The present invention relates to image forming apparatuses.
An image forming apparatus utilizing an electrophotographic process includes a plurality of image forming units for respective colors (black, yellow, cyan, and magenta). On the surface of a photosensitive drum in the image forming units each include, an electrostatic latent image is formed and developed into a toner image for visualization. Such an image forming unit includes a static eliminator for eliminating static electricity and an electrostatic latent image that remain redundantly on the surface of the photosensitive drum. The static eliminator performs static elimination by irradiating the surface of the photosensitive drum with light.
In view of environmental friendliness, amorphous silicon, which is excellent in abrasion resistance and durable under long-term use, is used generally in the photosensitive drum. Amorphous silicon has a surface having a molecular structure that is apt to adsorb moisture. As a result, moisture is liable to be adsorbed into the surface of the photosensitive drum. When moisture is adsorbed into the surface of the photosensitive drum, the surface resistance of the photosensitive drum may decrease, thereby reducing the surface potential at an edge of the electrostatic latent image. As a result, image quality may degrade.
In view of the foregoing, it has been proposed to provide in the vicinity of the photosensitive drum, a substrate on which a heating element that heats the surface of the photosensitive drum is mounted (e.g., Patent Literature 1). In an image forming apparatus recited in Patent Literature 1, a light emitting element that eliminates static electricity on the photosensitive drum is mounted on one of main surfaces of the substrate while the heating element that heats the photosensitive drum is mounted on the other main surface of the substrate.
[Patent Literature]
Japanese Patent Application Laid-Open Publication No. 2007-264167
However, in a configuration in which equivalent electric power is supplied to heating elements of image forming units located on opposite sides in an image forming section and of image forming units located in the middle of the image forming section where the respective opposite ends corresponding to upstream and downstream sides (entering side and discharge side) in terms of a direction in which paper enters respective developing devices in the image forming apparatus recited in Patent Literature 1, temperature variation differs between photosensitive drums included in the image forming units located on the opposite sides and photosensitive drums included in the image forming units located in the middle. For this reason, temperature may be uneven among the photosensitive drums and the photosensitive drums on the opposite sides may be heated insufficiently. As a result, degradation of image quality caused due to image deletion in a high humidity environment cannot be prevented.
The present invention has been made in view of the aforementioned problems and has its objective of providing an image forming apparatus in which degradation of image quality caused due to image deletion in a high humidity environment can be prevented.
An image forming apparatus according to the present invention is an image forming apparatus that forms an image on a recording medium and includes a plurality of image forming units. Of the plurality of image forming units, one or more image forming units are intermediate image forming units, and one or more image forming units adjacent to a side of the intermediate image forming units and one or more image forming units adjacent to an opposite side of the intermediate image forming units are side image forming units. The plurality of image forming units each include a photosensitive drum, a light emitting element that performs static elimination on the photosensitive drum, and a heating element that heats the photosensitive drum. The heating element of each of the intermediate image forming units receives supply of electric power different in quantity from electric power of which supply the heating element of each of the side image forming units receives.
According to the present invention, an image forming apparatus can be provided in which degradation of image quality caused due to image deletion in a high humidity environment can be prevented.
[
[
[
[
[
[
[
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that elements that are the same or equivalent are indicated by the same reference signs in the drawings and description thereof is not repeated.
Each of the image forming units 110 includes a photosensitive drum 120, a cleaner 180, and a developing device. The cleaner 180 includes a static eliminator 160. The static eliminator 160 includes a substrate 161, heating elements 163, and light emitting elements 162.
The image forming unit 110a includes a photosensitive drum 120a, a cleaner 180a, and a developing device. The cleaner 180a includes a static eliminator 160a. The static eliminator 160a includes a substrate 161a, heating elements 163a, and light emitting elements 162a. The image forming units 110b includes a photosensitive drum 120b, a cleaner 180b, and a developing device. The cleaner 180b includes a static eliminator 160b. The static eliminator 160b includes a substrate 161b, heating elements 163b, and light emitting elements 162b. The image forming unit 110c includes a photosensitive drum 120c, a cleaner 180c, and a developing device. The cleaner 180c includes a static eliminator 160c. The static eliminator 160c includes a substrate 161c, heating elements 163c, and light emitting elements 162c. The image forming unit 110d includes a photosensitive drum 120d, a cleaner 180d, and a developing device. The cleaner 180d includes a static eliminator 160d. The static eliminator 160d includes a substrate 161d, heating elements 163d, and light emitting elements 162d.
The light emitting elements 162 eliminate static electricity from corresponding photosensitive drums 120 by irradiating the surfaces of the corresponding photosensitive drums 120 with light. The respective heating elements 163 heat corresponding photosensitive drums 120 to evaporate moisture on the surfaces of the corresponding photosensitive drums 120.
In order to equalize the temperature variation of the photosensitive drums 120a and 120d with the temperature variation of the photosensitive drums 120b and 120c, electric power supplied to the heating elements 163a-163d is adjusted so that the heating elements 163a and 163d receive supply of electric power different from electric power of which supply the heating elements 163b and 163c receives. The control board 166 includes limiting resistors 164. The limiting resistors 164 each control a current value of corresponding heating elements 163 to adjust heat quantity of the heating elements 163.
The limiting resistors that adjust electric current to the heating elements are mounted on the control board. Values of limiting resistance depend on the corresponding image forming units. For example, the numbers of limiting resistors 164 may differ among the circuits of the respective heating elements 163a-163d. Specifically, the number of limiting resistors 164 for the circuits of the heating elements 163b or 163c is greater than the number of limiting resistors 164 for the circuits of the heating elements 163a or 163d. In the above configuration, the heat quantity of the heating elements 163 can be finely adjusted. Note that the respective limiting resistors 164 for the respective circuits of the respective heating elements 163a and 163d may be dispensed with.
Additional limiting resistors 164 control current values of the light emitting elements 162. Through the limiting resistors 164 controlling the current value of the light emitting elements 162, the amount of light that the light emitting elements 162 emit is adjusted. In comparison between a configuration with the limiting resistors 164 on the control board 166 and a configuration with the limiting resistors 164 on the substrate 161, the substrate 161 is not heated by heat of the limiting resistors 164 in the configuration with the limiting resistors 164 on the control board 166. As a result, the photosensitive drums 120 are not heated by the heat of the limiting resistors 164 during static elimination on the photosensitive drums 120 by the light emitting elements 162. Thus, degradation of image quality can be reduced.
The circuits of the light emitting elements 162 and the circuits of the heating element 163 are wired separately from each other on the input side and connected together through common wiring on the output side. In the above circuitry of the image forming unit 110, the light emitting elements 162 and the heating elements 163 can be turned on and off independently of each other. For example, the heating elements 163 can be turned off even in a state in which the light emitting elements 162 are turned on for static elimination on the photosensitive drums 120.
The substrate warping restraining members 165 restrain the substrate 161 from warping caused by heat of the heating elements 163 and can reduce warping of the substrate 161. The substrate warping restraining members 165 extend in the longitudinal direction of the substrate 161. A material of the substrate warping restraining members 165 is not limited specifically as long as it is an insulating material and may preferably be resin among insulating materials.
The cleaner 180 further includes a cleaning blade 171 and a toner collecting screw 172. The cleaning blade 171 scrapes toner remaining on the surface of the photosensitive drum 120. The toner collecting screw 172 conveys the scraped toner to an end part of a toner collecting path.
The substrate warping restraining members 165 are preferably disposed at respective opposite end parts of the substrate 161. In the above configuration, the substrate warping restraining members 165 extend in a direction perpendicular to the longitudinal direction of the substrate 161.
Note that the light emitting elements 162 and the heating elements 163 may be disposed in an alternating manner in a straight line in the longitudinal direction of the photosensitive drum 120, as illustrated in
The image forming units 110 include chargers 150, an exposure device 140, developing devices 130, and a fixing device 170 in addition to the photosensitive drums 120 and the static eliminators 160, which are described with reference to
In image formation, the photosensitive drums 120 rotate counterclockwise and the respective chargers 150 electrostatically charge the surfaces of the respective photosensitive drums 120 uniformly. The exposure device 140 then irradiates the surfaces of the respective photosensitive drums 120 with light based on image data input to an image input section from a personal computer or the like, thereby forming electrostatic latent images on the surfaces of the respective photosensitive drums 120. Next, toners in respective colors fly by developing bias voltage to adhere to the respective electrostatic latent images formed on the surfaces of the respective photosensitive drums 120, thereby forming toner images in the respective developing devices 130.
The toner images in the respective colors formed on the surfaces of the respective photosensitive drums 120 are primarily transferred in succession to an intermediate transfer belt by respective primary transfer rollers to be layered in color. In this manner, a full-color toner image is formed on the surface of the intermediate transfer belt.
Paper to which the full-color toner image is transferred is conveyed to the fixing device 170. Heat and pressure by a fixing roller fix the toner image to the surface of the paper. In this manner, a full-color image is formed. The paper on which the full color image is formed is then ejected outside the main body of the image forming apparatus 100 by an ejection roller.
The embodiment of the present invention has been described so far with reference to
Of the four image forming units 110a-110d described with reference to
In the image forming apparatus 100 according to the present invention, degradation of image quality caused due to image deletion in a high humidity environment can be prevented.
The present invention can be utilized in the fields of image forming apparatuses that utilize electrophotographic processes (e.g., printers, copiers, and multifunction peripherals).
Number | Date | Country | Kind |
---|---|---|---|
2014-057903 | Mar 2014 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2015/054624 | 2/19/2015 | WO | 00 |