JP3155765B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of reproducing a gradation image.

[0002]

2. Description of the Related Art Conventionally, in an image processing apparatus such as a copying machine or a laser beam printer of an electrophotographic system, a change in the environment where a developer is placed is measured by an environment sensor in order to keep the output density of a formed image constant. Image forming conditions and image processing conditions are changed by control means according to the type of agent, environmental conditions, and environmental history.

It has also been proposed to detect a plurality of predetermined density patterns formed on an image carrier for density detection, and feed the results back to image forming conditions and image processing conditions.

[0004]

However, in the above conventional example, when a higher quality image is to be obtained, for example, in the case of a color printer capable of forming a toner image of four colors and capable of outputting 256 gradations, 4 × It is necessary to output as many as 56 patterns, and performing this operation for each output of each pattern has the disadvantage that the output throughput is reduced and the toner consumption is increased. Further, when a pattern is formed on a photosensitive drum and its density is measured, there is a problem that a measurement error occurs depending on the position where the pattern is formed due to the eccentricity of the photosensitive drum. Also,
When measuring the density of the pattern formed on the photosensitive drum,
Since there is no need to transfer the pattern onto the recording paper, there is a problem that the formed drum stains the transfer drum and other parts. In addition, when measuring the density of the pattern formed on the photosensitive drum, there are inconveniences such as a measurement sensor being dirty, a fatigue of the photosensitive drum, a measurement error, and an inability to control image forming conditions. Therefore, the processing time for determining the image forming conditions is wasted. Further, when the feedback control for determining the regular image forming condition even if changes in the environment where the developer ransom <br/> Mari, and wasteful consumption of waste and toner Time turn into. Further, if the feedback control is always performed for all colors, waste of time and waste of toner will be wasted even for colors that are used less frequently.

[0005]

According to a first aspect of the present invention, there is provided an image forming means for forming an image on a recording medium, and a sample image formed on the recording medium by the image forming means. Generating means for generating an image signal representing a sample image having an arbitrary density for forming; first measuring means for measuring the density of the sample image formed on the recording medium; and an environment around the image forming means Second measuring means for repeatedly measuring conditions; control means for executing image stabilization control for determining operating conditions of the image forming means based on the density of the sample image measured by the first measuring means; Wherein the control means selects a density of an image signal representing a sample image to be generated from the generating means according to a temporal change state of the environmental condition measured by the second measuring means. Is shall. According to a fifth aspect of the present invention, there is provided an image forming means for forming an image on a rotating drum-shaped recording medium, and an image formed on the recording medium which rotates in synchronization with the rotation of the recording medium. And a cleaning unit for cleaning the surface of the transfer body, and generating an image signal representing a sample image of an arbitrary density for forming a sample image on the recording medium by the image forming unit. Means, measuring means for measuring the density of the sample image formed on the recording medium, and image stabilization control for determining operating conditions of the image forming means based on the density of the sample image measured by the measuring means. a control means for executing, and the control means, and during concentration measurement formation of the sample images, to remove the sample image to be transferred onto the transfer medium, collected by the said recording medium The surface of the transfer body which rotates as one which is cleaned by the cleaning means. The invention according to claim 6 is an image forming means for forming an image on a recording medium,
Generating means for generating an image signal representing a sample image of an arbitrary density for forming a sample image on the recording medium by the image forming means; and first measurement for repeatedly measuring environmental conditions around the image forming means Means, second measuring means for measuring the density of the sample image formed on the recording medium, and operating conditions of the image forming means based on the density of the sample image measured by the second measuring means. Control means for performing image stabilization control to be performed,
The controller is in a standby state in which it waits for an instruction to start image formation, and when a difference between a previous measurement result measured by the first measuring unit and a newly measured result is equal to or more than a predetermined value. The image stabilization control is executed, and if the difference is within a predetermined value, the image stabilization control is not executed. According to a seventh aspect of the present invention, there is provided an image forming means for forming a color image on a recording medium, comprising a plurality of color visualizing means, and forming a sample image on the recording medium by the image forming means. Generating means for generating an image signal representing a sample image having an arbitrary density, counting means for counting the number of times each of the plurality of color visualizing means is used, and a sample image formed on the recording medium. Measuring means for measuring the density of the sample image, and control means for executing image stabilization control for each color to determine operating conditions of the image forming means based on the density of the sample image measured by the measuring means. The control means selectively executes the image stabilization control for colors for which the counting result of the counting means exceeds a predetermined number.

[0006]

According to the present invention, the environment in which the apparatus is placed, the usage time of the apparatus, the type of toner, and the like are comprehensively determined, the density pattern of the density detection operation is minimized, and the throughput of the output operation is improved. This is to save toner consumption.

[0007]

FIG. 1 is a cross-sectional view illustrating the structure of a color copying apparatus according to an embodiment of the present invention.
Platen (platen glass) 11, document irradiation lamp 12,
It comprises an imaging lens 13, an image pickup device (for example, a charge-coupled device such as a CCD) 14, an optical motor 15, and the like.

Reference numeral 2 denotes a document feed unit, which includes feed rollers 30, 3
1. Transfer paper (transfer material) 63 is constituted by pickup rollers 32 and 33, etc., and is fed according to a drive command from the controller unit 16.

Reference numeral 3 denotes an image forming unit, which includes a scanner motor 17,
Polygon mirror 18, photosensitive drum 1 as image carrier
9, cleaner section 20, primary charger 250, pre-exposure lamp 2
54, and the controller section 16
A laser beam from a laser light source is formed on the photosensitive drum 19 based on an image signal obtained by processing the output of the above, to form an electrostatic latent image.

Reference numeral 4 denotes a transfer device, which is a suction charger 21, a transfer charger 22, a separation charger 23, a high-pressure unit 24, an inner pressing roller 25, a separation claw 26, a transfer material holder 27, a suction roller 28, a registration roller 29, a transfer cleaning device 260 and the like. And the paper feed roller 30
Alternatively, a predetermined amount of loop is formed at the position of the registration roller 29 by the paper feed roller 31 and stopped, and the transfer paper 63 is fed again by the registration roller 29 at the timing when the image head position with the photosensitive drum 19 is synchronized. Then, the transfer paper 63 fed by driving the registration roller 29 is
It is electrostatically attracted to the transfer material holder 27 by the attraction roller 28 and the attraction charger 21 serving as the opposite electrode. The transfer charger 22 transfers each color developer developed on the photosensitive drum 19 to the transfer paper 63. The separation charger 23 serving as a charge removing charger removes the charge of the transfer paper 63 and weakens the attraction force with the transfer material holder 27.

On the other hand, the controller section 16 adjusts the feeding timing of each transfer sheet 63 to be sequentially attracted to the transfer material holding member 27 by a selected transfer sheet size and each developing device of the developing section 5 driven in the horizontal direction by a motor. Adjustment is made based on the arrangement state of the photosensitive drums 19a to 5d, a plurality of transfer papers 63 are attracted to the transfer material holder 27 at predetermined intervals, and the subsequent transfer paper 63 is fed to the transfer material holder 27. Determine the suction timing.

As described above, when the transfer paper 63 attracted to the transfer material holding member 27 rotates between the positions where the transfer chargers 22 are provided, a charge having a polarity opposite to that of the toner is applied to the back surface of the transfer material holding member 27. The transfer of the first color is performed, and the developing devices 5a to 5d are sequentially moved. Then, when the development / transfer process of the necessary color is completed, the attraction force of the transfer paper 63 to the transfer material holding member 27 is weakened, and the AC corona discharge from the pair of separation chargers 23 opposed to each other with the transfer material holding member 27 interposed therebetween. To remove electricity.

FIG. 2 shows the controller section 16 shown in FIG.
FIG. 42 is a block diagram illustrating the configuration of a CPU.
The copy sequence is controlled overall according to the control program stored in the ROM 43. 44 is a RAM, a CPU
42 functions as a work memory.

The operation unit 51 has keys for inputting various information such as the number of sheets, paper size, and color mode set by the user.

Reference numeral 45 denotes an I / O port, which comprises various motors, clutches or sensors, and is controlled by the CPU 42 in accordance with an image forming operation.

Reference numeral 206 denotes a timer unit which manages a calendar function for managing a date and time, and data necessary for measuring time required during an image forming operation.

Reference numeral 46 denotes a position sensor (ITOP sensor) which detects predetermined positions (image leading end positions P _A and P _B ) of the transfer material holder 27 shown in FIGS. 3 and 4, and outputs an image output timing, a transfer timing, and a development. An image timing signal ITOP for determining the timing is output to the CPU. This image timing signal ITOP is transmitted to an image processing circuit 4 described later.
9 used.

Reference numeral 47 denotes a developing unit motor controller which drives a motor 48 to position and move a moving table (not shown) on which the developing units 5a to 5d shown in FIG. It is to be noted that, for example, in the case of forming an image of four colors, a plurality of transfer papers 63 (maximum of 2 in this embodiment).
When the sheet 42 is adsorbed onto the transfer material holding member 27, the CPU 42 feeds the sheet so that the feeding timing of the next subsequent transfer sheet 63 is delayed by a half rotation of the transfer material holding member 27 to perform the sheet feeding process. , The suction timing is determined.

Reference numeral 49 denotes an image processing circuit which reads a document on the document table 11 by the CCD 14 and performs a well-known image processing operation. Finally, a laser modulation unit (to be described later) is output together with a pixel synchronization signal CLK as an output image signal VIDEO. Transfer to 205.

Reference numeral 205 denotes a laser modulator, which controls a laser (not shown) according to the image signal VIDEO sent from the image processing circuit 49.

An optical motor controller 50 controls the driving of the optical motor 15 for reciprocating the original scanning unit.

FIG. 13 is a detailed block diagram of the image processing circuit 49.
And a detailed description will be given.

The CCD reading unit 101 has a color sensor which can independently obtain analog image signals of R (red), G (green), and B (blue).
And an amplifier for amplifying a signal for each color and an A / D converter for converting the signal into an 8-bit digital signal.

The signal subjected to shading correction for each color by the shading correction unit 102 is corrected for a shift between colors and between pixels by a shift memory unit 103, and a color determination unit 112 described later.
Conversion unit 1 for performing logarithmic correction for light density conversion
04.

The density signals Y (yellow), M (magenta), and C (cyan) output from the LOG converter 104 are input to the black generator 105. For example, the black signal Bk is output from Min (Y, M, C). Generated.

Further, the masking / UCR unit 106 corrects the filter characteristics and the toner density characteristics of the color sensor with respect to the Y, M, C, and Bk signals output from the black generation unit 105, and removes them. One to be developed out of
The color is selected.

Next, the image signal of each color is density-converted by the density conversion unit 107 in accordance with the development characteristics of the printer and the operator's preference, and then is edited by a trimming processing unit 108 in a desired section. The laser beam is sent to the laser beam, and is converted into a laser beam and irradiated on the photosensitive drum.

The synchronizing signal generation unit 109 outputs a horizontal synchronizing signal BD (beam detect) signal and a vertical synchronizing signal IT synchronized with printing of each line sent from the printer unit.
Image processing circuit 4 based on OP (image top) signal
9 generates a horizontal synchronizing signal HSYNC, a pixel synchronizing signal CLK, and the like used inside, and sends them to each processing unit.

The document position detection unit 110 detects the position and size of the document based on the green (G) signal after the shading correction. The scaling / movement processing unit 111 controls the cycle and timing of writing and reading data to and from the shift memory, thereby realizing scaling and movement of an image.

Reference numeral 113 denotes a pattern generation unit which is used to output a signal of a constant density instead of the image signal from the CCD reading unit 101, or to output an image for detecting the toner density on the photosensitive drum surface described later. You.

An optical motor controller 50 controls the driving of the optical motor 15 for reciprocating the original scanning unit.

Next, the image processing operation and the mechanical system operation in FIG. 1 will be described.

The transfer paper 63 fed by the pickup roller 32 or the pickup roller 33 is conveyed to the registration roller 29 by the feed roller 30 or the feed roller 31 to remove the skew and form a fixed amount of loop. And waits until the timing of scanning the optical system and winding it around the transfer drum 27. Next, the registration roller 29 rotates, and the transfer paper 63 is transferred to the transfer drum 2 by the suction charger 21 and the suction roller 28 also serving as a counter electrode thereof.
7 is adsorbed. At about the same time, the optical system (document scanning unit) starts scanning, and the image sensor 14
Is read by the image processing circuit 49.

Then, in the image processing circuit 49, the color is separated and various color correction processes are performed as described above, the laser beam is converted into a laser beam, and the laser beam is deflected and scanned by the polygon mirror 18.
The photosensitive drum 19 uniformly charged by a charger (not shown) is exposed to form a latent image.

The developing unit 5d for magenta toner, the developing unit 5c for cyan toner, the developing unit 5b for yellow toner, and the developing unit 5a for black toner perform horizontal movement on the latent image at a predetermined timing. Perform processing.

The toner image formed on the photosensitive drum 19 is transferred to the transfer paper 63 attracted by the transfer charger 22. After repeating this series of operations for the required number of development colors, the separation charger 23 weakens the attraction force to prevent image disturbance due to separation discharge due to separation.
As a result, the separation operation by the A-side separation or the B-side separation is performed while a high voltage is applied, and the sheet is fixed to the fixing roller 6a and the pressure roller 6b, and then discharged to the discharge tray 6c.

Next, referring to FIGS. 6 to 10, the detection of the toner concentration inside each developing device and the detection of the toner concentration of the development formed on the photosensitive drum 19 corresponding to the non-transfer area of the transfer material holding member 27 will be described. I do.

FIG. 6 shows each of the developing devices 5a, 5b,
It is an external view of each developing device of 5c, 5d. The toner hoppers H of the respective colors are arranged above the developing unit moving table (not shown) in FIG. 1. Each of the toner hoppers H is provided with a flexible replenishing connection portion so that the toner can be supplied no matter where the developing units come. It has become. Each toner supplied from each toner hopper H is supplied to a toner supply port 305, and is configured to circulate in the direction of the arrow in FIG. 6 by two screws 303 rotated by driving a sleeve motor (not shown).

The toner used in this embodiment is yellow,
A two-component development system is used for magenta, cyan, and black, which is advantageous in color purity and transparency. Yellow, magenta,
The cyan toner is formed by dispersing color materials of each color using a polyester resin as a binder. The reflectance of these toners at near infrared light (960 nm) is 80%.

On the other hand, the black toner uses a polyester-based resin as a binder and carbon black as a coloring material, and is useful for reducing the running cost in black single-color copying. The reflectance of this black toner at near infrared light (960 nm) is 10% or less. The reflectance of the photosensitive drum 19 for near infrared light (960 nm) is about 40%. Note that the photosensitive drum 19 is an OPC drum.

A magenta developing device 5d, a cyan developing device 5c,
The yellow developing device 5d employs a method of optically detecting the toner density inside the developing device.

FIG. 7 is a sectional view of the developing device. In FIG. 7, reference numeral 301 denotes a developing sleeve, and 303 denotes a screw.
The toner density detection sensor 500 is arranged at a position as shown in FIG. 7, and detects the toner density immediately before development. The toner density detection sensor 500 has a configuration as shown in FIG. 8, and is a view of the toner density detection unit 500 in FIG. 7 viewed from above. Reference numeral 501 denotes a detection window formed of a transparent member. The side in contact with the developer is covered with, for example, a Teflon-based sheet having a low surface energy so that toner and carriers do not adhere. Reference numeral 503 denotes an automatic toner regulator lamp (hereinafter, referred to as an ATR lamp), which detects the toner density by receiving the reflected light of the lamp light from the developer by the light receiving unit 502. The spectral distribution of this lamp is selected according to the toner agent. For example, 900 to 100 with reflection of toner resin
LEDs with a distribution of 0 nm are used. Light receiving unit 502
Receives the direct light of the ATR lamp 503 and compares the light with the initial state value of the ATR lamp 503 to obtain the light receiving unit 5.
02 can be corrected such as a change over time.

Specifically, a serviceman installs the developer controlled to a predetermined toner concentration in the developing devices 5b, 5c, and 5d when starting or adjusting the use of the machine, and the developer controlled to the predetermined toner concentration. , A toner density detecting operation is performed, and the light reflected from the developer at this time is
2, the magenta toner data, the cyan toner data, and the yellow toner data
M, SGiC and SGiY are stored in the RAM 44.
At the same time, the direct light from the ATR lamp 503 is
The data received at 04 is RFiM, RFiC, RFi
Y is stored in the RAM 44. These SGiM,
The six data SGiC, SGiY, RFiM, and RFiY are stored in a backed-up RAM area so that the data is not destroyed even when the power is turned off. Hereinafter, only the magenta toner density control will be described, and the description of the cyan, yellow, and toner density controls will be omitted because they are the same.

On the other hand, when the data read by the light receiving unit 502 during image formation is RFcM as in the case of SGcM, if the toner density decreases, the reflection signal from the developer decreases when the toner density decreases. The toner supply operation is performed, and a toner supply time Tst for realizing the toner supply operation is determined. The formula for calculating Tst is shown below. K is a constant. T _st = (SGiM− (RFiM / RF
cM) × SGcM) × K Replenishment is performed according to the toner replenishment time Tst thus determined, and the initial toner density is maintained.

FIG. 11 is a timing chart of the toner density detecting operation. The tip of the electrostatic latent image at the developing position Ps (V
In synchronization with IDEOd _V ), the drive of a sleeve motor (not shown) is transmitted by a sleeve clutch (not shown) for each developing color (not shown), and the screw 303 also rotates, so that the stirring operation in the developing device is performed. Done. In order to eliminate the influence of the toner density in the stop state, the ATR lamp 503 is turned on after a while (T _wait ), and the toner density detection operation is performed a plurality of times.
Is turned off, the toner supply amount is calculated, and the toner supply operation is performed. Development is performed simultaneously with the toner concentration detection and toner replenishment operation, and the electrostatic latent image is developed by the developing device.

FIG. 9 shows a state during development on the photosensitive drum 19 by the black developing device 5a. Developed image is detected by a black toner density detection sensor 600 located at the opposite the Pp point from the developing position P _S at a distance l _P content downstream position. As shown in FIG. 10, the black toner density detection sensor 600 includes a light emitting lamp 603, a direct light receiving unit 604 of the light emitting lamp 603, and a light receiving unit 602 reflected from a toner image on the photosensitive drum 19. As in the case of the toner concentration detection unit sensor 500, correction for a change with time is performed.

Specifically, the concept is the same as that of the above-described toner density control of magenta toner.

At the start of use or adjustment of the machine, a serviceman outputs a toner density detection image to a black developer controlled to a predetermined toner density in the same manner as in image formation, and develops the toner. A detection operation is performed, and the light receiving unit 6 of the reflected light from the photosensitive drum 19 at this time is used.
02 and the data of the direct light receiving unit 604 respectively.
k, RFiBk and stored in the backed up RAM 44 area. When the black toner density decreases, the amount of light absorbed by the toner on the photosensitive drum 19 decreases, and eventually the reflected light from the photosensitive drum 19 increases. More.

The data obtained by reading the toner image for black toner density detection by the light receiving unit 602 during image formation is represented by SGcB
k, the data read by the light receiving unit 604 at this time is RF
Assuming that cBk, the toner supply time T _st is T _st = ((RF
iBk / RFcBk) × SGcBk−SGiBk) × K
(K is a proportional constant).

FIG. 12 is a timing chart of the black toner density detecting operation.

[0051] Tdv is the time required for movement of the distance from Pl of the photosensitive drum 19 in FIG. 7 to P _S. Further, Tp is the time required to move the distance from Pl to Pp in FIG. 5, and _Tpatch is the output time of the toner density detection image.

At this time, the axial range of the density detecting toner image on the photosensitive drum 19 is sufficient by the size of the black toner density detecting sensor 600 in the axial direction.

The toner image for density detection formed in this way is black toner density detection sensor 600 after _TP time.
, The light emission lamp 603 is turned on to detect the toner density. Then, the CPU 42 determines the toner supply amount, and performs a supply operation to the developing device 5a from a black toner hopper (not shown) as necessary. At this time, as for the spectral distribution of the light-emitting lamp 603, a wavelength that does not absorb the photosensitive drum 19 is selected so as to prevent the deterioration of the photosensitive drum 19, and an LED having a distribution of 900 to 1000 nm is used.

Next, setting of image forming conditions in this embodiment will be described with reference to FIG. FIG. 14 shows FIGS. 1 and 2
5 schematically shows a part necessary for setting image forming conditions.

In FIG. 14, a primary high-voltage power supply 251 for supplying a required high voltage to the primary charger 250, a photosensitive drum 1
Primary charger 25 for controlling the amount of charge given to 9 to a desired value
A grid bias power supply 252 for supplying a required bias voltage to the grid 0, the developing device 5a or 5b, 5
a developing bias power source 2 for applying a required developing bias (usually a DC voltage superimposed on an AC voltage) to c and 5d
A CPU 42 for controlling each of the CPUs 53 is provided.
Data signals relating to humidity and temperature from the environment sensor 201 are input to the CPU 42 via the A / D converter 203, and output signals from the potential sensor 200 for detecting the surface potential of the photosensitive drum 19 are also supplied to the CPU 42 by A / D conversion.
It is input via the D converter 203. Further, a toner density sensor 600 for measuring the toner density on the surface of the photosensitive drum 19 is also supplied to the C / A converter 203 via the A / D converter 203.
It is input to PU42.

The operation of the control system having the above configuration will be described below.

[0057] Figure 15 is a graph showing the relationship between the grid bias voltage surface potential (horizontal axis) and the photosensitive drum 19 (vertical axis), the curve V _D in the figure represents the surface potential of when not irradiated with light The curve _VL represents the surface potential when irradiated with light. From the figure, the surface potential V _D, i.e., the charge amount is proportional to the grid bias voltage V _G is within the operating range. Further, there is a surface potential V _L is also similar tendency after light irradiation, the rate of change with respect to the change amount of the grid bias voltage V _G, i.e. greater than if proportionality factor towards V _D is V _L (FIG. 15 as shown, the proportional coefficient of V _D alpha, V _L
Let β be a proportionality coefficient of α). Therefore, before performing the image forming operation, the control means 18 measures the voltage values of V _D and V _{L at} the preset grid voltages V _G1 and V _G2 by the potential sensor 200, and FIG. Assume a charging curve of V _D and V _{L with} respect to a change in grid voltage as shown. Thereafter, when an image is actually formed, from the charging curve obtained by the above-described operation, the image contrast V _CONT , that is, the difference between the DC component of a developing bias described later and the surface potential _VL after light irradiation or V _D −
A grid voltage such that _VL becomes a predetermined value is determined by the CPU 42.
, And the grid bias power supply 252 is controlled. Further, CPU 42 is only constant potential V _B than V _D so as not to adhere toner (a portion corresponding to V _D because it uses reverse developing method in the present embodiment) portion corresponding to the white image A developing bias having a low value is obtained by calculation, and the developing bias power supply 253 is controlled based on the calculated value.

FIG. 16 is a graph showing the effect of image density on humidity when printing under the same image forming conditions. As shown in FIG. 16, under the same image forming conditions, the lower the humidity, the lower the density. As the concentration increases, the concentration increases. Therefore, if the humidity is detected and the contrast potential V _CONT corresponding to the detected humidity is obtained, and the image forming conditions are set based on the value, a stable image can be obtained regardless of changes in environmental conditions. Becomes possible. Also, as shown in the figure, since the density with respect to humidity is different due to the difference in color, if the image forming conditions are varied for each color, the difference in image density due to the difference in developer color can also be corrected. it can.

Next, how the image forming conditions are determined will be described in detail with reference to the flowchart of FIG. The processing A shown in FIG. 17 is for calculating an optimal environmental contrast potential V _C at the present time in consideration of the environmental history up to the present time. The process A is automatically executed when and other than during the image formation a new environmental data received from environmental sensor 201, is always to environmental contrast potential V _C is the latest environmental history is calculated.

The data of the environment sensor 201 composed of a temperature sensor and a humidity sensor is measured using the timer 206, for example, once every 30 minutes or several times during 30 minutes, and the average value is stored in the memory (RAM 44) for 8 hours. ). When 30 minutes have passed anew, the oldest data is removed and the data for the latest 8 hours is stored.
When the CPU 42 has just been operated and there is no past data at the time of turning on the power (S2001), the environmental data at the present time is stored in the memory as data for 8 hours (S2002). Next, the mixing ratio of water (absolute humidity) is obtained from the environmental data for eight hours by a predetermined calculation formula and stored in the RAM 44. Further, average values x, y, and z of the mixture ratios (absolute humidity) for the past two hours, four hours, and eight hours are obtained from the environmental data for eight hours (block S2003). These average values x, y, and z are used for the following condition determination, and are used as a variable H when calculating a contrast potential described later. First, decision block S20
At 04, it is determined whether or not the 2-hour average value x is 16.5 g or more, and if it is 16.5 g or more, the contrast flag is set to CONT1. This indicates that the high humidity state continued for 2 hours or more. Next, it is determined whether or not the current value w is 16.5 g or more in a determination block S2005. If the current value w is 16.5 g or more, the contrast flag is set to CONT2. This indicates that the humidity was low for 2 hours but is now heading for high humidity. Next, in the decision block S2006, the average value z for 8 hours is 9 g.
The contrast flag is set to CONT3 if it is 9 g or more. This indicates that the humidity is in a moderate humidity state for 8 hours or more. Next, in a decision block S2007, it is determined whether or not the 4-hour average value y is 9 g or more.
Change to NT4. This indicates that it is going from low humidity to moderate humidity. In other cases, that is, 4
If the average value y of the time is 9 g or less, it is determined that the state is low humidity, and the contrast flag is set to CONT5.

Incidentally, the above processing is performed because the speed of moisture absorption and dehumidification of the toner is different between when going from low humidity to high humidity and when going from high humidity to low humidity. That is, although the image density is proportional to the absolute humidity, it is determined not by the humidity of the atmosphere but by how much the toner absorbs moisture, so that the above-mentioned condition determination is performed.

Next, in block S2008, a variable H for contrast calculation is determined by the contrast flag. This is because, for example, in the case of CONT1, since the humidity is completely adjusted to a high humidity, the variable H is an average value x for 2 hours. In the case of CONT2, since the state is intermediate between low humidity and high humidity, the variable H is (x + w) / 2, which is the average value of the average value x and the current value w for 2 hours.

The general formula for calculating the contrast potential is as follows: When V _C is an environmental contrast potential and a and b are coefficients, V _C =
aH + b. Here, H is the variable described above. Table 1
Are contrast flags (CONT1, CONT2, COT
NT3,...) And a development color (magenta M, cyan C, yellow Y, black BK) are part of a list of variables H and coefficients a and b. This content is stored in the ROM 43, and a method of selecting the coefficients a and b and the variable H in the calculation formula may be searched from the contrast and the development color information (block S2008). The search results from calculating the environmental contrast potential V _C (block S2009).

This operation is repeated for four colors (S201).
0), environmental contrast potentials V _C , V _C (M), V for magenta, cyan, yellow, and black toners
_C (C), V _C (r), and V _C (Bk) are determined.

[0065]

[Table 1]

FIG. 18 is a plot of the above formula. As shown in the figure, since the coefficient is changed for each color, the difference in density change for each color shown in FIG. 16 can be absorbed and corrected.

Next, the processing B will be described with reference to FIGS. Process B is to measure each the relationship between the grid bias voltage V _G and the surface potential V _S shown in the aforementioned FIG. 15 when the laser lighting time and laser off.

In this embodiment, the laser modulator 2
When the image signal VIDEO is at it is for laser off of 8 bits to 05 when the time VIDEO _P = 00 _H laser lights shall mean VIDEO _P = FF _H. In this process, control is performed such that the latent image forming operation is performed, but the developing and transfer operations are not performed.

As with the normal image forming sequence, the CPU
42 rotates the photosensitive drum 19, and the primary high voltage power supply 25
Turn 1 on. Next to set the high-voltage control circuit 204 to output a grid bias V _G = V _G1, and outputs the grid bias _{V G = V G1 (S1100)} .
Then, the pattern generation unit 113 shown in FIG.
Such that the laser OFF data VIDEO _P = 00 _H, set so that the pattern is outputted as an image signal VIDEO _P, creating a laser OFF state. Since the primary high voltage supply position and the laser exposure position and the potential measurement position on the photosensitive drum 19 are different from each other, it goes without saying that these distance relationships are absorbed in the control.

Laser O at grid bias V _G = V _G1
The surface potential of the photosensitive drum 19 when latent image FF state has come to the position of the potential sensor 200 to measure the V _D1, the memory (R
AM44) (S1101). Then, without changing the grid bias potential V _G, to produce the laser lighting state, the pattern generation unit 111, a laser ON
Data VIDEO _P = FF _H is set, the laser is turned on, and the photosensitive drum 19 is irradiated with the maximum light amount.
The surface potential V _L1 after laser beam irradiation was measured, and stored in the memory (block S1102). Next, V in FIG.
Grid bias power supply 4b to measure _D2, V _L2
The grid bias another to a predetermined value V _G2 from (block S1103), Similarly by measuring V _L2 is stored in the memory (block S1104). Next, V _D2
The laser is turned off in order to measure, and _VD2 is measured and stored in the memory (block S1105). Then, the primary high voltage power supply 251 and the grid bias power supply 252 are turned off, and the operation ends.

The order of turning on / off the laser and the output timings of the grid bias voltages V _G1 and V _G2 may be changed depending on the sequence. In the present embodiment, the potential was measured when the laser was turned on and when the laser was turned off.
Further, the processing A and the processing B are independent of each other, and either one may be performed first.

Next, the process C will be described with reference to FIG. Process C must be performed after processes A and B have been performed.

[0073] processing C is the environmental contrast potential V _C Considering E environment history obtained in process A as the contrast potential is basically a developing bias DC component V _db optimal grid voltage V _G for each toner color Is what you want.

For this reason, the following description will be made on the assumption that the contrast potential V _CONT is equal to the environmental contrast potential V _C.

First, V _G1 , V _G2 and measurement data V _D1 ,
The slopes α, β and α−β of the respective charging curves shown in FIG. 15 of V _D2 , V _L1 and V _L2 to V _D and V _L are calculated according to the following equations (block S1200).

Α = (V _D2 −V _D1 ) / (V _G2 −
V _G1 ), β = (V _L2 −V _L1 ) / (V _G2 −V _G1 )

Next, the aforementioned fog removal voltage V _B stored in the buffer area of the memory and the environmental contrast voltage V _C calculated in the process A are read, and the contrast potential V
_CONT is set (block S1201). The grid bias voltage V _G is determined to a voltage sum of V _CONT and V _B are obtained. That is, the following calculation is performed (block S
1202).

V_G= (V_CONT + V_B− (V_D1 -V_L1)) / (Α−β) + V_G1 When the grid bias voltage is obtained by the above formula,
Then V_DIs obtained by calculation (block S1203).

V _D = α (V _G −V _G1 ) + V _D1 In step S1204, the DC component V _db of the developing bias is obtained.

V _db = V _D -V _B

When it is determined that the above processing has been completed for four colors (decision block S1205), the processing is terminated.

As described above, the grid bias control value V _G ,
This means that the developing bias control value _Vdb has been obtained for four colors of magenta, cyan, yellow, and black.

The grid bias and the developing bias obtained in this way take environmental conditions into account, and also take into account the difference in environmental conditions for each color, so that an image with an extremely stable appropriate density can be obtained.

Next, the output density stabilization control which is the main object of the present invention will be described.

The output density stabilization control is roughly classified into three types: high density output stabilization control, middle density output stabilization control, and low density output stabilization control.

Further, control for correcting a detection error due to contamination of the toner density sensor detection window and control for confirming the fluctuation of the potential of the photosensitive drum are performed to accurately perform the output density stabilization control.

Here, the outline of the output density stabilization control will be described.

Using the black toner density detection sensor 600, the developed toner images of all the colors of a fixed density sequentially formed under the predetermined image forming conditions are sequentially read, and the read data is fed back to the image forming conditions for each color. Is to multiply.

For this reason, it is necessary to perform control for correcting the contamination of the sensor window of the black toner density detection sensor 600 and control for confirming the potential fluctuation of the photosensitive drum.

(Sensor Window Dirt Correction Control) Before the operation of storing the initial black toner density, the black toner density detection sensor 600 is operated to detect the density of the photosensitive drum 19 to which no toner is attached.

At this time, the data read by the light receiving unit 602 is adjusted to a predetermined value SG _idrm using an adjustment function (not shown), and the data of the light receiving unit 604 at this time is _converted to RF.
_Back up as _idrm .

Thereafter, if the read data of the light receiving units 602 and 604 when the photosensitive drum 19 to which the toner is not adhered is detected again is SG _cdrm and RF _cdrm , respectively, SG _cdrm × RF _idrm / RF _cdrm and SG _icdrm are obtained. If different, it is considered that the window 501 of the black toner density sensor 600 is stained with toner. For this reason, the correction value D _crct for this window stain is calculated by the following equation. D _crct
= SG _idrm / (SG _cdrm × RF _idrm / RF _cdrm ) This is corrected by multiplying the data read by the light receiving unit 602 of the black toner density sensor 600.

The sensor window dirt correction control will be described with reference to the flowchart of FIG.

Sensor window dirt correction value D_crctTo seek
Requires a surface free of toner on the photosensitive drum.
Rotating to clean the photosensitive drum 19
(S1300). Clear the cleaner 20 more than once.
And the surface is black toner density detection
Wait for the sensor 600 to reach the opposite position (S130).
1). Thereafter, the ATR lamp 603 is turned on (S130).
2) Read the surface of the photoconductor drum where no toner is attached
The data read by the light receiving unit 602 at this time is
_cdrmAt the same time, the read data of the light_cdrm
Is stored in the RAM 44 (S1303).

Then, the above-described window dirt correction value D _crct is calculated (S1304).

When the window dirt correction value D _crct does not fall within the predetermined range (S1305) (for example, 60% or less or 20%).
(0% or more), it is determined that the window stain is severe, and a display indicating that the window stain is performed is output (S1308), and the image forming operation is not accepted thereafter.

Even if the window dirt correction value D _crct is within a predetermined value, if the dirt is unusable (for example, 70% or less or 150% or more) that cannot be used for output density stabilization control described later, a window dirt error flag is set. Then (S1309), the operation ends. On the other hand, if it is not dirty, the window dirt error flag is reset (S1307), and the window dirt correction value D
_crct is stored in the backup area of the _{RAM 44} ,
(S1310) The operation ends.

(Potential Fluctuation Confirmation Control) The potential fluctuation confirmation control is performed by irradiating a predetermined amount of laser light onto the surface of the photosensitive drum 19 and continuously measuring the irradiated position with a potential sensor 200. The surface potential unevenness on the body drum 19 is detected to determine whether the photosensitive drum 19 can be used for an image forming operation or can be used for output density stabilization control described later.

Hereinafter, description will be made with reference to the flowchart of FIG.

First, in order to start the control, the photosensitive drum 19 is rotated by rotating a motor (not shown), and the pre-exposure lamp 254 is turned on (S1400). Thereafter, a primary high voltage power supply 251 and a grid bias power supply 252
Is turned on via the high voltage control circuit 204 (S140).
1). In order to ensure that the photosensitive drum 19 is electrically cleaned by the pre-exposure lamp 254, the photosensitive drum 19 is waited for one or more rotations (S140).
2). Thereafter, the pattern generation unit 1 in the image processing circuit 49
13 is irradiated with a predetermined amount of laser, for example, V
Make settings to IDEO _P = 20 _H abscess, laser O
N is performed (S1403).

Thereafter, the potential sensor 200 continuously measures the potential for one rotation of the photosensitive drum 19 (S140).
4) After the completion of one round of measurement in which the measurement data is stored in the RAM 44 (S1405), when the potential fluctuation confirmation control is performed with another laser light amount, S1403 to S1405 are repeated (1406).

In the case of this embodiment, VIDEO = 20 _M and VIDEO for eliminating the measurement error due to the laser light quantity
Two measurements are made at = 70 _n . It is possible to increase or decrease the amount of sample laser light as needed.

After the measurement is completed, the maximum value and the minimum value of the measurement data stored in the RAM 44 are determined (S1407),
If the difference is large enough to affect the image forming operation (for example, 40 V) (S1408), a potential fluctuation error display is performed on the operation unit 51 (S1412), and the subsequent image forming operation is prohibited.

If the difference between the maximum value and the minimum value is smaller than the error limiter value and it is determined that the difference cannot be used for the output density stabilization control described later (for example, 20 V) (S140).
9) The potential swing error flag is set (S1411), and the process ends.

Conversely, if the output density stabilization control can be used, the potential swing error flag is reset (S1410), and the processing ends.

(Output Density Stabilization Control) Before describing the output density stabilization control, the relationship between the black toner density sensor 600 and the density of the toner attached to the photosensitive drum 19 will be described with reference to FIG.

FIG. 23 shows the relationship between the output image density and the output of the black toner density sensor 600.

The output is adjusted before the above-described black toner initial density storing operation so that the output value of the black toner density sensor 600 when the toner does not adhere to the photosensitive drum 19 becomes SG _idrm .

As can be seen from FIG. 30, the yellow, magenta, and cyan color toners have a larger amount of reflected light than the photosensitive drum 19 alone as the area coverage increases and the output image density increases. The output increases. On the other hand, as the area coverage of the black toner increases and the output image density increases, the photosensitive drum 19
The amount of reflected light is smaller than that of a single unit, and the output of the sensor 600 is smaller.

By utilizing these relationships, it is possible to accurately obtain the output image density from the sensor output without transferring and fixing the toner to the copy sheet even with toners having different reflection characteristics.

Next, a magenta toner having a predetermined density is applied to the entire surface of the photosensitive drum 19, and while the photosensitive drum 19 is being rotated, a black toner concentration detecting sensor 600 is provided.
FIG. 24 shows the state at the time of measurement. It can be confirmed that, due to the eccentricity of the photosensitive drum 19, the input signal of the same level is moved up and down in one cycle of the photosensitive drum 19. Therefore, in the subsequent density measurement in the output image stabilization control, in order to eliminate the signal error due to the eccentricity, either the average value of the data for one round of the drum or the average value of the data at two points 180 ° opposite to each other is used. Is calculated.

Next, FIG. 25 to FIG.
This will be described with reference to FIG.

In order to perform this processing, processing A, processing B, and processing C are performed to stabilize the output image (S15).
00). Contrast potential V _CONT for each developing color is in this case the process C may be calculated as the environmental contrast V _C obtained in the process A is performed. Next, the above-described sensor window dirt correction control is performed (S1501), and the window dirt correction value D _{crct is obtained.}
Ask for. Next, the sensor window dirt flag is checked to determine whether the output density stabilization control can be executed (S15).
02). Next, the above-described potential swing confirmation control is performed (S15).
03), the potential fluctuation error flag is checked to determine whether the output density stabilization control can be executed (S1504).

Next, since the output density stabilization control performed below involves a developing operation, the photosensitive drum 19 required for the developing operation is controlled.
Rotation and various I / O settings (S150)
5).

Next, assuming that this control is performed in the order of magenta, cyan, yellow, and black development colors, processing C
A grid bias value corresponding to the developed color obtained in step (1) is obtained from the RAM 44, set in the high voltage control circuit 204, and a primary high voltage grid bias is output (S150).
6).

Next, the developing device for the color to be developed is moved to the developing position (S1507). At this time, the developing bias DC _Vdb of the developing color obtained in the process C is output. Thereafter, a timing signal ITOP for one rotation of the photosensitive drum 19 for reducing a measurement error due to the drum eccentricity described above is waited (S15).
08). After the input of the ITOP signal, the transfer drum is cleaned (S1509). This is transfer drum 2
This is to prevent the transfer sheet 27a from being stained if the toner 7 is soiled with toner. The transfer cleaning tato brush portion including the transfer cleaning fur brush 261 is brought into contact with the transfer sheet 27a, and the inner brush 262 is moved inward. To backup from. When the transfer drum 27 rotates and the transfer cleaning fur brush 261 rotates in this state, the transfer cleaning operation is performed.

Next, an image processing circuit 49 is used as a measurement image.
Output image data is set in the inner pattern generation unit 113 such that VIDEO _P = FF _H. Further, it is also possible to use the trimming processing unit 108 so that the image data other than the image necessary for the measurement is not output.
(S1510).

Thereafter, the black toner density detection sensor 60
At timing 0, the density measurement of the measurement image is started (S1511). The measured data is ATR lamp 50
3 is corrected and the RAM 44 is successively changed at regular intervals.
To be stored. When the measurement for one rotation of the photosensitive drum 19 is completed (S1512), the density data stored in the RAM 44 is read, and the average value _SFF is calculated. Average value S
_FF is data from which the photoconductor drum eccentricity factor has been eliminated (S1513).

Here, the above operation is repeated for four colors (S1514), and the average value _SFF is obtained for four colors.

Next, by multiplying the obtained average value _SFF by the sensor window dirt correction value Dcrct, the window dirt is corrected (S1515). Next, the corrected average value S _FF is converted into density data D _FF ′ by accessing the conversion table storing the relationship shown in FIG.
516). If the difference between the ideal density data D _FF and the measured density data D _FF ′ is not within the predetermined range (S151
7) A density error display is performed without recognizing a subsequent image forming operation as a failure due to, for example, a high voltage (S15).
18).

[0121] Here, what the image signal VIDEO _P to be set in the pattern generation unit 113 represents the output density D _{FF 'H} and the ideal output density D _FFH is 27. Since the contrast potential Vcont when the operation is being performed is environmental contrast potential V _C obtained in process A, which will not match the ideal environment contrast potential due to changes in the characteristics of the photosensitive drum by temperature rise in the apparatus, high It is considered that the output density in the density region was different from the ideal value _DFF .

Accordingly, in this embodiment, the output density value D _FF ' _H approaches the ideal value D _FF by correcting the contrast potential V _cont . Formula is V _CS = V _C × the contrast correction value of the environmental contrast V _C and _{V CS (D FFH -D FFH '} ) / (D FFH) In obtained (S1519) is also the laser output to the other for the A method of feeding back the power, the current to the primary charger, and the original exposure amount is also considered.

If the obtained correction value V _CS is too large, the operation may be excessive. If the correction value V _CS is not within 20% of the calculated environmental contrast potential V _C , for example (S1520) to set the limit value to the V _CS (S1521). Then, the rotating transfer cleaning device, the laser, the photosensitive drum 19 and the high pressure are turned off.
(S1522) and the operation ends. The corrected contrast potential V _CS of each developed color obtained here is stored together with the date and time data in the timer 206 in a backup RAM area which is not destroyed even when the power is turned off. This data is used when confirming the control history.

(Low-density output stabilization control) The low-density output stabilization control to be described below is similar to the above-described high-density output stabilization control, and therefore only different parts will be described with reference to FIG. The different parts are the output of the sample image data twice and the feedback method.

Steps S1600 to S1609 are the same as steps S1500 to S1509 described above, and a description thereof will be omitted. As described above, the processing A, the processing B, the processing C, the sensor window dirt correction control, and the potential blur confirmation control necessary for the low density output stabilization control are performed.

Next, in steps S1610 to S1619, V
_{IDEO P = 10 H, VIDEO P} = 20 installed in the pattern generation unit 113 as _H, performs a developing operation for the latent image, drum eccentricity and ATR data S _10H for eliminating the effects of aging and power fluctuations of the lamp 503, Obtain _S20H for four colors.

[0127] Each of the developing color S _{1 OH} obtained for S _2OH, window stain correction value Dc obtained in the sensor window stain correction control
Rct is multiplied to perform window dirt correction (S1620).

Next, the window stain corrected S_1OH, S_2OH
Sensor signal-density table shown in FIG.
And convert these data into D
_1OH', D_2OH′ And

The measured values D _1OH ′, D _2OH ′ and the ideal value D
FIG. 29 shows the relationship between _1OH and _D2OH . The ideal values _D1OH and _D2OH are solid _lines , and the corrected measured values _D1OH 'and _D2OH
2OH 'is indicated by a dotted line.

If the obtained corrected measurement value does not fall within a predetermined range (for example, within ± 20% of the ideal value), it is determined that a malfunction has occurred in the high-voltage control system or the laser exposure system (S162).
2) The subsequent image forming operation is prohibited, and an error is displayed (S1624).

Next, the x-axis (VIDEO)
Determine the O _P) sections VD0 '. x intercept VD0 'is VID
Setting the VD0 'to EO _P is the image signal setting value as a zero concentration. ideal value VD0 of the x-intercept is not 00H, the configuration is performed in the density conversion unit 108 in the image processing circuit 49 to prevent the concentration output to separate low density output image signal from the potential V _B and fogging of the foregoing I have.

Incidentally, the calculated value VD is calculated from the ideal x intercept VD0.
If 0 is large, the output image will be a highlight skip,
On the other hand, when the output image is small, the output image is a fogged output image in which toner is applied to the output image to be a white background.

Thus, rather than measuring unstable VD0 'with VIDEO _P = 00H, a relatively stable VI
DEO _P = 10H, VD from two points of VIDEO _P = 20H
The feature of the present embodiment lies in finding 0.

[0134] The method of obtaining the correction value V _BS of the next VD0 obtained and fog by using the potential V _B will be described below.

[0135] For wearing output image from becoming normal image by increasing the value of V _B is VD0 '<
V _BS may the greater when the VD0. Therefore, the following equation is calculated.

V _BS = ((VD 0 −VD 0 ′) / VD 0) × V _B By adding this fog removal potential correction value V _BS to V _B , that is, assuming that V _B = V _B + V _BS , the above-described processing C is performed. Then, the calculated value VD0 matches the ideal value VD0 (S1625).

If the fogging potential correction value V _BS does not fall within the predetermined range (for example, 20% of V _B ) (S162
6) The fog removal potential correction value V _BS is used as a limiter value.
(S1627) These operations are performed for four colors, then an end operation (S1628) is performed, and the operation is ended.

[0138] Further, here and fog were determined potential correction value V _BS is previously stored in the backup RAM area even when the power is turned off not destroyed the data together with the date data in the timer 206. This data is used when confirming the control history.

(Medium-density output stabilization control) The medium-density output stabilization control is desirably performed after the above-described high-density output stabilization control and low-density output stabilization control, but can also be executed independently.

Hereinafter, the medium density output stabilization control will be described with reference to FIGS.
This will be described with reference to FIG. The outline of the medium-density output stabilization control is to output a medium-density gradation pattern, measure it with the sensor 600, and feed it back to a so-called γ table.

[0141] First processing A, the environment performs the processing B contrast potential V _C and the grid bias V _G and the light portion potential V
_L, is obtained in advance the relationship between the dark potential V _D (S1700). Next, if the high-density output stabilization control or the low-density output stabilization control has been performed before, the contrast potential V
_cont to be corrected by the correction contrast potential V _CS.

V _cont = V _C + V _{CS and the} fog removal potential V _B are also corrected by the fog removal potential correction value V _BS (S1701).

V _B = V _B + V _BS At this time, if the high-density output stabilization control and the low-density output stabilization control have been performed at least once before, the corrected contrast potential V _CS previously calculated and backed up in the RAM 44 and What is necessary is _just to use the correction fog removal potential VBS.

When the high-density output stabilization control and the low-density output stabilization control have never been performed, V _CS = 0 and V _BS =
The operation may be performed with 0.

Processing C is performed using the corrected contrast potential V _cont and fog removal potential V _B (S170).
2), grid bias value V _G for each developing color, obtains the developing bias DC component Vdb.

Thereafter, window dirt correction control and potential fluctuation confirmation control are performed as necessary (S1703, S1705). If an error occurs such that high-density output stabilization control cannot be performed because of large window dirt or potential blur (S1704). The operation ends in S1706).

Next, the photosensitive drum 1 for performing the developing operation
9 performs rotation, etc. (S1707), and outputs the grid bias value V _G for each developing color obtained in the process C (S170
8) The developer is moved (S1709). Further, a transfer cleaning operation is performed to prevent the surface of the transfer drum 27 from being stained (S1710).

Next, an output image selecting operation which is a feature of the medium density output stabilization control will be described. It has been confirmed by the inventor's experiments that the cause of the instability of the output density is largely due to environmental fluctuations, and that the influence is different depending on the developing color. Therefore, only when the environment changes, the density level of the output measurement image, the density level of the measurement image that is output when a predetermined time has elapsed after the previous measurement, and the density level of the measurement image that is always output are shown in FIG. The optimal output density level can be selected for each color (S1711).

In the following example, an example is shown in which a predetermined time has elapsed since the previous measurement for the developed color magenta. Output level VIDEO _P = 40H in this example, 60H, A0H, the E0H. This image is output in the required number of times and in the required number of colors in synchronization with the ITOP signal, and is measured by the sensor 600 (S171).
2 to S1717).

[0150] shows the timing relationship of this time, a diagram 35, a VIDEO _P 40H, 60H, A
0H and E0H, respectively, are output for one rotation of the photosensitive drum, and are continuously detected by the sensor to correct a data error due to the eccentricity of the photosensitive drum 19. ATR lamp 6
03 is also corrected.

Next, these measured data are used as the window stain correction D
corrected by crct (S1718), the corrected data density data _{D 4OH ', D 6OH',} D AOH ', D EOH' to convert (S1719). At this time, since each data must be monotonically increasing, it is checked whether or not the data is monotonically increasing (S1720). If there is an error, a γ table described later is not created. In this case, the γ table created by the previous correction operation or
Γ correction is performed using the basic γ table.

If the data is far from the ideal density data by a certain value or more (S1712), a limiter is applied to the density data so that no problem occurs in the created γ table (S1722).

FIG. 31 shows the relationship between the output image signal VIDEOP and the output density in this state. Measurement data is shown by dotted lines, and ideal data is shown by practice. The dotted line is created by first-order interpolation of the measurement points. In this example, it can be seen that there is no density for the ideal data.

FIG. 32 shows the relationship between the input (VIDEO _i ) and the output (VIDEO _O ) of the density converter 107 in the image processing circuit 49. This is usually called a γ table, and the shape of the solid line portion differs depending on each developing color and the density lever (not shown) of the operation unit 51. In this embodiment, the basic γ corresponding to the solid line portion is shown in FIG.
Is stored in the γ ROM 290, and the correction γ to be described below is stored in the γ RAM 291.
Select 292 switches SW 293 for use.

[0155] D _4OH shown in FIG. 31 ', D _6OH',
D _AOH ', D _EOH' respective ideal value D _4OH from the value of, D
_6OH, D _AOH, performs inverse transformation so that the D _EOH, 32
Is created (S1723). The concentration data D _4OH ′, D _6OH ′, D _AOH ′, and D _EOH ′ measured at this time.
Correction of density data other than the above is arbitrary, and the simplest one is primary interpolation. This operation is performed for four colors.

In general, the tables of basic γ are Y, M, C,
Since it differs for each K color, a color patch is created for each color as described above, and a correction γ table is created for each color.

After the γ table is created, the operated load is stopped, and the operation ends (S1724).

The image stabilization parameters described above are input to the operation unit 51 by depressing a serviceman-dedicated input key (not shown) and a key of the operation unit 51 in the machine.
36 and FIG. 37 show examples in which a liquid crystal display is adopted for the display unit, for example.

FIG. 36 shows the case where the latest parameter values are displayed, and FIG. 37 shows the case where the history of each parameter for each developing color is displayed. Switching between these displays is performed using keys on the operation unit 51. As a result, appropriate service information is obtained at the time of adjustment by a serviceman.

Next, how to use the image stabilization control described so far will be described with reference to the flowchart of FIG. Since various parameters used for the image stabilization control are backed up in the memory, a description will be given from power-on in the sense that nothing is operated here.

After the power is turned on, the current environment data is stored in the buffer for 8 hours, and the process A is performed (S1800). Normal,
When the power is turned on, the temperatures of the fixing roller 6a and the pressure roller 6b are the same as the room temperature. The temperature of the fixing roller is detected by the fixing roller temperature detection sensor 202, and when the measured temperature is equal to or lower than the predetermined temperature (S1801), the image stabilization control described below is performed using the fixing roller warm-up time.

First, processing B and processing C (S1802), sensor window dirt correction control (S1083), potential fluctuation confirmation control (S1804), high density output stabilization control, low density output stabilization control, middle density output stabilization control (S1805) I do. Also, a series of these processes will be referred to as a Z process.

At this time, overlapping parts can be omitted as necessary.

In the sensor window stain correction control and the potential swing check control, if a window stain error flag or potential swing error flag for which the output stabilization control cannot be executed is set, a new V _CS , V _BS , γ table Is not created and the operation is performed with the previously backed up data.

Next, as a process until an image forming operation is instructed from the operation unit 51, when new environment data is received every 30 minutes, the process A is performed (S1807).
Re-calculate the environmental contrast potential V _C.

Next, the humidity data calculated from the environmental data is monitored, and when there is a difference from the previous data by a predetermined value or more, it is determined that the environmental change is large (S180).
8), a series of processing Z described above is performed (S1809).

As a result, a density unstable element due to environmental fluctuation is removed, and a stable output image can be obtained during image formation.

Next, each element control of the image stabilization control can be performed in the service mode used by the serviceman from the service switch and the operation unit 51 in the machine (S
1810). The situation at this time is shown in FIG.

FIG. 39 shows a liquid crystal display section provided on the operation section 51. The cursor 265 displayed on the display section is moved by using a cursor movement key of the operation section 51, and a not-shown position is selected at a selected position. When the start key is pressed, CPU4
2 determines the selected process, and the selected image stabilization control can be independently performed (S1811).

Next, when the start key is pressed in the normal mode, the image forming operation is started (S1612).

At this time, if a predetermined time has elapsed from the previous image forming operation (S1813), the processing B and the processing C, that is, the potential control are performed, assuming that the potentials of the bright portion potential V _C and the dark portion potential V _D change. (S1814). Then, the developing device to be used is determined from the color mode designated by the operation unit 51 (S1815).

Next, the developing device use counter that is counting during image formation is checked (S1816).

At this time, if the number of developing device use counters exceeds a predetermined value among the developing devices used, high density output stabilization control, low density output stabilization control, and medium density output stabilization control are performed only for the development color. Then, the developing device use counter is reset (S1817).

Thereafter, an image forming operation is performed (S181).
8) The use counter of the used developing device is counted up for each developing operation (S1819). When the image forming operation for the designated number of sheets is completed (S1820), it is checked again whether or not environmental data is taken in every 30 minutes (S180).
6) Continue the operation during power-on or higher.

In the above-described embodiment, a two-component toner in which a black toner is a polyester-based resin as a binder and carbon black is a coloring material was considered. However, magnetite having magnetic properties was used as a coloring material, and this magnetite was used as a binder in the binder 100. It is also possible to use a one-component magnetic toner containing 35% to 120% with respect to%. The reflectance of this one-component black toner for near-infrared light (960 nm) is approximately 10% or less, which is almost the same as that of a black toner using carbon black as a coloring material, and can be used for the same density detection method and image stabilization control. .

In the above-described embodiment, a two-component toner using a black toner as a binder with a polyester resin as a binder and carbon black as a coloring material was considered.
Blue, red, polyester resin binder
It is also possible to use a black toner using a yellow pigment as a coloring material.

At this time, the reflectance of this black toner in near-infrared light (960 nm) is 80% or more, and the toner is detected in the same manner as the method for detecting the toner density of the magenta, cyan, and yellow toners described in the above embodiment. The density can be detected.

Therefore, it is not necessary to form a developing area for toner concentration detection on the photosensitive drum.

The tables used for the output density conversion in the high density output stabilization control, the low density output stabilization control, and the middle density output stabilization control are not shown in FIG. Become.

As described above, the density conversion table shown in FIG. 40 is used, and the initial signal value SGid on the surface of the photosensitive drum 19 to which no toner adheres in order to increase the S / N of the signal.
If rm is adjusted at a lower output than in the above embodiment,
Better control can be performed.

In the black toner density detection operation shown in the above-described embodiment, the sensor window stain correction value Dcr
ct is introduced, and the toner supply time Tst is Tst = ((RFiBk / RFcBK) × SGcBk ·
Dcrct−SGiBk) × K. As a result, an error in the signal value of the light receiving unit 602 due to the toner attached to the outer periphery of the black toner density sensor 600 is corrected, and a more accurate toner density detection operation can be performed.

In the high-density output stabilization control, the low-density output stabilization control, and the medium-density output stabilization control in the above-described embodiment, one round on the photosensitive drum 19 to correct a measurement error due to the eccentricity of the photosensitive drum 19. The image forming operation of a predetermined density is performed for each minute, the measurement is continuously performed, and the average value is taken as the measurement value. However, this method has a disadvantage that the toner consumption increases or the measurement time increases. I have.

Since the actual measurement signal shown in FIG. 24 fluctuates in one rotation of the photosensitive drum 19,
The output image area for density measurement that can be measured
9 are output at two 180 ° opposite points, measured, and the average of the measured values of these two areas is equivalent to the average of the above embodiment. FIG. 41 shows a conceptual diagram of the output image on the photosensitive drum at this time. FIG. 42 shows a timing chart corresponding to FIG. 35 at this time.

The present invention can be applied to a printer using an electrophotographic process, as well as a bubble jet type printer which generates bubbles by heat and discharges ink by the pressure. In this case, a sample image may be formed on a recording sheet using ink of each color, the density thereof may be measured, and the γ characteristics and the ink ejection amount may be controlled.

[0185]

As described above, according to the first aspect of the present invention, an image forming means for forming an image on a recording medium,
Generating means for generating an image signal representing a sample image having an arbitrary density for forming a sample image on the recording medium by the image forming means; and a first means for measuring the density of the sample image formed on the recording medium. Measuring means; second measuring means for repeatedly measuring environmental conditions around the image forming means; and operating conditions of the image forming means determined based on the density of the sample image measured by the first measuring means. Control means for performing image stabilization control to be performed,
The control means selects the density of an image signal representing a sample image to be generated from the generating means in accordance with the time-varying state of the environmental condition measured by the second measuring means. Image pattern can be optimally controlled, thereby improving throughput and saving toner consumption. According to the invention according to claim 5, an image forming means for forming an image on the rotating drum-shaped recording medium, and the image forming means is rotated in synchronization with the rotation of the recording medium, and is formed on the recording medium. A transfer member to which an image is transferred, cleaning means for cleaning the surface of the transfer member, and an image signal representing a sample image having an arbitrary density for forming a sample image on the recording medium by the image forming means. Generating means, measuring means for measuring the density of the sample image formed on the recording medium, and image stabilization control for determining operating conditions of the image forming means based on the density of the sample image measured by the measuring means And a control unit that executes the recording medium to remove the sample image transferred to the transfer body during the formation of the sample image and during the density measurement. By cleaning the surface of the transfer body that rotates together with the cleaning unit, the transfer body can be quickly cleaned during the density measurement of the sample image, and the surface of the transfer body remains dirty with the sample image. Can be prevented, and the image formation can be started immediately after the execution of the image stabilization control.
Further, according to the invention according to claim 6, an image forming means for forming an image on a recording medium, and an image representing a sample image having an arbitrary density for forming a sample image on the recording medium by the image forming means. Generating means for generating a signal; and a first means for repeatedly measuring environmental conditions around the image forming means.
Measuring means, second measuring means for measuring the density of the sample image formed on the recording medium, and operating conditions of the image forming means based on the density of the sample image measured by the second measuring means. Control means for executing image stabilization control for determining the image stabilization control, wherein the control means waits for an instruction to start image formation, and waits for an instruction to start image formation. When the difference between the measurement result and the newly measured result is equal to or greater than a predetermined value, the image stabilization control is performed.When the difference is within the predetermined value, the image stabilization control is not performed, so that the image stabilization control is performed when necessary. Only the image stabilization control is performed, so that useless time until image formation becomes possible can be reduced, and toner consumption can be reduced.
According to the invention according to claim 7, there is provided an image forming means for forming a color image on a recording medium, the image forming means having a plurality of color visualizing means, and a sample image on the recording medium by the image forming means. Generating means for generating an image signal representing a sample image of an arbitrary density to form the image data; counting means for counting the number of times each of the plurality of color visualizing means is used; Measuring means for measuring the density of the sample image, and control means for executing image stabilization control for each color to determine the operating conditions of the image forming means based on the density of the sample image measured by the measuring means, The control means selectively executes the image stabilization control for colors for which the counting result of the counting means exceeds a predetermined number of times, so that only the colors for which image stability needs to be controlled are performed. Because can perform image stabilization control, the time until the image formable can be shortened, it is possible to reduce toner consumption.

[Brief description of the drawings]

FIG. 1 is a sectional view of a color copying apparatus to which the present invention can be applied.

FIG. 2 is a block diagram illustrating a configuration of the copying apparatus of FIG. 1;

FIG. 3 is a diagram illustrating a state in which transfer paper is attracted to a transfer drum.

FIG. 4 is a diagram illustrating a state in which transfer paper is attracted to a transfer drum.

FIG. 5 is a diagram for explaining an output timing of a transfer timing signal.

FIG. 6 is a perspective view of a developing device.

FIG. 7 is a sectional view of a developing device.

FIG. 8 is a diagram illustrating a density detection method in the developing device.

FIG. 9 is a diagram illustrating a photosensitive drum and a toner density detecting unit disposed around the photosensitive drum.

FIG. 10 is a cross-sectional view of a toner density detecting unit.

FIG. 11 is a timing chart showing a toner concentration detection timing in the developing device.

FIG. 12 is a timing chart showing a toner concentration detection timing on a photosensitive drum.

FIG. 13 is a detailed block diagram of an image processing circuit.

FIG. 14 is a block diagram illustrating a configuration of a part that controls image forming conditions.

FIG. 15 is a diagram illustrating a relationship between a surface potential and a grid bias voltage.

FIG. 16 is a diagram showing humidity and the density of each developing color.

FIG. 17 is a flowchart illustrating a process of obtaining an environmental contrast potential.

FIG. 18 is a diagram illustrating a relationship between environmental contrast and humidity.

FIG. 19 is a flowchart showing a process for measuring V _D and V _L.

[Figure 20] V _G, is a flowchart showing processing to obtain V _db.

FIG. 21 is a flowchart showing sensor window dirt correction control.

FIG. 22 is a flowchart showing potential swing confirmation control.

FIG. 23 is a diagram showing the relationship between the output of a black toner density detection sensor and the density of each developed color.

FIG. 24 is a view showing measurement data obtained by eccentricity of one rotation of the photosensitive drum.

FIG. 25 is a flowchart illustrating a process of high density output stabilization control.

FIG. 26 is a timing chart showing processing timing of high-density output stabilization control.

FIG. 27 is a diagram illustrating a relationship between a pattern generation unit setting image signal and an output density.

FIG. 28 is a flowchart showing a process of low-density output stabilization control.

29 is a diagram showing a relationship between the pattern generator setting image signal VIDEO _P and the output density.

FIG. 30: VIDEO set during medium density output stabilization control
It is a diagram illustrating a _P.

31 is a diagram showing a relationship between the pattern generator setting image signal VIDEO _P and the output density.

FIG. 32 is a diagram illustrating a relationship between an input and an output of a density conversion unit.

FIG. 33 is a flowchart showing a process of medium density output stabilization control.

FIG. 34 is a block diagram illustrating a configuration of a density conversion unit.

FIG. 35 is a timing chart showing the processing timing of the medium density output stabilization control.

FIG. 36 is a diagram illustrating a display example of image forming conditions.

FIG. 37 is a diagram showing a history display of image forming conditions.

FIG. 38 is a flowchart illustrating a process of image stability control.

FIG. 39 is a diagram showing a selection screen for image stabilization control.

FIG. 40 is a diagram illustrating a relationship between output density and sensor output when black toner is changed.

FIG. 41 is a diagram illustrating a concept when a density detection image of a plurality of gradations is output on a photosensitive drum.

FIG. 42 is a timing chart showing timing when a density detection image of a plurality of gradations is output to the photosensitive drum and measured.

[Explanation of symbols]

 5 Development Unit 19 Photosensitive Drum 113 Pattern Generation Unit 600 Toner Density Detection Sensor

Continuation of the front page (56) References JP-A-61-219068 (JP, A) JP-A-64-54467 (JP, A) JP-A-60-257457 (JP, A) JP-A-59-48776 (JP) JP-A-2-308268 (JP, A) JP-A-2-259676 (JP, A) JP-A-64-582 (JP, A) JP-A-2-149864 (JP, A) 63-208368 (JP, A) JP-A-63-261375 (JP, A) JP-A-2-173689 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 303 G03G 21/00 370-540 G03G 15/01-15/01 117 G03G 15/16-15/16 103

Claims (8)

(57) [Claims] 1. An image forming means for forming an image on a recording medium, and a generating means for generating an image signal representing a sample image having an arbitrary density for forming a sample image on the recording medium by the image forming means. A first measuring unit for measuring a density of a sample image formed on the recording medium; a second measuring unit for repeatedly measuring environmental conditions around the image forming unit; and a measurement by the first measuring unit. And control means for executing image stabilization control for determining an operation condition of the image forming means based on the density of the sample image obtained, wherein the control means controls an environment measured by the second measuring means. An image forming apparatus, wherein a density of an image signal representing a sample image to be generated from the generating means is selected in accordance with a temporal change state of a condition. 2. An image forming apparatus according to claim 1, wherein said control means generates image signals representing a plurality of sample images having different gradations from said generating means. 3. The image forming means includes a plurality of visualizing means for forming an image in a plurality of colors, and the control means controls a sample image to be generated from the generating means according to the visual color. 2. The image forming apparatus according to claim 1, wherein a density of the image signal representing the image signal is selected. 4. The apparatus according to claim 1, wherein said control means selects a density of an image signal representing a sample image to be generated from said generating means in accordance with an elapsed time since a previous operation condition was determined. Image forming apparatus. 5. An image forming means for forming an image on a rotating drum-shaped recording medium, and a transfer which rotates in synchronization with the rotation of the recording medium and transfers an image formed on the recording medium. Cleaning means for cleaning the surface of the transfer body; generating means for generating an image signal representing a sample image having an arbitrary density for forming a sample image on the recording medium by the image forming means; Measuring means for measuring the density of the sample image formed on the medium; control means for executing image stabilization control for determining operating conditions of the image forming means based on the density of the sample image measured by the measuring means; Wherein the control means rotates together with the recording medium to remove the sample image transferred to the transfer body during the formation of the sample image and during the density measurement. The surface of the Utsushitai image forming apparatus for causing cleaned by the cleaning means. 6. An image forming means for forming an image on a recording medium, and a generating means for generating an image signal representing a sample image having an arbitrary density for forming a sample image on the recording medium by the image forming means. A first measuring means for repeatedly measuring environmental conditions around the image forming means, a second measuring means for measuring the density of a sample image formed on the recording medium, and a measurement by the second measuring means. And control means for executing image stabilization control for determining the operating conditions of the image forming means based on the density of the sampled image. The control means waits for an instruction to start image formation. In a standby state, when the difference between the previous measurement result measured by the first measurement unit and the newly measured result is equal to or more than a predetermined value, the image stabilization control is performed. If the difference is within a predetermined value, Is the image above Image forming apparatus characterized by not perform stabilization control. 7. An image forming unit for forming a color image on a recording medium, comprising: a plurality of color visualizing units; and an arbitrary unit for forming a sample image on the recording medium by the image forming unit. Generating means for generating an image signal representing a sample image of density; counting means for counting the number of times each of the plurality of color visualizing means is used; and measuring the density of the sample image formed on the recording medium. Measuring means, and control means for executing image stabilization control for each color to determine the operating conditions of the image forming means based on the density of the sample image measured by the measuring means, wherein the control means An image forming apparatus that selectively executes the image stabilization control for colors for which the counting result of the counting means exceeds a predetermined number. 8. The image forming apparatus according to claim 7 , wherein said counting means resets a count value of a corresponding color in response to execution of said image stabilization control.