JP2010020127A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing image defects, even while using a bending roller. <P>SOLUTION: The image forming apparatus includes: an image forming part (6) which includes an image carrier and develops a latent image on the image carrier by toner by the drive of the image forming part (6), to form a toner image; a belt member which is stretched between driving and driven rollers and directly or indirectly transfers the toner image to a paper by the drive of the belt member (14); the bending roller (24) which presses the contact surface (14a) of the belt member with the image carrier, to bend the belt member to the opposite side and includes a path (34) communicating with both end openings (28 and 31) in the axial direction of the bending roller (24); and a cooling means (40) which generates a current of external air in the path, to cool the bending roller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image using a transfer belt.

This type of image forming apparatus has an image carrier (for example, a photosensitive drum), and a toner image is developed on the surface of the drum. The toner image is transferred to a sheet via a transfer belt.
Here, the transfer belt is wound around a driving roller and a driven roller, and a configuration in which the transfer surface of the transfer belt is pressed at a position different from the drum is known ( For example, see Patent Document 1).

  Specifically, the folding roller is disposed downstream of the transfer position with the drum or paper as viewed in the rotation direction of the transfer belt, and the roller is convex with the transfer belt facing inward, that is, on the opposite side. To bend. This increases the degree of freedom in the layout of the transfer belt.

JP-A-8-146706

However, the conventional technique has a problem of causing an image defect.
Specifically, the transfer belt and the folding roller may be heated by heat from the fixing unit or heat from the paper in the case of an image forming apparatus capable of double-sided printing. When the temperature rises to the transition point temperature, the molten toner adheres to the surface of the folding roller.

This makes the running of the transfer belt unstable, scratches and toner adhere to the transfer surface of the transfer belt, and in the case of an image forming apparatus capable of color printing, the color resist performance deteriorates. is there.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that solves the above problems and can prevent image defects while using a folding roller.

  A first invention for achieving the above object has an image carrier, and by driving the latent image on the image carrier, the latent image on the image carrier is developed with toner, and a toner image is formed. The belt member that is wound around the driven roller and directly or indirectly transfers the toner image onto the paper by driving, and the contact surface between the belt member and the image carrier is pressed, and the belt member is reversed. And a bending roller having a passage communicating with both axial openings thereof, and a cooling means for cooling the bending roller by generating an air flow by outside air in the passage.

According to the first aspect of the invention, the belt member is wound around the driving and driven rollers, and the contact surface with the image carrier is pressed by the bending roller, and the belt member is on the opposite side. It is bent. This saves space in the image forming apparatus.
Here, the belt member and the folding roller are likely to be heated, and if the temperature rises to the glass transition temperature of the toner, the melted toner adheres to the surface of the folding roller and causes image defects. There are concerns.

  However, the folding roller of the present invention has a hollow structure, that is, a passage communicating with both axial openings thereof, and the air in this passage is cooled by a cooling means using outside air. The surface of the roller can be cooled. Therefore, as a result of preventing image defects, it contributes to improving the reliability of the image forming apparatus.

According to a second invention, in the configuration of the first invention, the cooling means is arranged in the vicinity of one of the openings and is configured to be rotatable independently of the folding roller, and from one of the openings through a passage. It is a blower fan that generates an air flow toward the other opening.
According to the second invention, in addition to the action of the first invention, the blower fan is disposed in the vicinity of one opening of the folding roller and cools the air in the passage, so that image defects are eliminated. It can be surely prevented.
In addition, since this blower fan can rotate independently of the bending roller, the air in this passage can be cooled to a desired temperature.

According to a third invention, in the configuration of the second invention, the cooling means is arranged in the vicinity of the other opening, is configured to be rotatable independently of the folding roller, and is directed from the passage toward the other opening. It is another blower fan that generates an air current.
According to the third aspect, in addition to the action of the second aspect, when another blower fan is also disposed in the vicinity of the other opening of the folding roller, the airflow in this passage can be increased. Therefore, image defects can be prevented more reliably.

According to a fourth aspect of the present invention, in the configuration of the first aspect of the invention, the cooling means is disposed in the passage and is configured to be rotatable independently of the folding roller, and from the one opening to the other opening through the passage. It is a spiral-shaped member that generates an airflow toward the head.
According to the fourth aspect of the invention, in addition to the action of the first aspect of the invention, the spiral-shaped member is disposed in the passage and the air in the passage is cooled. it can.
Further, the spiral-shaped member can be rotated independently of the rotation of the bending roller, and the air in the passage can be cooled to a desired temperature.

According to a fifth aspect of the present invention, in the configuration of the first or second aspect, the cooling means is disposed in one opening and is configured to be rotatable along with the rotation of the bending roller. And a blade-shaped member that generates an air flow toward the other opening.
According to the fifth invention, in addition to the effects of the first and second inventions, the blade-shaped member is disposed in one opening of the bending roller and cools the air in this passage. Can reliably prevent image defects.

Further, since the blade-shaped member rotates with the rotation of the bending roller, the control can be simplified.
Further, when the blower fan is disposed in the vicinity of one opening of the folding roller, the air in this passage can be further cooled, and image defects can be prevented more reliably.

According to a sixth aspect of the present invention, in the configuration of the first or second aspect of the invention, the cooling means is disposed in the passage and is configured to be rotatable along with the rotation of the bending roller, and from one opening through the passage. It is a spiral-shaped member that generates an airflow toward the other opening.
According to the sixth aspect of the invention, in addition to the effects of the first and second aspects of the invention, the spiral-shaped member is disposed in the passage and cools the air in the passage. Therefore, even in this case, image defects can be reliably prevented.

  Furthermore, since this spiral-shaped member rotates with the rotation of the folding roller, the control can be simplified, and when the blower fan is disposed in the vicinity of one opening of the folding roller, The air in this passage can be further cooled, and image defects can be more reliably prevented.

  According to the present invention, the surface of the bending roller is cooled, and it is possible to provide an image forming apparatus capable of preventing image defects while using the roller.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a tandem color printer according to a first embodiment, in which the right direction corresponds to the front of the printer 1 and the left direction corresponds to the back.
As shown in the figure, a sheet cassette 3 is arranged at the lower part of the apparatus main body 2, and sheets P before image formation are accommodated in the cassette 3 in a stacked state. It is separated and sent from the cassette 3 in the right direction.

The paper P sent out from the cassette 3 is transported toward the left of the main body 2 through the paper transport path 4. Inside the main body 2, a registration roller 5, an image forming unit 6, a transfer unit 17, and a fixing unit 18 are sequentially arranged on the downstream side when viewed in the paper transport direction, and the paper P discharged from the fixing unit 18. Is discharged to the paper discharge tray 22 through the paper transport path 20.
Here, the image forming unit 6 of the present embodiment includes four image forming units 6C, 6M, 6Y, and 6B.

  These units 6C, 6M, 6Y, and 6B are sequentially arranged from the back side to the front side of the printer 1, and are provided corresponding to images of four different colors (cyan, magenta, yellow, and black). Cyan, magenta, yellow, and black images are sequentially formed through charging, exposure, development, and transfer processes.

Specifically, each unit 6C, 6M, 6Y, 6B is provided with a photosensitive drum (image carrier) 7 that carries a visible image (toner image) of each corresponding color. Each drum 7 is rotatably installed with respect to the main body 2 and is driven counterclockwise in the figure by a drive motor (not shown).
Corresponding chargers 8, exposure devices (LED print head units, etc.) 9, developing devices 10, intermediate transfer rollers 12, and rubbing rollers 13 are provided at appropriate positions around each drum 7.

The charger 8 is disposed on the opposite side of the intermediate transfer roller 12 and uniformly charges the surface of each corresponding drum 7. Further, the exposure device 9 is arranged on the downstream side of the charger 8 when viewed in the rotation direction of the drum 7 and irradiates laser light toward each corresponding surface.
The developing device 10 is arranged on the downstream side of the exposure device 9 when viewed in the rotation direction of the drum 7, and is supplied with cyan, magenta, yellow, and black toners from the containers 11C, 11M, 11Y, and 11B, respectively. Each color toner is electrostatically attached to the surface of the drum 7.

Thereby, a toner image corresponding to the electrostatic latent image by the exposure device 9 is developed on the surface of each drum 7. The toner images formed on the drums 7 are transferred to a sheet via a transfer belt (belt member) 14.
Specifically, the belt 14 is an endless belt in which both ends of a dielectric resin sheet material are overlapped and joined, or a seamless belt without a seam, as shown in FIG. Further, it is wound around the drive roller 15 and the driven roller 16 and runs in the clockwise direction of the figure by a drive motor installed in the fixed housing 32.

In addition, as a sheet material made of dielectric resin, for example, a sheet of high resistance polymer dielectric resin such as a sheet made of polyethylene terephthalate resin (PET sheet) or a sheet made of polyvinylidene fluoride resin (PVDF sheet) can be used. It is.
Further, the belt 14 travels between the drum 7 and the intermediate transfer roller 12, whereby the toner images formed on the drums 7 are sequentially transferred to the transfer surface (contact surface) 14a. It is synthesized as a toner image for one page. Thereafter, the toner image on the transfer surface 14 a is indirectly transferred (secondary transfer) to the paper P sent from the registration roller 5 by the transfer unit 17 and transferred toward the fixing unit 18.

  On the other hand, the rubbing roller 13 is disposed on the upstream side of the charger 8 when viewed in the rotation direction of the drum 7. The roller 13 is configured so as to be able to contact the surface of each corresponding drum 7, and this surface is polished by being driven counterclockwise in the figure by a drive motor. The toner remaining on each drum 7 is removed by a cleaning device (not shown).

The belt 14 described above is rotatably supported on the driven roller 16 side with the drive roller 15 side as a fulcrum.
Specifically, as shown in FIG. 2, a belt contact / separation mechanism 30 is installed in the vicinity of the driven roller 16, and this contact / separation mechanism 30 brings the belt 14 into contact with and separates from each drum 7.

Specifically, the belt contact / separation mechanism 30 includes another motor installed in the fixed housing 32, and the drive shaft of the motor is connected to the housing operation unit 36 via a gear unit. A movable housing 34 is provided on the back side of the portion 36.
During color printing, the operating unit 36 lifts the movable housing 34 with respect to the fixed housing 32, and the belt 14 contacts all of the drums 7 (FIG. 2).

  On the other hand, during monochrome printing, the belt 14 contacts only the drum 7 that forms a black image, and is separated from the drums 7 for the other three colors. This is because, even when the three color toners are not used during monochrome printing, if the belt 14 and the drums 7 are still in contact with each other, the charge amount of the toner increases and cannot be used thereafter.

  Therefore, when the motor is driven again, the operating portion 36 is separated from the movable housing 34, and thus the housing 34 is lowered by a biasing force of a spring (not shown). As a result, the belt 14 contacts the drum 7 of the unit 6B, while the belt 14 is separated from the drum 7 of the units 6C, 6M, 6Y (FIG. 3).

Incidentally, the belt 14 is provided with a folding roller 24 in the vicinity of the fixing unit 18.
Specifically, the folding roller 24 is disposed at an appropriate position on the downstream side of the transfer unit 17 as viewed in the conveying direction of the belt 14 and on the upstream side of the driven roller 16. 14 is pressed toward the inside. As a result, the belt 14 is bent in a convex shape toward the opposite side, in other words, toward the inside of the belt 14.

Here, the bending roller 24 of the present embodiment is configured to be cooled by a cooling means. More specifically, as shown in FIG. 4, the roller 24 has a hollow structure, and a passage 34 is formed inside the cylindrical surface 25 thereof.
In addition, an outside air introduction port (one opening) 28 and an outside air outlet port (the other opening) 31 are formed on both end surfaces 26 and 29 in the axial direction of the roller 24 and communicate with the passage 34.

  In this embodiment, the blower fan 40 is disposed in the vicinity of the outside air inlet 28. The fan 40 is configured to be rotatable independently of the roller 24, and when the rotation shaft is driven by a motor (not shown), the outside air is introduced into the passage 34 from the outside air introduction port 28, and is supplied to the outside air outlet 31. Sent to. As a result, the air in the passage 34 is cooled, and the surface 25 of the roller 24 is cooled.

  It should be noted that another blower fan may be installed as a cooling means on the discharge side also in the vicinity of the above-described outside air outlet 31. If it is configured to be able to rotate independently of the roller 24, the outside air is passed from the passage 34. An airflow in the same direction as that of the blower fan 40 on the suction side can be generated toward the outlet 31.

In the printer 1 described above, the paper P is separated and sent from the cassette 3 one by one, and the paper P reaches the registration roller 5. The roller 5 feeds the paper P toward the transfer unit 17 while correcting the oblique feeding of the paper P and measuring the timing of the image transfer operation by each drum 7, the transfer roller 12, and the like.
In the printer 1, the laser beam irradiation by the exposure device 9 is controlled. As a result, an electrostatic latent image of the original image is created on each drum 7 in the image forming unit 6, and then a toner image is formed on each drum 7 from the latent image and transferred onto the paper P via the belt 14. Is done. The sheet P is fed toward the fixing unit 18 with an unfixed toner image carried thereon, and after a color image or a monochrome image is formed, the sheet P is discharged to the tray 22 through the conveyance path 20.

By the way, the above-mentioned cooling means may be provided in the bending roller itself.
Specifically, the bending roller 24A shown in FIG. 5 also has a hollow structure, and a passage 34 is formed in the surface 25, but flanges 30 and 30 are installed at both ends in the axial direction of the roller 24. ing.
In this example, a spiral-shaped member (cooling means) 44 is disposed in the passage 34. The member 44 includes a rotating shaft 46 that can rotate independently of the roller 24, and a spiral portion 47 formed on the peripheral wall of the shaft 46, and when the rotating shaft 46 is driven, the outside air is outside the flange 30. The air is introduced into the passage 34 from the introduction port 28 and sent toward the outside air outlet 31 of the flange 30.

On the other hand, the cooling means described above may be configured to be rotatable with the rotation of the bending roller.
Specifically, the flanges 30 and 30 of the bending roller 24B shown in FIG. 6 are provided with blade-shaped members (cooling means) 50 and 52. When the roller 24B is driven, outside air is introduced into the outside air inlet 28. Are introduced into the passage 34 and sent toward the outside air outlet 31.

  A spiral-shaped member (cooling means) 54 is provided on the inner wall of the passage 34 of the bending roller 24C shown in FIG. As in the case of the roller 24B in FIG. 6, the member 54 has a spiral portion 57. When the roller 24C is driven, outside air is introduced into the passage 34 from the outside air introduction port 28 and sent toward the outside air outlet 31. Will be.

  Further, as shown in FIG. 8A, a folding roller 24D in which the above-described fan 40 and blade-shaped members 50 and 52 are combined is also possible. Furthermore, as shown in FIG. 8B, The bending roller 24E which combined the fan 40 and the spiral-shaped member 54 mentioned above may be sufficient.

  As described above, according to each embodiment, the transfer belt 14 is wound around the driving and driven rollers 15 and 16, and the transfer surface 14 a is pressed by the folding rollers 24 to 24 </ b> E. And bent in a convex shape toward the inside of the belt 14. As a result, the wrapping angle of the belt 14 becomes large and the belt 14 becomes difficult to slip, and the space of the printer 1 can be saved.

Here, the belt 14 and the folding roller 24 are highly likely to be heated by heat from the fixing unit 18. If the temperature rises to the glass transition temperature of the toner, the surfaces of the folding rollers 24 to 24 </ b> E. 25, the melted toner adheres.
However, the folding rollers 24 to 24E of the present embodiment have a hollow structure, that is, a passage 34 that communicates the outside air introduction port 28 and the outside air outlet port 31 that are both end openings in the axial direction. Since the air is cooled using outside air, the surface 25 can be cooled. Therefore, the roller 24 is not easily heated, and image defects can be prevented. As a result, the reliability of the printer 1 is improved.

Further, as shown in FIG. 4, since the blower fan 40 is disposed near the outside air inlet 28 of the roller 24 and cools the air in the passage 34, image defects can be reliably prevented. In addition, since the fan 40 can rotate independently of the rotation of the roller 24, the air in the passage 34 can be cooled to a desired temperature.
Furthermore, when another blower fan is also disposed in the vicinity of the outside air outlet 31, the airflow in the passage 34 can be increased, and image defects can be prevented more reliably.

Furthermore, as shown in FIG. 5, since the spiral-shaped member 44 is disposed in the passage 34 and the air in the passage 34 is cooled, image defects can be reliably prevented also in this case. Moreover, this member 44 can also be rotated independently of the rotation of the roller 24, and in this case, the air in the passage 34 can be cooled to a desired temperature.
In addition, since the blade-shaped members 50 and 52 shown in FIG. 6 are respectively arranged in the outside air inlet 28 and the outside air outlet 31 and cool the air in the passage 34, image defects can be reliably ensured also in this case. Can be prevented. In addition, since the members 50 and 52 rotate with the rotation of the roller 24, the control can be simplified.

Further, as shown in FIG. 8A, when the blower fan 40 is disposed in the vicinity of the outside air inlet 28 in addition to the blade-shaped members 50 and 52, the air in the passage 34 can be further cooled. Image defects can be prevented more reliably.
Furthermore, as shown in FIG. 7, a spiral-shaped member 54 is disposed in the passage 34 to cool the air in the passage 34. Therefore, even in this case, image defects can be reliably prevented. In addition, since the member 54 also rotates with the rotation of the roller 24, the control can be simplified.

Further, as shown in FIG. 8B, when the blower fan 40 is arranged in the vicinity of the outside air inlet 28 in addition to the spiral-shaped member 54, the air in the passage 34 can be further cooled, resulting in an image defect. Can be prevented more reliably.
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims. For example, a part of the configurations of the above embodiments can be omitted or arbitrarily combined so as to be different from the above.

  Further, the transfer belt of the present invention is different from the intermediate transfer belt as long as it is wound between the driving roller 15 and the driven roller 16, that is, the toner image formed on each drum 7 is registered with the registration roller. The present invention can be applied to a case where images are directly transferred to the paper P sent out from the printer 5 one after another, and can also be applied to a printer capable of only monochrome printing.

Further, the bending roller of the present invention may be disposed at a position where it is difficult to be affected by the heat of the fixing unit 18. That is, there is a similar problem that the folding roller is heated even in a printer capable of duplex printing.
Further, the image carrier of the present invention is not limited to four photosensitive drums. Further, in the above embodiment, an example in which the image forming apparatus is embodied in a printer is shown. Naturally, it can also be applied to multifunction devices, copiers, facsimiles, and the like.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. It is a figure which shows the state at the time of color printing in FIG. It is a figure which shows the state at the time of the monochrome printing in FIG. It is explanatory drawing of the bending roller of FIG. It is explanatory drawing of the bending roller of 2nd Example. It is explanatory drawing of the bending roller of 3rd Example. It is explanatory drawing of the bending roller of 4th Example. It is explanatory drawing of the bending roller of 5th Example.

Explanation of symbols

6 Image forming unit 7 Photosensitive drum (image carrier)
14 Transfer belt (belt member)
14a Transfer surface (contact surface)
DESCRIPTION OF SYMBOLS 15 Drive roller 16 Driven roller 24, 24A, 24B, 24C, 24D, 24E Bending roller 25 Surface 28 Outside air introduction port (one opening)
31 Outside air outlet (the other opening)
34 Passage 40 Blower fan (cooling means)
44 Spiral shape member (cooling means)
50, 52 Blade-shaped member (cooling means)
54 Spiral shape member (cooling means)

Claims (6)

An image carrier that has an image carrier and develops a latent image on the image carrier with toner by driving to form a toner image;
A belt member that is hung between a driving roller and a driven roller, and transfers the toner image directly or indirectly to the paper by the driving;
A bending roller that presses a contact surface between the belt member and the image carrier, bends the belt member in the opposite direction, and has a passage communicating with both axial openings thereof;
An image forming apparatus comprising: a cooling unit configured to generate an air flow by outside air in the passage to cool the bending roller. The image forming apparatus according to claim 1,
The cooling means is disposed in the vicinity of one opening and is configured to be rotatable independently of the bending roller, and generates an air flow from the one opening to the other opening through the passage. An image forming apparatus which is a blower fan. The image forming apparatus according to claim 2,
The cooling means is disposed in the vicinity of the other opening, is configured to be rotatable independently of the bending roller, and is another air blowing fan that generates an air flow from the passage toward the other opening. An image forming apparatus, comprising: The image forming apparatus according to claim 1,
The cooling means is disposed in the passage and is configured to be rotatable independently of the folding roller, and generates a gas flow from one opening to the other opening through the passage. An image forming apparatus. The image forming apparatus according to claim 1, wherein
The cooling means is disposed in one opening and is configured to be rotatable in accordance with the rotation of the folding roller, and has a blade shape that generates an air flow from the one opening to the other opening through the passage. An image forming apparatus comprising a member. The image forming apparatus according to claim 1, wherein
The cooling means is disposed in the passage, and is configured to be rotatable with the rotation of the bending roller, and generates a gas flow from one opening toward the other opening through the passage. An image forming apparatus.

Images