of changing the initial target toner concentration in this control example. However, as in the case of FIG. 10, the absolute values of these relations vary depending on the conditions of the developing device (development gap, the amount of developer pumped up, etc.), the mounting accuracy of the toner density sensor, the dispersion of the toner density sensor itself, and the like. However, the relative values (differences) are the same. The current toner adhesion amount at point A is M0, and the target toner adhesion amount is M
If it is 0 ', the change amount of the control point of the toner density sensor, that is, the change amount of the control voltage Vcnt of the toner density sensor (actually, the difference between Vcnt0' and Vcnt0) can be obtained from FIG. Instead of actually calculating, for example, a look-up table may be prepared in advance, and the control voltage Vcnt may be obtained by referring to the table. The control flow in this control example is the same as that in FIG.

According to this control example, during the initial setting operation,
Since the amount of toner attached to any one of the reference patterns selected from a plurality of patch patterns within the calculation range used for calculating the developing capacity is detected, and the initial target toner density is set using the detection result, a plurality of The developing ability of the developing device can be more quickly set to the initial target developing ability as compared with the case where the patch pattern of (1) is used.

[Control Example 3] Next, another control example at the time of the initial setting operation will be described. The straight line Q in FIG. 13 indicates the developing capacity of the developing device immediately after the initial agent is set, and the straight line P
Indicates an initial target developing ability. In FIG. 13, data of the calculation range used for calculating the developing capacity is indicated by black circles. The minimum and maximum points of the toner adhesion amount within this calculation range are B and C, respectively. Of course, the inclination of the straight line connecting the points B and C indicates the developing ability of the developing device immediately after the initial agent is set. Here, in order to set the developing capability of the developing device to the initial target developing capability, the toner density is increased so that points B and C become points B 'and C', respectively.

The method of changing the initial target toner density in this control example is performed in the same manner as in the case of FIG. here,
Either of the minimum and maximum points B and C of the toner adhesion amount may be used. As a result, toner supply to the developing device is performed in order to adjust the toner concentration based on the value of the control voltage Vcnt obtained again.

FIG. 14 shows a control flow at the time of the initial setting operation according to this control example. After the initial agent is set in the developing device of the present color copier, the control flow of FIG. 4 is executed. When the calculation of the approximate straight line in step 510 is completed, the control flow is interrupted and the control flow of FIG. 14 is executed. First,
The above-described approximate straight line is obtained for the developing device in which the initial agent has been set, and the gradient a of the approximate straight line is defined as the developing capability a0 of the developing device in which the initial agent has been set (step 601). Next, the maximum value a [max] and the minimum value a [min] of the range of the developing ability a0 and the desirable developing ability in the initial agent, which is the initial target developing ability set in advance in consideration of the change of the developing ability over time, are set. Is performed (step 602). When the developing capacity a0 is larger than the maximum value a [max] or smaller than the minimum value a [min], the points in the calculation range where the toner adhesion amount is the minimum and the maximum (or a plurality of points including those points) ) Patch pattern (step 6)
03).

Next, as shown in FIG. 10, a toner pattern is set using the patch pattern of any one of the selected points to set the initial target toner density so as to attain the initial target developing capacity. Control point of the density sensor (control voltage Vcn
The changed value of t) is obtained (step 604). Then, the toner is supplied to the developing device (or the toner is consumed) so that the output value Vt of the toner density sensor becomes the control reference value Vref after the change of the control point (control voltage Vcnt) of the toner density sensor. (Step 605). Then, after adjusting the toner density based on the output value of the toner density sensor,
A plurality of patch patterns corresponding to the points selected in step 603 are created, and the slope (developing ability) and the X intercept are calculated from the relationship between the development potential and the amount of toner attached to those patch patterns (step 606). .
If the calculated developing capacity is not equal to the initial target developing capacity, the control point (control voltage Vcnt) of the toner density sensor for one of the plurality of patch patterns created immediately before, as shown in FIG. ) Is obtained, and toner is supplied to the developing device so that the output value Vt of the toner density sensor becomes the control reference value Vref after the change of the control point (control voltage Vcnt) of the toner density sensor (or). (Toner consumption is performed) (steps 607, 604, and 605).
On the other hand, if it is determined in step 607 that the calculated developing ability is the initial target developing ability, the processing is executed from the selection of the potential table in step 512 in FIG. 4 (step 608).

According to this control example, at the time of the initial setting operation, after controlling the toner density in the developing device to the initial target toner density, the developing capability is changed to the initial target developing capability by using the selected patch pattern. Since it is confirmed whether or not the developing ability is set, the developing ability of the developing device can be accurately set to the initial target developing ability.

[Control Example 4] Next, a control example at the time of the initial setting operation and a control example over time after the initial setting operation will be described. FIG. 15 shows a control flow at the time of the initial setting operation according to the present control example and at the time thereafter. First, it is determined whether or not the initial setting operation is performed when the initial agent is set in the developing device (step 601). If the initial setting operation is performed, the above approximate straight line is obtained for the developing device in which the initial agent is set. The slope a of the approximate line is defined as the developing capability a0 of the developing device in which the initial agent is set (step 60).
2). Next, the developing capability a0 and the maximum value a [ma of the range of the desirable developing capability of the initial agent which is the initial target developing capability set in advance in consideration of the change of the developing capability with time.
x] and a minimum value a [min] are compared (step 6).
03). The developing ability a0 is larger than the maximum value a [max];
Alternatively, if it is smaller than the minimum value a [min], the toner density control point of the toner density sensor (T sensor) is changed, thereby changing the setting of the initial target toner density (step 604). Then, the toner is supplied or consumed to the developing device, and the toner concentration in the developing device is adjusted to the level of the initial target toner concentration (step 605). Thereafter, the process is executed from the patch pattern creation in step 504 in FIG. 4 (step 606). On the other hand, when the developing capacity a0 is between the maximum value a [max] and the minimum value a [min], the adjustment of the toner density sensor is not performed, and step 51 in FIG.
(Step 60)
7).

When the operation is not the initial setting operation, the developing capability of the developing device is calculated in the same manner. In this case, the control flow of FIG. 4 is executed to the end (step 608). It is determined whether or not a difference a ′ between the calculated developing capability a and a target a ″ set within a range surrounded by the maximum value a [max] and the minimum value a [min] is within a certain range b. (Step 609) However, the value of a ″ ± b is also the maximum value a [ma
x] and the minimum value a [min]. If the difference a 'in the developing ability is not within the predetermined range b, the control voltage Vcnt of the toner density sensor is changed by one step, and the process ends (step 610). The change amount of the control voltage Vcnt for one step is set in advance, but is desirably at a level that does not greatly change the toner density. On the other hand, if the difference a 'in the developing ability is within the predetermined range b, the process is terminated without changing the control voltage Vcnt of the toner density sensor.

It should be noted that whether or not the above initial setting operation is performed
A setting unit may be provided for setting an initial setting operation mode when an initial agent is set in an operation unit (not shown), or a specific operation at the time of setting the initial agent (for example, whether initial setting of the toner density sensor is performed) is stored. It may be determined.

According to this control example, when the calculation result of the developing capacity of the developing device deviates from the initial target developing capacity by a predetermined value over time after the initial setting operation, the control voltage of the toner density sensor is determined in advance. By changing only one step, the setting of the target toner density is changed by a predetermined constant value. Therefore, compared with the case where the setting of the target toner density is changed according to the amount of deviation from the predetermined value. Thus, the user's waiting time for changing the setting of the target toner density can be minimized.

[Control Example 5] Next, still another control example at the time of the initial setting operation will be described. As described in the control example 2, an arbitrary point A is selected from the data points within the calculation range indicated by the black circle in FIG. 11, and the toner adhesion amount of the patch pattern corresponding to the point A is determined by the point A. If you change the initial target toner concentration so that
The straight line Q becomes a straight line P, and the developing capability of the developing device becomes the initial target developing capability.

As shown in FIG. 12 of the control example 2, if the current toner adhesion amount at the point A is M0 and the target toner adhesion amount is M0 ', the control point of the toner density sensor is determined according to FIG. The change amount, that is, the change amount of the control voltage Vcnt of the toner density sensor (actually, the difference between Vcnt0 ′ and Vcnt0) can be obtained. Instead of actually calculating, for example, a look-up table may be prepared in advance, and the control voltage Vcnt may be obtained by referring to the table.

FIG. 16 shows a control flow at the time of the initial setting operation according to this control example. Steps 601 to 603
Until this is the same as the control flow of FIG. 9, the description is omitted. In step 603, the control voltage V of the toner density sensor
After changing cnt to Vcnt ', a pattern for toner consumption (and toner replenishment) and the above-described selected pattern are created, and while the toner consumption (toner replenishment) is being performed, the toner adhesion amount of the selected patch pattern is targeted. Value M0 '± C
It is determined whether or not it has entered (steps 604, 60).
5). When the developing capacity a is larger than the maximum value a [max], the toner density is reduced. In this case, it is not necessary to create a toner supply pattern.

When it is determined in step 5 that the toner adhesion amount of the selected patch pattern has reached the target value M0 '± C, the output value Vt at that time is set as a new control reference value Vref (= Vref'). (Step 606). This C
May be set to a realistic value (for example, about 0.01 mg / cm ² ) for adjusting the toner density within a range that does not substantially cause a problem. After resetting the control reference value Vref,
The process is started from the patch pattern creation in step 504 in FIG. 4 (step 607).

If it is determined in step 602 in FIG. 16 that the developing capacity a is between the maximum value a [max] and the minimum value a [min], the toner density sensor is set in the same manner as in the control float of FIG. Is executed without performing the adjustment from the development potential calculation in step 511 of FIG. 4 (step 608).

FIG. 17 is a graph showing the output characteristics of the toner density sensor. The output voltage (output value) Vt of the toner density sensor decreases as the toner density increases. The control voltage Vcnt of the toner density sensor adjusts the output voltage Vt of the toner density sensor without changing the relationship (slope) between the toner density and the output voltage Vt. For example, when the toner density is TM and the control voltage Vcnt is VcntM, the output voltage Vt is VtM. However, when the control voltage Vcnt is changed from VcntM to VcntH, the output voltage becomes VtH.

If the output voltage Vt of the toner density sensor is higher than the control reference value Vref, it is determined that the toner density is low, and toner is replenished. Conversely, if the output voltage Vt is lower than the control reference value Vref, It is determined that the toner density is high. Here, assuming that the control reference value Vref = VtM, the toner supply (consumption) to the developing device is controlled so that the output voltage Vt is adjusted to Vref. Therefore, the control voltage Vcnt
Is changed from VcntM to VcntH, toner is supplied to the developing device, and the output voltage Vt becomes the same as Vref when the toner density becomes VH. Therefore, the target toner density can be set high. Conversely, the control voltage Vcnt is changed from VcntM to Vcnt.
If the value is changed to ntL, toner consumption is performed, and toner supply is not performed until the toner concentration reaches TL. Therefore, the target toner density can be set low.

According to this control example, the initial target toner density is set by using the detection result of the toner adhesion amount of the toner image of any one patch pattern selected from the plurality of reference patterns used for calculating the developing ability. Therefore, the developing capability of the developing device can be more quickly set to the initial target developing capability as compared with the case where a plurality of reference patterns are used.

[Control Example 6] Next, still another control example at the time of the initial setting operation will be described. FIG. 18 shows a control flow at the time of the initial setting operation according to this control example. This figure 1
The control flow of step 8 is to create a toner consumption pattern and a selected patch pattern, and to determine whether the toner adhesion amount M of the selected patch pattern is within the target value M0 '± C (steps 601 to 601). 605)
This is the same as FIG. 17 of the control example 5. In this control example, the toner adhesion amount M of the selected patch pattern is equal to the target value M0 ′.
When ± C is entered, Vcnt "is calculated from the output value Vt of the toner density sensor at that time so that Vref = d (step 606). This Vcnt" can be read from the graph of FIG. A table may be created in advance, and an appropriate selection may be made from the table. If the output value Vt of the toner density sensor is 5 V, the control reference value Vref is set to 2.5 V as the value of d. The reason is that if the control point of the toner density sensor is the center value of the output value Vt (in this case, 2.5 V), there is a control range of about ± 1.5 V above and below it (if it deviates from this control range). This is because, for example, when the control reference value Vref is set at 3 V, only 1 V is left in the upward direction.

Next, the selected patch pattern is created again (step 607), and the output value Vt of the toner density sensor is measured under the control voltage Vcnt ", and this output value Vt is used as the control reference value Vref ±. When you enter the range of e,
The output value Vt at that time is changed to a new control reference value Vref (= Vr
ef ′) (steps 608 and 609). After resetting the control reference value Vref, the process is started from the patch pattern creation in step 504 of FIG. 4 (step 607).

According to the present control example, the comparison between the output value Vt of the toner density sensor and the control reference value Vref can always be performed within a suitable setting range, so that the toner density in the developing device is initialized after the initial setting operation. The target toner density can be controlled accurately.

[0080]

According to the first aspect of the present invention, by controlling the toner density in the developing device to the initial target toner density,
Since the developing capacity of the developing unit is set to the initial target developing capacity,
After the initial setting operation, even if there is a change in the developing ability as considered when setting the initial target developing ability, various potentials at the time of image formation determined based on the calculation result of the developing ability are greatly changed. Therefore, it is possible to prevent the problems such as a decrease in image gradation from occurring.

According to the invention of claim 2 or 4, the output value of the toner density detecting means when the toner density in the developing device reaches the initial target toner density is newly set as the control reference value of the toner density detecting means. Accordingly, there is an effect that the toner density in the developing device can be accurately controlled to the initial target toner density after the initial setting operation.

According to the third aspect of the present invention, the initial target is determined by using the detection result of the toner adhesion amount of the toner image of any one of the plurality of reference patterns selected from the plurality of reference patterns used for calculating the developing ability. Since the toner density is set, there is an effect that the developing capability of the developing device can be more quickly set to the initial target developing capability than when a plurality of reference patterns are used.

According to the fifth aspect of the present invention, the comparison between the output value of the toner density detecting means and the control reference value can always be performed within a suitable range, so that the toner density in the developing device is initialized after the initial setting operation. There is an effect that the target toner density can be accurately controlled.

According to the present invention, at least one of the two reference patterns having the maximum and minimum toner adhesion amounts is selected from the plurality of reference patterns used for calculating the developing ability, and the selected reference pattern is selected. Since the initial target toner density is set using the detection result of the amount of toner attached to the toner image, the developing capability of the developing device can be more quickly increased as compared with the case where all the reference patterns are used. It has the effect of being able to be an ability. Also,
After controlling the toner density in the developing device to be the initial target toner density, a reference pattern is selected from the plurality of reference patterns so that the toner adhesion amount includes two reference patterns of maximum and minimum, Since the developing ability is checked using the selected reference pattern, there is an effect that the developing ability of the developing device can be accurately set to the initial target developing ability.

According to the seventh aspect of the invention, when the calculation result of the developing ability of the developing unit over time is within the range of the predetermined target developing ability, the setting of the target toner density is performed by using the deviation amount of the developing ability. Is changed by a predetermined constant value instead of the value according to the target toner density. Therefore, compared to the case where the setting of the target toner density is changed according to the deviation amount of the developing ability, the user needs to change the setting of the target toner density. This has the effect of minimizing the waiting time.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control system of a color copying machine according to an embodiment.

FIG. 2 is a schematic configuration diagram of the entire color copying machine.

FIG. 3 is an enlarged view around a photosensitive drum and an intermediate transfer belt of the color copying machine.

FIG. 4 is a flowchart of a potential control routine in the color copying machine.

FIG. 5 is an explanatory diagram of a patch pattern on a photosensitive drum in the color copying machine.

FIG. 6 is a characteristic diagram showing a relationship between a development potential and a toner adhesion amount during the patch pattern development and an approximate straight line of development characteristics.

FIG. 7 is an explanatory diagram showing a relationship between the approximation straight line and a development electric field (Vgp) and a development potential Vkp corresponding to a maximum toner adhesion amount Mmax.

FIG. 8 is a diagram showing a potential table used to determine various potentials during image formation from a development potential Vkp corresponding to a maximum toner adhesion amount Mmax.

FIG. 9 is a flowchart of control at the time of an initial setting operation in the color copying machine.

FIG. 10 is a characteristic diagram illustrating a relationship between a toner density, a developing ability, and a control voltage of a toner density sensor.

FIG. 11 is a characteristic diagram illustrating a relationship between a developing potential and a toner adhesion amount in a patch pattern used in control according to a modified example.

FIG. 12 is a characteristic diagram illustrating a relationship between a toner density, a toner adhesion amount, and a control voltage of a toner density sensor.

FIG. 13 is a characteristic diagram illustrating a relationship between a developing potential and a toner adhesion amount in a patch pattern used in control according to another modification.

FIG. 14 is a flowchart of control according to the modification.

FIG. 15 is a flowchart of control according to still another modification.

FIG. 16 is a flowchart of control according to still another modification.

FIG. 17 is a characteristic diagram illustrating a relationship between a toner density and an output voltage in the toner density sensor.

FIG. 18 is a flowchart of control according to still another modification.

[Explanation of symbols]

 9 Photoconductor drum 13 Surface potential sensor 14 Bk developing device 14c Toner density sensor 15 C developing device 15c Toner density sensor 16 M developing device 16c Toner density sensor 17 Y developing device 17c Toner density sensor 18 Optical sensor 201 Main control unit

Claims (7)

[Claims] A toner concentration detecting means for detecting a toner concentration of the developing device, and controlling the toner concentration in the developing device to a target toner concentration based on a result of the detection.
An image for calculating the developing capability of the developing device based on the potential of the reference pattern formed on the image carrier and the detection result of the toner adhesion amount, and determining various potentials during image formation based on the calculation result of the developing capability. In the forming apparatus, at the time of an initial setting operation when a new developer is set in the developing device, the developing capability of the developing device is calculated, and the calculated developing capability and the initial setting which is set in advance in consideration of the change of the developing capability over time are calculated. Based on the result of comparison with the target developing ability, the initial target toner density of the developing device is set so that the calculated developing ability becomes the initial target developing ability, and various potentials are determined based on the result of calculating the next developing ability. An image forming apparatus comprising: a control unit that controls a toner concentration in a developing unit to be equal to the initial target toner concentration by time. 2. A method for controlling toner supply to a developing device based on a comparison result between an output value of the toner density detecting means and a control reference value so that a toner concentration in the developing device becomes a target toner concentration. Item 1. In the image forming apparatus according to Item 1, at the time of the initial setting operation, after the initial target toner density is set, the amount of toner adhered to the image carrier is detected while toner is consumed from the developing device or toner is supplied to the developing device. And
The initial target toner density of the developing device is set based on the result of comparison between the toner adhesion amount and the initial target toner adhesion amount set according to the initial target developing ability so that the toner adhesion amount becomes the initial target toner adhesion amount. An image forming apparatus comprising: 3. A latent image having a plurality of reference patterns having different potentials is formed on an image carrier, and the plurality of latent images are developed by a developing device to form a toner image of the reference pattern. 3. The image forming apparatus according to claim 2, wherein the potential of the latent image of the pattern and the amount of toner attached to the toner image are detected, and the developing capability of the developing device is calculated based on the detection results of the plurality of sets of potentials and the amount of toner attached. At the time of the initial setting operation, the amount of toner adhering to the toner image of any one of the reference patterns selected from the plurality of reference patterns used for calculating the developing capacity is detected, and the amount is determined according to the amount of toner adhering and the initial target developing ability. An image forming apparatus which sets an initial target toner density of a developing device based on a comparison result with an initial target toner adhesion amount set in step S1 so that the toner adhesion amount becomes the initial target toner adhesion amount. . 4. A toner supply to the developing device is controlled based on a comparison result between the output value of the toner concentration detecting means and a control reference value so that the toner concentration in the developing device becomes a target toner concentration. Item 3. In the image forming apparatus according to Item 3, at the time of the initial setting operation, after setting the initial target toner density, creating the selected reference pattern while performing toner consumption from the developing device or toner supply to the developing device,
The toner adhesion amount of the toner image of the selected reference pattern is detected, and the output value of the toner density detection means when the detection result of the toner adhesion amount becomes the initial target toner adhesion amount is newly set as the control reference value. The image forming apparatus is set to: 5. The image forming apparatus according to claim 4, wherein the control of the toner density detecting means is set when the detection result of the toner adhesion amount of the toner image of the selected reference pattern becomes the initial target toner adhesion amount. An image forming apparatus, wherein a control parameter of the toner density detecting means is changed so that a reference value falls within a predetermined suitable setting range. 6. A latent image of a plurality of reference patterns having different potentials is formed on an image carrier, and the plurality of latent images are developed by a developing device to form a toner image of the reference pattern. 2. The image forming apparatus according to claim 1, wherein the potential of the latent image of the pattern and the amount of toner attached to the toner image are detected, and the developing capability of the developing device is calculated based on the detection results of the plurality of sets of potentials and the amount of toner attached. At the time of the initial setting operation, at least one of the two reference patterns having the maximum and minimum toner adhesion amounts is selected from the plurality of reference patterns used for calculating the developing ability, and the latent image of the selected reference pattern is selected. The potential and the amount of toner adhering to the toner image are detected, the developing capability of the developing device is calculated based on the detection result, and the developing capability is set in advance in consideration of the calculated developing capability and a change in the developing capability with time. An initial target toner density of a developing device is set based on a result of comparison with the initial target developing capability so that the calculated developing capability becomes the initial target developing capability, and a toner density in the developing device is set to the initial target toner density. After selecting the reference pattern, a reference pattern is selected from the plurality of reference patterns so as to include the two reference patterns having the maximum and minimum toner adhesion amounts, and the developing ability is confirmed using the selected reference pattern. And an image forming apparatus. 7. The image forming apparatus according to claim 1, wherein after the initial setting operation is performed, a calculation result of the developing capability of the developing device over time is a predetermined target developing capability. Is within the range, the setting of the target toner density is changed by a predetermined constant value, and when the calculation result of the developing ability over time is out of the range of the predetermined target developing ability, An image forming apparatus, wherein the setting of the target toner density is changed based on the calculation result of the developing ability as in the case of the initial setting operation.