JP2012189843A - Image forming unit and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming unit and an image forming device which can obtain sufficient image density.SOLUTION: A process unit 11 as an image forming unit includes: a photosensitive drum 14; a developing roller 16 for supplying a developer to the photosensitive drum 14; first and second supplying rollers 17 and 18, respectively, for supplying the developer to the developing roller 16; and a transfer belt unit for carrying a recording medium along a predetermined carrying surface CP so that the recording medium contacts with the photosensitive drum 14. The first supplying roller 17 is disposed on the side closer to the carrying surface CP in a direction orthogonal to the carrying surface CP, as compared with the second supplying roller 18. The supplying rollers 17 and 18 are disposed so as to make a tangent line A of a circumference of the first supplying roller 17 on a side separated from the developing roller 16 in the direction orthogonal to the carrying surface CP have a longer distance from the developing roller 16 within a surface parallel with the carrying surface CP, than a tangent line B of a circumference of the second carrying roller 18 on a side separated from the developing roller 16 in the same direction.

Description

  The present invention relates to an image forming apparatus such as a printer or a copier using an electrophotographic system, and an image forming unit thereof.

  In an image forming apparatus using electrophotography, the surface of an image carrier (photosensitive drum) uniformly charged by a charging device is exposed by an exposure device to form an electrostatic latent image and statically developed by a developing device. The electrostatic latent image is developed to form a developer image (toner image) and transferred to a recording medium. The developing device causes the developer to adhere to the surface of the image carrier on which the electrostatic latent image is formed, by a developer carrier (developing roller) disposed opposite to the image carrier.

  In recent years, in order to suppress fluctuations in image density, there has been proposed a developing device that supplies a sufficient amount of developer to the developer carrier by providing two supply rollers so as to be in contact with the surface of the developer carrier. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 10-39628 (refer to claim 1, FIG. 1)

  However, in the conventional developing device, when a sufficient amount of developer is not supplied from the developer container (toner cartridge) to each supply roller, the density of the image is lowered and good image quality cannot be obtained. there were.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming unit and an image forming apparatus that can obtain a sufficient image density.

  An image forming unit according to the present invention includes an image carrier, a developer carrier that supplies a developer to the image carrier, a first developer supply member that supplies a developer to the developer carrier, and a developer. A second developer supply member for supplying a developer to the carrier and a medium are conveyed along a predetermined conveyance surface so as to be in contact with the image carrier, and the developer image carried on the image carrier is a medium. And the first developer supply member is disposed closer to the conveyance surface in the direction orthogonal to the conveyance surface than the second developer supply member, and the first developer supply member The tangent line in the direction perpendicular to the transport surface of the outer periphery on the side away from the developer carrier in FIG. 2 is transported more than the tangent line in the same direction on the outer periphery on the side away from the developer carrier in the second developer supply member. The first and the first so that the distance from the developer carrier in the plane parallel to the plane is increased. Wherein the second developer supplying member is disposed.

  The image forming unit according to the present invention also includes an image carrier, a developer carrier that supplies the developer to the image carrier, a first developer supply member that supplies the developer to the developer carrier, A second developer supply member for supplying the developer to the developer carrying member, and a developer image carried on the image carrier by conveying the medium along a predetermined conveying surface so as to be in contact with the image carrier; With respect to the medium, the developer carrying member, the first developer supply member, and the second developer. And a partition wall for distributing the developer in the storage chamber to the toner supplied to the first developer supply member and the toner supplied to the second developer supply member. To do.

  In addition, an image forming apparatus according to the present invention includes the above-described image forming unit.

  According to the present invention, in the image forming unit, the developer moving in a direction orthogonal to the transport surface (for example, the vertical direction) is the surface (outer periphery) of the first developer supply member and the second developer supply member. Therefore, a sufficient amount of developer is supplied from each developer supply member to the developer carrier. As a result, a sufficient image density can be obtained.

1 is a side view showing a basic configuration of an image forming apparatus according to a first embodiment of the present invention. It is sectional drawing which shows the process cartridge in the 1st Embodiment of this invention. It is a schematic diagram for demonstrating the measuring method of the pressing amount of the supply roller to the developing roller. 2 is a block diagram illustrating a control system of the image forming apparatus according to the first embodiment of the present invention. FIG. FIG. 3 is a schematic diagram illustrating a toner flow in a process cartridge according to the first embodiment of the present invention. It is a figure which shows the 1st comparative example (A) and 2nd comparative example (B) with respect to the process cartridge of the 1st Embodiment of this invention. 7 is a graph showing a change in toner supply amount to the developing roller when the peripheral speed ratio of the supplying roller to the developing roller is changed. It is sectional drawing which shows the other structural example of the process cartridge in the 1st Embodiment of this invention. It is sectional drawing which shows the 1st modification of the process cartridge of the 1st Embodiment of this invention. It is sectional drawing which shows the 2nd modification of the process cartridge of the 1st Embodiment of this invention. It is sectional drawing which shows the 3rd modification of the process cartridge of the 1st Embodiment of this invention. It is sectional drawing which shows the process cartridge of the 2nd Embodiment of this invention.

  FIG. 1 is a diagram showing a basic configuration of an image forming apparatus 10 according to the first embodiment of the present invention. The image forming apparatus 10 is, for example, a color electrophotographic printer, and includes process cartridges 11a, 11b, 11c, and 11d as four image forming units that form black, yellow, magenta, and cyan images. The process cartridges 11a, 11b, 11c, and 11d are arranged in a line in order from the upstream side (from right to left in FIG. 1) along the conveyance path 21 of the recording medium 20.

  The process cartridges 11a to 11d have a common configuration except for the toner (developer) to be used, and all have a photosensitive drum 14 as an image carrier that rotates in one direction (clockwise in FIG. 1). is doing. Details of the process cartridges 11a to 11d will be described later. Above each of the process cartridges 11a to 11d, an LED (Light Emitting Diode) head 13 as an exposure apparatus is disposed. The LED head 13 exposes the surface of each photosensitive drum 14 of the process cartridges 11a to 11d to form an electrostatic latent image.

  The process cartridges 11a to 11d are equipped with a detachable toner cartridge 12 as a developer container that contains toner of each color. The toner cartridges 12 have a common configuration, and supply toner to the process cartridges 11a to 11d.

  In the lower part of the image forming apparatus 10, a paper feed cassette 31 for storing and storing recording media 20 (for example, printing paper), and a hopping roller 32 for separating and feeding the stacked recording media 20 one by one. Are arranged. The hopping roller 32 rotates to feed the recording medium 20 to the transport path 21 one by one. In the transport path 21, a pair of transport rollers 33 and 34 that correct the skew of the recording medium 20 and transport it to the process cartridges 11 a to 11 d are arranged.

  Under the process cartridges 11a to 11d, a transfer belt unit 35 (that is, the medium) is transported as a transfer unit that transports the recording medium 20 and transfers the toner image formed on each photosensitive drum 14 to the recording medium 20. Means for conveying and transferring the developer image onto the medium are disposed. The transfer belt unit 35 includes a transfer belt 36 that sucks and holds the recording medium 20 and conveys the recording medium 20 along the process cartridges 11a to 11d. The transfer belt 36 is stretched over the driving roller 36a and the driven roller 36b, and moves by the rotation of the driving roller 36a. Further, four transfer rollers 37 are arranged so as to sandwich the transfer belt 36 between the respective photosensitive drums 14. The transfer roller 37 is applied with a voltage for forming an electric field with the opposing photosensitive drum 14, and the toner image formed on each photosensitive drum 14 is transferred to the recording medium 20 by this voltage. Is done.

  Here, the transfer belt unit 35 (conveyance transfer means) conveys the recording medium 20 along the horizontal plane (conveying surface CP shown in FIG. 2) so as to pass through the process cartridges 11a to 11d. The conveyance surface CP on which the recording medium 20 is conveyed is not limited to a horizontal plane, and may be an inclined surface.

  A fixing device 41 is disposed on the downstream side of the process cartridges 11 a to 11 d in the conveyance direction of the recording medium 20. The fixing device 41 includes a heating roller 41a and a backup roller 41b, and fixes the toner image transferred to the recording medium 20 to the recording medium 20 by applying heat and pressure. Disposed on the downstream side of the fixing device 41 in the conveyance direction of the recording medium 20 is a pair of discharge rollers 42 and 43 for discharging the recording medium 20 discharged from the fixing device 41 through the conveyance path 21. A stacker 44 for loading the discharged recording medium 20 is provided on the upper part of the image forming apparatus 10.

  Next, the configuration of the process cartridges 11a to 11d will be described in detail. Since the process cartridges 11a to 11d have a common configuration except for the toner to be used, the process cartridges 11a to 11d are collectively referred to as “process cartridge 11”.

  FIG. 2 is a cross-sectional view showing the configuration of the process cartridge 11. The process cartridge 11 includes a charging roller 15 as a charging member for uniformly charging the surface of the photosensitive drum 14 around the photosensitive drum 14 and a photosensitive member (formed by exposure of the LED head 13). A developing roller 16 as a developer carrier for developing the electrostatic latent image on the surface of the drum 14 with toner, supply rollers 17 and 18 as developer supply members for supplying toner to the developing roller 16, And a regulating blade 19 as a developer regulating member that regulates the thickness of the toner layer formed on the surface.

  The photosensitive drum 14 is obtained by forming a photoconductive layer on the surface of a drum-shaped conductor made of, for example, aluminum. The photosensitive drum 14 has a drive gear at its shaft end, and is driven to rotate clockwise in FIG. The charging roller 15 is obtained by coating the surface of a metal shaft with a conductive elastic body such as epichlorohydrin, and is disposed so as to contact the surface of the photosensitive drum 14. The charging roller 15 rotates following the rotation of the photosensitive drum 14, and a high voltage (charging voltage) is applied simultaneously with the start of rotation to uniformly charge the surface of the photosensitive drum 14.

  The developing roller 16 has a metal shaft 16A covered with a conductive elastic body such as urethane. The developing roller 16 is disposed so as to contact the surface of the photosensitive drum 14 on the downstream side of the LED head 13 in the rotation direction of the photosensitive drum 14. The developing roller 16 includes a gear at the end of the shaft 16 </ b> A, and rotates in a direction opposite to the rotation direction of the photosensitive drum 14 by driving transmission from the photosensitive drum 14. Further, a high voltage is applied to the developing roller 16 at the same time as the rotation starts, and an electric field is formed between the developing roller 16 and the surface of the photosensitive drum 14, and toner is applied to the electrostatic latent image on the surface of the photosensitive drum 14 by this electric field. Adhere.

  The supply rollers 17 and 18 are formed by coating the surface of the metal shafts 17 </ b> A and 18 </ b> A with a foaming elastic body such as silicon and are in contact with the developing roller 16. The supply rollers 17 and 18 have gears at the ends of the shafts 17A and 18A, respectively, and rotate in the same direction as the rotation direction of the developing roller 16 by drive transmission from the photosensitive drum 14. The supply rollers 17 and 18 are in sliding contact with the developing roller 16 to frictionally charge the toner, and supply the toner to the developing roller 16.

  In the following description, of the two supply rollers 17 and 18, the supply roller 17 that contacts the development roller 16 on the upstream side in the rotation direction of the development roller 16 is referred to as a “first supply roller 17” (first developer supply member). ). The supply roller 18 that contacts the developing roller 16 downstream of the first supply roller 17 is referred to as a “second supply roller 18” (second developer supply member). The second supply roller 18 is located between the first supply roller 17 and the regulating blade 19 in the rotation direction of the developing roller 16. Further, the first supply roller 17 is positioned below the second supply roller 18 in the vertical direction.

  Although the supply rollers 17 and 18 are in contact with the developing roller 16 here, for example, when a sufficient amount of toner can be supplied to the developing roller 16 by electrostatic force or the like, the supply rollers 17 and 18 are supplied. May be separated from the developing roller 16.

  The regulating blade 19 is an elastic blade made of, for example, a stainless steel thin plate, and has a shape that is long in the axial direction of the developing roller 16. One end of the regulating blade 19 in the width direction is fixed to a holder 56 attached in the frame 50 of the process unit 11, and the other end is pressed against the surface of the developing roller 16. The regulating blade 19 regulates the thickness of the toner layer adhering to the surface of the developing roller 16 and thins the toner while frictionally charging the toner.

  The cleaning blade 51 is an elastic blade made of urethane, for example, and has a shape that is long in the axial direction of the photosensitive drum 14. One end of the cleaning blade 51 in the width direction is pressed against the surface of the photosensitive drum 14 and scrapes off the toner remaining on the surface of the photosensitive drum 14 after the transfer of the toner image. Below the cleaning blade 51, a collected toner transport spiral 52 that transports the toner scraped off by the cleaning blade 51 to the outside of the process cartridge 11 is provided.

  The toner cartridge 12 detachably attached to the process cartridge 11 is a developer container that contains toner to be replenished to the process cartridge 11, has a toner supply port 12 </ b> A at its bottom, and further opens and closes the toner supply port 12 </ b> A. A shutter 53 is provided.

  The frame 50 of the process cartridge 11 is a housing that houses the developing roller 16, the supply rollers 17 and 18, and the regulating blade 19. A cartridge mounting portion 50A to which the process cartridge 11 is mounted is formed on the upper side of the frame 50. A toner supply port 54 corresponding to the toner supply port 12A of the toner cartridge 12 is formed in the cartridge mounting portion 50A. ing. The toner replenished from the toner replenishing port 54 is held in a toner hopper (accommodating chamber) 55 which is an area surrounded by the developing roller 16, the first supply roller 17, the second supply roller 18, the regulating blade 19 and the frame 50. .

  The frame 50 also has an outer wall 57 extending in the Z direction (vertical direction). The toner supplied from the toner supply port 54 to the toner hopper 55 is generally along the outer wall 57 in the lower direction in the Z direction. Moving. Further, a wall portion 50 </ b> B having a shape along the outer periphery of the first supply roller 17 is formed below the outer wall 57 so as to face the first supply roller 17. With this configuration, the toner stored in the lower region of the toner hopper 55 is likely to adhere to the rotating first supply roller 17.

  When the toner cartridge 12 is attached to the process cartridge 11 and the toner supply port 12A is opened by the shutter 53 of the toner cartridge 12, the toner contained in the toner cartridge 12 is supplied into the process cartridge 11 from the toner supply port 54. The toner is stored in the toner hopper 55. The toner accommodated in the toner hopper 55 is supplied to the developing roller 16 by the first supply roller 17 and the second supply roller 18, thinned by the regulating blade 19, and then transferred from the developing roller 16 to the photosensitive drum 14. The As a result, the electrostatic latent image formed on the surface of the photosensitive drum 14 is developed, and a toner image is formed.

  In this embodiment, in the process cartridge 11 configured as described above, the outer diameter (drum diameter) of the photosensitive drum 14 is 30 mm, the outer diameter (roller diameter) of the developing roller 16 is 20 mm, and the first supply roller 17 and the second supply roller 17 The outer diameter of each supply roller 18 is 15 mm.

  The first supply roller 17 and the second supply roller 18 are both arranged so that the amount of pressing into the developing roller 16 is 1 mm. Further, as described below, the first supply roller 17 and the second supply roller 18 are configured so that the outer periphery of the first supply roller 17 is the second supply roller 18 in a state where the process cartridge 11 is mounted on the image forming apparatus 10. It arrange | positions so that it may protrude outside (outer wall 57 side of the flame | frame 50) rather than outer periphery.

The pushing amount (N) of the first supply roller 17 into the developing roller 16 is, as schematically shown in FIG. 3, the outer diameter D1 of the developing roller 16, the outer diameter D2 of the first supply roller 17, and From the distance L between the axial center of the shaft 16A of the developing roller 16 and the axial center of the shaft 17A of the first supply roller 17, the following equation is obtained.
N = {(D1 + D2) / 2} -L
The amount by which the second supply roller 18 is pushed into the developing roller 16 is obtained in the same manner.

  With the process cartridge 11 of FIG. 2 mounted on the main body of the image forming apparatus 10, the axial direction of the photosensitive drum 14 (the axial direction of the developing roller 16) is defined as the X direction. Further, the transport direction (moving direction) when the recording medium 20 is transported while being in contact with the photosensitive drum 14 is defined as the Y direction. Therefore, the XY plane is parallel to the transport plane CP described above. A direction perpendicular to the XY plane is taken as a Z direction. Here, the XY plane is assumed to be a horizontal plane and the Z direction is assumed to be a vertical direction, but the present invention is not limited to these.

  In FIG. 2, a tangent line in the Z direction of the outer periphery of the first supply roller 17 on the side away from the developing roller 16 (that is, the side opposite to the contact portion with the developing roller 16) is defined as “tangent line A”. The tangent line B in the Z direction on the outer periphery of the second supply roller 18 on the side away from the developing roller 16 is referred to as “tangent line B”. In addition, a tangent line in the Z direction on the outer periphery of the developing roller 16 on the supply rollers 17 and 18 side is defined as a “tangent line R”.

  In the present embodiment, the tangent line A in the Z direction on the outer periphery of the first supply roller 17 on the side away from the developing roller 16 is the tangent line B in the Z direction on the outer periphery on the side of the second supply roller 18 away from the developing roller 16. The rollers 16, 17, and 18 are arranged so that the distance from the tangent line R in the Z direction on the outer periphery of the developing roller 16 becomes longer.

  In other words, the supply rollers 17 and 18 are such that the first supply roller 17 located on the lower side in the Z direction (the direction of toner movement due to gravity) is outside the second supply roller 18 located on the upper side (the developing roller 16). Of the outer periphery of the outer periphery of the outer periphery of the outer periphery of the outer periphery of the outer periphery of the outer periphery. In other words, the surface (outer periphery) of the first supply roller 17 is at a position where the toner moving (lowering) in the toner hopper 55 in the Z direction can easily reach.

  In this embodiment, since the outer diameters of the supply rollers 17 and 18 are the same, the distance from the contact point P between the outer periphery of the development roller 16 and the tangent line R to the contact portion between the development roller 16 and the first supply roller 17. However, the rollers 16, 17, and 18 are arranged so as to be shorter than the distance from the contact point P to the contact portion between the developing roller 16 and the second supply roller 18.

  With this arrangement, when the outer diameters of the supply rollers 17 and 18 are the same, it is possible to realize a configuration in which the first supply roller 17 projects outward from the second supply roller 18 as described above.

  It is to be noted that a straight line α and β in the Z direction passing through the shaft centers of the shafts 17A and 18A of the supply rollers 17 and 18 and a straight line γ in the Z direction passing through the shaft center of the shaft 16A of the developing roller 16 are defined as straight lines. The distance from γ to the straight line β is shorter than the distance from the straight line γ to the straight line α.

  The tangent line A of the first supply roller 17 and the tangent line B of the second supply roller 18 are located inside the toner supply port 54 (that is, between both ends of the toner supply port 54 in the Y direction) in the Y direction. Preferably it is. This is because the toner moving downward in the Z direction from the toner supply port 54 easily reaches the surface of the first supply roller 17 and the surface of the second supply roller 18.

  The rotation directions of the developing roller 16 and the supply rollers 17 and 18 are as follows. First, the rotation direction of the developing roller 16 is the counterclockwise direction in FIG. 2, that is, the direction opposite to the rotation direction of the photosensitive drum 14. Therefore, at the contact portion between the developing roller 16 and the photosensitive drum 14, the moving direction of the surface of the developing roller 16 is the forward direction (same direction) with respect to the moving direction of the surface (outer periphery) of the photosensitive drum 14. .

  The rotation direction of the supply rollers 17 and 18 is the counterclockwise direction in FIG. 2, that is, the same direction as the rotation direction of the developing roller 16. Therefore, at the contact portion between the first supply roller 17 and the developing roller 16, the front moving direction of the first supplying roller 17 is the counter direction (opposite direction) with respect to the moving direction of the surface of the developing roller 16. Similarly, at the contact portion between the second supply roller 18 and the developing roller 16, the moving direction of the surface of the second supplying roller 18 is the counter direction with respect to the moving direction of the surface of the developing roller 16. As a result, the toner adhering to the supply rollers 17 and 18 can be mechanically scraped to the developing roller 16 side, thereby preventing overcharging of the toner (due to the same toner remaining on the surfaces of the supply rollers 17 and 18). can do.

  Needless to say, the rotation direction of the supply rollers 17 and 18 is not limited to the above direction. It is sufficient that the toner can be effectively moved from the supply rollers 17 and 18 to the developing roller 16 side according to the characteristics of the toner and the supply rollers 17 and 18.

  Here, the peripheral speeds of the developing roller 16, the first supply roller 17, and the second supply roller 18 are, for example, 200 mm / second, 160 mm / second, and 160 mm / second, respectively. The applied voltages of the developing roller 16, the first supply roller 17, and the second supply roller 18 are, for example, −200V, −300V, and −300V, respectively.

  The relationship between the applied voltage of the developing roller 16 and the applied voltages of the supply rollers 17 and 18 is such that the frictionally charged toner is directed toward the developing roller 16 from the first supply roller 17 and the second supply roller 18 by electrostatic force. Any relationship that generates an electric field may be used. For example, when negatively chargeable toner is used and each applied voltage is a negative voltage, the absolute value of the applied voltage of each of the first supply roller 17 and the second supply roller 18 is equal to the applied voltage of the developing roller 16. It only needs to be larger than the absolute value. Further, the applied voltages of the first supply roller 17 and the second supply roller 18 may not be the same.

  Next, the control system of the image forming apparatus 10 will be described. FIG. 4 is a block diagram illustrating a control system of the image forming apparatus 10.

  As shown in FIG. 4, the recording control unit 80 provided in the image forming apparatus 10 applies a charging voltage control unit 81 that applies a charging voltage to the charging roller 15 of each process cartridge 11, and applies a developing voltage to the developing roller 16. A developing voltage control unit 82, a first supply voltage control unit 83 that applies a supply voltage to the first supply roller 17, a second supply voltage control unit 84 that applies a supply voltage to the second supply roller 18, and a regulating blade The control blade voltage control unit 85 that applies a control blade voltage to the transfer roller 37 and the transfer voltage control unit 86 that applies the transfer voltage to the transfer roller 37 are controlled.

  Further, the recording control unit 80 controls an LED light emission control unit 87 that causes the LED head 13 to emit light according to the input image data, and a fixing control unit 88 that controls the heater of the fixing device 41. Further, the recording control unit 80 includes a motor that rotates the photosensitive drum 14 of each process cartridge 11, a hopping roller 32 that feeds and conveys the recording medium 20, a pair of conveyance rollers 33 and 34, a pair of transfer rollers 37, and a pair of discharge rollers. The motor control unit 90 that controls driving of the motors that rotate the motors 42 and 43 is controlled.

  The recording control unit 80 is controlled by a controller 8 that controls the entire image forming apparatus 10.

Next, the operation of the image forming apparatus 10 will be described with reference to FIG. 1, FIG. 2, and FIG.
When the controller 8 of the image forming apparatus 10 receives image data transmitted from an external host device (for example, a personal computer), the image data is transmitted to the recording control unit 80 via an image processing circuit in the controller 8. . The recording control unit 80 rotates the hopping roller 32 and the conveyance roller pair 33 and 34 via the motor control unit 90 to start feeding and conveying the recording medium 20 and transmits image data to the LED light emission control unit 87. To do. Further, at the timing when the recording medium 20 reaches each process cartridge 11, a voltage is applied to the charging roller 15, the developing roller 16, the supply rollers 17 and 18, the regulating blade 19, and the transfer roller 37 by the voltage control units 81 to 86. Further, the LED light emission control unit 87 causes the LED head 13 to emit light according to the image data. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 14 of each process cartridge 11.

  In each process cartridge 11, as shown in FIG. 2, toner replenished from the toner cartridge 12 via the toner replenishing port 54 is accommodated in a hopper 55 in the frame 50, and the first supply roller 17 and the second supply roller 18 is supplied to the developing roller 16, thinned by the regulating blade 19, and then supplied to the photosensitive drum 14. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 14 is developed, and a toner image is formed.

  The toner image formed on the surface of the photosensitive drum 14 is transferred to the recording medium 20 on the transfer belt 36 due to the potential difference between the photosensitive drum 14 and the transfer roller 37 at the contact portion. As the recording medium 20 passes through the process cartridges 11a to 11d, four color toner images are transferred onto the recording medium 20.

  The recording medium 20 onto which the toner image has been transferred is conveyed to the fixing device 41 by the transfer belt 36. In the fixing device 41, the toner is melted and fixed on the recording medium 20 by heat and pressure. The recording medium 20 on which the toner image is fixed is discharged from the image forming apparatus 10 by the discharge roller 42 and placed on the stacker 43. Thereby, the image forming process for forming an image on the surface of the recording medium 20 is completed.

  FIG. 5 is a schematic diagram illustrating the flow of toner in the process cartridge 11 during, for example, continuous printing of solid images. The toner replenished from the toner cartridge 12 moves in the toner hopper 55 of the process cartridge 11 downward in the Z direction (vertically downward) along the outer wall 57 of the frame 50, and the first supply roller 17 and the second supply roller 18. It is deposited mainly in the upper region of the surface. At this time, the toner adhering to the region C on the surface of the first supply roller 17 reaches the region D which is a contact portion between the first supply roller 17 and the developing roller 16 by the rotation of the first supply roller 17.

  The toner that reaches the region D is charged by friction with the developing roller 16 and electrostatically adheres to the surface of the developing roller 16, and the developing roller 16 and the second supply roller 18 are rotated by the rotation of the developing roller 16. The region E that is the entrance portion of the contact portion is reached.

  Part of the toner that reaches the region E adheres to the surface of the second supply roller 18, and most of the toner is conveyed by the rotation of the second supply roller 18. On the other hand, the toner remaining on the developing roller 16 without adhering to the second supply roller 18 passes through a contact portion between the developing roller 16 and the second supply roller 18.

  In the region F that is the exit portion of the contact portion between the developing roller 16 and the second supply roller 18, the toner that has passed through the contact portion between the developing roller 16 and the second supply roller 18 and the first supply roller 17 to the developing roller 16. Then, the toner adhered to and conveyed by the second supply roller 18 and the toner replenished from the toner cartridge 12 and adhered to the region G on the upper side of the second supply roller 18 merge. The toner merged in the region F is further charged by friction with the developing roller 16 and electrostatically adheres to the developing roller 16 and reaches the region H that is a contact portion with the regulating blade 19.

  The toner that reaches the region H is frictionally charged by the developing roller 16 and the regulating blade 19, and further, after the thickness of the toner layer is regulated, the developing roller 16 rotates to rotate the developing roller 16 and the photosensitive drum 14. The region I that is the contact portion is reached. The toner that reaches the region I adheres to the photosensitive drum 14 having the electrostatic latent image formed on the surface, and develops the electrostatic latent image.

  When solid images are continuously printed, almost all of the toner on the developing roller 16 is consumed by developing the electrostatic latent image. In the present embodiment, the developing roller is driven by the first supply roller 17. Since a large amount of toner is sent to the contact portion (area E) between the first supply roller 18 and the second supply roller 18, the toner adhered to the developing roller 16 and conveyed and the toner adhered to the second supply roller 18 and conveyed The amount can be increased. Further, since the outer periphery of the first supply roller 17 protrudes outward from the outer periphery of the second supply roller 18, the toner that moves downward in the Z direction in the toner hopper 55 is transferred only by the upper second supply roller 18. The lower first supply roller 17 can be easily reached, and as a result, a larger amount of toner can be supplied from the supply rollers 17 and 18 to the developing roller 16.

  Next, experimental results using the process cartridge 11 of the present embodiment will be described. Here, the change in the toner supply amount when the peripheral speed ratio of the supply rollers 17 and 18 to the developing roller 16 was changed was measured.

  As a first comparative example for the process cartridge of the present embodiment, as shown in FIG. 6A, an experiment was conducted using a process cartridge having only one supply roller (here, the first supply roller 108). Went. The process cartridge shown in FIG. 6A is configured in the same manner as the process cartridge in this embodiment except that it has only one supply roller.

  As a second comparative example, an experiment was performed using a process cartridge shown in FIG. In the process cartridge shown in FIG. 6B, the outer periphery of the upper second supply roller 108 in the Z direction (vertical direction) of the two supply rollers 107 and 108 in contact with the developing roller 16 is arranged on the lower side. 1 Suppose that it protrudes outside the outer periphery of the supply roller 107 (the side far from the developing roller 16). Other configurations are the same as those of the process cartridge according to the present embodiment.

  FIG. 7 shows a change in toner supply amount when the peripheral speed ratio of the supply roller to the developing roller is changed in the range of 0.5 to 3.0. Here, after the solid image was continuously printed by the image forming apparatus 10 equipped with the process cartridge, the amount of toner adhered to the surface of the developing roller 16 was measured, and the value was used as the toner supply amount to the developing roller 16. In FIG. 7, the vertical axis represents the toner supply amount to the developing roller, and the horizontal axis represents the peripheral speed ratio of the supply roller to the developing roller. The peripheral speeds of the supply rollers 17 and 18 (supply rollers 107 and 108) are the same.

  In FIG. 7, the experimental result using the process cartridge 11 of the present embodiment is shown by a plot P1. Further, the experimental result using the process cartridge of the first comparative example (FIG. 6A) is shown by a plot P2, and the experimental result using the process cartridge of the second comparative example (FIG. 6B) is plotted. Indicated by P3.

  From FIG. 7, in the second comparative example (plot P3) in which two supply rollers are provided, the toner supply amount is larger than that in the first comparative example (plot P2) in which only one supply roller is provided. You can see that the minutes are relatively small. On the other hand, in the present embodiment (plot P1), a larger amount of toner supply is obtained than in the first and second comparative examples. For example, in the first comparative example (plot P2), the same toner supply amount as when the peripheral speed ratio of the supply roller to the developing roller is 3 times, and in this embodiment (plot P1), the circumference of the supply roller relative to the development roller is the same. This is achieved when the speed ratio is 0.8 times.

  In the present embodiment, such a result is obtained because the outer periphery of the first supply roller 17 disposed on the lower side in the Z direction (the toner movement direction) of the two supply rollers 17 and 18 is obtained. Since the upper second supply roller 18 protrudes outward from the outer periphery, the toner moving downward in the Z-direction in the toner hopper 55 is caused only by the upper second supply roller 18 as shown in FIG. This is considered to be because the toner could easily reach the lower first supply roller 17 and supply a sufficient amount of toner from the supply rollers 17 and 18 to the developing roller 16.

  As described above, in this embodiment, of the two supply rollers 17 and 18 that supply the developer to the developing roller 16, the outer periphery of the first supply roller 17 disposed on the lower side in the Z direction is By configuring so as to protrude outward from the outer periphery of the upper second supply roller 18, a sufficient amount of toner for continuously printing a solid image can be supplied to the developing roller 16. As a result, the image density can be stabilized and high image quality can be maintained.

  Further, since the peripheral speed ratio of the supply rollers 17 and 18 to the developing roller 16 can be set to 1 or less, the wear of the supply rollers 17 and 18 can be reduced and the life of the process cartridge 11 can be extended.

  Further, in the tandem type color printer in which the four process cartridges 11a to 11d are arranged and color printing is performed by one paper run, the configuration in which the toner cartridge 12 is mounted on the upper part of the process cartridges 11a to 11d is as described above. In addition, a sufficient amount of toner can be ensured, and a small color printer with high image quality can be realized.

  Although the case where the conveyance surface CP of the recording medium 20 is a horizontal plane has been described here, the conveyance surface CP may be inclined with respect to the horizontal plane as shown in FIG. In this case, the first supply roller 17 is disposed closer to the conveyance surface CP in the direction (Z direction) perpendicular to the conveyance surface CP than the second conveyance roller 18, and the development on the first supply roller 17 is performed. The tangent A in the Z direction on the outer periphery on the side away from the roller 16 is in a plane parallel to the transport surface CP (XY) than the tangent B in the Z direction on the outer periphery on the side away from the developing roller 16 in the second supply roller 18. The rollers 16, 17, and 18 may be arranged so that the distance from the developing roller 16 in the plane) becomes longer. Further, the toner hopper 55 may be located on the side away from the conveyance surface in the direction orthogonal to the conveyance surface CP.

  The reason for using the transport surface CP as a reference is as follows. The process cartridges 11a to 11d are generally designed such that the outer wall 57 of the frame 50 is orthogonal to the transport surface CP. Further, the moving direction of the toner in the toner hopper 55 is substantially parallel to the outer wall 57. Therefore, by arranging the first supply roller 17, the second supply roller 18 and the developing roller 16 as described above, a large amount of toner reaches not only the second supply roller 18 but also the surface of the first supply roller 17. Can be ensured, and the image density can be stabilized.

  In the process cartridge 11, an agitation roller for agitating the toner accommodated above the supply rollers 17 and 18 may be provided. Moreover, it is also possible to configure as in a modified example described below.

First modification.
FIG. 9 shows a process cartridge 11A according to a first modification of the present embodiment. The process cartridge 11A of the first modified example shown in FIG. 9 differs from the process cartridge 11 (FIG. 2) of the first embodiment described above in the outer diameter and arrangement of the supply rollers.

  In the first modification, the outer diameters of the first supply roller 27 and the second supply roller 28 are different from each other. Further, the contact portion M between the first supply roller 27 and the developing roller 16 and the contact portion N between the second supply roller 28 and the developing roller 16 include the contact portion N between the second supply roller 28 and the developing roller 16. This is closer to the contact portion P with the tangent line R in the Z direction on the outer periphery of the developing roller 16. Here, the outer diameter of the first supply roller 27 is 16 mm, and the outer diameter of the second supply roller 28 is 11 mm. The outer diameter of the developing roller 16 is 20 mm.

  Thus, with the process cartridge 11A mounted in the image forming apparatus 10, the tangent A in the Z direction on the outer periphery of the first supply roller 27 on the side away from the development roller 16 extends from the development roller 16 of the second supply roller 28. An arrangement is realized in which the distance from the tangent line R in the Z direction on the outer periphery of the developing roller 16 is longer than the tangent line B in the Z direction on the outer periphery on the far side.

  That is, of the supply rollers 27 and 28 that supply toner to the developing roller 16, the first supply roller 27 located on the lower side in the Z direction (toner movement direction) is more than the second supply roller 28 located on the upper side. The position protrudes outward, that is, the position where the toner moving downward in the Z direction in the toner hopper 55 easily reaches.

  Therefore, also in the first modification, sufficient toner for continuously printing solid images can be supplied to the developing roller 16, the image density can be stabilized, and the image quality can be maintained.

  Further, in the first modification, the outer diameters of the supply rollers 27 and 28 are different, and therefore, a straight line β in the Z direction passing through the center of the shaft 28A of the second supply roller 28 is changed to that of the shaft 27A of the first supply roller 27. It is not necessary to employ an arrangement (FIG. 2) in which the distance from the straight line γ in the Z direction passing through the center of the shaft 16A of the developing roller 16 is shorter than the straight line α in the Z direction passing through the center. Therefore, the arrangement of the supply rollers 27 and 28 can be set relatively freely.

Second modification.
FIG. 10 shows a process cartridge 11B according to a second modification of the present embodiment. The process cartridge 11B of the second modification shown in FIG. 10 is provided with a pair of roller pairs 101 and 102 instead of the first supply roller 17 of the process cartridge 11 (FIG. 2) of the first embodiment described above. Is.

  The first roller 101 of the roller pair 101, 102 is disposed so as to contact the surface (outer periphery) of the developing roller 16, and the second roller 102 is disposed so as to contact the surface of the first roller 101. The rotation directions of the roller pairs 101 and 102 are the same as those of the developing roller 16. Therefore, the moving directions of the surfaces of both rollers at the contact portion between the developing roller 16 and the first roller 101 are counter directions (opposite directions). Further, the moving directions of the surfaces of both rollers at the contact portion between the first roller 101 and the second roller 102 are counter to each other. The outer diameters of the first roller 101 and the second roller 102 may be the same or different.

  In the state where the process cartridge 11B is mounted on the image forming apparatus 10, the tangent line A in the Z direction on the outer side of the first roller 102 away from the developing roller 16 is separated from the developing roller 16 of the second supply roller 18. The rollers 16, 18, 101, 102 are arranged so that the distance from the tangent line R in the Z direction on the outer periphery of the developing roller 16 is longer than the tangent line B in the Z direction on the outer periphery on the side.

  That is, of the roller pair 101, 102 and the second supply roller 18, the second roller 102 of the roller pair 101, 102 located on the lower side in the Z direction (the direction of toner movement) is the second supply roller located on the upper side. 18 is a position protruding outward from 18, that is, a position where the toner moving downward in the Z direction in the toner hopper 55 easily reaches. Therefore, also in the second modified example, sufficient toner for continuously printing solid images can be supplied to the developing roller 16, and the image density can be stabilized and the image quality can be maintained.

Third modification.
FIG. 11 shows a process cartridge 11C according to a third modification of the present embodiment. A process cartridge 11C of the third modified example shown in FIG. 11 includes a pair of roller pairs 101 and 102 and an endless belt instead of the first supply roller 17 of the process cartridge 11 (FIG. 2) of the first embodiment described above. 103 is provided.

  Of the roller pairs 101 and 102, the first roller 101 is disposed to face the surface of the developing roller 16, and the second roller 102 is disposed in parallel with a certain distance from the first roller 101. The endless belt 103 spanned between the roller pair 101 and 102 is pressed against the surface of the developing roller 16 by the first roller 101. The rotation directions of the roller pairs 101 and 102 are the same, and the same as the rotation direction of the developing roller 16. The endless belt 103 moves around by the rotation of the pair of rollers 101 and 102.

  Further, in the state where the process cartridge 11C is mounted on the image forming apparatus 10, the Z-direction tangent A on the outer side of the second roller 102 away from the developing roller 16 is separated from the developing roller 16 of the second supply roller 18. The rollers 16, 18, 101, 102 are arranged so that the distance from the tangent line R in the Z direction on the outer periphery of the developing roller 16 is longer than the tangent line B on the outer periphery on the side.

  Also in the third modified example, as in the second modified example, the second roller 102 of the roller pair 101, 102 located on the lower side in the Z direction (toner movement direction) is the second supply located on the upper side. It is in a position protruding outward from the roller 18, that is, a position where the toner moving in the Z direction within the toner hopper 55 can easily reach. Therefore, also in the third modified example, sufficient toner for continuously printing solid images can be supplied to the developing roller 16, and the image density can be stabilized and the image quality can be maintained.

Second embodiment.
FIG. 12 is a sectional view showing a process cartridge 61 (image forming unit) according to the second embodiment of the present invention. The same components as those described in the first embodiment are denoted by the same reference numerals.

  The process cartridge 61 of the second embodiment has a partition wall 70 formed along the outer periphery of the second supply roller 68 on the side away from the developing roller 16 (the side opposite to the contact portion with the developing roller 16). It has. For example, the partition wall 70 is formed integrally with the frame 50 of the process cartridge 61.

  More specifically, the partition wall 70 includes a first wall portion 71 extending in the Z direction upward (on the toner cartridge 12 side) from substantially the same height as the shaft 68A of the second supply roller 68, and a second supply. A second wall 72 extending along the outer periphery of the second supply roller 68 is provided downward from substantially the same height as the shaft 68 </ b> A of the roller 68. The first wall 71 of the partition wall 70 is located substantially at the center in the Y direction of the toner supply port 54 formed in the frame 50. The second wall 72 reaches, for example, between the first supply roller 67 and the second supply roller 68.

  The partition wall 70 is supplied from the toner supply port 54 and moves to the lower side in the Z direction due to gravity. The partition wall 70 moves to the right side in the figure (the outer wall 57 side of the frame 50) and the left side in the figure (second supply roller). 68).

  Here, the outer diameter (drum diameter) of the photosensitive drum 14 is 30 mm, and the outer diameter (roller diameter) of the developing roller 16 is 20 mm. The outer diameters of the first supply roller 67 and the second supply roller 68 are both 13 mm, and the pushing amounts of the first supply roller 67 and the second supply roller 68 into the developing roller 16 are both 1 mm. The method for measuring the push-in amount is as described with reference to FIG.

  Further, the peripheral speed of each of the supply rollers 17 and 18 is set smaller than the peripheral speed of the developing roller 16 as described in the first embodiment. Specific examples of applied voltages and peripheral speeds of the developing roller 16 and the supply rollers 17 and 18 are as described in the first embodiment. In addition, as described in the first embodiment, it is preferable that the lower wall portion 50B of the frame 50 has a shape along the outer peripheral surface of the first supply roller 67.

  The flow of toner in the process cartridge 61 of the second embodiment is as follows.

  The toner replenished from the toner cartridge 12 via the toner replenishing port 54 moves in the toner hopper 55 downward in the Z direction, and moves to the outer wall 57 side (right side in the figure) of the frame 50 by the partition wall 70. The toner is distributed to the toner moving to the middle left side (second supply roller 68 side).

  The toner distributed to the outer wall 57 side of the frame 50 is accommodated in a region P surrounded by the outer periphery of the first supply roller 17, the outer wall 57 of the frame 50, and the partition wall 70. The toner that has reached the surface (outer periphery) of the first supply roller 67 in the region P reaches the contact portion with the developing roller 16 by the rotation of the first supply roller 67, and is charged and developed by friction with the developing roller 16. The roller 16 electrostatically adheres to the surface of the roller 16 and reaches the contact portion between the developing roller 16 and the second supply roller 68 by the rotation of the developing roller 16.

  Part of the toner that has reached the contact portion between the developing roller 16 and the second supply roller 68 adheres to the second supply roller 68, and most of the toner adheres to the surface of the second supply roller 68. It is conveyed by the rotation of the roller 68. The toner remaining on the developing roller 16 without adhering to the second supply roller 68 passes through a contact portion between the developing roller 16 and the second supply roller 68.

  Further, the toner distributed to the second supply roller 68 side (left side in the drawing) of the partition wall 70 is accommodated in a region Q surrounded by the outer periphery of the second supply roller 18, the regulation blade 19, and the partition wall 70. . The toner that has reached the surface of the second supply roller 68 in the region Q is mixed with the toner that has been attached to the second supply roller 68 and conveyed from the first supply roller 67 via the developing roller 16, and is supplied to the second supply roller 68. The toner reaches the exit portion of the contact portion between the developing roller 16 and the developing roller 16 and merges with the toner passing through the contact portion between the developing roller 16 and the second supply roller 68. The toner is further charged by friction with the developing roller 16 and electrostatically adheres to the developing roller 16, and is conveyed to a contact portion with the regulating blade 19 by the rotation of the developing roller 16.

  The toner that has reached the contact portion between the developing roller 19 and the regulating blade 19 is frictionally charged by contact with the regulating blade 19, and after the thickness of the toner layer is made uniform, the developing roller 16 is rotated by the rotation of the developing roller 16. And the photosensitive drum 14 are conveyed to the contact portion. The toner reaching the contact portion between the developing roller 16 and the photosensitive drum 14 adheres to the photosensitive drum 14 on which the electrostatic latent image is formed, and develops the electrostatic latent image.

  As described above, in the second embodiment of the present invention, the partition wall 70 is provided in the toner hopper 55, and the toner replenished from the toner replenishing port 54 is disposed on the first supply roller 67 side and the second supply roller 68 side. It is configured to distribute. Therefore, even when the amount of toner around the first supply roller 67 disposed on the lower side is reduced, the periphery of the second supply roller 68 disposed on the upper side (that is, the partition with the second supply roller 68 is separated). Since the toner is accommodated in the space surrounded by the wall 70 and the regulation blade 19, a sufficient amount of toner can be supplied to the developing roller 16. As a result, the image density can be stabilized and the image quality can be maintained.

  Similarly to the first embodiment, by setting the peripheral speed ratio of the supply rollers 17 and 18 to the developing roller 16 to 1 or less, the wear of the supply rollers 17 and 18 is reduced, and the life of the process cartridge 11 is reduced. Can be lengthened.

  The process cartridge 61 (image forming unit) in the second embodiment is not limited to the configuration shown in FIG. 12, and a partition wall 70 is provided in the toner hopper 55 and replenished from the toner cartridge 12. Any toner can be used as long as it can distribute the toner to the first supply roller 67 side and the second supply roller 68 side. Therefore, for example, the partition wall 70 does not need to be formed integrally with the frame 50, and may be one in which a sheet metal is fixed to the frame with screws. Further, the outer diameters of the first and second supply rollers 67 and 68 may be different.

  As described in the first embodiment, when the conveyance surface CP of the recording medium 20 is inclined with respect to the horizontal plane (see FIG. 9), the toner hopper 55 is in a direction orthogonal to the conveyance surface CP. In this case, it suffices to be located on the side away from the conveying surface. Further, the partition wall 70 may be located inside the toner supply port 54 in a direction parallel to the transport surface CP (Y direction) and extend in a direction perpendicular to the transport surface CP.

  The first embodiment described above and its modification examples may be combined with the second embodiment as appropriate. For example, the partition wall 70 of the second embodiment may be added to the process cartridge 11 shown in FIG.

  In the first embodiment, its modification, and the second embodiment, the recording medium 20 is transported by the transfer belt unit 35, and the toner image (developer image) is transferred to the recording medium 20. Although the direct transfer method has been described, the present invention is not limited to the direct transfer method. In other words, an intermediate transfer system in which the toner image is transferred from the photosensitive drum 14 to the transfer belt 36 of the transfer belt unit 35 (primary transfer), and further the toner image is transferred from the transfer belt 36 to the recording medium 20 (secondary transfer). It may be used. In this case, the transfer belt 36 corresponds to the “medium”, and the conveyance surface when the transfer belt 36 moves while contacting the photosensitive drum 14 corresponds to the conveyance surface CP of the recording medium 20 in the direct transfer method described above. .

  DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11, 11, 11a, 11b, 11c, 11d, 61 Process cartridge (image forming unit), 12 Toner cartridge, 14 Photosensitive drum (image carrier), 16 Developing roller (Developer carrier), 17, 27, first supply roller (first developer supply member), 18, 28 second supply roller (second developer supply member), 19 regulating blade (developer regulating member), 20 recording medium (medium), 35 Transfer belt unit, 36 transfer roller, 50 frame, 50B wall, 54 toner supply port, 57 outer wall, 70 partition plate, 71 first wall, 72 second wall, 101 first roller, 102 second roller 103 belts.

Claims (24)

An image carrier;
A developer carrier for supplying a developer to the image carrier;
A first developer supply member for supplying a developer to the developer carrying member;
A second developer supply member for supplying a developer to the developer carrying member;
Means for transporting the medium along a predetermined transport surface so as to be in contact with the image carrier, and transferring the developer image carried on the image carrier to the medium,
The first developer supply member is disposed closer to the transport surface in a direction perpendicular to the transport surface than the second developer supply member,
A tangent line in a direction perpendicular to the transport surface of the outer periphery of the first developer supply member on the side away from the developer carrier is separated from the developer carrier in the second developer supply member. The first and second developer supply members are arranged such that the distance from the developer carrier in a plane parallel to the transport surface is longer than a tangent in the same direction of the outer periphery on the side. An image forming unit. The transport surface is a horizontal plane,
The direction orthogonal to the transport surface is a vertical direction,
The image forming unit according to claim 1, wherein a side closer to the conveyance surface is a lower side.   The first developer supply member is disposed upstream of the second developer supply member in a moving direction of the outer periphery of the developer carrier. The image forming unit described.   In the moving direction of the outer periphery of the developer carrier, the developer layer attached to the outer periphery of the developer carrier is further upstream than the first developer supply member and the second developer supply member. The image forming unit according to claim 3, wherein a developer regulating member that regulates the thickness is disposed.   The first developer supply member and the second developer supply member are both in contact with the outer periphery of the developer carrying member. The image forming unit described in 1.   In the contact portion between the first developer supply member and the developer carrier, the movement directions of the outer circumferences are opposite to each other, and in the contact portion between the second developer supply member and the developer carrier. 6. The image forming unit according to claim 5, wherein the movement directions of the outer circumferences are opposite to each other.   A container that accommodates the developer on a side away from the conveyance surface in a direction perpendicular to the conveyance surface with respect to the developer carrier, the first developer supply member, and the second developer supply member. The image forming unit according to claim 1, further comprising a chamber. Has a developer replenishment port for receiving developer replenishment,
The vertical tangent of the outer periphery of the first developer supply member on the side remote from the developer carrier, and the vertical of the outer periphery of the second developer supply member on the side remote from the developer carrier. 8. The image formation according to claim 1, wherein the tangent of the direction is located inside the developer supply port in a plane parallel to the conveyance surface. 9. unit.   The image forming unit according to claim 1, further comprising a wall portion formed along an outer periphery of the first developer supply member.   10. The peripheral speed of the first developer supply member and the peripheral speed of the second developer supply member are smaller than the peripheral speed of the developer carrying member. 2. The image forming apparatus according to item 1.   11. The image forming unit according to claim 1, wherein an outer diameter of the first developer supply member is larger than an outer diameter of the second developer supply member.   The image forming unit according to any one of claims 1 to 11, wherein the first developer supply member includes at least one roller.   The image forming unit according to claim 12, wherein the first developer supply member includes two rollers.   The image forming unit according to claim 12, wherein the first developer supply member includes two rollers and a belt spanned between the two rollers. The medium is a recording medium,
The means conveys the recording medium along a predetermined conveying surface so as to contact the image carrier, and directly transfers the developer image carried on the image carrier to the recording medium. The image forming unit according to any one of claims 1 to 14. An image carrier;
A developer carrier for supplying developer to the image carrier; a first developer supply member for supplying developer to the developer carrier;
A second developer supply member for supplying a developer to the developer carrying member;
Means for transporting the medium along a predetermined transport surface so as to be in contact with the image carrier, and transferring the developer image carried on the image carrier to the medium;
The developer carrier, the first developer supply member, and the second developer are disposed on the side away from the transport surface in a direction orthogonal to the transport surface, and store the developer. Room,
An image forming apparatus, comprising: a partition wall that distributes the developer in the storage chamber into toner supplied to the first developer supply member and toner supplied to the second developer supply member. unit.   The image forming unit according to claim 16, wherein the transport surface is a horizontal plane, and a direction orthogonal to the transport surface is a vertical direction.   18. The image forming unit according to claim 16, wherein the storage chamber has a developer replenishing port for receiving developer replenishment on a side away from the transport surface in a direction orthogonal to the transport surface. .   The image forming unit according to claim 18, wherein the partition wall is positioned inside the developer supply port in a plane parallel to the transport surface.   The partition wall includes a first wall portion extending in a direction orthogonal to the transport surface, and a second wall portion extending between the first and second developer supply members. The image forming unit according to claim 16, wherein the image forming unit is an image forming unit.   The image forming unit according to claim 20, wherein the second wall portion of the partition wall extends along an outer periphery of the second developer supply member.   The peripheral speed of the first developer supply member and the peripheral speed of the second developer supply member are smaller than the peripheral speed of the developer carrying member. 2. An image forming unit according to item 1. The medium is a recording medium,
The means conveys the recording medium along a predetermined conveying surface so as to contact the image carrier, and directly transfers the developer image carried on the image carrier to the recording medium. The image forming unit according to any one of claims 16 to 22.   An image forming apparatus comprising the image forming unit according to any one of claims 1 to 23.

Images