JP6897600B2 - Image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus.

In the electrophotographic and tandem image forming apparatus, electrostatic latent images for a plurality of colors are formed on the plurality of image carriers. Toners of corresponding colors are supplied to each of the electrostatic latent images for a plurality of colors by a plurality of developing units.

A magnetic permeability sensor may be provided in each of the plurality of developing units. From each of the magnetic permeability sensors, a density signal represented by the toner density in the corresponding developing unit is output. The plurality of density signals are input to the signal selection unit. The signal selection unit sequentially selects and outputs a plurality of the density signals one by one. In the image forming apparatus, the amount of toner used in development by each of the developing units is determined based on the density signals sequentially received from the signal selection unit. An amount of toner corresponding to the amount of toner used is supplied to the plurality of developing units by the plurality of toner replenishing units (see, for example, Patent Document 1).

JP-A-2017-026918

The signal selection unit outputs a plurality of the density signals one by one in order. Therefore, the amount of toner used in each of the developing units is a value based on the density signals output at different times. Therefore, when the image forming apparatus executes toner supply to the plurality of developing units at the same timing, it becomes difficult to maintain the toner concentration in the plurality of developing units constant.

An object of the present invention is to provide an image forming apparatus capable of more easily maintaining a constant toner concentration in a plurality of developing units.

The image forming apparatus according to one aspect of the present invention includes a plurality of image carriers, a plurality of developing units, a plurality of signal output units, a signal selection unit, a toner amount measuring unit, a toner amount estimating unit, and the like. It includes a plurality of toner replenishment units and a replenishment control unit. An electrostatic latent image based on image data is formed on the plurality of image carriers. The plurality of developing units are provided corresponding to each of the plurality of image carriers, and develop an electrostatic latent image formed on the corresponding image carriers. The plurality of signal output units are provided corresponding to each of the plurality of developing units, and output a density signal representing the density of toner in the corresponding developing units. The signal selection unit sequentially selects and outputs a plurality of the density signals input from the plurality of signal output units one by one. The toner amount measuring unit measures the first toner amount used in development by a specific developing unit corresponding to the density signal output from the signal selection unit at a predetermined measurement time among the plurality of developing units. , The measurement is performed based on the concentration signal input at the measurement time. Based on the image data, the toner amount estimation unit estimates a second toner amount used in development by at least the remaining developing units other than the specific developing unit among the plurality of developing units. The plurality of toner replenishment units are provided corresponding to the plurality of developing units, and replenishment toner can be replenished to the corresponding developing units. The replenishment control unit causes the toner replenishment unit corresponding to the specific developing unit to replenish the replenishing toner in an amount corresponding to the first toner amount, and causes the toner replenishing unit corresponding to the remaining developing unit to replenish the toner. The replenishment toner is replenished in an amount corresponding to the second toner amount.

According to the present invention, it is possible to provide an image forming apparatus capable of more easily maintaining the toner density in a plurality of developing units.

FIG. 1 is a schematic view showing a configuration of an image forming apparatus according to an embodiment. FIG. 2 is a schematic view showing a detailed configuration of the developing unit shown in FIG. FIG. 3 is a block diagram showing a main part of the image forming apparatus shown in FIG. FIG. 4 is a diagram showing a waveform of a density signal in a main part of an image forming apparatus. FIG. 5 is a flowchart showing the operation and processing procedure of the image forming apparatus shown in FIG. FIG. 6 is a flowchart showing the operation and processing procedure of the image forming apparatus according to the modified example.

Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings for the purpose of understanding the present invention. The following embodiments are examples that embody the present invention, and do not limit the technical scope of the present invention.

[Embodiment]
In FIGS. 1 and 2, arrows X, Y, and Z indicate the left-right direction, the front-back direction, and the up-down direction of the image forming apparatus 100. Hereinafter, the left-right direction, the front-rear direction, and the up-down direction are referred to as left-right direction X, front-back direction Y, and up-down direction Z.

In FIG. 1, the image forming apparatus 100 is a copier, a printer, a facsimile, a multifunction device, or the like. The multifunction device has a copy function, a printing function, a fax function, and the like. The image forming apparatus 100 performs color printing by an electrophotographic method and a tandem method based on image data sent from a connected personal computer or the like. The color printing is to print a full-color image represented by the image data on a printing medium PM1 (for example, paper).

Specifically, the image forming apparatus 100 includes a photoconductor drum 1 for a plurality of colors, a charging unit 2, a developing unit 3, a primary transfer unit 4, an exposure unit 5, an intermediate transfer body 6, and a secondary transfer unit 7. , And a fixing portion 8. The plurality of colors are yellow, magenta, cyan and black. In FIG. 1, the leftmost photoconductor drum 1 is for magenta. The second and third photoconductor drums 1 from the left are for cyan and yellow. The rightmost photoconductor drum 1 is for black. The charging unit 2, the developing unit 3, and the primary transfer unit 4 are provided corresponding to the photoconductor drum 1, and are arranged one by one around the photoconductor drum 1.

Each photoconductor drum 1 is an example of an image carrier in the present invention, and is juxtaposed in the left-right direction X inside the image forming apparatus 100. Each photoconductor drum 1 has a columnar shape that is long in the front-rear direction Y. During the color printing, each photoconductor drum 1 rotates about its own axis in the first rotation direction RD1 at a predetermined constant linear velocity LV1.

Each charging unit 2 faces the corresponding charging region and uniformly charges the peripheral surface of the corresponding photoconductor drum 1. The charged region is a region including the vicinity of the lower end of the photoconductor drum 1.

The exposure unit 5 is provided inside the image forming apparatus 100 below each charging unit 2. The exposure unit 5 irradiates the exposure region of the corresponding photoconductor drum 1 with the modulated light for each color modulated by the image data. As a result, electrostatic latent images for a plurality of colors are formed on each of the plurality of photoconductor drums 1 based on the image data. The exposed region is a region downstream of the charged region in each photoconductor drum 1 in the first rotation direction RD1.

Each developing unit 3 contains a developing agent containing toner and a carrier of a corresponding color. Each developing unit 3 supplies the toner contained therein to the developing region DA1 (see FIG. 2) of the corresponding photoconductor drum 1. As a result, each developing unit 3 develops the electrostatic latent image formed on the corresponding photoconductor drum 1 with the toner of the corresponding color. As a result, a toner image of the corresponding color is formed on each photoconductor drum 1. The developing region DA1 is a region downstream of the exposure region of each photoconductor drum 1 in the first rotation direction RD1.

Each primary transfer unit 4 faces the primary transfer region of the corresponding photoconductor drum 1 in the upward direction. The primary transfer region is a region downstream of the development region DA1 (see FIG. 2) in the first rotation direction RD1 in each photoconductor drum 1, and is a region including the upper end of each photoconductor drum 1. Further, an intermediate transfer body 6 is interposed between each primary transfer unit 4 and the corresponding photoconductor drum 1. The toner image supported on the photoconductor drum 1 is transferred from the corresponding primary transfer region to the same area on the intermediate transfer body 6. As a result, a synthetic toner image in which the toner images of the plurality of colors are superimposed is formed on the intermediate transfer body 6.

The intermediate transfer body 6 is an endless belt and is stretched on the driving roller 6A and the driven roller 6B. When the drive roller 6A rotates in the second rotation direction RD2, the intermediate transfer body 6 rotates, and the driven roller 6B rotates driven. Further, the intermediate transfer body 6 is driven in the traveling direction TD1 between each primary transfer unit 4 and each photoconductor drum 1. As a result, the intermediate transfer body 6 carries the synthetic toner image toward the secondary transfer region described later while carrying the synthetic toner image.

The drive roller 6A and the secondary transfer unit 7 face each other in the left-right direction. An intermediate transfer body 6 is interposed between the drive roller 6A and the secondary transfer unit 7. The synthetic toner image and the printing medium PM1 having a predetermined size are conveyed to the secondary transfer region between the intermediate transfer body 6 and the secondary transfer unit 7. In the secondary transfer region, the synthetic toner image is transferred from the intermediate transfer body 6 to the print medium PM1. The print medium PM1 sent out from the secondary transfer region is sent to the fixing unit 8. The fixing unit 8 fixes the synthetic toner image on the print medium PM1 and sends it out. The print medium PM1 is discharged as a color printed matter to the outside of the image forming apparatus 100.

The image forming apparatus 100 further includes a plurality of toner replenishment units 9. The plurality of toner replenishing units 9 are provided inside the image forming apparatus 100 in the upward direction above the intermediate transfer body 6 corresponding to the plurality of developing units 3. Each toner replenishment unit 9 contains a replenishment toner to be replenished to the corresponding developing unit 3. A discharge port 9A is provided at the bottom of each toner supply unit 9. Each discharge port 9A is connected to the corresponding developing unit 3 by a supply path 9B so that fluid can communicate with each other. In FIG. 1, for convenience, the illustration of the downstream portion of the supply path 9B is omitted.

Further, each discharge port 9A is provided with a discharge screw 9C. A first driving force transmission unit 9D (see FIG. 3) including a motor, a gear, a belt, and the like is mechanically connected to each discharge screw 9C. Each discharge screw 9C is rotated by a driving force given by the corresponding first driving force transmitting unit 9D. As a result, from each discharge port 9A, an amount of the toner corresponding to the rotation amount of the corresponding discharge screw 9C is discharged to the corresponding supply path 9B.

A transport screw 9E is provided inside each supply path 9B. A first driving force transmission unit 9D (see FIG. 3) is mechanically connected to each transfer screw 9E. Each transfer screw 9E is rotated by a driving force given by the corresponding first driving force transmitting unit 9D, and conveys the replenishing toner in the corresponding replenishment path 9B to the downstream side. The replenishing toner is sent to the developing unit 3 from the downstream end of the replenishment path 9B. As described above, the plurality of toner replenishment units 9 are configured to be able to replenish the replenishment toner to the corresponding developing unit 3.

Next, the detailed configuration of each developing unit 3 will be described with reference to FIG.

In FIG. 2, each developing unit 3 includes a housing 31, a developer accommodating unit 32, a first rotating shaft 33, a second rotating shaft 34, a developing roller 35, a signal output unit 36, and the like.

Each housing 31 has a box-like shape that is long in the front-rear direction Y, and is arranged along the development region DA1 in the corresponding photoconductor drum 1. Inside each housing 31, a developer accommodating portion 32, a first rotating shaft 33, a second rotating shaft 34, and a developing roller 35 are provided.

Each developer accommodating portion 32 is formed on the bottom of the corresponding housing 31. Each developer accommodating portion 32 accommodates the developer containing the toner of the corresponding color and the carrier. Each developer accommodating portion 32 is divided into a first accommodating chamber 32A and a second accommodating chamber 32B by a partition member 31A projecting from the bottom of the corresponding housing 31.

Each first storage chamber 32A is provided to the left of the second storage chamber 32B with respect to the corresponding developing region DA1. Each of the first accommodation chamber 32A and the second accommodation chamber 32B has a groove-like shape that is long in the front-rear direction Y and recessed in the downward direction. The developer supplied to the corresponding photoconductor drum 1 is housed in each of the first storage chamber 32A and the second storage chamber 32B.

Further, each of the first accommodation chamber 32A and the second accommodation chamber 32B communicates with each other at both ends in the front-rear direction Y. In each housing 31, a replenishment port 31B for the replenishment toner of the corresponding color is formed above the portion near the front end of the first storage chamber 32A. A downstream end of the corresponding supply path 9B is connected to each supply port 31B so that fluid can communicate with each other.

Each of the first rotating shafts 33 has a rod-like shape long in the front-rear direction Y, and is rotatably bridged to the corresponding first accommodating chamber 32A. Specifically, the portion near the front end and the portion near the rear end of each of the first rotating shafts 33 are rotatably supported by the front wall and the rear wall of the corresponding first accommodation chamber 32A. A driving force is applied to each of the first rotating shafts 33 from the corresponding second driving force transmitting unit 3A. Each second driving force transmission unit 3A includes a motor, gears, and the like. Each of the first rotation shafts 33 rotates in the third rotation direction RD3 at the rotation speed NR1 by the driving force applied to itself. The third rotation direction RD3 is a counterclockwise direction when viewed from the front. The rotation speed NR1 is a predetermined number of times each of the first rotation shafts 33 rotates per time required for the electrostatic latent image to be formed on the photoconductor drum 1, for example, 10 times.

A first spiral blade 33A and a sheet-shaped blade 33B are integrally provided on each first rotating shaft 33. Each of the first spiral blades 33A is rotated in the third rotation direction RD3 by the rotation of the corresponding first rotation shaft 33, and the developer housed in the first storage chamber 32A is stirred and the first transport direction CD1 is agitated. Transport to. The first transport direction CD1 is a direction from the front to the rear of the image forming apparatus 100.

Each sheet-shaped blade 33B is provided on the corresponding first rotating shaft 33 at a portion closer to the front end than the corresponding supply port 31B. Each sheet-shaped blade 33B is provided above the corresponding signal output unit 36 on the corresponding first rotating shaft 33. Each sheet-shaped blade 33B is made of a flexible material such as PET film. Each sheet-shaped blade 33B projects along the centrifugal direction away from the rotation center of the corresponding first rotation shaft 33. Further, in the sheet-shaped blade 33B, the tip in the centrifugal direction reaches the corresponding signal output unit 36 during the rotation of the corresponding first rotating shaft 33.

Each sheet-shaped blade 33B rotates in the third rotation direction RD3 at a rotation speed NR1 together with the corresponding first rotation shaft 33 and the first spiral blade 33A, and corresponds to the developer in the corresponding first storage chamber 32A. Collect on the signal output unit 36. Each sheet-shaped blade 33B may have a function as a scraper for cleaning the upper surface of the signal output unit 36.

Each of the second rotating shafts 34 has a rod-like shape long in the front-rear direction Y, and is rotatably bridged to the corresponding second accommodating chamber 32B. The driving force given by the corresponding second driving force transmitting unit 3A is given to each second rotating shaft 34. As a result, each of the second rotation shafts 34 rotates in the fourth rotation direction RD4 at the rotation speed NR1. The fourth rotation direction RD4 is, for example, opposite to the third rotation direction RD3. In FIG. 3, the second rotating shaft 34 is not shown for convenience.

A second spiral blade 34A is integrally provided on each second rotating shaft 34. Each of the second spiral blades 34A is rotated in the fourth rotation direction RD4 by the rotation of the corresponding second rotation shaft 34, and the developer housed in the second storage chamber 32B is stirred and the second transport direction CD2 is agitated. Transport to. The second transport direction CD2 is in the opposite direction to the first transport direction CD1.

Each first containment chamber 32A and the corresponding second containment chamber 32B communicate with each other at their downstream ends. The developer is transported to the downstream end of each first storage chamber 32A, then moved to the corresponding second storage chamber 32B, transported to the downstream end of each second storage chamber 32B, and then the corresponding first storage chamber 32B. Move to containment chamber 32A.

Each developing roller 35 is a magnetic roller having a long cylindrical shape in the front-rear direction Y. Each developing roller 35 rotates in the fifth rotation direction RD5 in the same direction as the third rotation direction RD3 by the driving force given by the corresponding second driving force transmission unit 3A. In FIG. 3, the development roller 35 is not shown for convenience. Each developing roller 35 adsorbs and supports the developing agent in the corresponding second storage chamber 32B by rotating. Each developing roller 35 carries the developing agent and conveys it to the corresponding developing region DA1. The developer moves from each developing roller 35 to the corresponding developing region DA1 and adheres to the electrostatic latent image formed on the corresponding photoconductor drum 1. As a result, each electrostatic latent image is developed, and a toner image of a corresponding color is formed on each photoconductor drum 1.

Each signal output unit 36 is provided corresponding to each of the developing units 3. Each signal output unit 36 is arranged below the corresponding sheet-shaped blade 33B at the bottom of the corresponding first accommodation chamber 32A. Each signal output unit 36 includes a detection surface 36A exposed to the corresponding first accommodation chamber 32A and a sensor circuit 36B.

Each sensor circuit 36B is a magnetic permeability sensor including a Colpitts oscillator circuit and the like, and is provided below the corresponding detection surface 36A. Each sensor circuit 36B outputs the density signal DS1. The density signal DS1 represents the density of the toner in the developer housed in the corresponding developing unit 3. Specifically, the frequency of the density signal DS1 changes according to the ratio of the carrier and the toner contained in the developer existing on the detection surface 36A.

In the following description, the signal output unit 36 corresponding to the developing unit 3 in which the yellow toner is housed may be described as the signal output unit 36Y (see FIG. 4). Similarly, the signal output unit 36 corresponding to the developing unit 3 in which magenta, cyan, and black toners are housed may be described as signal output units 36M, 36C, 36K. Further, the density signal DS1 output from the signal output unit 36Y may be described as the density signal DS1Y. Similarly, the density signal DS1 output from the signal output unit 36M, the signal output unit 36C, and the signal output unit 36K may be described as the density signal DS1M, the density signal DS1C, and the density signal DS1B.

During one rotation of each sheet-shaped blade 33B (that is, during one rotation cycle), there is a first time zone in which the tip end portion of each sheet-shaped blade 33B passes on the corresponding detection surface 36A. In the first time zone, as compared with the second time zone other than the first time zone, a relatively large amount of the developer is collected by the corresponding sheet-shaped blade 33B on the corresponding detection surface 36A. Therefore, the frequency of each density signal DS1 changes during one rotation of the corresponding sheet-shaped blade 33B. Specifically, the frequency of each density signal DS1 becomes lower as the toner density becomes smaller. Therefore, when the minimum frequency of the density signal DS1 in the rotation cycle of the sheet-shaped blade 33B is equal to or lower than the predetermined reference frequency, the toner concentration in the developer accommodating portion 32 is smaller than the predetermined reference density. Can be considered to be.

In FIG. 3, the image forming apparatus 100 further includes a signal selection unit 10 and a control unit 11.

The signal selection unit 10 is a switch that is electrically connected between each signal output unit 36 and the control unit 11. A plurality of density signals DS1 are input to the signal selection unit 10. Further, the control signal CS1 output from the control unit 11 is input to the signal selection unit 10. The signal selection unit 10 sequentially outputs the plurality of input density signals DS1 one by one in a predetermined order each time the predetermined measurement time MT1 elapses during the color printing by the control signal CS1. It is selected and output to the control unit 11. In the above order, the density signal DS1Y is assigned the first order. Further, the density signal DS1M, the density signal DS1C, and the density signal DS1B are assigned the second, third, and fourth orders. In the present embodiment, the measurement time MT1 is the time required from the output of the control signal CS1 by the control unit 11 to the completion of the development of one of the electrostatic latent images. In other words, the measurement time MT1 is the time required for each first rotation shaft 33 to rotate 10 times. As shown in FIG. 4, the plurality of density signals DS1 are arranged in chronological order in the above order for each measurement time MT1 and output from the signal selection unit 10. Specifically, the plurality of density signals DS1 are repeatedly output from the signal selection unit 10 in the order of the density signal DS1Y, the density signal DS1M, the density signal DS1C, and the density signal DS1B.

The centrifugal directions of the plurality of sheet-shaped blades 33B protruding at the start of the color printing may be different from each other as shown in FIG.

The control unit 11 includes a CPU, a non-volatile memory, a RAM, and the like. The control unit 11 may be an electronic circuit such as an ASIC (Application Specific Integrated Circuit) or a DSP (Digital Signal Processor). The CPU executes a program stored in advance in the non-volatile memory while using the RAM as a work area. As a result, the CPU comprehensively controls the image forming apparatus 100 during the color printing by the image forming apparatus 100.

By executing the program, the control unit 11 functions as a toner amount measuring unit 11A, a toner amount estimation unit 11B, and a replenishment control unit 11C.

The toner amount measuring unit 11A is the first of the plurality of developing units 3 used in development by a specific developing unit corresponding to the density signal DS1 output from the signal output unit 36 during the measurement time MT1 (see FIG. 4). The amount of toner is measured based on the density signal input to MT1 at the same measurement time.

The toner amount estimation unit 11B estimates the second toner amount used in development by at least the remaining developing units other than the specific developing unit among the plurality of developing units 3 based on the image data.

The replenishment control unit 11C causes the toner replenishment unit 9 corresponding to the specific developing unit to replenish the replenishing toner in an amount corresponding to the first toner amount, and causes the toner replenishing unit 9 corresponding to the remaining developing unit to replenish the toner. The replenishment toner is replenished in an amount corresponding to the second toner amount.

Further, the replenishment control unit 11C causes the toner replenishment unit 9 corresponding to the specific developing unit to replenish the replenishment toner in an amount corresponding to the first toner amount at a predetermined replenishment timing, and the remaining amount. The toner replenishing unit 9 corresponding to the developing unit is replenished with the replenishing toner in an amount corresponding to the second toner amount.

Further, it is conceivable that the replenishment timing is the timing after the development in the plurality of developing units 3 is completed.

Hereinafter, the operation and processing of each part in the image forming apparatus 100 will be described in more detail with reference to FIG.

Upon receiving the image data, the control unit 11 starts the color printing shown in FIG.

First, the control unit 11 functions as a toner amount estimation unit 11B. Based on the received image data, the toner amount estimation unit 11B estimates the toner amount used by each of the plurality of developing units 3 to develop one electrostatic latent image during the color printing as the second toner amount. (Step S1). In other words, the amount of the second toner is estimated for each of the plurality of colors and for each electrostatic latent image.

Specifically, the toner amount estimation unit 11B obtains the dot count number for each electrostatic latent image formed on each of the photoconductor drums 1 based on the image data. The dot count number is the number of dots formed when one electrostatic latent image is formed on each of the photoconductor drums 1 by the modulated light from the exposure unit 5. Next, the toner amount estimation unit 11B obtains the toner amount corresponding to each of the dot count numbers as the second toner amount.

Next, the control unit 11 starts operating each unit of the image forming apparatus 100 in order to start the color printing (step S2). As a result, in the image forming apparatus 100, an electrostatic latent image based on the image data begins to be formed in units of PM1 of the print medium. In particular, the control unit 11 gives a second drive signal DS22 to each of the second drive force transmission units 3A in step S2. Each of the second driving force transmitting units 3A rotates the first rotating shaft 33, the second rotating shaft 34, and the developing roller 35 included in the corresponding developing unit 3. Specifically, the developing roller 35 rotates in the fifth rotation direction RD5. The first rotation shaft 33 rotates in the third rotation direction RD3 at the rotation speed NR1. The second rotation shaft 34 rotates in the fourth rotation direction RD4 at the rotation speed NR1.

In step S3, the control unit 11 gives a control signal CS1 to the signal selection unit 10 in order to select the density signal DS1 to which the next order is assigned among the plurality of colors. In the first step S3, the density signal DS1Y is selected. After that, in the second, third, and fourth steps S3, the density signals DS1M, DS1C, and DS1K are selected. As a result, the signal selection unit 10 selects the density signal DS1 from the plurality of input density signals DS1 according to the control signal CS1 from the control unit 11 and outputs the density signal DS1 to the control unit 11 (step S3).

In the next step S4, the control unit 11 functions as the toner amount measuring unit 11A. The control unit 11 counts the frequency of the input density signal DS1 according to the operation clock by using a timer counter (not shown) provided inside. Each of the frequencies of the density signal DS1 is stored in the RAM (step S4).

Next, the control unit 11 determines whether or not each of the plurality of developing units 3 has completed developing one electrostatic latent image (step S5). When the control unit 11 determines that the development of the electrostatic latent image has not been completed (NO in step S5), the process returns to step S4. On the other hand, when the control unit 11 determines that the development of the electrostatic latent image is completed (YES in step S5), the control unit 11 considers that the measurement time MT1 has been completed, and proceeds to the process in step S6.

At the start of step S6, a plurality of frequencies of the density signal DS1 are stored in the RAM. Specifically, the frequency stored in the RAM is the frequency of the concentration signal DS1 selected in step S3 and input to the control unit 11 during the current measurement time MT1 (see FIG. 4). The control unit 11 functions as the toner amount measuring unit 11A in step S6. The control unit 11 is the first used in development by the developing unit 3 (that is, the specific developing unit) corresponding to the density signal DS1 input to the measurement time MT1 this time based on the frequency stored in the RAM. 1 Measure the amount of toner (step S6). Specifically, the control unit 11 acquires the lowest frequency in the first and last rotation cycles in the measurement time MT1 from the frequencies stored in the RAM. The control unit 11 can determine the amount of first toner used by the specific developing unit in development from the difference between the lowest frequency in the first rotation cycle and the lowest frequency in the last rotation cycle. In addition, the first toner amount may be obtained from the average value of all frequencies obtained in the current measurement time MT1.

In the next step S7, the control unit 11 functions as the toner amount estimation unit 11B. The control unit 11 acquires the second toner amount corresponding to the remaining developing units other than the specific developing unit among the plurality of developing units 3 from the second toner amount estimated in step S1 (). Step S7).

In the next step S8, the control unit 11 functions as the supply control unit 11C. Further, the execution timing of step S8 corresponds to the replenishment timing in the present invention. Specifically, the control unit 11 gives the first drive signal DS21 to the first drive force transmission unit 9D corresponding to the specific developing unit based on the first toner amount obtained in step S6. When the first driving signal DS21 is given to itself, the first driving force transmitting unit 9D rotationally drives the discharge screw 9C (see FIG. 1) provided in the corresponding toner replenishing unit 9. As a result, the amount of the replenishing toner corresponding to the first toner amount is discharged from the discharge port 9A of the corresponding toner replenishment unit 9 to the replenishment path 9B from the discharge port 9A (see FIG. 1). The first driving force transmitting unit 9D further rotationally drives the transport screw 9E provided in the corresponding toner replenishing unit 9. As a result, the replenishment toner is conveyed downstream in the replenishment path 9B and flows into the first storage chamber 32A from the replenishment port 31B of the specific developing unit.

The control unit 11 gives the first drive signal DS21 to the first drive force transmission unit 9D corresponding to the remaining developing unit based on the acquired second toner amount. The first driving force transmission unit 9D rotationally drives the discharge screw 9C (see FIG. 1) of the corresponding toner replenishment unit 9 based on the first drive signal DS21. The first driving force transmitting unit 9D further rotationally drives the transport screw 9E provided in the corresponding toner replenishing unit 9. As a result, the amount of the replenishing toner corresponding to the second toner amount is discharged from the discharge port 9A of the corresponding toner replenishment unit 9 from the discharge port 9A (see FIG. 1) to the replenishment path 9B, and finally. Is replenished to each of the remaining developing units.

Next, the control unit 11 determines whether or not to end the color printing (step S9). In other words, the control unit 11 determines whether or not the next electrostatic latent image is formed on the plurality of photoconductor drums 1. When the control unit 11 determines that the color printing is finished (YES in step S9), the control unit 11 ends the process of FIG. On the other hand, when the control unit 11 determines that the color printing is not completed (NO in step S9), that is, when it is determined that another electrostatic latent image is formed, the process returns to step S3.

The signal selection unit 10 sequentially selects and outputs a plurality of density signals DS1 one by one. Therefore, assuming that the amount of toner used by each of the plurality of developing units 3 is obtained based on the density signal DS1 output from the signal selection unit 10, the plurality of toner amounts are output at different times from each other. The value is based on the density signal DS1. Therefore, when the replenishment control unit 11C controls the plurality of toner replenishment units 9 so as to replenish the toner to the plurality of developing units 3 at the replenishment timing, it is difficult to maintain the toner concentration in the plurality of developing units 3 constant. Become.

On the other hand, in the embodiment, the toner amount measuring unit 11A measures the first toner amount used in the development by the specific developing unit based on the density signal DS1 input to the measurement time MT1. The toner amount estimation unit 11B estimates the second toner amount used by the remaining developing unit for development based on the image data. In other words, the toner amount estimation unit 11B does not measure the second toner amount used by the remaining developing unit in development based on the density signal DS1. The replenishment control unit 11C causes the toner replenishment unit 9 corresponding to the specific developing unit to replenish the replenishing toner in an amount corresponding to the first toner amount, and the toner replenishing unit 9 corresponding to the remaining developing unit. Is replenished with the replenishing toner in an amount corresponding to the second toner amount. Therefore, even when the signal selection unit 10 sequentially selects and outputs the plurality of density signals DS1 one by one, the image forming apparatus capable of easily maintaining the toner density in each of the plurality of development units 3. It becomes possible to provide 100.

Further, the replenishment control unit 11C and the toner replenishment unit 9 corresponding to the specific developing unit at the replenishment timing (that is, after the development of one electrostatic latent image is completed in each of the plurality of developing units 3). , The toner replenishing unit 9 corresponding to the remaining developing unit is replenished with the replenishing toner. This makes it possible to prevent the amount of toner accommodated in the plurality of developing units 3 from becoming too small while the plurality of electrostatic latent images are being developed. As a result, it is possible to prevent deterioration of the image quality of the toner images formed on the plurality of photoconductor drums 1.

The replenishment timing is not limited to after the development of one electrostatic latent image is completed in each of the plurality of developing units 3, and the development of one electrostatic latent image is performed in each of the plurality of developing units 3. It is also conceivable to set a predetermined timing inside.

In addition, the toner amount estimation unit 11B estimated the second toner amount of all the developing units 3 in step S1, and acquired the second toner amount of the remaining developing unit in step S7. However, not limited to this, the toner amount estimation unit 11B does not execute step S1, and in step S7, based on the image data, the remaining developing unit performs one electrostatic latent image during the color printing. The amount of toner used for developing the above may be estimated as the amount of the second toner.
[Modification example]

Hereinafter, a modified example of the above-described embodiment will be described. In the modified examples described below, the same reference numerals and step numbers will be assigned to the same configurations and steps as in the above embodiment, and the description of each will be omitted.

In FIG. 3, the toner amount estimation unit 11B has a plurality of developing units 3 based on the image data before developing an electrostatic latent image formed on the corresponding photoconductor drum 1 by the plurality of developing units 3. The amount of the second toner used in development may be estimated. In this case, the control unit 11 further functions as the determination unit 11D by executing the program.

The determination unit 11D determines whether or not the specific second toner amount having the maximum value among the second toner amounts estimated by the toner amount estimation unit 11B is equal to or higher than a predetermined reference value.

When the determination unit 11D determines that the specific second toner amount is less than the reference value, the signal selection unit 10 selects the density signals DS1 input from the plurality of signal output units 36. The density signal DS1 according to a predetermined order is selected and output as the first density signal. When the determination unit 11D determines that the specific second toner amount is equal to or greater than the reference value, the signal selection unit 10 selects the density signals DS1 input from the plurality of signal output units 36. The density signal DS1 corresponding to the specific amount of toner is selected and output as the second density signal.

When the specific second toner amount is less than the reference value, the specific developing unit is the developing unit 3 corresponding to the first density signal among the plurality of developing units 3. Further, the specific developing unit is a developing unit 3 corresponding to the second density signal when the specific second toner amount is equal to or more than the reference value.

Hereinafter, the operation and processing of each part of the image forming apparatus 100 according to the modified example will be described in more detail with reference to FIG.

In FIG. 6, the control unit 11 advances the process to step S11 after executing step S2. The control unit 11 functions as the determination unit 11D in steps S11 and S12. In step S11, the control unit 11 selects the second toner amount used by the plurality of developing units 3 in the current development from the plurality of second toner amounts obtained in step S1. The control unit 11 further selects, from the selected second toner amount, the second toner amount having the maximum value as a specific second toner amount (step S11).

Next, the control unit 11 determines whether or not the specific second toner amount is equal to or higher than a predetermined reference value (step S12). The reference value is a reference value indicating whether or not the developing unit 3 corresponding to the specific toner amount uses a large amount of toner in the development of the electrostatic latent image, and is used for experiments or at the design stage of the image forming apparatus 100. It is predetermined by simulation.

When the control unit 11 determines that the specific second toner amount is not equal to or greater than the reference value (NO in step S12), the control unit 11 proceeds to the process in step S3. On the other hand, when the control unit 11 determines that the specific second toner amount is equal to or greater than the reference value, the control unit 11 proceeds to step S13.

In step S3, a control signal CS1 is given to the signal selection unit 10 in order to select the density signal DS1 to which the next order is assigned as the first density signal according to the order. As a result, the signal selection unit 10 selects the first density signal from the plurality of input density signals DS1 according to the control signal CS1 from the control unit 11 and outputs the first density signal to the control unit 11 (step S3).

In step S13, the control unit 11 gives a control signal CS1 to the signal selection unit 10 in order to select the density signal DS1 corresponding to the specific second toner amount among the plurality of colors as the second density signal. As a result, the signal selection unit 10 selects the second density signal from the plurality of input density signals DS1 according to the control signal CS1 from the control unit 11 and outputs the second density signal to the control unit 11 (step S13). After that, the control unit 11 advances the process to step S4.

In step S4, the control unit 11 counts the frequency of the input density signal DS1 (specifically, the first density signal or the second density signal) and stores it in the RAM (step S4). After that, when the control unit 11 determines that the development of the electrostatic latent image is completed (YES in step S5), the control unit 11 measures the amount of the first toner used in the development by the specific developing unit (step S6). .. Here, the specific developing unit is the developing unit 3 corresponding to the first density signal among the plurality of developing units 3 when the specific second toner amount is less than the reference value. Further, the specific developing unit is a developing unit 3 corresponding to the second density signal when the specific second toner amount is equal to or more than the reference value.

The control unit 11 executes steps S7 and S8 after step S6. Further, when the control unit 11 determines in step S9 that the color printing is not completed (NO in step S9), the process returns to step S11.

As described above, when the specific second toner amount is equal to or higher than a predetermined reference value, the signal selection unit 10 corresponds to the specific second toner amount having the maximum value based on the control signal CS1. The second density signal is selected. In this case, the specific developing unit corresponds to the second density signal and becomes a developing unit 3 that uses a large amount of toner in developing the electrostatic latent image. In the modification, the specific developing unit 3 is supplied with the replenishing toner in an amount corresponding to the measured first toner amount, not the estimated second toner amount. Therefore, it becomes easy to maintain the toner concentration constant even in the specific developing unit 3 in which a large amount of toner is used for development.

100 Image forming device 1 Photoreceptor drum 3 Developing unit 36 Signal output unit 9 Toner replenishment unit 10 Signal selection unit 11A Toner amount measurement unit 11B Toner amount estimation unit 11C Replenishment control unit 11D Judgment unit

Claims (3)

Multiple image carriers on which electrostatic latent images based on image data are formed,
A plurality of developing units provided corresponding to each of the plurality of image carriers and developing an electrostatic latent image formed on the corresponding image carriers.
A plurality of signal output units provided corresponding to each of the plurality of developing units and outputting a density signal indicating the density of toner in the corresponding developing units, and a plurality of signal output units.
A signal selection unit that sequentially selects and outputs a plurality of the density signals input from the plurality of signal output units one by one, and a signal selection unit.
Among the plurality of developing units, the amount of first toner used in development by a specific developing unit corresponding to the density signal output from the signal selection unit at a predetermined measurement time is input to the measurement time. Toner amount measuring unit that measures based on the density signal
A toner amount estimation unit that estimates a second toner amount used in development by at least the remaining developing units other than the specific developing unit among the plurality of developing units based on the image data.
A plurality of toner replenishment units provided corresponding to the plurality of developing units and capable of replenishing the corresponding developing units with replenishing toner.
The toner replenishing unit corresponding to the specific developing unit is replenished with the replenishing toner in an amount corresponding to the first toner amount, and the toner replenishing unit corresponding to the remaining developing unit is supplied with the second toner amount. A replenishment control unit that replenishes a corresponding amount of the replenishment toner,
Equipped with a,
The toner amount estimation unit is used by the plurality of developing units in development based on the image data before the plurality of developing units develop an electrostatic latent image formed on the corresponding image carrier. Estimate the amount of second toner
A determination unit for determining whether or not a specific second toner amount having a maximum value among the plurality of second toner amounts estimated by the toner amount estimation unit is equal to or higher than a predetermined reference value is further provided. ,
The signal selection unit
When the determination unit determines that the specific second toner amount is less than the reference value, a predetermined order is selected from the plurality of density signals input from the plurality of signal output units. Select and output the first density signal according to
When the determination unit determines that the specific second toner amount is equal to or greater than the reference value, the specific toner amount is selected from the plurality of density signals input from the plurality of signal output units. Select and output the corresponding second density signal,
The specific developing unit
When the specific second toner amount is less than the reference value, it is the developing unit corresponding to the first density signal among the plurality of developing units.
When the specific second toner amount is equal to or more than the reference value, the image forming apparatus which is the developing unit corresponding to the second density signal. The replenishment control unit replenishes the toner replenishment unit corresponding to the specific development unit with the replenishment toner in an amount corresponding to the first toner amount at a predetermined replenishment timing, and the remaining development unit. The toner replenishment unit corresponding to the unit is replenished with the replenishment toner in an amount corresponding to the second toner amount.
The image forming apparatus according to claim 1. The replenishment timing is the timing after the development in the plurality of developing units is completed.
The image forming apparatus according to claim 2.

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