Developing device and image forming apparatus

Abstract

To suppress image defects caused by foreign matters (sheet powder and the like) collected together with transfer residual toner being caught between a developer carrier and a layer thickness regulating member, and maintain image quality at a high image area ratio.SOLUTION: A developing device 4 supplies a developer in a developer accommodating section 46 onto a developer carrier 41 which is rotationally driven by a supply rotating body 42, develops a latent image on a latent image carrier 1 and collects transfer residual toner T3 on the latent image carrier after thinning the developer on the developer carrier by a layer thickness regulating member 44. The supply rotating body is rotationally driven such that its surface moving direction is opposite to the surface moving direction of the developer carrier at an opposing part to the developer carrier. The surface of the supply rotating body is an adhesion-suppressing surface that suppresses adhesion of foreign matters collected together with the transfer residual toner.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, a developing device is known in which a developer in a developer storage section is supplied onto a rotationally driven developer carrier by a supply rotor, the developer on the developer carrier is made into a thin layer by a layer thickness regulating member, a latent image on a latent image carrier is developed, and residual toner remaining on the latent image carrier is collected.

[0003] For example, Patent Document 1 discloses a developing device used in a cleanerless system that collects residual toner in a developing device, which uses a supply roller (supply rotor) with a surface layer made of an open-cell urethane foam layer. In this developing device, the supply roller is driven to rotate in the same direction as the surface movement direction of the developing roller (developer carrier) at the portion facing the developing roller. According to Patent Document 1, this configuration allows foreign matter (paper dust) collected by the developing roller together with residual toner from the latent image carrier to accumulate in an area upstream of the portion facing the supply roller and the developing roller in the surface movement direction of the supply roller. As a result, it is said that the foreign matter (paper dust) collected by the developing roller together with residual toner from the latent image carrier is prevented from becoming trapped between the developing roller and the developing blade (layer thickness regulating member), which causes image defects. Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional developing devices used in cleanerless systems, it was difficult to simultaneously suppress image defects caused by foreign matter (paper dust, etc.) collected along with the residual toner after transfer becoming trapped between the developer carrier and the layer thickness regulating member, and maintain image quality with a high image area ratio. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides a developing device that supplies developer from a developer storage section onto a developer carrier that is rotated by a supply rotor, thins the developer on the developer carrier by a layer thickness regulating member, develops a latent image on a latent image carrier, and collects residual toner from the latent image carrier, wherein the supply rotor is rotated so that the surface movement direction is opposite to the surface movement direction of the developer carrier at the portion facing the developer carrier, and the surface of the supply rotor is an adhesion-inhibiting surface that inhibits adhesion of foreign matter that is collected together with the residual toner from being transferred. [Effects of the Invention]

[0006] According to the present invention, it is possible to suppress image defects caused by foreign matter (paper powder, etc.) collected together with the residual toner after transfer being caught between the developer carrier and the layer thickness regulating member, while maintaining image quality with a high image area ratio. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram for explaining an image forming unit of the image forming apparatus. [Figure 3] FIG. 2 is an explanatory diagram showing the configuration of a developing device of the image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The image forming apparatus of this embodiment is an electrophotographic image forming apparatus, and is a so-called single-drum type direct transfer monochrome machine. However, this embodiment can also be applied to other image forming apparatuses, such as a single-drum type intermediate transfer type full-color machine, a four-tandem type direct transfer type or intermediate transfer type full-color machine, etc.

[0009] FIG. 1 is an explanatory diagram showing the configuration of an image forming apparatus according to this embodiment. FIG. 2 is an explanatory diagram for explaining the image forming unit of the image forming apparatus according to this embodiment. FIG. 3 is an explanatory diagram showing the configuration of the developing device 4 of this embodiment. The imaging unit in the image forming apparatus 10 of this embodiment includes a drum-shaped photosensitive member 1 as a latent image carrier. The imaging unit includes, around the photosensitive member 1, a charger 2 as a charging means, an optical writing device 3 as a latent image forming means, a developing device 4 as a developing means, a transfer device 5 as a transfer means, and a static eliminator 6 as a static eliminator.

[0010] The image forming apparatus 10 according to this embodiment is a cleanerless system image forming apparatus that does not include a dedicated cleaning device for collecting residual toner remaining on the photoreceptor 1 after transfer. Instead, the residual toner on the photoreceptor 1 is collected by the developing device 4. The cleanerless system eliminates the need for a dedicated cleaning device around the photoreceptor 1, allowing the diameter of the photoreceptor 1 to be reduced. This allows the recording material to be reliably separated from the photoreceptor 1 using only the curvature of the photoreceptor 1, even if the recording material onto which the toner image is transferred is thin paper or the like that tends to adhere to the photoreceptor surface after transfer. As a result, there is no need to provide a recording material separation device around the photoreceptor. Therefore, the cleanerless system allows for cost reduction and downsizing of the image forming apparatus.

[0011] In the image forming apparatus 10 of this embodiment, a charging bias of, for example, -1100V is applied to the charging roller 21 of the charger 2, uniformly charging the surface of the photoreceptor 1 to approximately -500V. Then, the optical writing device 3, which is composed of an LED array, is driven to expose the surface of the photoreceptor 1 according to image data, and the potential of the exposed area is reduced to form an electrostatic latent image. Then, in the development area, the developing device 4 supplies toner as a developer to the electrostatic latent image on the photoreceptor 1, forming a toner image on the photoreceptor 1. At this time, in this embodiment, any residual toner remaining on the photoreceptor 1 after the previous transfer is collected by the developing device 4.

[0012] In the developing device 4, a developing roller 41 as a developer carrier and a supply roller 42 as a supply rotor are arranged inside a developing case 43, which is a developer container. Toner is stored in a toner storage section 46 inside the developing case 43, and the toner in the toner storage section 46 is sent to the supply roller 42 side by an agitator 45. Toner is supplied to the developing roller 41, which is driven to rotate in the direction of the arrow in the figure (counterclockwise in the figure), from the supply roller 42, which is also driven to rotate in the direction of the arrow in the figure (counterclockwise in the figure). The toner supplied to the developing roller 41 is transported as the surface of the developing roller 41 moves, and is thinned by a regulating blade 44, which serves as a layer thickness regulating member, before being sent to a development area facing the photosensitive member 1.

[0013] A developing bias of, for example, -300V is applied to the developing roller 41. The toner sent to the developing area is charged to the normal negative polarity when it passes through the regulating blade 44. In the developing area, the negatively charged toner does not adhere to the background portion (about -500V) which is the non-exposed portion, but adheres to the latent image portion (about -50V) which is the exposed portion, thereby developing the electrostatic latent image.

[0014] Meanwhile, paper P as a recording material fed from paper feeder 11 at a predetermined timing is stopped temporarily by registration rollers 12. Thereafter, registration rollers 12 send paper P to the transfer area in time with the timing at which toner image T1 on photoreceptor 1 is transported to the transfer area. In the transfer area, a transfer roller of transfer device 5 is disposed opposite the surface of photoreceptor 1, and a positive transfer bias is applied to this transfer roller. As a result, toner image T1 on photoreceptor 1 is transferred to paper P fed between photoreceptor 1 and the transfer roller in the transfer area. Paper P with transferred toner image T1 is then sent to fixing device 13, where toner image T1 is fixed by pressure and heat. After the fixing process, paper P is discharged to discharge tray 14.

[0015] The surface potential of the photoconductor 1 after transfer is equalized to a negative polarity (for example, about -50 V) by the static eliminator 6. Furthermore, the transfer residual toners T2 and T3 remaining on the photoconductor 1 after transfer are transported to a charging region facing the charging roller 21 of the charger 2. At this time, the transfer residual toners T2 and T3 are a mixture of transfer residual toner T2 that has been reversely charged (charged to a positive polarity) by the positive transfer bias and transfer residual toner T3 that remains at the normal charge polarity (negative polarity).

[0016] Most of the positively charged residual toner T2 becomes negatively charged residual toner T3, which is the normal charging polarity, due to pre-charge discharge that occurs in the upstream portion of the charging area in the direction of movement of the photosensitive member surface. The remaining positively charged residual toner T2 is collected onto the charging roller 21 by the charging bias in the area facing the charging roller 21 of the charger 2 (charging area).

[0017] The charger 2 is provided with a cleaning brush 22 as a charge cleaning member for cleaning toner and the like adhering to the charging roller 21. When collecting the positively polarized transfer residual toner T2, a cleaning bias of, for example, −1300 V is applied to the cleaning brush 22. As a result, the positively polarized transfer residual toner T2 adhering to the charging roller 21 to which a charging bias of −1100 V is applied moves toward the cleaning brush 22 and is held by the cleaning brush 22.

[0018] On the other hand, the negatively charged residual toner T3 passes through the charging area while remaining attached to the photoconductor 1. Because the amount of the negatively charged residual toner T3 is small, it does not interfere with the charging process by the charger 2 or the exposure process by the optical writing device 3. When the negatively charged residual toner T3 is transported to the development area, it faces the development roller 41 to which a development bias of −300 V is applied. At this time, due to the potential difference between the potential (−500 V) of the non-exposed portion (background portion) of the photoconductor 1 and the development bias (−300 V), the transfer residual toner on the photoconductor 1 moves toward the development roller 41 and is collected by the development device 4. As described above, in this embodiment, the transfer residual toner T3 is collected by the development device 4 during image formation, thereby realizing a cleaner-less system.

[0019] The residual toner T2 of positive polarity held by the cleaning brush 22 during the image forming operation is returned to the surface of the photosensitive member 1 and collected by the developing device 4 during a non-image forming operation period, such as when the device is started up.

[0020] More specifically, during a non-image forming operation period, first, a charging bias of −1100 V is applied to the charging roller 21 to uniformly charge the surface of the photosensitive member 1 to approximately −500 V. Then, with the transfer bias and the static eliminator 6 turned off, when the surface portion uniformly charged to −500 V is transported back to the charging region, a voltage of −350 V, for example, is applied to the charging roller 21, and a voltage of −150 V, for example, is applied to the cleaning brush 22. As a result, the positively charged residual toner T2 held on the cleaning brush 22 moves from the cleaning brush 22 to the charging roller 21, and then from the charging roller 21 to the surface of the photosensitive member 1.

[0021] Thereafter, the positively charged residual toner T3 discharged from the charger 2 to the photosensitive member 1 is transported to the development area. At this time, a voltage of, for example, +250 V is applied to the development roller 41 in the development area. As a result, the negatively charged residual toner T2 present on the photosensitive member 1 moves toward the development roller 41 and is collected, and the positively charged residual toner T3 passes through the development area.

[0022] The positively charged residual toner T3 that has passed through the development area is then transported back to the charging area. At this time, the static eliminator 6 is turned on to uniformly level the surface of the photoconductor 1 at about -50 V, and a charging bias of -1100 V is applied to the charging roller 21. As a result, the positively charged residual toner T3 transported to the charging area becomes negatively charged, which is the normal charged polarity, due to pre-charge discharge that occurs in the upstream portion of the charging area in the direction of movement of the photoconductor surface.

[0023] Thereafter, when the negatively polarized transfer residual toner T3 is transported to the development area, it faces the development roller 41 to which a development bias of -300V is applied, so the negatively polarized transfer residual toner T3 moves toward the development roller 41 and is collected by the development device 4.

[0024] Generally, after transfer, not only residual toner but also foreign matter such as paper dust adheres to the surface of the photosensitive member 1. Therefore, the developing device 4 collects not only residual toner but also foreign matter such as paper dust. There is no particular problem if such foreign matter simply enters the developing device 4, but if the foreign matter gets caught in the contact area between the developing roller 41 and the regulating blade 44 and accumulates, aggregates, and grows there, a problem occurs in which a defective image occurs. Specifically, toner on the developing roller 41 is blocked in the area corresponding to the area where the foreign matter aggregates, and toner cannot be sent to the development area in that area, resulting in an image defect in which white streaks appear on the image.

[0025] Among conventional developing devices used in cleanerless systems, there are configurations in which the surface movement directions of the supply roller and the developing roller are the same at the opposing portion. However, in a configuration in which the surface movement directions of the supply roller and the developing roller are the same at the opposing portion, even if it is possible to prevent the occurrence of image defects by preventing the accumulation of foreign matter at the contact point between the developing roller and the regulating blade, there remains the problem that it is difficult to maintain image quality with a high image area ratio. In other words, a configuration in which the surface movement directions of the supply roller and the developing roller are the same at the opposing portion usually leads to an insufficient supply of toner to the development area and a decrease in image density when performing continuous development processes for images with a high image area ratio.

[0026] Therefore, in this embodiment, the supply roller 42 is driven to rotate in a surface movement direction opposite to the surface movement direction of the developing roller 41 at the portion facing the developing roller 41. Therefore, even in cases where continuous development processing is performed on images with a high image area ratio, a shortage of toner supply to the development area is unlikely to occur, and it is possible to maintain image quality with a high image area ratio.

[0027] On the other hand, in a configuration in which the surface movement directions of the supply roller and the developing roller are opposite at the opposing portion, a configuration has been conventionally adopted that increases the scraping force of the surface of the supply roller (for example, a configuration in which the surface of the supply roller is provided with numerous raised portions by grinding with a grindstone). This configuration increases the ability of the surface of the supply roller to remove foreign matter, such as paper dust, collected on the developing roller from the developing roller, thereby preventing the foreign matter collected on the developing roller from being sent directly to the contact point between the developing roller and the regulating blade. As a result, foreign matter is prevented from becoming trapped at the contact point between the developing roller and the regulating blade, and the trapped foreign matter is prevented from growing and causing image defects.

[0028] However, when a configuration is adopted that increases the scraping force of the surface of the supply roller, the scraped foreign matter remains trapped on the surface of the supply roller, and the foreign matter accumulates on the supply roller. The foreign matter accumulated on the supply roller gradually aggregates and grows, and eventually the aggregates of foreign matter peel off from the surface of the supply roller. As a result, it was discovered that a new problem occurs in which the aggregates of foreign matter are carried and transported by the developing roller and get caught at the contact point between the developing roller and the regulating blade, causing image defects.

[0029] Therefore, in this embodiment, the surface of the supply roller 42 is an adhesion-preventing surface that prevents adhesion of foreign matter. Specifically, the surface of the supply roller 42 is a non-protruding surface that does not have any protrusions. However, considering the ability of the supply roller 42 to supply toner to the development roller 41 and the ability of the supply roller 42 to remove foreign matter from the development roller 41, it is preferable to provide recesses on the non-protruding surface. Specifically, the surface of the supply roller 42 is formed of a foam layer, for example, made of urethane foam.

[0030] By making the surface of the supply roller 42 an adhesion prevention surface, foreign matter collected by the developing roller 41 from the photosensitive member 1 is less likely to accumulate on the surface of the supply roller 42. As a result, agglomerates of foreign matter do not grow on the supply roller 42, and it is possible to prevent the agglomerates of foreign matter from getting caught at the contact point between the developing roller 41 and the regulating blade 44, thereby preventing image defects from occurring.

[0031] 2, the inlet region of the opposing portion between the supply roller 42 and the developing roller 41 (the region upstream in the direction of movement of the surface of the developing roller 41) is configured to be located vertically downward. With this configuration, foreign matter that is transported to the inlet region of the opposing portion as the surface of the developing roller 41 moves and is removed from the developing roller 41 by the surface of the supply roller 42 moves downward by its own weight and accumulates on the bottom of the inner wall of the developing case 43 at the location surrounded by the symbol A in FIG.

[0032] Specifically, foreign matter carried to the entrance area of the opposing portion as the surface of developing roller 41 moves is unable to enter the opposing portion due to the surface movement of supply roller 42, and is removed from developing roller 41 and remains in the entrance area of the opposing portion. The foreign matter remaining in the entrance area of the opposing portion then moves downward by its own weight and accumulates on the curved portion of the bottom inner wall of developing case 43 that faces developing roller 41 (the area surrounded by symbol A in FIG. 3). This prevents the collected foreign matter from moving around the toner storage section 46 side inside developing case 43 and being carried by developing roller 41, and also prevents the foreign matter from becoming caught in the contact area between developing roller 41 and regulating blade 44, growing, and causing image defects.

[0033] In particular, the bottom of the inner wall of the developer case 43 in this embodiment is curved to conform to the circumferential surfaces of the developing roller 41 and the supply roller 42, as shown in FIG. 3 . A protrusion 43a is formed on the bottom of the inner wall of the developer case 43 toward the inlet region where the supply roller 42 and the developing roller 41 face each other. The location A where foreign matter accumulates is farther from the toner storage compartment 46 inside the developer case 43 than the protrusion 43a on the bottom of the inner wall of the developer case 43. Therefore, the protrusion 43a on the bottom of the inner wall of the developer case 43 functions to prevent foreign matter accumulated at location A from moving toward the toner storage compartment 46 inside the developer case 43. This prevents foreign matter accumulated on the bottom of the inner wall of the developer case 43 due to its own weight from moving around the toner storage compartment 46 inside the developer case 43 and being carried by the developing roller 41. This also prevents foreign matter from becoming caught in the contact area between the developing roller 41 and the regulating blade 44, growing, and causing image defects.

[0034] Furthermore, in this embodiment, it is preferable to set the surface movement speed (linear speed) of supply roller 42 to be slower than the surface movement speed (linear speed) of development roller 41, that is, to set the linear speed ratio (supply roller linear speed / development roller linear speed) to be less than 1. This makes it easier to scrape off foreign matter on development roller 41 with the surface of the supply roller, thereby improving the effect of suppressing white streaks.

[0035] Furthermore, in this embodiment, it is preferable that the developing roller 41 bites into the supply roller 42 by 1 mm or more at the portion where the developing roller 41 and the supply roller 42 face each other. This makes it easier to scrape off foreign matter on the developing roller 41 with the surface of the supply roller, thereby improving the effect of suppressing white streaks.

[0036] The inventors evaluated the types and diameters of cells suitable for the adhesion prevention surface when the surface of the supply roller 42 is formed of a foam layer in the developing device 4 of this embodiment. The evaluation results are shown in Table 1 below.

[0037] [Table 1]

[0038] As shown in Table 1 above, when the surface of the supply roller 42 is formed from a foam layer containing open cells of 300 μm or more (the equivalent circular diameter of the cells opening on the surface of the supply roller 42, i.e., the diameter of a circle having an area equal to the area of the opening), it was confirmed that foreign matter such as paper dust is trapped in the cells (depressions caused by air bubbles) present on the surface of the supply roller 42. It was also confirmed that aggregates of foreign matter are caught at the contact point between the developing roller 41 and the regulating blade 44, causing image defects (white streaks). In contrast, when the surface of the supply roller 42 is formed from a foam layer containing closed cells of less than 300 μm, foreign matter such as paper dust is not trapped in the cells present on the surface of the supply roller 42, and no image defects (white streaks) occur.

[0039] The above description is merely an example, and each of the following aspects provides unique effects. [First aspect] In the first aspect, a developing device 4 supplies a developer (e.g., toner) from a developer storage section (e.g., a toner storage section 46) onto a rotationally driven developer carrier (e.g., a developing roller 41) by a supply rotor (e.g., a supply roller 42), thins the developer on the developer carrier by a layer thickness regulating member (e.g., a regulating blade 44), develops a latent image on a latent image carrier (e.g., a photosensitive body 1), and collects transfer residual toner T3 on the latent image carrier, characterized in that the supply rotor is rotated so that the surface movement direction is opposite to the surface movement direction of the developer carrier at the portion facing the developer carrier, and the surface of the supply rotor is composed of a foam layer containing closed cells of less than 300 μm. In a developing device employed in a cleanerless system, foreign matter such as paper dust collected from the latent image carrier together with the residual toner after transfer can easily become caught between the developer carrier and the layer thickness regulating member, where the foreign matter accumulates, aggregates, and grows, resulting in image defects. Specifically, for example, if foreign matter is caught between the developer carrier and the layer thickness regulating member and grows into an aggregate of foreign matter, the developer is blocked on the developer carrier in the area corresponding to the aggregate, resulting in an image defect in which white streaks appear on the image. In order to suppress such image defects, a developing device has been proposed in which a supply rotor is rotated so that the surface movement direction of the supply rotor faces the developer carrier in the same direction as the surface movement direction of the developer carrier at the portion facing the developer carrier (Patent Document 1). However, it is difficult to sufficiently suppress the occurrence of the above-mentioned image defects with this developing device. Specifically, in a conventional developing device in which the surface movement directions of the supply rotor and the developer carrier are the same at the opposing portion, developer present in an inlet region upstream of the opposing portion in the direction of developer carrier surface movement is sent to the opposing portion as both the supply rotor and the developer carrier move. Meanwhile, foreign matter collected from the latent image carrier along with the transfer residual toner is transported to this inlet region as the developer carrier moves. Therefore, foreign matter transported to this inlet region is likely to be carried to the opposing portion by the flow of developer that is sent to the opposing portion as both the supply rotor and the developer carrier move. When foreign matter is transported to the opposing portion, it is carried on the developer carrier and transported to the position of the layer thickness regulating member, causing the foreign matter to become trapped between the developer carrier and the layer thickness regulating member, resulting in image defects such as white streaks. Furthermore, even if a conventional developing device could be configured so that foreign matter transported from the latent image carrier as the developer carrier moves on its surface would not be sent to the opposing section but would instead remain in the inlet area, there would still be the problem that it would be difficult to maintain image quality with a high image area ratio. That is, a configuration in which the surface movement directions of the supply rotor and the developer carrier are the same at the opposing section would normally result in an insufficient amount of developer being supplied to the development area, and image density would likely decrease, when performing continuous development processing on images with a high image area ratio. On the other hand, some conventional developing devices used in cleanerless systems are configured so that the surface movement directions of the supply rotor and the developer carrier are opposite each other at the opposing portion (see, for example, Patent Document 2). This configuration typically prevents a shortage of developer supply to the development area, even in cases where images with a high image area ratio are continuously developed, making it possible to maintain high image quality. However, in this conventional developing device, the surface of the supply rotor is ground with a grindstone so that the grinding marks are opposite to the surface movement direction of the developer carrier at the opposing portion in order to reliably scrape off foreign matter, such as paper dust, collected on the developer carrier from the developer carrier. With this configuration, foreign matter transported as the developer carrier moves is scraped off the developer carrier by the grinding marks (protrusions) on the surface of the supply rotor, preventing the foreign matter from being sent directly between the developer carrier and the layer thickness regulating member. Therefore, it is considered possible to prevent the occurrence of image defects caused by foreign matter being caught between the developer regulating member and the layer thickness regulating member, and the foreign matter accumulating, agglomerating, and growing there. However, in this conventional developing device, the scraped foreign matter remains trapped in the polishing grooves on the surface of the supply rotor, causing the foreign matter to accumulate on the supply rotor. The foreign matter accumulated on the supply rotor gradually aggregates and grows, eventually peeling off from the supply rotor. As a result, it was discovered that the aggregates of foreign matter are carried on the developer carrier and transported, becoming caught between the developer carrier and the layer thickness regulating member, causing a new problem: poor image quality. In this embodiment, the supply rotor is driven to rotate in a direction opposite to the surface movement direction of the developer carrier at the portion facing the developer carrier, and the surface of the supply rotor is formed of a foam layer containing closed cells of less than 300 μm. This configuration ensures that the surface movement directions of the supply rotor and the developer carrier are opposite to each other at the opposing portion, making it less likely that a shortage of developer will be supplied to the development area, even in cases where images with a high image area ratio are continuously developed, thereby maintaining image quality with a high image area ratio. Furthermore, the foam layer containing closed cells of less than 300 μm on the surface of the supply rotor allows the supply rotor to function as a supply rotor while also providing a surface that is less likely to trap foreign matter. In other words, the closed cells (recesses) on the surface of the supply rotor of this embodiment ensure the supply rotor's function of supplying developer to the developer carrier and its function of removing foreign matter from the developer carrier. On the other hand, because the size (circular equivalent diameter) of the closed cell is less than 300 μm, foreign matter is less likely to be trapped in the recesses (cells) on the surface of the supply rotor. This prevents the growth of foreign matter aggregates on the supply rotor, and prevents the occurrence of image defects caused by foreign matter aggregates being caught between the developer carrier and the layer thickness regulating member. Therefore, it is possible to suppress image defects caused by foreign matter (paper dust, etc.) collected together with the residual toner being caught between the developer carrier and the layer thickness regulating member, while maintaining image quality with a high image area ratio.

[0040] [Second mode] A second aspect is the first aspect, characterized in that the upstream side of the facing portion in the surface movement direction of the developer carrier is positioned below the facing portion in the vertical direction. According to this, foreign matter that is carried to the opposing portion as the surface of the developer carrier moves and is removed from the developer carrier by the surface of the supply rotor moves downward by its own weight and accumulates on the bottom of the inner wall of the developer storage portion. This prevents the collected foreign matter from moving around the developer storage portion and being carried by the developer carrier, and prevents the foreign matter from becoming caught between the developer carrier and the layer thickness regulating member, growing, and causing image defects.

[0041] [Third aspect] A third aspect is the first or second aspect, characterized in that the surface movement speed of the supply rotator is slower than the surface movement speed of the developer carrier. This makes it easier for the surface of the supply rotor to scrape off foreign matter on the developer carrier, thereby improving the effect of suppressing image defects caused by foreign matter.

[0042] [Fourth aspect] A fourth aspect is the first to third aspect, characterized in that, in the opposing portion, the developer carrier bites into the supply rotor by 1 mm or more. This makes it easier for the surface of the supply rotor to scrape off foreign matter on the developer carrier, thereby improving the effect of suppressing image defects caused by foreign matter.

[0043] [Fifth mode] The fifth aspect is an image forming apparatus 10 having a cleanerless configuration in which residual toner on a latent image carrier is collected by a developing device, and is characterized in that the developing device is any of the developing devices of the first to fourth aspects. According to this embodiment, it is possible to suppress image defects that occur when foreign matter (paper powder, etc.) collected together with the residual toner after transfer is caught between the developer carrier and the layer thickness regulating member, while maintaining image quality with a high image area ratio. [Explanation of symbols]

[0044] 1: Photoreceptor 2: Charger 3: Optical writing device 4: Developing device 5: Transfer device 6: Static eliminator 10: Image forming device 11: Paper feeder 12: Registration roller 13: Fixing device 14: Output tray 21: Charging roller 22: Cleaning brush 41: Developing roller 42: Supply roller 43: Developing case 43a: Convex part 44: Regulatory blade 45: Agitator 46: Toner storage compartment P:Paper T1: Toner image T2: Positive residual toner T3: Negative residual toner [Prior art documents] [Patent documents]

[0045] [Patent Document 1] Japanese Patent Publication No. 2023-75865 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-149328

Claims

1. A developing device that supplies developer from a developer storage unit onto a developer carrier that is driven to rotate by a supply rotor, and then forms a thin layer of developer on the developer carrier by a layer thickness regulating member, and then develops a latent image on a latent image carrier and collects transfer residual toner on the latent image carrier, the supply rotor is driven to rotate in a surface movement direction opposite to a surface movement direction of the developer carrier at a portion facing the developer carrier, A developing device, wherein the surface of the supply rotor is made of a foam layer containing closed cells of less than 300 μm.

2. 2. The developing device according to claim 1, The developing device is configured such that the upstream side of the facing portion in the direction of surface movement of the developer carrier is positioned below the facing portion in the vertical direction.

3. 3. The developing device according to claim 1, a developing device in which the surface movement speed of the supply rotor is slower than the surface movement speed of the developer carrier;

4. 3. The developing device according to claim 1, In the developing device, the developer carrier is pressed into the supply rotor by 1 mm or more at the opposing portion.

5. An image forming apparatus having a cleanerless configuration in which residual toner remaining on a latent image carrier is collected by a developing device, 3. An image forming apparatus, comprising the developing device according to claim 1 or 2 as the developing device.

Images