JP3002278B2 - Digital image forming equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital image forming apparatus such as a digital copying machine and a printer.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus having a developing device for developing an electrostatic latent image on a photoreceptor with a two-component developer composed of a toner and a carrier, the toner concentration of the developer is made uniform, and charging is performed. It is necessary to stir the developer in order to bring the amount to a predetermined value. For this reason, in the developing device, the position where the toner is supplied and the position where the electrostatic latent image is developed are separated. Therefore, there is a time lag until the supplied toner contributes to the development. Therefore, conventionally, in order to compensate for a decrease in toner density due to toner consumption due to development, an image density after development on a photoreceptor is measured and toner is supplied when the measured value is lower than a predetermined value, An apparatus that detects toner density by a toner density detector provided in a developing device and replenishes toner when the toner density becomes low is used. Japanese Patent Application Laid-Open No. Sho 60-49362 discloses that in an electrophotographic apparatus having a scanning beam type exposure apparatus, a counting means for counting black data included in an image signal for modulating a scanning beam, A toner density detecting means for detecting a toner density, and a toner replenishing means for controlling toner replenishment to a developing unit based on a count result of the counting means and a detection result of the toner density detecting means are provided, Specifically, the black data is counted, and if the toner density is lower than a predetermined value, the toner is replenished in a fixed amount so that the toner concentration becomes a predetermined value. Are described. JP-A-1-244481 discloses that in an image forming apparatus, a toner conveying unit is operated in synchronization with an image signal to be developed, and the toner conveying unit is operated after a predetermined time has elapsed after the input of the image signal is stopped. What is stopped is described. More specifically, it is described that the toner conveying unit is operated at the head of a page of an image on which an image is to be formed, and is stopped after a predetermined time from a signal at the rear end of the page. U.S. Pat. No. 4,875,078 discloses that in an image forming apparatus, the density of an image formed on a photoreceptor by charging, exposure, and development is detected, and the detection result is compared with the target image density. A feedback control system for controlling toner replenishment so as to eliminate the difference and adding a function of compensating a dead time (dead time) at the time of toner replenishment to the feedback control system is described. In order to compensate for this, the difference between the detected toner concentration value and the target value and the toner replenishment amount at that time are stored in a table as time-series data, and the past data for the dead time is extracted from the table. Based on P
It is described that by performing I control, a toner replenishment command that compensates for a dead time is output and the toner density is stabilized at a target value.

[0003]

Conventionally, an image forming apparatus measures an image density after development on a photoreceptor and replenishes toner when the measured value becomes lower than a predetermined value. The toner density detector provided in the printer detects the toner density and replenishes the toner when the toner density decreases.However, there is a time delay from the toner replenishment to the contribution to the development. Alternatively, due to the time delay required from the replenishment of the toner until the toner is agitated and the toner concentration of the developer becomes uniform, the recovery of the toner concentration of the developer used for development is delayed even if the toner is replenished. During this delay, the electrostatic latent image is developed with a developer having a low toner density, and the toner density remains low. Also, the longer the delay time and the greater the amount of toner consumed during the delay time, the greater the drop in toner density. Conventionally, the number of tones to reproduce an image was not so large, and the developing device was large and the amount of toner inside was large. Since it served as a buffer that the concentration did not decrease, it was not recognized as a major issue. However, with the demand for downsizing of the image forming apparatus, the downsizing of the developing apparatus has progressed, and the buffer effect due to the large capacity cannot be expected much. In digital copiers, multi-level images are written much more than conventional analog copiers by processing electric signals. Particularly recently, multi-level image data is written for each pixel even at a write density of about 400 dpi. As a result, both the gradation and the resolving power have been improved. In order to faithfully reproduce this, it has become necessary to stabilize the toner density with higher precision than before.

In the electrophotographic apparatus described in Japanese Patent Application Laid-Open No. Sho 60-49362, the position at which the toner replenishing means replenishes the toner and the position at which the developing unit develops the photoreceptor are separated from each other. In order to use the toner for development, the wasted time required to send the toner from the replenishing position to the developing position by the agitating / conveying mechanism, and the toner concentration gradually increases when the replenished toner reaches the developing position after the elapse of the dead time There is a delay time due to the phenomenon of going up. In order to control a system with such dead time and delay time with high accuracy,
It is necessary to perform control to cope with the delay. However, since control for dealing with the delay is not performed, fluctuations in toner density cannot be sufficiently stabilized. The image forming apparatus described in JP-A-1-244481 operates a toner conveying unit in synchronization with an image signal to be developed, and stops the toner conveying unit after a predetermined time has elapsed after the input of the image signal is stopped. It is not to replenish the toner according to the amount of toner consumed, but to replenish the toner quantitatively according to the so-called number of copies, so that the balance between the amount of toner consumed and the amount of replenishment can be achieved. However, stabilization of the toner concentration cannot be expected. The image forming apparatus described in U.S. Pat. No. 4,875,078 detects the density of an image formed on a photoreceptor and replenishes toner so that there is no difference between the detection result and the target image density. Is added with a function of compensating for the dead time at the time of toner replenishment to the feedback control system for controlling the toner concentration. Therefore, data of toner consumption, which is one of the major factors for determining the toner density, is not used. Therefore, even if the data which is retroactive to the dead time is used, if the amount of toner consumed during this period differs from the amount of toner consumed during the dead time period after replenishment, the toner density fluctuates. In other words, a control system that compensates for the dead time is used on the assumption that the toner consumption does not change. In an actual copying machine, an image portion represented by applying toner to transfer paper greatly differs depending on a document to be copied. For example, most are white and have a little text, while others are almost black, and there is a range of areas where the toner adheres, ranging from less than 1% to nearly 100%. I do. The same applies to printers.
Since the fluctuation of the toner consumption is not directly detected as a control parameter in this control system, it acts as a disturbance of the system, resulting in deterioration of control accuracy, that is, fluctuation of toner density. SUMMARY OF THE INVENTION It is an object of the present invention to provide a digital image forming apparatus which can solve the above-mentioned disadvantages, stabilize the toner density with higher precision, and form a high quality image.

[0005]

In order to achieve the above object, the invention according to claim 1 includes a recording medium that is moved,
Writing means for writing digitally expressed image data on the recording body to form an electrostatic latent image, and developing means for supplying toner to a developer by a toner supply command and developing the electrostatic latent image with the developer. A digital image forming apparatus comprising: a toner consumption estimating unit for estimating a toner consumption amount by counting digitally expressed image data to be written on the recording medium; and a toner for detecting a toner concentration of a developer in the developing unit. Density detection means, feedback control means for comparing the detected value of the toner density detection means with a target value and issuing a first toner supply operation amount based on the comparison result, and comparing the predicted value of the toner consumption amount prediction means with the predicted value Feedforward control means for issuing a second toner supply operation amount based on the result; And a control means for issuing a toner replenishment command by chromatography replenishment operation amount is a control loop initiation interval of the feed-forward control means those narrowed from the control loop initiation interval of the feedback control means.

According to a second aspect of the present invention, in the digital image forming apparatus according to the first aspect, when the image forming cycle is stopped due to an abnormality during the image forming, the toner consumption is preceded by the toner supply command by the developing means. A toner replenishing amount correcting means for correcting the amount of unconsumed toner among the replenished toner with respect to the toner replenishing amount at the time of toner replenishment after recovery from the abnormality.

According to a third aspect of the present invention, there is provided a recording medium to be moved, writing means for writing digitally expressed image data on the recording medium to form an electrostatic latent image, A developing means for developing the electrostatic latent image with a developer supplied to the recording medium, and counting the digitally expressed image data to be written on the recording medium to estimate the toner consumption. Predicting means, control means for issuing a toner supply command based on a predicted value of the toner consumption predicting means based on image data corresponding to the electrostatic latent image earlier than the developing means develops the electrostatic latent image, and When the image forming cycle is stopped due to an abnormality during the formation, the toner supplied by the developing unit prior to the consumption of the toner according to the toner supply command. The amount of toner unconsumed, in which a toner supply amount correcting means for correcting the toner replenishing amount during toner replenishment after returning from the abnormal.

According to a fourth aspect of the present invention, there is provided a recording medium to be moved, writing means for writing digitally represented image data on the recording medium to form an electrostatic latent image, A developing means for developing the electrostatic latent image with a developer supplied to the recording medium, and counting the digitally expressed image data to be written on the recording medium to estimate the toner consumption. Prediction means; toner concentration detection means for detecting the toner concentration of the developer in the development means; and toner consumption by image data corresponding to the electrostatic latent image earlier than the development means develops the electrostatic latent image. Control means for issuing a toner supply command based on the predicted value of the amount predicting means and the detected value of the toner density detecting means; When the toner stops, the amount of unconsumed toner among the toner replenished prior to toner consumption by the toner replenishment command by the developing unit is changed to the toner replenishment amount at the time of toner replenishment after recovery from the abnormality. And a toner replenishing amount correcting means for correcting the toner supply amount.

According to a fifth aspect of the present invention, there is provided a recording medium to be moved, writing means for writing digitally expressed image data on the recording medium to form an electrostatic latent image, A developing means for developing the electrostatic latent image with a developer supplied to the recording medium, and counting the digitally expressed image data to be written on the recording medium to estimate the toner consumption. Predicting means, toner concentration detecting means for detecting the toner concentration of the developer in the developing means, and comparing the detected value of the toner concentration detecting means with a target value to determine the first toner supply operation amount based on the comparison result. Feedback control means for issuing a second toner supply operation amount based on the predicted value of the toner consumption amount estimation means and the comparison result. Word control means, control means for issuing a toner replenishment command based on the first toner replenishment operation amount and second toner replenishment operation amount, and toner when the image forming cycle is stopped due to an abnormality during image formation. Toner supply amount correction means for correcting the amount of unconsumed toner among toner replenished prior to toner consumption by a replenishment command with respect to the toner replenishment amount at the time of toner replenishment after recovery from an abnormality. It is provided.

[0010]

According to the first aspect of the present invention, the toner consumption estimating means counts digitally expressed image data to be written on the recording medium to estimate the toner consumption, and the toner density detecting means uses the developer in the developing means. Is detected.
The feedback control means compares the detection value of the toner density detection means with the target value and issues a first toner supply operation amount based on the comparison result, and the feedforward control means compares the predicted value of the toner consumption prediction means with the comparison result. Based on the second
Is issued. The control unit issues a toner supply command based on the first toner supply operation amount and the second toner supply operation amount, and the control loop activation interval of the feedforward control unit is narrower than the control loop activation interval of the feedback control unit.

According to a second aspect of the present invention, in the digital image forming apparatus according to the first aspect, the toner replenishment amount correcting means is provided with a toner replenishment command by the developing means when the image forming cycle is stopped due to an abnormality during image formation. The amount of unconsumed toner among the toner replenished prior to toner consumption is corrected with respect to the toner replenishment amount at the time of toner replenishment after recovery from the abnormality.

According to the third aspect of the present invention, the toner consumption predicting means counts digitally expressed image data to be written on the recording medium to predict the toner consumption, and the control means controls the developing means to generate the electrostatic latent image. A toner replenishment command is issued earlier than development based on a predicted value of the toner consumption predicting means based on image data corresponding to the electrostatic latent image. When the image forming cycle is stopped due to an abnormality during the image formation, the toner replenishment amount correcting means determines the amount of the unconsumed toner among the toner replenished prior to the toner consumption by the toner replenishment command by the developing means. Is corrected for the toner supply amount at the time of toner supply after recovery from the abnormality.

According to the present invention, the toner consumption amount estimating means counts digitally expressed image data to be written on the recording medium to estimate the toner consumption amount, and the toner density detecting means includes a developer in the developing means. Is detected. The control unit issues a toner replenishment command based on the predicted value of the toner consumption prediction unit based on the image data corresponding to the electrostatic latent image and the detection value of the toner density detection unit before the developing unit develops the electrostatic latent image. When the image forming cycle is stopped due to an abnormality during image formation, the toner replenishment amount correcting means calculates the amount of unconsumed toner among toner replenished prior to toner consumption by the toner replenishment command by the developing means.
Correction is made to the toner supply amount at the time of toner supply after recovery from the abnormality.

According to the fifth aspect of the present invention, the toner consumption estimating means counts digitally expressed image data to be written on the recording medium to estimate the toner consumption, and the toner density detecting means uses the developer in the developing means. Is detected. The feedback control means compares the detected value of the toner density detection means with the target value, and issues a first toner supply operation amount based on the comparison result. The feedforward control means compares the predicted value of the toner consumption amount prediction means with the comparison result. A second toner replenishment operation amount is issued based on this. The control means issues a toner replenishment command based on the first toner replenishment operation amount and the second toner replenishment operation amount, and the toner replenishment amount correction means replenishes the toner with the developing means when the image forming cycle is stopped due to an abnormality during image formation. The amount of unconsumed toner among toner replenished prior to toner consumption in accordance with the command is corrected with respect to the toner replenishment amount at the time of toner replenishment after recovery from the abnormality.

[0015]

FIG . 1 shows an embodiment of the present invention. This embodiment is a digital copying apparatus for identifying mono-color image data from a document and obtaining a two-color hard copy from the image data and black image data. In the reading system 12, a document on the document table is scanned by a light source 13 in a direction orthogonal to the slit while receiving a slit-like illumination. An image is formed on two linear imaging units 14 arranged in a direction parallel to the slit and photoelectrically converted. in this case,
A reflected light image that does not include image data of a predetermined color is formed on one of the imaging units via a transmission type filter 15 of a color to be used to identify the original from the original, and the other imaging unit applies a filter 15 from the original to the original. The reflected light image of the entire band of the light spectrum determined by the illumination light source, the lens, the reflecting mirror and the like is formed without intervention.
The output signal of the imaging unit 14 is separated by the color separation circuit 16 into a monochrome image signal in which all colors are converted into a brightness signal and a color image signal of the filter 15. The two image signals from the color separation circuit 16 are A / D-converted by an A / D converter 17 and, when there is an adjacent pixel between the two image signals in an adjacent pixel removal circuit 18, the adjacent pixel Is converted to blank data, and predetermined image processing is performed by the image processing circuit 19 as needed. The image signal from the image processing circuit 19 is written in a writing system.
The data is written to buffer memories 22 and 23 in an image memory 21 for adjusting the timing with 20. The writing system 20 receives the command signals from the controller 24 and
The image data from 3 is converted into an optical signal at a predetermined timing and written on the photoconductor. The image forming unit 25 is controlled by a controller 26, writes an image on a photoreceptor by electrophotography, develops the image, and transfers it to a transfer paper. The controller 26 exchanges data with the controller 24, thereby sending a timing signal for the writing system 20 to start writing to the controller 24, and controlling the image forming unit 25 to match the timing signal, and A mono-color hard copy corresponding to the color data identified in step 15 is created. The reading system 12, the writing system 20, and the image forming unit 25 are controlled and adjusted in timing by controllers 24 and 26, which are connected to each other via a communication path. Executes each function while sending and receiving under the control of 24,26. The black data counter 27 counts the number of image data (black data on which an image is formed with black toner) from the image processing circuit 19 to the buffer memory 22 from 0 for each page (for each copy), The count result is sent to the controller 24 as prediction data of the toner consumption.

FIG. 6 shows a part of the reading system 12 in this embodiment. The reflected light from the original on the platen is an imaging lens
2 with a half mirror 29 on the interface
The light enters the prisms 30 and 31 and is split by the half mirror 29 into transmitted light and reflected light. After the transmitted light and the reflected light are totally reflected by the prisms 30 and 31, they are imaged on charge-coupled devices (CCDs) 32 and 33 constituting the imaging unit 14. CCD33
A filter 15 of a color to be used for identifying a document is inserted in front of. As the filter 15, when the color of the document to be identified is, for example, red, a red absorption filter is used. Here, an advantage of using two prisms 30, 31 is that the CCDs 32, 33 can be placed on the same plane. CC
If D32 and D33 are placed on the same plane, assembling and adjustment become easier. The reflecting surfaces of the lens 28, the prism 30, and the half mirror 29 have characteristics that do not absorb light of a specific spectrum in the luminosity band from the reflected light of the original, and a white light original image is formed on the CCD 32. Is done. That is, the CCD 32 receives the image information of the document as the information of the brightness of the reflected light.
When a red filter is inserted as a filter 15 in front of the CCD 33, light other than red is absorbed by the red filter 15, and the document information from the red filter 15 is reflected from the non-red and black images of the document. The light is darkened by the red filter 15. Further, the reflected light from the red image of the document passes through the red filter 15, and only the red component of the reflected light from the white image of the document passes through the red filter 15. Therefore,
In the image information received by the CCD 33, the image information from the white portion of the document and the image information from the red portion of the document have the same level, and the data cannot be distinguished from white and red. Also, the amount of reflected light received by the CCD 33 from a portion of the document other than red and white is reduced by the absorption of the red filter 15, resulting in dark image data. In other words, CC
The image information received by D33 from the document is image information obtained by removing the red image information from the image information received by CCD 32 from the document. If a color filter other than the red filter is used as the filter 15, the image information excluding the image information of that color
CD33 will receive it. The reason why the filter 15 is inserted in front of the CCD 31 in this embodiment is that when the color of the toner accommodated in the second color developing device described later is changed to another color, the changed color and the original are compared. This is because it is possible to easily cope with replacement of the filter 15 when matching the color to be identified. Unless it is necessary to replace the filter 15 alone, the prism 31 can be provided with the function of the filter 15,
A method of giving the effect of the filter 15 to the light transmitted through the half mirror 29 or bonding the filter 15 to the CCD 33 can be adopted.

In this embodiment, the apparatus shown in FIG. 7 can be used in place of the apparatus shown in FIG. The apparatus shown in FIG. 7 includes a light receiving section 34, 35 of a two-line CCD in which a large number of light receiving elements are provided adjacently at an interval corresponding to one pixel, and a section for scanning a signal obtained by the light receiving section 34, 35. And is housed in an IC package having a window for receiving light at the top. Here, the light receiving unit 35 is provided with a filter 15 at the surface of the IC chip.
Are formed, and the reflected light from the document on the document table enters through the imaging lens and the filter 15 and has the same function as the CCD 33 in FIG. The light-receiving unit 34 receives the reflected light from the original on the original table via the imaging lens without passing through the filter 15,
It has the same function as the CCD 32 in FIG. Light receiving part 34 and light receiving part 35
Are arranged in a direction perpendicular to the direction in which the reading system 12 scans while illuminating the original with slit exposure, and are arranged along the image plane formed by the imaging lens. This 2-line CCD
Is moved according to the scanning for reading the original, the light receiving units 34 and 35 are arranged such that the light receiving unit 34 is located on the image forming plane on the upstream side in the image moving direction.
The images formed on the light receiving units 34 and 35 arranged in the direction of scanning the original move in accordance with the speed at which the original is scanned. The line interval between the light receiving units 34 and 35 is an interval equivalent to one pixel, and the scanning speed is determined so that the image on the imaging plane moves a distance equivalent to one pixel during the time when the reading system 12 scans one pixel. Therefore, the image detected by the upstream light receiving unit 34 is delayed by one pixel in the sub-scanning direction.
Detected at 35. In order to identify the color of the document, the image data at the same position on the document is compared, so that the upstream light receiving unit 34 is compensated for the above-mentioned one-pixel equivalent to match the detected images of the light receiving units 34 and 35. An analog memory 36 is provided for this. The light receiving units 34 and 35 convert the reflected light from the original into electric signals with each photoelectric conversion element. Specifically, change the flowing current according to the intensity of the reflected light, integrate the change in current, and convert it into the amount of electric charge. I do. The photo storage gates 37 and 38 control the start and stop of the integration in the light receiving units 34 and 35, respectively, and the electric charge accumulated by integrating each photoelectric conversion element of the light receiving unit 34 for a predetermined time corresponds to one pixel in the analog memory 36. The data is delayed by an amount and transferred to the shift register 41 in parallel by the shift gate 39. The electric charge accumulated by integration for a predetermined time in each photoelectric conversion element of the light receiving unit 35 is stored in a shift gate.
The data is transferred to the shift register 42 in parallel by 40. The electric charges transferred in parallel to the shift registers 41 and 42 are sequentially transferred in the line direction of the shift registers 41 and 42 by a shift clock, and the electric charges are converted into voltages at an output unit and output as analog image data. This image data corresponds to the image data output from the CCDs 32 and 33 in FIG.

In the apparatus shown in FIG. 7, a red, green and blue color image of an original is formed by a three-line CCD having red, green and blue filters.
Compared to the method of identifying and reading each blue component, only specific color components of the original can be identified, but photo storage gates 37 and 38, shift gates 39 and 40, and shift gates other than the two-line light receiving units 34 and 35 Since the peripheral circuit elements including the registers 41 and 42 and the analog memory 36 can be arranged on both sides of the light receiving sections 34 and 35, the two light receiving sections 34 and 35 can be adjacent to each other. Therefore, only one analog memory 36 for adjusting the time shift of the image signals from the light receiving units 34 and 35 of two lines is required. Since the IC manufacturing technology can be applied as it is, the degree of parallelism and the degree of alignment of the two lines of light receiving units 34 and 35 can be easily increased, and the adjustment of the reading system 12 can be facilitated. However, since the filter is built in, the color to be identified cannot be changed by replacing only the filter.

FIG. 8 shows a part of the reading system 12. C
The image signals input from the CDs 32 and 33 (or the apparatus shown in FIG. 7) are an image signal not passing through the filter 15 and an image signal excluding the image signal of the color of the filter 15, and the former is represented by W (white). The latter is represented by W (white image signal) -R (red image signal). W is input to an amplifier 43 whose amplification degree can be set by an external signal AGC1. The external signal AGC1 is set in the amplifier 43 from the memory in synchronization with the image signal by the start command from the controller 24 shown in FIG. 5, and W is a decrease in the amount of light in the peripheral portion due to the imaging lens 28 in the amplifier 43, Non-uniformity, variation in sensitivity between the photoelectric conversion elements of the CCD, and the like are corrected, that is, so-called shading correction is performed. The amplifier 43 is an inverting amplifier, and its output signal is set to B (black image signal). In the amplifier 44, W and (WR) are input to input terminals having different polarities, respectively.
−R) and at the same time, the external signal AGC is
The shading correction is performed by 2 to output the same image signal R as the color of the filter 15. B from amplifier 43 is A
The data is converted into 6-bit digital data by the / D converter 45 and converted into (BR) image data by the gate circuit 46 as described later. R from the amplifier 44 is a 1-bit A / D
The data is A / D converted by the converter 48, that is, binarized at a predetermined binarization level and written into the buffer memory 23. A /
The D converter 48 is configured such that the binarization level can be changed by a signal from the controller 24. For example, when the original to be copied is light pink, it may be desired to copy the original so that the background of the original is red, or to copy the background of the original to be white. In such a case, each of the above-mentioned cases can be dealt with by changing the binarization level of the A / D converter 48 via the controller 24 according to a selection signal from the operation unit according to the user's selection. . The gate circuit 46 is closed by the R from the A / D converter 48 when this R exists, and the A / D converter is closed.
Open when R from 48 is not present. The gate circuit 46 is pulled down on the output side so that the output data becomes blank data when closed. Therefore, the A / D converter
When R from the A / D converter 48 does not exist, B from 45 passes through the gate circuit 46 as it is, and when R from the A / D converter 48 exists, the gate circuit 46 converts it into blank data. (BR). Thus, A / D converter
If B from 46 is converted to blank data by R from A / D converter 48, even if there is a problem in CCD alignment and parallelism, the image at a certain position is said to be red and black at the same time. That essentially does not happen.

The 6-bit (BR) from the gate circuit 46 is configured so that the γ converter 47 selects any 64 states that can be represented by 6 bits from 256 states that can be represented by 8 bits. The data is converted into 8-bit data by the table and written into the buffer memory 22. This gamma converter
47 rewrites the data in the table by the controller 24, thereby correcting the input / output characteristics of the reading system 12, correcting the relationship between the writing light amount of the electrophotographic image forming unit 25 and the image density of the copy, binarizing, Negative / positive reversal can be performed. When writing red image data as multi-valued data, the circuit of FIG.
Circuit is used. In FIG. 9, the same parts as those in FIG. 8 are denoted by the same reference numerals, and R from the amplifier 44 is binarized by an A / D converter 49 at a predetermined binarization level. A / D conversion to 6-bit data
Is converted. The A / D converter 49 is configured so that the binarization level can be changed by a signal from the controller 24. When the binary data from the A / D converter 49 does not exist, the B from the A / D converter 45 passes through the gate circuit 50 as it is, and when the binary data from the A / D converter 49 exists, the B from the A / D converter 49 exists. The data is converted into blank data by the gate circuit 50 and becomes (BR). 6-bit R from A / D converter 49
Is converted into 8-bit data by a table configured to select any 64 states that can be represented by 6 bits from 256 states that can be represented by 8 bits in the γ conversion unit 51, and is written to the buffer memory 23. . Therefore, the B and R image data are switched by the gate circuit 50 to become (BR) and R, and do not overlap.

FIG. 10 is a sectional view showing an outline of the structure of this embodiment. In this embodiment, the upper original manipulating / reading unit 100
And a printer unit 200 for forming an image by electrophotography. A document operation / reading unit 100 includes a document table 101 on which a document to be copied is placed, and a document pressure plate 10 for pressing a document on the document table 101.
2, a light source 13 for illuminating the original on the original table 101, a reflecting mirror 109 for condensing the light of the light source 13 on a portion for reading the original,
It is composed of mirrors 104 to 106 for guiding reflected light from a document on the document table 101 to the imaging device 108 to form an image, an imaging lens 28, a driving mechanism including a motor (not shown) for scanning the document, and the like. . As the imaging device 108, the devices 15, 29 to 33 in FIG. 6 or the devices in FIG. 7 are used. The user places the document on the platen 101
When the copying operation is started by pressing the print switch on the operation unit after setting the
A document on the document 101 is illuminated, and a motor for scanning the document is driven to scan the document. The reflected light from the original on the platen 101 is imaged by mirrors 104 to 106 and an imaging lens 28.
An image is formed on the image 108, and the image data of the document is sequentially output from the imaging device 108 line by line in accordance with the change in the document scanning position. The image data from the imaging device 108 is processed by the circuits 16 to 19 of the reading system 12 as described above, and
Is written to. The printer unit 200 includes a writing unit 250, a photoconductor 201, and a black developing unit 21 surrounded by a chain line in the drawing.
0, red developing unit 220, transfer / transport unit 230, cleaning unit 240, main charger 203 for charging photoconductor 201, fixing unit 260, transfer / transport unit 230
Cleaning belt cleaning unit 270,
Paper feed unit 290 that supplies transfer paper, transfer paper and photoconductor 201
A registration unit 280 that aligns with the image above,
It is composed of a static elimination charger 202 and the like. Writing unit 2
Reference numeral 50 denotes the writing system 20 shown in FIG. 1 , and the image forming unit 25 shown in FIG . The writing unit 250 is an eight-sided polygon mirror 251
And an optical component such as an fθ lens for scanning the photosensitive member 201 at a constant speed with laser light modulated by a black image signal and deflected by a polygon mirror, a reflecting mirror, and dustproof glass. Lens 252 for reflecting the photosensitive member 201 at a constant speed by a beam 252 to be scanned and a laser beam modulated by a red image signal and deflected on a surface different from the beam 252 of the polygon mirror 251, a reflecting mirror, and dustproofing. Black image data and red image data are written on the photoconductor 201 by a beam 253 formed by an optical component such as glass. In this writing unit 250, one polygon mirror 251 is used.
Since the two beams 252 and 253 are scanned using the two surfaces,
The scanning directions of the beams 252 and 253 on the photoconductor 201 are reversed.

FIG. 11 shows the writing unit 250 with the polygon mirror 251 viewed from above and the reflection mirror omitted, and the beam 25
FIG. 2 is a diagram in which 2,253 scanning planes are developed on a plane. The polygon mirror 251 is rotated by a motor in the direction of the arrow shown
The scanning direction by the beams 252 and 253 on 01 is reversed as shown in the figure. Positional relationship between the polygon mirror 251 and the semiconductor laser LD1 that outputs the laser light modulated with the black image signal to the polygon mirror 251 and the semiconductor laser LD2 that outputs the laser light modulated with the red image signal to the polygon mirror 251 By setting the beam at a predetermined position, the beams 252, 2
Since the positional relationship between 53 is determined, the sensor D for detecting the beam outside the image area and generating the beam modulation start timing based on the image data of each line is provided by the beam 252.
The modulation start timing of the beam 253 by the image data of each line is generated by the same sensor D. The beam 252 writes on the photosensitive drum 201 at the position A, and the beam 253 writes on the photosensitive drum 201 at the position B. Accordingly, by delaying the writing of the red image data by the beam 253 by the number of lines corresponding to the distance between A and B, an image without deviation between the black image data and the red image data is formed on the photosensitive drum 201. Formed. For this reason, the red image data written on the photosensitive drum 201 on the downstream side is read from the original by the reading system 12 and processed, and then delayed by the number of lines corresponding to the distance between A and B to the buffer memory 23. , The time lag between the writing of the black image data and the writing of the red image data is compensated.

Next, a series of image forming processes in this embodiment will be described. The photoconductor 201 is rotated by a main motor in the direction of the arrow shown in the figure, is uniformly charged by the main charger 203, and is written at a point A by a beam 252 modulated by a black image signal (BR) from the buffer memory 21. To form an electrostatic latent image. This electrostatic latent image is developed with black toner by the black developing unit 210 to become a black visible image. Next, the photoconductor 201 is stored in the buffer memory 22.
At the point B, writing is performed on the black image by the beam 253 modulated by the red image signal R, thereby forming an electrostatic latent image. Only the electrostatic latent image disturbs the black image. As a result, the image is developed with the red toner by the red developing unit 220 so that a red visible image is obtained. At the same time, transfer paper is fed from the paper feed unit 290, and the transfer paper is transferred and transferred by the registration unit 280 so that the leading edge of the transfer paper coincides with the visible image on the photoconductor 201.
It is sent out to the transport unit 230. Transfer / transport unit 23
In the case of 0, the transfer paper is transported by the transport belt, and a two-color visible image on the photoconductor 201 is transferred to the transfer paper from behind by corona charging using a charger. The transfer paper is further transported by the transport belt of the transfer / transport unit 230, the visible image is fixed by the fixing unit 260, and is discharged as a copy outside the machine. Further, the photosensitive member 201 is neutralized by the static elimination charger 202 after the transfer of the visible image and is cleaned by the cleaning unit 240, so that an image can be formed in the next cycle. The transfer belt of the transfer / transport unit 230 is cleaned by the belt cleaning unit 270 after the transfer of the transfer paper, so that the back surface of the next transfer paper is not stained. In the series of operations described above, if there is a red portion in the original placed on the platen 101, that portion is automatically separated, and at the same speed as when copying an original in which the image is only black. The image is copied as a two-color image combined with a black image. If the image of the original is only black, black image copying is performed as in a normal copying machine. The person who operates the copying machine does not need to worry about whether or not the original has a red portion, and the red portion is automatically processed, so that it is not bothersome. In this embodiment, not only the color is copied by the function of identifying the color of the document but also the same function as a conventional monocolor copying machine or a copying machine having a partial color changing function is provided. It is also possible to make it.

FIG. 12 shows a configuration of a part of the embodiment which mainly performs control of the printer unit 200 of the controller 26 which controls other than the image reading system 12 and the writing system 20. The controller 26 includes microcomputers 57 to 59. The microcomputer 57 drives various AC loads 60 and various DC loads 61 such as motors, solenoids and clutches of the printer unit 200 via drivers 62 and 63, and takes in signals from various sensors 64 via a signal processing circuit 65. Further, the microcomputer 57 has a high-voltage power supply.
It controls peripheral devices such as 66, sorter 67, and automatic document feeder 68. The microcomputer 58 controls the operation unit / display unit 56, and the microcomputer 59 includes a driving unit 69 for scanning a document, the document illumination light source 13, and the fixing unit 260.
The fixing heater 71 is controlled. Microcomputer
57 to 59 are connected by a communication path using the microcomputer 57 as a master. Paths for exchanging signals that cannot be timely provided only by the communication path are provided between the microcomputer 57 and the microcomputer 59 and between the microcomputers 57 to 59 and the controller 24 as shown in FIG. An interface is provided between the controller 24 to be handled and the microcomputers 57 to 59.

In this embodiment, the toner consumption is predicted from the image data read from the original. The predicted data is obtained by counting the black data of the image data by the black data counter 27 as described above. . The controller 24 sets, resets, and reads the black data counter 27, and obtains the count value of the black image data from the black data counter 27 at each predetermined timing as a predicted value of the toner consumption. Then, the controller 24 transmits the predicted value of the toner consumption obtained from the black data counter 27 to the controller 26, and the microcomputer 57 in the controller 26 receives the predicted value of the toner consumption. The toner concentration of the developer in the black developing unit 210 is detected by a toner concentration sensor (not shown), and this toner concentration sensor is included in various sensors 64 shown in FIG. The microcomputer 57 receives a toner density detection signal from the toner density sensor via a signal processing circuit 65. It is the toner replenishing clutch that causes the developer in the black developing unit 210 to replenish the toner. The toner supply clutch is included in various DC loads 61 shown in FIG. 12, and is driven via a driver 63 by an output signal of the microcomputer 57 to rotate a toner supply roller and the like in the black developing unit 210.

FIGS. 13A and 13B show the black developing unit 210.
Is shown. The developer inside the black developing unit 210 is stirred by the developer stirring roller 211 while the developer supply roller 2
The developer is supplied to the developing sleeve 213 by the developer supply roller 212. A magnet is arranged inside the developing sleeve 213, and the magnet holds the developer supplied by the developer supply roller 212 on the surface of the developing sleeve 213 by magnetic force. The developer held on the surface of the developing sleeve 213 passes through the separator 214 and the developer regulating member 215
After the excess is removed and regulated to a certain thickness, the toner is moved to a developing position opposed to the photosensitive drum 201 to develop the electrostatic latent image on the photosensitive drum 201. After passing through the developing position, the developer on the developing sleeve 213 passes through a portion (or low) where no magnetic force is generated by the magnet, and separates from the developing sleeve 213. The developer separated from the developing sleeve 213 is transported from the developer supply roller 212 to the developer stirring roller 211, and is again stirred. Also, the developer regulating member 215
The excess developer removed from above the developing sleeve 213 is sent to the developer stirring roller 211 through the separator 214,
The toner is stirred with the toner supplied from the hopper 216. The developer stirring roller 211 and the developer supply roller 212 are rotationally driven by a motor 2110, and the developing sleeve 213 is rotationally driven by a motor 2110 via a clutch 2111. The toner supply from the hopper 216 to the developer in the developing chamber 219 is performed by rotating the toner supply roller 217. The above-described toner density sensor detects a change in the amount of toner in the developer as a change in the magnetic permeability of the developer. The toner concentration sensor is attached to the developer regulating member 215 and the separator in the developing chamber 219.
The toner density of the developer is detected at a position adjacent to the development sleeve 214 and close to the development sleeve 213 and close to the position where the electrostatic latent image on the photosensitive drum 201 is developed.

FIG. 14 is a functional block diagram of the toner density control section in this embodiment. The black data counter 27 obtains a predicted value of toner consumption by counting image data (black data) from the image reading system 12, and the predicted value TU is input to the multiplication block 72. The target value SP of the toner concentration of the developer in the black developing unit 210 is input to the two-input adder / subtractor 73. The two-input adder / subtractor 73 subtracts the output value PV of the toner density sensor 218 from the target value SP of the toner density to obtain a deviation e.
Execute PI operation with PI controller 75 and use the result as MV
Output as PI. The operation amount PI and the toner replenishment amount TR obtained from the predicted value of the toner consumption amount as described later are stored in the ring buffer and output as the operation amount D via the recovery processing unit 76. The toner supply clutch is driven by the operation amount D, and the amount of toner determined by the operation amount D is supplied by the toner supply roller 217. Here, if the toner supply amount TR is ignored, the target value SP of the toner concentration of the developer and the detection value PV are added to the two-input adder / subtractor 73.
Thus, a feedback control system is configured to perform the PI calculation by comparison, and replenish the toner with the PI as a result.

Further, a deviation e from the two-input adder / subtractor 73 is input to a function generation block 77 to determine a toner correction coefficient FX, and the toner correction coefficient FX and a predicted value of toner consumption are calculated.
The multiplication block 72 multiplies the estimated value TU of the toner consumption and the current black developing unit 210
The toner replenishment amount TR can be obtained in consideration of the toner concentration of the developer inside. This toner supply amount TR is stored in the ring buffer and input to the recovery processing unit 76. The recovery processing unit 76 normally passes the value obtained by adding the toner supply amount TR and the operation amount PI stored in the ring buffer as the operation amount D as it is, but supplies the toner supply data of the toner replenished prior to consumption. If the copy cycle is interrupted due to an abnormality such as a transfer paper jam and the expected toner consumption is not performed, the toner supply amount in the copy cycle after the error recovery is adjusted This is performed based on the replenishment data of the toner that has not been removed. Figure 2 This recovery process will be described in detail later with reference to the flowchart of FIG. The functional block diagram of FIG. 14 shows a feedforward control system for replenishing toner by estimating the amount of consumed toner by counting image data, and detecting the toner concentration of the developer and comparing it with a target value. This is a combination with a feedback control system that performs replenishment.

The functional block diagram of FIG. 14 is realized by using a microcomputer 57,
The schematic flow of 57 is shown in FIGS. First, main processing of the toner consumption prediction processing flow of the feedforward control system will be described with reference to FIG. The toner consumption predicting process is performed by periodically generating an interrupt by a timer to generate a kick signal. The microcomputer 57 controls the image reading system 12 in the toner consumption prediction processing.
If the image is being read, steps 300 to 303 are performed, and if the image reading system 12 is not reading, the next interrupt by the timer is waited. The microcomputer 57 predicts the toner consumption TU by causing the black data counter 27 to count the image data (black data) from the image reading system 12 in step 300, and calculates the toner correction coefficient FX from the deviation e in step 301. Search for. Then, the microcomputer 57 multiplies the toner consumption amount TU and the toner correction coefficient FX in step 302 to obtain a toner supply amount TR, and in step 303
Stores the data (toner supply amount TR) input this time in the ring buffer.

Next, main processing of the toner supply processing flow of the feedback control system will be described with reference to FIG.
In the toner supply process flow, a kick signal is generated by executing the toner consumption amount prediction process five times. In the toner supply processing flow, the microcomputer 57 first
In step 310, the target value SP of the toner density is read, and in step 311, the control amount PV from the toner density sensor 74 is read.
Next, the microcomputer 57 calculates a deviation e by subtracting the control amount PV from the target value SP of the toner concentration in step 312,
In step 313, a PI calculation is performed on the deviation e to determine an operation amount PI by feedback control. Next, the microcomputer 57 performs a recovery process described later in step 314, and drives the toner replenishing clutch by the value of the operation amount D in step 315 to replenish the toner. The microcomputer 57 has a toner supply processing function of a feedback control system by repeatedly performing such processing. The reason why the startup interval of the feedforward control system is narrower than the startup interval of the feedback control system is that excessive toner replenishment by the feedback control system due to dead time and delay time causes the toner concentration of the developer to be too high. This is to prevent the situation.

FIG. 15 shows the relationship between the deviation e and the toner correction coefficient FX. The microcomputer 57 retrieves a preset toner correction coefficient FX from a deviation e = SP-PV between the target value SP of the toner concentration and the control amount PV. As the characteristic curve indicating the relationship between the deviation e and the toner correction coefficient FX, one of the one shown by the solid line, the one shown by the dotted line, and the one shown by the one-dot chain line in FIG. 15 is used. Actually, it is possible to obtain and use a characteristic curve with good control performance by an experiment in consideration of the following (1) to (3). (1) When the deviation e is close to "0", the toner correction coefficient is set to a value close to "1". (2) Deviation e is +
When there is a tendency to increase in the direction, when e = 0, a characteristic curve having a large slope with a toner correction coefficient of “1” is selected.
(3) When the deviation e tends to increase in the negative direction,
When e = 0, a characteristic curve with a small slope and a toner correction coefficient of “1” is selected. In other words, even if the predicted toner consumption is the same, if the toner concentration at that time is high, the toner supply amount is reduced, and if the toner concentration is low, the toner supply amount is increased, so that the toner concentration of the developer becomes more stable. I did it.

FIG . 2 is a flowchart showing a recovery process when the microcomputer 57 is in an abnormal state. The microcomputer 57 determines in step 316 whether or not the recovery / toner replenishment flag is "1" to determine whether or not the copy cycle has been interrupted due to an abnormality such as a transfer paper jam, and the copy cycle is interrupted. If the recovery / toner supply flag is not "1", step 317 is executed.
The toner supply amount TR stored in the ring buffer at
The value obtained by adding the operation amount PI and the operation amount PI is set as the operation amount D, and the recovery process ends. If the copy cycle is interrupted and the recovery / toner supply flag is set to "1", the microcomputer 57 determines in step 318 whether the data (toner supply amount TR) input this time is equal to or greater than the recovery / toner supply amount described later. Determine whether or not. And a microcomputer
If the data input this time is equal to or more than the recovery toner supply amount, the recovery toner supply amount is subtracted from the data input this time in step 319, and the result is set as the recovery toner supply amount. The leverage / toner supply amount and the operation amount PI are added, and the result is set as the operation amount D. In addition, the microcomputer 57
Is the toner supply amount TR in the ring buffer in step 321
Is set to "0", and in step 322, the recovery / toner supply flag is set to "0", and the recovery process ends. If the data input this time is smaller than the recovery toner supply amount, the microcomputer 57 proceeds to step 32.
At step 3, the data input this time is subtracted from the recovery toner supply amount, and the result is set as the recovery toner supply amount. At step 324, the operation amount PI is set to the operation amount D, and the recovery process ends.

FIG . 3 is a flow chart showing the operation of the microcomputer 57 for calculating the amount of recovery / toner supply. When the copy cycle is interrupted due to an abnormality such as a transfer paper jam, the microcomputer 57 records the history data of the toner supply command signal stored in the ring buffer.
(Data in which toner is supplied but toner is not consumed) is processed as follows. In step 325, the microcomputer 57 calculates the recovery toner supply amount, that is, adds all the data stored from the address indicated by the input pointer 1 to the address indicated by the output pointer in the ring buffer, and adds the recovery toner supply amount. In step 326, it is determined whether or not the recovery / toner supply amount is “0”. Then, the microcomputer 57 determines that the recovery toner supply amount is "0".
If not, the recovery / toner supply flag is set to “1” and the recovery / toner supply amount calculation is terminated. If the recovery / toner supply amount is “0”, the recovery / toner supply amount calculation is terminated.

FIG . 4 shows a memory used for the recovery processing. The memory that stores the history of the toner supply command signal by the microcomputer 57 is the ring buffer 78, and writes the tip of digitally expressed image data (black data) to the photosensitive drum 201, and then stores the tip data. The time until development is about 300 mS. Since the start of the toner consumption prediction processing is in a cycle of 50 ms, the toner density control is executed six times by the toner supply command signal during that time. The minimum required capacity of the ring buffer 78 is 6
This is data (or 7 data). The input pointer and the output pointer indicate the input and output addresses of the ring buffer 78, and manage the input and output of the toner supply amount TR. The recovery / toner replenishment flag stored in the memory 79 by the microcomputer 57 indicates the presence or absence of an unconsumed toner replenishment amount. It becomes “0”. The microcomputer 57 stores an unconsumed toner supply amount in a recovery toner supply amount memory 80.

FIG . 5 shows an example of toner supply timing before and after the occurrence of a jam in this embodiment. The jam detection timing indicates the timing at which the transfer cycle is interrupted upon detecting the transfer paper conveyance abnormality and the present embodiment is stopped. The toner replenishment command,..., Is based on the toner consumption prediction data obtained by counting the image data and the toner density data obtained by the toner density sensor 74 in the black developing unit 210. This is data indicating the amount of toner replenishment obtained by the software, whereby the rotation of the toner replenishment roller 217 is controlled and toner replenishment is performed. The timing of toner consumption ',', '... is such that the image data counted to predict the amount of toner consumption is then written on the photosensitive drum 201 by the optical writing device 250 and developed by the black developing unit 210. It shows the time during which the toner in the black developing unit 210 moves to the photosensitive drum 201 and is consumed. In the example of FIG. 5 , four toner replenishment commands are issued before the jam occurs, and the toner in the black developing unit 210 is replenished with toner. The copy cycle is interrupted due to the occurrence of the jam, and the toner actually consumed is only the toner supplied by one toner supply command, and the toner supplied by the other three toner supply commands. Is not consumed. Therefore, when the jam is cleared and the copy cycle is restarted, if the image data of the original is read and counted and the normal toner supply is performed, the toner supplied by the toner supply command ~ becomes excessive, and the black toner is supplied. Since the toner amount of the developer in the developing unit 210 becomes excessive, the stability of the toner concentration of the developer is impaired. Therefore, in this embodiment, the microcomputer 57
Stores the history of the toner replenishment command signal in the ring buffer 78 and corrects the amount of unconsumed toner as described above when issuing the toner replenishment command signal after the jam has been cleared. Issue a command. The present invention can be applied to an electrophotographic printer or the like. In the above embodiment, the first developing unit
210 develops with the black toner and the second developing unit 2
20 developed with red toner and matched the function of identifying the color of the original to those colors, but it is also possible to aim for a special effect by changing the color to be identified and the color to be developed . Further, the color to be set which is set regardless of the color to be changed is changed so as to match the color of the toner contained in the second developing unit 220 which can be set by changing the color of the toner in the printer unit 200. Therefore, in order to cope with this, the color of the toner stored in the second developing unit 220 and
The colors to be identified may be individually displayed on the operation unit / display unit 56.

As described above, according to the first aspect of the present invention, a recording medium to be moved, writing means for writing digitally expressed image data on the recording medium to form an electrostatic latent image, and toner supply A digital image forming apparatus having a developing means for supplying toner to the developer by a command and developing the electrostatic latent image with the developer; , A toner concentration detecting means for detecting the toner concentration of the developer in the developing means, and a detection value of the toner concentration detecting means being compared with a target value. Feedback control means for issuing a toner replenishment operation amount, and a second toner replenishment operation amount based on the predicted value of the toner consumption amount prediction means and the comparison result. And a control unit for issuing a toner replenishment command based on the first toner replenishment operation amount and the second toner replenishment operation amount, so that more accurate toner density stabilization can be performed. As a result, high quality image formation can be performed. Further, since the control loop activation interval of the feedforward control unit is narrower than the control loop activation interval of the feedback control unit, toner replenishment by the feedback control unit becomes excessive due to dead time and delay time, and the toner concentration of the developer becomes high. It can be prevented from becoming too much.

According to the second aspect of the present invention, in the digital image forming apparatus according to the first aspect, when the image forming cycle is stopped due to an abnormality during the image formation, the toner is consumed by the toner supply command by the developing means. Since there is provided a toner replenishing amount correcting means for correcting the amount of unconsumed toner among the previously replenished toner with respect to the toner replenishing amount at the time of toner replenishment after the recovery from the abnormality, the image forming process includes Even if the balance between toner replenishment and consumption occurs when the image forming cycle is stopped due to an abnormality, the amount of unconsumed toner can be corrected after recovery from the abnormality, and more accurate toner density stabilization And a high quality image can be formed.

According to the third aspect of the present invention, a recording medium to be moved, and writing means for writing digitally represented image data on the recording medium to form an electrostatic latent image,
And developing means for developing the electrostatic latent image with the developer by supplying toner to the developer according to a toner supply command. A toner consumption estimating means for estimating consumption, and toner replenishment based on a predicted value of the toner consumption estimating means based on image data corresponding to the electrostatic latent image earlier than the developing means develops the electrostatic latent image. Since a control unit for issuing a command is provided, the toner density can be stabilized with higher accuracy, and a high-quality image can be formed. Further, when the image forming cycle is stopped due to an abnormality during image formation, the amount of unconsumed toner among the toner replenished prior to the consumption of the toner by the toner replenishment command is returned from the abnormality by the developing unit. Since the toner supply amount correction means for correcting the toner supply amount at the time of the subsequent toner supply is provided, when the image forming cycle is stopped due to an abnormality during the image formation, the balance between the toner supply and the consumption is not correct. Even if it occurs, the amount of unconsumed toner can be corrected after the recovery from the abnormality, and the toner density can be stabilized with higher accuracy, and high-quality image formation can be performed.

According to the fourth aspect of the present invention, a recording medium to be moved, and writing means for writing digitally expressed image data on the recording medium to form an electrostatic latent image,
And developing means for developing the electrostatic latent image with the developer by supplying toner to the developer according to a toner supply command. Toner consumption estimating means for estimating consumption, toner concentration detecting means for detecting a toner concentration of a developer in the developing means, and developing means for developing the electrostatic latent image faster than the developing means develops the electrostatic latent image. A control unit for issuing a toner replenishment command based on a predicted value of the toner consumption prediction unit based on the corresponding image data and a detection value of the toner density detection unit,
It is possible to stabilize the toner density with higher precision, and to form a high-quality image. Further, when the image forming cycle is stopped due to an abnormality during image formation, the amount of unconsumed toner among the toner replenished prior to the consumption of the toner by the toner replenishment command is returned from the abnormality by the developing unit. Since the toner supply amount correction means for correcting the toner supply amount at the time of the subsequent toner supply is provided, when the image forming cycle is stopped due to an abnormality during the image formation, the balance between the toner supply and the consumption is not correct. Even if it occurs, the amount of unconsumed toner can be corrected after the recovery from the abnormality, and the toner density can be stabilized with higher accuracy, and high-quality image formation can be performed.

According to the fifth aspect of the present invention, a recording medium to be moved, and writing means for writing digitally represented image data on the recording medium to form an electrostatic latent image,
And developing means for developing the electrostatic latent image with the developer by supplying toner to the developer according to a toner supply command. A toner consumption amount estimating unit for estimating a consumption amount, a toner concentration detecting unit for detecting a toner concentration of the developer in the developing unit, and a detection value of the toner concentration detecting unit being compared with a target value. A feedback control unit for issuing a first toner supply operation amount; a feedforward control unit for issuing a second toner supply operation amount based on a predicted value of the toner consumption amount prediction unit and the comparison result;
Control means for issuing a toner replenishment command according to the toner replenishment operation amount and the second toner replenishment operation amount, so that more accurate toner density stabilization can be performed and a high-quality image can be formed. Can be. Further, when the image forming cycle is stopped due to an abnormality during image formation, the amount of unconsumed toner among the toner replenished prior to the consumption of the toner by the toner replenishment command is returned from the abnormality by the developing unit. Since the toner supply amount correction means for correcting the toner supply amount at the time of the subsequent toner supply is provided, when the image forming cycle is stopped due to an abnormality during the image formation, the balance between the toner supply and the consumption is not correct. Even if it occurs, the amount of unconsumed toner can be corrected after the recovery from the abnormality, and the toner density can be stabilized with higher accuracy, and high-quality image formation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a recovery process of the microcomputer in the embodiment.

FIG. 3 is a flowchart showing a recovery / toner supply amount calculation of the microcomputer in the embodiment.

FIG. 4 is a diagram showing a memory used for recovery processing of the embodiment.

FIG. 5 is a timing chart showing an example of toner supply timing before and after the occurrence of a jam in the embodiment.

FIG. 6 is a diagram showing an imaging device of the embodiment.

FIG. 7 is a diagram illustrating an imaging apparatus according to another embodiment of the present invention.

FIG. 8 is a block diagram showing a reading system of the embodiment.

FIG. 9 is a block diagram showing a reading system according to another embodiment of the present invention.

FIG. 10 is a sectional view showing an outline of the structure of the embodiment.

FIG. 11 is a view in which a polygon scanning mirror is viewed from above and a reflecting mirror is omitted from the writing unit of the embodiment, and the scanning surface of the beam is developed into a plane.

FIG. 12 is a block diagram showing a circuit centering on the controller of the embodiment.

FIG. 13 is a sectional view showing a black developing unit of the embodiment.

FIG. 14 is a block diagram showing functional blocks of a toner density control unit in the embodiment.

FIG. 15 is a characteristic curve diagram showing a relationship between a deviation e and a toner correction coefficient FX in the embodiment.

FIG. 16 is a flowchart illustrating a toner supply process of the microcomputer in the embodiment.

FIG. 17 is a flowchart illustrating a toner consumption estimation process of the microcomputer in the embodiment.

[Explanation of symbols]

 12 Reading System 20 Writing System 21 Image Memory 24 Controller 25, 26 Image Forming Unit 210, 220 Developing Unit 218 Toner Density Sensor

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/08 G03G 21/00 370

Claims (5)

(57) [Claims] A recording medium to be moved; writing means for writing digitally represented image data on the recording medium to form an electrostatic latent image; A digital image forming apparatus having developing means for developing a latent image with a developer, wherein a toner consumption estimating means for counting digitally expressed image data to be written on the recording medium and estimating a toner consumption amount; Toner concentration detection means for detecting the toner concentration of the developer in the means, feedback control means for comparing the detection value of the toner concentration detection means with a target value and issuing a first toner supply operation amount based on the comparison result; A feedforward control unit for issuing a second toner supply operation amount based on the predicted value of the toner consumption amount prediction unit and the comparison result; Control means for issuing a toner replenishment command based on the first toner replenishment operation amount and the second toner replenishment operation amount, wherein the control loop activation interval of the feedforward control means is narrower than the control loop activation interval of the feedback control means. A digital image forming apparatus characterized by the above-mentioned. 2. The digital image forming apparatus according to claim 1, wherein when the image forming cycle is stopped due to an abnormality during the image forming, the toner supplied by the developing unit prior to the consumption of the toner by a toner replenishing command is supplied. A digital image forming apparatus comprising: a toner replenishment amount correction unit that corrects the amount of unconsumed toner among the toner replenishment amounts at the time of toner replenishment after recovery from an abnormality. 3. A recording medium to be moved, writing means for writing digitally represented image data on the recording medium to form an electrostatic latent image, and a toner replenishment command for supplying toner to a developer to supply the toner to the developer. A digital image forming apparatus having developing means for developing a latent image with a developer, wherein a toner consumption estimating means for counting digitally expressed image data to be written on the recording medium and estimating a toner consumption amount; Control means for issuing a toner replenishment command based on a predicted value of the toner consumption predicting means based on image data corresponding to the electrostatic latent image before the means develops the electrostatic latent image; When the formation cycle is stopped, the amount of unconsumed toner among toner replenished prior to toner consumption by the toner replenishment command in the developing unit. The digital image forming apparatus characterized by comprising a toner supply amount correcting means for correcting the toner replenishing amount during toner replenishment after returning from the abnormal. 4. A recording medium to be moved, writing means for writing digitally expressed image data on the recording medium to form an electrostatic latent image, and toner supplied to a developer by a toner supply command to supply said electrostatic latent image. A digital image forming apparatus having developing means for developing a latent image with a developer, wherein a toner consumption estimating means for counting digitally expressed image data to be written on the recording medium and estimating a toner consumption amount; A toner concentration detecting unit for detecting a toner concentration of a developer in the unit, and a predicted value of the toner consumption amount predicting unit based on image data corresponding to the electrostatic latent image earlier than the developing unit develops the electrostatic latent image. And control means for issuing a toner supply command based on the detection value of the toner concentration detection means, and before the image forming cycle is stopped due to an abnormality during image formation. Toner replenishment for correcting the amount of unconsumed toner among toner replenished prior to toner consumption by the toner replenishment command by the developing means with respect to the toner replenishment amount at the time of toner replenishment after recovery from abnormality A digital image forming apparatus comprising: an amount correcting unit. 5. A recording medium to be moved, writing means for writing digitally represented image data on the recording medium to form an electrostatic latent image, and a toner replenishment command for supplying toner to a developer to supply the toner to the developer. A digital image forming apparatus having developing means for developing a latent image with a developer, wherein a toner consumption estimating means for counting digitally expressed image data to be written on the recording medium and estimating a toner consumption amount; Toner concentration detection means for detecting the toner concentration of the developer in the means, feedback control means for comparing the detection value of the toner concentration detection means with a target value and issuing a first toner supply operation amount based on the comparison result; A feedforward control unit for issuing a second toner supply operation amount based on the predicted value of the toner consumption amount prediction unit and the comparison result; Control means for issuing a toner replenishment command based on the first toner replenishment operation amount and the second toner replenishment operation amount; and when the image formation cycle is stopped due to an abnormality during image formation, toner consumption is performed by the toner replenishment command by the developing means. And a toner replenishment amount correcting means for correcting an amount of unconsumed toner among toner replenished in advance with respect to a toner replenishment amount at the time of toner replenishment after recovery from an abnormality. Digital image forming apparatus.