Developing device and image forming apparatus

Abstract

A developing device includes: a supply conveyance mechanism that conveys a developer while supplying the developer to a developer holder that holds the developer; a stirring / conveying mechanism that conveys the developer while stirring the developer in a hollow conveying path disposed adjacent to the lower side of the supply / conveying mechanism in the vertical direction; an upper conveyance path that is disposed on the downstream side of the stirring conveyance mechanism in the conveyance direction and that feeds the developer to an upper supply conveyance mechanism; an air flow path which is disposed adjacent to the lower part of the conveying path in the vertical direction, and through which the air taken in from the inflow port flows toward the exhaust port in the conveying direction of the stirring and conveying mechanism; a detection mechanism that is disposed in the air flow path and detects the toner concentration of the developer on the upstream side in the conveyance direction; and a removing mechanism which, for the detection surface of the detection mechanism, is in contact with the detection surface in a manner of crossing from one end of the detection surface to the other end of the detection surface so as to remove the developer retained on the detection surface.

Description

Technical Field

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

[0002] A powder conveying device is known, which comprises: a first stirring and conveying mechanism for stirring and conveying powder; a receiving mechanism for receiving powder from the first stirring and conveying mechanism; a second stirring and conveying mechanism arranged below the first stirring and conveying mechanism in a vertical direction, for stirring and conveying powder; an upper conveying mechanism arranged on the downstream side of the conveying direction of the second stirring and conveying mechanism, for conveying the powder conveyed from the second stirring and conveying mechanism to the first stirring and conveying mechanism above; and a speed increasing mechanism for accelerating the rotation of the rotating shaft of any one of the first stirring and conveying mechanism, the second stirring and conveying mechanism and the receiving mechanism and transmitting the rotation to the upper conveying mechanism (Patent Document 1).

[0003] There is also known a developing device comprising: a frame forming a hollow conveying path; a conveying member that conveys the developer within the conveying path; a supporting portion that is fixed to an end portion of the frame by a fastening member to support the conveying member at the end portion of the conveying path; and a cooling portion that is fixed by being sandwiched between the supporting portion and the frame (Patent Document 2).

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2023-88153

[0005] Patent Document 2: Japanese Patent Application Laid-Open No. 2022-178646

[0006] The present invention reduces the space of the developing device and suppresses erroneous detection of toner concentration of the developer in a developing device in which a mixing and stirring auger and a supply auger are arranged adjacent to each other in the direction of gravity. Summary of the Invention

[0007] In order to solve the above-mentioned problem, the developing device according to claim 1 is characterized by comprising:

[0008] a supply and conveying mechanism for conveying the developer while supplying the developer to a developer holding member holding the developer containing a toner and a carrier;

[0009] a stirring and conveying mechanism for conveying the developer while stirring it in a hollow conveying path disposed adjacent to and vertically below the supply and conveying mechanism;

[0010] an upper conveying path disposed on the downstream side of the conveying direction of the stirring conveying mechanism and conveying the developer conveyed from the stirring conveying mechanism to the supply conveying mechanism above;

[0011] An air flow path is provided adjacent to and vertically below the conveying path, and flows along the conveying direction of the stirring conveying mechanism, and the air taken in from the inlet flows toward the exhaust port;

[0012] a detection mechanism disposed in the air flow path and configured to detect a toner concentration of the developer upstream of the upper conveying path in the conveying direction of the stirring conveying mechanism; and

[0013] The removing mechanism contacts the detection surface of the detection mechanism exposed in the conveying path so as to extend from one end to the other end of the detection surface to remove the developer accumulated on the detection surface.

[0014] The invention described in claim 2 is characterized in that, in the developing device described in claim 1,

[0015] In the conveying path, the cross-sectional shape in the direction intersecting the conveying direction of the developer is circular, and there is essentially no space above the vertical direction of the stirring and conveying mechanism that can be rotatably accommodated inside, in which the toner stirred by the stirring and conveying mechanism and mixed with the carrier floats from the agent surface of the developer and is conveyed.

[0016] The invention described in claim 3 is characterized in that, in the developing device described in claim 1 or 2,

[0017] The air flow path is formed by a gap between an outer surface of the conveying path and a plate-shaped body provided opposite to the outer surface.

[0018] The invention described in claim 4 is characterized in that, in the developing device described in any one of claims 1 to 3,

[0019] The detection mechanism is arranged vertically below the rotation center of the stirring and conveying mechanism.

[0020] The invention described in claim 5 is characterized in that, in the developing device described in any one of claims 1 to 3,

[0021] The detection mechanism is disposed within a range of +10 to -10 degrees with a straight line connecting the rotation center of the supply conveying mechanism and the rotation center of the stirring conveying mechanism being 0 degrees.

[0022] The invention described in claim 6 is characterized in that, in the developing device described in any one of claims 1 to 5,

[0023] The detection mechanism detects a toner concentration of the developer by bringing a detection surface exposed to the inside of the conveyance path into contact with the developer.

[0024] The invention described in claim 7 is characterized in that, in the developing device described in any one of claims 1 to 6,

[0025] The removal mechanism is a developer that is attracted to a magnetic material provided integrally with the stirring and conveying mechanism to form a magnetic spike.

[0026] In order to solve the above-mentioned problem, the image forming apparatus according to claim 8 is characterized by comprising:

[0027] Air supply mechanism;

[0028] an image holding member that holds an electrostatic latent image; and

[0029] a developing mechanism for developing the electrostatic latent image on the image holding member;

[0030] As the developing mechanism, the developing device according to any one of aspects 1 to 7 is used.

[0031] Effects of the Invention

[0032] According to the first aspect of the present invention, it is possible to suppress erroneous detection of the toner concentration of the developer while achieving space saving of the developing device.

[0033] According to the second aspect of the present invention, it is possible to suppress the toner from being agitated while floating on the surface of the developer.

[0034] According to the third aspect of the present invention, it is possible to form an air flow path below the developing device while achieving space saving of the developing device.

[0035] According to the fourth aspect of the present invention, it is possible to achieve space saving of the developing device.

[0036] According to the fifth aspect of the present invention, it is possible to further improve the detection accuracy of the toner concentration while achieving space saving of the developing device.

[0037] According to the sixth aspect of the present invention, the toner concentration of the developer can be detected.

[0038] According to the seventh aspect of the present invention, the developer accumulated on the detection surface of the detection mechanism can be removed.

[0039] According to the eighth aspect of the present invention, it is possible to achieve space saving of the developing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0041] Figure 1 is a schematic cross-sectional view showing an example of a schematic structure of an image forming apparatus;

[0042] Figure 2 is a schematic longitudinal sectional view showing a photosensitive body unit and a developing device;

[0043] Figure 3 is a schematic longitudinal sectional view showing the structure of a developing device;

[0044] Figure 4 This is a schematic cross-sectional view taken along line ABC in the horizontal direction, illustrating the transport of the developer in the developing device;

[0045] Figure 5 This figure explains toner density detection by the ATC sensor;

[0046] Figure 6 A diagram illustrating removal of developer from the detection surface of the ATC sensor;

[0047] Figure 7 is a cross-sectional schematic diagram showing the arrangement position of an ATC sensor in a modified example;

[0048] Figure 8 is a diagram showing the structure of an air flow path in a developing device;

[0049] Figure 9 It is a schematic cross-sectional view showing the flow of air in the air flow path.

[0050] Explanation of symbols

[0051] 1-image forming device, 10-image forming unit, 11-system control device, 12-exposure device, 13-photosensitive unit, 14-developing device, 41-developing housing, 41A-first developer conveying path, 41B-second developer conveying path, 41C-third developer conveying path, 42-developing roller, 43-supply auger, 44-mixing auger, 44A-magnetic paddle, 45-counting auger, 46A-opening (upper conveying path), 46B-opening, 46C-receiving port, 47-air flow path, 47a-inflow port, 47b-exhaust port, 48-layer thickness limiting component, 15-transfer device, 17-fixing device, 20-paper feeding device, 30-paper discharge unit, 40-operation display unit, 50-image processing unit, SR-toner concentration sensor. DETAILED DESCRIPTION

[0052] Next, the present invention will be described in more detail below with reference to the drawings by giving embodiments and specific examples, but the present invention is not limited to these embodiments and specific examples.

[0053] In the following description using the drawings, it should be noted that the drawings are schematic and that the ratios of dimensions and the like differ from actual ones. For ease of understanding, illustration of components other than those necessary for the description is omitted as appropriate.

[0054] (1) Overall structure and operation of image forming apparatus

[0055] (1.1) Overall structure of image forming apparatus

[0056] Figure 1 is a schematic cross-sectional view showing an example of a schematic configuration of the image forming apparatus 1 according to the present embodiment. Figure 2 It is a schematic longitudinal sectional view showing the photoconductor unit 13 and the developing device 14 .

[0057] The image forming apparatus 1 is configured to include: an image forming unit 10; a paper feeding device 20 installed below the image forming unit 10; a paper discharge unit 30 provided at one end of the image forming unit 10 and discharging printed paper; an operation display unit 40; and an image processing unit 50 for generating image information based on print information sent from a host device.

[0058] The image forming unit 10 includes a system control device 11 , an exposure device 12 , a photoreceptor unit 13 , a developing device 14 , a transfer device 15 , paper conveying devices 16 a , 16 b , and 16 c , and a fixing device 17 , and forms a toner image on a recording medium fed from a paper feeding device 20 .

[0059] The paper feed device 20 supplies recording media to the image forming unit 10. Specifically, it includes a plurality of paper loading sections 21 and 22 for accommodating recording media of different types (e.g., material, thickness, paper size, and paper grain), and supplies recording media drawn from one of these plurality of paper loading sections 21 and 22 to the image forming unit 10.

[0060] The paper discharge unit 30 discharges recording media on which a toner image has been formed in the image forming unit 10 and fixed in the fixing device 17. Therefore, the paper discharge unit 30 includes a conveyance path 30a for conveying the fixed recording media and a paper accommodating portion T1 for accommodating the discharged recording media. Furthermore, the paper discharge unit 30 includes a paper reversing unit 18, which reverses the front and back of the recording media when toner images have been formed on both sides of the recording media, and then delivers the recording media to the paper conveying device 16b. Furthermore, the paper discharge unit 30 may also perform post-processing such as cutting or stapling the bundle of paper discharged from the image forming unit 10.

[0061] The operation display unit 40 is used for inputting various settings and commands and displaying information, and corresponds to a so-called user interface, and is composed of a combination of a liquid crystal display panel, various operation buttons, a touch panel, and the like.

[0062] The image processing unit 50 is configured as, for example, a dedicated processor or a processing board, and performs image processing such as color correction and grayscale correction. The data processed by the image processing unit 50 is sent to the image forming unit 10 .

[0063] (1.2) Structure and Operation of Image Forming Unit

[0064] In the image forming apparatus 1 having such a configuration, recording media drawn from the paper loading sections 21 and 22 are fed into the image forming section 10 each time a designated paper loading section 21 and 22 is printed in a print job, according to the timing of image formation.

[0065] The image forming section 10 includes a photoreceptor unit 13 and a developing device 14 .

[0066] The photoreceptor units 13 are arranged in parallel below the exposure devices 12 and include a photoreceptor drum 31 serving as a rotationally driven image holder. Along the rotational direction of the photoreceptor drum 31 (indicated by the arrow in the figure), the charger 32, the exposure device 12, the developing device 14, the primary transfer roller 52, and the cleaning device 33 are arranged.

[0067] In the developing device 14, a developing roller 42 serving as a developer carrier is disposed opposite the photosensitive drum 31. Each developing device 14 has substantially the same configuration except for the developer, and forms yellow (Y), magenta (M), cyan (C), and black (K) toner images on the opposing photosensitive drum 31 using the developing rollers 42.

[0068] Disposed above the developing device 14 are replaceable toner cartridges TC that store toner and a toner supply device (not shown) that supplies toner and carrier from each toner cartridge TC to the developing device 14 .

[0069] The surface of the rotating photosensitive drum 31 is uniformly charged by the charger 32, and an electrostatic latent image is formed 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.

[0070] The transfer device 15 is constructed to include: an intermediate transfer belt 51, which is used to transfer the color toner images formed on the photosensitive drum 31 of each photosensitive unit 13 multiple times; a primary transfer roller 52, which transfers the color toner images formed on each photosensitive unit 13 to the intermediate transfer belt 51 in sequence (primary transfer); and a secondary transfer roller 53, which transfers the color toner images overlapped and transferred to the intermediate transfer belt 51 to the recording medium at the same time (secondary transfer).

[0071] The color toner images formed on the photosensitive drum 31 of each photosensitive unit 13 are electrostatically transferred (primary transfer) to the intermediate transfer belt 51 in sequence through the primary transfer roller 52, thereby forming overlapping toner images with overlapping color toners. The primary transfer roller is applied with a specified transfer voltage from a power supply device (not shown) controlled by the system control device 11.

[0072] The superimposed toner images on the intermediate transfer belt 51 are transported to the secondary transfer portion TR as the intermediate transfer belt 51 moves. In the secondary transfer portion TR, the secondary transfer roller 53 is arranged in pressure contact with the backup roller 65 via the intermediate transfer belt 51 .

[0073] When the superimposed toner images are conveyed to the secondary transfer section TR, a recording medium is supplied to the secondary transfer section TR from the paper feed device 20 according to the timing. Then, a predetermined secondary transfer voltage is applied from a power supply device (not shown) controlled by the system control device 11 to the backup roller 65, which is opposed to the secondary transfer roller 53 via the intermediate transfer belt 51, to transfer the multiple toner images on the intermediate transfer belt 51 onto the recording medium at once.

[0074] The residual toner on the surface of the photosensitive drum 31 is removed by the cleaning device 33 and collected in a waste toner container (not shown). Then, the surface of the photosensitive drum 31 is uniformly charged again by the charger 32, and the next image forming cycle begins.

[0075] The fixing device 17 includes: 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.

[0076] The recording medium to which the toner image has been transferred in the transfer device 15 is conveyed to the fixing device 17 via the paper conveying device 16a, while the toner image is still unfixed. The recording medium conveyed to the fixing device 17 passes through a pair of fixing belts 17a and a pressure roller 17b, where the toner image is fixed by heat and pressure.

[0077] The recording medium after fixing is fed to the paper discharge section 30 and loaded on the paper discharge container T1. If necessary, post-processing such as cutting or stapling (stitching) is performed on the recording medium.

[0078] (2) Developing device

[0079] Figure 3 is a schematic longitudinal sectional view showing the structure of the developing device 14, Figure 4 It is a schematic cross-sectional view developed in the horizontal direction along line ABC for explaining the transportation of the developer in the developing device 14 .

[0080] Hereinafter, the structure and operation of the developing device 14 will be described with reference to the drawings.

[0081] (2.1) Overall structure of the developing device

[0082] The developing device 14 includes: a developing housing 41, which accommodates a developer including a colorant and a carrier; a developing roller 42, which is an example of a developer retaining body, which holds and transports the developer to a developing area opposite to the photosensitive drum 31; a supply auger 43, which is an example of a supply and conveying mechanism, which stirs and conveys the developer so that it is supplied through the developing roller 42; a mixing auger 44, which is an example of a stirring and conveying mechanism, which stirs and conveys the developer to the supply auger 43; a counting auger 45, which conveys the developer peeled off from the developing roller 42 in a direction opposite to the conveying direction of the mixing auger 44; and a layer thickness limiting component 49, which limits the amount of developer (layer thickness) retained on the developing roller 42; etc.

[0083] The developing roller 42 has a magnet inside and rotates with the developer magnetically attracted to its surface, thereby conveying 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 developed developer is returned to the developing housing 41 by the rotation of the developing roller 42.

[0084] (2.2) Developer circulation

[0085] Figure 4 The transport (movement) of the developer in the developing device 14 will be described using a schematic cross-sectional view taken along line ABC in the horizontal direction in the schematic longitudinal cross-sectional view.

[0086] like Figure 3 As shown, a first developer accommodating portion 41A and a second developer accommodating portion 41B, each having a substantially cylindrical cross-section, are provided in the developer housing 41 to accommodate the supply auger 43 and the mixing auger 44 .

[0087] The second developer accommodating portion 41B is separated by a partition wall 41a provided in the developer housing 41 and is arranged adjacent to the first developer accommodating portion 41A in the vertical direction. In addition, a third developer accommodating portion 41C is provided in the developer housing 41. The third developer accommodating portion 41C is used to accommodate the developer peeled off from the counter auger 45 and the developing roller 42 and to convey the developer in a direction opposite to the conveying direction of the mixing auger 44. Figure 4 As schematically shown in FIG, openings 46A and 46B are provided at both ends of the partition wall 41 a in the longitudinal direction, respectively. The openings 46A and 46B pass the developer between the supply auger 43 and the mixing auger 44 that are arranged adjacent to each other in the vertical direction.

[0088] In the supply auger 43 and the mixing auger 44, spiral blades 43b and 44b are formed around the rotating shafts 43a and 44a, and they receive rotational driving force from a driving source (not shown) and rotate along the inner walls of the first developer accommodating section 41A and the second developer accommodating section 41B, thereby transporting the developer in the first developer accommodating section 41A and the second developer accommodating section 41B in a specified direction.

[0089] Specifically, the mixing auger 44 stirs the developer in the second developer accommodating portion 41B while conveying it in the direction of arrow (Y), and the supply auger 43 stirs the developer in the first developer accommodating portion 41A while conveying it in the direction of arrow (-Y). The developer conveyed in the direction of arrow (Y) moves (is sucked) from the opening 46A, which is an example of an upper conveying path, to the first developer accommodating portion 41A, while the developer conveyed in the direction of arrow (-Y) moves (is dropped) from the opening 46B to the second developer accommodating portion 41B.

[0090] Thus, the developer in the developing housing 41 is circulated while being stirred by the mixing auger 44 and the supply auger 43. The toner in the developer is charged by the stirring of the developer.

[0091] A receiving port 46C (at the entrance side (-Y direction, the back side of the device) for receiving toner and carrier supplied from the toner cartridge TC) is provided on the upper surface of the developing housing 41. Figure 4 ( 46C ) The toner received by the developing device 14 at the receiving port 46C is transported by the supply auger 43 to the second developer accommodating portion 41B of the developing housing 41 and mixed with the developer.

[0092] The toner supplied from the toner cartridge TC via the receiving port 46C is transported from the inlet side to the outlet side (Y direction: the front side of the device) while being stirred together with the carrier by the mixing auger 44. The toner is then moved through the opening 46A on the outlet side to the first developer storage section 41A where the supply auger 43 is disposed. The toner is then supplied to the developing roller 42 together with the carrier while being transported toward the inlet side by the supply auger 43.

[0093] (2.3) Detection of toner concentration

[0094] Figure 5 This is a diagram explaining toner density detection by the ATC sensor.

[0095] The developing device 14 is provided with an ATC (Auto Toner Control) sensor SR as an example of a detection mechanism for measuring the ratio of toner and carrier (toner concentration: TC) in the developer circulating in the developing housing 41 .

[0096] like Figure 5 As shown, the ATC sensor SR measures changes in magnetic permeability corresponding to the toner concentration (TC) in the developer via a detection surface SRa in contact with the developer. For example, the toner concentration (TC) is detected by detecting a changing analog output voltage. In the image forming apparatus 1, the system control unit 11 commands toner cartridge TC to replenish toner based on the value measured by the ATC sensor SR, thereby maintaining the TC value of the developer at a predetermined value.

[0097] The toner supplied from the toner cartridge TC is mixed with the carrier and conveyed from the inlet side to the outlet side within the second developer accommodating portion 41B while being stirred by the mixing auger 44. The toner concentration in the developer is preferably detected, for example, at the outlet side (where the toner is drawn through the opening 46A to the suction position of the supply auger 43), where the toner is fully stirred. However, at the suction position, the amount and bulk density of the developer within the detection range of the ATC sensor SR are unstable, and the output of the ATC sensor SR may vary.

[0098] In this embodiment, if Figure 4 As shown, the ATC sensor SR is arranged upstream of the suction position in the developer conveying direction by the mixing auger 44 .

[0099] More specifically, the ATC sensor SR is positioned approximately in the center of the second developer accommodating portion 41B in the direction in which the developer is conveyed by the mixing auger 44. At the approximately center of the second developer accommodating portion 41B, the developer amount and accumulation density are more stable than at the suction position, thereby improving the accuracy of toner concentration detection by the ATC sensor SR.

[0100] And, as Figure 3 As shown, the ATC sensor SR is arranged vertically below the rotation center c2 of the mixing auger 44 in the rotation direction of the mixing auger 44. This can achieve space saving of the developing device 14 ( Figure 3 (represented by W in the figure).

[0101] In this embodiment, if Figure 3 (See also Figure 6As shown in (b) of FIG. 2 , the second developer accommodating portion 41B has a circular cross-sectional shape in a direction intersecting the developer conveying direction. There is substantially no space vertically above the mixing auger 44 rotatably accommodated therein, through which the toner, stirred and mixed with the carrier by the mixing auger 44, would float from the developer surface and be conveyed. This prevents the toner from being stirred while floating on the developer surface, and allows stable detection of the toner concentration even when the ATC sensor SR is positioned approximately in the center of the second developer accommodating portion 41B in the developer conveying direction.

[0102] Figure 6 This is a diagram for explaining removal of the developer on the detection surface SRa of the ATC sensor SR.

[0103] A magnetic paddle 44A as an example of a removal mechanism is provided in the mixing auger 44, which contacts the detection surface SRa of the ATC sensor SR in a manner spanning from one end of the detection surface SRa to the other end at a position opposite to the ATC sensor SR to remove the developer retained on the detection surface SRa.

[0104] The magnetic paddle 44A includes an arm 44Aa radially projecting from the rotation shaft 44a of the mixing auger 44 and a magnet 44Ab provided at the front end of the arm 44Aa, and is rotatable integrally with the mixing auger 44 around the rotation shaft 44a.

[0105] When the paddle 44A rotates, the developer attracted to the magnet 44Ab and forming a magnetic spike contacts the detection surface SRa of the ATC sensor SR, removing the developer on the detection surface SRa. This prevents the developer from accumulating on the detection surface SRa and improves the detection accuracy of the toner concentration.

[0106] "Variation"

[0107] Figure 7 It is a schematic cross-sectional view showing the arrangement position of the ATC sensor SR in a modified example.

[0108] The ATC sensor SR may be positioned within a range of +10 to -10 degrees, with the straight line connecting the rotation center c1 of the supply auger 43 and the rotation center c2 of the mixing auger 44 at 0 degrees. Compared to positioning the ATC sensor SR vertically below the rotation center c2 of the mixing auger 44, the stirred developer is more easily compressed, thereby achieving space savings in the developing device and further improving the accuracy of toner concentration detection.

[0109] (2.4) Air flow path

[0110] Figure 81 is a diagram showing the structure of the air flow path 47 in the developing device 14. Figure 9 It is a schematic cross-sectional view showing the flow of air in the air flow path 47 .

[0111] In the developing device 14 , an air flow path 47 is formed adjacent to and vertically below the second developer accommodating portion 41B. In this air flow path 47 , air taken in from an inlet flows toward an outlet along the conveying direction of the mixing auger 44 .

[0112] The air flow path 47 is formed by utilizing a portion of the outer surface 41Ba of the second developer accommodating portion 41B that accommodates the mixing auger 44. Specifically, Figure 8 As shown, the air flow path 47 is composed of a gap (indicated by dots in the figure) between the outer surface 41Ba of the second developer accommodating portion 41B, the outer surface 41Ca of the third developer accommodating portion 41C, and a plate-like body 48 arranged opposite to the outer surface 41Ba of the second developer accommodating portion 41B and the outer surface 41Ca of the third developer accommodating portion 41C.

[0113] A plurality of ribs R1, R2, and R3 are continuously provided upright along the longitudinal direction of the developing device 14 on the outer surface 41Ba of the second developer accommodating portion 41B, which accommodates the mixing auger 44, and on the outer surface 41Ca of the third developer accommodating portion 41C, which accommodates the counter auger 45 and conveys developer in a direction opposite to the conveying direction of the mixing auger 44. A plate-like body 48 is provided in the longitudinal direction of the developing device 14 so as to oppose the plurality of ribs R1, R2, and R3. An air flow path 47 is formed between the inner surface 48a of the plate-like body 48 and the outer surfaces 41Ba of the second developer accommodating portion 41B and 41Ca of the third developer accommodating portion 41C, communicating along the longitudinal direction of the developing device 14 from the outlet side (inlet) to the inlet side (exhaust outlet) of the developing device 14.

[0114] In the developing device 14 of this embodiment, the developer is transported from the inlet side (the back side of the device) to the outlet side (the front side of the device) by the mixing auger 44. The developer is then moved from the outlet side, which serves as a suction position, to the first developer storage section 41A where the supply auger 43 is located. As a result, the developer circulating in the developing device 14 is compressed at the outlet side, and the developer temperature tends to be higher than at other locations.

[0115] In this embodiment, if Figure 9As schematically shown in FIG, a louver-like opening is formed on the front surface side (exit side) of the image forming apparatus 1, and an air intake fan F is arranged on the back side (inlet side) of the image forming apparatus 1. In the developing device 14 mounted in this image forming apparatus 1, outside air flowing in through the inlet 47a on the outlet side of the air flow path 47 circulates within the air flow path 47 and is exhausted through the exhaust port 47b on the inlet side. This allows space saving of the developing device 14 while preventing erroneous detection of toner concentration by the ATC sensor SR due to developer clogging.

[0116] (3) Function of the developing device

[0117] The developing device 14 includes a supply auger 43 that conveys developer while supplying it to a developing roller 42 that holds a developer containing toner and a carrier; a mixing auger 44 that stirs and conveys the developer within a hollow conveying path located vertically below the supply auger 43; an opening 46A, serving as an upper conveying path, located downstream of the mixing auger 44 in the conveying direction and conveying the developer conveyed from the mixing auger 44 to the supply auger 43 above; and an ATC sensor SR that detects the toner concentration of the developer upstream of the opening 46A in the conveying direction of the mixing auger 44. The ATC sensor SR is located upstream of the mixing auger 44 in the conveying direction, i.e., in the approximate center of the second developer storage section 41B that houses the mixing auger 44. This ensures a more stable developer amount and bulk density compared to the upper conveying path, improving the accuracy of toner concentration detection.

[0118] The second developer accommodating portion 41B has a circular cross-sectional shape in a direction intersecting the developer conveying direction. There is substantially no space vertically above the mixing auger 44 rotatably accommodated therein, through which the toner stirred and mixed with the carrier by the mixing auger 44 floats from the developer surface and is conveyed. This prevents the toner from being stirred while floating on the developer surface.

[0119] The ATC sensor SR is arranged vertically below the rotation center c2 of the mixing auger 44. This allows the developing device 14 to be space-saving.

[0120] The ATC sensor SR may be disposed within a range of +10 to -10 degrees with the straight line connecting the rotation center c1 of the supply auger 43 and the rotation center c2 of the mixing auger 44 being 0 degrees. This can save space in the developing device 14 and further improve the accuracy of toner concentration detection.

[0121] The paddle 44A is equipped with a magnetic paddle. This paddle 44A contacts the detection surface SRa of the ATC sensor SR, which is exposed within the second developer storage section 41B, spanning from one end of the detection surface SRa to the other, thereby removing developer accumulated on the detection surface SRa. The magnetic paddle 44A includes an arm 44Aa that radially protrudes from the rotating shaft 44Aa of the mixing auger 44, and a magnet 44Ab provided at the tip of the arm 44Aa. Developer attracted to the magnet 44Ab, forming a magnetic spike, contacts the detection surface SRa of the ATC sensor SR, removing developer accumulated on the detection surface SRa. This stabilizes the detection of the toner concentration of the developer.

[0122] An air flow path 47 is formed adjacent to and vertically below the second developer accommodating portion 41B. This air flow path 47 circulates air taken in from the inlet toward the outlet along the conveying direction of the mixing auger 44. The air flow path 47 utilizes a portion of the outer surface 41Ba of the second developer accommodating portion 41B and is formed by the gap between the outer surface 41Ba of the second developer accommodating portion 41B and a plate-like member 48 disposed opposite the outer surface 41Ba. This reduces the space required for the developing device 14 while suppressing erroneous detection of the toner concentration of the developer.

[0123] (Note)

[0124] This specification discloses at least the following inventions. [1]

[0126] A developing device comprising:

[0127] a supply and conveying mechanism for conveying the developer while supplying the developer to a developer holding member holding the developer containing a toner and a carrier;

[0128] a stirring and conveying mechanism for conveying the developer while stirring it in a hollow conveying path disposed adjacent to and vertically below the supply and conveying mechanism;

[0129] an upper conveying path disposed on the downstream side of the conveying direction of the stirring conveying mechanism and conveying the developer conveyed from the stirring conveying mechanism to the supply conveying mechanism above;

[0130] An air flow path is provided adjacent to and vertically below the conveying path, and flows along the conveying direction of the stirring conveying mechanism, and the air taken in from the inlet flows toward the exhaust port;

[0131] a detection mechanism disposed in the air flow path and configured to detect a toner concentration of the developer upstream of the upper conveying path in the conveying direction of the stirring conveying mechanism; and

[0132] The removing mechanism contacts the detection surface of the detection mechanism exposed in the conveying path so as to extend from one end to the other end of the detection surface to remove the developer accumulated on the detection surface. [2]

[0134] The developing device according to [1], wherein

[0135] In the conveying path, the cross-sectional shape in the direction intersecting the conveying direction of the developer is circular, and there is essentially no space above the vertical direction of the stirring and conveying mechanism that can be rotatably accommodated inside, in which the toner stirred by the stirring and conveying mechanism and mixed with the carrier floats from the agent surface of the developer and is conveyed. [3]

[0137] The developing device according to [1] or [2], wherein:

[0138] The air flow path is formed by a gap between an outer surface of the conveying path and a plate-shaped body provided opposite to the outer surface. [4]

[0140] The developing device according to any one of [1] to [3], wherein

[0141] The detection mechanism is arranged vertically below the rotation center of the stirring and conveying mechanism. [5]

[0143] The developing device according to any one of [1] to [3], wherein

[0144] The detection mechanism is disposed within a range of +10 to -10 degrees with a straight line connecting the rotation center of the supply conveying mechanism and the rotation center of the stirring conveying mechanism being 0 degrees. [6]

[0146] The developing device according to any one of [1] to [5], wherein

[0147] The detection mechanism detects a toner concentration of the developer by bringing a detection surface exposed to the inside of the conveyance path into contact with the developer. [7]

[0149] The developing device according to any one of [1] to [6], wherein

[0150] The removal mechanism is a developer that is attracted to a magnetic material provided integrally with the stirring and conveying mechanism to form a magnetic spike. [8]

[0152] An image forming apparatus comprising:

[0153] Air supply mechanism;

[0154] an image holding member that holds an electrostatic latent image; and

[0155] a developing mechanism for developing the electrostatic latent image on the image holding member;

[0156] As the developing mechanism, the developing device described in any one of [1] to [7] is used.

[0157] According to the invention described in [1], it is possible to suppress erroneous detection of the toner concentration of the developer while achieving space saving of the developing device.

[0158] According to the invention described in [2], it is possible to suppress the toner from being stirred while floating on the surface of the developer.

[0159] According to the invention described in [3], it is possible to form an air flow path below the developing device while achieving space saving of the developing device.

[0160] According to the invention described in [4], it is possible to achieve space saving of the developing device.

[0161] According to the invention described in [5], it is possible to further improve the detection accuracy of the toner concentration while achieving space saving of the developing device.

[0162] According to the invention described in [6], the toner concentration of the developer can be detected.

[0163] According to the invention described in [7], the developer accumulated on the detection surface of the detection mechanism can be removed.

[0164] According to the invention described in [8], it is possible to achieve space saving of the developing device.

[0165] The above-described embodiments of the present invention are provided for the purpose of illustration and explanation. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed embodiments. It is obvious that various modifications and variations are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily explain the principles of the present invention and its application. Thus, other technical personnel in this field can understand the present invention through various modifications optimized for specific uses of the assumed various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. A developing device, characterized in that: have: a supply and conveying mechanism for conveying the developer while supplying the developer to a developer holding member holding the developer containing a toner and a carrier; a stirring and conveying mechanism for conveying the developer while stirring it in a hollow conveying path disposed adjacent to and vertically below the supply and conveying mechanism; an upper conveying path disposed on the downstream side of the conveying direction of the stirring conveying mechanism and conveying the developer conveyed from the stirring conveying mechanism to the supply conveying mechanism above; An air flow path is provided adjacent to and vertically below the conveying path, and flows along the conveying direction of the stirring conveying mechanism, and the air taken in from the inlet flows toward the exhaust port; a detection mechanism disposed in the air flow path and configured to detect a toner concentration of the developer on an upstream side of the upper conveying path in a conveying direction of the stirring conveying mechanism; and The removing mechanism contacts the detection surface of the detection mechanism exposed in the conveying path so as to extend from one end to the other end of the detection surface to remove the developer accumulated on the detection surface.

2. The developing device according to claim 1, wherein In the conveying path, the cross-sectional shape in the direction intersecting the conveying direction of the developer is circular, and there is essentially no space above the vertical direction of the stirring and conveying mechanism that can be rotatably accommodated inside, in which the toner stirred by the stirring and conveying mechanism and mixed with the carrier floats from the agent surface of the developer and is conveyed.

3. The developing device according to claim 1 or 2, wherein: The air flow path is formed by a gap between an outer surface of the conveying path and a plate-shaped body provided opposite to the outer surface.

4. The developing device according to any one of claims 1 to 3, wherein: The detection mechanism is arranged vertically below the rotation center of the stirring and conveying mechanism.

5. The developing device according to any one of claims 1 to 3, characterized in that: The detection mechanism is disposed within a range of +10 to -10 degrees with a straight line connecting the rotation center of the supply conveying mechanism and the rotation center of the stirring conveying mechanism being 0 degrees.

6. The developing device according to any one of claims 1 to 5, characterized in that: The detection mechanism detects a toner concentration of the developer by bringing a detection surface exposed to the inside of the conveyance path into contact with the developer.

7. The developing device according to any one of claims 1 to 6, characterized in that: The removal mechanism is a developer that is attracted to a magnetic material provided integrally with the stirring and conveying mechanism to form a magnetic spike.

8. An image forming apparatus, characterized in that: have: Air supply mechanism; an image holding member that holds an electrostatic latent image; and a developing mechanism for developing the electrostatic latent image on the image holding member; As the developing mechanism, the developing device according to any one of claims 1 to 7 is used.

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