JP2012063553A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus that can refresh and recycle toner at the same time.SOLUTION: A second toner hopper 13 consumes toner and executes toner refreshing by supplying recycled toner only when the character print density to form an image on one sheet of paper is more than a first character print density; and, when the character print density to form an image on one sheet of paper is a second character print density, which is less than the first character print density, so controlling an exposure device 24 and a development device 10 so as to cause a latent image to be formed even in an area where image formation is possible and to perform image development so that the total area comprising the square measure of a sheet image-formed area on a photosensitive drum 1 for image formation matching the sheet of paper and the square measure of the area where image formation is possible outside the sheet image-formed area on the photosensitive drum 1 is kept at a prescribed character print density all the time.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter, etc., and a multifunction machine having two or more functions, and more particularly, a latent image formed on an image carrier is composed of toner and carrier. The present invention relates to a technology related to toner recycling and toner refresh in an image forming apparatus which is reversely developed using a two-component developer to form a toner image.

  In an electrophotographic image forming apparatus, a toner hopper and a developing device for supplying new toner are used to form an electrostatic latent image formed on a photoreceptor. In order to reduce the image forming speed and improve the quality of an image to be formed, a developing device including a plurality of developing rollers whose rotational directions are different from those of a photoconductor is used. A developing device having a pair of developing rollers having different rotation directions will be described with reference to FIG. The detailed configuration of the developing device 10 ′ shown in FIG. 7 is the same as that disclosed in, for example, FIGS. 1 and 2 of Japanese Patent Laid-Open No. 2000-231263.

  As shown in FIG. 7, the developing device 10 ′ is provided with two developing rollers 3 and 4 so as to face and be close to the photoconductive drum 1. The developer 11 accommodated in the developing container 10A of the developing device 10 ′ is developed on the lower side in the drawing rotated counterclockwise in the opposite direction to the photosensitive drum 1 by the auger screws 7 and 8 and the impeller 6. It is carried to the lower part of the roller 4 and adheres to the surface of the sleeve 41 by the attractive force of the fixed magnet 42 that constitutes the lower developing roller 4. The attached developer moves along the rotation direction of the sleeve 41 of the lower developing roller 4, and the developer adhering amount contributing to the development is regulated by the developer regulating member 2, and at the same time the upper developing in the figure. The developer is distributed to the roller 3 and the lower developing roller 4 and conveyed to the developing area.

  The developer conveyed to the upper developing roller 3 adheres to the surface of the sleeve 31 by the attractive force of the fixed magnet 32 constituting the upper developing roller 3. The attached developer moves along the rotation direction of the sleeve 31 of the upper developing roller 3 that rotates in the clockwise direction in the same direction as the photosensitive drum 1 and performs reverse development. By 40, it is returned again to the developing container 10A. Further, the developer 11 leaked by the developer regulating member 2 is caused by the magnetic attraction force of the fixed magnet 42 that constitutes the lower developing roller 4 that rotates counterclockwise in the opposite direction to the photosensitive drum 1. It adheres to the lower developing roller 4 and moves along the rotational direction of the sleeve 41 of the lower developing roller 4 to perform the same direction development. Further, after the development is completed, the developer 11 is returned to the developing container 10A again.

  In such a developing device, since the rotation direction of the upper developing sleeve 31 is opposite to the rotation direction of the photosensitive drum 1 at the development position, reverse development with high development capability is performed. On the other hand, since the rotation direction of the lower developing sleeve 41 is the forward direction with respect to the rotation direction of the photosensitive drum 1 at the developing position, the lower developing sleeve 41 causes the background stain to be fogged. The same direction development is performed to remove and improve the image quality.

In the electrophotographic system, there is a charging device for charging to a desired surface potential, the photosensitive member as an image carrier is charged, a potential latent image is created with a light source such as laser light or LED, and the potential latent image is developed. It is visualized by a machine (developing device) and transferred to a sheet-like recording medium such as paper or an OHP film sheet. Toner remaining without being transferred is collected by a cleaner as a toner collecting device that also serves as a cleaning device, that is, toner collected by a brush or blade is collected in a waste toner box.
In FIG. 7, reference numeral 49 denotes a toner hopper for storing the toner T in the developing container 10 </ b> A, and 45 is formed on the upper lid of the toner hopper 49 for supplying new toner T to the toner hopper 49. A toner bottle (toner container) attaching / detaching portion is shown.

  Patent Documents 1 to 4 are known as techniques related to toner recycling. In the technique described in Patent Document 1, a route for sending toner collected by a cleaner (cleaning device) to a waste toner box (a waste container) according to a print density (image area ratio) and a route for returning to a toner hopper (toner recycling route) It is to be divided and selectable.

  In the technique disclosed in Patent Document 2, regarding toner refresh, in low density printing, the toner in the developing unit is not replaced, and the external additive of the toner is buried, or the ratio of the small particle size toner due to selective development Focusing on the problem that filming is likely to occur due to low printing density and poor cleaning, and mentions the necessity of a toner refresh function that replaces the toner in the developing device with new toner to solve this problem .

  The techniques described in Patent Documents 3 and 4 classify waste toner from a cleaner, or classify toner from a cleaner using a difference in sedimentation speed.

However, the technique described in Patent Document 2 requires a part called a polishing roller that removes filming for toner refreshing, which increases the cost.
Patent Documents 1 to 4 generally do not make a full-scale proposal from the viewpoint of simultaneously performing toner refresh and toner recycle.

  Accordingly, the present invention has been made in view of the above-described problems and circumstances, and a main object thereof is to realize and provide an image forming apparatus capable of simultaneously performing toner refresh and toner recycle.

In order to solve the above-described problems and achieve the above-mentioned object, the invention according to each claim employs the following characteristic means / invention-specific matters (hereinafter referred to as “configuration”).
According to the first aspect of the present invention, there is provided an image carrier, a charging device for uniformly charging the image carrier, and a latent image for forming a latent image for reversal development on the image carrier charged by the charging device. A developer carrying body that rotates in a state of being close to the image carrying body and carries a two-component developer, and reverse-develops the latent image by the two-component developer supplied by the developer carrying body A developing device for forming a toner image, a transfer device for transferring the toner image on the image carrier to a sheet, and a toner collecting device for collecting residual toner remaining on the image carrier. In an image forming apparatus configured to be able to recycle toner collected by a collecting device and returning the toner to the developing device, a first toner containing unit for containing new toner and recycle toner from the toner collecting device are contained. Second to do The first and second toner storage units each include a replenishing unit capable of replenishing the developing device, and the second toner storage unit has a print density for forming an image on the sheet. The recycle toner is replenished only when the print density is higher than the first print density, and the print density to be imaged on the sheet is the second print density lower than the first print density, The total area obtained by adding the area of the sheet image formation area formed on the image carrier to form an image and the area of the image formation area outside the sheet image formation area on the image carrier is always a predetermined print. The latent image forming device and the developing device are controlled so that a latent image is formed even in the image-formable region so as to have a density and development is performed, so that the toner is consumed and the toner is refreshed. Characterized in that it.
According to the first aspect of the present invention, the toner consumption can be reduced by performing the toner recycling and the toner refresh at the same time with the above-described configuration.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the first print density is 16 to 30%. In the present invention, when the print density is high, the recycled toner can be positively used.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the second print density is 3 to 6%. In the present invention, when the print density is low, the toner in the second toner storage unit is not replaced, and in order to prevent the toner from deteriorating, an image formable region (between the sheets in the image carrier or the sheet end portion is removed. It is possible to promote the consumption of the toner in the developing device by exposing and developing the (contained region).

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the second toner storage portion constitutes a unit that can be attached to and detached from the developing device. A full detection unit that detects a full state of the recycled toner in the second toner storage unit, and a waste toner storage unit that stores the recycled toner sent from the second toner storage unit. And a feeding means for feeding a part of the recycled toner in the second toner container to the waste toner container when a full state of the recycled toner in the second toner container is detected. To do.
In the present invention, the amount of recycled toner that has entered the second toner storage unit does not increase, and when the toner becomes full, a part of the recycled toner is sent to the waste toner storage unit. The toner amount can be adjusted.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the developing device includes two conveyance agitating members, and the second toner containing portion is the developer. Recycled toner is replenished onto the conveying stirring member on the side close to the carrier.
In the present invention, since the recycled toner is likely to be a highly charged toner that is difficult to transfer from the beginning, it is preferable to replenish the toner on the conveyance stirring member on the side close to the developer carrier of the developing device.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the replenishment amount of the recycled toner in the second toner storage portion is changed depending on the print density at which an image is to be formed on the sheet. It is characterized by that.
In the present invention, it is possible to efficiently consume the toner when the replenishment amount of the recycled toner is made variable according to the print density.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, a maintenance mode for performing image formation for confirming print quality can be executed, and execution of the maintenance mode is performed. In this case, the recycle toner is preferentially supplied from the second toner storage unit.
In the present invention, it is possible to minimize the use of customer toner from the viewpoint of service.

According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the developing device includes a plurality of the developer carriers, and among the plurality of developer carriers. At least one rotates in the same direction as the rotation direction of the image carrier, and the rest of the plurality of developer carriers rotate in the direction opposite to the rotation direction of the image carrier, The developer carrier that rotates in the same direction as the rotation direction of the image carrier is arranged upstream of the rotation direction of the image carrier.
According to the present invention, in a developing device having a developer carrying member (for example, a developing roller) that rotates in opposite directions, it is advantageous in reducing development problems in which the rear end portion of a solid image lacks the teeth of a comb.

  According to the present invention, a novel image forming apparatus can be realized and provided by solving the above-described problems. That is, according to the present invention, toner refresh can be performed simultaneously with toner recycling while reducing the toner consumption of the developer.

1 is a simplified front view illustrating a configuration of an entire image forming apparatus to which the present invention is applied. FIG. 3 is a front sectional view of an essential part of an enlarged development process portion of the image forming apparatus showing the first embodiment of the present invention. FIG. 3 is a rear view of FIG. 2. (A), (b) is a figure explaining the relationship between a photoconductive drum, the image formation area in which an image is formed on one sheet, and the image formable area other than the image formation area on one sheet. is there. FIG. 3 is a block diagram illustrating a control configuration of a main part in the image forming apparatus according to the first embodiment. 3 is a flowchart illustrating an operation sequence of the image forming apparatus according to the first embodiment. FIG. 10 is a front sectional view of an essential part in which a development process portion of a conventional image forming apparatus is enlarged.

  Hereinafter, embodiments of the present invention including examples will be described in detail with reference to the drawings. In each embodiment and each modification, etc., components (members, components, etc.) having the same function, shape, etc. will be described by giving the same reference numerals after having been described once unless there is a possibility of confusion. Is omitted. In order to simplify the drawings and the description, even if the components are to be represented in the drawings, the components that do not need to be specifically described in the drawings may be omitted as appropriate. When quoting and explaining constituent elements such as published patent gazettes, the reference numerals are shown in parentheses to distinguish them from those of the embodiments.

  FIG. 1 is a simplified front view illustrating the overall configuration of an image forming apparatus to which the present invention is applied. In FIG. 1, reference numeral 10 with parentheses indicates a developing device used in the first embodiment of the present invention shown in FIGS. 2 and 3 described later.

  First, the overall configuration and operation of a laser printer as an image forming apparatus to which the present invention is applied will be described with reference to FIG. In the figure, reference numerals 26a, 26b, and 26c denote sheet feeding units, which store sheets as sheet-like recording media in a sheet feeding cassette. Reference numeral 1 denotes a photosensitive drum as an image carrier, which starts rotating based on a signal from a controller (not shown). When the photosensitive drum 1 starts rotating, the surface of the photosensitive drum 1 is uniformly charged by the corona charger 23 which is a charging device. An electrostatic latent image is formed on the surface of the charged photosensitive drum 1 by a scanning beam from the exposure device 24. When the electrostatic latent image reaches the developing position of the pair of upper and lower developing rollers 3 and 4 in the developing device 10 ′, the electrostatic latent image is developed with toner and visualized on the photosensitive drum 1 as a toner image.

  On the other hand, from the paper feeding units 26a, 26b, and 26c, at the timing when the toner image formed on the photosensitive drum 1 and the paper face each other at the position of the transfer unit 25 that is a transfer device, The paper P selected from 26b or 26c is sent out, and the toner image is transferred to the paper P. A fixing device 27 fixes the toner image transferred onto the paper P. The toner remaining on the surface of the photosensitive drum 1 after the toner image is transferred to the paper P is removed from the surface of the photosensitive drum 1 by a cleaner 15 as a cleaning device.

  In FIG. 1, reference numeral 33 denotes a flap which controls the direction of the conveyed paper. Reference numeral 28 denotes a paper discharge tray serving as a paper discharge unit, which stacks and stores sheets on which image formation has been completed. Reference numeral 34 denotes a paper feed path that communicates between the paper feed units 26a, 26b, and 26c, image forming means (the photosensitive drum 1, the corona charger 23, the developing rollers 3 and 4, the transfer unit 25), and the paper discharge tray 28. Reference numeral 35 denotes a drawing path, which is provided to be branched from the sheet feeding path 34 on the downstream side in the sheet conveying direction with respect to the image forming unit. The sheet fed from the fixing device 27 by the switching control of the flap 33 is selectively selected. Pull in. Reference numeral 36 denotes a return path, which branches from the middle of the drawing path 35, and has its end joined to the sheet feeding path 34 on the upstream side in the sheet conveying direction with respect to the image forming means.

  Therefore, when printing on both sides of the paper, the paper sent out from the fixing device 27 is drawn into the drawing path 35, and the drawn paper is sent out to the return path 36, whereby the single-side printed paper is again printed on the image. This is sent to the forming means, whereby double-sided printing is executed. In FIG. 1, 37a and 37b are a pair of conveying rollers provided before and after the flap 33, 51 and 52 are a pair of conveying rollers provided on the drawing path 35 and capable of switching between normal / reverse rotation, and 53 is a drawing path 35. Flap 29 for switching whether the paper drawn into the return path 36 is sent out or returned to the paper feed path 34 side and discharged to the paper discharge tray 28, and the paper 29 that passes through the transfer unit 25 is exposed to light. A peeling device 30 for peeling the body drum 1 from the body drum 1 is a transport belt device that transports the sheet toward the fixing device 27.

  As shown in FIGS. 1 and 7, a toner hopper 49 containing a new toner T is provided at the upper part of the developing device 10 ′ in order to replenish the toner according to the consumption of the toner in the developing container 10 </ b> A. Yes. In FIG. 1, a cleaner 15 as a cleaning device and a toner hopper 49 are connected by a toner recycle path (route) (not shown), and toner collected by the cleaner 15 passes through the toner recycle path (not shown). (See FIG. 3 of Japanese Patent Laid-Open No. 2001-109335). The toner conveyance path (not shown) includes a hollow member (not shown) such as a cylindrical tube and an auger screw (not shown) passed through the hollow member, and rotates the auger screw. Thus, toner conveyance is performed.

In addition, as shown in FIG. 3 of Japanese Patent Laid-Open No. 2000-109335, toner returned from the cleaner 15 is placed outside the toner conveyance path (not shown) in a part of the toner conveyance path (not shown). A toner discharge portion (not shown) for discharging the toner is provided. A toner collection bottle (not shown) is disposed below the toner discharge portion (not shown). The toner discharge portion (not shown) is provided with a toner discharge port (not shown). When the toner discharge port is closed by an opening / closing member (not shown), the toner conveyed in the toner conveyance path (not shown) When the toner is returned to the toner hopper 49 and the toner discharge port (not shown) is opened, the toner conveyed in the toner conveyance path (not shown) is discarded into the toner collection bottle (not shown).
In the toner hopper 49, a toner agitator (not shown) for agitating the toner T is rotatably provided. A tooth wheel 12 is also called a feed roller for supplying the toner T to the developing container 10A.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. The image forming apparatus according to the first embodiment uses a developing device 10 as shown in FIGS. 2 and 3 instead of the developing device 10 ′, as compared with the image forming apparatus shown in FIGS. The point is that the first toner hopper 9 is used instead of the toner hopper 49, the second toner hopper 13 is newly provided, and the second toner hopper 13 and the cleaner 15 are communicated and connected through a toner recycling path. The second toner hopper 13 and a waste toner box 20 as a waste toner container are communicated and connected by a waste toner path, and the image forming means (developing device 10, corona charger as a charging device) shown in FIG. 23, the exposure device 24, and a transfer device 25 as a transfer device) are mainly different in that a control unit 55 (see FIG. 5) is used as a control means for controlling the transfer device 25) with a specific control function as described later. .
The first embodiment is the same as the image forming apparatus shown in FIGS. 1 and 7 except for the above differences. Hereinafter, the configuration and operation of the difference will be mainly described, but the basic configuration of the developing device 10 will be described in detail again.

  There are two toner hoppers, and the first toner hopper 9 functions as a first toner storage unit for storing a normal new toner T-. The second toner hopper 13 functions as a second toner storage unit that stores the recycled toner from the cleaner 15 as a toner recovery device that also serves as a cleaning device.

  In the first toner hopper 9, a rotatable toner agitator (not shown) for agitating the new toner T, and a replenishing means for supplying the new toner T to the developing container 10A of the developing device 10 are provided. As shown in FIG. An upper lid of the first toner hopper 9 for supplying new toner T to the first toner hopper 9 is formed on the upper portion of the first toner hopper 9 in the same manner as the toner hopper 49 shown in FIG. Although the toner bottle (toner container) attaching / detaching portion is provided, the illustration thereof is omitted in FIGS. 2 and 3 for the sake of simplicity.

Similarly, in the second toner hopper 13, a rotatable recycled toner agitator (not shown) for agitating the recycled toner, and a feed roller as a replenishing means for supplying the recycled toner to the developing container 10A are provided. A pawl wheel 14, also referred to as a so-called “pawl wheel” 14 is provided. The handwheels 12 and 14 have a large number of grooves carved along the generatrix on the outer circumference of the roller, and the toner enters the grooves and rotates to perform a replenishment action.
The second toner hopper 13 has a full sensor 58 (only shown in FIGS. 2 and 5 and omitted in FIG. 3) as a full detection means for detecting the full state of the recycled toner in the second toner hopper 13. Is arranged.

  The second toner hopper 13 constitutes a hopper unit 22 that can be attached to and detached from the developing container 10 </ b> A of the developing device 10. Examples of the attaching / detaching means at this time include a clamp structure for connecting and connecting the developing container 10A and the hopper unit 22 detachably, and a plug-in type using a slide rail. In the present embodiment, since the hopper unit 22 is configured, there is an advantage that only the hopper unit 22 needs to be replaced when a failure occurs.

  Two developing rollers 3 and 4 are provided as developer carrying members for carrying the developer so as to face and be close to the photoconductive drum 1 having photoconductivity. The developer 11 in the developing container 10 </ b> A is supplied from an upper developing roller 3 that rotates clockwise in the same direction as the photosensitive drum 1 by auger screws 7 and 8 and an impeller 6 as stirring members for stirring the developer. It is carried to the lower part and adheres to the surface of the sleeve 31 by the attractive force of the fixed magnet 32 constituting the upper developing roller 3. The adhering developer moves along the rotation direction of the sleeve 31 of the upper developing roller 3, the developer adhering amount contributing to the development is regulated by the developer regulating member 2, transported to the developing area, and in the reverse direction After the development, the developer 11 is returned again to the developing container 10A by the guide plate 40.

  Further, the developer 11 leaked by the developer regulating member 2 is lowered by the magnetic attraction force of the fixed magnet 41 constituting the lower developing roller 4 that rotates counterclockwise in the opposite direction to the photosensitive drum 1. The developer roller 4 moves along the rotational direction of the sleeve 41 of the lower developing roller 4, and the developer regulating member 2 regulates the amount of the developer 11 that contributes to the development in the same direction, Develop in the same direction. Further, after the development is completed, the developer 11 is returned to the developing container 10A again. Reference numeral 5 shown in FIGS. 2 and 7 is a catch-up roller for returning the scattered carrier onto the developing roller again.

The photosensitive drum 1 is supported by the image forming apparatus main body so as to be rotatable in the clockwise direction.
The cleaner 15 includes a brush roller 16 and a blade 17 that remove and collect remaining toner on the surface of the photosensitive drum 1, and a recycle screw 18 as a conveying member that conveys the removed remaining toner and the like. .

  Hereinafter, an image forming operation will be supplementarily described with reference to the overall view of the image forming apparatus shown in FIG. As the photosensitive drum 1 rotates, the photosensitive drum 1 is uniformly charged to a desired surface potential by a corona charger 15 as a charging device shown in FIG. An electrostatic latent image is formed on the surface of the drum 1. The electrostatic latent image on the surface of the photosensitive drum 1 is visualized as a toner image by attaching toner in the developing areas of the developing rollers 3 and 4. This toner image is carried to the transfer position as the photosensitive drum 1 rotates, and is fed from one selected paper feed unit of the paper feed units 26a to 26c by the action of the transfer unit 25 as a transfer device. It is transferred onto a sheet P as a sheet-like recording medium.

  The paper P holding the toner image is conveyed to a fixing device 27 including, for example, a heating roller 27 a and a pressure roller 27 b, and the toner image is fixed on the paper P by the heating and pressing action of the identification fixing device 27. On the other hand, residual toner that remains on the photosensitive drum 1 without being transferred to the paper P at the transfer position is removed and collected from the photosensitive drum 1 by the cleaner 15.

FIG. 3 is a rear view of FIG. As shown in FIG. 3, the recycled toner collected from the cleaner 15 is returned from the recycling screw 18 of the cleaner 15 to the second toner hopper 13 through a toner recycling path 19 indicated by a broken line. Further, a waste toner path (route) 21 as a feeding means indicated by a broken line for sending a part of the recycled toner contained in the second toner hopper 13 directly to the waste toner box 20 from the second toner hopper 13. Also have. The feeding means for sending a part of the recycled toner in the second toner hopper 13 to the waste toner box 20 includes a waste toner path 21, a full sensor 58, and a screw (not shown).
The second toner hopper 13 replenishes toner on the auger screw 7 of the developing device 10. Recycled toner is a toner that is highly charged and difficult to transfer, so if it is replenished on the auger screw 7 near the developing rollers 3 and 4, it can come out on the developing rollers 3 and 4 without increasing the charge amount. High nature.

Next, referring to FIG. 4, the relationship between the photosensitive drum 1, an image forming area where an image is formed on one sheet of paper P, and an image formable area other than the image forming area of one sheet of paper P is described. This will be explained (claim 1).
4 (a) and 4 (b) show a region where the toner image is developed and transferred onto one sheet P corresponding to the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 1, and the sheet. The outside exposure / latent image and the developable area are represented by the difference in size and vertical / horizontal placement of the paper P. When the photosensitive drum 1 and the paper P shown in FIG. 4A have a size corresponding to, for example, A4 vertical placement and paper passing, the photosensitive drum 1 and the paper P shown in FIG. This shows the case of the size corresponding to the horizontal placement and paper passing.

  The outer peripheral surface of the photosensitive drum 1 can be exposed along the main scanning direction (also the axial direction of the photosensitive drum 1) Y and the sub-scanning direction (also the rotational direction of the photosensitive drum 1) X orthogonal thereto. Thus, it has an image-formable region 1A shown by hatching in the figure, where an electrostatic latent image and a toner image can be formed and developed. The image formable area 1A is an area other than the sheet image formation area formed on the photosensitive drum 1 so as to form an image corresponding to one sheet of paper P. The image formable area 1A can be exposed to form an electrostatic latent image and It means an area where a toner image can be formed and developed. 4A and 4B, Px is the distance between the front and rear sheets in the image formable area 1A of the photosensitive drum 1, and Py is the outside of the sheet in the main scanning direction Y of the photosensitive drum 1. Each end is shown.

With reference to FIG. 5, the control configuration of the present embodiment will be described. In the figure, a control unit 55 includes a CPU, a ROM, a RAM, a timer, and the like (not shown), and functions as a control means including a microcomputer having a configuration in which they are connected by a signal bus (not shown).
The CPU is based on various signals from an operation unit (not shown) for operating the image forming apparatus, detection signals from various sensors including a full sensor 58 provided in the image forming apparatus, and an operation program called from the ROM. Controls the operation of each driving unit, particularly the image forming means (exposure device 24, developing device 10), the second toner hopper tooth wheel 14 and the like, and transmits / receives to / from the print density measuring unit 56 and the comparison unit 57. The operation of the entire image forming apparatus is controlled. The ROM stores an operation program for the entire image forming apparatus (including the flowchart of FIG. 6 and the like), and this operation program is appropriately called by the CPU. The RAM has a function of temporarily storing calculation results of the CPU, a function of storing data signals and ON / OFF signals set and input from various sensors as needed.

  The CPU of the control unit 55 operates the pawl wheel 14 of the second toner hopper 13 so that the recycle toner is replenished only when the print density to be imaged on one sheet is higher than the first print density. And the photosensitive drum 1 to form an image corresponding to one sheet when the print density to form an image on one sheet is a second print density lower than the first print density. Image formation so that the total area of the sheet image forming area formed on the image forming area and the area of the image forming area 1A outside the sheet image forming area on the photosensitive drum 1 always has a predetermined print density. It has a function of controlling the exposure device 24 and the developing device 10 so as to form a latent image in the possible region and perform development.

With reference to the flowchart of FIG. 6, an implementation method of this embodiment that is controlled and executed under the control of a CPU (not shown) of the control unit 55 will be described.
First, when printing is started, the print density measuring unit 56 measures the print density at which an image is formed on one sheet of paper P (step S1). If the second print density (image area ratio) formed on one sheet of paper P is 3%, an image corresponding to a print density of 1% is obtained other than the single sheet P in FIG. Image forming area 1A (sheet interval Px and sheet outer edge Py in the main scanning direction Y) of the electrostatic latent image formed so that the exposure device 24 is exposed and the developing device 10 is formed at the exposure portion. The toner is consumed by controlling the toner to adhere to the image and developing (step S2).

In step S1, when the print density is 16 to 30%, the process proceeds to step S5, and the second toner hopper 13 supplies about 10% of the total number of times of supply. The toner collected by the cleaner 15 is returned to the second toner hopper 13 by the auger screws 7 and 8. When returning the toner to the second toner hopper 13, it is possible to further classify the toner into a coarse toner and a smaller toner by using a known toner classification method, and to discard only the coarse toner into the waste toner box 20. Will improve.
In step S5, when the second toner hopper 13 is full due to the full detection signal from the full sensor 58, the recycle toner of about half (50%) to about 1/3 of the capacity of the toner hopper 13 is obtained. The toner is sent to the waste toner box 20 (step S7).

  In the maintenance mode, it is possible to select such that the toner can be preferentially supplied only from the second toner hopper 13. The maintenance mode means that when a maintenance person (service person in charge) performs printing at a customer, image formation of a dedicated pattern is performed in order to confirm the print quality. The maintenance mode is set by, for example, a maintenance staff (service staff) performing a special key operation on an operation unit (not shown) of the image forming apparatus.

  To refresh and recycle toner at the same time, by constantly refreshing toner, apparent transfer efficiency can be improved and the addition of waste toner (recycled toner) paths can be reduced. Since the waste toner is reduced, there is an advantage that the page cost is lowered, the number of times the waste toner is discarded is reduced, and the management cost of the customer's device is reduced.

  As described above, the present invention has been described with respect to specific embodiments and modifications. However, the technology disclosed by the present invention is limited to those exemplified in the embodiments and modifications including the above-described embodiments. However, those skilled in the art can configure various embodiments, modifications, and examples in accordance with the necessity and application within the scope of the present invention. If so, it is clear.

In the above embodiment, the developing rollers 3 and 4 of the developing device 10 are two rotating in the opposite directions. However, the present invention is not limited to this, and the entire number of developing rollers (mag rollers) may be changed. Needless to say, the present invention is also applicable to forward rotation development in which the developing roller rotates in the same direction.
The image forming apparatus to which the present invention can be applied is not limited to the one shown in FIG. 1, but can be applied to, for example, an intermediate transfer type or a direct transfer type tandem type color image forming apparatus.
Further, the developing device to be used is not limited to the one provided with a plurality of developing rollers or developing rolls disclosed in FIGS. 2 and 3 and FIGS. 1 and 2 of JP-A-2000-231263, Needless to say, the present invention can also be applied to one having a single developing roller.

1 Photosensitive drum (image carrier)
2 Developer regulating member 3 Developer roller (developer carrier)
4 Development roller (developer carrier)
5 Catch-up roller 6 Impeller 7 Auger screw (developer conveyance stirring member)
8 Auger screw (developer conveying and stirring member)
9 First toner hopper (first toner container)
DESCRIPTION OF SYMBOLS 10 Developing apparatus 11 Developer 12 Claw wheel 13 2nd toner hopper (2nd toner accommodating part)
14 Claw wheel 15 Cleaner (toner recovery device)
16 Brush 17 Blade 18 Recycling screw 19 Toner recycling pass 20 Waste toner box (waste toner container)
21 Pass to waste toner box 23 Corona charger (transfer device)
24 Exposure device (latent image forming device)
27 Fixing Device 55 Control Unit (Control Unit)

JP 2007-41047 A Japanese Patent Laid-Open No. 2005-134776 JP 2003-345205 A JP-A-10-232542

Claims (8)

An image carrier, a charging device that uniformly charges the image carrier, a latent image forming device that forms a latent image for reversal development on the image carrier charged by the charging device, and the image carrier A developing device comprising a developer carrying member that rotates in the vicinity of the developer carrying the two-component developer and reversely develops the latent image with the two-component developer supplied by the developer carrying member to form a toner image. And a transfer device that transfers the toner image on the image carrier to a sheet, and a toner collection device that collects residual toner remaining on the image carrier, and the toner collected by the toner collection device In the image forming apparatus configured to allow toner recycling to be returned to the developing device,
A first toner storage unit for storing new toner; and a second toner storage unit for storing recycled toner from the toner recovery device. The first and second toner storage units are provided in the developing device. Each has replenishment means that can be replenished,
The second toner storage unit replenishes the recycle toner only when the printing density to be imaged on the sheet is higher than the first printing density, and the printing density to be imaged on the sheet is the first printing density. When the second print density is smaller, the area of the sheet image forming area formed on the image carrier to form an image corresponding to the sheet, and the image formation outside the sheet image forming area on the image carrier. The latent image forming device and the developing device are controlled so that a latent image is formed in the image formable region and developed so that the total area including the area of the possible region always has a predetermined print density. An image forming apparatus that consumes toner and refreshes the toner.   The image forming apparatus according to claim 1, wherein the first printing density is 16 to 30%.   The image forming apparatus according to claim 1, wherein the second print density is 3 to 6%. The second toner container constitutes a unit that can be attached to and detached from the developing device,
A full detection unit for detecting a full state of the recycled toner in the second toner storage unit, and a waste toner storage unit for storing the recycled toner sent from the second toner storage unit,
A feeding means for sending a part of the recycled toner in the second toner accommodating portion to the waste toner accommodating portion when the full toner detecting portion detects a full state of the recycled toner in the second toner accommodating portion; The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   2. The developing device according to claim 1, wherein the developing device includes two conveying agitating members, and the second toner storage unit replenishes recycled toner onto the conveying agitating member on the side close to the developer carrying member. The image forming apparatus according to any one of 4.   6. The image forming apparatus according to claim 1, wherein a replenishment amount of the recycled toner in the second toner storage unit is changed according to a print density on which an image is to be formed on the sheet. A maintenance mode for image formation to check print quality is possible,
7. The image forming apparatus according to claim 1, wherein when the maintenance mode is executed, replenishment of recycled toner from the second toner storage unit is performed preferentially.   The developing device includes a plurality of the developer carriers, and at least one of the plurality of developer carriers rotates in the same direction as the rotation direction of the image carrier, and the plurality of developers The rest of the carrier is one that rotates in the opposite direction to the rotation direction of the image carrier, and the developer carrier that rotates in the same direction as the rotation direction of the image carrier is the rotation direction of the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed upstream of the image forming apparatus.

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