Developing device and image forming apparatus

Abstract

To stabilize the detection of the concentration of toner in a developer regarding a developing device in which an admix auger and a supply auger are disposed vertically adjacent to each other in a gravity direction.SOLUTION: A developing device includes: supply and transportation means that transports a developer containing toner and carrier to a developer holder holding the developer while supplying the developer; agitation and transportation means that transports the developer while agitating the developer in a hollow transport path that is disposed to be adjacent to and below the supply and transportation means in a vertical direction; an upward transport path that is disposed on a downstream side in a transport direction of the agitation and transportation means and through which the developer transported from the agitation and transportation means is sent to the supply and transportation means on an upper side; detection means that detects the concentration of the toner in the developer at a position upstream of the upward transport path in the transport direction of the agitation and transportation means; and removal means that removes the developer remaining on a detection surface, which is exposed in the transport path, of the detection means by coming into contact with the detection surface across from one end to the other end of the detection surface.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a developing device and an image forming apparatus. [Background technology]

[0002] A powder conveying device is known that includes a first mixing and conveying means that mixes and conveys powder, a receiving means that receives the powder from the first mixing and conveying means, a second mixing and conveying means that is arranged vertically below the first mixing and conveying means and mixes and conveys the powder, an upper conveying means that is arranged downstream in the conveying direction of the second mixing and conveying means and conveys the powder conveyed from the second mixing and conveying means to the upper first mixing and conveying means, and a speed increasing means that increases the rotation speed of the rotation shaft of any of the first mixing and conveying means, the second mixing and conveying means, and the receiving means and transmits the rotation to the upper conveying means (Patent Document 1).

[0003] A developing device is also known that includes a housing in which a hollow transport path is formed, a transport member that transports developer within the transport path, a support part that is fixed to the end of the housing with a fastening member to support the transport member at the end of the transport path, and a cooling part that is fixed by being sandwiched between the support part and the housing (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-88153 [Patent Document 2] Japanese Patent Publication No. 2022-178646 Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION An object of the present invention is to stabilize detection of the toner concentration of developer in a developing device in which an admix auger and a supply auger are arranged adjacent to each other vertically in the direction of gravity. [Means for solving the problem]

[0006] In order to solve the above problem, the developing device according to claim 1 is a supplying and conveying means for supplying and conveying a developer containing a toner and a carrier to a developer carrier holder; a stirring and conveying means for stirring and conveying the developer in a hollow conveying path disposed vertically below and adjacent to the supply and conveying means; an upper conveying path disposed downstream of the agitating and conveying means in a conveying direction, for sending the developer conveyed from the agitating and conveying means to the supply and conveying means above; a detecting means for detecting a toner concentration of the developer on an upstream side of the upper conveying path in a conveying direction of the agitating and conveying means; a removing means for removing the developer remaining on a detection surface of the detecting means, the detection surface being exposed in the transport path, by coming into contact with the detection surface so as to cross the detection surface from one end to the other end; Equipped with It is characterized by:

[0007] The invention described in claim 2 is the developing device described in claim 1, the removing means is the developer attracted to a magnetic material provided integrally with the stirring and conveying means and standing up in a chain; It is characterized by:

[0008] The invention described in claim 3 is the developing device described in claim 2, The detection means is disposed vertically below the rotation center of the stirring and conveying means. It is characterized by:

[0009] The invention described in claim 4 is the developing device described in claim 2, The detection means is arranged in a range of +10 degrees to -10 degrees, with a straight line connecting the rotation center of the supply transport means and the rotation center of the stirring transport means being 0 degrees. Characterized by

[0010] In order to solve the above problem, the image forming apparatus according to claim 4 is an image carrier that holds an electrostatic latent image; a developing means for developing the electrostatic latent image on the image carrier; Equipped with The developing device according to any one of claims 1 to 4 is used as the developing means. It is characterized by: [Effects of the Invention]

[0011] According to the first aspect of the present invention, in a developing device in which an admix auger and a supply auger are arranged adjacent to each other in the vertical direction in the direction of gravity, detection of the toner concentration of the developer can be stabilized.

[0012] According to the second aspect of the present invention, the developer remaining on the detection surface of the detection means can be removed.

[0013] According to the invention as set forth in claim 3, it is possible to save space in the developing device.

[0014] According to the invention as set forth in claim 4, it is possible to further improve the accuracy of detecting the toner concentration while saving space for the developing device.

[0015] According to the fifth aspect of the present invention, it is possible to stabilize the detection of the toner concentration of the developer. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view illustrating an example of a schematic configuration of an image forming apparatus. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view showing a photosensitive unit and a developing device. [Figure 3] FIG. 2 is a schematic vertical cross-sectional view showing the configuration of a developing device. [Figure 4] 3 is a schematic cross-sectional view developed horizontally along line ABC, illustrating the transport of developer within the developing device. FIG. [Figure 5] FIG. 2 is a diagram illustrating toner concentration detection by an ATC sensor. [Figure 6]10A and 10B are diagrams illustrating removal of developer from the detection surface of the ATC sensor. [Figure 7] FIG. 10 is a cross-sectional view showing the arrangement position of an ATC sensor in a modified example. [Figure 8] FIG. 2 is a diagram showing the configuration of an air flow path in the developing device. [Figure 9] FIG. 4 is a cross-sectional view showing the flow of air in an air flow path. DETAILED DESCRIPTION OF THE INVENTION

[0017] Next, the present invention will be described in more detail below with reference to the drawings, showing embodiments and specific examples, but the present invention is not limited to these embodiments and specific examples. Furthermore, in the following explanation using the drawings, it should be noted that the drawings are schematic and the ratios of the dimensions, etc. may differ from those of the actual product, and in order to facilitate understanding, illustrations of components other than those necessary for the explanation have been omitted as appropriate.

[0018] (1) Overall Configuration and Operation of Image Forming Apparatus (1.1) Overall configuration of image forming apparatus FIG. 1 is a cross-sectional view showing an example of the general configuration of an image forming apparatus 1 according to this embodiment, and FIG. 2 is a vertical cross-sectional view showing a photosensitive unit 13 and a developing device 14. As shown in FIG. The image forming device 1 is configured to include an image forming unit 10, a paper feeding device 20 attached below the image forming unit 10, a paper discharge unit 30 provided at one end of the image forming unit 10 and from which printed paper is discharged, an operation display unit 40, and an image processing unit 50 that generates image information from printing information sent from a higher-level device.

[0019] The image forming unit 10 is composed of a system control device 11, an exposure device 12, a photosensitive unit 13, a developing device 14, a transfer device 15, paper transport devices 16a, 16b, 16c, and a fixing device 17, and forms a toner image on a recording medium fed from a paper feed device 20.

[0020] The paper feeder 20 supplies recording media to the image forming unit 10. That is, the paper feeder 20 is provided with a plurality of paper stacking units 21, 22 that accommodate recording media of different types (e.g., material, thickness, paper size, paper grain), and supplies a recording medium fed from any one of the plurality of paper stacking units 21, 22 to the image forming unit 10.

[0021] The paper discharge unit 30 discharges the recording medium on which a toner image has been formed in the image forming unit 10 and fixed by the fixing device 17. To this end, the paper discharge unit 30 is equipped with a transport path 30a that transports the recording medium after fixing, and a paper discharge storage unit T1 that stores the discharged recording medium. In addition, when toner images are formed on both sides of the recording medium, the paper discharge unit 30 is equipped with a paper reversing unit 18 that turns the recording medium over and sends it to the paper transport device 16b. The paper discharge unit 30 may also have a function of performing post-processing such as cutting and stapling on the stack of paper output from the image forming unit 10.

[0022] The operation display unit 40 is used to input various settings and instructions and to display information. In other words, it corresponds to a so-called user interface and is configured by combining a liquid crystal display panel, various operation buttons, a touch panel, etc.

[0023] The image processing unit 50 is configured as, for example, a dedicated processor or processing board, and executes image processing such as color correction, gradation correction, etc. The data processed by the image processing unit 50 is sent to the image forming unit 10.

[0024] (1.2) Configuration and operation of the image forming unit In the image forming device 1 configured as described above, the recording medium fed out from the paper stacking unit 21, 22 specified for each sheet to be printed in the print job is sent to the image forming unit 10 in accordance with the timing of image formation.

[0025] The image forming section 10 includes a photosensitive unit 13 and a developing device 14 .

[0026] The photosensitive unit 13 includes photosensitive drums 31 as image carriers that are arranged in parallel below the exposure device 12 and are driven to rotate. A charger 32, exposure device 12, developing device 14, primary transfer roller 52, and cleaning device 33 are arranged along the rotation direction of the photosensitive drum 31 (indicated by the arrow in the drawing).

[0027] The developing device 14 has a developing roller 42 as a developer carrier disposed opposite the photosensitive drum 31. Each developing device 14 is configured in substantially the same manner except for the developer, and forms a toner image of yellow (Y), magenta (M), cyan (C), or black (K) on each photosensitive drum 31 that it faces with its respective developing roller 42.

[0028] Above the developing device 14, replaceable toner cartridges TC that contain toner, and a toner supply device (not shown) that supplies toner and carrier from each toner cartridge TC to the developing device 14 are arranged.

[0029] The surface of the rotating photosensitive drum 31 is uniformly charged by the charger 32, and an electrostatic latent image is formed on it by latent image forming light emitted from the exposure device 12. The electrostatic latent image formed on the photosensitive drum 31 is developed into a toner image by the developing roller 42.

[0030] The transfer device 15 is configured to include an intermediate transfer belt 51 onto which the color toner images formed on the photosensitive drums 31 of each photosensitive unit 13 are transferred in multiple layers, a primary transfer roller 52 which sequentially transfers (primary transfer) the color toner images formed on each photosensitive unit 13 onto the intermediate transfer belt 51, and a secondary transfer roller 53 which collectively transfers (secondary transfer) the color toner images transferred in superimposed form onto the intermediate transfer belt 51 onto a recording medium.

[0031] The color toner images formed on the photosensitive drum 31 of each photosensitive unit 13 are electrostatically transferred (primary transfer) sequentially onto the intermediate transfer belt 51 by a primary transfer roller 52 to which a predetermined transfer voltage is applied from a power supply device (not shown) controlled by the system control device 11, and a superimposed toner image in which the color toners are superimposed is formed.

[0032] As the intermediate transfer belt 51 moves, the superimposed toner image on the intermediate transfer belt 51 is transported to a secondary transfer portion TR where a secondary transfer roller 53 is placed in pressure contact with a backup roller 65 via the intermediate transfer belt 51 . When the superimposed toner image is transported to the secondary transfer unit TR, a recording medium is supplied to the secondary transfer unit TR from the paper feeder 20 in time with this. A predetermined secondary transfer voltage is applied from a power supply unit (not shown) controlled by the system control unit 11 to a backup roller 65 that faces the secondary transfer roller 53 across the intermediate transfer belt 51, and the multiple toner images on the intermediate transfer belt 51 are collectively transferred onto the recording medium.

[0033] Residual toner on the surface of the photosensitive drum 31 is removed by a cleaning device 33 and collected in a waste toner container (not shown). The surface of the photosensitive drum 31 is then uniformly recharged by the charger 32, and the next image formation cycle begins.

[0034] The fixing device 17 has an endless fixing belt 17a that rotates in one direction and a pressure roller 17b that contacts the peripheral surface of the fixing belt 17a and rotates in one direction, and a nip portion (fixing area) is formed in the pressure contact area between the fixing belt 17a and the pressure roller 17b. The recording medium onto which the toner image has been transferred in the transfer device 15 is transported via the paper transport device 16a to the fixing device 17 without the toner image being fixed thereon. The recording medium transported to the fixing device 17 has the toner image fixed thereon by the action of heat and pressure applied by a pair of fixing belt 17a and pressure roller 17b.

[0035] The recording medium on which the fixing has been completed is sent to the paper discharge unit 30 and stacked on the discharged paper storage unit T1. In addition, post-processing such as cutting and stapling is performed as necessary.

[0036] (2) Developing device FIG. 3 is a schematic vertical cross-sectional view showing the configuration of the developing device 14, and FIG. 4 is a schematic cross-sectional view developed horizontally along line ABC, illustrating the transport of developer within the developing device 14. The configuration and operation of the developing device 14 will be described below with reference to the drawings.

[0037] (2.1) Overall structure of the developing device The developing device 14 includes a developing housing 41 that contains developer containing toner and carrier, a developing roller 42 as an example of a developer holder that holds the developer and transports it to a development area facing the photosensitive drum 31, a supply auger 43 as an example of a supply transport means that transports the developer so that it passes through the developing roller 42 while stirring it, an admix auger 44 as an example of a stirring transport means that transports the developer to the supply auger 43 while stirring it, a counter auger 45 that transports the developer peeled off from the developing roller 42 in a direction opposite to the transport direction of the admix auger 44, and a layer thickness regulating member 49 that regulates the amount (layer thickness) of developer held on the developing roller 42.

[0038] The developing roller 42 has a magnet inside, and rotates with the developer magnetically attracted to its surface, thereby transporting the developer from the developing housing 41 to a developing position facing the photosensitive drum 31. At the developing position, the electrostatic latent image formed on the surface of the photosensitive drum 31 is developed, and the developer after development returns into the developing housing 41 as the developing roller 42 rotates.

[0039] (2.2) Developer circulation 4 is a schematic cross-sectional view expanded horizontally along line ABC in the vertical cross-sectional view to explain the transport (movement) of developer within the developing device 14. In FIG. In order to accommodate the supply auger 43 and the admix auger 44, the development housing 41 is provided with a first developer storage section 41A and a second developer storage section 41B, each having a substantially cylindrical cross section, as shown in FIG. 3. The second developer accommodating section 41B is separated by a partition wall 41a provided in the development housing 41, and is disposed adjacent to and vertically below the first developer accommodating section 41A. The development housing 41 is also provided with a third developer accommodating section 41C for accommodating the developer peeled off from the counter auger 45 and development roller 42 and transporting the developer in the direction opposite to the transport direction of the admix auger 44. As schematically shown in FIG. 4, openings 46A and 46B are provided at both longitudinal ends of the partition wall 41a, respectively, for transferring developer between the supply auger 43 and the admix auger 44, which are disposed adjacent to each other in the vertical direction.

[0040] The supply auger 43 and the admix auger 44 have spiral blades 43b and 44b formed around the rotation shafts 43a and 44a, and receive rotational driving force from a drive source (not shown) to rotate along the inner walls of the first developer storage section 41A and the second developer storage section 41B, thereby transporting the developer in a predetermined direction within the first developer storage section 41A and the second developer storage section 41B.

[0041] Specifically, the admix auger 44 transports the developer in the second developer storage unit 41B in the direction of the arrow (Y) while stirring it, and the supply auger 43 transports the developer in the first developer storage unit 41A in the direction of the arrow (-Y) while stirring it. The developer transported in the direction of the arrow (Y) moves (is pumped up) from an opening 46A, which is an example of an upper transport path, to the first developer storage unit 41A, and the developer transported in the direction of the arrow (-Y) moves (falls) from the opening 46B to the second developer storage unit 41B. As a result, the developer in the development housing 41 circulates while being agitated by the admix auger 44 and the supply auger 43. The toner in the developer is charged by this agitation of the developer.

[0042] An inlet 46C (shown schematically in FIG. 4 to explain its function) that receives toner and carrier supplied from the toner cartridge TC is provided on the top surface portion of the IN side (-Y direction, rear side of the device) of the development housing 41. The toner received by the development device 14 at the inlet 46C is transported by the supply auger 43 to the second developer accommodating section 41B of the development housing 41, where it is mixed with the developer.

[0043] The toner supplied from the toner cartridge TC through the receiving port 46C is transported from the IN side to the OUT side (Y direction: the front side of the device) while being agitated together with the carrier by the admix auger 44, and is moved through the opening 46A on the OUT side to the first developer storage unit 41A in which the supply auger 43 is disposed. Then, while being transported to the IN side by the supply auger 43, the toner is supplied to the developing roller 42 together with the carrier.

[0044] (2.3) Toner concentration detection FIG. 5 is a diagram illustrating toner concentration detection by an ATC sensor. The developing device 14 is provided with an ATC (Auto Toner Control) sensor SR as an example of a detection means for measuring the ratio of toner to carrier in the developer circulating inside the developing housing 41 (toner concentration: TC). 5, the ATC sensor SR measures the change in magnetic permeability according to the toner concentration (TC) in the developer through a detection surface SRa that comes into contact with the developer, and detects the toner concentration (TC) by detecting, for example, a changing analog output voltage. In the image forming apparatus 1, the system control device 11 instructs the supply of toner from the toner cartridge TC based on the measurement value by the ATC sensor SR, thereby maintaining the TC value of the developer at a predetermined value.

[0045] The toner supplied from the toner cartridge TC is mixed with the carrier and transported from the IN side to the OUT side within the second developer container 41B while being stirred by the admix auger 44. It is desirable to detect the toner concentration in the developer at the OUT side where the toner is sufficiently stirred (the pumping position where the toner is pumped up to the supply auger 43 through the opening 46A), but at the pumping position, the amount and bulk density of the developer within the detection range of the ATC sensor SR are unstable, and there is a risk that the output of the ATC sensor SR will change.

[0046] In this embodiment, the ATC sensor SR is disposed at a position upstream of the scooping position in the direction in which the admix auger 44 transports the developer, as shown in FIG. More specifically, the ATC sensor SR is disposed in the approximate center of the second developer storage unit 41B in the direction in which the developer is transported by the admix auger 44. In the approximate center of the second developer storage unit 41B, the amount and bulk density of the developer are more stable than at the pumped-up position, improving the accuracy of detection of the toner concentration by the ATC sensor SR.

[0047] 3, the ATC sensor SR is disposed vertically below the rotation center c2 of the admix auger 44 in the rotation direction of the admix auger 44. This allows for space saving (indicated by W in FIG. 3) of the developing device 14.

[0048] 3 (see also FIG. 6(b)), the second developer accommodating section 41B has a circular cross section in a direction intersecting the developer transport direction, and there is substantially no space formed vertically above the admix auger 44 rotatably accommodated therein, through which the toner stirred by the admix auger 44 and mixed with the carrier floats up from the developer surface and is transported. This makes it possible to prevent the toner from being stirred while floating on the developer surface, and the toner concentration can be stably detected even when the ATC sensor SR is disposed approximately in the center of the second developer accommodating section 41B in the developer transport direction.

[0049] FIG. 6 is a diagram illustrating the removal of developer from the detection surface SRa of the ATC sensor SR. The admix auger 44 is provided with a magnetic paddle 44A, an example of a removal means, at a position opposite the ATC sensor SR, which contacts the detection surface SRa of the ATC sensor SR across the detection surface SRa from one end to the other and removes developer remaining on the detection surface SRa.

[0050] The magnetic paddle 44A consists of an arm 44Aa that protrudes radially from the rotation shaft 44a of the admix auger 44 and a magnet 44Ab attached to the tip of the arm 44Aa, and is rotatable around the rotation shaft 44a integrally with the admix auger 44. When the magnetic paddle 44A rotates, the developer attracted to the magnet 44Ab and formed into spikes comes into contact with the detection surface SRa of the ATC sensor SR and removes the developer on the detection surface SRa, thereby preventing the developer from accumulating on the detection surface SRa and improving the accuracy of detecting the toner concentration.

[0051] "Variations" FIG. 7 is a schematic cross-sectional view showing the arrangement position of the ATC sensor SR in a modified example. The ATC sensor SR may be placed in the range of +10 degrees to -10 degrees, with the line connecting the rotation center c1 of the supply auger 43 and the rotation center c2 of the admix auger 44 being 0 degrees. Compared to placing the ATC sensor SR vertically below the rotation center c2 of the admix auger 44, the stirred developer is more easily compressed, making it possible to further improve the accuracy of toner concentration detection while saving space in the developing device.

[0052] (2.4) Air flow path FIG. 8 is a diagram showing the configuration of an air flow path 47 in the developing device 14, and FIG. 9 is a cross-sectional schematic diagram showing the flow of air in the air flow path 47. The developing device 14 has an air flow path 47 formed adjacent to and vertically below the second developer accommodating section 41B, through which air taken in from an inlet along the transport direction of the admix auger 44 flows toward the exhaust port. The air flow path 47 is formed by utilizing a part of the outer surface 41Ba of the second developer accommodating portion 41B that accommodates the admix auger 44. Specifically, as shown in Fig. 8, the air flow path 47 is formed by a gap (shown by dots in the drawing) between the outer surface 41Ba of the second developer accommodating portion 41B and the outer surface 41Ca of the third developer accommodating portion 41C and a plate-like body 48 that is provided opposite the outer surface 41Ba of the second developer accommodating portion 41B and the outer surface 41Ca of the third developer accommodating portion 41C.

[0053] A plurality of ribs R1, R2, and R3 are provided upright continuously in the longitudinal direction of the developing device 14 on an outer surface 41Ba of the second developer accommodating portion 41B that accommodates the admix auger 44, and on an outer surface 41Ca of the third developer accommodating portion 41C that accommodates the counter auger 45 and transports the developer in the opposite direction to the transport direction of the admix auger 44. A plate-like body 48 is provided in the longitudinal direction of the developing device 14 facing the plurality of ribs R1, R2, and R3, and an air flow path 47 that communicates from the OUT side (inlet) to the IN side (exhaust port) of the developing device 14 in the longitudinal direction of the developing device 14 is formed between an inner surface 48a of the plate-like body 48 and the outer surface 41Ba of the second developer accommodating portion 41B and the outer surface 41Ca of the third developer accommodating portion 41C.

[0054] In the developing device 14 of this embodiment, the developer is transported from the IN side (the back side of the device) to the OUT side (the front side of the device) by the admix auger 44, and is moved to the first developer storage section 41A where the supply auger 43 is located on the OUT side, which is the pumping position. As a result, in the developing device 14, the circulating developer is compressed on the OUT side, and the temperature of the developer tends to become higher than in other places.

[0055] 9, a louver-shaped opening is formed on the front side (OUT side) of the image forming apparatus 1, and an intake fan F is disposed on the rear side (IN side) of the image forming apparatus 1. In the developing device 14 mounted on such an image forming apparatus 1, outside air flows in from an inlet 47a on the OUT side of the air flow path 47, flows through the air flow path 47, and is discharged from an outlet 47b on the IN side. This makes it possible to reduce the space required for the developing device 14 while preventing erroneous detection of the toner concentration by the ATC sensor SR due to clogging with developer.

[0056] (3) Function of the developing device The developing device 14 includes a supply auger 43 that transports developer while supplying it to a developing roller 42 that holds developer containing toner and carrier, an admix auger 44 that transports the developer while stirring it in a hollow transport path located adjacent to and vertically below the supply auger 43, an opening 46A that is located downstream of the admix auger 44 in the transport direction and serves as an upper transport path through which the developer transported from the admix auger 44 is sent to the upper supply auger 43, and an ATC sensor SR that detects the toner concentration of the developer upstream of the opening 46A in the transport direction of the admix auger 44. The ATC sensor SR is located approximately in the center of the second developer storage unit 41B that houses the admix auger 44, upstream of the admix auger 44 in the transport direction, so that the amount and bulk density of the developer are more stable than in the upper transport path, improving the accuracy of detecting the toner concentration.

[0057] The second developer accommodating section 41B has a circular cross section in a direction intersecting the developer transport direction, and there is substantially no space formed vertically above the admix auger 44 rotatably accommodated inside, where the toner stirred by the admix auger 44 and mixed with the carrier floats up from the developer surface and is transported. This makes it possible to prevent the toner from being stirred while floating on the developer surface.

[0058] The ATC sensor SR is disposed vertically below the rotation center c2 of the admix auger 44. This allows the developing device 14 to be space-saving.

[0059] The ATC sensor SR may be disposed in the range of +10 degrees to -10 degrees, with the line connecting the rotation center c1 of the supply auger 43 and the rotation center c2 of the admix auger 44 being 0 degrees. This allows the development device 14 to be space-saving while further improving the accuracy of toner concentration detection.

[0060] The ATC sensor SR is provided with a magnetic paddle 44A that crosses the detection surface SRa exposed in the second developer storage section 41B from one end to the other and comes into contact with the detection surface SRa to remove developer remaining on the detection surface SRa. The magnetic paddle 44A consists of an arm 44Aa that protrudes radially from the rotation shaft 44a of the admix auger 44 and a magnet 44Ab attached to the tip of the arm 44Aa. The developer attracted to the magnet 44Ab and forming spikes comes into contact with the detection surface SRa of the ATC sensor SR and removes the developer remaining on the detection surface SRa. This stabilizes the detection of the toner concentration of the developer.

[0061] An air flow path 47 is formed adjacent to and below the second developer accommodating portion 41B in the vertical direction, through which air taken in from an inlet along the transport direction of the admix auger 44 flows toward the exhaust port. The air flow path 47 is formed by utilizing a part of the outer surface 41Ba of the second developer accommodating portion 41B, and is formed by a gap between the outer surface 41Ba of the second developer accommodating portion 41B and a plate-like body 48 provided opposite the outer surface 41Ba. This makes it possible to reduce the space required for the developing device 14 while suppressing erroneous detection of the toner concentration of the developer.

[0062] (Addendum) This specification discloses at least the following inventions. [1] a supplying and conveying means for supplying and conveying a developer containing a toner and a carrier to a developer carrier holder; a stirring and conveying means for stirring and conveying the developer in a hollow conveying path disposed vertically below and adjacent to the supply and conveying means; an upper conveying path disposed downstream of the agitating and conveying means in a conveying direction, for sending the developer conveyed from the agitating and conveying means to the supply and conveying means above; an air flow path provided adjacent to and below the conveying path in the vertical direction, through which air taken in from an inlet along the conveying direction of the agitating and conveying means flows toward an exhaust port; a detecting means for detecting a toner concentration of the developer, the detecting means being disposed in the air flow path and located upstream of the upper conveying path in a conveying direction of the agitating and conveying means; a removing means for removing the developer remaining on a detection surface of the detecting means, the detection surface being exposed in the transport path, by coming into contact with the detection surface so as to cross the detection surface from one end to the other end; Equipped with A developing device characterized by: [2] the transport path has a circular cross section in a direction intersecting the transport direction of the developer, and a space is not substantially formed above the stirring and transporting means in a vertical direction, where the toner, which is stirred by the stirring and transporting means and mixed with the carrier, floats up from the developer surface and is transported; The developing device according to [1]. [3] The air flow path is formed by a gap between an outer surface of the conveying path and a plate-like body provided opposite the outer surface. The developing device according to [1] or [2]. [4] The detection means is disposed vertically below the rotation center of the stirring and conveying means. The developing device according to any one of [1] to [3]. [5] The detection means is disposed within a range of +10 degrees to -10 degrees, with a straight line connecting the rotation center of the supply transport means and the rotation center of the stirring transport means being 0 degrees. The developing device according to any one of [1] to [3]. [6] the detecting means detects the toner concentration of the developer by contacting a detecting surface exposed inside the transport path with the developer; The developing device according to any one of [1] to [5] above. [7] the removing means is developer that has been attracted to a magnetic material provided integrally with the stirring and conveying means and formed into spikes; The developing device according to any one of [1] to [6]. [8] A blowing means; an image carrier that holds an electrostatic latent image; a developing means for developing the electrostatic latent image on the image carrier; Equipped with An image forming apparatus using the developing device according to any one of [1] to [7] as the developing means.

[0063] According to the invention described in [1], it is possible to reduce the space required for the developing device while suppressing erroneous detection of the toner concentration of the developer. According to the invention described in [2], it is possible to prevent the toner from being stirred while floating on the surface of the developer. According to the invention described in [3], it is possible to form an air flow path below the developing device while saving space for the developing device. According to the invention described in [4], it is possible to save space in the developing device. According to the invention described in [5], it is possible to further improve the accuracy of detecting the toner concentration while saving space for the developing device. According to the invention described in [6], the toner concentration of the developer can be detected. According to the invention described in [7], the developer remaining on the detection surface of the detection means can be removed. According to the invention described in [8], it is possible to save space in the developing device. [Explanation of symbols]

[0064] 1. Image forming device 10. Image forming unit 11. System control device 12. Exposure equipment 13 Photoconductor unit 14....Developing device, 41....Developing housing, 41A....First developer transport path, 41B....Second developer transport path, 41C....Third developer transport path, 42....Developing roller, 43....Supply auger, 44....Admix auger, 44A....Magnetic paddle, 45....Counter auger, 46A....Opening (upper transport path), 46B....Opening, 46C···· Inlet port, 47··· Air flow path, 47a··· Inlet port, 47b··· Outlet port, 48··· Layer thickness control member 15. Transfer device 17. Fixing device 20. Paper feeder 30....Paper ejection section 40...Operation display section 50 Image processing unit SR···Toner concentration sensor

Claims

1. a supplying and conveying means for supplying and conveying a developer containing a toner and a carrier to a developer carrier holder; a stirring and conveying means for stirring and conveying the developer in a hollow conveying path disposed vertically below and adjacent to the supply and conveying means; an upper conveying path disposed downstream of the agitating and conveying means in a conveying direction, for sending the developer conveyed from the agitating and conveying means to the supply and conveying means above; a detecting means for detecting a toner concentration of the developer on an upstream side of the upper conveying path in a conveying direction of the agitating and conveying means; a removing means for removing the developer remaining on a detection surface of the detecting means, the detection surface being exposed in the transport path, by coming into contact with the detection surface so as to cross the detection surface from one end to the other end; Equipped with A developing device characterized by:

2. the removing means is the developer attracted to a magnetic material provided integrally with the stirring and conveying means and standing up in a chain; 2. The developing device according to claim 1.

3. The detection means is disposed vertically below the rotation center of the stirring and conveying means.

3. The developing device according to claim 2.

4. the detection means is disposed within a range of +10 degrees to -10 degrees, with a straight line connecting the rotation center of the supply transport means and the rotation center of the stirring transport means being 0 degrees; 3. The developing device according to claim 2.

5. an image carrier that holds an electrostatic latent image; a developing means for developing the electrostatic latent image on the image carrier; Equipped with 5. The developing device according to claim 1, wherein the developing means is a developing device according to claim 1. An image forming apparatus characterized by:

Images