JPH11258873A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device capable of comparatively easily and optimally controlling image quality in a short time and capable of adequately keeping the image quality. SOLUTION: The adhering amounts of developer to the two test patterns of high density and low density are measured by a toner density measuring part 8, the deviations of the high density part and the low density part are calculated by the measured adhering amounts of the developer of the high density part and the low density part, and the target values of those, the manipulated variable of a contrast voltage adequate to the correction of the deviations of the high density part and the low density part, and the manipulated variable of a background voltage are selected according to an adjusting rule, test operation is performed according to the selected manipulated variable, so that the sensitivity of the deviation to the manipulated variable is detected, and the manipulated variable is decided in accordance with the detection result. The contrast voltage and the background voltage are adjusted in accordance with the decided manipulated variable, so that good image. quality can be kept by eliminating the deviation.

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 color laser printer and a color digital copying machine and an image forming method.

[0002]

2. Description of the Related Art For example, it is considered that many people have the experience that the density of a copied matter differs for the same original in the same copying machine. Fluctuations in image density in electrophotography are due to changes in image forming conditions and deterioration due to the environment and aging. Not only analog copiers, but also multi-tone printers or digital copiers suppress this image density fluctuation,
It is important to stabilize. In particular, in the case of color, not only the density reproducibility but also the color reproducibility are affected, so it can be said that stabilization of the image density is an indispensable requirement.

Therefore, conventionally, a plurality of test patterns are formed on an image carrier, the change in gradation characteristics is grasped by detecting the image densities of these test patterns, and the adjustment of the operating section of the image forming section and the quality judgment are performed. Repeated fade-back control is performed. At this time, the operation amount corresponding to the control amount deviation is calculated based on a look-up table prepared in advance.

[0004]

The contents of the look-up table as described above are produced off-line. In the production, various experiments are performed to determine the characteristics of the object to be adjusted (the amount of operation with respect to the control amount). Need to figure out.
Therefore, a large amount of labor and time are required for the manufacturing operation.

Further, in a multi-input multi-output system, generally, dependencies between inputs and outputs are not independent from each other. Since a number of lookup tables are required, a system having a large number of dimensions requires a large amount of storage memory, and the identification work is extremely enormous.

[0006] Further, the relationship is a nonlinear characteristic, the difference between solids,
Due to reproducibility and aging, it may not always match the target device. The adoption of the fade-back control is practical even when the identification is incomplete to some extent, but the number of convergences and the control time until the pass / fail of the pass / fail judgment is increased by the deviation from the identified apparatus.

Therefore, the image quality can be controlled relatively easily and in a short time, thereby improving the development efficiency, reducing the manufacturing cost by reducing the memory capacity, and further improving the difference between solids and the reproducibility.
It is an object of the present invention to provide an image forming apparatus and an image forming method capable of maintaining appropriate image quality according to aging.

[0008]

According to the present invention, there is provided an image forming apparatus, comprising: an image forming means for forming a developer image on an image carrier based on image data; and an image quality of an image formed on the image carrier. Detection means, a plurality of operation means for adjusting the image quality formed on the image carrier, and a deviation calculation for calculating a control amount deviation between the image quality detected by the detection means and a preset image quality. Means for determining whether the calculated control amount deviation is within a predetermined allowable range, and correcting the calculated control amount deviation when the deviation exceeds the allowable range. Selecting means for selecting the operating means, test sensitivity of the image quality by the selected operating means, sensitivity detecting means for detecting the sensitivity of the control amount to the adjustment operation amount of the operating means, Depending on Control means comprising: an operation amount determining means for determining an adjustment operation amount of the corresponding operation means; and a means for activating the corresponding operation means in accordance with the determined operation amount and correcting the deviation. It is characterized by that.

According to another aspect of the present invention, there is provided an image forming apparatus which forms a developer image on an image carrier based on image data, and an image density of the developer image formed on the image carrier. Detecting means for detecting the image density, a plurality of operating means for adjusting the image density of the developer image formed on the image carrier, and controlling the image density detected by the detecting means and a preset image density Deviation calculating means for calculating the amount deviation, determining means for determining whether the calculated control amount deviation is within a predetermined allowable range, and calculating the calculated amount when the deviation exceeds the allowable range. Selecting means for selecting an operating means for correcting the control amount deviation; and sensitivity detection for detecting the sensitivity of the control amount to the adjusting operation amount of the operating means by test-adjusting the image density by the selected operating means. means An operation amount determination unit that determines an adjustment operation amount of the corresponding operation unit according to the detected sensitivity, and a unit that operates the corresponding operation unit according to the determined operation amount to correct the deviation, And control means for repeating the above determination, selection of operation means, sensitivity detection, operation amount determination, and correction until all deviations converge to an allowable range.

In the image forming method according to the present invention, the image carrier is charged by using a grid to generate a high-density test pattern and a low-density test pattern, and a high-density test pattern is formed on the charged image carrier. Forming a latent image on the basis of the test pattern and the low-density test pattern, developing the formed latent image on the image carrier with a developer, and attaching the developer to the developed high-density test pattern. The amount of the developer and the amount of the developer attached to the low-density test pattern are measured, and dependency information indicating whether or not there is sensitivity for changing the amount of the developer attached to the change in the operation amount between the grit bias and the developing bias is prepared in advance. The deviation between the high-density part and the low-density part is determined by the target value for the adhesion amount of the high-density part and the low-density part and the adhesion amount of the developer in the high-density part and the low-density part obtained by measuring the adhesion amount of the developer. Is calculated It is determined whether or not the calculated deviation between the high-density part and the low-density part is within an allowable range. If the determination result is out of the allowable range, the high-density part and the low-density part are determined based on the dependency information. The operation amounts of the grid bias and the developing bias corresponding to the deviation of the selected operation amount are selected, and the bias corresponding to the selected operation amount is test-adjusted, so that the sensitivity of the deviation to the adjusted operation amount is detected. Determining the corresponding grid bias value and developing bias value in accordance with the above, and, in accordance with the determined grid bias value and developing bias value, fully adjusting the grid bias voltage and the developing bias voltage. I have.

Further, the image forming apparatus according to the present invention forms latent images of a high-density portion and a low-density portion on an image carrier based on image data, and can control an exposure amount in accordance with target exposure amount information. Exposure means, developing means for developing a latent image of a high-density part and a low-density part on the image carrier formed by the exposure means with a developer, and developing on the image carrier by development of the developing means. A developer adhering amount measuring means for measuring the adhering amount of the developer to the adhering high-density portion and the low-density portion respectively; and, for the gradation data per unit pixel of the image data, the light emitting time per unit pixel is calculated as the light emitting time. Emission time correction means for correcting based on the correction information; modulation control means for performing modulation control of the exposure means as a pulse width per unit pixel based on the emission time information corrected by the emission time correction means; and Deviation calculating means for calculating a deviation between each of the measured values of the high-density part and the low-density part measured by the measuring means and a preset target value, and the respective deviations calculated by the deviation calculating means are respectively Determining means for determining whether or not the value is within an allowable range; and correcting the calculated deviation from the light emission time correcting means and the modulation control means when the determining means determines that the value is not within the allowable range. Selecting means for selecting the means, and sensitivity detecting means for detecting the sensitivity of the deviation control amount with respect to the adjustment operation amount by test-adjusting the developer adhesion amount by the selected emission time correction means and modulation control means. Operation amount determining means for determining an adjustment operation amount of the light emission time correction means and the modulation control means in accordance with the detected sensitivity; and an operation amount determining means in accordance with the determined operation amount. Means for correcting the deviation by activating the time correction means and the modulation control hand, and performing the determination, selection of operation means, sensitivity detection, operation amount determination, and correction until all the deviations converge to an allowable range. And control means for repeating.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows a configuration of a color laser printer as an example of the image forming apparatus according to the present invention. As shown in FIG. 2, the color laser printer includes a photosensitive drum 1 as an image carrier, and the photosensitive drum rotates counterclockwise with respect to the drawing. Around the photoreceptor drum 1, a charger 2, which is a charging unit, a first developing unit 4, a second developing unit 5, a third developing unit 6, a fourth developing unit 7, which is a developing unit, a toner adhesion amount measuring unit 8, a transfer drum 9 as a transfer material support, a static eliminator 10 before cleaning, a cleaner 11, and a static elimination lamp 12 are sequentially arranged.

The surface of the photosensitive drum 1 is uniformly charged by the charger 2. Between the charger 2 and the first developing device 4, the surface of the photosensitive drum 1 is exposed to laser beam light 14 emitted from a laser exposure device 13, which is an exposing means, so that static electricity corresponding to image data is obtained. An electrostatic latent image is formed.

The first to fourth developing units 4 to 7 develop electrostatic latent images on the photosensitive drum 1 corresponding to respective colors into color toner images. For example, the first developing unit 4 Magenta, the second developing device 5 is cyan, the third developing device 6 is yellow,
The fourth developing device 7 performs black development.

On the other hand, the transfer paper as a transfer material is sent out from a paper feed cassette 15 by a paper feed roller 16, is temporarily aligned by a registration roller 17, and is positioned at a predetermined position on the transfer drum 9 by a registration roller 17. And electrostatically attracted to the transfer drum 9 by the attraction roller 18 and the attraction charger 19. The transfer sheet is conveyed with the transfer drum 9 rotating in the clockwise direction while being attracted to the transfer drum 9.

The developed toner image on the photosensitive drum 1 is transferred to a transfer sheet by a transfer charger 20 at a position where the photosensitive drum 1 and the transfer drum 9 face each other. In the case of printing of a plurality of colors, the process of setting one rotation of the transfer drum 9 as one cycle is performed by switching the developing device, and the multicolor toner images are transferred onto the transfer paper in a multiplex manner.

The transfer sheet on which the toner image has been transferred is further transported with the rotation of the transfer drum 9 and is subjected to the internal static eliminator 2 before separation.
1. After being neutralized by the pre-separation outer static eliminator 22 and the separate static eliminator 23, the charge is separated from the transfer drum 9 by the separation claw 24,
The sheet is conveyed to the fixing device 27 by the conveying belts 25 and 26.
The toner on the transfer sheet heated by the fixing unit 27 is melted and fixed on the transfer sheet immediately after being discharged from the fixing unit 27. The transfer sheet after the fixing is discharged to the tray.

FIG. 1 is a block diagram showing charging, exposing, developing means and control means of the color laser printer according to this embodiment. In the figure, the photosensitive drum 1
Rotates in the counterclockwise direction (the direction of the arrow shown) with respect to the drawing. The charger 2 mainly includes a charging wire 31 and a conductive case 3
2. It is composed of a grid electrode 33. The charging wire 31 is connected to a high voltage power supply 34 for corona,
The surface of the photosensitive drum 1 is charged by corona discharge. The grid electrode 33 is connected to a high-voltage power supply 35 for grid bias.
, And controls the charge amount on the surface of the photosensitive drum 1 by the grid bias voltage.

An electrostatic latent image is formed on the surface of the photosensitive drum 1 uniformly charged by the charger 2 by exposure to the modulated laser beam 14 from a laser exposure device. The gradation data buffer 36 stores gradation data from an external device or a controller (not shown), corrects gradation characteristics of the printer, and converts the data into laser exposure time (pulse width) data.

The laser driving circuit 37 outputs the laser beam 1
4 so as to be synchronized with the scanning position 4
The laser drive current (light emission time) is modulated in accordance with the laser exposure time data from. Then, the semiconductor laser oscillator (not shown) in the laser exposure apparatus is driven by the modulated laser drive current. As a result, the semiconductor laser oscillator emits light according to the exposure time data.

Further, the laser drive circuit 37 compares the output of a monitoring light receiving element (not shown) in the laser exposure apparatus with a set value, and controls the output light amount of the semiconductor laser oscillator to a set value by a drive current. I do.

On the other hand, the pattern generating circuit 38 generates tone data of two different density test patterns of low density and high density for measuring the amount of adhered toner, and sends it to the laser drive circuit 37. . The above test pattern is
The information may be stored in a storage unit 61 described later.

Of the test patterns corresponding to the two gradation data, the one with the higher density is the high density test pattern, and the one with the lower density is the low density test pattern.

The photosensitive drum 1 on which the electrostatic latent image has been formed is developed by the developing device 4. The developing device 4 is, for example, a two-component developing system, in which a developer composed of toner and a carrier is stored. The weight ratio of the toner to the developer (hereinafter referred to as “toner concentration”) is determined by a toner concentration measuring unit 39.
Is measured by The toner replenishing motor 41 for driving the toner replenishing roller 40 is controlled in accordance with the output of the toner density measuring unit 39, so that the toner hopper 4
2 is supplied to the developing device 4.

The developing roller 43 of the developing device 4 is formed of a conductive member, is connected to a high-voltage power supply 44 for developing bias, rotates in a state where a developing bias voltage is applied, and rotates the photosensitive drum. First, toner is attached to an image corresponding to the electrostatic latent image on the first image forming apparatus. The toner image in the image area developed in this way is transferred to a transfer sheet supported and transported by the transfer drum 9.

The control circuit 45 generates the gradation data from the pattern generation circuit 38 at the end of the warm-up processing after the power is turned on, so that the high and low levels for measuring the amount of toner adhering on the photosensitive drum 1 are obtained. The two gradation patterns are exposed.

Then, the positions where the high and low gradation patterns on the photosensitive drum 1 are exposed are developed, respectively, and synchronized with the position of the toner adhesion amount measuring section 8, Measures the amount of toner adhesion. The output of the toner adhesion amount measuring unit 8 is digitized by the A / D converter 46 and input to the control circuit 45.

On the photosensitive drum 1, by the above-mentioned development,
As shown in FIG. 3, a test pattern area corresponding to high-density gradation data (high-density patch: high-density part) and a test pattern area corresponding to low-density gradation data (low-density patch: low-density part) ) Are formed.

The control circuit 45 compares the output (measured value) of the toner adhesion amount measuring unit 8 corresponding to each test pattern with a preset reference value, and according to the comparison result, sets the image forming condition. Is performed to change two of the grid bias voltage of the charger 2 and the developing bias voltage of the developing device 4.

The control circuit 45 controls the switching of the gradation data from an external device or controller (not shown) and the gradation data of the test pattern of the printer alone and the pattern for measuring the toner adhesion amount. , Control of the output amounts of the high-voltage power supplies 34, 35, and 44, setting of the target value of the laser drive current, setting of the target value of the toner density, toner supply control, and correction processing of the gradation characteristics of the gradation data of the printer. And so on.

The high-voltage power supplies 35 and 44 are controlled by output voltage control signals supplied from a control circuit 45 via D / A converters 47 and 48, respectively.

The control circuit 45 measures a rewritable storage unit 61 such as an EEPROM that is not erased even when the power is turned off, a storage unit 62 such as a RAM for storing data, a standby time, and the like. It comprises a timer 63 and a CPU 64 that controls the entire control circuit 45. The control circuit 45 is connected to an adjustment rule generation device 200 described later.

Various setting values are stored in the storage unit 61 in advance. For example, an initial grid bias voltage value and an initial developing bias voltage value corresponding to a bias condition that provides a reference gradation characteristic of normal temperature and normal humidity. , Test pattern gradation data (high-density portion, low-density portion), a predetermined target value for the toner adhesion amount in the high-density portion (used when calculating the deviation), and a predetermined target value for the toner adhesion amount in the low-density portion Target value (used to calculate the deviation), the control specification value for the high-density part deviation, the control specification value for the low-density part deviation,
Coefficient representing surface potential characteristics, predetermined number of printed sheets, predetermined elapsed time, maximum number of controls, bias condition value, abnormal range of toner adhesion amount measuring unit 8, reflected light amount other than test pattern area,
The upper limit value and the lower limit value (predetermined range) of the reflected light amount of the high density portion and the reflected light amount of the low density portion are stored.

The bias condition values are the upper limit value and the lower limit value (predetermined range) of the grid bias and the developing bias, and whether the difference voltage between the grid bias and the developing bias is within a predetermined range.

The target value of the high-density portion and the target value of the low-density portion can be changed and input by the control panel 49 and displayed.

The storage unit 61 also stores a dependency table relating to the amount of change in the contrast voltage and a dependence table relating to the amount of change in the background voltage.

The storage unit 62 stores a bias value (stored when the bias change mode is set) set before the abnormality of the toner adhesion amount measuring unit 8, a counter for counting the number of times of control, and a count for the number of printed sheets. And a sensor abnormality flag that is turned on when the toner adhesion amount measuring unit 8 is abnormal, and a toner empty flag that is turned on when the toner is empty.

FIG. 4 shows the surface potential of the photosensitive drum 1 uniformly charged by the charger 2 with respect to the absolute value VG of the bias voltage with respect to the grid electrode 33 of the charger 2 (hereinafter simply referred to as grid bias voltage). (Hereinafter referred to as an unexposed portion potential) V0, a surface potential (hereinafter referred to as an exposed portion potential) VL of the photosensitive drum 1 which has been entirely exposed with a constant light amount by the laser exposure device 13 and attenuated, and a developing bias voltage VD
(Dashed-dotted line).

In the present embodiment, the polarity of the voltage is negative for reversal development. When the grid bias voltage VG increases, the absolute values of the unexposed portion potential VO and the exposed portion potential VL decrease. Grid bias voltage VG
Is linearly approximated to the exposed portion potential VL and the unexposed portion potential VO with respect to the following equation. VO (VG) = K1 · VG + K2 (1) VL (VG) = K3 · VG + K4 (2) where K1 to K4 are constants, VO, VG, and VL are absolute values, VO (VG), VL ( VG) represents the magnitude of VO and VL for an arbitrary VG.

Here, the absolute value VD of the developing bias voltage,
The development density changes depending on the relationship between the exposed portion potential VL and the unexposed portion potential VO described above. Now, the contrast voltage VC and the background voltage VBG are defined as follows. VC = VD (VG) -VL (VG) (3) VBG = VO (VG) -VD (VG) (4) where VD (VG) is the magnitude of VD with respect to an arbitrary VG. .

The contrast voltage VC particularly affects the density of the solid portion (see FIG. 5). The background voltage VBG mainly relates to the density of the low-density portion in the multi-tone system using pulse width modulation (see FIG. 6).

FIG. 7 shows the toner adhesion amount Q with respect to the gradation data when the magnitude of the background voltage VBG is increased. The low concentration area changes in the direction of the arrow C in the figure. Therefore, the contrast voltage VC and the background voltage VBG
Thus, the development density can be changed.

Here, the following equations can be obtained from the equations (1) to (4). VG (VC, VBG) = (VC + VBG-K2 + K4) / (K1-K3) (5) VD (VBG, VG) = K1 · VG + K2-VBG (6) From the above equations (5) and (6) , Grid bias voltage VG
Between the exposed portion potential VL and the unexposed portion potential VO (K
1 to K4) are known, the contrast voltage VC and the background voltage VBG are determined so that the grid bias voltage V
G and the developing bias voltage VD can be uniquely determined.

The surface potential of the photosensitive drum 1 is measured in advance,
After obtaining the relationship (K1 to K4) between the exposed portion potential VL and the unexposed portion potential VO with respect to the grid bias voltage VG, the contrast voltage VC and the background voltage VBG are set. The grid bias voltage VG and the developing bias voltage VD are uniquely determined from the equations (5) and (6), a plurality of density patterns are formed under these conditions, and the toner adhesion amount Q after development is measured. Then, the measured value is compared with a preset reference value, and from the deviation ΔQ, the respective correction values ΔVC and ΔVBG of the contrast voltage VC and the background voltage VBG for obtaining an appropriate development density are inferred. Based on this inference result, the grid bias voltage VG and the developing bias voltage VD are set again, the amount of toner attached to the density pattern is measured, and the process is repeated until the density falls within the allowable range.

Next, the toner adhesion amount measuring section 8 will be described in detail. As shown in FIG.
In the above, the light from the light source 51 is applied to the surface of the photosensitive drum 1, and the reflected light reflected by the photosensitive drum 1 or the toner that has been developed and adhered to the photoelectric conversion unit 52 according to the amount of the reflected light. Is converted to current, and
After voltage conversion, the A / D converter 46 is transmitted by the transmission circuit 53.
Is converted to a digital signal and taken into the control circuit 45.

The light source 51 is current-driven by a light source driving circuit 54. The light source driving circuit 54 includes a control circuit 45
On / off control or a signal for adjusting the amount of drive current to the light source 51.

Next, the processing operation in the bias change mode in the color printer having such a configuration will be described with reference to the flowchart shown in FIG. The bias change mode includes a warm-up step, a test pattern image forming step, an adhesion amount detection step, a determination step,
It is constituted by a bias changing step.

First, in the warm-up step, when a power supply (not shown) of the printer is turned on, the CPU 64 of the control circuit 45 of the apparatus performs an initial process and executes a predetermined sequence of each initial operation. In particular, it takes time to warm up the fixing device 27. When the warm-up is completed, or when the temperature reaches a predetermined temperature lower than the predetermined temperature at the end of the warm-up, an initial operation of the image forming system including a cleaning operation is performed.

In the initial operation, the temperature of the photosensitive drum 1, the temperature and humidity in the apparatus, the stirring of the developer, the charging,
Stabilization, cleaning of the photosensitive drum 1, etc. are performed, and normal image formation (printing by user image data) is performed.
The imaging environment is almost the same as the state.

After completion of the warm-up step, the CP
U64 checks whether or not the toner adhesion amount measuring unit 8 is normal.
In this case, as a result of a sensor output check in an adhesion amount detection step described later, the presence or absence of a sensor abnormality flag is confirmed.
(When the power is turned on, it is determined that the toner adhesion amount is normal because the flag is cleared.) As a result, when it is determined that the toner adhesion amount measurement unit 8 is abnormal, the CPU 64 stores the reference gradation of normal temperature and normal humidity stored in the storage unit 61. When the high voltage power supplies 35 and 44 are controlled by the initial grid bias voltage value and the initial developing bias voltage value corresponding to the bias condition that becomes the characteristic, the standby state is established. That is, the initial grid bias voltage value and the initial development bias voltage value read from the storage unit 61 are converted into output voltage control signals by the D / A converters 47 and 48, respectively, and output to the high voltage power supplies 35 and 44, respectively. Thus, the high-voltage power supplies 35 and 44 have the grid bias voltage value and the developing bias voltage value, respectively.

At this time, the CPU 64, the control number counter, the number of printed sheets counter and the timer 63 for counting the standby time in the storage unit 62 are cleared.

When it is determined that the toner adhesion amount measuring section 8 is normal, the CPU 64 enters the bias change mode,
Proceed to test pattern imaging step. At this time, the CPU 6
4 stores the grid bias voltage value and the developing bias voltage value currently set by the high-voltage power supplies 35 and 44 in the storage unit 62 (a reference value when the power is turned on, and a toner adhesion amount measurement otherwise). Bias value set before the abnormality of the unit 8).

In the test pattern image forming step, after completion of the initial operation, the charging, exposure, development, cleaning, and charge elimination processes are operated in the same manner as a normal image forming sequence, and the high density test generated by the pattern generating circuit 38 is performed. An image forming operation is performed on the pattern and the low density test pattern.

At this time, the grid bias voltage value of the charger 2 and the developing bias voltage value of the developing device 4 are set to predetermined values, respectively. This value is a bias condition that provides a reference gradation characteristic of normal temperature and normal humidity.

That is, the CPU 64 reads out the output voltage control signal as the initial grid bias voltage value and the initial developing bias voltage value from the storage unit 61, and
It is executed by supplying the high voltage power supplies 35 and 44 via 7 and 48.

In the exposure process, two test pattern latent images of a predetermined size corresponding to two different predetermined gradation data are formed. Of the test patterns for the two gradation data, the one with the higher density is the high density test pattern, and the one with the lower density is the low density test pattern.

Each test pattern has a predetermined width centered on the center of the image area in the axial direction of the photosensitive drum 1 and a predetermined length in the rotating direction of the photosensitive drum 1. They are formed separated by a predetermined distance. The predetermined width corresponds to the axial position of the photosensitive drum 1 of the toner adhering amount measuring unit 8, and is a minimum size at which the detected spot size is not affected by an edge effect or the like peculiar to electrophotography. The minimum size is set so that the effects such as effects and the response characteristics of the sensor do not affect the detection result.

In this embodiment, the predetermined width is 1.5 to 5 mm larger than the detected spot size, and the predetermined length is
The detection spot size is multiplied by the length of movement in four times the time constant of one sensor and the number of times of detection, and the length is obtained by adding 1.5 to 5 mm.

In the developing process, the developing is performed by the developing roller 43 to which the initial developing bias voltage is applied.
Three test pattern latent images are developed to form two test pattern toner images having different densities as shown in FIG. Of the two test patterns, a test pattern area corresponding to low-density gradation data is called a low-density part, and a test pattern area corresponding to high-density gradation data is called a high-density part.

Next, in the adhesion amount detecting step, in synchronization with the arrival of the two test patterns at the positions facing the toner adhesion amount measuring unit 8, respectively, the reflection of each test pattern by the toner adhesion amount measuring unit 8 is performed. The amount of light is detected. Further, the toner adhesion amount measuring unit 8 also detects the amount of reflected light in the undeveloped area of the photosensitive drum 1 at a predetermined timing.

The amount of reflected light in the undeveloped area of the photosensitive drum 1, the amount of reflected light in the low-density part, and the amount of reflected light in the high-density part detected by the toner adhesion amount measuring unit 8 are calculated by the A / D converter 46.
Is supplied to the CPU 64 via the. CPU 64 is A / D
The reflected light amount other than the test pattern area, the reflected light amount of the high-density part, and the reflected light amount of the low-density part supplied from the converter 46 are compared with the upper limit value and the lower limit value (predetermined range) read from the storage unit 61. .

As a result of this comparison, if any one of them is out of the range, the CPU 64 determines that the output value of the toner adhesion amount measuring unit 8 is abnormal, and sets the sensor abnormality flag in the storage unit 62. On the display of the control panel 49, it is displayed that the output value of the toner adhesion amount measuring unit 8 is abnormal, and the bias value before entering the current bias change mode is read from the storage unit 62, and this read is performed. Each of the high-voltage power supplies 35 and 44 is controlled by an output voltage control signal as a bias voltage value, and the apparatus enters a standby state.

When the output value of the toner adhesion amount measuring section 8 is normal, the CPU 64 controls the low-density section and the high-density section based on the reflected light amount of the undeveloped area supplied from the A / D converter 46. The calculation result of the predetermined function related to the optical reflectance is determined as the toner adhesion amount of the low density portion and the toner adhesion amount of the high density portion, respectively.

Then, the CPU 64 compares the predetermined target value stored in the storage unit 61 with the determined toner adhesion amount of the high-density portion and the toner adhesion amount of the low-density portion. The deviation of the high density part and the deviation of the low density part as the deviation are calculated.

Next, a decision step is entered and the CPU 64
Determines whether the calculated deviation of the high-density part and the deviation of the low-density part are within the predetermined standard values stored in the storage unit 61, respectively. If the deviation of the high-density part and the deviation of the low-density part are both within the respective standard value ranges, the storage unit 6
The control count counter, the number-of-printed-sheets counter, and the timer 63 for counting the standby time are cleared, and the printer enters a standby state (a state in which printing can be performed by a user's print request).

If at least one of the deviations is not within the standard value, the flow proceeds to the bias changing step. In this bias changing step, a grid bias voltage value and a developing bias voltage value to be changed are obtained and changed in order to make both the deviation of the high density portion and the deviation of the low density portion fall within the standard values.

This bias changing step is mainly divided into three small steps. (1) determining a control amount of a potential relationship represented by two parameters from the relationship between the two deviations; and (2) a coefficient representing the changed potential relationship and a surface potential characteristic of the photosensitive drum 1 prepared in advance. Calculating a bias value to be changed from a function including (3)
In this step, the grid bias and the developing bias are set to the changed values calculated at the respective predetermined timings.

This causes a problem in a method in which the developing bias voltage value and the grid bias voltage value are selected from preset settings directly from the deviation of the high density portion and the deviation of the low density portion, respectively. For development characteristics that change over time as well as environmental effects, the amount of bias change that is appropriate differs depending on the use of the photoconductor drum 1 and the developer, leaving history, individual differences, and changes over time. Therefore, there is a possibility that the convergence value when the detection and operation are repeatedly performed may deviate from the target value over time.

In this case, the amount of change in the contrast voltage, the amount of change in the contrast voltage, and the position-type control data for associating the contrast voltage value, the background voltage value, and the grid bias value / development bias value.
It is desirable to use the speed-type control data method corresponding to the background voltage change amount.

Further, since the effect of the potential change acting on the high-concentration portion and the low-concentration portion is not necessarily independent and has a dependency, it is inconsistent to determine each bias value from each deviation.

FIG. 10 shows the change in the gradation characteristic when the contrast voltage is changed. The horizontal axis shows the gradation data, and the vertical axis shows the output image density. Similarly, FIG.
It shows a change in gradation characteristics when the background voltage is changed. However, the change in the contrast voltage and the change in the background voltage act on the high-density portion and the low-density portion, respectively, and the manner of the action has a dependency.

The contrast voltage is a voltage between the exposed portion potential, which is the surface potential of the developing position when the entire surface is exposed with a predetermined exposure amount, and the developing bias voltage, and the background voltage is the developing position which is not exposed after charging. The voltage between the unexposed portion potential and the developing bias voltage, which is the surface potential of the device, is such that the change in the contrast voltage is larger in the higher density portion and the change in the background voltage is larger in the lower density portion.

(1) Therefore, when the control circuit 45 of the printer according to the present embodiment adjusts any one of the grid bias and the developing bias, the control circuit 45 optimizes the adjustment based on the dependence of the other adjustment points on the control amount. An adjustment rule generation device 200 that generates an appropriate adjustment rule is provided.

As shown in FIG. 12, the adjustment rule generation device 200 adjusts the adjustment rule according to a dependency table indicating the relationship between the control amount of another bias, which depends on one operation amount of the grid bias and the developing bias, which will be described later. Adjustable control amount selection unit 202 and adjustment rule format generation unit 204 that generates
It has. The adjustable control amount selection unit 202 selects a control amount that can be adjusted from the input dependency table information, and the adjustment rule format generation unit 204 determines the result of the selection by the adjustable control amount selection unit 202 and the dependency table information. To convert the correspondence between the control amount and the operation amount into a format as an adjustment rule.

Here, the operation amount refers to an adjustment operation input of each bias, and the control amount refers to an output of an adjustment portion that affects the adjustment operation input.

As will be described later, the control circuit 45 determines the optimum adjustment position and operation according to the adjustment rule generated by the adjustment rule generation device 200, the toner density detected by the toner density measuring unit, and other various conditions. Various components for selecting and controlling the quantity are provided.

(2) A new contrast voltage and a new background voltage to be changed are obtained from the obtained control amount of the contrast voltage, the control amount of the background voltage, the contrast voltage at the time of forming the test pattern, and the background voltage.

Since these are parameters representing the voltage relationship, a grid bias voltage value and a developing bias voltage value to be set to realize these voltage relationships are calculated.

In this calculation, a function including a coefficient representing the surface potential characteristic of the photosensitive drum 1 and prepared in advance in the storage unit 61 (described in the above equations (5) and (6)) is used. Can be.

(3) The obtained new grid bias voltage value and developing bias voltage value are respectively
Change the setting to the output control value of 4.

When the test pattern is formed again after the setting has been changed, the grid bias voltage value and the developing bias voltage value are changed at predetermined timings.

The predetermined timing means that the developing bias is changed in synchronization with at least the position on the photosensitive drum 1 where the grid bias has been changed reaches the developing position. If the change timing is properly performed, fogging may be caused depending on the changed value, and in the two-component development, the photosensitive drum 1 may be stained due to carrier adhesion.

FIG. 13 shows the timing of changing the grid bias and the developing bias in this embodiment. In this embodiment, when lowering the grid bias voltage to prevent carrier adhesion, the delay time T of the change in the charging potential due to the delay of the grid bias high-voltage power supply 35 or the like.
4 and the setting change of the developing bias value is performed at time t3, which is a time T3 which has elapsed from the setting change time t1 of the grid bias value for a time T2 longer than the time obtained by adding the moving time T1 from the grid electrode 33 to the developing position of the photosensitive drum 1. .

When increasing the grid bias voltage, the grid bias is reduced by a time T3 shorter than a time T3 obtained by subtracting a delay time T5 of the high-voltage power supply 44 for the developing bias from a moving time T1 from the grid electrode 33 to the developing position of the photosensitive drum 1. Time t elapsed from voltage setting change time t4
At 5, the setting of the developing bias voltage value is changed.

That is, at the time of the change, by preventing the background voltage from increasing at the same position on the photosensitive drum 1,
The carrier is prevented from adhering to the photosensitive drum 1.

However, if the difference between T2, T3 and T1 is too large, the fogging amount of the photosensitive drum 1 may increase. Therefore, in the embodiment, T4 = 50 msec or less.
When T5 = 50 msec or less, T2−T1 = 200 msec
Hereinafter, T1−T3 = 200 msec or less.

Next, two test pattern latent images were formed again by exposing the photosensitive drum 1 charged with the changed grid bias voltage by performing image formation, detection, and determination of the test pattern again, and the test pattern was changed. An adhesion amount detection step and a determination step are performed on the two test patterns developed with the development bias voltage.

In the determination step, the deviation of the high density portion
If the deviation of the low density part is within the standard value, with the changed grid bias voltage value and development bias voltage value held,
After the cleaning operation, a standby state is set. If at least one of the deviations is not within the standard value, the bias change, pattern image formation, detection, and determination are repeated.

Next, an adjustment rule generation algorithm in the above-described bias changing step will be described. As described above, when one adjustment point is operated to change the control amount of the grid bias or the development bias, the adjustment point does not uniquely correspond to the control amount, and another control is performed by operating one adjustment point. A change in the amount may occur. Therefore, in the bias change step, it is necessary to specify the dependency between the operation amount of each adjustment point and the control amounts of the other adjustment points, and to adjust each unit according to the adjustment rule generated according to the dependency.

As shown in FIG. 10, it can be seen that as the contrast voltage increases, the density on the high density side increases and the gradient increases. Also, as shown in FIG.
When the background voltage is increased, the start of development of the low density portion is shifted to the higher gradation data, and the gradient is increased.

Further, it can be seen from FIGS. 10 and 11 that the effect on the gradation characteristics is greater even if the amount of change in the background voltage is smaller than the amount of change in the contrast voltage. further,
Fog on the photoreceptor drum 1 and adhesion of oppositely charged toner;
Since there is a risk of carrier adhesion when the developer is a two-component developer, the background voltage is not largely changed, and the contrast voltage is mainly adjusted to make a rough adjustment focusing on the high-density portion. Consideration is given to fine-tuning with the background voltage.

Control circuit 4 of printer according to this embodiment
Reference numeral 5 denotes an adjustment rule generated by the adjustment rule generation device 200 according to a dependency table indicating a relationship between the operation amounts of the contrast voltage and the background voltage and the control amounts of the high-density portion and the low-density portion. And qualitatively manage the selection and order of adjustment.

FIG. 14 shows definitions of control amounts and operation amounts of the grid bias and the developing bias. FIG.
4 (a) shows the definition of the control amount. The subscript of the control amount deviation e is the control amount number, and the corresponding expression defines this.
Here, e1 = ΔQH (= QH−QHT): high concentration part deviation e2 = ΔQL (= QL−QHL): low concentration part deviation

Here, QH indicates the toner adhesion amount value of the high density portion, QHT indicates its target value, QL indicates the toner adhesion amount value of the high density portion, and QHL indicates the target value, respectively.

FIG. 14B shows the definition of the operation amount. The suffix of the operation amount a is the operation amount number, and defines a label indicating the corresponding actual operation means. Here, a1 = ΔVC (contrast voltage change amount) a2 = ΔVBG (background voltage change amount).

FIG. 15 shows a dependency table showing the dependency between the control amount and the operation amount described above. The dependency table is created by inputting the following three types of data. 1. 1. Number of operation amounts (the number of operation amounts and the number of control amounts are the same) 2. Which controlled variable each manipulated variable affects? Whether each operation amount changes the control amount relatively in the same direction or in different directions. That is, in the dependency table, e1, e2, a1, a2
Indicates a control amount and an operation amount respectively defined in FIG. In this dependency table, a control amount having a sensitivity when one of the operation amounts a is operated, that is, an affected control amount is marked with a circle, and an unaffected control amount is marked with a cross. Conversely, if a plurality of operation amounts have a circle with respect to a certain control amount ei, it indicates that there is a dependency on those operation amounts. In consideration of ease of adjustment, it is desirable that the control amount uniquely corresponds to one operation amount, that is, be independent of the other.

In the above dependency table, the O / G column shows O: offset and G: gradient, respectively, and shows the dependence property of two or more control amounts depending on a certain operation amount. In other words, basically, in a change pattern of two control amounts corresponding to one operation amount change, a change in the same direction is an offset (change pattern “0”), and a change in a different direction is a gradient (change pattern “1”). ). Therefore, in the case of independent operation, one operation amount is determined for one operation means, so that it is regarded as a gradient.

In this embodiment, a2 (background voltage)
There are two types of dependency tables depending on whether or not there is a dependency of e1 (high-density portion deviation) with respect to. e1 for a2
Varies depending on the characteristic of the developing system including the developer, and on the basis of the number of gradation levels. The dependency table (1) shown in FIG. 15A is a case where e1 does not change with respect to a2.
The dependency table (2) shown in (b) is a case where e1 also changes with respect to a2.

Further, in the dependency table (2), all become "O", so that knowledge for determining the priority of the adjustment rules is required. In the present embodiment, e1, e with respect to the change of a1
Comparing the changes of 2, it can be determined that the relative difference between the changes of e1 and e2 with respect to the change of a2 is large, that is, the change of e2 is small as compared with the change of e1 with respect to the change of a2. Therefore, by setting a1 as the offset operation amount O and a2 as the gradient operation amount G, the basis of the priority order is obtained by the algorithm of the offset priority when the rule is generated later.

In the dependency table (1), since there is a portion indicated by x, conversely, only e1 can be operated with respect to e1, and e1 is uniquely adjusted by a1. In the rule generation, e2 is adjusted to a2 in order to preferentially adjust the control amount having a large dependence, and then e1 is adjusted to a
A rule to adjust by 1 is obtained. Dependency table (2)
It is necessary to look at the two control amount deviations or the relative value of the control amount deviations, whichever is closer to the target, that is, the smaller of the deviations. Then, after adjusting the offset operation amount a1 by adjusting the operation amount, and after checking the control amount that is not within the allowable range or the difference between the two deviations, operating the gradient operation amount a2. Adjustment rules are obtained.

When generating an adjustment rule based on such a dependency table, the adjustable control amount selection unit 202 of the adjustment rule generation device 200 receives the data of the dependency table, and based on this dependency table data, Checklist 1 shown below
2, and according to the processing procedure shown in FIG.
The combination of the operation amount and the control amount is determined. According to these procedures, the order of each operation amount and, if there is a control amount that must be adjusted with each operation amount, these are output as “rule data”.

[Check List 1]: Calculate the row sum and the column sum for the square matrix of the portion of the dependency table that describes whether each operation amount affects each control amount. II. The operation amounts having the highest priority are set in descending order of the numerical value of the column sum (if the values are the same, the offset operation amount is prioritized; if the values are the same, the operation amount number is prioritized). III. The control amounts having the highest priority are set in ascending order of the numerical value of the row sum (if they have the same value, the same rank is allowed). [Check list 2]: (see FIGS. 16 to 21) Step I. Selecting a lower-order operation amount (“selection operation amount”) Step II. Whether the amount is an offset operation amount (“selected offset operation amount”) (II-i) One of the higher-order control amounts for which the operation amount is not determined is selected (“selection control amount”) (II-ii) ) Whether the number of control amounts adopted as a rule together with the selection operation amount is “0” or “1” (less than “2”) Step II-ii-1. Check 0: There is an offset operation amount corresponding to the selected control amount other than the selected offset operation amount. → Check 0 flag: The number of the offset operation amount (other than the selected offset operation amount) (the first one that corresponds) Step II- ii-2. Check 1: Corresponds to the selected offset operation amount → Check 1 flag: 1 <Exists> (II-iii) Whether the number of control amounts adopted as a rule together with the selection operation amount is “1” Step II-iii- 1. Check 2: There is a gradient operation amount that does not adopt the rule and that corresponds to the selected control amount by searching from the operation amount of the lower rank. → Check 2 flag: The number of the gradient operation amount (the first one corresponding to the gradient operation amount) Step II-iii-2. Check 3: There is a gradient operation amount that does not adopt the rule and that corresponds to the selection control amount based on another offset operation amount, which is retrieved from the operation amount of the lower rank and corresponds to the selection control amount. → Check 3 flag: the number of the gradient manipulated variable (the one that corresponds first) (II-iv) Dependency pattern search (initial value: check level 0) Step II-iv-1. When the check level is “0”: When no control amount is selected → Rule flag: Contents of check 1 flag Step II-iv-2. When the check level is “1”: When no control amount is selected → Rule flag: Contents of check 1 flag Step II-iv-3. When the check level is “2”: When one control amount is selected → Rule flag: Contents of check 2 flag Step II-iv-4. When the check level is “3”: When one control amount is selected → Rule flag: Contents of the check 3 flag Step II-iv-5. When the check level is “4”: When one control amount is selected → Rule flag: Contents of check 2 flag (II-v) Combination determination (when flag is different from initial value) Step II-v-1 . When one control amount is selected → Check level = 2 Step II-v-2. When two control variables are selected → Rule determination, check level = unchanged Step II-v-3. Update processing → Flag initialization (II-vi) Special processing when two control variables are selected (the control variable corresponding to the offset control variable is “main”, and the control variable corresponding to the gradient control variable is “sub” Step II-vi-1. When check level = 3,
Step II-vi-2. Display when master-slave control cannot be performed Step III. When determining the combination regarding the offset operation amount, a gradient operation amount that is not selected as and that corresponds to only one control amount is selected.

The adjustment rule format generation unit 204 of the adjustment rule generation device 200 includes an adjustable control amount selection unit 202.
The rule data output from is arranged for each operation amount and changed to an adjustment rule format that is easy to use for adjustment. This adjustment rule format generation procedure will be described with reference to FIG. 32, checklist 3 and format 1 shown below.

[Check List 3]: Conversion of operation volume with high priority to rule format II. Operation amount selected for rule data III. Pair adjustment rule (when rule data has a flag of “2”) Describe the adjustment rule for the gradient operation amount following the offset operation amount adjustment rule IV. Operation amount not described in the rule data (all corresponding undetermined control amounts are selected) [Format 1]: Operating amount number II. Offset operation amount or gradient operation amount III. Control amount pattern (III-1) Offset operation amount “2” with flag “2” at the end of rule in rule data, gradient operation amount “1” (III-ii) Flag “3” at the end of rule in rule data 2 ”regardless of offset operation amount and gradient operation amount without“ IV ”IV. Control variable number to be adjusted Adjustment rule end identifier (−1) The adjustment rule format according to the present embodiment obtained by such a procedure is as follows. (Adjustment rule 1) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |} Priority1: Delta.U1 = G1 * Grad.e: e = Min {| Error.x2 |} (Adjustment rule 2) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |, | Error.x2 |} 2-Error case Priority2: Delta.U1 = G1 * Grad.e: e = Min {| Error .x2 |, | Error.x2 |} 1-Error case In the above adjustment rule, each symbol is Priority: priority of adjustment, Delta U: change amount of operation amount, e: value of adopted control amount deviation , Grade.e: slope of the deviation (difference from other deviations), Error x: deviation value of the target control variable,
Min ｛｝: Use the smaller value of the values in ｛、
2-Error case: a case where both two target control amount deviations are outside the allowable value, and 1-Error case: a case where only one of the two target control amount deviations is outside the allowable value.

In the adjustment rule 1, the rule of Priority 1 adopts the control amount deviation of x1 as the deviation e used for calculating the change amount Delta U2 of the operation amount when the control amount deviation of x1 is not an allowable value. , And the adjustment gain G2 as the change amount Delta U2 of the operation amount. When the adjustment gain is obtained from the test process, the adjustment gain is obtained from the sensitivity of the control variable deviation x1 to the manipulated variable U2 in the test process.

The rule of Priority 2 is that if the deviation of the controlled variable of x2 is not an allowable value, the deviation of the manipulated variable should be
Deviation gradient Grad. Used to calculate Delta U1.
It is adopted as the deviation e of e, and in this case, it means that the product of the adjustment gain G1 is used as the operation amount change amount Delta U1 based on the rate of change of the difference from the other deviation x1. When the adjustment gain is obtained from the test process, the adjustment gain is obtained from the sensitivity of the control variable deviation x2 with respect to the manipulated variable U1 in the test process.

Then, the above two rules are checked in accordance with the priority order to determine whether or not the control state is compatible. If the control state is satisfied, the operation is performed based on the adjustment rule.

In the adjustment rule 2, the rule of Priority 1 is such that when the two control amount deviations of x1 and x2 are not allowable values, the deviation is used to calculate the operation amount change amount Delta U2. The smaller absolute value is adopted as e, and the product of the adjustment gain G2 is changed by the change amount Delt of the operation amount.
a means U2.

The rule of Priority 2 is that if one of the two control variable deviations x1 and x2 is not an allowable value, it is used to calculate the change amount Delta U1 of the manipulated variable. As the deviation e of Grad.e, it means that the product of the adjustment gains G1 is used as the change amount Delta U1 of the manipulated variable based on the rate of change of the difference from the other deviation.

Then, the control circuit 45 checks whether or not the control state is compatible with the two adjustment rules according to the priority order, and if so, selects an operation amount for adjusting the deviation based on the adjustment rule. Then, the adjustment operation is performed.

FIG. 23 shows functional blocks of a control circuit 45 for executing the above-described adhesion amount detection step, determination step, and bias change step. The control circuit 45 includes a deviation amount calculation unit 206, which calculates a target value based on the control amount definition expression input from the control amount definition input unit 208 to the control amount definition storage unit 210, Each control amount deviation is calculated from the toner adhesion amount detected by the amount measurement unit 8 and the pass / fail judgment unit 212 and the deviation storage unit 213.
Enter

Then, the pass / fail judgment section 212 judges pass / fail of the deviation calculated by the deviation amount calculation section 206 based on the permissible value of each deviation inputted from the permissible value input section 214 to the permissible value storage section 216 (all If the control amount deviation is within the respective allowable values, it is good, otherwise it is no).

If the pass / fail judgment is made, the adjustment process is completed. If the pass is not satisfied, an adjustment portion is selected in a bias change step. In this case, the adjustment rule generation device 200 of the control circuit 45 uses the dependency table stored in the dependency table storage unit 220 via the dependency table input unit 218,
An adjustment rule is generated in advance and stored in the adjustment rule storage unit 222. The adjustment rule of the image forming apparatus according to the present embodiment generated by adjustment rule generation apparatus 200 is shown in FIG.
(A).

Then, the adjusting mechanism selecting unit 2 of the control circuit 45
Reference numeral 24 designates an operation amount number to be adjusted based on the adjustment rule stored in the adjustment rule storage unit 222 and each control amount deviation stored in the deviation storage unit 213, and an operation amount definition input unit. The operation amount number stored in the operation amount definition storage unit 228 via the operation amount number 226 is compared with the selected operation amount number, and an adjustment mechanism corresponding to the selected operation amount number is selected.

Then, as shown in FIG. 24 (b), the control circuit 45 performs test adjustment by the selected adjusting mechanism, and stores the test operation amount at that time in the test operation amount storage unit 230.
To be stored. Further, the control circuit 45 detects a change in the control amount deviation according to the test operation by detecting the toner adhesion amount in the high-density part and the low-density part after the test adjustment, and the sensitivity calculation part 236 detects the change. The sensitivity of the control amount to the operation amount is calculated based on the change in the control amount deviation and the test operation amount. The operation amount calculation unit 232 calculates an actual operation amount of the adjustment mechanism based on the sensitivity calculated by the sensitivity calculation unit 236, and stores the actual operation amount in the operation amount storage unit 234.

Subsequently, the control circuit 45 operates the selected adjustment mechanism according to the calculated operation amount, and adjusts the bias. After the adjustment, the control circuit 45 again forms the test pattern, develops the toner, and measures the amount of toner adhered. The control circuit 45 adjusts the operation with a higher priority according to the adjustment rule, and all deviations converge to an allowable value in the pass / fail judgment. Repeat the above steps until

In the initial state, if the deviation of the control quantity having the higher priority is within the tolerance, the control quantity having the next priority is detected and the adjustment operation is executed.

Next, the change of the toner adhesion amount and the bias value which are the inputs of the measurement system in the control process will be described with reference to FIGS. 25 to 27.

FIGS. 25 and 26 show the high-density toner adhesion amount QH and the low-density toner adhesion amount QH in, for example, a low-temperature and low-humidity environment.
This is an example when L is lower than the respective target values QHT and QLT. The abscissas of FIGS. 25 and 26 indicate the number of times of control, the ordinate of FIG. 25 indicates the toner adhesion amount detection value, and the ordinate of FIG. 26 indicates the bias value.

When the number of times of control is 0, the grid bias voltage value VG and the developing bias voltage value VD are set to predetermined initial values to form high-density and low-density test patterns.
The toner adhesion value QH of the high density portion and the toner adhesion value QL of the low density portion detected for the test pattern are lower than the target values QHT and QLT, respectively, and are outside the ranges of the respective control standard values. The change amount in the bias change step is calculated.

In this case, since the high-density part is very small (the deviation of the high-density part is large negatively), the grid bias voltage value VG and the developing bias voltage value VD are changed so as to increase the contrast voltage (control times). 1).

Then, with the changed bias voltage value, a test pattern is formed and the toner adhesion amount is detected. FIG.
As can be understood from FIG. 5, by increasing the contrast voltage, both the toner adhesion amount values QH and QL increase and approach the respective target values (control number 1).

At this time, a change amount for slightly increasing the contrast voltage and increasing the background voltage is extracted according to the adjustment rule, and the grid bias voltage value VG and the developing bias voltage value VD are calculated according to the change amounts of these voltages.
It is changed (control count 2).

The test pattern is formed and the toner adhesion amount is detected again with the changed bias voltage value. On this occasion,
Since the toner adhesion amount values QH and QL do not reach the control specification values (control number 2), the same bias change as described above is repeated (control number 3). As a result, both the toner adhesion amount values QH and QL fall within the control standard value, and the control ends.
FIG. 27 shows changes in the operation amounts (VC, VBG) corresponding to the number of times of control when the above-described control is performed.

FIGS. 28 (a) and 28b (b) show the target values QHT and QLT for both the high-density toner adhesion amount QH and the low-density toner adhesion amount QL in a high-temperature and high-humidity environment.
An example of control at a higher time is shown.

In this example, at the initial bias value, the toner adhesion value QH of the high density portion and the toner adhesion value QL of the low density portion are higher than the target values QHT and QLT, respectively (control count 0), and the contrast voltage is reduced. As a result, the grid bias voltage value VG and the developing bias voltage value VD are changed (control count 1). The toner adhesion amount QH and the toner adhesion amount QL of the low density portion are respectively set to target values QHT and QLT.
Approach. After that, mainly the background voltage is changed and the contrast voltage is minutely changed to converge within the respective control standard values. In this example, convergence requires four control times.

As described above, from the relationship between the deviation of the high-density part and the deviation of the low-density part, the effective change amount for the high-density part and the low-density part is derived in accordance with the adjustment rule, and the change is defined as the image forming condition. This is realized by the change, the effect is confirmed again, and the control is repeated when it is out of the standard value range to converge to the target value.

In the above example, the control was performed when the power of the apparatus was turned on. In this embodiment, when a device door (not shown) is opened and closed, when an external control execution command is issued, when a predetermined time is exceeded after the control is completed, and when a predetermined number of printed sheets are exceeded after the control is completed. The above control can be performed when the toner empty is released.

That is, when the apparatus door is opened and closed, that is, when a jam occurs inside the apparatus such as a paper feeding system and a paper discharging system, and when the apparatus door is opened and closed for the purpose of paper removal or maintenance, the photosensitive drum is opened. There is a possibility that external light may enter the body drum 1 and affect the surface potential characteristics of the photosensitive drum 1;
In addition, since there is a possibility that the temperature and humidity inside the apparatus may suddenly change, control is performed after an initial operation such as a warm-up operation is completed based on a detection result of a door sensor (not shown) that detects opening and closing of the apparatus.

Further, when a control execution command from outside is given, that is, at the time of maintenance, the serviceman operates the control panel 49 or when a control execution command from outside of the apparatus is received, control is performed.

Further, when a predetermined time has passed after the control is completed,
In other words, when a long time has elapsed since the end of the control, the temperature and humidity inside the apparatus change due to the change in temperature and humidity outside the apparatus, the surface potential characteristic changes due to the recovery from light fatigue of the photosensitive drum 1, and the development once stirred. There is a possibility that a change in gradation characteristics, such as a change in halo density or charge amount due to leaving the agent, may occur.

Therefore, the control is performed when the predetermined elapsed time stored in the storage unit 61 is exceeded by the timer 63 which measures the time since the last control.

Further, when a predetermined number of prints is exceeded after the control is completed, when a large number of prints are performed after the control is completed, the change in the surface potential characteristic due to the light fatigue of the photosensitive drum 1 and the change in the charge amount of the developer. For example, there is a possibility that a change occurs in gradation characteristics.

Therefore, a counter in the storage unit 62 that measures the number of printed sheets since the last control is completed is calculated by
The control is performed when the predetermined number of printed sheets stored in the storage unit 61 is exceeded. However, in the case of continuous printing, control is performed after printing of the number of prints set by the user is completed.

When the toner empty state is released, that is, after the toner is replenished after the toner empty state, the cartridge containing the toner is replaced, or the process unit including the toner or the photosensitive drum 1 is replaced, the toner empty flag of the storage unit 62 is cleared. When it is done, control is performed.

This is because, as a control effect, the bias value is adjusted so that the density is as high as possible within the above-mentioned bias condition even if the toner is less than the specified amount and the density decreases. However, when the toner is replenished and the toner amount reaches the specified value, the control is performed again in order to further increase the target value.

In any of the above cases, from the start of the control to the end of the control, a display indicating that the control is being performed is displayed. A busy signal is generated for an external input (the control panel 49 or the outside of the apparatus) so as to wait for printing.

Next, the control termination condition will be described. That is, when the deviation of the high-density portion and the deviation of the low-density portion are both within a predetermined control standard value stored in the storage unit 61 (normal termination), the control of the predetermined number of times stored in the storage unit 61 is performed. When (bias change) is performed (maximum control count is executed), when the calculation result of the bias change value reaches a predetermined bias condition value stored in the storage unit 61 (operation amount limit), the toner adhesion amount measurement unit The time when the output of No. 8 becomes a predetermined condition (abnormal range) stored in the storage unit 61 (abnormal sensor output) is a control end condition.

When the deviation of the high-density portion and the deviation of the low-density portion are both within a predetermined control standard value (normal end), that is, in the determination step, the high-density portion falls within a predetermined control standard value which is a target range. When the deviation of the low concentration part enters
The apparatus shifts to the apparatus standby state while maintaining the grid bias voltage value and the developing bias voltage value. That is, normal termination is achieved by achieving the target.

When the predetermined number of times of control (bias change) has been performed (maximum number of times of control executed), that is, when the operation is not normally completed, the process proceeds to the bias change step, and the test pattern image formation, adhesion amount detection, and determination are repeated again. However, if the convergence but the steady-state deviation does not fall within the predetermined standard value for some reason, the control is repeated forever.

Further, it is necessary to limit the maximum time required for the control to finite. In this embodiment, the change amount of the parameter relating to the operation amount with respect to the deviation from the target is given, and the change amount is made to correspond to 0 with respect to the deviation 0. For example, when the effect on the tonal characteristic changes in the history or the like, the number of repetitions (control times) required for convergence may increase or decrease.

Therefore, it is sufficiently effective to change the bias value in a direction to decrease a large deviation qualitatively with the permitted number of times of control. Therefore, the number of times the bias has been changed since the start of the control is measured by a counter in the storage unit 62, so that the grid bias voltage value and the developing bias voltage value at the time when the predetermined number of control times have been performed are maintained. It goes into a standby state.

When the calculated result of the bias change value is a predetermined bias condition (operating amount limit), that is, the calculated value of the bias value to be changed and the bias voltage to be actually set are determined by the D / A converter 47, An output voltage corresponding to the value set to 48 is sent to the high voltage power supplies 35 and 44 as an output voltage control signal of the high voltage power supplies 35 and 44. D / A converter 4
The set values to 7 and 48 and the output voltage values of the high-voltage power supplies 35 and 44 are adjusted in advance, and the set bias value is output.

However, if the calculated bias value falls outside the output variable range of the high-voltage power supplies 35 and 44, the CPU
There is a possibility that the output voltage recognized by the H.64 differs from the actual output voltage and erroneous control is performed.

In addition, the voltage must be varied within a bias range in which there is no possibility that a defect such as an image defect or contamination of the photosensitive drum 1 will occur. Further, the difference voltage between the grid bias and the developing bias is related to the background voltage, and the background voltage is
If the size is too large, the oppositely charged toner adheres, and in the case of two-component development, the carrier adheres. If the size is too small, fogging increases.

Therefore, the CPU 64 sets the grid bias and the developing bias as the bias condition values stored in the storage unit 61 to predetermined upper limit values and lower limit values, respectively, and sets the difference voltage between the grid bias and the developing bias to a predetermined value. Are actually set in the D / A converters 47 and 48. Under conditions other than these conditions, the bias value is not changed to the D / A converters 47 and 48, and the control ends with the current setting of the grid bias voltage value and the developing bias voltage value, and enters a standby state. .

In this embodiment, the predetermined value is set experimentally as follows. (In this embodiment, the bias voltage value is negative because normal development is performed using negatively charged toner. The following numerical values represent absolute values.) The upper limit value of the grid bias is 1000 V or less, and the lower limit value is 250 V. It is set with the above values. The developing bias is set at a value of 920 V or less, and the lower limit is set at a value of 170 V or more. The difference voltage between the grid bias and the developing bias is set to an upper limit value of 400 V or less and a lower limit value of 80 V or more.

When the output of the toner adhesion amount measuring section 8 becomes a predetermined condition (abnormal sensor output), that is, the CPU 64
The reflected light amount of the photosensitive drum 1 other than the test pattern area, the reflected light amount of the high-density test pattern, and the reflected light amount of the low-density test pattern supplied from the / D converter 46 are stored in the storage unit 61, respectively. It is checked whether or not the measurement section 8 is in an abnormal range.

At this time, a change in reflectance such as a defective sensor power supply, deterioration of the light source 51, dirt on the light emitting / receiving optical path, defective light receiving circuit, sensor / receiver circuit, scratches on the photosensitive drum 1, and filming. In addition, the detection accuracy may be degraded due to a defect in the test pattern image forming system, and the control system may malfunction.

Therefore, predetermined upper and lower limits are set for the sensor output values corresponding to the reflected light amount other than the test pattern area of the photosensitive drum 1, the reflected light amount of the high density test pattern, and the reflected light amount of the low density test pattern. If any one of the outputs is out of the range, the calculation and determination are not performed thereafter, the sensor abnormality flag is set, and the control panel 49 displays that the toner adhesion amount measuring unit 8 is abnormal, The standby state is established in a state where the bias value before the occurrence of the abnormality of the adhesion amount measuring unit 8 is held.

Note that the sensor abnormality flag in the storage unit 62 is reset by an initial process while the apparatus power is on. Further, at the time of maintenance, it can also be reset by a reset command from the control panel 49 by a service person. When the sensor abnormality flag is set, no control is performed.

Next, the detection sequence (test pattern image formation, development, adhesion amount detection step) will be described. In an apparatus without a transfer drum, an operation other than transfer, paper feeding, paper discharging operation, and fixing is performed at the same timing as that of a normal printing operation. To turn off transcription
This is because the toner does not scatter on the photosensitive drum 1 without the transfer material (paper).

The light source 51 of the toner adhesion amount measuring unit 8 is
It can be turned on / off by the light source remote signal of U64, and after the time required for the light amount to stabilize after turning on,
Turns on at a timing that can be detected.

Therefore, in the normal printing operation, the light source 51 of the toner adhesion amount measuring section 8 does not emit light. This is because the potential of the unexposed portion, which is the surface potential that has not been exposed before transfer, is removed by light emission from the light source 51 to prevent dust or toner scattering on the image. Since it is performed at the same position in the axial direction of the body drum 1, the purpose is to prevent an adverse effect on image quality due to light fatigue of the photosensitive drum 1 in that portion in the long term.

In the above embodiment, the transfer drum 9 is provided, and not only the transfer, paper feed, and paper discharge operations, but also the suction and peeling operations on the transfer drum 9 are not performed. In the transfer drum 9, only the cleaning of the transfer material support is performed. As a result, the amount of the toner image of the test pattern developed on the photosensitive drum 1 adheres to the transfer material support. For this reason, it is possible to form an image of the test pattern and detect the amount of adhesion without considering the positional relationship with the transfer drum 9.

According to the printer configured as described above, even when the image forming section having a plurality of adjustment portions having a correlation with each other is provided, the adjustment is performed based on the dependency between the operation amount and the control amount. By generating a rule and adjusting the image density based on the adjustment rule, standardization and automation of the adjustment work can be achieved, and efficient and accurate adjustment can be performed. As a result, stable image density can be easily maintained, productivity can be improved, manufacturing cost can be reduced, and development efficiency can be improved.

In the above embodiment, the image density is adjusted and the image quality is maintained stably by adjusting the grid bias and the developing bias. However, the present invention is not limited to this. May be adjusted to maintain image quality.

For example, according to the second embodiment described below, the image density of the formed image is adjusted by adjusting the exposure amount and the light emission time by the laser exposure device, and the stable image quality is maintained. Configuration.

In the second embodiment, the basic configuration of the laser printer is the same as that of the first embodiment, and only different parts will be described in detail. FIG.
Indicates image data (including gradation information) according to the present embodiment
2 shows a detailed flow and a functional block relating to an exposure system.

In normal printing, image data (hereinafter referred to as gradation data) including gradation information from an external device or a document reading unit and an image processing unit is converted according to an image transfer clock and command / status information. Are transferred to the interface (I / F) 161 of the apparatus. The control circuit 45 manages transmission / reception of a command / status including a data request, a printer busy, and the like.

The control circuit 45 sets the selector 162 to select the gradation data from the interface 161. The selected gradation data is sent to the data conversion unit 163, where it is converted into laser beam light pulse width data according to the conversion data given from the control circuit 45, and stored in the line buffer 164. The data transfer so far is performed in synchronization with the image transfer clock.

Here, the selector 162 and the data converter 1
63 and the line buffer 164 constitute the gradation data buffer 36.

On the other hand, the laser beam emitted from the laser diode 165 in the laser exposure device 13 passes through a pre-deflection optical system (not shown) and passes through a motor 16 as deflection means.
The light beam is deflected and scanned by the polygon mirror 167 rotated at 6. The motor 166 is driven by a motor driver 168. Here, the laser exposure device 13 is constituted by the laser diode 165, the motor 166, the polygon mirror 167, and the motor driver 168.

The horizontal synchronization detector 169 detects the position of the laser beam 14 deflected by the polygon mirror 167 to generate a horizontal synchronization signal at the write scan position, and outputs the horizontal synchronization signal to the synchronization clock generation circuit 17.
Send to 0. The synchronous clock generating circuit 170 generates a write synchronous clock signal for each pixel based on the input horizontal synchronous signal, and outputs the horizontal synchronous signal and the write synchronous clock signal to the line buffer 164 and a counter 171 managed by the control circuit 45. , PWM (pulse width modulation) circuit 1
72 and the laser driver 173.

Note that scanning with laser beam light is synchronized with the write synchronization signal and the horizontal synchronization signal signal.

The counter 171 generates a horizontal synchronizing signal, a write synchronizing signal, and a timing signal of a write area (top, bottom, right, left margin) based on the print start position information under the control of the control circuit 45.
Read / transfer from the line buffer 164 and the PWM circuit 7 based on the timing signal and the synchronous clock signal.
2 and exposure writing of the laser driver 173 are executed in synchronization.

That is, until the gradation data is written to the line buffer 164, the image transfer clock is used as a reference.
Processing from reading from the line buffer 164 to exposure with the laser beam light is performed based on the laser scanning position. This is due to the difference between the external image transfer rate and the writing speed due to the effective angle of view of the laser optical system. This speed is temporarily stored in the line buffer 164 and absorbed.

The PWM circuit 172 generates a gate pulse corresponding to the emission time of the laser diode 165 per unit pixel based on the pulse width data per unit pixel. The laser driver 173 supplies a drive current according to the gate pulse to the laser diode 165, and performs on / off control of the laser diode 165.

Therefore, when the pulse width data per unit pixel is large, the light emission time of the laser diode 165 per unit pixel is long, the energy exposed to the photosensitive drum 1 is large, and the area is wide. Conversely, when the pulse width data per unit pixel is small, the light emission time of the laser diode 165 per unit pixel is short, the energy exposed to the photosensitive drum 1 is small, and the area is also small. As a result, the latent image pattern after exposure forms a latent image of a gradation pattern expressed in gradation by exposure to the laser beam light 14 based on the pulse width data.

The amount of light emitted from the laser diode 165, that is, the amount of exposure is controlled by the light amount control circuit 174. The laser diode 165 has a main light emission (front surface) used for exposure and a monitor light emission emitted on the back surface, and includes a monitor diode (not shown) for detecting the monitor light emission amount. The light amount control circuit 174
The output of the monitor diode is detected and compared with a target value, and a signal for correcting the amount of the laser drive current is generated for the laser driver 173 so as to reduce the deviation.

Here, the laser drive circuit 37 is constituted by a horizontal synchronization detector 169, a synchronization clock generation circuit 170, a PWM circuit 172, a laser driver 173, and a light quantity control circuit 174.

When the pulse width correction characteristic is changed, the pulse width correction characteristic is changed by transferring the conversion data from the control circuit 45 to the data conversion unit 163. This makes it possible to change the conversion characteristic (pulse width correction characteristic) of the pulse width data from the gradation data.

When the exposure amount, that is, the light emission amount of the laser diode 165 is changed, the change is performed by transferring the target value of the light amount control circuit 174 from the control circuit 45. Thereby, the exposure amount can be changed.

On the other hand, when creating a test pattern, the control of the control circuit 45 switches the selection of the selector 162 to select the test pattern image data generated from the pattern generation circuit 38 and the internal image transfer clock. The pattern generation circuit 38 transfers the test pattern image data to the selector 62 in synchronization with the internal image clock based on the data including the gradation information in accordance with the data from the control circuit 45. The data flow is the same as that of the image data from the interface 161.

In order to set the image writing area to a predetermined test pattern size, the control circuit 45 operates the counter 171.
The image writing area information (top, bottom, right, and left margin) is rewritten into test pattern data, and test pattern exposure is performed accordingly. Therefore, the type, size, and printing position of the test pattern including the gradation can be designated by the setting from the control circuit 45.

Next, the laser printer having such a configuration will be described mainly with reference to a flowchart shown in FIG. This processing operation
The process is roughly divided into a warm-up step S1, a test pattern image forming step S2, a toner adhesion amount measuring step S3, a determining step S4, and an image forming condition changing step S5.

Warm-up step S1, test pattern image formation step S2, toner adhesion amount measurement step S
3 and the determination step S4 are the same as those in the first embodiment, and here, the image forming condition changing step S5
Will be described in detail.

That is, as in the first embodiment, in the determination step S4, if at least one of the high-density portion deviation and the low-density portion deviation is not within the standard value, the image forming condition changing step S5 is performed. Proceed to.

As shown in FIG. 31, the image forming condition changing step includes changing the light amount control target value of the exposure optical system to be changed so that both the high density portion deviation and the low density portion deviation fall within the standard value, The exposure amount and the exposure width are changed by changing the width modulation data correction table. Here, first, an operation amount to be adjusted is selected according to the adjustment rule generated by the above-described adjustment rule generation device 200, that is, an exposure amount or an exposure width is selected, and the selected operation amount is changed to perform a test operation. Do. Then, by measuring the toner adhesion amount, the control amount associated with the change of the selected operation amount, that is, the sensitivity of the deviation is calculated, and the change amount of the operation amount is calculated according to the calculation result. Then, the exposure amount or the exposure width is corrected according to the calculated change amount.

FIG. 32 shows the effect of the gradation characteristic of the light quantity change. The horizontal axis represents the gradation data, and the vertical axis represents the output image density ID.
P0 is the reference light amount, P1 to P4 are the changed light amounts, and the gradation characteristics at that time are shown. P1 <P2 <P
0 <P3 <P4. It can be seen that the higher the density, the greater the change in the light amount, the greater the light amount, the greater the gradient of the gradation, and the smaller the light amount, the smaller the gradient. Therefore, by changing the light amount with respect to the gradation characteristic changed as the density increases, the gradation characteristic can be corrected to the reference gradation characteristic. However, it is difficult to correct a nonlinear change on the low density side only by changing the light amount.

FIG. 33 shows the relationship between pulse width correction characteristics and changes in gradation characteristics. The first quadrant represents the reference gradation characteristic by the output image density for the original data before correction. The third quadrant represents correction data for the original data. The second quadrant represents a reference gradation characteristic and a changed gradation characteristic for the correction data.

The number of divisions of the correction data is larger than the number of divisions of the gradation data so that the original data can be corrected more finely. That is, the actual number of pulse width modulation stages is larger than the number of division stages of the original data. In this embodiment, the original number of gradation steps is 16 and the pulse width data is 25.
Each of the six stages is the number of stages including 0 (no exposure). Therefore, the pulse width correction means (data conversion unit 63) selectively corresponds to the pulse width data having the ideal reference gradation characteristic from among the prepared pulse width modulation stages corresponding to the gradation data. Role.

In principle, the data relationship before and after the correction by the pulse width correction means corresponds to data in which the ratio is evenly proportional. All image forming conditions including the light amount are the reference conditions, and the environmental conditions are the standard room temperature and normal humidity. When the unit and the material related to the image formation are in the initial state, the output image density for the original data has the reference gradation characteristic indicated by γ0.

Now, it is assumed that the gradation characteristic changes with the environment and the aging, so that the density decreases as the density becomes lower, such as γ1. At this time, in order to realize an image density corresponding to each original data of the reference gradation characteristic shown in the first quadrant, it is necessary to correct data such as φ1. The gradation characteristic itself is a non-linear characteristic with respect to the pulse width, and the change is not always linear. However, when the original data and the correction data are linearly approximated, each correction data value can be obtained relatively easily. In order to increase the reduced density, φ1 increases the correction data, that is, the pulse width, as the density becomes lower, thereby approaching the reference gradation characteristic.

It is also assumed that the gradation characteristics change with the environment and the aging, such that the density increases as the density decreases in a low density portion such as γ2. At this time, in order to realize an image density corresponding to each original data of the reference gradation characteristic shown in the first quadrant, it is necessary to correct data such as φ2. For φ2, the correction data, that is, the pulse width is made smaller as the density becomes lower in order to lower the increased density, thereby bringing the density closer to the reference gradation characteristic.

In principle, any change in gradation characteristics can be corrected by pulse width correction. However, the maximum density cannot be corrected, especially when the density is reduced. Further, when the gradation characteristic changes drastically and the gradient of the image density with respect to the pulse width increases, the resolution becomes insufficient with the prepared number of gradation steps, and a larger number of gradation steps is required. 163), an increase in the size of the pulse width modulation means (PWM circuit 172), the luminous responsiveness, the limit of high-speed driving, and the influence of uneven charging and jitter in the image area appear. Therefore, it is desirable to reduce the amount of change (the amount of correction) by division of labor with other means.

Therefore, the maximum value and the minimum value of the original data ("15" and "0" in this embodiment) are respectively the maximum value and the minimum value of the correction data ("255" and "0" in this embodiment). Is fixed and no correction is performed. Other original data is converted into correction data according to a predetermined function.

FIG. 34 shows the linearly approximated relationship between the original data and the correction data. The horizontal axis is the original data before correction, and the vertical axis is the corrected data after correction, and shows the correction approximate straight lines of φ0 and φ1 in the third quadrant of FIG. here,
The minimum value of the original data is “0”, the maximum value is “n”, and each data is defined as Di. Here, i is an integer from 0 to n. Therefore, in the present embodiment, D0 = 0,
.., Dn = 15.

In the correction data, the minimum value is 0, the maximum value is Dmax, and the correction data corresponding to the i-th original data is represented by Dc (i). In this embodiment, Dc
(0) = 0,..., Dc (i),..., Dc (n) = D
max = 255. Therefore, the following equation is defined.

Φ; Dc (i) = C1 × D (i) + C2 (7) where C1 and C2 are coefficients. The above equation (1) is a linear equation representing the original data and the correction data. C1 indicates the inclination, and C2 indicates the intercept of the correction data axis. When φ0 is obtained from the above equation (7), C2 = 0,
Since Dc (n) = Dmax, φ0; Dc (i) = (Dmax / Dn) × D (i) (8), and generally φ; Dc (i) = (Dmax−C2 / Dn) ) × D (i) + C2 (9) Therefore, by moving C2, that is, the intercept of the correction data axis, the correction can be performed with a larger change amount on the lower density side.

In the example of φ1, when the gradation characteristic changes so that the image data decreases as the density decreases (see γ1 in FIG. 33), the correction is made so that the pulse width increases as the density decreases. This is realized by changing the coefficient C2 when using equation (9). Therefore, if the amount ΔC for changing the current value of C2 is obtained, a new C2 can be obtained by summing them.

Therefore, in the second embodiment, the operation amount of the exposure light amount (light amount control amount target value) and the exposure width (pulse width data correction coefficient) and the control amount deviation of the high density portion and the low density portion are different. An adjustment rule is generated by the adjustment rule generation device 200 in accordance with the dependency table indicating the relationship, and the adjustment is performed by qualitatively managing the selection of adjustment points, the order of adjustment, and the like according to the adjustment rules.

FIG. 35 (a) shows the definition of the control amount. The suffix of the control amount deviation e is the control amount number, and the corresponding expression defines this. Here, e1 = ΔQH (= QH−QHT): high concentration part deviation e2 = ΔQL (= QL−QHL): low concentration part deviation

Here, QH indicates the toner adhesion value of the high density portion, QHT indicates its target value, QL indicates the toner adhesion amount value of the high density portion, and QHL indicates the target value.

FIG. 35B shows the definition of the operation amount. The suffix of the operation amount a is the operation amount number, and defines the label indicating the corresponding actual operation means. Here, a1 = ΔP (the amount of change in the light amount control target value) and a2 = ΔC (the amount of change in the pulse width data correction coefficient).

FIG. 36 shows a dependence table showing the dependence between the above-mentioned control amount and operation amount. The dependency table is created by inputting the following three types of data. 1. 1. Number of operation amounts (the number of operation amounts and the number of control amounts are the same) 2. Which controlled variable each manipulated variable affects? For each operation amount, whether the control amount changes in the same direction or in the different direction relatively, that is, in the dependency tables (1) and (2), e1 and e
2, a1 and a2 indicate the control amount and the operation amount defined in FIG. 35, respectively. The meaning of each symbol in each dependency table is the same as in the first embodiment. When generating an adjustment rule based on such a dependency table, when the data of the dependency table is input, the adjustable control amount selecting unit 202 of the adjustment rule generation device 200 performs the above-described check based on the dependency table data. The combination of the operation amount and the control amount is determined by the processes according to the lists 1 and 2 and the processing procedure. According to these procedures, the order of each operation amount and, if there is a control amount that must be adjusted with each operation amount, these are output as “rule data”.

The adjustment rule format according to the present embodiment obtained by such a procedure is as follows. (Adjustment rule 1) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |} Priority2: Delta.U1 = G1 * Grad.e: e = Min {| Error.x2 |} (Adjustment rule 2) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |, | Error.x2 |} 2-Error case Priority2: Delta.U1 = G1 * Grad.e: e = Min {| Error .x2 |, | Error.x2 |} 1-Error case In the above adjustment rules 1 and 2, the meaning of each symbol can be the same as in the first embodiment. Then, the control circuit 45
Selects an operation amount for adjusting the deviation according to the above-described adjustment rule format, and executes the adjustment operation.

First, the control circuit 45 selects an optimal operation amount (a change amount of the light amount control target value and a change amount of the pulse width data correction coefficient) according to the control amount deviations ΔQH and ΔQL in accordance with the above adjustment rule, and corrects the light amount. A new light amount and a pulse width correction coefficient value to be changed are obtained from the amount, the pulse width correction coefficient change amount, the light amount when forming the test pattern, and the pulse width correction coefficient value.

In the present embodiment, the light quantity is calculated by the following equation with the voltage value given to the target value of the light quantity control means (light quantity control circuit 174) of the exposure optical system. Pnew = P + ΔP (10) where Pnew is the new light amount, P is the current light amount, and ΔP
Is the light amount change amount obtained by the adjustment rule.

The pulse width correction data is created by ΔC
.., N−1 and Dc (i) corresponding to the original data Di by using the equation (9). The correction data including 0 and Dmax is transferred to the pulse width correction unit.

Next, the obtained voltage value data to be applied to the target value of the light amount control means of the new exposure optical system is transferred to the light amount control circuit 174 which is the light amount control means, and the correction data including 0 and Dmax is subjected to the pulse width control. Data conversion unit 6 as correction means
Transfer to 3.

Next, test pattern image formation, measurement,
When making the determination, two test pattern latent images are formed by the target value of the light quantity control means of the exposure optical system changed as described above and the pulse width correction means of the changed correction data, and the two test patterns developed are developed. Then, the toner adhesion amount measurement step S3 and the determination step S4 are performed. If the high-density portion deviation and the low-density portion deviation are within the standard values in the determination step S4, a standby state is set after the cleaning operation with the changed target value of the light amount control means and the changed correction data held. If at least one of the deviations is not within the standard value, the steps of changing the imaging condition, forming the pattern, measuring and determining are repeated.

FIGS. 37 and 38 show the measured toner adhesion amount Q in the control process and the light emission amount of the laser diode 165 (hereinafter referred to as the light emission amount).
An example of a graph showing how the laser light emission amount) P and the pulse width correction coefficient C are changed is shown. FIG. 37 is a plot of the high-density portion toner adhesion amount measurement value QH and the low-density portion toner adhesion amount measurement value QL with respect to the control count. In the drawing, broken lines QHT and QLT indicate target values of the toner adhesion amount in the high density portion and the low density portion, respectively.

FIG. 38 is a plot of the laser light emission amount P and the pulse width correction coefficient C with respect to the control count. The control count "0" is initially set in the toner adhesion amount measurement step S3.
, The conditions when the test pattern is formed are the values of P and C. QH
Both QH and QL are lower than T and QLT, that is, have a large negative deviation. Therefore, in the above-described image forming condition changing step S5, a change to increase the laser emission amount P is performed (the first control number).

When the toner adhesion amount of the test pattern was measured under these conditions, both QH and QL increased. In this example, QH was still lower than QHT and QL was higher than QLT. Again, in the image forming condition changing step S5, a change is made to increase the laser emission amount P and decrease the pulse width correction coefficient C. As a result, within the control standard value (QHP), QL decreased and approached QLT. Further, the laser emission amount P and the pulse width correction coefficient C are changed in the same direction (the third control count). As a result, QH,
Both QL fall within the respective control standard values, and the control is terminated.

In the second embodiment configured as described above, an adjustment rule is generated based on the dependency between the operation amount and the control amount having a correlation with each other, and the exposure rule is generated based on the adjustment rule. By adjusting the light amount and the exposure width, the adjustment work can be standardized and automated, and the image density can be adjusted efficiently and accurately. As a result, stable image quality can be easily maintained, productivity can be improved, manufacturing cost can be reduced, and development efficiency can be improved.

Next, a third embodiment of the present invention will be described. According to the present embodiment, the image density is controlled by combining the control using the grid bias and the developing bias described above and the control using the exposure light amount.

That is, in the image forming condition changing step described above, in the third embodiment, the light amount control target of the exposure optical system to be changed so that both the high density portion deviation and the low density portion deviation fall within the standard value. The exposure amount and the background potential are changed by changing the value, the grid bias voltage, and the developing bias voltage.

From the relationship between the high density portion deviation and the low density portion deviation, 2
The amount of change related to the exposure condition represented by the two parameters and the amount of change related to the background potential
The high-density portion deviation and the low-density portion deviation are determined by changing the exposure amount optical system light amount control target value, the grid bias voltage, and the developing bias voltage, which are determined according to the adjustment rule generated by 0.

This causes a problem in a method in which a light amount target value and a bias value are directly selected from a table prepared in advance from the high density portion deviation and the low density portion deviation, respectively. Not only the influence of the environment but also the development characteristics which change over time, the history of the photoreceptor drum 2, the developer, etc., the appropriate amount of change differs depending on the individual difference, and also changes over time. There is a possibility that the convergence value when the detection and operation are repeatedly performed may deviate from the target value over time.

Further, the effect of the exposure condition change acting on the high density portion and the low density portion is not necessarily independent, and there is an interaction. Therefore, it is inconsistent to determine each exposure condition from each deviation.

Therefore, in the third embodiment, the relationship between the exposure light amount (light amount control amount target value), the operation amounts of the grid bias and the developing bias, and the control amount deviations of the high density portion and the low density portion is shown. An adjustment rule is generated by the adjustment rule generation device 200 in accordance with the dependency table, and adjustment is performed by qualitatively managing the selection of adjustment locations, the order of adjustment, and the like in accordance with the adjustment rules.

FIG. 39 (a) shows the definition of the control amount. The suffix of the control amount deviation e is the control amount number, and the corresponding expression defines this. Here, e1 = ΔQH (= QH−QHT): high concentration part deviation e2 = ΔQL (= QL−QHL): low concentration part deviation

QH is the toner adhesion amount of the high density portion, and QHT
Indicates the target value, QL indicates the toner adhesion amount value of the high density portion, and QHL indicates the target value.

FIG. 39B shows the definition of the operation amount. The suffix of the operation amount a is the operation amount number, and defines a label indicating the corresponding actual operation means. In this case, a1 = ΔP (the amount of change in the target light amount control value) and a2 = ΔVBG (the amount of change in the background voltage).

FIG. 40 shows dependency tables (1) and (2) showing the above-described dependency between the control amount and the operation amount. The meaning of each symbol in each dependency table is the same as in the first embodiment, and a detailed description will be omitted.

That is, in the dependency table, e1, e2,
a1 and a2 indicate the control amount and the operation amount defined in FIG. 39, respectively. When generating an adjustment rule based on such a dependency table, when the data of the dependency table is input, the adjustable control amount selecting unit 202 of the adjustment rule generation device 200 performs the above-described check based on the dependency table data. The combination of the operation amount and the control amount is determined by the processes according to the lists 1 and 2 and the processing procedure. According to these procedures, the order of each operation amount and, if there is a control amount that must be adjusted with each operation amount, these are output as “rule data”.

An adjustment rule format according to the present embodiment obtained by such a procedure is as follows. (Adjustment rule 1) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |} Priority2: Delta.U1 = G1 * Grad.e: e = Min {| Error.x2 |} (Adjustment rule 2) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |, | Error.x2 |} 2-Error case Priority2: Delta.U1 = G1 * Grad.e: e = Min {| Error .x2 |, | Error.x2 |} 1-Error case Then, the control circuit 45 selects an operation amount for adjusting the deviation according to the above-described adjustment rule format, and executes the adjustment operation.

First, the control circuit 45 selects an optimal operation amount (a light amount control target value change amount, a background voltage change amount) in accordance with the control amount deviations ΔQH and ΔQL according to the above adjustment rules,
The change amount of the target value of the light amount control of the laser exposure device, the change amount of the comparison voltage (target voltage) with the signal photoelectrically converted by the light amount monitor, and the developing bias voltage and the unexposed portion potential of the photosensitive drum 1. The grid bias voltage and the developing bias voltage for controlling the unexposed portion potential are determined based on the difference in the background potential, which is the difference, and after performing a test operation, the change is calculated in accordance with the sensitivity of the control amount.

As shown in FIG. 32, the effect of the light quantity change on the gradation characteristics shows a larger change as the light quantity changes, as the density increases, and as the light quantity increases, the gradient of the gradation increases. It can be seen that the gradient decreases as the amount of light decreases.

Therefore, by changing the light quantity with respect to the gradation characteristics that have changed as the density increases, the correction can be made so as to approach the reference gradation characteristics. However, it is difficult to correct a nonlinear change on the low density side only by changing the light amount.

On the other hand, as shown in FIG. 11 described above, the change in the background potential has a greater effect on a lower density portion. It can be seen that when the background potential is increased, the density decreases as the density decreases.

A new exposure amount and background potential to be changed are obtained from the obtained exposure amount correction amount, background potential change amount, exposure amount at the time of test pattern image formation, and background potential. Further, a new light amount and a pulse width correction coefficient value to be changed are obtained from the light amount correction amount, the light amount at the time of forming the test pattern, and the pulse width correction coefficient value.

In the light quantity calculation, a voltage value to be applied to the target value of the light quantity control means (light quantity control circuit 174) of the exposure optical system is calculated by the following equation. Pnew = P + ΔP Further, a bias (grid bias, developing bias) voltage value is calculated from the obtained background potential. This calculation can be uniquely obtained by a previously prepared function including a coefficient representing the surface potential characteristic of the photosensitive drum 1 (see the description of the above equations (5) and (6), where Vc
Is constant).

Next, the new exposure amount thus obtained is set and changed as a target value of the light amount control circuit 174 as the light amount control means.
The new grid bias voltage value and new developing bias voltage value are set and changed to the output control values of the high voltage power supplies 35 and 45, respectively.

When the test pattern is formed again after the setting is changed, the settings of the grid bias voltage value and the developing bias voltage value are changed at predetermined timings. The predetermined timing changes the developing bias voltage value in synchronization with at least the position on the photosensitive drum 2 where the grid bias voltage value has been changed reaches the developing position.
If the change timing is properly performed, depending on the change value,
For fogging or two-component development, the photosensitive drum 2 with carrier
May cause dirt. The change timing of the grid bias voltage and the developing bias voltage is set in the same manner as in FIG.

Next, image formation, detection, and determination of a test pattern are performed again to form two test pattern latent images on the photosensitive drum 1 charged with the changed grid bias voltage again by exposure, thereby changing the latent image. The toner adhesion amount measurement step S3 and the determination step S4 are performed on the two test patterns developed with the development bias voltage.

In the judgment step S4, if the high density portion deviation and the low density portion deviation are within the standard values, the changed exposure
After the cleaning operation with the grid bias voltage value and the developing bias voltage value being held, a standby state is set. If at least one deviation is not within the standard value, the change of the bias voltage value, the pattern image formation, the detection, and the determination are repeated.

When the exposure amount change amount and the background potential are determined based on the relationship between the low density portion deviation and the high density portion deviation, the operation amount change amount is determined independently for each deviation. Misjudgment may occur. On the other hand, even when one deviation is the same value and the other is different, an appropriate operation amount can be determined by a parameter change amount suitable for the effect.

FIGS. 41 and 42 show the measured toner adhesion amount Q in the control process and the light emission amount of the laser diode 165 (hereinafter referred to as “light emission amount”).
FIG. 3 shows an example of a graph representing the state of change in the bias voltage and P, which is simply referred to as the laser emission amount. FIG.
Is a high-density portion toner adhesion amount measurement value QH with respect to the control count.
And the measured value QL of the toner adhesion amount in the low density portion. In the drawing, broken lines QHT and QLT indicate target values of the toner adhesion amount in the high density portion and the low density portion, respectively.

FIG. 42 is a plot of the laser emission amount P and the bias value (grid bias voltage value, developing bias voltage value) with respect to the number of times of control. Control count "0"
Are QH and QL measured at first in the toner adhesion amount measuring step S3, and the conditions when the test pattern is formed are the values of P, VG and VD. QHT, Q
Both QH and QL are lower than LT, that is, a large negative deviation. Therefore, in the above-described image forming condition changing step S5, a change to increase the laser emission amount P is performed (the first control number).

When the toner adhesion amount of the test pattern was measured under these conditions, both QH and QL increased. In this example, QH was still lower than QHT and QL was higher than QLT. Again, in the image forming condition changing step S5, the laser emission amount P increases, that is, VG, VD
Make changes that increase the difference between As a result, QH increased and QL decreased, approaching QHT and QLT, respectively. Further, in the same direction, the laser emission amounts P and VG,
And VD (the third control count). As a result, Q
Both H and QL fall within the respective control standard values, and the control ends.

As described above, by combining the exposure amount control and the background potential control, it is possible to perform the control for maintaining the gradation characteristics from the high density portion to the low density portion in a range where the image defect does not occur due to the bias change. Become.

Further, according to the fourth embodiment of the present invention, the contrast potential and the pulse width data correction coefficient are changed so as to adjust both the high density portion deviation and the low density portion deviation to be within the standard values. It is configured to do so.

The change amount relating to the contrast potential and the change amount relating to the background potential are determined according to the adjustment rule generated by the adjustment rule generation device 200 from the relationship between the high density portion deviation and the low density portion deviation, and the pulse width data correction coefficient is determined. ,
By changing the grid bias voltage and the developing bias voltage, the high density portion deviation and the low density portion deviation are corrected.

This causes a problem in a method in which the pulse width data correction value and the bias value are directly selected from a table prepared in advance from the high density portion deviation and the low density portion deviation, respectively. Not only the influence of the environment but also the development characteristics which change over time, the history of the photoreceptor drum 2, the developer, etc., the appropriate amount of change differs depending on the individual difference, and also changes over time. There is a possibility that the convergence value when the detection and operation are repeatedly performed may deviate from the target value over time.

Further, the effect of the exposure condition change acting on the high-density portion and the low-density portion is not necessarily independent, and there is an interaction. Therefore, it is inconsistent to determine each exposure condition from each deviation.

Therefore, in the fourth embodiment, a dependency table showing the relationship between the operation amounts of the pulse width data correction coefficient, grid bias, and developing bias and the control amount deviations of the high density portion and the low density portion is used. , Adjustment rule generation device 2
00, an adjustment rule is generated, and adjustment is performed by qualitatively managing the selection of an adjustment portion, the order of adjustment, and the like in accordance with the adjustment rule.

FIG. 43 (a) shows the definition of the control amount. The suffix of the control amount deviation e is the control amount number, and the corresponding expression defines this. Here, e1 = ΔQH (= QH−QHT): high concentration part deviation e2 = ΔQL (= QL−QHL): low concentration part deviation

QH is the toner adhesion amount of the high density portion, and QHT
Indicates the target value, QL indicates the toner adhesion amount value of the high density portion, and QHL indicates the target value.

FIG. 43B shows the definition of the operation amount. The suffix of the operation amount a is the operation amount number, and defines the label indicating the corresponding actual operation means. Here, a1 = ΔVC (contrast voltage change amount) a2 = ΔC (pulse width data correction coefficient change amount).

FIG. 44 shows a dependence table showing the dependence between the above-mentioned control amount and operation amount. That is, in the dependency table, e1, e2, a1, and a2 indicate the control amounts and the operation amounts defined in FIG. 43, respectively. When an adjustment rule is generated based on such a dependency table, the adjustable control amount selection unit 2 of the adjustment rule generation device 200
02, when the data of the dependency table is input, the combination of the operation amount and the control amount is determined based on the dependency table data by the processing according to the checklists 1 and 2 and the processing procedure described above. According to these procedures, the order of each operation amount and, if there is a control amount that must be adjusted with each operation amount, these are output as “rule data”.

The adjustment rule format according to the present embodiment obtained by such a procedure is as follows. (Adjustment rule 1) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |} Priority2: Delta.U1 = G1 * Grad.e: e = Min {| Error.x2 |} (Adjustment rule 2) Priority1: Delta.U2 = G2 * e: e = Min {| Error.x1 |, | Error.x2 |} 2-Error case Priority2: Delta.U1 = G1 * Grad.e: e = Min {| Error .x2 |, | Error.x2 |} 1-Error case Then, the control circuit 45 selects an operation amount for adjusting the deviation according to the above-described adjustment rule format, and executes the adjustment operation.

First, the control circuit 45 selects an optimal operation amount (a pulse width data coefficient change amount and a contrast voltage change amount) according to the control amount deviations ΔQH and ΔQL according to the above adjustment rule, and sets the pulse of the laser exposure apparatus. The amount of change in the target value of the width control, the amount of change in the comparison voltage (target voltage) with the signal photoelectrically converted by the light amount monitor, and the contrast potential, which is the difference between the developing bias voltage and the exposed portion potential of the photosensitive drum 1. The grid bias voltage and the developing bias voltage for controlling the exposure unit potential are determined based on the change amount, and after the test operation, the change amount is calculated according to the sensitivity of the control amount.

The gradation characteristics when the contrast potential is changed are shown in FIG. 10 described above. Due to the change in the contrast potential Vc, the change becomes larger in the higher density portion. As the contrast potential increases, the gradation characteristics change in a direction to increase the gradient with respect to the gradation data. Therefore, it is possible to correct the gradation characteristics fluctuated by the change in the contrast potential so that the higher the density, the closer to the initial gradation characteristics. The relationship between the change in the pulse width correction characteristic and the change in the gradation characteristic is as described in detail in the second embodiment, and is shown in FIG.

Based on the relationship between the high-density portion deviation and the low-density portion deviation, the control circuit 45 controls the contrast potential change amount and the pulse width data correction coefficient change amount, and the contrast potential value and pulse width data correction amount during test pattern image formation. Numbers and
, A new contrast potential value to be changed and a pulse width data correction coefficient value are obtained.

In the present embodiment, the contrast potential is calculated by adding the contrast potential change amount ΔVc to the current contrast potential Vc at the time of forming the test pattern to become a new contrast potential Vcnew.

Vcnew = Vc + ΔVc Assuming that the background potential is constant and an initial predetermined value, the surface potential characteristic coefficient (K1) of the photosensitive drum 1 is the same as in the first embodiment.
-K4), a new grid bias voltage value and a new developing bias voltage value to be set are calculated by equations (5) and (6).

The pulse width correction data is generated by ΔC
And the current C2 as the new C2,
., N−1 and Dc (i) corresponding to the original data Di. The correction data including 0 and Dmax is transferred to the pulse width correction unit.

Next, the obtained new grid bias voltage value and developing bias voltage value are respectively applied to the high voltage power supplies 35 and 4.
The setting is changed to 5, and the correction data including 0 and Dmax is transferred to the data conversion unit 63 which is a pulse width correction unit.

FIGS. 45 and 46 are graphs showing how the measured toner adhesion amount Q, bias values (grid bias value VG, development bias value VD) and pulse width data correction coefficient C are changed in the control process. An example is shown. FIG.
5 is a high-density portion toner adhesion amount measurement value Q with respect to the number of controls.
7 is a plot of H and the measured toner amount QL of the low-density portion. In the figure, broken lines QHT and QLT indicate the target values of the toner adhesion amount in the high density portion and the low density portion, respectively.

FIG. 46 shows the bias value V with respect to the control count.
7 is a plot of G, VD and a pulse width data correction coefficient C. The control count “0” is QH and QL measured at the first toner adhesion amount measurement step, and the conditions when the test pattern is formed are the values of P and C. Both QH and QL are lower than QHT and QLT, that is, have a large negative deviation. Therefore, a change to increase the contrast potential is performed in the above-described image forming condition changing step S5 (first control; the difference between VG and VD is almost the same and both increase).

When the amount of toner adhering to the test pattern is detected under these conditions, as a result, both QH and QL increase, and
In this example, QH is still lower than HT and QL is QL
It was higher than T. Again, in the image forming condition changing step, a change is made to increase the contrast potential and decrease the pulse width data correction coefficient C. As a result, both QH and QL fall within the control standard values (QHP, QLP), and the control ends.

According to the fourth embodiment configured as described above, by combining the pulse width control and the contrast potential control, it is possible to reduce the density from the high density portion to the low density portion in a range where the image defect does not occur due to the bias change. It is possible to control to maintain the gradation characteristics up to the portion. Thus, similarly to the above-described embodiment, it is possible to maintain good image quality of the color printer.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, the present invention is not limited to a color printer but can be applied to other image forming apparatuses.

[0256]

As described in detail above, according to the present invention,
Optimum control of image density can be performed relatively easily and in a short period of time, improving development efficiency, reducing manufacturing cost by reducing memory capacity, and appropriate for individual differences, reproducibility, and aging. An image forming apparatus and an image forming method capable of maintaining high image quality can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram relating to charging, exposure, developing means and control means of a color laser printer according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a color laser printer.

FIG. 3 is a diagram illustrating a high-density portion corresponding to high-density gradation data developed on a photosensitive drum, a low-density portion corresponding to low-density gradation data, and a toner adhesion amount measurement unit.

FIG. 4 is a diagram showing an unexposed portion potential, an exposed portion potential, and a developing bias voltage of the photosensitive drum with respect to a grid bias voltage of a charger;

FIG. 5 is a view showing the image density of a solid portion with respect to a contrast voltage.

FIG. 6 is a diagram showing the relationship between the potential of an unexposed portion on the surface of a photosensitive drum, a voltage based on a low-density pattern, and a developing bias voltage.

FIG. 7 is a diagram illustrating a toner adhesion amount with respect to gradation data when a background voltage is increased.

FIG. 8 is a block diagram illustrating a configuration of a toner adhesion amount measurement unit.

FIG. 9 is a flowchart illustrating a processing operation in a bias change mode.

FIG. 10 is a diagram showing a change in gradation characteristics when a contrast voltage is changed.

FIG. 11 is a diagram showing a change in gradation characteristics when a background voltage is changed.

FIG. 12 is a block diagram schematically showing an adjustment rule generation device.

FIG. 13 is a diagram showing a change timing of a grid bias and a developing bias.

FIG. 14 is a diagram showing definitions of a control amount and an operation amount.

FIG. 15 is a dependency table showing a dependency between the control amount and the operation amount.

FIG. 16 is a flowchart showing a processing operation of an adjustable control amount selection unit in the adjustment rule generation device.

FIG. 17 is a flowchart showing a processing operation of an adjustable control amount selection unit in the adjustment rule generation device.

FIG. 18 is a flowchart showing a processing operation of an adjustable control amount selection unit in the adjustment rule generation device.

FIG. 19 is a flowchart showing a processing operation of an adjustable control amount selection unit in the adjustment rule generation device.

FIG. 20 is a flowchart showing a processing operation of an adjustable control amount selection unit in the adjustment rule generation device.

FIG. 21 is a flowchart showing a processing operation of an adjustable control amount selection unit in the adjustment rule generation device.

FIG. 22 is a flowchart showing a processing operation of an adjustment rule format generation unit in the adjustment rule generation device.

FIG. 23 is a functional block diagram of a controller of the adjustment device.

FIG. 24 is a diagram showing adjustment rules and adjustment operations generated by the adjustment rule generation device.

FIG. 25 is a graph showing a change in the amount of applied toner which is an input of the measurement system in a control process.

FIG. 26 is a graph showing a change in a bias value which is an input of the measurement system in a control process.

FIG. 27 is a graph showing a change in an operation amount in a control step.

FIG. 28 is a graph showing a change in a toner adhesion amount and a change in a bias value which are inputs to the measurement system in a control process.

FIG. 29 is a diagram showing functional blocks relating to the flow of image data and an exposure system in a color printer according to a second embodiment of the present invention.

FIG. 30 is a flowchart for explaining a processing operation of a main part.

FIG. 31 is a flowchart mainly illustrating an image forming condition changing process in the color printer.

FIG. 32 is a view showing the relationship between gradation data and output image density for explaining the effect of changing the light amount.

FIG. 33 is a view showing a relationship between a pulse width correction characteristic and a change in gradation characteristic.

FIG. 34 is a diagram showing a linearly approximated relationship between original data and correction data.

FIG. 35 is a diagram showing definitions of a control amount and an operation amount.

FIG. 36 is a dependency table showing a dependency relationship between the control amount and the operation amount.

FIG. 37 is a graph showing a state of a change in a measured toner adhesion amount in a control process.

FIG. 38 is a graph showing how a laser light emission amount and a pulse width correction coefficient are changed in a control process.

FIG. 39 is a diagram showing definitions of a control amount and an operation amount according to the third embodiment of the present invention.

FIG. 40 is a dependency table showing a dependency between the control amount and the operation amount.

FIG. 41 is a graph showing a change in the amount of applied toner which is an input of the measurement system in a control process.

FIG. 42 is a graph showing a change in a bias value which is an input of the measurement system in a control process.

FIG. 43 is a diagram showing definitions of a control amount and an operation amount according to the fourth embodiment of the present invention.

FIG. 44 is a dependency table showing a dependency between the control amount and the operation amount.

FIG. 45 is a diagram illustrating a change in the amount of toner adhesion which is an input of the measurement system in a control process.

FIG. 46 is a graph showing a change in a bias value which is an input of the measurement system in a control process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum (image carrier) 2 ... Charging device (charging means) 4-7 ... Developing device (developing means) 8 ... Toner adhesion amount measuring part 9 ... Transfer drum 13 ... Laser exposure device 14 ... Laser beam light 20 ... Transfer charger 34 ... Corona high voltage power supply 35 ... Grid bias high voltage power supply 36 ... Gray level data buffer 37 ... Laser drive circuit 38 ... Pattern generation circuit 39 ... Toner density measurement unit 43 ... Development roller 44 ... Development bias high voltage power supply 45: Control circuit 64: CPU 200: Adjustment rule generation device 202: Adjustable control amount selection unit 204: Adjustment rule format generation unit

Claims (18)

[Claims] An image forming means for forming a developer image on an image carrier based on image data; a detecting means for detecting image quality of an image formed on the image carrier; A plurality of operating means for adjusting the image quality formed in the image forming apparatus; a deviation calculating means for calculating a control amount deviation between the image quality detected by the detecting means and a preset image quality; Determining means for determining whether the deviation is within the allowable range; selecting means for selecting an operating means for correcting the calculated control amount deviation when the deviation exceeds the allowable range; The test quality of the image quality is adjusted by the operation means. The sensitivity detection means detects the sensitivity of the control amount deviation with respect to the operation amount of the operation means, and the adjustment operation amount of the corresponding operation means is adjusted according to the detected sensitivity. Decide An image forming apparatus comprising: an operation amount determining unit configured to operate the corresponding operation unit according to the determined operation amount and a unit that corrects the deviation. 2. An image forming means for forming a developer image on an image carrier based on image data; a detecting means for detecting image quality of an image formed on the image carrier; A plurality of operating means for adjusting the image quality formed in the image forming apparatus; a deviation calculating means for calculating a control amount deviation between the image quality detected by the detecting means and a preset image quality; Determining means for determining whether the deviation is within the allowable range; selecting means for selecting an operating means for correcting the calculated control amount deviation when the deviation exceeds the allowable range; The test quality of the image quality is adjusted by the operation means. The sensitivity detection means detects the sensitivity of the control amount deviation with respect to the operation amount of the operation means, and the adjustment operation amount of the corresponding operation means is adjusted according to the detected sensitivity. Decide Operating amount determining means, and means for activating the corresponding operating means in accordance with the determined operating amount to correct the deviation, wherein the determination and the operating means are performed until all deviations converge to an allowable range. And control means for repeating selection, sensitivity detection, operation amount determination, and correction. 3. An image forming means for forming a developer image on an image carrier based on image data; a detecting means for detecting an image density of the developer image formed on the image carrier; A plurality of operation means for adjusting the image density of the developer image formed on the carrier; deviation calculation means for calculating a control amount deviation between the image density detected by the detection means and a preset image density; Determining means for determining whether the calculated control amount deviation is within a predetermined allowable range; and an operation for correcting the calculated control amount deviation when the deviation exceeds the allowable range. Selecting means for selecting a means, sensitivity detecting means for detecting the sensitivity of the control amount deviation with respect to the operation amount of the operating means by test-adjusting the image quality by the selected operating means, and according to the detected sensitivity Above Control means having an operation amount determining means for determining an adjustment operation amount of the operating means, and means for operating the corresponding operation means in accordance with the determined operation amount and correcting the deviation. An image forming apparatus comprising: 4. An image forming means for forming a developer image on an image carrier based on image data; a detecting means for detecting an image density of the developer image formed on the image carrier; A plurality of operation means for adjusting the image density of the developer image formed on the carrier; deviation calculation means for calculating a control amount deviation between the image density detected by the detection means and a preset image density; Determining means for determining whether the calculated control amount deviation is within a predetermined allowable range; and an operation for correcting the calculated control amount deviation when the deviation exceeds the allowable range. Selecting means for selecting a means, sensitivity detecting means for detecting the sensitivity of the control amount deviation with respect to the operation amount of the operating means by test-adjusting the image quality by the selected operating means, and according to the detected sensitivity Above Operating amount determining means for determining an adjusting operating amount of the operating means, and means for operating the corresponding operating means in accordance with the determined operating amount to correct the deviation, wherein all deviations are within an allowable range. And control means for repeating the above determination, selection of operation means, sensitivity detection, operation amount determination, and correction until convergence is achieved. 5. The control means includes an adjustment rule generating means for generating an adjustment rule indicating a priority of the operation amount from a dependency between the operation amount of each operation means and the control amount deviation. The image forming apparatus according to claim 1, wherein the unit selects an operation unit according to the adjustment rule. 6. A latent image forming means for forming a latent image of a high-density portion and a low-density portion on an image carrier based on image data, and a height of the latent image on the image carrier formed by the latent image forming device. Developing means for developing the latent image in the density portion and the low density portion with a developer, and developing for measuring the amount of the high density portion and the low density portion of the developer adhered on the image carrier by the development of the developing means. A plurality of operating means for adjusting the amount of developer attached to the high-density portion and the low-density portion; Deviation calculating means for calculating a deviation from each of the set reference values; determining means for determining whether each of the calculated deviations is within a predetermined allowable range; and wherein the deviation exceeds the allowable range. Operation to correct the detected deviation. Selecting means for selecting a means, sensitivity detecting means for detecting the sensitivity of deviation correction with respect to the adjusting operation amount of the selecting means by test-adjusting the amount of developer attached by the selected operating means, and detecting the detected An operation amount determination unit that determines an adjustment operation amount of the corresponding operation unit according to sensitivity;
Means for activating the corresponding operating means in accordance with the determined operation amount, and correcting the deviation, having the above-described determination and selecting the operating means until all deviations converge to an allowable range.
An image forming apparatus comprising: a control unit that repeats sensitivity detection, operation amount determination, and correction. 7. A charging means for charging an image carrier using a grid, a first application means for applying a grid bias voltage to the grid, and a high density test pattern and a low density test pattern. Generating means, and a latent image forming means for forming a latent image on the image carrier charged by the charging means based on the high density test pattern and the low density test pattern generated by the generating means; Developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer; second applying means for applying a developing bias voltage to the developing means; When forming on the body, holding to hold a contrast voltage, which is a relationship between the exposed portion potential and the developing bias voltage value, and a background voltage, which is a relationship between the unexposed portion potential and the developing bias voltage value. And a developer adhesion amount measuring means for measuring an adhesion amount of the developer to the high-density test pattern developed on the image carrier by the developing means and an adhesion amount of the developer to the low-density test pattern. Setting means for setting a target value for the adhesion amount of the high-density portion and the low-density portion; a target value for the adhesion amount of the high-density portion and the low-density portion set by the setting means; Deviation calculating means for calculating a deviation between the high-density part and the low-density part based on the obtained adhesion amounts of the developer in the high-density part and the low-density part; Determining means for determining whether or not is within an allowable range; and applying means for correcting the detected deviation from the first and second applying means when the deviation exceeds the allowable range. Selection A selecting means for performing the test adjustment of the grid bias value or the developing bias value by the selected applying means; and a sensitivity detecting means for detecting the sensitivity of the control amount deviation with respect to the adjusting operation amount of the applying means. An operation amount determining unit that determines an adjustment operation amount of the corresponding application unit in accordance with the sensitivity; and a grid bias value or a development bias value that is adjusted by the corresponding application unit in accordance with the determined operation amount. And means for correcting the contrast voltage and the background voltage with respect to the deviation of the low-density portion, and the above-described determination, selection of operation means, sensitivity detection, operation amount determination, and correction until all deviations converge to an allowable range. An image forming apparatus comprising: control means for repeating. 8. The apparatus according to claim 7, wherein said developer adhesion amount measuring means measures the amount of reflected light in a high density portion, the amount of reflected light in a low density portion, and the amount of reflected light from an image carrier. An image forming apparatus according to claim 1. 9. The image forming apparatus according to claim 7, wherein said operating means changes the developing bias voltage after a predetermined time has elapsed after changing the grid bias voltage. 10. The control means includes an adjustment rule generating means for creating an adjustment rule indicating a priority of the operation amount from a dependency relationship between an operation amount of each operation means and the control amount deviation. The image forming apparatus according to claim 6, wherein the unit selects an operation unit according to the adjustment rule. 11. An image carrier is charged using a grid to generate a high density test pattern and a low density test pattern, and a high density test pattern and a low density test pattern are formed on the charged image carrier. A latent image is formed on the basis of the test pattern, and the formed latent image on the image carrier is developed with a developer. The amount of the developer attached to the test pattern is measured, and dependency information indicating whether or not there is sensitivity to change the amount of the developer attached to the change in the operation amount between the grit bias and the developing bias is prepared in advance. By calculating the deviation between the high-density part and the low-density part, based on the target value for the adhesion amount of the low-density part and the adhesion amount of the developer in the high-density part and the low-density part obtained by measuring the adhesion amount of the developer, this It is determined whether or not the calculated deviation of the high-density part and the low-density part is within an allowable range. If the determination result is out of the allowable range, the high-density part and the low-density part are determined based on the dependency information. The operation amounts of the grid bias and the developing bias corresponding to the deviation are selected, and the bias corresponding to the selected operation amount is test-adjusted, so that the sensitivity of the deviation to the adjustment operation amount is detected. And determining a corresponding grid bias value and a developing bias value according to the determined grid bias value and the developing bias value according to the determined grid bias value and the developing bias value. Image forming method. 12. The method according to claim 11, wherein the quality judgment, the selection of the operation amount, the detection of the sensitivity, the determination of the bias value, and the adjustment are repeated until all the control amount deviations converge to an allowable range. Image forming method 13. Exposure means for forming a latent image of a high-density part and a low-density part on an image carrier on the basis of image data and capable of controlling an exposure amount in accordance with target exposure amount information; Developing means for developing the formed latent image of the high-density portion and the low-density portion on the image carrier with a developer; and a high-density portion and a low-density portion adhered on the image carrier by development of the developing device. A developer adhering amount measuring means for measuring an amount of the developer adhering to the image data; and a light emitting time correction for correcting the light emitting time per unit pixel based on the light emitting time correction information with respect to the gradation data per unit pixel of the image data. Means, modulation control means for performing modulation control of the exposure means as a pulse width per unit pixel based on the light emission time information corrected by the light emission time correction means, and high density measured by the developer adhesion amount measurement means. Department Deviation calculating means for calculating a deviation between each measured value of the low-concentration part and a preset target value, and determining whether each of the deviations calculated by the deviation calculating means is within an allowable range. A determination unit, and a selection unit that selects a unit for correcting the calculated deviation from the emission time correction unit and the modulation control unit when the determination unit determines that the difference is not within the allowable range, Test adjustment of the developer adhesion amount by the selected light emission time correction unit and modulation control unit, thereby detecting sensitivity of the deviation control amount with respect to the adjustment operation amount, and the sensitivity detection unit according to the detected sensitivity. An operation amount determining unit that determines an adjustment operation amount of the emission time correction unit and the modulation control unit; and the emission time correction unit and the modulation control unit according to the determined operation amount. An image forming apparatus characterized by comprising a control means and means for correcting the deviation is activated. 14. Exposure means for forming a latent image of a high-density part and a low-density part on an image carrier based on image data and controlling an exposure amount according to target exposure amount information; Developing means for developing the formed latent image of the high-density portion and the low-density portion on the image carrier with a developer; and a high-density portion and a low-density portion adhered on the image carrier by development of the developing device. A developer adhering amount measuring means for measuring an amount of the developer adhering to the image data; and a light emitting time correction for correcting the light emitting time per unit pixel based on the light emitting time correction information with respect to the gradation data per unit pixel of the image data. Means, modulation control means for performing modulation control of the exposure means as a pulse width per unit pixel based on the light emission time information corrected by the light emission time correction means, and high density measured by the developer adhesion amount measurement means. Department Deviation calculating means for calculating a deviation between each measured value of the low-concentration portion and a preset target value, respectively, and determining whether each of the deviations calculated by the deviation calculating means is within an allowable range. A determination unit, and a selection unit that selects a unit for correcting the calculated deviation from the emission time correction unit and the modulation control unit when the determination unit determines that the difference is not within the allowable range, Test adjustment of the developer adhesion amount by the selected light emission time correction unit and modulation control unit, thereby detecting sensitivity of the deviation control amount with respect to the adjustment operation amount, and the sensitivity detection unit according to the detected sensitivity. An operation amount determining unit that determines an adjustment operation amount of the emission time correction unit and the modulation control unit; and the emission time correction unit and the modulation control unit according to the determined operation amount. Operating means for correcting the deviation, and control means for repeating the determination, selection of operation means, sensitivity detection, operation amount determination, and correction until all deviations converge to an allowable range. An image forming apparatus comprising: 15. A pattern generating means for generating a high-density test pattern and a low-density test pattern, respectively, based on the high-density test pattern and the low-density test pattern generated from the pattern generating means on the image carrier. An exposure unit that forms a latent image with the exposure amount controllable in accordance with the target exposure amount information; and a latent image of the high-density test pattern and the low-density test pattern on the image carrier formed by the exposure unit. Developing means for developing an image with a developer; and a developer adhesion amount for measuring an adhesion amount of the developer to the high-density test pattern and the low-density test pattern adhered to the image carrier by the development of the developing means, respectively. A measuring unit that corrects the light emission time per unit pixel based on the light emission time correction information with respect to the gradation data per unit pixel of the image data. Emission time correction means, modulation control means for performing modulation control of the exposure means as a pulse width per unit pixel based on the emission time information corrected by the emission time correction means, and measurement by the developer adhesion amount measurement means. Deviation calculating means for calculating a deviation between each of the measured values of the high-density portion and the low-density portion and a preset target value, respectively; and each of the deviations calculated by the deviation calculating means is within an allowable range. And a means for correcting the calculated deviation is selected from the light emission time correction means and the modulation control means when the determination means determines that the difference is not within the allowable range. By performing test adjustment of the developer adhesion amount by the selection unit and the selected emission time correction unit and modulation control unit, the sensitivity of the deviation control amount with respect to the adjustment operation amount is adjusted. Sensitivity detection means for detecting the degree, operation amount determination means for determining an adjustment operation amount of the light emission time correction means and modulation control means according to the detected sensitivity, and light emission time correction according to the determined operation amount. And a means for operating the modulation control hand to correct the deviation, and repeating the determination, selection of the operation means, sensitivity detection, operation amount determination, and correction until all the deviations converge to an allowable range. And an image forming apparatus. 16. Exposure means for forming a latent image of a high-density portion and a low-density portion on an image carrier based on image data and capable of changing exposure conditions such as luminous intensity or luminous time, and applying a bias voltage. Developing means for developing a latent image in the high-density part and low-density part on the image carrier formed by the exposure means with a developer; and a developing means for developing the latent image on the image carrier by development of the developing means. A developer adhesion amount measuring unit for measuring the amount of the developer attached to the density portion and the low density portion, respectively, and the measurement values of the high density portion and the low density portion measured by the developer adhesion amount measurement device are preset. Deviation calculating means for calculating a deviation from each target value, a determining means for determining whether each of the deviations calculated by the deviation calculating means is within an allowable range, and an allowable range by the determining means. Inside When it is determined that the exposure conditions of the exposure unit, the contrast potential is the difference between the bias voltage of the developing unit and the exposure unit potential of the image carrier, and the bias voltage of the developing unit and the image carrier By selecting an operation amount for correcting the deviation from among the background potential which is a difference from the unexposed portion potential and performing test adjustment of the developer adhesion amount based on the selected operation amount, the deviation with respect to the adjustment operation amount is obtained. Sensitivity detection means for detecting the sensitivity of the control amount, and operation amount determination means for determining the adjustment operation amount of the selected operation amount according to the detected sensitivity,
Means for permanently adjusting the selected operation amount in accordance with the determined adjustment operation amount and correcting the deviation, the determination, selection of the change amount until all deviations converge to an allowable range, An image forming apparatus comprising: a control unit that repeats sensitivity detection, operation amount determination, and correction. 17. A charging means for charging the surface of an image carrier and controlling the charge amount by an applied bias voltage; and a high-density image on the image carrier charged by the charging means based on image data. And a low-density portion latent image, and an exposure unit capable of controlling the exposure amount in accordance with the target exposure amount information, and a bias voltage applied thereto, and a high density on the image carrier formed by the exposure unit. Developing means for developing the latent image of the low density portion and the low density portion with a developer, and developing for measuring the amount of the developer attached to the high density portion and the low density portion which have adhered to the image carrier by the development of the developing means, respectively. Agent adhesion amount measurement means, deviation calculation means for calculating a deviation between each measurement value of the high-density portion and the low-density portion measured by the developer adhesion amount measurement means and a preset target value, The above deviation calculating means Determining means for determining whether each of the calculated deviations is within an allowable range; and if the determining means determines that the deviation is not within an allowable range, the exposure amount of the exposure means and the bias of the developing means are determined. An operation amount selecting means for selecting an operation amount for correcting the deviation among a background potential which is a difference between a voltage and an unexposed portion potential of the image carrier, and an amount of the developer adhering according to the selected operation amount. By test adjustment, sensitivity detection means for detecting the sensitivity of the deviation control amount to the adjustment operation amount, and operation amount determination means for determining the adjustment operation amount of the selected operation amount according to the detected sensitivity, Means for permanently adjusting the selected operation amount in accordance with the determined adjustment operation amount and correcting the deviation, the determination, selection of the operation amount until all deviations converge to an allowable range, Sensitivity detection, Integer operation amount determination, and a control means repeating the correction, the image forming apparatus characterized by comprising a. 18. A charging means for charging a surface of an image carrier and controlling a charge amount by an applied bias voltage; and a high-density image based on image data on the image carrier charged by the charging means. Exposure means for forming a latent image of a low density part and a low density part, and a bias voltage is applied to develop a latent image of a high density part and a low density part on the image carrier formed by the exposure means with a developer. A developing unit; a developer adhering amount measuring unit for measuring an adhering amount of the developer to the high density portion and the low density portion adhering to the image carrier by the development of the developing unit; and a unit pixel of the image data. Light emission time correction means for correcting the light emission time per unit pixel based on the light emission time correction information for the gradation data, and a pulse width per unit pixel based on the light emission time information corrected by the light emission time correction means. And a modulation control means for performing modulation control of the exposure means, and a deviation between each measured value of the high-density part and the low-density part measured by the developer adhesion amount measuring means and a preset target value. A deviation calculating means for calculating each; a determining means for determining whether each of the deviations calculated by the deviation calculating means is within an allowable range; and if the determining means determines that the deviation is not within the allowable range, A contrast potential which is a difference between a bias voltage of the developing means and a potential of an exposed portion of the image carrier; and an operation amount selecting means for selecting an operation amount for correcting the deviation among the light emission times. A sensitivity detection means for detecting the sensitivity of the deviation control amount with respect to the adjusted operation amount by test-adjusting the developer adhesion amount according to the operation amount, and the operation amount selected in accordance with the detected sensitivity. An operation amount determining means for determining the adjustment operation amount, and means for adjusting the selected operation amount in accordance with the determined adjustment operation amount to correct the deviation, wherein all deviations are allowable. Control means for repeating the above determination, selection of an operation amount, sensitivity detection, determination of an adjustment operation amount, and correction until the range converges.