JP4248422B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus that convey recording paper on which an image is formed using rollers.

  FIG. 5 is a schematic cross-sectional view showing a part of the inside of a conventional image forming apparatus. In an electrophotographic image forming apparatus, an image is formed on the surface of a recording sheet with a developer, and then the developer is fixed on the surface by being heated by a fixing unit 2, and then by a conveying roller. It is discharged outside the image forming apparatus. The fixing unit 2 includes a pair of heating rollers 21 and a pressure roller 22, and the recording paper is heated by passing between the heating roller 21 and the pressure roller 22. Since there is a temperature difference between the surface temperature of the heating roller 21 and the surface temperature of the pressure roller 22, there is a difference in the amount of moisture evaporation between the side of the recording paper in contact with the heating roller 21 and the side of contact with the pressure roller 22. Will occur. For this reason, there is a difference in the amount of expansion / contraction when passing through the fixing unit 2 between the front and back sides of the recording paper, so that the recording paper passing through the fixing unit 2 is in a curved state. If the curved recording sheet is discharged as it is to the outside of the image forming apparatus, an image formation that is difficult for the user to use is provided.

In order to solve the above problems, in the conventional image forming apparatus, the curved recording sheet that has passed through the fixing unit 2 is corrected by being squeezed by the conveying rollers 11 and 12 and then discharged. FIG. 6 is a schematic front view showing a conventional conveying roller. The conveying roller is composed of a front roller 11 that contacts the surface on which the image of the recording paper is formed, and back rollers 12, 12,... That contact the back surface of the recording paper. The front roller 11 is a drive roller that is connected to the motor 13 via the gears 14 and 14 and rotates when the motor 13 is driven. The rear rollers 12, 12,... Are driven rollers that are arranged substantially in parallel with the front roller 11 and are composed of a plurality of substantially coaxial rollers separated in the axial direction. Each back roller 12 is pressed against the front roller 11 by a spring and is in contact with a part of the surface of the front roller 11. As the front roller 11 rotates, the back rollers 12, 12,... Also rotate, and the front roller 11 and the back rollers 12, 12,. Patent Document 1 includes first and second rollers arranged in parallel, and a third roller that faces the first and second rollers and presses the first and second rollers. A technique for correcting a recording sheet into a flat shape by bending the recording sheet in a direction that cancels the curvature of the recording sheet by passing the recording sheet between the third roller and the third roller is disclosed.
Japanese Patent Laid-Open No. 3-223063

  By the way, since the recording paper that has passed through the fixing unit 2 is in a heated state, the surface temperature of the roller for squeezing the recording paper is increased by receiving heat from the recording paper. In particular, when image formation is performed continuously, the surface temperature of the conveying roller continues to rise. When the surface temperature of the front roller 11 continues to rise and exceeds the softening temperature of the developer, a phenomenon occurs in which the fixed developer on the recording paper is softened and reversely transferred to the surface of the front roller 11. When reverse transfer of the developer to the front roller 11 occurs, there is a problem that the quality of the image formed on the recording paper is degraded. Further, since the contact between the front roller 11 and the recording paper becomes non-uniform due to the reversely transferred developer, there is a problem that the recording paper is jammed or obliquely conveyed. Further, there is a problem in that the recording paper is smeared by the developer reversely transferred to the front roller 11 being further transferred to the recording paper.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus that reduce an increase in the surface temperature of a roller that conveys a sheet such as recording paper. There is to do.

The sheet conveying apparatus according to the present invention includes two rollers disposed so as to be in pressure contact with each other with their rotation axes being substantially parallel to each other , and by heating the sheet on which the image has been formed , the image is formed on the sheet. has passed through the fixing unit for fixing the sheet is inserted between both rollers, the sheet conveying apparatus for conveying the sheet by the rotation of both rollers, by providing a plurality of recesses in one surface of the roller, to increase the surface area And the other of the rollers is provided with a plurality of substantially coaxial roll bodies having an axial length shorter than that of one of the rollers and spaced apart in the axial direction. One of the rollers includes the plurality of recesses in a portion other than a portion that contacts the roll body via the sheet.

The sheet conveying apparatus according to the present invention includes two rollers disposed so as to be in pressure contact with each other with their rotation axes being substantially parallel to each other , and by heating the sheet on which the image has been formed , the image is formed on the sheet. In a sheet conveying apparatus in which a sheet that has passed through a fixing unit to be fixed is inserted between both rollers , and the sheet is conveyed by rotation of both rollers, one of the rollers has a cylindrical shape, and the outer surface and the inner surface of the cylinder are formed. By providing a plurality of through-holes penetrating, one of the rollers and the sheet are radiated by an air flow generated by the plurality of through-holes as the rollers rotate, and the other of the rollers A plurality of substantially coaxial roll bodies having an axial length shorter than that of the one are provided in the axial direction, and one of the rollers is a portion that is in contact with the roll body via the sheet. Wherein the on portion includes a plurality of through-holes.

The image forming apparatus according to the present invention includes means for forming an image on a surface of the sheet, a fixing unit for fixing an image on a sheet by heating the sheet on which the image is formed, an image has been fixed by the fixing unit A sheet conveying device according to the present invention for conveying a sheet, wherein one of the rollers provided in the sheet conveying device is disposed on a side where an image-formed surface of the sheet contacts. .

In the present invention, a sheet conveying apparatus that conveys a sheet by inserting the sheet between two rollers that rotate while being pressed against each other has a plurality of recesses formed on the surface of one of the rollers. This increases the contact area between the roller and the air, so that the roller easily radiates heat.
In the present invention, the other of the two rollers is composed of a plurality of roll bodies spaced apart in the direction of the rotation axis, and the plurality of recesses formed in one roller is in contact with the other roll body. It is not formed in the part which does, and it is formed in the part which the other roller does not contact.

In the present invention, the sheet conveying apparatus that conveys a sheet by inserting the sheet between two rollers that rotate in pressure contact with each other has a cylindrical shape, and a plurality of penetrations that penetrate the outer surface and the inner surface of the cylinder A hole is formed. As the roller rotates, the plurality of through holes agitate the surrounding air to generate an air flow, so that the roller and the sheet are radiated.
In the present invention, the other of the two rollers is composed of a plurality of roll bodies spaced apart in the rotation axis direction, and the plurality of through holes formed in one of the rollers has the other roll body. It is not formed in the part which contacts, and is formed in the part which the other roller does not contact.

  Furthermore, in the present invention, the sheet conveying device provided in the image forming apparatus conveys a sheet having an image formed by a developer on the surface, and one roller having a plurality of concave portions or through holes formed on the surface It is a roller on the side in contact with the surface on which the image formed by the developer is formed.

  In the present invention, the sheet conveying apparatus that conveys the sheet by inserting the sheet between two rollers that rotate while being pressed against each other has a surface area of the roller by forming a plurality of recesses on the surface of one of the rollers. Increases, the roller easily dissipates heat. As a result, an increase in the surface temperature of the roller is suppressed, so that the reverse transfer of the developer from the recording paper to the roller due to the roller surface temperature exceeding the softening temperature of the developer can be suppressed as much as possible. .

  In the present invention, the sheet conveying apparatus that conveys the sheet by inserting the sheet between two rollers that are pressed against each other and rotated is formed with a plurality of through holes that penetrate the outer surface and the inner surface of the cylinder. As the cylindrical roller rotates, the air around the roller is agitated to generate an air flow, so that the heat dissipation effect of the roller and the sheet is improved. As a result, an increase in the surface temperature of the roller is suppressed, so that the reverse transfer of the developer from the recording paper to the roller due to the roller surface temperature exceeding the softening temperature of the developer can be suppressed as much as possible. . Accordingly, it is possible to suppress image quality degradation, recording paper jam, oblique conveyance, and recording paper contamination caused by reverse transfer of the developer.

  In the present invention, a roller having a plurality of recesses or through-holes is not formed with a recess or a through-hole in a portion where the other roller in a pair contacts, and the other roller contacts. Since a plurality of recesses or through-holes are formed in the portion that is not, the occurrence of unevenness in the recording paper due to the other roller coming into contact with the recess or through-hole portion is prevented. Therefore, in addition to the reverse transfer of the developer, it is possible to effectively suppress the deterioration of the image quality caused by the unevenness of the recording paper, the paper jam of the recording paper, and the oblique conveyance.

  Furthermore, in the present invention, since a plurality of recesses or through holes are formed in the roller that contacts the surface of the sheet on which the image formed by the developer is formed, an increase in the surface temperature of the roller is suppressed. Thus, the present invention has an excellent effect that the reverse transfer of the developer can be effectively suppressed.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a schematic sectional view showing an image forming apparatus of the present invention. The image forming apparatus of the present invention includes the sheet conveying apparatus of the present invention inside, receives an image output instruction from the outside, and forms an image on a recording sheet that is a sheet according to the present invention, and reads an image of a document. To copy to recording paper. The image forming apparatus includes a feeder unit 4 that conveys a copy source document and an image reading unit 5 that reads an image. The feeder unit 4 is provided on the upper side of the image reading unit 5, and sequentially conveys the original image to the opening 41 to the image reading unit 5. The image reading unit 5 includes a CCD 51, irradiates light on a document located in the opening 41 of the feeder unit 4, and reads an image recorded on the document by the CCD 51. The image forming apparatus also includes a photosensitive drum 61, a transfer unit 6 that transfers a developed image on the photosensitive drum 61 to a recording sheet, a heating roller 21, and a pressure roller 22. And a fixing unit 2 for fixing the image by heating the recording paper on which the image is transferred. The image forming apparatus also includes a paper feed tray 7 that stores recording paper below the transfer unit 6 and the fixing unit 2. The recording paper is conveyed from the paper feed tray 7 to the transfer unit 6, the image read by the image reading unit 5 is transferred by the transfer unit 6, and the image is fixed by the fixing unit 2. The image forming apparatus also includes a conveyance path 32 connected from the fixing unit 2 to the outside of the image forming unit. The sheet conveying apparatus 1 of the present invention is provided in the middle of the conveying path 32, and discharge rollers 31 and 31 are provided at the exit of the conveying path 32.

  FIG. 2 is a schematic front view showing the sheet conveying apparatus 1 of the present invention. The sheet conveying apparatus 1 according to the present invention includes a front roller 11 that contacts a surface of a recording paper on which an image formed by a developer is formed, and a plurality of back rollers (roll bodies) 12, 12,. I have. The front roller 11 is formed in a cylindrical shape, and further has a plurality of through holes penetrating the outer surface and the inner surface of the cylinder. The front roller 11 is connected to a motor 13 via gears 14 and 14 and rotates by driving the motor 13. The back side rollers 12, 12,... Are constituted by a plurality of substantially coaxial roll bodies having an axial length shorter than that of the front side roller 11 and separated in the axial direction. Each back roller 12 is pressed against the front roller 11 by a spring and is in contact with a part of the surface of the front roller 11. As the front roller 11 rotates, the back rollers 12, 12,. The recording paper on which the image has been fixed by passing through the fixing unit 2 is sandwiched between the front roller 11 and the back rollers 12, 12,..., And is conveyed along the rotation of the front roller 11 and the back rollers 12, 12,. 32 is conveyed. The recording sheet conveyed in the conveyance path 32 is discharged to the outside of the image forming apparatus by the rotation of the discharge rollers 31 and 31.

  Along with the rotation of the front roller 11, a plurality of through holes that penetrate the cylinder of the front roller 11 agitate the surrounding air and an air flow is generated in the vicinity of the front roller 11. Since the generated air flow dissipates heat from the front roller 11 and the recording paper, the surface temperature of the front roller 11 is suppressed from increasing even when image formation is continuously performed. Thereby, it is possible to suppress as much as possible the reverse transfer of the developer from the recording paper to the front roller 11 when the surface temperature of the front roller 11 exceeds the softening temperature of the developer. Accordingly, it is possible to suppress image quality degradation, recording paper jam, oblique conveyance, and recording paper contamination caused by reverse transfer of the developer. Further, since the roller in which the through hole is formed is the front roller 11 that contacts the surface of the recording paper on which the image by the developer is formed, it is effective to increase the surface temperature in order to suppress reverse transfer of the developer. Can be suppressed.

  Further, the back-side rollers 12, 12,... Are made of a material whose surface is harder than that of the front-side roller 11, so that the surface hardness of the back-side rollers 12, 12,. Yes. FIG. 3 is an enlarged schematic cross-sectional view showing a contact portion between the front roller 11 and the back roller 12. 3A shows a case where the surface of the back roller 12 is harder than the surface of the front roller 11, and FIG. 3B shows a case where the surface of the back roller 12 is softer than the surface of the front roller 11. Yes. When the surface of the back roller 12 is harder than the surface of the front roller 11, the surface shape of the back roller 12 does not change as shown in FIG. However, when the surface of the back roller 12 is softer than the surface of the front roller 11, the back roller 12 is pressed against the front roller 11 by a spring, so that the surface of the back roller 12 penetrates the surface of the front roller 11. Deforms to enter the hole. Due to the deformation of the surface of the back roller 12, the portion of the recording paper that is in contact with the deformed portion is deformed, and the recording paper is uneven. Due to the unevenness of the recording paper, the quality of the image formed on the recording paper is degraded. Further, the irregularities generated on the recording paper may cause the recording paper to be jammed and obliquely conveyed. In the present invention, since the back side rollers 12, 12,... Are harder than the front side roller 11, it is possible to suppress the occurrence of unevenness on the recording paper. Therefore, it is possible to suppress the deterioration of image quality caused by the unevenness of the recording paper, the paper jam of the recording paper, and the occurrence of oblique conveyance.

  As described above, when the front side roller 11 and the back side roller 12 in which the through holes are formed contact with each other, the recording paper may be uneven. Therefore, in order to prevent the unevenness of the recording paper from occurring, the front roller 11 may be configured not to form a through hole in a portion where the back roller 12 contacts. FIG. 4 is a schematic front view showing a second configuration example of the sheet conveying apparatus 1 of the present invention. A through hole is not formed in a portion of the front roller 11 that contacts the back roller 12, 12,..., And a plurality of through holes are formed in a gap between the back rollers 12, 12,. Yes. Since a through hole is not formed in a portion where the front roller 11 and the back roller 12 contact each other with the recording paper interposed therebetween, it is possible to prevent the recording paper from being uneven. Since a plurality of through holes are formed in a portion of the front roller 11 where the back roller 12 does not contact, an increase in the surface temperature of the front roller 11 is suppressed. Therefore, it is possible to effectively suppress the deterioration of image quality, the paper jam of the recording paper, and the occurrence of oblique conveyance.

  In the present embodiment, a configuration is shown in which a plurality of through holes that penetrate the outer surface and the inner surface of the cylindrical front roller 11 are formed, but a plurality of recesses are formed on the surface of the front roller 11. It may be a form. In this case, an air flow that radiates heat from the front roller 11 and the recording sheet cannot be generated, but the surface area of the front roller 11 increases, so that the front roller 11 easily dissipates heat and the surface temperature of the front roller 11 increases. Can be suppressed.

  Further, the image forming apparatus provided with the sheet conveying apparatus 1 of the present invention is a copying apparatus that reads and copies an image. However, the image forming apparatus is not limited to this, and the sheet conveying apparatus of the present invention receives an image received from the outside. The printer may be provided in a printer device or a facsimile device that forms an image based on data.

1 is a schematic cross-sectional view showing an image forming apparatus of the present invention. It is a typical front view showing a sheet conveying device of the present invention. It is typical sectional drawing which expands and shows the contact part of a front side roller and a back side roller. FIG. 6 is a schematic front view illustrating a second configuration example of the sheet conveying apparatus of the present invention. FIG. 10 is a schematic cross-sectional view showing a part of the inside of a conventional image forming apparatus. It is a typical front view which shows the roller for the conventional conveyance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sheet conveying apparatus 11 Front side roller 12 Back side roller (roll body)
2 Fixing section 21 Heating roller 22 Pressure roller 31 Paper discharge roller 32 Transport path 6 Transfer section

Claims (3)

Provided with two rollers which are arranged in pressure-contact with each other in a substantially parallel axis of rotation of each other, the sheet that has passed through the fixing unit for fixing an image on a sheet by heating the sheet on which the image is formed In a sheet conveying device that is inserted between both rollers and conveys the sheet by the rotation of both rollers,
By providing a plurality of recesses on one surface of the roller, the surface area is increased to facilitate heat dissipation from one of the rollers,
The other of the rollers is provided with a plurality of substantially coaxial roll bodies having an axial length shorter than that of one of the rollers and separated in the axial direction.
One of the said rollers is equipped with these recessed parts in parts other than the part which contacts the said roll body via the said sheet | seat. The sheet conveying apparatus characterized by these. Provided with two rollers which are arranged in pressure-contact with each other in a substantially parallel axis of rotation of each other, the sheet that has passed through the fixing unit for fixing an image on a sheet by heating the sheet on which the image is formed In a sheet conveying device that is inserted between both rollers and conveys the sheet by the rotation of both rollers,
One of the rollers has a cylindrical shape, and includes a plurality of through holes that penetrate the outer surface and the inner surface of the cylinder, so that the air flow generated by the plurality of through holes as the roller rotates can be It is configured to dissipate one side and the sheet,
The other of the rollers is provided with a plurality of substantially coaxial roll bodies having an axial length shorter than that of one of the rollers and separated in the axial direction.
One of the said rollers is equipped with these through-holes in parts other than the part which contacts the said roll body via the said sheet | seat. The sheet conveying apparatus characterized by these. Claim conveying means for forming an image on a surface of the sheet, a fixing unit for fixing an image on a sheet by heating the sheet on which the image is formed, a sheet an image has been fixed by the fixing unit 1 or 2 And a sheet conveying device as described in
One of the rollers provided in the sheet conveying device is disposed on the side where the surface on which the image of the sheet is formed contacts.

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