JP7501004B2 - Image forming apparatus and control method - Google Patents

Description

This disclosure relates to an image forming apparatus and a method for controlling the image forming apparatus.

Conventionally, as shown in Patent Documents 1 and 2, electrophotographic image forming devices are known that form images on an image carrier using a developer (two-component developer) that contains toner and carrier.

The developer is contained in a developing tank of the developing device. The developer is stirred and transported (circulated) in the developing tank. A sensor in the developing tank measures the toner concentration in the developer (hereinafter also referred to as "toner concentration"). Toner is replenished from a toner hopper into the developing tank so that the toner concentration is at an appropriate value. A magnetic permeability sensor is typically used as the sensor.

JP 2006-154001 A Japanese Patent Application Laid-Open No. 09-305015

In recent years, image forming devices have become more space-saving and less expensive. This has led to demand for smaller, less expensive components that make up the developing units in image forming devices.

As the components of the developer are made smaller, it becomes necessary to agitate and circulate a small amount of developer in a short section (circulation path) inside the developer tank of the developer. Furthermore, the electrostatic attraction between the carrier and toner increases due to a low print rate, a low humidity operating environment, or an increase in the amount of charge caused by an increase in the number of consecutive printed pages. As a result, it becomes difficult for the toner newly replenished to the developer tank (hereinafter also referred to as "new toner") to be incorporated into the developer that was in the developer tank before the replenishment.

The toner concentration in the developer tank is typically measured by a magnetic permeability sensor as a detection unit. To improve the measurement accuracy of the magnetic permeability sensor, it is necessary to reduce the transport force in the detection area of the magnetic permeability sensor and pack (solidify) the developer to a certain extent. For this reason, the movement of the developer per unit time is reduced in the area where the toner concentration is detected by the magnetic permeability sensor (hereinafter also referred to as the "detection area") compared to other locations. As a result, part of the developer accumulates near the detection area, making it difficult for new toner to mix with the accumulated developer.

This causes the toner concentration near the permeability sensor to become lower than the toner concentration in other locations in the developer tank. Also, as mentioned above, toner is less likely to be absorbed into the developer near the permeability sensor, so even if new toner is replenished into the developer tank, the toner concentration near the permeability sensor will still show a low value.

This phenomenon can cause various problems. For example, the amount of toner replenished is repeatedly adjusted so that the toner concentration measured by the magnetic permeability sensor reaches an appropriate value. This results in over-replenishment of toner. This causes the toner concentration in the developing unit to increase, resulting in problems such as fogging and powder smoke.

The developing device disclosed in Patent Document 1 prevents developer from accumulating by cleaning the sensing surface of the magnetic permeability sensor with a sheet. However, in this configuration, when the sheet physically comes into contact with the housing, the developer is rubbed, causing spent (adhesion of toner components to the carrier), which can lead to poor toner charging. This can also result in a deterioration of image quality.

The developing device disclosed in Patent Document 2 attempts to prevent developer from accumulating near the magnetic permeability sensor by providing the detection surface of the magnetic permeability sensor closer to the outer periphery of the stirring member than to the inner wall surface of the developing tank. However, in this configuration, the distance (clearance) between the stirring member and the detection surface is narrow, so the developer is easily rubbed and spent developer occurs. This can result in a deterioration of image quality, just as in Patent Document 1.

The present disclosure aims to provide an image forming device that can resolve the phenomenon in which the toner concentration near a detection unit (sensor) that detects the toner concentration in a storage chamber (developing tank) that contains toner becomes lower than the toner concentration in other locations in the storage chamber.

According to one aspect of the present disclosure, an image forming apparatus includes a storage chamber that stores a developer containing toner, stirring means for stirring the developer in the storage chamber, detection means for detecting the concentration of toner at a predetermined location in the storage chamber, supply means for supplying toner to the storage chamber, and control means for causing the supply means to supply toner and the stirring means to perform stirring. When a predetermined amount of toner is supplied by the supply means and the stirring means performs a first stirring, if the concentration does not reach or exceed a predetermined value, the control means executes control to cause the developer in the storage chamber to flow within the storage chamber.

Preferably, the control means further controls the image forming operation in the image forming device. The control means stops the image forming operation when the developer in the storage chamber is caused to flow within the storage chamber.

Preferably, the control means stops the supply of toner by the supply means when the developer in the storage chamber is caused to flow within the storage chamber.

Preferably, the control means causes the developer in the storage chamber to flow within the storage chamber by the second stirring by the stirring means.

Preferably, the control means executes control to forcibly discharge the toner from the storage chamber when the second stirring is being performed.

Preferably, the second stirring includes stirring at the first stirring speed and stirring at the second stirring speed.

Preferably, the image forming device further includes a vibration means for vibrating the storage chamber. The control means causes the vibration means to vibrate the storage chamber, thereby causing the developer in the storage chamber to flow within the storage chamber.

Preferably, the image forming device further includes a vibration means for vibrating the storage chamber. The control means causes the developer in the storage chamber to flow within the storage chamber by causing the vibration means to vibrate the storage chamber and by the second agitation by the agitation means.

Preferably, the control means determines the length of the mixing time of the second mixing based on one of the concentration detected by the detection means, environmental information indicating the environment around the image forming device, and operation information indicating the operation history of the image forming device.

Preferably, the environmental information includes temperature information. When the temperature is a first temperature and the humidity is a first humidity, the control means lengthens the stirring time of the second stirring compared to when the temperature is a second temperature lower than the first temperature and the humidity is a second humidity lower than the first humidity.

Preferably, the environmental information includes temperature information. When the temperature is a first temperature and the humidity is a first humidity, the control means lengthens the stirring time of the second stirring compared to when the temperature is a second temperature higher than the first temperature and the humidity is a second humidity higher than the first humidity.

Preferably, the environmental information includes temperature information. When the temperature becomes equal to or higher than a first reference temperature, or becomes equal to or lower than a second reference temperature that is lower than the first reference temperature, the control means lengthens the stirring time of the second stirring.

Preferably, the environmental information includes humidity information. The control means increases the stirring time of the second stirring when the humidity becomes equal to or greater than a first reference humidity, or becomes equal to or less than a second reference humidity that is less than the first reference humidity.

Preferably, the operation information includes information on the number of sheets printed by the image forming device. The control means increases the mixing time of the second mixing as the number of sheets printed increases.

Preferably, the operation information includes information on the operating time of the image forming device. The control means increases the mixing time of the second mixing as the operating time increases.

Preferably, the control means increases the mixing time of the second mixing step as the difference between the concentration detected by the detection means and the predetermined value increases.

According to another aspect of the present disclosure, a control method is executed in an image forming apparatus having a storage chamber that stores developer including toner. The control method includes a step of stirring the developer in the storage chamber, a step of detecting a concentration of toner at a predetermined location in the storage chamber, a step of replenishing the toner in the storage chamber, and a step of causing the developer in the storage chamber to flow within the storage chamber, on condition that the concentration does not exceed a predetermined value when a predetermined amount of toner is supplied and stirring is performed.

According to the present disclosure, when a phenomenon occurs in which the toner concentration near a toner concentration detection unit that detects the toner concentration in a storage chamber that contains toner becomes lower than the toner concentration in other locations within the storage chamber, this phenomenon can be eliminated.

1 is a diagram showing an outline of an overall configuration of an image forming apparatus; FIG. 2 is a cross-sectional view showing a typical configuration of a developing unit. 3 is an exploded perspective view showing a part of the developing unit taken along line PP in FIG. 2. 3 is a cross-sectional view taken along line QQ in FIG. 2. 11 is a schematic diagram showing a state in which a part of the developer sticks to and remains on a wall surface near the detection area. FIG. 13 is a diagram showing the relationship between the toner concentration measured by the magnetic permeability sensor, the toner concentration on the developing roller, and the amount of toner replenished into the developing unit when polarization of the developer occurs; FIG. FIG. 2 is a schematic diagram for explaining a control unit of the image forming apparatus. FIG. 2 is a functional block diagram illustrating a functional configuration of the image forming apparatus. 11 is a diagram showing a transition of toner concentration after a predetermined amount of toner is replenished. FIG. FIG. 4 is a flowchart illustrating a flow of a process executed in the image forming apparatus. FIG. 13 is a diagram showing the relationship between temperature, humidity, and additional stirring time. 13 is a diagram showing the relationship between the number of printed sheets and the additional stirring time. 13 is a diagram showing the relationship between the difference in toner concentration and the additional stirring time. FIG. 2 is a diagram for explaining a vibration generating device. 15 is a diagram showing a state in which the cam has been further rotated from the state shown in FIG. 14 . FIG. 2 is a schematic diagram for explaining a control unit of the image forming apparatus 1.

The image forming apparatus in each embodiment will be described below with reference to the drawings. In the embodiments described below, the same or corresponding parts will be given the same reference numbers, and duplicate descriptions may not be repeated.

The image forming device may be a monochrome printer, a color printer, a fax machine, or a multi-functional peripheral (MFP) that combines a monochrome printer, a color printer, and a fax machine.

[First embodiment]
<A. Overall Configuration of Image Forming Apparatus>
FIG. 1 is a diagram showing an outline of the overall configuration of an image forming apparatus 1 according to the present embodiment.

Referring to FIG. 1, the image forming device 1 mainly includes imaging units 2Y, 2M, 2C, and 2K corresponding to the reproduction colors of yellow (Y), magenta (M), cyan (C), and black (K), an intermediate transfer unit 3, a feed unit 4, and a fixing unit 5.

Image forming device 1 is connected to a network (e.g., a LAN (Local Area Network)) and receives an instruction to execute a print job from an external terminal device (not shown). Based on the instruction, image forming device 1 forms toner images of yellow (Y), magenta (M), cyan (C) and black (K). Furthermore, image forming device 1 transfers each of the formed toner images onto a recording sheet S to form a color image. Image forming device 1 can also selectively form a monochrome image using only a black (K) toner image.

The imaging units 2Y, 2M, 2C, and 2K are arranged in this order alongside the running direction (direction of arrow B) of the intermediate transfer belt 15 of the intermediate transfer unit 3.

The imaging unit 2K includes a photoconductor drum 10K that rotates in the direction of arrow A, a charging unit 11K, a developing unit 13K, and a cleaner 14K. The imaging unit 2K creates a K-color toner image on the photoconductor drum 10K. The imaging units 2Y, 2M, and 2C basically have the same configuration as the imaging unit 2K. The imaging units 2Y, 2M, and 2C include photoconductor drums 10Y, 10M, and 10C, charging units 11Y, 11M, and 11C, developing units 13Y, 13M, and 13C, and cleaners 14Y, 14M, and 14C. The imaging units 2Y, 2M, and 2C create Y, M, and C-color toner images on the photoconductor drums 10Y, 10M, and 10C.

The specific configuration of the developing units 13Y, 13M, 13C, and 13K will be described later.
The intermediate transfer unit 3 includes an intermediate transfer belt 15 disposed above the image forming units 2Y, 2M, 2C, and 2K. The intermediate transfer unit 3 further includes a drive roller 16, a driven roller 17, primary transfer rollers 18Y, 18M, 18C, and 18K, a secondary transfer roller 19, and a cleaner 20.

The intermediate transfer belt 15 is stretched around a drive roller 16, a driven roller 17, and primary transfer rollers 18Y, 18M, 18C, and 18K. The intermediate transfer belt 15 is driven to rotate in the direction of arrow B.

The primary transfer rollers 18Y, 18M, 18C, and 18K are disposed opposite the corresponding photoconductor drums 10Y, 10M, 10C, and 10K via the intermediate transfer belt 15. The secondary transfer roller 19 is disposed opposite the drive roller 16 via the intermediate transfer belt 15. The position 19a where the secondary transfer roller 19 contacts the intermediate transfer belt 15 is the secondary transfer position.

The exposure unit 12 is located below the image forming units 2Y, 2M, 2C, and 2K. In response to a drive signal from the main control unit 51, the exposure unit 12 emits light beams L from light-emitting elements to form images of each color (Y, M, C, and K).

For each of the imaging units 2Y, 2M, 2C, and 2K, the photoconductor drums 10Y, 10M, 10C, and 10K, which have been charged by the charging units 11Y, 11M, 11C, and 11K, are exposed and scanned by the light beam L emitted from the exposure unit 12. As a result, an electrostatic latent image is formed on the photoconductor drums 10Y, 10M, 10C, and 10K. The electrostatic latent image is developed by the developer (more specifically, a two-component developer containing toner and carrier) of the development units 13Y, 13M, 13C, and 13K, and as a result, a toner image of the corresponding color is formed on the photoconductor drums 10Y, 10M, 10C, and 10K.

The toner images of each color formed on the photoconductor drums 10Y, 10M, 10C, and 10K are primarily transferred to the intermediate transfer belt 15 by the electrostatic action of the primary transfer rollers 18Y, 18M, 18C, and 18K. At this time, the image forming operation for each color is performed with a staggered timing so that the toner images of each color are transferred and superimposed at the same position on the intermediate transfer belt 15. During the primary transfer, residual toner remaining on the photoconductor drums of the toner images on the photoconductor drums 10Y, 10M, 10C, and 10K that has not been transferred to the intermediate transfer belt 15 is removed by cleaners 14Y, 14M, 14C, and 14K.

The toner images of each color transferred onto the intermediate transfer belt 15 are moved to the secondary transfer position 19a as the intermediate transfer belt 15 rotates.

The feed unit 4 feeds the recording sheet S stored in a paper feed cassette (not shown) to the transport path (dashed line) using a feed roller 21. The feed unit 4 transports the sheet S to the timing roller 22, which is stopped.

The timing roller 22 starts rotating in accordance with the timing at which the toner images of each color, which have been multiplex-transferred onto the rotating intermediate transfer belt 15, reach the secondary transfer position 19a. The timing roller 22 transports the sheet S to the secondary transfer position 19a.

When the sheet S passes through the secondary transfer position 19a, the toner images of each color that have been multiply transferred onto the intermediate transfer belt 15 are secondarily transferred onto the sheet S by the electrostatic action of the secondary transfer roller 19. This forms a color toner image on the sheet S. During the secondary transfer, of the toner images on the intermediate transfer belt 15, any residual toner that is not transferred to the sheet S and remains on the intermediate transfer belt 15 is transported to the cleaner 20 by the circular movement of the intermediate transfer belt 15. The residual toner is removed from the intermediate transfer belt 15 by the cleaner 20.

The sheet S onto which the color toner image has been secondarily transferred by the secondary transfer position 19a is transported to the fixing unit 5. The fixing unit 5 has a heating roller 5a and a pressure roller 5b that presses against the heating roller 5a to form a fixing nip. When the sheet S transported by the secondary transfer roller 19 passes through the fixing nip, the fixing unit 5 thermally fixes the color toner image (unfixed image) on the sheet S by applying heat and pressure. The sheet S that has passed through the fixing unit 5 is discharged outside the machine by discharge rollers 23, and then stored in the paper discharge tray 24.

The above describes the operation of color printing, but in monochrome printing, after a black toner image is formed on the photoconductor drum 10K by the image forming unit 2K alone, primary transfer from the photoconductor drum 10K to the intermediate transfer belt 15, secondary transfer to the sheet S, and fixing to the sheet S are performed in that order. That is, the processes of charging, exposure, development, transfer, and fixing are performed.

Directly above the developing units 13Y, 13M, 13C, and 13K, toner hoppers 7Y, 7M, 7C, and 7K are located, which supply replenishment toner to each of the developing units 13Y, 13M, 13C, and 13K.

Toner hopper 7Y supplies new yellow toner for refilling to developing unit 13Y according to the amount of yellow (Y) toner to be replenished instructed by toner concentration control unit 9Y, which will be described later. The other toner hoppers 7M, 7C, and 7K basically have the same configuration as toner hopper 7Y. Toner hoppers 7M, 7C, and 7K supply new magenta, cyan, and black toner for refilling to the corresponding developing units 13M, 13C, and 13K, respectively.

Toner concentration control units 9Y, 9M, 9C, and 9K are disposed near the developing units 13Y, 13M, 13C, and 13K. The toner concentration control units 9Y, 9M, 9C, and 9K control the amount of toner supplied from the toner hoppers 7Y, 7M, 7C, and 7K to the developing units 13Y, 13M, 13C, and 13K, and control the toner concentration in each developing unit 13Y, 13M, 13C, and 13K to be constant. In the following, the developing unit 13Y and the developing unit control unit 120Y (see Figures 8 and 9) having the toner concentration control unit 9Y are collectively referred to as the "developing unit 6Y". Similarly, the developing units 13M, 13C, and 13K and the toner concentration control units 9M, 9C, and 9K respectively constitute the developing units 6M, 6C, and 6B for the colors magenta (M), cyan (C), and black (K). The developing units are also referred to as developing devices.

The toner concentration control unit 9Y determines the amount of toner to be replenished to the developing unit 13Y based on the image signal input from the main control unit 51 and the output of the magnetic permeability sensor 8Y provided in the developing unit 13Y, and supplies the determined amount of toner from the toner hopper 7Y. The other toner concentration control units 9M, 9C, and 9K basically have the same configuration as the toner concentration control unit 9Y. The toner concentration control units 9M, 9C, and 9K control the amount of toner to be replenished to the corresponding developing units 13M, 13C, and 13K.

The configuration of the yellow developing unit 13Y is described below. Note that developing units 13M, 13C, and 13K are basically configured in the same way as developing unit 13Y, so the description will not be repeated.

<B. Configuration of developing unit 13Y>
FIG. 2 is a cross-sectional view showing a typical configuration of the developing section 13Y.

Referring to FIG. 2, the developing unit 13Y mainly comprises a housing 30, a developing roller 31, a supply screw 32, an agitating screw 33, and a regulating member 34. Each of the housing 30, the developing roller 31, the supply screw 32, the agitating screw 33, and the regulating member 34 is elongated along the axial direction of the developing roller 31 (perpendicular to the plane of the drawing). The axial direction is parallel to the rotational axis of the photoconductor drum 10Y. Below, the up-down direction is defined based on the position of the supply screw 32.

The housing 30 is made of resin, such as ABS (acrylonitrile butadiene styrene copolymer synthetic resin). Developer D (two-component developer) is contained inside the housing 30. The housing 30 has a first storage chamber 38 and a second storage chamber 39, which are separated by a partition (divider) 37. In the figure, only a portion of the developer D in the housing 30 that exists in the second storage chamber 39 is shown. The first storage chamber 38 and the second storage chamber 39 are collectively referred to as the "developer tank."

The first chamber 38 contains the developing roller 31 and the supply screw 32. The second chamber 39 contains the stirring screw 33.

The supply screw 32 is disposed diagonally below the developing roller 31. The stirring screw 33 is disposed diagonally below the supply screw 32. A partition wall 37 that separates the first storage chamber 38 and the second storage chamber 39 is erected at an angle to the vertical direction. The second storage chamber 39 is disposed diagonally below the first storage chamber 38, with the partition wall 37 in between.

The developing roller 31 comprises a cylindrical developing sleeve 31a and a magnet body 31b. The part of the developing roller 31 opposite the side where the supply screw 32 is located protrudes from an opening in the first storage chamber 38, located at a position facing the photosensitive drum 10Y. Inside the developing sleeve 31a, a cylindrical magnet body 31b is provided, which is inserted along the axial direction.

Magnetic body 31b is provided so that multiple magnetic poles (for example, the portions where S1, N1, etc. are formed) are arranged in sequence in the circumferential direction. The axial end of magnetic body 31b is fixed to housing 30 so that it cannot rotate. Each magnetic pole extends along the axial direction.

The developing sleeve 31a rotates in the direction of arrow E with the portion facing the photoconductor drum 10Y exposed through the opening of the housing 30. The developing sleeve 31a rotates around the stationary magnet body 31b while holding (carrying) the developer D on its surface by the magnetic force of the magnet body 31b.

The supply screw 32 rotates in the direction of the arrow F in the figure to transport the developer D in the first storage chamber 38 along the axial direction, and during this transport, supplies a portion of the developer D to the developing roller 31.

The stirring screw 33 rotates in the direction of the arrow G to stir and transport the developer D in the second storage chamber 39 in the opposite direction to the transport direction by the supply screw 32.

The regulating member 34 is positioned so that there is a predetermined gap between the tip of the regulating member 34 and the surface of the developing roller 31. The regulating member 34 regulates the amount of developer D passing through the gap so that the amount of developer on the surface of the developing roller 31 is appropriate at the developing position 29 where the photoconductor drum 10Y and the developing roller 31 face each other.

FIG. 3 is an exploded perspective view of a part of the developing unit 13Y taken along line PP in FIG.
3, the direction in which the supply screw 32 and the stirring screw 33 are aligned is referred to as the "X-axis direction." The axial direction of the developing roller 31 is referred to as the "Z-axis direction." The direction perpendicular to both the X-axis and the Z-axis is referred to as the "Y-axis direction."

As shown in FIG. 3, the first storage chamber 38 and the second storage chamber 39 provided in the housing 30 are formed in a long cylindrical shape along the axial direction (Z-axis direction). The first storage chamber 38 and the second storage chamber 39 are separated by a partition wall 37. The first storage chamber 38 and the second storage chamber 39 are configured to communicate with each other via a communication hole 37a provided at one axial end of the partition wall 37 and a communication hole 37b provided at the other axial end, respectively.

The supply screw 32 has a rotating shaft (shaft body) 32a and screw blades 32b that are arranged in a spiral shape along the outer circumferential surface of the rotating shaft 32a.

The rotating shaft 32a has both axial ends rotatably supported on both axial side walls of the first storage chamber 38 via bearing members (not shown) or the like. The left end shaft portion 32z of the rotating shaft 32a extends outside the side walls. A gear (not shown) is attached to the shaft portion 32z of the rotating shaft 32a. The rotating shaft 32a is driven to rotate in the direction of arrow F by the rotational driving force from the gear.

The screw blades 32b provided on the outer peripheral surface of the rotating shaft 32a apply a transport force in the transport direction (arrow T1 direction) to the developer D in the first storage chamber 38 as the rotating shaft 32a rotates.

The screw blade 33b is provided on the outer circumferential surface of the rotating shaft 33a. When the rotating shaft 33a rotates, the screw blade 33b applies a transport force to the developer D in the second storage chamber 39 in the transport direction (the direction of the arrow T2, which is the opposite direction to the arrow T1).

The supply screw 32 and the stirring screw 33 are made of metal such as iron or aluminum, or resin such as ABS. The supply screw 32 and the stirring screw 33 have, for example, a rotating shaft diameter of 5 mm, an outer diameter of the screw blade of 12 mm, and a pitch of 25 mm.

In each of the first storage chamber 38 and the second storage chamber 39, the bulk height (liquid surface height) of the developer D is positioned slightly above the rotation shaft 32a of the supply screw 32 and the 33a of the stirring screw 33. Also, the dashed line 39a shown at the right end of the second storage chamber 39 in FIG. 3 indicates the receiving port that receives the replenishment Y color toner newly supplied from the toner hopper 7Y.

Next, the flow of the developer will be described.
When the developing roller 31, the supply screw 32, and the stirring screw 33 are each driven to rotate, the developer D in the housing 30 is transported in the direction of the arrow shown in FIG.

Specifically, developer D in first storage chamber 38 is transported in the direction of arrow T1 (to the right in the figure) by supply screw 32. When developer D is transported to the end downstream in the developer transport direction, it falls due to gravity through communication hole 37b of partition 37 into second storage chamber 39, which is located diagonally below first storage chamber 38. As a result, developer D in first storage chamber 38 is transported in the direction of arrow T3 to second storage chamber 39 through communication hole 37b of partition 37.

The developer D transported to the second storage chamber 39 is transported while being stirred in the direction of arrow T2 (to the left in the figure) by the stirring screw 33. In addition, new replenishment Y-color toner is supplied from the toner hopper 7Y via the receiving port 39a to the end of the second storage chamber 39 on the upstream side in the developer transport direction. Therefore, the developer D already present in the second storage chamber 39 and the newly supplied new toner (replenished toner) are mixed and transported while being stirred by the stirring screw 33.

When the developer D being transported through the second storage chamber 39 reaches the side wall 30z of the housing 30, which is the downstream end in the developer transport direction, the developer D is transported to the first storage chamber 38. Specifically, the developer D is transported in the direction of arrow T4 through the communication hole 37a of the partition wall 37. More specifically, the developer D accumulates in the downstream end portion 39z of the second storage chamber 39, and is transported against gravity to the first storage chamber 38, which is located diagonally above the second storage chamber 39.

The developer D transported from the second storage chamber 39 to the first storage chamber 38 through the communication hole 37a is transported in the direction of the arrow T1 by the supply screw 32.

In this way, the downstream side of the first storage chamber 38 in the developer transport direction and the upstream side of the second storage chamber 39 in the developer transport direction are connected by the communication hole 37b. Furthermore, the downstream side of the second storage chamber 39 in the developer transport direction and the upstream side of the first storage chamber 38 in the developer transport direction are connected by the communication hole 37a. Therefore, the first transport path 98 through which the developer D is transported by the supply screw 32 and the second transport path 99 through which the developer D is transported by the stirring screw 33 are connected via the communication holes 37a and 37b (first and second communication paths). As a result, a circulation path for the developer D (a path through which the developer D is transported in the order of the arrows T1, T3, T2, and T4) is formed in the housing 30. The developer D is circulated through the circulation path.

When developer D is transported by the supply screw 32 through the first storage chamber 38 on the circulation path, a portion of the developer D is supplied to the developing roller 31 arranged adjacent to the supply screw 32. The developer D supplied to the developing roller 31 is used to visualize the electrostatic latent image on the photoconductor drum 10Y with toner.

C. Polarization of Developer
FIG. 4 is a cross-sectional view taken along line QQ in FIG.

Referring to FIG. 4, the second storage chamber 39 in the housing 30 contains an agitating screw 33 that agitates and transports the developer D. As described above, the agitating screw 33 has a rotating shaft 33a and a screw blade 33b that is spirally arranged along the outer circumferential surface of the rotating shaft 33a.

The rotating shaft 33a has both axial ends rotatably supported on both axial side walls of the second storage chamber 39 via bearing members (not shown) or the like. The left end shaft portion 33z of the rotating shaft 33a extends outside the side walls. A gear (not shown) is attached to the shaft portion 33z of the rotating shaft 33a, and the rotating shaft 33a is rotated by the rotational driving force from the gear.

The screw blades 33b provided on the outer peripheral surface of the rotating shaft 33a apply a transport force in the transport direction (the direction of the arrows T2A and T2B) to the developer in the second storage chamber 39 as the rotating shaft 33a rotates. A magnetic permeability sensor 8Y is provided at the bottom of the second storage chamber 39. The magnetic permeability sensor 8Y measures the magnetic permeability of the developer D in the detection area 81.

The stirring screw 33 is configured so that there is no screw blade 33b near the detection area 81 of the magnetic permeability sensor 8Y. The transport force imparted to the developer D near the detection area 81 of the magnetic permeability sensor 8Y (the transport force near the arrow T2B) is smaller than the transport force imparted to the developer D at the location where the screw blade 33b is present (the transport force near the arrow T2A). By reducing the transport force near the detection area 81 of the magnetic permeability sensor 8Y in this way, the measurement accuracy of the magnetic permeability sensor 8Y is improved.

In the image forming device 1, it is necessary to stir the developer D in the circulation path (path) of the developer D in the developing unit 13Y. The smaller the image forming device 1, the shorter the circulation path of the developer D. If the rotation amount of the stirring screw 33 is increased to compensate for this drawback, the charge amount of the developer D will increase due to frictional charging. In addition, the charge amount of the developer D will further increase under conditions such as a low humidity environment or an increase in the number of continuous prints at a low print rate.

When the charge amount of developer D increases, the fluidity of developer D decreases. In addition, new toner newly replenished to the second storage chamber 39 becomes less likely to be absorbed into the developer D that was present in the second storage chamber 39 before the replenishment.

The transport force of the developer D is reduced near the detection area 81 of the magnetic permeability sensor 8Y, and the amount of charge on the developer D increases, reducing its fluidity, which makes it easier for some of the developer D to stick to and remain on the wall surface near the detection area 81 of the magnetic permeability sensor 8Y.

Figure 5 is a schematic diagram showing a state in which a portion of developer D is stuck to and remains on the wall surface near the detection area 81.

Referring to FIG. 5, when some of the developer D remains, the developer D is separated into developer 82 that remains near the detection area 81 of the magnetic permeability sensor 8Y and is not stirred and transported, and developer 83 that is stirred and transported as usual. In this state, when the magnetic permeability sensor 8Y detects that the toner concentration is low, toner is replenished from the toner hopper 7Y to the second storage chamber 39.

Because newly replenished new toner has a low charge and high fluidity, it is difficult for the new toner to be absorbed into the remaining developer 82. Therefore, the toner concentration of the developer 82 remains low near the detection area 81.

Even if the toner concentration in the developer 83 has actually increased to the target value, toner continues to be replenished to the second storage chamber 39. As a result, the toner concentration in the developer 83 becomes higher than the target value, resulting in a situation in which toner is over-replenished.

In the following, for ease of explanation, the situation where some developer 82 accumulates near the detection area 81 of the magnetic permeability sensor 8Y, resulting in a difference in toner concentration between the detection area 81 and other areas is also referred to as "polarization of the developer." Note that developer polarization can occur in the development units 13M, 13C, and 13K, just as it does in the development unit 13Y.

Figure 6 shows the relationship between the toner concentration measured by magnetic permeability sensor 8Y (corresponding to the toner concentration of developer 82), the toner concentration on developing roller 31 (corresponding to the toner concentration of developer 83), and the amount of toner replenished into developing unit 13Y when polarization of the developer occurs.

Referring to FIG. 6, even if the amount of toner replenishment increases after time td, the toner concentration measured by magnetic permeability sensor 8Y (magnetic permeability sensor measurement value) remains lower than the target toner concentration. The toner concentration on developing roller 31 continues to rise above the target toner concentration, resulting in toner oversupply.

<D. Functional Configuration>
FIG. 7 is a schematic diagram for explaining the control section of the image forming apparatus 1. As shown in FIG.

Referring to FIG. 7, the control unit 100 (controller) that operates each unit of the image forming device 1 includes a main control unit 51, a yellow developer control unit 120Y, a magenta developer control unit 120M, a cyan developer control unit 120C, and a black developer control unit 120B. The main control unit 51 controls the operation of members other than the developers 6Y, 6M, 6C, and 6B. The main control unit 51 may be composed of multiple control units.

The main control unit 51 is typically realized by a processor such as a CPU executing a program stored in memory. The main control unit 51 may also be realized by hardware such as an ASIC. Each of the developer control units 120Y, 120M, 120C, and 120B is also realized by a processor such as a CPU executing a program stored in memory. Each of the developer control units 120Y, 120M, 120C, and 120B may also be realized by hardware such as an ASIC.

Note that, although FIG. 7 shows an example in which the control unit 100 is configured with multiple control units, this is not limiting. A single control unit (e.g., a single control board) may be configured to control the entire image forming device 1.

FIG. 8 is a functional block diagram for explaining the functional configuration of the image forming apparatus 1. As shown in FIG.
8, image forming apparatus 1 includes main control unit 51, developing units 6Y, 6M, 6C, and 6B, a temperature sensor 182, a humidity sensor 184, and toner supply units 130Y, 130M, 130C, and 130K. A control method using temperature sensor 182 and humidity sensor 184 will be described later.

The developing unit 6Y includes a developing unit control unit 120Y and a second storage chamber 39. The developing unit control unit 120Y includes a toner concentration control unit 9Y and a determination unit 122. The toner concentration control unit 9Y has a replenishment amount calculation unit 121. The second storage chamber 39 includes a toner concentration detection unit 140 and a stirring unit 150.

The developer control unit 120Y controls the operation of the developer 6Y. The toner concentration control unit 9Y controls the toner concentration in the developer 6Y. The determination unit 122 determines whether or not polarization has occurred. The supply amount calculation unit 121 calculates the amount of toner to be supplied from the toner hopper 7Y to the second storage chamber 39.

The toner concentration detection unit 140 corresponds to the magnetic permeability sensor 8Y. In other words, the toner concentration detection unit 140 detects the toner concentration within the detection area 81.

The stirring unit 150 stirs the developer in the second storage chamber 39. The stirring unit 150 mixes the carrier and toner by stirring the developer. The stirring unit 150 corresponds to the stirring screw 33.

The toner supply unit 130Y supplies toner to the second storage chamber 39. More specifically, the toner supply unit 130Y supplies toner based on instructions from the developer control unit 120Y. In one aspect, the toner supply unit 130Y supplies the amount of toner calculated by the supply amount calculation unit 121 based on instructions from the toner concentration control unit 9Y. The toner supply unit 130Y corresponds to the toner hopper 7Y.

Below, we will explain how to detect the occurrence of polarization and how to eliminate the polarization that has occurred. In the following, we will also use the yellow developer 6Y as an example to avoid repeating redundant explanations for the other developers 6M, 6C, and 6K.

(Method of detecting polarization)
The determination unit 122 determines that polarization of the developer has occurred when the toner concentration based on the magnetic permeability sensor 8Y does not increase to the target toner concentration (hereinafter referred to as the "target value J") even after a predetermined time Ta has elapsed, despite the fact that a sufficient amount (hereinafter also referred to as the "predetermined amount") of toner has been replenished from the toner hopper 7Y to the second storage chamber 39 to increase the toner concentration in the developing unit 13Y to the target toner concentration (hereinafter referred to as the "target value J"). A method for detecting polarization will be described in detail below.

The toner concentration control unit 9Y instructs the toner supply unit 130Y to supply the predetermined amount of toner. For example, the toner concentration control unit 9Y instructs the toner supply unit 130Y to supply 0.5% of the developer weight in the developing unit 13Y as the predetermined amount of toner. The supply amount calculation unit 121 calculates the developer weight in the developing unit 13Y. The supply amount calculation unit 121 calculates the developer weight based on the volume of the developer obtained by detecting the height from the bottom surface of the developing unit 13Y to the liquid surface of the developer using an optical sensor or the like.

Based on the amount of toner supplied from the toner supply unit 130Y, the toner concentration control unit 9Y calculates a target value J of the toner concentration based on the amount of toner supplied. Based on the toner concentration calculated based on the current weight of developer in the development unit 13Y and the measurement results of the magnetic permeability sensor 8Y, the toner concentration control unit 9Y calculates the toner concentration after replenishment of an amount of toner that is 0.5% of the developer weight. The toner concentration control unit 9Y sets the calculated toner concentration as the target value J.

The determination unit 122 determines whether the toner concentration based on the measurement results of the magnetic permeability sensor 8Y has risen to the target value J within a predetermined time Ta after the above-mentioned predetermined amount of toner has been replenished. The determination unit 122 determines whether the toner concentration based on the measurement results of the magnetic permeability sensor 8Y has risen to the target value J within, for example, the time it takes for the developer to make two revolutions around the circulation path of the development unit 13Y (the path along which the developer is transported in the order of arrows T1, T3, T2, and T4 in FIG. 3) (here, for example, 20 seconds).

If the detection result (toner concentration) by the toner concentration detection unit 140 rises to the target value J within the above-mentioned predetermined time Ta, the judgment unit 122 judges that polarization of the developer has not occurred. If the detection result by the toner concentration detection unit 140 does not rise to the target value J within the above-mentioned predetermined time Ta, the judgment unit 122 judges that polarization of the developer has occurred. In this way, the image forming device 1 can judge the polarization of the developer.

Figure 9 shows the progression of toner concentration after a given amount of toner is replenished in a certain situation.

Referring to FIG. 9, even after the time (20 seconds) required for the developer in developing unit 13Y to make two revolutions around the circulation path has elapsed, the detection result by toner concentration detection unit 140 does not exceed the target value. Therefore, in such a case, determination unit 122 determines that polarization of the developer has occurred.

(Methods to resolve polarization)
Next, a process for eliminating polarization when the polarization occurs will be described.

(1) When a predetermined amount of toner is supplied to the second storage chamber 39 by the toner supply unit 130Y and stirring (hereinafter also referred to as "stirring #1") is performed by the stirring unit 150 for a predetermined time Ta (e.g., 20 seconds), if the toner concentration does not reach or exceed the target value J (a predetermined value), the developer control unit 120Y executes control to cause the developer in the second storage chamber 39 to flow within the second storage chamber 39. In other words, when it is determined that polarization of the developer has occurred, the developer control unit 120Y executes control to cause the developer in the second storage chamber 39 to flow within the second storage chamber 39.

This process allows the developer 82 (see FIG. 5) near the magnetic permeability sensor 8Y (toner concentration detection unit 140) to flow. Therefore, if a phenomenon (polarization) occurs in which the toner concentration near the magnetic permeability sensor 8Y (toner concentration detection unit 140) becomes lower than the toner concentration in other locations in the second storage chamber 39, this phenomenon can be eliminated.

(2) The main control unit 51 controls the image forming operation in the image forming device. Furthermore, the main control unit 51 stops the image forming operation when the developer in the second storage chamber 39 is caused to flow within the second storage chamber 39.

In addition, when the developer in the second storage chamber 39 is caused to flow within the second storage chamber 39, the developer control unit 120Y stops the toner supply unit 130Y from supplying toner. This makes it possible to prevent further oversupply of toner.

In this example, the developer control unit 120Y causes the developer in the second storage chamber 39 to flow within the second storage chamber 39 through further stirring (hereinafter also referred to as "stirring #2") by the stirring unit 150. In an experiment, it was found that after it was determined that polarization had occurred, the polarization could be eliminated by performing further stirring #2 for a predetermined time Tb (e.g., 90 seconds) while the supply of toner was stopped.

Although toner supply was stopped, several hundred milligrams of toner sometimes naturally fell from the toner hopper. Even in such cases, the polarization problem was resolved.

(3) It is preferable that the developer control unit 120Y executes control to forcibly discharge toner from the second storage chamber 39 when the above-mentioned further stirring #2 is being performed.

The reason for this is as follows. When the developer is polarized, the toner concentration in the second storage chamber 39 (and the first storage chamber 38) tends to be high. Therefore, by forcibly consuming toner, the toner concentration in the developer tank can be reduced. In this way, stirring control can be performed while bringing the toner concentration in the housing 30 closer to the toner concentration of the retained developer 82 (Figure 5). As a result, the implementation time required to eliminate polarization can be shortened. In an experiment, it was found that by forcibly consuming 1% of the toner concentration, the stirring time could be shortened by 20 seconds compared to when forcibly consuming no toner.

The developer control unit 120Y forcibly consumes toner by consuming toner internally by forming a patch image. In the case of forcibly consuming toner, no printout is performed.

(4) In further stirring #2, it is preferable to change the stirring speed. Specifically, the developer control unit 120Y may change the rotation speed of the stirring screw 33 and the supply screw 32. For example, the developer control unit 120Y may control the operation of the stirring screw 33 and the supply screw 32 so that stirring at a first stirring speed is performed, and then stirring at a second stirring speed that is faster (or slower) than the first stirring speed. Alternatively, the developer control unit 120Y may control the operation of the stirring screw 33 and the supply screw 32 so that stirring at the first stirring speed and stirring at the second stirring speed are alternately repeated.

By carrying out this type of processing, accumulated developer is easily loosened. As a result, the mixing time can be shortened compared to a configuration in which the mixing speed is not changed. In an experiment, by alternating between the normal mixing speed and a speed half the normal mixing speed every 10 seconds, the mixing time could be shortened by 20 seconds compared to when the mixing speed was not changed.

E. Control Structure
10 is a flow diagram for explaining the flow of the process executed in the image forming apparatus 1. Note that, again, the explanation will be given with a focus on the yellow developing unit 6Y.

Referring to FIG. 10, in step S2, the developer control unit 120Y supplies a predetermined amount of toner from the toner hopper 7Y to the second storage chamber. In step S4, the developer control unit 120Y rotates the stirring screw 33 to stir the developer D in the second storage chamber 39 for a predetermined time Ta (e.g., 20 seconds). That is, in step S4, the above-mentioned stirring #1 is performed.

In step S6, the developer control unit 120Y determines whether the toner concentration detected by the magnetic permeability sensor 8Y (toner concentration detection unit 140) has exceeded the target value J. If it is determined that the toner concentration has exceeded the target value J (YES in step S6), the developer control unit 120Y ends the series of processes.

If it is determined that the target value J has not been exceeded (NO in step S6), the developer control unit 120Y determines in step S8 whether image formation processing is being performed. Since the developer control unit 120Y operates based on instructions from the main control unit 51, it can determine whether image formation processing is being performed.

If it is determined that image formation processing is being performed (YES in step S8), the main control unit 51 stops the image formation processing in step S10. The main control unit 51 then proceeds to step S12. If it is determined that image formation processing is not being performed (NO in step S8), the main control unit 51 transitions to a mode in which toner replenishment is prohibited in step S12.

In step S14, the developer control unit 120Y rotates the stirring screw 33 to stir the developer D in the second storage chamber 39 for a predetermined time Tb (e.g., 90 seconds), thereby causing the developer in the second storage chamber 39 to flow within the second storage chamber 39. That is, in step S14, the above-mentioned stirring #2 is performed.

After the stirring for the predetermined time Tb has ended, in step S16, the main control unit 51 cancels the mode that prohibits toner replenishment and transitions the operation mode to a mode that permits toner replenishment.

F. Modifications
A configuration for changing the stirring time of the stirring #2 to eliminate the polarization will be described below, taking the yellow developer 6Y as an example.

(f1. First Modification)
The developer control unit 120Y of developer 6Y determines the length of the mixing time for mixing #2 based on at least one of the toner concentration detected by the toner concentration detection unit 140, environmental information indicating the environment surrounding the image forming device 1, and operation information (durability information) indicating the operating history of the image forming device 1.

Examples of environmental information include temperature information and humidity information. Examples of operation information include information on the number of printed pages and information on operating time (operating time information). Note that the operating time may be the operating time of the developing unit 6Y.

Below, we explain a configuration that uses temperature and humidity information, a configuration that uses information on the number of printed pages, and a configuration that uses information on drive time.

(Use of temperature and humidity information)
In high temperature and high humidity conditions, it is preferable to lengthen the stirring time of Stir #2. In low temperature and low humidity conditions, it is also preferable to lengthen the stirring time of Stir #2. Hereinafter, a configuration for changing the stirring time based on temperature and/or humidity will be described.

FIG. 11 is a diagram showing the relationship between temperature, humidity, and additional stirring time.
11, the stirring time is determined depending on which of three regions R1, R2, and R3 the temperature and humidity combination belongs to. Regions R1 and R2 are adjacent. Regions R2 and R3 are adjacent. Regions R1 and R3 are not adjacent.

Regions R1 and R2 are separated by a line (curve in this example) connecting humidity V1 and temperature K1. V1 is, for example, 20%, and K1 is, for example, 10 degrees. Regions R2 and R3 are separated by a line (curve in this example) connecting humidity V2 and temperature K2. V2 is, for example, 80%, and K2 is, for example, 30 degrees. Roughly speaking, humidity and temperature increase in the order of regions R1, R2, and R3. Note that, although monotonically decreasing curves are given as examples of the above lines, this is not limiting. The above lines may be composed of a single straight line (line segment) or multiple straight lines.

The temperature is measured by a temperature sensor 182 provided in the image forming device 1. The measurement result is notified to the developer control unit 120Y. The humidity is measured by a humidity sensor 184 provided in the image forming device 1. The measurement result is notified to the developer control unit 120Y.

In region R2, no additional mixing time is added. In this example, the developer control unit 120Y performs mixing for a predetermined time Tb (90 seconds) as mixing #2.

In region R1, the developer control unit 120Y adds mixing time to the predetermined time Tb (default mixing time). In this example, the developer control unit 120Y adds 30 seconds to 90 seconds, making the mixing time 120 seconds.

In low temperature and low humidity conditions such as region R1, the charge on the toner increases. This reduces the fluidity of developer D. Therefore, in region R1, it is preferable to extend the stirring time of stirring #2.

In region R3, as in region R1, the developer control unit 120Y adds mixing time to the predetermined time Tb. In this example, as in region R1, the developer control unit 120Y adds 30 seconds to 90 seconds to make the mixing time 120 seconds.

In high temperature and high humidity conditions such as in region R3, developer D is more likely to absorb moisture, and the fluidity of developer D decreases. For this reason, it takes longer to eliminate the polarization of the developer compared to normal temperature and humidity conditions such as in region R2. Therefore, it is preferable to extend the stirring time of stirring #2 even in region R3.

For example, when we look at specific point G1 ((temperature, humidity) = (Kg1, Vg1)) contained in region R2, specific point G2 (Kg2, Vg2) contained in region R2, and specific point G3 (Kg3, Vg3) contained in region R3, the following can be said. Note that points on line W passing through the origin of the graph are given as an example of specific points G1, G2, and G3. The relational equation for temperature, "Kg1<Kg2<Kg3", and the relational equation for humidity, "Vg1<Vg2<Vg3", hold.

When the temperature is Kg3 and the humidity is Vg3, the developer control unit 120Y lengthens the stirring time of stirring #2 compared to when the temperature is Kg2, which is lower than Kg3, and the humidity is Vg2, which is lower than Vg3.

When the temperature is Kg1 and the humidity is Vg1, the developer control unit 120Y lengthens the stirring time of stirring #2 compared to when the temperature is Kg2, which is higher than Kg1, and the humidity is Vg2, which is higher than Vg1.

In the above, the developer control unit 120Y determines whether or not to perform additional stirring based on a combination of temperature and humidity. However, this is not limited to the above. The developer control unit 120Y may determine whether or not to perform additional stirring based only on the temperature of the temperature and humidity. Similarly, the developer control unit 120Y may determine whether or not to perform additional stirring based only on the humidity of the temperature and humidity.

In other words, with regard to temperature, the developer control unit 120Y lengthens the agitation time of agitation #2 when the temperature measured by the temperature sensor 182 is equal to or higher than temperature K2, or is equal to or lower than temperature K1, which is lower than temperature K2. With regard to humidity, the developer control unit 120Y lengthens the agitation time of agitation #2 when the humidity is equal to or higher than humidity V2, or is equal to or lower than humidity V1, which is lower than humidity V2.

(Use of printed sheets)
As the number of printed sheets increases, the fluidity of the developer D decreases. Therefore, as the number of printed sheets increases, the stirring time of the stirring #2 is lengthened.

FIG. 12 is a diagram showing the relationship between the number of printed sheets and the amount of stirring time to be added.
12, when the number of printed sheets exceeds, for example, 10,000 sheets, the developer control unit 120Y lengthens the stirring time. More specifically, when the number of printed sheets increases, the developer control unit 120Y lengthens the added stirring time. More specifically, the developer control unit 120Y adds a time determined by the number of printed sheets to the predetermined time Tb to set the stirring time for stirring #2.

Experiments have shown that this process can completely eliminate the polarization of developer D.

(Utilization of drive time)
As the driving time of the image forming apparatus 1 increases, the fluidity of the developer D decreases. Therefore, as the driving time increases, the stirring time of stirring #2 is increased. More specifically, the developer control unit 120Y increases the additional stirring time as the driving time of the image forming apparatus 1 increases. When an experiment was conducted, it was found that such a process could reliably eliminate the polarization of the developer D.

The developer control unit 120Y may be configured to increase the additional stirring time when the drive time of the developer 6Y increases.

(f2. Second Modification)
When the difference between the target value J and the toner concentration detected by the toner concentration detection unit 140 (magnetic permeability sensor 8Y) is large, the range of the retained developer may be wide. For this reason, it is preferable that the developer control unit 120Y lengthens the stirring time of further stirring #2 as the difference between the toner concentration detected by the toner concentration detection unit 140 (magnetic permeability sensor 8Y) and the target value J increases.

In the following example, we will explain the case where the difference is expressed as a percentage. Specifically, the difference is divided by the target value J, and the quotient is multiplied by 100, and the resulting value is treated as the difference.

FIG. 13 is a diagram showing the relationship between the toner concentration difference (%) and the additional stirring time.
13, the developer control unit 120Y increases the stirring time when the difference exceeds 0.5%. More specifically, the developer control unit 120Y increases the added stirring time when the difference increases. More specifically, the developer control unit 120Y adds a time determined by the difference to the predetermined time Tb to set the stirring time for stirring #2.

Experiments have shown that this process can completely eliminate the polarization of developer D.

[Embodiment 2]
In the first embodiment, in order to eliminate the generated polarization, the developer in the second storage chamber 39 is caused to flow within the second storage chamber 39 by further stirring #2 by the stirring unit 150. In the present embodiment, a configuration will be described in which the developer in the second storage chamber 39 is caused to flow within the second storage chamber 39 by vibrating the developing unit 13Y including the second storage chamber 39, instead of stirring #2.

Note that the following will describe the differences from embodiment 1, and will not repeat the explanation of the same points as in embodiment 1. Also, in this example, the explanation will mainly focus on the yellow developer 6Y.

FIG. 14 is a diagram for explaining the vibration generator 190Y.
14, the vibration generator 190Y is provided near the end of the developing unit 13Y. The vibration generator 190Y includes a positioning member 191, a cam member 192, and a spring member 193 which is a biasing member.

The positioning member 191 restricts the movement of the developing unit 13Y in the positive direction along the Z axis. When the end of the developing unit 13Y abuts against the positioning member, the movement of the developing unit 13Y in the positive direction along the Z axis stops.

The spring member 193 has a spring and a base portion to which one end of the spring is fixed. The base portion is fixed. The spring member 193 is provided on the opposite side of the developing unit 13Y to the positioning member 191 and the cam member 192.

The spring biases the developing unit 13Y in the positive direction of the Z axis. More specifically, the spring biases the end of the developing unit 13Y in the positive direction of the Z axis.

The cam member 192 rotates around the central axis N. The cam member 192 rotates under the control of the developing unit 6Y. When the cam is in the state shown in FIG. 14, the spring is compressed and the end of the developing unit 13Y (the end on the right side in the figure) is separated from the positioning member 191.

Figure 15 is a diagram showing the state in which the cam has rotated further from the state shown in Figure 14. In detail, Figure 15 is a diagram showing the state in which the cam member 192 has rotated by an angle θ (0 degrees < θ < 90 degrees) from the state shown in Figure 14. Referring to Figure 15, when the cam member 192 rotates from the state shown in Figure 14, the restoring force of the spring moves the developing unit 13Y in the positive direction of the Z axis.

After that, as the cam member 192 continues to rotate, the developer 6Y repeatedly moves in the positive and negative directions on the Z axis.

In this way, by vibrating the developing unit 13Y including the second storage chamber 39 using the vibration generating device 190Y, it is possible to cause the developer in the second storage chamber 39 to flow within the second storage chamber 39. As a result, it is possible to eliminate the polarization of the developer that has occurred.

Figure 16 is a schematic diagram for explaining the control unit of the image forming device 1 according to this embodiment.

Referring to FIG. 16, the control unit 100A (controller) that operates each unit of the image forming device 1 includes a main control unit 51, a yellow developer control unit 120Y, a magenta developer control unit 120M, a cyan developer control unit 120C, a black developer control unit 120B, a yellow vibration control unit 170Y, a magenta vibration control unit 170M, a cyan vibration control unit 170C, and a black vibration control unit 170B.

Control unit 100A differs from control unit 100 of embodiment 1 in that it includes vibration control units 170Y, 170M, 170C, and 170B, which do not include these.

The vibration control unit 170Y controls the operation of the vibration generating device 190Y for yellow. More specifically, the vibration control unit 170Y controls the rotation of the cam member 192. Similarly, the vibration control units 170M, 170C, and 170B control the operation of the vibration generating devices 190C, 190M, and 190B for each color, respectively.

Each of the vibration control units 170Y, 170M, 170C, and 170B is also realized by a processor such as a CPU executing a program stored in memory. Each of the vibration control units 170Y, 170M, 170C, and 170B may be realized by hardware such as an ASIC. Note that, although FIG. 16 shows an example in which the control unit 100 is composed of multiple control units, this is not limiting. A single control unit (e.g., a single control board) may be configured to control the entire image forming device 1.

The vibration control unit 170Y may also change the rotation speed of the cam member 192. By such processing, the movement speed (vibration period) of the developing unit 6Y can be changed. The same applies to the other vibration control units 170M, 170C, and 170B.

In addition, the image forming device 1 may perform both stirring #2 of the first embodiment and the vibration operation of the present embodiment in order to eliminate the polarization that has occurred. By performing stirring #2 and the vibration operation, the image forming device 1 can eliminate the polarization earlier than if only one of the processes was performed.

Both stirring #2 of embodiment 1 and the vibration operation of this embodiment may be performed simultaneously, or may be performed alternately. The timing and order are not particularly limited. For example, the image forming device 1 may perform the vibration operation if the polarization is not resolved even after performing stirring #2 of embodiment 1.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Image forming apparatus, 2C, 2K, 2M, 2Y Imaging section, 3 Intermediate transfer section, 4 Feeding section, 5 Fixing section, 5a Heating roller, 5b Pressure roller, 6B, 6C, 6M, 6Y Developing device, 7C, 7K, 7M, 7Y Toner hopper, 8Y Permeability sensor, 9C, 9K, 9M, 9Y Toner concentration control section, 10C, 10K, 10M, 10Y Photoconductor drum, 11C, 11K, 11M, 11Y Charging section, 12 Exposure section, 13C13K, 13C, 13K, 13M, 13Y Developing section, 14C, 14K, 14M, 14Y, 20 Cleaner, 15 Intermediate transfer belt, 16 Driving roller, 17 Driven roller, 18C, 18K, 18M, 18Y Primary transfer roller, 19 Secondary transfer roller, 19a secondary transfer position, 21 delivery roller, 22 timing roller, 23 discharge roller, 24 paper discharge tray, 29 development position, 30 housing, 30z side wall, 31 development roller, 31a development sleeve, 31b magnet body, 32 supply screw, 32a, 33a rotation shaft, 32b, 33b screw blade, 32z, 33z shaft portion, 33 stirring screw, 34 regulating member, 37 partition wall, 37a, 37b communication hole, 38 first storage chamber, 39 second storage chamber, 39a receiving port, 39z downstream end portion, 51 main control unit, 81 detection area, 82, 83, D developer, 98 first transport path, 99 second transport path, 100, 100A control unit, 120B, 120C, 120M, 120Y developer control unit, 121 Supply amount calculation unit, 122 judgment unit, 130C, 130K, 130M, 130Y toner supply unit, 140 toner concentration detection unit, 150 stirring unit, 170B, 170C, 170M, 170Y vibration control unit, 182 temperature sensor, 184 humidity sensor, 190B, 190C, 190M, 190Y vibration generator, 191 positioning member, 192 cam member, 193 spring member, W straight line, L light beam, N central axis, R1, R2, R3 area, S sheet, T1, T2B, T2, T2A, T3, T4 arrows.

Claims (17)

a storage chamber for storing a developer including a toner;
a stirring means for stirring the developer in the developer storage chamber;
a detection means for detecting a concentration of the toner at a predetermined location in the storage chamber;
a supplying means for supplying the toner to the storage chamber;
a control means for controlling the supply means to supply toner and the stirring means to perform stirring,
An image forming apparatus, wherein the control means executes control to cause the developer in the storage chamber to flow within the storage chamber when a predetermined amount of the toner is supplied by the replenishing means and a first stirring is performed by the stirring means and the concentration does not become equal to or greater than a predetermined value. The control means
Further controlling an image forming operation in the image forming apparatus,
2. The image forming apparatus according to claim 1, wherein the image forming operation is stopped when the developer in the container chamber is caused to flow within the container chamber. The image forming apparatus according to claim 1 or 2, wherein the control means stops the supply of the toner by the supply means when the developer in the storage chamber is caused to flow within the storage chamber. The image forming apparatus according to any one of claims 1 to 3, wherein the control means causes the developer in the storage chamber to flow within the storage chamber by the second stirring by the stirring means. The image forming device according to claim 4, wherein the control means executes control to forcibly discharge the toner from the storage chamber when the second stirring is being performed. The image forming apparatus according to claim 4 or 5, wherein the second stirring includes stirring at a first stirring speed and stirring at a second stirring speed. Further comprising a vibration means for vibrating the storage chamber,
4. The image forming apparatus according to claim 1, wherein the control means causes the vibration means to vibrate the container chamber, thereby causing the developer in the container chamber to flow within the container chamber. Further comprising a vibration means for vibrating the storage chamber,
7. The image forming apparatus according to claim 4, wherein the control means causes the developer in the storage chamber to flow within the storage chamber by causing the vibration means to vibrate the storage chamber and by performing a second agitation by the agitation means. 9. The image forming apparatus according to claim 4, wherein the control unit determines a length of the mixing time of the second mixing based on any one of the concentration detected by the detection unit, environmental information indicating an environment surrounding the image forming apparatus, and operation information indicating an operation record of the image forming apparatus. The environmental information includes temperature and humidity information,
10. The image forming apparatus according to claim 9, wherein the control means, when the temperature is a first temperature and the humidity is a first humidity, makes the stirring time of the second stirring longer than when the temperature is a second temperature lower than the first temperature and the humidity is a second humidity lower than the first humidity. The environmental information includes temperature and humidity information,
10. The image forming apparatus according to claim 9, wherein the control means, when the temperature is a first temperature and the humidity is a first humidity, makes the stirring time of the second stirring longer than when the temperature is a second temperature higher than the first temperature and the humidity is a second humidity higher than the first humidity. The environmental information includes temperature information,
10. The image forming apparatus according to claim 9, wherein the control unit extends a stirring time of the second stirring when the temperature becomes equal to or higher than a first reference temperature or equal to or lower than a second reference temperature that is lower than the first reference temperature. The environmental information includes humidity information,
10. The image forming apparatus according to claim 9, wherein the control unit extends a stirring time of the second stirring when the humidity becomes equal to or higher than a first reference humidity or equal to or lower than a second reference humidity that is lower than the first reference humidity. The operation information includes information on the number of printed sheets of the image forming apparatus,
The image forming apparatus according to claim 9 , wherein the control unit extends the stirring time of the second stirring as the number of printed sheets increases. the operation information includes information about a driving time of the image forming apparatus,
15. The image forming apparatus according to claim 9, wherein the control unit is configured to increase the stirring time of the second stirring as the driving time increases. The image forming apparatus according to claim 9, wherein the control means increases the mixing time of the second mixing as the difference between the density detected by the detection means and the predetermined value increases. A method for controlling an image forming apparatus having a storage chamber for storing a developer including a toner, comprising the steps of:
agitating the developer in the developer chamber;
detecting a concentration of the toner at a predetermined location in the storage chamber;
replenishing the toner to the storage chamber;
a step of causing the developer in the storage chamber to flow within the storage chamber, provided that when a predetermined amount of the toner is supplied and the stirring is performed, the concentration does not exceed a predetermined value.

Images