JP7792063B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

This invention relates to a developing device that develops a latent image formed on an image carrier such as a photosensitive drum, as well as a process cartridge and an image forming apparatus that include the same.

In developing devices installed in image forming devices such as copiers and printers, a technique has been known in which a flexible sheet member (sheet-like member) is installed in the developing case to prevent toner from scattering (see, for example, Patent Document 1).

More specifically, the developing device in Patent Document 1 is provided with a development case that covers the top of a development roller (developer carrier) that faces a photosensitive drum (image carrier). The development case also holds a base (one end) of a sheet-like member (flexible sheet member) as a fixed end at a position downstream of the development area in the direction of rotation of the development roller. The sheet-like member is then positioned so that its free end (the other end) is aligned with the direction of rotation between the development case and the development roller. The sheet-like member installed in this way in the development case creates a suction airflow in the gap between the development case and the development roller, reducing the problem of toner blowing out from that gap.

With conventional technology, a large amount of developer could get between the developer case and the flexible sheet member, causing the flexible sheet member to deform significantly. In such cases, the flexible sheet member's intended functionality could not be fully realized, resulting in toner scattering and other problems.

This invention was made to solve the above-mentioned problems, and aims to provide a developing device, process cartridge, and image forming apparatus that are less likely to cause the problem of developer getting between the developing case and the flexible sheet member.

The developing device of this invention comprises 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 rotational direction; a developing case that faces the developer carrier downstream of the development area in the rotational direction with a gap between them; a flexible sheet member that is held as a fixed end by the developing case downstream of the development area in the rotational direction and is arranged in the gap between the developer carrier and the developing case along the rotational direction; and a holding portion that holds the other end of the flexible sheet member as a free end without fixing it, and the developing case has a convex portion that narrows the gap with the developer carrier formed along the rotational axis direction perpendicular to the rotational direction at a position corresponding to between the one end and the other end of the flexible sheet member .

This invention makes it possible to provide a developing device, process cartridge, and image forming apparatus that are less susceptible to problems such as developer getting between the developing case and the flexible sheet member.

1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; FIG. FIG. 2 is a longitudinal view of the developing device. FIG. 2 is an enlarged view showing a main part of the developing device. FIG. 10 is a diagram showing a state when the developing roller is rotated in reverse. 10A is a diagram showing the development case in the longitudinal direction as viewed from the development roller side, and FIG. 10B is a diagram showing the holding portion in the longitudinal direction as viewed from the development roller side, as a first modified example. 7A and 7B are diagrams illustrating an operation of assembling the holding portion shown in FIG. 6B to the developing case shown in FIG. 6A. FIG. 10 is an enlarged view showing a main part of a developing device according to a second modified example. FIG. 9 is a bottom view showing the development case of the development device of FIG. 8 . FIG. 11 is an enlarged view showing a main part of a developing device according to a third modified example. As variant example 4, (A) is an enlarged view showing the main parts of the developing device when no developer is carried on the developing roller, and (B) is an enlarged view showing the main parts of the developing device when developer is carried on the developing roller.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that in each drawing, identical or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

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 provided so as to face the photosensitive drums 21 of the plurality of process cartridges 20Y, 20M, 20C, and 20BK.

In FIG. 1, reference numeral 1 denotes a main body of a color copier as an image forming apparatus, 2 denotes a document transport unit that transports a document to a document reading unit 3, 3 denotes a document reading unit that reads image information of the document, and 4 denotes a writing unit (exposure unit) that emits laser light based on input image information.
Also, 20Y, 20M, 20C, and 20BK denote process cartridges corresponding to the respective colors (yellow, magenta, cyan, and black), and 40 denotes an intermediate transfer belt onto which toner images of a plurality of colors are transferred in an overlapping manner.
Also, 61 denotes a paper feeding 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.

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.

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 image information of the document placed on the contact glass.
The image information for each color of yellow, magenta, cyan, and black is then sent to the writing unit 4. Then, laser light L (exposure light) based on the image information for each color is emitted from the writing unit 4 toward the surface of the photosensitive drum 21 (see FIG. 2) of the corresponding process cartridge 20Y, 20M, 20C, and 20BK.

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

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, to form an electrostatic latent image of the cyan component. 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, to form an electrostatic latent image of the magenta component. 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, to form an electrostatic latent image of the black component.

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 succession, superimposed on top of each other (this is the primary transfer process).

After the primary transfer process, the surface of each photosensitive drum 21 reaches a position facing the cleaning device 23. The cleaning device 23 then collects untransferred toner remaining on the photosensitive drum 21 (this is the cleaning process). The untransferred toner collected by the cleaning device 23 passes through a waste toner transport path (not shown) and is collected into 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.

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 .

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 sheet feed roller 62 from a sheet 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.

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.

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 different colors of 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.

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.

As shown in Figures 2 and 3, the developing device 26 is primarily composed of a developing roller 26a as a developer carrier, a first transport screw 26b1 (first transport member) that faces the developing roller 26a, a second transport screw 26b2 (second transport member) that faces the first transport screw 26b1 via a partition member 26e, and a doctor blade 26c (developer regulation member) that faces the developing roller 26a and regulates the amount of developer carried on the developing roller 26a.

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.

Developing roller 26a is configured to face photosensitive drum 21 with a small gap between them, forming a development area. As shown in Figure 3, developing roller 26a is composed of magnet 26a1, which is fixed inside and forms multiple magnetic poles H1 to H5 (see Figure 4) on the outer surface of the roller, and sleeve 26a2, which rotates around magnet 26a1.

Referring to FIG. 4 in detail, the lifting magnetic pole H5 acts on the carrier as a magnetic material, lifting the developer G contained 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 lifting 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. At the position of the doctor blade 26c, the developer G stands up 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 passing the position of main magnetic pole H1, developer G 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 developer release magnetic pole H4. At the position of developer release magnetic pole H4, a repulsive magnetic field (a magnetic field that acts in a direction away from the developer roller 26a) acts on the carrier, causing the post-development process developer G carried on the developer roller 26a to detach from the developer roller 26a. After detachment, the developer G falls into the first transport path B1 and is transported downstream along the first transport path B1 by the first transport screw 26b1 (see Figures 2 and 3).

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 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 ends 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 ends.

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 while supplying the developer toward the developing roller 26a and recovering the post-development developer that has been released 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 replenished from the replenishing 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 speed of about 600 rpm.

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) that penetrates 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 upper developing 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.

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 an intake 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 leakage of developer and scattering of toner.
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 upper developing case 26k, which will be described in detail later with reference to Figure 4 etc.

The image forming process described above will now be further explained, focusing on the development process.
The developing roller 26a rotates in a predetermined direction (counterclockwise in the direction of the arrow in FIG. 2). As shown in FIG. 3, the developer in the developing device 26 is circulated in the longitudinal direction (in the direction of the dashed arrow in FIG. 3) while being stirred and mixed with the toner supplied from the toner container 70 through the toner supply port 26d by the rotation of the first transport screw 26b1 and the second transport screw 26b2, which are arranged with a 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 along 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 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 then released from the developing roller 26a. 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.

The toner in the toner container 70 is supplied appropriately to the developing device 26 from the supply port 26d via a toner supply 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) and above the second transport screw 26b2 (second transport path B2).

The configuration and operation of the developing device 26, which is a feature of this embodiment, will now be described in detail.
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) downstream of the developing area in the rotation direction (counterclockwise in FIGS. 2 and 4).

Referring now 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 upper developing case 26k described above.
The lower developing case 26j is a casing that serves as the base of the developing device 26, and rotatably holds the developing roller 26a and the transport screws 26b1 and 26b2, as well as 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.

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 (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 that is not fixed to any member and is in a displaceable state. The flexible sheet member 26r is positioned so as to come into contact with the developer G carried by the developing roller 26a.
In this embodiment, the flexible sheet member 26r is a substantially rectangular urethane sheet having a thickness of approximately 0.1 mm. The flexible sheet member 26r is formed so that its entire length (the range from one end 26r1 to the other end 26r2) substantially coincides with the opposing surface 26k10 of the upper developer case 26k (the surface facing the developing roller 26a).

By providing a 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 upper developing case 26k increases or decreases, the flexible sheet member 26r flexibly deforms (bends) in accordance with the amount of developer, making it easier to maintain a state of belly contact with the developer G carried on the developing roller 26a (making it less likely to become separated from the developer G overall). As a result, a stable suction airflow (see the white arrow in Figure 4) is formed in the gap between the developing roller 26a and the upper developing case 26k, reducing the problem of toner blowing out from that gap (toner scattering).

Referring now to Figure 4 etc., the developing device 26 in this embodiment is provided with a holding portion 26m (holding member) that holds the other end side 26r2 of the flexible sheet member 26r as a free end without fixing it.
That is, in this embodiment, the other end 26r2 of the flexible sheet member 26r is loosely held (displaceably held) by the holding portion 26m, and is maintained in a free end state.
Specifically, in this embodiment, the holding portion 26m is a thin plate-like member made of a resin material. The material of the holding portion 26m is preferably one to which the developer G does not easily adhere (i.e., one that has low affinity for the developer G (toner)). Furthermore, it is sufficient for the holding portion 26m to be strong enough to loosely hold the other end 26r2 (free end) of the flexible sheet member 26r.

More specifically, in this embodiment, the holding portion 26m, together with the opposing surface 26k10 that faces the developing roller 26a in the developing upper case 26k (developing case), extends in the rotational direction (direction along the outer peripheral surface of the developing roller 26a) so as to cover the other end side 26r2 of the flexible sheet member 26r, and is configured to block the gap between the other end side 26r2 of the flexible sheet member 26r and the developing roller 26a.
That is, the flexible sheet member 26r is disposed so that its midsection, excluding one end side 26r1 and the other end side 26r2, faces the developing roller 26a (so as to come into sliding contact with the developer G carried on the developing roller 26a). However, the other end side 26r2 (free end side) of the flexible sheet member 26r is covered with the holding portion 26m and is disposed so as not to directly face the developing roller 26a (so as not to come into sliding contact with the developer G carried on the developing roller 26a).
Furthermore, in other words, the holding portion 26m provided on the opposing surface 26k10 of the upper developing case 26k forms a bag-like portion that covers the other end side 26r2 (free end side) of the flexible sheet member 26r.

In this way, by loosely holding the other end side 26r2 (free end side) of the flexible sheet member 26r by the holding portion 26m, it becomes difficult for developer G to get between the flexible sheet member 26r and the developing upper case 26k while maintaining the function of the flexible sheet member 26r described above (see Figure 5 (A)).
That is, as shown in FIG. 5B as a comparative example of a developing device 126, if the upper developer case 126k does not have a retaining portion and the other end 26r2 (free end) of the flexible sheet member 26r is completely free (i.e., its position is difficult to determine), developer G is likely to get between the flexible sheet member 26r and the upper developer case 126k (e.g., it is likely to climb up). This problem is particularly likely to occur when the developing roller 26a rotates in the reverse direction (clockwise, as indicated by the arrow in FIG. 5) at a predetermined timing, as shown in FIG. 5 . If developer G gets between the flexible sheet member 26r and the upper developer case 126k, the flexible sheet member 26r deforms significantly from its intended position, hitting the developer G on the developing roller 26a too hard, making it difficult to create a good suction airflow in the casing gap W. This makes it more likely for toner to scatter from the casing gap W to the outside of the device.
In contrast, the developing device 26 in this embodiment is configured so that developer G is less likely to get between the flexible sheet member 26r and the developing upper case 126k, as shown in Figure 5 (A), so such toner scattering is less likely to occur.

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 has been 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).

In this embodiment, the holding portion 26m is formed to extend in the rotation axis direction (the direction perpendicular to the plane of the paper in FIG. 4, i.e., the longitudinal direction), and is set so that the range of the rotation axis direction (longitudinal direction) of the holding portion 26m includes the range of the rotation axis direction of the flexible sheet member 26r.
With this configuration, deformation such as waving or undulation is less likely to occur on the free end side (other end side) of the flexible sheet member 26r loosely held by the holding portion 26m.

In this embodiment, it is preferable that the holding portion 26m is detachably installed in the upper developer case 26k (developer case).
In particular, in this embodiment, the holding portion 26m is configured so as to be able to be attached to the upper developing case 26k at the time of manufacturing.
Specifically, prior to the manufacturing process (assembly) of the developing device 26, the upper developer case 26k, the flexible sheet member 26r, and the holding portion 26m are each prepared as separate components. 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. Around this time, the holding portion 26m is attached to the upper developer case 26k by adhesion, fitting, or the like, and the other end 26r2 of the flexible sheet member 26r is inserted into the holding portion 26m. In this way, a subassembly consisting of the upper developer case 26k, the flexible sheet member 26r, and the holding portion 26m is completed, and this subassembly is then connected to the lower developer case 26j, which holds the developing roller 26a, the transport screws 26b1 and 26b2, and the doctor blade 26c. In this way, the developing device 26 is completed.

Referring now to Figure 4 etc., in this embodiment, the upper developing case 26k (developing case) has a convex portion 26k2 formed in a position corresponding to between one end side 26r1 and the other end side 26r2 of the flexible sheet member 26r, which narrows the gap (casing gap W) with the developing roller 26a, and which extends in the direction of the rotation axis perpendicular to the rotation direction (the direction perpendicular to the paper surface of Figure 4, which is 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.

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, the flexible sheet member 26r is preferably positioned so that its belly (backing portion) is in sliding contact with at least the developer G (where the spikes 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. Because developer G tends to accumulate in the casing gap W when the gap W is narrowed in the area where the spikes 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 contacts the belly of the developer G at the part where the spikes stand up (the P2 magnetic pole where the normal magnetic force is strong) in the casing gap W. This is because the suction airflow is more likely to occur at the part where the spikes stand up than at the part where the spikes lie flat.

2, the developing device 26 in this embodiment is provided with the opening 26k1 and the filter 26t that reduce the increase in internal pressure of the developing device 26. Even if the developing device 26 in this embodiment does not have such opening 26k1 and filter 26t, the flexible sheet member 26r and the retaining portion 26m function as described above to reduce toner scattering outside the device. However, by providing the opening 26k1 and the filter 26t as in this embodiment, the effect of reducing toner scattering is further enhanced.
In this case, in the present embodiment, the flexible sheet member 26r comes into contact with 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.

<Modification 1>
In the first modified example, the upper developer case 26k as a developer case is also detachably installed in the developing device 26 (lower developer case 26j).
As shown in Figures 6 and 7, in the developing device 26 in variant example 1, the holding portion 26m is attached and detached by sliding it in the direction of the rotation axis perpendicular to the rotation direction relative to the developing upper case 26k (the direction perpendicular to the paper surface of Figure 4, the longitudinal direction, and the left-right direction in Figures 6 and 7).
More specifically, as shown in Fig. 6A, the upper developer case 26k has a facing surface 26k10 facing the developing roller 26a, on which a plurality of L-shaped hooks 26k4 and snap-fit grooves 26k5 are provided. Furthermore, a plurality of ribs 26k3 (see Figs. 2 and 6A) for reinforcing the strength of the upper developer case 26k are provided on the surface of the upper developer case 26k opposite the facing surface 26k10. The ribs 26k3 are disposed between the hooks 26k4, respectively, making it difficult for the holder 26m held by the upper developer case 26k to deform.
As shown in FIG. 6B, the holding portion 26m is provided with a plurality of openings 26m1 and snap-fit portions 26m2.
7A, the flexible sheet member 26r is set in the upper developer case 26k so that the hook portion 26k4 fits into the opening 26m1, and then the flexible sheet member 26r is slid relatively in the longitudinal direction (the direction of the arrow in FIG. 5A) with respect to the upper developer case 26k. Then, as shown in FIG. 7B, the snap-fit portion 26m2 fits into the snap-fit groove 26k5, the edge of the opening 26m1 fits into the hook portion 26k4, and the longitudinal position of the flexible sheet member 26r relative to the upper developer case 26k is determined, completing the assembly of the flexible sheet member 26r to the upper developer case 26k.
By configuring the upper developer case 26k and the flexible sheet member 26r in this manner, the ease of assembly, maintenance, and recyclability of the flexible sheet member 26r to the upper developer case 26k is improved. Furthermore, because the direction in which the flexible sheet member 26r is attached to and detached from the upper developer case 26k is approximately perpendicular to the direction in which the developer G slides, the problem of the flexible sheet member 26r coming off the upper developer case 26k due to the sliding of the developer G when the device is driven is prevented.
The method for holding the flexible sheet member 26r in the upper developing case 26k is not limited to that of the first modified example, and various holding methods can be employed.

<Modification 2>
As shown in FIGS. 8 and 9, in the developing device 26 in the second modified example, a holding portion 26k20 is formed integrally with the upper developing case 26k (developing case).
In addition, in Modification 2, the holding portion 26k20 is a plurality of holding portions 26k20 (six holding portions 26k20 in Modification 2) arranged side by side with gaps in the rotation axis direction (a direction perpendicular to the rotation direction, that is, a direction perpendicular to the paper surface in FIG. 8 and a left-right direction in FIG. 9). In addition, openings 26k1 (six openings 26k1) are formed in the upper developing case 26k (developing case) at positions corresponding to the respective positions of the plurality of holding portions 26k20 in the rotation axis direction.
Furthermore, the developing device 26 in the second modification is provided with a filter 26t that covers the plurality of openings 26k1.
Specifically, the upper developing case 26k is made of a resin material, and is integrally molded with a plurality of holding portions 26k20 divided in the rotation axis direction (longitudinal direction). Similar to the holding portion 26m shown in Fig. 4, these holding portions 26k20 hold the other end 26r2 of the flexible sheet member 26r as a free end without being fixed.
Here, the upper developer case 26k has openings 26k1 above the multiple holding portions 26k20 (in the mold removal direction), which simplifies the structure of the mold (which is divided into upper and lower portions) used to mold the upper developer case 26k (enabling integral molding). Furthermore, although the upper developer case 26k is more likely to warp the longer it is in the longitudinal direction (direction of rotation axis), because the holding portions 26k20 are divided in the longitudinal direction, it is easier to maintain dimensional accuracy without being affected by such warping.
A filter 26t is attached to the upper developer case 26k with double-sided tape or the like so as to cover the multiple openings 26k1. Note that in the developing device 26 in Modification 2, the openings 26k1 and the filter 26t (see FIG. 2) are not provided above the first transport path B1, and the openings 26k1 and the filter 26t provided above the holding portion 26k20 function in the same way. That is, the filter 26t collects toner and carrier, while the openings 26k1 function as ventilation holes.
Furthermore, the developing device 26 in variant 2 configured in this manner is also provided with a holding portion 26k20 that loosely holds the other end side 26r2 of the flexible sheet member 26r, making it less likely that developer G will get in between the developing case 26k and the flexible sheet member 26r.

<Modification 3>
As shown in Figure 10, the developing device 26 in variant example 3 is provided with a biasing member 26w between the upper developing case 26k (developing case) and the holding portion 26m, which biases the other end side 26r2 of the flexible sheet member 26r toward the holding portion 26m.
This biasing member 26w can be formed from materials such as film, PET sheet, or polyurethane foam, and by pressing the other end side 26r2 of the flexible sheet member 26r against the holding portion 26m with a not-too-strong force, it makes it less likely for deformation such as swells or waves to occur on the other end side 26r2 (free end) of the flexible sheet member 26r while maintaining the function of the holding portion 26k20 which loosely holds the other end side 26r2 of the flexible sheet member 26r (it corrects deformation).
In this way, by providing the urging member 26w, the other end side 26r2 of the flexible sheet member 26r is held loosely in the holding portion 26k20 without deformation, making it less likely that developer G will get in between the developing case 26k and the flexible sheet member 26r.
In addition, when the holding portion 26k20 is divided into multiple parts in the longitudinal direction (rotation axis direction) as in the above-mentioned variant example 2, deformation of the flexible sheet member 26r is likely to occur in the portion located between the holding portions 26k20, so a configuration in which a biasing member 26w is provided as in this variant example 3 becomes useful.

<Modification 4>
11A, in the developing device 26 in Modification 4, when the developing roller 26a (developer carrier) is not carrying developer G (such as when it is new), the other end 26r2 (free end) of the flexible sheet member 26r is separated from the opposing surface 26k10 (the surface facing the developing roller 26a) of the upper developing case 26k. In contrast, as shown in FIG. 11B, when the developing roller 26a is carrying developer G (such as during normal use), the other end 26r2 (free end) of the flexible sheet member 26r comes into contact with the opposing surface 26k10 of the upper developing case 26k.
To achieve such a configuration, the degree of flexibility of the flexible sheet member 26r (degree of material, thickness, etc.), the gap between the holding portion 26m and the opposing surface 26k20, etc. are optimized.
When developer G is carried on the developing roller 26a, the other end side 26r2 of the flexible sheet member 26r is pressed against the opposing surface 26k10 of the developing upper case 26k with a not-so-strong force, so that the other end side 26r2 of the flexible sheet member 26r is loosely held by the holding portion 26k20, and deformation such as undulation or wavering is less likely to occur on the other end side 26r2 (free end) of the flexible sheet member 26r.
Furthermore, when the developing roller 26a is not carrying the developer G, almost no force is applied to hold the other end 26r2 of the flexible sheet member 26r, so the other end 26r2 of the flexible sheet member 26r is hardly deformed. Therefore, even when the new developing device 26 is stored for a long period of time, the other end 26r2 of the flexible sheet member 26r is unlikely to undergo plastic deformation.
In addition, when the holding portion 26k20 is divided into multiple parts in the longitudinal direction (rotation axis direction) as in the above-mentioned variant example 2, deformation of the flexible sheet member 26r is likely to occur in the portion located between the holding portions 26k20, making a configuration such as that of variant example 4 useful.

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 downstream of the development area in the rotational direction. Also, a flexible sheet member 26r is provided downstream of the development area in the rotational direction, with one end held as a fixed end by the developing case 26k and positioned in the gap between the developing roller 26a and the developing case 26k along the rotational direction. Furthermore, a holding portion 26m is provided that holds the other end of the flexible sheet member 26r as a free end and not fixed.
This makes it possible to prevent the developer G from getting into the gap between the developing case 26k and the flexible sheet member 26r.

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. Alternatively, the developing device 26 can be one of the components of the process cartridge 20, and can be attached to and detached from the image forming apparatus main body 1 as a single unit.
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 is detachably attached to the image forming apparatus main body and 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 the image carrier.

In this embodiment, the present invention is applied to a developing device 26 in which two transport screws 26b1, 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, 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 the developing roller.
In this embodiment, the present invention is applied to the 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 configured to contact the photosensitive drum (image carrier) to form a development area.
In such cases, the same effect as that of this embodiment can be obtained.

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, modifications to each embodiment may be made as appropriate in addition to those suggested in each embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and may be any number, position, shape, etc. suitable for implementing the present invention.

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),
26k1 opening (ventilation path),
26k2 convex part,
26k3 rib part,
26k4 hook part,
26k5 Snap fit groove,
26k10 Opposite surface,
26k20 holding part,
26m holding part,
26m1 opening,
26m2 snap fit section,
26t filter,
26r flexible sheet member,
26r1 One end side (fixed end),
26r2 Other end side (free end),
26w: biasing member (correcting member),
G Developer.

Japanese Patent Application Laid-Open No. 2020-154010

Claims (11)

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 holding portion that holds the other end of the flexible sheet member as a free end without fixing it;
Equipped with
The developing device is characterized in that the developing case has a convex portion formed in a position corresponding to between the one end side and the other end side of the flexible sheet member, which narrows the gap with the developer carrier, and which extends in a rotation axis direction perpendicular to the rotation direction . 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 holding portion that holds the other end of the flexible sheet member as a free end without fixing it;
Equipped with
The developing device is characterized in that the holding portion extends in the rotational direction so as to cover the other end side of the flexible sheet member together with the opposing surface facing the developer carrier in the developing case, thereby blocking the gap between the other end side of the flexible sheet member and the developer carrier. 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 holding portion that holds the other end of the flexible sheet member as a free end without fixing it;
Equipped with
The developing device is characterized in that the holding portion is detachably installed in the developing case. the developing case is detachably installed in the developing device,
4. The developing device according to claim 3, wherein the holding portion is attached to and detached from the developing case by sliding in a direction of a rotation axis perpendicular to the rotation direction. 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 holding portion that holds the other end of the flexible sheet member as a free end without fixing it;
Equipped with
The holding portion is a plurality of holding portions that are integrally formed with the developing case and are arranged side by side with gaps in a rotation axis direction perpendicular to the rotation direction,
the developing case has openings formed at positions corresponding to the positions of the plurality of holding portions in the rotation axis direction,
The developing device further comprises a filter for covering the plurality of openings. 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 holding portion that holds the other end of the flexible sheet member as a free end without fixing it;
Equipped with
a developing device comprising: a biasing member disposed between the developing case and the holding portion, the biasing member biasing the other end of the flexible sheet member toward the holding portion; 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 holding portion that holds the other end of the flexible sheet member as a free end without fixing it;
Equipped with
The other end of the flexible sheet member is
When the developer carrier does not carry the developer, the developer case is spaced apart from the surface facing the developer carrier,
a developer carrier that contacts the opposing surface of the developing case when the developer carrier carries the developer; the developing case is disposed so as to cover the developer carrier from above,
8. The developing device according to claim 1, wherein the flexible sheet member is disposed so as to contact the developer carried on the developer carrier. 9. 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. A process cartridge that is detachably installed in an image forming apparatus main body,
10. 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. An image forming apparatus comprising the developing device according to any one of claims 1 to 9.