JP4773699B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a plotter that forms a single color image or a multicolor image.

  The image forming apparatus includes an optical writing unit that writes a latent image by deflecting and irradiating a light beam on the surface (scanned surface) of the image carrier, and a developer that develops the latent image formed on the image carrier with a developer. And an image unit. After the developed image is transferred to a recording sheet, it is fixed by a fixing unit to form a single-color or multicolor image.

  In such an image forming apparatus, the temperature in the apparatus body rises due to the heat generated by the motor of the polygon mirror in the optical writing unit that deflects and scans the light beam, and the heat generated from the fixing means, resulting in poor optical characteristics of the optical system. The problem is that the image becomes stable and the sharpness of the image is lowered. For this reason, an image forming apparatus having a structure for cooling the inside of the apparatus main body has been conventionally developed.

For example, Patent Document 1 discloses a structure in which cooling is performed by providing a duct between the optical writing unit and the fixing unit and arranging a plurality of fans in the duct. Patent Document 2 discloses a structure in which an intake fan is provided in the vicinity of an optical writing unit and a developing unit of an image forming unit provided below the optical writing unit, thereby simultaneously cooling them. Yes. Further, Patent Document 3 discloses a structure in which cooling is performed by forming an air flow path by separating the optical writing unit and the photosensitive unit by a partition plate.
JP 2002-108177 A JP-A-7-191593 Japanese Patent No. 3363398

  However, each of the structures described above requires a fan and a duct for each of the optical writing unit and the image forming unit. Therefore, the structure is complicated, and the assembly is troublesome and the cost is high. Yes. Further, members such as a duct and a partition plate are required, and there is a problem that is not suitable for downsizing the apparatus main body.

  In particular, in an image forming apparatus having a structure in which an image forming unit for developing with a developer is disposed above the optical writing unit, the developer of the image forming unit or the optical writing unit disposed on the lower side Unit-driven friction powder falls. When these adhere to the upper part of the dust-proof glass, the light beam for image formation is interrupted, so that there is a fatal problem that the image quality deteriorates due to white streaks, black streaks, etc. in the image. .

  The present invention has been made in consideration of such problems, and can be cooled with a simple structure, and also in a structure in which the image forming unit is disposed above the optical writing unit. An object of the present invention is to provide an image forming apparatus capable of preventing adhesion of an agent and friction powder.

According to the first aspect of the present invention, there is provided an optical writing unit for forming a latent image on a surface of an image carrier by deflecting and scanning a light beam and guiding it to the image carrier, and a photosensitive unit comprising at least the image carrier. And a developing unit that develops the latent image on the surface of the image carrier with a developer in a side-by-side arrangement, the image forming unit provided above the optical writing unit, and the image forming unit. A fan for supplying an air flow for cooling the image unit and the optical writing unit, and a gap between the image forming unit and the optical writing unit serves as the air flow path, and each corner of the fan arrangement side of the optical slope portion for guiding the air flow into the passage so the air volume is increased to the write unit the imaging unit and the optical writing unit than the air volume of the image forming unit Is formed in the opposing state to end by cutting out in order, the inclined start and slope ending point of the inclined portion of the image forming unit is substantially coincident with the inclination starting point and slope ending point of the inclined portion of the optical writing unit, the operation The inclination of the inclined portion of the image unit is larger than the inclination of the inclined portion of the optical writing unit.

  According to the present invention, since the gap between the image forming unit and the optical writing unit is used as a passage for airflow from the fan, a cooling-dedicated duct is unnecessary, the structure is simple, and the apparatus is downsized. Can do.

  In addition, an inclined portion is formed at the end of the image forming unit and the optical writing unit on the fan arrangement side, and the air flow is passed through the passage so that the amount of air flow to the optical writing unit is larger than the image forming unit. Therefore, it is possible to reliably prevent the developer and the friction powder from adhering to the optical writing unit below the image forming unit. For this reason, it is possible to prevent a decrease in image quality. In addition, since the air volume adjustment is performed only by the inclined portion formed in the image forming unit and the optical writing unit, not only the structure for air volume adjustment is simplified, but a member such as a fan for air volume adjustment is not required. The apparatus can be downsized.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings. In each embodiment, the same members are assigned the same reference numerals.

(Embodiment 1)
1 to 3 show Embodiment 1 of the present invention, FIG. 1 is a cross-sectional view showing the overall configuration of the image forming apparatus, FIG. 2 is a cross-sectional view of an image forming unit, and FIG. FIG.

  The image forming apparatus of this embodiment forms a color image with four colors of yellow (Y), cyan (C), magenta (M), and black (B). As shown in FIG. A writing unit 5 and a process cartridge 200 for forming a color image are arranged in the apparatus main body 1. The process cartridge 200 is detachable from the apparatus main body 1 and is disposed above the optical writing unit 5.

  In the process cartridge 200, each of the image forming units 1Y, 1M, 1C, and 1B for forming images of each color of Y, M, C, and K is set as one unit, and these one unit of the image forming units 1Y, 1M, and 1C. 1B are arranged side by side. The optical writing unit 5 forms a latent image on the surface of the photoconductor 3 by deflecting and scanning the light beam on the photoconductor 3 as an image carrier in each of the image forming units 1Y, 1M, 1C, and 1B. To do. For this reason, an optical polarizer such as a polygon mirror that is rotated at a high speed by a mirror motor is provided inside. A paper feed tray 20 that stores and supplies recording paper 21 is disposed below the optical writing unit 5, and an intermediate transfer belt 4 of the transfer unit is disposed above the image forming unit 200. .

  FIG. 2 shows the structure of the process cartridge 200 in each of the image forming units 1Y, 1M, 1C, and 1B. The process cartridge 200 for each color is configured by arranging a photoconductor unit 200A and a developing unit 200B side by side. In this case, as long as the photosensitive unit 200A and the developing unit 200B are arranged side by side, these units 200A and 200B may be integrated.

  The photoreceptor unit 200A includes a photoreceptor 3 as an image carrier. Around the photoconductor 3, a charger 7 and a cleaning device 11 are arranged. The photosensitive member 3 rotates in the clockwise direction, and the surface of the photosensitive member 3 that rotates in the clockwise direction is charged to a predetermined potential by the charging roller 7A of the charger 7. In order to prevent the surface of the charging roller 7 from being soiled, the charger 7 cleans the surface by a cleaning roller 7B. The photosensitive member 3 uniformly charged by the charger 7 is irradiated with the light beam L deflected and scanned by the optical writing unit 5 and exposed by the irradiation of the light beam L to form an electrostatic latent image on the surface. Is done.

  The developing unit 200B has a developing case 9A that forms an outer shell. Inside the developing case 9A, a developing roller 31, a conveying screw 9C and 9B, and a developing doctor 9D that are arranged to be partially exposed. A toner density sensor 9E is disposed. Further, the developing case 9A is formed with a hopper portion 9F above the conveying screw 9C, and the toner container 20 (20Y, 20M, 20C) of FIG. 1 is provided to the hopper portion 9F in each color developing unit 200B. , 20K), the toner can be replenished.

  The developing case 9A contains a two-component developer (hereinafter, developer) containing a magnetic carrier and negatively charged toner. The developer is frictionally charged while being agitated and conveyed by the conveying screws 9C and 9B, and is then carried on the surface of the developing roller 31. Then, after the layer thickness is regulated by the developing doctor 9D, the layer is transported to the developing position facing the photoconductor 3, and the toner adheres to the electrostatic latent image on the photoconductor 3. Due to this adhesion, a toner image of a predetermined color is developed on the photoreceptor 3. The developer that has consumed the toner by the development is returned to the developing case 9 </ b> A as the developing roller 31 rotates. The toner concentration of the developer in the developing case 9A is detected by the toner concentration sensor 9E, and toner is supplied from the toner storage container 20Y to the hopper portion 9F as necessary.

  The photoreceptor 3 on which the toner image has been developed contacts the intermediate transfer belt 4 of the transfer unit disposed above to form a transfer nip as a transfer position. The toner developed on the photoreceptor 3 is transferred onto the intermediate transfer belt 4. The toner remaining on the photosensitive member 3 without being transferred is removed by the cleaning blade 11B, and is transported to a storage unit (not shown) by the toner transport auger 11C.

  Note that such a process cartridge 200 is provided with a reference for attachment to and detachment from the apparatus main body 1. In this reference, holes provided in the flanges at both ends of the photoconductor 3 are used as positioning main reference parts, while positioning sub-reference parts are provided on the front side and the back side. When the photoreceptor unit 200A is attached to the apparatus main body 1, the reference unit and the engaging portion provided in the apparatus body 1 are used for positioning, whereby the photoreceptor unit 200A is mounted on the apparatus body 1 in a predetermined manner. The position can be reliably positioned.

  In the above structure, the air flow path is formed between the image forming units 1Y, 1M, 1C, and 1B that are arranged side by side and positioned on the upper side and the optical writing unit 5 that is positioned on the lower side. 30. A fan 300 that supplies an air flow to the passage 30 is disposed on the start end side of the passage 30. The fan 300 is provided inside the fan cover 400 facing the passage 30, thereby sucking air from the outside of the apparatus main body 1 and supplying an air flow to the passage 30. By supplying an air flow to the passage 30, the optical writing unit 5 and the image forming units 1Y, 1M, 1C, and 1B are cooled.

  Next, the cooling structure in this embodiment will be described with reference to FIG. As shown in FIG. 3, an upper cover 101 is provided on the upper part of the optical writing unit 5, and a dustproof glass 102 is attached to the upper cover 101 by fitting or the like. The dust-proof glass 102 transmits the light beams irradiated on the photoreceptors 3 of the respective image forming units 1Y, 1M, 1C, and 1B.

  As shown in FIG. 3, inclined portions 33 and 35 are formed in an opposed state at the ends of the image forming units 1Y, 1M, 1C, and 1B and the optical writing unit 5 on the side where the fan 300 is disposed. . In the side-by-side image forming units, the inclined portion 33 may be formed on the end of the image forming unit 1Y closest to the fan 300, and the inclined portion is formed on the other image forming units. This is not necessary, and the inclined portion 33 on the image forming unit 1Y side will be described below.

  The inclined portion 33 of the image forming unit 1Y is formed by obliquely cutting off the corner portion on the fan 300 side in the developing case 9A of the developing unit 200B, and the inclined portion 35 of the optical writing unit 5 is an upper cover thereof. 101 is formed by notching diagonally the corner on the fan 300 side. These inclined portions 33 and 35 are inclined so that the width of the passage 30 gradually decreases as the distance from the fan 300 increases.

  The inclined portion 33 has an inclination start point B on the air flow inlet side of the developing unit 200B in the image forming unit 1Y and an inclination end point C on the downstream side. The same applies to the inclined portion 35, and the air flow inlet side of the upper cover 101 of the optical writing unit 5 is set as the inclination start point D, and the downstream side thereof is set as the inclination end point E. In this embodiment, when the inclination start point and the inclination end point in the inclined portions 33 and 35 are set as the horizontal distance in which the airflow flows from the fan 300 side, the relations D <B and E <C are established. . By setting in this way, the inclination end point C of the inclined portion 33 of the image forming unit 1Y is positioned downstream of the inclination end point E of the inclined portion 35 of the optical writing unit 5, and the image forming unit 1Y. The inclination start point B of the inclined portion 33 is located upstream of the inclination end point E of the inclined portion of the optical writing unit 5 in the air flow.

  In the configuration set as described above, the wind from the fan 300 is directed upward by the inclination of the inclined portion 35 of the optical writing unit 5 and directed downward by the inclination of the inclined portion 33 of the developing unit 200B. At this time, since there is a relationship set as E <C, the air flow toward the lower side (optical writing unit 5 side) occupies a large amount. For this reason, in the passage 30, as shown by the thick arrow 37 in FIG. 3, the air flow is along the lower side of the axis A of the fan 300. This air flow increases the amount of air blown onto the upper surface of the dust-proof glass 102 of the optical writing unit 5, so that the toner falling on the dust-proof glass 102 and the wear powder when driving the unit can be pushed out of the dust-proof glass 102. . Thereby, it is possible to prevent a decrease in image quality.

  Further, since the air volume adjustment described above is performed only by the inclined portions 33 and 35 formed in the image forming unit 1Y and the optical writing unit 5, a dedicated duct, a partition plate, etc. for air volume adjustment are not required, and the structure is simplified. In addition, the apparatus can be miniaturized.

(Embodiment 2)
FIG. 4 shows a second embodiment of the present invention. In this embodiment, the inclination start point and the inclination end point of the inclined portion 33 in the image forming unit 1Y (development unit 200B) are B ′ and C ′, and the inclination start point and the inclination end point of the inclined portion 35 in the optical writing unit 5 are D. 'And E'. These are set to have a relationship of D ′ = B ′ and E ′ = C ′ with respect to the horizontal distance from the fan 300. In addition, the inclination degree in the inclined portion 33 of the image forming unit 1Y is set to be larger than the inclination degree in the inclined portion 35 of the optical writing unit 5.

  By setting the relationship between the inclined portions 33 and 35 in this manner, the air flow from the fan 300 is higher in pressure due to the inclined portion 33 of the image forming unit 1Y and the flow velocity is increased. For this reason, the airflow synthesized in the vicinity of the inclined end points C ′ and E ′ is directed downward (on the optical writing unit 5 side) and flows along the lower side of the axis A as indicated by the thick arrow 37. This air flow increases the amount of air blown onto the upper surface of the dust-proof glass 102, and the toner falling on the dust-proof glass 102 and the wear powder when driving the unit can be pushed out of the dust-proof glass 102. Thereby, it is possible to prevent a decrease in image quality.

  In the first embodiment, even if the positional relationship between the tilt end points C and E is E <C, if the difference between C and E is small, an air flow is caused to flow downward (on the optical writing unit 5 side). In contrast to the reduced effect, in this embodiment, since the air flow to the lower side (optical writing unit 5 side) can be generated reliably, the amount of air blown to the dust-proof glass 102 increases, and the toner It is possible to reliably push out the wear powder out of the dust-proof glass 102.

(Embodiment 3)
FIG. 5 shows a third embodiment of the present invention. In FIG. 5, L _BK is black image forming light, L _Y is yellow image forming light, and image forming units 1K, 1Y... Corresponding to these are arranged side by side so as to be adjacent to each other. Further, in the image forming units 1K, 1Y,..., The developing unit 200B and the photosensitive unit 200A are arranged side by side.

  In this embodiment, a guide member 39 is provided between the adjacent image forming units 1K and 1Y. The guide member 39 is formed so as to extend from the end face on the passage 30 side of the photoreceptor unit 200A in the upstream image forming unit 1K in the direction of the developing unit 200B in the downstream image forming unit 1Y. The guide member 39 is provided in parallel with the passage 30 through which the airflow from the fan 300 flows, and smoothly guides the airflow from the fan 300 to the downstream side.

  As described above, the guide member 39 extends from the upstream image forming unit to the downstream image forming unit, so that the upstream image forming unit 1K (photosensitive member unit 200A) and the downstream image forming unit are disposed adjacent to each other. The gap d between the units 1Y (development unit 200B) becomes extremely small, and the airflow that escapes upward from the gap d can be reduced. Thereby, it can control so that the airflow which flows to the opposite side to the optical writing unit 5 can be decreased, and it can adjust so that the air volume sprayed on the dustproof glass 102 of the optical writing unit 5 may increase. .

  In the above embodiment, the case of a tandem type color laser printer has been described. However, the present invention is also applicable to a monochrome laser printer having a set of toner image forming units using black toner. Can do. The present invention can also be applied to other image forming apparatuses such as copying machines, printers, and facsimile machines.

1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus to which the present invention is applied. It is sectional drawing of an image formation unit. FIG. 3 is a cross-sectional view showing the structure of the first embodiment. 5 is a cross-sectional view showing a structure of a second embodiment. FIG. FIG. 6 is a cross-sectional view showing the structure of a third embodiment.

Explanation of symbols

5 Optical writing unit 1Y, 1M, 1C, 1K Image forming unit 3 Photoconductor 30 Passage 33, 35 Inclined portion 39 Guide member 200A Photoconductor unit 200B Developing unit 300 Fan B, D Inclination start point C, E Inclination end point

Claims (1)

An optical writing unit that forms a latent image on the surface of the image carrier by deflecting and scanning the light beam to the image carrier;
A photoconductor unit including at least the image carrier and a developing unit for developing a latent image on the surface of the image carrier with a developer are arranged side by side, and the optical writing unit includes: An image forming unit provided above;
A fan for supplying an air flow for cooling the imaging unit and the optical writing unit;
With
The gap between the image forming unit and the optical writing unit is used as the air flow path, and the air flow is set so that the air flow to the optical writing unit is larger than the air flow to the image forming unit. An inclined portion leading into the passage is formed in an opposed state to the end portion by obliquely notching each corner portion on the fan arrangement side in the image forming unit and the optical writing unit,
The inclination start point and the inclination end point of the inclined portion of the image forming unit substantially coincide with the inclination start point and the inclination end point of the inclined portion of the optical writing unit, and the inclination degree of the inclined portion of the image forming unit is equal to that of the optical writing unit. An image forming apparatus, wherein the gradient is larger than the inclination of the inclined portion.

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