JP2010197574A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents temperature rise of a belt by space saving, and simultaneously prevents belt travel from becoming unstable since scattering toner invades inside the belt to reduce friction force of a belt drive roller. <P>SOLUTION: An air cooling route in an intermediate transfer belt is set to only one by: substantially eliminating a gap between front and rear frames constituting an intermediate transfer belt unit and an end part of the cylindrical intermediate transfer belt; providing the front and rear frames with an inlet having an air filter and an outlet; and connecting the outlet to airflow including a cooling fan of a fixing device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that includes a belt unit and transfers a toner image onto a transfer material such as paper to form an image, and more particularly to a configuration that prevents scattered toner from entering the belt unit.

  2. Description of the Related Art Conventionally, there is known an electrophotographic image forming apparatus that forms characters and images on a sheet by transferring and fixing a toner image formed on a photosensitive member onto a transfer material such as a sheet.

  In particular, in recent years, an image forming apparatus using a belt body that circulates and moves from the standpoint of ease of repair and maintenance work when a paper jam occurs and the ability to reduce the size of the entire apparatus while enabling full color image formation. Is being used frequently.

  The belt body is generally incorporated in the vicinity of the photosensitive member and in the vicinity of the image forming section as a belt unit spanned by a plurality of rollers pivotally supported between a pair of frames.

  In such an image forming apparatus, the toner image formed on the photosensitive member is directly transferred onto the conveyed sheet while adsorbing the outer peripheral surface of the belt member, and the toner image is temporarily transferred from the photosensitive member to the belt as an intermediate transfer member. It is known that the image is primarily transferred to the body and then transferred from the belt body to the paper further, but in any case, the unfixed toner image transferred to the paper via the belt body is conveyed from the transfer position to the paper. The image is fixed by a heat fixing unit provided on the downstream side in the direction and discharged outside the apparatus main body.

  By the way, in the apparatus main body, since a temperature rise occurs due to a heat source such as the heat fixing unit, a cooling fan is provided for the necessity of suppressing it. And as the device becomes smaller, more efficient airflow design for the heat source and its neighboring members is desired.

  Therefore, in order to efficiently cool the belt body corresponding to the downsizing of the apparatus, a fan is provided inside the intermediate transfer belt (for example, refer to Patent Document 1), or an air flow is provided in a duct portion provided between the belt frames. Proposals have been made. (For example, see Patent Document 2.)

  However, the air flow generated in the apparatus main body scatters the toner leaked from the developing unit, the photoconductor cleaning unit, the intermediate transfer belt cleaning unit, and the like provided in the image forming apparatus. Such scattered toner is transported by the air flow formed in the apparatus main body and adheres to the inner periphery of the intermediate transfer belt, and further adheres to the surface of each roller provided in the belt rotation path in contact with the inner periphery of the belt.

JP 2005-31503 A

JP 2007-147862 A

  As described above, the belt body is configured to be stretched around a plurality of rollers. Of the plurality of rollers, in particular, the belt driving roller needs to transmit the belt driving force to the belt with high efficiency, so that a so-called rubber roller whose surface is coated with high friction rubber is generally used.

  The rubber surface has fine irregularities, and if scattered toner adheres to the rubber surface, the frictional power on the rubber surface decreases, and the belt driving roller and the belt body slip to prevent stable belt driving. The problem occurs.

  On the other hand, in the configurations described in Patent Document 1 and Patent Document 2, although the size of the device is achieved, the side of the belt body is opened inside the device main body, so that air flow into the belt causes As a result of the scattered toner being transported also to the inner periphery of the intermediate transfer belt, the problem that the scattered toner adheres to the surface of the plurality of rollers, particularly the belt driving roller, contacting the inner periphery of the belt has not been solved, and the belt drive is not stabilized. There are issues to be solved.

  In order to solve the above problems, the present invention provides a pair of opposed frames, a plurality of rollers pivotally supported between the pair of frames, and a belt body that is looped over the plurality of rollers to circulate. A belt unit having an intake port provided on one side of the frame, an exhaust port provided on the other side, an air flow forming unit that forms an air flow from the intake port to the exhaust port, and a heat fixing unit. At least, the toner image formed on the image carrier is configured to be transferred to a transfer material carried and conveyed on the outer peripheral surface of the belt member, or the toner image is primarily transferred to the outer peripheral surface of the belt member. An image that is configured to be secondary-transferred to a transfer material to be conveyed later, and forms an image by fixing an unfixed toner image transferred to the transfer material to the transfer material by the heat fixing unit. The deposition apparatus is assumed.

  In the image forming apparatus of the present invention, the belt unit is surrounded by the air flow forming means, the pair of frames, and the belt body so that no air flow is generated in the belt unit except for an air flow path by the air flow forming means. The frame and the belt body side portion are arranged close to each other so that the space to be sealed is a sealed space.

  The image forming apparatus according to the present invention may further include a cooling fan that exhausts air inside the apparatus main body to the outside of the apparatus main body and an exhaust duct that connects the exhaust port to cool the heat fixing unit. Moreover, it is preferable to provide an air filter at the intake port.

  According to the present invention, the scattered toner can be prevented from entering the inside of the belt unit, so that the toner contamination of each component inside the belt unit is prevented. As a result, the surface friction resistance of the driving roller is reduced due to the toner contamination. Therefore, it is possible to prevent performance degradation such as occurrence of belt slip due to the toner, and toner contamination on the backup driven roller, resulting in partial unevenness in the surface resistance and uneven transfer.

1 is a cross-sectional view illustrating an internal configuration of a color image forming apparatus (printer) including a belt unit according to Embodiment 1 of the present invention. FIG. 2 is an enlarged view schematically showing the configuration of the belt unit and the air flow according to the first embodiment of the present invention together with the configuration in the vicinity of the secondary transfer belt. FIG. 3 is a cross-sectional view taken along line AA ′ in FIG. 2. It is the typical side view which took out the belt unit which concerns on Example 1 of this invention, and was seen from the one frame side.

  Hereinafter, embodiments of the present invention will be described in detail. In the following description, the image carrier described in the claims includes, for example, the photosensitive drum 7, the belt body includes the intermediate transfer belt 30, the transfer target includes, for example, the paper 60, and the like. The heat fixing unit includes, for example, a belt type fixing device 67 and the like.

  FIG. 1 is a schematic side sectional view schematically showing an internal configuration of a color image forming apparatus (hereinafter simply referred to as a printer) including a belt unit according to Embodiment 1 of the present invention. The figure shows a tandem color image forming apparatus as an example. 2 is an enlarged view schematically showing the configuration and airflow of the belt unit of FIG. 1 together with the configuration in the vicinity of the secondary transfer belt, FIG. 3 is a cross-sectional view taken along line AA ′ of FIG. FIG. 4 is a schematic side view of the belt unit of the present invention taken out and viewed from one frame (front frame) side. In the drawings, the same components are denoted by the same reference numerals.

  First, the printer 1 shown in FIG. 1 is an electrophotographic secondary transfer type tandem color image forming apparatus, and includes an image forming unit 2, an intermediate transfer belt unit 3, a paper feeding unit 4, and a duplex printing conveyance. It consists of unit 5 and the like.

  The image forming unit 2 has a configuration in which four image forming units 6 (6M, 6C, 6Y, 6K) are arranged side by side in a multistage manner from right to left as shown in an enlarged manner in FIG.

  Of the four image forming units 6, three image forming units 6M, 6C and 6Y on the upstream side (the right side in the figure) are magenta (M), cyan (C) and yellow (subtractive three primary colors, respectively). A mono-color image is formed with the color toner of Y), and the image forming unit 6K forms a monochrome image with the black (K) toner mainly used for the dark portion or characters of the image.

  Each of the image forming units 6 has the same configuration except for the color of the toner stored in the toner container (toner cartridge). Therefore, the configuration of the black (K) image forming unit 6K will be described below as an example.

  The image forming unit 6 includes a photosensitive drum 7 at the bottom. The peripheral surface of the photosensitive drum 7 is made of, for example, an organic photoconductive material. A cleaner 8, a charging roller 9, an optical writing head 10, and a developing roller 12 of the developing device 11 are disposed around the periphery of the photosensitive drum 7.

  The developing unit 11 puts one of magenta (M), cyan (C), yellow (Y), and black (K) toners in the upper toner container as indicated by M, C, Y, and K in the figure. An intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  Further, the developing roller 12 is provided in the lower side of the developing device 11 at the side opening, and the toner stirring member 13, the toner supply roller 14 for supplying toner to the developing roller 12, and the toner layer on the developing roller 12 are fixed. The doctor blade 15 etc. which regulates to the layer thickness are provided.

  The intermediate transfer belt unit 3 is an endless intermediate transfer belt 30 formed of a thin layer resin film such as ETFE that extends in a flat loop shape from substantially the left and right sides of the figure in the center of the main body. And a belt drive roller 31 and a backup driven roller 32 that circulate and move the intermediate transfer belt 30 counterclockwise as indicated by arrows A and B in FIG.

  These are supported by the near side frame 33 and the back side frame 34 shown in FIGS. The front frame 33 is provided with an intake port 35, and the back frame 34 is provided with an exhaust port 36. The belt driving roller 31 is a so-called rubber roller whose surface is covered with rubber because it is necessary to transmit the belt driving force to the belt with high efficiency.

  Further, in addition to the belt driving roller 31 and the backup driven roller 32, the intermediate transfer belt 30 has a tension roller 37 for applying tension to the intermediate transfer belt 30 and a position facing the photosensitive drum 7. A primary transfer roller 38 is provided.

  Further, a belt cleaner unit 47 is disposed on the intermediate transfer belt unit 3 further upstream of the image forming unit 6M on the uppermost stream side in the belt movement direction on the upper surface, and is flat so as to be almost along the entire lower surface. A thin waste toner collecting container 20 is detachably disposed.

  A partition plate 40 which is a feature of the present invention is provided integrally with the front frame 33 and the back frame 34.

  As shown in FIG. 2, the partition plate 40 extends in the horizontal direction so as to divide the belt unit from the belt drive roller 31 to the backup driven roller 32 side. In addition, an air filter 39 made of, for example, a nonwoven fabric or the like is attached to the air intake port 35 without a gap at the air intake port 35 of the near frame 33 of the intermediate transfer belt unit 3.

  As shown in FIG. 3, the cylindrical opening ends 41 a and 41 b of the intermediate transfer belt 30 are in contact with the air seal sponges 42 and 43 attached to the front frame 33 and the back frame 34, and the front side Air seal sponges 44a and 44b are also provided at the opposing portions of the frame 33 and the partition plate 40 and the rear side frame 34 and the partition plate 40, respectively.

  In addition, as shown in FIG. 2, an air seal sponge 45 is provided in the entire longitudinal direction of the partition plate 40 at a portion facing the backup driven roller 32 at the right end 40a and at a portion facing the belt driving roller 31 at the left end 40b. 46 are provided.

  Further, a belt level roller 48 provided in order to keep the belt height of the belt cleaner unit 47 always constant is provided near the downstream of the belt cleaner unit 47 in the belt traveling direction. An air seal sponge 54 is provided on the belt level roller 48 and the partition plate 40 at a position facing the belt level roller 48.

  Therefore, the air that can flow inside the intermediate transfer belt 30 is substantially only the air that passes from the intake port 35 to the exhaust port 36. As will be described later, the exhaust port 36 of the back frame 34 is connected to an exhaust duct 52 connected to an exhaust fan 51 that constitutes an air flow for cooling the heat fixing means.

  The cleaner unit 47 disposed on the upper surface portion of the intermediate transfer belt unit 3 includes a cleaning blade 49, which is in contact with the upper surface of the intermediate transfer belt 30 to scrape off and remove the waste toner, and the waste removed by the cleaning blade 49. The toner is fed into the waste toner collecting container 20 by the conveying screw 50 through the dropping cylinder.

  Further, in order to press the cleaning blade 49 against the intermediate transfer belt 30 with an appropriate pressure, a pressing roller 53 that presses the intermediate transfer belt 30 toward the cleaner unit 47 from below is provided on the intermediate transfer belt unit 3 side. Is provided.

  In this embodiment, since the tandem method is adopted, a toner image (not shown) formed on the surface of the photosensitive drum 7 is applied to the primary transfer roller 38 while the intermediate transfer belt 30 moves in the direction indicated by the arrow B in FIG. By the electric field generated by the generated voltage, the toner image is temporarily attracted and transferred sequentially to the outer peripheral surface of the intermediate transfer belt 30, and a full-color image with each color toner is obtained on the intermediate transfer belt 30. Further, a secondary transfer roller 66 (described later) is disposed opposite to the backup driven roller 32 via the intermediate transfer belt 30.

  The intermediate transfer belt 30 transfers the toner image directly to the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The entire unit is called an intermediate transfer belt unit.

  Returning to FIG. 1, the paper feed unit 4 includes two paper feed cassettes 61 arranged in two upper and lower stages, and these two paper feed cassettes 61 include a material to be transferred, which is not shown in the figure. A large number of sheets 60 are stored.

  A sheet take-out roller 62, a feeding roller 63, a separating roller 64, and a standby conveying roller pair 65 are disposed in the vicinity of the sheet feeding opening (right side in the drawing) of the two sheet feeding cassettes 61, respectively.

  A secondary transfer roller 66 that is in pressure contact with the backup driven roller 32 via the intermediate transfer belt 30 is disposed in the sheet conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 65 to perform secondary transfer to the sheet. Forming part.

  A belt-type fixing device 67 is disposed downstream (upward in the drawing) of the secondary transfer portion. As shown in FIG. 2, the belt-type fixing device 67 includes a heat source using a halogen lamp 68 and the like, a heat roller 69 incorporating the heat source, and a heat fixing belt 70 that is in close contact with the heat roller 69 over almost the entire circumference in the width direction. And a heating part composed of a fixing roller 71 and the like, which is in close contact with the heat fixing belt 70 and wound around an elastic body such as heat-resistant sponge around the cored bar pipe, and a position facing the fixing roller 71 A backup roller 72 provided with a hard material such as metal and having improved surface peelability from the heated toner is provided, and these are arranged in a housing of a fixing case 73 to form a fixing unit.

  The fixing roller 71 is rotated in the direction of arrow D by a driving source (not shown) to drive the heat fixing belt 70 in the direction of arrow E. Further, the backup roller 72 is driven by pressure contact with the fixing roller 71 and rotates in the direction of arrow F, and the linear rotation speed thereof is kept substantially equal to the conveyance speed of the paper 60.

  Further downstream of the belt-type fixing device 67, a pair of carry-out rollers 78 for carrying out the fixed paper from the belt-type fixing device 67 and a paper discharge tray 79 formed on the upper surface of the device. A paper discharge roller pair 81 for paper is arranged. The paper 60 to which the toner image has been transferred passes through the belt-type fixing device 67 to melt and fix the toner image, and the paper 60 advances in the direction of arrow G in FIG. 2 and is discharged out of the apparatus.

  On the other hand, the air heated by the halogen lamp 68 rises in the direction of arrow H due to convection heat transfer, and is discharged outside the apparatus by an exhaust fan 51 provided in a printer main body frame (not shown). At the same time, the intermediate transfer belt 30 is heated by heat transfer of heat radiation (arrow I).

  The duplex printing transport unit 5 includes a start return path 82a branched from the intermediate transport path between the carry-out roller pair 78 and the paper discharge roller pair 81 in the right lateral direction in the figure, and then an intermediate return path 82b bent downward. A terminal return path 82c that bends in the left lateral direction opposite to the above and eventually reverses the return sheet, and four return roller pairs 83a, 83b, 83c, and 83d arranged in the middle of these return paths. ing.

  The exit of the end return path 82 c communicates with a conveyance path to the standby conveyance roller pair 65 corresponding to the sheet feeding cassette 61 below the sheet feeding unit 4.

  Further, between the intermediate transfer belt 30 and the upper sheet feeding cassette 61 of the sheet feeding unit 4, an electrical unit (not shown) equipped with an appropriate circuit board is disposed, and the circuit board includes a plurality of electronic components. A control device is mounted. The control device includes a controller unit and an engine unit (not shown).

  The controller unit comprises a CPU (Central Processing Unit), ROM (Read Only Memory), EEPROM (Rewritable Read Memory), Frame Memory, Image Data Transfer Circuit, etc., and print data input from a host computer etc. Is analyzed, print data is created and transferred to the engine unit.

  The engine unit includes a CPU, a ROM, and the like. Data and command signals from the controller unit, an output of a temperature sensor (not shown), an output of a paper detection sensor, etc. are input to the input side, and a motor (not shown) is input to the output side. A motor driver that drives the motor, a clutch driver that switches a drive system that transmits the drive of the motor to each part, a print driver that drives the optical writing head 10 based on the print data, a charging roller 9, a primary transfer roller 38, etc. A bias power supply driver for supplying a bias current (or bias voltage) is connected. The engine unit drives and controls each unit based on data and command signals from the controller unit, outputs from various sensors, and the like.

  The sheet 60 conveyed from the sheet feeding unit 4 is superimposed on the intermediate transfer belt 30 on which the above-described full color image is superimposed, and passes through the nip provided between the backup driven roller 32 and the secondary transfer roller 66. A voltage is applied to the next transfer roller 66, and the toner image in which the respective colors are superimposed on the intermediate transfer belt 30 is transferred onto the paper 60 by the electric field generated thereby.

  In such a printer 1, the air flow by the belt unit 3 of the present invention will be described below.

  As shown in FIGS. 2 and 3, in the present invention, the intermediate transfer belt 30 is heated by heat radiation (arrow I), but an air flow is provided in the casing of the intermediate transfer belt unit 3 to exhaust heat. Thus, an air filter 39 is provided to prevent the temperature from rising and to remove in advance the scattered toner from the air flowing into the housing.

  Further, the exhaust fan 51 provided in the printer main body frame (not shown) is set so that the air flow is in the direction of arrow J. An exhaust duct 52 is provided in the suction side opening, and one end of the exhaust duct 52 that is not on the exhaust fan 51 side is connected to an exhaust port 36 provided in the back frame 34 of the intermediate transfer belt unit 3.

  Therefore, the air heated by the belt-type fixing device 67 rises in the direction of arrow H due to convection heat transfer, and is discharged outside the apparatus along the air flow K generated by the exhaust heat fan 51.

  On the other hand, the heat transfer of heat radiation (arrow I) is led out of the apparatus in the order of air flows L, M, N, but the air flow L sucked from the outside of the intermediate transfer belt unit 3 contains not a little scattered toner. ing. However, the scattered toner is filtered by the air filter 39, and the air that can flow inside the intermediate transfer belt 30 is air-seal sponges 42, 43, 44a, 44b, 45, 46, 54 as described above. Since it is hermetically sealed, no convection occurs except for passing from the intake port 35 to the exhaust port 36. Accordingly, the scattered toner does not enter the space inside the intermediate transfer belt unit 3, particularly the arrangement space of the belt driving roller 31.

  As described above, in the present invention, the gap between the front and rear frames constituting the intermediate transfer belt unit and the end of the cylindrical intermediate transfer belt is substantially eliminated, and the air inlets provided with the air filters in the front and rear frames are provided. Since the exhaust port is connected to the air flow including the cooling fan of the fixing device to provide only one air cooling path in the intermediate transfer belt, space saving belt cooling and scattered toner inside the belt Intrusion to the belt can be prevented and the belt running can be stabilized.

  The present invention can be used in an image forming apparatus that includes a belt unit and transfers a toner image onto a transfer material such as paper to form an image.

DESCRIPTION OF SYMBOLS 1 Printer 2 Image formation part 3 Intermediate transfer belt unit 4 Paper feed part 5 Duplex printing conveyance unit 6 (6M, 6C, 6Y, 6K) Image formation unit 7 Photosensitive drum 8 Cleaner 9 Charging roller 10 Optical writing head 11 Development Container 12 Developing roller 13 Toner stirring member 14 Toner supply roller 15 Doctor blade 20 Waste toner collection container 30 Intermediate transfer belt 31 Belt drive roller 32 Backup driven roller 33 Front side frame 34 Back side frame 35 Inlet port 36 Exhaust port 37 Tension roller 38 Primary transfer roller 39 Air filter 40 Partition plate 40a Right end 40b Left end 41a, 41b Cylindrical open end 42, 43, 44a, 44b, 45, 46, 54 Sponge for air seal 47 Belt cleaner unit 48 Belt level roller 49 Leaning blade 50 Conveying screw 51 Exhaust fan 52 Exhaust duct 53 Press roller 61 Paper feed cassette 62 Paper take-out roller 63 Feeding roller 64 Rolling roller 65 Standby conveyance roller pair 66 Secondary transfer roller 67 Belt type fixing device 68 Halogen lamp 69 Heat roller 70 Heat-fixing belt 71 Fixing roller 72 Backup roller 73 Fixing case 78 Unloading roller pair 79 Discharging tray 81 Discharging roller pair 82a Start returning path 82b Intermediate returning path 82c End returning path 83a, 83b, 83c, 83d Returning roller pair

Claims (3)

A pair of opposed frames, a plurality of rollers pivotally supported between the pair of frames, a belt body stretched over the plurality of rollers to circulate, and an air inlet provided on one of the frames; A belt unit having an exhaust port provided on the other side and an airflow forming unit that forms an airflow from the intake port to the exhaust port, and a heating fixing unit,
The toner image formed on the image carrier is configured to be transferred to a transfer material carried and conveyed on the outer peripheral surface of the belt member, or the toner image is first transferred to the outer peripheral surface of the belt member and then conveyed. An image forming apparatus configured to perform secondary transfer to a transfer material to be transferred, and fixing an unfixed toner image transferred to the transfer material to the transfer material by the heat fixing unit,
The belt unit is
The frame and the belt so that a space surrounded by the air flow forming means, the pair of frames, and the belt body is a sealed space so that air flow does not occur in the belt unit except for an air flow path by the air flow forming means. An image forming apparatus characterized in that a body side part is placed close to the body side part.   The image forming apparatus according to claim 1, further comprising: a cooling fan that exhausts air in the apparatus main body to the outside of the apparatus main body to cool the heat fixing unit, and an exhaust duct that connects the exhaust port. apparatus.   The image forming apparatus according to claim 1, wherein an air filter is provided at the intake port.

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