JP5807327B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus.

  For example, Patent Document 1 has an opening at an opening portion facing a photoreceptor, a developing housing that contains a two-component developer containing a carrier and toner, and a rotatable housing disposed at a location facing the opening of the developing housing. A two-component developing type developing device including a developing roll provided is disclosed.

JP 2000-98730 A

  Here, in the case of adopting a structure that can maintain the amount of developer in the developing device within an appropriate range by replenishing the developer and discharging the developer in the developing device of the two-component development system, replenishment When the amount of developer to be discharged is smaller than the amount of developer to be discharged, the amount of developer in the developing device may be reduced.

  An object of the present invention is to provide a developing device or the like that can maintain the amount of developer in the apparatus within a certain range even when a relatively small amount of developer is supplied.

According to the first aspect of the present invention, a support member that is supported so as to be able to rotate with respect to the apparatus main body, the support member is rotated with respect to the apparatus main body, and an electrostatic latent image is formed. Driving means for stopping the supporting member at a predetermined position with respect to the image holding member, and a developer replenishing portion attached to the supporting member and for receiving replenishment of two-component developer comprising toner and carrier And a developer discharge portion for discharging the developer to the outside, and when the driving means stops at a position facing the image carrier, the electrostatic latent image on the image carrier is acquisition a plurality of developing device for developing, as information about the replenishment amount of the developer-supply unit with a print instruction, and acquires the information specifying the number of printed sheets of information and the print instruction specifying an image density of the print instruction It based the stage, the acquired information by the acquisition unit, after completion of execution of the print instruction, the by the developer discharging section in the case of the above first image density image density of the print instruction is predetermined When the developer is discharged and the image density of the print instruction is less than the first image density and the number of prints of the print instruction is equal to or greater than a predetermined first print number, the developer is discharged. The image density of the print instruction is less than the first image density and higher than a predetermined second image density lower than the first image density, and Control to discharge the developer when the number of prints in the print instruction is less than the first print number and greater than a predetermined second print number that is less than the first print number. and control means for, the including a developing device A.
According to a second aspect of the present invention, the acquisition unit further acquires, after the execution of the print instruction, information specifying a toner replenishment time as information relating to a replenishment amount by the developer replenishing unit accompanying the print instruction. The developing device according to claim 1.
According to a third aspect of the present invention, the control unit acquires information for specifying a toner replenishment time during execution of the print instruction, and uses the information to discharge the developer discharge unit after completion of execution of the print instruction. The developing device according to claim 2, wherein discharge of the developer due to is suppressed.

According to a fourth aspect of the present invention, there is provided an image holding member for forming an electrostatic latent image, a developing unit for developing the electrostatic latent image formed by the image holding member into a toner image, and a toner by the developing unit. A transfer unit that transfers the image onto the recording material; and a fixing unit that fixes the toner image transferred onto the recording material to the recording material. The developing unit is capable of rotating relative to the apparatus body. A support member that is supported so that the support member is rotated, and the support member is rotated with respect to the apparatus main body, and the support member is stopped at a predetermined position with respect to an image carrier that forms an electrostatic latent image. A driving means for causing the developer to be replenished, and a developer replenishing portion attached to the support member for receiving replenishment of a two-component developer comprising toner and carrier, and a developer discharging portion for discharging the developer to the outside. , Holding the image by the driving means The electrostatic latent image of the image carrier as information on the amount of toner to be consumed and a plurality of developing device for developing in the toner, by the execution of print instruction when stopped at a position opposed to, of the print instruction An acquisition unit that acquires information specifying the image density and information specifying the number of prints of the print instruction, and an image density of the print instruction after the execution of the print instruction is completed based on the information acquired by the acquisition unit Is discharged from the developer discharge unit when the image density is equal to or higher than a predetermined first image density, and the print instruction is less than the first image density and the print instruction The developer is discharged when the number of printed sheets is equal to or greater than a predetermined first printed number, the image density of the print instruction is less than the first image density, and the first image density Lower than A predetermined second image density is set, and the number of prints in the print instruction is less than the first print number and less than the first print number. and control means for controlling to perform the discharge of the developer when more than two of the number of printed sheets, which is a including an image forming apparatus.
The invention according to claim 5 is characterized in that the acquisition means further acquires, as information relating to the amount of toner consumed by execution of the print instruction, information for specifying a toner replenishment time by execution of the print instruction. The image forming apparatus according to claim 4 .
According to a sixth aspect of the present invention, the control unit acquires information for specifying a toner replenishment time during execution of the print instruction, and uses the information to discharge the developer discharge unit after completion of execution of the print instruction. The image forming apparatus according to claim 5 , wherein the developer discharge due to the ink is suppressed.

According to the first aspect of the present invention, it is determined whether or not the trickle operation is performed based on the relationship between the image density of the print instruction and the number of printed sheets of the print instruction, and the apparatus can be used even when a relatively small amount of developer is supplied. The amount of the developer can be maintained within a certain range.
According to the second aspect, the amount of the developer in the apparatus can be more easily maintained within a certain range.
According to the third aspect, the amount of the developer in the apparatus can be maintained within a certain range with higher accuracy.

According to the fourth aspect of the present invention , it is determined whether or not the trickle operation is performed based on the relationship between the image density of the print instruction and the number of printed sheets of the print instruction. The amount of the developer can be maintained within a certain range.
According to the fifth aspect , the amount of the developer in the apparatus can be more easily maintained within a certain range.
According to the sixth aspect , the amount of the developer in the apparatus can be maintained within a certain range with higher accuracy.

1 is a schematic configuration diagram showing a color image forming apparatus according to the present embodiment. It is sectional drawing explaining the structure of a developing device. It is sectional drawing explaining the structure of a developing device. It is a perspective view explaining a developing housing. It is a figure for demonstrating the attachment position of the mark formed in a developing sleeve, and an optical sensor. It is a figure explaining the structure of the control system in an image forming apparatus. It is a block diagram explaining the structure of a control part. It is a flowchart which shows the example of a process sequence of the control part which concerns on 1st Embodiment. It is a flowchart which shows the process sequence example of the control part which concerns on 2nd Embodiment. It is a flowchart which shows the process sequence example of the control part which concerns on 3rd Embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing a color image forming apparatus according to the present embodiment.
The color image forming apparatus according to the present embodiment is provided with a photosensitive drum 11 as an image holding member that is rotatably arranged in an arrow A direction, and a photosensitive drum 11 that is rotatably arranged in an arrow B direction. And an intermediate transfer belt 20 as a transfer material for sequentially transferring (primary transfer) and holding the respective color component toner images formed thereon. In addition, the color image forming apparatus includes a secondary transfer unit 30 that collectively transfers (secondary transfer) the superposed toner image transferred onto the intermediate transfer belt 20 onto a sheet S that is a recording material, and a secondary transferred image. Are fixed on the sheet S, and a control unit 60 that controls each mechanism unit of the color image forming apparatus is provided.

  Around the photosensitive drum 11, there are a charging roll 12 as a contact charging member for charging the photosensitive drum 11, and a laser exposure device 13 as a latent image forming unit on which an electrostatic latent image is written on the photosensitive drum 11. (The exposure beam is indicated by a symbol Bm in the drawing) The yellow (Y), magenta (M), cyan (C), and black (K) color component toners are accommodated to form an electrostatic latent image on the photosensitive drum 11. Each developing unit 14Y, 14M, 14C, 14K as a developing unit that visualizes with toner, a rotary developing device 14 that is rotatably mounted in the direction of arrow C, and each color component toner formed on the photosensitive drum 11. An electrophotographic device such as a primary transfer roll 15 serving as a transfer unit that transfers an image to the intermediate transfer belt 20 and a refresher 16 that temporarily collects residual toner on the photosensitive drum 11 is sequentially disposed. In other words, the rotary developing device 14 according to the present embodiment includes six accommodating portions that are equally divided in the circumferential direction, and is configured such that a developing device can be attached to each of the six accommodating portions. . In the rotary developing device 14 according to the present embodiment, four developing devices 14Y, 14M, 14C, and 14K are attached. However, for example, a developing device such as a special color may be attached to the remaining two storage units. Conceivable.

  Here, the charging roll 12 is formed by coating the surface of the metal shaft with an epichlorohydrin rubber layer and further coating the surface of the epichlorohydrin rubber layer with a polyamide containing tin oxide conductive powder by about 3 μm.

  Further, the photosensitive drum 11 is formed by forming an organic photosensitive layer on the surface of a metal thin cylindrical drum, and the organic photosensitive layer is made of a material that is negatively charged. The development by the developing units 14Y, 14M, 14C, and 14K is performed by a reversal development method. Accordingly, the toner used in the developing units 14Y, 14M, 14C, and 14K is of the negative charge type. A charging bias power source (not shown) for applying a charging bias to the charging roll 12 and a developing bias (not shown) for applying a developing bias to each of the developing devices 14Y, 14M, 14C, and 14K to the rotary developing device 14 are provided. A primary transfer bias power source (not shown) for applying a primary transfer bias is connected to the primary transfer roll 15. The rotary developing device 14 is provided with a developing device driving motor 17b as an example of a driving unit for rotating a predetermined developing device to face the photosensitive drum 11 by rotation. The driving of the developing device drive motor 17b is controlled by the control unit 60 as described later. The photosensitive drum 11 is grounded.

The intermediate transfer belt 20 is stretched over a plurality of (six in this embodiment) rolls 21 to 26. Among these, the rolls 21 and 25 are driven rolls, the roll 22 is a metal idle roll used for positioning the intermediate transfer belt 20 and forming a flat primary transfer surface, and the roll 23 has a constant tension of the intermediate transfer belt 20. The tension roll used for this purpose, the roll 24 is a drive roll for the intermediate transfer belt 20, and the roll 26 is a backup roll for secondary transfer described later. Further, the intermediate transfer belt 20 is made of a resin such as polyimide, polycarbonate, polyester, polypropylene, polyethylene terephthalate, acrylic, vinyl chloride, or various rubbers containing carbon black as a conductive agent, and has a surface resistivity. ^{10 11 Ω / □, 10 11} Ω · cm in volume resistivity, and used after a 150μm thickness.

  The secondary transfer unit 30 includes a secondary transfer roll 31 disposed on the toner image holding surface side of the intermediate transfer belt 20, a backup roll 26, and the like. The backup roll 26 is a tube of EPDM and NBR blend rubber in which carbon is dispersed on the surface, the inside is made of EPDM rubber, and the surface resistivity is 7 to 10 logΩ / □, and the hardness is, for example, 70 ° ( Asuka C). The backup roll 26 is connected to a secondary transfer bias power source (not shown) for applying a secondary transfer bias, while the secondary transfer roll 31 is grounded. A paper transport guide 32 that guides the transported paper S to the secondary transfer section 30 is attached to the upstream side of the secondary transfer section 30.

  On the other hand, on the downstream side of the secondary transfer unit 30, a belt cleaner 27 is provided as a cleaner for removing residual toner adhering to the intermediate transfer belt 20 after the secondary transfer, and the intermediate transfer belt 20 is interposed therebetween. A sheet metal member 28 is disposed along the inner surface of the intermediate transfer belt 20 at a position facing the belt cleaner 27. The belt cleaner 27 includes a scraper 41 that is formed of a stainless steel plate or the like and is disposed on the image holding surface side of the intermediate transfer belt 20, and a cleaner housing 42 in which the scraper 41 is accommodated. Further, one end side of the scraper 41 is fixed by being sandwiched between blocks 43, and this block 43 is attached to a holder 44 that swings about a shaft 44a. Further, a spring 45 that urges the scraper 41 toward the intermediate transfer belt 20 is attached between a recess 44b provided on the lower end side of the holder 44 and a bulging portion provided at a lower portion of the cleaner housing 42. A film seal 46 is attached on the upstream side of the moving direction of the intermediate transfer belt 20 as viewed from the scraper 41 to prevent the removed foreign matter from scattering to the outside.

  The holder 44 can be urged or released in a direction opposite to the urging direction of the spring 45 by a cam (not shown) connected to a cleaner drive motor (not shown). The transfer belt 20 can be contacted and separated. In this embodiment, when a color image composed of a plurality of colors is formed, the secondary transfer roll 31 and the toner image before the final color pass through the secondary transfer roll 31 and the belt cleaner 27. A belt cleaner 27 is separated from the intermediate transfer belt 20.

  Further, the fixing unit 50 includes a heating roll 51 containing a heating source such as a halogen lamp, and a pressure roll 52 arranged in pressure contact with the heating roll 51. Fixing is performed by passing a sheet on which a toner image is transferred to a fixing nip area formed between the two.

  Next, the toner and developer used in the present embodiment will be described in detail. The toner used in the present embodiment has a polarity that is negatively charged as described above, and may be polyester, styrene acrylic, etc. by suspension polymerization, emulsion aggregation and coalescence, dissolution suspension, or the like. Fine particles obtained by internally adding a colorant and wax to the binder resin. As a result of measurement with a Coulter counter (manufactured by Coulter Co., Ltd.), the volume average particle size was about 5 μm, and the particle size distribution index (GSD) was 1.23. The toner shape (degree of sphere) is represented by a shape factor, and an enlarged photograph of the toner obtained with an optical microscope (microphoto FXA: manufactured by Nikon Corporation) is subjected to image analysis using an image analyzer Luzex3 (manufactured by Nireco Corporation), and the following formula Calculated with

  This expression is expressed as a ratio of the projected area of the toner to the area of the circle circumscribing the toner, and is 100 for a true sphere, and the number increases as the shape moves away from the sphere. If the shape factor is small, the amount of toner (residual toner) that remains without being transferred during transfer decreases, so the shape factor of the toner is preferably about 100 to 140. In this embodiment, The shape factor of each color component toner of yellow, magenta, cyan, and black was in the range of 129 to 134. To this toner, inorganic fine particles such as silica and titania having an average particle diameter of 5 to 200 nm were externally added as external additives, and mixed with a carrier made of ferrite beads having an average particle diameter of 35 μm to obtain a two-component developer.

  Next, an image forming process of the color image forming apparatus according to the present embodiment will be described. When a start switch (not shown) is turned on, an image forming process is executed. First, the surface of the photosensitive drum 11 is charged to a predetermined potential by the charging roll 12, and then an electrostatic latent image corresponding to the image is written by the laser exposure unit 13, and the corresponding developing units 14Y, 14M, 14C, 14K. The electrostatic latent image is developed by either of the above. For example, if the electrostatic latent image written on the photosensitive drum 11 corresponds to yellow, the electrostatic latent image is developed by the yellow developing device 14Y containing yellow toner, and the photosensitive drum A yellow toner image is formed on 11. The toner image formed on the photoconductive drum 11 is transferred from the photoconductive drum 11 by the primary transfer bias applied to the primary transfer roll 15 at the primary transfer position where the photoconductive drum 11 and the intermediate transfer belt 20 are in contact with each other. Primary transfer is performed on the belt 20. On the other hand, the toner remaining on the photosensitive drum 11 after the primary transfer is mechanically leveled by the refresher 16. In this embodiment, since so-called spherical toner is used, transfer efficiency is very high, and almost no residual toner is generated. Therefore, it is possible to form a good image without providing a drum cleaner. It has become.

  At this time, when a single color image is formed, the toner image primary-transferred to the intermediate transfer belt 20 is immediately secondary-transferred to the paper S, but a color image is formed by superimposing a plurality of color toner images. In this case, the toner image formation on the photosensitive drum 11 and the primary transfer process of the toner image formed on the photosensitive drum 11 are repeated for the number of colors. For example, when a full color image is formed by superimposing four color toner images, yellow, magenta, cyan, and black toner images are sequentially formed on the photosensitive drum 11, and the toner images of these colors are sequentially transferred to the intermediate transfer belt. 20 is primarily transferred. On the other hand, the intermediate transfer belt 20 rotates in the same cycle as the photosensitive drum 11 while holding the primary transferred toner image, and magenta, cyan, and black toner images are formed on the intermediate transfer belt 20 for each rotation. Transcribed and overlaid.

  The toner image primarily transferred to the intermediate transfer belt 20 in this way is conveyed to the secondary transfer position as the intermediate transfer belt 20 rotates. On the other hand, the sheet S is supplied to a secondary transfer position via a sheet conveyance guide 32 at a predetermined timing by a resist roll (not shown), and the secondary transfer roll with respect to the intermediate transfer belt 20 (backup roll 26). 31 nips the paper S. Then, at the secondary transfer position, the toner image held on the intermediate transfer belt 20 is transferred to the sheet S by the action of the secondary transfer electric field that acts between the secondary transfer roll 31 that is the secondary transfer unit 30 and the backup roll 26. Electrostatic transfer (secondary transfer). Thereafter, the sheet S on which the toner image has been transferred is conveyed to the fixing unit 50 where the toner image on the sheet S is heated and pressurized and fixed, while remaining on the intermediate transfer belt 20 that has passed through the secondary transfer position. The toner is removed by the belt cleaner 27.

Next, the developing device 14 will be described in detail.
The rotation shaft 17a of the developing device 14 is rotatably mounted on a front frame and a rear frame (both not shown) provided in the image forming apparatus main body. Further, a gear (not shown) is attached to the rear of the developing device 14, and the developing device 14 is rotationally driven in the direction of arrow C by the developing device drive motor 17b. The developing device drive motor 17b is constituted by, for example, a stepping motor, and has a function of rotating the developing device 14 and positioning the developing devices 14Y, 14M, 14C, and 14K constituting the developing device 14. Further, a connecting block (not shown) for attaching the developing units 14Y, 14M, 14C, and 14K to a support 17c as an example of a support member is formed on the outer peripheral surface of the rotary shaft 17a. As a result, the developing devices 14Y, 14M, 14C, and 14K constituting the developing device 14 are rotated and moved with the rotation of the rotating shaft 17a, and the first stop position P1 that is the position facing the photosensitive drum 11 sequentially. The second stop position P2 positioned next to the first stop position P1, the third stop position P3 positioned next to the second stop position P2, and the fourth stop position P4 positioned next to the third stop position P3. Is configured to stop. Stop control by the control part 60 is performed by detecting the pulse signal sent from the optical sensor 49 (refer FIG. 6) in the 1st stop position P1. In the present embodiment, four developing units 14Y, 14M, 14C, and 14K are provided. However, when two developing units are further provided, a fifth stop position that is positioned next to the fourth stop position P4. P5 and the sixth stop position P6 positioned next to the fifth stop position P5 are also configured to stop.
In the present embodiment, the first stop position P1 is a development position for developing the electrostatic latent image on the photosensitive drum 10 so as to face the photosensitive drum 11, and at the same time, a new developer is added as described later. The developer replenishment position to be replenished, the fifth stop position P5 and the sixth stop position P6 are developer discharge positions for discharging the developer that has become excessive due to replenishment.

Next, the configuration of each developing unit 14Y, 14M, 14C, 14K will be described. The developing units 14Y, 14M, 14C, and 14K have the same configuration except for the developer stored therein, and therefore, here, the yellow developing unit 14Y will be described as an example.
2 and 3 are diagrams for explaining the configuration of the developing device 14Y. FIG. 2A is a longitudinal sectional view thereof, and FIG. 2B is a perspective view of the periphery of the shutter 69. FIG. 3 is a cross-sectional view.
As shown in FIG. 2A or 3, the yellow developing device 14 </ b> Y has an opening (for development) at a portion facing the photosensitive drum 11 when it is disposed at the first stop position P <b> 1 (see FIG. 1). A developing housing 71 having an opening) is formed. A pair of projecting pins 72 (see FIG. 2A) projecting outward are formed on the rear side of the developing housing 71. The protruding pin 72 is inserted into an insertion port provided in a connection block (not shown) of the support body 17c, and is used for positioning and fixing the developing housing 71.

The yellow developing device 14Y includes a developing roll 73 disposed facing the opening of the developing housing 71, and a first auger 74 disposed in the developing housing 71 on the side close to the developing roll 73. And a second auger 75 disposed on the side far from the developing roll 73 and a trimmer 78 as a regulating member for regulating the thickness of the developer layer attached to the developing roll 73. The first auger 74 and the second auger 75 constitute a developer supply member for supplying a two-component developer composed of toner and carrier to the developing roll 73.
Here, the developing roll 73 as one of the developer carrying members has a magnet roll 77 in which a plurality of magnetic poles are arranged fixedly included in a rotatable developing sleeve 76 made of a nonmagnetic metal. It is a thing. The developing sleeve 76 is made of, for example, a non-magnetic aluminum pipe. When the yellow developing device 14Y is at the first stop position P1 (see FIG. 1), the developing sleeve 76 is spaced from the peripheral surface of the photosensitive drum 11. In addition, it is driven to rotate while maintaining a predetermined interval. Here, the diameter of the developing roll 73 (developing sleeve 76) is φ18.
In the present embodiment, the rotation direction of the developing sleeve 76 is set to be the same as the rotation direction of the photosensitive drum 11 at a position facing the photosensitive drum 11 at the first stop position P1 (see FIG. 1). . The developing sleeve 76 is driven to rotate at a speed 1.35 times that of the photosensitive drum 11.

  Moreover, as shown in FIG. 3, both the first auger 74 and the second auger 75 are configured by attaching spiral blades around the rotation axis. The first auger 74 stirs and conveys the developer in the developing housing 71, for example, in the left direction in the figure, while the second auger 75 directs the developer in the developing housing 71, for example, in the right direction in the figure. Transport with stirring. The developing housing 71 is provided with a partition wall 71 a that partitions the first auger 74 and the second auger 75. The partition walls 71a do not exist at both ends in the longitudinal direction of the developing housing 71. As a result, the developer in the developing housing 71 is stirred inside the developing housing 71 by the first auger 74 and the second auger 75. It will be circulated and conveyed. For this reason, the toner having a negative charging polarity is rubbed by being agitated and conveyed together with a carrier having a positive charging polarity and magnetism, and is charged negatively. A trimmer 78 shown in FIG. 2A is made of, for example, a metal plate and is fixed to the developing housing 71. A predetermined gap is formed between the developing sleeve 76 and the free end of the trimmer 78 in order to obtain a preferable developer layer thickness.

Further, as shown in FIG. 3, on the second auger 75 side of the developing housing 71, a carry-in port 71 b for carrying a new developer is formed. On the other hand, a developer discharge port 71 c for discharging excess developer is formed on the second auger 75 side of the development housing 71.
The carry-in port 71b is provided with a supply pipe 81 that supplies a new developer from a developer supply bottle (not shown), and a supply auger 82 that is rotatably disposed inside the supply pipe 81. . On the other hand, on the lower side of the side portion of the developer discharge port 71c, a communication path forming member 83 (see FIG. 3) formed as a communication path through which excess developer is discharged, and a communication path forming member 83 are connected. A waste pipe 84 (see FIG. 3) for transporting excess developer to a collection container (not shown) is provided.

  Further, as shown in FIGS. 2A and 2B, a shutter 85 for opening and closing the discharge port is disposed at the developer discharge port 71c. The shutter 85 is composed of a plate member or plate. One end (left end in the figure) of the shutter 85 is hinged to be rotatable, and the free end side, which is the other end (right end in the figure) of the shutter 85, is a frame provided inside the upper wall of the developing housing 71. It is arranged on the inner side of the shaped shutter locking member 86. When the developing housing 71 is moved to the first stop position P1 (see FIG. 1), the shutter 85 opens to the inside of the developing housing 71 by the action of gravity, and the frame-shaped shutter locking member 86 is connected to the first auger 74 and the second auger 74. When the two-component developer in the developer circulation area that is agitated and conveyed by the auger 75 is excessive, it is locked at a position where the excess developer is conveyed to the outer surface of the shutter 85.

At the first stop position P1 (see FIG. 1), the shutter 85 rotates about the hinge shaft at the upper end due to its own weight, and the free end side of the shutter 85 is locked to the shutter locking member 86, thereby tilting the shutter 85. Held in the closed state (opening position). At this time, the developer discharge port 71c is open.
In addition, the shutter 85 is rotated about the hinge shaft at the upper end portion by its own weight or the pressure of the developer in the developing housing 71 and hangs downward at the second stop position P2 and the third stop position P3 (see FIG. 1). Kept in a state. At this time, the shutter 85 closes the developer discharge port 71c (closed position).
Further, the shutter 85 closes the developer discharge port 71c (closed position) in a state of being in contact with the inner surface of the upper wall of the development housing 71 at the fourth stop position P4 (see FIG. 1).
The shutter 85 has an upper end at the free end of the shutter 85 at the fifth stop position P5 and the sixth stop position P6 (see FIG. 1), and the upper wall of the developer housing 71 due to its own weight or the pressure of the developer in the developer housing 71. And is in contact with the inner surface of the upper wall of the developing housing 71. In this state, the shutter 85 closes the developer discharge port 71c (closed position).

  More specifically, when the developing devices 14Y, 14M, 14C, and 14K are stopped at the fifth stop position P5 (see FIG. 1) or the sixth stop position P6 (see FIG. 1), the excess developer discharged from the developing housing 71 is Then, it is conveyed to a collection container (not shown).

4A and 4B are perspective views for explaining the developing housing 71. FIG. 4A is a drawing of the developing housing 71 alone (the developer supply cylinder 88 is mounted in the rotary developing device 14), and FIG. Is a state in which a developer supply cylinder is attached to the development housing 71.
As shown in FIG. 4A, a member having a pair of circular arc surfaces for receiving cylinders in front of and behind the carry-in port 71b of the developing housing 71 is a member that supports the cylindrical outer surface of the developer supply cylinder 88. A supply cylinder support member 87 is provided. When the developing housing 71 moves to the first stop position P1 (see FIG. 1), the developer supply cylinder 88 is disposed outside the upper surface of the developing housing 71, and thereby, a carry-in port for carrying in a new developer. 71b.
In the developer supply cylinder 88, as shown in FIG. 4B, a supply developer transport screw (supply developer transport member) 88a is rotatably arranged. The replenishment developer conveying screw 88a has a rotating shaft 88b and a screw 88c fixed around the rotating shaft 88b. The replenishment developer conveying screw 88a extends forward from an opening (developer carrying-in port) 88d of one end portion (left end portion in the figure) of the developer replenishing cylinder 88, and the rotation of the replenishing developer conveying screw 88a. A bearing 88e is rotatably supported at one end (the left end in the figure) of the shaft 88b. In other words, the developer supply cylinder 88 and the developer supply screw 88a for supply constitute a part of the developer supply member Th.
The supply pipe 81, the supply auger 82, the supply cylinder support member 87, the developer supply cylinder 88, and the supply developer transport screw 88a are examples of the developer supply section. The communication path forming member 83, the waste pipe 84, the shutter 85, and the shutter locking member 86 are an example of a developer discharge portion.

  A gear 89a is fixed to the other end portion (the right end portion in FIG. 4) of the rotating shaft 88b of the replenishing developer conveying screw 88a in the developer replenishing cylinder 88. The gear 89a meshes with the gear 89b of the developer supply member. With the rotation of the gear 89b, the replenishment developer conveying screw 88a rotates, and the developer carried into the developer replenishing cylinder 88 is conveyed to the other end (the right end in FIG. 4) and from the carry-in port 71b. It is supplied to the second auger 75 side.

FIG. 5 is a view for explaining the marks formed on the developing sleeve 76 and the attachment positions of the optical sensor 79.
In this embodiment, as shown in FIG. 5, only one spot is marked black on the axial end of the developing roll 73 (actually the developing sleeve 76) of each developing unit 14Y, 14M, 14C, 14K. A portion (mark) is formed, and the reflectance is different from other portions of the developing sleeve 76 made of aluminum. An optical sensor 79 as one of the sensors is disposed on the axial end portion side of the developing sleeve 76 so as to face the outer peripheral surface of the developing sleeve 76. As the optical sensor 79, a so-called reflective sensor that performs sensing by irradiating light and receiving reflected light from an object is used. Therefore, when the developing sleeve 76 rotates, a portion (mark) having a different reflectance is read by the optical sensor 79 every rotation, and the rotation period of the developing sleeve 76 can be detected based on the detection result. .
Instead of such a mark, for example, a part of the surface state (for example, surface roughness) of the developing sleeve 76 is changed, or a part of the developing sleeve 76 is provided with a notch. Similarly, the rotation period of the developing sleeve 76 can be obtained. In addition, the rotation cycle of the developing sleeve 76 can be obtained by providing a sensor for detecting the driving torque of the developing sleeve 76 in place of the optical sensor 79, or by counting the number of pulse signals of the motor that drives the developing sleeve 76. Is possible.

Next, a control system in the image forming apparatus will be described.
FIG. 6 is a diagram illustrating the configuration of a control system in the image forming apparatus.
As shown in FIG. 6, the control unit 60 includes a CPU (Central Processing Unit) 60 a that functions as an arithmetic processing unit, a ROM that stores a program that is interpreted and executed by the CPU 60 a, data that is used when the program is executed, and the like. (Read Only Memory) 60b, a RAM (Random Access Memory) 60c that functions as a temporary storage unit when the program is executed, and an interface (I / F) 60d that exchanges data with a controller or the like described later. ing. The CPU 60a implements various functions by loading various programs and data stored in the ROM 60b into the RAM 60c and executing them.
The control unit 60 includes an image signal controller 61 that controls the image signal processing device 18 based on preset signal processing conditions, and a driver 62 that controls a developing device drive motor 17b that rotates the developing device 14. The developing sleeve 76 in the developing device arranged at the first stop position P1, the drive controller 64 for controlling the motor 63 for driving the first auger 74 and the second auger 75 (see FIG. 2), and the first stop position A developing bias controller 65 for controlling the developing power source 19 for applying a developing bias to the developing roller 73 (actually the developing sleeve 46) of the developing device arranged at P1 according to a preset bias applying condition is connected. ing. The developing power source 19 that functions as a power source is connected to a current measuring unit 66 as one of ammeters for measuring the magnitude of the current flowing between the developing roll 73 and the photosensitive drum 11 when a developing bias is applied. The measured current value is input to the control unit 60 via the developing bias controller 65. Furthermore, in the present embodiment, among the optical sensors 79 provided in the developing devices 14Y, 14M, 14C, and 14K, the detection result by the optical sensor 79 of the developing device at the first stop position P1 is sent to the control unit 60. It is designed to be entered.

  Here, in the image forming apparatus, the toner concentration in the developer in the development housing 71 gradually decreases as the toner in the developer is used for development. In addition, unlike the toner, the carrier in the developer is basically not discharged to the outside. Therefore, the characteristics (particularly, the charging performance of the toner) gradually deteriorate with long-term use. For this reason, in the present embodiment, detection of the toner density in each of the developing units 14Y, 14M, 14C, and 14K is performed at an appropriate timing, and when the toner density is lowered, each developing unit 14Y, New developer is supplied to 14M, 14C and 14K. Further, as a result of supplying the new developer as described above, surplus developer is discharged to the outside as a waste developer by using its own weight by using the waste pipe 84 or the like (trickle operation). By adopting such a so-called trickle system, each of the developing units 14Y, 14M, 14C, and 14K simultaneously performs the replenishment of the toner reduced by the development and the removal of the carrier deteriorated with the long-term use. Yes. For example, when the toner density increases due to excessive supply of a new developer, the toner density is adjusted by discharging the toner from the developing devices 14Y, 14M, 14C, and 14K.

In this way, the developer in each developing device 14Y, 14M, 14C, 14K is controlled to be discharged out of the device by trickle operation in order to maintain the developer in an appropriate range, and the amount of developer in the developing device is set appropriately. Maintained within range. However, for example, if a single-color development operation (for example, black-and-white printing in which printing is performed using only black component toner) is continued by printing a low image density document, the amount of developer in the developing device is reduced, and image defects or the like occur. There is a fear.
Therefore, in the present embodiment, as a control for preventing the occurrence of such image defects and the like, control is performed not to execute the trickle operation in the case of low image density printing, thereby reducing the developer in the developing device. This prevents the occurrence of image defects.
This will be specifically described below.

FIG. 7 is a block diagram illustrating the configuration of the control unit 60.
As shown in FIG. 7, the control unit 60 calculates a replenishment time measurement unit 91 that measures toner replenishment time, an image density calculation unit 92 that calculates image density in a print job, and calculates the number of prints in the print job. A print number calculation unit 93, a determination unit 94 that determines whether or not to perform a trickle operation, and a trickle operation execution unit 95 that outputs a trickle operation instruction according to the determination result of the determination unit 94 are provided. The determination unit 94 is an example of a control unit.
The functions of the replenishment time measurement unit 91, the image density calculation unit 92, the print number calculation unit 93, the determination unit 94, and the trickle operation execution unit 95 are read by the CPU 60a and read the program stored in the ROM 60b or the like. This is realized.

The supply time measuring unit 91 starts measuring the toner supply time when a print job is received. This toner replenishment time is used, for example, in terms of a toner replenishment amount. That is, the toner replenishment time and the toner replenishment amount have a correlation with each other, and the toner replenishment amount can be obtained by counting the toner replenishment time.
When a print job for K color printing is received, the image density calculation unit 92 starts calculating the image density of black toner in the print job. More specifically, the image density calculation unit 92 acquires (samples) pixel information when the laser exposure unit 13 irradiates the photosensitive drum 11 with laser light to create an electrostatic latent image. Since the density of the image is controlled by the number of irradiation pixels, the image density calculation unit 92 can count the number of pixels per unit area and acquire the image density as pixel information. The image density calculation unit 92 acquires such an image density and adds it to the print job.
When a print job for black and white printing is accepted, the print number calculation unit 93 starts calculating the number of prints in the print job (the number of prints after the job is started).
The replenishment time measured by the replenishment time measurement unit 91, the image density calculated by the image density calculation unit 92, and the number of prints calculated by the print number calculation unit 93 are examples of information relating to the supply amount, and 3 is an example of information on the amount of toner to be applied.

The determination unit 94 determines whether to perform the trickle operation based on one or a combination of the measurement result of the replenishment time measurement unit 91, the calculation result of the image density calculation unit 92, and the calculation result of the print number calculation unit 93. Determine whether.
When the trickle operation execution unit 95 receives an instruction from the determination unit 94 to perform the trickle operation, the trickle operation execution unit 95 executes the trickle operation.

FIG. 8 is a flowchart illustrating a processing procedure example of the control unit 60 according to the first embodiment.
The flowchart shown in FIG. 8 shows processing in a case where a print job as an example of the accepted print instruction is for performing K-color printing, for example. Further, the flowchart shown in FIG. 8 performs control (steps 101 to 104) for trickle operation during continuous printing and control (steps 105 to 107) for trickle operation at the end of printing. In other words, trickle discharge is forcibly performed by controlling the trickle operation during continuous printing. Further, by controlling the trickle operation at the end of printing, the trickle operation at the time of low area coverage printing is limited, and the developer discharge amount is suppressed.

When the control unit 60 receives a print job, the replenishment time measuring unit 91 starts measuring the toner replenishment time Dt (step 101). Then, the determination unit 94 determines whether the toner replenishment time Dt has reached a predetermined value, that is, the threshold value D1 based on the measurement result by the replenishment time measurement unit 91 (step 102). As the threshold value D1 here, for example, a value for 10 seconds may be adopted.
If the toner replenishment time has reached a predetermined value (Yes in step 102), that is, if the toner replenishment time Dt is greater than or equal to the threshold D1 (Dt ≧ D1), the determination unit 94 determines to perform a trickle operation. In response to the determination, the trickle operation execution unit 95 executes the trickle operation (step 103). Thereafter, the replenishment time measuring unit 91 performs a count reset (step 104). In this case, the trickle operation is to temporarily stop printing during continuous printing and execute the trickle operation.
If the toner replenishment time has not reached the predetermined value (No in step 102), that is, if the toner replenishment time Dt is less than the threshold value D1 (Dt <D1), the process proceeds to step 105. Therefore, the trickle operation is not executed unless the toner replenishment time reaches a predetermined value.

Next, the determination unit 94 determines whether or not printing has been completed (step 105). If printing has not ended (No in step 105), the process returns to step 101.
If printing has ended (Yes in step 105), the determination unit 94 determines whether the toner replenishment time Dt at the end of printing has reached a predetermined value, that is, the threshold value D2 (step 106). As the threshold value D2 here, for example, a value of 0.5 seconds may be adopted.

  When the toner replenishment time at the end of printing has reached a predetermined value (Yes in step 106), that is, when the toner replenishment time Dt is greater than or equal to the threshold D2 (Dt ≧ D2), the determination unit 94 performs a trickle operation. In response to the determination, the trickle operation executing unit 95 executes the trickle operation (step 107). Thereafter, the replenishment time measuring unit 91 resets the count (step 108). On the other hand, if the toner supply time at the end of printing has not reached the predetermined value (No in step 106), that is, if the toner supply time Dt is less than the threshold D2 (Dt <D2), the process proceeds to the end.

Here, various things can be considered as modifications of the example of the processing procedure according to the first embodiment. More specifically, when the trickle operation is performed in step 107, the stop time at the discharge position of the trickle operation is not made constant, but the stop time is adjusted according to whether or not a predetermined condition is satisfied. An example of control is conceivable.
More specifically, in step 106, the determination unit 94 determines whether or not the toner replenishment time Dt has reached a predetermined value, that is, the threshold value D2, and adjusts the stop time according to the conditions in the print job. To do. For example, the determination unit 94 determines a trickle operation condition in which the stop time is shorter as the toner supply time Dt measured during the print job is shorter, and the trickle operation execution unit 95 performs the trickle operation according to the trickle operation condition. Do.
As a modification applied to the second embodiment and the third embodiment described later, the determination unit 94 has a trickle in which the stop time is shorter as the image density Ic calculated during the print job is lower. Determine operating conditions.

FIG. 9 is a flowchart illustrating a processing procedure example of the control unit 60 according to the second embodiment. Note that the second embodiment has a processing procedure common to the first embodiment. That is, steps 202 to 204, 206, 207, 209, and 211 in FIG. 9 correspond to steps 101 to 105, 107, and 108 in FIG. Therefore, description of these common contents may be omitted.
When the control unit 60 accepts a print job, the image density calculation unit 92 starts calculating the image density Ic (step 201), and the replenishment time measuring unit 91 starts measuring the toner replenishment time Dt (step 202).
When determining unit 94 determines that toner replenishment time Dt is equal to or greater than threshold value D1 (Dt ≧ D1) (Yes in step 203), trickle operation executing unit 95 executes a trickle operation (step 204). The image density calculation unit 92 and the replenishment time measurement unit 91 perform count reset (steps 205 and 206).
After the end of printing (Yes in Step 207), the determination unit 94 determines whether or not the image density Ic has reached a predetermined value, that is, the threshold value I1 (Step 208). For example, a value of 3% may be adopted as the threshold value I1 here.

  When the image density has reached a predetermined value (Yes in Step 208), that is, when the image density Ic is equal to or greater than the threshold value I1 (Ic ≧ I1), the determination unit 94 determines to perform the trickle operation, In response to the determination, the operation execution unit 95 executes a trickle operation (step 209). Thereafter, the image density calculation unit 92 and the replenishment time measurement unit 91 perform count reset (steps 210 and 211). On the other hand, if the image density has not reached the predetermined value (No in step 208), that is, if the image density Ic is less than the threshold value I1 (Ic <I1), the process proceeds to the end without performing the trickle operation.

FIG. 10 is a flowchart illustrating an example of a processing procedure of the control unit 60 according to the third embodiment. The third embodiment has a processing procedure common to the first embodiment and the second embodiment. That is, steps 301, 302, 304 to 309, 311 to 313 in FIG. 10 correspond to steps 201 to 211 in FIG. Therefore, description of these common contents may be omitted.
When the control unit 60 accepts a print job, the image density calculation unit 92 starts calculating the image density Ic (step 301), and the replenishment time measurement unit 91 starts measuring the toner replenishment time Dt (step 302). The print number calculating section 93 starts calculating the print number Pc (step 303).

After the printing is completed (Yes in Step 308), the determination unit 94 determines whether or not the image density Ic has reached a predetermined value, that is, the threshold value I1 (Step 309). When the image density does not reach the predetermined value (No in step 309), that is, when the image density Ic is less than the threshold value I1 (Ic <I1), the determination unit 94 further uses the value of the number of printed sheets Pc to trickle. It is determined whether or not to perform an operation (step 310).
More specifically, the determination unit 94 controls the trickle operation according to the image density Ic and the number of printed sheets Pc. More specifically, when the number of printed sheets Pc is 5 or more (Pc ≧ 5), the determination unit 94 determines to perform a trickle operation (No in step 310). In addition, when the number of images is four or less (Pc <4), the determination unit 94 determines whether to perform the trickle operation using the image density Ic as well. That is, when the image density Ic is 3% or less and the number of printed sheets Pc is 4 or less (Ic ≦ 3%, Pc ≦ 4), it is determined not to perform the trickle operation (Yes in step 310). When the image density Ic is 6% or less and the number of printed sheets Pc is 2 or less (Ic ≦ 6%, Pc ≦ 2), it is determined not to perform the trickle operation (Yes in step 310). When the image density Ic is less than 9 and the number of printed sheets Pc is 1 or less (Ic <9%, Pc ≦ 1), it is determined not to perform the trickle operation (Yes in step 310).
After the image density calculation unit 92 and the replenishment time measurement unit 91 perform count reset (steps 312 and 313), the print number calculation unit 93 performs count reset (step 314).

DESCRIPTION OF SYMBOLS 11 ... Photosensitive drum, 12 ... Charging roll, 13 ... Laser exposure device, 14 ... Developing device, 14Y, 14M, 14C, 14K ... Developing device, 17a ... Rotating shaft, 17b ... Developing device drive motor, 17c ... Support, 60 ... Control unit 71 ... Developing housing 71a ... Partition wall 71b ... Loading port 71c ... Developer discharge port 81 ... Supply pipe 82 ... Supply auger 83 ... Communication path forming member 84 ... Disposal pipe 85 ... Shutter, 86 ... Shutter locking member, 87 ... Supply cylinder support member, 88 ... Developer supply cylinder, 91 ... Supply time measurement unit, 92 ... Image density calculation unit, 93 ... Print number calculation unit, 94 ... Determination unit

Claims (6)

A support member supported so as to be capable of rotational movement with respect to the apparatus main body;
Driving means for rotating the support member with respect to the apparatus main body and stopping the support member at a predetermined position with respect to an image carrier that forms an electrostatic latent image;
A developer replenishing portion attached to the support member for receiving replenishment of a two-component developer comprising toner and carrier; and a developer discharging portion for discharging the developer to the outside; A plurality of developers for developing the electrostatic latent image of the image carrier with the toner when stopped at a position facing the image carrier;
Acquisition means for acquiring information for specifying an image density of the print instruction and information for specifying the number of prints of the print instruction, as information relating to the replenishment amount by the developer supply unit accompanying the print instruction;
Based on the information acquired by the acquisition unit, after the execution of the print instruction, when the image density of the print instruction is equal to or higher than a predetermined first image density, the developer discharge unit When the image density of the print instruction is less than the first image density and the number of printed sheets of the print instruction is equal to or greater than a predetermined first print number, the developer is discharged. The image density of the print instruction is lower than the first image density and higher than a predetermined second image density lower than the first image density, and the print instruction Control means for controlling to discharge the developer when the number of printed sheets is less than the first printed number and larger than a predetermined second printed number that is smaller than the first printed number When,
The including the developing device. 2. The information acquisition apparatus according to claim 1, wherein the acquisition unit further acquires, after the execution of the print instruction, information specifying a toner replenishment time as information relating to a supply amount by the developer supply unit accompanying the print instruction. Development device.   The control unit acquires information specifying a toner replenishment time during execution of the print instruction, and uses the information to suppress discharge of the developer by the developer discharge unit after execution of the print instruction is completed. The developing device according to claim 2. An image carrier for forming an electrostatic latent image;
Developing means for developing the electrostatic latent image formed by the image carrier into a toner image;
Transfer means for transferring a toner image by the developing means onto a recording material;
Fixing means for fixing the toner image transferred onto the recording material to the recording material;
Including
The developing means includes
A support member supported so as to be capable of rotational movement with respect to the apparatus main body;
Driving means for rotating the support member with respect to the apparatus main body and stopping the support member at a predetermined position with respect to an image carrier that forms an electrostatic latent image;
A developer replenishing portion attached to the support member for receiving replenishment of a two-component developer comprising toner and carrier; and a developer discharging portion for discharging the developer to the outside; A plurality of developers for developing the electrostatic latent image of the image carrier with the toner when stopped at a position facing the image carrier;
Acquisition means for acquiring information specifying the image density of the print instruction and information specifying the number of prints of the print instruction as information on the amount of toner consumed by execution of the print instruction ;
Based on the information acquired by the acquisition unit, after the execution of the print instruction, when the image density of the print instruction is equal to or higher than a predetermined first image density, the developer discharge unit When the image density of the print instruction is less than the first image density and the number of printed sheets of the print instruction is equal to or greater than a predetermined first print number, the developer is discharged. The image density of the print instruction is lower than the first image density and higher than a predetermined second image density lower than the first image density, and the print instruction Control means for controlling to discharge the developer when the number of printed sheets is less than the first printed number and larger than a predetermined second printed number that is smaller than the first printed number When,
The including image forming apparatus. 5. The image according to claim 4 , wherein the acquisition unit further acquires, as information relating to the amount of toner consumed by execution of the print instruction, information specifying a toner replenishment time by execution of the print instruction. Forming equipment. The control unit acquires information specifying a toner replenishment time during execution of the print instruction, and uses the information to suppress discharge of the developer by the developer discharge unit after execution of the print instruction is completed. The image forming apparatus according to claim 5 .

Images