JP2005148458A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently cool respective component elements in an image forming apparatus without using a plurality of cooling fans or larger-sized cooling fan. <P>SOLUTION: A laser scanner unit is arranged so that the rotational plane of its rotating member may be nearly vertical, and air is fed into an air duct-shaped part formed between the laser scanner unit and a recording material transporting part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine.

  FIG. 5 is a cross-sectional view of an apparatus main body 100 of a laser printer that is a color image forming apparatus, in which image forming stations are arranged vertically (see, for example, Patent Document 1). Sheets P, which are recording materials stacked on a middle plate 53 of a sheet feeding cassette 50 as a sheet stacking means, are separated one by one by a sheet feeding roller 51, and pass through an intermediate conveyance roller pair 61 and a registration roller pair 62, The paper is fed to the secondary transfer portion T2.

  In the color image forming system, a plurality of process cartridges 1A, 1B, 1C, 1D corresponding to a plurality of color components are formed by laser exposure emitted from laser scanner units 70A, 70B, 70C, 70D corresponding to a plurality of color components. A latent image is formed on each of the image carriers 40A, 40B, 40C, and 40D, and each latent image is developed on the image carriers 40A to 40D by a developer, that is, a toner. Toner images corresponding to a plurality of color component images formed on the image carrier are sequentially superimposed on the intermediate transfer belt 42 at the primary transfer portion T1 sandwiched between the image carrier and the primary transfer rollers 41A, 41B, 41C, and 41D. The transferred toner image is formed on the intermediate transfer belt 42 with four colors. The toner image on the intermediate transfer belt 42 is collectively transferred onto the sheet P by the secondary transfer portion T2 formed by the secondary transfer roller 43 and the secondary transfer counter roller 44, and an unfixed toner image is formed on the sheet P. The

The sheet P carrying the unfixed toner image is introduced into the fixing device 30 and heated and fixed. Thereafter, the sheet P is discharged by the plurality of discharge roller pairs 7 and 8 through the discharge conveyance path 10 to the discharge stacking unit 11.
JP-A-8-160839 (FIGS. 4 and 5)

  The image forming apparatus according to the background art shown in FIG. 5 has the following technical problems caused particularly by the fixing device as a heat source.

  First, in the image forming apparatus shown in FIG. 5, the laser scanner units 70A to 70D are arranged in the horizontal direction of the apparatus. In this configuration, as shown in FIG. 6, the laser irradiation direction with respect to the image carrier 40 (A to D) coincides with the direction of the rotation plane of the rotating member such as the polygon mirror and the scanner motor 71 (that is, the laser irradiation direction and the rotation of the rotating member). However, as shown by the arrow H in FIG. 5, the heated air from the fixing device 30 that is a heat source rises. Then, it is blocked by the lowermost laser scanner unit 70A and flows toward the process cartridge 1A containing the image carrier 40A. For this reason, only the lowermost laser scanner unit 70A is extremely heated by the heat from the fixing device 30, and the mounting position of each component such as a lens and a mirror in the laser scanner unit slightly moves due to thermal expansion. End up. As a result, the irradiation position of the laser exposure is deviated. As a result, only the color component of the lowermost image carrier 40A is formed at a position deviated from the predetermined position on the intermediate transfer belt, and each color component is accurately set. The image cannot be superimposed on the intermediate transfer belt 42 and color misregistration occurs. At the same time, since heat from the fixing device 30 flows toward the process cartridge 1A, the toner in the process cartridge is heated, and in the worst case, the toner may melt in the process cartridge in a high temperature environment. There is. Further, the image carrier 40 (A to D) is a photoconductor using an organic material or the like, and this changes the photosensitive characteristic due to a temperature change, so that, for example, the lowermost image carrier 40A and the process cartridge housing. If the temperature rises extremely only in the vicinity of the portion that is more exposed and in contact with the primary transfer roller 41A, density unevenness on the image occurs, and the image quality deteriorates remarkably.

  In particular, when a color image is formed, there is a problem that the trace of the conveyance roller formed when the sheet P is nipped by the conveyance roller pair 7 immediately after the fixing device 30 is more conspicuous than in the case of monochrome monochrome. This is because the toners of a plurality of colors are superposed at substantially the same point on the sheet, so that the toner immediately after heat fixing does not cool easily and comes into contact with the pair of conveying rollers before being completely cured on the sheet.

  To solve the above problems, a cooling fan may be used. However, in the configuration of the background art shown in FIG. 5, the laser scanner unit 70A blocks most of the air flow as described above. Therefore, it is necessary to use a larger cooling fan, or the rated heat quantity of the fixing device, such as a fan that only releases the heat of the fixing device and a fan that cools the entire image forming device. Depending on the usage environment, a plurality of cooling fans may be required, which is disadvantageous in terms of the size and cost of the image forming apparatus.

  In order to solve the above-described problems, the present invention provides a plurality of image carriers, a plurality of laser scanner units each including a rotating member that irradiates the plurality of image carriers with laser light, and an unfixed image on a recording material. A fixing unit configured to heat and fix; and a conveyance unit configured to convey a recording material, wherein the plurality of image carriers and the plurality of laser scanner units are arranged in a vertical direction, and the fixing unit includes the plurality of laser scanner units. In the image forming apparatus provided below between the conveying unit and the fixing unit, a cooling unit is provided above the fixing unit, and the plurality of laser scanner units have a rotation plane of the rotating member in a substantially vertical direction. The cooling means is arranged to send air between the plurality of laser scanner units and the transport unit.

  According to the present invention, the air flow becomes an air curtain that covers the entire wall surface of the laser scanner unit, and this air curtain serves as a heat insulating layer to suppress heat transfer to the laser scanner unit, and the difference in temperature rise between the plurality of laser scanner units. The heat transfer to the process cartridge can be prevented and a good color image can be obtained without increasing the size, complexity, and cost of the image forming apparatus.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, about the member regarding the same structure effect | action as the background art of FIG.

(First embodiment)
1 to 3 are configuration diagrams of a first embodiment of a color image forming apparatus 200 according to the present invention. As shown in FIGS. 1 and 2, the laser scanner units 170 </ b> A, 170 </ b> B, 170 </ b> C, and 170 </ b> D are installed in the vertical direction of the image forming apparatus, and the rotation plane of the polygon mirror and the scanner motor 171 is irradiated with laser on the image carrier 40. It is arranged perpendicular to the direction, that is, in the vertical direction of the apparatus. (That is, the rotation axis of the polygon mirror and the scanner motor 171 is parallel to the laser irradiation direction with respect to the image carrier 40.)
The laser scanner units 170A to 170D shown in FIG. 2 are arranged so as to overlap in the vertical direction of the apparatus as shown in FIG. 1, so that the image forming apparatus main body 100 according to the background art of the same size and the same specification is used. A space that can serve as an air duct is formed between the wall surfaces of the paper discharge unit 6 and the wall surfaces of the laser scanner units 170A to 170D. That is, the space between the plurality of laser scanner units 170A to 170D and the paper discharge conveyance unit 6 forms an air duct shape portion extending in the vertical direction. Above this space, there is only one fan 90 for blowing outside air into this space.

  When the fan 90 rotates, the flow of air by the fan 90 and the flow of heated air generated in the fixing device 30 are as shown by arrows C and H shown in FIGS. Become. That is, the cooling air flow C generated by the fan 90 also serves as an air curtain covering almost the entire wall surface of the laser scanner units 170A to 170D, and the cooling air flow C removes the heated air H from the fixing device 30. In addition to the role of pulling to the exhaust port 110, it also serves as a heat insulating layer for the laser scanner units 170A to 170D. As a result, the heated air H is less likely to flow in the direction of the process cartridge 1A, and the laser scanner unit The difference in temperature rise between 170A to 170D can be reduced, and deterioration of the image quality transferred to the sheet P can be prevented.

  As described above, according to this embodiment, each component in the image forming apparatus can be efficiently cooled without using a plurality of or larger cooling fans.

(Second embodiment)
FIG. 4 is a configuration diagram of a second embodiment of a color image forming apparatus 300 according to the present invention. The difference from the first embodiment is that a slit S, which is an opening, is formed in the wall surface of the paper discharge conveyance unit 6 that forms an air flow. A part of the cooling air flow C can also cool the sheet P immediately after being fixed by the fixing device 30 through the slit S. Therefore, the toner on the sheet P that has not been completely cured immediately after fixing can be cooled before the sheet P engages with the conveying roller pair 7 to accelerate the curing of the toner, so that the roller marks by the conveying roller pair 7 are not noticeable. It becomes possible to do.

  As described above, according to the present exemplary embodiment, the image on the sheet immediately after fixing can be cooled by a simple configuration change. Therefore, color deviation, density unevenness, and conveyance roller traces are more conspicuous than the background art. It is possible to obtain a satisfactory color image.

1 is a diagram illustrating an image forming apparatus that is an embodiment of the present invention. The figure which shows the laser scanner unit of FIG. AA sectional drawing of FIG. FIG. 6 is a diagram illustrating an image forming apparatus according to another embodiment of the present invention. 1 is a diagram illustrating an image forming apparatus that is a background art of the present invention. The figure which shows the laser scanner unit of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A-D Process cartridge 6 Paper discharge conveyance part 7 Paper discharge conveyance roller 10 Paper discharge conveyance path 30 Fixing device 40A-D Image carrier 70A-D, 170A-D Laser scanner unit 90 Cooling fan 100, 200, 300 Device main body P Sheet C Air flow by cooling fan H Air flow heated by fixing device

Claims (3)

A plurality of image carriers, a plurality of laser scanner units each provided with a rotating member and irradiating each of the plurality of image carriers with a laser beam, fixing means for heating and fixing an unfixed image on the recording material, and conveying the recording material The plurality of image carriers and the plurality of laser scanner units are arranged in a vertical direction, and the fixing unit is provided below the plurality of laser scanner units and the conveyance unit. In the image forming apparatus,
A cooling unit is provided above the fixing unit, and the plurality of laser scanner units are arranged such that a rotation plane of a rotating member thereof is substantially vertical, and the cooling unit includes the plurality of laser scanner units and the transport unit. An image forming apparatus characterized in that air is fed in between.   The image forming apparatus according to claim 1, wherein a space between the plurality of laser scanner units and the conveyance unit forms an air duct shape portion extending in a vertical direction. The conveyance unit has an opening for guiding a part of air sent between the plurality of laser scanner units and the conveyance unit to a recording material heated by the fixing unit. The image forming apparatus according to 1.

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