Developing device and image forming apparatus

Abstract

To provide a developing device capable of suitably suppressing toner scattering compared with conventional one.SOLUTION: A developing device includes: a developer carrier 50; developing cases 58a-d with an opening for exposing a surface of the developer carrier 50; and a flexible sheet member 70 that contacts a developer carried by the developer carrier 50, passing through the opening, and entering the developing case. In the sheet member 70, an end 70a on an opening side in a developer moving direction and an end 70b opposite to the end on the opening side in a developer moving direction are supported by the developing case, and a non-contact portion which is not in contact with the developing case is formed between both ends in the developer moving direction. The non-contact portion is in contact with the developer carrier in a state where the developer is not on the developer carrier, and is apart from the developer carrier in a state where a predetermined amount of the developer adheres to the developer carrier.SELECTED DRAWING: Figure 1

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. For example, Patent Document 1 describes such a developing device, which has a developer case portion that comes into contact with the developer carried on the developer carrier and that passes through an opening and enters the developer case, and which also sucks air around the developer carrier into the developer case as the developer is transported. This is said to be able to prevent toner from scattering from the development area. Summary of the Invention [Problem to be solved by the invention]

[0003] It is desirable to suppress toner scattering. [Means for solving the problem]

[0004] In order to solve the above-mentioned problems, the present invention provides a developer carrying body, a developing case having an opening that exposes the surface of the developer carrying body, and a flexible sheet member that comes into contact with developer that is carried on the developer carrying body and passes through the opening and enters the developing case, wherein the sheet member has an end on the side of the opening in the developer moving direction and an end on the opposite side to the opening in the developer moving direction that are in contact with the developing case. a case contact portion that contacts a developing case between both ends of the sheet member in the developer moving direction, and the sheet member is bent toward the developer carrier between the end of the sheet member on the opening side and the case contact portion; A non-contact portion that does not come into contact with the developing case is formed, and the developer carrier abuts against the non-contact portion when there is no developer on the developer carrier, and is separated from the developer carrier when a predetermined amount of developer has adhered to the developer carrier. [Effects of the Invention]

[0005] According to the present invention, toner scattering can be effectively suppressed. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is an explanatory diagram of a developing device to which the present invention can be applied. [Figure 2] FIG. [Figure 3] FIG. 2 is an enlarged explanatory view of four image forming units to which the present invention can be applied. [Figure 4] FIG. 10 is an explanatory diagram of a method for attaching a flexible sheet. [Figure 5] FIG. 10 is another explanatory diagram of a method for attaching a flexible sheet. [Figure 6] Graph of an experiment on the effect of reducing the amount of dust dispersed and extending the life of the filter. [Figure 7] FIG. 10 is an enlarged view of a main part of a developing device showing a modified flexible sheet. [Figure 8] 10 is an enlarged view of a main part of a developing device showing an example in which a downstream end of a flexible sheet is held by a holding portion according to a modified example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of a tandem 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. FIG. 2 is a schematic diagram of the copier 500. The copier 500 includes an original reading unit 4 and an original transport unit 3 above a printer unit 100, which serves 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 from 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 feeds the transfer paper P in the paper feed cassette 26 toward the printer unit 100. The dashed-dotted line in FIG. 2 indicates the transport path of the transfer paper P within the copier 500.

[0008] The top of the printer section 100 is a paper output tray 30 on which transfer paper P with an output image formed thereon is stacked. The printer section 100 includes four imaging units 6 (Y, M, C, K) as imaging sections that form toner images of each color (yellow, magenta, cyan, black), and an intermediate transfer unit 10. Each imaging unit 6 (Y, M, C, K) includes a drum-shaped photoconductor 1 (Y, M, C, K) as an image carrier on which the toner image of each color is formed, and a developing device 5 (Y, M, C, K) that develops the electrostatic latent image formed on the surface of each photoconductor 1 (Y, M, C, K).

[0009] 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, forming 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.

[0010] 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 above the secondary transfer nip for fixing an unfixed toner image on the transfer paper P. Toner containers 11 (Y, M, C, K) for each color are arranged below the paper discharge tray 30 and above the intermediate transfer unit 10 in the printer section 100. The toner containers 11 (Y, M, C, K) for each color contain toner of each color (yellow, magenta, cyan, black) to be supplied to the respective developing devices 5 (Y, M, C, K).

[0011] FIG. 3 is an enlarged explanatory diagram of one of four imaging units 6 (Y, M, C, K) to which the present invention can be applied. The four imaging units 6 (Y, M, C, K) are substantially identical in configuration and operation except for the color of toner used in the image formation process. Therefore, in the following description, the reference symbols Y, M, C, and K indicating corresponding colors will be omitted as appropriate. As shown in FIG. 3 , the imaging unit 6 is a process cartridge that integrally supports the photosensitive element 1 and the developing device 5. This process cartridge is detachable from the main body of the copier 500. The imaging unit 6 also includes a photosensitive element cleaning device 2, a lubricant application device 41, and a charging device 40, in addition to the developing device 5, around the photosensitive element 1. In the imaging unit 6 of this embodiment, the photosensitive element cleaning device 2 is configured to perform cleaning using a cleaning blade 2a, and the charging device 40 is configured to perform charging using a charging roller 4a.

[0012] The following describes the operation of the copying machine 500 of this embodiment during normal color image formation. First, when a document is set on the document table of the document transport unit 3 and the start button is pressed, the document is transported from the document table by the transport rollers of the document transport unit 3 and placed on the contact glass of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document placed on the contact glass.

[0013] 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 light reflected from the document is then imaged 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 in units of RGB (red, green, and blue) color separation light, and then converted into electrical image signals. Furthermore, the image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, and other processing based on the RGB color separation image signals, thereby obtaining color image information of yellow, magenta, cyan, and black.

[0014] The image information for each color (yellow, magenta, cyan, and black) is then sent to a writing unit, which then emits laser light L based on the image information for each color onto the corresponding photoconductor 1 (Y, M, C, K).

[0015] Meanwhile, the four photoconductors 1 (Y, M, C, K) are each rotating clockwise in FIGS. 2 and 3 (the direction of arrow A in FIG. 3). First, the surfaces of the photoconductors 1 (Y, M, C, K) are uniformly charged where they face the charging roller 4a of the charging device 40 (charging process). Thus, the surfaces of the photoconductors 1 (Y, M, C, K) reach a charged potential. Then, the charged surfaces of the photoconductors 1 (Y, M, C, K) reach the irradiation position of the laser light L. In the writing section, four light sources emit laser light L corresponding to an image signal, one for each color. Each laser light L passes through a separate optical path for each color component (yellow, magenta, cyan, and black) and is irradiated onto the surface of each photoconductor 1 (Y, M, C, K) (exposure process).

[0016] The laser light L corresponding to the yellow component is irradiated onto the surface of the yellow photoconductor 1Y, which is the first from the left side of the paper in Figure 2. 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 40.

[0017] 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. 2, to form an electrostatic latent image corresponding to the magenta component. The laser light L for the cyan component is irradiated onto the surface of the cyan photoconductor 1C, which is the third from the left in Fig. 2, to form an electrostatic latent image for the cyan component. The laser light L for the black component is irradiated onto the surface of the black photoconductor 1K, which is the fourth from the left in Fig. 2, to form an electrostatic latent image for the black component.

[0018] Thereafter, the surfaces of the photoconductors 1 (Y, M, C, K) on which the electrostatic latent images of each color have been formed reach positions facing the developing devices 5. Then, the toner of each color is supplied from the developer on the developing rollers 50 of the developing devices 5 (Y, M, C, K) that contains the developer consisting of the toner of each color and a carrier 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 direction of transport of the developer by the developing rollers 50 is counterclockwise, as indicated by arrow B.

[0019] After passing through the area facing the developing device 5, the surfaces of the photoconductors 1 (Y, M, C, K) each reach the area facing the intermediate transfer belt 8. Here, a primary transfer bias roller 9 (Y, M, C, K) is installed at each of the facing areas so as to abut against the inner circumferential 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 across the intermediate transfer belt 8, 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).

[0020] After passing through the primary transfer nip, the surface of the photoconductor 1 reaches a position facing the photoconductor cleaning device 2. At the position facing the photoconductor cleaning device 2, untransferred toner remaining on the photoconductor 1 is scraped off and collected by a 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 removal section where residual charge is removed, completing a series of image formation processes on the photoconductor 1 and preparing for the next image formation operation.

[0021] Meanwhile, the color toner images on the four photoreceptors 1 (Y, M, C, K) are transferred and superimposed, and the intermediate transfer belt 8 carrying the color toner images moves counterclockwise in FIG. 2 to reach the secondary transfer nip, which is the position facing the secondary transfer bias roller 19. Also, transfer paper P fed by a paper feed roller 27 from a paper feed cassette 26 containing transfer paper P passes through a conveyance guide and is guided to a pair of registration rollers 28, where it strikes the pair of registration rollers 28 and stops. Having struck the pair of registration rollers 28, the transfer paper P is conveyed toward the secondary transfer nip in time with the color toner image formed on the intermediate transfer belt 8 moving 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).

[0022] After passing through the secondary transfer nip, the surface of the intermediate transfer belt 8 reaches the area facing the intermediate transfer belt cleaning device. At this area, 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.

[0023] The untransferred toner scraped off the surface of the photosensitive member 1 by the cleaning blade 2a passes through a recovered toner transport path and is collected in a waste toner 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 collected in a waste toner container.

[0024] 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 the fixing nip formed by a fixing roller and a pressure roller. After passing through the fixing device 20, the transfer paper P 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 the series of image formation processes.

[0025] FIG. 1 is an explanatory diagram of a developing device 5 to which the present invention can be applied. FIG. 1(a) is a cross-sectional view, and FIG. 1(b) is a partially enlarged view. This developing device 5 includes a developing roller 50 as a developer carrier and a casing 58 as a developing case with an opening that exposes the surface of the developer carrier. The area where the developing roller 50 and the photosensitive element 1 face each other through the opening is the developing area. The casing 58 is composed of a lower developing case 58a, an upper developing case 58b, a developing roller cover 58c, and a filter cover 58d. The casing 58 also includes a flexible sheet 70 as a flexible sheet member that comes into contact with the developer carried on the developer carrier and that passes through the opening and enters the developing case.

[0026] The developing device 5 includes a supply screw 53 and a recovery screw 54, which are developer transport members. It also includes a doctor blade 52, which is a developer regulating member that regulates the amount of developer flowing toward the development zone. It also includes a pressure relief filter 60, which constitutes a pressure relief mechanism. A development zone entrance seal 57 may be disposed between the doctor portion of the doctor blade 52, where the doctor blade 52 faces the development roller 50, and the development zone to prevent toner scattering. The hatched areas indicated by reference numeral 58b' in FIG. 1 are end seal members that seal between the peripheral surfaces at both ends of the development 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 rotational shafts. By rotating, they transport developer in opposite directions along an axial direction parallel to the rotational shaft. A two-component developer consisting of toner and carrier (including cases where additives, etc., are added) is used.

[0027] The supply screw 53 and the recovery screw 54 transport the developer in the longitudinal direction (axial direction of the developing roller 50) to form a circulation path. Toner is supplied through a toner supply port at a part of this circulation path, for example, at one end of the recovery screw 54. To supply toner, the developing device 5 is also provided with a toner container that stores the replenishment toner, a toner hopper to which toner is supplied from the toner container, and a toner supply screw that supplies toner from the toner hopper to the circulation path based on the output of a toner concentration sensor provided in the developing device 5.

[0028] Within 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 that has been sufficiently mixed with the replenished 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.

[0029] The developing roller 50 is composed of a magnet roller 55 consisting of multiple magnets fixed inside, and a developing sleeve 51 that rotates around the magnet roller 55. The developing sleeve 51 is a cylindrical member made of a non-magnetic material that encloses the magnet roller 55 and is freely rotatable. The magnet roller 55 of this embodiment has five magnetic poles: a first magnetic pole P1 (north pole), a second magnetic pole P2 (south pole), a third magnetic pole P3 (north pole), a fourth magnetic pole P4 (north pole), and a fifth magnetic pole P5 (south pole). P1 to P5 in FIG. 1(a) indicate the distribution of 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, the magnetic poles will be referred to as poles P1 to P5.

[0030] A specific example of the developing device 5 of this embodiment is as follows: The two-component developer is filled at 380 [G] with a toner (average particle size 5.2 [Mm]) whose main component is polyester resin and a carrier (average particle size 35 [Mm]) that is magnetic fine particles, uniformly mixed to achieve a toner concentration of 7 [WT %]. By rotating the supply screw 53 and the recovery screw 54, which are arranged in parallel, at 600 [RPM], the developer is transported and new toner supplied from the toner supply port is simultaneously stirred, uniformly mixing the toner and carrier and providing a charge.

[0031] The uniformly mixed developer is transported in the longitudinal direction by a supply screw 53 provided parallel to and close 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 within the developing sleeve 51. The developer transferred to the surface of the developing sleeve 51 reaches the developing zone as the developing sleeve 51 rotates counterclockwise as indicated by arrow B in FIG. 1(a). A voltage is applied to the developing sleeve 51 from a high-voltage power supply, and a developing electric field is formed between the developing sleeve 51 and the photosensitive member 1 in the developing zone. 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 photosensitive member 1, thereby developing the latent image on the photosensitive member 1.

[0032] After passing through the development zone, 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. 1(b), and is sucked into the casing 58. The sucked airflow passes through the filter 60 and is discharged to the outside of the developing unit.

[0033] The thickness of the flexible sheet 70 is preferably 0.05 mm or more, 0.3 mm being preferred. In this embodiment, a 0.1 mm thick urethane sheet is used. If the thickness is less than 0.05 mm, the flexible sheet 70 is too elastic and does not follow the developer on the developing sleeve. As a result, there are areas where contact between the developer and the flexible sheet 70 is not ensured, which may result in failure to achieve the effect of suppressing toner scattering. On the other hand, if the thickness exceeds 0.3 mm, the flexible sheet 70 is too elastic and crushes the developer on the developing sleeve. As a result, developer may accumulate on the developing sleeve like a dam from that point, causing problems such as developer overflow (excess developer accumulated on the developing sleeve falling outside the developing unit). By making the thickness of the flexible sheet 70 between 0.05 mm and 0.3 mm, it becomes moderately elastic, can effectively suppress toner scattering, and is preferable because it can suppress problems such as image agent overflow (excess developer accumulated on the developing sleeve falling outside the developing machine).

[0034] The flexible sheet 70, a key feature of this embodiment, will now be described in detail. FIG. 4(a) is an explanatory diagram of a method for attaching the flexible sheet 70. FIG. 4(b) is an explanatory diagram of a conventional configuration. Conventionally, the gap CG between the developing roller 50 and the developer case in the direction LP2 of the second magnetic pole P2 was set large enough to generate a suction airflow when the developer spikes passed through, preventing toner scattering. When the amount of developer (pickup amount) on the developing roller 50 decreases, the gap between the developing roller 50 and the case becomes larger relative to the amount of developer. This weakens the suction force, causing backflow and toner scattering. Setting the gap CG between the developing roller cover 58c and the developing roller 50 narrower allows the developing roller cover 58c to contact the developer on the developing roller 50, generating a suction airflow. However, when the pick-up amount (amount of developer on the sleeve) is large, developer accumulation occurs in the CG area, and the gap could not be narrowed beyond a certain point. In other words, the developer accumulation margin was small.

[0035] In contrast, in this embodiment, the flexible sheet 70 is supported (contacts) by the developing roller cover 58c serving as a developer case at its opening end 70a, which is the end on the opening side, and its downstream end 70b, which is the end opposite the opening end 70a in the developer movement direction, and a non-contact portion between the end portions in the developer movement direction that does not contact the developing roller cover 58c contacts the developer on the developing roller 50. Specifically, the opening end 70a is fixed to the developing roller cover 58c by adhesive 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 back-contact contact. The portion of the flexible sheet 70 that contacts back-contact is referred to as the back-contact portion 70c. The inner surface of the developing roller cover 58c where the back-contact portion 70c abuts corresponds to the contact point. The portion where the developing roller cover 58c is fixed corresponds to the fixed portion. The flexible sheet 70 is bent to form a non-contact portion between both ends that does not contact the developing roller cover 58c. When no developer is attached to the developing roller, this non-contact portion between both ends of the flexible sheet 70 abuts against the developing roller at its belly. Depending on the amount of developer on the developing roller 50, the non-contact portion of the flexible sheet 70 bends and moves away from the developing roller 50, coming into contact with the developer on the developing roller 50. Note that the "free end" means that it is not fixed by adhesive or the like, and that at least the contact position can change depending on the direction of rotation of the developing roller 50.

[0036] The dotted line 71 in FIG. 4(a) shows the state of the flexible sheet 70 when the developing roller 50 is removed. The open end 70a of the flexible sheet 70 is attached and fixed to the attachment portion 58e of 58e using adhesive such as double-sided tape. The portion of the flexible sheet 70 on the downstream end 70b side extends along an imaginary straight line 71 that is a linear extension of the attachment portion 58e, and assumes a posture extending into the space previously 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 attachment portion 58e is formed to assume this posture. The solid line shows the state of the flexible sheet 70 when the developing roller 50 is installed. The portion of the flexible sheet 70 between the open end 70a and the downstream end 70b abuts against 50 and bends, and the downstream end 70b abuts against the inner surface of the developing roller cover 58c. That is, when no developer is attached to the developing roller 50, the flexible sheet 70 is in contact with the developing roller 50 at its belly, and the portion near the downstream end 70b is in contact with the inner wall surface of the developing roller cover 58c.

[0037] Figures 5(a) and 5(b) show the cases where the downstream end 70b of the flexible sheet 70 is not backed by the developing roller cover 58c and where it is backed by the flexible sheet 70. In the case of Figure 5(a) where there is no backing, the contact width between the developer and the flexible sheet 70 is narrow and the contact strength is also weak. In contrast, in the case of Figure 5(b) where there is backing, the contact width between the flexible sheet and the developer is wider and the contact strength is stronger. As a result, a very stable suction airflow can be ensured.

[0038] By using the flexible sheet 70, the sheet bends according to the amount of developer (pumped-up amount) on the developing roller 50, so a stable suction airflow can be maintained even if the pumped-up amount fluctuates due to component tolerances or deterioration of the developer over time.

[0039] By supporting the flexible sheet 70 at two points, the upstream end and the downstream end in the direction of developer movement, by attaching and fixing one end to the casing and abutting the other end against the inner wall of the developing casing, the sheet position can be stabilized. This makes it possible to maintain a stable suction airflow. The two-point support may be fixed at both ends or abutting at both ends, but as will be described later, it is most preferable to fix the upstream end in the direction of developer movement and abut the opposite end.

[0040] The flexible sheet 70 bends and the area between both ends comes into contact with the developer, that is, the flexible sheet 70 is placed against the developer, so that the flexible sheet 70 can be pressed firmly against the developer on the developing roller 50, thereby suppressing the airflow blown out from inside the casing 58 of the developing device 5. Furthermore, even if the amount of developer picked up fluctuates, the sheet bends to follow the amount of developer picked up, ensuring a stable suction airflow and achieving both a sufficient amount of developer retention and suppression of the airflow blown out.

[0041] 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 developer case without being adhered, which allows the sheet to easily deflect when the pumping amount fluctuates. If this portion were adhered, the amount of deflection of the sheet would be less likely to change even when the pumping amount changes, reducing the developer retention margin. Furthermore, if the attachment position is misaligned, the sheet is more likely to ripple, which can reduce productivity. Furthermore, by having one end of the flexible sheet 70 adhered and fixed to the casing and the other end backed by the casing, the developer and flexible sheet 70 come into contact over a wider area and with a stronger force, ensuring a stable airflow. Therefore, it is preferable to leave the backing portion unattached and allow it to move freely relative to the upper case.

[0042] Figure 5(c) is a cross-sectional view of the cross section taken along line XX in Figure 5(b) as viewed from the direction of arrow c. The gaps G1 and G2 between the developing roller cover 58c of the backing portion 70c of the flexible sheet 70 and the developing roller 50 may be uniform in the longitudinal direction, but it is preferable to narrow the gap G2 at the end and widen the gap G1 at the center. In this embodiment, the gaps are 1.2 mm at the longitudinal center (G1) and 1.0 mm at the end (G2), resulting in a gap difference of 0.2 mm. Because the stiffness of the urethane sheet is weak at the end, which weakens the contact between the developer D and the flexible sheet 70, narrowing the gap at the end ensures uniform airflow in the longitudinal direction.

[0043] Furthermore, as shown in FIG. 5B, it is preferable to position the backing portion 70c of the flexible sheet 70 in the area where the spikes of developer D lie flat 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 at the backing portion 70c, the stronger the contact between the flexible sheet 70 and the developer D at the P2 pole, resulting in a stable airflow. However, if the gap is too narrow, the developer D cannot pass through the gap and accumulates, resulting in the developer D being blown out of the machine. This type of accumulation is more likely to occur when the gap is narrowed in the area where the spikes are standing. Therefore, by narrowing the gap between the P2 and P3 poles where the spikes lie flat and positioning the backing portion 70c in the area where the spikes lie flat, the contact between the flexible sheet 70 and the developer at the P2 pole is strengthened, preventing the developer D from accumulating and ensuring a stable suction airflow.

[0044] Furthermore, it is preferable that the flexible sheet 70 be in contact with the spike portion of the developer D (the portion with the strongest normal magnetic force: the portion in the LP2 direction, which is the P2 pole direction in Figure 5(b) and Figure 1(a)). Since the suction airflow is generated in the standing portion of the spike, not in the lying portion, by contacting the flexible sheet 70 with the spike portion, a strong suction airflow can be generated.

[0045] FIG. 5(d) shows an example in which the flexible sheet 70 does not dig into the developing roller 50, rather than the portion of the flexible sheet 70 on the downstream end 70b side digging into the developing roller 50. If the flexible sheet 70 is configured not to dig into the developing roller 50, the area between both ends of the flexible sheet 70 will not abut the developing roller when no developer is attached to the developing roller. As a result, when developer is attached to the developing roller, the area between both ends of the flexible sheet 70 will not abut the developer relatively weakly, resulting in a weak suction airflow. However, if the flexible sheet 70 is configured so that the area between both ends of the flexible sheet 70 abuts the developing roller when no developer is attached to the developing roller 50, and the flexible sheet 70 is pushed up, a stable and strong suction airflow can be obtained.

[0046] This embodiment is equipped with a pressure relief mechanism (filter 60), but the effect of reducing the amount of toner scattered by stabilizing the airflow can be obtained even without the filter 60. The flexible sheet 70 of this embodiment is particularly effective when combined with the filter 60. That is, the strong suction airflow obtained by the flexible sheet 70 causes air sucked into the developing unit to pass through the filter 60 and be discharged to the outside of the machine. The air before passing through the filter 60 contains toner, but because the toner is adsorbed to the filter 60, only air that does not contain toner is discharged to the outside of the machine.

[0047] The toner adsorbed to the filter 60 reduces the pressure relief performance of the filter 60, and the internal pressure of the developing unit increases over time as the toner clogs the filter 60. Even if a strong suction airflow is generated, if the internal pressure inside the developing unit increases, the toner cannot be sucked in and the airflow may flow back.

[0048] On the other hand, by strongly pressing the flexible sheet 70 against the developer ears, the airflow becomes less likely to flow back strongly, but the amount of air drawn in with the developer is also reduced. This reduces the amount of air passing through the filter 60, and less toner gets stuck in the filter 60. This has the effect of significantly extending the life of the filter 60 compared to conventional casings, and particularly when combined with the pressure relief filter 60, this significantly extends the life of the filter 60.

[0049] Figure 6 is a graph showing the results of an experiment to confirm the effect of reducing the amount of scattering and the effect of extending the life of the filter 60. The graph shows the results of an experiment in which a developer that easily scatters was loaded into a Ricoh "RICOH MPC6003" (registered trademark), continuous printing was performed, and the amount of toner scattered to the top of the developing unit was measured. The horizontal axis is the number of sheets (k sheets), and the vertical axis is the amount of scattering (mg / cm 2 ) The dashed line shows the results for a conventional example without the flexible sheet 70, and the solid line shows the results for an embodiment equipped with the flexible sheet 70 according to the specific example of FIG. 6(b) above. It can be seen that the flexible sheet 70 significantly reduces the amount of toner scattered outside the developing unit.

[0050] Some developing devices perform a reverse rotation operation, rotating the developing sleeve 51 in the reverse direction at a predetermined timing to clear clogging between the developing sleeve 51 and the doctor blade 52. During this reverse rotation, the developer on the developing roller moves toward the downstream end 70b of the flexible sheet 70, which is in contact with the inner surface of the developing roller cover 58c. Because the downstream end 70b of the flexible sheet 70 is a free end that is not fixed to the developing roller cover 58c, 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, as the urethane flexible sheet 70 wears down over time, the contact pressure of the downstream end 70b against the developing roller cover 58c decreases, making it easier for developer to enter between the downstream end 70b and the developing roller cover 58c during the reverse rotation operation.

[0051] If 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 can cause developer to accumulate upstream of the flexible sheet 70, making it impossible to transport the developer into the developing case.

[0052] If the downstream end 70b of the flexible sheet 70 is fixed to the developing roller cover 58c in order to prevent the developer from entering between the downstream end 70b and the developing roller cover 58c, the above-mentioned advantage cannot be obtained, i.e., the advantage that the flexible sheet 70 can bend in accordance with the amount of developer picked up, ensuring a stable airflow.

[0053] In order to prevent the developer from entering the space between the developing roller cover 58c and the flexible sheet 70, it is preferable that the flexible sheet 70 have the configuration shown in FIG. FIG. 7 is an enlarged view of a main part of a developing device showing a modified flexible sheet 70. In FIG. 7, the flexible sheet 70 of this modified example has a backing portion 70c formed between the opening end 70a and the downstream end 70b as a case contact portion that contacts the inner surface of the developing roller cover 58c, and the downstream end 70b is fixed to the inner circumferential surface of the developing roller cover 58c with an adhesive 70d. Note that the method for fixing the downstream end 70b to the inner circumferential surface of the developing roller cover 58c is not limited to adhesive, and known methods such as double-sided tape can also be used.

[0054] In this modification, the flexible sheet 70 is placed against the backing of the developing roller cover 58c in substantially the same position as in the embodiment, and is placed against the developer on the developing roller near the opening of the casing 58, as in the embodiment.

[0055] By fixing the downstream end 70b to the developing roller cover 58c, it is 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.

[0056] Furthermore, the flexible sheet 70 of the modified example has a backing portion 70c between the opening end 70a and the downstream end 70b, which serves as a case contact portion that contacts the inner surface of the developing roller cover 58c. This allows the flexible sheet to be supported at two points, upstream and downstream in the developer movement direction, between the opening end 70a and the backing portion 70c, and allows the flexible sheet to bend toward the developing roller between the opening end 70a and the backing portion 70c and contact the developer on the developing roller. Thus, the backing portion 70c of the flexible sheet 70 of the modified example is not fixed to the developing roller cover 58c. Therefore, as in the embodiment, the amount of bending at the portion that contacts the developer between the opening end 70a and the backing portion 70c can be effectively changed, effectively following changes in the amount of developer on the developing roller. Furthermore, the contact width between the developer and the flexible sheet 70 can be widened and the contact strength can be increased, ensuring a stable airflow.

[0057] 7, the downstream end 70b of the flexible sheet 70 is fixed to the developing roller cover 58c in an inclined position relative to the surface of the developing roller cover 58c against which the flexible sheet 70 rests. This allows the flexible sheet to extend from the downstream end 70b toward the surface of the developing roller cover 58c against which the flexible sheet 70 rests, allowing the flexible sheet to be properly rested against the surface against which the flexible sheet rests. This allows the backing portion 70c to be formed between the downstream end 70b and the opening end 70a of the flexible sheet.

[0058] In Figure 7, the downstream end 70b of the flexible sheet 70 is fixed to the developing roller cover 58c, but as shown in Figure 8, a holding portion 76 for holding the downstream end 70b of the flexible sheet 70 may be provided on the developing roller cover 58c, and the downstream end may be inserted into this holding portion 76 to be held.

[0059] 8, the downstream end 70b of the flexible sheet 70 is covered by the retaining portion 76. This allows the retaining portion 76 to block developer from moving toward the contact point between the downstream end 70b of the flexible sheet 70 and the developing roller cover 58c. Therefore, even if the downstream end 70b of the flexible sheet 70 is not fixed to the inner circumferential surface of the developing roller cover 58c, it is possible to prevent developer from entering between the downstream end 70b and the inner circumferential surface of the developing roller cover 58c.

[0060] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) A developing device includes 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, and includes a flexible sheet member such as a flexible sheet 70 that comes into contact with the developer that is carried on the developer carrier and passes through the opening to enter the developing case. The sheet member contacts the developing case at its end on the opening side in the developer movement direction (in this embodiment, the opening side end 70a) and its end on the opposite side from the opening side in the developer movement direction (in this embodiment, the downstream side end 70b), forming a non-contact portion that does not come into contact with the developing case between both ends in the developer movement direction, and the developer carrier abuts against the non-contact portion when there is no developer on the developer carrier, and moves away from the developer carrier when a predetermined amount of developer has adhered to the developer carrier. This makes it possible to prevent gaps from forming between the developer on the developer carrier and the sheet member, as described in the embodiment, and effectively prevents toner scattering. Furthermore, when a predetermined amount of developer has adhered to the developer carrier, the non-contact portion can be strongly applied to the developer, thereby obtaining a stable and strong suction airflow.

[0061] (Aspect 2) In the first embodiment, the thickness of the sheet member such as flexible sheet 70 is 0.05 mm or more and 0.30 mm or less. As a result, as described in the embodiment, sheet members such as the flexible sheet 70 have appropriate elasticity, which can effectively suppress toner scattering and prevent problems such as image agent overflow (excess developer accumulated on the developing sleeve falling outside the developing machine).

[0062] (Aspect 3) In embodiment 1 or 2, an end portion on the opening side, such as the opening side end portion 70a, of a sheet member such as the flexible sheet 70 is fixed to a developing case such as the casing 58, and a case contact portion, such as the backing portion 70c, that contacts the developing case is formed between both ends of the sheet member in the developer movement direction, and a non-contact portion is formed by bending the sheet member toward the developer carrier between the opening side end portion of the sheet member and the case contact portion, and an end portion on the opposite side to the opening side, such as the downstream side end portion 70b of the sheet member, is fixed to the developing case. As a result, as explained using Figure 7, the occurrence of toner scattering can be effectively suppressed, and developer can be prevented from entering between the developer case and the end opposite the opening, such as the downstream end 70b of the sheet member.

[0063] (Aspect 4) In embodiment 1 or 2, the end portion on the opening side, such as the opening side end portion 70a, of a sheet member such as flexible sheet 70 is fixed to a developer case such as casing 58, and a case contact portion, such as backing portion 70c, that contacts the developer case is formed between both ends of the sheet member in the developer movement direction, and a non-contact portion is formed by bending the sheet member toward the developer carrier between the end portion on the opening side of the sheet member and the case contact portion, and the end portion on the opposite side to the opening side, such as the downstream side end portion 70b of the sheet member, is inserted into and held in a holding portion 76 provided on the developer case. As a result, as explained using Figure 8, the occurrence of toner scattering can be effectively suppressed, and developer can be prevented from entering between the developer case and the end opposite the opening, such as the downstream end 70b of the sheet member.

[0064] (Aspect 5) In embodiment 3 or 4, the end opposite the opening side, such as the downstream end 70b of the sheet member, such as the flexible sheet 70, contacts the developing case in an inclined position relative to the surface with which the case contact portion, such as the backing portion 70c of the developing case, such as the casing 58, contacts the developing case. 7, this allows the case contact portion such as the backing portion 70c to be brought into good contact with the development case such as the casing 58.

[0065] (Aspect 6) In embodiment 1 or 2, the end portion of the sheet member such as the flexible sheet 70 on the opening side, such as the opening side end portion 70a, is fixed to the developing case such as the casing 58, and the end portion of the sheet member opposite the opening, such as the downstream side end portion 70b, is a free end that contacts the inner surface of the developing case. As a result, as described in the embodiment, compared to when the end opposite the opening, such as the downstream end 70b of the sheet member, is used as the fixed end, the sheet is more likely to deflect when the amount of developer adhering to the developer carrier, such as the developing roller 50, fluctuates, thereby increasing the margin for developer retention.

[0066] (Aspect 7) In aspect 6, the fixing point of a sheet member such as the flexible sheet 70 in a developing case such as the casing 58 is formed so that the free end side of the sheet member extends into the space occupied by the developer carrier such as the developing roller 50 when the developer carrier is removed, and the non-contact portion bends when it comes into contact with the developer carrier, and the free end comes into contact with the contact point on the inner surface of the developing case. As described in the embodiment, this allows the non-contact portion of a sheet member such as flexible sheet 70 to be placed against a developer carrier such as developing roller 50, and the free end such as downstream end 70b to be placed against the developer case. This allows the non-contact portion of the sheet member to be pressed firmly against the developer on the developer carrier, thereby suppressing the blown-out airflow from inside the developer case. Furthermore, even if the amount of developer pumped up fluctuates, the non-contact portion bends to follow the amount of developer pumped up, ensuring a stable suction airflow and achieving both developer retention margin and blown-out airflow suppression.

[0067] (Aspect 8) In the first, second or sixth embodiment, the sheet member is bent to form a non-contact portion between both ends. As a result, as described in the embodiment, the non-contact portion can be bent to follow (follow) the amount of pumped up, ensuring a stable suction airflow and achieving both a margin for agent retention and suppression of the blowing airflow.

[0068] (Aspect 9) In any of aspects 1 to 8, a magnet is provided that forms developer spikes at predetermined locations on a developer carrier such as the developing roller 50, and the non-contact portion comes into contact with the spikes (spike portions) when a predetermined amount of developer has adhered to the developer carrier. This makes it possible to generate a strong suction airflow, as described in the embodiment.

[0069] (Aspect 10) In any of the first to ninth embodiments, the developing case such as the casing 58 is provided with a pressure relief mechanism (filter 60). As a result, as described in the embodiment, the strong suction airflow obtained by the sheet member such as the flexible sheet 70 can expel the air sucked into the developing device to the outside of the device, thereby suppressing an increase in internal pressure inside the developing device.

[0070] (Aspect 11) The image forming apparatus includes the developing device according to any one of the first to tenth embodiments. 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 1C: Cyan photoconductor 1K: Black photoconductor 1M: Magenta photoconductor 1Y: Yellow photoconductor 2: Photoconductor cleaning device 2a: Cleaning blade 3: Document transport section 4: Document reader 4a: Charging roller 5: Developing device 6: Imaging unit 7:Paper feed section 8: Intermediate transfer belt 9: Primary transfer bias roller 10: Intermediate transfer unit 11: Toner container 19: Secondary transfer bias roller 20: Fixing device 25: Paper discharge roller pair 26: Paper cassette 27: Paper feed roller 28: Registration roller pair 30: Paper output tray 35: Average particle size 40: Charging device 41: Lubricant application device 50: Developing roller 51: Developing sleeve 52: Doctor Blade 53: Supply screw 53a: Supply conveying path 54: Recovery screw 54a: Collection and transport route 55: Magnetic roller 57: Development area entrance seal 58: Casing 58a: Developing case 58b: Upper case for developing film 58b´: End seal member 58c: Developing roller cover 58d: Filter cover 58e: Adhesive part 60: Pressure relief filter 70: Flexible sheet 70a: Opening side end 70b: Downstream end 70c: Backing part 76: Holding part 100: Printer section 500: Copier A: Arrow CG: Gap D: Developer F: Arrow G1: Gap G2: Gap G3: Gap L: Laser light LP2: Direction P: Transfer paper 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 case having an opening that exposes the surface of the developer carrier; a flexible sheet member that is supported on the developer support and that comes into contact with the developer that has passed through the opening and entered the developing case; an end of the sheet member on the side of the opening in the developer movement direction and an end of the sheet member on the opposite side of the opening in the developer movement direction are fixed to a developing case; a case contact portion that contacts a developer case between both ends of the sheet member in the developer moving direction; a non-contact portion that is not in contact with the developing case is formed by bending the sheet member toward the developer carrier between the end of the sheet member on the opening side and the case contact portion; The non-contact portion is in contact with the developer carrier when there is no developer on the developer carrier, and is separated from the developer carrier when a predetermined amount of developer has adhered to the developer carrier.

2. A developer carrier; a developing case having an opening that exposes the surface of the developer carrier; a flexible sheet member that is supported on the developer support and that comes into contact with the developer that has passed through the opening and entered the developing case; the sheet member has an end portion on the opening side in the developer moving direction fixed to a developing case; an end portion of the sheet member opposite to the opening side is inserted into and held by a holding portion provided in the developing case; a case contact portion that contacts a developer case between both ends of the sheet member in the developer moving direction; a non-contact portion that is not in contact with the developing case is formed by bending the sheet member toward the developer carrier between the end of the sheet member on the opening side and the case contact portion; The non-contact portion is in contact with the developer carrier when there is no developer on the developer carrier, and is separated from the developer carrier when a predetermined amount of developer has adhered to the developer carrier.

3. 3. The developing device according to claim 1, The developing device is characterized in that an end of the sheet member opposite to the opening contacts the developing case in an inclined position with respect to a surface of the developing case that contacts the case contact portion.

4. A developer carrier; a developing case having an opening that exposes the surface of the developer carrier; a flexible sheet member that is supported on the developer support and that comes into contact with the developer that has passed through the opening and entered the developing case; the sheet member has an end portion on the opening side in the developer moving direction fixed to a developing case; an end portion of the sheet member opposite to the opening is a free end and contacts the inner surface of the developing case; a non-contact portion that does not come into contact with the developing case is formed between both end portions in the developer moving direction; The non-contact portion is in contact with the developer carrier when there is no developer on the developer carrier, and is separated from the developer carrier when a predetermined amount of developer has adhered to the developer carrier.

5. 5. The developing device according to claim 4, a fixing portion of the sheet member in the developing case is formed so that a free end side of the sheet member extends into a space that was occupied by the developer carrier when the developer carrier is removed, a developing device, wherein the non-contact portion bends upon contact with the developer carrier, and the free end abuts against a contact point on the inner surface of the developing case;

6. 5. The developing device according to claim 4, a developing device, wherein the sheet member is bent to form the non-contact portion between the both end portions;

7. A developing device according to any one of claims 1 to 6, The developing device is characterized in that the thickness of the sheet member is 0.05 mm or more and 0.30 mm or less.

8. A developing device according to any one of claims 1 to 7, a magnet that forms a developer chain at a predetermined position on the developer carrier; The developing device is characterized in that the non-contact portion comes into contact with the ears when a predetermined amount of developer is attached on the developer carrier.

9. 9. The developing device according to claim 1, The developing device is characterized in that the developing case is provided with a pressure relief mechanism.

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

Images