Image forming device

Abstract

To efficiently detect a toner scattering near a developing area.SOLUTION: An image forming apparatus is provided with a photoreceptor drum 21 (image carrier), and a developing device 26 provided with a developing roller 26a (developer carrier) that stores toner therein, rotates in a predetermined rotation direction, and develops a latent image formed on the surface of the photoreceptor drum 21 in a developing area opposite to (or in contact with) the photoreceptor drum 21. The image forming apparatus is further provided with a detection device 40 that detects scattered toner near the developing area and at the ends in a width direction orthogonal to the rotation direction of the developing roller 26a.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine thereof. [Background technology]

[0002] Conventionally, in a developing device installed in an image forming device such as a copier or printer, a technology has been known in which a toner scattering detection sensor that detects toner scattering from the developing device is installed below the developing device (see, for example, Patent Document 1).

[0003] More specifically, in the developing device disclosed in Patent Document 1, a toner scattering detection sensor is installed downstream of the developing area and below the developing case, and the toner scattering detection sensor optically detects toner scattering from the developing device.

[0004] On the other hand, Patent Document 2 discloses a technique in which an electrode that detects the amount of remaining toner inside the developing device as electrostatic capacitance is installed inside the developing device. Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional technology has not been able to efficiently detect toner scattering near the development area, resulting in image defects caused by toner scattering.

[0006] SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide an image forming apparatus in which toner scattered in the vicinity of a development area can be efficiently detected. [Means for solving the problem]

[0007] The image forming apparatus of the present invention comprises an image carrier, a developing device having a developer carrier that contains toner inside and rotates in a predetermined rotation direction to develop a latent image formed on the surface of the image carrier in a development area that faces or comes into contact with the image carrier, and a detection device that detects scattered toner near the development area and at an end in a width direction perpendicular to the rotation direction. the detection device comprises an electrode pair consisting of a plurality of electrodes, and a measurement unit that measures the electrostatic capacitance between the electrodes in the electrode pair, The developing device includes a developing case that covers the developer carrier from above on the downstream side of the developing area in the rotation direction, and the electrode pair is located opposite an upper surface of the developing case in the vicinity of the developing area and outside an image area at an end in the width direction. It is something. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an image forming apparatus in which toner scattered in the vicinity of a development area can be efficiently detected. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] FIG. 2 is a view showing the developing device in the width direction. [Figure 4] FIG. 2 is an enlarged view showing a main part of the developing device. [Figure 5] FIG. [Figure 6] FIG. 2 is a schematic view showing a state in which a developing device is attached to the image forming apparatus main body. [Figure 7] 10A is a diagram showing one end side in the width direction of a developing device as a modified example, and FIG. 10B is a diagram showing other positions in the width direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0011] First, the overall configuration and operation of an image forming apparatus 1 will be described with reference to FIG. The image forming apparatus 1 in this embodiment is a tandem color image forming apparatus in which a plurality of process cartridges 20Y, 20M, 20C, and 20BK are arranged side by side so as to face an intermediate transfer belt 8. In addition, a developing device 26 (see FIG. 2) is installed so as to face the photosensitive drums 21 of the plurality of process cartridges 20Y, 20M, 20C, and 20BK.

[0012] In Figure 1, 1 indicates the main body of a color copier as an image forming device, 2 indicates a document transport unit that transports a document to a document reading unit 3, 3 indicates a document reading unit that reads image information from the document, and 4 indicates a writing unit (exposure unit) that emits laser light based on input image information. Also, 20Y, 20M, 20C, and 20BK indicate process cartridges corresponding to the respective colors (yellow, magenta, cyan, and black), and 40 indicates an intermediate transfer belt onto which toner images of multiple colors are transferred in an overlapping manner. Also, 61 denotes a paper feed device in which sheets P such as paper are stored, 65 denotes a secondary transfer roller that transfers the toner image formed on the intermediate transfer belt 8 to the sheet P, and 66 denotes a fixing device that fixes the unfixed image on the sheet P. Also, 70 denotes a toner container for replenishing toner of each color to each developing device 26 corresponding to the multiple process cartridges 20Y, 20M, 20C, and 20BK, and 80 denotes a waste toner collection container in which untransferred toner collected by the cleaning device 23 (see Figure 2) or the intermediate transfer belt cleaning device 81 is collected as waste toner. Reference numeral 100 denotes an operation display panel for inputting various commands relating to printing (image forming operation) and for displaying various information about the image forming apparatus 1.

[0013] 2, each of the process cartridges 20Y, 20M, 20C, and 20BK integrates a photosensitive drum 21 as an image carrier, a charging device 22, and a cleaning device 23. When each of the process cartridges 20Y, 20M, 20C, and 20BK reaches the end of its life, it is removed from the image forming apparatus main body 1 and replaced with a new one. Each developing device 26 is disposed opposite the photosensitive drum 21 of each process cartridge 20Y, 20M, 20C, and 20BK. When the developing device 26 reaches the end of its life, it is removed from the image forming apparatus main body 1 and replaced with a new one. The operation of attaching and detaching the developing device 26 to and from the image forming apparatus main body 1 and the operation of attaching and detaching the process cartridges 20Y, 20M, 20C, and 20BK to and from the image forming apparatus main body 1 can be performed separately and independently. A toner image of each color (yellow, magenta, cyan, black) is formed on the photosensitive drum 21 (image carrier) of each of the process cartridges 20Y, 20M, 20C, and 20BK.

[0014] Hereinafter, the operation of the image forming apparatus during normal color image formation will be described. First, the document is transported from the document table by the transport rollers of the document transport unit 2 and placed on the contact glass of the document reading unit 3. Then, the document reading unit 3 optically reads the image information of the document placed on the contact glass. Then, the image information for each color of yellow, magenta, cyan, and black is sent to the writing unit 4. Then, from the writing unit 4, laser light L (exposure light) based on the image information for each color is irradiated onto the surface of the photosensitive drum 21 (see FIG. 2) of the corresponding process cartridge 20Y, 20M, 20C, 20BK.

[0015] Meanwhile, each of the four photosensitive drums 21 rotates clockwise in FIGS. 1 and 2. First, the surface of each photosensitive drum 21 is uniformly charged at a position facing the charging device 22 (charging roller) (charging process). In this way, a charging potential is formed on the photosensitive drum 21. Thereafter, the charged surface of each photosensitive drum 21 reaches a position where a laser beam is irradiated by each writing unit 4, and an electrostatic latent image based on image information is formed at that position (exposure process).

[0016] The laser light corresponding to the yellow component is irradiated onto the surface of the photosensitive drum 21 of the first process cartridge 20Y from the left side of the drawing. At this time, the laser light of the yellow component is scanned in the direction of the rotation axis (main scanning direction) of the photosensitive drum 21 by a polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 21 after it has been charged by the charging device 22. Similarly, the cyan laser light is irradiated onto the surface of the photosensitive drum 21 of the process cartridge 20C, which is the second from the left on the paper, and an electrostatic latent image of the cyan component is formed. The magenta laser light is irradiated onto the surface of the photosensitive drum 21 of the process cartridge 20M, which is the third from the left on the paper, and an electrostatic latent image of the magenta component is formed. The black laser light is irradiated onto the surface of the photosensitive drum 21 of the process cartridge 20BK, which is the fourth from the left on the paper, and an electrostatic latent image of the black component is formed.

[0017] Thereafter, the surface of the photosensitive drum 21 on which the electrostatic latent image of each color is formed reaches a position facing the developing device 26. Then, toner of each color is supplied from each developing device 26 onto the photosensitive drum 21, and the latent image on the photosensitive drum 21 is developed (this is the developing process). Thereafter, the surfaces of the photosensitive drums 21 after the development process reach positions facing the intermediate transfer belt 8. Here, primary transfer rollers 24 are installed at each facing position so as to abut against the inner circumferential surface of the intermediate transfer belt 8. Then, at the positions of the primary transfer rollers 24, the toner images of each color formed on the photosensitive drums 21 are transferred onto the intermediate transfer belt 8 in order, superimposed on top of each other (this is the primary transfer process).

[0018] After the primary transfer process, the surfaces of the photosensitive drums 21 reach a position facing the cleaning devices 23. The cleaning devices 23 then collect untransferred toner remaining on the photosensitive drums 21 (this is the cleaning process). The untransferred toner collected by the cleaning devices 23 passes through a waste toner transport path (not shown) and is collected in the waste toner collection container 80. Thereafter, the residual potential on the surface of the photosensitive drum 21 is removed at the position of a charge removal device (not shown), and a series of image forming processes on the photosensitive drum 21 is completed.

[0019] Meanwhile, the surface of the intermediate transfer belt 8 onto which the images of each color on the photosensitive drum 21 are transferred and superimposed runs in the direction of the arrow in the figure and reaches the position of the secondary transfer roller 65. Then, at the position of the secondary transfer roller 65, the full-color image on the intermediate transfer belt 8 is secondarily transferred onto the sheet P (secondary transfer process). Thereafter, the surface of the intermediate transfer belt 8 reaches the position of the intermediate transfer belt cleaning device 81. Then, the untransferred toner on the intermediate transfer belt 8 is collected by the intermediate transfer belt cleaning device 81, and the series of transfer processes on the intermediate transfer belt 8 is completed. The untransferred toner collected by the intermediate transfer belt cleaning device 81 passes through a waste toner transport path (not shown) and is collected in a waste toner collection container 80 .

[0020] Here, the sheet P conveyed to the position of the secondary transfer roller 65 is conveyed from the paper feeder 61 via the registration roller 64 and the like. More specifically, a sheet P fed by a paper feed roller 62 from a paper feed device 61 that stores sheets P passes through a conveyance path and is then guided to the position of a registration roller 64. The sheet P that has reached the position of the registration roller 64 is conveyed toward the position of a secondary transfer roller 65 in synchronization with the toner image on the intermediate transfer belt 8.

[0021] Thereafter, the sheet P onto which the full-color image has been transferred is guided to the position of the fixing device 20. Then, in the fixing device 20, the color image is fixed onto the sheet P at the nip between a fixing roller and a pressure roller. After the fixing process, the sheet P is discharged as an output image outside the apparatus main body 1 by a discharge roller 69, and then stacked on the discharge tray 5, completing a series of image forming processes.

[0022] Next, the image forming unit of the image forming apparatus will be described in detail with reference to FIGS. The four image forming units installed in the image forming apparatus main body 1 have almost the same structure except for the color of the toner used in the image forming process, so they are illustrated without the alphabetical symbols (Y, M, C, BK) for components such as process cartridges and developing devices.

[0023] As shown in FIG. 2, the process cartridge 20 mainly includes a photosensitive drum 21 as an image carrier, a charging device 22, and a cleaning device 23 housed integrally in a case. The photosensitive drum 21 is a negatively charged organic photosensitive member, and is formed by providing a photosensitive layer and the like on a drum-shaped conductive support. The charging device 22 is a charging roller made of a conductive core metal and a medium-resistance elastic layer coated on the outer periphery thereof. A predetermined voltage is applied to the charging device 22 (charging roller) from a power supply unit, thereby uniformly charging the surface of the opposing photosensitive drum 21. The cleaning device 23 is equipped with a cleaning blade 25a and a cleaning roller 25b that come into contact with the photosensitive drum 21. The cleaning blade 25a is made of a rubber material such as urethane rubber, and comes into contact with the surface of the photosensitive drum 21 at a predetermined angle and with a predetermined pressure. The cleaning roller 25b is a brush roller with brush bristles arranged around a core metal.

[0024] As shown in Figures 2 and 3, the developing device 26 is mainly composed of a developing roller 26a as a developer carrier, a first transport screw 26b1 (first transport member) facing the developing roller 26a, a second transport screw 26b2 (second transport member) facing the first transport screw 26b1 via a partition member 26e, a doctor blade 26c (developer regulating member) facing the developing roller 26a and regulating the amount of developer carried on the developing roller 26a, a filter 26t (and an opening 26j1) for reducing an increase in internal pressure of the device, an electrode pair 26r for detecting toner scattering, and the like.

[0025] The developing device 26 contains a developer (two-component developer) made up of carrier and toner. The developing roller 26a is configured to form a developing area by facing the photosensitive drum 21 with a small gap therebetween. As shown in Fig. 3, the developing roller 26a is configured with a magnet 26a1 that is fixed inside and forms multiple poles (magnetic poles) on the outer circumferential surface of the roller, and a sleeve 26a2 that rotates around the magnet 26a1.

[0026] The transport screws 26b1 and 26b2 as transport members transport the developer contained inside the developing device 26 in the longitudinal direction to form a circulation path (the circulation path indicated by the dashed arrow in FIG. 3). That is, a developer circulation path is formed by a first transport path B1 formed by the first transport screw 26b1 and a second transport path B2 formed by the second transport screw 26b2. The first transport path B1 and the second transport path B2 are separated by a partition member 26e (wall portion), and both longitudinal end portions of the two transport paths B1 and B2 communicate with each other via communication openings 26f and 26g. Specifically, referring to FIG. 3, the upstream end of the first transport path B1 in the transport direction communicates with the downstream end of the second transport path B2 in the transport direction via the first communication opening 26f. Furthermore, the downstream end of the first transport path B1 in the transport direction communicates with the upstream end of the second transport path B2 in the transport direction via the second communication opening 26g. In other words, the partition member 26e is disposed at a position excluding both longitudinal end portions. The first transport screw 26b1 (first transport path B1) is disposed opposite the developing roller 26a, and the second transport screw 26b2 (second transport path B2) is disposed opposite the first transport screw 26b1 (first transport path B1) via a partition member 26e. The first transport screw 26b1 transports the developer in the width direction (the direction perpendicular to the paper surface in FIG. 2, the left-right direction in FIG. 3, and the longitudinal direction), while supplying the developer toward the developing roller 26a and recovering the post-development developer that has separated from the developing roller 26a. The second transport screw 26b2 agitates and mixes the post-development developer transported from the first transport path B1 with fresh toner supplied from the supply port 26d while transporting them in the width direction. In this embodiment, the two conveying screws 26b1 and 26b2 are arranged side by side in the horizontal direction. Each of the two conveying screws 26b1 and 26b2 has a screw portion wound around a rotation shaft.

[0027] The image forming process described above will now be explained in more detail, focusing on the development process. Developing roller 26a rotates in a predetermined direction (the direction of the arrow in FIG. 2.) As shown in FIG. 3, the developer in developing device 26 is circulated in the longitudinal direction (the direction of the dashed arrow in FIG. 3) while being stirred and mixed with toner supplied from toner container 70 through supply port 26d via the toner supply path by rotation of first transport screw 26b1 and second transport screw 26b2, which are arranged with partition member 26e interposed therebetween, in the direction of the arrow. The toner, which has been frictionally charged and attracted to the carrier, is then lifted up onto the developing roller 26a together with the carrier by a developer lift-up pole formed on the developing roller 26a. The developer carried on the developing roller 26a is transported in the direction of the arrow in FIG. 2 until it reaches a position facing the doctor blade 26c. The developer on the developing roller 26a is then adjusted to an appropriate amount at this position and then transported to a position facing the photosensitive drum 21 (the developing area). The toner is then attracted to the latent image formed on the photosensitive drum 21 by an electric field formed in the developing area. The developer remaining on the developing roller 26a then reaches above the first transport path B1 as the sleeve rotates and is detached from the developing roller 26a at this position. The electric field in the developing area is formed by a predetermined voltage (developing bias) applied to the developing roller 26a by a development power supply and a surface potential (latent image potential) formed on the surface of the photosensitive drum 21 during the charging and exposure processes.

[0028] The toner in the toner container 70 is appropriately replenished into the developing device 26 from the replenishing port 26d via a toner replenishing path (not shown) as the toner in the developing device 26 is consumed. The consumption of the toner in the developing device 26 is detected by a toner concentration sensor (not shown) that magnetically detects the toner concentration of the developer in the developing device 26 (the proportion of toner in the developer). The supply port 26d is provided at one end of the second transport screw 26b2 in the longitudinal direction (the left-right direction in FIG. 3), above the second transport screw 26b2 (second transport path B2).

[0029] Referring to FIG. 2, developing device 26 in this embodiment has a filter 26t installed in an opening 26j1 that connects the inside of the device with the outside of the device. Specifically, the developing device 26 is provided with an upper developing case 26j and a lower developing case 26k that function as developing cases (housings) and are detachable. The developing lower case 26k rotatably holds the developing roller 26a and the transport screws 26b1 and 26b2, and also holds the doctor blade 26c. The upper developer case 26j functions as a developer case that covers the upper side of the developing roller 26a downstream of the developing area in the rotation direction of the developing roller 26a. The upper developer case 26j is connected to the lower developer case 26k so as to cover the upper side of the developing device 26. The upper developer case 26j has an opening 26j1 (air passage) that penetrates from the inside to the outside. A filter 26t is provided to close the opening 26j1. The filter 26t is used to collect toner (and carrier) and allow ventilation. The filter 26t is made of a mesh that is smaller than the particle size of the toner and carrier, and is formed so that only air can pass through.

[0030] Here, the gap H (casing gap) between the developing roller 26a and the upper developing case 26j on the downstream side of the developing area is set to be within the range of 0.6 to 1.0 mm. If the casing gap H becomes smaller than 0.6 mm, the developer carried on the developing roller 26a after the development process will not be transported smoothly to the gap H between the developing roller 26a and the developing case 26j, and will be more likely to overflow and leak out of the developing device 26. On the other hand, if the casing gap H is larger than 1.0 mm, it becomes difficult for the developer carried by the developing roller 26a to slide against the inner surface of the developing case 26j, making it difficult for the pump action to form an intake airflow toward the inside of the developing device 26, and toner scattering from the developing device 26 (toner scattering around the development area) becomes more likely to occur. By maintaining the casing gap H within an appropriate range, developer leakage and toner scattering can be reduced. Furthermore, the internal pressure of the developing device 26 tends to increase due to the suction airflow in the casing gap H described above (airflow in the direction of the white arrow in FIG. 4), and if the internal pressure increases, toner will scatter from the gaps in the developing device 26. In contrast, in this embodiment, the opening 26j1 in which the filter 26t is installed is provided, so that the toner is collected and prevented from scattering to the outside, while only allowing ventilation, thereby suppressing an increase in the internal pressure of the developing device 26. In other words, toner scattering due to an increase in the internal pressure of the developing device 26 is prevented.

[0031] Referring now to Figure 4, in the developing device 26 of this embodiment, a flexible sheet member 26m is installed in the developing upper case 26j as a developing case so as to slide in the trailing direction against the developer carried on the surface of the developing roller 26a downstream of the rotation direction of the developing roller 26a relative to the development area. In detail, the flexible sheet member 26m is an approximately rectangular urethane sheet with a thickness of about 0.1 mm, and is arranged in the gap (casing gap W) between the developing roller 26a (developer carrier) and the developing upper case 26j (developing case) along the rotation direction of the developing roller 26a. One end of the flexible sheet member 26m is held as a fixed end by the upper developer case 26j downstream of the development area (the position where the development roller 26a faces the photosensitive drum 21) in the direction of rotation indicated by the arrow in FIG. 4. Specifically, in this embodiment, one end of the flexible sheet member 26m is affixed to the end face of the upper developer case 26j (the end face facing the photosensitive drum 21) with double-sided tape or the like. The other end of the flexible sheet member 26m is a free end. The flexible sheet member 26m is disposed so as to be in contact with the developer G carried on the development roller 26a. By providing the flexible sheet member 26m configured in this manner, a stable suction airflow (see the white arrow in Figure 4) is formed in the gap between the developing roller 26a and the developing upper case 26j, thereby reducing the problem of toner blowing out from the gap (toner scattering).

[0032] The configuration and operation of the image forming apparatus 1, which are characteristic of this embodiment, will be described in detail below. As previously described with reference to Figure 2 etc., the image forming apparatus 1 is provided with a developing device 26. The developing device 26 contains toner (and carrier). The developing device 26 also includes a developing roller 26a as a developer carrier that rotates in a predetermined rotational direction and develops the latent image formed on the surface of the photosensitive drum 21 in a development area facing the photosensitive drum 21 as an image carrier.

[0033] Now, referring to Figure 4 etc., the image forming apparatus 1 in this embodiment is provided with a detection device 40 that detects scattered toner (that is, toner that is scattered near the development area and at the end of the width direction perpendicular to the rotation direction of the development roller 26a). 4, 5, etc., the detection device 40 is a capacitance sensor that includes an electrode pair 26r, a measurement unit 41, harnesses 26x and 42, a relay connector 45, and the like.

[0034] The electrode pair 26r is a substantially plate-shaped member made up of a plurality of electrodes 26r1 and 26r2 (see FIG. 5). 5, the electrode pair 26r is formed by two interdigitated electrodes 26r1 and 26r2 made of copper, iron, or the like. Each of the two electrodes 26r1 and 26r2 is connected to a harness 26x (two wires joined together as one wire, with only the portion connected to the electrodes 26r1 and 26r2 branching out). 4 and other figures, in this embodiment, the electrode pair 26r is installed with a gap therebetween at a position facing the upper surface of the upper developer case 26j serving as a developer case in the vicinity of the development area. Although not shown in the figures, a holding portion for holding the electrode pair 26r is formed at each end in the width direction of the upper developer case 26j.

[0035] The measuring unit 41 is a member that measures the electrostatic capacitance between the electrode 26r1 and the electrode 26r2 in the electrode pair 26r. More specifically, measuring unit 41 has a microcomputer and the like provided on a control board electrically connected to harness 42. In the present embodiment, measuring unit 41 is fixedly installed in image forming apparatus main body 1, not in developing device 26 (see FIG. 6(A)). Then, information on the capacitance detected by electrode pair 26r is input to measurement unit 41 via harnesses 26x and 42 (and relay connector 45), and the amount of toner (scattered toner) accumulated on the developing upper case 26j is measured by measurement unit 41.

[0036] The detection device 40 (capacitance sensor) detects the amount of scattered toner (amount of accumulated toner) based on the principle that capacitance changes depending on whether air or toner is present within the detection range of the electrode pair 26r. While the relative dielectric constant of air is 1, the relative dielectric constant of toner (e.g., mainly polyester resin) is about 3 to 4, and the amount of scattered toner can be measured as the difference in capacitance value due to the relationship of capacitance (C=ε×S / D). The shape and material of the electrode 26r are not limited to those of the present embodiment, and various materials can be used as long as they are capable of detecting the amount of scattered toner.

[0037] In this manner, in this embodiment, since the detector 40 is provided that can detect toner scattered near the development area and at the widthwise end, toner scattered near the development area can be detected efficiently, which reduces the occurrence of problems such as poor image quality and device failure due to toner scattering. A detailed explanation is provided below. The scattered toner near the development area eventually accumulates in a specific location. Therefore, by detecting the amount of toner accumulated in that specific location, it is possible to predict the occurrence of problems such as poor image quality and device failure. In this case, the specific location to be detected does not have to be a location where the above-mentioned problems directly occur, as long as it is a location that is strongly correlated with an increase in the amount of toner accumulation in that location. Specifically, in this embodiment, toner scattered near the development area accumulates on the end surface of the developer upper case 26j facing the photosensitive drum 21, and when the amount of toner accumulates to a certain extent, it falls onto the photosensitive drum 21 and adheres to it, resulting in an image defect (toner-dropped image). In this case, because the gap between the developer upper case 26j and the photosensitive drum 21 is narrow, it is difficult to position the electrode pair 26r so that it faces the end surface of the developer upper case 26j. Therefore, in this embodiment, the electrode pair 26r is positioned on the top surface of the developer upper case 26j (the position in FIG. 4 ), which is close to the end surface of the developer upper case 26j and has a strong correlation with the amount of toner accumulated on the end surface of the developer upper case 26j, and it is possible to predict whether the amount of toner accumulation (amount of scattered toner) is large enough to cause problems such as the image defect described above. In particular, the amount of toner scattering is greater at the widthwise ends than at the widthwise center because the suction airflow in the casing gap H described above is weaker and the sealing performance of the flexible sheet member 26m is weaker. Therefore, by installing the electrode pair 26r at the widthwise ends, toner scattering can be detected efficiently.

[0038] In this embodiment, the electrode pair 26r is arranged outside the image area M at the end in the width direction (on the left side in FIG. 3), as shown in FIG. That is, the electrode pair 26r is not disposed within the image region M, but is disposed outside the image region M (non-image region). The "image area M" is the maximum area in which an image can be formed, corresponding to the image to be formed on a sheet P of the maximum size that can be passed through the image forming apparatus 1. Therefore, the action of the magnetic poles of the magnet 26a1 of the developing roller 26a is weaker in the non-image area than in the image area M, resulting in a greater amount of scattered toner. Therefore, by providing the electrode pair 26r in the non-image area, scattered toner can be detected efficiently.

[0039] In this embodiment, the electrode pair 26r is arranged only on one end side in the width direction (on the left side in FIG. 3), as shown in FIG. This allows the cost and weight of the device to be reduced compared to when electrode pairs 26r are provided at both ends in the width direction. In particular, in this embodiment, electrode pair 26r is provided on the drive side (the side where drive is input from image forming apparatus main body 1 to developing device 26) rather than on the non-drive side. In developing device 26, the drive side has larger vibrations than the non-drive side, resulting in a larger amount of scattered toner. Therefore, by providing electrode pair 26r on the drive side, scattered toner can be detected efficiently.

[0040] Here, in this embodiment, the developing device 26 is detachably installed with one end side in the width direction (the left side of FIG. 6(A), the side where the electrode pair 26r is installed) at the rear side in the installation direction relative to the image forming apparatus main body 1, as shown in FIG. 6(A). Specifically, an opening / closing cover (not shown) is provided on the front side in the installation direction of the image forming apparatus main body 1. The user opens the opening / closing cover to expose the inside of the image forming apparatus main body 1, and then pushes the developing device 26 from the position shown by the solid line in Fig. 6 to the position shown by the dashed line to install the developing device 26 into the image forming apparatus main body 1. When removing the developing device 26 from the image forming apparatus main body 1, the operation reverse to the above-described installation operation is performed. By configuring it in this way, even if the widthwise end where the electrode pair 26r is arranged is intentionally configured to be more susceptible to toner scattering than other widthwise positions, it is possible to reduce the inconvenience of the user directly touching the part that has become soiled by toner scattering when removing the developing device 26.

[0041] In particular, referring to Figures 5 and 6(A), in this embodiment, the electrode pair 26r is installed in the developing device 26 and is formed so as to be electrically connectable to and disconnectable from the measuring section 41 installed in the image forming apparatus main body 1. That is, the electrode pair 26r of the developing device 26 is electrically connected to and disconnected from the measuring unit 41 of the image forming apparatus main body 1 in conjunction with the attachment and detachment of the developing device 26 to and from the image forming apparatus main body 1. 4, electrode pair 26r and harness 26x, one end of which is connected to electrode pair 26r and the other end of which is connected to connector A, are fixedly installed in developing device 26. Meanwhile, measurement unit 41, harness 42, one end of which is connected to measurement unit 41 and the other end of which is connected to relay connector 45 via connector B, and relay connector 45 are fixedly installed in image forming apparatus main body 1. Connector A of developing device 26 is connected to and disconnected from relay connector 45 of image forming apparatus main body 1 in conjunction with the attachment and detachment of developing device 26 to and from image forming apparatus main body 1. With this configuration, maintenance of the electrode 26r can be easily performed.

[0042] As shown in FIG. 6(B), the detection device 40 can also be installed in the image forming apparatus main body 1 to which the developing device 26 is detachably installed. That is, instead of installing a part of the detection device 40 (mainly the electrode pair 26r) on the side of the developing device 26 as in FIG. 6(A), the entire detection device 40 including the electrode pair 48 is installed on the side of the image forming apparatus main body 1 as shown in FIG. 6(B). When configured in this manner, in conjunction with the mounting operation of the developing device 26 to the image forming device main body 1, the electrode pair 48 of the image forming device main body 1 is positioned at the desired opposing position at one end of the width direction of the developing upper case 26j of the developing device 26. When configured in this manner, an electrode pair is not installed in the developing device 26, which is replaced at a short replacement cycle relative to the life of the image forming device main body 1, and the cost of the developing device 26 can be reduced, thereby reducing the running costs of the image forming device 1.

[0043] In this embodiment, when the detector 40 detects that the amount of scattered toner exceeds a predetermined value, a notification is issued to prompt maintenance of the developing device 26. For more details, referring to FIG. 4 etc., information on the amount of scattered toner (capacitance) measured by the detection device 40 (measurement unit 41) is sent to the control unit 50 of the image forming apparatus main body 1. The control unit 50 then determines whether the amount of scattered toner (capacitance) exceeds a predetermined value Z. This predetermined value Z is a value that is set in advance based on the viewpoint of whether or not problems such as poor image quality due to scattered toner will occur if the development device 26 continues to operate as is. If the control unit 50 determines that the amount of toner scattering (capacitance) exceeds the predetermined value Z, a message is displayed on the operation display panel 100 (see Figures 1 and 4) urging the user to perform maintenance on the developing device 26. By configuring in this way, it is possible to prevent problems such as poor image quality caused by toner scattering.

[0044] <Modification> Referring to FIG. 7, in a modified developing device 26, the flexible sheet member 26m is formed so that the sealing property at one end side in the width direction (the side where the electrode pair 26r is installed) is lower than the sealing property at the other end side. Specifically, as shown in FIGS. 7A and 7B, the flexible sheet member 26m is formed so that the length of one widthwise end where the electrode pair 26r is located (the length that protrudes toward the developing roller 26a) is shorter than the length of the other widthwise positions. Therefore, the sealing ability of the flexible sheet member 26m (the effect of reducing toner scattering, as described above) is lower at the one widthwise end than at the other portions, including the other end. This increases the amount of toner scattering at the one widthwise end, and the electrode pair 26r can efficiently detect toner scattering (which is intentionally made to occur more easily) with improved responsiveness. Furthermore, as previously described with reference to FIG. 3, the one widthwise end where toner scattering is likely to occur is located outside the image area M (non-image area), so toner scattering there does not directly affect image defects. In this modification, the difference in sealing performance is caused by the length of the flexible sheet member 26m, but the difference in sealing performance can also be caused by the thickness or contact pressure of the flexible sheet member 26m.

[0045] As described above, the image forming apparatus 1 in this embodiment is provided with the photosensitive drum 21 (image carrier) and the developing device 26 including the developing roller 26a (developer carrier) that accommodates toner therein and rotates in a predetermined rotational direction to develop a latent image formed on the surface of the photosensitive drum 21 in a development area facing (or contacting) the photosensitive drum 21. In addition, a detector 40 is further provided near the development area, at an end in the width direction perpendicular to the rotational direction of the developing roller 26a, for detecting scattered toner. This makes it possible to efficiently detect toner scattered near the development area.

[0046] In this embodiment, the developing device 26 is not a component of the process cartridge 20, but is a unit that can be attached to and detached from the image forming apparatus main body 1 on its own. Alternatively, the developing device 26 can be one of the components of the process cartridge 20, and can be attached and detached integrally as a process cartridge to the image forming apparatus main body 1. In other words, at least the photosensitive drum 21 (image carrier) and the developing device 26 can be integrated as a process cartridge. In such a case, the same effect as that of this embodiment can be obtained. In this application, a "process cartridge" is defined as a unit that integrates at least one of a charging device that charges an image carrier, a developing device that develops a latent image formed on the image carrier, and a cleaning device that cleans the image carrier, with an image carrier, and is configured to be detachable from the image forming apparatus main body.

[0047] In this embodiment, the present invention is applied to a developing device 26 in which two transport screws 26b1 and 26b2 (transport members) are arranged side by side in the horizontal direction and a doctor blade 26c is arranged below the developing roller 26a. However, the configuration of the developing device to which the present invention is applied is not limited to this. For example, the present invention can be applied to a developing device in which three or more transport members are arranged side by side in the horizontal direction, a developing device in which multiple transport members are arranged side by side in the vertical direction, or a developing device in which a doctor blade is arranged above the developing roller. However, in a developing device in which the doctor blade 26c is arranged below the developing roller 26a, as in the developing device 26 of this embodiment, toner scattered near the development area is likely to accumulate on the developing case (upper developing case 26j), making the configuration of the present invention useful. In this embodiment, the present invention is applied to a developing device 26 that uses a two-component developer consisting of toner and carrier. However, the present invention can also be applied to a developing device that uses a one-component developer consisting only of toner (including external additives, etc.). In such a case, a developer carrier (developing roller) that comes into contact with the image carrier (photosensitive drum) can be used as the developer carrier (developing roller) installed in the developing device (a contact-type one-component development system). Furthermore, in this embodiment, the electrode pair 26r is provided only on one end side in the width direction, but the electrode pair 26r can also be provided on both end sides in the width direction. In such cases, the same effect as that of this embodiment can be obtained.

[0048] It is clear that the present invention is not limited to the present embodiment, and that within the scope of the technical concept of the present invention, each embodiment may be appropriately modified in addition to what is suggested in each embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and the number, position, shape, etc. of the components may be any number, position, shape, etc. that is suitable for implementing the present invention. [Explanation of symbols]

[0049] 1 Image forming apparatus (image forming apparatus main body), 20, 20Y, 20M, 20C, 20BK process cartridges, 21 photosensitive drum (image carrier), 26 developing device, 26a developing roller (developer carrier), 26j developing case (developing case), 26m flexible sheet member, 26r electrode pair, 26r1, 26r2 electrode, 26x harnesses, 40 detection devices, 41 Measuring part, 42 harnesses, 45 relay connector, A, B connector, M image area. [Prior art documents] [Patent documents]

[0050] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-221012 [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-244414

Claims

1. an image carrier; a developing device including a developer carrier that contains toner therein and rotates in a predetermined rotation direction to develop a latent image formed on the surface of the image carrier in a development area that faces or comes into contact with the image carrier; a detection device that detects scattered toner at an end portion in a width direction perpendicular to the rotation direction and near the development area; Equipped with the detection device includes an electrode pair consisting of a plurality of electrodes, and a measurement unit that measures a capacitance between the electrodes in the electrode pair; the developing device includes a developing case that covers an upper portion of the developer carrier downstream of the developing region in the rotation direction, The image forming apparatus is characterized in that the electrode pair is disposed at a position facing the upper surface of the developing case in the vicinity of the developing area, and outside the image area at the end in the width direction.

2. An image carrier; a developing device including a developer carrier that contains toner therein and rotates in a predetermined rotation direction to develop a latent image formed on the surface of the image carrier in a development area that faces or comes into contact with the image carrier; a detection device that detects scattered toner at an end portion in a width direction perpendicular to the rotation direction and near the development area; Equipped with the detection device includes an electrode pair consisting of a plurality of electrodes, and a measurement unit that measures a capacitance between the electrodes in the electrode pair; The image forming apparatus is characterized in that the electrode pair is disposed only on one end side in the width direction.

3. The image forming apparatus described in Claim 2, characterized in that the developing device is detachably installed with one end side in the width direction toward the rear side in the mounting direction relative to the image forming apparatus main body.

4. The developing device includes a developing case that covers the developer carrier downstream of the developing area in the direction of rotation, the developing device includes a flexible sheet member disposed in the developing case so as to be in sliding contact with the developer carried on the surface of the developer carrier downstream of the developing region in the rotation direction, 4. The image forming apparatus according to claim 2, wherein the flexible sheet member is formed so that the sealing property at one end in the width direction is lower than the sealing property at the other end.

5. An image forming apparatus as described in any one of claims 1 to 4, characterized in that the electrode pair is installed in the developing device and is formed so as to be electrically connectable and detachable to the measuring unit installed in the image forming apparatus main body.

6. An image forming apparatus as described in any one of claims 1 to 4, characterized in that the detection device is installed in the image forming apparatus main body to which the developing device is detachably installed.

7. An image forming apparatus as described in any one of claims 1 to 6, characterized in that when the detection device detects that the amount of scattered toner exceeds a predetermined value, an alert is issued to prompt maintenance of the developing device.

8. An image forming apparatus according to any one of claims 1 to 7, characterized in that at least the image carrier and the developing device are integrated as a process cartridge.

Images