JPH0795203B2 - Recording device density control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a density cantrol system in a 1-pass 2-color (1P2C) system.

[Conventional technology]

Recording devices such as copiers and facsimiles have made remarkable progress in high image quality, multi-functionality, high reliability, etc., and are widely used in various fields.
In recent years, a device having a function of outputting a color image has become popular. In order to realize a recording apparatus with such performance, in order to prevent the deterioration of copy quality over a long period of time even if there is a change in the environment of the machine or a change in the characteristics of the photosensitive material and the developer. The state of each part of the xerography is detected by a sensor, the developing bias, the toner dispensing, etc. are controlled based on this information, and the density is controlled so as to always maintain the best copying conditions.

Speaking of toner dispense control, conventionally, the AC-DC method that detects the AC (area coverage) of the original to determine the toner dispense time, the developability in the developing machine to determine the toner dispense time
ADC method, toner density is detected from developer permeability change A
TC method is adopted.

Further, the image toner density of the photosensitive drum is detected, and the developing bias voltage is controlled based on the detection result to prevent excessive toner from adhering and achieve high image quality.

[Problems to be solved by the invention]

In such a conventional toner dispense control, for example, the AC-DC method has an advantage that the cost can be reduced and the mechanism is simple, but on the other hand, the accuracy is changed depending on the document size, and the responsiveness is poor. is there. In addition, the conventional ADC method is less susceptible to the influence of other subsystems because it detects the developability inside the developing machine, and it is possible to perform data sampling at all times, but it is necessary to detect the developability for each developing machine. However, there is a drawback that it changes with time and is easily affected by temperature rise. Furthermore, although the ATC method has the same advantages as the ADC method, there are problems that it cannot absorb changes in development characteristics and that the developer must be fluid.

In addition, the conventional ADC that only controls the developing bias cannot always obtain a sufficient image quality, and when the reading sensor is abnormal, it is not possible to adequately deal with it.

Furthermore, the conventional method cannot support the density control in the 1P2C method.

The present invention is to solve the above problems.

An object of the present invention is to provide a density control method in the 1P2C method that can obtain a high-quality two-color image.

Another object of the present invention is 1P2C with good operability and high reliability.
It is to provide a concentration control method in the method.

Another object of the present invention is to provide a concentration control method in the 1P2C method with low cost and high productivity.

[Means and Actions for Solving the Problems]

As shown in FIG. 1, the present invention relates to an optical density detecting means 2 for developing and non-developing areas on an optical density reference surface formed on a photoconductor, a first developing means based on the detected optical density,
It is characterized in that it has a density control means 1 for controlling the second developing means to control the density.

According to the present invention, after an inverted electrostatic latent image for a color image is formed on a photosensitive drum and a first development is performed with color toner,
A normal rotation electrostatic latent image for a black image is formed, second development is performed with black toner, and the potential and charge polarities of both toner developing portions are aligned by corona discharge, and then transfer is performed, so that one rotation of the photosensitive drum is performed. A 1P2C method that enables copying of two-color images, and an image based on the above-mentioned ratio in the halftone in which the linearity of the optical density ratio of the developing area and the non-developing area of the reference surface with respect to the output density is relatively maintained. It controls the concentration.

First, regarding the developing bias that determines the toner transfer amount from the developing device to the photoconductor, since the second developing is performed after the first developing, if the toner is too thick in the first developing, the second bias is generated.
The magnetic brush may cause image disturbance during development, while such image disturbance does not occur during the second development.
Only for developing devices. In this case, control is performed based on the optical density ratio when the optical density ratio between the developing area on the reference surface and the specific developing area is within the predetermined range and when the power is turned on, which tends to increase the density, and the optical density ratio is outside the predetermined range. That is, when the density is too high or too low, a fixed bias is applied so that a moderate image quality can be obtained.

Also, since the output density depends on the toner density of the developing machine,
When the optical density ratio is within the specified range, the toner motor ON time is calculated by setting the toner dispense reference time to be larger or smaller for each developing machine depending on whether the ratio is larger or smaller than the specified value. Turn the toner motor on only while the motor is on. When the optical density ratio is out of the predetermined range, the toner dispense reference time is fixed to a medium value and open loop control is performed to obtain a moderate image quality. Further, when the power is turned on, it is considered that the toner density has not become a value far apart by the previous control, so the toner dispense reference time is fixed to a medium value.

For the density detection interval, depending on whether the optical density ratio is within a predetermined range and is larger or smaller than the specified value, the density detection interval of each developing machine is lengthened, and when the density is low, toner is replenished. Since the development condition easily changes, shorten it. When the optical density ratio is out of the specified range, the density detection interval is lengthened to reduce the burden on the cleaner.When the power is turned on, the density changes most easily, so the density is detected most frequently and an appropriate density is obtained early. Get it.

〔Example〕

 Examples will be described below.

In this embodiment, a color copying machine will be described as an example of a recording apparatus, but the present invention is not limited to this, and it goes without saying that it can be applied to printers, facsimiles, and other image recording apparatuses.

(I) Outline of apparatus (I-1) Apparatus configuration FIGS. 2 and 3 are diagrams showing an example of the overall configuration of a copying machine to which the present invention is applied.

The copier to which the present invention is applied can be equipped with some additional devices to the base machine 100. A base machine 100 having a basic configuration includes an IIT (Image Input Terminal) 120 that reads information light from the document surface, a laser light source 121 whose output light is modulated by a signal from the IIT, a first light path and a second light path for the laser light. And a reflecting / scanning mirror system 122 including a polygon mirror for scanning a laser beam, a reflecting mirror 123 provided in the first optical path, a reflecting mirror 124 provided in the second optical path, and an electrostatic latent image is formed. The photoconductor drum 125, the first developing device 126 for color, the second developing device 127 for black, the fixing device 128 and the like are provided.

In the present invention, the 1P2C system is adopted. Therefore, the output light from the laser light source 121 is modulated with the color image information light, and the reflection / scanning mirror system 12 including the polygon mirror is used.
2. After forming an inverted electrostatic latent image on the photoconductor through the reflection mirror 123 and color developing with the first developing device 126, similarly, the laser light is modulated with the black image information light, and the polygon mirror is included. A normal electrostatic latent image is formed on the photoconductor drum 125 via the reflection / scanning mirror system 122 and the reflection mirror 124, and is developed by the second developing device 127 to form two color toner images on the drum.
Two-color copying is realized with one transfer. Also,
Base machine 100 has upper tray 102 and suspend tray 10
3. Lower tray 104 is attached so that all of the paper feed trays can be pulled out to the front to improve operability and save space for the copier, and to allow base machine 100
In contrast, we have realized a copier with a clean design that has no protrusions.

Further, an inverter 105 and an intermediate tray 109 are arranged in a paper carrying system for carrying the paper in the paper feeding tray, and a large capacity tray 108 is provided below the inverter 105 and the intermediate tray 109. Also,
A top tray 106 and a control panel 101 are provided on the base machine 100, and a standard tray 110 for ejecting copied sheets is further provided.

Next, regarding the additional device of the base machine 100, an ESS (Electronic Sub System) 112, a CRT 113 as a user interface, a keyboard 114, and a floppy disk drive 115 can be installed, and input through the keyboard 114 while observing the CRT screen. The data is temporarily stored in a floppy disk, and if necessary, the data from the floppy disk is read by the ESS112 and a signal is sent to the IIT, which is equipped with a printer function that enables printing by the 1P2C method. Further, a manual feed tray 107 can be attached, and a large-capacity stacker 111 is also attached so that a large number of copies can be supported.

Also, DADF (Duplex Auto Document Feeder: Automatic Duplex Document Feeder) can be installed, the sorter can be installed with 10/20 bins, and the electronic R
DH (Recycled Document Handler: A device that returns originals to the original feed state and automatically repeats original feeding),
Furthermore, a finisher or the like for stopping the copied one set with a staple can be attached.

(I-2) Features of the system (A) Providing high image quality Users who want to make beautiful copies of pictures, want to make beautiful copies from copy to copy, want to keep image quality during continuous copying, and want to reproduce light colors as they are. In order to meet the demands of the above, this device aims to achieve the photo document reproducibility, the reproducibility of mixed text and photo originals, generation copy quality, image quality maintenance, and single color reproducibility. Image quality compensation, image manipulation, etc. in IIT, and IOT (I
mage Ouput Terminal) controls color reproduction and density.

(B) Creating an active document I want to easily add clarity to a part of the text by copying a halftone or part of the text in color, want to eliminate misalignment, make the operation procedure easy to understand, and express OHP copy in color. , Bold print function, plus 1 color, halftone, color conversion, compositing precision, area designation, control panel operation, color OHP reproduction to meet user's request such as making dirty copy beautiful, adding pages, etc. , Various functions such as delete function and annotation are provided.

(C) Compactification All the paper feed trays can be taken out to the front side, eliminating lateral protrusions, realizing a compact machine that can effectively utilize office space, and minimizing noise generation.

(D) System up This device not only functions as a copier, but also functions as a printer that prints data at any time by combining it with a personal computer, word processor, or workstation. It also has a fax function for sending and receiving. When outputting various image quality information, if the moving speed of the photoconductor varies, the pixel shape of the halftone dots, the pixel spacing, etc. will change, causing a stripe pattern. The image quality is improved by strictly setting it.

(E) Improved operability The fuser has been improved to shorten the warm-up time, make it easier to set the original, and reduce mistakes in the direction in which the original is set. Also, by installing multiple trays, paper conversion is not required, paper can be replenished without removing the cassette, and it is possible to copy without density adjustment by automatic image quality adjustment. The operability is improved with the function of.

(I-3) System Configuration FIG. 4 is a diagram showing the system configuration of this device.

In this machine, the system controller 150 (CPU: 68000, 1001 Kbytes) that controls the entire copying machine, the document image reading IIT controller (8 Kbytes), and the user interface that allows the operator to enter keys 15
3 (CPU: HD64180), IOT to control around Xero
It consists of a controller 152 (30 to 40 Kbytes), and the system controller issues commands to the IIT controller 151 and IOT controller 152 according to the job mode set by the user through the user interface 153. Image reading, image quality compensation, image manipulation, etc. are performed, and the IOT controller 152 modulates the laser light according to the result to form color and black electrostatic latent images on the photoconductor drum, and digital color in the 1P2C system. I am trying to copy images.

(I-4) Hardware Configuration FIG. 5 is a block diagram showing the hardware configuration of the digital copying machine.

The IIT 120 includes a sensor interface 120a, an image quality compensation unit 120b, and an image operation unit 120c. The image signal read by the line sensor 200 is amplified, then A / D converted and converted into a digital signal. The zigzag compensating circuit 203 compensates the deviation of the reading timing in the sub operation direction of the line sensor including a plurality of sensors arranged in a staggered pattern. The RGB signal thus obtained is compensated for the variation in signal intensity due to the light amount variation of the light source in the main operation direction in the RGB spatial compensation circuit 204,
Further, the shading compensation circuit 205 corrects variations in sensor sensitivity. The color separation circuit 206 and the area recognition circuit 207 perform color separation and area recognition from the R, G, B signals, and output a density signal indicating image density, a color flag indicating color or black, and an area signal indicating an image area. To do.
Then, erase the ghost with Ghost Canceller 208,
Further, the digital filter 209 corrects blurring etc., and V
The flag and the image data are corrected through the BC 210, DC 211, and the flag / image data compensating circuit 212, and the image density signal and the color flag signal are passed to the image operation unit 120c. In the image operation unit 120c, the reduction / enlargement processing unit 213 performs image inclination, reduction / enlargement, etc., and outputs an image density signal and a color flag. On the one hand, this output signal
The shadow forming circuit 215, the meshing circuit 216, and the binary multi-value conversion circuit 217 perform processing such as edge enhancement, shadow formation, and meshing, and the signal that has passed through the delay circuit 214 is simply added to the inverter circuit 218 to obtain the density. The signal and color flag are output. At the same time, the VVARID signal, VCLK signal, etc. are output to the IOT. In IOT, TRC (To
ne Reproduction Control: Color correction control circuit 219a, 21
9b is selected, color tone correction is performed depending on whether it is color or black, and the screen generators 220a and 220b convert the gradation toner signal into an on / off binary toner signal. At this time, the output image can be appropriately changed by the ESS 112. Further, color signal data is stored in the gap memory 221 to correct the timing deviation between the first beam exposure and the second beam exposure to prevent image distortion. And ROS (raster output scanner)
The controller 222 modulates a laser beam with a color image signal or a black image signal and irradiates the photosensitive drums with each other to form an electrostatic latent image.

(II) Concentration Control (II-1) Configuration of ADC Sensor FIG. 6A is a diagram showing an ADC (Automatic Density Control) sensor.

The ADC sensor 250 includes a light emitting element 250a and a light receiving element 250b,
The toner image is irradiated with light from the light emitting element, the reflected light is detected by the light receiving element 250b, converted into an electric signal, and amplified.

A reflective sensor that reads specularly reflected light as an ADC sensor,
There are both diffusion type sensors that take good diffused light, but this IOT
The sensitivity of the reflective type sensor using light of wavelength 550 to 900nm is black>blue>green>brown> red in the order of the toner for toner, and the diffusion type sensor is red>brown>green>blue> black in order. Therefore, the diffusion type sensor has a characteristic that it has almost no sensitivity to blue and black. In the present invention, since a single sensor detects the densities of all colors, a diffusion type sensor cannot be used, so a reflection type sensor is used. Red is the most difficult to capture with reflected light, so it is conceivable to use complementary blue light as a light source to increase red sensitivity, but in general, blue LEDs have low power and should be used for sensors. I can't. Therefore, it is conceivable to use a red light or infrared light LED, but since long-wavelength light is easily taken as power, infrared light of 900 nm is used for the sensor in the present invention.

In the case of an infrared photosensor, the amount of reflected light VCL on the clean surface on which the toner is placed and the amount of reflected light VIM on the toner image VIM
The ratio has a characteristic as shown in FIG. 6 (b) with respect to the toner image density, and the toner image change can be seen in the sensor output.

FIG. 7 is a diagram showing the mounting position of the ADC sensor.

As shown in FIG. 7 (a), a plurality of strip fingers 258 are provided in the axial direction so as to face the photoconductor drum 125 so that the paper is not wound around the drum. In this device, the ADC sensor 250 is provided in the gap between the strip fingers. If the strip finger 258 is in a fixed position, it will inevitably damage the photoconductor and develop white or black streaks, so as shown by the arrow in the figure, slowly drive it by a drive mechanism (not shown). It is configured to reciprocate left and right. Therefore, in the present invention, as shown in the cross section of FIG. 7B, the strip fingers 258 are arranged so that the surface of the strip fingers 258 rubs the glass surface of the ADC sensor 250. I try to remove the dirt by cleaning with fingers.

(II-2) Density control method The relationship between the contrast potential and the density (SAD: Solid Area Density) has characteristics as shown in FIG. 8, and the A zone (for example, 28.5 ° C., 85% humidity), the B zone ( 22 ° C, humidity
55%), C zone (eg 10 ° C, humidity 30%),
Mainly changes greatly with humidity. Further, the ADC sensor output ratio (Vpatch / Vclean) with respect to the concentration shows the characteristics shown in FIG. Here, Vpatch is the sensor output voltage when the reflected light from the area (reference patch) on the photoreceptor formed to detect the density is received, and Vclean is the reflected light from the clean surface of the photoreceptor drum. Is the sensor output voltage. The curve becomes D → E as the sensor stains increase.
→ It changes like F, and the sensitivity at high concentration decreases extremely. By the way, the concentration control can detect the value at the target high concentration, but as shown in FIG. 9, the output of the ADC sensor saturates at a high concentration, the sensitivity is extremely lowered, and the detected value varies. Cannot be used for control. Therefore, it is possible to perform more accurate control by keeping the halftone that maintains the linearity between the density and the detected value relatively, for example, a density of about 0.7 at a certain density range. Therefore, Vpat in halftone
The ch / Vclean is controlled so as to fall within a predetermined range so that the change in the intended higher concentration falls within the predetermined range.

As shown in FIG. 10, the ADC patch is formed at the position 20 mm away from the image section 240 at the end of the job.
20 × 25mm color image patch 241 by the exposure beam of
Further, a black patch 242 of the same size is formed by the second exposure beam at a position 20 mm away from the patch 241 in the sub operation direction.

FIG. 11 is a diagram showing a schematic configuration in the ADC control system of the present invention.

The reference patch formed on the photoconductor by the ADC sensor 230 and the clean surface of the photoconductor are irradiated with light from the light emitting element 230a as shown in FIG. 6A, and the reflected light is received by the light receiving element.
230b is detected and converted into an electric signal, the detection signal from each patch is sampled a predetermined number of times, for example, 6 times, and Vpatch and Vclean are calculated from the average of four data excluding the maximum value and the minimum value of the sampling data. The voltage ratio calculation unit 225a of the sequence controller 225 obtains Vpatch / Vclean. It takes about 5 seconds for the light quantity to stabilize after the LED is turned on, so sample after the light quantity stabilizes. Furthermore, if necessary, the light emitting element 230a
Is turned off, the dark current of the light-receiving element 230b flowing at this time is obtained, and the voltage ratios for color and black are calculated by the following equations, respectively, whereby the sensitivity can be further enhanced.

Bias control unit 225b based on the value of Pcolor
Controls the bias of the first developing machine. First
Bias control only for the developing machine
This is because in the 1P2C method, if the toner is too thick on the first developing machine, the image will be disturbed when the image surface is rubbed again with the brush of the mag roll in the second developing machine. This is because there is no further rubbing with a Magroll brush.

In addition, Pcolor, Pb are controlled by the dispense control unit 225c.
Based on the lack value, the dispense motor ON time of each of the first developing device 126 and the second developing device 127 is controlled to control the toner concentration (TC) in the developing device. Also AD
Ccolor control unit 225d allows Pcolor, Pbl
It controls the ADC drive circuit 231 based on the value of ack to control how often ADC is performed, creates more ADC patches than necessary, and increases the burden on the cleaner to scrape off the toner on the patches. Prevent.

Since the density tends to be high immediately after the power is turned on, bias control is performed on the first developing machine to avoid image disturbance, and the dispense control is normally set to a value that is far from the previous control. No feedback control is done because it is not. However, since the density fluctuation is likely to occur, the ADC interval is set to the shortest so that the ADC control is performed frequently.

Next, the bias control, the dispense control, and the ADC interval control according to the values of Pcolor and Pblack will be described in more detail with reference to FIG.

FIG. 12 (a) shows the control in the case of color, and FIG. 12 (b) shows the control in the case of black. TH _C-3 (THb _-3 ) ≤ Pcolor
Feedback control when (Pblack) <TH _C-1 (THb _-1 ), Pcolor (Pblack) <TH _C-3 (THb _-3 ), Pcol
When or> TH _C-1 (THb _-1 ), it is the open loop control. TH _C- n and TH b _- n are threshold values that are variable in NVM. However, in the case of black, image distortion does not occur, so bias control is not performed with a fixed bias of Bb _-1 (-400V). Pcolor, (Pblack) <THc _-3 (T
If Hb _-3 ), Pcolor (Pblack)> TH _C-1 (THb _-1 ), the density is extremely high or thin, and it is possible that some cause such as sensor contamination or developing machine failure has occurred. , It is difficult to return to the normal output density with the feedback control. Therefore, by setting the fixed bias and the dispense time per page to the medium value T _DC-1 , it is possible to make a reasonable copy of the image quality. On the other hand, the ADC interval should be the shortest, and only the check should be performed frequently. Pcolor (Pblack)
Is monitored and TH _C-3 (THb _-3 ) ≤ Pcolor (Pblack) <TH
_{When it} becomes _C-1 (THb _-1 ), it returns to the feedback control.

Bias control in the case of color is Bc = A ×
It is based on Pcolor + B (A = -1.7, B = -250). This means that the large Pcolor means that the density is low, and the bias value is increased in proportion to the low density to increase the amount of toner transferred to the photoconductor so that the patch density becomes constant. The fixed bias values B _C-2 and Bb _-1 of -400 V for Pcolor <TH _C-3 , Pcolor> TH _C-1 and for black are because the development density is too low when the absolute value of the bias is too low. This is because the carrier may not be removed and the carrier may be developed, and if the carrier is raised too much, the background is developed and a so-called fogging phenomenon occurs. In the case of color, since the density tends to increase immediately after the power is turned on, the bias control is performed on the first developing machine in order to avoid image disturbance.

Dispense control is TH _C-2 (THb _-2 ) ≤ Pcolor (Pblac
When k) <TH _C-1 (THb _-1 ), the reference time per page is T
_DC-2 (T _D b _-2 ), TH _C-3 (THb _-3 ) <Pcolor (Pblack) <T
T _DC-3 (T _D b _-3 ) for H _C-2 (THb _-2 ) (T
Set _DC-2 (T _D b _-2 )> T _DC-3 (T _D b _-3 )) to set the reference time in two steps for low and high concentrations to improve responsiveness. There is. Immediately after the power is turned on, the values are not so far apart by the control up to the previous time, so set it to a medium value T _DC-1 so that a reasonable image quality can be obtained.

Next, the calculation of the dispense time will be explained.
The standard dispense time per page fed back by, that is, T during feedback control
_DC-2 (T _D b _-2 ) or T _DC-3 (T _D b _-3 ), T _DC-1 (T _D b _-1 ) during open loop control, and 1 page depending on the size of paper being printed The dispense time per hit is calculated as follows for color and black respectively.

_{T DC = T DC + α ×} T DC- n, T D b = T D b + α × T D b - n, a. Here, T _DC- n and T _D b _- n are both T _DC-1
(T _D b _-1 ) is normal, 1.5 seconds, T _DC-2 (T _D b _-2 )
Is 3.0 seconds for long and T _DC-3 (T _D b _-3 ) is 0.5 seconds for short. α is 1 for paper size A3, B4 is 0.67, A4 is
For example, 0.5 and postcards are 0.125, and the dispense time is added every time one page is copied. If the toner consumption is large, the dispense time is lengthened. The dispense motor is rotated at the timing of the developing machine ON for the dispense ON time calculated in this way, and toner is supplied from the toner cassette to the developing machine only while the developing machine motor is ON. The remaining dispense motor ON time at this time is T _DC = T _DC − (color dispense motor ON time) T _D b = T _D b − (black dispense motor ON time), and based on this value, the next dispense motor The ON time will be calculated. It should be noted that the reason why the dispense motor is rotated only while the developing machine motor is ON is that if the developing machine is stopped and the toner is being dispensed, the toner will accumulate excessively in some places inside the developing machine. This is because when it is developed, the density may suddenly change or the inside of the machine may become dirty as a cloud, and if the developing machine motor is running, the toner will remain with the carrier even if dispensed. This is because there is no sudden change in concentration or cloud formation as it is supplied without condensation. This means that when the toner consumption is large, for example, one page is printed in two seconds, but the calculated dispense time is five.
There is a possibility that it will be for a second, and if dispensing is performed as calculated, the developing machine motor will stop about one second after completion of printing, but will continue to dispense.

In the present invention, ICDC (Im
age Counting Density Control). Since the present invention is a digital copying machine, the image data is represented as "1" and "0" data, and the toner consumption amount can be determined by counting the "1" points. The toner control can be performed based on In the present invention, one line is sampled for every 25 lines, and the data there is counted to predict the toner consumption amount on the entire surface. In this case, for example, the toner consumption amount can be predicted completely by providing six gradations of density grades 1 to 6 and integrating all of them, but the present invention requires a large number of counters. In order to reduce the number of, for example, only the number of grade 5 or higher is counted. And although there are only two methods, full dispense or nothing, with ADC alone, by using ICDC to count the number of reference dots, it is possible to predict how much toner was consumed for each copy.
The reference dispense time can be made variable. In this case, the number of dots having a certain density or higher may be integrated, and when the number of reference dots is reached, the dispense motor may be rotated by the time determined by the ADC, or the number of reference dots may be changed by the ADC.

To explain the ADC sampling interval, the number of prints after the previous ADC patch was created is added up for each color,
After this value exceeds PV-n, an ADC patch will be created at the job end or when the first duplex color development is completed. P
color (Pblack) <TH _C-3 (THb _-3 ), TH _C-1 (THb _-1 ) ≤ P
PV-1 (30P / V at the time of open loop of color (Pblack)
(Print Volume) takes a relatively long interval and frequently creates ADC patches to reduce the load on the cleaner. TH _C-2 (THb _-2 ) ≤Pcolor
(Pblack) <TH _C-1 (THb _-1 ), THb _-3 (THb _-3 ) ≤ Pcolor
When (Pblack) <TH _C-2 (THb _-2 ) feedback control is used, PV-2 (10P / V) is used to quickly increase the density when the density is low, and toner is reduced when the density is high. Since it is not possible, set the ADC interval to PV-1 (30P / V) and lengthen the ADC interval to reduce the toner supply amount.
Also, since the concentration tends to be high when the power is turned on, go to 5P / V most frequently so that the proper concentration can be obtained early. These TH _C- n, B _C- n, T _DC- n, PV-
The value of n is stored in NVM so that it can be changed in diagnostic mode.

(II-3) Structure of Developing Machine FIG. 13 is a view showing a wearable toner cartridge used in the present invention.

The cartridge 280 is provided with a coupling gear 281. When the cartridge is mounted on the machine, the gear 281
Is connected to a transmission system driven by the dispense motor 300, and an agitator 282 provided inside is driven, and the cartridge also serves as a toner box. The toner agitated and supplied by the agitator 282 is supplied to the auger 284 through the communication port 283 and further supplied to the developing machine main body through the communication port 285. In this way, the cartridge can be mounted on the machine and used as the toner box, so that the operability can be improved.

FIG. 14 is a diagram showing the structure of the developing device.

In the present invention, since the 1P2C method is adopted, which makes it possible to copy an image of two colors with one rotation of the drum,
It is characterized in that a developing machine 126 (color developing machine) and a second developing machine 127 (black developing machine) are provided. The 1P2C method develops, transfers, and fixes the paper once, then develops it again,
The 2P2C method, which produces color and black by transferring and fixing, was developed because copying takes time.

Since the photoconductor 125 forms a latent image with a laser,
If there is no sensitivity around nm, only the power is required for latent image formation, so a photoconductor that is sensitive to infrared is used. To write on the photoconductor, divide the laser light from the two laser light sources, scan with a polygon mirror, and scan the first laser beam.
271 and the second laser beam 272 is applied to the photosensitive member.

The first developing device 126 has an agitator 126a and a dispense auger 126b. The toner dispensed by the agitator and auger is mixed with carrier beads and toner by three augers 126c, and is adjusted by a trimmer 126e to be exposed by a mag roll 126d. Supplying toner to the body surface. Further, the second developing device 127 includes an auger 127a, two paddles 127b.
Toner is supplied to the mag roll 127d, and the trimmer 12
Black toner is supplied to the photoconductor while adjusting the supply amount with 7c. It should be noted that the first developing device performs reverse development, the second developing device performs normal development, and the second developing device performs (+)
Since the toner and (-) carrier are used and there is currently no good quality (-) carrier, the catch-up roller 12
7e is provided to prevent development by the carrier.

The pre-transfer corotron 252 uses (−) toner and (+) toner that have undergone reversal development and normal development by corona discharge
Convert the polarity of the electric charge of the toner and make it uniform to equalize the electric potential,
It works to facilitate the transfer of toner to paper. The baffle plate is designed so that the right end side in the figure can be lowered to remove the paper when a paper jam occurs. The transfer corotron 256 transfers the toner to the paper side, and the detack corotron 257 functions to peel the paper from the photoconductor. The strip finger 258 has a function of peeling the paper that has not been peeled by the Detac Corotron 257 so that the paper is not wound around the photoconductor. An ADC sensor 230 is provided at the strip finger 258 as shown in FIG. 7 (a). The brush 259 cleans the toner on the photoconductor, and the scraped toner is collected by the toner collecting device 260. Further, the charge remaining on the photoconductor is erased by the irradiation of the charge eliminating lamp 261.

Next, the toner development in the 1P2C system will be briefly described with reference to FIG.

The photoconductor 125 is uniformly charged to, for example, −700 V by the scorotron 251 (step). Then the first laser beam 27
The first exposure is performed by 1 and the potential of the exposed portion becomes, for example, −100 V (step). The electrostatic latent image thus formed is negatively charged and reverse-developed by setting the bias potential of the first developing device to about -450V. Next, when the second exposure is performed including the portion already developed by the second laser beam 272, the unexposed portion is-
Since it remains as a potential of 700 V, it is developed by the second developing machine and is normally developed by the (+) toner (step,). In this way, the (-) toner and the (+) toner are left on the photoconductor, and the toner cannot be transferred to the paper as it is. Therefore, the (+) corona discharge is uniformly applied by the pre-transfer 252 to make the first transfer. The potentials and charge polarities of the first toner image and the second toner image are made uniform (step). Then, the register gate solenoid 253 is operated at a predetermined timing to open the register gate 254, the electrostatic latent image and the sheet are made to coincide with each other at the baffle plate (transfer blade) 255, and the transfer corotron 256 transfers the toner image to the sheet. Then, the paper is peeled off by the Detack Corotron 257 and supplied to a fixing unit (not shown) (step).

[II-4] Software Configuration FIG. 16 is a diagram showing the software configuration.

The concentration control of the present invention is performed by the ADC module, and its configuration is as shown in the figure. The time management processing unit 350 controls the timing of ADC processing, and notifies each unit of operation timing. The patch creation processing unit 352 creates a reference patch for color and black by ON / OFF controlling the first exposure beam 271 and the second exposure beam 272 at a position apart from the image by a predetermined distance. AD
The signal read by the C sensor 230 is processed by the ADC sensor sampling processing unit 356 at the timing notified by the time processing unit 350.
6 times, the average value is obtained and the ratio of the voltage between the patch portion and the clean surface is calculated. The open loop OR feedback judgment processing unit 351 judges whether it is an open loop or feedback by referring to the obtained voltage ratio and upper limit lower limit value table 359, and the ADC interval change processing unit 353, bias calculation processing unit 354, dispense ON time Each instruction is given to the arithmetic processing unit 356. The ADC interval change processing unit 353 drives the ADC sensor at an interval according to the obtained voltage ratio and immediately after the power is turned on. The bias calculation processing unit 354 calculates a bias value according to the voltage ratio, and the bias change processing unit 358 controls the bias of the first developing device 126 according to the result and applies a fixed bias to the second developing device. Output.
The dispense motor ON time change processing unit 356 calculates the dispense motor ON time according to the reference dispense time according to the voltage ratio and the paper size, and based on this result, the dispense motor ON processing unit 359 determines whether the developing machine motor is ON. Only the first dispense motor 300a and the second dispense motor 300b are driven to control the toner density.

[II-5] Timing Chart FIG. 17 is a timing chart in ADC control, in which the horizontal axis represents time and the vertical axis represents processing at each angular position around Xero. The process speed is
It has a diameter of 160.045mm and a drum diameter of 84mm.

FIG. 17 (a) is a timing chart when the power is turned on. After turning on the power, the main motor will
When turned on, the photoconductor is uniformly charged at the position of the charge corotron (CC). Irradiation with the first exposure beam is performed at the first exposure position to form a color reference patch. Color development is performed on the formed reference patch at the first developing machine position. Further, at the second exposure beam position, the black reference patch is formed by irradiating the entire surface except for the black patch, and the patch is developed by the second developing machine. The catch-up roll stops after the second developing machine is turned off. When the color reference patch and the black reference patch reach the position of the ADC sensor, the color reference patch and the black reference patch are sampled 6 times, respectively, and similarly on the clean surface where no image is formed, 6 Sampling is performed once. Discard the maximum value and the minimum value of the data obtained with the color reference patch and the black reference patch, calculate the average of the remaining four, calculate Vpatch / Vclean, and according to the calculation result, bias control, dispense control, The ADC interval is controlled. After sampling is completed, the main motor turns off. The LED is off immediately after the clean surface sampling.

FIG. 17 (b) is a timing chart at the end of the job. A color patch is formed at the first exposure position on the part charged by CC (position after the image), and reversal development is performed with the first developing machine turned on, and then black at the second exposure position. Forming a patch for normal development with the second developing machine ON. The ADC sensor samples color patches, black patches, and clean surfaces in the same way as when the power is turned on, and then turns off the main motor.

[II-6] Process Flow FIG. 18 is a diagram showing an ADC main flow in the 1P2C system.

Even in the 1P2C method, monochrome copying is possible without installing a color developing machine, so if the color developing machine is not installed, turn off the first ROS (raster output scanner) and check whether the machine power is on. Since the ADC patch creation interval differs depending on whether or not the processing is different, ADC control is performed at the time of printout for each specified number of sheets, or at the end of one job when the specified number of sheets is exceeded, unless the machine power is turned on. If no color or black copy has been made since the last ADC patch was created, the process will end without performing ADC control, and the ADC process will be performed at the end of a specified number of sheets or at the end of a job that exceeds a specified number of sheets (step 1001
~ 1004).

Whether the ADC processing is immediately after power is turned on, the ADC processing is
By applying a voltage to the sensor, color and black reference patches are created by the first exposure and the second exposure, respectively, and the color, black, and clean surfaces are sampled while the light emission of the light emitting element of the ADC sensor is stable. Furthermore, the light emission of the light emitting element is stopped, the dark current of the light receiving element is sampled, and based on these values, and (Steps 1005 to 1010, Steps 1014 to 101)
9). Based on these calculated values, in steps 1011 to 1013, bias control of the first developing device is performed to prevent the toner from being overly thick so as to prevent image disturbance, and dispense feedback to each developing device. The toner supply is controlled by performing the feedback of the ADC interval. Also, step 10
In Nos. 20 to 1022, the bias feedback is similarly performed to the first developing machine, and since the power has just been turned on.
Read the data stored in NVM, input the desired dispense value to the first and second developing machines, and then AD
Enter the desired value for the C interval.

FIG. 19 is a diagram showing a processing flow of forming a reference ADC batch on the drum when the power is turned on, developing it, and sampling the ADC output value of this patch.

First, a reference solid patch is created, and whether it is in the two-color mode or not is sorted, and in the single-color mode, processing corresponding to black and color is executed (steps 1200 to 1204). In the 2-color mode, the color and black reference patches are formed, and then the ADC sensor output sampling is performed and the output value (Vblack
Vcolor) is stored (steps 1205 to 120)
7). Similarly, in the case of monochromatic black, a black reference patch is formed, A
The DC sensor sampling output value is stored, and the same processing is performed in the case of a single color (steps 1208 to 12).
13). Next, the clean surface is sampled and the value is stored, and the light emitting element of the ADC sensor is turned off to measure the dark current and the value is stored (steps 1214 to 1216).

In addition, in each sampling, 6 times every 10 msec,
The maximum value and the minimum value are deleted, and the remaining four average values are used as output values. The output voltage ratio of the patch surface for each color is calculated from the obtained values (steps 1217 to 121).
9) In the two-color mode, footback is performed on the first developing machine and the second developing machine. Bias control is performed only for the first developing machine, density control and dispense time control, and ADC interval is performed for the first and second developing machines (steps 1220, 1).
221). In the black monochromatic mode, the dispense time, the dispense control, and the interval control for the second developing machine are performed, and in the color monochromatic mode, the bias control, the dispense control, and the ADC interval control are performed (steps 1222 and 1223).

FIG. 20 is a diagram showing a processing flow for performing bias control, dispense control, and ADC interval control according to Pcolor and Pblack described in FIG.

FIG. 20 (a) shows a processing flow in the case of color,
As described in FIG. (A), TH _C-1 ≤ Pcolor, TH
_C-2 ≤ Pcolor <TH _C-1 , TH _C-3 ≤ Pcolor <TH _C-2 , Pcolor <
Bias setting, dispense control, and ADC interval control are performed according to TH _C-3 .

FIG. 20 (b) shows the flow in the case of black, and since it has a fixed bias as described in FIG. 12 (b), THb during open loop of pblack <TH _C-3 and THb _-1 ≤Pblack. Dispense control and ADC interval control are performed according to _-2 ≤ Pblack <THb _-1 , THb _-3 ≤ Pblack <THb _-2 .

FIG. 21 is a diagram showing an operation flow of ADC initial setting.

ADC initial setting is at machine shipment and X
This is done by the manufacturer or system engineer when replacing the ero module. For the clean side, the ADC patch output voltage value at the target copy density is stored in the machine. This is when setting the control point for each machine,
Since it takes a very long time to set the target density, it is intended to simplify the setting operation by storing this in the NVM of the machine in advance.
First, a voltage is applied to the ADC sensor, and then the first developing machine (color) or black is selected in the single color mode by the designated diagnostic (steps 1501 and 1502). Then create a reference patch,
_PATCH is sampled for each color and black,
Further, Vclean and dark current Vdark are sampled respectively (steps 1504-1506). Then, the patch relative voltage is calculated, and the result is stored in NVM as TH _R2 . Based on this value, color and black are multiplied by appropriate constants to set other reference values. Note that if the smooth surface of the drum is peeled off in advance to form a rough surface, this part will show characteristics similar to toner, so an EPROM is installed in the photoconductor module and the reflected light detection values V _PATCH and Vclean on the smooth and rough surfaces If it is stored, it is possible to simplify the setting of the initial value.

〔The invention's effect〕

As described above, according to the present invention, in the 1P2C method, separate control is performed for each color and black, and high quality 2
It is possible to obtain a color image, improve reliability, reduce cost, and improve operability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a density control system of the present invention, FIGS. 2 and 3 are schematic diagrams of a copying machine to which the present invention is applied, and FIG. Shows a system configuration of the present invention, FIG. 5 is a block diagram showing a hardware configuration, and FIG. 6 is an AD.
FIG. 7 is a diagram showing the configuration of the C sensor, FIG. 7 is a diagram showing the mounting position of the ADC sensor, FIG. 8 is a diagram showing the relationship between contrast potential and density, and FIG. 9 is a diagram showing the relationship between Vpatch / Vclean with respect to density. FIG. 10 is a diagram for explaining formation of an ADC patch, FIG. 11 is a diagram showing a configuration of an ADC control system of the present invention, FIG. 12 is a diagram for explaining a method of density control, and FIG. 13 is FIG. 14 is a diagram showing a wearable toner cartridge used in the present invention, FIG. 14 is a diagram showing a configuration of a developing device, FIG. 15 is a diagram for explaining toner development in the 1P2C system, and FIG. 16 is a software configuration. Figure, Figure 17
FIG. 18 is a diagram showing a timing chart in ADC control, FIG. 18 is a diagram showing an ADC main flow in the 1P2C system, FIG. 19 is a diagram showing a process flow in a two-color mode and a single color mode, and FIG. 20 is a process in a color density control. FIG. 21 is a diagram showing a flow, and FIG. 21 is a diagram showing a processing flow in the black density control. 1 ... Concentration control means, 2 ... Detection means, 3 ...
Developing means.

Claims (12)

[Claims] 1. An optical density detecting means for a developing portion and a non-developing portion on an optical density reference surface formed on a photoconductor, a first developing means and a normal rotating means for performing reversal development based on the detected optical density. And a density control unit having a developing bias control unit, a toner supply control unit, and a density detection interval control unit for controlling the density by controlling the second developing unit to perform the density control at the end of recording a predetermined amount or at a predetermined amount. The density control method of the recording device is characterized in that when the number of jobs exceeding the limit is selected, it is performed at the end of the job. 2. The developing bias controller is powered on.
At the time and when the optical density ratio of the developing portion and the non-developing portion of the optical density reference surface is within the predetermined range, the developing bias of the first developing means is controlled according to the optical density ratio, and the optical density ratio is within the predetermined range. 2. The density control system according to claim 1, wherein the first developing means and the second developing means are set to a fixed bias when outside. 3. The density control system according to claim 1, wherein the developing bias control section sets the second developing means to a fixed bias. 4. The density control method according to claim 1, wherein the toner supply control unit calculates the toner supply time by adding the toner supply reference time corrected according to the paper size for each recording. 5. The density control method according to claim 1, wherein the toner supply control unit calculates the toner supply time by obtaining the toner consumption amount by the number of pixels having a predetermined density or more. 6. The density control method for a storage device according to claim 4, wherein the toner is supplied only when the developing machine is operating based on the calculated toner supply time. 7. The next toner supply time is calculated by adding the toner supply reference time for each recording to the time obtained by subtracting the actual toner supply time from the calculated toner supply time. Item 4. The concentration control method according to item 4. 8. The toner supply control section, when the optical density ratio in the developing section and the non-developing section of the optical density reference surface is within a predetermined range, the toner supply control section determines whether the optical density ratio is larger or smaller than a specified value. The toner supply reference time of the developing means and the second developing means is made different, and the toner supply reference time of the first developing means and the second developing means is fixed when the power is turned on and when the optical density ratio is out of a predetermined range. The density control method according to claim 4, wherein 9. A density detection interval control unit,
When the optical density ratios of the developing portion and the non-developing portion of the optical density reference surface are within a predetermined range, the density detecting intervals of the first developing means and the second developing means are determined depending on whether the optical density ratio is larger or smaller than a specified value. 2. When the optical density ratio is out of a predetermined range, the density detection intervals of the first developing means and the second developing means are fixed.
The density control method of the recording device described. 10. The density control system according to claim 1, wherein the density detection interval control section minimizes the density detection interval of the first developing means and the second developing means when the power is turned on. 11. The optical density ratio of the developing portion and the non-developing portion is within the prescribed range even when the open density is controlled when the optical density ratio of the developing portion and the non-developing portion of the optical density reference surface is outside the prescribed range. The concentration control method according to claim 1, wherein whether or not it is monitored. 12. The density control system according to claim 1, wherein a rough surface is formed on the photoconductor, and the rough surface is used as a developing portion on the optical density reference surface.