Developing device and image forming apparatus

Abstract

To provide a development apparatus and an image formation apparatus capable of suitably preventing toner scattering.SOLUTION: A development apparatus includes: a development roller 50 being a developer carrier; and a casing 58 being a development case having an opening for exposing a surface of the development roller 50. The development apparatus further includes a flexible sheet 70 being a flexible sheet member with an opening side end part 70a being one end thereof fixed to the development case, and a downstream side end part 70b being the other end thereof not fixed. The flexible sheet 70 includes a backing part 70c being a case contact part contacting with the development case, between the opening side end part 70a and the downstream side end part 70b. The downstream side end part 70b is located further away from a developer on the development roller than the backing part 70c.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] 2. Description of the Related Art Conventionally, a developing device is known that includes a developer carrier and a developing case that has an opening that exposes the surface of the developer carrier.

[0003] Patent Document 1 describes a developing device that has a developing case portion that contacts the developer carried on the developer carrier and that passes through an opening to enter the developing case, and that sucks air around the developer carrier into the developing case as the developer is transported. This is said to be able to prevent toner from scattering from the developing area. Summary of the Invention [Problem to be solved by the invention]

[0004] Further improvements in suppressing toner scattering are desired. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides a developing device including a developer carrier and a developing case having an opening for exposing a surface of the developer carrier, a flexible sheet member that is supported on the developer support and contacts the developer that has passed through the opening and entered the developing case, one end of the sheet member is fixed to the developing case, and the other end of the sheet member is located downstream of the one end in a developer movement direction during a developing operation and is not fixed; The sheet member has a case contact portion between the one end and the other end, the case contact portion being in contact with the developing case. a portion that contacts the developer on the developer carrier between the one end and the case contact portion, the other end of the sheet member covers the surface of the developer carrier, and the other end and The developer blocking means is provided to block the developer flowing toward the developing case. Effect of the Invention

[0006] According to the present invention, toner scattering can be effectively suppressed. [Brief description of the drawings]

[0007] [Figure 1]FIG. [Diagram 2] FIG. 2 is an explanatory diagram of a developing device to which the present invention can be applied. [Diagram 3] FIG. 1 is an explanatory diagram of a developing device having a conventional configuration. [Figure 4] 2A to 2C are diagrams illustrating characteristic parts of the configuration of the developing device according to the embodiment. [Diagram 5] 13 is an enlarged view of a main portion of a developing device provided with a holding portion that holds a downstream end portion of a flexible sheet. FIG. [Figure 6] 13A and 13B are diagrams illustrating modified examples of the developing roller cover. [Figure 7] FIG. 13 is a diagram showing a modified example of the holding portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of a tandem type color copier (hereinafter referred to as copier 500) as an image forming apparatus to which the present invention can be applied will be described below. 1 is a schematic diagram of a copying machine 500. The copying machine 500 includes an original reading unit 4 and an original transport unit 3 above a printer unit 100 as the main body of the image forming apparatus, and a paper feed unit 7 below the printer unit 100. The original transport unit 3 transports an original to the original reading unit 4, which reads image information of the transported original. The paper feed unit 7 includes a paper feed cassette 26 that stores transfer paper P, which is a recording medium, and a paper feed roller 27 that sends the transfer paper P in the paper feed cassette 26 toward the printer unit 100. The dashed line in FIG. 1 indicates the transport path of the transfer paper P within the copying machine 500.

[0009] The upper part of the printer section 100 is a paper output tray 30 on which transfer paper P on which an output image is formed is stacked. The printer section 100 includes four image forming units 6 (Y, M, C, K) as an image forming section that forms toner images of each color (yellow, magenta, cyan, black), and an intermediate transfer unit 10.

[0010] The imaging units 6 (Y, M, C, K) are substantially the same in configuration and operation, except for the color of the toner used in the imaging process. The imaging units 6 (Y, M, C, K) are process cartridges that integrally support the photoconductor 1 as a latent image carrier and the developing device 5, and this process cartridge is detachable from the main body of the copier 500. The imaging units 6 (Y, M, C, K) are provided with the photoconductor cleaning device 2 (Y, M, C, K) and the charging device 12 (Y, M, C, K) in addition to the developing device 5 (Y, M, C, K) around the photoconductor 1. In the imaging units 6 (Y, M, C, K) of this embodiment, the photoconductor cleaning device 2 (Y, M, C, K) is configured to clean with a cleaning blade, and the charging device 12 is configured to charge with a charging roller.

[0011] The intermediate transfer unit 10 includes an intermediate transfer belt 8 and primary transfer bias rollers 9 (Y, M, C, K). The intermediate transfer belt 8 is an intermediate transfer body onto which the toner images of each color formed on the surface of each photoconductor 1 (Y, M, C, K) are transferred in an overlapping manner to form a color toner image on its surface. The primary transfer bias rollers 9 (Y, M, C, K) are primary transfer means that transfer the toner images formed on the surfaces of each photoconductor 1 (Y, M, C, K) to the intermediate transfer belt 8.

[0012] The printer unit 100 includes a secondary transfer bias roller 19 for transferring the color toner image on the intermediate transfer belt 8 onto the transfer paper P. It also includes a pair of registration rollers 28 for adjusting the timing at which the transfer paper P sent out by the paper feed roller 27 is transported to the secondary transfer nip where the intermediate transfer belt 8 and the secondary transfer bias roller 19 face each other. The printer unit 100 also includes a fixing device 20 for fixing an unfixed toner image on the transfer paper P above the secondary transfer nip.

[0013] Toner containers 11 (Y, M, C, K) of each color are disposed below the paper discharge tray 30 in the printer section 100 and above the intermediate transfer unit 10. The toner containers 11 (Y, M, C, K) of each color contain toner of each color (yellow, magenta, cyan, black) to be supplied to each developing device 5 (Y, M, C, K).

[0014] The following describes the operation of the copying machine 500 of this embodiment during normal color image formation. First, when a start button is pressed with an original set on the original platen of the original transport unit 3, the original is transported from the original platen by the transport rollers of the original transport unit 3 and placed on the contact glass of the original reading unit 4. Then, the image information of the original placed on the contact glass is optically read by the original reading unit 4.

[0015] More specifically, the document reading unit 4 scans the image of the document on the contact glass while irradiating it with light emitted from an illumination lamp. The document reading unit 4 then forms an image of the light reflected from the document on a color sensor via a group of mirrors and a lens. The color image information of the document is read by the color sensor for each color separation light of RGB (red, green, blue), and then converted into an electrical image signal. Furthermore, based on the RGB color separation image signal, the image processing unit performs processing such as color conversion processing, color correction processing, and spatial frequency correction processing to obtain color image information of yellow, magenta, cyan, and black.

[0016] Then, the image information of each color (yellow, magenta, cyan, black) is sent to a writing section, from which a laser beam L based on the image information of each color is emitted toward the corresponding photoconductor 1 (Y, M, C, K).

[0017] Meanwhile, the four photoconductors 1 (Y, M, C, K) are each rotating in a clockwise direction in FIG. 1. First, the surfaces of the photoconductors 1 (Y, M, C, K) are uniformly charged at the portions facing the charging rollers of the charging devices 12 (Y, M, C, K) (charging process). Thus, the surfaces of the photoconductors 1 (Y, M, C, K) are charged to a charging potential. Then, the charged surfaces of the photoconductors 1 (Y, M, C, K) reach the irradiation positions of the laser light L. In the writing section, the four light sources emit laser light L corresponding to the image signal, respectively, corresponding to each color. Each laser light L passes through a separate optical path for each color component of yellow, magenta, cyan, and black, and is irradiated onto the surface of each photoconductor 1 (Y, M, C, K) (exposure process).

[0018] The laser light L corresponding to the yellow component is irradiated onto the surface of the first yellow photoconductor 1Y from the left side of the paper in Fig. 1. At this time, the laser light L of the yellow component is scanned in the direction of the rotation axis (main scanning direction) of the yellow photoconductor 1Y by a polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the surface of the yellow photoconductor 1Y after it has been charged by the charging device 12Y.

[0019] Similarly, the laser light L corresponding to the magenta component is irradiated onto the surface of the magenta photoconductor 1M, which is the second from the left in Fig. 1, to form an electrostatic latent image corresponding to the magenta component. The laser light L of the cyan component is irradiated onto the surface of the cyan photoconductor 1C, which is the third from the left in Fig. 1, to form an electrostatic latent image of the cyan component. The laser light L of the black component is irradiated onto the surface of the black photoconductor 1K, which is the fourth from the left in Fig. 1, to form an electrostatic latent image of the black component.

[0020] Thereafter, the surfaces of the photoconductors 1 (Y, M, C, K) on which the electrostatic latent images of the respective colors have been formed reach positions facing the developing devices 5. Then, the toners of the respective colors are supplied from the developer on the developing rollers 50 of the developing devices 5 (Y, M, C, K) that contain the developer consisting of the toners of the respective colors and carriers onto the surfaces of the photoconductors 1 (Y, M, C, K), and the latent images on the photoconductors 1 (Y, M, C, K) are developed (developing process). The developer is transported by the developing rollers 50 in the counterclockwise direction indicated by the arrow B.

[0021] After passing through the portion facing the developing device 5, the surfaces of the photoconductors 1 (Y, M, C, K) reach the portion facing the intermediate transfer belt 8. Here, at each of the facing portions, primary transfer bias rollers 9 (Y, M, C, K) are installed so as to abut against the inner peripheral surface of the intermediate transfer belt 8. The photoconductors 1 (Y, M, C, K) and the primary transfer bias rollers 9 (Y, M, C, K) face each other with the intermediate transfer belt 8 in between, forming a primary transfer nip. Then, at this primary transfer nip, the toner images of each color formed on each photoconductor 1 (Y, M, C, K) are transferred onto the intermediate transfer belt 8 in a sequentially overlapping manner (primary transfer process).

[0022] After passing through the primary transfer nip, the surface of the photoconductor 1 reaches a position facing the photoconductor cleaning device 2. Then, at the position facing the photoconductor cleaning device 2, the untransferred toner remaining on the photoconductor 1 is scraped off and collected by the cleaning blade 2a (photoconductor cleaning process). After passing the portion facing the photoconductor cleaning device 2, the surface of the photoconductor 1 passes through a charge removing section where residual charges are removed, completing a series of image formation processes on the photoconductor 1 and preparing for the next image formation operation.

[0023] Meanwhile, the color toner images on the four photoconductors 1 (Y, M, C, K) are transferred and superimposed, and the intermediate transfer belt 8 carrying the color toner images moves counterclockwise in FIG. 1 and reaches the secondary transfer nip, which is a position facing the secondary transfer bias roller 19. Also, the transfer paper P fed by the paper feed roller 27 from the paper feed cassette 26 storing the transfer paper P passes through a conveyance guide and is guided to the pair of registration rollers 28, where it strikes the pair of registration rollers 28 and stops once. The transfer paper P that strikes the pair of registration rollers 28 is conveyed toward the secondary transfer nip in accordance with the timing at which the color toner image formed on the intermediate transfer belt 8 moves toward the secondary transfer nip. Then, the color toner image carried on the intermediate transfer belt 8 is transferred onto the transfer paper P at the secondary transfer nip (secondary transfer process).

[0024] After passing through the secondary transfer nip, the surface of the intermediate transfer belt 8 reaches a portion facing an intermediate transfer belt cleaning device. At this portion, the residual toner adhering to the intermediate transfer belt 8 is collected by the intermediate transfer belt cleaning device, and the series of transfer processes on the intermediate transfer belt 8 is completed.

[0025] The untransferred toner scraped off the surface of the photoconductor 1 by the cleaning blade 2a passes through a recovered toner transport path and is stored in a waste toner storage container. In addition, the untransferred toner scraped off the surface of the intermediate transfer belt 8 by the intermediate transfer belt cleaning device and the toner of the pattern image for process control also pass through a recovered toner transport path and are stored in a waste toner storage container.

[0026] The transfer paper P onto which the color toner image has been transferred at the secondary transfer nip is guided to the fixing device 20. In the fixing device 20, the color image is fixed onto the transfer paper P by heat and pressure at a fixing nip formed by a fixing roller and a pressure roller. The transfer paper P that has passed through the fixing device 20 is discharged as an output image outside the printer unit 100 by a pair of paper discharge rollers 25 and stacked on a paper discharge tray 30, completing a series of image formation processes.

[0027] 2A and 2B are explanatory diagrams of a developing device 5 to which the present invention can be applied, in which Fig. 2A is a cross-sectional view and Fig. 2B is a partially enlarged view. The developing device 5 includes a developing roller 50 as a developer carrier, and a casing 58 as a developing case having an opening that exposes the surface of the developer carrier. The developing area is an area where the developing roller 50 and the photoconductor 1 face each other through the opening. The casing 58 includes a lower developing case 58a, an upper developing case 58b, a developing roller cover 58c, and a filter cover 58d. The developing device 5 also includes a flexible sheet 70 as a flexible sheet member that comes into contact with the developer carried by the developer carrier and passing through the opening to enter the developing case.

[0028] The developing device 5 includes a supply screw 53 and a recovery screw 54, which are developer transport members. The developing device 5 also includes a doctor blade 52, which is a developer regulating member that regulates the amount of developer moving toward the developing area. The doctor blade 52 faces the surface of the developing sleeve 51 with a predetermined gap therebetween in order to adjust the developer carried on the developing sleeve 51 to a predetermined thickness. The developing device 5 also includes a pressure relief filter 60 that constitutes a pressure relief mechanism. A developing area entrance seal 57 for preventing toner scattering may be disposed between the doctor portion of the doctor blade 52 facing the developing roller 50 and the developing area. The hatched areas indicated by the reference numeral 58b' in FIG. 2 are end seal members that seal between the peripheral surfaces of both ends of the developing roller 50 and the surface portions of the developing roller cover 58c that face these peripheral surfaces. The supply screw 53 and the recovery screw 54 are screw members with spiral blades on their rotation shafts, and when they rotate, they transport the developer in opposite directions along an axial direction parallel to the rotation shaft. The developer is a two-component developer consisting of toner and carrier (including cases where additives, etc., are added).

[0029] Supply screw 53 and recovery screw 54 transport the developer in the longitudinal direction (axial direction of developing roller 50) to form a circulation path. Toner is replenished through a toner refill port at a part of this circulation path, for example, at one end of recovery screw 54. To replenish toner, the device is also provided with a toner container that stores the replenishment toner, a toner hopper to which toner is replenished from the toner container, and a toner refill screw that replenishes toner from the toner hopper to the circulation path based on the output of a toner concentration sensor provided in developing device 5.

[0030] In the space within the casing of the developing device 5, a supply transport path 53a in which the supply screw 53 is disposed and a recovery transport path 54a in which the recovery screw 54 is disposed are spatially separated by a partition plate. The supplied toner is transported while being mixed with the developer by the recovery screw 54. The developer sufficiently mixed with the supplied toner is delivered to the supply screw 53 through a transfer portion formed at one end of the circulation path, and is then drawn up from the supply transport path 53a to the developing roller 50 by magnetic force.

[0031] The developing roller 50 is composed of a magnet roller 55 made of a plurality of magnets fixed inside, and a developing sleeve 51 that rotates around the magnet roller 55. The developing sleeve 51 is a cylindrical member that contains the magnet roller 55 and is made of a rotatable non-magnetic material. The magnet roller 55 of this embodiment is provided with five magnetic poles, namely, a first magnetic pole P1 (N pole), a second magnetic pole P2 (S pole), a third magnetic pole P3 (N pole), a fourth magnetic pole P4 (N pole), and a fifth magnetic pole P5 (S pole). P1 to P5 in FIG. 2(a) indicate the distribution of the magnetic flux density (absolute value) in the normal direction of the magnetic field formed by each magnetic pole on the surface of the developing sleeve 51. Hereinafter, each magnetic pole is referred to as P1 pole to P5 pole by a symbol.

[0032] A specific example of the developing device 5 of this embodiment is as follows. As a two-component developer, 250 [g] of two-component developer is filled, which is a uniform mixture of toner (average particle size 5.2 [μm]) mainly composed of polyester resin and carrier (average particle size 35 [μm]) which is magnetic fine particles, so that the toner concentration is 7 [WT%]. The developing device 5 rotates a supply screw 53 and a recovery screw 54 arranged in parallel at 600 [RPM], and simultaneously transports the developer and stirs new toner supplied from a toner supply port, uniformly mixing the toner and carrier and providing charging.

[0033] The uniformly mixed developer is conveyed in the longitudinal direction by a supply screw 53 provided in parallel to and adjacent to the developing sleeve 51, and is transferred to the outer peripheral surface of the developing sleeve 51 by the magnetic force of a fifth magnetic pole P5 of a magnet roller 55 contained in the developing sleeve 51. The developer transferred to the surface of the developing sleeve 51 reaches the developing area as the developing sleeve 51 rotates counterclockwise as indicated by an arrow B in FIG. 2(a). A developing electric field is formed between the developing sleeve 51 and the photoconductor 1 in the developing area by applying a voltage to the developing sleeve 51 from a high-voltage power source. This developing electric field supplies the toner in the developer on the surface of the developing sleeve 51 to the latent image on the surface of the photoconductor 1, and the latent image on the photoconductor 1 is developed.

[0034] After passing through the development area, the developer on the surface of the developing sleeve 51 passes between the flexible sheet 70 and the developing sleeve 51 as the developing sleeve 51 rotates. At this time, air entrained in the developer generates an airflow in the direction indicated by the outlined arrow F in FIG. 2(b), and is sucked into the casing 58. The sucked airflow passes through the pressure relief filter 60 and is discharged outside the developing unit. The flexible sheet 70 is a urethane sheet, and has a thickness of 0.1 mm. The thickness and material of the flexible sheet 70 are not limited to this, as long as it is flexible.

[0035] Foreign matter that has entered the casing or toner aggregates that have formed inside the casing due to the environmental conditions in which the developing device is installed may be blocked by the doctor blade 52 and block the gap between the developing sleeve 51 and the doctor blade 52. If the gap is blocked by foreign matter or toner aggregates, developer cannot pass through the blocked area, and the latent image portion corresponding to that area is not developed, resulting in a streaky blank image.

[0036] Therefore, the developing device 5 executes a reverse rotation operation to rotate the developing sleeve 51 in the reverse direction at a predetermined timing, such as when a predetermined number of sheets are output. By executing the reverse rotation operation, foreign matter and toner aggregates blocked by the doctor blade 52 can be removed, and clogging between the developing sleeve 51 and the doctor blade 52 can be eliminated.

[0037] FIG. 3 is an explanatory diagram of a conventional configuration. In the conventional configuration shown in FIG. 3(a), the gap CG between the developing roller 50 and the developing case in the direction LP2 of the second magnetic pole P2 is set to a size that generates a suction airflow when the developer ear passes through, thereby preventing toner scattering. When the amount of developer (pumped-up amount) on the developing roller 50 becomes small, the gap between the developing roller 50 and the case becomes large relative to the amount of developer, so the suction force becomes weak and the developer flows back, which makes it easy for toner scattering to occur. If the gap CG between the developing roller cover 58c and the developing roller 50 is set narrower, the developing roller cover 58c can come into contact with the developer on the developing roller 50 to generate a suction airflow. However, when the amount of developer (pumped-up amount on the sleeve) is large, agent retention occurs in the CG portion, so it cannot be narrowed beyond a certain level. In other words, the agent retention margin is small.

[0038] In contrast, in the configuration of FIG. 3(b), the flexible sheet 70 has an opening end 70a, which is the end on the opening side, and a downstream end 70b, which is the end opposite to the opening end 70a in the developer movement direction, supported (contacted) by the developing roller cover 58c as a developing case. By supporting (contacting) both ends of the flexible sheet 70 by the developing case, a portion between the both ends in the developer movement direction contacts the developer on the developing roller 50. Specifically, the opening end 70a is fixed to the developing roller cover 58c by adhesion or the like, and the downstream end 70b is a free end that contacts the inner surface of the developing roller cover 58c. This is so-called backing contact. The portion of the flexible sheet 70 that is in contact with the backing is called the backing portion 70c. The inner surface portion of the developing roller cover 58c where the backing portion 70c abuts corresponds to the contact portion. The portion where the developing roller cover 58c is fixed corresponds to the fixing portion. The flexible sheet 70 is bent so that the portion between both ends of the flexible sheet 70 comes into contact with the developer. The free end means that the free end is not fixed by adhesive or the like, and at least the contact position can change depending on the direction of rotation of the developing roller 50.

[0039] The dotted line 71 in FIG. 3(b) shows the state of the flexible sheet 70 when the developing roller 50 is removed. The flexible sheet 70 is fixed by attaching the opening end 70a to the attaching portion 58e of 58e by adhesion using double-sided tape or the like. The portion of the flexible sheet 70 on the downstream end 70b side extends along the imaginary straight line 71 obtained by linearly extending the attaching portion 58e due to its stiffness, and assumes a posture in which it extends into the space occupied by the developing roller 50. In other words, the portion of the flexible sheet 70 on the downstream end 70b side is configured to bite into the developing roller 50. The attaching portion 58e is formed so as to assume such a posture. The state of the flexible sheet 70 when the developing roller 50 is assembled is shown by the solid line. The portion between the opening end 70a and the downstream end 70b of the flexible sheet 70 abuts against 50 and bends, and the downstream end 70b abuts against the inner surface of the developing roller cover 58c. That is, the flexible sheet 70 is placed against the developing roller 50, and the portion adjacent to the downstream end 70b is placed against the inner wall surface of the developing roller cover 58c.

[0040] By using the flexible sheet 70, the sheet bends according to the amount of developer (pumped-up amount) on the developing roller 50, so that a stable suction airflow can be maintained even if the pumped-up amount varies due to component tolerances or deterioration of the developer over time.

[0041] The flexible sheet 70 is supported at two points, the upstream end and the downstream end in the developer movement direction, by attaching and fixing one end to the casing and abutting the other end against the inner wall of the developing casing, thereby stabilizing the sheet position.

[0042] The flexible sheet 70 bends and the portion between both ends comes into contact with the developer, that is, the flexible sheet 70 serves as a belly rest, so that the flexible sheet 70 can be pressed firmly against the developer on the developing roller 50, and the blowing airflow from within the casing 58 of the developing device 5 can be suppressed. Even if the amount of developer pumped up fluctuates, the sheet bends in accordance with (follows) the amount of developer pumped up, so a stable suction airflow can be ensured, and both a sufficient amount of developer retention and suppression of the blowing airflow can be achieved.

[0043] In particular, having one end fixed and the other end abutting has the following advantages. That is, one end of the sheet member abuts the inner wall of the developing case without being adhered thereto, so that the sheet can easily follow the deflection when the pumping amount changes. If this part is adhered, the amount of deflection of the sheet is difficult to change even if the pumping amount changes, and the developer retention margin becomes small. Also, if the position is shifted when the sheet is attached, the sheet is likely to ripple, which may reduce productivity. Also, by having one end of the flexible sheet 70 adhered and fixed to the casing and the other end backed by the casing, the width where the developer and the flexible sheet 70 come into contact with each other is wider and the contact is stronger, so that a stable air flow can be ensured. Therefore, it is preferable to leave the backing part unadhered and allow it to move freely relative to the upper case.

[0044] As described above, the developing device performs a reverse rotation operation to rotate the developing sleeve 51 in the reverse direction at a predetermined timing in order to eliminate clogging between the developing sleeve 51 and the doctor blade 52. During this reverse rotation operation, the developer on the developing roller moves toward the location where the downstream end 70b of the flexible sheet 70 is in contact with the inner surface of the developing roller cover 58c. Since the downstream end 70b of the flexible sheet 70 is a free end that is not fixed to the developing roller cover 58c, the developer may enter the space between the developing roller cover 58c and the flexible sheet 70 from between the downstream end 70b and the developing roller cover 58c. In particular, when the urethane flexible sheet 70 becomes worn down over time, the contact pressure of the downstream end 70b against the developing roller cover 58c decreases, and the developer is likely to enter between the downstream end 70b and the developing roller cover 58c during the reverse rotation operation.

[0045] When developer gets into the space between the developing roller cover 58c and the flexible sheet 70, the developer is attracted toward the developing roller 50 by the magnetic force of the magnet roller 55. As a result, the flexible sheet 70 is prevented from bending in accordance with the amount of developer picked up, and the developer cannot pass between the flexible sheet 70 and the developing roller 50. This causes developer to accumulate on the upstream side of the flexible sheet 70, and there is a risk that the developer cannot be transported into the developing case.

[0046] FIG. 4 is a diagram illustrating the characteristic parts of the developing device of this embodiment. The flexible sheet 70 of this embodiment is provided with a backing portion 70c as a case contact portion that contacts the inner surface of the developing roller cover 58c between the opening end 70a and the downstream end 70b. The downstream end 70b of the flexible sheet 70 is located at a position farther away from the developer on the developing roller 50 than the backing portion 70c.

[0047] In the flexible sheet 70 of this embodiment, the downstream end 70b is positioned farther away from the developer on the developing roller 50 than the backing portion 70c. This allows the downstream end 70b to be sufficiently separated from the layer of developer on the developing roller, compared to the conventional configuration shown in FIG. 3B in which the downstream end 70b is in contact with the inner surface of the developing roller cover 58c to form the backing portion 70c. This makes it possible to prevent the developer on the developing roller from entering through the gap between the downstream end 70b and the developing roller cover 58c during reverse rotation.

[0048] In the flexible sheet 70 of this embodiment, a backing portion 70c that contacts the inner surface of the developing roller cover 58c is formed between the opening end 70a and the downstream end 70b, and the flexible sheet 70 is supported at two points, upstream and downstream, in the developer movement direction. This allows the flexible sheet to bend toward the developing roller between the opening end 70a and the backing portion 70c and to be in contact with the developer on the developing roller. In addition, the flexible sheet can be brought into contact with the developer on the developing roller widely and strongly in the axial direction, and the airflow blowing out from inside the casing 58 of the developing device 5 can be suppressed.

[0049] In addition, the backing portion 70c and the downstream end portion 70b are not fixed to the inner surface of the developing roller cover 58c. As a result, even if the amount of the developer fluctuates, the sheet bends according to (follows) the amount of the developer, and a stable suction airflow can be ensured, making it possible to achieve both a sufficient amount of developer retention and suppression of the blowing airflow.

[0050] In addition, it is preferable to position the backing portion 70c of the flexible sheet 70 at the part where the developer spikes lie down between the P2 pole (LP2) and the P3 pole (LP3). This is for the following reason. The narrower the gap between the developing roller cover 58c and the developing roller 50 with which the backing portion 70c comes into contact, the stronger the contact between the flexible sheet 70 and the developer at the P2 pole, and a stable airflow can be created. However, if the gap is too narrow, the developer cannot pass through the gap and accumulates. Such accumulation is likely to occur when the gap is narrowed at the part where the spikes are standing. Therefore, by positioning the backing portion 70c at the part between the P2 and P3 poles where the spikes lie down, it is possible to narrow the gap between the developing roller cover 58c and the developing roller 50 with which the backing portion 70c comes into contact while suppressing accumulation. This makes it possible to strengthen the contact between the flexible sheet 70 and the developer at the P2 pole, and ensure a stable suction airflow.

[0051] By increasing the contact between the flexible sheet 70 and the developer, the blown airflow from inside the casing 58 of the developing device 5 can be suppressed, and the amount of air drawn in together with the developer can also be reduced. As described above, the airflow drawn into the casing 58 passes through the pressure relief filter 60 and is discharged to the outside of the developing device, and the airflow passing through the pressure relief filter 60 contains toner. The toner contained in the airflow is adsorbed by the pressure relief filter 60, and the air without toner is discharged to the outside of the developing device. By reducing the amount of air drawn in, the amount of air passing through the pressure relief filter 60 also decreases, and the amount of toner adhering to the pressure relief filter also decreases. As a result, clogging of the pressure relief filter 60 by toner over time can be suppressed, and the life of the pressure relief filter 60 can be extended.

[0052] In this embodiment, the contact between the flexible sheet 70 and the developer is strengthened, and the amount of air in the suction airflow is reduced, so that the internal pressure in the developing device is suppressed from increasing. In addition, by strengthening the contact between the flexible sheet 70 and the developer, the generation of the blown airflow from inside the casing 58 can also be suppressed. Therefore, even if the internal pressure of the developing device increases to some extent, the generation of the blown airflow can be prevented. Therefore, depending on the device configuration, the occurrence of toner scattering can be suppressed even if the pressure relief filter 60 is not provided and the airflow sucked into the casing 58 is not actively discharged from the developing device, so that the occurrence of toner scattering can be suppressed. However, it is preferable to provide the pressure relief filter 60 and actively discharge the airflow sucked into the casing 58 from the developing device, since this effectively suppresses the occurrence of toner scattering.

[0053] Furthermore, it is preferable that the flexible sheet 70 is in belly contact with the spike portion of the developer (the portion with the strongest magnetic force in the normal direction: the portion in the LP2 direction, which is the P2 pole direction in FIG. 2(a)). Since the suction airflow is generated not in the portion where the spikes lie flat, but in the portion where the spikes stand up, by having the flexible sheet 70 in belly contact with this portion, a strong suction airflow can be generated.

[0054] It is preferable that the axial end of the flexible sheet 70 be spaced apart from the adjacent member so as not to interfere with the adjacent member, such as the end seal member 58b', that is adjacent to the flexible sheet in the axial direction. The appropriate gap between the adjacent member and the flexible sheet 70 is several millimeters, for example, about 0.5 mm. If the gap is too large, the function of the flexible sheet 70 is reduced and airflow will be blown out. The entire flexible sheet 70 may be spaced apart from the adjacent member, or only the portion from the backing portion 70c to the downstream end 70b may be spaced apart from the adjacent member.

[0055] In addition, it is preferable that the portion of the developing roller cover 58c that the backing portion 70c of the flexible sheet 70 contacts is recessed so that the axial center portion is spaced apart from the surface of the developing roller. This allows the backing portion 70c of the flexible sheet 70 to deform following the shape of the developing roller cover 58c, and the gap between the axial end portion of the flexible sheet 70 and the surface of the developing roller can be narrower than the gap between the axial center portion of the developing roller. The axial end portion of the urethane sheet is weaker in stiffness, and the developer and the flexible sheet 70 come into contact with each other less strongly than the axial center portion. Therefore, by narrowing the gap at the axial end portion of the flexible sheet 70, the developer can come into contact with the flexible sheet 70 uniformly in the axial direction, and a uniform air flow can be ensured in the axial direction.

[0056] FIG. 5 is a schematic diagram showing a configuration in which a holding portion 76 for holding a downstream end 70b of the flexible sheet is provided. A holding portion 76 is formed by partitioning the downstream side in the developer movement direction of a recess 158c of the developing roller cover 58c recessed in a direction away from the developing roller 50 by a sheet-like partition member 75 serving as a developer blocking means. The downstream end 70b of the flexible sheet 70 is inserted through a gap between the tip of the partition member 75 and the upstream end of the recess 158c, and the downstream end 70b is held by the holding portion 76. The partition member 75 is a PET sheet or the like, and its downstream side is fixed to the developing roller cover 58c by double-sided tape or the like.

[0057] 5, the downstream end 70b of the flexible sheet is covered by the partition member 75 with respect to the surface of the developing roller. This makes it possible to block developer heading toward the gap between the downstream end 70b of the flexible sheet 70 and the developing roller cover 58c during reverse rotation by this partition member 75. As a result, it is possible to further prevent developer from entering the space between the flexible sheet and the developing roller cover 58c.

[0058] Furthermore, when the flexible sheet 70 becomes worn due to use over time and the downstream end 70b of the flexible sheet is displaced toward the developing roller, the downstream end 70b of the flexible sheet abuts against the partition member 75. This makes it possible to prevent the downstream end 70b of the flexible sheet from being positioned in the layer of developer on the developing roller, and the downstream end 70b can be held by the holding portion 76. This makes it possible to prevent developer from entering the space between the flexible sheet and the developing roller cover 58c over time.

[0059] The developing roller cover 58c is generally made of a resin material and molded using two dies. Depending on the shape of the developing roller cover 58c, the recess 158c of the developing roller cover 58c may not be formed. In this case, as shown in FIG. 6, a through hole 258c may be provided in the developing roller cover 58c, and the outer opening of the through hole 258c may be blocked with a sheet member 77 to form the recess. The sheet member 77 may be fixed to the outer peripheral surface of the developing roller cover 58c by, for example, double-sided tape. Also, the outer opening of the through hole 258c may be blocked with a sealant.

[0060] FIG. 7 is a diagram showing a modified example of the holding portion 76. In FIG. In the modified example shown in FIG. 7, a holding portion 76 is provided further downstream in the developer movement direction than in the configuration shown in FIG. 5, and the extension distance from the backing portion 70c of the flexible sheet 70 is increased.

[0061] In the configuration shown in FIG. 5, for example, due to manufacturing errors or assembly errors of the partition member 75, the gap between the tip of the partition member 75 and the upstream end of the recess 158c may become narrower than the specified gap. When this gap becomes narrower than the specified gap, the part between the backing part 70c and the downstream end 70b of the flexible sheet may hit the tip of the partition member 75. When the part between the backing part 70c and the downstream end 70b of the flexible sheet hits the tip of the partition member 75, the attitude of the flexible sheet may be affected, and the contact pressure between the opening side end 70a of the flexible sheet and the backing part 70c against the developer may decrease. As a result, the airflow blown out from inside the casing 58 of the developing device 5 may not be suppressed well.

[0062] 7, the area between the opening end 70a of the flexible sheet and the backing portion 70c is sufficiently far from the area near the downstream end 70b. This prevents the area between the opening end 70a and the backing portion 70c from being affected by changes in the posture near the downstream end 70b due to variations in the shape of the holding portion 76. This effectively suppresses the airflow blown out from inside the casing 58 of the developing device 5 even if there is variation in the shape of the holding portion 76.

[0063] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) In a developing device having a developer carrier such as a developing roller 50 and a developing case such as a casing 58 having an opening that exposes the surface of the developer carrier, the device is provided with a flexible sheet member such as a flexible sheet 70 having one end such as an opening side end 70a fixed to the developing case and the other end such as a downstream side end 70b not fixed, the sheet member has a case contact portion such as a backing portion 70c that contacts the developing case between one end and the other end, and the other end is located at a position farther from the developer on the developer carrier than the case contact portion. As explained with reference to FIG. 3(a), in the configuration described in Patent Document 1, when the amount of developer (pumped-up amount) on the developer carrier becomes small, a gap occurs between the developer carrier and the development case, which may cause toner scattering. On the other hand, in the first aspect, one end of the flexible sheet member (hereinafter, referred to as the fixed end) is fixed to the development case, and a case contact portion that contacts the development case is provided between the one end and the other end of the flexible sheet member, so that the flexible sheet member can bend between the fixed end and the case contact portion, and the bent portion can be brought into contact with the developer on the surface of the developer carrier. In addition, by making the other end of the sheet member a free end, the amount of bending of the sheet member changes depending on the amount of developer on the surface of the developer carrier, and it is possible to prevent a gap from being generated between the developer on the developer carrier and the sheet member. This makes it possible to effectively prevent toner scattering. Furthermore, the free end, which is the other end of the sheet member, is located at a position farther away from the developer on the developer carrier than the case contact portion. This makes it possible to suppress the developer on the developer carrier from entering between the developer case and the sheet member from between the free end of the sheet member and the developer case during the reverse rotation operation in which the developer carrier is rotated in the reverse direction, compared to when the free end is located at the same position as the case contact portion. As a result, it is possible to suppress the developer that has entered between the developer case and the sheet member from hindering the movement of the portion between the fixed end of the sheet member and the case contact portion in the direction away from the surface of the developer carrier. Therefore, the developer can pass between the sheet member and the developer carrier smoothly.

[0064] (Aspect 2) In the first embodiment, developer blocking means such as the partition member 75 is provided for blocking developer flowing between the other end, such as the downstream end 70b, of the sheet member such as the flexible sheet 70 and the developing case. As a result, as explained using Figure 5, developer heading toward the gap between the other end of the sheet member and a developing case such as casing 58 during reverse rotation operation can be blocked by a developer blocking means such as partition member 75, thereby effectively preventing developer from entering between the developing case and the sheet member from between the other end of the sheet member and the developing case.

[0065] (Aspect 3) In a developing device having a developer carrier such as a developing roller 50 and a developing case such as a casing 58 having an opening for exposing the surface of the developer carrier, a flexible sheet member such as a flexible sheet 70 having one end such as an opening side end 70a fixed to the developing case and the other end such as a downstream side end 70b not fixed, and a developer blocking means such as a partition member 75 for blocking developer flowing between the other end such as the downstream side end 70b of the sheet member such as the flexible sheet 70 and the developing case are provided. 5, the developer on the developer carrier that moves toward the gap between the other end of the sheet member and a developing case such as the casing 58 during the reverse rotation operation can be blocked by a developer blocking means such as a partition member. This effectively prevents the developer from entering between the developing case and the sheet member from between the other end of the sheet member and the developing case.

[0066] (Aspect 4) In the third embodiment, a sheet member such as the flexible sheet 70 has a case contact portion such as a backing portion 70c that contacts a development case such as the casing 58 between one end such as the opening side end 70a and the other end such as the downstream side end 70b. According to this, as described in the embodiment, the portion between one end of the sheet member and the case contact portion comes into contact with the developer on the surface of the developer carrier, so that a gap is not generated between the developer carrier and the development case. Also, by making the other end of the sheet member a free end, it is possible to suppress the sheet from bending depending on the amount of developer on the surface of the developer carrier, and to suppress the generation of a gap between the developer of the developer carrier and the sheet member, and to effectively suppress the occurrence of toner scattering.

[0067] (Aspect 5) In the first, second or fourth embodiment, a sheet member such as flexible sheet 70 has a portion that contacts the developer on the developer carrier between one end such as opening side end 70a and a case contact portion such as backing portion 70c. According to this, as described in the embodiment, it is possible to prevent a gap from being generated between the developer on the developer carrier and the sheet member, and it is possible to effectively prevent the toner from scattering.

[0068] (Aspect 6) In any of the first to fifth embodiments, the other end, such as the downstream end 70b, of the sheet member, such as the flexible sheet 70, is located downstream of one end, such as the opening end 70a, in the developer movement direction during the developing operation. According to this, the sheet member can be bent so that the sheet member comes into contact with the developer on the developer carrier.

[0069] (Aspect 7) In any one of the aspects 1 to 6, a reverse operation is performed at a predetermined timing, in which the developer carrying body is moved a specified amount on the surface in a direction opposite to the surface movement direction during the developing operation. As a result, as described in the embodiment, clogging of the gap between the developer carrier and a regulating member such as the doctor blade 52 that regulates the developer on the developer carrier can be eliminated, and the occurrence of abnormal images such as white streaks can be suppressed. In addition, during this reverse rotation operation, developer can be effectively prevented from entering between the developing case and the sheet member, such as the casing 58, from between the other end, such as the downstream end 70b, of the sheet member, such as the flexible sheet 70, and the developing case.

[0070] (Aspect 8) In an image forming apparatus including a latent image carrier such as a photoreceptor 1 and a developing device 5 that develops a latent image on the latent image carrier with a developer, any of the developing devices according to embodiments 1 to 7 was used as the developing device. This makes it possible to prevent contamination of the device and distortion of images caused by toner scattering from the developing device. [Explanation of symbols]

[0071] 1: Photoreceptor 5: Developing device 50: Developing roller 51: Developing sleeve 52: Doctor Blade 55: Magnetic roller 57: Development area entrance seal 58: Casing 58a: Developing case 58b: Developing case 58b´: End seal member 58c: Developing roller cover 58d: Filter cover 58e: Paste part 60: Pressure relief filter 70: Flexible sheet 70a: Opening side end 70b: Downstream end 70c: Backing 75: Partition material 76: Holding part 77: Sheet material 100: Printer section 158c: Recess 258c: Through hole 500: Copy machine B: Arrow CG : Gap P1: First magnetic pole P2 :Second magnetic pole P3: Third magnetic pole P4: Fourth magnetic pole P5: Fifth magnetic pole [Prior art documents] [Patent documents]

[0072] [Patent Document 1] JP 2016-035545 A

Claims

1. A developer carrier; A developing device including a developing case having an opening for exposing a surface of the developer carrier, a flexible sheet member that is supported on the developer support and that contacts the developer that has passed through the opening and entered the developing case, One end of the sheet member is fixed to the developing case, the other end of the sheet member is located downstream of the one end in a developer moving direction during a developing operation and is not fixed; the sheet member has a case contact portion between the one end and the other end, the case contact portion being in contact with the developing case, and a portion between the one end and the case contact portion being in contact with the developer on the developer carrier, a developer blocking means for covering the other end of the sheet member against the surface of the developer carrier and blocking developer flowing between the other end and the developing case, the developing device comprising: a developer blocking means for blocking developer flowing between the other end and the developing case;

2. In the developing device according to claim 1, the other end of the sheet member is located at a position farther from the developer on the developer carrier than the case contact portion is.

3. In the developing device according to claim 1 or 2, A developing device characterized in that a reverse operation is performed at a predetermined timing to move the surface of the developer carrier by a specified amount in a direction opposite to the surface movement direction during a developing operation.

4. A latent image carrier; a developing device that develops the latent image on the latent image carrier with a developer, 4. An image forming apparatus, comprising the developing device according to claim 1 as the developing device.

Images