Developing device and image forming apparatus

Abstract

To prevent a suction port from being blocked by toner accumulated in a toner receiver. [Solution] A developing device 18 includes a housing 60 that contains developer containing at least toner, a developer carrier 61 that carries the developer and supplies the toner to a latent image on an image carrier 16, a suction port 70 that sucks in toner that has scattered outside the housing 60 below the developer carrier 61, and a toner receiver 69 that receives toner that has scattered outside the housing 60 or toner that has fallen outside the housing 60 below the developer carrier 61, and the suction port 70 is positioned so that the angle α formed by the line segment C connecting the tip 69a of the toner receiver 69 protruding from the housing 60 to the lowest part 70a of the suction port 70 and the horizontal line extending horizontally from the tip 69a of the toner receiver 69 toward the housing 60 is greater than the angle of repose θ of the toner.

Description

[Technical Field]

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

[0002] 2. Description of the Related Art As an image forming apparatus such as a copying machine or a printer, an electrophotographic image forming apparatus is known which develops a latent image formed on the surface of an image carrier such as a photosensitive member by supplying toner thereto.

[0003] Such image formation is carried out using a developing device that supplies toner to a latent image on an image carrier. Generally, the developing device includes a developing roller that serves as a developer carrier, carrying developer containing toner on its surface. The developer carried on the surface of the developing roller is transported to a position facing the image carrier as the developing roller rotates, and the toner is supplied to the latent image on the image carrier, thereby developing the latent image into a toner image. However, some of the toner in the developing device can scatter outside the developing device, contaminating the interior of the image forming apparatus.

[0004] In response to these issues, Patent Document 1 (JP 2012-198290 A) proposes a developing device equipped with a suction port that sucks in scattered toner and a toner receiver that receives the toner below the suction port. In this case, toner scattered from the developing device is collected by being sucked through the suction port. This makes it possible to prevent the inside of the image forming device from being contaminated by toner. Furthermore, even if toner adhering to the outer surface of the developing device falls, the toner receiver can catch the toner, thereby preventing contamination caused by toner falling into the image forming device.

[0005] However, in a configuration equipped with the above-described suction port, it is necessary to maintain the function of the suction port well, but if toner accumulates in the toner receiver, the suction port may become clogged with the accumulated toner. If the suction port becomes clogged and its function deteriorates, sufficient toner cannot be sucked in, and the inside of the image forming apparatus may become contaminated with toner. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to prevent the suction port from being blocked by toner accumulated in the toner receiver. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a developing device comprising a housing that contains developer containing at least toner, a developer carrier that carries the developer and supplies toner to a latent image on an image carrier, a suction port that sucks toner that has scattered outside the housing below the developer carrier, and a toner receiver that receives toner that has scattered outside the housing or toner that has fallen outside the housing below the developer carrier, wherein the suction port is positioned so that the angle formed by the line connecting the tip of the toner receiver protruding from the housing to the bottom of the suction port and a horizontal line extended horizontally from the tip of the toner receiver toward the housing is greater than the angle of repose of the toner. [Effects of the Invention]

[0008] According to the present invention, the suction port can be prevented from being blocked by toner accumulated in the toner receiver. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to a first embodiment of the present invention. [Figure 2] 1 is a schematic configuration diagram of a developing device according to a first embodiment of the present invention. [Figure 3] 2 is a schematic diagram of a developing device showing the arrangement of suction ports and the configuration of a toner receiver according to the first embodiment of the present invention. FIG. [Figure 4] FIG. 2 is a schematic diagram of a bulk density measuring instrument for measuring the angle of repose of toner. [Figure 5] 5A and 5B are diagrams illustrating the inclination angle of the inclined portion of the toner receiver according to the first embodiment of the present invention. [Figure 6] FIG. 10 is a schematic diagram of a developing device according to a comparative example. [Figure 7] FIG. 1 is a diagram showing the configuration of an embodiment (second embodiment of the present invention) different from the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are designated by the same reference numerals as far as they can be distinguished, and once they have been described, their description will be omitted.

[0011] <Configuration of image forming device> FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention.

[0012] First, the overall configuration of an image forming apparatus according to a first embodiment of the present invention will be described with reference to Figure 1. Note that the image forming apparatus according to the present invention includes printers, copiers, facsimiles, printing machines, as well as multifunction machines that combine two or more of these. Furthermore, the term "image formation" used in the following description refers not only to the formation of meaningful images such as characters and figures, but also to the formation of meaningless images such as patterns.

[0013] 1 is an example of an electrophotographic image forming apparatus that forms an image using toner. In this case, the image forming apparatus 100 includes a document feeder 1 that feeds a document, an image reader 2 that reads an image on the document, an image forming unit 3 that forms an image, and a paper feeder 4 that supplies paper as a recording medium.

[0014] The document transport device 1 includes a document tray 25 on which a document is placed, a document transport section 26 that transports the document from the document tray 25 onto the contact glass 30 of the image reading device 2, and a document discharge tray 27 onto which the document is discharged.

[0015] In addition to the contact glass 30, the image reading device 2 includes a first moving body 31 having a light source, a second moving body 32 having a mirror, an imaging lens 33, and a reading sensor .

[0016] The image forming section 3 includes a plurality of imaging units 10Y, 10M, 10C, and 10K that form images of different colors such as yellow (Y), magenta (M), cyan (C), and black (K), an optical writing device 11, an intermediate transfer device 12, a secondary transfer device 13, a pair of timing rollers 14, and a fixing device 15.

[0017] The imaging units 10Y, 10M, 10C, and 10K have the same configuration except that they form images of different colors. Taking one imaging unit 10Y as an example, imaging unit 10Y includes a drum-shaped photoconductor 16 as an image carrier, a charging device 17 that charges the surface of photoconductor 16, a developing device 18 that supplies toner to the surface of photoconductor 16 to form a toner image, and a cleaning device 19 that cleans the surface of photoconductor 16.

[0018] The optical writing device 11 is a device that irradiates the surface of the photosensitive member 16 of each of the imaging units 10Y, 10M, 10C, and 10K with laser light based on the image information read by the image reading device 2.

[0019] The transfer device 12 includes an intermediate transfer belt 20, a plurality of primary transfer rollers 21, a tension roller 22, a drive roller 23, a secondary transfer backup roller 24, and a belt cleaning member 28. The intermediate transfer belt 20 is tensioned by the primary transfer roller 21, the tension roller 22, the drive roller 23, and the secondary transfer backup roller 24. The plurality of primary transfer rollers 21 contact the outer circumferential surfaces of the photoreceptors 16 with the intermediate transfer belt 20 sandwiched therebetween. This forms a primary transfer nip between the intermediate transfer belt 20 and each photoreceptor 16.

[0020] The secondary transfer device 13 includes a secondary transfer roller 35, a secondary transfer belt 36, and a tension roller 37. The secondary transfer belt 36 is stretched across and stretched between the secondary transfer belt 36 and the tension roller 37. The secondary transfer roller 35 contacts the secondary transfer backup roller 24 via the secondary transfer belt 36 and the intermediate transfer belt 20. This forms a secondary transfer nip between the intermediate transfer belt 20 and the secondary transfer belt 36.

[0021] The fixing device 15 includes a heating roller 41 having an internal heat source, a fixing belt 42, and a pressure roller 43. The pressure roller 43 contacts the heating roller via the fixing belt, thereby forming a fixing nip between the pressure roller and the fixing belt.

[0022] The paper feed device 4 includes a plurality of paper feed cassettes 5 that store paper, a feed roller 6 that feeds paper from each paper feed cassette 5, a separation roller 8 that separates the fed paper and supplies it to a paper feed path 7, and a transport roller 9 that transports the paper in the paper feed path 7. Here, paper is used as the recording medium on which an image is formed, but the recording medium may be paper (paper), an overhead projector sheet, fabric, metal sheet, plastic film, or a prepreg sheet made of carbon fiber pre-impregnated with resin.

[0023] In addition, in the image forming apparatus 100 according to the first embodiment of the present invention, a side wall (the right side wall in FIG. 1) of the housing of the image forming unit 3 is provided with a manual feed tray 44 for manually feeding paper, a manual feed roller 45 for feeding paper from the manual feed tray 44, and a separation roller 46 for separating the paper one by one.

[0024] In addition, on the side wall opposite the manual feed tray 44 side of the image forming unit 3 (the left side wall in Figure 1), there is provided a paper output tray 38 to which paper is output, and a paper output roller 39 that outputs paper to the paper output tray 38.

[0025] Furthermore, below the secondary transfer belt 36 and the fixing device 15, there is provided a reversing conveying device 50 that turns over the paper and conveys the paper.

[0026] <Operation of image forming device> Next, the operation of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIG.

[0027] When printing begins with a document placed on document tray 25, the document is transported from document tray 25 toward contact glass 30. Then, as the document passes a predetermined reading position on contact glass 30, light is irradiated from a light source on first traveling body 31. At this time, light reflected from the document is guided by a mirror on second traveling body 32 to imaging lens 33, and then enters reading sensor 34 through imaging lens 33, whereby a signal of the incident light is photoelectrically converted to generate image information. After that, the document that has passed the predetermined reading position is discharged to document discharge tray 27.

[0028] Furthermore, if an original is placed on the contact glass 30 instead of the original tray 25, when printing starts, the first traveling body 31 and the second traveling body 32 start traveling parallel to the original on the contact glass 30. Then, light is irradiated from the light source of the first traveling body 31 toward the original, and the reflected light is guided by the mirror of the second traveling body 32 to the imaging lens 33 and incident on the reading sensor 34, thereby generating image information.

[0029] Also, when printing starts, in the image forming section 3, the photoconductors 16 of each of the imaging units 10Y, 10M, 10C, and 10K begin to rotate, and through a charging process, an exposure process, and a developing process, a toner image of each color is formed on the surface of each photoconductor 16. Specifically, the charging device 17 charges the surface of the photoconductor 16 to a uniform high potential, and then the optical writing device 11 irradiates the surface (charged surface) of the photoconductor 16 with laser light based on the image information generated by the reading sensor 34. This reduces the potential of the area irradiated with the laser light, and an electrostatic latent image based on the image information is formed on the photoconductor 16. Then, the developing device 18 supplies toner to this electrostatic latent image, forming a toner image on the surface of the photoconductor 16.

[0030] The toner images of each color formed on each photoconductor 16 reach the primary transfer nip (the position of the primary transfer roller 21) as each photoconductor 16 rotates, and are transferred to the intermediate transfer belt 20 in a sequentially overlapping manner by a transfer electric field formed at the primary transfer nip. Thus, a full-color toner image is formed on the intermediate transfer belt 20. Image formation is not limited to forming a full-color image using all four imaging units 10Y, 10M, 10C, and 10K. It is also possible to form a monochromatic image using any one of the imaging units 10Y, 10M, 10C, and 10K, or to form a two- or three-color image using any two or three of the imaging units. After the toner images are transferred, each photoconductor 16 is cleaned by a cleaning device 19 to remove any residual toner and the like from the photoconductor 16.

[0031] The toner image transferred onto the intermediate transfer belt 20 is transported to the secondary transfer nip (position of the secondary transfer roller 35) as the intermediate transfer belt 20 rotates, and the toner image is transferred onto paper by a secondary transfer electric field formed in the secondary transfer nip. Here, the paper onto which the toner image is transferred is the paper supplied from the paper feeder 4 to the secondary transfer nip.

[0032] In the paper feed device 4, almost simultaneously with the start of the image reading operation by the image reading device 2, one of the feed rollers 6 starts to rotate, and paper is fed out from the paper feed cassette 5. The fed out paper is separated one by one by a separation roller 8, enters the paper feed path 7, and is then conveyed by a conveyance roller 9. Furthermore, when paper is set in the manual feed tray 44, the paper is separated one by one and fed by the rotational drive of the manual feed roller 45 and the separation roller 46.

[0033] Paper supplied from the paper feed cassette 5 or manual feed tray 44 hits the pair of timing rollers 14 just before the secondary transfer nip and its transport is temporarily stopped. Thereafter, the pair of timing rollers 14 is driven to rotate, and the paper is transported to the secondary transfer nip in time with the toner image on the intermediate transfer belt 20. As a result, the toner image on the intermediate transfer belt 20 is transferred onto the paper being transported to the secondary transfer nip.

[0034] The paper is then transported to the fixing device 15. The paper transported to the fixing device 15 enters the fixing nip between the fixing belt 42 and the pressure roller 43, where the toner image is fixed to the paper by heating and pressing. After the toner image is transferred to the paper, the belt cleaning member 28 removes any residual toner and the like from the intermediate transfer belt 20.

[0035] In the case of single-sided printing, the paper is guided to paper discharge rollers 39 by a switching member 49 disposed downstream of the fixing device 15, and the paper is then discharged to a paper discharge tray 38 by the paper discharge rollers 39. On the other hand, in the case of double-sided printing, the paper transport path is switched by the switching member 49, and the paper is guided to a reversing conveying device 50. The paper is then turned over by the reversing conveying device 50 and supplied to the secondary transfer nip again, where the toner image formed through the same image forming processes (charging process, exposure process, and development process) as above is transferred to the back side of the paper.

[0036] Then, after the image is fixed on the rear surface of the paper by the fixing device 15, the paper is discharged onto the paper discharge tray 38 by the paper discharge rollers 39. This completes the series of operations of the image forming apparatus 100.

[0037] <Configuration of the developing device> Next, the configuration of the developing device 18 according to the first embodiment of the present invention will be described with reference to Fig. 2. The developing devices 18 provided in the imaging units 10Y, 10M, 10C, and 10K basically have the same configuration except that they contain toners of different colors. Therefore, in the following description, the configuration of one developing device 18 shown in Fig. 2 will be described as an example.

[0038] FIG. 2 is a schematic diagram of the developing device 18 according to the first embodiment of the present invention.

[0039] 2, developing device 18 according to the first embodiment of the present invention includes a housing 60 that accommodates developer, a developing roller 61 that carries developer on its surface, a regulating blade 62 that regulates the amount of developer on developing roller 61, a supply conveying screw 63, a collection conveying screw 64, and an agitation conveying screw 65. In developing device 18 according to the first embodiment of the present invention, a two-component developer containing toner and carrier is used as the developer.

[0040] The housing 60 has therein a supply conveying path 51 in which a supply conveying screw 63 is housed, a recovery conveying path 52 in which a recovery conveying screw 64 is housed, and an agitation conveying path 53 in which an agitation conveying screw 65 is housed. The supply conveying path 51, the recovery conveying path 52, and the agitation conveying path 53 are separated from one another by partitions 66, 67, and 68 disposed therebetween. Specifically, the supply conveying path 51 and the agitation conveying path 53 are separated from one another by a first partition 66 disposed therebetween. However, the supply conveying path 51 and the agitation conveying path 53 are not completely separated from one another by the first partition 66, and communicate with one another through two communication ports provided on the front and back sides in FIG. 2 . Furthermore, the recovery conveying path 52 and the agitation conveying path 53 are separated from one another by a second partition 67 disposed therebetween, but these conveying paths 52 and 53 communicate with one another through a single communication port provided on the front side in FIG. 2 . On the other hand, the supply conveying path 51 and the recovery conveying path 52 are partitioned so as not to communicate with each other. That is, the supply conveying path 51 and the recovery conveying path 52 are continuously partitioned from the front side to the back side in FIG. 2 by a third partition section 68 provided between them.

[0041] The developing roller 61 is an example of a developer carrier that carries a developer on its surface. The developing roller 61 is disposed so as to be partially exposed from the housing 60 at a position facing the photoconductor 16 (developing area).

[0042] The regulating blade 62 is an example of a regulating member that regulates the amount of toner carried on the surface of the developing roller 61. The regulating blade 62 is disposed so as to face the surface of the developing roller 61 with a predetermined gap therebetween.

[0043] The supply conveying screw 63 is an example of a supply conveying member that conveys the developer to be supplied to the developing roller 61. The supply conveying screw 63 has a rotation shaft and a spiral blade portion provided on the outer circumferential surface of the rotation shaft, and conveys the developer by rotating. In this case, the supply conveying screw 63 is configured to convey the developer from the back side to the front side in FIG. 2.

[0044] The recovery conveying screw 64 is an example of a recovery conveying member that conveys the recovered developer. Like the supply conveying screw 63, the recovery conveying screw 64 also has a rotation shaft and a spiral blade portion provided on the outer peripheral surface of the rotation shaft, and conveys the developer by rotating. In this case, like the supply conveying screw 63, the recovery conveying screw 64 is configured to convey the developer from the back side to the front side in FIG. 2.

[0045] The stirring and conveying screw 65 is an example of an stirring and conveying member that stirs and conveys the developer. Like the supply and conveying screw 63 and the recovery and conveying screw 64, the stirring and conveying screw 65 is a conveying screw that has a rotating shaft and a spiral blade portion provided on the outer peripheral surface of the rotating shaft and conveys the developer by rotating. However, the stirring and conveying screw 65 conveys the developer in a different direction from the supply and conveying screw 63 and the collection and conveying screw 64. In other words, the stirring and conveying screw 65 is configured to convey the developer from the front side to the back side in FIG. 2, opposite to the supply and conveying screw 63 and the collection and conveying screw 64.

[0046] <Operation of the developing device> The developing device 18 according to the first embodiment of the present invention operates as follows.

[0047] In the developing device 18, when the developing roller 61 starts to rotate, the developer is carried on the surface of the developing roller 61. More specifically, when the developer is transported from the rear side to the front side in FIG. 2 by the supply transport screw 63, the toner in the developer is charged by friction with the carrier, and the charged toner is attracted to and carried on the surface of the developing roller 61 together with the carrier by the magnetic force of the developing roller 61.

[0048] Then, when developer (toner and carrier) is carried on the surface of the developing roller 61, the developer moves in the rotation direction of the developing roller 61 (arrow A in FIG. 2) as the developing roller 61 rotates, and reaches a position opposite the tip of the regulating blade 62. Then, the regulating blade 62 scrapes off excess developer, and the amount of developer is regulated to an appropriate amount.

[0049] Thereafter, the developer on the developing roller 61 reaches a position (developing area) facing the photosensitive member 16, and the toner on the developing roller 61 is transferred to the electrostatic latent image on the photosensitive member 16 by the electric field between the developing roller 61 and the photosensitive member 16. As a result, the electrostatic latent image is developed into a toner image.

[0050] Furthermore, the developer that has passed the position facing the photosensitive member 16 (developing area) is transported into the recovery transport path 52 as the developing roller 61 rotates, and at that position it separates from the developing roller 61 and is recovered. The recovered developer is transported from the back side to the front side in FIG. 2 by the recovery transport screw 64, and is transported to the stirring transport path 53 through the communication port on the front side.

[0051] Subsequently, the developer transported to the agitation transport path 53 is transported from the front side to the back side of FIG. 2 by the agitation transport screw 65, and is transported to the supply transport path 51 through the communication port on the back side.

[0052] A part of the developer transported to the supply transport path 51 is then supplied again to the developing roller 61 while being transported by the supply transport screw 63, and the remaining developer is returned to the agitation transport path 53 through the communication port on the front side of Figure 2. In this way, the developer is circulated and transported between the supply transport path 51 and the agitation transport path 53.

[0053] <Toner scattering issue> Here, the problem of toner scattering in the developing device will be described using the configuration according to the first embodiment of the present invention (FIG. 2) as an example.

[0054] As shown in FIG. 2, in developing device 18 according to the first embodiment of the present invention, as developing roller 61 rotates, the developer on developing roller 61 is transported to a position facing photoconductor 16 (development area). However, at this time, some toner may not be supplied to photoconductor 16 but may scatter outside housing 60 due to developer deterioration or the influence of the surrounding environment. The scattered toner may float and then adhere to the outer surface of developing device 18 (housing 60) or fall due to gravity and adhere to devices inside the image forming apparatus, which may contaminate the inside of the image forming apparatus. In particular, in the first embodiment of the present invention, because intermediate transfer belt 20 is disposed below developing device 18 (see FIG. 1), if toner adhering to the outer surface of developing device 18 (housing 60) peels off due to vibration or the like and falls onto intermediate transfer belt 20, it may cause image defects.

[0055] Therefore, in the developing device 18 according to the first embodiment of the present invention, as shown in FIG. 2, a suction port 70 for sucking the scattered toner and a toner receiver 69 for receiving the dropped toner are provided.

[0056] The suction port 70 is disposed below the development area where the development roller 61 and the photosensitive member 16 face each other, and downstream of the development area in the direction of rotation of the development roller 61. The toner receiver 69 is disposed below the development area, further below the suction port 70. The toner receiver 69 is preferably disposed across at least the entire width of the development roller 61 in the longitudinal direction (axial direction) so that it can receive toner across the entire longitudinal direction of the development roller 61.

[0057] The suction port 70 communicates with a duct 71 provided in the housing 60 of the developing device 18. Therefore, the toner sucked through the suction port 70 is guided to the duct 71. The duct 71 is provided to extend in the longitudinal direction (axial direction) of the developing roller 61. In this case, a plurality of suction ports 70 are provided in the longitudinal direction of the duct 71 (the longitudinal direction of the developing roller 61); however, as long as the strength of the duct 71 can be ensured, the suction port 70 may be a single opening that is continuous in the longitudinal direction of the duct 71.

[0058] Duct 71 is configured to connect to a toner collection path provided in the image forming apparatus main body when developing device 18 is installed in the image forming apparatus main body. A suction fan serving as an airflow generating unit for generating a suction airflow and a dust collection filter for capturing toner are provided at one end of the toner collection path (the end opposite to duct 71). Therefore, when the suction fan is driven, a suction airflow is generated in the toner collection path, drawing air from suction port 70 into duct 71. The toner scattered within the image forming apparatus is then sucked in through suction port 70. The sucked toner is then transported via duct 71 to the toner collection path on the main body side and captured by the dust collection filter provided in the toner collection path. Toner that is not completely collected by suction through suction port 70 and toner that has fallen off the outer surface of housing 60 are received by toner receiver 69. This prevents toner from falling onto the intermediate transfer belt 20, etc.

[0059] In the developing device 18 having the toner receiver 69 below the suction port 70 as in the first embodiment of the present invention, as toner accumulates in the toner receiver 69 during use of the developing device 18, the height of the accumulated toner gradually increases toward the suction port 70. Therefore, if the suction port 70 is blocked by toner accumulated in the toner receiver 69, the suction function of the suction port 70 is reduced, and the suction port 70 is unable to sufficiently suck in toner, which may result in contamination of the interior of the image forming apparatus. Furthermore, if the suction function of the suction port 70 is reduced, the amount of toner accumulated in the toner receiver 69 increases because the suction port 70 is no longer able to suck in toner. As a result, the toner receiver 69 becomes full prematurely, and toner that cannot be received by the toner receiver 69 falls, which may result in contamination of the interior of the image forming apparatus.

[0060] In this way, if the suction port 70 is blocked by toner accumulated in the toner receiver 69, not only will the suction port 70 be unable to adequately collect the scattered toner, but the toner receiver 69 will also become full prematurely, so measures to solve these problems are required.

[0061] Therefore, in the first embodiment of the present invention, the following configuration is proposed to prevent the suction port 70 from being blocked by the accumulated toner. The configuration of the characteristic parts of the first embodiment of the present invention will be described below.

[0062] <Configuration of suction port and toner receiver> FIG. 3 is a schematic diagram of the developing device 18 showing the arrangement of the suction port 70 and the configuration of the toner receiver 69 according to the first embodiment of the present invention.

[0063] In FIG. 3, a dotted line (semi-straight line) B extending obliquely upward from the tip 69a of the toner receiver 69 indicates the slope of the accumulated toner when it is assumed that the toner has accumulated to the maximum extent in the toner receiver 69.

[0064] Here, the inclination angle θ of the toner slope (dotted line B) when the toner is piled up to the maximum on the toner receiver 69 is expressed by the "angle of repose" of the toner. This "angle of repose" means the inclination angle θ of the toner slope with respect to the horizontal line when the toner is piled up to the maximum without collapsing spontaneously, and if the inclination angle θ of the toner slope exceeds the angle of repose, the toner will collapse and fall.

[0065] The angle of repose θ of the toner (the inclination angle of the toner slope) can be measured using a bulk density measuring instrument 200, as shown in Figure 4, which is equipped with a funnel 201 for dropping toner T and a platform 202 for receiving the dropped toner T. For example, when the angle of repose θ of toner in ProC5300 manufactured by Ricoh Company, Ltd. was measured using a bulk density measuring instrument manufactured by Tokyo Glass Instruments Co., Ltd., the angle of repose θ was found to be 50°.

[0066] Furthermore, from the value of the angle of repose θ of the toner measured in this manner, it is possible to calculate the position of the peak Q (see FIG. 3) of the maximum amount of toner accumulated on the toner receiver 69. Specifically, in the developing device 18 shown in FIG. 3, if the width X from the housing 60 to the tip 69a of the toner receiver 69 is 7.5 mm and the angle of repose θ of the toner is 50°, then the height Y from the tip 69a of the toner receiver 69 to the peak Q of the maximum amount of toner accumulated is 8.9 mm. Therefore, if the suction port 70 is located at a position higher than the height Y of the maximum amount of toner accumulated, 8.9 mm, the suction port 70 will not be blocked by the accumulated toner.

[0067] Therefore, in the first embodiment of the present invention, to prevent the suction port 70 from being blocked by the accumulated toner, the position of the suction port 70 is set so that the line segment C connecting the tip 69a of the toner receiver 69 to the lowest portion 70a of the suction port 70 is located above the dotted line B, which represents the slope of the maximum amount of accumulated toner in the toner receiver 69. In other words, the suction port 70 is positioned so that the angle α formed by the line segment C connecting the tip 69a of the toner receiver 69 to the lowest portion 70a of the suction port 70 and a horizontal line extending from the tip 69a of the toner receiver 69 toward the housing 60 is larger than the angle of repose θ of the toner. By making the angle α larger than the angle of repose θ of the toner, the suction port 70 is positioned higher than the peak Q of the toner accumulated in the toner receiver 69, which prevents the suction port 70 from being blocked by the accumulated toner.

[0068] <Effectiveness verification test> Next, an effect confirmation test conducted to confirm the effect of the present invention will be described.

[0069] This effectiveness confirmation test was conducted using the image forming apparatus configured according to the first embodiment of the present invention, using Ricoh Co., Ltd.'s ProC5300 toner. Each set consisted of 95 pages with an image area ratio of 0.5%, which is the ratio at which toner is most likely to scatter, and 5 pages with an image area ratio of 100%, and 300,000 sheets were printed. As a result, with the configuration according to the first embodiment of the present invention, no toner fell out of the toner receiver 69 even after printing 300,000 sheets. This lack of toner falling out of the toner receiver 69 is believed to be due to the suction port 70 not being blocked by the toner accumulated in the toner receiver 69. Specifically, because the suction port 70 was positioned higher than the peak Q of the maximum toner accumulation in the toner receiver 69, the suction port 70 was not blocked by the toner, maintaining its suction function effectively and preventing the toner receiver 69 from becoming prematurely full.

[0070] In contrast, similar effect confirmation tests were also conducted on comparative examples different from the present invention, and the following results were obtained.

[0071] 6, in the comparative example, the position of the suction port 70 was set to a position lower than the peak Q of the maximum accumulated toner in the toner receiver 69. Note that the configuration other than the height of the suction port 70 (such as the width X from the housing 60 to the tip 69 of the toner receiver 69) was the same as that of the first embodiment of the present invention.

[0072] As a result, in the comparative example, toner fell out of the toner receiver 69 after printing around 200,000 sheets. This result is thought to have occurred because, in the comparative example, the suction port 70 was blocked by the toner accumulated in the toner receiver 69. In other words, because the suction port 70 was positioned lower than the peak Q of the maximum amount of accumulated toner in the toner receiver 69, the suction port 70 was blocked by the toner, reducing its suction function and causing the toner receiver 69 to become full early.

[0073] <Effects of the present invention> As can be seen from the results of the above-described effectiveness confirmation test, according to the present invention, by preventing suction port 70 from being blocked by toner accumulated in toner receiver 69, it is possible to maintain good function of suction port 70 and extend the time until toner receiver 69 becomes full. As a result, toner receiver 69 can receive toner for a long period of time, which prevents toner from falling from toner receiver 69 and prevents toner from contaminating the inside of the image forming apparatus. Furthermore, according to the present invention, since it is possible to extend the time until toner receiver 69 becomes full, it is possible to reduce the frequency of cleaning work for toner receiver 69, thereby reducing the workload.

[0074] To delay the time it takes for toner receiver 69 to become full, it is effective to prevent suction port 70 from being blocked by toner, and also to increase the bottom area of ​​toner receiver 69 so that toner receiver 69 can hold more toner. For this reason, in the first embodiment of the present invention, toner receiver 69 is configured to have a horizontal portion 690 that is disposed horizontally and an inclined portion 691 that is disposed so as to incline obliquely upward from horizontal portion 690, as shown in FIG.

[0075] Because toner receiver 69 has horizontal portion 690 protruding from housing 60, toner receiver 69 can hold more toner than a configuration in which toner receiver 69 has only inclined portion 691 as shown in FIG. 7. That is, in the example of FIG. 7, inclined portion 691 extends diagonally upward from housing 60, so that tip 69a of toner receiver 69 (inclined portion 691) easily approaches photoconductor 16, making it difficult to make toner receiver 69 large. In contrast, in the first embodiment of the present invention, toner receiver 69 extends horizontally in the lower region where the gap between developing device 18 (housing 60) and photoconductor 16 is wide, so toner receiver 69 can be effectively enlarged. Therefore, in the first embodiment of the present invention, the bottom surface area of ​​toner receiver 69 can be increased, allowing toner receiver 69 to hold more toner. Incidentally, in the example of FIG. 7, the width X from the housing 60 to the tip 69 of the toner receiver 69 was 4 mm, which was shorter than the width X (7.5 mm) of the toner receiver 69 in the first embodiment of the present invention. Therefore, when an effectiveness confirmation test similar to that described above was conducted, the toner receiver 69 became full and toner fell out when the number of printed sheets reached about 100,000.

[0076] As described above, in the first embodiment of the present invention, toner receiver 69 has horizontal portion 690 extending horizontally in the lower region where the gap between developing device 18 (housing 60) and photoconductor 16 is wide, so that the bottom surface area of ​​toner receiver 69 can be made larger and it can hold more toner than the example in Fig. 7. This further extends the time until toner receiver 69 becomes full, so that contamination of the inside of the image forming apparatus with toner can be suppressed for a longer period of time, and the frequency of cleaning work of toner receiver 69 can also be reduced.

[0077] Furthermore, in the first embodiment of the present invention, in order to ensure that the bottom area of ​​the toner receiver 69 is as large as possible, the lower surface of the horizontal portion 690 is positioned at the same height as the lower surface of the housing 60. That is, because the distance between the developing device 18 (housing 60) and the photoconductor 16 increases as it goes downward, the toner receiver 69 is positioned over as large an area as possible. This allows the toner receiver 69 to hold more toner, effectively delaying the time it takes for the toner receiver 69 to become full. Note that the lower surface of the horizontal portion 690 may be positioned lower than the lower surface of the housing 60, but in that case, the toner receiver 69 would protrude downward from the housing 60, which could cause the toner receiver 69 to come into contact with the surrounding area and be damaged, or make it difficult to hold the developing device 18, for example, when installing the developing device 18 in the image forming apparatus main body. Furthermore, in a configuration in which the intermediate transfer belt 20 is disposed below the developing device 18 (see FIG. 1 ), if the toner receiver 69 were to protrude downward from the housing 60, the toner receiver 69 would come close to the intermediate transfer belt 20, and if the toner receiver 69 came into contact with the intermediate transfer belt 20, there is a risk of the image on the intermediate transfer belt 20 being distorted. Therefore, in the first embodiment of the present invention, the toner receiver 69 is designed not to protrude downward from the housing 60, thereby preventing damage to the toner receiver 69 and a decrease in the grip of the developing device 18, and preventing image defects due to the toner receiver 69 coming into contact with the intermediate transfer belt 20. Note that the lower surface of the horizontal portion 690 does not need to be at exactly the same height as the lower surface of the housing 60, and may be disposed at approximately the same height as the lower surface of the housing 60, for example, at a position slightly higher than the surface of the housing 60, as long as it does not protrude below the lower surface of the housing 60.

[0078] Furthermore, in order to increase the amount of toner that the toner receiver 69 can hold, it is preferable to bring the tip 69a of the toner receiver 69 as close as possible to the photosensitive member 16 to ensure a large bottom surface area for the toner receiver 69; however, if the tip 69a of the toner receiver 69 is brought too close to the photosensitive member 16, the slope of the toner accumulated in the toner receiver 69 (dotted line B in Figure 3) may come into contact with the surface of the photosensitive member 16, causing the photosensitive member 16 to become soiled.

[0079] For this reason, in the first embodiment of the present invention, the position of the tip of toner receiver 69 is determined so that a half line extending diagonally upward from tip 69a of toner receiver 69 toward housing 60 by the angle of repose θ of the toner, i.e., dotted line B in Figure 3, does not come into contact with the surface of photoreceptor 16. As a result, even if the maximum amount of toner accumulates in toner receiver 69, the slope of the accumulated toner (dotted line B) does not come into contact with the surface of photoreceptor 16, preventing the surface of photoreceptor 16 from becoming soiled.

[0080] Furthermore, in order to increase the amount of toner that toner receiver 69 can hold, a vertical portion extending vertically upward may be provided at the tip of horizontal portion 690 instead of inclined portion 691 of toner receiver 69. In this case, horizontal portion 690 can be effectively extended, thereby increasing the amount of toner that toner receiver 69 can hold.

[0081] On the other hand, a configuration in which toner receiver 69 has inclined portion 691 makes it difficult to increase the amount of toner that toner receiver 69 can hold, but has the advantage of making it easier to prevent toner from falling from tip 69a. That is, by having inclined portion 691 on the tip 69a side of toner receiver 69, toner can be moved along the slope of inclined portion 691 toward horizontal portion 690 (toward housing 60), thereby preventing toner from falling from tip 69a. To effectively achieve the toner fall prevention effect of inclined portion 691, it is preferable to set the inclination angle β of inclined portion 691 with respect to the horizontal direction to an angle greater than the angle of repose θ of the toner, as shown in FIG. 5 . This makes it easier for toner accumulated on inclined portion 691 to collapse toward horizontal portion 690, thereby more effectively preventing toner from falling from tip 69a.

[0082] Although the present invention has been described above, the present invention is not limited to the configurations according to the above-described embodiments, and various design modifications are possible within the scope of the gist of the invention.

[0083] In the above description, the example of Fig. 7 was given as an example of a configuration different from the first embodiment of the present invention, but in this example, the suction port 70 is positioned higher than the peak Q of the toner that has accumulated to the maximum in the toner receiver 69, so that, similar to the first embodiment of the present invention, it is possible to prevent the suction port 70 from being blocked by the toner accumulated in the toner receiver 69. Therefore, even an example such as that of Fig. 7 may be adopted as an embodiment (second embodiment) different from the first embodiment of the present invention.

[0084] In the above description, a developing device using a two-component developer containing toner and carrier has been described as an example of the developing device according to the first embodiment of the present invention, but the present invention is not limited to developing devices using two-component developers, and can also be applied to developing devices using a one-component developer made of magnetic toner containing magnetic powder. Even in developing devices using such one-component developers, if toner scatters or falls, there is a risk of the inside of the image forming device being contaminated by toner. Therefore, by applying the present invention, it is possible to prevent the suction port 70 from being blocked by toner, thereby suppressing contamination of the inside of the image forming device by toner.

[0085] To summarize the above-described aspects of the present invention, the present invention includes at least the following aspects.

[0086] [First aspect] The first aspect is a developing device comprising a housing that contains developer containing at least toner, a developer carrier that carries the developer and supplies toner to a latent image on an image carrier, a suction port below the developer carrier that sucks in toner that has scattered outside the housing, and a toner receiver below the developer carrier that receives toner that has scattered outside the housing or toner that has fallen outside the housing, wherein the suction port is positioned so that the angle formed by the line connecting the tip of the toner receiver protruding from the housing to the bottom of the suction port and a horizontal line extending horizontally from the tip of the toner receiver toward the housing is greater than the angle of repose of the toner.

[0087] [Second aspect] In a second aspect, in the first aspect, the toner receiver has a horizontal portion and an inclined portion inclined obliquely upward from the horizontal portion, and a tip of the inclined portion is a tip of the toner receiver.

[0088] [Third aspect] In a third aspect, in the second aspect, the inclination angle of the inclined portion with respect to the horizontal direction is set to an angle larger than the angle of repose of the toner.

[0089] [Fourth aspect] A fourth aspect is any one of the first to third aspects, in which the tip of the toner receiver is positioned so that a semi-linear line extending diagonally upward from the tip of the toner receiver toward the housing by the angle of repose of the toner does not come into contact with the surface of the image carrier.

[0090] [Fifth aspect] A fifth aspect is any one of the first to fourth aspects, wherein a lower surface of the toner receiver is disposed at approximately the same height as a lower surface of the housing.

[0091] [Sixth aspect] A sixth aspect is an image forming apparatus including the developing device according to any one of the first to fifth aspects. [Explanation of symbols]

[0092] 16 Photoconductor (image carrier) 18 Developing device 60 cabinets 61 Developing roller (developer carrier) 69 Toner tray 69a tip 70 Suction port 70a Bottom 100 Image forming device 690 Horizontal part 691 Slope θ Angle of repose of toner [Prior art documents] [Patent documents]

[0093] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-198290

Claims

1. a housing that contains a developer containing at least toner; a developer carrier that carries the developer and supplies toner to a latent image on an image carrier; a suction port below the developer carrier for sucking toner scattered outside the housing; a toner receiver located below the developer carrier for receiving toner scattered outside the housing or toner that has fallen outside the housing; A developing device comprising: A developing device characterized in that the suction port is positioned so that the angle formed by the line segment connecting the tip of the toner receiver protruding from the housing to the bottom of the suction port and the horizontal line extending horizontally from the tip of the toner receiver toward the housing is larger than the angle of repose of the toner.

2. the toner receiver has a horizontal portion and an inclined portion inclined obliquely upward from the horizontal portion, 2. The developing device according to claim 1, wherein the tip of the inclined portion is the tip of the toner receiver.

3. 3. The developing device according to claim 2, wherein the angle of inclination of said inclined portion relative to the horizontal direction is set to be larger than the angle of repose of toner.

4. 2. The developing device according to claim 1, wherein the tip of the toner receiver is positioned so that a half line extending diagonally upward from the tip of the toner receiver toward the housing by an amount equal to the angle of repose of the toner does not come into contact with the surface of the image carrier.

5. 2. The developing device according to claim 1, wherein the lower surface of the toner receiver is disposed at substantially the same height as the lower surface of the housing.

6. An image forming apparatus comprising the developing device according to claim 1.

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