Image forming apparatus

Abstract

To provide an image forming apparatus that is configured such that toner cartridges storing toners to be supplied to a plurality of developing chambers are removably attached to a rotatable rotary comprising the developing chambers, and prevents the occurrence of supply fogging.SOLUTION: An image forming apparatus 1 has a rotatable rotary 90 that moves developing members 51 to a developing position to supply toner to an image carrier 2, and toner cartridges 70 that are removably attached to the rotary 90, and a reception opening 53b and a discharge opening 71b communicate with each other to supply the toner from the toner cartridges 70 to developing chambers 53a. The developing chamber 53a includes a partition wall W that partitions the developing chamber 53a into a first area 53a1 including the developing member 51 and a second area 53a2. The rotary 90 rotates to move the toner stored in the toner cartridge 70 and the toner stored in the first area 53a1 to the second area 53a2, and the toners are mixed therein.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine having a plurality of functions among these, which uses an electrophotographic system. [Background technology]

[0002] Conventionally, in image forming devices using electrophotography, a rotary development method has been known in which an electrostatic latent image on the surface of a photosensitive member is developed with toners of different colors by rotating a rotary equipped with multiple development chambers, each equipped with a development roller.

[0003] Patent document 1 describes an image forming apparatus that includes a rotary with multiple developing units (developing chambers) and multiple toner cartridges (toner storage containers) that are detachable from the rotary and contain toner to be replenished to each developing unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-183305 Summary of the Invention [Problem to be solved by the invention]

[0005] The toner in the developing chamber is carried by the developing roller and subjected to mechanical stress as it rubs against the developing blade, photoconductor, etc., and gradually deteriorates. As the toner deteriorates, the toner becomes deformed from its original particle shape, or the external additives peel off from the particle surface, and the toner tends to have reduced triboelectric charging performance.

[0006] When new toner is replenished from a toner cartridge to the developing chamber, a difference in triboelectric charging performance (frictional charging ability) occurs between the deteriorated toner damaged in the developing chamber and the new toner. Deteriorated toner is less likely to be charged to the normal polarity, while new toner tends to be more likely to be charged to the normal polarity. Therefore, immediately after deteriorating toner with poor triboelectric charging performance is mixed with new toner, the charge of the deteriorating toner tends to be low. If toner in this state is coated on the developing roller, a phenomenon known as "fog" can occur, in which toner is deposited on non-image-forming areas of the photoreceptor. This type of fogging caused by replenishment of toner to the developing chamber is called "supply fogging."

[0007] Therefore, an object of the present invention is to suppress the occurrence of replenishment fogging in a configuration in which a toner cartridge containing toner to be replenished to the developing chambers can be attached and detached to a rotatable rotary equipped with multiple developing chambers. [Means for solving the problem]

[0008] The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus comprising: an image carrier on which an electrostatic image is formed; a developing chamber containing toner; and a developing member that supplies the toner contained in the developing chamber to the image carrier to develop the electrostatic image; a rotatable rotary that moves the developing member to a developing position where the toner is supplied to the image carrier; and a toner cartridge that contains toner to be replenished to the developing chamber and is detachably attached to the rotary, wherein a receiving opening provided in the developing chamber and a discharge opening provided in the toner cartridge are connected to each other so that toner is replenished from the toner cartridge to the developing chamber, and the developing chamber includes a partition wall that separates the developing chamber into a first region including the developing member and a second region, and the toner contained in the toner cartridge and the toner contained in the first region move to the second region and are mixed with each other by rotation of the rotary. [Effects of the Invention]

[0009] According to the present invention, in a configuration in which a toner cartridge containing toner to be replenished to the developing chambers is detachably attached to a rotatable rotary having multiple developing chambers, the occurrence of replenishment fogging can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Figure 2] FIG. 2 is a schematic cross-sectional view of a developing unit according to the first embodiment. [Figure 3] FIG. 2 is a schematic cross-sectional view of a developing unit. [Figure 4] 4 is a schematic cross-sectional view of a developing unit for explaining an example of a toner surface in a developing chamber. FIG. [Figure 5] 10 is a schematic cross-sectional view of a developing unit for explaining another example of the toner agent surface in the developing chamber. FIG. [Figure 6] FIG. 10 is a schematic cross-sectional view of a developing unit of a comparative example. [Figure 7] FIG. 2 is a schematic cross-sectional view of a rotary developing device for explaining the mechanism of toner mixing in the first embodiment. [Figure 8] FIG. 2 is a schematic cross-sectional view of a rotary developing device for explaining the mechanism of toner mixing in the first embodiment. [Figure 9] 10 is a schematic cross-sectional view of a developing unit for explaining another example of the toner agent surface in the developing chamber. FIG. [Figure 10] FIG. 10 is a schematic cross-sectional view of another example of the developing unit. [Figure 11] FIG. 10 is a schematic cross-sectional view of a rotary developing device for explaining the mechanism of toner mixing in Example 2. [Figure 12] FIG. 10 is a schematic cross-sectional view of a rotary developing device for explaining the mechanism of toner mixing in Example 2. [Figure 13] 10A and 10B are a schematic cross-sectional view of a developing unit and a schematic front view of an inner wall of a developing chamber for explaining another example of the developing unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] The image forming apparatus according to the present invention will be described in more detail below with reference to the drawings.

[0012] [Example 1] 1. Overall configuration of image forming device First, the overall configuration of the image forming apparatus 1 of this embodiment will be described. Fig. 1 is a schematic cross-sectional view of the image forming apparatus 1 of this embodiment. The image forming apparatus 1 of this embodiment is a laser beam printer that forms an image on a sheet S by electrophotography. More specifically, the image forming apparatus 1 of this embodiment is a color laser beam printer that includes four development units 50y, 50m, 50c, and 50k within a rotatable rotary 90.

[0013] As the recording material (recording medium, transfer material), a variety of sheet materials of different sizes and materials can be used, such as paper such as plain paper and cardboard, sheet materials with surface treatments such as plastic film, cloth, and coated paper, and sheet materials with special shapes such as envelopes and index paper.

[0014] Furthermore, with respect to the image forming apparatus 1 and its elements, the vertical direction (direction of gravity) when the image forming apparatus 1 is installed on a horizontal surface is referred to as the "Z direction." Furthermore, the direction that intersects with the Z direction (orthogonal in this embodiment) and is parallel to the rotation axis 90C of the rotary 90 (direction of the rotation axis of the rotary 90) is referred to as the "Y direction." The direction that intersects with both the Z direction and the Y direction (orthogonal in this embodiment) is referred to as the "X direction." When the image forming apparatus 1 is installed on a horizontal surface, the X direction and the Y direction are horizontal. Furthermore, with respect to the image forming apparatus 1 and its elements, "up" and "down" refer to up and down in the vertical direction (direction of gravity), but do not mean just directly above or just below, and also include above and below a horizontal plane that passes through the element or position of interest.

[0015] As shown in FIG. 1, the image forming apparatus 1 has an image forming apparatus main body (hereinafter also simply referred to as the "apparatus main body") 1A, and toner cartridges 70y, 70m, 70c, and 70k that are detachable from the apparatus main body 1A (rotary 90).

[0016] The apparatus main body 1A has a photosensitive drum 2, which is a drum-shaped (cylindrical) electrophotographic photosensitive member (photoconductor) that serves as an image carrier for carrying an electrostatic latent image or a toner image. The photosensitive drum 2 is rotatably supported by a frame or the like that constitutes the apparatus main body 1A. Around the photosensitive drum 2, there are arranged a charging roller 3, a scanner 4 that serves as an exposure device, a rotary developing device 91 equipped with four developing units 50y, 50m, 50c, and 50k, and a cleaning unit 6.

[0017] The charging roller 3 is an example of a charging means for uniformly charging the surface of the photosensitive drum 2. The charging roller 3 is composed of a roller-type charging member arranged in contact with the surface (outer circumferential surface) of the photosensitive drum 2. The scanner 4 is an example of an exposure means for irradiating the surface of the photosensitive drum 2 with laser light according to image information to expose it. The scanner 4 forms an electrostatic latent image (electrostatic image) on the surface of the photosensitive drum 2 by irradiating the surface of the photosensitive drum 2 with laser light after charging. The cleaning unit 6 is an example of a cleaning means for removing toner remaining on the surface of the photosensitive drum 2.

[0018] The rotary developing device 91 has a rotary (rotary main body) 90 equipped with developing units 50y, 50m, 50c, and 50k. The rotary 90 is rotatably supported by a frame or the like constituting the device main body 1A. The rotary 90 is also fitted with trays 80y, 80m, 80c, and 80k, which serve as mounting units. Toner cartridges (toner containers) 70y, 70m, 70c, and 70k are removably mounted to the trays 80y, 80m, 80c, and 80k, respectively. A yellow toner cartridge 70y is mounted in the yellow tray 80y corresponding to the yellow developing unit 50y. Similarly, a magenta toner cartridge 70m is mounted in the magenta tray 80m corresponding to the magenta developing unit 50m. A cyan toner cartridge 70c is mounted in the cyan tray 80c corresponding to the cyan developing unit 50c. A black toner cartridge 70k is mounted in a black tray 80k corresponding to the black developing unit 50k. The four developing units 50 are arranged at approximately equal intervals of 90° around the rotation axis 90C of the rotary 90. A rotary developing device 91 is configured with a rotary (rotary main body) 90 equipped with developing units 50y, 50m, 50c, and 50k, trays 80y, 80m, 80c, and 80k, and toner cartridges 70y, 70m, 70c, and 70k. The developing units 50 may be detachable from the rotary 90. Each toner cartridge 70 is slid relative to the rotary 90 and attached to or detached from the device main body 1A (rotary 90) via the attachment / detachment portion 15 while the rotary 90 is in the replacement position described below. At this time, the tray 80 may move together with the toner cartridge 70, allowing the toner cartridge 70 to be attached to or detached from the tray 70. The tray 80 may be formed integrally with the rotary 90.

[0019] Here, the subscripts y, m, c, and k attached to the developing units 50y, 50m, 50c, and 50k, the toner cartridges 70y, 70m, 70c, and 70k, and the trays 80y, 80m, 80c, and 80k, etc., indicate the toner colors yellow, magenta, cyan, and black, respectively. In this embodiment, the developing units 50y, 50m, 50c, and 50k for each color have substantially the same basic configuration and function. Similarly, in this embodiment, the toner cartridges 70y, 70m, 70c, and 70k for each color have substantially the same basic configuration and function. Furthermore, in this embodiment, the trays 80y, 80m, 80c, and 80k for each color have substantially the same basic configuration and function. Elements having the same or corresponding functions or configurations for each color may be generally described without the subscripts y, m, c, and k.

[0020] The developing units 50y, 50m, 50c, and 50k are examples of developing means that supply toner to develop (visualize) the electrostatic latent image formed on the surface of the photosensitive drum 2. The developing units 50y, 50m, 50c, and 50k develop the electrostatic latent image formed on the surface of the photosensitive drum 2 using toner of each color, yellow, magenta, cyan, and black, and form toner images (toner images, developer images) of each color on the surface of the photosensitive drum 2.

[0021] The developing unit 50 has a developing roller 51, a supply roller 52, and a developing blade 54 (FIG. 2). The developing roller 51 is a developer carrier (developing member) that carries toner as a developer and rotates to supply the toner to the photosensitive drum 2. The supply roller 52 is a supply member that is disposed in contact with the developing roller 51 and supplies toner to the developing roller 51. The developing blade 54 is a regulating member that regulates the thickness of the toner layer (amount of toner) carried by the developing roller 51. Details of the developing unit 50 will be described later.

[0022] The rotary 90 rotates around the rotation axis 90C in the direction of arrow R2 (clockwise) in the figure. This allows the rotary 90 to assume a "development position" in which the development unit 50 for one of the colors is in the development position facing the photosensitive drum 2. In this embodiment, when the development unit 50 (development roller 51) is in the "development position," the development roller 51 of that development unit 50 faces (abuts in this embodiment) the surface of the photosensitive drum 2. The position of the rotary 90 in which the yellow development unit 50y is in the development position and its development roller 51 faces the photosensitive drum 2 is called the "yellow development position." The position of the rotary 90 in which the magenta development unit 50m is in the development position and its development roller 51 faces the photosensitive drum 2 is called the "magenta development position." The position of the rotary 90 in which the cyan development unit 50c is in the development position and its development roller 51 faces the photosensitive drum 2 is called the "cyan development position." The orientation of the rotary 90 in which the black developing unit 50k is in the developing position and its developing roller 51 faces the photosensitive drum 2 is referred to as the "black developing orientation." In other words, the rotary 90 can rotate around the rotation axis 90C so that the position of the developing roller 51 of the developing unit 50 for each color relative to the photosensitive drum 2 can be changed.

[0023] Furthermore, the apparatus main body 1A has a sheet storage section 300, a pickup roller 310, a feed roller 311, a separation roller 312, a pair of conveying rollers 320, a secondary transfer roller 12, a fixing device 40, and an intermediate transfer unit 10. The pickup roller 310 is an example of a feeding means that feeds the sheet S. The feed roller 311 and the separation roller 312 (separation conveying unit) are examples of a separating conveying means that separates and conveys the sheets S one by one by frictional force. The secondary transfer roller 12 is an example of a secondary transfer means that transfers an image from the intermediate transfer belt 10a to the sheet S. The fixing device 40 is an example of a fixing means that fixes the toner image to the sheet S.

[0024] The intermediate transfer unit 10 includes an intermediate transfer belt 10a, a belt drive roller 10b, a tension roller 10c, a belt cleaning device 13, and a primary transfer roller 11. The intermediate transfer belt 10a is an example of an intermediate transfer body that carries an image (toner image) transferred (primary transfer) from the photosensitive drum 2 and transports it for transfer (secondary transfer) to a sheet S. The intermediate transfer belt 10a, which is an endless belt, is stretched over a belt drive roller 10b and a tension roller 10c as tension rollers and stretched with a predetermined tension. The belt drive roller 10b is a drive member that transports the intermediate transfer belt 10a. The belt drive roller 10b is driven to rotate by a drive force transmitted from a motor (not shown), which is a drive source constituting the intermediate transfer body drive means. The tension roller 10c is a tension applying member that applies a predetermined tension to the intermediate transfer belt 10a. A primary transfer roller 11, which is a roller-type primary transfer member serving as primary transfer means, is disposed on the inner peripheral surface of the intermediate transfer belt 10a at a position corresponding to the photosensitive drum 2. The primary transfer roller 11 presses the intermediate transfer belt 10a toward the photosensitive drum 2, forming a primary transfer portion (primary transfer nip portion) N1, which is a contact portion (nip portion) between the photosensitive drum 2 and the intermediate transfer belt 10a. Furthermore, a secondary transfer roller 12, which is a roller-type secondary transfer member serving as secondary transfer means, is disposed on the outer peripheral surface of the intermediate transfer belt 10b at a position opposite the belt drive roller 10b, which also serves as a secondary transfer opposing roller. The secondary transfer roller 12 is pressed toward the belt drive roller 10b and contacts the belt drive roller 10b via the intermediate transfer belt 10a, forming a secondary transfer portion (secondary transfer nip portion) N2, which is a contact portion (nip portion) between the intermediate transfer belt 10a and the secondary transfer roller 12. The belt cleaning device 13 is an example of a cleaning means that removes toner remaining on the surface of the intermediate transfer belt 10a.

[0025] The photosensitive drum may be detachably attached to the apparatus main body 1A substantially alone or together with at least one other element such as the charging roller 3 (charging means) or the cleaning unit 6 (cleaning means).

[0026] 2. Image formation operation Next, the image forming operation in the image forming apparatus 1 of this embodiment will be described.

[0027] The photosensitive drum 2 is driven to rotate in the direction of arrow R1 (counterclockwise) in the figure by a driving force transmitted from a motor (not shown), which is a driving source constituting the photosensitive body driving means. The rotation of the photosensitive drum 2 starts in synchronization with the rotation of the intermediate transfer belt 10a. The intermediate transfer belt 10a rotates (circulates) in the direction of arrow R5 (clockwise) in the figure by the driving force transmitted from the belt drive roller 10b. The surface of the rotating photosensitive drum 2 is then charged approximately uniformly by the charging roller 3 to a predetermined potential of a predetermined polarity (negative polarity in this embodiment).

[0028] When a color image is formed on the sheet S, the charged surface of the photosensitive drum 2 is scanned and exposed by the scanner 4 with laser light based on image data corresponding to a yellow image. As a result, an electrostatic latent image corresponding to the yellow image is formed on the surface of the photosensitive drum 2. Concurrently with the formation of this electrostatic latent image, the rotary 90 is rotated, and the rotary 90 assumes a yellow developing position. The rotary 90 is rotated by a driving force transmitted from a motor, which is a driving source constituting a rotary drive unit 92 as a rotary drive means. The yellow developing unit 50y, located at the developing position, develops the electrostatic latent image formed on the surface of the photosensitive drum 2 with yellow toner. In this embodiment, toner charged with the same polarity as the charge polarity of the photosensitive drum 2 (negative polarity in this embodiment) adheres to the exposed area (image area) of the photosensitive drum 2, which has been uniformly charged and then exposed to light, thereby reducing the absolute value of the potential (reverse development method). In this embodiment, the normal charge polarity of the toner (normal charge polarity), which is the main charge polarity of the toner during development, is negative. In this embodiment, when the developing unit 50 is in the developing position, the developing roller 51 is in contact with the surface of the photosensitive drum 2, and the electrostatic latent image is developed. In other words, the image forming apparatus 1 in this embodiment employs a contact development system. However, the present invention is not limited to this, and the image forming apparatus may be configured to develop the electrostatic latent image in a state where a gap is left between the developer carrier and the image carrier at the developing position. In other words, the image forming apparatus 1 may employ a non-contact development system.

[0029] At the primary transfer portion N1, the yellow toner image formed on the surface of the photosensitive drum 2 is transferred (primary transfer) to the surface (outer peripheral surface) of the rotating intermediate transfer belt 10a by the action of the primary transfer roller 11. During the primary transfer, a primary transfer voltage (primary transfer bias) of a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the primary transfer roller 11.

[0030] Thereafter, electrostatic latent images corresponding to magenta, cyan, and black are sequentially formed on the photosensitive drum 2 in the same manner as described above. Each time an electrostatic latent image corresponding to a color is formed, the rotary 90 rotates, and the developing units 50y, 50m, and 50c for magenta, cyan, and black are sequentially moved to the developing positions. A toner image of each color is then formed on the photosensitive drum 2. Each time a toner image of each color is formed, the toner images of each color are sequentially transferred (primary transfer) to the same image forming area on the intermediate transfer belt 10a so that they are superimposed on top of each other. That is, after a yellow toner image is formed on the intermediate transfer belt 10a, the rotary 90 assumes the magenta developing position, and a magenta toner image is formed on the intermediate transfer belt 10a. After a magenta toner image is formed on the intermediate transfer belt 10a, the rotary 90 assumes the cyan developing position, and a cyan toner image is formed on the intermediate transfer belt 10a. After the cyan toner image is formed on the intermediate transfer belt 10a, the rotary 90 assumes the black developing position, and a black toner image is formed on the intermediate transfer belt 10a. In this way, the primary transfer is repeated so that the four color toner images are superimposed on the intermediate transfer belt 10a, and a multi-toner image corresponding to the desired color image is formed on the intermediate transfer belt 10a.

[0031] When a monochrome image (black single-color image) is formed on the sheet S, the rotary 90 takes the black developing position. In this state, an electrostatic latent image is formed on the surface of the photosensitive drum 2 by charging and exposing the photosensitive drum 2, and then the electrostatic latent image is developed with black toner by the black developing unit 50k located at the developing position. The subsequent process is the same as when a color image is formed on the sheet S.

[0032] Meanwhile, sheets S are fed from a sheet storage unit 300 provided at the bottom of the apparatus main body 1A by a pickup roller 310. The sheets S are separated into individual sheets by a feed roller 311 and a separation roller 312 and then fed to a pair of conveying rollers 320. The pair of conveying rollers 320 sends the fed sheets S to the secondary transfer unit N2 in synchronization with the toner images on the intermediate transfer belt 10a.

[0033] At the secondary transfer portion N2, the toner image formed on the surface of the intermediate transfer belt 10a is transferred (secondary transfer) by the action of the secondary transfer roller 12 onto the surface of the sheet S, which is being conveyed while being sandwiched between the intermediate transfer belt 10a and the secondary transfer roller 12. During the secondary transfer, a secondary transfer voltage (secondary transfer bias) of a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the secondary transfer roller 12.

[0034] The sheet S onto which the toner image has been transferred is sent to the fixing device 40. The fixing device 40 applies heat and pressure to the sheet S carrying the unfixed toner image, thereby fixing (melting and adhering) the toner image to the sheet S. The sheet S that has passed through the fixing device 40 is discharged (output) as a finished product to a sheet discharge section 14 provided on the outside (top) of the apparatus main body 1A.

[0035] As described above, the toner cartridges 70y, 70m, 70c, and 70k are detachable from the rotary 90. When the toner in the toner cartridge 70y, 70m, 70c, or 70m falls below a predetermined amount (typically when it is substantially empty), an operator such as a user can replace the toner cartridge 70y, 70m, 70c, or 70k. This allows toner to be replenished in the image forming apparatus 1 (the corresponding developing units 50y, 50m, 50c, and 50k).

[0036] 3.Developing unit Next, the developing unit 50 of this embodiment will be described. Figure 2 is a schematic cross-sectional view of the developing unit 50 of this embodiment. Figure 2 shows a cross section of the developing unit 50 at the development position, taken approximately perpendicular to the rotation axis 51C of the developing roller 51. Note that Figure 2 also shows the photosensitive drum 2 and the toner cartridge 70, but toner is not shown in Figure 2.

[0037] The developing unit 50 has a developing frame 53 as a frame of the developing unit 50, a developing roller 51, a supply roller 52, and a developing blade 54. The developing frame 53 may be separate from the rotary 90 and attached to the rotary 90, or may be formed integrally with the rotary 90.

[0038] <Developing roller> The developing roller 51 is a multilayer roller with a conductive elastic layer consisting of a base layer and a surface layer disposed around a core metal made of metal such as aluminum, its alloy, or stainless steel. The base layer of the elastic layer is formed of rubber such as butadiene acrylonitrile rubber (NBR), ethylene-propylene-diene polyethylene (EPDM), silicone rubber, or urethane rubber. The surface layer of the elastic layer is formed of ether urethane or nylon. However, the materials for the elastic layer are not limited to these. For example, a structure in which the base layer is formed of a foam such as sponge and a rubber elastic layer is formed as the surface layer may be used. Alternatively, the elastic layer may have a single-layer structure consisting solely of a rubber elastic layer such as NBR, EPDM, or urethane rubber. In this embodiment, the developing roller 51 is configured with a conductive elastic layer disposed around a core metal with an outer diameter of 6 mm, resulting in an outer diameter of 10 mm.

[0039] The developing roller 51 is rotatably supported by the developing frame 53. When the rotary 90 is in the developing posture, the developing roller 51 of the developing unit 50 at the developing position is driven to rotate in the direction of arrow R3 in the figure (clockwise direction) by a driving force transmitted from a motor (not shown) which is a driving source constituting the developing drive means. Furthermore, when the developing unit 50 is at the developing position, the developing roller 51 of the developing unit 50 comes into contact with the photosensitive drum 2 to form a developing portion (developing nip portion) N3 which is a contact portion (nip portion) between the photosensitive drum 2 and the developing roller 51. That is, in this embodiment, the developing roller 51 is driven to rotate so that the surface of the photosensitive drum 2 and the surface of the developing roller 51 move forward in the developing portion N3.

[0040] The developing roller 51 is provided with penetration amount regulating rollers (not shown) at both ends in the direction of its rotation axis (longitudinal direction). The developing unit 50 is configured so that the penetration amount of the developing roller 51 into the surface of the photosensitive drum 2 becomes a predetermined value by bringing these rollers at both ends into contact with the photosensitive drum 2.

[0041] During development, a predetermined development voltage (development bias) having the same polarity as the normal charging polarity of the toner is applied to the development roller 51 via the core metal by a development power supply (not shown) as a development voltage application means.

[0042] <Developing blade> The developing blade 54 is supported by a pressure plate 541 serving as a support member, and the pressure plate 54 is fixed to the developing frame 53. The developing blade 54 is a plate-like member having a predetermined thickness and a predetermined length in both a longitudinal direction substantially parallel to the rotation axis 51C of the developing roller 51 and a lateral direction perpendicular to the longitudinal direction. The developing blade 54 has a fixed end, which is one end in the lateral direction, fixed to the developing frame 53 by the pressure plate 54. The developing blade 54 is disposed so as to abut against the surface (outer peripheral surface) of the developing roller 51 near the tip (side) of the free end, which is the other end in the lateral direction. Here, the portion of the developing roller 51 in the circumferential direction where the developing blade 54 abuts (the abutment portion between the developing roller 51 and the developing blade 54) is referred to as a "regulating portion Q." At the regulating portion Q, the developing blade 54 regulates the thickness (amount of toner) of the toner layer on the developing roller 51 and imparts an electric charge to the toner by rubbing. The regulating portion Q is located downstream of a supply portion N4 (described later) and upstream of a developing portion N3 in the rotation direction of the developing roller 51. In this embodiment, the regulating portion Q is located below a rotation axis 51C of the developing roller 51 in the cross section shown in FIG.

[0043] The developing blade 54 is made of a thin metal plate having spring elasticity, such as a thin stainless steel plate or a thin phosphor bronze plate, and is brought into contact with the surface of the developing roller 51 with a predetermined linear pressure (contact pressure per predetermined length in the direction of the rotation axis of the developing roller 51).

[0044] During development, a blade voltage (blade bias) is applied to the developing blade 54 via the presser plate 541 by a blade power supply (not shown) as a blade voltage application means so that a predetermined potential difference is achieved between the developing blade 54 and the potential of the developing roller 51. When the toner is negatively charged toner (toner whose normal charging polarity is negative), the blade voltage is set so that the potential of the developing blade 54 (blade voltage) is higher on the negative polarity side than the potential of the developing roller 51 (developing voltage). This makes it easier to impart a negative charge to the toner.

[0045] In this embodiment, the developing blade 54 is made of a 0.1 mm thick stainless steel thin plate having spring elasticity. In this embodiment, a blade voltage of −200 V with respect to the potential of the developing roller 51 is applied to the developing blade 54.

[0046] As another example of the developing blade 54, the following configuration may be used. For example, an elastic member made of polyamide elastomer or the like is attached to the tip of a spring-elastic thin metal plate in the short direction by adhesive or injection molding. Then, the elastic member side of the thin metal plate in the short direction is brought into contact with the surface of the developing roller 51 with a predetermined linear pressure.

[0047] <Toner> In this embodiment, the developer used is a toner having an average particle size of 6 μm and a normal negative charge polarity. In this embodiment, the toner is, for example, a polymerized toner produced by a polymerization method. In this embodiment, the toner is a so-called non-magnetic single-component developer that does not contain a magnetic component and is supported on the developing roller 51 mainly by intermolecular forces and electrostatic forces (image forces). However, a single-component developer containing a magnetic component may also be used. In addition to toner particles, a single-component developer may also contain additives (e.g., wax or silica particles) to adjust the fluidity and charging performance of the toner. Alternatively, a two-component developer containing a non-magnetic toner and a magnetic carrier may also be used. When a magnetic developer is used, a cylindrical developing sleeve with a magnet disposed inside is used as the developer carrier.

[0048] <Circumferential speed of developing roller> The toner layer formed by the toner carried on the developing roller 51 is regulated to a desired thickness by the contact pressure of the developing blade 54. When developing the electrostatic latent image on the photosensitive drum 2, the peripheral speed (surface speed) of the developing roller 51 can be set to a speed different from that of the photosensitive drum 2 in order to obtain an appropriate image density. The peripheral speed ratio, which is the ratio of the peripheral speed of the developing roller 51 to that of the photosensitive drum 2, is preferably in the range where the peripheral speed of the developing roller 51 is 0.5 to 3.0 times the peripheral speed of the photosensitive drum 2. Note that the symbol "to" used in the numerical range indicates that the range includes the numerical values ​​before and after it. In this embodiment, the peripheral speed ratio was set so that the peripheral speed of the developing roller 51 was 1.5 times the peripheral speed of the photosensitive drum 2.

[0049] <Supply roller> The supply roller 52 contacts the surface of the developing roller 51 and supplies toner to the surface of the developing roller 51. It also scrapes off and collects toner (residual toner) remaining on the developing roller 51 that has not adhered to the photosensitive drum 2. The supply roller 52 preferably has the following configuration from the viewpoints of supplying toner to the developing roller 51 and scraping off residual toner from the developing roller 51. For example, the supply roller 52 may have a sponge structure in which a foamed elastic layer is formed around a core metal, or a fur brush structure in which fibers such as rayon or nylon are implanted around a core metal. The sponge structure using a foamed elastic material may be a closed-cell structure in which the internal cells are independent, or a continuous-cell structure in which the internal cells are interconnected. However, a continuous-cell structure is more preferable because it can store a larger amount of toner inside and therefore can supply toner more stably. In this embodiment, the supply roller 52 is a foam roller in which a foamed elastic layer is formed to a diameter of 11 mm around a metal core metal with an outer diameter of 5 mm. In this embodiment, an open-cell polyurethane foam having interconnected cells with diameters of 10 to 800 μm, in which a conductive agent such as carbon is dispersed to impart conductivity, is used as the foam elastic material constituting the supply roller 52. Thus, in this embodiment, the supply roller 52 has a foam (porous member) on its surface (outer circumferential surface).

[0050] The supply roller 52 is rotatably supported by the developing frame 53. When the rotary 90 is in the developing posture, the supply roller 52 of the developing unit 50 in the developing position is driven to rotate in the direction of arrow R4 (clockwise) in the figure by a driving force transmitted from a motor (not shown) which is a driving source constituting the developing drive means. The supply roller 52 also comes into contact with the developing roller 51 to form a supply portion (supply nip portion) N4, which is a contact portion (nip portion) between the developing roller 51 and the supply roller 52. That is, in this embodiment, the supply roller 52 is driven to rotate so that the surface of the developing roller 51 and the surface of the supply roller 52 move in opposite directions (counter directions) in the supply portion N4.

[0051] <Supply Roller Peripheral Speed ​​and Potential> In this embodiment, the peripheral speed (surface speed) of the supply roller 52 was set to 75% of the peripheral speed (surface speed) of the developing roller 51. However, this is not limited to this, and the ratio of the peripheral speed of the supply roller 52 to the peripheral speed of the developing roller 51 can be set appropriately from the viewpoints of supplying toner to the developing roller 51 and stripping off residual toner from the developing roller 51. Here, the penetration amount of the supply roller 52 into the surface of the developing roller 51 is preferably in the range of 0.1 to 1.5 mm from the viewpoints of supplying toner to the developing roller 51 and stripping off residual toner from the developing roller 51. In this embodiment, the penetration amount of the supply roller 52 into the surface of the developing roller 51 was set to 1.0 mm. The penetration amount of the supply roller 52 into the surface of the developing roller 51 (I in FIG. 2) is represented by the maximum amount by which the supply roller 52 is pressed by the developing roller 51 in the radial direction of the rotation of the supply roller 52.

[0052] During development, a supply voltage (supply bias) is applied to the supply roller 52 via the core metal by a supply power source (not shown) as a supply voltage application means so that a predetermined potential difference is established between the supply roller 52 and the potential of the developing roller 51. When the toner is negatively charged toner, the supply voltage is set so that the potential of the supply roller 52 (supply voltage) is negatively higher than the potential of the developing roller 51 (developing voltage). This creates an electric field between the developing roller 51 and the supply roller 52 in a direction that supplies negatively charged toner from the supply roller 52 side to the developing roller 51 side. In this embodiment, a supply voltage of -200 V relative to the potential of the developing roller 51 is applied to the supply roller 52.

[0053] The rotation axis 2C of the photosensitive drum 2, the rotation axis 51C of the developing roller 51, and the rotation axis 52C of the supply roller 52 are generally parallel to one another and also to the rotation axis 90C of the rotary 90.

[0054] <Developing frame> 3 is a schematic cross-sectional view of the developing unit 50 to explain the developing frame 53 in the developing unit 50 of this embodiment. Fig. 3 shows a cross section of the developing unit 50 at the development position, which is approximately perpendicular to the rotation axis 51C of the developing roller 51. Note that toner is not shown in Fig. 3.

[0055] As shown in FIG. 3, the developing frame 53 defines a developing chamber 53a capable of accommodating toner. In this embodiment, the developing chamber 53a is separated into a first region 53a1 and a second region 53a2 by a partition wall W, which is a wall formed as part of the developing frame 53. The partition wall W is provided over the entire longitudinal length of the developing chamber 53a, which is generally parallel to the rotational axis 51C of the developing roller 51. The first region 53a1 and the second region 53a2 are connected by a connecting portion (connecting region) 53a3 (described later), and the connecting portion 53a3 allows the first region 53a1 and the second region 53a2 to communicate with each other so that toner can move between them. The first region 53a1 can be said to be a region of the developing chamber 53a that includes the developing roller 51 and the supply roller 52. The second region 53a2 can be said to be a region of the developing chamber 53a that does not include the developing roller 51 and the supply roller 52. When the developing roller 51 is disposed at the development position, it supplies the toner contained in the first region 53a1 to the photosensitive drum 2. When the developing roller 51 is disposed at the development position, the supply roller 52 supplies the toner contained in the first region 53a1 to the developing roller 51.

[0056] The developing chamber 53a (developing frame 53) has a developing opening 53c in an area facing the photosensitive drum 2 in the cross section shown in FIG. 3, and the developing roller 51 is arranged so that a portion of the developing opening 53c is exposed to the outside of the developing chamber 53a (developing frame 53). In the cross section shown in FIG. 3, the rotation axis 52C of the supply roller 52 is located on the opposite side of the photosensitive drum 2 with respect to a vertical line G1 passing through the rotation axis 51C of the developing roller 51. In this embodiment, the rotation axis 51C of the developing roller 51 and the rotation axis 52C of the supply roller 52 are located at approximately the same height in the vertical direction in the cross section shown in FIG. 3. However, this is not limited to this, and the rotation axis 52C of the supply roller 52 may be located above or below the rotation axis 51C of the developing roller 51 in the vertical direction in the cross section shown in FIG. 3.

[0057] In the cross section shown in FIG. 3, a horizontal line H2 passing through the apex P1 (the highest point in the vertical direction) of the partition W intersects with the inner wall surface 53d of the developing frame 53 on the opposite side of the developing roller 51 with respect to a vertical line G2 passing through the rotational axis 52C of the supply roller 52. In this case, the first region 53a1 and the second region 53a2 are connected by a line segment P1P4. That is, this line segment P1P4 corresponds to a connecting portion 53a3 between the first region 53a1 and the second region 53a2. In this embodiment, in the cross section shown in FIG. 3, the connecting portion 53a3 is located on the opposite side of the developing roller 51 with respect to the vertical line G2 passing through the rotational axis 52C of the supply roller 52. In this embodiment, the connecting portion 53a3 is formed by the apex P1 of the partition W and the inner wall surface 53d. The toner in the developing chamber 53a can move from the first region 53a1 to the second region 53a2 and from the second region 53a2 to the first region 53a1 by the rotation of the rotary 90 in the direction of the arrow R2 in FIG.

[0058] The connecting portion 53a3 can be said to be a space connecting the first region 53a1 and the second region 53a2. Alternatively, the connecting portion 53a3 can be said to be a boundary between the first region 53a1 and the second region 53a2. The connecting portion (space) 53a3 includes an opening defined by one end of the partition wall W and the developing frame 53. Toner in the first region 53a1 can pass through the opening defined by one end of the partition wall W and the developing frame 53 and move to the second region 53a. Toner in the second region 53a can pass through the opening defined by one end of the partition wall W and the developing frame 53 and move to the first region 53a1.

[0059] <Bulkhead> FIG. 4 is a schematic cross-sectional view of the developing unit 50 to explain the position of the partition wall W in the developing unit 50 of this embodiment. FIG. 4 shows a cross section of the developing unit 50 at the development position, which is approximately perpendicular to the rotation axis 51C of the developing roller 51. Note that FIG. 4 also shows the photosensitive drum 2 and the toner cartridge 70. In FIG. 4, "new toner" is indicated by a white circle (◯), and "deteriorated toner" is indicated by a black circle (●). Details of "new toner" and "deteriorated toner" will be described later.

[0060] 4, the height of the toner surface in the first region 53a1 is determined by the apex P1 of the partition W, and is approximately the position of a horizontal line H2 passing through this apex P1. In the cross section shown in FIG. 4, it is desirable that the apex P1 of the partition W be located vertically above the apex P2 of the developing roller 51 and the apex P3 of the supply roller 52.

[0061] FIG. 5 is a diagram similar to FIG. 4 but illustrating a developing unit 50 in which the position of the apex P1 of the partition W is different from that of FIG. 4. If, as shown in FIG. 5, the apex P1 of the partition W is positioned vertically lower than the apex P2 of the developing roller 51 and the apex P3 of the supply roller 52, the height of the toner surface in the first region 53a1 will be approximately the position of a line H1 passing through the apex P2 of the developing roller 51 and the apex P3 of the supply roller 52. In this case, for example, if monochrome continuous printing without rotation of the rotary 90 is performed with a high print coverage, the following situation may occur. That is, if the toner accumulated in the region V1 near the downstream side of the supply unit N4 in the rotation direction of the supply roller 52 (the direction of the arrow R4 in the figure) shown in FIG. 2 is consumed, it may become impossible to supply a sufficient amount of toner to the developing roller 51, resulting in blank areas in the image. More specifically, the supply section downstream area V1 is an area surrounded by the developing roller 51, the supply roller 52, and the line H1.

[0062] 2 to 4, the developing unit 50 in this embodiment is configured so that the apex P1 of the partition W is positioned vertically above the apex P2 of the developing roller 51 and the apex P3 of the supply roller 52. This increases the number of prints that can be made before blank areas appear in the image.

[0063] 2, the partition wall W is formed so as to extend from a position below the developing roller 51 adjacent to the developing opening 53c to a position below the supply roller 52 and to an apex P1 along the outer peripheral surface of the supply roller 52. In the cross section shown in FIG. 2, the connecting portion 53a3 opens from the lower second region 53a2 toward the upper first region 53a1.

[0064] <Toner supply port location> 2, the developing frame 53 is provided with a receiving opening 53b for receiving toner into the developing chamber 53a. The toner cartridge 70 is also provided with a discharge opening 71b for discharging toner from the toner storage portion (storage chamber) 71a at a position corresponding to the receiving opening 53b of the developing frame 53 when the toner cartridge 70 is attached to the rotary 90 via the tray 80. The developing chamber 53a of the developing frame 53 (developing unit 50) and the toner storage portion 71a of the toner cartridge 70 are in communication with each other via the receiving opening 53b of the developing frame 53 and the discharge opening 71b of the toner cartridge 70.

[0065] In this embodiment, the receiving opening 53b is located within the first region 53a1 of the developing chamber 53a. That is, when the developing roller 51 is located at the development position, the receiving opening 53b and the discharge opening 71b are located vertically above a horizontal line passing through the apex of the partition wall W. In this embodiment, in the cross section shown in FIG. 2, the receiving opening 53b is located on the opposite side of the developing roller 51 from a vertical line passing through the supply portion N4. In particular, in this embodiment, the receiving opening 53b is located on the opposite side of the developing roller 51 from a vertical line G2 passing through the rotation axis 52C of the supply roller 52. As will be described in more detail later, new toner is replenished into the developing chamber 53a through the receiving opening 53b, as shown in FIG. 4.

[0066] <Check valve> As shown in FIG. 2, the developing frame 53 is provided with a check valve 55 as a backflow prevention means to prevent toner from flowing back from the developing chamber 53a to the toner storage portion 71a. In this embodiment, the check valve 55 is configured as a door-like structure that is capable of opening and closing the receiving opening 53b provided in the developing chamber 53a. The check valve 55 includes a door portion 56 made of a Mylar sheet and a weight 57. In the cross section shown in FIG. 2, a fixed end portion, which is one upper end of the door portion 56, is fixed to the inner wall surface 53d of the developing frame 53 located above the receiving opening 53b. In this embodiment, the door portion 56 is fixed to the inner wall surface 53d of the frame 53 with double-sided tape as a fixing means. However, this is not limited to this, and the door portion 56 can be fixed to the developing frame 53 by any fixing means, such as adhesive, welding, or fastening. In the cross section shown in FIG. 2, the other end portion on the lower side of the door portion 56 is a free end portion, and a weight 57 is attached to this free end portion of the door portion 56 .

[0067] The check valve 55 moves by gravity as the rotary 90 rotates in the direction of arrow R2 in Figure 1, opening and closing the receiving opening 53b. As will be described in detail later, the check valve 55 is closed when the developing unit 50 is in positions (1) to (2) in Figure 7 and (7) to (10) in Figure 8, and is open when the developing unit 50 is in positions (3) to (6) in Figure 7 and (11) to (14) in Figure 8. Closing the check valve 55 suppresses (almost stops) the movement of toner from the toner storage section 71a into the developing chamber 53a.

[0068] <Mechanism of removal, supply and circulation> 2, in this embodiment, the supply roller 52 abuts against the developing roller 51 with a predetermined intrusion amount at the supply portion N4, which is the abutment portion (nip portion) between the developing roller 51 and the supply roller 52. Therefore, the cells of the foamed elastic layer of the supply roller 52 are in contact with the developing roller 51 in a collapsed state (compressed state) at the supply portion N4.

[0069] As the supply roller 52 rotates, the cells of the supply roller 52 are released from their collapsed state downstream of the supply unit N4 in the rotation direction (the direction of the arrow R4 in the figure) of the supply roller 52. Then, the supply roller 52 takes in the toner in the supply unit downstream region V1 into its cells, and scrapes and collects the toner on the developing roller 51 with the cell walls.

[0070] Furthermore, upstream of the supply section N4 in the rotation direction of the supply roller 52, the cells of the supply roller 52 collapse, causing the toner in the cells of the supply roller 52 to be discharged and supplied onto the developing roller 51. Thereafter, the developing blade 54 imparts a charge to the toner on the developing roller 51, and the thickness of the toner layer on the developing roller 51 (the amount of toner supplied) is regulated.

[0071] At this time, the toner in a region V2 near the upstream side of the supply unit N4 in the rotation direction of the supply roller 52 (hereinafter also referred to as the "supply unit upstream region") moves as follows: The toner is pushed out by the toner discharged from the supply roller 52 and moves through the gap between the supply roller 52 and the partition wall W in the direction opposite to the rotation direction of the supply roller 52, as indicated by arrow R6 in the figure. The toner that has moved in the direction of arrow R6 in the figure circulates to the supply unit downstream region V1 and is again taken into the cells of the supply roller 52. More specifically, the supply unit upstream region V2 is the region surrounded by the developing roller 51, the supply roller 52, and a line passing through the lowest points of the developing roller 51 and the supply roller 52.

[0072] In this way, the toner contained in the first region 53a1 of the developing chamber 53a circulates in the direction of the arrow R6 in the figure, which is opposite to the rotation direction of the supply roller 52.

[0073] 4.Preventing overfilling <Second area> One of the features of the image forming apparatus 1 of this embodiment is that the developing chamber 53a is provided with a second region 53a2. As will be described in detail later, the presence of the second region 53a2 allows new toner and degraded toner to be uniformly mixed before being supplied onto the developing roller 51. As a result, it is possible to suppress replenishment fogging, which occurs when new toner takes charge from degraded toner.

[0074] <Supply Cover> Here, replenishment fogging will be explained using a comparative example. FIG. 6 is a schematic cross-sectional view of a developing unit 50 of the comparative example. FIG. 6 shows a cross section of the developing unit 50 of the comparative example at the development position, taken approximately perpendicular to the rotation axis 51C of the developing roller 51. Note that FIG. 6 also shows the photosensitive drum 2 and toner cartridge 70. In FIG. 6, "new toner" is indicated by a white circle (◯), and "deteriorated toner" is indicated by a black circle (●). In addition, in the comparative example, elements having the same or corresponding functions or configurations as those in this embodiment will be described using the same reference numerals.

[0075] Unlike the developing unit 50 of this embodiment, the developing unit 50 of the comparative example does not have a partition wall W separating the areas of the developing chamber 53a, and the developing chamber 53a consists of a single area including the developing roller 51 and the supply roller 52. The other points of the developing unit 50 of the comparative example are substantially the same as those of the developing unit 50 of this embodiment.

[0076] In the comparative example of the developing unit 50, new toner stored in the toner storage section 71a is discharged from the discharge opening 71b, and the toner discharged from this discharge opening 71b moves directly into the developing chamber 53a, which consists of a single area, through the receiving opening 53b.

[0077] The toner carried by the developing roller 51 is subjected to mechanical stress as it rubs against the developing blade 54, the photosensitive drum 2, the supply roller 52, and the like. This causes external additives to be removed from the toner particle surface and the toner particles to become deformed, making the toner less likely to be charged to the correct polarity. Toner in this state is called "degraded toner." On the other hand, the toner contained in the toner storage section 71a, which has not been subjected to the above-mentioned rubbing and is more likely to be charged to the correct polarity than the degraded toner, is called "new toner." When these two different toner states are mixed, the new toner, which is more likely to be charged to the correct polarity, takes charge from the degraded toner, tending to significantly reduce the charge of the degraded toner.

[0078] In the comparative example of the developing unit 50, the area where new toner is replenished is the same as the area where the developing roller 51 and the supply roller 52 are located. Therefore, when new toner is replenished near the supply roller 52 in the developing chamber 53a through the receiving opening 53b, the toner near the surface of the supply roller 52 circulates in the direction of rotation of the supply roller 52 (the direction of arrow R4 in the figure). This causes the new toner to move upstream of the supply portion N4 in the direction of rotation of the supply roller 52. When the new toner that has moved upstream of the supply portion N4 in the direction of rotation of the supply roller 52 rubs against the degraded toner in that area, the degraded toner with a significantly low charge is more likely to be supplied to the developing roller 51. As a result, the developing blade 54 cannot fully replenish the charge, and toner adheres to areas of the surface of the photosensitive drum 2 where no electrostatic latent image is formed (non-image forming areas), resulting in an image defect known as "fogging." This type of image defect is called "supply fogging."

[0079] <Replenishment fogging suppression mechanism> Next, the mechanism for suppressing replenishment fogging in the developing unit 50 of this embodiment (the toner mixing mechanism) will be described. Figures 7 and 8 are schematic cross-sectional views of a rotary developing device 91 (showing a cross section substantially perpendicular to the rotation axis 90C of the rotary 90) to explain the mechanism for toner mixing in the developing unit 50 as the rotary 90 rotates. Note that, for ease of understanding, only one developing unit 80 and its corresponding toner cartridge 70 are shown in Figures 7 and 8. Also, in Figures 7 and 8, "new toner" is indicated by a white circle (◯), and "deteriorated toner" is indicated by a black circle (●).

[0080] 7(1) shows a state in which the rotary 90 is in an "exchange position" in which the toner cartridge 70 can be replaced (detached), and one of the developing units 50 shown is in an "exchange position" in which the toner cartridge 70 can be replaced (detached). In the state of FIG. 7(1), the check valve 55 is closed.

[0081] The rotary 90 assumes the development posture whenever it rotates in the direction of the arrow R2 in the drawing by an angle that is an even multiple of approximately 45° from the state in which it is in the development posture (approximately every 90° rotation). Also, the rotary 90 assumes the replacement posture whenever it rotates in the direction of the arrow R2 in the drawing by an odd multiple of approximately 45° from the state in which it is in the development posture (approximately every 90° rotation in the direction of the arrow R2 in the drawing from the state in which it is in the replacement posture).

[0082] As shown in FIG. 7(1), when the rotary 90 is in the replacement position, the toner cartridge 70 corresponding to the developing unit 50 in the replacement position is slid outward in the radial direction of rotation of the rotary 90, as indicated by arrow S1 in the figure. This allows the toner cartridge 70 to be removed from the apparatus main body 1A (rotary 90). Meanwhile, as shown in FIG. 7(1)-2, when the rotary 90 is in the replacement position, the toner cartridge 70 corresponding to the developing unit 50 in the replacement position is slid inward in the radial direction of rotation of the rotary 90, as indicated by arrow S2 in the figure. This allows the toner cartridge 70, typically a new (brand new) toner cartridge 70, to be installed in the apparatus main body 1A (rotary 90). The toner cartridge 70 may be slid (removed) by an operator's operation, or the image forming apparatus 1 may be provided with a mechanism for sliding (removing) the toner cartridge 70. Such a mechanism may be configured to operate based on an instruction or operation from the operator.

[0083] Figure 7 (2) shows a state in which the rotary 90 has rotated approximately 45° in the direction of arrow R2 from the state shown in Figure 7 (1). Figures 7 (3) to (6) and Figure 8 (7) to (14) similarly show states in which the rotary 90 has rotated approximately 45° from the previous state.

[0084] In the state of FIG. 7(2), the check valve 55 is closed, so that new toner does not move from the toner storage portion 71a into the developing frame 53, and toner does not move in the opposite direction.

[0085] In the state of FIG. 7(3), the check valve 55 begins to open, and the toner begins to move from the toner storage portion 71a to the developing frame 53.

[0086] In the state of FIG. 7(4), the check valve 55 opens, and new toner moves from the toner storage section 71a to the first region 53a1.

[0087] In the state of FIG. 7(5), new toner further moves from the toner storage section 71a to the first region 53a1.

[0088] 7(6) shows a state in which one of the developing units 50 shown in the figure is in the developing position similar to that shown in FIGS. 2 and 4, and the rotary 90 is in the developing posture. In this state, the developing roller 51 and the supply roller 52 rotate, so that toner is supplied to the developing roller 51, and an image forming operation (developing operation) is performed.

[0089] In the state of (6) in FIG. 7, toner located vertically above the horizontal line H2 passing through the vertex P1 of the partition wall W shown in FIG. 4 spills from the first region 53a1 to the second region 53a2. As a result, most of the new toner supplied to the first region 53a1 spills into the second region 53a2, and almost no new toner remains in the first region 53a1. As a result, new toner is taken into the cells of the supply roller 52 in the supply section downstream region V1 shown in FIG. 2, moves in the rotation direction of the supply roller 52 (the direction of arrow R4 in the figure), and then is prevented from moving to the supply section upstream region V2 shown in FIG. 2. This prevents supply fogging from occurring.

[0090] 7(6), in the second region 53a2, the deteriorated toner and the new toner are mixed and rubbed together, so that the charge of the deteriorated toner, from which the external additives have been removed or embedded, is significantly taken away by the new toner, which has a large amount of external additives attached. In this way, as the rotary 90 rotates, the toner contained in the toner cartridge 70 and the toner contained in the first region 53a1 move to the second region 53a2 and are mixed.

[0091] In the state of (7) in FIG. 8, toner moves from the first region 53a1 to the second region 53a2. Also, the check valve 55 closes. Then, in the second region 53a2, the degraded toner that has lost a significant amount of charge in the state of (6) in FIG. 7 and the normal degraded toner that has moved from the first region 53a1 to the second region 53a2 in the state of (7) in FIG. 8 are mixed and rubbed. As a result, the toner that has lost a significant amount of charge takes back charge from the normal degraded toner, and its charge is restored. Note that "normal degraded toner" is degraded toner whose charge has not been significantly taken away by new toner.

[0092] 8 (8) to (11), the toner mixed in the second region 53a2 returns from the second region 53a2 to the first region 53a1, and the toner is mixed in. This further restores the charge of the deteriorated toner that has lost a significant amount of charge.

[0093] 8, the toner is further mixed in the first region 53a1, which further restores the charge of the toner that has lost a significant amount of charge.

[0094] Here, the check valve 55 begins to open in the state shown in FIG. 8 (11), and is open in the states shown in FIG. 8 (12) and (13). Therefore, in the states shown in FIG. 8 (12) and (13), new toner moves from the toner storage section 71a to the first region 53a1. However, this new toner moving into the first region 53a1 is blocked by other toner in the first region 53a1. In other words, the toner moving from the toner cartridge 70 to the developing chamber 53a is prevented from remaining in the first region 53a1 by the toner that has moved from the second region 53a2 to the first region 53a1 as the rotary 90 rotates, and is instead able to move to the second region 53a2. As a result, after the new toner is taken into the cells of the supply roller 52 in the supply section downstream region V1 shown in FIG. 2 and moves in the rotation direction of the supply roller 52 (the direction of arrow R4 in the figure), it is prevented from moving to the supply section upstream region V2 shown in FIG. 2. Therefore, the occurrence of replenishment fogging can be suppressed.

[0095] The state (14) in FIG. 8 is a state in which the rotary 90 has made one rotation from the state (6) in FIG. 7 and is in the developing position. In this state, the developing roller 51 and the supply roller 52 rotate, supplying toner to the developing roller 51 and performing the image forming operation (developing operation). As described above, the toner is sufficiently mixed in the first region 53a1 and the charge is averaged, so there is almost no toner that has lost a significant amount of charge. Therefore, it is possible to prevent the occurrence of replenishment fogging, as in the developing unit 50 of the comparative example described above.

[0096] Thus, in this embodiment, the image forming apparatus 1 is provided with an image carrier (photosensitive drum) 2 on which an electrostatic image is formed, a developing chamber 53a that contains toner, and a developing member (developing roller) 51 that supplies the toner contained in the developing chamber 53a to the image carrier 2 to develop the electrostatic image, a rotatable rotary 90 that moves the developing member 51 to a development position where toner is supplied to the image carrier 2, and a toner cartridge 70 that contains toner to be replenished to the developing chamber 53a and is detachably attached to the rotary 90, and the receiving opening 53b provided in the developing chamber 53a and the discharge opening 71b provided in the toner cartridge 70 are connected to each other, so that toner is replenished from the toner cartridge 70 to the developing chamber 53a. In this embodiment, the developing chamber 53a includes a partition wall W that separates the developing chamber 53a into a first region 53a1 including the developing member 51 and a second region 53a2. As the rotary 90 rotates, the toner contained in the toner cartridge 70 and the toner contained in the first region 53a1 move to the second region 53a2 and are mixed therewith. In this embodiment, when the developing member 51 is disposed at the developing position, the receiving opening 53b and the discharging opening 71b are positioned vertically above a horizontal line passing through the apex of the partition wall W. In this embodiment, the toner moving from the toner cartridge 70 to the developing chamber 53a is prevented from remaining in the first region 53a1 by the toner that has moved from the second region 53a2 to the first region 53a1 as the rotary 90 rotates, and can instead move to the second region 53a2. In this embodiment, when the developing member 51 is disposed at the developing position, the apex of the partition W is located vertically above the apex of the developing member 51. In this embodiment, the rotary 90 is provided with a supply member (supply roller) 52 that supplies the toner contained in the first region 53a1 to the developing member 51 when the developing member 51 is disposed at the developing position. In this embodiment, when the developing member 51 is disposed at the developing position, the apex of the partition W is located vertically above the apex of the developing member 51 and the apex of the supply member 52.

[0097] As described above, in this embodiment, the image forming apparatus 1 has the partition wall W that separates the first area 53a1 and the second area 53a2 of the developing chamber 53a. This makes it possible to suppress the occurrence of replenishment fogging.

[0098] [Example 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted.

[0099] 1. Overview of this Example Figure 10 is a schematic cross-sectional view of the developing unit 50 of this embodiment. Figure 10 shows a cross section of the developing unit 50 at the development position, taken approximately perpendicular to the rotation axis 51C of the developing roller 51. Figure 10 also shows the photosensitive drum 2 and the toner cartridge 70. In Figure 10, "new toner" is indicated by a white circle (◯), and "deteriorated toner" is indicated by a black circle (●).

[0100] In this embodiment, the receiving opening 53b is located in the second region 53a2 of the developing chamber 53a. In addition, in this embodiment, the discharge opening 71b of the toner cartridge 70 is provided at a position corresponding to this receiving opening 53b. In other words, when the developing roller 51 is located at the developing position, the receiving opening 53b and the discharge opening 71b are located vertically below a horizontal line passing through the apex of the partition wall W. As such, this embodiment differs from the first embodiment in that the receiving opening 53b is provided at a position where new toner can be directly replenished from the toner storage section 71a to the second region 53a2.

[0101] In the configuration of the first embodiment, when new toner is supplied into the developing chamber 53a through the receiving opening 53b, if the toner surface in the first region 53a1 reaches the position of the horizontal line H2 passing through the apex P1 of the partition wall W as shown in Figure 4, the following occurs: In other words, as the rotary 90 rotates, the new toner basically spills into the second region 53a2 and does not remain in the first region 53a1.

[0102] In contrast, FIG. 9 is a schematic cross-sectional view of the developing unit 50 of Example 1, similar to FIG. 4, showing a different state of the toner surface. As shown in FIG. 9, when the toner surface in the first region 53a1 does not reach the horizontal line H2 passing through the apex P1 of the partition wall W (is below the horizontal line H2), the following situation may occur. That is, new toner remains in the first region 53a1 and is taken into the cells of the supply roller 52 in the supply unit downstream region V1 shown in FIG. 2. The new toner then moves in the rotation direction of the supply roller 52 (the direction of arrow R4 in the figure), is expelled in the supply unit upstream region V2 shown in FIG. 2, and is supplied to the developing roller 51. This may result in supply fogging.

[0103] In this embodiment, the possibility of this supply fogging is reduced by providing the receiving opening 53b at a position where new toner is directly supplied from the toner storage section 71a to the second region 53a2. In other words, by locating the receiving opening 53b in such a position, supply fogging can be suppressed by the toner mixing mechanism described below, even if the toner level in the first region 53a1 does not reach the horizontal line H2 as shown in FIG.

[0104] 2. Mechanism for suppressing replenishment Next, a description will be given of the mechanism for suppressing replenishment fogging (the mechanism for mixing toner) in the developing unit 50 of this embodiment. Figures 11 and 12 are schematic cross-sectional views of a rotary developing device 91 similar to those in Figures 7 and 8, for explaining the mechanism for mixing toner in the developing unit 50 as the rotary 90 rotates.

[0105] FIG. 11(1) shows a state in which the rotary 90 is in a replacement position in which the toner cartridge 70 can be replaced, and one of the illustrated developing units 50 is in a replacement position in which the toner cartridge 70 can be replaced. In the state of FIG. 11(1), the check valve 55 is closed. As shown in FIG. 11(1), when the rotary 90 is in the replacement position, the toner cartridge 70 corresponding to the developing unit 50 in the replacement position is slid in the direction of arrow S1 in the figure. This allows the toner cartridge 70 to be removed from the device main body 1A (rotary 90). On the other hand, as shown in FIG. 11(1)-2, when the rotary 90 is in the replacement position, the toner cartridge 70 corresponding to the developing unit 50 in the replacement position is slid in the direction of arrow S2 in the figure. This allows the toner cartridge 70, typically a new (brand new) toner cartridge 70, to be installed in the device main body 1A (rotary 90).

[0106] Figure 11 (2) shows a state in which the rotary 90 has rotated approximately 45° in the direction of arrow R2 from the state shown in Figure 11 (1). Similarly, Figures 11 (3) to (6) and Figure 12 (7) to (14) also show states in which the rotary 90 has rotated approximately 45° from the previous state.

[0107] In the state of FIG. 11(2), the check valve 55 is closed, so that new toner does not move from the toner storage portion 71a into the developing frame 53, and toner does not move in the opposite direction.

[0108] 11(3), the check valve 55 begins to open, and the toner begins to move from the toner storage portion 71a to the developing frame 53. In the state shown in FIG.

[0109] In the state shown in FIG. 11(4), the check valve 55 opens, and new toner moves from the toner storage section 71a to the second region 53a2. In this embodiment, the new toner is guided by the check valve 55 and enters the second region 53a2. In addition, in this embodiment, the check valve 55 restricts the movement of new toner to the first region 53a1. That is, in this embodiment, in the state shown in FIG. 11(4) (and in FIG. 11(5) described later), the weight 57 at the free end of the check valve 55 abuts against the side surface W1 (FIG. 9) of the partition W facing the second region 53a2. In this manner, in this embodiment, the check valve 55 functions both as a guide member that guides the movement of new toner from the toner storage section 71a to the second region 53a2 and as a restricting member that restricts the movement of new toner from the second region 53a2 to the first region 53a1. In this manner, in this embodiment, the toner moving from the toner cartridge 70 to the developing chamber 53a can move directly to the second region 53a2 without passing through the first region 53a1.

[0110] In the state (5) of FIG. 11, new toner further moves from the toner storage section 71a to the second region 53a2.

[0111] 11 (6) is a state in which one of the developing units 50 shown in the figure is in the developing position of the rotary 90, which is in the same developing position as in FIG. 10. In this state, the developing roller 51 and the supply roller 52 rotate, supplying toner to the developing roller 51, and an image forming operation (developing operation) is performed.

[0112] In the state shown in FIG. 11(6), the degraded toner located vertically above the horizontal line H2 (see FIG. 4) passing through the vertex P1 of the partition wall W spills from the first region 53a1 into the second region 53a2. As a result, the degraded toner and the new toner are mixed and rubbed together in the second region 53a2, and the charge of the degraded toner, from which the external additives have been removed or embedded, is significantly taken away by the new toner, which has a large amount of external additives attached. In this way, as the rotary 90 rotates, the toner contained in the toner cartridge 70 and the toner contained in the first region 53a1 move to the second region 53a2 and are mixed there.

[0113] 11(6), since almost no new toner is present in the first region 53a1, the occurrence of replenishment fogging can be suppressed. Also, since the check valve 55 is open in the state of FIG. 11(6), new toner further moves from the toner storage section 71a to the second region 53a2.

[0114] In the state of (7) in FIG. 12, the degraded toner further moves from the first region 53a1 to the second region 53a2. The check valve 55 also closes. Then, in the second region 53a2, the degraded toner that has significantly lost its charge in the state of (6) in FIG. 11 and the normal degraded toner that has moved from the first region 53a1 to the second region 53a2 in the state of (7) in FIG. 12 are mixed and rubbed together. As a result, the toner that has significantly lost its charge takes back charge from the normal degraded toner, restoring its charge.

[0115] 12 (8) to (11), the toner mixed in the second region 53a2 returns from the second region 53a2 to the first region 53a1, and the toner is mixed therein. This further restores the charge of the toner that has lost a significant amount of charge.

[0116] In the states (12) and (13) of FIG. 12, more toner is mixed in the first region 53a1. This further restores the charge of the toner that has lost a significant amount of charge. Here, the check valve 55 begins to open in the state (11) of FIG. 12, and is open in the states (12) and (13) of FIG. 12. Therefore, in the states (12) and (13) of FIG. 12, new toner moves from the toner storage section 71a to the second region 53a2.

[0117] (14) in Figure 12 shows the state in which the rotary 90 has made one rotation from the state in (6) in Figure 11 and is in the developing position. In this state, the developing roller 51 and the supply roller 52 rotate, supplying toner to the developing roller 51 and performing the image forming operation (developing operation). As described above, the toner is sufficiently mixed in the first region 53a1 and the charge is averaged, so there is almost no toner that has lost a significant amount of charge. Therefore, it is possible to prevent the occurrence of replenishment fogging, as in the developing unit 50 of the comparative example described above.

[0118] Thus, in this embodiment, when the developing member 51 is disposed at the developing position, the receiving opening 53b and the discharge opening 71b are located vertically below a horizontal line passing through the apex of the partition wall W. In this embodiment, toner moving from the toner cartridge 70 to the developing chamber 53a can move directly to the second region 53a2 without passing through the first region 53a1. In this embodiment, a guide member 55 is provided in the developing chamber 53a to guide the movement of toner from the toner cartridge 70 to the second region 53a2. In this embodiment, this guide member 55 is configured as a check valve that opens and closes the receiving opening 53b in accordance with the rotation of the rotary 90.

[0119] As described above, in this embodiment, the receiving opening 53b is disposed in the second region 53a2. As a result, even when the toner level in the first region 53a1 is low, the occurrence of replenishment fogging can be more stably suppressed compared to the first embodiment.

[0120] [others] Although the present invention has been specifically described above with reference to the examples, the present invention is not limited to the above examples.

[0121] In the above-described embodiment, the rotary development posture is the posture shown in (6) of Figure 7 and (6) of Figure 11. However, the present invention is not limited to this, and even if the rotary development posture is another posture, the mechanism for sufficiently mixing the toner before it is supplied onto the developer carrier (developing roller) will work in the same way.

[0122] In the above-described embodiment, the development unit is provided with a check valve. However, the present invention is not limited to this, and even in a configuration in which a check valve is not provided, the mechanism for sufficiently mixing the toner before it is supplied to the developer carrier (developing roller) works in the same way.

[0123] In the above-described embodiment, the developer carrier (developing roller) and the supply member (supply roller) are provided in the first region. However, the present invention is not limited to this, and even if the supply member (supply roller) is not provided in the first region, the mechanism of sufficiently mixing the toner before it is supplied to the developer carrier (developing roller) works in the same way.

[0124] In the above embodiment, the toner in the developing chamber is moved by the rotation of the rotary. However, a toner transport member (which may also function as an agitator) for transporting the toner may be provided in the developing chamber. FIG. 13(a) is a schematic cross-sectional view of a developing unit 50 showing an example in which a transport member is provided in the developing chamber 53a, and FIG. 13(b) is a schematic front view of the inner wall surface 53d of the developing chamber. For example, as shown in FIG. 13(b), the receiving opening 53b may be positioned at a position offset, such as toward the end, in the longitudinal direction of the developing chamber 53a. In such a case, for example, a transport member 58 may be provided in the first region 53a1, and a transport member 59 may be provided in the second region 53a2, in order to even out the toner in the longitudinal direction of the developing chamber 53a. Either one of these may be provided, or both may be provided. Examples of the transport member include a screw and an auger. Also, for example, a device having a rotatable shaft member and a sheet-like conveying section (agitating section) attached to the shaft member may be used. [Explanation of symbols]

[0125] 1. Image forming device 50 Development unit 51 Developing roller 52 Supply roller 53 Developing frame 53a Developing chamber 53a1 1st area 53a2 2nd area 53b Receiving opening 55 Check valve 70 Toner Cartridges 71a Toner storage section 71b Discharge opening 90 Rotary (rotary body) 91 Rotary developing device

Claims

1. an image carrier on which an electrostatic image is formed; a developing chamber that accommodates toner, and a developing member that supplies the toner accommodated in the developing chamber to the image carrier to develop the electrostatic image, and a rotatable rotary that moves the developing member to a developing position where the toner is supplied to the image carrier; a toner cartridge that contains toner to be replenished to the developing chamber and is detachably attached to the rotary; and an image forming apparatus in which a receiving opening provided in the developing chamber and a discharge opening provided in the toner cartridge are communicated with each other, and toner is replenished from the toner cartridge to the developing chamber; the developing chamber includes a partition wall that separates the developing chamber into a first region including the developing member and a second region; an image forming apparatus, characterized in that, by rotation of the rotary, the toner contained in the toner cartridge and the toner contained in the first area move to the second area and are mixed;

2. 2. The image forming apparatus according to claim 1, wherein, when the developing member is disposed at the developing position, the receiving opening and the discharge opening are positioned above a horizontal line passing through the apex of the partition wall in the vertical direction.

3. The image forming apparatus described in claim 2, characterized in that the toner moving from the toner cartridge to the developing chamber is prevented from remaining in the first area by toner that moves from the second area to the first area as the rotary rotates, and is therefore able to move to the second area.

4. 2. The image forming apparatus according to claim 1, wherein, when the developing member is disposed at the developing position, the receiving opening and the discharge opening are positioned below a horizontal line passing through the apex of the partition wall in the vertical direction.

5. 5. The image forming apparatus according to claim 4, wherein the toner moving from the toner cartridge to the developing chamber can move directly to the second region without passing through the first region.

6. 5. The image forming apparatus according to claim 4, wherein a guide member is provided in the developing chamber to guide the movement of the toner from the toner cartridge to the second region.

7. 7. The image forming apparatus according to claim 6, wherein the guide member is formed of a check valve that opens and closes the receiving opening in accordance with the rotation of the rotary.

8. 8. The image forming apparatus according to claim 1, wherein, when the developing member is disposed at the developing position, the apex of the partition wall is positioned higher than the apex of the developing member in the vertical direction.

9. An image forming apparatus according to any one of claims 1 to 7, characterized in that the rotary is provided with a supply member that supplies toner contained in the first region to the developing member when the developing member is positioned at the developing position.

10. 10. The image forming apparatus according to claim 9, wherein, when the developing member is disposed at the developing position, the apex of the partition wall is positioned higher than the apex of the developing member and the apex of the supply member in the vertical direction.

11. 8. The image forming apparatus according to claim 1, wherein the rotary has a transport member that transports the toner contained in the developing chamber.

Images