Image formation device

Abstract

To properly implement control in responce to a level of a developer.SOLUTION: An image formation device comprises: a developing device that has a first magnetic permeability sensor, and second magnetic permeability sensor; a drive unit that rotates to drive a conveyance screw; a developer replenishment unit; an oscillation-application unit that applies oscillation to the developing device; and a control unit. A second detection unit of the second magnetic permeability sensor exists upward in a vertical direction with respect to a first detection unit of the first magnetic permeability sensor. The control unit is configured to: implement first control of controlling the developer replenishment unit to replenish the developer to a developer container on the basis of an output value of the first magnetic permeability sensor during a period of the drive unit rotating for driving the conveyance screw; and implement second control of controlling the oscillation-application unit to implement an oscillation action applying the oscillation to the developing device on the basis of an output value of the second magnetic permeability sensor for a period of the drive unit rotating for driving the conveyance screw.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having a plurality of these functions.

Background Art

[0002] In an image forming apparatus using an electrophotographic method, an electrostatic latent image formed on an image carrier is developed into a toner image by a developing device. As such a developing device, one using a two-component developer having toner and a magnetic carrier has been conventionally used. In a developing device using a two-component developer, for the purpose of suppressing the deterioration of the carrier, toner containing a small amount of the carrier is supplied to the developing device, and accordingly, the surplus developer is discharged outside the developing device. The so-called ACR (Auto Carrier Refresh) method is widely adopted.

[0003] In an ACR type developing device, in order to keep the quality of the developed image constant, it is required to maintain a constant amount of developer in the developing device. In Patent Document 1, a sensor for detecting the surface height (bulk height) of the developer in the developing device is used to indirectly predict the amount of developer in the developing device, and the amount of developer in the developing device is adjusted according to the result, for example, by controlling the rotation speed of a conveying screw. A developing device has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the developing device of Patent Document 1, the height of the developer surface is detected by measuring the magnetic permeability of the developer in the developing device. In an inductance sensor that measures the magnetic permeability of the developer, a change in the abundance of magnetic carriers contained in the developer is detected as a change in the apparent magnetic permeability. As a result, when the developer surface rises, the magnetic permeability increases due to an increase in magnetic carriers near the sensor, and the output value of the sensor rises. Conversely, when the surface level drops and the magnetic carriers near the sensor decrease, the output value of the sensor drops. From the relationship between the output response of the sensor to such changes in the developer surface, the developer surface can be accurately predicted.

[0006] However, as the use of the developing device continues, the fluidity of the developer in the developing device may decrease. And when the fluidity of the developer decreases, an immobile layer of the developer may be formed near the detection surface of the inductance sensor that detects the developer surface. In such a case, the output value of the inductance sensor is saturated near the upper limit value under the influence of the immobile layer, and there is a risk that the developer surface cannot be detected correctly.

[0007] In the case of the configuration described in Patent Document 1, when the height of the developer surface becomes higher than the upper limit from the output value of the sensor, a developer discharge mode is executed in which the discharge amount of the developer is increased by increasing the speed of the conveyance screw or the like. For this reason, if the output value of the inductance sensor is saturated near the upper limit value due to the influence of the immobile layer and the developer surface cannot be detected correctly, the developer discharge mode cannot be appropriately performed.

[0008] An object of the present invention is to provide an image forming apparatus capable of appropriately executing control according to the surface level of the developer.

Means for Solving the Problems

[0009] One aspect of the present invention is an image forming apparatus including an image carrier, a developer carrier that carries a developer including toner and carrier for developing an electrostatic latent image formed on the image carrier, a developing container that stores the developer supplied to the developer carrier, a conveying screw that conveys the developer stored in the developing container, a developer discharging portion for discharging a part of the developer stored in the developing container, a first magnetic permeability sensor having a first detecting portion that detects the magnetic permeability of the developer stored in the developing container, a second magnetic permeability sensor having a second detecting portion that detects the magnetic permeability of the developer stored in the developing container, a driving portion that rotationally drives the conveying screw, a developer replenishing portion that replenishes the developing container with the developer, a vibration applying portion that applies vibration to the image forming apparatus, and a control portion. The second detecting portion is located vertically above the first detecting portion. The control portion executes a first control for controlling the developer replenishing portion to replenish the developing container with the developer based on an output value of the first magnetic permeability sensor while the driving portion rotationally drives the conveying screw, and the control portion executes a second control for controlling the vibration applying portion to execute a vibration applying operation for applying vibration to the image forming apparatus based on an output value of the second magnetic permeability sensor while the driving portion rotationally drives the conveying screw.

[0010] One aspect of the present invention is an image forming apparatus including an image carrier; a developer carrier that carries a developer including toner and carrier for developing an electrostatic latent image formed on the image carrier; a developer container that stores the developer supplied to the developer carrier; a conveyance screw that conveys the developer stored in the developer container; a developer discharge portion for discharging a part of the developer stored in the developer container; a first magnetic permeability sensor having a first detection portion for detecting the magnetic permeability of the developer stored in the developer container; a second magnetic permeability sensor having a second detection portion for detecting the magnetic permeability of the developer stored in the developer container; a drive portion that rotationally drives the conveyance screw; a developer supply portion that supplies the developer to the developer container; a vibration application portion that applies vibration to the image forming apparatus; and a control portion, wherein the second detection portion is located vertically above the first detection portion, and the control portion executes a first control for controlling the developer supply portion to supply the developer to the developer container based on an output value of the first magnetic permeability sensor while the drive portion rotationally drives the conveyance screw, and the control portion executes a second control for controlling the vibration application portion to execute a vibration application operation for applying vibration to the image forming apparatus when an absolute value of a difference between a maximum output value and a minimum output value of the second magnetic permeability sensor while the drive portion rotationally drives the conveyance screw for a predetermined time is smaller than a predetermined value, and does not execute the second control when the absolute value of the difference between the maximum output value and the minimum output value of the second magnetic permeability sensor while the drive portion rotationally drives the conveyance screw for the predetermined time is equal to or greater than the predetermined value.

[0011] One aspect of the present invention is an image forming apparatus including an image carrier, a developer carrier that carries a developer including toner and carrier for developing an electrostatic latent image formed on the image carrier, a developing container that stores the developer supplied to the developer carrier, a conveying screw that conveys the developer stored in the developing container, a developer discharging unit for discharging a part of the developer stored in the developing container, a first magnetic permeability sensor having a first detection unit for detecting the magnetic permeability of the developer stored in the developing container, a second magnetic permeability sensor having a second detection unit for detecting the magnetic permeability of the developer stored in the developing container, a driving unit that rotationally drives the conveying screw, a developer supply unit that supplies the developer to the developing container, a vibration applying unit that applies vibration to the image forming apparatus, and a control unit. The second detection unit is located vertically above the first detection unit. The control unit executes a first control for controlling the developer supply unit to supply the developer to the developing container based on an output value of the first magnetic permeability sensor while the driving unit rotationally drives the conveying screw. When an integrated value of an output value of the second magnetic permeability sensor while the driving unit rotationally drives the conveying screw for a predetermined time is greater than a predetermined integrated value, the control unit executes a second control for controlling the vibration applying unit to execute a vibration applying operation for applying vibration to the image forming apparatus. When the integrated value of the output value of the second magnetic permeability sensor while the driving unit rotationally drives the conveying screw for the predetermined time is less than or equal to the predetermined integrated value, the second control is not executed.

[0012] One aspect of the present invention includes an image carrier, a developer carrier that carries a developer containing toner and a carrier for developing an electrostatic latent image formed on the image carrier, a developer container that houses the developer supplied to the developer carrier, a transport screw that transports the developer housed in the developer container, a developer discharge unit for discharging a part of the developer housed in the developer container, a first magnetic permeability sensor having a first detection unit for detecting the magnetic permeability of the developer housed in the developer container, a second magnetic permeability sensor having a second detection unit for detecting the magnetic permeability of the developer housed in the developer container, a driving unit that rotationally drives the transport screw, a developer supply unit that supplies the developer to the developer container, a vibration unit that applies vibration to the image forming apparatus, and a control unit. The second detection unit is located vertically above the first detection unit. The control unit executes a first control for controlling the developer supply unit to supply the developer to the developer container based on an output value of the first magnetic permeability sensor while the driving unit rotationally drives the transport screw. When a standard deviation of an output value of the second magnetic permeability sensor while the driving unit rotationally drives the transport screw for a predetermined time is smaller than a predetermined standard deviation, the control unit executes a second control for controlling the vibration unit to execute a vibration operation for applying vibration to the image forming apparatus. When the standard deviation of the output value of the second magnetic permeability sensor while the driving unit rotationally drives the transport screw for the predetermined time is equal to or greater than the predetermined standard deviation, the second control is not executed. An image forming apparatus is characterized by this.

Advantages of the Invention

[0013] According to the present invention, control according to the surface of the developer can be appropriately executed.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0015] <The First Embodiment> The first embodiment will be described with reference to FIGS. 1 to 13. First, the schematic configuration of the image forming apparatus according to this embodiment will be described with reference to FIG. 1.

[0016] [Image Forming Apparatus] The image forming apparatus 100 is a full-color image forming apparatus, and in this embodiment, for example, it is an MFP (Multi-Function Peripheral) having a copy function, a printer function, and a scan function. As shown in FIG. 1, the image forming apparatus 100 is provided with image forming units PY, PM, PC, and PK that perform the image forming processes of yellow, magenta, cyan, and black toner images in parallel.

[0017] Each color image forming unit PY, PM, PC, and PK includes a primary charger 21Y, 21M, 21C, 21K, a developing device 1Y, 1M, 1C, 1K, an optical writing unit (exposure device) 22Y, 22M, 22C, 22K, a photosensitive drum 28Y, 28M, 28C, 28K, and a cleaning device 26Y, 26M, 26C, 26K. Further, the image forming apparatus 100 includes a transfer device 2 and a fixing device 3. Since the configurations of the image forming units PY, PM, PC, and PK for each color are the same, hereinafter, the image forming unit PY will be described as a representative.

[0018] The photosensitive drum 28Y as a rotatable image carrier is a photoreceptor having a photosensitive layer made of a resin such as polycarbonate containing an organic photo conductor (OPC), and is configured to rotate at a predetermined speed. The primary charger 21Y is composed of a corona discharge electrode disposed around the photosensitive drum 28Y, and charges the surface of the photosensitive drum 28Y with the generated ions.

[0019] The optical writing unit 22Y incorporates a scanning optical device and exposes the charged photosensitive drum 28Y based on image data, thereby reducing the potential of the exposed portions and forming a charge pattern (electrostatic latent image) corresponding to the image data. The developing device 1Y transfers the contained developer onto the photosensitive drum 28Y to develop the electrostatic latent image formed on the photosensitive drum 28Y. The developer is formed by mixing a carrier and toner corresponding to each color, and the electrostatic latent image is visualized by the toner.

[0020] The transfer device 2 includes primary transfer rollers 23Y, 23M, 23C, 23K, an intermediate transfer belt 24, and a secondary transfer roller 25. The intermediate transfer belt 24 is wound by the primary transfer rollers 23Y, 23M, 23C, 23K and a plurality of rollers and is supported so as to be capable of running. The primary transfer rollers 23Y, 23M, 23C, 23K correspond to the respective colors of Y (yellow), M (magenta), C (cyan), and K (black) in order from the top in FIG. 1. The secondary transfer roller 25 is disposed outside the intermediate transfer belt 24 and is configured such that a recording material can pass between the secondary transfer roller 25 and the intermediate transfer belt 24. The recording material is, for example, a sheet such as paper or a plastic sheet.

[0021] The toner images of each color formed on the photosensitive drums 28Y, 28M, 28C, 28K are sequentially transferred onto the intermediate transfer belt 24 by the primary transfer rollers 23Y, 23M, 23C, 23K, and a color toner image in which layers of yellow, magenta, cyan, and black are superimposed is formed. The formed toner image is transferred by the secondary transfer roller 25 onto a recording material conveyed from a cassette or the like in which the recording material is accommodated. The recording material onto which the toner image is transferred is subjected to pressure and heat in the fixing device 3. Thereby, the toner on the recording material is melted and the color image is fixed to the recording material.

[0022] The developer storage units 27Y, 27M, 27C, and 27K are respectively provided corresponding to the developing devices 1Y, 1M, 1C, and 1K. Bottles for storing developers corresponding to the respective colors of yellow, magenta, cyan, and black are loaded in a replaceable manner in order from above. The developer storage units 27Y, 27M, 27C, and 27K are configured to be able to convey (supply) the developer to the developing devices 1Y, 1M, 1C, and 1K corresponding to the color of the stored developer.

[0023] For example, the toner weight ratio of the developer stored in the bottle (that is, the toner concentration: the ratio of the toner weight to the total weight of the carrier and the toner) is 80 to 95%, and the toner weight ratio of the developer in the developing devices 1Y, 1M, 1C, and 1K is 5 to 10%. Therefore, when the toner is consumed by development in the developing devices 1Y, 1M, 1C, and 1K, a developer containing toner corresponding to the consumption amount is supplied, and the toner weight ratio of the developer in the developing devices 1Y, 1M, 1C, and 1K is maintained constant.

[0024] [Control Configuration] FIG. 2 is a control block diagram showing the main part of the control system of the image forming apparatus 100. The image forming apparatus 100 includes an operation unit 96, an image forming unit 97, a recording material conveyance unit 98, a fixing unit 99, and a control unit 80. The operation unit 96 has a display unit capable of displaying various information, operation buttons, and the like. The display unit may be a touch panel capable of touch operation. The image forming unit 97 includes various motors for driving the configurations such as the photosensitive drums 28Y, 28M, 28C, and 28K of the image forming units PY, PM, PC, and PK for forming an image on the recording material and the developing devices 1Y, 1M, 1C, and 1K as described above, and a power source for applying a voltage to these configurations. The image forming unit 97 has a drive unit 94 such as a motor for rotationally driving the developer supply screw 42 and the developer stirring screw 43 described later. The recording material conveyance unit 98 includes various motors for driving the conveyance rollers for conveying the recording material. The fixing unit 99 includes a heater of the fixing device 3 and a motor for driving the fixing device. These operation unit 96, image forming unit 97, recording material conveyance unit 98, and fixing unit 99 are connected to the control unit 80 and are controlled by the control unit 80.

[0025] The control unit 80 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, etc. The CPU 81 reads out a program according to the processing content from the ROM 82 and expands it in the RAM 83, and controls the operations of the respective components of the image forming apparatus 100 in cooperation with the expanded program. At this time, various data stored in the storage unit 91 are referred to.

[0026] The storage unit 91 is composed of, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive. The control unit 80 performs transmission and reception of various data with an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 92. The control unit 80 receives, for example, image data (input image data) transmitted from an external device, and forms an image on a recording material based on this image data. The communication unit 92 is composed of a communication control card such as a LAN card.

[0027] Further, the control unit 80 is connected to a toner density sensor 49, a developer surface detection sensor 50, a supply unit 93, and a vibration device 200. The toner density sensors 49 are respectively provided in the developing devices 1Y, 1M, 1C, and 1K, and detect the toner density of the developer in the developing devices 1Y, 1M, 1C, and 1K as will be described later. The developer surface detection sensors 50 are also respectively provided in the developing devices 1Y, 1M, 1C, and 1K, and detect the surface of the developer in the developing devices 1Y, 1M, 1C, and 1K as will be described later. The supply unit 93 as a developer supply unit includes a motor that drives a supply mechanism for supplying developer from the developer storage units 27Y, 27M, 27C, and 27K to the developing devices 1Y, 1M, 1C, and 1K. The vibration device 200 applies vibration to the developing devices 1Y, 1M, 1C, and 1K as will be described later. The control unit 80 controls the supply unit 93 and the vibration device 200 based on the detection results of the toner density sensor 49 and the developer surface detection sensor 50.

[0028] [Developing device] Next, the developing devices 1Y, 1M, 1C, and 1K will be described in detail with reference to FIGS. 3 and 4. Since the configurations of the developing devices 1Y, 1M, 1C, and 1K are the same, hereinafter, the developing device 1Y will be described as a representative. FIG. 3 is a conceptual diagram for explaining the developing device 1Y shown in FIG. 1, and FIG. 4 is a schematic view of the developing device 1Y seen from above after being cut in a direction parallel to the rotation axis direction of the first developing roller 30.

[0029] As shown in FIG. 3, the developing device 1Y includes a first developing roller 30, a second developing roller 31, a peeling roller 32, a developer supply screw 42, a developer stirring screw 43, and a developer recovery screw 44, and these members are housed in a developing container 60.

[0030] The first developing roller 30 is a rotatably driven developer carrier (developing rotating body), and is arranged at a position adjacent to the photosensitive drum 28Y such that its rotation axis is substantially parallel to the rotation axis of the photosensitive drum 28Y. The first developing roller 30 includes a rotating first sleeve 33 and a first magnet (fixed magnet) 36 that is non-rotatably arranged inside the first sleeve 33 and adsorbs the developer to the surface of the first sleeve 33 by magnetic force. Then, the first developing roller 30 adsorbs (carries) the developer pumped up from the developer supply screw 42 based on magnetic force, and develops the electrostatic latent image formed on the rotating photosensitive drum 28Y (on the image carrier) with the developer.

[0031] The first sleeve 33 is a non-magnetic cylindrical member and is rotationally driven about the rotation axis 39. The rotation direction of the first sleeve 33 is clockwise as shown by the arrow in FIG. 3, and in this embodiment, it is in the direction opposite to the rotation direction of the photosensitive drum 28Y. For this reason, the first sleeve 33 and the photosensitive drum 28Y rotate in the same direction at positions facing each other. That is, it is forward development in which the photosensitive drum 28 rotates from vertically downward to vertically upward at the position where the photosensitive drum 28 faces the first sleeve 33. A space that allows the rotation of the first sleeve 33 is arranged between the inner circumference of the first sleeve 33 and the outer circumference of the first magnet 36.

[0032] The developer adsorbed on the first sleeve 33 is conveyed toward the photosensitive drum 28Y by the rotation of the first sleeve 33 to develop the latent image formed on the photosensitive drum 28Y. After developing the latent image formed on the photosensitive drum 28Y, the developer on the first sleeve 33 is conveyed by the rotation of the first sleeve 33 to the vicinity of the second developing roller 31. Then, in the vicinity of the closest position between the first developing roller 30 and the second developing roller 31, due to the magnetic field generated by the first magnet 36 enclosed in the first developing roller 30 and the second magnet 37 enclosed in the second developing roller 31, the developer is peeled off from the first sleeve 33 and transferred onto the second sleeve 34.

[0033] As described below, the second developing roller 31 of the developing device 1Y of the present embodiment is disposed vertically above the first developing roller 30. Therefore, it is also necessary to transfer the developer from the first sleeve 33 to the second sleeve 34 against gravity from vertically downward to upward. Note that the first sleeve 33 and the second sleeve 34 are disposed with a predetermined gap at their closest part.

[0034] The second developing roller 31 is a rotatably driven developer carrier (developing rotator), and is disposed downstream of the first developing roller 30 with respect to the rotation direction of the photosensitive drum 28Y, and the rotation center O2 of the second developing roller 31 is located above the rotation center O1 of the first developing roller 30 in the vertical direction, so that the developer is transferred from the first developing roller 30 by magnetic force. In the present embodiment, the entire second developing roller 31 is located above the rotation center O1 of the first developing roller 30. Similar to the first developing roller 30, the second developing roller 31 is disposed at a position adjacent to the photosensitive drum 28Y such that its rotation axis is substantially parallel to the rotation axis of the photosensitive drum 28Y. Therefore, the rotation axes of the second developing roller 31 and the first developing roller 30 are substantially parallel to each other.

[0035] Such a second developing roller 31 includes a rotating second sleeve 34 and a second magnet (fixed magnet) 37 that is non-rotatably disposed inside the second sleeve 34 and adsorbs a developer to the surface of the second sleeve 34 by magnetic force. Then, based on magnetic force, the second developing roller 31 receives the developer from the first developing roller 30 (first sleeve 33), adsorbs (carries) it, and develops an electrostatic latent image formed on the rotating photosensitive drum 28Y with the developer. Note that a peeling roller 32, which will be described later, is positioned on the side of the second developing roller 31.

[0036] The second sleeve 34 is a non-magnetic cylindrical member and is rotationally driven about a rotation axis 40. The rotation direction of the second sleeve 34 is the same as that of the first sleeve 33, i.e., clockwise as indicated by the arrow in FIG. 3. In the present embodiment, it is the reverse direction of the rotation direction of the photosensitive drum 28Y. For this reason, the second sleeve 34 and the photosensitive drum 28Y rotate in the same direction at positions facing each other. That is, it is a forward development in which the photosensitive drum 28 rotates from vertically downward to vertically upward at the position where the photosensitive drum 28 faces the second sleeve 34. Also, the second sleeve 34 and the first sleeve 33 rotate in opposite directions at positions facing each other. A space that allows the rotation of the second sleeve 34 is disposed between the inner circumference of the second sleeve 34 and the outer circumference of the second magnet 37.

[0037] The developer adsorbed on the second sleeve 34 is conveyed toward the photosensitive drum 28Y by the rotation operation of the second sleeve 34, and develops the latent image formed on the photosensitive drum 28Y. After developing the latent image formed on the photosensitive drum 28Y, the developer remaining on the second sleeve 34 is conveyed to the vicinity of the peeling roller 32 by the rotation operation of the second sleeve 34. Then, in the vicinity of the closest position between the second developing roller 31 and the peeling roller 32, the developer is transferred from the second sleeve 34 to the third sleeve 35 of the peeling roller 32 by the magnetic field generated by the second magnet 37 included in the second developing roller 31 and the third magnet 38 included in the peeling roller 32.

[0038] The peeling roller 32 as the peeling part is arranged on the side opposite to the photosensitive drum 28Y with respect to the rotation center of the second sleeve 34, and peels off the developer after developing the electrostatic latent image on the photosensitive drum 28Y by the second developing roller 31 from the second developing roller 31. Specifically, the peeling roller 32 is a developer carrier that is rotationally driven, and is arranged between the second developing roller 31 and the developer recovery screw 44 such that its rotation center is above the rotation center R of the second developing roller 31.

[0039] Also, the peeling roller 32 is arranged such that its rotation axis is substantially parallel to the rotation axis of the second developing roller 31. Such a peeling roller 32 has a rotating third sleeve 35 and a third magnet (fixed magnet) 38 that is non-rotationally arranged inside the third sleeve 35 and adsorbs the developer to the surface of the third sleeve 35 by magnetic force, and is configured to transfer the developer from the second developing roller 31 based on magnetic force.

[0040] The third sleeve 35 is a non-magnetic cylindrical member and is rotationally driven about the rotation shaft 41. The rotation direction of the third sleeve 35 is counterclockwise as shown by the arrow in FIG. 3, and in this embodiment, it is opposite to the rotation direction of the second sleeve 34. For this reason, the third sleeve 35 and the second sleeve 34 rotate in the same direction at positions facing each other. A space that allows the rotation of the third sleeve 35 is arranged between the inner circumference of the third sleeve 35 and the outer circumference of the third magnet 38.

[0041] The developer adsorbed on the third sleeve 35 is conveyed to the downstream side in the rotation direction by the rotation operation of the third sleeve 35, and at a position close to the developer recovery screw 44, is peeled off from the third sleeve 35 by the third magnet 38 included in the peeling roller 32, and falls toward the guide member 45 located vertically downward by its own weight. Then, the developer that has fallen onto the guide member 45 is guided by its own weight toward the developer recovery screw 44.

[0042] The guide member 45 and the developer recovery screw 44 constitute a developer recovery unit 47 as a recovery unit that recovers the developer peeled from the third sleeve 35 on the peeling roller 32. In the developer recovery unit 47, the developer recovery screw 44 is arranged such that the center of rotation is located below the center of rotation of the peeling roller 32 with respect to the vertical direction, and conveys (recovers) the developer delivered from the peeling roller 32 while stirring it.

[0043] The guide member 45 as a guide part is arranged vertically below the peeling roller 32, and guides the developer peeled by the peeling roller 32 toward the developer recovery screw 44. Such a guide member 45 has an inclined surface 45a on which the peeled developer slides down due to its own weight in order to more reliably guide the peeled developer toward the developer recovery screw 44. The inclined surface 45a is inclined with respect to the horizontal direction such that the side closer to the developer recovery screw 44 is lower than the position below the peeling roller 32.

[0044] The developer recovery screw 44 as a recovery member and a conveyance part conveys the recovered developer to a developer circulation part 46 described below. That is, the developer recovery screw 44 is a screw conveyance member used to convey the developer recovered by sliding down the inclined surface of the guide member 45 in one direction while stirring it.

[0045] The developer circulation part 46 is a supply part for supplying the developer to the first developing roller 30. The developer circulation part 46 includes a regulating member 52, a developer supply screw 42 as a first conveyance screw, and a developer stirring screw 43 as a second conveyance screw. The developer supply screw 42 and the developer stirring screw 43 are rotationally driven by a drive part 94. In the developer circulation part 46, the developer is conveyed substantially horizontally while being stirred in the developer supply screw 42 and the developer stirring screw 43, and is supplied to the first developing roller 30. Also, as described above, the developer recovered by the developer recovery unit 47 falls due to its own weight and is introduced into the developer circulation part 46.

[0046] The developer supply screw 42, the developer agitation screw 43, and the developer recovery screw 44 are screw conveyance members that convey the developer in one direction while agitating it. The developer supply screw 42 and the developer agitation screw 43 are located vertically below the developer recovery screw 44. Also, these developer supply screw 42, developer agitation screw 43, and developer recovery screw 44 are arranged such that their rotation axes are substantially parallel to each other. The rotation axes of these respective screws are also substantially parallel to the rotation axis of the first developing roller 30.

[0047] The developer supply screw 42 is located between the first developing roller 30 and the developer agitation screw 43, and a partition wall 48 of the developing container 60 is arranged between the developer supply screw 42 and the developer agitation screw 43. The partition wall 48 of the developing container 60 extends along the rotation axis direction of the developer supply screw 42 and the developer agitation screw 43. The partition wall 48 is provided with communication ports 48a, 48b (FIG. 4) that communicate a first conveyance path 61 as a first chamber in which the developer is conveyed by the developer supply screw 42 and a second conveyance path 62 as a second chamber in which the developer is conveyed by the developer agitation screw 43. And a circulation path of the developer is formed between the first conveyance path 61 and the second conveyance path 62.

[0048] The developer agitated by the developer recovery screw 44 falls by its own weight toward the developer supply screw 42 via a communication port (not shown) formed in a partition wall 63 of the developing container 60 that is between the developer recovery screw 44 and the developer supply screw 42. That is, the developer agitated by the developer recovery screw 44 is introduced into the developer supply screw 42. Note that the above-described guide member 45 is integrally formed with the partition wall 63, and the developer recovery screw 44 is arranged above the partition wall 63.

[0049] The position of the communication port where the developer agitated by the developer recovery screw 44 falls by its own weight and is introduced into the developer circulation unit 46 is preferably arranged so as to avoid the area where the developer is being supplied toward the first developing roller 30 (the intermediate part in the axial direction of the developer supply screw 42). In the present embodiment, the position of the communication port is set to a position included in the range of the downstream end (terminal end) in the developer conveyance direction of the first conveyance path 61 where the developer supply screw 42 is arranged.

[0050] The developer conveyance directions of the developer supply screw 42 and the developer agitation screw 43 are opposite to each other as indicated by the arrows in FIG. 4. And the start end side (the upstream end side in the developer conveyance direction) and the end side (the downstream end side in the developer conveyance direction) of the first conveyance path 61 where the developer supply screw 42 is arranged communicate with the end side and the start end side of the second conveyance path 62 where the developer agitation screw 43 is arranged via the communication ports 48a and 48b provided in the partition wall 48. Therefore, the developer circulates in the developing container 60 in the substantially horizontal direction in the rotation directions of the developer supply screw 42 and the developer agitation screw 43 indicated by the arrows in FIG. 3, and a part of it is supplied toward the first developing roller 30.

[0051] The developer supply port 51 is arranged above the developer agitation screw 43 in the developing container 60 and is connected to the developer storage unit 27Y (see FIG. 1). And the developer supply port 51 is configured to be able to supply the developer stored in the bottle loaded in the developer storage unit 27Y to the second conveyance path 62 where the developer agitation screw 43 is arranged.

[0052] As described above, since the toner concentration (toner weight ratio) of the developer stored in the bottle of the developer storage unit 27Y is higher than the toner concentration of the developer in the developing device 1Y, it is possible to maintain the toner weight ratio of the developer in the developing device 1 constant by adjusting the developer supplied to the developer agitation screw 43.

[0053] As shown in FIG. 4, the developer discharge unit 53 is disposed at the most downstream position in the developer conveyance direction of the developer supply screw 42, and discharges the surplus developer in the developing device 1Y from the developer discharge port 54 to the outside of the developing device 1Y. In the developer discharge unit 53, a screw 55 is formed whose developer conveyance direction is opposite to the developer conveyance direction of the developer supply screw 42. The screw 55 is provided coaxially with the developer supply screw 42, rotates together with the developer supply screw 42, and generates a flow that pushes the developer back from the developer discharge unit 53 toward the developer circulation unit 46.

[0054] Also, with respect to the developer conveyance direction of the developer supply screw 42, a screw 56 that conveys the developer in the same direction as the developer conveyance direction of the developer supply screw 42 is provided coaxially with the developer supply screw 42 and the screw 55 on the downstream side of the screw 55. The screw 56 rotates together with the developer supply screw 42 and the screw 55, conveys the developer that has been conveyed over the screw 55 to the developer discharge port 54, and discharges it from the developer discharge port 54.

[0055] Thereby, when the amount of developer in the developing device 1Y is appropriately maintained, the developer is pushed back by the screw 55, thereby suppressing the amount of developer discharged from the developer discharge port 54. On the other hand, when toner is replenished from the developer replenishment port 51 into the developing device 1Y and the amount of developer that attempts to move from the developer supply screw 42 to the developer discharge unit 53 increases, the developer moves over the screw 55 to the screw 56, and the surplus developer is discharged from the developer discharge port 54 to the outside of the developing device 1Y. At this time, if the rotation speeds of the developer supply screw 42 and the developer agitation screw 43 are increased, the developer easily moves to the developer discharge unit 53, so that the amount of developer discharged from the developer discharge port 54 can be increased. Conversely, if the rotation speeds of the developer supply screw 42 and the developer agitation screw 43 are decreased, the movement of the developer to the developer discharge unit 53 is suppressed, so that the amount of developer discharged from the developer discharge port 54 can be decreased.

[0056] The toner concentration sensor 49 as the second inductance sensor (first magnetic permeability sensor) is arranged to detect the toner concentration in the developer contained in the developer circulation unit 46. The toner concentration sensor 49 is an inductance sensor that detects the magnetic permeability of the developer. The detection of the magnetic permeability of the developer by the toner concentration sensor 49 can stabilize the output value, for example, by taking the average value of the magnetic permeability of the developer with respect to the rotation period of the developer stirring screw 43 during a sampling time longer than the time for one rotation of the developer stirring screw 43. That is, the output value of the toner concentration sensor 49 is, for example, the average value of the output values at times that are integer multiples of the rotation pitch of the developer stirring screw 43. Since the toner concentration corresponds to the consumption amount of toner in the developing device 1Y, it is used for controlling the replenishment of the developer from the developer storage unit 27Y. When it is detected that the toner concentration has dropped below a predetermined toner concentration, for example, the control unit 80 (Fig. 2) replenishes the developer from the developer storage unit 27Y (executes a replenishment operation). That is, the control unit 80 executes a replenishment operation as a first control for controlling the replenishment unit 93 to replenish the developer to the developing container 60 based on the output value of the toner concentration sensor 49 while the drive unit 94 is rotationally driving the developer supply screw 42 and the developer stirring screw 43.

[0057] Note that since the magnetic permeability of the developer changes more than the toner concentration, it is possible to detect the toner concentration using the magnetic permeability that is the output value of the toner concentration sensor 49. The toner concentration sensor 49 is arranged in the second conveyance path 62. Specifically, as shown in Fig. 3, the toner concentration sensor 49 is vertically below the rotation axis of the developer stirring screw 43, and as shown in Fig. 4, it is provided at the downstream end of the second conveyance path 62 with respect to the developer conveyance direction of the developer stirring screw 43.

[0058] The developer surface detection sensor 50 as the first inductance sensor (second magnetic permeability sensor) is arranged to detect the surface of the developer contained in the developer circulation unit 46. The developer surface detection sensor 50 is an inductance sensor that detects the magnetic permeability of the developer. The control unit 80 executes developer discharge control to keep the amount of developer in the developing device 1Y constant based on the developer surface detected by the developer surface detection sensor 50. The developer surface detection sensor 50 is arranged in the second conveyance path 62. Specifically, as shown in FIG. 3, the developer surface detection sensor 50 is provided vertically above the rotation axis of the developer stirring screw 43 and, as shown in FIG. 4, upstream of the toner concentration sensor 49 in the developer conveyance direction of the developer stirring screw 43.

[0059] The detection surface (second detection part) of the developer surface detection sensor 50 is located vertically above the detection surface (first detection part) of the toner concentration sensor 49 and is preferably arranged within a range corresponding to four pitches of the blades of the developer stirring screw 43 in the rotation axis direction of the developer stirring screw 43. Thereby, the detection range of the toner concentration of the developer and the detection range of the surface of the developer can be regarded as substantially the same. In this embodiment, one pitch of the blades of the developer stirring screw 43 is 30 mm, and the detection surface of the developer surface detection sensor 50 is located 20 mm above the detection surface of the toner concentration sensor 49 in the vertical direction. Also, in the rotation axis direction of the developer stirring screw 43, the detection surface of the developer surface detection sensor 50 is arranged at a position 50 mm upstream in the developer conveyance direction of the developer stirring screw 43 from the detection surface of the toner concentration sensor 49.

[0060] The regulating member 52 is arranged adjacent to the first developing roller 30 and is used to regulate the amount of developer supplied from the developer circulation unit 46 to the first developing roller 30. The regulating member 52 can be configured to regulate the amount of developer adsorbed to the first developing roller 30 based on, for example, the gap between the surface of the first sleeve 33 of the first developing roller 30 and the end of the regulating member 52.

[0061] The circulation path of the developer in the developing container 60 is conveyed in a substantially horizontal direction while being agitated in the developer circulation section 46, then supplied to the first developing roller 30, and transferred from the first developing roller 30 to the upper second developing roller 31 based on magnetic force. Next, it is transferred again from the second developing roller 31 to the peeling roller 32 on the side surface of the second developing roller 31 based on magnetic force, and then peeled off from the peeling roller 32 by the third magnet 38 enclosed in the peeling roller 32, and further recovered by the developer recovery section 47 and introduced again into the developer circulation section 46.

[0062] [Vibration device] The image forming apparatus 100 of the present embodiment includes a vibration device 200 as a vibration unit that applies vibration to the developing container 60. The vibration device 200 has a role of eliminating the stationary layer of the developer generated in the developing container 60 by applying vibration to the developing container 60. As shown in FIG. 3, the vibration device 200 is disposed above the developer circulation section 46 on the side opposite to the photosensitive drum 28 of the developing container 60. In the present embodiment, the vibration device 200 is disposed at a position facing the side wall 60a on the side opposite to the photosensitive drum 28 of the developing container 60 vertically above the second conveyance path 62. Further, in the present embodiment, the vibration device 200 is disposed at the central portion in the rotational axis direction (longitudinal direction) of the first developing roller 30. Note that the longitudinal position of the vibration device 200 is preferably vertically above the agent surface detection sensor 50. Further, in the present embodiment, the vibration device 200 is disposed vertically above the detection surface of the agent surface detection sensor 50.

[0063] As shown in FIGS. 5(a) and 5(b), the vibration device 200 includes a vibration member 201, a fixed shaft 202, an electromagnetic solenoid 203, and a return spring 204. The vibration member 201 is a component that applies vibration to the developing container 60 and is disposed at a position facing the side wall 60a of the developing container 60. The vibration member 201 is attached to the fixed shaft 202 so as to be rotatable about the fixed shaft 202 as a rotation center. The vibration member 201 hits the side wall 60a as the vibration-receiving portion of the developing container 60 by rotating about the fixed shaft 202, and applies vibration to the developing apparatus 1. The vibration direction of the vibration member 201 is set in the horizontal direction of the developing apparatus 1.

[0064] The electromagnetic solenoid 203 is a drive unit that rotates the vibration member 201. The electromagnetic solenoid 203 incorporates a plunger 203A and operates the plunger 203A based on a control signal from the control unit 80. The plunger 203A is connected to the vibration member 201, and when the plunger 203A performs a suction operation, the vibration member 201 rotates toward the developing container 60. The return spring 204 is connected to the vibration member 201 and has a tensile force for returning the vibration member 201 to the initial position.

[0065] The vibration operation will be described with reference to FIGS. 5(a) and 5(b). The determination as to whether to execute the vibration operation is made based on the output value of the agent surface detection sensor 50 (details will be described later). When it is determined to execute the vibration operation, an on-signal is transmitted to the electromagnetic solenoid 203 by a control signal from the control unit 80, and the plunger 203A performs a suction operation. When the plunger 203A is suctioned, the vibration member 201 is pulled by the plunger 203A, so the vibration member 201 rotates about the fixed shaft 202 and moves in the vibration direction indicated by the arrows in FIGS. 5(a) and 5(b) and hits the side wall 60a of the developing container 60, and vibration is applied to the developing device 1Y by the impact. After outputting the on-signal, the control unit 80 transmits an off-signal to the electromagnetic solenoid 203 as a control signal when a predetermined period has elapsed. Thereby, the plunger 203A returns to the initial position.

[0066] During the vibration application operation, the rotation control of the first developing roller 30, the second developing roller 31, the separation roller 32, the developer supply screw 42, the developer agitation screw 43, and the developer recovery screw 44 is stopped. Regarding the rotation control of the photosensitive drum 28Y, it does not have to be stopped. Also, the vibration application to the developing device 1Y by the vibration application device 200 may be executed in the following applications. In the process of supplying toner from the developing device 1Y to the photosensitive drum 28Y, the toner may scatter and accumulate in the developing container 60. Furthermore, when the toner accumulated in the developing container 60 drops onto the photosensitive drum 28Y at an unexpected timing, image defects may occur. In such a case, by executing the vibration application operation to the developing device 1Y by the vibration application device 200 and removing the toner accumulated in the developing container 60, the occurrence of image defects is suppressed.

[0067] Also, the vibration application operation is performed during non-image formation (i.e., during the non-development operation in which the electrostatic latent image formed on the photosensitive drum 28Y is not developed with a developer). Examples of non-image formation include before the start of an image formation job, between an image formation job and the next image formation job, during an image stabilization operation, during various operation corrections, etc. However, even during continuous image formation, an operation control may be interrupted such that the image formation operation is stopped midway and the vibration application operation is executed. For example, during continuous image formation, every time an image is formed on a predetermined number of recording materials since the vibration application operation was last executed, the operation control may be interrupted to interrupt the image formation operation and execute the vibration application operation. Note that an image formation job is a period from the start of image formation to the completion of image formation based on a print signal (image formation signal) for forming an image on a recording material. That is, an image formation job is a period in which a series of operations including a pre-operation (pre-rotation) performed before the image formation operation, the image formation operation, and a post-operation (post-rotation) performed after the image formation operation are performed by the input of an image formation signal.

[0068] [Developer] As described above, in this embodiment, a two-component development system is used as the development method, and the developer is a mixture of a negatively charged non-magnetic toner and a magnetic carrier. The non-magnetic toner encapsulates a colorant, a wax component, etc. in a resin such as polyester or styrene-acrylic, and fine powders such as titanium oxide and silica are added to the surface of the powder obtained by pulverization or polymerization. The magnetic carrier is obtained by applying a resin coat to the surface layer of a core composed of resin particles kneaded with ferrite particles or magnetic powder. The toner concentration (weight ratio of toner contained in the developer) in the developer in the initial state is 9% in this embodiment.

[0069] Generally, in the two-component development system using toner and carrier, since the toner and the carrier are charged to a predetermined polarity by friction contact, the toner is subjected to less stress than in the one-component development system using a one-component developer. On the other hand, due to long-term use, the dirt (spent) adhering to the carrier surface increases, and as a result, the ability to charge the toner gradually decreases. As a result, problems such as fogging and toner scattering occur. In order to extend the life of the two-component development device, it is conceivable to increase the amount of carrier accommodated in the development device, but this is not desirable because it leads to an increase in the size of the development device.

[0070] To solve the above problems related to the two-component developer, in this embodiment, the ACR (Auto Carrier Refresh) method is adopted. The ACR method is a method of suppressing an increase in deteriorated carriers by replenishing a small amount of new developer from the developer storage unit 27Y into the development device 1Y little by little, and discharging the developer with deteriorated charging performance little by little from the developer discharge port 54 of the development device 1Y. As a result, the deteriorated carriers in the development device 1Y are gradually replaced with new carriers, and it becomes possible to keep the charging performance of the carriers in the development device 1Y substantially constant.

[0071] Incidentally, in the developing device 1Y equipped with the ACR system as in the present embodiment, if the use of the developing device 1Y continues, the amount of developer discharged from the developer discharge port 54 may vary with changes in the fluidity of the developer. For example, at the initial stage of using the developing device 1Y, the fluidity of the developer is high and the amount of developer discharged tends to increase. However, if the use of the developing device 1Y continues and the developer deteriorates, the fluidity of the developer decreases, and the amount of developer discharged may be suppressed.

[0072] When the amount of developer in the developing device 1Y decreases, image defects may occur due to insufficient amount of developer required for image formation. On the other hand, if the amount of developer in the developing device 1Y becomes excessive, it may lead to overflow of the developer from the vicinity of the first developing roller 30 and the second developing roller 31, and jamming of various screws in the developing device 1Y. In preparation for such a situation, in the present embodiment, a developer surface detection sensor 50 for detecting the height of the developer surface in the developing device 1Y is provided, and when the developer surface in the developing device 1Y deviates from a predetermined range, developer discharge control is performed to vary the rotation speed (rotational speed) of the developer supply screw 42 and the developer agitation screw 43, and the developer surface is adjusted to be constant.

[0073] For example, when the developer surface in the developing device 1Y falls below a predetermined position, a developer discharge suppression mode is executed to suppress developer discharge by reducing the rotation speed of the developer supply screw 42 and the developer agitation screw 43. Also, when the developer surface in the developing device 1Y exceeds a predetermined position, the image forming operation is stopped, and the forward and reverse rotation operations of the developer supply screw 42 and the developer agitation screw 43 are repeated for a preset time to execute a developer discharge mode for discharging the excess developer outside the developing device 1Y.

[0074] That is, the rotation conditions of the developer supply screw 42 and the developer agitation screw 43 in the developer discharge mode are different from those of the developer supply screw 42 and the developer agitation screw 43 during the developing operation. Specifically, when the developing device 1Y develops the electrostatic latent image formed on the photosensitive drum 28Y, the drive unit 94 rotationally drives the developer supply screw 42 and the developer agitation screw 43 under the first rotation conditions. On the other hand, as will be described later, when the drive unit 94 executes the developer discharge mode during a non-developing operation in which the developing operation is not performed, the drive unit 94 rotationally drives the developer supply screw 42 and the developer agitation screw 43 under second rotation conditions different from the first rotation conditions. Note that the first rotation conditions are, for example, rotating the developer supply screw 42 and the developer agitation screw 43 in a first rotation direction (forward rotation). The second rotation conditions are repeating rotating the developer supply screw 42 and the developer agitation screw 43 in the first rotation direction and rotating the developer supply screw 42 and the developer agitation screw 43 in a second rotation direction (reverse rotation) opposite to the first rotation direction. Such a developer discharge suppression mode and a developer discharge mode are referred to as developer discharge control.

[0075] In the developer discharge suppression mode that is executed when the developer level inside the developing device 1Y is below a predetermined range, an example of reducing the rotation speeds of the developer supply screw 42 and the developer agitation screw 43 during image formation (during the developing operation) has been described, but the present invention is not limited to this. When the developer level inside the developing device 1Y is below a predetermined range, a modified example in which the developer discharge suppression mode is performed during non-image formation (during a non-developing operation) instead of during image formation (during the developing operation) may be used. In this modified example, the rotation conditions of the developer supply screw 42 and the developer agitation screw 43 in the developer discharge suppression mode are different from those of the developer supply screw 42 and the developer agitation screw 43 during the developing operation. Further, when the developer level inside the developing device 1Y is below a predetermined range, a modified example in which the developer discharge suppression mode is performed during non-image formation (during a non-developing operation) in addition to during image formation (during the developing operation) may be used.

[0076] However, in the case of a configuration in which the developer surface detection sensor 50 is used to detect the developer surface in the developing device 1Y, there is a risk of erroneously detecting the developer surface due to the non-moving layer of the developer generated in the developing device 1Y. The erroneous detection of the developer surface due to such a non-moving layer of the developer will be described with reference to FIGS. 6 to 11.

[0077] [False Detection of Developer by Non-Moving Layer] FIG. 6 shows a schematic diagram of the developer surface T when the fluidity of the developer in the developing device 1Y is high, and FIG. 7 shows the output result of the developer surface detection sensor 50 in the state of FIG. 6. When the developer moves in the transport direction by the rotation of the developer supply screw 42 and the developer agitation screw 43, the developer surface T fluctuates according to the rotation pitch of the developer supply screw 42 and the developer agitation screw 43. Therefore, as shown in FIG. 7, the output value of the developer surface detection sensor 50 shows periodic fluctuations. The periodicity of the output value of the developer surface detection sensor 50 depends on the rotation speed of the developer agitation screw 43 and the number of blades. At this time, the average value of the output of the developer surface detection sensor 50 over a predetermined time and the developer surface T in the developing device 1Y can be related to a primary straight line as shown in FIG. 8.

[0078] Next, FIG. 9 shows a schematic diagram of the developer surface T when the fluidity of the developer is low, and FIG. 10 shows the output result of the developer surface detection sensor 50 in the state of FIG. 9. When the fluidity of the developer is low, it is known that the developer tends to accumulate in the gap between the developer agitation screw 43 and the inner wall of the developing container 60. In particular, as shown in FIG. 4, since the installation position of the developer surface detection sensor 50 is near the most downstream in the developer transport direction of the developer agitation screw 43 and near the communication port 48b which is the developer transfer portion from the second transport path 62 to the first transport path 61, the moving direction of the developer in the vicinity of the detection surface of the developer surface detection sensor 50 is not in one direction. Therefore, in the case of such a configuration, in particular, there is a tendency for the developer to easily accumulate in the vicinity of the detection surface of the developer surface detection sensor 50. The accumulated developer grows along the vertical direction on the inner wall of the developing container 60 as shown in FIG. 9, and is eventually formed as the non-moving layer Ti.

[0079] Since the developer surface detection sensor 50 detects the abundance of magnetic carriers contained in the developer near the detection surface, when an immobile layer Ti of the developer has occurred near the detection surface, it is strongly affected. As a result, as shown in FIG. 10, the output value of the developer surface detection sensor 50 becomes high, and the amplitude of the periodic variation becomes small. At this time, the average output value of the developer surface detection sensor 50 within a predetermined time and the developer surface T in the developing device 1Y have the relationship as shown in FIG. 11. In FIG. 11, since the average output value of the developer surface detection sensor 50 is constant regardless of the developer surface T, it becomes difficult to accurately detect the developer surface. Due to such an immobile layer Ti of the developer in the developing device 1Y, accurate developer surface detection is inhibited, and there is a possibility that developer discharge control cannot be appropriately executed.

[0080] [Vibration operation] Therefore, in the present embodiment, when it is determined from the detection result of the developer surface detection sensor 50 that an immobile layer of the developer has occurred in the developing device 1Y, a vibration application operation (second control) for applying vibration to the developing device Y1 by the vibration device 200 is executed to eliminate the immobile layer of the developer. Thereby, false detection of the developer surface detection sensor 50 is suppressed, and the developer surface in the developing device 1Y can be detected more accurately.

[0081] In the present embodiment, the control unit 80 controls the vibration device 200 to execute a vibration application operation for applying vibration to the developing device 1Y based on the output value of the developer surface detection sensor 50 while the driving unit 94 rotationally drives the developer supply screw 42 and the developer agitation screw 43. Specifically, the control unit 80 executes a vibration application operation for applying vibration to the developing container 60 by the vibration device 200 when the absolute value Vpp of the difference between the maximum output value Vmax and the minimum output value Vmin of the developer surface detection sensor 50 within a predetermined time is smaller than a predetermined value Vth. That is, when Vpp is smaller than Vth, it is determined that an immobile layer of the developer has occurred, and the vibration application operation of the vibration device 200 to the developing container 60 is executed to eliminate the immobile layer.

[0082] Here, the predetermined time is set as an integer multiple of the rotation pitch of the developer stirring screw 43. For example, the predetermined time is set to the rotation time of one pitch of the developer stirring screw 43. Specifically, if the pitch of the developer stirring screw is 30 mm and the rotation speed is 600 rpm, the required time for one pitch is 100 msec, and this is set as the predetermined time.

[0083] In consideration of the variation in Vpp, the predetermined time may also be set as the time required for the developer to make one round in the developer circulation section 46. Specifically, if the length of the circulation path in the developer circulation section 46 is 660 mm, the pitch of the developer supply screw 42 and the developer stirring screw 43 is 30 mm, and the rotation speed is 600 rpm, the required time for the developer to make one round in the developer circulation section 46 is about 2.2 sec, and this is set as the predetermined time. And when Vpp is low even though the developer has made one round in the circulation path, as will be described later, it is determined that a stagnant layer has occurred.

[0084] Vpp is the absolute value of the difference between Vmax and Vmin, where Vmax is the maximum value and Vmin is the minimum value of the output value of the agent surface detection sensor 50 at a predetermined time shown in FIGS. 7 and 10. Such Vpp is the magnitude of the periodic fluctuation of the output value of the agent surface detection sensor 50 and represents the fluctuation width of the developer surface that varies with the rotation of the developer stirring screw 43. When the fluidity of the developer in the developing device 1Y is high and no stagnant layer of the developer has occurred, Vpp becomes a high value. On the other hand, when the fluidity of the developer in the developing device 1Y decreases and a stagnant layer of the developer occurs in the gap between the developer stirring screw 43 and the inner wall of the developing container 60, Vpp becomes low. This is because the agent surface detection sensor 50 detects the developer contained in the stagnant layer and cannot correctly detect the fluctuation of the developer surface accompanying the rotation of the developer stirring screw 43.

[0085] From this, as the immobile layer of the developer in the developing device 1Y grows, Vpp decreases as shown in FIG. 12. The immobile layer index on the horizontal axis of FIG. 12 indicates the occurrence status of the immobile layer. The larger this index becomes, that is, the more it goes to the right side of the horizontal axis in FIG. 12, the more the immobile layer of the developer is growing. Therefore, from the relationship in FIG. 12, Vpp can be used as an index indicating the occurrence of the immobile layer of the developer in the developing device Y1. For this reason, in the present embodiment, when Vpp falls below the threshold value (predetermined value) Vth of the immobile layer generation, the vibration application operation is executed. Therefore, in the present embodiment, when the absolute value of the difference between the maximum output value and the minimum output value of the agent surface detection sensor 50 while the drive unit 94 is rotationally driving the developer supply screw 42 and the developer agitation screw 43 for a predetermined time is smaller than a predetermined value, the vibration application operation is executed. On the other hand, when the absolute value of the difference between the maximum output value and the minimum output value of the agent surface detection sensor 50 while the drive unit 94 is rotationally driving the developer supply screw 42 and the developer agitation screw 43 for a predetermined time is equal to or greater than a predetermined value, the control unit 80 does not execute the vibration application operation.

[0086] The determination as to whether an immobile layer of the developer has occurred in the developing device 1Y and the execution procedure of the vibration application operation of the developing device 1Y will be described using the flowchart shown in FIG. 13. In S101, the determination process as to whether an immobile layer of the developer has occurred in the developing device 1Y is started. The timing for executing S101 is at least one of the periods during the image forming operation, during the previous rotation before the image forming operation, and during the subsequent rotation after the image forming operation. Any one of these periods may be used, or a plurality of them may be used. Also, the start timing of the determination process is preferably at a timing according to the usage time of the developing device 1Y, such as when an image is formed on a predetermined number of recording materials, and within the above-mentioned periods. When the determination process is performed during the image forming operation, if it is determined as a result of the determination process to execute the vibration application operation as described later, the image forming operation is interrupted and the vibration application operation is executed.

[0087] In S102, Vpp is derived. Specifically, with the developer supply screw 42 and the developer agitation screw 43 rotating, detection is performed by the agent surface detection sensor 50 for a predetermined time, and Vpp is calculated from Vmax and Vmin for the predetermined time.

[0088] Then, in S103, the control unit 80 performs a determination process as to whether or not a non-moving layer of the developer has occurred in the developing device 1Y. The determination of the non-moving layer is made by comparing Vpp with Vth, which is the threshold for the occurrence of the non-moving layer. When Vpp is less than Vth, it is determined that a non-moving layer of the developer has occurred in the developing device 1Y. In FIG. 12 described above, Vth is set to 2V, and when Vpp is less than 2V (Vpp < Vth), it is determined that a non-moving layer of the developer has occurred in the developing device 1Y.

[0089] In S104, when it is determined in S103 that a non-moving layer of the developer has occurred in the developing device 1Y (Yes in S103), the vibration operation of the developing device 1Y by the vibration device 200 is executed. For example, when Vpp at a predetermined time during the image forming operation is smaller than Vth, the control unit 80 interrupts the image forming operation and executes the vibration operation. When this vibration operation is executed, the rotation of at least the developer supply screw 42, the developer agitation screw 43, the first developing roller 30, and the second developing roller 31 is stopped. In the present embodiment, as described above, when the vibration operation is executed, the rotation of the first developing roller 30, the second developing roller 31, the peeling roller 32, the developer supply screw 42, the developer agitation screw 43, and the developer recovery screw 44 is stopped. Also, the rotation of the photosensitive drum 28Y is not stopped.

[0090] In such a vibration operation, the vibration member 201 abuts against the side wall 60a of the developing container 60, and the developing device 1Y vibrates due to the impact. When the developing device 1Y vibrates, the stationary layer of the developer in the developing device 1Y is eliminated. In the present embodiment, the execution of the vibration operation by the vibration device 200 is an operation of hitting the developing container 60 only once with the vibration member 201. Since the stationary layer of the developer in the developing container 60 is deposited in an unstable state, it collapses by hitting the developing container 60 once with the vibration member 201. Note that the vibration operation is not limited to this, and the vibration member 201 may hit the developing container 60 a plurality of times.

[0091] In S105, the determination as to whether or not a stationary layer of the developer has occurred in the developing device 1 ends. Note that in S103, if Vpp≥Vth, the process proceeds to S105.

[0092] As described above, when it is determined that Vpp, which is the fluctuation of the output value of the developer surface detection sensor 50, is less than or equal to Vth, that is, when a stationary layer of the developer has occurred in the developing device 1Y, the vibration operation is executed to eliminate the stationary layer. As a result, accurate developer surface detection based on the output value of the developer surface detection sensor 50 becomes possible, and appropriate developer discharge control can be performed according to the developer surface detection result in the developing device 1Y.

[0093] In the above description, the case where Vpp is used as an index indicating the occurrence of the stationary layer of the developer has been described. However, as this index, the integral value or standard deviation of the output value of the developer surface detection sensor 50 over a predetermined time may be used. When the stationary layer occurs, as shown in FIG. 10, the output fluctuation (fluctuation of the output value) becomes small, but as shown in FIG. 11, the average of the output values of the developer surface detection sensor 50 becomes high. For this reason, due to the occurrence of the stationary layer, the above-mentioned Vpp becomes low, but the integral value of the output value over a predetermined time becomes large. This is because the state where the average value of the output value is high continues over a predetermined time. Further, due to the occurrence of the stationary layer, the standard deviation of the output value over a predetermined time becomes small. This is because the output fluctuation is small, so the deviation of the output value also becomes small.

[0094] As described above, when using the integrated value as an index, if the integrated value of the output value of the agent surface detection sensor 50 at a predetermined time is greater than a predetermined integrated value, the control unit 80 determines that an immobile layer has occurred and executes a vibration application operation. That is, when the integrated value of the output value of the agent surface detection sensor 50 while the drive unit 94 is rotationally driving the developer supply screw 42 and the developer agitation screw 43 for a predetermined time is greater than the predetermined integrated value, the control unit 80 executes a vibration application operation. On the other hand, when the integrated value of the output value of the agent surface detection sensor 50 while the drive unit 94 is rotationally driving the developer supply screw 42 and the developer agitation screw 43 for a predetermined time is less than or equal to the predetermined integrated value, the control unit 80 does not execute a vibration application operation.

[0095] On the other hand, when using the standard deviation as an index, if the standard deviation of the agent surface detection sensor 50 at a predetermined time is less than a predetermined standard deviation, the control unit 80 determines that an immobile layer has occurred and executes a vibration application operation. Whether the index is the integrated value or the standard deviation, similar to the case of using the above-mentioned Vpp, the occurrence of the immobile layer of the developer can be appropriately determined, and the immobile layer can be eliminated by executing the vibration application operation based on this determination. That is, when the standard deviation of the output value of the agent surface detection sensor 50 while the drive unit 94 is rotationally driving the developer supply screw 42 and the developer agitation screw 43 for a predetermined time is less than the predetermined standard deviation, the control unit 80 executes a vibration application operation. On the other hand, when the standard deviation of the output value of the agent surface detection sensor 50 while the drive unit 94 is rotationally driving the developer supply screw 42 and the developer agitation screw 43 for a predetermined time is greater than or equal to the predetermined standard deviation, the control unit 80 does not execute a vibration application operation.

[0096] <Second Embodiment> The second embodiment will be described with reference to FIG. 14. In this embodiment, when the Vpp is below the threshold value Vth even after executing the vibration application operation, the developer discharge mode is executed. Since the other configurations and operations are the same as those of the first embodiment described above, the same reference numerals are given to the same configurations, and the description and illustration are omitted or simplified. Hereinafter, the differences from the first embodiment will be mainly described.

[0097] In the above-described first embodiment, when a stationary layer of developer occurred in the developing device 1Y, vibration of the developing device 1Y by the vibration device 200 was executed to eliminate the stationary layer, enabling accurate detection of the developer surface. In contrast, in the second embodiment, when Vpp, which is the fluctuation of the output value of the developer surface detection sensor 50, is equal to or less than the threshold value Vth even when the vibration device 200 vibrates the developing device 1Y, it is determined that the amount of developer in the developing device 1Y is excessive, and the developer discharge mode (third control) is executed.

[0098] When the amount of developer in the developing device 1Y becomes excessive and the developer surface rises above the detection surface of the developer surface detection sensor 50, Vpp decreases. It is difficult to distinguish such a decrease in Vpp from the decrease in Vpp in a state where a stationary layer of developer has occurred in the gap between the developer stirring screw 43 and the inner wall of the developing container 60 as in the first embodiment, and to determine which state the developer surface is in. When the amount of developer in the developing device 1Y is excessive, there is a risk of developer overflow or screw lock as described above, so it is required to quickly discharge the developer from the developing device 1Y.

[0099] Therefore, in this embodiment, the vibration device 200 vibrates the developing device 1Y. After the stationary layer of the developer is eliminated, if Vpp is less than or equal to Vth continuously, it is determined that the developer surface is likely to cause developer overflow or screw lock, and the developer discharge mode is executed. That is, after the vibration operation is executed, the control unit 80 controls the drive unit 94 to rotate the developer supply screw 42 and the developer agitation screw 43 under the second rotation condition during the rotation driving of the drive unit 94 for the output value of the agent surface detection sensor 50, so as to execute the developer discharge mode for performing the non-developing operation without executing the developing operation. Specifically, when the absolute value of the difference between the maximum output value Vmax and the minimum output value Vmin of the agent surface detection sensor 50 at the first predetermined time, that is, Vpp, is smaller than a predetermined value Vth, the control unit 80 executes a vibration operation to apply vibration to the developing container 60 by the vibration device 200. In addition, after the vibration operation is executed, if Vpp at the second predetermined time is smaller than Vth, the control unit 80 executes the developer discharge mode as a developer forced discharge operation for forcibly discharging the developer from the developer discharge unit 53.

[0100] Note that the first predetermined time is the predetermined time described in the first embodiment. The second predetermined time may be the same as or different from the first predetermined time. However, even when the second predetermined time is different from the first predetermined time, it is preferably set to a time that is an integer multiple of the rotation pitch of the developer agitation screw 43. In addition, as described above, the developer discharge mode is an operation of repeatedly rotating the developer supply screw 42 and the developer agitation screw 43 forward and backward for a preset time (the third predetermined time).

[0101] Regarding the control flow of such an embodiment, it will be described using the flowchart shown in FIG. 14. Since S201 to S204 are the same as S101 to 104 in the control content described in FIG. 13, the details will be omitted. Note that the timing for executing this control is the same as the timing for executing S101 described above. After the vibration operation of the developing device 1Y by the vibration device 200 is executed in S204, in S205, similar to S202, Vpp is derived again. Specifically, after the execution of the vibration operation, with the developer supply screw 42 and the developer stirring screw 43 rotating, the detection by the agent surface detection sensor 50 is performed for a second predetermined time, and Vpp is calculated from Vmax and Vmin for the predetermined time.

[0102] In S206, similar to S203, it is determined whether Vpp is less than or equal to Vth. When Vpp is greater than or equal to Vth (No in S206), it can be determined that the immobile layer has been eliminated by the vibration operation and the amount of developer is not excessive. Therefore, the process proceeds to S208 and the control ends.

[0103] On the other hand, in S206, when Vpp is smaller than Vth, since the immobile layer has already been eliminated by the vibration operation of the developing device 1Y by the vibration device 200 in S204, it is determined that the developer surface in the developing device 1Y has risen above the detection surface of the agent surface detection sensor 50 and the amount of developer in the developing device 1 has become excessive. That is, although the immobile layer collapses when the developing device 1Y is vibrated, if Vpp is below Vth for a second predetermined time while the developer supply screw 42 and the developer stirring screw 43 are rotating after the vibration operation is executed, it can be determined that the cause is not due to the immobile layer but the state where the developer surface has risen significantly.

[0104] In S206, when Vpp is smaller than Vth (Yes in S206), in S207, the developer discharge mode is executed. In this case, the image forming operation is stopped, and by repeating the forward and reverse rotation operations of the developer supply screw 42 and the developer agitation screw 43 for a third predetermined time (the second rotation condition), an operation is executed to promote the discharge of the developer from the developer discharge port 54. Then, in S208, a series of determinations are terminated.

[0105] Note that when the environmental humidity is low, the fluidity of the developer is lower compared to when the environmental humidity is high, and there is a tendency that the discharge of the developer is difficult. Therefore, in the developer discharge mode of S207, when repeating the forward and reverse rotation operations of the developer supply screw 42 and the developer agitation screw 43 for a predetermined time, the rotation speeds (rotation rates) of the developer supply screw 42 and the developer agitation screw 43 may be made variable according to the environmental humidity. That is, the second rotation condition may be set according to the environmental humidity.

[0106] Specifically, when the environmental humidity is the first humidity, the developer supply screw 42 and the developer agitation screw 43 are repeatedly rotated forward and backward at the first rotation speed. On the other hand, when the environmental humidity is the second humidity lower than the first humidity, by setting the rotation speeds of the developer supply screw 42 and the developer agitation screw 43 to a second rotation speed faster than the first rotation speed when repeating the forward and reverse rotation operations of the developer supply screw 42 and the developer agitation screw 43 for a predetermined time, the discharge of the developer may be promoted. At this time, the rotation speed of the developer recovery screw 44 may also be increased in the same manner.

[0107] Also, in S207, as the rotation condition of the developer supply screw 42 and the developer agitation screw 43 when executing the developer discharge mode, instead of repeating the forward and reverse rotation operations of the developer supply screw 42 and the developer agitation screw 43 for a predetermined time, the following modification example may be used.

[0108] For example, in S207, when executing the developer discharge mode, the rotation speeds of the developer supply screw 42 and the developer agitation screw 43 may be made faster than the rotation speeds of the developer supply screw 42 and the developer agitation screw 43 during the developing operation, thereby promoting the discharge of the developer. That is, under the first rotation condition, the developer supply screw 42 and the developer agitation screw 43 are rotated at the first rotation speed, and under the second rotation condition, the developer supply screw 42 and the developer agitation screw 43 may be rotated at a second rotation speed faster than the first rotation speed. At this time, the rotation speed of the developer recovery screw 44 may also be increased in the same manner.

[0109] Also, in this modification, in S207, the number of rotations (rotation speed) of the developer supply screw 42 and the developer agitation screw 43 when executing the developer discharge mode may be made variable according to the environmental humidity. This is because, as described above, when the environmental humidity is low, the fluidity of the developer is lower than when the environmental humidity is high, and the discharge of the developer tends to be difficult. Therefore, specifically, when the environmental humidity is low, the discharge of the developer may be promoted by making the rotation speeds of the developer supply screw 42 and the developer agitation screw 43 when executing the developer discharge mode faster than when the environmental humidity is high. That is, when the environmental humidity is the first humidity, the developer supply screw 42 and the developer agitation screw 43 are rotated at a second rotation speed faster than the first rotation speed, and when the environmental humidity is a second humidity lower than the first humidity, the developer supply screw 42 and the developer agitation screw 43 may be rotated at a third rotation speed faster than the second rotation speed. At this time, the rotation speed of the developer recovery screw 44 may also be increased in the same manner.

[0110] As described above, in this embodiment, when Vpp is low even when the vibration operation for vibrating the developing device 1Y is executed, it is determined that the amount of developer in the developing device 1Y is excessive, and the developer discharge mode is performed. Therefore, it is possible to prevent the occurrence of developer overflow and screw lock.

[0111] Note that, also in this embodiment, as an index indicating the generation of the non-moving layer of the developer, the integrated value or the standard deviation of the output value of the agent surface detection sensor 50 over a predetermined time may be used. When using the integrated value as the index, in S206 and S207, the control unit 80 executes the developer discharge mode when the integrated value of the output value of the agent surface detection sensor 50 at the second predetermined time is greater than a predetermined integrated value. On the other hand, when using the standard deviation as the index, in S206 and S207, the control unit 80 executes the developer discharge mode when the standard deviation of the agent surface detection sensor 50 at the second predetermined time is smaller than a predetermined standard deviation.

[0112] <Other Embodiments> In each of the above-described embodiments, the developing device having two developing rollers has been described. However, the present invention is applicable even when there is one developing roller. That is, the present invention is applicable even to a configuration having one developing roller for developing an electrostatic latent image on an image carrier such as a photosensitive drum, an inductance sensor for detecting the developer surface in the developing container, and an inductance sensor for detecting the toner concentration.

[0113] The present invention is not limited to the configurations of the above-described embodiments. For example, the image forming apparatus 100 is not limited to an MFP, and may be a copying machine, a printer, or a facsimile apparatus. Further, the configurations of the developer supply screw 42, the developer agitation screw 43, and the developer recovery screw 44 are not particularly limited as long as they can convey the developer. For example, spiral blades or paddle-shaped blades can be applied.

[0114] In the above-described embodiment, the first sleeve 33 and the photosensitive drum 28Y rotate in the same direction at positions facing each other, and the second sleeve 34 and the photosensitive drum 28Y rotate in the same direction at positions facing each other. However, the present invention is not limited to this. The rotation center O2 of the second developing roller 31 is arranged above the rotation center O1 of the first developing roller 30 in the vertical direction. The first sleeve 33 and the photosensitive drum 28Y may rotate in opposite directions at positions facing each other, and the second sleeve 34 and the photosensitive drum 28Y may rotate in opposite directions at positions facing each other. That is, it is a counter-development in which the photosensitive drum 28 rotates from above in the vertical direction to below in the vertical direction at the position where the photosensitive drum 28 faces the first developing roller 30, and it is a counter-development in which the photosensitive drum 28 rotates from above in the vertical direction to below in the vertical direction at the position where the photosensitive drum 28 faces the second developing roller 31. The present invention can also be applied to such a configuration. Further, when three or more developing rollers are provided, the present invention can also be applied to any two developing rollers.

Explanation of Signs

[0115] 1Y, 1M, 1C, 1K ··· Developing device 28Y, 28M, 28C, 28K ··· Photosensitive drum (image carrier) 30 ··· First developing roller (developing rotating body) 31 ··· Second developing roller (developing rotating body) 42 ··· Developer supply screw (conveying screw) 43 ··· Developer agitation screw (conveying screw) 49 ··· Toner density sensor (first magnetic permeability sensor) 50 ··· Agent surface detection sensor (second magnetic permeability sensor) 60 ··· Developing container 80 ··· Control unit 93 ··· Supply unit (developer supply unit) 100 ··· Image forming apparatus 200 ··· Vibration device (vibrating unit)

Claims

1. An image carrier, a developer carrier that carries a developer containing toner and a carrier for developing an electrostatic latent image formed on the image carrier, a developing container that houses the developer supplied to the developer carrier, a transport screw that transports the developer housed in the developing container, a developer discharge unit for discharging a part of the developer housed in the developing container, a first magnetic permeability sensor having a first detection unit for detecting the magnetic permeability of the developer housed in the developing container, and a second magnetic permeability sensor having a second detection unit for detecting the magnetic permeability of the developer housed in the developing container, a drive unit that rotationally drives the transport screw, a developer supply unit that supplies the developer to the developing container, a vibration unit that applies vibration to the developing device, a control unit, and comprising, wherein the second detection unit is located vertically above the first detection unit, the control unit executes a first control for controlling the developer supply unit to supply the developer to the developing container based on an output value of the first magnetic permeability sensor while the drive unit rotationally drives the transport screw, the control unit executes a second control for controlling the vibration unit to perform a vibration operation for applying vibration to the developing device based on an output value of the second magnetic permeability sensor while the drive unit rotationally drives the transport screw. An image forming apparatus characterized by the above.

2. The drive unit rotationally drives the transport screw under a first rotation condition during a developing operation in which the developing device develops an electrostatic latent image formed on the image carrier, after the vibration operation is executed, the control unit executes a third control for controlling the drive unit to rotationally drive the transport screw under a second rotation condition different from the first rotation condition during a non-developing operation in which the developing operation is not performed, based on an output value of the second magnetic permeability sensor while the drive unit rotationally drives the transport screw. The image forming apparatus according to claim 1, characterized by the above.

3. The first rotation condition is rotating the transport screw in a first rotation direction, the second rotation condition is repeating rotating the transport screw in the first rotation direction and rotating the transport screw in a second rotation direction opposite to the first rotation direction. The image forming apparatus according to claim 2, characterized by the above.

4. The first rotation condition is to rotate the transport screw in a first rotation direction. The second rotation condition is that when the environmental humidity is a first humidity, the transport screw is rotated in the first rotation direction at a first rotation speed, and the transport screw is rotated in a second rotation direction opposite to the first rotation direction at the first rotation speed, and this is repeated; when the environmental humidity is a second humidity lower than the first humidity, the transport screw is rotated in the first rotation direction at a second rotation speed higher than the first rotation speed, and the transport screw is rotated in the second rotation direction at the second rotation speed, and this is repeated. The image forming apparatus according to claim 2, characterized in that.

5. The first rotation condition is to rotate the transport screw at a first rotation speed. The second rotation condition is to rotate the transport screw at a second rotation speed higher than the first rotation speed. The image forming apparatus according to claim 2, characterized in that.

6. The first rotation condition is to rotate the transport screw at a first rotation speed. The second rotation condition is that when the environmental humidity is a first humidity, the transport screw is rotated at a second rotation speed higher than the first rotation speed, and when the environmental humidity is a second humidity lower than the first humidity, the transport screw is rotated at a third rotation speed higher than the second rotation speed. The image forming apparatus according to claim 2, characterized in that.

7. The control unit executes a third control for controlling the vibration unit so as to execute the vibration operation each time an image is formed on a predetermined number of recording materials. The image forming apparatus according to claim 1, characterized in that.

8. The vibration unit is located vertically above the second detection unit. The image forming apparatus according to claim 1, characterized in that.

9. The first detection unit and the second detection unit are arranged within a range of a distance corresponding to four pitches of the blades of the transport screw with respect to the developer transport direction of the transport screw. The image forming apparatus according to claim 1, characterized in that.

10. An image carrier, A developing device having a developer carrier that carries a developer containing toner and a carrier for developing an electrostatic latent image formed on the image carrier, a developing container that stores the developer supplied to the developer carrier, a transport screw that transports the developer stored in the developing container, a developer discharge unit for discharging a part of the developer stored in the developing container, a first magnetic permeability sensor having a first detection unit that detects the magnetic permeability of the developer stored in the developing container, and a second magnetic permeability sensor having a second detection unit that detects the magnetic permeability of the developer stored in the developing container, a drive unit that rotationally drives the transport screw, a developer supply unit that supplies the developer to the developing container, a vibration unit that applies vibration to the developing device, a control unit, comprising: the second detection unit is located vertically above the first detection unit, the control unit executes a first control for controlling the developer supply unit to supply the developer to the developing container based on an output value of the first magnetic permeability sensor while the drive unit is rotationally driving the transport screw, the control unit, when an absolute value of a difference between a maximum output value and a minimum output value of the second magnetic permeability sensor while the drive unit is rotationally driving the transport screw for a predetermined time is smaller than a predetermined value, the control unit executes a second control for controlling the vibration unit to execute a vibration operation of applying vibration to the developing device, when the absolute value of the difference between the maximum output value and the minimum output value of the second magnetic permeability sensor while the drive unit is rotationally driving the transport screw for the predetermined time is equal to or greater than the predetermined value, the second control is not executed characterizing an image forming apparatus.

11. the drive unit rotationally drives the transport screw under a first rotation condition during a developing operation in which the developing device develops an electrostatic latent image formed on the image carrier, after the vibration operation is executed, when the absolute value of the difference between the maximum output value and the minimum output value of the second magnetic permeability sensor while the drive unit is rotationally driving the transport screw for the predetermined time is smaller than the predetermined value, the control unit executes a third control for controlling the drive unit to rotationally drive the transport screw under a second rotation condition different from the first rotation condition during a non-developing operation in which the developing operation is not executed characterizing the image forming apparatus according to claim 10.

12. The first rotation condition is to rotate the conveying screw in a first rotation direction. The second rotation condition is to repeat rotating the conveying screw in the first rotation direction and rotating the conveying screw in a second rotation direction opposite to the first rotation direction. The image forming apparatus according to claim 11, characterized in that.

13. The first rotation condition is to rotate the conveying screw in a first rotation direction. The second rotation condition is, when the environmental humidity is a first humidity, to repeat rotating the conveying screw in the first rotation direction at a first rotation speed and rotating the conveying screw in a second rotation direction opposite to the first rotation direction at the first rotation speed; and when the environmental humidity is a second humidity lower than the first humidity, to repeat rotating the conveying screw in the first rotation direction at a second rotation speed higher than the first rotation speed and rotating the conveying screw in the second rotation direction at the second rotation speed. The image forming apparatus according to claim 11, characterized in that.

14. The first rotation condition is to rotate the conveying screw at a first rotation speed. The second rotation condition is to rotate the conveying screw at a second rotation speed higher than the first rotation speed. The image forming apparatus according to claim 11, characterized in that.

15. The first rotation condition is to rotate the conveying screw at a first rotation speed. The second rotation condition is, when the environmental humidity is a first humidity, to rotate the conveying screw at a second rotation speed higher than the first rotation speed; and when the environmental humidity is a second humidity lower than the first humidity, to rotate the conveying screw at a third rotation speed higher than the second rotation speed. The image forming apparatus according to claim 11, characterized in that.

16. The control unit executes a third control to control the vibration adding unit so as to execute the vibration adding operation every time an image is formed on a predetermined number of recording materials. The image forming apparatus according to claim 10, characterized in that.

17. The vibration adding unit is located vertically above the second detection unit. The image forming apparatus according to claim 10, characterized in that.

18. The first detection unit and the second detection unit are arranged within a range of a distance corresponding to four pitches of the blades of the conveyance screw with respect to the developer conveyance direction of the conveyance screw. The image forming apparatus according to claim 10, characterized in that.

19. An image carrier, A developer carrier that carries a developer containing toner and a carrier for developing an electrostatic latent image formed on the image carrier, a developing container that stores the developer supplied to the developer carrier, a conveyance screw that conveys the developer stored in the developing container, a developer discharge unit for discharging a part of the developer stored in the developing container, a first magnetic permeability sensor having a first detection unit for detecting the magnetic permeability of the developer stored in the developing container, and a second magnetic permeability sensor having a second detection unit for detecting the magnetic permeability of the developer stored in the developing container. A drive unit that rotationally drives the conveyance screw, A developer supply unit that supplies the developer to the developing container, A vibration unit that applies vibration to the developing device, A control unit, Comprising, The second detection unit is vertically above the first detection unit. The control unit executes a first control for controlling the developer supply unit to supply the developer to the developing container based on an output value of the first magnetic permeability sensor while the drive unit rotationally drives the conveyance screw. The control unit, When an integrated value of the output value of the second magnetic permeability sensor while the drive unit rotationally drives the conveyance screw for a predetermined time is greater than a predetermined integrated value, the control unit executes a second control for controlling the vibration unit to perform a vibration operation of applying vibration to the developing device. When the integrated value of the output value of the second magnetic permeability sensor while the drive unit rotationally drives the conveyance screw for the predetermined time is less than or equal to the predetermined integrated value, the second control is not executed. An image forming apparatus, characterized in that.

20. An image carrier, A developing device including a developer carrier that carries a developer containing toner and a carrier for developing an electrostatic latent image formed on the image carrier, a developing container that stores the developer supplied to the developer carrier, a transport screw that transports the developer stored in the developing container, a developer discharge unit for discharging a part of the developer stored in the developing container, a first magnetic permeability sensor having a first detection unit that detects the magnetic permeability of the developer stored in the developing container, and a second magnetic permeability sensor having a second detection unit that detects the magnetic permeability of the developer stored in the developing container, a drive unit that rotationally drives the transport screw, a developer supply unit that supplies the developer to the developing container, a vibration unit that applies vibration to the developing device, a control unit, is provided, wherein the second detection unit is located vertically above the first detection unit, the control unit executes a first control for controlling the developer supply unit to supply the developer to the developing container based on an output value of the first magnetic permeability sensor while the drive unit rotationally drives the transport screw, the control unit, when a standard deviation of an output value of the second magnetic permeability sensor while the drive unit rotationally drives the transport screw for a predetermined time is smaller than a predetermined standard deviation, executes a second control for controlling the vibration unit to perform a vibration operation for applying vibration to the developing device, when the standard deviation of the output value of the second magnetic permeability sensor while the drive unit rotationally drives the transport screw for the predetermined time is equal to or greater than the predetermined standard deviation, does not execute the second control An image forming apparatus characterized by the above.

Images