Developing device, process cartridge, and image forming apparatus

Abstract

To reduce a likelihood of occurrence of deformation of a flexible sheet.SOLUTION: A developing device is provided with a flexible sheet member 26r that is held by a developing case 26k at one end as a fixed end on a downstream side in a rotation direction of a developing area and arranged in a gap between a developing roller 26a and the developing case 26k along the rotation direction. The developing device is further provided with a restriction part 26m that does not fix the other end of the flexible sheet member 26r while leaving the other end as a free end and restricts at least displacement in the rotation direction of the flexible sheet. The flexible sheet member 26r is formed with at least one through hole part 26r3 on the other end 26r2. The restriction part 26m is formed with an insertion part 26m1 that is inserted into the through hole part 26r3.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a developing device that develops a latent image formed on an image carrier such as a photosensitive drum, and to a process cartridge and an image forming apparatus that include the same. [Background technology]

[0002] Conventionally, in developing devices installed in image forming devices such as copiers and printers, a technique of installing a flexible sheet member (sheet member) in a developing case for the purpose of preventing toner scattering has been known (see, for example, Patent Document 1).

[0003] Specifically, the developing device in Patent Document 1 is provided with a developing case that covers the top of a developing roller (developer carrier) that faces a photosensitive drum (image carrier). The developing case also holds a base (one end) of a sheet member (flexible sheet member) as a fixed end at a position downstream of the developing roller in the direction of rotation relative to the development area. The sheet member is then positioned such that its free end (the other end) is aligned with the direction of rotation between the developing case and the developing roller. The sheet member installed in the developing case in this manner creates a suction airflow in the gap between the developing case and the developing roller, reducing the problem of toner blowing out from the gap. Summary of the Invention [Problem to be solved by the invention]

[0004] With conventional technology, when a measuring tool such as an R gauge is inserted and removed into a manufacturing plant to check the gap between a developer carrier (developing roller) and a flexible sheet member, the flexible sheet member can become significantly deformed, and in such cases the flexible sheet member is unable to fully perform its intended function, resulting in toner scattering and other problems.

[0005] SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide a developing device, a process cartridge, and an image forming apparatus in which deformation of a flexible sheet member is unlikely to occur. [Means for solving the problem]

[0006] The developing device of the present invention includes: a developer carrier that faces or contacts an image carrier to form a development area, and develops a latent image formed on the surface of the image carrier in the development area while rotating in a predetermined rotation direction; a development case that faces the developer carrier with a gap therebetween on the downstream side of the development area in the rotation direction; a flexible sheet member that has one end held as a fixed end by the development case on the downstream side of the development area in the rotation direction and is arranged in the gap between the developer carrier and the development case along the rotation direction; and a limiting portion that limits displacement of the flexible sheet member at least in the rotation direction, leaving the other end side of the flexible sheet member as a free end and not fixed, wherein the flexible sheet member has at least one through hole formed on the other end side, and the limiting portion has an insertion portion that is inserted into the through hole. and is detachably installed in the developing case. It is something. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a developing device, a process cartridge, and an image forming apparatus in which deformation of the flexible sheet member is unlikely to occur. [Brief explanation of the drawings]

[0008] [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 longitudinal view of the developing device. [Figure 4] FIG. 2 is an enlarged view showing a main part of the developing device. [Figure 5] FIG. 2 is an enlarged view showing the free end side of a flexible sheet member in the developing device. [Figure 6]3 is a cross-sectional view showing the free end side of a flexible sheet member in the developing device in the width direction. FIG. [Figure 7] FIG. 10 is a diagram showing the state in which an R gauge is inserted into and removed from a casing gap. [Figure 8] FIG. 10 is a diagram showing a state when the developing roller is rotated in reverse. [Figure 9] 10 is a cross-sectional view showing the free end side of a flexible sheet member in a developing device according to a first modification in the width direction. FIG. [Figure 10] FIG. 10 is an enlarged view showing the free end side of a flexible sheet member in a developing device according to a second modified example. [Figure 11] 11A to 11C are diagrams showing the operation of placing the flexible sheet member of FIG. 10 in the developing case. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 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 40. 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.

[0011] 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 40 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.

[0012] 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.

[0013] 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.

[0014] 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).

[0015] 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.

[0016] 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 40. Here, primary transfer rollers 24 are installed at each of the facing positions so as to abut against the inner circumferential surface of the intermediate transfer belt 40. 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 40 in order, superimposed on top of each other (this is the primary transfer process).

[0017] 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 the charge removal device, and a series of image forming processes on the photosensitive drum 21 is completed.

[0018] Meanwhile, the surface of the intermediate transfer belt 40 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 40 is secondarily transferred onto the sheet P (secondary transfer process). Thereafter, the surface of the intermediate transfer belt 40 reaches the position of the intermediate transfer belt cleaning device 81. Then, the untransferred toner on the intermediate transfer belt 40 is collected by the intermediate transfer belt cleaning device 81, and the series of transfer processes on the intermediate transfer belt 40 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 .

[0019] 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 40.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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, and a doctor blade 26c (developer regulating member) facing the developing roller 26a to regulate the amount of developer carried on the developing roller 26a.

[0024] The developing device 26 contains a developer (two-component developer) made up of carrier and toner. In this embodiment, the average particle size of the toner is set to about 5.2 μm, the average particle size of the carrier is set to about 35 μm, the toner concentration is set to about 7 wt %, and the amount of developer in the developing device 26 is set to about 250 g.

[0025] 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 magnetic poles H1 to H5 (see Fig. 4) on the outer circumferential surface of the roller, and a sleeve 26a2 that rotates around the magnet 26a1.

[0026] 4, the drawing-up magnetic pole H5 acts on the carrier as a magnetic body, drawing up the developer G accommodated in the first transport path B1 (see FIG. 2) onto the developing roller 23a. A portion of the developer G carried on the developing roller 23a is scraped off at the position of the doctor blade 26c (see FIG. 2) and returned to the first transport path B1. Meanwhile, at the position of the doctor blade 26c where the magnetic force of the drawing-up magnetic pole H5 acts, the developer G carried on the developing roller 26a passes through the doctor gap between the doctor blade 26c and the developing roller 26a, and becomes raised at the position of the main magnetic pole H1, becoming a magnetic brush in the development area and sliding against the photosensitive drum 21. In this way, the toner in the developer G carried on the developing roller 26a adheres to the latent image on the photosensitive drum 21. After that, the developer G that has passed the position of the main magnetic pole H1 is transported between the upper developer case 26k (developer case) and the developer by multiple transport magnetic poles H2 and H3, and then transported to the position of the developer releasing magnetic pole H4. Then, at the position of the developer releasing magnetic pole H4, a repulsive magnetic field (a magnetic field that acts in a direction away from the developing roller 26a) acts on the carrier, causing the developer G carried on the developing roller 26a after the development process to be detached from the developing roller 26a. The detached developer G falls into the first transport path B1 and is transported downstream of the first transport path B1 by the first transport screw 26b1 (see FIGS. 2 and 3).

[0027] 2 and 3, the transport screws 26b1 and 26b2 as transport members transport the developer contained inside the developing device 26 in the longitudinal direction (width direction) to form a circulation path (the circulation path indicated by the dashed arrow in FIG. 3). That is, a circulation path for the developer 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.

[0028] 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 longitudinal direction (width direction, rotation axis 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 stirs 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 longitudinal 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 rotating shaft, and is driven to rotate at a rotation speed of about 600 rpm.

[0029] 2 and other figures, developing device 26 in this embodiment has a filter 26t installed in an opening 26k1 that connects the inside of the device with the outside of the device. More specifically, an opening 26k1 (ventilation path) penetrating from the inside to the outside is formed in the ceiling of the upper developer case 26k (developer case) of the developing device 26. A filter 26t is provided to close the opening 26k1. The filter 26t is used to collect toner and allow ventilation. In other words, an opening 26k1 for sending air from the inside to the outside of the developing device 26 is formed in the developing upper case 26k. The filter 26t is installed at the opening 26k1. 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 W (casing gap) between the developing roller 26a and the upper developing case 26k 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 W is too small, the developer carried on the developing roller 26a after the development process will not be transported smoothly to the gap W between the developing roller 26a and the developing upper case 26k, and will easily overflow and leak out of the developing device 26. On the other hand, if the casing gap W is too large, the developer carried by the developing roller 26a will have difficulty sliding against the inner surface of the developing case 26k (flexible sheet member 26r), making it difficult for a suction airflow toward the inside of the developing device 26 due to the pump action to be formed, and toner scattering from the developing device 26 (toner scattering around the development area) will be more likely to occur. By maintaining the casing gap W within an appropriate range, it is possible to reduce developer leakage and toner scattering. Furthermore, the internal pressure of the developing device 26 tends to increase due to the suction airflow in the casing gap W described above, and if the internal pressure increases, toner will scatter from the gaps in the developing device 26. In contrast, in this embodiment, the opening 26k1 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. In this embodiment, a flexible sheet member 26r is provided so as to enter the gap (casing gap W) between the developing roller 26a and the developing upper case 26k, which will be described in detail later with reference to FIG. 4 etc.

[0031] The image forming process described above will now be further explained, focusing on the development process. Developing roller 26a rotates in a predetermined rotation direction (counterclockwise direction indicated by the arrow in FIG. 2). As shown in FIG. 3, the developer in developing device 26 is circulated in the longitudinal direction while being stirred and mixed with toner supplied from toner container 70 through toner 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 (circulation in the direction of the dashed arrow in FIG. 3). 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 the developer lift-up pole H5 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 development area). The toner is then attracted to the latent image formed on the photosensitive drum 21 by the electric field formed in the development 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 development area is formed by a predetermined voltage (development 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.

[0032] 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).

[0033] The configuration and operation of the developing device 26, which is a feature of this embodiment, will be described in detail below. As previously described with reference to FIGS. 2 and 3, the developing device 26 is provided with a developing roller 26a as a developer carrier and an upper developing case 26k as a developing case. The developing roller 26a, which serves as a developer carrier, faces the photosensitive drum 21, which serves as an image carrier, to form a developing area, and develops the latent image formed on the surface of the photosensitive drum 21 in the developing area while rotating in a predetermined rotational direction (counterclockwise (arrow direction) in Figures 2 and 4). The upper developer case 26k as a developer case is a casing that faces the developing roller 26a across a gap (casing gap W) on the downstream side of the developing area in the rotation direction (counterclockwise in FIGS. 2 and 4).

[0034] Referring to FIG. 2, in this embodiment, the developing device 26 is provided with a casing (housing) including a lower developing case 26j in addition to the above-described upper developing case 26k. The developing lower case 26j is a casing that serves as the base of the developing device 26, and rotatably holds the developing roller 26a and the conveying screws 26b1 and 26b2, as well as holds the doctor blade 26c. On the other hand, the upper developer case 26k (developer case) is arranged to cover the upper side of the developing roller 26a (developer carrier). The upper developer case 26k is configured to be detachable from the lower developer case 26j, which holds the developing roller 26a, the conveying screws 26b1 and 26b2, and the doctor blade 26c, by snapping or screwing.

[0035] Now, referring to Figure 4 etc., in the developing device 26 in this embodiment, a flexible sheet member 26r is arranged in the gap (casing gap W) between the developing roller 26a (developer carrier) and the developing upper case 26k (developing case) along the rotation direction of the developing roller 26a. One end 26r1 of the flexible sheet member 26r is held as a fixed end by the upper developer case 26k downstream of the development area (the position where the developing roller 26a faces the photosensitive drum 21) in the direction of rotation indicated by the arrow in FIG. 4. Specifically, in this embodiment, the one end 26r1 of the flexible sheet member 26r is affixed to the end face of the upper developer case 26k (the end face facing the photosensitive drum 21) with double-sided tape or the like. The other end 26r2 of the flexible sheet member 26r is a free end and is not fixed to any member. The flexible sheet member 26r is disposed so as to come into contact with the developer G carried on the developing roller 26a. In this embodiment, a substantially rectangular urethane sheet having a thickness of approximately 0.1 mm is used as the flexible sheet member 26r. In this embodiment, the flexible sheet member 26r is formed so that its overall length (from one end 26r1 to the other end 26r2) is substantially the same as or slightly shorter than the opposing surface 26k10 of the developing upper case 26k (the surface opposing the developing roller 26a).

[0036] By providing the flexible sheet member 26r configured in this manner, even if the amount of developer carried on the developing roller 26a (pumped-up amount) between the developing roller 26a and the developing upper case 26k increases or decreases, the flexible sheet member 26r flexibly deforms (bends) in accordance with the amount of developer, and therefore the flexible sheet member 26r is more likely to maintain a state of being in contact with the developer G carried on the developing roller 26a (it is less likely to become separated from the developer G as a whole). Therefore, a stable suction airflow (see the white arrow in FIG. 4) is formed in the gap between the developing roller 26a and the developing upper case 26k, and the problem of toner blowing out from the gap (toner scattering) is reduced.

[0037] 4 to 6, the developing device 26 in this embodiment is provided with a limiting portion 26m (limiting member) that limits displacement in at least the rotational direction (the rotational direction of the developing roller 26a, which is the direction of the arrow in Figures 4 and 5 or the opposite direction) of the other end side 26r2 of the flexible sheet member 26r, leaving it as a free end and not fixed. In particular, the limiting portion 26m in this embodiment is configured to limit not only the displacement in the rotational direction of the other end side 26r2 of the flexible sheet member 26r, but also the displacement in multiple directions including the rotational axis direction (width direction) perpendicular to the rotational direction. That is, in this embodiment, the other end side 26r2 of the flexible sheet member 26r is loosely held (held so as to be able to displace to a certain extent) by the limiting portion 26m, and although the state of a free end is maintained, it is not allowed to displace indefinitely, and its displacement is limited so as not to exceed a certain range. Specifically, in this embodiment, limiting portion 26m is a rivet-shaped member made of a resin material. The material of limiting portion 26m is preferably one to which developer G does not easily adhere (i.e., one with low affinity for developer G (toner)). Furthermore, limiting portion 26m only needs to be strong enough to loosely hold the other end 26r2 (free end) of flexible sheet member 26r and to limit displacement.

[0038] More specifically, in this embodiment, flexible sheet member 26r has at least one through-hole 26r3 formed on other end 26r2. Specifically, flexible sheet member 26r in this embodiment has one substantially elongated through-hole 26r3 formed in the center in the rotation axis direction (width direction) at a position slightly away from end surface 26r20 of other end 26r2. On the other hand, the restricting portion 26m (restricting member) has a generally cylindrical insertion portion 26m1 formed therein to be inserted into the through-hole 26r3 of the flexible sheet member 26r. The insertion portion 26m1 of the restricting portion 26m is inserted into the through-hole 26r3 with a gap therebetween. That is, the insertion portion 26m1 is loosely inserted into the through-hole 26r3. In other words, as shown in FIG. 6, the cross-sectional area of ​​the insertion portion 26m1 is formed to be smaller than the hole area of ​​the through-hole 26r3.

[0039] With this configuration, even if the other end 26r2 of the flexible sheet member 26r is about to be displaced significantly, the through-hole 26r3 interferes with the limiting portion 26m (insertion portion 26m1), thereby limiting the displacement. Therefore, even if a measuring tool such as an R gauge 200 (see Figure 7) is inserted or removed from the gap between the developing roller 26a and the flexible sheet member 26r, or even if the developing roller 26a is rotated in the reverse direction, the flexible sheet member 26r is less likely to be significantly deformed, such as curled up.

[0040] For more details, referring to Figure 7, in a manufacturing plant for the developing device 26, R gauges 200 (measuring instruments) of various thicknesses are inserted and removed into the gap between the developing roller 26a and the flexible sheet member 26r to check the gap. 7(B) as a comparative example, if no limiting portion is provided to limit the displacement (movement) of the other end 126r2 of the flexible sheet member 126r, the flexible sheet member 126r may be pulled by the R gauge 200 as the R gauge 200 moves in the direction of the double arrow in the figure, causing the flexible sheet member 126r to be rolled up, become bellows-like, or become significantly deformed. In the developing device 126 shipped in such a state, the original function of the flexible sheet member is not fully exhibited, resulting in toner scattering and the like. In contrast, the developing device 26 in this embodiment is provided with a limiting portion 26m that limits the displacement (movement) of the other end 26r2 of the flexible sheet member 26r, so that even if the R gauge 200 moves in the direction of the double arrow in the figure, the flexible sheet member 26r is not dragged by the R gauge 200 and does not undergo significant deformation, as shown in Figure 7(A). Therefore, the original function of the flexible sheet member is fully exhibited.

[0041] Furthermore, as in the comparative example of the developing device 126 shown in FIG. 8B, if no limiting portion is provided to limit the displacement (movement) of the other end 126r2 of the flexible sheet member 126r, the other end 126r2 (free end) of the flexible sheet member 126r becomes completely free (its position is difficult to determine), and the developer G easily gets between the flexible sheet member 126r and the upper developer case 126k (it easily climbs up). This problem is particularly likely to occur when the developing roller 26a is rotated in the reverse direction (clockwise as indicated by the arrow in FIG. 8) at a predetermined timing, as shown in FIG. 8. If the developer G gets between the flexible sheet member 126r and the upper developer case 126k, the flexible sheet member 126r is significantly deformed from its intended position and hits the developer G on the developing roller 26a too hard, making it difficult to form a good suction airflow in the casing gap W. Therefore, toner is likely to scatter from the casing gap W to the outside of the device. In contrast, the developing device 26 in this embodiment is provided with a limiting portion 26m that limits the displacement (movement) of the other end side 26r2 of the flexible sheet member 26r, and the other end side 26r2 (free end side) of the flexible sheet member 26r is loosely held by the limiting portion 26m. As a result, as shown in Figure 8(A), developer G is less likely to get between the flexible sheet member 26r and the developing upper case 126k, and such toner scattering is less likely to occur.

[0042] In this embodiment, during the non-developer process (non-image formation), the developing roller 26a is controlled to rotate in the opposite direction (clockwise in Figure 4) to the rotation direction at a predetermined timing (for example, after a series of printing operations is completed). By performing such control, it is possible to reduce problems such as developer G staying (clogging) between the developing roller 26a and the doctor blade 26c (doctor gap).

[0043] Here, in the flexible sheet member 26r in this embodiment, the through-hole portion 26r3 is formed so that its length in the rotation direction (the up-down direction in Figure 6) is longer than its length in the rotation axis direction (the left-right direction in Figure 6) which is perpendicular to the rotation direction. Specifically, in this embodiment, the through-hole portion 26r3 is an elongated hole with the rotation direction as the longitudinal direction, and the length of the through-hole portion 26r3 in the short direction (rotation axis direction) is formed to be slightly larger than the outer diameter of the insertion portion 26m1 of the limiting portion 26m. By configuring the flexible sheet member 26r in this manner, the other end side 26r2 (free end) is less likely to displace (become misaligned) in the width direction (direction of rotation axis), and the sealing properties of the flexible sheet member 26 are maintained across the width direction. Furthermore, since the other end side 26r2 (free end) of the flexible sheet member 26r can be displaced to a certain extent in the rotational direction, even if the amount of developer carried on the developing roller 26a in the casing gap W increases or decreases, the flexible sheet member 26r flexibly deforms accordingly, thereby maintaining the sealing properties of the flexible sheet member 26.

[0044] Now, referring to Figure 5 etc., in this embodiment, the limiting portion 26m is formed with a stopper portion 26m2 that limits displacement of the other end side 26r2 of the flexible sheet member 26r in a direction approaching the developing roller 26a (developer carrier). In detail, the stopper portion 26m2 is formed to have a cross-sectional area that is sufficiently large compared to the hole area (particularly, the length in the short direction) of the through-hole portion 26r3 (the projection surface of the stopper portion 26m2 is formed to overlap with the through-hole portion 26r3), and is arranged to be located between the flexible sheet member 26r and the developing roller 26a. This configuration prevents the flexible sheet member 26r from being separated too far from the opposing surface 26k10 of the upper developing case 26k, and determines the separation distance from the developing roller 26a to some extent, thereby making it easier to maintain the effects described above with reference to FIG. In this way, the flexible sheet member 26r is arranged so that its bottom, excluding one end side 26r1 and the other end side 26r2, faces the developing roller 26a (so that it comes into sliding contact with the developer G carried on the developing roller 26a).

[0045] In this embodiment, the limiting portion 26m is detachably installed in the upper developer case 26k (developer case). In particular, in this embodiment, the limiting portion 26m is configured so as to be able to be attached to the upper developing case 26k at the time of manufacturing. Specifically, before the manufacturing process (assembly) of the developing device 26, the developer upper case 26k, the flexible sheet member 26r, and the limiting portion 26m are each prepared as separate members. Then, during the manufacturing process (assembly) of the developing device 26, one end 26r1 of the flexible sheet member 26r is attached to the developer upper case 26k, and then the limiting portion 26m is joined to the developer upper case 26k with the insertion portion 26m1 inserted into the through-hole portion 26r3 (the insertion portion 26m1 is riveted into a fitting hole formed in the opposing surface 26k10). In this way, a subassembly consisting of the developer upper case 26k, the flexible sheet member 26r, and the limiting portion 26m is completed, and the subassembly is connected to the developer lower case 26j in a state in which the developing roller 26a, the conveying screws 26b1 and 26b2, and the doctor blade 26c are held. In this way, the developing device 26 is completed.

[0046] Now, referring to Figure 4 etc., in this embodiment, the developing upper case 26k (developing case) has a convex portion 26k2 that narrows the gap (casing gap W) with the developing roller 26a at a position corresponding to between one end side 26r1 of the flexible sheet member 26r and the through hole portion 26r3, and is formed along the rotation axis direction perpendicular to the rotation direction (the direction perpendicular to the paper surface of Figure 4, which is the width direction and the longitudinal direction). Specifically, a convex portion 26k2 that narrows the casing gap W is formed on a part of the opposing surface 26k10 of the upper developing case 26k, and the casing gap W in other parts is configured to be approximately uniform. In addition, the gap (casing gap W) between the convex portion 26k2 and the developing roller 26a is set to approximately match the target separation distance of the flexible sheet member 26r from the developing roller 26a (gap for forming a good intake airflow). By providing the protrusion 26k2 in this manner, the posture of the flexible sheet member 26r in the casing gap W is stabilized, and a good suction airflow is more likely to be formed stably, compared to when the protrusion 26k2 is not provided. As a result, toner is less likely to scatter from the casing gap W to the outside of the device.

[0047] In this embodiment, the casing gap W between the upper developer case 26k and the developing roller 26a is configured to be approximately uniform in the longitudinal direction. Alternatively, the casing gap W at both longitudinal ends may be configured to be narrower than the casing gap W at the longitudinal center. In this configuration, even if the stiffness of the flexible sheet member 26r at both longitudinal ends is weaker than that at the longitudinal center, a good suction airflow can be formed along the longitudinal direction. In this embodiment, it is preferable that the flexible sheet member 26r is disposed so that its abdomen (backing portion) is in sliding contact with at least the developer G (where the ears lie flat) between the two transport magnetic poles P2 and P3. This configuration strengthens the contact between the developer at the P2 magnetic pole and the flexible sheet member 26r, making it easier to form a stable suction airflow. Since developer G tends to accumulate in the casing gap W when the gap W is narrowed in the portion where the ears stand, the configuration of this embodiment in which the gap W is narrowed by the protrusion 26k2 between the two transport magnetic poles P2 and P3 is useful. It is also preferable that the flexible sheet member 26r be in contact with the upright portion of the developer G (the P2 magnetic pole with a strong normal magnetic force) in the casing gap W. This is because the suction airflow is more likely to occur in the upright portion of the developer G than in the flat portion of the developer G.

[0048] As previously described with reference to FIG. 2, developing device 26 in this embodiment is provided with opening 26k1 and filter 26t to reduce an increase in internal pressure of developing device 26. Even if developing device 26 in this embodiment is not provided with opening 26k1 and filter 26t, flexible sheet member 26r and limiting portion 26m function as described above to reduce toner scattering outside the device. However, providing opening 26k1 and filter 26t as in this embodiment further enhances the effect of reducing toner scattering. In this case, in the present embodiment, the flexible sheet member 26r hits the developer G on the developing roller 26a with a stable and strong force to some extent, making it difficult for the suction airflow to flow backward and reducing the amount of air drawn in together with the developer G. Therefore, the amount of air escaping to the outside of the device through the opening 26k1 (filter 26t) also decreases, reducing clogging of the filter 26t.

[0049] <Variation 1> As shown in Figure 9, in the developing device 26 of variant example 1, the flexible sheet member 26r has a reinforcing portion 26r5 formed on the other end side (the side closer to the end face 26r20 of the other end side 26r2) of the through-hole portion 26r3 to reinforce the strength of the flexible sheet member 26r. More specifically, in Modification 1, the reinforcing portion 26r5 is formed by adhering one or more sheets of the same material as the flexible sheet member 26r, which have the same width but are shorter in the rotational direction, to the other end of the flexible sheet member 26r. In other words, the flexible sheet member 26r is reinforced by increasing the thickness only at the reinforcing portion 26r5. With this configuration, even if the through-holes 26r3 are formed in the flexible sheet member 26r, the other end 26r2 of the flexible sheet member 26r has a significantly reduced strength and is prone to deformation, which can be alleviated. 9, in the first modification, a plurality of through-holes 26r3 are formed in the flexible sheet member 26r at positions spaced apart in the width direction, and correspondingly, a plurality of limiting portions 26m are provided to be inserted into the respective through-holes 26r3. Even with this configuration, deformation of the flexible sheet member 26r can be made less likely to occur.

[0050] <Variation 2> As shown in Figure 10, in the developing device 26 of variant example 2, a protrusion 26k5 that functions as a limiting portion that limits the displacement of the flexible sheet member 26r is integrally formed so as to protrude in a direction approaching the developing roller 26a (developer carrier) relative to the developing upper case 26k (developing case). That is, in the second modification, the protrusion 26k5 that functions as a limiting portion is not provided as a separate component from the upper developer case 26k, but is provided integrally as part of the upper developer case 26k. The protrusion 26k5 serving as the limiting portion is formed with an insertion portion 26k51 that is inserted into the through-hole portion 26r3 of the flexible sheet member 26r. Further, the protruding portion 26k5 serving as a limiting portion is formed with a stopper portion 26k52 that limits displacement of the other end side 26r2 of the flexible sheet member 26r in a direction approaching the developing roller 26a (developer carrier). 10, the protrusion 26k5 (restriction portion) is formed in a generally hook shape, and its head (extending along the rotation direction) functions as the stopper portion 26k52. The stopper portion 26k52 is formed so that its projection surface is included within the through-hole portion 26r3, as shown in FIG. 11(A). The insertion portion 26k51 is connected to one end of the stopper portion 26k52 (upstream side in the rotation direction).

[0051] When the protruding portion 26k5 (limiting portion) is formed integrally with the upper developer case 26k as in the second modified example, the upper developer case 26k (on which the protruding portion 26k5 is formed) and the flexible sheet member 26r are prepared as separate members prior to the manufacturing process (assembly) of the developing device 26. Then, during the manufacturing process (assembly) of the developing device 26, one end 26r1 of the flexible sheet member 26r is attached to the upper developer case 26k, and around the same time, as shown in FIG. 11(A), the other end 26r2 of the flexible sheet member 26r is further shifted toward the other end, the stopper portion 26k52 is passed through the through-hole portion 26r3, and the insertion portion 26k51 is inserted into the through-hole portion 26r3. 11(B), the other end 26r2 of the flexible sheet member 26r is shifted to its normal position in the direction of the white arrow so that the stopper portion 26k52 overlaps the through-hole portion 26r3 (moved to a position where it functions as the stopper portion 26k52). In this way, a subassembly consisting of the upper developer case 26k (and the protrusion 26k5) and the flexible sheet member 26r is completed, and this subassembly is connected to the lower developer case 26j in a state in which the developing roller 26a, the conveying screws 26b1 and 26b2, and the doctor blade 26c are held. In this way, the developing device 26 is completed. Even with this configuration, deformation of the flexible sheet member 26r can be made less likely to occur. In particular, in Modification 2, the protruding portion 26k5 (limiting portion) is formed integrally with the upper developing case 26k, so the number of parts can be reduced compared to when the limiting portion and the upper developing case 26k are formed as separate parts.

[0052] As described above, the developing device 26 in this embodiment includes a developing roller 26a (developer carrier) that faces (or contacts) the photosensitive drum 21 (image carrier) to form a development area and develops a latent image formed on the surface of the photosensitive drum 21 in the development area while rotating in a predetermined rotational direction, and a developing case 26k (upper developing case) that faces the developing roller 26a with a gap therebetween and downstream of the development area in the rotational direction. Also provided is a flexible sheet member 26r that is fixed at one end to the developing case 26k downstream of the development area in the rotational direction and is positioned in the gap between the developing roller 26a and the developing case 26k along the rotational direction. Furthermore, the other end of the flexible sheet member 26r is left free and unfixed, and is provided with a limiting portion 26m that limits displacement at least in the rotational direction. The flexible sheet member 26r has at least one through-hole 26r3 formed in the other end 26r2. The restricting portion 26m is formed with an insertion portion 26m1 that is inserted into the through-hole portion 26r3. This makes it possible to make the flexible sheet member 26r less likely to deform.

[0053] In the present 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 independently. However, the developing device 26 can also be one of the components of the process cartridge 20, and configured to be attached and detached from the image forming apparatus main body 1 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.

[0054] 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 a developing roller 26a. However, the configuration of the developing device to which the present invention is applied is not limited to this, and the present invention can also be applied to, for example, 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 a developing roller. 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 this case, the developing roller (developer carrier) can be in contact with the photosensitive drum (image carrier) to form a development area. In addition, in this embodiment, the limiting portion 26m is formed to limit displacement in multiple directions, including the rotational direction, of the flexible sheet member 26r, but the limiting portion can also be formed to limit displacement only in the rotational direction of the flexible sheet member. In such cases, the same effect as that of this embodiment can be obtained.

[0055] 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]

[0056] 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, 26k developing case (developing case), 26k2 convex part, 26k5 protrusion (restriction), 26k51 Insertion part, 26k52 Stopper part, 26m limit, 26m1 insertion part, 26m2 stopper part, 26r flexible sheet member; 26r1 One end side (fixed end), 26r2 Other end side (free end), 26r3 Through hole part, 26r5 reinforcement part, G Developer. [Prior art documents] [Patent documents]

[0057] [Patent Document 1] Japanese Patent Publication No. 2020-75482

Claims

1. a developer carrier that faces or contacts an image carrier to form a development area and develops a latent image formed on the surface of the image carrier in the development area while rotating in a predetermined rotation direction; a developing case facing the developer carrier with a gap therebetween, the developing case being located downstream of the developing area in the rotation direction; a flexible sheet member, one end of which is held as a fixed end by the developing case downstream of the developing region in the rotation direction, and which is disposed in the gap between the developer carrier and the developing case along the rotation direction; a limiting portion that limits displacement of the other end of the flexible sheet member at least in the rotational direction without fixing the other end of the flexible sheet member as a free end; Equipped with the flexible sheet member has at least one through-hole formed on the other end side, The developing device is characterized in that the limiting portion has an insertion portion that is inserted into the through-hole portion and is detachably installed on the developing case.

2. A developer carrier that faces or contacts an image carrier to form a development area, and that develops a latent image formed on the surface of the image carrier in the development area while rotating in a predetermined rotation direction; a developing case facing the developer carrier with a gap therebetween, the developing case being located downstream of the developing area in the rotation direction; a flexible sheet member, one end of which is held as a fixed end by the developing case downstream of the developing region in the rotation direction, and which is disposed in the gap between the developer carrier and the developing case along the rotation direction; a limiting portion that limits displacement of the other end of the flexible sheet member at least in the rotational direction without fixing the other end of the flexible sheet member as a free end; Equipped with the flexible sheet member has at least one through-hole formed on the other end side, and a reinforcing portion formed on the other end side relative to the through-hole portion to reinforce the strength of the flexible sheet member; The developing device, wherein the restricting portion includes an insertion portion that is inserted into the through-hole portion.

3. A developer carrier that faces or contacts an image carrier to form a development area, and that develops a latent image formed on the surface of the image carrier in the development area while rotating in a predetermined rotation direction; a developing case facing the developer carrier with a gap therebetween, the developing case being located downstream of the developing area in the rotation direction; a flexible sheet member, one end of which is held as a fixed end by the developing case downstream of the developing region in the rotation direction, and which is disposed in the gap between the developer carrier and the developing case along the rotation direction; a limiting portion that limits displacement of the other end of the flexible sheet member at least in the rotational direction without fixing the other end of the flexible sheet member as a free end; Equipped with the flexible sheet member has at least one through-hole formed on the other end side, the limiting portion includes an insertion portion that is inserted into the through-hole portion, The developing device is characterized in that the developing case has a convex portion formed in a position corresponding to the area between the one end side of the flexible sheet member and the through-hole portion, which narrows the gap with the developer carrier, and which extends in a rotational axis direction perpendicular to the rotational direction.

4. 4. The developing device according to claim 2, wherein the limiting portion is detachably provided on the developing case.

5. 4. The developing device according to claim 2, wherein the limiting portion is integrally formed with the developing case so as to protrude in a direction approaching the developer carrier.

6. A developing device as described in any one of claims 1 to 5, characterized in that the insertion portion is inserted into the through-hole portion with a gap therebetween.

7. A developing device described in any one of claims 1 to 6, characterized in that the length of the through hole portion in the rotational direction is longer than the length in the rotational axis direction perpendicular to the rotational direction.

8. A developing device described in any one of claims 1 to 7, characterized in that the limiting portion is formed with a stopper portion that limits displacement of the other end side of the flexible sheet member in a direction approaching the developer carrier.

9. the developing case is disposed so as to cover the developer carrier from above, 9. The developing device according to claim 1, wherein the flexible sheet member is disposed so as to be in contact with the developer carried on the developer carrier.

10. 10. The developing device according to claim 1, wherein the developer carrier is rotated in a direction opposite to the rotation direction at a predetermined timing during a non-developing step.

11. A process cartridge that is detachably installed in an image forming apparatus main body, 11. A process cartridge comprising the developing device according to claim 1 and the image carrier, the process cartridge being integrally provided with the developing device.

12. An image forming apparatus comprising the developing device according to any one of claims 1 to 10.

Images