JP2005274685A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing the deterioration of developer by discharging the developer neither too much nor too little. <P>SOLUTION: In the case of forming an image by forming an electrostatic latent image corresponding to image data showing an image to be formed on a photoreceptor drum 16, developing the electrostatic latent image with toner by a developing unit 22 where the developer containing the toner and carrier are stored, and transferring the obtained toner image to the intermediate transfer belt 14, the consumption of the toner is predicted based on the image data, and the opening of a developer discharge port 45 is derived based on the predicted toner consumption (throughput), and the opening is set in a driving part 54 for adjusting the opening of the developer discharge port 45. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  According to the present invention, an electrostatic latent image corresponding to image data indicating an image to be formed is formed on an image carrier, and the electrostatic latent image is converted into toner by developing means containing a developer containing toner and carrier. The present invention relates to an image forming apparatus that forms an image by developing and transferring a toner image obtained thereby to a recording medium.

  Conventionally, image forming apparatuses such as laser printers, facsimile machines, and copiers are provided with a photosensitive drum as an image carrier, and the surface of the photosensitive drum is uniformly charged, and then a light beam based on image data is irradiated. In some cases, an electrostatic latent image is formed on a photosensitive drum, the electrostatic latent image is developed using toner, and the image developed on the photosensitive drum is transferred to a recording medium to form an image. It was.

  In this type of image forming apparatus, when the developed image on the photosensitive drum is transferred, not all toner can be transferred, and a small amount of toner remains on the photosensitive drum after transfer. It remains as a toner.

  There is also toner (retransfer toner) that has been once transferred to the recording medium but again adheres to the photosensitive drum. In an image forming apparatus that supports color image formation, a color image is obtained by superimposing and transferring images of different colors. Therefore, at the time of transfer, another color toner that has already been transferred adheres to the photosensitive drum. Sometimes.

  The toner adhering to the photosensitive drum after the transfer may adhere to a charger or an exposure device provided around the photosensitive drum, or may be mixed into the developing device. Will prevent formation.

  For this reason, a cleaner having a mechanism for collecting the toner on the photosensitive drum and a mechanism for discarding the collected toner is generally disposed around the photosensitive drum on the downstream side of the transfer position. It was.

  However, in recent years, with the spread of such image forming apparatuses, it has been desired to reduce the cost and size of the apparatus, and it has been proposed to simplify the cleaner described above (also referred to as a cleaner-less system). )

  That is, it is necessary for a mechanism for discarding toner to secure a storage space for waste toner, a space for disposal work, and the like. Therefore, by omitting the mechanism, the apparatus can be reduced in size efficiently. Note that in an image forming apparatus that includes a plurality of photosensitive drums and supports color images, the cleaner is provided in a number corresponding to the number of the respective photosensitive members, and thus the cleaner is particularly effective for downsizing the apparatus. .

  Incidentally, in an image forming apparatus including an image forming apparatus to which the above cleanerless system is applied, a developing device using a two-component developer in which toner and a carrier are mixed may be used. In the two-component developer, the toner is consumed because it adheres onto the photosensitive member by development, but the carrier remains in the developing unit. For this reason, the carrier in the developing device is continuously stirred, and due to the impact and friction caused by stirring, a part of the toner adheres to the carrier and the carrier is contaminated. It will cause a decline.

  Therefore, in order to prevent the deterioration of the developer due to the contamination of the carrier, etc., conventionally, the toner is replenished in the same manner as in the past, and a new carrier is further replenished in the developer unit, so that the developer in the developer unit becomes excessive. A trickle method has been proposed.

As a technique using such a trickle method, conventionally, a developer that is a mixture of a toner and a carrier is stored in a developer layer, and the developer is carried on a developing roll, and then the developer is applied to the photoreceptor. When supplying toner, the amount of toner and carrier replenished in the developer layer is appropriately controlled according to the amount of toner consumed for development, and the balance between deteriorated developer overflow and new developer supply There has been proposed a technique for efficiently performing the trickle (see Patent Document 1, for example).
JP-A-9-204105

  However, in Patent Document 1, although the toner and carrier replenishment amount is determined according to the toner consumption amount, the developer corresponding to the toner and carrier replenishment amount and the toner consumption amount can be discharged. However, there is a problem in that an appropriate amount of developer cannot be discharged in a timely manner, resulting in deterioration of the developer.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can prevent deterioration of a developer by discharging the developer without excess or deficiency.

  In order to achieve the above object, the invention according to claim 1 forms an electrostatic latent image corresponding to image data indicating an image to be formed on an image carrier and contains a developer containing toner and carrier. An image forming apparatus that forms an image by developing the electrostatic latent image with the developed developing means and transferring the toner image obtained thereby to a recording medium, the development housed in the developing means Discharge means for discharging the agent by a preset discharge amount, prediction means for predicting the toner consumption amount based on the image data, and the discharge amount based on the toner consumption amount predicted by the prediction means. Setting means for deriving and setting the discharge means.

  According to the first aspect of the present invention, the electrostatic latent image corresponding to the image data indicating the image to be formed is formed on the image carrier, and the developing unit containing the developer including the toner and the carrier is used. The electrostatic latent image is developed with toner, and the toner image obtained thereby is transferred to a recording medium to form an image.

  Further, the developer stored in the developing means is discharged by the discharging means by a preset discharge amount. Thereby, the developer that leads to deterioration of the developer due to carrier contamination or the like is discharged.

  Here, in the present invention, the toner consumption is predicted by the prediction unit based on the image data, and the discharge amount is derived by the setting unit based on the predicted toner consumption and set in the discharge unit. Is done.

  That is, in the present invention, attention is paid to the fact that the degree of deterioration of the developer varies depending on the toner consumption, and the toner consumption is predicted based on the image data, and an amount of developer corresponding to the toner consumption is determined. It is trying to discharge. Accordingly, the developer can be prevented from being deteriorated by discharging the developer without excess or deficiency.

  As described above, according to the first aspect of the present invention, the electrostatic latent image corresponding to the image data indicating the image to be formed is formed on the image carrier, and the developer containing the developer including the toner and the carrier is accommodated. When the electrostatic latent image is developed with toner and an image is formed by transferring the resulting toner image to a recording medium, the toner consumption is predicted based on the image data. Since the discharge amount of the developer stored in the developing unit is derived based on the toner consumption amount, the developer is set as a discharge unit that discharges the developer by a preset discharge amount. The developer can be prevented from being deteriorated by discharging the toner without excess or deficiency.

  Further, according to the present invention, as in the invention described in claim 2, the setting means can be derived so that the discharge amount is increased as the predicted toner consumption amount is increased.

  Furthermore, as in the invention described in claim 3, the present invention further includes storage means for storing in advance information indicating a relationship between the predicted toner consumption amount and the discharge amount, and the setting means includes: The information may be read from the storage unit, and the discharge amount may be derived based on the information.

  The storage means includes a RAM (Random Access Memory), a ROM (Read Only Memory), an EEPROM (Electrically Erasable and Programmable ROM), a flash EEPROM (Flash EEPROM), a floppy disk, a CD-R (Compact A portable recording medium such as a Disc-Recordable), a CD-RW (Compact Disc-ReWritable), a magneto-optical disk, or a fixed recording medium such as a hard disk can be included.

  According to a fourth aspect of the present invention, there is provided a toner replenishing unit that replenishes the toner by a toner replenishing amount per unit period that is preset in the developing unit, and a developing unit that is preset in the developing unit. And a carrier replenishing unit that replenishes the carrier by a carrier replenishment amount per unit period, wherein the setting unit is responsive to the estimated toner consumption and the discharge amount set in the discharge unit. The replenishment amount may be derived and set in the toner replenishment unit, and the carrier replenishment amount may be derived and set in the carrier replenishment unit according to the discharge amount set in the discharge unit.

  As a result, the discharged toner and carrier and the consumed toner can be replenished to the developing means, and the toner and carrier in an amount necessary for good development processing are stored in the developing means. Can be kept.

  Further, according to the present invention, as in the invention described in claim 5, the discharge means has an opening portion that allows the inside and outside of the development means to communicate with each other and has an opening area that is variable, and the preset discharge amount. It is good also as what changes the area of the said opening part according to.

  As described above, according to the present invention, the electrostatic latent image corresponding to the image data indicating the image to be formed is formed on the image carrier, and the developing unit containing the developer including the toner and the carrier is used. When an image is formed by developing the electrostatic latent image with toner and transferring the resulting toner image to a recording medium, the toner consumption is predicted based on the image data, and the predicted toner consumption The amount of developer discharged in the developing unit is derived on the basis of the amount of developer, and the developer is set as a discharging unit that discharges the developer by a preset amount of discharge. By discharging, the developer can be prevented from being deteriorated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows a configuration of an image forming apparatus 10 according to the present embodiment. As shown in the figure, the image forming apparatus 10 has an endless belt-like intermediate transfer belt 14 that is stretched around a plurality of winding rollers 12 and conveyed in the direction of arrow E by driving a motor (not shown). A plurality of image forming units 15 (details will be described later) are arranged along the longitudinal direction.

  Note that the image forming apparatus 10 in the present embodiment also supports color image formation, and toners corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K). Image forming units 15Y, 15M, 15C, and 15K that form images are provided. Hereinafter, the members provided for each color are shown by adding alphabets (Y / M / C / K) indicating the respective colors at the end of the reference numerals. Explanation will be made by omitting the alphabet at the end of the code.

  The different color toner images formed by the image forming units 15 are transferred onto the intermediate transfer belt 14 so as to overlap each other on the belt surface of the intermediate transfer belt 14. As a result, a color toner image is formed on the intermediate transfer belt 14. In this embodiment, the toner image in which the four color toner images are transferred in a superimposed manner is referred to as a final toner image.

  On the downstream side of the four image forming units 15 in the conveying direction of the intermediate transfer belt 14, a transfer device 26 including two rollers 26A and 26B facing each other is disposed. The final toner image formed on the intermediate transfer body belt 14 is sent between the rollers 26A and 26B, taken out from the paper tray 29 provided at the bottom of the image forming apparatus 10, and is similarly supplied to the rollers 26A and 26B. It is transferred to the paper 28 that has been conveyed in between.

  In addition, a fixing device 30 including a pressure roller 30A and a heating roller 30B is disposed on the conveyance path of the paper 28 onto which the final toner image has been transferred. The sheet 28 conveyed to the fixing device 30 is nipped and conveyed by the pressure roller 30A and the heating roller 30B, whereby the toner on the sheet 28 is melted and pressed against the sheet 28 to be fixed. As a result, a desired image (color image) is formed on the paper 28. The paper 28 on which the image is formed is discharged out of the apparatus.

  On the other hand, a cleaner 32 that collects the toner remaining on the intermediate transfer belt without being transferred to the paper 28 by the transfer device 26 is disposed downstream of the transfer device 26 in the transport direction of the intermediate transfer belt 14. Yes. The cleaner 32 is provided with a blade 34 so as to be in contact with the intermediate transfer belt 14, and collects residual toner by rubbing it.

  A sensor unit 36 for detecting the density of the toner transferred to a predetermined position other than the image forming area on the intermediate transfer belt 14 is provided on the downstream side of the image forming unit 15 in the conveyance direction of the intermediate transfer belt 14. It has been.

  FIG. 2 shows the configuration of the image forming unit 15. Since the configuration of each image forming unit 15 is the same, the description is omitted here by omitting the last symbol indicating each color.

  As shown in the figure, the image forming unit 15 includes a photosensitive drum 16 that is disposed in contact with the intermediate transfer belt 14 and rotates at a predetermined speed in the arrow F direction.

  A charging roller 18 for charging the photosensitive drum 16 is disposed on the circumferential surface of each photosensitive drum 16. The charging roller 18 is a conductive roller, and its peripheral surface is in contact with the peripheral surface of the photosensitive drum 16, and is arranged so that the axial direction of the charging roller 18 coincides with the axial direction of the photosensitive drum 16. Has been.

  A predetermined voltage (a DC voltage of −500 V in the present embodiment) in which a DC voltage and an AC voltage are superimposed is applied to the charging roller 18, while rotating so as to follow the rotation of the photosensitive drum 16, The surface of the photosensitive drum 16 is uniformly charged to a predetermined potential (in the present embodiment, about −500 V).

  Further, an exposure device 20 for forming an electrostatic latent image on the photosensitive drum 16 is provided on the peripheral surface downstream of the charging roller 18 in the rotational direction F of each photosensitive drum 16. The exposure device 20 includes an LED array in which a plurality of LEDs (light emitting diodes) are arranged, and light based on image data in the axial direction of the photosensitive drum 16 uniformly charged by the charging roller 18. Irradiate the beam. The potential of the region irradiated with the light beam from the exposure device 20 is increased (in this embodiment, about −200 V), and an electrostatic latent image is formed on the photosensitive drum 16.

  Further, an electrostatic latent image formed on the photosensitive drum 16 is provided in a predetermined color (yellow / magenta / cyan / black) around the exposure device 20 in the rotation direction F of each photosensitive drum 16. A developing device 22 is provided for developing with toner and forming a toner image. In this embodiment, a developer including two components of a negative polarity toner and a positive polarity carrier is applied. In order to improve the development efficiency and the transfer efficiency described later, the toner particles are preferably spherical.

  As shown in the figure, the developing unit 22 includes a developing roller 38 and a blade 40 that are disposed close to the photosensitive drum 16. The developing roller 38 is applied with a predetermined voltage in which a DC (direct current) component having the same polarity as the surface of the photosensitive drum 16 (negative polarity in this embodiment) and an AC (alternating current) component are superimposed. The toner is conveyed to the peripheral surface together with the carrier of positive polarity loaded in the container 22. Further, the developing roller 38 is rotationally driven in the same direction as the rotation direction F of the photosensitive drum 16 (the direction of the arrow G in the drawing), and the carrier and toner that have adhered to the developing roller 38 are dropped by the blade 40 and developed. The roller 38 is uniformly attached.

  The toner attached to the developing roller 38 is developed on the surface of the photosensitive drum 16 by the rotation of the developing roller in the rotation direction G.

  If the surface potential Vh of the unexposed part of the photosensitive drum 16 is −500 V and the surface potential Vl of the exposed part is −200 V, a DC voltage is applied to the developing roller 38 by applying a bias voltage to the developing roller 38. The voltage (developing potential) Vdev is set to −400 V, and the toner adhering to the developing roller 38 adheres to the exposed portion on the photosensitive drum 16. Therefore, the electrostatic latent image formed on the photosensitive drum 16 is reversely developed.

  Further, a transfer roller 25 for transferring the toner image on each photoconductive drum 16 to the intermediate transfer belt 14 is provided around the downstream side of the developing device 22 in the rotation direction F of each photoconductive drum 16. . The transfer roller 25 rotates in the direction indicated by the arrow H, conveys the intermediate transfer belt 14 at a predetermined speed, and sequentially opposes the photosensitive drum 16. A positive bias voltage is applied to the transfer roller 25 to transfer the toner on the photosensitive drum 16 onto the intermediate transfer belt 14.

  Here, the transfer roller 25 cannot transfer all of the toner on the photosensitive drum 16 to the intermediate transfer belt 14, and a slight amount of toner remains on the photosensitive drum 16 that has passed through the transfer roller 25. (Transfer residual toner).

  There is also toner (retransfer toner) whose polarity is reversed to plus by the transfer roller 25 and reattached on the photosensitive drum 16. In addition, when the other color toner image has already been transferred onto the intermediate transfer belt 14 when passing through the transfer roller 25, the retransfer toner includes the other color toner.

  Therefore, a cleaning roll 24 that temporarily holds the transfer residual toner or the retransfer toner on the photosensitive drum 16 is disposed downstream of the transfer roller 25 on the peripheral surface of the photosensitive drum 16. The cleaning roll 24 has conductive brush bristles planted on the surface thereof, and is arranged so that the bristles come into contact with the photosensitive drum 16 so that a bias voltage is applied and the brush roll is driven to rotate. It has become.

  The cleaning roller 24 is rotated in the same direction as the rotation direction of the photosensitive drum 16 while a bias voltage having a negative polarity (-500 V in the present embodiment) is applied during a period in which image formation is being performed. As a result, the positive polarity retransfer toner adhering to the surface of the photosensitive drum 16 is attracted to the brush hair and collected.

  The negative transfer residual toner is not collected by the cleaning roll 24, and is charged and exposed to the photosensitive drum 16 while remaining on the photosensitive drum 16, and adheres to the non-image portion of the photosensitive drum 16. The transferred residual toner is collected in the developing device 22 by the rubbing with the carrier and the toner attached to the developing roller 38 of the developing device 22.

  The retransfer toner collected by the cleaning roll 24 is discharged onto the photosensitive drum 16 in a cleaning mode executed during non-image formation such as when a job is completed.

  In the cleaning mode, a bias voltage having a positive polarity (+500 V in the present embodiment) is applied to the cleaning roll 24, and the rotation direction of the photosensitive drum 16 is different (following the rotation of the photosensitive drum 16). As rotated). As a result, the positive polarity retransfer toner held on the cleaning roll 24 is discharged onto the photosensitive drum 16.

  The retransfer toner discharged on the photosensitive drum 16 in this way is conveyed to the transfer position by the rotation of the photosensitive drum 16.

  In the cleaning mode, a negative bias voltage is applied to the transfer roller 25, and the retransfer toner conveyed to the transfer position is transferred onto the intermediate transfer belt 14 by the transfer roller 25, and the intermediate transfer is performed. It is conveyed to the cleaner 32 by the body belt 14 and scraped off by the blade 34 of the cleaner 32.

  FIG. 3 shows the configuration inside and around the developing device 22.

  As shown in the figure, the developing device 22 is provided with a developer stirring chamber 46 therein, and around the developing device 22, there are a toner replenishing portion 48 and a carrier replenishing portion 49, respectively. 46 so as to be adjacent to 46.

  Inside the toner replenishing section 48, a toner storage chamber 48A is provided in which a toner discharge port 48B for storing the toner and discharging the stored toner to the outside is provided. The toner storage chamber 48A is provided with a transport screw 48C, and the toner stored in the toner storage chamber 48A is transported to the toner discharge port 48B by the rotational drive of the transport screw 48C and discharged. .

  Further, the carrier replenishing portion 49 is provided with a carrier storage chamber 49A in which carriers are stored. The carrier storage chamber 49A is provided with a carrier discharge port 49B and a conveying screw 49C. The configuration is the same as that of the supply unit 48.

  As shown in the figure, the developer stirring chamber 46 is provided with a toner supply port 43A and a carrier supply port 43B. The toner supply port 43A has an opening corresponding to the toner discharge port 48B of the toner supply unit 48 described above, and the carrier supply port 43B has an opening corresponding to the carrier discharge port 49B of the carrier supply unit 49. A toner discharge port 48B is connected to the toner supply port 43A, and a carrier discharge port 49B is connected to the carrier supply port 43B, so that the toner and the carrier are supplied to the developer stirring chamber 46.

  On the other hand, the developer stirring chamber 46 is divided into a first chamber 46A and a second chamber 46B by a partition wall 44. The developer stirring screw 42A is provided in the first chamber 46A, and the developer stirring screw 42A is provided in the second chamber 46B. Screws 42B are respectively disposed. The developer agitating screw 42A agitates and conveys the developer in the first chamber 46A, and the developer agitating screw 42B and the toner replenishing portion 49 through the toner replenishing port 43A and the carrier replenishing portion 49. The carrier replenished through the carrier replenishing port 43B and the developer already present in the developing device 22 are stirred and conveyed.

  Further, the partition wall 44 is formed with a developer passage (not shown) that allows the first chamber 46A and the second chamber 46B to communicate with each other at the front and back end portions of FIG. Due to the conveying force of 42A and developer stirring screw 42B, the developer in the first chamber 46A in which the toner has been consumed by the development moves from one passage into the second chamber 46B, and in the second chamber 46B, the toner replenishing section The developer supplied with toner and carrier from the carrier supply unit 49 and the carrier supply unit 49 moves from the other passage into the first chamber 46A.

  Further, the developer stirring chamber 46 is provided with a developer discharge port 45 so that the developer excessively contained in the developer stirring chamber 46 can be discharged to the outside of the developer stirring chamber 46. ing. In the vicinity of the position where the developer discharge port 45 is disposed, there is an opening at a position corresponding to the developer discharge port 45, and the developer discharged from the developer discharge port 45 can be accommodated inside. A discharged developer accommodating portion 47 having a discharged developer accommodating chamber 47A is provided.

  By the way, in the image forming apparatus 10 according to the present embodiment, when the electrostatic latent image is developed by the developing unit 22, toner and carrier in an amount corresponding to the amount of toner consumption are supplied from the toner supply unit 48 and the carrier supply unit 49. In addition, by changing the opening of the developer discharge port 45, the discharge rate is set and the developer discharge amount is adjusted.

  For this reason, as shown in FIG. 3, in the present embodiment, a movable wall 45A is embedded in the outer wall of the developer stirring chamber 46 where the developer discharge port 45 is provided. The developer discharge port is moved by a driving force of a drive unit 54 (not shown in FIG. 3; see FIG. 4) configured by a motor or the like in the direction of reducing the opening cross section of the developer discharge port 45 in FIG. The opening degree of 45 can be changed.

  In the figure, the toner supply port 43A, the carrier supply port 43B, and the developer discharge port 45 are shown to be provided in the same cross section. However, for example, the toner supply port 43A and the carrier supply port 43B For example, the toner replenishing port 43A is provided at the end on the front side of the sheet of FIG. 3, the carrier replenishing port 43B is provided at the end of the back side of the sheet of FIG. It is good also as providing in the position where the opening | mouth is not provided.

  FIG. 4 is a block diagram showing a functional configuration related to the setting of the discharge rate in the image forming apparatus 10.

  As shown in the figure, the image forming apparatus 10 includes a control unit 50 that controls the entire operation of the image forming apparatus 10. The intermediate transfer belt 14 and the image forming units 15 described above are included in the image forming apparatus 10. The operation of the photosensitive drum 16, the charging roller 18, the exposure device 20, the developing device 22, the drive unit 54 for moving the movable wall 45 </ b> A of the developing device 22, the toner supply unit 48, and the carrier supply unit 49 is controlled by the control unit 50. Is done. In the drawing, only connection lines from the control unit 50 to the charging roller 18, the toner replenishing unit 48, the carrier replenishing unit 49, and the driving unit 54 are shown in order to avoid complications.

  In addition, the image forming apparatus 10 includes a storage unit 56 for storing various programs, various table information, and the like in advance and temporarily storing image data indicating an image to be formed. The storage unit 56 is also electrically connected to the control unit 50, and the control unit 50 can access the storage unit 56 at any time.

  Further, when forming an image, the control unit 50 derives a throughput indicating the amount of toner expected to be consumed per unit period based on the image data, and the developer discharge port 45 according to the throughput. The discharge opening degree for the driving unit 54 for moving the movable wall 45A of the developing device 22 is set.

  In addition, the control unit 50 derives the toner replenishment amount according to the discharge port opening degree and the throughput, derives the carrier replenishment amount according to the discharge port opening degree, sets the toner replenishment amount for the toner replenishment unit 48, and The carrier supply amount for the carrier supply unit 49 is set.

  FIG. 5 shows an example of the opening degree of the developer outlet 45 corresponding to the throughput. This figure shows, as throughput, the amount of toner consumed per unit period (in this case, the time for forming an A4 size image) when an image with a print size of A4 size is formed. . As shown in the figure, as the throughput increases, the developer is discharged to prevent deterioration of the developer. In the present embodiment, information indicating the opening degree of the developer outlet 45 with respect to the throughput as shown in the figure is stored in advance in the storage unit 56 as outlet opening degree information.

  Further, the control unit 50 derives the discharged developer amount according to the discharge port opening degree, derives the toner replenishment amount according to the discharged developer amount and the throughput, and the carrier according to the discharged developer amount. The toner supply amount is set for the toner supply unit 48 and the carrier supply amount for the carrier supply unit 49 is set.

  Hereinafter, the operation of the image forming apparatus 10 according to the present embodiment will be described. In the image forming apparatus 10 according to the present embodiment, the developer discharge amount is set at the time of execution of a print job and before the start of image formation, and the developer supply unit 48 and the carrier supply unit 49 are connected to the developing device. A discharge rate setting process for setting toner and carrier replenishment to 22 is executed.

  FIG. 6 is a flowchart showing a processing flow of a discharge rate setting process program executed by the control unit 50 when executing the discharge rate setting process in the image forming apparatus 10, and the program is a predetermined area of the storage unit 56. Is stored in advance. Hereinafter, the discharge rate setting process according to the present embodiment will be described with reference to FIG.

  Here, it is assumed that image data indicating an image to be printed, information indicating the print size and the number of prints are stored in a predetermined area of the storage unit 56 by the control unit 50 for each print job. Here, in order to avoid complications, only control related to one image forming unit 15 will be described, but the control unit 50 performs similar processing on each image forming unit 15.

  First, in step 100, based on the image data of the print job being executed and the number of prints stored in the storage unit 56, the image occupancy ratio of the toner image developed by the developing device 22 in the print job to the image formation area Is derived.

  Here, as the image occupancy rate, when there are a plurality of print sheets of one print job, the average value of one print job is derived instead of deriving a plurality of values per sheet.

  In the next step 102, the throughput is derived based on the derived image occupancy rate and the print size, and then the process proceeds to step 104. The throughput is stored in the storage unit 56 and the image occupancy derived in step 100 by storing in the storage unit 56 information indicating the throughput according to the image occupation rate and the print size. It can be derived based on the print size.

  In step 104, based on the derived throughput, the outlet opening degree is derived using the outlet opening information (for example, see FIG. 5) stored in the predetermined area of the storage unit 56, and the process proceeds to step 106. Then, the carrier replenishment amount is derived, and then the process proceeds to step 108 to derive the toner replenishment amount.

  In this embodiment, the replenishment amount of the carrier is set according to the opening degree of the discharge port, and the replenishment amount of the toner is set according to the opening degree of the discharge port and the toner consumption amount. That is, since the developer discharge amount varies depending on the opening degree of the developer discharge port 45, the developer discharge amount can be derived from the opening degree of the developer discharge port 45.

  For example, since the carrier remains in the developer agitating chamber 46 as long as it is not discharged from the developer discharge port 45, the amount obtained by multiplying the developer discharge amount by a predetermined coefficient α can be used as the carrier replenishment amount. Further, an amount obtained by adding a predetermined coefficient β to an amount obtained by adding the developer discharge amount and the toner consumption amount (the amount indicated by the throughput) can be set as the toner replenishment amount.

  The coefficients α and β are determined by the development processing by the developing unit 22 obtained in advance by an experiment using an actual machine using a developer actually used, a computer simulation based on a design specification of the image forming apparatus 10, or the like. The values necessary for good performance are applied.

  In the next step 110, the derived outlet opening degree is set for the developing device 22, and then the process proceeds to step 112, where the derived carrier replenishment amount is set for the carrier replenishment unit 49, and then in step 114. Then, the derived toner replenishment amount is set for the toner replenishing unit 48, and then the discharge rate setting process is terminated.

  As described above in detail, according to the present embodiment, an electrostatic latent image corresponding to image data indicating an image to be formed is formed on the photosensitive drum 16, and a developer containing toner and carrier is accommodated. The developing unit 22 develops the electrostatic latent image with toner, and transfers the toner image obtained thereby onto the intermediate transfer belt 14 to form an image. When the image is formed, the toner consumption is based on the image data. Based on the predicted toner consumption (throughput), the opening amount of the developer discharge port 45 is derived and set in the drive unit 54 for adjusting the opening amount of the developer discharge port 45. Therefore, the developer can be prevented from being deteriorated by discharging the developer without excess or deficiency.

  Further, according to the present embodiment, the larger the throughput, the larger the outlet opening of the developer outlet 45, so the relationship between the toner consumption and the deterioration of the developer (particularly the carrier) is shown. It is possible to set the opening degree of the outlet in consideration, and to perform delicate control.

  Further, according to the present embodiment, information indicating the relationship between the throughput and the opening degree of the developer discharge port 45 is stored in advance in the storage unit 56 as discharge opening degree information, and the discharge opening degree information is stored in the storage unit 56. Since the opening degree of the developer discharge port 45 is derived based on this, the derivation process can be performed quickly and easily.

  Further, according to the present embodiment, the toner replenishing section 48 that replenishes the toner by the toner replenishment amount per unit period preset in the developing device 22 and the carrier per unit period preset in the developing device 22. And a carrier replenishing unit 49 for replenishing the carrier by the replenishing amount, deriving the toner replenishing amount according to the throughput and the opening degree of the developer discharge port 45 and setting it in the toner replenishing unit 48. Since the carrier replenishment amount is derived and set in the carrier replenishment unit 49 according to the degree, it is possible to replenish the developer 22 with the toner and carrier for the discharged amount and the toner for the consumed amount. In addition, the developing device 22 can store a necessary amount of toner and carrier for performing good development processing.

  Furthermore, according to the present embodiment, the developer discharge port 45 having a variable opening area is provided which allows the inside and outside of the developer stirring chamber 46 of the developing device 22 to communicate with each other. Since the opening area is changed in accordance with the above, the developer discharge amount can be easily controlled. Compared with the case where the developer discharge port 45 remains unchanged and the developer discharge amount is indirectly controlled according to the toner and carrier replenishment amount, the responsiveness is better, so the developer is discharged without delay. Can be made.

  Note that the above-described configuration of the image forming apparatus 10 (see FIGS. 1 to 4) is merely an example, and it is needless to say that the configuration can be changed as appropriate without departing from the gist of the present invention.

  In this embodiment, the case where the present invention is applied to a so-called tandem type image forming apparatus having four image forming units 15 has been described. However, the present invention is not limited to this, and for example, The present invention can be applied to an image forming apparatus having only one image forming unit 15, and in this case, the same effect as that of the present embodiment can be obtained. In this case, however, the discharge rate setting processing program (see FIG. 6) is executed for one image forming unit.

  Further, it is needless to say that the processing flow of the flowchart (see FIG. 6) described in the present embodiment is an example, and can be appropriately changed without departing from the gist of the present invention.

  Furthermore, in the discharge rate setting processing program according to the present embodiment, the case has been described in which the discharge opening is set using the discharge opening information stored in advance, but the present invention is not limited to this. Alternatively, any value can be obtained in advance by an arithmetic expression capable of calculating the same value as in the present embodiment. Also in this case, the same effects as in the present embodiment can be obtained.

  In the present embodiment, the control unit 50 has explained the form in which the outlet opening is derived from the throughput and set in the drive unit 54. However, the present invention is not limited to this, and the discharge amount itself is determined. The driving state of the driving unit 54 may be controlled in accordance with the discharge amount.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. 1 is a schematic configuration diagram of an image forming unit according to an embodiment. FIG. 2 is a schematic configuration diagram of a developing device according to the embodiment. 3 is a functional block diagram relating to setting of a discharge rate of the image forming apparatus according to the embodiment. FIG. 6 is a diagram illustrating an example of an outlet opening degree corresponding to the throughput of the image forming apparatus according to the embodiment. FIG. It is a flowchart which shows the flow of a process of the discharge rate setting process program which concerns on embodiment.

Explanation of symbols

10 Image forming apparatus 14 Intermediate transfer belt (recording medium)
16 Photosensitive drum (image carrier)
22 Developer (Developer)
45 Developer outlet (discharge means, opening)
45A movable wall (discharge means)
48 Toner supply part (toner supply means)
49 Career replenishment part (carrier replenishment means)
50 control unit (setting means, prediction means)
54 Drive unit (discharge means)
56 Storage unit (storage means)

Claims (5)

An electrostatic latent image corresponding to image data indicating an image to be formed is formed on the image carrier, and the electrostatic latent image is developed with toner by a developing unit containing a developer containing toner and a carrier. An image forming apparatus that forms an image by transferring the toner image obtained by the above to a recording medium,
Discharging means for discharging the developer contained in the developing means by a preset discharge amount;
Predicting means for predicting toner consumption based on the image data;
Setting means for deriving the discharge amount based on the toner consumption predicted by the prediction means and setting the discharge amount in the discharge means;
An image forming apparatus. The image forming apparatus according to claim 1, wherein the setting unit derives the discharge amount so as to increase as the predicted toner consumption amount increases. Storage means for storing in advance information indicating a relationship between the predicted toner consumption and the discharge amount;
The image forming apparatus according to claim 1, wherein the setting unit reads the information from the storage unit and derives the discharge amount based on the information. Toner replenishing means for replenishing the toner by a toner replenishing amount per unit period preset in the developing means;
Carrier replenishing means for replenishing the carrier by a carrier replenishment amount per unit period preset in the developing means;
Further comprising
The setting means derives the toner replenishment amount according to the predicted toner consumption amount and the discharge amount set in the discharge means, sets the toner supply amount in the toner supply means, and sets the discharge amount to be set in the discharge means. 4. The image forming apparatus according to claim 1, wherein the amount of carrier replenishment is derived and set in the carrier replenishment unit according to claim 1. 2. The discharge unit includes an opening that communicates the inside and outside of the developing unit and has a variable opening area, and changes the area of the opening according to the preset discharge amount. The image forming apparatus according to claim 4.

Images