JPH09211911A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely and properly correct the excess/lack and error in the correction of various kinds of potentials and a toner concentration control reference value caused by error at the time of measuring developing capacities without increasing the downtime of the machine by executing control for correcting various kinds of potentials and a reference value for changing a toner concn., in accordance with the results of the developing capacity calculated by a simple method, at a short interval. SOLUTION: The electrical part of this device is constituted of a main control part 201 and plural peripheral control parts. The main control part 201 is constituted of a main CPU 202, a ROM 203 and a RAM 204. Then, the main control part 201 executes the following control: the control for the potential and the toner concn., which is accompanied by the calculation of the developing capacity 1 at a comparatively long execution interval and the control for calculating the developing capacity 2 by a method simpler than the process of calculating the developing capacity 1, at an interval shorter than that of the developing capacity 1 and correcting various kinds of potentials and the reference value for changing the toner concn., according to the results of the developing capacity 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, a printer or the like, in which a patch pattern is formed on a rear carrier and the development characteristics are determined from the potential and the toner adhesion amount. The present invention relates to an image forming apparatus that measures various potentials, determines various potentials during image formation from the obtained developing characteristics, and controls the developing ability of the developing device.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a facsimile, a printer, a photoconductor as an image carrier is charged, the charged photoconductor is exposed with a light image, and the potential of the exposed portion is changed. To form an electrostatic latent image, electrostatically attract toner having a predetermined charge to the electrostatic latent image to form a toner image, and transfer the toner image to a transfer material to form an image. In the above process, the toner image is transferred onto the intermediate transfer member, and this process is repeated a plurality of times for each color to form a superimposed toner image on the surface of the intermediate transfer member with the color toners of multiple colors. An image forming method of forming a color image on the transfer material by collectively transferring the superposed toner image onto the transfer material, and forming the single color toner image on the photoconductor without providing the intermediate transfer body, thereby forming the same transfer material. Transfer process to different color Image forming method in which a color toner image is formed on the transfer material by repeating a plurality of times for each image, and a single color toner image is formed on the photoconductor without providing an intermediate transfer member, and then the color toner image is formed on the transfer material at once. There is an image forming method for forming the image.

In the toner density control device in such an electrophotographic image forming apparatus, (1) a toner density sensor is arranged in the developing device, and the toner density sensor copies the toner density in the developing device. The amount of toner supplied from the toner hopper to the inside of the developing device is controlled so that the toner density is constant, while detecting each sheet.
(2) A sensor for detecting the toner adhesion amount on the image carrier is arranged in the vicinity of the image carrier, and it is provided for each non-image forming part (between image forming regions) on the image carrier or once every several times. To create a pattern latent image with a specific surface potential, develop this pattern latent image with a developing device to create a toner pattern with a toner adhesion amount, and use a toner hocher to make this toner adhesion amount constant. It is known to control the amount of toner replenished in the developing device.

Regarding the potential control, (3) a plurality of patterns having different surface potentials on the image carrier at the time when the power of the image forming apparatus is turned on, or at a fixed number of copies, or at a fixed elapsed time. A latent image is created, a plurality of pattern latent images are developed by a developing device to create a toner pattern having a toner adhesion amount, and the surface potential of the pattern latent image and the toner adhesion amount of the toner pattern after development are determined. Each is measured, a linear approximation formula is obtained from the data of the surface potential and the amount of adhered toner involved in these measurements, and the developing capability including the developer and the developing device is calculated from this linear approximating formula. (4) Power source O of the image forming apparatus for determining various potentials (charger output, exposure power, developing bias, etc.) when the image is formed by the image forming apparatus.
At N hours, or at every fixed number of copies, or at every constant elapsed time, a plurality of surface potentials are created by the charger, and the surface potential is measured to obtain the relationship between the output of the charger and the surface potential. It is known to adjust the output of the charger so that the potential is always constant.

For example, in the above (1), a plurality of pattern latent images having different surface potentials are formed on the image carrier,
These plural pattern latent images are developed by a developing device to form a toner pattern having a toner adhesion amount, and the surface potential of the pattern latent image and the toner adhesion amount of the toner pattern after development are measured, and these measurements are made. A linear approximation formula is obtained from the data of the pair of surface potential and toner adhesion amount, the developing ability including the developer and the developing device is calculated from the linear approximation formula, and the image by the image forming apparatus is calculated according to the developing ability. Various potentials at the time of formation are determined and an image is formed, and the magnitude relationship between the developing capacity and the specific developing capacity set as a fixed value is compared, and the level of toner density is detected according to the comparison result. The detection standard is changed. Further, the surface potential of the photoconductor and the toner concentration are usually controlled by combining the above (3) and (1) or (2) or (4) and (1) or (2). Further, in the above (3), the magnitude relationship between the calculated developing capacity and the intrinsic developing capacity set as a fixed value is compared, and the detection reference for detecting the high and low toner density is changed according to the comparison result. By doing so, it is possible to correct a longer range fluctuation such as deterioration of the developer.

[0006]

By the way, the above (3)
In the calculation of the developing ability based on a plurality of surface potentials and the amount of adhered toner in (1) and the calculation of the relationship between the output of the charger and the surface potential in (4) above, it takes time to create and detect and calculate the pattern. It cannot be done during copying like 1) and (2).
Therefore, it is executed when the power of the image forming apparatus is turned on (waiting time until the temperature of the fixing roller rises), or every fixed copy number, or every fixed elapsed time.

However, when the copying is performed every fixed number of copies or every fixed elapsed time, it takes a long time for one developing ability measuring step and the copying operation cannot be performed during that step. Will cause problems. Further, if the implementation interval is too long, it is difficult to perform the necessary correction, and it becomes difficult to maintain an optimum image. Furthermore, the toner consumption increases due to the toner pattern creation, and since the toner is collected by the cleaning device, the amount of discharged toner increases and the replacement cycle of the discharged toner container also increases.

When a two-component developer is used, a toner concentration sensor is often used to measure the permeability of the developer and detect the change as a change in toner concentration. The bulk density and fluidity of the developer change due to deterioration and deterioration due to the environment, and the magnetic permeability changes even though the actual toner concentration does not change.
Therefore, if the detection result of the toner density sensor is used as it is, there is a problem that the toner density control point deviates from the original control point. Therefore, a technique has been proposed for preventing the trouble caused by the deviation of the control points (Japanese Patent Laid-Open No. 60-84558, Shokai 63-).
No. 284581 and Japanese Patent Laid-Open No. 2-273769). In the conventional technique according to this proposal, the bulk density and the fluidity of the developer change due to the deterioration of the carrier over time and the deterioration due to the environment, and the magnetic permeability changes even though the actual toner concentration does not change. The deviation of the control point of the toner density due to this is estimated by the number of copies, the amount of toner replenishment, the image area of the original, and the like, and is corrected.

However, the degree of deterioration of the developer is also influenced by factors that change depending on the state of use of the machine, and cannot be estimated only by the determined number of copies, toner replenishment amount, image area of the original, and the like. There is no guarantee that the toner density control point can be correctly determined only by the element. Further, since the change in permeability due to deterioration of the developer and the change in permeability due to actual toner concentration cannot be discriminated by the toner concentration sensor alone, there will be an excess or deficiency in correction, and the toner generality should be controlled within a preferable range. Is difficult for non-sea. Therefore, there is a high possibility that problems such as insufficient image density due to toner density decrease, carrier adhesion and background stain due to excessive toner density, and toner scattering will occur.

Further, in the above (3), "the various potentials at the time of image formation by the image forming apparatus are determined according to the developing ability to form an image, and at the same time, the developing ability and the intrinsic development set as a fixed value. As described above, it is possible to perform the “control process in which the comparison of the magnitude relationship with the capability and changing the detection reference for detecting the high and low of the toner density according to the result of the comparison” is performed at a proper timing. extremely difficult. In addition, some error occurs in the linear approximation performed with the variation of multiple sets of data, and even if accurate linear approximation can be made with the sacrificed data, the accuracy of the sensor, output fluctuation, noise, etc. It is unavoidable that some degree of fluctuation will occur. For this reason, there is some error in the numerical value of the developing ability as the measurement result. Therefore, there is a possibility that the correction of each captured potential and the toner concentration reference value may not be optimally performed. Further, normally, the output voltage of the reflective sensor decreases with an increase in the toner adhesion amount, but due to the characteristics of the reflective sensor, the output increases at a certain adhesion amount as a boundary and at a higher adhesion amount. Therefore, when the adhesion amount becomes high due to the change in the potential of the photoconductor or the developer, the sensor sensitivity may decrease, and it becomes very difficult to obtain the toner adhesion amount from the sensor output. However, there is a problem in that toner scattering and toner stains on the copy occur.

The present invention has been made in view of the above background, and an object of the present invention is to cause the deviation of the control point of the toner concentration sensor due to the characteristics of the developer varying with time. In addition to eliminating the improper state of the toner density, it corrects accurately and accurately the excess and deficiency and the error of the correction of various potentials and the toner density control reference value due to the error at the time of measuring the developing ability. It is to provide an image forming apparatus that can do this. Specifically, the invention of claim 1 accurately and properly corrects various potentials due to errors at the time of measuring the developing ability, and deficiencies or errors in correction of toner concentration control reference values without increasing downtime of the machine. The purpose is to correct. A second aspect of the present invention is intended to further improve the measurement accuracy of the toner adhesion amount and to accurately compare the variation amounts. According to the third aspect of the present invention, by obtaining the optimum developing conditions according to the change in the potential of the photoconductor, it is possible to prevent excessive or deficiency or error in correction of various potentials and toner concentration control reference values without increasing machine downtime. The purpose is to accurately and properly correct. It is an object of the invention of claim 4 to increase the accuracy of measurement of the toner adhesion amount and to accurately compare the change lengths. According to the fifth aspect of the present invention, the accuracy of measuring the amount of toner attached is increased and the amounts of change are compared accurately, so that a pattern having a toner adhesion amount closest to a predetermined toner attachment amount is selected. It is an object of the present invention to use the method of calculating the developing ability 2 under image forming conditions.

[0012]

According to a first aspect of the present invention, a plurality of pattern latent images having different surface potentials are formed on an image carrier, and the plurality of pattern latent images are developed by a developing device. Create a toner pattern that has an adhesion amount,
The surface potential of the pattern latent image and the toner adhesion amount of the toner pattern after development are measured, and a linear approximation formula is obtained from the data of the combination of the surface potential and the toner adhesion amount involved in the measurement. And, the developing ability including the developing device is calculated, and various potentials at the time of image formation by the image forming apparatus are determined according to the developing ability,
Comparing the magnitude relationship between the developing capacity and the specific developing capacity set as a fixed value, and calculating in a timely manner in the image forming apparatus that changes the reference value for changing the toner density according to the comparison result. The developing ability 2 is calculated by a method simpler than the developing ability 1 calculating step at a shorter interval than the developing ability 1 calculating step, and the various potentials are calculated according to the result of the developing ability 2. And a control means for correcting the reference value for changing the toner density.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the method of calculating the developing capacity 2 is the surface potential of the plurality of pattern latent images in the step of calculating the developing capacity 1 and after development. In the toner adhesion amount data of the toner pattern, the pattern image forming condition that gives a predetermined toner adhesion amount is calculated, an electrostatic latent image is created, and it is developed by a developing device to determine the toner adhesion amount. It has a control means for preparing the toner pattern, measuring the toner adhesion amount of the toner pattern after development, and correcting the reference value of the toner concentration sensor so as to change the toner concentration in an appropriate direction based on the measurement result. It is a feature.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, when the amount of change in the surface potential of the pattern at the time of measuring the developing ability 2 deviates from a predetermined fixed value, the developing ability 1 And a control unit for re-determining various electric potentials and reference values for changing the toner density.

According to a fourth aspect of the invention, in the image forming apparatus of the first, second or third aspect, after the redetermination of the various potentials, the image forming condition of the pattern used in the developing ability 2 is obtained again. It is what

According to a fifth aspect of the present invention, in the image forming apparatus according to the first, second, third or fourth aspect, the measurement pattern of the developing ability 2 is selected from a plurality of patterns when the developing ability 1 is measured. It is characterized by that.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described with reference to an embodiment applied to a full-color copying machine having a plurality of developing devices. FIG. 1 is a schematic configuration diagram of a color copying apparatus according to this embodiment, and FIG. 2 is an enlarged view around the photoconductor / intermediate transfer belt. First, the outline of the configuration and operation of this device will be described. The color scanner 1 forms an image of the document 3 on the force sensor 7 through the illumination lamp 4, the mirror group 5 and the lens 6, and outputs force image information of the document, for example, Bl.
Each color separation light of ue, green, and red is read and converted into an electrical image signal. Then, the image processing unit performs color conversion processing on the color-separated image signal, and the Blac
k (BK), Cyan (C), Magenta (M),
Yellow (Y) color image data is obtained.

The dynamic printer 2 forms head images of BK, C, M, and Y based on the color image data, and superimposes them to form a four-color full-color image. That is, the laser optical unit 8 converts the force image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the original image, and forms an electrostatic latent image on the photosensitive drum 9. The photosensitive drum 9 rotates counterclockwise as indicated by the arrow. Around this area, a photoconductor cleaning unit (including a pre-cleaning static eliminator) 10 and a slow discharge lamp 1
1, charger 12, surface potential sensor 13, BK developing device 1
4, a C developing device 15, an M developing device 16, a Y developing device 17, a development density pattern detector 18, an intermediate transfer belt 19 and the like are arranged. Each developing device includes a developing sleeve (14-1, 15-1, 16-1, 17-1) that rotates so that the developer faces the photoconductor 9 in order to develop the electrostatic latent image, and
Developing paddles (14-2, 15-2, 16-2, 17-2) that rotate to draw up and stir the developer and toner concentration detection sensors (14-3, 15-3, 1) of the developer.
6-3, 17-3) and the like.

When the copying operation is started, reading of BK image data is started by the force laser scanner 1 at a predetermined timing, and optical writing / latent image formation by laser light is started based on this image data. Hereinafter, the electrostatic latent image based on the BK image data will be referred to as a BK latent image. In order to enable development from the front end of the BK latent image, the developing sleeve 14-1 is started to rotate before the front end of the latent image reaches the developing position, and the spikes of the developer are generated, so that the BK latent image is transferred to the BK toner. To develop. After that, the developing operation of the BK latent image area is continued, and when the trailing end of the BK latent image passes the BK developing position, the developer on the developing sleeve 14-1 is quickly cut off to put it in a development absent state. . It should be noted that the brush cutting is performed by switching the rotation direction of the developing sleeve 14-1 to the opposite direction to that during the developing operation.
The BK toner image formed on the photoconductor 9 is transferred (belt transfer) onto the surface of the intermediate transfer belt 19 which is driven at the same speed as the photoconductor. The belt transfer is performed by the photoconductor 9 and the intermediate transfer belt 1.
This is done by applying a predetermined bias voltage to the transfer bias roller 20 when 9 is in contact. By the same operation, toner images of C, M, and Y are sequentially formed on the photoconductor 9 (BK, C, and
The order of M and Y is not limited to this.) The belt transfer images are sequentially aligned on the intermediate transfer belt 19 to form a four-color superposed belt transfer image, and then the paper transfer unit 23 consolidates the transfer paper 24. And transfer the paper.

In the intermediate transfer belt unit, an intermediate transfer belt 19 is stretched around a driving roller 21, a belt transfer bias roller 20 and a driven roller group, and is driven and controlled by a driving motor. Belt cleaning unit 2
2 is the entrance seal 22-1, the cleaning blade 2
2-2 and a contact / separation mechanism 22-3 from the belt. When cleaning is unnecessary, the contact / separation mechanism 22-3 separates the cleaning blade and the inlet seal from the belt surface. The paper transfer unit 23 includes a paper transfer bias loaf 23-1, a roller cleaning blade 23-2, a belt contact / separation mechanism 23-3, and the like. The bias loaf-23-1 is normally separated from the surface of the belt 19, but the intermediate transfer belt 1
When the four-color superposed images formed on the nine sides are collectively transferred to the transfer paper, they are pressed by the contact / separation mechanism 23-3 at a timing, and a predetermined bias voltage is applied to the roller 23-1 to transfer the paper. Transfer. The transfer paper 24 is a paper feed roller 25,
The registration roller 26 feeds the four-color superimposed image on the surface of the intermediate transfer belt at the timing when the leading end of the four-color superimposed image reaches the paper transfer position. 4 from the surface of the intermediate transfer belt
The transfer paper 24 onto which the color-superposed toner images have been collectively transferred is conveyed to the fixing device 28 by the paper conveying unit 27, and the fixing roller 28-1 and the pressure roller 28 controlled to a predetermined temperature.
-2 and the toner image is fused and fixed, then the Coby tray 2
It is carried out to 9. This gives a full color coby. The surface of the photoconductor 9 after the belt transfer is cleaned by the photoconductor cleaning unit 10 and uniformly discharged by the charge eliminating lamp 1I. The intermediate transfer belt 19 after transferring the toner image onto the transfer paper 24 cleans the surface by pressing the cleaning blade 22-2 by the contact / separation mechanism 22-3. Note that the transfer paper force sets 30, 31, 3
Transfer sheets 2 and 33 of various sizes are stored, and the sheets are fed and conveyed in the direction of the registration roller 26 at a timing from the storage force set of the size sheet designated by the operation panel (not shown). Reference numeral 34 is a manual paper feed tray for OHP paper or thick paper.

The above is the description of the Coby mode in which four full colors are obtained, but 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. It will be. In the single-color copy mode, until the predetermined number of sheets are finished, only the developing device of that color is in a developing operation (agent standing) state, and the intermediate transfer belt 19 remains in contact with the surface of the photoreceptor 9. Forward movement-constant speed drive, belt cleaner 22 and belt 19
The copying operation is performed while keeping the contact with.

FIG. 3 shows an example of the electrical components of the image forming apparatus according to this embodiment. The electrical component section is composed of a main control section 201 and a plurality of peripheral control sections.
Reference numeral 1 is composed of a main CPU 2O2, a ROM 203 which stores a control program and various data, and a RAM 204 which temporarily stores various data as a work area. Further, the main control unit 202, via a 1/0 interface unit 205 for inputting / outputting with each peripheral control unit, a laser optical system control unit 206, a power supply circuit 207, a toner adhesion amount detection density sensor 18, a toner density detection. Sensors (14-3, 15-3, 16-3, 17-3), toner supply circuit 212, intermediate transfer belt drive control circuit 21
3, surface potential sensor, 3 and the like are connected. The laser optical system controller 206 controls the laser optical unit 8 based on a command from the main CPU 2O2, and the power supply circuit 207 based on a command from the main CPU 2O2.
A high voltage is applied to the charger 12, and a developing bias voltage is applied to each of the developing sleeves (14-1, 15-1, 16-1, 17-1). Reflection density 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. Toner supply circuit 212 is the main CPU
Based on the command from 2O2, the toner replenishing motors of the respective toner replenishing portions are controlled to replenish the toners of the respective colors to the respective developing devices.

Next, the potential control and the toner density control in this embodiment will be described. In the present embodiment, the control of the potential and the toner density accompanied by the calculation of the developing ability (hereinafter, the one calculated by this is referred to as the developing ability 1) is performed at a relatively long execution interval, and the developing is performed at an interval shorter than this. The developing capacity is calculated by a method simpler than the capacity 1 calculating step (hereinafter, the calculated capacity is referred to as developing capacity 2), and the various potentials and the toner concentrations are changed according to the result of the developing capacity 2. Control for correcting the reference value is performed. Both are executed by the main control unit 201. (Hereinafter, margin)

First, the potential control and toner density control performed at relatively long execution intervals will be described. FIG. 4 shows this potential control and toner concentration control routine, which includes the step of calculating the developing capability 1. The potential control by this potential control routine is basically performed at the time of starting the apparatus (copier), but may be performed as required every predetermined number of copies or every fixed time. In this case, FIG.
Step 502 is performed. In FIG. 4, in the potential control routine, the main control unit 201 determines in step 50 in order to distinguish the state when the power is turned on from the time when an abnormality such as a jam is processed.
When the fixing temperature of the fixing device 28 is 100.degree. C. from the input signal from the fixing temperature sensor that detects the fixing temperature of the fixing device 28 in 1
When the fixing temperature of the fixing device 28 exceeds 100 ° C., the potential control is not performed. This step is provided to prevent the electric potential control routine from being executed every time the power of the machine is turned on / off intentionally or by some abnormality. When the fixing temperature is 1OO ° C. or less in step 501, the surface voltage sensor 13 is calibrated by applying the reference voltage from the power supply circuit 207 to the photosensitive drum 9 in step 502, and the calibration is performed in the subsequent potential calculation. Use the value.

Next, the main control unit 201 causes the step 50.
By adjusting Vsg of 3, the output value from the reflection density sensor 18 to the background portion of the photosensitive drum 9 is taken in, and the reflected light of the light emitted from the reflection density sensor 18 to the background portion of the photosensitive drum 9 becomes a constant value. The amount of light emitted by the reflection density sensor 18 is adjusted as described above.

Next, in the batch pattern formation in step 504, as shown in FIG. 5, electrostatic clear images 301, 302, 30 having N gradation densities 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, and for example, the electrostatic latent image 30 having a rectangular pattern having 40 mm on each side having 14 different gradation densities.
, 302, ..., 314 are created at intervals of 10 mm, and in step 505, these electrostatic latent images 30 are formed.
The output value of the surface potential sensor 13 with respect to the potentials 1, 302, ..., 314 is read, converted into a surface voltage value by the potential sensor calibration value, and stored in the RAM 204. In this case, the main controller 202 sets the electrostatic latent images 301, 302, ..., 314 of 14 patterns to Bk,
The four colors C, M, and Y are sequentially formed on the photosensitive drum 9 at predetermined intervals.

Next, the main control unit 201, step 5
., 314 of four colors on the photoconductor drum 9 by BK developing device 14, C developing device 15, M developing device for each color 16, a toner image of each color is developed by the Y developing device 17 to form a head image, and the output value of the reflection density sensor 18 for the toner image of each color is stored in the RAM 204 as Vpi (i: 1 to 14) for each color. To do. The main control unit 201
Causes the charger 12 to uniformly charge the photoconductor drum 9 and changes the output of the laser optical unit 8 through the laser optical system controller 206 to change the electrostatic latent image 3 0 1 of the pattern.
.., 314 are created, but the developing bias voltage of each of the developing devices 14 to 17 is switched without operating the laser optical unit 8 to create a toner image of each pattern. Is also good.

Next, the main controller 202 causes the step 5
In the calculation of the adhesion amount of 07, the output value of the reflection density sensor 18 stored in the RAM 204 is converted into the toner adhesion amount per unit area by referring to the table stored in the ROM 203 and is stored in the RAM 204.

FIG. 6 is a diagram in which the relationship in each pattern between the potential data obtained in step 505 and the toner amount data obtained in step 507 is plotted on the xy coordinates. The development potential (the difference between the development bias voltage VB at the time of batch patterning and the surface potential Vs of the photosensitive drum 9: VB-Vs) (unit V) is plotted on the x-axis, and the adhesion amount per unit area (mg) is plotted on the y-axis. / Square centimeter). An infrared light reflection type sensor, which is usually used as an optical reflection density sensor, exhibits saturation characteristics in a high adhesion amount portion where the toner adhesion amount is large as shown in FIG. 6, and the sensitivity of the high adhesion amount portion is low. Further, generally, in the developing characteristics, the relation between the electric potential and the adhesion amount is not linear in the low adhesion amount region. Therefore, as shown in FIG.
As shown in, the approximate straight line is obtained by using only the data points in the high sensitivity region of the sensor and in the region where the adhesion amount data obtained from the potential and the sensor output is a straight line. In addition, the RO points are set in advance so that the number of data points in this area is larger than that in other areas.
The light amount data at the time of creating each batch pattern stored in M203 is set to a desired value.

Next, in step 508, the data in the above area (effective area) is selected. The method of this selection is, for example,
Paying attention to the adhesion amount data calculated in step 507,
A set of the adhesion amount and the electric potential within the range of 15 to 0.45 mg / square centimeter may be selected.

Next, the smoothing process in step 509 is performed by the following calculation. 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) where i ≤n≤j (that is, the data at the end of the section is not processed.)

Next, the least squares method is applied to the data obtained as described above in step 510 to perform a linear approximation of the developing characteristics of the developing units 14 to 17 to obtain a linear equation of the developing characteristics ( E) is obtained for each color. The following formula is used to calculate the least squares method. (For convenience, “′” of the data after the flattening is omitted.) Xave = ΣXn / k (K: number of data) Yave = ΣYn / k Sx = Σ (Xn−Xave) × (Xn−Xave) Sy = Σ (Yn) −Yave) × (Yn−Yave) Sxy = Σ (Xn−Xave) × (Yn−Yave) Approximate straight line obtained from the data of the hatch pattern potential and the toner adhesion amount, which are obtained from the surface potential sensor 13 and the reflection density sensor 18. When the equation (E) is Y = a · X + b,
The coefficients a and b can be expressed as a = Sxy / Sx b = Yave-a · Xave using the above variables. In addition, as another method, since a plurality of data sets of continuous numerical values (for example, four) are obtained from the selected data sub-strings, linear regression is performed for each of them, and the value of the slope (a) is the highest among them. A large one, a slope (a) thereof close to the average value, or a linear regression equation having the largest correlation coefficient may be selected.

Next, the main controller 201 proceeds to step 5
In the calculation of the potential potential of 11, the above step 5
Using the approximate linear equation (E) calculated for each color in 10,
The potential difference (Vgp) required to obtain the maximum toner adhesion amount Mmax that is the value on the y axis and that achieves the darkest image density required by the user, and x of the linear approximation formula (E).
Vkp (= developing bias voltage VB-photoconductor surface potential Vs), which is a reference for potential setting, is determined from the voltage value Vk (= one b / a: development start voltage), which is the axis intercept, as follows. (See FIG. 7) Vgp = Mmax / a Vkp = Vgp + Vk

Next, in step 512, the potential table as shown in FIG. 8 stored in advance in the ROM 204 is referred from the value of Vgp, and in step 513, the charging potential (VD), the developing bias value (VB), the maximum value. The exposure potential (VL) is obtained as the target potential. In this potential table, as the control amount for controlling the maximum toner adhesion amount Mmax that achieves the darkest image density required by the user,
No. 1 to No. With respect to the potential difference (Vgp) in 20 steps up to 20, the values of the charging potential (VD), the developing bias value (VB), and the maximum exposure potential (VL) of the photoconductor correspond to the potential difference (Vgp) in each step. It is specified. For example, when the potential difference (Vgp) obtained by measurement and calculation is 460V, No. 16
From the data column of, the photoconductor charging potential VD = 829V, the developing bias value VB = 646V, the maximum exposure potential VL = 186.
V is obtained.

At the next step 514, the charging potential of the charging drum 2 of the photosensitive drum 9 is changed to the target potential VD.
The power supply circuit 207 is adjusted so that the laser emission power by the laser optical system 8 becomes the target potential VL, and the developing bias of the developing device becomes the target voltage VB. . by the way,
Steps 504 to 515 are performed for each color developing device, and the potential table and the presence / absence of toner correction are independently determined for each color.

In the next step 515, the above step 51
From the gradient in the linear approximation formula (E) for each developing device obtained by 0, the toner concentration detection sensor (14-
3, 15-3, 16-3, 17-3) each control voltage Vc
nt is changed to change the toner density for each developing device so that the developing characteristic obtained in step 510 approaches the optimum value.

FIG. 9 shows the relationship between the toner concentration sensor output voltage and toner concentration for any one of these toner concentration sensors. In FIG. 9, the control voltage V
By changing cnt, "toner density and output voltage"
There is a relationship in which the level of changes. In the example of FIG. 9, the control voltages Vcnt are VcntH and Vcnt.
M, VcntL (VcntH>VcntM> Vcnt
The relationship between the toner concentration and the output voltage of the toner concentration sensor is shown for three values of L). Control voltage Vcnt is Vcn
The sign when tM is M, the sign when the control voltage Vcnt is VcntH is H, and the sign when the control voltage Vcnt is VcntL is L.
The relationship between the toner density and the output voltage of the toner density sensor is settled.

Here, the VcntM is a control voltage Vc so that the output voltage Vt of the toner concentration sensor becomes Vref when the toner concentration is the reference toner concentration Tref (wt%).
nt is adjusted. Therefore, the control voltage Vcnt
If the value of is changed to VcntH that is larger than VcntM, the output voltage Vt of the density sensor is changed with respect to the same reference density Tref.
Is larger than the reference voltage Vref. Further, when the value of the control voltage Vcnt is changed to VcntL which is smaller than VcntM, the output voltage Vt of the density sensor becomes a value smaller than the reference voltage Vref for the same reference density Tref. Without changing the reference voltage Vref, the control voltage Vcnt
Is changed from VcntM to VcntH, even if the toner concentration is the reference toner concentration Tref, the density sensor output Vt
Is output higher than Vref (it is detected that the toner concentration is low), and the control pressure Vcnt is changed from VcntM to Vcn.
When the toner density is changed to tL, the density sensor output Vt is output lower than Vref (it is detected that the toner density is high) even if the toner density is the reference toner density Tref. In this way, by changing the control voltage Vcnt, the control characteristic of the toner density changes, so that the control voltage Vcnt can be changed in accordance with the fluctuation of the developing ability, and an image having an appropriate density can be obtained.

The developing ability is corrected by the inclination a obtained in step 510 of FIG.
Details of 15 will be described. As described above, the linear approximation formula obtained from the surface potential sensors 3, the potential of the hatch pattern obtained from the development density pattern detector 18 and the toner adhesion amount data is Y = AxX ′ + B (where the surface potential The data is represented by X-axis, the toner adhesion amount data by Y-axis, the developing bias by VB, A by developing capacity, B by a coefficient, and X ′ = VB−X). Is Amax and the lower limit is A
The toner density of the developing device is corrected using mln as the upper and lower limit darkness values.

An example of making the same increase / decrease amount once will be described below with reference to the flowchart shown in FIG. Here, A (n) is the current value of the linear approximation formula obtained as a result of performing the flow of FIG. 4, Vcnt (n) is the value of Vcnt after the change, and Vcnt (n-1 )
Indicates the value before the change. In step 601, A (n) is compared with the upper limit value Amax, and when A (n) exceeds the upper limit value Amax, in step 602 the value of Vcnt is reduced by one step from the previous time (the toner density should be lowered. The value of the control voltage Vcnt is reduced so that the developing ability becomes small.) If A (n) is not more than the upper limit value Amax, the lower limit value Amln is compared in step 603 to obtain A
If (n) is smaller than the lower limit value Amln, the value of Vcnt is increased by one step from the previous time in step 604 (if the value of Vcnt is increased, the toner density is controlled to be high, so the slope a ( n) moves to the method of raising). In step 603, A (n) is the lower limit value A.
If it is greater than or equal to min, the value of Vcnt is made the same (not changed) as the previous value in step 605. One step is 1 digit obtained by dividing the control voltage 0 to 1 zv by 8 bits, but it may be appropriately determined. In the above, the control voltage (Vcnt) of the toner concentration sensor is changed, but the control reference voltage (Vr
The same result is obtained even if ef) is changed.

Next, at a relatively short interval, the developing capacity 1
The control for calculating the developing capacity 2 by a method simpler than the calculating step and correcting the reference value for changing the various potentials and the toner density according to the result of the developing capacity 2 will be described.
FIG. 11 shows an overall flow including the potential control and the toner concentration control which are performed at the relatively long execution intervals described above. Here, steps 701 to 704 correspond to the potential control and toner density control performed at the relatively long execution intervals, and step 702 corresponds to steps 503 to 511 of FIG.
Step 703 corresponds to steps 512 to 514 and step 704 corresponds to step 515. Then, steps 705 to 710.
Corresponds to the control involving the calculation of the developing ability 2. The description will be made in the following order. In step 701, it is determined whether it is the timing for measuring the developing ability 1. As described above, the measurement timing is preset to be executed when the power of the image forming apparatus is turned on (waiting time until the temperature of the fixing roller rises), or every fixed number of copies, or every constant elapsed time. ing. If the timing for measuring the developing capacity T is reached, steps 702, 703, and 704 are performed. If it is not the measurement timing of the developing ability 1, step 70
At 5, it is determined whether it is the timing for measuring the developing ability 2. If it is not the timing for measuring the developing capacity 2, the process returns to step 701. If it is the timing for measuring the developing ability 2, the developing ability 2 is measured in step 706. The developing capacity 2 was measured by first forming a toner adhesion amount closest to a predetermined toner adhesion amount, which was a predetermined reference, from a plurality of sets of surface potentials and toner addition amounts measured in the latest development capacity 1. One set of the surface potential and the actual toner adhesion amount is stored. Specifically, for example, as shown in FIG.
In the case where the measurement result in the above is a straight line A, the developing potential at that time is V8 (the developing potential of the eighth pattern from the one having the smallest amount of adhesion) when the toner amount which is a predetermined reference is 0.4 mg / square centimeter. ), And the amount of exposure when the pattern is formed (pattern / laser power output at the time of imprinting) is stored. Here, the result measured with the developing ability 1 is 0.4 m as shown by the line B.
If there is no point of g / square centimeter, then 0.
The measurement point V6 closest to 4 mg / square centimeter may be selected, or the point of 0.4 mg / square centimeter is estimated (V6 '), and the exposure amount at that time is interpolated from the front and back points. Then, an electrostatic latent image is formed with the exposure amount that forms the surface potential, the surface potential of the pattern is measured by the surface potential sensor 13, and the toner is developed by a developing device to form a toner pattern having a toner adhesion amount and reflected. The type sensor 18 calculates the toner adhesion amount from the reflected light amount of the toner pattern.

At the next step 707, the surface potential measured at step 706 and the latest developing ability 1 are selected.
If the difference is compared with the stored value and the difference is within a predetermined range, the process proceeds to step 708, and if it is out of the range, the process proceeds to step 702 to measure the developing ability 1, reset the potential, and correct the toner concentration. This is because the surface potential is largely deviated and the surface potential needs to be reset.

In step 708, the toner adhesion amount calculated in step 706 is standardized. In this normalizing process, when the surface potential measured in step 706 is slightly different from the surface potential measured in the developing ability 1, the developing ability does not change although the toner adhesion amount changes due to the change in developing ability. This is done to determine if the surface potential of has changed due to a slight deviation. This will be described with reference to the graph of FIG.
Similar to FIGS. 6 and 7, this graph shows the development potential on the X axis and the toner adhesion amount on the Y axis. The straight line P is a straight line obtained by linear approximation from the surface potentials of a plurality of patterns having the developing ability 1 and the toner adhesion amount. Latest development capability 1
From the multiple sets of surface potential and toner adhesion amount measured in step 1, the rope of the surface potential and the actual toner adhesion amount that formed a toner adhesion amount that is close to the toner adhesion amount that is a reference in advance even in summer is point A (at that time). The development potential and the toner richness of toner are defined as V0 ′ and M0 ′, respectively, and the measurement result at the development capacity 2 is defined as point B (also defined as V1 ′ and M1). Here, in reality, VI ′ = Vpl−VB, V0 · = Vpo
-VB. (Vpl is the potential of the pattern at the developing ability of 2, Vpo is the pattern potential when the developing ability of 1 is measured, V
(B is a developing bias) Here, a straight line is drawn through the point B and is not parallel to the straight line P and has the same inclination as the straight line Q. Then, the following formula is established. a = (M0'-M1) / (V0'-V1 ') a (V0'-V1') = (M0'-M1) Therefore M0 '= a (V0'-V1') + M1 Therefore, the coordinates of the point C Is required. This M0 ′ (normalized toner amount) is compared with M0, and if the difference is within a predetermined range, no correction is necessary. In step 709, it is determined whether or not it is within this range. If it is out of the range, the process proceeds to step 710 to correct the toner density. The correction of the toner density is performed, for example, as shown in FIG.
Change cnt.

In FIG. 13, in step 801, the M
The absolute value of 0'-M0 is compared with a predetermined fluctuation width Mx, and if it is smaller than Mx, it is determined that the amount of adhered particles does not change, and Vcnt is made equal to the previous value (no correction is performed).
If the absolute value of M0'-M0 is larger than the fluctuation range Mx, the process proceeds to step 803, and the sign of M0'-M0 is checked. When M0'-M0 is negative, it is determined that the adhesion amount has become small, the process proceeds to step 804, and the value of Vcnt is increased by one step from the previous value (the toner concentration control point is shifted to the side where the toner concentration becomes high). . On the other hand, M0 '
If -M0 is positive, it is determined that the adhesion amount has increased, the process proceeds to step 805, and the value of Vcnt is reduced by one step from the previous value (the toner concentration control point is shifted to the side where the toner concentration decreases). This step 7
An example of 10 is similar to step 704, but it may be different.

[0045]

According to the first aspect of the present invention, the developing ability is calculated by a simpler method than the calculating step of the developing ability 1 at an interval shorter than the calculating interval of the calculating step of the developing ability 1 calculated in a timely manner. 2 is calculated, and the potential change of the photoconductor and the toner concentration are corrected during the execution interval of the developing capability 1 according to the result of the developing capability 2. Therefore, various potentials and toner concentration control due to errors in measuring the developing capability 1 are performed. Excess, deficiency, and error in correction of the reference value can be corrected accurately and properly without increasing downtime of the machine.

According to the invention of claim 2, the developing capacity 2
In the step of calculating the developing capability 1 so that a predetermined toner adhesion amount is obtained from the surface potentials of the plurality of pattern latent images and the toner adhesion amount data of the toner pattern after development. Since the pattern is created, the measurement accuracy of the toner adhesion amount can be increased, there is no measurement error or reading error due to the variation of the pattern adhesion amount, and the sensor sensitive area can always be used, so the measurement accuracy is high and the toner density is high. You can also prevent runaway.

According to the third aspect of the present invention, when the variation amount of the surface potential of the pattern at the time of measuring the developing ability 2 deviates from a predetermined fixed value, the step of calculating the developing ability 1 is executed and various potential and Since the reference value for changing the toner density is re-determined, there is no erroneous reading of the adhesion amount due to the change in the potential of the photoconductor, and the optimum developing conditions that match the change in the potential of the photoconductor are obtained. Excess, deficiency, or error in correction of the density control reference value can be corrected accurately and properly without increasing downtime of the machine.

According to the fourth aspect of the present invention, since the latest developing ability is always referred to, it is possible to accurately compare the variation amounts.

According to the invention of claim 5, the developing capacity 2
Of the surface potentials of the plurality of pattern latent images and the toner adhesion amount data of the toner pattern after development in the step of calculating the developing ability 1, the pattern having the closest predetermined toner adhesion amount. Is selected, it is easy to compare with the data of the developing ability 1, and the change in the toner adhesion amount can be measured accurately.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of the device.

FIG. 3 is a block diagram of an electric component section of the device.

FIG. 4 is a flowchart of control in the device.

FIG. 5 is a developed view showing a photosensitive drum and a patch pattern of the apparatus.

FIG. 6 is a graph regarding a toner adhesion amount of the apparatus.

FIG. 7 is another graph relating to the toner adhesion amount of the apparatus.

FIG. 8 is an explanatory diagram of a table used for controlling the device.

FIG. 9 is a graph showing the relationship between the toner concentration of the apparatus and the output voltage of the toner concentration sensor.

10 is a flowchart of a control subroutine shown in FIG.

FIG. 11 is a flowchart of main control in the same device.

FIG. 12 is a graph showing the relationship between the developing potential and the toner adhesion amount of the apparatus.

13 is a flowchart of a control subroutine shown in FIG.

FIG. 14 is another graph showing the relationship between the developing potential and the toner adhesion amount of the apparatus.

[Explanation of symbols]

 1 Color image reading device (color scanner) 2 Color image recording device (color printer) 3 Original document 4 Illumination lamp 5 Mirror group 6 Lens 7 Light silkworm conversion element (eg CCD) 8 Laser optical unit 9 Photosensitive drum 1O Photosensitive Body Cleaning Unit 11 Decommissioning Lamp 12 Normal Electric Appliance 13 Potential Sensor 14 Black (BK) Developer 15 Cy Skin (C) 〃 16 Mag Mark ta (M) 〃 17 Yellow (Y) 〃 14-1 BK Development Sleeve 15- 1 C 〃 16-1 M 〃 17-1 Y 〃 14-2 BK Development paddle 15-2 C 〃 16-2 M 〃 17-2 Y 〃 14-3 BK Toner density sensor 15 -3 C 〃 16-3 M 〃 17-3 Y 〃 18 Development density pattern detector 19 Intermediate transfer belt 20 Belt transfer bypass Roller 21 Belt drive roller 22 Belt cleaning unit 22-1 Entrance seal 22-2 Cleaning blade 22-3 Contact / separation mechanism 23 Paper transfer unit 23-1 Paper transfer bias roller 23-2 Roller cleaning link blade 23-3 Scaler 24 Kashiwa 24 Transfer paper 25 Paper feed port 26 Registration roller 27 Paper transport unit 28 Fixing device 28-1 Fixing roller 28-2 Pressure roller 29 Copy tray 30 Transfer paper cassette (A) 31 〃 (B) 32 〃 〃 (C) 33 〃 〃 (D) 34 Manual paper feed tray 201 Main control unit 202 Main CPU 203 ROM 204 RAM 205 1/0 interface unit 206 Laser optical system control unit 207 Power supply circuit 213 Intermediate transfer belt drive circuit

Claims (5)

[Claims] 1. A plurality of pattern latent images having different surface potentials are formed on an image carrier, and the plurality of pattern latent images are developed by a developing device to form a toner pattern having a toner adhesion amount. The surface potential of the pattern latent image and the toner adhesion amount of the toner pattern after development are measured, and a linear approximation formula is obtained from the data of the combination of the surface potential and the toner adhesion amount involved in the measurement. The developing ability including the developing device is calculated, and various potentials at the time of image formation by the image forming apparatus are determined according to the developing ability, and the developing ability and the intrinsic developing ability set as a fixed value are set. In the image forming apparatus in which the magnitude relationship is compared and the reference value for changing the toner density is changed according to the comparison result, the developing capacity calculation step calculated at a proper time. (Hereinafter, the developing capacity according to this calculation step is referred to as developing capacity 1) The developing capacity is calculated at a shorter interval than the calculation interval of the developing capacity 1 by a simpler method (hereinafter, this simple calculation An image forming apparatus comprising: a developing capability related to a process), and a control unit that corrects a reference value for changing the various potentials and the toner density according to the result of the developing capability 2. 2. The method for calculating the developing ability 2 is characterized in that, in the step of calculating the developing ability 1, among the surface potentials of the plurality of pattern latent images and the toner adhesion amount data of the toner pattern after development, Calculate the pattern image formation condition that gives a predetermined toner adhesion amount, create an electrostatic latent image, develop with a developing device to create a toner pattern with the toner adhesion amount, and develop the toner pattern toner. 2. The image forming apparatus according to claim 1, further comprising control means for measuring the adhesion amount and correcting the reference value of the toner concentration sensor so as to change the toner concentration in an appropriate direction based on the measurement result. 3. When the amount of change in the surface potential of the pattern at the time of measuring the developing ability 2 deviates from a predetermined fixed value, the step of calculating the developing ability 1 is executed to change various potentials and toner concentrations. 3. The image forming apparatus according to claim 1, further comprising control means for redetermining the reference value. 4. The image forming apparatus according to claim 1, 2 or 3, wherein after the redetermination of the various potentials, the image forming condition of the pattern used in the developing ability 2 is obtained again. 5. The image forming apparatus according to claim 1, wherein the measurement pattern of the developing ability 2 is selected from a plurality of patterns when the developing ability 1 is measured.