JP2020071378A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce uneven density of an image due to bias of a developer. An image forming apparatus 1 is provided with a developing device 40 that develops an electrostatic latent image formed on a photosensitive drum 10 by a developer supplied from a developer carrying member in a developing area D. The developing container 41 stirs the stirring unit 43, the developer supply unit 42 that supplies the developer supplied from the stirring unit 43 to the developer carrier, and the stirring unit 43 and the developer in the developer supply unit 42. And a stirring member 44 that conveys and circulates the developer of the stirring unit 43 and the developer supplying unit 42, and the stirring member 44 causes the developer in the developer supplying unit 42 to pass through the shaft of the photosensitive drum 10. The density of the photosensitive member on the surface of the photosensitive drum 10 is increased along the conveying direction of the developer in the developer supplying section 42, so that unevenness in image density is reduced. can do. [Selection diagram]

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus such as a copying machine or a laser printer, a developing device that supplies a developer (toner) to a photosensitive drum supplies a developing container that stores the developer and the developer in the developing container to the photosensitive drum. A developer carrier is provided. The developer is supplied to the developer carrier from the developing section in the developing container. Further, a conveying screw is arranged in the developing section, and the developer is conveyed along the axial direction of the photosensitive drum.

  While the developer is transported in the developing section, a part of it is magnetically adsorbed on the surface of the developer carrier, and the developer is carried to the surface of the photosensitive drum at the developing position. Then, the electrostatic latent image on the surface of the photosensitive drum is developed with a developer, and a toner image is formed on the surface of the photosensitive drum.

  When the developer in the developing chamber is conveyed from the upstream side to the downstream side in the developer conveying direction, the amount of the developer becomes smaller in the downstream side than in the upstream side of the developing chamber, so that the developer carrier is developed. The portion corresponding to the downstream side of the developing chamber becomes smaller than the portion corresponding to the upstream side of the chamber. As a result, in the photoconductor drum, the toner image formed on the photoconductor drum corresponding to the downstream side of the developing chamber is better than the toner image formed on the photoconductor drum corresponding to the upstream side of the developing chamber. Although there is a possibility that density unevenness may occur where the density becomes thin, there is known an image forming apparatus that alleviates the bias of the developer and reduces the density unevenness by disposing the low-repulsion member on the downstream side of the developing chamber. (For example, see Patent Document 1).

JP2012-150205A

  However, when the amount of the developer in the developing chamber becomes small, it becomes difficult to control the bias of the developer, and it may not be possible to reduce the uneven density.

  The image forming apparatus of the present disclosure includes a photosensitive drum capable of forming an electrostatic latent image, a developing container that stores a developer, and a cylindrical developer carrying member that conveys the developer in the developing container to a developing area. An image forming apparatus, comprising: a developing device having a body, the developing device developing the electrostatic latent image formed on the photosensitive drum with a developer supplied from the developer carrying body in the developing area. In the developing container, a stirring unit, a developer supply unit that supplies the developer supplied from the stirring unit to the developer carrier, and a developer in the stirring unit and the developer supply unit are provided. And a stirring member that conveys and circulates the developer in the developer supply unit while stirring, and the stirring member is configured to transfer the developer in the developer supply unit to the shaft of the photosensitive drum. Transport in one direction along the direction , The sensitivity of the photoreceptor surface of the photoreceptor drum, is characterized in that is higher in the transport direction of the developer in the developer supply unit.

  According to the image forming apparatus of the present disclosure, variations in the supply of the developer due to the uneven distribution of the developer in the developer supply member can be canceled by the characteristics of the photoconductor drum to reduce the uneven density of the image.

FIG. 1 is a diagram showing a configuration of an image forming apparatus that is an example of the present exemplary embodiment. FIG. 3 is a schematic diagram illustrating a developing device of an image forming apparatus that is an example of the exemplary embodiment. FIG. 3 is a side view showing a photosensitive drum of the image forming apparatus which is an example of the exemplary embodiment. 6 is a graph showing a sensitivity distribution of a photosensitive drum of an image forming apparatus which is an example of the exemplary embodiment.

The image forming apparatus according to the present exemplary embodiment will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an image forming apparatus which is an example of the present embodiment.
The image forming apparatus 1 has a photoconductor drum 10 in which a photoconductor is formed on the outer peripheral surface of a cylindrical aluminum tube. Around the photosensitive drum 10, a charging roller 20, an exposure device 30, a developing device 40, a transfer roller 50, and a cleaning blade 60 are arranged.

  In the image forming apparatus 1 of this embodiment, the photoconductor drum 10 rotates in the direction of arrow C. The exposure device 30 irradiates the surface of the photoconductor drum 10 charged by the charging roller 20 with the laser light L in accordance with image information to form an electrostatic latent image. The electrostatic latent image formed on the surface of the photoconductor drum 10 is developed as a toner image by the developing device 40 and transferred to the transfer medium P by the transfer roller 50. Then, the untransferred developer on the surface of the photoconductor drum 10 is scraped off by the cleaning blade 60 and collected in the developer collecting container.

  As the transfer medium P, not only paper but also a transfer belt can be used. For example, a plurality of image forming apparatuses 1 are arranged on a transfer belt, yellow, magenta, cyan, and black developers are sequentially transferred to the transfer belt, and a toner image on the transfer belt is secondarily transferred and fixed on paper. It is also possible to apply to a color image forming apparatus.

  FIG. 2 is a schematic diagram illustrating how the developer moves in the developing device. The configuration of the developing device 40 will be described with reference to FIGS. 1 and 2. The developer shown by the hatched area in FIG. 2 is stored in the developing container 41 of the developing device 40. The developing container 41 is vertically partitioned by a partition plate 41a, the developer supply unit 42 is on the upper side of the partition plate 41a, and the stirring unit 43 is on the lower side.

  A conveying screw 44a is arranged in the developer supplying section 42, a conveying screw 44b is arranged in the stirring section 43, and the conveying screw 44a and the conveying screw 44b constitute a stirring member 44. The conveying screws 44a and 44b are arranged such that their respective axial directions are parallel to the direction of the rotation axis of the photosensitive drum 10. The conveying screws 44a and 44b move in conjunction with each other, and can agitate the developer inside the developer supplying section 42 and the agitating section 43. Further, the developer is moved in the direction of the rotation axis of the photoconductor drum 10 by rotating the transport screws 44a and 44b. In the developer supply unit 42, the developer moves in the direction of arrow A, and in the stirring unit 43, the developer moves in the direction of arrow B.

  Openings 41b and 41c are provided at both ends of the partition plate 41a. The developer supply unit 42 and the stirring unit 43 communicate with each other through the openings 41b and 41c, and the developer is supplied to the developer supply unit 42 and the stirring unit 43. It is possible to move between 43. When the agitating member 44 is operated, the developer in the agitating section 43 moves from right to left while being agitated by the carrying screw 44b, as indicated by an arrow B in FIG. The developer that has reached the left end of the stirring unit 43 is pushed by the subsequent developer, rises through the opening 41b, and is transferred to the developer supply unit 42. After that, the developer moves from left to right along the axial direction of the photoconductor drum 10 as indicated by an arrow A while being stirred by the transport screw 44a.

  A magnet roller 45a and a developing sleeve 45b, which are a developer bearing member, are arranged in the developer supplying section 42. The longitudinal direction of the magnet roller 45a and the developing sleeve 45b is arranged along the rotational axis of the photosensitive drum 10 and the longitudinal directions of the conveying screws 44a and 44b. By the magnet roller 45a, the developer is attracted onto the developing sleeve 45b and the developing sleeve 45b rotates, so that the developer can be supplied to the developing area D near the surface of the photosensitive drum 10.

  When the developer is conveyed in the developer supply unit 42, a part of the developer is attracted onto the developing sleeve 45b by the magnet roller 45a, the developing sleeve 45b rotates, and is conveyed to the developing area D. When the developer is carried to the end of the developer supply unit 42 by the carrying screw 44a, the developer moves from the opening 41c to the stirring unit 43. The stirring member 44 allows the developer to be circulated between the developer supply unit 42 and the stirring unit 43.

  The developer adsorbed on the developing sleeve 45b is adjusted to a predetermined thickness by the regulation blade 46, is conveyed to the developing area D in the vicinity of the photoconductor drum 10, and is electrostatically formed on the surface of the photoconductor drum 10. The image can be developed to form a toner image.

  In the developer supply unit 42, the developer is supplied from the opening 41b, a part of the developer is adsorbed on the developing sleeve 45b and conveyed to the development area D, and a part of the developer is consumed by the development, and the opening 41c is formed. Sent to the stirring section 43. Therefore, the amount of the developer is large in the vicinity of the opening 41b and small in the vicinity of the opening 41c. That is, the amount of the developer decreases along the arrow A that indicates the developer transport direction in the developer supply unit 42.

  The height of the spikes of the developer attracted to the surface of the developing sleeve 45b by the magnet roller 45a is adjusted by the regulating blade 46, but is adjusted so as to be uniform in the width direction of the magnet roller 45a. Further, the amount of the developer adsorbed on the surface of the developing sleeve 45b changes depending on the pressure of the developer applied to the regulation blade 46. Therefore, the amount of the developer is large in the vicinity of the opening 41b and small in the vicinity of the opening 41c. That is, the amount of the developer adsorbed on the surface of the developing sleeve 45b is smaller on the downstream side than on the upstream side of the developer flowing in the developer supply section 42. That is, the amount decreases along the arrow A indicating the developer transport direction in the developer supply unit 42.

  FIG. 3 is a side view showing the photosensitive drum of the image forming apparatus which is an example of this embodiment. The photoconductor drum 10 includes, for example, a charge injection blocking layer containing an amorphous silicon material formed on a side surface of a cylindrical conductive substrate such as aluminum, and a light containing the amorphous silicon material formed on the charge injection blocking layer. A conductive layer and a surface layer containing an amorphous silicon material formed on the photoconductive layer can be sequentially stacked to be formed. It is also possible to use an organic photoconductor instead of the amorphous silicon photoconductor. The photosensitive drum 10 that constitutes the image forming apparatus 1 rotates around the rotation axis X in the direction of arrow C to perform printing.

  FIG. 4 is a graph showing the intermediate sensitivity of the photosensitive drum of the image forming apparatus according to the exemplary embodiment. The horizontal axis indicates the position of the surface of the photosensitive drum 10, and shows one end 10a, the central portion 10b, and the other end 10c on the drum side surface of the photosensitive drum 10. The vertical axis represents the intermediate sensitivity. The higher the intermediate sensitivity, the easier the toner is transferred from the developing sleeve 45b to the photoconductor drum 10, and the toner developed when the electrostatic latent image is developed under the same conditions. The image becomes darker.

Here, the intermediate sensitivity refers to one end portion when the photosensitive drum 10 is charged by a charger and then the surface potential of the central portion 10b is irradiated with light having a light energy of about 1/2 value after irradiation. The surface potential at each measurement position of 10a, the central portion 10b, and the other end portion 10c. The results shown in FIG. 4 are obtained by charging the photoconductor drum 10 having an outer diameter of 40 mm so as to have a surface potential of 230 V at each measurement position, and then applying light having a wavelength of 670 nm and a light amount of 0.25 μJ / cm ² . The surface potential after irradiation is measured.

  The intermediate sensitivity of the one end portion 10a of the photosensitive drum 10 is 115.9V, the intermediate sensitivity of the central portion 10b of the photosensitive drum 10 is 113.3V, and the intermediate sensitivity of the other end portion 10c of the photosensitive drum 10. The sensitivity is 110.3 V, the intermediate sensitivity of the photoconductor drum 10 is low from one end 10a to the other end 10c, and the surface of the photoconductor drum 10 is in the direction of the rotation axis X of the photoconductor drum 10. Along with the difference in height of the surface sensitivity.

  The photoconductor drum 10 in which the intermediate sensitivity of the photoconductor is increased from the other end 10c to the one end 10a along the rotation axis of the photoconductor drum is, for example, a cylindrical raw tube made of aluminum as a material. When the photoconductor is formed by a plasma vapor deposition (P-CVD) method or the like, the photoconductor can be produced by controlling the flow of the raw material gas around the cylindrical aluminum tube.

  The photoconductor drum 10 has areas E1 and E3 on which images are not formed on both sides of the image forming area E2. A display portion 11 indicating the direction of high and low sensitivity is formed on the inner surface of the base body in the area E1 where the image is not formed, which is the one end portion 10a of the photosensitive drum 10. The display unit 11 indicates that the one end 10a is on the high sensitivity side. The display unit 11 may be provided in a portion of the photosensitive drum 10 where an image is not formed. For example, the display portion 11 indicating that the sensitivity is low may be provided on the inner surface of the substrate in the non-imaged area E3 of the other end portion 10c. The display unit 11 can be formed by attaching a sticker at a predetermined position on the inner surface of the photoconductor drum 10. In addition, it is also possible to form unevenness on the inner surface of the photoconductor drum 10. It is also possible to engrave the display unit 11 on the inner surface of the photoconductor drum 10 or on a part of the photoconductor layer on the surface by a laser marking method or the like.

  Such a photosensitive drum 10 is attached such that the one end 10a on the high sensitivity side corresponds to the downstream side in the developer conveying direction in the developer supply unit 42 of the developing device 40. By mounting the photoconductor drum 10 in this way, the sensitivity of the photoconductor on the surface of the photoconductor drum 10 is increased along the developer transport direction in the developer supply unit 42 indicated by arrow A. It can be 1.

  In the developer supply unit 42, the amount of the developer decreases along the developer conveying direction in the developer supply unit 42, and as a result, the amount of the developer adsorbed on the surface of the developing sleeve 45b is The amount decreases along the developer transport direction in the agent supply unit 42. On the other hand, the sensitivity of the photoconductor on the surface of the photoconductor drum 10 increases along the developer feeding direction in the developer supply unit 42. Therefore, a relatively small amount of developer is supplied to the one end portion 10a side of the photosensitive drum 10 having a high sensitivity, and a relatively large amount of developer is supplied to the other end portion 10c side of the photosensitive drum 10 having a low sensitivity. Therefore, when the electrostatic latent image formed on the surface of the photoconductor drum 10 is developed by the developing device 40, variations in the supply of the developer due to the bias of the developer in the developer supply unit 42 may occur. Therefore, the unevenness of the density of the developed toner image can be reduced, and an image forming apparatus with high output image quality can be obtained.

  Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the gist of the present invention.

1 Image Forming Apparatus 10 Photosensitive Drum 40 Developing Device 41 Developing Container 42 Developer Supplying Section 43 Stirring Section 44 Stirring Member 45a Magnet Roller 45b Developing Sleeve D Development Area

Claims (2)

A photosensitive drum capable of forming an electrostatic latent image,
A developing device having a developing container for accommodating a developer, and a cylindrical developer carrier for transporting the developer in the developing container to a developing region,
An image forming apparatus comprising: a developing device that develops an electrostatic latent image formed on the photoconductor drum by a developer supplied from the developer carrying member in the developing area,
The developing container is
A stirring section,
A developer supply unit for supplying the developer supplied from the stirring unit to the developer carrier,
While stirring the developer in the stirring unit and the developer supply unit, a stirring member for conveying and circulating the developer of the stirring unit and the developer supply unit,
The stirring member conveys the developer in the developer supply unit in one direction along the axial direction of the photosensitive drum,
In the image forming apparatus, the sensitivity of the photoconductor on the surface of the photoconductor drum is increased along the conveying direction of the developer in the developer supply unit.   The image forming apparatus according to claim 1, wherein the photoconductor drum includes a display unit that indicates a direction in which the sensitivity of the surface photoconductor is high or low.