JPH04348372A - Digital image forming device - Google Patents

Abstract

PURPOSE:To stabilize toner concentration with high accuracy and to form a high-quality image by issuing a toner supplying command based on the predicted value of a toner consumption predicting means. CONSTITUTION:The toner consumption predicting means 1 and a control means 2 which issues the toner supplying command are installed in a digital image forming device provided with a recording body which is moved, a write means for forming an electrostatic latent image by writing digitally expressed image data on the recording body, and a developing means for developing the electrostatic latent image with developer by supplying the toner in the developer according to the toner supplying command. Then, the digitally expressed image data which is written on the recording body is counted so as to predict toner consumption by the predicting means 1, and the toner supplying command is issued by the control means 2 based on the predicted value of the predicting means 1 by the image data corresponding to the electrostatic latent image earlier than the developing means develops the electrostatic latent image.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to digital image forming apparatuses such as digital copying machines and printers.

0002

2. Description of the Related Art Generally, in an image forming apparatus having a developing device that develops an electrostatic latent image on a photoreceptor with a two-component developer consisting of toner and carrier, the toner concentration of the developer is made uniform and the charging It is necessary to stir the developer to adjust the amount to a predetermined value. Therefore, in the developing device, the position where toner is replenished and the position where the electrostatic latent image is developed are separated. Therefore, there is a time lag before the supplied toner contributes to development. Conventionally, in order to compensate for the decrease in toner density due to toner consumption associated with development, there have been methods that measure the image density after development on the photoreceptor and replenish toner when the measured value becomes lower than a predetermined value. A device is used that detects the toner concentration using a toner concentration detector provided in the developing device and replenishes toner when the toner concentration becomes low. Furthermore, Japanese Patent Application Laid-Open No. 60-49362 discloses, in an electrophotographic apparatus equipped with a scanning beam type exposure device, a counting means for counting black data included in an image signal for modulating the scanning beam, and a developing section. A toner concentration detecting means for detecting toner concentration, and a toner replenishing means for controlling toner replenishment to a developing section based on the counting result of the counting means and the detection result of the toner concentration detecting means are described, Specifically, if the black data is counted and the toner density is lower than a predetermined value, then a fixed amount of toner is refilled to reach the predetermined toner density, and when this fixed amount replenishment alone is not sufficient, toner is replenished using another process. It describes what to do. JP-A-1-244481
The publication describes an image forming apparatus in which a toner conveying means is operated in synchronization with an image signal to be developed, and the toner conveying means is stopped after a predetermined time has elapsed after the input of the image signal is stopped. Specifically, it is described that the toner conveyance means is activated at the beginning of a page of an image 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 an image forming apparatus detects the density of an image formed on a photoreceptor through charging, exposure, and development, and compares the detection result with the desired image density. It has a feedback control system that controls toner replenishment so that the difference is eliminated, and a function is added to this feedback control system to compensate for dead time during toner replenishment.
Specifically, to compensate for dead time, the difference between the detected toner concentration value and the target value and the amount of toner replenishment at that point are stored in a table as time series data, and past data corresponding to the dead time is stored in the table. There is described a device that outputs a toner replenishment command that compensates for dead time and stabilizes the toner concentration at a target value by performing PI control based on this data.

0003

[Problems to be Solved by the Invention] Conventionally, image forming apparatuses measure the image density after development on a photoreceptor and replenish toner when the measured value becomes lower than a predetermined value, or The toner concentration detector installed in the toner sensor detects the toner concentration and replenishes the toner when the toner concentration becomes low. Alternatively, even if toner is replenished, recovery of the toner concentration of the developer used for development is delayed due to the time delay required from the time the toner is replenished until the toner concentration of the developer is made uniform by stirring. During this delay, the electrostatic latent image is developed with a developer having a low toner concentration, and the toner concentration remains low. Furthermore, the longer the delay time and the greater the amount of toner consumed during the delay time, the greater the drop in toner concentration. Conventionally, this problem was caused by the fact that the number of tones to be reproduced in an image was not very large, and the developing device was large and had a large amount of toner inside. It was not recognized as a major issue because it served as a buffer to prevent the concentration from decreasing. However, due to the demand for downsizing of image forming apparatuses, development devices have become increasingly downsized, and a buffer effect due to a large capacity cannot be expected to be very effective. In addition, digital copying machines process electrical signals to write multi-tone images far beyond those of conventional analog copying machines, and in particular, recently, multi-valued image data can be written for each pixel even at a writing density of around 400 dpi. As a result, efforts have been made to improve both gradation and resolution. In order to faithfully reproduce this, it has become necessary to stabilize the toner concentration with higher precision than before.

Furthermore, in the electrophotographic apparatus described in Japanese Patent Application Laid-Open No. 60-49362, the position where the toner replenishing means replenishes toner and the position where the developing section develops the photoreceptor are separated, so that the replenished toner is In order to use the toner for development, there is a wasted time required for the agitation/conveyance mechanism to send the toner from the replenishment position to the development position, and the toner density gradually decreases as the replenished toner reaches the development position after the wasted time. There is a delay time due to the rising phenomenon. In order to accurately control a system with such dead time and delay time, it is necessary to perform control to deal with the delay. However, since no control is performed to deal with the delay, fluctuations in toner concentration cannot be sufficiently stabilized. Unexamined Patent Publication 1-24
The image forming apparatus described in Japanese Patent No. 4481 operates a toner conveying means in synchronization with an image signal to be developed, and stops the toner conveying means after a predetermined time has elapsed after the input of the image signal is stopped. , the toner is not replenished according to the amount of toner consumed, but a fixed amount of toner is replenished according to the number of copies, so it is not always possible to maintain a balance between the amount of toner consumed and the amount of replenishment. Stabilization of toner concentration cannot be expected. U.S. Patent No. 4,87
The image forming apparatus described in the specification of No. 5,078 detects the density of the image formed on the photoreceptor and controls toner replenishment so that there is no difference between the detection result and the target image density. The control system has a function that compensates for dead time when replenishing toner, so
Data on toner consumption, which is one of the major factors determining toner density, is not used. Therefore, even if data traced back by 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, fluctuations in toner density will occur. In other words, a control system that compensates for dead time is used, assuming that the amount of toner consumption does not change. In actual copying machines, the image area that is expressed by applying toner to transfer paper varies greatly depending on the original to be copied. For example, there are things that are mostly white with a little text, and things that are almost entirely black, such as photographs, and the ratio of the area covered by toner can range from less than 1% to nearly 100%. do. The same goes for printers. Fluctuations in toner consumption are not directly detected as control parameters within this control system, and therefore act as disturbances to the system, leading to deterioration in control accuracy, that is, fluctuations in toner concentration. SUMMARY OF THE INVENTION An object of the present invention is to provide a digital image forming apparatus that can improve the above-mentioned drawbacks, stabilize toner density with higher precision, and form high-quality images.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the invention of claim 1 includes a moving recording medium and writing digitally expressed image data onto the recording medium to form an electrostatic latent image. In a digital image forming apparatus having a writing means and a developing means for replenishing a developer with toner according to a toner replenishment command and developing the electrostatic latent image with the developer, as shown in FIG. toner consumption prediction means 1 for predicting toner consumption by counting expressed image data; and toner consumption by image data corresponding to the electrostatic latent image earlier than the developing means develops the electrostatic latent image. and a control means 2 for issuing a toner replenishment command based on the predicted value of the amount prediction means 1,

[0006] The invention according to claim 2 provides a recording medium that is moved, a writing means that writes digitally expressed image data onto the recording medium to form an electrostatic latent image, and a toner supplying command that converts the toner into a developer. In a digital image forming apparatus having a developing means that is supplied and develops the electrostatic latent image with a developer, toner consumption is calculated by counting digitally expressed image data to be written on the recording medium, as shown in FIG. a toner consumption amount predicting means 3 for predicting; a toner concentration detecting means 4 for detecting the toner concentration of the developer in the developing means; and a toner concentration detecting means 4 for detecting the toner concentration of the developer in the developing means; The predicted value of the toner consumption amount predicting means 3 based on the image data and the toner concentration detecting means 4
control means 5 for issuing a toner replenishment command based on the detected value of
It is equipped with

[0007] The invention as claimed in claim 3 provides a recording medium that is moved, a writing means that writes digitally expressed image data onto the recording medium to form an electrostatic latent image, and a toner that is transferred to a developer by a toner replenishment command. In a digital image forming apparatus having a developing means that is supplied and develops the electrostatic latent image with a developer, toner consumption is calculated by counting digitally expressed image data to be written on the recording medium, as shown in FIG. A toner consumption amount predicting means 6 for predicting, a toner concentration detecting means 7 for detecting the toner concentration of the developer in the developing means, and a detected value of the toner concentration detecting means 7 is compared with a target value, and based on the comparison result, a feedback control means 8 for issuing a first toner replenishment operation amount; a feedforward control means 9 for issuing a second toner replenishment operation amount based on the predicted value of the toner consumption amount prediction means 6 and the comparison result; control means 1 for issuing a toner replenishment command based on a first toner replenishment operation amount and a second toner replenishment operation amount;
0,

According to a fourth aspect of the present invention, in the digital image forming apparatus according to the third aspect, the control loop execution interval of the feedforward control means 8 is narrower than the control loop execution interval of the feedback control means 9,

[
In the digital image forming apparatus according to claim 1, 2, 3, or 4, when the image forming cycle is stopped due to an abnormality during image formation as shown in FIG. Toner replenishment amount correction means 11 that corrects the amount of unconsumed toner out of the toner replenished prior to toner consumption in response to a toner replenishment command with respect to the toner replenishment amount at the time of toner replenishment after recovery from an abnormality. It is equipped with the following.

0010

[Operation] In the invention of claim 1, the toner consumption amount predicting means 1
The control means 2 counts the digitally expressed image data to be written on the recording medium and predicts the amount of toner consumption, and the control means 2 generates image data corresponding to the electrostatic latent image faster than the developing means develops the electrostatic latent image. A toner replenishment command is issued based on the predicted value of the toner consumption amount predicting means 1.

In the second aspect of the invention, the toner consumption amount predicting means 3 counts the digitally expressed image data to be written on the recording medium to predict the toner consumption amount, and the toner concentration detecting means 4 calculates the amount of toner consumed by the developing device in the developing means. Detects the toner concentration of the agent. Then, the control means 5 operates based on the predicted value of the toner consumption amount predicting means 3 and the detected value of the toner concentration detecting means 4 based on the image data corresponding to the electrostatic latent image earlier than the developing means develops the electrostatic latent image. Issues a toner replenishment command.

In the third aspect of the invention, the toner consumption amount predicting means 6 counts the digitally expressed image data to be written on the recording medium to predict the toner consumption amount, and the toner concentration detecting means 7 calculates the amount of toner consumed by the developing device in the developing means. Detects the toner concentration of the agent. Feedback control means 8 is toner concentration detection means 7
The detected value of is compared with the target value, a first toner replenishment operation amount is issued based on the comparison result, and the feedforward control means 9 outputs a second toner replenishment operation amount based on the predicted value of the toner consumption amount predicting means 6 and the comparison result. Issues the supply operation amount. Then, the control means 10 issues a toner replenishment command based on the first toner replenishment operation amount and the second toner replenishment operation amount.

According to the fourth aspect of the present invention, in the digital image forming apparatus according to the third aspect, the control loop execution interval of the feedforward control means 8 is narrower than the control loop execution interval of the feedback control means 9.

In the fifth aspect of the present invention, when the image forming cycle is stopped due to an abnormality during image formation, the toner replenishment amount correction means 11 replenishes the toner that has been replenished by the developing means prior to toner consumption according to a toner replenishment command. The amount of unconsumed toner among them is corrected with respect to the amount of toner replenishment at the time of toner replenishment after recovery from the abnormality.

[0015]

Embodiment FIG. 5 shows an embodiment of the present invention. This embodiment is a digital copying apparatus that identifies monochrome image data from a document and obtains a two-color hard copy using this image data and black image data. In the reading system 12, the document on the document table is illuminated by a light source 13 in the form of a slit and is scanned in a direction perpendicular to the slit. The light is imaged on two linear imaging sections 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 imaging section through the transmission filter 15 of the color to be identified from the original, and on the other imaging section, a reflected light image is formed from the original. A reflected light image of the entire optical spectrum determined by the illumination light source, lens, reflecting mirror, etc. is formed without passing through the filter 15. The output signal of the imaging unit 14 is a monochrome image signal in which all colors are converted into brightness signals by a color separation circuit 16,
The filter 15 separates the color image signal. The two image signals from the color separation circuit 16 are A/D converted by the A/D converter 17, and if there are adjacent pixels between the two image signals, the adjacent pixel is removed by the adjacent pixel removal circuit 18. At least one of the data is removed and converted to blank data, and the image processing circuit 19 performs predetermined image processing as necessary. The image signal from the image processing circuit 19 is written into buffer memories 22 and 23 in the image memory 21 for timing adjustment with the writing system 20. The writing system 20 converts the image data from the buffer memories 22 and 23 into optical signals at a predetermined timing according to a command signal from the controller 24, and writes the optical signals onto the photoreceptor. The image forming section 25 is controlled by a controller 26,
An image is written on a photoreceptor using electrophotography, developed, and then transferred to transfer paper. By exchanging data with the controller 24, the controller 26 sends a timing signal for the writing system 20 to start writing to the controller 24, controls the image forming section 25 in accordance with the timing signal, and controls the filter. 1
A monochrome hard copy corresponding to the color data identified in step 5 is created. These reading system 12, writing system 20, and image forming section 25 are controlled by adjusting the timing by controllers 24 and 26, which are connected to each other through a communication path, and at the same time, data necessary for each operation is sent to the controller. It executes its respective functions while sending and receiving under the control of 24 and 26. Also,
The black data counter 27 counts the number of image data (black data in which an image is formed with black toner) from the image processing circuit 19 to the buffer memory 22 for each page (for each copy of one sheet).
The count result is sent to the controller 24 as predicted data of toner consumption.

FIG. 6 shows the reading system 12 in this embodiment.
Shows a part of. The reflected light from the document on the document table is focused by the imaging lens 28, enters two prisms 30 and 31 having a half mirror 29 on the boundary surface, and is converted into transmitted light and reflected light by the half mirror 29. be divided. After the transmitted light and reflected light are totally reflected by prisms 30 and 31, charge coupled devices (CCDs) 32 and 3 that constitute the imaging section 14
The image is focused on 3. In front of the CCD 33, a filter 15 of a color to be used to identify the original is inserted. As the filter 15, a red absorption filter is used when the color of the document to be identified is red, for example. Here, the advantage of using two prisms 30 and 31 is that the CCD 32,
33 can be placed on the same plane. CCD32,33
Placing them on the same plane will make assembly and adjustment easier. The reflective surfaces of the lens 28, prism 30, and half mirror 29 have characteristics that do not absorb light in a specific spectrum in the visibility band from the light reflected from the original.
2, a white light original image is formed. In other words, CCD3
2 receives image information of the original as information on the brightness of reflected light. When a red filter is inserted as the filter 15 in front of the CCD 33, light other than red is absorbed by the red filter 15, so the document information from the red filter 15 is reflected from the image of colors other than red and black on the document. Light is red filter 15
It becomes darker. Further, the reflected light from the red image of the original passes through the red filter 15, and only the red component of the reflected light from the white image of the original passes through the red filter 15. Therefore, the image information received by the CCD 33 has the same level as the image information from the white part of the original and the image information from the red part of the original, resulting in data in which white and red cannot be distinguished. In addition, the amount of reflected light that the CCD 33 receives from parts of the original in colors other than red and white is reduced by absorption by the red filter 15, resulting in dark image data. In other words, the image information that the CCD 33 receives from the original is C
The image information obtained by removing the red image information from the image information received by the CD 32 from the original is obtained. If a color filter other than the red filter is used as the filter 15, the CCD 33 will similarly receive image information excluding the image information of that color. The reason why the filter 15 is inserted in front of the CCD 31 in this embodiment is that when changing the color of the toner stored in the second color developing device, which will be described later, to another color, the filter 15 is inserted in front of the CCD 31. This is to make it easier to replace the filter 15 when matching the color to be identified. If it is not necessary to replace the filter 15 alone, the prism 31
to have the function of a filter 15, or a half mirror 29.
The effect of the filter 15 is applied to the transmitted light of C.
A method such as adhering the filter 15 to the CD 33 can be adopted.

In this embodiment, the device shown in FIG. 7 can be used instead of the device shown in FIG. The device shown in FIG. 7 includes light receiving sections 34 and 35 of a two-line CCD in which a large number of light receiving elements are arranged adjacently at intervals equivalent to one pixel, and this light receiving section 34.
, 35, and is housed in an IC package having a window for receiving light at the top. Here, a filter 15 is formed in front of the light receiving section 35 on the surface of the IC chip, and the reflected light from the document on the document table enters through the imaging lens and the filter 15, and is transmitted to the CCD 33 in FIG. has the same functionality. The light receiving section 34 receives reflected light from the document on the document table through the imaging lens without passing through the filter 15, and has the same function as the CCD 32 shown in FIG. The line of the light receiving section 34 and the light receiving section 35 is arranged in a direction perpendicular to the scanning direction of the reading system 12 while illuminating the document with slit exposure, so as to be aligned with the image formation plane by the imaging lens. Since the image formed on this two-line CCD moves according to the scan for reading the original, the light receiving parts 34 and 35 are arranged so that the light receiving part 34 is on the upstream side in the image movement direction on the image forming plane. Ru. The images formed on the light receiving sections 34 and 35 arranged in the direction in which the document is scanned move in accordance with the speed at which the document is scanned. The line spacing between the light receiving sections 34 and 35 is 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 it takes for the reading system 12 to scan one pixel. Therefore, the image detected by the upstream light receiving section 34 is detected by the light receiving section 35 with a delay equivalent to one pixel in the sub-scanning direction. To identify the color of a document, image data at the same position on the document is compared, so 1.
An analog memory 36 is provided for the light receiving section 34 on the upstream side in order to compensate for the delay corresponding to a pixel and to match the detected images of the light receiving sections 34 and 35. The light receiving units 34 and 35 each convert the reflected light from the original into an electric signal using each photoelectric conversion element, and in detail, the flowing current is changed depending on the intensity of the reflected light, and the change in the current is integrated and converted into the amount of charge. do. The photo storage gates 37 and 38 control the start and stop of integration in the light receiving sections 34 and 35, respectively,
Charges accumulated by integrating for a predetermined time in each photoelectric conversion element of the light receiving section 34 are delayed by one pixel in the analog memory 36 and transferred in parallel to the shift register 41 by the shift gate 39 . Charges accumulated by each photoelectric conversion element of the light receiving section 35 by integrating for a predetermined time are transferred in parallel to a shift register 42 by a shift gate 40 . The 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 amount of charges is converted into voltage at the output section 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 three-line CCD equipped with red, green, and blue filters detects the red, green, and
Compared to a method that identifies and reads each blue component, only specific color components of the document can be identified, but the photo storage gates 37 and 3 other than the 2-line light receiving sections 34 and 35
8, shift gates 39, 40, shift registers 41, 4
2. Since the peripheral circuit elements consisting of the analog memory 36 can be placed on both sides of the light receiving sections 34 and 35, the two light receiving sections 34
, 35 can be placed adjacent to each other. Therefore, only one analog memory 36 is required to adjust the time lag of the image signals from the two lines of light receiving sections 34 and 35. And I.C.
Since the manufacturing technology can be applied as is, the parallelism and alignment of the two lines of light receiving sections 34 and 35 can be easily increased, and the reading system 12 can be easily adjusted. However, since the filter is built-in, the color to be identified cannot be changed by simply replacing the filter.

FIG. 8 shows a part of the reading system 12. The image signals inputted from the CCDs 32 and 33 (or the device shown in FIG. 7) are image signals excluding the image signal not passed through the filter 15 and the image signal of the color of the filter 15, and the former is represented by W (white). , the latter is W (white image signal) −
It is represented by R (red image signal). W is external signal AGC1
The signal is input to an amplifier 43 whose amplification degree can be set by . The external signal AGC1 is set from the memory to the amplifier 43 in synchronization with the image signal by a start command from the controller 24 in FIG. Unevenness, C above
Variations in sensitivity between photoelectric conversion elements of the CD are corrected, that is, so-called shading correction is performed. amplifier 4
3 is an inverting amplifier whose output signal is B (black image signal). The amplifier 44 inputs W and (WR) to input terminals with different polarities, and subtracts (W-R) from W, and at the same time, similarly to the amplifier 43, outputs the external signal AGC2.
Shading correction is performed by the following and output as an image signal R having the same color as that of the filter 15. B from the amplifier 43 is converted into 6-bit digital data by the A/D converter 45, and converted into (BR) image data by the gate circuit 46 as described later. R from the amplifier 44 is A/D converted by a 1-bit A/D converter 48, that is, it is binarized at a predetermined binarization level and written into the buffer memory 23. The A/D converter 48 is configured such that its binarization level can be varied by a signal from the controller 24. For example, when the original paper to be copied is light pink, there are cases where it is desired to copy the original so that the background of the original is red or the background of the original is white. In such a case, each of the above-mentioned cases can be handled by changing the binarization level of the A/D converter 48 via the controller 24 in response to a selection signal from the operation unit according to the user's selection. . Gate circuit 46 is closed by R from A/D converter 48 when this R is present and opens when R from A/D converter 48 is not present. This gate circuit 46 is pulled down on the output side so that the output data becomes blank data when it is closed. Therefore, B from the A/D converter 45 is A/D
Gate circuit 46 when R from converter 48 is not present.
, and when R from the A/D converter 48 is present, it is converted into blank data by the gate circuit 46 and becomes (B-R). In this way, if B from the A/D converter 46 is converted into blank data by R from the A/D converter 48, even if there is a problem with the alignment or parallelism of the CCD, the image at a certain position will turn red. In essence, it does not occur that the color is both black and black at the same time.

The 6 bits (B-R
) can be expressed in 8 bits in the γ conversion unit 47 as 25
The data is converted into 8-bit data using a table configured to select any 64 states that can be expressed in 6 bits from 6 states, and is written into the buffer memory 22. This γ conversion unit 47 rewrites the data in the table using the controller 24, thereby converting the data into the reading system 12.
It is possible to correct the input/output characteristics of , correct the relationship between the amount of writing light of the electrophotographic image forming unit 25 and the image density of the copy, binarize, invert negative/positive, and so on. When writing red image data as multi-value data, use Figure 8 above.
The circuit shown in FIG. 9 is used instead of the circuit shown in FIG. In FIG. 9, the same parts as in FIG. 8 are given the same reference numerals, and the amplifier 4
R from 4 is binarized at a predetermined binarization level by the A/D converter 49, and when it is higher than the binarization level, it becomes 6
A/D conversion is performed to bit data. This A/D converter 49 is configured so that the binarization level can be varied by a signal from the controller 24. A/D converter 45
B from the A/D converter 49 passes through the gate circuit 50 as it is when there is no binary data from the A/D converter 49, and
When binary data from the converter 49 is present, it is converted into blank data by the gate circuit 50 and becomes (BR). The 6-bit R from the A/D converter 49 is converted to 8 bits by a table configured to select any 64 states that can be expressed in 6 bits from 256 states that can be expressed in 8 bits in the γ converter 51. The data is converted into data and written to the buffer memory 23. therefore,
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 the outline of the structure of this embodiment. This embodiment includes an upper document operation/reading section 100 and a printer section 20 that forms images using an electrophotographic method.
0. The document operation/reading unit 100 includes a document table 101 on which a document to be copied is placed, a document pressure plate 102 that presses the document on the document table 101, a light source 13 that illuminates the document on the document table 101, and a light source 13 that illuminates the document on the document table 101. A reflecting mirror 109 that focuses light on the area to be read, mirrors 104 to 106 that guide the reflected light from the original on the original platen 101 to the imaging device 108 and form an image, an imaging lens 28, and an illustration for scanning the original. It consists of a drive mechanism including a motor, etc. The imaging device 108 is the devices 15, 29 to 33 in FIG.
Alternatively, the apparatus of FIG. 7 is used. The user places the original on document table 1.
01 and press the print switch on the operation unit to start the copying operation, the light source 13 lights up and illuminates the original on the original platen 101, and the motor that scans the original is driven to scan the original. A scan is performed. Reflected light from the original on the original platen 101 is imaged by the mirrors 104 to 106 and the imaging lens 28 on the imaging device 108, and image data of the original is sequentially transferred line by line to the imaging device in response to changes in the scanning position of the original. It is output from 108. The image data from this imaging device 108 is transferred to the circuit 16 of the reading system 12 as described above.
The image data is processed in steps 1 to 19 and written to the image memory 21. The printer section 200 includes a writing section 250 surrounded by a chain line in the figure, a photoconductor 201, a black developing unit 210, a red developing unit 220, a transfer/conveyance unit 230, a cleaning unit 240, a main charger 203 that charges the photoconductor 201, and a fixing unit. unit 260, a belt cleaning unit 270 that cleans the transfer/transport unit 230, and a paper feed unit 29 that supplies transfer paper.
0, a resist unit 280 that aligns the transfer paper and the image on the photoreceptor 201, a static elimination charger 202, and the like. The writing section 250 constitutes the writing system 20 in FIG. 5, and the image forming section 25 in FIG. 5 constitutes the printer section 20.
0 except for the writing section 250. The writing unit 250 includes a motor integrated with an eight-sided polygon mirror 251, an fθ lens for scanning the photoconductor 201 at a constant speed with a laser beam modulated by a black image signal and deflected by the polygon mirror, and a reflection lens. A beam 252 formed by an optical component such as a mirror or dust-proof glass, and a laser beam modulated by a red image signal and deflected in a plane different from the beam 252 of the polygon mirror 251 are used to strike the photoreceptor 2.
Beam 253 formed by optical components such as an fθ lens, a reflector, and dustproof glass to scan 01 at a constant speed.
As a result, black image data and red image data are written on the photoreceptor 201. In this writing section 250, two beams 25 are generated using two surfaces of one polygon mirror 251.
2,253, the beam 2 on the photoreceptor 201
The scanning directions of 52 and 253 are reversed.

FIG. 11 is a plan view of the writing section 250, with the polygon mirror 251 viewed from above and the scanning plane of the beams 252 and 253, with the reflecting mirror omitted. The polygon mirror 251 is rotated by a motor in the direction of the arrow in the figure, and the scanning directions of the beams 252 and 253 on the photoreceptor 201 are reversed as indicated by the arrow in the figure. Positional relationship between the semiconductor laser LD1 that outputs a laser beam modulated by a black image signal to the polygon mirror 251, the semiconductor laser LD2 that outputs a laser beam modulated by a red image signal to the polygon mirror 251, and the polygon mirror 251 The positional relationship between the beams 252 and 253 is determined by setting the beam to a predetermined position. Therefore, it is necessary to detect the beam outside the image area and generate the beam modulation start timing using the image data of each line. The sensor D is provided only for the beam 252, and the sensor D is provided only for the beam 252.
The modulation start timing of 53 is generated by the same sensor D. The beam 252 writes on the photoreceptor drum 201 at a position A, and the beam 253 writes on the photoreceptor drum 201 at a position B. Therefore, 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 any deviation between the black image data and the red image data can be created on the photoreceptor drum 201. is formed. For this reason, the photoreceptor drum 2
The red image data written on the downstream side on A 01 is read from the original by the reading system 12 and processed.
, B by the number of lines corresponding to the distance between them, thereby compensating for the time difference between writing black image data and writing red image data.

Next, a series of image forming processes in this embodiment will be explained. The photoreceptor 201 is rotated by the main motor in the direction of the arrow shown in the figure, and is connected to the main charger 203.
Writing is performed at point A by the beam 252 which is uniformly charged and modulated by the black image signal (B-R) from the buffer memory 21, thereby forming an electrostatic latent image. This electrostatic latent image is developed with black toner by a black developing unit 210 to become a black developed image. Next, writing is performed on the photoreceptor 201 at point B by the beam 253 modulated by the red image signal R from the buffer memory 22, overlapping the black developing image, forming an electrostatic latent image. Only the latent image is developed with red toner by a red developing unit 220 so as not to disturb the black developed image, and becomes a red developed image. In parallel with this, a transfer sheet is fed from the sheet feeding section 290, and this transfer sheet is sent to the transfer/conveyance unit 230 by the registration unit 280 so that the developed image on the photoreceptor 201 coincides with the leading edge. In the transfer/conveyance unit 230, the transfer paper is conveyed by a conveyance belt, and the two-color developed image on the photoreceptor 201 is transferred to the transfer paper from the back side by corona charging by a charger. The transfer paper is further transported by the transport belt of the transfer/transport unit 230, the developed image is fixed by the fixing unit 260, and the paper is discharged outside the machine as a copy. Further, after the image transfer, the photoreceptor 201 is neutralized by a static elimination charger 202 and cleaned by a cleaning unit 240, so that image formation can be performed in the next cycle. The conveyance belt of the transfer/conveyance unit 230 is cleaned by a belt cleaning unit 270 after the transfer paper is conveyed to prevent the back side of the next transfer paper from becoming dirty. In the series of operations described above, if there is a red part in the original placed on the original platen 101, that part is automatically separated and the copying process is performed at exactly the same speed as when copying an original whose image is only black. It is copied as a two-color image combined with a black image. Furthermore, if the original image is only black, the black image is copied as in a normal copying machine. The person operating the copying machine does not have to worry about whether or not there is a red part in the document; the red part is automatically processed, so it is not troublesome. In this embodiment, not only the color identification function of the original is used to add color to the copy, but also the function is similar to that of a conventional monochrome copying machine or a copying machine with a partial color change function. It is also possible to

FIG. 12 shows the configuration of the portion of the controller 26 that controls everything other than the image reading system 12 and the writing system 20 that mainly controls the printer section 200 in this embodiment. The controller 26 is composed of microcomputers 57-59. The microcomputer 57 drives various AC loads 60 and various DC loads 61 such as motors, solenoids, and clutches of the printer section 200 via drivers 62 and 63, and receives signals from various sensors 64 via a signal processing circuit 65. Furthermore, the microcomputer 57 also includes a high voltage power supply 66, a sorter 67,
Controls peripheral devices such as the automatic document feeder 68. Further, the microcomputer 58 controls the operation section/display section 56, and the microcomputer 59 controls the drive section 69 for scanning the document, the document illumination light source 13, and the fixing unit 260.
The fixing heater 71 and the like are controlled. The microcomputers 57 to 59 are connected through a communication path with the microcomputer 57 serving as a master. As shown in the figure, a path for exchanging signals that cannot be completed in time by the communication path alone is between the microcomputer 57 and the microcomputer 5.
An interface is provided between the microcomputers 57-59 and the controller 24, and between the controller 24 and the microcomputers 57-59 that handle image data.

In this embodiment, the amount of toner consumption is predicted from the image data read from the original, and 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 a count value of black image data from the black data counter 27 at every predetermined timing as a predicted value of toner consumption. And controller 24
transmits the predicted value of the toner consumption amount 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 amount. 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 connected to the various sensors 64 shown in FIG.
include. The microcomputer 57 inputs the toner concentration detection signal from the toner concentration sensor to a signal processing circuit 65.
Input via . A toner replenishment clutch replenishes toner to the developer in the black developing unit 210. This toner replenishment clutch is included in various DC loads 61 shown in FIG. 12, and is driven by an output signal from the microcomputer 57 via a driver 63 to rotate the toner replenishment roller and the like in the black developing unit 210.

FIGS. 13(a) and 13(b) show the structure of the black developing unit 210. The developer inside the black developing unit 210 is sent to the developer supply roller 212 while being stirred by the developer stirring roller 211.
The developing sleeve 213 is transported by the developer sleeve 213 and supplied to the developing sleeve 213 . A magnet is disposed inside the developing sleeve 213, and this 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 is conveyed to the developer regulating member 215 through the separator 214, where the excess is removed and the developer is regulated to a constant thickness.
The electrostatic latent image on the photoreceptor drum 201 is developed by moving to a developing position opposite to the photoreceptor drum 201 . After passing through the development position, the developer on the developing sleeve 213 passes through a part where there is no (or low) magnetic force due to the magnet, and then reaches the developing sleeve 21.
Move away from 3. The developer separated from the developing sleeve 213 is transferred from the developer supply roller 212 to the developer stirring roller 21.
1 and stirred again. Further, the excess developer removed from the developing sleeve 213 by the developer regulating member 215 is sent to the developer stirring roller 211 through the separator 214 and is stirred with the toner replenished 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 driven by the motor 21 via a clutch 2111.
Rotationally driven by 10. From the hopper 216 to the developing chamber 2
Toner replenishment roller 21 supplies toner to the developer in 19.
7 is rotated. The toner concentration sensor described above 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 installed at a position adjacent to the developer regulating member 215 and separator 214 in the developing chamber 219 and close to the developing sleeve 213, and at a position where the electrostatic latent image on the photoreceptor drum 201 is developed. Detects the toner density of the developer at a nearby location.

FIG. 14 shows a functional block diagram of the toner density control section in this embodiment. Above black data counter 2
7 is image data (black data) from image reading system 12
A predicted value of toner consumption is obtained by counting TU, and this 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 . This two-input adder/subtracter 73 subtracts the output value PV of the toner concentration sensor 218 from the target value SP of the toner concentration, and calculates the difference e.
is calculated, and the PI controller 75 calculates P for this deviation e.
Executes I calculation and outputs the result as manipulated variable 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 a ring buffer and output as the operation amount D via the recovery processing section 76. This operation amount D drives the toner replenishment clutch, and the amount of toner determined by the operation amount D is replenished by the toner replenishment roller 217. Here, if the toner supply amount TR is ignored, the target value SP and the detected value PV of the toner concentration of the developer are input to the two-input adder/subtractor 73.
A feedback control system is constructed which performs a PI calculation based on the comparison, and replenishes toner based on the resulting PI.

Furthermore, the deviation e from the two-input adder/subtractor 73
is input to the function generation block 77 and the toner correction coefficient F
X is obtained, and the toner correction coefficient FX and the predicted value TU of the toner consumption amount are multiplied in the multiplication block 72, so that the predicted value TU of the toner consumption amount and the developer in the black developing unit 210 at the present time are The toner replenishment amount TR is obtained in consideration of the toner concentration. This toner supply amount TR is stored in a ring buffer and input to the recovery processing section 76. Normally, the recovery processing unit 76 passes through the sum of the toner replenishment amount TR stored in the ring buffer and the operation amount PI as is as the operation amount D, but the recovery processing unit 76 passes through the value obtained by adding the toner replenishment amount TR stored in the ring buffer and the operation amount PI as is. 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 replenishment amount is adjusted in the copy cycle after the abnormality is recovered. This is done based on the toner replenishment data that was not used. Figure 1 shows this recovery process.
8, will be explained in detail later based on the flowchart of FIG. The functional block diagram in FIG. 14 includes a feedforward control system that replenishes toner by predicting toner consumption by counting image data, and a feedforward control system that replenishes toner by predicting toner consumption by counting image data, and a feedforward control system that detects the toner concentration of the developer and compares it with a target value. It is combined with a feedback control system that performs replenishment.

The functional block diagram of FIG. 14 is realized using a microcomputer 57, and the schematic flow of the microcomputer 57 is shown in FIGS. 16 and 17. first,
The main processes of the toner consumption prediction process flow of the feedforward control system will be explained with reference to FIG. Toner consumption prediction processing is performed by periodically generating an interrupt using a timer to generate a kick signal. In the toner consumption prediction process, the microcomputer 57 executes step 30 if the image reading system 12 is currently reading.
0 to 303 are executed, and if the image reading system 12 is not reading, it waits for the next interrupt by the timer. The microcomputer 57 predicts the toner consumption amount 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. And microcomputer 57
In step 302, the toner consumption amount TU is multiplied by the toner correction coefficient FX to obtain the toner replenishment amount TR, and in step 30
At step 3, the data input this time (toner supply amount TR) is stored in the ring buffer.

Next, the main processes of the toner replenishment process flow of the feedback control system will be explained with reference to FIG. The toner replenishment process flow is performed by generating a kick signal by executing the toner consumption amount prediction process five times. In the toner replenishment processing flow, the microcomputer 57 first reads the target value SP of the toner concentration in step 310.
In step 311, the control amount PV from the toner concentration sensor 74 is read. Next, in step 312, the microcomputer 57 subtracts the control amount PV from the target value SP of the toner concentration to obtain the deviation e.
is calculated, and in step 313, PI calculation is performed for this deviation e to determine the manipulated variable PI for feedback control. Next, the microcomputer 57 performs step 31.
4 performs the recovery process described later, and then returns to step 315.
At , the toner replenishment clutch is driven by the value of the operation amount D to perform toner replenishment. By repeatedly performing such processing, the microcomputer 57 has a toner replenishment processing function of a feedback control system. The reason why the startup interval of the feedforward control system is narrower than the startup interval of the feedback control system is that due to wasted time and delay time, toner replenishment by the feedback control system becomes excessive and the toner concentration of the developer becomes too high. This is to prevent

FIG. 15 shows the deviation e and the toner correction coefficient FX.
Indicates the relationship between The microcomputer 57 searches for a preset toner correction coefficient FX from the deviation e=SP-PV between the target value SP of the toner concentration and the control amount PV. As the characteristic curve showing the relationship between the deviation e and the toner correction coefficient FX, one of the characteristic curves shown by the solid line, the dotted line, and the dashed-dotted line in FIG. 15 is used. In practice, a characteristic curve with good control results can be determined and used through experiments that take the following points (1) to (3) into consideration. (1) When the deviation e is close to "0", the toner correction coefficient is set to a value close to "1". (2) When the deviation e tends to increase in the + direction, the toner correction coefficient is “1” when e=0.
Select the characteristic curve with the largest slope. (3) When the deviation e tends to increase in the negative direction, select a characteristic curve with a small slope and a toner correction coefficient of "1" when e=0. In other words, even if the predicted toner consumption is the same, if the toner concentration at that time is high, the amount of toner replenishment is reduced, and if the toner concentration is low, the amount of toner replenishment is increased, thereby making the toner concentration of the developer more stable. Make it what you want.

FIG. 18 is a flowchart showing the recovery process of the microcomputer 57 when an abnormality occurs. The microcomputer 57 determines whether or not the recovery toner replenishment flag is "1" in step 316 to determine whether the copy cycle has been interrupted due to an abnormality such as a transfer paper jam, and the copy cycle is interrupted. If not and the recovery toner replenishment flag is not "1", in step 317, the operation amount D is set as the value obtained by adding the toner replenishment amount TR stored in the ring buffer and the operation amount PI, and the recovery process is terminated. Further, if the copy cycle is interrupted and the recovery toner replenishment flag becomes "1", the microcomputer 57 performs step 318.
, it is determined whether the data input this time (toner replenishment amount TR) is greater than or equal to the recovery toner replenishment amount, which will be described later. If the currently input data is equal to or greater than the recovery toner replenishment amount, the microcomputer 57 subtracts the recovery toner replenishment amount from the currently input data in step 319, and sets the result as the recovery toner replenishment amount. In step 320, this recovery toner replenishment amount and the manipulated variable PI are added, and the result is set as the manipulated variable D. Furthermore, the microcomputer 57 performs step 32.
At step 1, the toner replenishment amount TR in the ring buffer is set to "0", and at step 322, the recovery toner replenishment flag is set to "0", and the recovery process is completed. Furthermore, if the currently input data is smaller than the recovery toner replenishment amount, the microcomputer 57 subtracts the currently input data from the recovery toner replenishment amount in step 323, and sets the result as the recovery toner replenishment amount.
In step 324, the manipulated variable PI is set to the manipulated variable D, and the recovery process ends.

FIG. 19 is a flowchart showing the calculation of the recovery toner replenishment amount by the microcomputer 57. When the copy cycle is interrupted due to an abnormality such as a transfer paper jam, the microcomputer 57 uses the history data of the toner replenishment command signal stored in the ring buffer (data indicating that toner has been replenished but toner has not been consumed). ) is processed as follows. The microcomputer 57 calculates the recovery toner supply amount in step 325. That is, the microcomputer 57 calculates the recovery toner supply amount by adding 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. Then, in step 326, it is determined whether the recovery toner replenishment amount is "0". Then, if the recovery toner replenishment amount is not "0", the microcomputer 57 sets the recovery toner replenishment flag to "1" and finishes the recovery toner replenishment amount calculation, and also sets the recovery toner replenishment amount to "0". If so, the recovery toner replenishment amount calculation ends.

FIG. 20 shows the memory used for recovery processing. The ring buffer 78 is a memory that stores the history of toner replenishment command signals from the microcomputer 57, and after writing the leading edge of digitally expressed image data (black data) to the photosensitive drum 201, the leading edge data is stored. The time required for development is approximately 300 mS. Since the toner consumption amount prediction process is started at a 50 mS cycle, toner concentration control is executed six times during that time using the toner replenishment command signal. The minimum required capacity of the ring buffer 78 is 6 data (or 7 data). Input pointer and output pointer are ring buffer 7
8, and manages 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”. In the recovery toner replenishment amount memory 80, the unconsumed toner replenishment amount is stored by the microcomputer 57.

FIG. 21 shows an example of toner replenishment timing before and after a jam occurs in this embodiment. The jam detection timing indicates the timing at which an abnormality in conveyance of the transfer paper is detected, the copy cycle is interrupted, and this embodiment is stopped. The toner replenishment commands ■, ■, ■, etc. are based on the predicted toner consumption data obtained by counting image data and the toner density data obtained by the toner density sensor 74 in the black developing unit 210, as shown in FIG. This is data indicating the amount of toner replenishment obtained by software in a functional block, and the rotation of the toner replenishment roller 217 is controlled based on this data to perform toner replenishment. Timing of toner consumption■',■'
, ■'..., the image data counted in order to predict the toner consumption amount is then written on the photosensitive drum 201 by the optical writing device 250 and the black developing unit 21
0, the black developing unit 21
0 indicates the time required for the toner to move to the photoreceptor drum 201 and be consumed. In the example shown in FIG. 21, four toner replenishment commands ■ to ■ are issued before the jam occurs, and the developer in the black developing unit 210 is replenished with toner. Then, the copy cycle is interrupted due to the occurrence of a jam, and the only toner actually consumed is that which was replenished by one toner replenishment command ■, and the toner is replenished by the other three toner replenishment commands ■ to ■. The stored toner 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 normal toner replenishment is performed, the toner replenishment command is issued.
The supplied toner becomes redundant due to (2), and the amount of toner in the developer in the black developing unit 210 becomes excessive, which impairs the stability of the toner concentration in the developer. Therefore, in this embodiment, the microcomputer 57 stores the history of the toner replenishment command signal in the ring buffer 78,
When issuing a toner replenishment command signal after clearing a jam, the amount of unconsumed toner is corrected as described above and the toner replenishment command is issued.
and issues subsequent toner replenishment commands. Note that the present invention can also be applied to electrophotographic printers and the like. Further, in the above embodiment, the first developing unit 210 performs development with black toner, the second developing unit 220 performs development with red toner, and the function for identifying the color of the original is made to match those colors. However, 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 identified, which is set regardless of the color to be identified, is changed to match the color of the toner stored in the second developing unit 220, which can be set in the printer section 200 with different toner colors. Therefore, in order to cope with this, the color of the toner stored in the second developing unit 220 and the color to be identified may be separately displayed on the operation section/display section 56.

[0036]

[Effect of the invention] As described above, according to the invention of claim 1,
A recording body to be moved; a writing means for writing digitally expressed image data onto the recording body to form an electrostatic latent image; In the digital image forming apparatus, the digital image forming apparatus includes a toner consumption amount predicting means for predicting toner consumption amount by counting digitally expressed image data to be written on the recording medium; and a control means for issuing a toner replenishment command based on the predicted value of the toner consumption amount prediction means based on the image data corresponding to the electrostatic latent image earlier than the image is developed. It is possible to replenish the toner, stabilize the toner concentration with higher precision, and form a high-quality image.

Further, according to the second aspect of the invention, there is provided a recording body that is moved, a writing means for writing digitally expressed image data onto the recording body to form an electrostatic latent image, and a toner replenishment command that causes the toner to replenish. In the digital image forming apparatus, the toner consumption amount is predicted by counting the digitally expressed image data to be written on the recording medium in a digital image forming apparatus having a developing means for developing the electrostatic latent image with the developer. a toner consumption amount predicting means, a toner concentration detecting means for detecting the toner concentration of the developer in the developing means, and image data corresponding to the electrostatic latent image earlier than the developing means develops the electrostatic latent image; The control means for issuing a toner replenishment command based on the predicted value of the toner consumption amount predicting means and the detected value of the toner concentration detecting means is provided. By replenishing the toner, it is possible to stabilize the toner concentration with higher precision and to form a high-quality image.

According to the third aspect of the invention, there is provided a recording medium that is moved, a writing means that writes digitally expressed image data onto the recording medium to form an electrostatic latent image, and a toner that is developed by a toner replenishment command. In a digital image forming apparatus having a developing means that is supplied with a developer and develops the electrostatic latent image with a developer, toner consumption is predicted by counting digitally expressed image data to be written on the recording medium. an amount predicting means; a toner concentration detecting means for detecting the toner concentration of the developer in the developing means;
feedback control means for comparing the detection value of the toner concentration detection means with a target value and issuing a first toner replenishment operation amount based on the comparison result; 2, and a control means that issues a toner replenishment command based on the first toner replenishment operation amount and the second toner replenishment operation amount. By performing toner replenishment using the first toner replenishment operation amount based on the comparison result with the toner consumption amount and the second toner replenishment operation amount based on the predicted value of toner consumption and the comparison result, more accurate toner concentration can be achieved. can be stabilized, and high-quality images can be formed.

According to the fourth aspect of the present invention, in the digital image forming apparatus according to the third aspect, since the control loop execution interval of the feedforward control means is made shorter than the control loop execution interval of the feedback control means, wasted time and The delay time can prevent the toner concentration of the developer from becoming too high due to excessive toner replenishment by the feedback control means.

According to the invention of claim 5, claim 1 or 2
Or, in the digital image forming apparatus according to 3 or 4, when the image forming cycle is stopped due to an abnormality during image formation, unconsumed toner is replenished by the developing means prior to toner consumption by a toner replenishment command. Equipped with a toner replenishment amount correction means that corrects the amount of toner refilled with respect to the toner replenishment amount when replenishing toner after recovering from an error, the toner replenishment amount can be adjusted even if the image forming cycle is stopped due to an error during image formation. Even if the balance between replenishment and consumption is out of order, the amount of unconsumed toner can be corrected after the error has been recovered, allowing for more accurate toner density stabilization and high-quality image formation. It can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the invention of claim 1.

FIG. 2 is a block diagram showing the invention according to claim 2.

FIG. 3 is a block diagram showing the invention according to claim 3.

FIG. 4 is a block diagram showing the invention according to claim 5.

FIG. 5 is a block diagram showing one embodiment of the present invention.

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

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

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

FIG. 11 is a diagram of the writing unit of the above embodiment, viewed from above with a polygon mirror and with the beam scanning surface developed on a plane with the reflecting mirror omitted.

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

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

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

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

FIG. 16 is a flowchart showing toner replenishment processing of the microcomputer in the above embodiment.

FIG. 17 is a flowchart showing toner consumption prediction processing of the microcomputer in the above embodiment.

FIG. 18 is a flowchart showing recovery processing of the microcomputer in the above embodiment.

FIG. 19 is a flowchart showing recovery toner replenishment amount calculation by the microcomputer in the above embodiment.

FIG. 20 is a diagram showing a memory used for recovery processing in the above embodiment.

FIG. 21 is a timing chart showing an example of toner replenishment timing before and after a jam occurs in the above embodiment.

[Explanation of symbols]

1, 3, 6 Toner consumption prediction means 2, 5, 10
control means

Claims (5)

[Claims] 1. A recording medium that is moved; a writing device that writes digitally expressed image data onto the recording medium to form an electrostatic latent image; A digital image forming apparatus having a developing means for developing a latent image with a developer, a toner consumption predicting means for predicting toner consumption by counting digitally expressed image data to be written on the recording medium, and a toner consumption predicting means for predicting toner consumption by counting digitally expressed image data to be written on the recording medium; A control means for issuing a toner replenishment command based on a predicted value of the toner consumption amount predicting means based on image data corresponding to the electrostatic latent image earlier than the means develops the electrostatic latent image. Digital image forming device. 2. A recording medium that is moved; a writing device that writes digitally expressed image data onto the recording medium to form an electrostatic latent image; A digital image forming apparatus having a developing means for developing a latent image with a developer, a toner consumption predicting means for predicting toner consumption by counting digitally expressed image data to be written on the recording medium, and a toner consumption predicting means for predicting toner consumption by counting digitally expressed image data to be written on the recording medium; a toner concentration detecting means for detecting the toner concentration of the developer in the means; and a predicted value of the toner consumption amount predicting means based on image data corresponding to the electrostatic latent image earlier than the developing means develops the electrostatic latent image. and a control means for issuing a toner replenishment command based on the detected value of the toner concentration detection means. 3. A recording medium that is moved; a writing device that writes digitally expressed image data onto the recording medium to form an electrostatic latent image; A digital image forming apparatus having a developing means for developing a latent image with a developer, a toner consumption predicting means for predicting toner consumption by counting digitally expressed image data to be written on the recording medium, and a toner consumption predicting means for predicting toner consumption by counting digitally expressed image data to be written on the recording medium; toner concentration detection means for detecting the toner concentration of the developer within the means; feedback control means for comparing the detected value of the toner concentration detection means with a target value and issuing a first toner replenishment operation amount based on the comparison result; feedforward control means for issuing a second toner replenishment operation amount based on the predicted value of the toner consumption amount prediction means and the comparison result; and toner replenishment using the first toner replenishment operation amount and the second toner replenishment operation amount. A digital image forming apparatus comprising: a control means for issuing a command. 4. A digital image forming apparatus according to claim 3, wherein the control loop execution interval of the feedforward control means is narrower than the control loop execution interval of the feedback control means. 5. In the digital image forming apparatus according to claim 1, when the image forming cycle is stopped due to an abnormality during image formation, the developing means issues a toner replenishment command to precede toner consumption. A digital image forming apparatus comprising: a toner replenishment amount correction means for correcting the amount of unconsumed toner out of the toner replenished during toner replenishment with respect to the toner replenishment amount at the time of toner replenishment after recovery from an abnormality. Device.