JP3912489B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
According to the present invention, an image forming station having a charging unit and a developing unit arranged around an image carrier is provided for each color along a transfer belt, and a color image is formed by passing the transfer belt through each station. The present invention relates to an image forming apparatus.
[0002]
[Prior art]
The tandem type image forming apparatus is roughly classified as follows.
(1) A plurality of image forming stations are arranged in a line, the recording paper is electrostatically adsorbed to the transport belt, and the recording paper is sequentially brought into contact with each station and transported between the stations and the recording paper. A paper transport system that applies color transfer while applying electrostatic transfer force to a toner image of multiple colors directly onto a recording paper; and
(2) A plurality of image forming stations are arranged in a line, and an intermediate transfer belt formed of a dielectric is brought into contact with each station and conveyed, and the toner image formed at each station is transferred to the station. An intermediate transfer method in which an electrostatic transfer force is applied between the belts to sequentially perform primary transfer, color superimposition on the intermediate transfer belt, and secondary transfer collectively from the intermediate transfer belt to the recording paper;
The following two methods are adopted.
[0003]
The above paper transport method requires means (rollers and brushes) for adsorbing the recording paper to the transport belt and a high voltage power supply, but the intermediate transfer method does not require these means and power supply, and the paper transport method. However, it is necessary to strictly control the transfer bias applied to each image transfer unit according to the size, thickness, and type of the recording paper.In the intermediate transfer method, the resistance and thickness are independent of these factors of the recording paper. Transfer conditions such as transfer voltage, transfer current, and contact pressure are only performed when a primary transfer of a toner image is performed on an intermediate transfer belt with a constant surface roughness, and then secondary transfer is performed collectively on a recording sheet. Therefore, the intermediate transfer method has many advantages.
[0004]
On the other hand, if divided according to the arrangement method of each image forming station, there are a method in which each station is arranged in the horizontal direction and a method in which each station is arranged in the vertical plane direction. The former has a disadvantage that the installation area is large, and the latter is There is a drawback that the height of the apparatus becomes high and it is difficult to install on the desk.
[0005]
For this purpose, conventionally, Japanese Patent Application Laid-Open No. 11-95520 and Japanese Patent Application Laid-Open No. 8-305115 have known a method in which image forming stations are arranged in an oblique direction.
[0006]
[Problems to be solved by the invention]
However, in the above-described conventional method, each image forming station is disposed above the belt surface arranged in an oblique manner regardless of whether it is a recording paper conveyance belt or an intermediate transfer belt. There is a problem in that the toner spills from the developing means and stains the belt and other image forming means, resulting in image quality deterioration. Further, since the exposure means must be disposed above the apparatus main body, there is a problem that the vibration of the apparatus main body is increased and the image quality is deteriorated.
[0007]
The present invention solves the above-described conventional problems, and in an image forming apparatus in which each image forming station is disposed in an oblique direction, toner contamination on the belt and the image forming means can be prevented, and the exposure means An object of the present invention is to provide an image forming apparatus capable of reducing the vibration of the image.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention provides an intermediate transfer of an image forming station in which a charging means (19) and a developing means (20) are arranged around an image carrier (17). In the tandem type image forming apparatus, which is provided for each color along the belt (14) and forms the color image by passing the intermediate transfer belt (14) through each image forming station, the intermediate transfer belt (14) is driven. It is stretched between the roller (12) and the driven roller (13), the driven roller (13) is disposed obliquely above the drive roller (12) , and the belt tension side when the intermediate transfer belt (14) is driven is The intermediate transfer belt (14) is disposed so as to face downward, the image carrier (17) of each image forming station is brought into contact with the belt tension side, and is opposed to the drive roller (12). Secondary transfer roller (39) provided in pressure contact, a rubber layer having high friction and shock absorption with (12a) provided on the peripheral surface of the drive roller (12), a driven roller diameter of the driving roller (12) ( A cleaning means (15) which is smaller than the diameter of 13) and is brought into contact with the intermediate transfer belt (14) at the winding portion of the driven roller (13) on the belt tension side, and the intermediate transfer belt (14) is provided. The fixing means (40) is disposed obliquely above the slack side of the belt during driving.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show an embodiment of an image forming apparatus according to the present invention. FIG. 1 is a schematic cross-sectional view showing the overall configuration, and FIG. 2 is an enlarged view of a main part of FIG. This embodiment is an embodiment of the intermediate transfer method described above.
[0010]
In FIG. 1, an image forming apparatus 1 according to the present embodiment includes a housing 2, a paper discharge tray 2 a formed on the top of the housing 2, and a door body 3 that can be opened and closed on the front surface of the housing 2. A control unit 4, a power supply unit 5, an exposure unit 6, an image forming unit 7, an exhaust fan 8, a transfer unit 9, and a paper feed unit 10 are disposed in the housing 2, and a paper transport unit 11 is disposed in the door 3. Is arranged. Each unit has a configuration that can be attached to and detached from the main body, and can be removed and repaired or replaced integrally during maintenance or the like.
[0011]
The transfer unit 9 includes a drive roller 12 disposed below the housing 2 and driven to rotate by a drive source (not shown), a driven roller 13 disposed obliquely above the drive roller 12, and the two rollers. An intermediate transfer belt 14 that is stretched between and driven to circulate in the direction of the arrow shown in the figure (counterclockwise), and a cleaning unit 15 that contacts the surface of the intermediate transfer belt 14. The driven roller 13 and the intermediate transfer belt 14 are The drive roller 12 is disposed in a direction inclined to the left in the drawing. Thus, the belt tension side (side pulled by the drive roller 12) 14a when the intermediate transfer belt 14 is driven is positioned below, and the belt slack side 14b is positioned above.
[0012]
The drive roller 12 also serves as a backup roller for a secondary transfer roller 39 described later. As shown in FIG. 2, a rubber layer 12a having a thickness of about 3 mm and a volume resistivity of 10 ⁵ Ω · cm or less is formed on the peripheral surface of the drive roller 12 and is grounded through a metal shaft. Thus, a conductive path for the secondary transfer bias supplied via the secondary transfer roller 39 is provided. Thus, by providing the driving roller 12 with the rubber layer 12a having high friction and shock absorption, it is difficult for the impact when the recording medium enters the secondary transfer portion to be transmitted to the intermediate transfer belt 14, and the image quality is deteriorated. Can be prevented.
[0013]
In the present invention, the diameter of the driving roller 12 is smaller than the diameter of the driven roller 13. Thereby, the recording paper after the secondary transfer can be easily peeled by the elastic force of the recording paper itself.
[0014]
The cleaning means 15 is provided on the belt tension side 14a. As shown in FIG. 2, a cleaning blade 15a that removes toner remaining on the surface of the intermediate transfer belt 14 after the secondary transfer and a toner transport member 15b that transports the collected toner are provided. The cleaning blade 15a is driven. The intermediate transfer belt 14 is in contact with the intermediate transfer belt 14 around the roller 13.
[0015]
Further, a primary transfer member 16 made of a leaf spring electrode is brought into contact with the back surface of the intermediate transfer belt 14 by an elastic force so as to face an image carrier 17 of each image forming station Y, M, C, K described later. A transfer bias is applied to the primary transfer member 16.
[0016]
The image forming unit 7 includes a plurality of (four in this embodiment) image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form images of different colors. As shown in detail in FIG. 2, each of the image forming stations Y, M, C, and K has an image carrier 17 composed of a photosensitive drum, and a corona charger disposed around the image carrier 17. Or it has the charging means 19 and the developing means 20 which consist of a charging roller. The order of arrangement of the image forming stations Y, M, C, and K is arbitrary.
[0017]
Then, the image carrier 17 of each image forming station Y, M, C, K is brought into contact with the belt tension side 14a of the intermediate transfer belt 14, and as a result, each image forming station Y, M, C, K is also arranged in a direction inclined to the left in the drawing with respect to the drive roller 12. The image carrier 17 is rotationally driven in the opposite direction to the intermediate transfer belt 14 as indicated by the arrows in the figure.
[0018]
The exposure unit 6 is disposed obliquely below the image forming unit 7 and has a polygon mirror motor 21, a polygon mirror 22, an f-θ lens 23, a reflection mirror 24, and a folding mirror 25. Are modulated and formed based on a common data clock frequency, emitted through the f-θ lens 23, the reflecting mirror 24, and the folding mirror 25, and then the images of the image forming stations Y, M, C, and K. The carrier 17 is irradiated to form a latent image. The folding mirror 25 is arranged so that the optical path lengths of the image forming stations Y, M, C, and K to the image carrier 17 are substantially the same.
[0019]
Next, details of the developing unit 20 will be described on behalf of the image forming station Y in FIG. In the present invention, since each of the image stations Y, M, C, and K is arranged in a direction inclined to the left side in the drawing, the toner storage container 26 is arranged obliquely downward, so that the developing means 20 A special configuration is adopted.
[0020]
That is, the developing unit 20 includes a toner storage container 26 that stores toner, a toner storage unit 27 (hatched portion in the figure) formed in the toner storage container 26, and a toner disposed in the toner storage unit 27. The stirring member 29, the partition member 30 partitioned on the upper part of the toner storage unit 27, the toner supply roller 31 disposed above the partition member 30, and the toner supply roller 31 provided on the partition member 30 The charging blade 32, the developing roller 33 disposed so as to be in contact with the toner supply roller 31 and the image carrier 17, and the regulation blade 34 that is in contact with the developing roller 33.
[0021]
The developing roller 33 and the supply roller 31 are driven to rotate in the direction opposite to the rotation direction of the image carrier 17 as shown by the arrows in the figure, while the stirring member 27 is rotated in the direction opposite to the rotation direction of the supply roller 31. Driven. The toner stirred and carried up by the stirring member 29 in the toner storage unit 27 is supplied to the toner supply roller 31 along the upper surface of the partition member 30, and the supplied toner is supplied by being rubbed with the flexible blade 32. The roller 31 is supplied to the surface of the developing roller 33 by the mechanical adhesion force on the surface irregularities and the adhesion force due to frictional band power. The toner supplied to the developing roller 33 is regulated to a coating layer having a predetermined thickness by the regulating blade 34, and the thinned toner layer is conveyed to the image carrier 17 so that the developing roller 33 and the image carrier 17 are in contact with each other. The latent image portion of the image carrier 17 is developed at the nip portion configured as described above and in the vicinity thereof.
[0022]
Returning to FIG. 1, the paper feed unit 10 includes a paper feed cassette 35 in which the recording media P are stacked and held, and a pickup roller 36 that feeds the recording media P from the paper feed cassette 35 one by one.
[0023]
The paper transport unit 11 includes a gate roller pair 37 (one roller is provided on the housing 2 side) that defines the timing of feeding the recording medium P to the secondary transfer unit, a drive roller 12 and an intermediate transfer belt 14. It can be said that the apparatus includes a secondary transfer roller 39 as a secondary transfer unit pressed against the main recording medium, a main recording medium conveyance path 38, a fixing unit 40, a discharge roller pair 41, and a duplex printing conveyance path 42. The fixing means 40 includes at least one heating element such as a halogen heater incorporated therein and a rotatable fixing roller pair 40a, and at least one roller of the fixing roller pair 40a is pressed and urged to the other side. The secondary image secondarily transferred to the recording medium P is pressed to the recording medium P, and the secondary image secondarily transferred to the recording medium is at a predetermined temperature at the nip portion formed by the fixing roller pair 40a. It is fixed on the recording medium.
[0024]
In the present invention, since the intermediate transfer belt 14 is disposed in a direction inclined to the left in the drawing with respect to the driving roller 12, a wide space is generated in the right space, and the fixing means 40 can be disposed in the space. In addition, downsizing can be realized, and heat generated by the fixing unit 40 is transmitted to the exposure unit 6, the intermediate transfer belt 14 and the image forming stations Y, M, C, and K located on the left side. Can be prevented.
[0025]
The outline of the operation of the entire image forming apparatus as described above is as follows.
(1) When a print command signal (image formation signal) from a host computer or the like (not shown) is input to the control unit 4 of the image forming apparatus 1, each of the image forming stations Y, M, C, and K The image carrier 17, the rollers of the developing unit 20, and the intermediate transfer belt 14 are driven to rotate.
(2) The outer peripheral surface of the image carrier 17 is uniformly charged by the charging means 19.
(3) The exposure unit 6 selectively exposes the outer peripheral surface of the image carrier 17 uniformly charged in each image forming station Y, M, C, K according to the image information of each color, for each color. An electrostatic latent image is formed.
(4) The toner image is developed by the developing means 20 from the electrostatic latent image formed on each image carrier 17.
(5) The primary transfer member 16 of the intermediate transfer belt 14 is applied with a primary transfer voltage having a polarity opposite to the charging polarity of the toner, and the toner image formed on the image carrier 17 is transferred to the intermediate transfer belt at the primary transfer portion. As the lens 14 moves, the images are sequentially transferred onto the intermediate transfer belt 14.
(7) In synchronization with the movement of the intermediate transfer belt 14 that has primarily transferred the primary image, the recording medium P stored in the paper feed cassette 35 is fed to the secondary transfer roller 39 through the registration roller pair 37. Is done.
(8) The primary transfer image is synchronized with the recording medium at the secondary transfer portion, and is primary-transferred by the secondary transfer roller 39 pressed toward the driving roller 12 of the intermediate transfer belt 14 by a pressing mechanism (not shown). A bias having a polarity opposite to that of the transfer image is applied, and the primary transfer image formed on the intermediate transfer belt 14 is secondarily transferred to the recording medium fed synchronously.
(9) The transfer residual toner in the secondary transfer is conveyed in the direction of the driven roller 13 and scraped off by the cleaning means 15 disposed opposite to the roller 13, and the intermediate transfer belt 14 is refreshed. Once again, the above cycle can be repeated.
(10) The toner image on the recording medium is fixed by passing the recording medium through the fixing unit 40, and then the recording medium is directed toward a predetermined position (or double-sided printing toward the paper discharge tray 2a if not double-sided printing). In this case, the paper is conveyed toward the conveyance path 42 for double-sided printing.
[0026]
FIG. 3 is a schematic cross-sectional view showing the entire configuration of another embodiment of the image forming apparatus of the present invention. In addition, about the structure same as the said embodiment, the same number is attached | subjected and description is abbreviate | omitted. This embodiment is an embodiment of the above-described paper conveyance system, and uses a paper conveyance belt 43 instead of the intermediate transfer belt 14 of FIG.
[0027]
In the present embodiment, a transfer unit 9 and a paper transport unit 11 are provided in the door body 3. The transfer unit 9 includes a drive roller 12 disposed above the housing 2 and driven to rotate by a drive source (not shown), a driven roller 13 and a backup roller 44 disposed obliquely below the drive roller 12, and these three units. A paper conveying belt 43 that is stretched around the roller and driven to circulate in the direction of the arrow shown in the figure (clockwise direction), and a cleaning means 15 that contacts the surface of the paper conveying belt 43 so as to face the backup roller 44. 12 and the paper transport belt 43 are arranged in a direction inclined to the left in the drawing with respect to the driven roller 13. Thus, the belt tension side (side pulled by the drive roller 12) 43a when the paper transport belt 43 is driven is positioned below, and the belt slack side 43b is positioned above.
[0028]
Further, a transfer member 45 made of a leaf spring electrode is brought into contact with the back surface of the paper conveying belt 43 by the elastic force so as to face the image carrier 17 of each image forming station Y, M, C, K. A transfer bias is applied to 45. Then, the image carrier 17 of each image forming station Y, M, C, K is brought into contact with the belt tension side 43a of the paper transport belt 43. As a result, each image forming station Y, M, C, K is also arranged in a direction inclined to the left in the drawing with respect to the driven roller 13.
[0029]
Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications are possible. For example, in the embodiment of FIG. 1, in order to arrange the paper feeding unit 10 in the lower part of the housing 2 and to make the driving roller 12 also serve as a backup roller for the secondary transfer roller 39, the driving roller 12 is moved downwardly to the driven roller 13. However, the driven roller 13 may also be used as the backup roller 39 of the secondary transfer roller, and the driven roller 13 may be disposed below and the drive roller 13 may be disposed above.
[0030]
In the present invention, the intermediate transfer belt 14 and the paper transport belt 43 are collectively defined as a transfer belt.
[0031]
【The invention's effect】
As is apparent from the above description, according to the present invention, an image forming station in which charging means and developing means are arranged around the image carrier is provided for each color along the transfer belt, and the transfer belt is provided for each image forming station. In the tandem type image forming apparatus for forming a color image by passing through, the transfer belt is stretched between a driving roller and a driven roller, and one of the driving roller and the driven roller is in relation to the other roller. Since the belt tension side when the transfer belt is driven is arranged downward and the image carrier of each image forming station is in contact with the belt tension side, the transfer belt and the exposure means As a result, the toner can be prevented from being stained and vibration of the exposure means can be reduced. In addition, it is possible to dispose fixing means in a space formed obliquely above the apparatus, and heat transfer to the exposure means, transfer belt, and image forming means can be reduced, and color misregistration correction operation for each color. Can be performed less frequently.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
[Explanation of symbols]
12 ... Driving roller 13 ... Follower roller 14 ... Intermediate transfer belt (transfer belt)
14a ... belt tension side 14b ... belt slack side 15 ... cleaning means 17 ... image carrier 19 ... charging means 20 ... developing means 39 ... secondary transfer roller 43 ... paper transport belt (transfer belt)

Claims (1)

An image forming station in which a charging unit (19) and a developing unit (20) are arranged around the image carrier (17) is provided for each color along the intermediate transfer belt (14), and the intermediate transfer belt (14) is provided for each image. In the tandem type image forming apparatus for forming a color image by passing it through a forming station, the intermediate transfer belt (14) is stretched between a driving roller (12) and a driven roller (13), and the driven roller (13). Is disposed obliquely above the drive roller (12) , and the belt tension side when the intermediate transfer belt (14) is driven is located below, and the image bearing of each image forming station is supported on the belt tension side. contact body (17) This, the secondary transfer roller in pressure contact with the intermediate transfer belt (14) (39) provided opposite to said drive roller (12), said drive roller (12) Rubber layer having high friction and shock absorption on the surface of (12a) is provided, the diameter of the driving roller (12) smaller than the diameter of the driven roller (13), in the belt tight side to the driven roller (13) A cleaning means (15) to be brought into contact with the intermediate transfer belt (14) is provided at the winding portion, and the fixing means (40) is disposed obliquely above the belt slack side when the intermediate transfer belt (14) is driven. An image forming apparatus.

Images