JP4319833B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer. In particular, a developing device that visualizes an electrostatic latent image formed on an image carrier such as a photoreceptor using a two-component developer composed of toner and a magnetic carrier (hereinafter simply referred to as “carrier”). And an image forming apparatus including means for supplying consumed toner to a developing device.
[0002]
[Prior art]
In an electrophotographic apparatus using a two-component developer composed of toner and carrier, the density of the output image is affected by the mixing ratio. Therefore, in order to stabilize the density of the output image, it is essential to control the toner density in the developer by supplying toner corresponding to the amount consumed by printing to the developing device. A conventional toner supply device that performs this is described in, for example, Japanese Patent Application Laid-Open No. H10-228707. This conventional toner supply apparatus will be described with reference to the drawings.
[0003]
Generally, an electrophotographic image forming apparatus records an image in one color. However, with the recent spread of color image processing by computers and the increase in the number of printed materials, what is recorded in two or more colors has become widespread. Here, for simplicity, an apparatus for recording in two colors will be described.
[0004]
FIG. 10 is a configuration diagram in the vicinity of a photosensitive drum in an image forming apparatus using a conventional toner supply device. Around the photosensitive drum 101, a first developing unit 104 that performs development with the first recording color and a second developing unit 107 that performs development with the second recording color are arranged. In FIG. 10, the photosensitive drum 101 rotates in the direction of arrow A. A charger 108 for uniformly charging the surface of the photosensitive drum 101 is disposed on the upstream side of the first developing unit 104. A first exposure unit 102 is provided between the charging unit 108 and the first developing unit 104, and a laser beam 103 from the first exposure unit 102 scans the photosensitive drum 101. Further, a second exposure unit 105 is provided between the first developing unit 104 and the second developing unit 107, and the laser beam 106 from there scans the photosensitive drum 101.
[0005]
The first developing device 104 develops the first electrostatic latent image formed on the photosensitive drum 101 by the scanning of the laser beam 103 with, for example, black toner, and the black toner image on the photosensitive drum 101. Form. The second developing device 107 has substantially the same structure as the first developing device 104, and the first electrostatic latent image formed on the photosensitive drum 101 by scanning with the laser beam 106 is used for the first development. Development is performed using toner having a polarity opposite to that of the toner used in the device 104, and a red toner image, for example, is superimposed on the photosensitive drum 101.
[0006]
A transfer unit 109 is disposed downstream of the second developing unit 107 and transfers a toner image onto a recording sheet (not shown) conveyed by a conveyance belt 110 conveyed in the direction of arrow B. Unnecessary toner is removed from the photosensitive drum 101 after the transfer by the cleaning blade 111 and then irradiated by the static elimination lamp 112 to remove unnecessary charges.
[0007]
Next, the developing device and the toner supply device will be described. Since the first developing device 104 and the second developing device 107 have substantially the same structure, only the first developing device 104 will be described here. As shown in FIG. 10, a toner supply device 113 that supplies toner to the developing device is integrally assembled with the developing device. A toner reservoir (not shown) that supplies toner to the toner supply device 113 is provided at the upper end of the toner supply device 113.
[0008]
The developing unit includes a developer stirring roll 114 disposed below the toner supply device 113, a developing roll 115 disposed at a position facing the photosensitive drum 101, and a developer transport that transports the developer to the developing roll 115. Each roll is rotated in the direction of an arrow. Further, a layer thickness regulating member 117 that regulates the layer thickness of the developer on the developing roll 115 is provided above the developing roll 115, and the developer is supplied from the developing roll 115 side above the developer conveying roll 116. A reverse plate 118 for returning to the stirring roll 114 side is provided.
[0009]
A carrier (not shown) is accommodated in the developing device, and the carrier and the toner supplied from the toner supply device 113 are mixed and stirred by the developer stirring roll 114 to become a developer. The developer is conveyed to the developing roll 115 side by the developer conveying roll 116, is adhered to the outer peripheral surface of the developing roll 115, is conveyed, is subjected to layer thickness regulation by the layer thickness regulating member 117, and then is exposed to light in the developing unit. Toner is transferred and attached to the electrostatic latent image on the body drum 101.
[0010]
FIG. 11 is a perspective view of a part of the toner supply device 113. FIG. 12 is a perspective view of the firing member roll 123 and the holed member 122 of the toner supply device 113. As shown in FIGS. 11 and 12, an opening 121 is formed at the bottom of the housing 120 of the toner supply device 113 along the rotation axis direction of the developer stirring roll 114, and a holed member 122 is formed in the opening 121. It is attached. The holed member 122 is formed by forming a large number of holes in a plate. A firing member roll 123 is disposed above the holed member 122. Two screws 125 and 126 are arranged above the firing member roll 123 with the partition portion 124 interposed therebetween. The screws 125 and 126 rotate in opposite directions to drop the toner substantially evenly on the foam member roll 123 while circulating the toner above the foam member roll 123. A hole 127 for receiving toner supplied from a toner reservoir (not shown) is formed on the upper surface of the housing 120.
[0011]
The toner held in the toner reservoir falls into the toner supply device 113 by gravity, is circulated by the screws 125 and 126, falls onto the firing member roll 123, and adheres to the firing member roll 123. The foaming member roll 123 is driven to rotate by a toner supply motor, which will be described later, so that the adhered toner is rubbed against the holed member 122 and the toner is dropped through the hole and supplied to the developing devices 104 and 107.
[0012]
FIG. 13 is a block diagram of the control unit of the toner supply device 113. As illustrated in FIG. 13, the control unit includes a CPU 130, a ROM 131, a RAM 132, and an input / output control device 133 that are connected to each other via a bus 137. The input / output control device 133 includes an interface 134 for inputting image data to be printed, a console 135 disposed on the front surface of the housing of the image forming apparatus, and a toner supply motor that drives the firing member roll 123 of the toner supply device 113. 136 etc. are connected. In this control unit, the CPU 130 performs toner supply control by executing a program stored in the ROM 131 using the RAM 132 as a work area.
[0013]
FIG. 14 is a functional block diagram illustrating functions of the control unit of the toner supply device. In this way, the control unit stores the pixel number integration / storage unit 143 that accumulates and stores the number of print pixels of the image data, and the driving time of the toner supply motor 136 per predetermined number of pixels corresponding to a plurality of stages. The storage unit 140, the selection unit 141 for selecting any one of the plurality of steps stored in the storage unit 140, and the integrated value obtained by the pixel number integration / storage unit 143 is set to a predetermined number of pixels. And a motor control unit 142 that drives the toner supply motor 136 for a driving time corresponding to the stage selected by the selection unit 141. Here, the pixel number integration / storage unit 143 is realized by the CPU 130, the RAM 132, and the ROM 131 that calculate and store the number of pixels from the image data input to the interface 134. The motor control unit 142 is realized by the CPU 130, the ROM 131, and the RAM 132 in FIG. The pixel number integration / storage unit 143 in FIG. 14 sends the pixel number integration value 144 to the motor control unit 142 and receives a reset signal 145 from the motor control unit 142 to reset the pixel number integration value. . When the integrated value 144 of the number of pixels sent from the pixel number integration / storage unit 143 reaches a predetermined number of pixels, the motor control unit 142 drives the drive signal 146 for the drive time corresponding to the stage selected by the selection unit 141. And the toner supply motor 136 is driven, and a reset signal 145 is sent to the pixel number integration / storage means 143.
[0014]
Here, the selection unit 141 selects a stage relating to the driving time of the toner supply motor 136 corresponding to the toner consumption per unit pixel specific to the image forming apparatus in order to maintain the reference output density required for the image forming apparatus. To do. However, even in the same image forming apparatus, the stage that can be selected for each apparatus varies depending on the potential state on the photosensitive material, development characteristics, and transfer characteristics.
[0015]
When image data is input to the interface 134, the printing operation starts. Further, based on the image data, the pixel number integration / storage means 143 calculates an integration value 144 of the number of pixels. When the integrated value 144 reaches a predetermined number of pixels, the motor control unit 142 drives the toner supply motor 136 for the driving time corresponding to the stage selected by the selecting unit 141, and reset signal for resetting the integrated value 144. 145 is output. In response to the reset signal 145, the pixel number integration / storage unit 143 newly starts the integration of the number of pixels. Only while the toner supply motor 136 is driven, toner is supplied from the toner supply device 113 to the first developing device 104 and the second developing device 107. In this way, a predetermined amount of toner is supplied each time the integrated value of the number of pixels of the image data reaches a predetermined value. Therefore, even if the image size changes, the fluctuation of the toner consumption amount between the toner supply operations is reduced, and an amount of toner close to the consumption amount can be supplied.
[0016]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-15248
[Problems to be solved by the invention]
In the above-described conventional image forming apparatus, only the number of pixels to be printed is counted, and toner is supplied when the integrated value (total number of printed pixels) reaches a predetermined number. Therefore, the difference between the toner concentration immediately after the toner supply and the toner concentration immediately before the next toner supply becomes large. As a result, there is a problem that the density of the printed image is not stable.
[0018]
In addition, toner supply is performed by driving the toner supply motor 136 for a driving time corresponding to the stage selected by the selection unit 141. The stage selected by the selection unit 141 varies depending on the potential state on the photosensitive material, development characteristics, transfer characteristics, and the like. That is, the amount of toner that is actually supplied during the toner supply operation varies from time to time, and the amount of toner supplied is controlled by changing the drive time of the toner supply motor 136. Since the developer is constantly circulated in the developing units 104 and 107, the toner density is large in the portion of the developer that flows under the toner supply device 113 during the time when the toner supply motor 136 is driven. When the toner supply motor 136 is not driven, the toner density is reduced in the portion that has flowed in the lower part of the toner supply device 113, and the toner density is uneven in the developing device. There has been a problem that unevenness of the density of the printed image is caused by the unevenness of the toner density.
[0019]
If the toner supply amount per unit time is reduced in order to reduce the toner density unevenness, there is a problem that the time for supplying a necessary amount of toner becomes longer.
[0020]
An object of the present invention is to solve the above-described conventional problems and to provide an image forming apparatus capable of printing an image having a stable density.
[0021]
[Means for Solving the Problems]
[0022]
A first image forming apparatus of the present invention is an image forming apparatus of a two-component developing system using a developer composed of toner and a magnetic carrier, and each page on which image characteristic information of a plurality of pixels is printed. An image characteristic counting unit that counts the toner consumption amount, a toner consumption amount estimation unit that estimates a consumed toner amount for each page to be printed based on the characteristic information counted by the image characteristic counting unit, and the toner consumption amount estimation unit A memory that sequentially accumulates the estimated values of the toner consumption estimated by the means and stores them as an integrated value; and a toner supply means that supplies toner into the developing device. The characteristic information includes a plurality of pixels. The image includes the number of pixels, the number of edges, and the number of pixels constituting a local angle, and the toner consumption estimation means calculates the number of pixels, the number of edges, and the local angle. Configure A value obtained by multiplying each of the number of pixels to be multiplied by a predetermined coefficient is used as a toner consumption estimated value, and the integrated value of the toner consumption estimated value stored in the memory is preset per toner. When the toner supply means exceeds the minimum supply amount in the supply operation, the toner supply means supplies toner corresponding to the integrated value into the developing device, clears the integrated value stored in the memory, and stores it in the memory. The toner supply means does not supply toner when the accumulated value of the stored estimated toner consumption value is less than the minimum supply amount.
[0023]
A second image forming apparatus of the present invention is an image forming apparatus of a two-component development system using a developer composed of toner and a magnetic carrier, and each page on which characteristic information of an image composed of a plurality of pixels is printed. An image characteristic counting unit that counts the toner consumption amount, a toner consumption amount estimation unit that estimates a consumed toner amount for each page to be printed based on the characteristic information counted by the image characteristic counting unit, and the toner consumption amount estimation unit A memory that sequentially accumulates the estimated values of the toner consumption estimated by the means and stores them as an integrated value; and a toner supply means that supplies toner into the developing device. The characteristic information includes a plurality of pixels. The image includes the number of pixels, the number of edges, and the number of pixels constituting a local angle, and the toner consumption estimation means calculates the number of pixels, the number of edges, and the local angle. Configure A value obtained by multiplying each of the number of pixels to be multiplied by a predetermined coefficient is used as a toner consumption estimated value, and the integrated value of the toner consumption estimated value stored in the memory is preset per toner. When less than the maximum supply amount in the supply operation, the toner supply means supplies toner corresponding to the integrated value stored in the memory, clears the integrated value stored in the memory, and stores the accumulated value in the memory. When the accumulated value of the stored estimated toner consumption value exceeds the maximum supply amount and there is an unprinted page, the toner supply means supplies toner corresponding to the maximum supply amount, and The maximum supply amount is subtracted from the integrated value stored in the memory, the integrated value of the estimated toner consumption amount stored in the memory exceeds the maximum supply amount, and an unprinted page exists. When not, the toner supply unit supplies toner corresponding to the integrated value stored in said memory, and wherein the clearing stored the accumulated value in the memory.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
[0027]
A first image forming apparatus of the present invention is an image forming apparatus of a two-component developing system using a developer composed of toner and a magnetic carrier, and each page on which image characteristic information of a plurality of pixels is printed. An image characteristic counting unit that counts the toner consumption amount, a toner consumption amount estimation unit that estimates a consumed toner amount for each page to be printed based on the characteristic information counted by the image characteristic counting unit, and the toner consumption amount estimation unit A memory that sequentially accumulates the estimated values of the toner consumption estimated by the means and stores them as an integrated value; and a toner supply means that supplies toner into the developing device. The characteristic information includes a plurality of pixels. The image includes the number of pixels, the number of edges, and the number of pixels constituting a local angle, and the toner consumption estimation means calculates the number of pixels, the number of edges, and the local angle. Configure A value obtained by multiplying each of the number of pixels to be multiplied by a predetermined coefficient is used as a toner consumption estimated value, and the integrated value of the toner consumption estimated value stored in the memory is preset per toner. When the toner supply means exceeds the minimum supply amount in the supply operation, the toner supply means supplies toner corresponding to the integrated value into the developing device, clears the integrated value stored in the memory, and stores it in the memory. The toner supply means does not supply toner when the accumulated value of the stored estimated toner consumption value is less than the minimum supply amount.
[0028]
As a result, the number of toner supply operations can be reduced, and the supply error in the toner supply means is also reduced. Accordingly, the accumulated error of the toner density in the developing device is reduced. As a result, a print image with a stable density can be provided.
[0029]
In the first image forming apparatus of the present invention, it is preferable that the minimum supply amount is determined based on a lower limit value of a range in which the toner supply unit can stably supply the toner. As a result, the supply error in the toner supply means is further reduced, and the accumulated error of the toner density in the developing device can be further reduced.
[0030]
A second image forming apparatus of the present invention is an image forming apparatus of a two-component development system using a developer composed of toner and a magnetic carrier, and each page on which characteristic information of an image composed of a plurality of pixels is printed. An image characteristic counting unit that counts the toner consumption amount, a toner consumption amount estimation unit that estimates a consumed toner amount for each page to be printed based on the characteristic information counted by the image characteristic counting unit, and the toner consumption amount estimation unit A memory that sequentially accumulates the estimated values of the toner consumption estimated by the means and stores them as an integrated value; and a toner supply means that supplies toner into the developing device. The characteristic information includes a plurality of pixels. The image includes the number of pixels, the number of edges, and the number of pixels constituting a local angle, and the toner consumption estimation means calculates the number of pixels, the number of edges, and the local angle. Configure A value obtained by multiplying each of the number of pixels to be multiplied by a predetermined coefficient is used as a toner consumption estimated value, and the integrated value of the toner consumption estimated value stored in the memory is preset per toner. When less than the maximum supply amount in the supply operation, the toner supply means supplies toner corresponding to the integrated value stored in the memory, clears the integrated value stored in the memory, and stores the accumulated value in the memory. When the accumulated value of the stored estimated toner consumption value exceeds the maximum supply amount and there is an unprinted page, the toner supply means supplies toner corresponding to the maximum supply amount, and The maximum supply amount is subtracted from the integrated value stored in the memory, the integrated value of the estimated toner consumption amount stored in the memory exceeds the maximum supply amount, and an unprinted page exists. When not, the toner supply unit supplies toner corresponding to the integrated value stored in said memory, and wherein the clearing stored the accumulated value in the memory.
[0031]
Thereby, it is possible to suppress the variation in the toner density in the developing device. As a result, a print image with a stable density can be provided.
[0032]
In the second image forming apparatus of the present invention, it is preferable that the maximum supply amount is determined based on an upper limit value of a range in which the toner supply unit can stably supply the toner. As a result, the supply error in the toner supply means is further reduced, and the accumulated error of the toner density in the developing device can be further reduced.
[0034]
In the first and second image forming apparatuses of the present invention, the image characteristic counting unit may include a pattern counter that counts the number of print pixels in which a print pixel and its peripheral pixels form a predetermined pattern. preferable. This makes it possible to estimate the toner consumption more accurately.
[0035]
Hereinafter, specific embodiments of the present invention will be described in detail.
[0036]
FIG. 1 shows a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention. The image forming apparatus of FIG. 1 is roughly divided into an image signal processing unit that processes input image data, and a laser optical system unit that generates light for exposure based on the image data processed by the image signal processing unit. An image forming unit that forms an image by an electrophotographic process, a toner supply mechanism that supplies toner to a developing device of the image forming unit, and a toner supply control unit that controls the toner supply mechanism. Each will be described below.
[0037]
The image signal processing unit includes an image signal processing circuit 1 that performs various correction processes on input image data and a laser driving circuit 2 that generates a laser driving signal based on the processed image data.
[0038]
The laser optical system unit includes a laser 3 that emits light based on a laser drive signal, a rotary polygon mirror 4 that sweeps laser light emitted from the laser 3, a lens system 5 that includes an f / θ lens that guides the swept light, and the like. And a mirror 6 for directing the guided light onto the photosensitive drum 7.
[0039]
The image forming unit realizes an electrophotographic process, and includes a photosensitive drum 7, a charger 8 that uniformly charges the surface of the photosensitive drum 7 around the photosensitive drum 7, and a post-charging laser optical system unit. A developing device 9 that visualizes an electrostatic latent image formed by exposure by attaching toner, and a toner image visualized on an intermediate transfer belt 13 supported by support rollers 11 and 12 are transferred. A first transfer device 10 that transports the recording paper 32, a second transfer roller 14 that transfers the toner image on the intermediate transfer belt 13 to the recording paper 32 transported by the transport belt 15, and an intermediate The cleaner 16 removes toner remaining on the photosensitive drum 7 without being transferred to the transfer belt 13, and the static eliminator 17 that removes residual charge remaining on the surface of the photosensitive drum 7. The recording paper 32 to which the toner image has been transferred is then heated and pressured by a fixing device (not shown) to fix the toner image, and then discharged outside the apparatus. Further, the developing device 9 is configured so that the developer composed of toner and carrier accommodated in the developer 9 adheres to the surface of the photosensitive drum 7, and the developer and toner are mixed uniformly with the carrier. And stirring screws 19 and 20 for circulating the inside of the developing device 9 while stirring. A density sensor 31 that detects the density of the toner image on the intermediate transfer belt 13 is installed in the vicinity of the intermediate transfer belt 13.
[0040]
The toner supply control unit 26 and the toner supply mechanism unit prevent the toner concentration in the developer inside the developing device 9 from being lowered by the toner adhering to the photosensitive drum 7 by the developing process, as necessary. Toner is supplied.
[0041]
The toner supply control unit 26 includes an image characteristic detection unit 27 that detects characteristics of the image from input image data, an integration unit 28 that integrates and stores numerical information detected by the image characteristic detection unit 27, and integration. A consumption amount estimation unit 29 that estimates the amount of toner that is expected to be consumed based on the numerical value stored in the unit, and the driving time of the toner supply motor 24 that is necessary to supply the estimated amount of toner And a supply amount calculation unit 30.
[0042]
The toner supply mechanism unit includes a conveyance screw 22 that conveys toner from the toner reservoir 21 to the developing device 9, a toner supply motor 24 that drives the conveyance screw 22, and a gear train that transmits the rotation of the toner supply motor 24 to the conveyance screw 22. And a motor drive circuit 25 that outputs a drive signal to the toner supply motor 24 only during the drive time calculated by the supply amount calculation unit 30.
[0043]
The operation of the image forming apparatus of the present embodiment configured as described above will be described.
[0044]
First, the input image data enters the image signal processing circuit 1. Here, image processing necessary for tilt correction such as skew correction is performed. The image signal processing circuit 1 outputs the processed image data to the subsequent laser driving circuit 2 and the image characteristic detection unit 27.
[0045]
The laser drive circuit 2 generates a laser drive signal for causing the laser 3 to emit light based on the input image data. The laser 3 emits light based on the drive signal generated by the laser drive circuit 2. The emitted light scans the surface of the photosensitive drum 7 through the rotary polygon mirror 4, the lens system 5 and the mirror 6.
[0046]
The photosensitive drum 7 rotates in the direction of the arrow at a predetermined timing. This will be described in the order of the electrophotographic process. First, the charger 8 charges the surface of the photosensitive drum 7 to a uniform potential. Next, the surface of the photosensitive drum 7 charged to a uniform potential is scanned with light irradiated from the laser optical system unit, and an electrostatic latent image corresponding to image data is formed on the surface of the photosensitive drum 7. It is formed. Thereafter, a developing device 9 using a two-component developer in which toner particles and carrier particles are mixed attaches toner to the electrostatic latent image on the photosensitive drum 7 to form a visible image. Inside the developing device 9, the agitating screws 19 and 20 are rotated so that the toner and the carrier are uniformly mixed. Through the flow described above, a toner image corresponding to the image data is formed on the surface of the photosensitive drum 7.
[0047]
The support rollers 11 and 12 are driven according to the timing of exposure. When the support rollers 11 and 12 are driven, the intermediate transfer belt 13 suspended thereon rotates in the direction of the arrow. Then, the first transfer device 10 transfers the toner image on the photosensitive drum 7 onto the intermediate transfer belt 13. The second transfer roller 14 transfers the toner image on the rotating intermediate transfer belt 13 onto the recording paper 32 that is conveyed by the conveyance roller 15 in time. The toner image transferred to the recording paper 32 is only placed on the recording paper 32 at this time. Thereafter, the recording paper 32 is heated and pressed by a fixing device (not shown) to fix the unfixed toner image, and is then discharged outside the apparatus.
[0048]
The cleaner 16 removes residual toner remaining on the photosensitive drum 7 after the transfer. Next, the static eliminator 17 neutralizes the residual charge on the photosensitive drum 7 to complete a series of electrophotographic processes.
[0049]
Here, the description is made using an example of a single color image forming apparatus. However, in the case of a multicolor image forming apparatus or a color image forming apparatus, peripheral elements including the photosensitive drum 7 and the developing device 9 have constituent colors. The toner images of the respective colors are superimposed on the intermediate transfer belt 13 to form an image.
[0050]
Next, the toner supply operation will be described. The image data processed by the image signal processing circuit 1 is also input to the image characteristic detection unit 27. The image characteristic detection unit 27 detects the characteristic of the image based on the input image data. Specifically, based on image data sequentially input for an image printed on one page of recording paper, the number of print pixels, the number of edges, and the number of pixel patterns that match a predetermined pattern (number of pattern matching) are determined. Detect and output to the integrating unit 28. Here, the number of edges is the number of sides that are edges among the four sides of one pixel to be printed. For example, when all the print pixels are isolated points, the number of edges is four times the number of print pixels. However, the edge in the main scanning direction and the edge in the sub scanning direction need to be counted separately. The accumulating unit 28 accumulates and stores the number of pixels, the number of edges, and the number of pattern matching that are sequentially input. When the printing of one page is completed, the accumulating unit 28 stores characteristic information of the printed one page image. This characteristic information is output to the consumption amount estimation unit 29.
[0051]
The consumption amount estimation unit 29 estimates the amount of toner consumed by printing the page based on the image characteristic information read from the integration unit 28. Specifically, the toner consumption amount is added by multiplying each integrated value of the image characteristic information by a predetermined coefficient. This predetermined coefficient is a value obtained experimentally in advance.
[0052]
The supply amount calculation unit 30 calculates a driving time of the toner supply motor 24 necessary for supplying an amount of toner corresponding to the estimated toner consumption amount. The toner accommodated in the toner reservoir 21 is conveyed by the rotation of the conveying screw 22 driven by the toner supply motor 24 and falls into the developing device 9. In this embodiment, a stepping motor is used as the toner supply motor 24. If the maximum pulse rate is fixed, the amount of toner supplied to the developing device 9 is uniquely determined by the total number of pulses. Therefore, the supply amount calculation unit 30 calculates the total number of pulses for driving the toner supply motor 24 from the amount of toner to be supplied, and outputs it to the motor drive circuit 25. Here, even when the so-called slow-up and slow-down operations in which the pulse rate is changed stepwise at the start and stop of driving of the toner supply motor 24, the total number of pulses and the supply are provided if the slope of the change is kept constant. A correlation can be obtained with the toner amount. The motor drive circuit 25 drives the toner supply motor 24 for a time corresponding to the total number of pulses input. The toner supply motor 24 rotates the conveying screw 22 through the gear train 23 and supplies a predetermined amount of toner to the developing device 9.
[0053]
As described above, when the printing operation for one page of recording paper is completed, the amount of toner consumed for printing the page is estimated, and the toner supply operation is immediately performed. Is kept substantially constant, so that an image having a stable density can always be obtained.
[0054]
Next, the toner supply control unit 26 will be described in detail. FIG. 2 shows a block diagram of the toner supply control unit 26. The image characteristic detection unit 27 includes a pixel detection circuit 40 that detects a print pixel of an image, a main scan edge detection circuit 41 that detects whether the print pixel is an edge in the main scanning direction, and an edge in the sub scanning direction as well. A sub-scanning edge detection circuit 42 for detecting whether or not a plurality of pixels, and a pattern detection circuit 43 for detecting whether or not a plurality of pixels centering on a print pixel coincide with a preset reference pattern 44. The accumulating unit 28 also counts the pixel counter 45 that counts the number of detections by the pixel detection circuit 40, the pixel register 49 that temporarily stores the value of the pixel counter 45, and the main scanning edge detection circuit 41 that counts the number of detections by the main scanning edge detection circuit 41. A scanning edge counter 46, a main scanning edge register 50 that temporarily stores the value of the main scanning edge counter 46, a sub scanning edge counter 47 that counts the number of detections by the sub scanning edge detection circuit 42, and a sub scanning edge counter 47 The sub-scanning edge register 51 that temporarily stores the value of the pattern counter 48, the pattern counter 48 that counts the number of detections of the pattern detection circuit 43, and the pattern register 52 that temporarily stores the value of the pattern counter 48.
[0055]
The operation of the toner supply control unit 26 having the above configuration will be described. The image data processed by the image signal processing circuit 1 is input in parallel to the pixel detection circuit 40, the main scanning edge detection circuit 41, the sub-scanning edge detection circuit 42, and the pattern detection circuit 43. Here, the image data input to the main scanning edge detection circuit 41, the sub-scanning edge detection circuit 42, and the pattern detection circuit 43 is image data of a plurality of pixels around the pixel of interest. That is, the image data of the target pixel and its left and right pixels are input to the main scanning edge detection circuit 41, and the image data of the target pixel and its upper and lower pixels are input to the sub-scanning edge detection circuit 42. It is. Also, the 3 × 3 pixel image data centered on the pixel of interest is input to the pattern detection circuit 43. This is determined by the size of the reference pattern 44 set in advance.
[0056]
At this time, the detection signals output from the pixel detection circuit 40, the main scanning edge detection circuit 41, the sub-scanning edge detection circuit 42, and the pattern detection circuit 43 are at a high level when they meet the respective conditions.
[0057]
That is, the pixel detection circuit 40 outputs a high-level detection signal when the pixel of interest is a print pixel, and remains at a low level otherwise.
[0058]
The main scanning edge detection circuit 41 detects whether the pixel of interest is an edge in the main scanning direction. That is, a high-level detection signal is output when the pixel of interest is a printing pixel and the left and right pixels are non-printing pixels. At this time, it is determined whether each of the left and right pixels is a non-printing pixel, and both the left and right pixels may be non-printing pixels. Therefore, the detection signal needs 2 bits. Similarly, the sub-scanning edge detection circuit 42 outputs a high-level detection signal when the pixel of interest is a print pixel and the upper and lower pixels are non-print pixels. Also at this time, it is determined whether or not each of the upper and lower pixels is a non-printing pixel, and both the upper and lower pixels may be non-printing pixels, so that the detection signal requires 2 bits.
[0059]
The pattern detection circuit 43 outputs a high-level detection signal when the arrangement of print pixels in the target pixel and its peripheral pixels matches a preset reference pattern 44. At this time, the number of bits of the detection signal is determined by the number of reference patterns. FIG. 3 shows four reference patterns used in the present embodiment. Reference is made to a maximum of 3 × 3 pixels in the vertical and horizontal directions around the pixel of interest (blacked portion). Black indicates printing pixels, white indicates non-printing pixels, and diagonal lines may be used. As can be seen from FIGS. 3A to 3D, it is detected here whether or not the pixel of interest is a print pixel constituting a local corner. In this example, since there are four reference patterns, it is necessary to output signals from 0 to 4, so that the detection signal requires at least 3 bits. In this way, when the reference pattern is determined in advance and does not need to be changed, the combinational logic for determining whether the pattern detection circuit 43 matches the reference pattern from the image signal of a maximum of 9 pixels of 3 × 3 pixels is determined. You may comprise with a circuit.
[0060]
Each detection signal generated by each detection circuit 40, 41, 42, 43 of the image characteristic detection unit 27 is input to a corresponding counter of the integration unit 28. The pixel counter 45, the main scanning edge counter 46, the sub-scanning edge counter 47, and the pattern counter 48 are cleared immediately before the printing of one page, and the respective detection signals are integrated during printing. Each subsequent pixel register 49, main scanning edge register 50, sub-scanning edge register 51, and pattern register 52 latch and store the corresponding counter values at the end of printing.
[0061]
Thereafter, the values of the pixel register 49, the main scanning edge register 50, the sub-scanning edge register 51, and the pattern register 52 are input to the subsequent consumption estimation unit 29 to estimate the amount of toner that may have been consumed in the current printing. . The estimation process is defined as a function of each register value. Specifically, the estimation process is obtained by multiplying each register value by a predetermined coefficient and summing them. Here, the value stored in the pixel register 49 is Cpix, the value stored in the main scanning edge register 50 is Cem, the value stored in the sub-scanning edge register 51 is Ces, and stored in the pattern register 52. If the current value is Cpat, the toner consumption amount Tcon is estimated using the following equation.
[0062]
Tcon = K1 × Cpix + K2 × Cem + K3 × Ces + K4 × Cpat
Here, the coefficients K1, K2, K3 and K4 are experimentally determined in advance.
[0063]
As described above, since the toner consumption amount due to printing can be estimated, the toner for this consumption is supplied. The supply amount calculation unit 30 calculates a necessary motor driving time from the amount of toner to be supplied. The motor drive circuit 25 generates a motor drive signal based on the drive time calculated by the supply amount calculation unit 30.
[0064]
FIG. 4 shows a first embodiment of the motor drive signal. Here, the supplied toner amount has a relationship of (b) <(a) <(c), but the maximum value of the drive pulse rate is Pmax, which is the same in any case. The amount of change in the pulse rate of the slow-up and slow-down (inclination angle of the inclined portion in FIG. 4) is also the same. That is, the toner supply amount is controlled by controlling the time during which the maximum pulse rate Pmax is output. The supply operation is performed after the printing of the page is completed and the toner amount to be supplied is calculated.
[0065]
Here, if a large amount of toner is supplied in a short time when the amount of toner to be supplied is large, the toner density distribution in the developing device 9 may vary, resulting in uneven image density. End up. Therefore, it is desirable to supply the toner as slowly as possible. In the first embodiment, the maximum pulse rate Pmax of the drive pulse for driving the toner supply motor 24 is fixed to a value that does not cause unevenness, and the time for outputting the maximum pulse rate Pmax is changed. The toner supply amount is controlled.
[0066]
Next, a second embodiment of toner supply control will be described. In the second embodiment, the toner is supplied for as long a time as possible. However, the amount of toner consumed for printing is supplied until the printing of the next page is completed. Specifically, when an engine capable of printing 20 pages per minute is used, the time required for printing per page is 3 seconds, so the toner supply is completed within 3 seconds. In this method, since it is necessary to change the maximum pulse rate of the toner supply motor 24 for each page, it is necessary to temporarily stop the driving of the motor 24 when the toner supply corresponding to printing of one page is completed. Therefore, it is desirable that the toner supply be completed in about 2.5 seconds in consideration of the time required for accessing each register and the toner consumption estimation process. FIG. 5 shows a motor drive signal in the second embodiment of the present invention. Also in FIG. 5, the toner supply amount has a relationship of (b) <(a) <(c). Again, the amount of change in pulse rate in the slow-up and slow-down operations, that is, the slope of the slope is the same.
[0067]
Next, the first embodiment (FIG. 4) and the second embodiment (FIG. 5) will be compared and examined with reference to FIG. In FIGS. 6A and 6B, F1 represents a motor drive signal for supplying toner corresponding to printing of the first page, and F2 represents toner supply corresponding to printing of the second page following this. The motor drive signal for performing is shown. The horizontal axis indicates time, and T0 means the time required for printing each page. The vertical axis represents the pulse rate of the drive pulse for driving the toner supply motor 24. Since the pulse rate is uniquely correlated with the toner supply amount per unit time, the vertical axis can be regarded as the toner supply amount per unit time. Accordingly, the trapezoidal areas V1 and V2 surrounded by the drive signals F1 and F2 and the time axis can be regarded as the total amount of toner supplied corresponding to the printing of the first page and the second page, respectively. . In this example, V1 <V2.
[0068]
FIG. 6A corresponds to the first embodiment (FIG. 4), and the maximum pulse rate is made constant at Pc, and the toner supply time is set to T1 according to the toner supply amounts of the first and second pages. By changing to T2 (time control), necessary toner supply amounts V1 and V2 are secured.
[0069]
FIG. 6B corresponds to the second embodiment (FIG. 5). The toner supply time is made constant at Tc, and the pulse rate (that is, the unit) according to the toner supply amount of the first page and the second page. By changing the supply amount per hour) to P1 and P2 (supply amount control), necessary toner supply amounts V1 and V2 are secured.
[0070]
From FIG. 6A and FIG. 6B, in the first embodiment (FIG. 6A) in which the total toner supply amount is controlled by the toner supply time, the toner supply time is not set as the time. Are clearly distinguished from each other, the toner density variation in the developing device 9 tends to increase. On the other hand, in the second embodiment (FIG. 6B) in which the total supply amount of toner is controlled by the supply amount of toner per unit time (FIG. 6B), although there is a difference in amount, toner is supplied almost constantly. Therefore, toner density variations in the developing device 9 are unlikely to occur. Therefore, as in the second embodiment (FIG. 6B), it is preferable to supply the toner with the toner supply time constant at Tc, since the density unevenness of the printed image is reduced.
[0071]
In this case, it is preferable that the toner supply time Tc substantially coincides with the time T0 required for printing one page. As a result, the time during which toner is not supplied can be reduced, so that variations in toner density in the developing device 9 can be further reduced.
[0072]
In the first embodiment (FIG. 4) and the second embodiment (FIG. 5), it is preferable to set a maximum supply amount of toner supplied in one toner supply operation. Then, the estimated toner consumption amount calculated for each printing of one page is sequentially accumulated and stored in the memory. When the integrated value of the estimated toner consumption amount stored in the memory is equal to or less than the maximum supply amount, an amount of toner corresponding to the integrated value is supplied, and the integrated value stored in the memory is cleared. When the integrated value stored in the memory exceeds the maximum supply amount, it is determined whether there is a next page to be printed. If there is a next page, an amount of toner corresponding to the maximum supply amount is supplied, and an amount corresponding to the maximum supply amount to which toner has been supplied is subtracted from the integrated value stored in the memory. When there is no next page, the toner corresponding to the accumulated value stored in the memory is supplied and the accumulated value stored in the memory is cleared. In this way, the maximum supply amount per one toner supply operation is set, and the portion exceeding the maximum supply amount is accumulated in the memory as an unsupplied portion, and the estimated toner consumption amount calculated thereafter is maximum. When the supply amount falls below, the unsupplied portion stored in the memory is added and supplied.
[0073]
In the first embodiment (FIG. 4), when the maximum supply amount per one toner supply operation is set as described above, for example, when continuously printing pages with a high printing rate, the maximum pulse rate is set. The toner supply motor 24 is continuously driven at Pmax. Thereby, the variation in the toner density in the developing device 9 can be suppressed. Further, the continuous driving of the toner supply motor 24 can reduce supply errors caused by backlash of the gear train 23 when driving and stopping are repeated. Also by this, it is possible to suppress variation in toner density in the developing device 9. As a result, image density variations can be reduced. Therefore, it is preferable that the maximum supply amount of the toner is determined based on an upper limit value of a range in which the toner supply mechanism unit can stably supply the toner.
[0074]
In the second embodiment (FIG. 5), when the maximum supply amount per one toner supply operation is set as described above, the pulse rate (P1, P2 in FIG. 6B) is set between the toner supply operations. ) Becomes smaller. Thereby, the variation in the toner density in the developing device 9 can be suppressed. In addition, the toner supply accuracy of the toner supply mechanism unit including the conveying screw 22, the toner supply motor 24, and the gear train 23 is improved, and the variation in the toner density in the developing device 9 can also be suppressed. As a result, image density variations can be reduced. Therefore, the maximum value of the toner supply amount can reduce the difference in the pulse rate for supplying toner corresponding to each page, and as a result, the upper limit value of the range in which the toner supply mechanism unit can stably supply toner. It is preferable to be determined based on this.
[0075]
However, when the maximum value of the toner supply amount that can be supplied by one toner supply operation is set as described above and a plurality of pages are continuously printed, the printing rate (number of printing pixels / total number of pixels) is large in the first half. When a page including an image is printed, in some cases, the next new page must be printed in a state in which the amount of toner consumption greatly exceeds the supply amount (that is, the integrated value in the memory is large). Can happen. Therefore, when the toner concentration (ratio of toner in the developer) obtained from the integrated value stored in the memory exceeds the normal range, the printing operation is forcibly stopped and the toner concentration is in the center of the normal range. It is preferable to forcibly supply the toner until the value returns to the vicinity. Here, the normal range of the toner density can be set to, for example, a design value (for example, a range of 8% ± 2%) of the toner density that can guarantee good print image quality.
[0076]
Conversely, in the first embodiment (FIG. 4) and the second embodiment (FIG. 5), the minimum supply amount of toner supplied in one toner supply operation may be set. Good. Then, the estimated toner consumption amount calculated for each printing of one page is sequentially accumulated and stored in the memory. When the integrated value of the estimated toner consumption amount stored in the memory is less than the minimum supply amount, toner supply is not performed. On the other hand, when the integrated value is equal to or greater than the minimum supply amount, toner is supplied when printing of the page is completed, and the integrated value stored in the memory is cleared. As a result, the number of toner supply operations can be reduced. In particular, when the rotation of the toner supply motor 24 is transmitted to the conveying screw 22 through the gear train 23 as in the present embodiment, the toner supply frequency decreases due to backlash of the gear train 23. This is preferable because a cumulative error of toner density generated based on the supply error can be reduced. Therefore, it is preferable that the minimum value of the toner supply amount is determined based on the lower limit value of the range in which the toner supply mechanism can stably supply the toner.
[0077]
Furthermore, the maximum supply amount and the minimum supply amount of the toner supplied in the above one toner supply operation may be set. Thereby, the density variation of the image can be further reduced.
[0078]
The toner supply operation performed for each printing operation has been described above. Here, since the value calculated as the toner supply amount is only an estimated value, it is inevitable that an error will occur between the actual toner consumption amount. Even if the error in the estimated value of toner consumption for one time is small, the error may swell to a non-negligible error as it accumulates. Therefore, a means for canceling this accumulated error is required. Hereinafter, the density correction process for canceling the accumulated error will be described.
[0079]
In order to perform the density correction process, it is necessary to detect the toner density in the developing device 9 by some method. Conventionally, a magnetic permeability sensor is installed inside the developing device 9 to detect the toner concentration by utilizing the fact that the magnetic permeability of the developer changes when the mixing ratio of the toner and the carrier changes. However, this magnetic permeability sensor is a relatively expensive component, and the color image forming apparatus forms images with four developing units of cyan, magenta, yellow, and black, so that four magnetic permeability sensors are required and the cost is increased. It was a factor. Therefore, instead of directly detecting the toner density in the developing unit, a method of indirectly detecting the toner density in the developing unit by detecting the density of the toner image developed in a predetermined pattern may be used. is there. In this case, a pattern for density detection can be formed on the photosensitive drum 7 and the detection can be performed using an inexpensive density sensor including a light emitting element and a light receiving element installed in the vicinity of the photosensitive drum 7. Further, in order to reduce the cost, the toner image on the photosensitive drum 7 can be detected with the toner image on the intermediate transfer member instead of being detected. This is because the color image forming apparatus requires four density sensors to detect on the photosensitive drum. Also in this embodiment, density detection is performed on the intermediate transfer belt 13.
[0080]
FIG. 7 shows a configuration diagram of the density sensor 31. The density sensor 31 shown in FIG. 7 includes a light emitting element 32 that emits infrared light, and light receiving sensors 33 and 34 that receive the infrared light. Here, the light emitting element 32 is attached so that the emitted infrared light is incident on the intermediate transfer belt 13 at a predetermined incident angle, and the light receiving sensor 33 is an intermediate part of the infrared light from the light emitting element 32. The transfer belt 13 is attached to a position where infrared light reflected at the same reflection angle as the incident angle is incident. On the other hand, the light receiving sensor 34 is disposed at a position where the reflected light reflected at the same reflection angle as the incident angle does not enter so as to receive the scattered light.
[0081]
The operation of the above configuration will be described. The light emitting element 32 irradiates infrared light at a predetermined incident angle when a density patch (that is, a toner image formed in a predetermined pattern) 35 formed on the intermediate transfer belt 13 moves. The irradiated light is reflected by the density patch 35. Of the reflected light, the reflected light reflected at the same reflection angle as the incident angle enters the light receiving sensor 33. On the other hand, a part of the light irregularly reflected on the surface of the toner image enters the light receiving sensor 34 as scattered light. Which one of the light receiving sensors 33 and 34 detects is changed depending on the color to be detected. For three colors of cyan, magenta, and yellow, the density is detected by scattered light. As the toner density on the intermediate transfer belt 13 increases, the amount of toner adhering increases accordingly, so the amount of scattered light components also increases, and the sensor output of the light receiving sensor 34 also increases. On the other hand, for black, the density is detected using directly reflected light. This is because the black toner absorbs light, so that the scattered light component can hardly be detected. In general, the intermediate transfer belt is black, and its surface has a relatively high reflectance. Therefore, when the toner is not attached, the amount of the directly reflected light is large, and when the toner attached amount increases, the scattered light component increases and the directly reflected light component decreases. Accordingly, the density of the black toner can be detected based on the light receiving level of the light receiving sensor 33.
[0082]
A density correction process using the above density sensor will be described. As a procedure, the density patch 35 is formed on the intermediate transfer belt 13, and the density detection is performed as described above when the intermediate transfer belt 13 rotates and the density patch 35 comes to the position of the density sensor 31. Here, the difference between the detected density and the density detected from the density patch 35 formed in advance using a developer having a reference density corresponds to the cumulative error. Accordingly, the excess or deficiency of the toner amount is calculated from the detected density, and if it is insufficient, the toner supply motor 24 is driven to forcibly supply the toner. On the other hand, when the amount is too large, the driving of the toner supply motor 24 is stopped until an excessive amount of toner is consumed from the next printing.
[0083]
By performing the density correction process of the above procedure, it is possible to cancel the accumulated error of the estimated toner consumption when printing each page.
[0084]
However, if this density correction processing is executed regardless of the user's intention, there is a disadvantage that the toner is consumed excessively or printing is interrupted due to toner supply during continuous printing. Therefore, it is desirable not to perform this correction process as much as possible, or to reduce the frequency as much as possible. Therefore, in the present invention, the estimated value of the toner consumption after the density correction process is integrated, and the density correction process is performed when the integrated value exceeds a predetermined amount (threshold value).
[0085]
FIG. 8 shows a flowchart of the density correction processing timing. As shown in FIG. 8, when waiting for a print instruction (S1), the apparatus waits until a print instruction is received. When a printing instruction is received, a normal printing operation is performed (S2), the toner consumption is estimated as described above (S3), and toner is supplied. Then, the estimated values are integrated (S4), and the integrated value is compared with a predetermined threshold value (S5). At this time, when the integrated value ≦ the threshold value, the density correction process is not necessary yet, so nothing is done and the print instruction waits (S1). However, when the integrated value> the threshold value, it means that the toner consumption amount is equal to or greater than the predetermined amount regardless of the number of printed pages. Therefore, the above-described density correction processing is performed (S6), and then the integrated value is cleared (S7). ). Then, the process returns to the print instruction waiting state (S1), and enters the initial state.
[0086]
As described above, the advantage of determining the timing of the density correction process based on the integrated value of the estimated toner consumption amount instead of the number of printed pages is that the frequency of the density correction process is not increased more than necessary. That is, when continuously printing an image with a low printing rate (number of printing pixels / total number of pixels), since the toner consumption is small, the accumulated error of the toner consumption estimation value is also small. It is not necessary to perform correction processing frequently. As in the present embodiment, by determining the density correction processing timing based on the toner consumption instead of the number of printed pages, the interval for performing the density correction processing is widened when printing with a low printing rate is performed. Become. On the contrary, when an image with a high printing rate is printed, the amount of toner consumption also increases. Therefore, compared to the case where the density correction processing timing is determined based on the number of printed sheets, the present invention performs the density correction processing. The frequency may increase. However, if the toner consumption is large, the error should be increased accordingly, so that the accumulated error also increases. Therefore, according to the present invention, the density correction process is performed before the accumulated error exceeds the allowable amount, and the density correction according to the actual toner density state in the developing device 9 can be performed. Print quality can be maintained.
[0087]
Furthermore, by providing two threshold values for comparing the integrated values so that the printing operation is not stopped as much as possible during the execution of the print job from the user, the user can be kept from waiting. That is, since the image quality cannot be guaranteed any more than this, the first threshold value having a high requirement level that the density correction processing should be executed immediately, and the second threshold value having a low requirement level that it is desirable to perform the density correction processing if possible. Set. Naturally, a larger value is set for the first threshold value. Here, the print job is a print unit that is determined in units of print request documents and can be requested by one user at a time. The number of print pages included in one print job may be one page or more.
[0088]
FIG. 9 shows a flowchart of the second density correction timing. The timing control of the density correction process will be described with reference to FIG. Here, the two threshold values are set such that threshold value 1> threshold value 2 as described above. First, when a print job is requested by the user (S11), first, one page is printed (S12). Then, as described above, the toner consumption is estimated and the toner is supplied at the end of printing. At the same time, the estimated value of toner consumption is integrated. The integrated value is compared with the threshold value 1 (S13). If the integrated value is larger than the threshold value 1, it is very likely that the image quality is out of the guaranteed range. Therefore, the printing operation is interrupted at that time. Then, density correction processing is performed (S14), and the integrated value is cleared. If the integrated value is equal to or less than the threshold value 1, it means that there is a high possibility that the image quality is still within the guaranteed range of image quality. Therefore, it is checked whether there is an unprinted page in the print job without performing density correction processing ( S15). If there is an unprinted page, the next page is printed (S12). Then, the processing from S12 to S14 is looped until the print job is completed. After that, when one print job is finished, the integrated value of the estimated toner consumption is compared with the threshold 2 (S16). If the integrated value is larger than the threshold value 2, density correction processing is performed (S17), the integrated value is cleared, and the initial state is restored. If the integrated value is equal to or less than the threshold value 2, nothing is performed and the process returns to the initial state and waits until a new print job is requested.
[0089]
In the above processing, if the integrated value of the estimated toner consumption amount exceeds the threshold value 2 but is equal to or less than the threshold value 1, the density correction processing is not performed in the middle of the print job, and the print job ends. When you do. This prevents the user from waiting for the printing operation to stop in the middle of the print job. However, if one print job is a print request for a large number of pages, there is a possibility that the accumulated value of errors included in the estimated toner consumption amount may exceed the allowable range for image quality guarantee during the execution of the print job. is there. Therefore, the threshold value 1 is determined in consideration of an error that may be included in the estimated toner consumption amount and an allowable range of toner concentration required from the viewpoint of image quality assurance, and an integrated value of the estimated toner consumption amount If this exceeds this, density correction processing is performed when printing of the page is completed even during the print job. Thereby, it is possible to prevent unnecessary printing with degraded image quality.
[0090]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, it is possible to provide a print image with a stable density.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram of a toner supply control unit of the image forming apparatus according to the embodiment of the invention.
FIGS. 3A to 3D are reference patterns of print pixels detected by an image characteristic detection unit of an image forming apparatus according to an embodiment of the present invention.
4A to 4C are motor drive signals in the first example of the image forming apparatus according to the embodiment of the present invention. FIG.
FIGS. 5A to 5C are motor drive signals in the second example of the image forming apparatus according to the embodiment of the present invention.
FIG. 6 is a motor drive signal in time control and supply amount control in the image forming apparatus according to the embodiment of the present invention.
FIG. 7 is a configuration diagram of a density sensor in an image forming apparatus according to an embodiment of the present invention.
FIG. 8 is a timing flowchart of density correction processing in the image forming apparatus according to an embodiment of the present disclosure.
FIG. 9 is a timing flowchart of another density correction process in the image forming apparatus according to the embodiment of the present disclosure.
FIG. 10 is a side view showing a configuration diagram in the vicinity of a photosensitive drum in an image forming apparatus using a conventional toner supply device.
FIG. 11 is a perspective view of a part of a toner supply device in a conventional image forming apparatus.
FIG. 12 is a perspective view of a foaming member roll and a holed member of a toner supply device in a conventional image forming apparatus.
FIG. 13 is a block diagram of a control unit of a toner supply device in a conventional image forming apparatus.
FIG. 14 is a functional block diagram illustrating functions of a control unit of a toner supply device in a conventional image forming apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 9 Developing device 21 Toner reservoir 22 Conveyor screw 24 Toner supply motor 27 Image characteristic detection part 28 Accumulation part 29 Consumption estimation part 30 Supply amount calculation part 31 Density sensor 32 Light emitting element 33, 34 Light reception sensor 35 Density patch 40 Pixel detection circuit 41 Main scanning edge detection circuit 42 Sub scanning edge detection circuit 43 Pattern detection circuit 44 Reference pattern 45 Pixel counter 46 Main scanning edge counter 47 Sub scanning edge counter 48 Pattern counter 49 Pixel register 50 Main scanning edge register 51 Sub scanning edge register 52 Pattern register

Claims (5)

An image forming apparatus of a two-component development system using a developer composed of toner and a magnetic carrier,
Image characteristic counting means for counting characteristic information of an image composed of a plurality of pixels for each printed page;
Toner consumption estimation means for estimating toner consumption consumed for each printed page based on the characteristic information counted by the image characteristic counting means;
A memory that sequentially accumulates the estimated values of the toner consumption estimated by the toner consumption estimation means and stores them as integrated values;
Toner supply means for supplying toner into the developing device,
The characteristic information includes the number of pixels, the number of edges, and the number of pixels constituting a local corner in the image composed of a plurality of pixels.
The toner consumption amount estimation means sets a value obtained by multiplying each of the number of pixels, the number of edges, and the number of pixels constituting the local corner by a predetermined coefficient as a toner consumption amount estimated value,
When the integrated value of the estimated toner consumption amount stored in the memory is equal to or greater than a preset minimum supply amount per toner supply operation, the toner supply means corresponds to the integrated value. Supplying toner into the developing device, and clearing the integrated value stored in the memory;
The image forming apparatus according to claim 1, wherein the toner supply unit does not supply toner when the integrated value of the estimated toner consumption amount stored in the memory is less than the minimum supply amount. The image forming apparatus according to claim 1 , wherein the minimum supply amount is determined based on a lower limit value of a range in which the toner supply unit can stably supply the toner. An image forming apparatus of a two-component development system using a developer composed of toner and a magnetic carrier,
Image characteristic counting means for counting characteristic information of an image composed of a plurality of pixels for each printed page;
Toner consumption estimation means for estimating toner consumption consumed for each printed page based on the characteristic information counted by the image characteristic counting means;
A memory that sequentially accumulates the estimated values of the toner consumption estimated by the toner consumption estimation means and stores them as integrated values;
Toner supply means for supplying toner into the developing device,
The characteristic information includes the number of pixels, the number of edges, and the number of pixels constituting a local corner in the image composed of a plurality of pixels.
The toner consumption amount estimation means sets a value obtained by multiplying each of the number of pixels, the number of edges, and the number of pixels constituting the local corner by a predetermined coefficient as a toner consumption amount estimated value,
When the integrated value of the estimated toner consumption amount stored in the memory is equal to or less than a preset maximum supply amount in a single toner supply operation, the toner supply means stores the integrated value stored in the memory. Supplying the toner corresponding to the value, and clearing the integrated value stored in the memory;
When the integrated value of the estimated toner consumption amount stored in the memory exceeds the maximum supply amount and there is an unprinted page, the toner supply unit supplies toner corresponding to the maximum supply amount. And subtracting the maximum supply amount from the integrated value stored in the memory,
When the integrated value of the estimated toner consumption amount stored in the memory exceeds the maximum supply amount and there is no unprinted page, the toner supply means adds the integrated value stored in the memory to the integrated value. An image forming apparatus that supplies corresponding toner and clears the integrated value stored in the memory. The image forming apparatus according to claim 3 , wherein the maximum supply amount is determined based on an upper limit value of a range in which the toner supply unit can stably supply the toner. It said image characteristic counting means, the image forming apparatus according to claim 1 or 3 print pixel and its surrounding pixels comprises a pattern counter for counting the number of the print pixels constituting the predetermined pattern.

Images