JP2010079048A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To protect a driving roller, which is disposed near a fixing device, from the heat of the fixing device with a simple configuration. <P>SOLUTION: When an exhaust fan 21 is operated, air flowing into a lower side of a transfer belt 17 from a suction port 3B reaches a first space 15A via a gap 3C provided between the driving roller 17A and the fixing device 11, and then passes through an image agent filter 19A and an ozone filter 19B, and flows toward an exhaust port 3A to be exhausted to a housing 3 side. Thus, the driving roller 17A is positioned in cooling air flowing from the suction port 3B to the exhaust port 3A, and disposed so that a shaft direction of the driving roller 17A may cross a main current direction of the cooling air. The driving roller 17A is protected, therefore, from the heat of the fixing device 11 with the simple configuration. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

For example, in the invention described in Patent Document 1, in order to protect the driving roller of the belt unit from the heat generated from the fixing device, the driving roller has a hollow structure and cooling air is directed from one end side in the axial direction toward the other end side. It is distributed.
JP 10-48972 A

  However, in the invention described in Patent Document 1, it is necessary to dispose a blower such as a blower or a blow duct on the axial end portion side of the drive roller, and the arrangement structure of the devices constituting the image forming apparatus becomes complicated. Since there is a high risk, it is considered that it is very difficult to adopt the invention described in Patent Document 1 as it is in a commercial product.

  An object of the present invention is to protect a roller such as a driving roller disposed in the vicinity of a fixing device with a simple configuration from the heat of the fixing device.

  In order to achieve the above object, the present invention provides an electrophotographic image forming apparatus that forms an image on a recording sheet by transferring a developer image to the recording sheet. The belt (17) is bridged between the endless belt (17), the driving roller (17A) for rotationally driving the belt (17), and the driving roller (17A). A driven roller (17B) that is driven to rotate, and a fixing device (11) that is disposed in the vicinity of the drive roller (17A) or the driven roller (17B) and heats and fixes the developer image transferred to the recording sheet; A fan (21) that generates an airflow that is provided on one side of the belt (17) and flows from an air inlet (3B) toward an exhaust port (3A) of the other side of the belt (17). Equipped with drive low The fixing side roller (17A) located on the fixing device (11) side among the (17A) and the driven roller (17B) is located in the airflow flowing from the air inlet (3B) toward the air outlet (3A), and The axial direction is arrange | positioned so that it may cross | intersect with the mainstream direction of airflow, It is characterized by the above-mentioned.

  Thus, in the invention described in claim 1, the fixing side roller (17A) is positioned in the airflow flowing from the intake port (3B) toward the exhaust port (3A) (hereinafter, this airflow is referred to as cooling air). In addition, since the axial direction is arranged so as to intersect the main flow direction of the cooling air, the fixing side roller (17A) is protected from the heat of the fixing device (11) with a simple configuration. can do.

  The “fixing device (11) disposed near the driving roller (17A) or the driven roller (17B) and fixing the developer image transferred to the recording sheet by heating” means “background art” and As is clear from the description in the section “Problems to be Solved by the Invention”, “the driving roller (17A) or the driven roller (17B) are close enough to be affected by the heat from the fixing device (11)”. The specific dimensions differ depending on the specifications of the image forming apparatus.

  According to the second aspect of the present invention, the belt (17) includes the photosensitive drum (7A) disposed opposite to the tension surface (17C) of the belt (17) and carrying the developer image. 17), and is provided on the opposite side to the photosensitive drum (7A).

Accordingly, in the invention according to the second aspect, since the transferred developer image is not directly exposed to the cooling air, the fixing side roller (17A) can be cooled even during the transfer. The fixing roller (17A) can be protected from the heat of the fixing device (11) while preventing the developer image from being disturbed. After the transfer, an intermediate transfer method for transferring the transferred developer image to the recording sheet, or a direct method for transferring the developer image directly to the recording sheet while conveying the recording sheet by the belt (17). It can be applied to either method.

  When the invention according to claim 2 is applied to the direct type image forming apparatus, cooling air is blown from the back side of the recording sheet, that is, from the belt (17) side, so that the recording sheet is belt (17). It becomes easy to peel from.

  For this reason, when the invention according to claim 2 is applied to the direct type image forming apparatus, the recording sheet on which the transfer of the developer image has been completed is peeled off from the belt (17) to ensure the fixing device (11). Therefore, jamming such as sheet jamming can be suppressed.

  In the invention according to claim 3, the intake port (3B) or the exhaust port (3A) is a space on the sheet mounting portion (13) side where the recording sheet before the developer image is transferred is mounted. It is characterized by communicating with.

  Thus, in the invention described in claim 3, since the airflow can be generated in the space on the sheet placement portion (13) side, the inside of the sheet placement portion (13) can be dehumidified, and the recording sheet The transportability and the quality of the image formed on the recording sheet can be improved.

  In the invention described in claim 4, a gap (3C) through which an airflow can flow is provided between the fixing side roller (17A) and the fixing device (11). 17A), the side facing the fixing device (11) rotates in the direction opposite to the flow direction of the airflow flowing through the gap (3C).

  Accordingly, in the invention according to the fourth aspect, the side facing the fixing unit (11) in the periphery of the fixing side roller (17A) is in a turbulent state, and the heat transfer rate is increased, so that the fixing side roller (17A) Cooling efficiency is improved.

  The invention according to claim 5 is characterized in that a transfer roller (14) for transferring the developer image onto the recording sheet conveyed by the belt (17) is provided. That is, the invention described in claim 5 is the one in which the invention described in any one of claims 1 to 4 is applied to a direct image forming apparatus that directly transfers a developer image onto a recording sheet. is there.

  By the way, since the drive roller (17A) drives and rotates the belt (17), when the drive roller (17A) thermally expands and the outer peripheral diameter varies, the rotational speed of the belt (17) varies greatly. There is a risk that.

  On the other hand, the invention according to claim 6 is characterized in that the fixing side roller is the drive roller (17A). Therefore, the drive roller (17A) can be sufficiently cooled, and the belt (17 ) Can be prevented from greatly fluctuating.

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

Embodiments of the present invention will be described below with reference to the drawings.
1. FIG. 1 is a central sectional view showing a schematic configuration of an image forming apparatus 1 according to the present embodiment, and FIG. 2 is an enlarged view showing a main part of the image forming apparatus 1 according to the present embodiment. These are the figures which looked at the inlet 3B from the downward side.

2. Configuration of image forming apparatus 2.1. Schematic Structure of Image Forming Apparatus In the housing 3 of the image forming apparatus 1, as shown in FIG. 1, a developer image is transferred to a recording sheet (hereinafter referred to as a sheet) such as a recording sheet or an OHP sheet. An electrophotographic image forming unit 5 for forming an image on a sheet is accommodated. As is well known, the image forming unit 5 includes a process cartridge 7, an exposure unit 9, a fixing unit 11, and the like.

  The paper feed cassette 13 is a sheet placement portion on which paper conveyed to the image forming portion 5, that is, paper before the developer image is transferred, is placed on the apparatus main body. It is detachably attached to.

  The sheets placed in the sheet feeding cassette 13 are transported toward the image forming unit 5 by the pickup roller 13A, and then separated one by one by the separation roller 13B and the separation pad 13C, and are then fed to the image forming unit 5. Be transported.

  In addition, since the image forming apparatus 1 according to the present embodiment is a direct tandem color laser printer, a plurality of (four in the present embodiment) process cartridges 7 are arranged in series along the sheet conveyance direction. It is installed.

  Specifically, the process cartridge 7K for black, the process cartridge 7Y for yellow, the process cartridge 7M for magenta, and the process cartridge 7C for cyan are sequentially arranged from the upstream side in the sheet conveyance direction.

  The process cartridges 7K to 7C differ only in the color of the stored developer, and the structure and the like are almost the same. Specifically, each process cartridge 7K to 7C carries a developer image. The photosensitive drum 7A, the charger 7B for charging the photosensitive drum 7A, the cleaner 7D for cleaning the surface of the photosensitive drum 7A after the transfer, and the like.

  The exposure unit 9 is composed of four exposure units 9K to 9C corresponding to the process cartridges 7K to 7C. Specifically, the exposure unit 9K for the process cartridge 7K and the exposure unit for the process cartridge 7Y. 9Y, an exposure unit 9M for the process cartridge 7M, and an exposure unit 9C for the process cartridge 7C.

  Each of the exposure units 9K to 9C is an exposure unit that exposes the photosensitive drum 7A by arranging a large number of LEDs in a direction parallel to the axial direction of the photosensitive drum 7A and performing blinking control of these LEDs.

  Further, the fixing device 11 is disposed on the printing surface side of the sheet, and is disposed on the opposite side of the heating roller 11A with the sheet sandwiched between the heating roller 11A that applies a conveying force to the sheet while heating the developer. A pressure roller 11B that presses the sheet toward the heating roller 11A is included.

  Then, after exposing the charged photosensitive drum 7A with the exposure device 9 to form an electrostatic latent image on the outer peripheral surface of the photosensitive drum 7A, when a charged developer is supplied to the photosensitive drum 7A, the photosensitive drum 7A A developer image is carried (formed) on the outer peripheral surface.

  Further, a transfer roller 14 for transferring the developer carried on the photosensitive drum 7A to the sheet is provided at a position facing the photosensitive drum 7A across the stretching surface 17C of the transfer belt 17 that conveys the sheet. The transfer roller 14 is applied with a potential having a polarity opposite to the charge of the developer.

  For this reason, the developer image carried on the photosensitive drum 7 </ b> A is transferred onto the sheet conveyed by the transfer belt 17. Then, the sheet on which the developer image is transferred is conveyed to the fixing device 11 and heated, and the developer image transferred onto the sheet is fused (fixed) to the sheet.

  Further, the driving roller 17A rotates the transfer belt 17 formed in an endless manner, and the driven roller 17B has the transfer belt 17 spanned between the driving roller 17A and as the transfer belt 17 rotates. Followed rotation.

  In this embodiment, the transfer belt 17, the driving roller 17A, and the driven roller 17B are integrated as a belt unit, and this belt unit is detachably attached to the apparatus main body.

  Then, as described above, the sheet on which the developer image has been transferred is carried out from the transfer belt 17 to the fixing unit 11, but the developer before being heated by the fixing unit 11 is easily peeled off from the sheet. In the present embodiment, by disposing the driving roller 17A disposed on the fixing device 11 side in the vicinity of the fixing device 11, the distance from the image forming unit 5 (driving roller 17A) to the fixing device 11 is reduced. The developer before fixing is prevented from peeling off.

  Note that “disposing the driving roller 17A in the vicinity of the fixing device 11” means that the driving roller 17A is close enough to be affected by the heat from the fixing device 11 ”. Specifically, in this embodiment, “the axis O1 of the driving roller 17A is positioned closer to the fixing device 11 than the photosensitive drum 7A or the transfer roller 14 closest to the fixing device 11”.

2.2. As shown in FIG. 1, the inside and outside of the housing 3 communicate with each other on the upper side surface of the housing 3 so that the air (hot air) in the housing 3 is exhausted to the upper side surface of the housing 3. An exhaust port 3A is provided outside the housing 3, and the exhaust port 3A is provided above the position (line L1) where the transfer belt 17 is disposed.

  Further, between the process cartridge 7C closest to the fixing device 11 and the fixing device 11, as shown in FIG. 2, the first space 15A side and the charging device 7B side through which the sheet conveyed to the fixing device 11 passes. A partition wall 15 is provided to partition the second space 15B side, and the partition wall 15 has a double wall structure in which a gap portion 15C is provided.

  Further, a developer filter (toner filter) 19A for removing the developer (toner) is provided above the first space 15A, and the air in the first space 15A is guided to the partition wall 15. It flows into the developer filter 19A.

  Further, an ozone filter 19B for reducing ozone contained in the air in the housing 3 is disposed on the downstream side of the air flow of the developer filter 19A, that is, on the upper side of the developer filter 19A. Almost all of the air that has passed through the developer filter 19A flows into 19B.

  In addition, a communication port 15E for communicating the second space 15B and the passage 15D is provided in the substantially linear airflow passage 15D from the developer filter 19A to the ozone filter 19B, and the air in the second space 15B is provided. Enters the passage 15D from the communication port 15E and flows into the ozone filter 19B. Therefore, in the present embodiment, the air that has passed through the developer filter 19A and the air in the second space 15B that has entered from the communication port 15E flow into the ozone filter 19B.

  An exhaust duct 19 that guides the air that has passed through the ozone filter 19B to the exhaust port 3A is provided on the downstream side of the air flow of the ozone filter 19B. The exhaust duct 19 is in the left-right direction of the image forming apparatus 1, that is, A tubular airflow passage extending substantially parallel to the axial direction of the photosensitive drum 7A is formed.

  Further, on one end side in the longitudinal direction of the exhaust duct 19 (right side toward the image forming apparatus 1 in this embodiment), exhaust that generates an airflow flowing from the first space 15A and the second space 15B toward the exhaust port 3A. A fan 21 is provided, and the exhaust side of the exhaust fan 21 faces the exhaust port 3A. In the present embodiment, the exhaust fan 21 is constituted by an axial fan (see JIS B 0132 number 1012 or the like) through which air passes in the rotation axis direction.

  Further, below the position (line L1) where the transfer belt 17 is disposed, the space communicates with the space 13D in which the paper feed cassette 13 is mounted so as to face the paper placed on the paper feed cassette 13. An intake port 3B is provided.

  For this reason, when the air in the housing 3 is discharged out of the housing 3 by the exhaust fan 21, it passes through the air inlet 3B from the space 13D and is below the transfer belt 17 as shown by an arrow A1 in FIG. The air that flows into the air reaches the first space 15A via a gap 3C provided between the driving roller 17A and the fixing device 11.

  The air flowing into the first space 15A passes through the developer filter 19A and the ozone filter 19B, flows toward the exhaust port 3A, and is discharged to the housing 3 side. Incidentally, when the air in the space 13D flows toward the gap 3C, the atmospheric pressure in the space 13D decreases, so that external air flows into the space 13D from the gap between the paper feed cassette 13 and the housing 3 or the like.

  Further, as shown in FIG. 3, the air inlet 3 </ b> B is formed in a long hole shape such that the major axis direction coincides with the front-rear direction of the image forming apparatus 1, and not the entire width direction of the image forming apparatus 1. It is provided on one end side in the width direction from the substantially central portion in the width direction (in this embodiment, on the same side as the exhaust fan 21).

The intake port 3B may be provided on the side opposite to the exhaust fan 21 or may be provided in the entire width direction, and can be appropriately set according to the air flow inside the image forming apparatus 1.
3. Features of the Image Forming Apparatus According to the Present Embodiment In the present embodiment, as described above, when the exhaust fan 21 operates, the air that flows into the lower side of the transfer belt 17 from the air inlet 3B (the airflow indicated by the arrow A1 in FIG. 2). ) Reaches the first space 15A via a gap 3C provided between the driving roller 17A and the fixing device 11, and then passes through the image agent filter 19A and the ozone filter 19B toward the exhaust port 3A. It flows and is discharged to the housing 3 side.

  Accordingly, in the present embodiment, the driving roller 17A is positioned in the cooling air flowing from the intake port 3B toward the exhaust port 3A, and the axial direction of the driving roller 17A intersects the main flow direction of the cooling air. Thus, the driving roller 17A can be protected from the heat of the fixing device 11 with a simple configuration.

  Further, in the present embodiment, the air inlet 3B is provided on the opposite side of the photosensitive drum 7A across the transfer belt 17, that is, on the lower side of the transfer belt 17, so that the fixing device is connected to the sheet being transferred or the transfer belt 17. When the paper is transported to the paper 11, the transferred developer image is not directly exposed to the cooling air.

Accordingly, since the driving roller 17A can be cooled while forming an image on the paper, the driving roller 17A can be protected from the heat of the fixing device 11 while preventing the developer image before fixing from being disturbed. Since the cooling air is blown from the back side of the paper, that is, from the transfer belt 17 side, the paper is easily peeled off from the transfer belt 17 by the wind pressure of the cooling air. For this reason, in the present embodiment, the sheet on which the transfer of the developer image has been completed can be peeled off from the transfer belt 17 and reliably conveyed to the fixing device 11, so that the occurrence of a jam such as a paper jam can be suppressed.

  In the present embodiment, since the air inlet 3B communicates with the space 13D in which the paper feed cassette 13 is mounted, an airflow can be generated in the space 13D. Therefore, since the inside of the paper feed cassette 13 can be dehumidified, the paper transportability and the quality of the image formed on the paper can be improved.

  In the present embodiment, the side of the driving roller 17A that faces the fixing device 11 rotates in the direction opposite to the direction of airflow flowing through the gap 3C as shown in FIG. Of the periphery of the roller 17A, the side facing the fixing device 11 is in a turbulent state. For this reason, since the heat transfer coefficient around the drive roller 17A is increased, the cooling efficiency of the drive roller 17A is improved.

  Incidentally, since the driving roller 17A drives the transfer belt 17 to rotate, if the driving roller 17A thermally expands and the outer peripheral diameter changes, the rotational speed of the transfer belt 17 may greatly change.

On the other hand, in the present embodiment, the driving roller 17A is sufficiently cooled by the cooling air, so that the rotation speed of the transfer belt 17 can be prevented from greatly fluctuating.
(Other embodiments)
In the above-described embodiment, the driving roller 17A is disposed on the fixing device 11 side. However, the present invention is not limited to this, and the driven roller 17B may be disposed on the fixing device 11 side.

  In the above-described embodiment, the intake port 3B is provided on the lower side with the transfer belt 17 interposed therebetween, and the exhaust port 3A is provided on the upper side with the transfer belt 17 interposed therebetween. However, the present invention is limited to this. Instead, the intake port 3B may be provided above the transfer belt 17 and the exhaust port 3A may be provided below the transfer belt 17.

  In the above-described embodiment, the two filters 19A and 19B are arranged horizontally. However, the present invention is not limited to this. For example, the two filters 19A and 19B are arranged vertically. Also good.

  In the above-described embodiment, the ozone filter 19B is disposed on the downstream side of the developer filter 19A. However, the present invention is not limited to this, and the ozone filter 19B is disposed on the upstream side of the developer filter 19A. May be provided.

  In the above-described embodiment, the intake port 3B communicates with the space 13D in which the paper feed cassette 13 is mounted. However, the present invention is not limited to this, and the exhaust port 3A communicates with the space 13D. It is good also as a structure which makes neither the inlet port 3B nor the exhaust port 3A communicate with the space 13D.

  In addition, the exposure unit 9 according to the above-described embodiment is configured by an LED. However, the present invention is not limited to this, and exposure that exposes the photosensitive drum 7A while scanning with a laser beam. It may be a vessel.

In the above-described embodiment, an axial fan is used as the exhaust fan 21, but the present invention is not limited to this, and other types of fans such as a centrifugal fan may be used.
Moreover, in the above-mentioned embodiment, although the partition wall 15 was made into the double wall structure, this invention is not limited to this.

  In the above-described embodiment, the present invention is applied to a direct tandem type laser printer. However, the application of the present invention is not limited to this, and a monochrome electrophotographic image forming apparatus or an intermediate transfer It can also be applied to a color laser printer of the type.

  Further, the present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

1 is a central sectional view showing a schematic configuration of an image forming apparatus 1 according to the present embodiment. 2 is an enlarged view showing a main part of the image forming apparatus 1 according to the present embodiment. FIG. It is the figure which looked at the inlet 3B from the downward side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 3 ... Housing, 3A ... Exhaust port, 3B ... Intake port, 3C ... Clearance,
5 ... Image forming unit, 7 ... Process cartridge, 7A ... Photosensitive drum, 7B ... Charger,
DESCRIPTION OF SYMBOLS 9 ... Exposure device, 11 ... Fixing device, 11A ... Heating roller, 13 ... Paper feed cassette,
13A ... Pickup roller, 13B ... Separation roller, 13C ... Separation pad,
14 ... transfer roller, 15 ... partition wall, 15A ... first space, 15B ... second space,
15C ... Gap, 15D ... Passage, 15E ... Communication port, 17 ... Transfer belt,
17A ... Driving roller, 17B ... Driven roller, 17C ... Stretching surface, 19 ... Exhaust duct,
19A ... Developer filter, 19B ... Ozone filter, 21 ... Exhaust fan.

Claims (6)

An electrophotographic image forming apparatus that forms an image on a recording sheet by transferring a developer image to the recording sheet,
An endless belt,
A driving roller for rotating the belt;
A driven roller that is laid across the belt between the drive rollers and that rotates following the rotation of the belt;
A fixing device that is disposed in the vicinity of the driving roller or the driven roller and heats and fixes the developer image transferred to the recording sheet;
A fan that generates an airflow that is provided on one side across the belt and flows from an air inlet toward an exhaust port provided on the other side across the belt;
Among the driving roller and the driven roller, the fixing side roller located on the fixing device side is located in the airflow flowing from the air inlet to the air outlet, and its axial direction is relative to the main flow direction of the airflow. And an image forming apparatus arranged so as to intersect each other. A photosensitive drum disposed opposite to the belt tension surface and carrying a developer image;
The image forming apparatus according to claim 1, wherein the intake port is provided on a side opposite to the photosensitive drum with the belt interposed therebetween.   3. The air intake port or the air exhaust port communicates with a space on a sheet placement portion side on which a recording sheet before a developer image is transferred is placed. Image forming apparatus. Between the fixing side roller and the fixing device, a gap through which the airflow can flow is provided,
4. The fixing roller according to claim 1, wherein a side facing the fixing unit of the fixing side roller rotates in a direction opposite to the direction of the airflow flowing through the gap. The image forming apparatus described.   5. The image forming apparatus according to claim 1, further comprising a transfer roller configured to transfer a developer image to the recording sheet conveyed by the belt. The image forming apparatus according to claim 1, wherein the fixing roller is the driving roller.

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