JP2007091382A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of performing an effective dew condensation countermeasures without impairing the conveyance of paper sheets. <P>SOLUTION: A copier 1 conveys a paper sheet P with a toner image transferred by a transfer roller 106 via a conveying passage directed from a fixing roller 107 to a delivery unit 108 or the transfer roller 106 in a thermal fixing state by the fixing unit 107. The conveying passage consists of a longitudinal conveying passage 109 directed upward from the fixing roller 107, and a transverse conveying passage 115 extending from an upper end of the longitudinal conveying passage 109 in the orthogonal direction. A PET film 117 is affixed to an upper structure 115a of the transverse conveying passage 115 via a heat insulating sheet 116. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile machine, and a multifunction machine having these functions.

  FIG. 5 is a cross-sectional view showing a schematic configuration around a paper discharge portion in a conventional image forming apparatus. Here, duplex printing is possible, and after the unfixed toner transferred by the transfer unit 501 on the surface of the paper P is thermally fixed by the fixing unit 502, the paper P is temporarily discharged by the discharge roller 503 side. , And returns to the transfer unit 501 again for printing on the back surface of the paper P by the reverse rotation of the discharge roller 503. In the figure, reference numeral 508 denotes a photosensitive drum, and 509 denotes a cleaning device.

At this time, vapor generated in the fixing unit 502 may be condensed in the downstream guide unit 505, and the water droplets may adhere to the paper P. For this purpose, a sheet in which a water absorbing sheet 510 is attached to the inside of the guide portion 505 has been proposed (see, for example, Patent Document 1).
JP-A-9-204112

  In Patent Document 1, a water absorbent sheet 510 such as a non-woven paper is stuck inside the vertical conveyance path 506 that is exclusively upward from the fixing unit 502 in the downstream guide unit 505. However, the dew condensation phenomenon is rather vertical. It is likely to occur at the upper part on the inner side of the horizontal conveyance path 507 that goes in the direction perpendicular to the upper end of the conveyance path 506. The reason is that since the horizontal conveyance path 507 is away from the fixing unit 501, a temperature difference is likely to occur between the sheet P and the start of operation in a cold region or winter. Therefore, it is not possible to effectively prevent dew condensation simply by attaching a water absorbent sheet 510 such as non-woven paper to the inside of the vertical conveyance path 506.

  As shown in FIG. 6, even if the waterproof sheet 510 is pasted on the inner upper portion of the horizontal conveyance path 507, the vertical conveyance path 506 hits the inner upper portion of the horizontal conveyance path 507 at its upper end (in FIG. 6). The sheet P is bent at a portion D) surrounded by a circle, and the leading end of the sheet P is pressed against the inner upper portion of the lateral conveyance path 507 by the elastic restoring force of the sheet P. For this reason, simply attaching the waterproof sheet 510 to the inner upper portion of the lateral conveyance path 507 increases the frictional resistance between the sheet P and the water absorbing sheet 510 and prevents the conveyance of the sheet P.

  In FIG. 6, during single-sided printing, the sheet P passes through the horizontal conveyance path 507 and is discharged as it is to the discharge unit 504 (in the case of moving from the A direction to the B direction in FIG. 6). However, even if the back side of the printing surface becomes wet due to the dew condensation phenomenon, the image on the printing surface itself is hardly affected. However, during double-sided printing, the paper P is conveyed from the horizontal conveying path 507 to the conveying rollers 511, In 512, the image is returned to the transfer unit 501 again (in the case of moving from the A direction to the C direction in FIG. 6), and the image is transferred to the wet back side by the transfer unit 501. May occur.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming apparatus capable of taking effective dew condensation measures without hindering the conveyance of paper.

  The present invention provides an image forming apparatus including a fixing unit that thermally fixes a sheet on which a toner image is transferred by a transfer unit, and a conveyance path that conveys the thermally fixed sheet to a predetermined position. By disposing the synthetic resin film in a contact state, the sheet is transported along the surface of the synthetic resin film.

  The heat insulating member includes non-woven paper, and the synthetic resin film includes a PET (polyethylene phthalate) film.

  According to a second aspect of the present invention, the conveyance path includes a vertical conveyance path that extends upward from the fixing unit and a horizontal conveyance path that extends in a direction perpendicular to the upper end of the vertical conveyance path. It is preferable to arrange the synthetic resin film on the inner upper part.

  According to a third aspect of the present invention, the horizontal conveyance path is a discharge path toward the discharge portion, and it is preferable that the synthetic resin film is disposed on the inner upper portion of the discharge path.

  According to a fourth aspect of the present invention, the lateral conveyance path is a return path that reverses the direction of the back surface of the paper and returns it to the transfer portion, and the synthetic resin film is disposed on the inner upper side of the return path. It is preferable to do.

  As in the invention described in claim 5, it is preferable that the synthetic resin film is attached to the inner wall of the conveyance path via a heat insulating member.

  As in the invention described in claim 6, it is preferable that the synthetic resin film is cantilevered by the heat insulating member.

  According to the present invention, the synthetic resin film is disposed in a non-contact state on the inner wall of the conveyance path, and the sheet is conveyed along the surface of the synthetic resin film. Since this synthetic resin film is extremely thin and has a small heat capacity, it is heated in a very short time by the sheet heat-fixed at the fixing portion. Therefore, due to the contact between the conveyed paper and the synthetic resin film, the temperature difference between the two immediately disappears and no condensation occurs on the surface of the synthetic resin film.

  Moreover, since the surface of the synthetic resin film is smooth, its friction coefficient is very small compared to the friction coefficient of nonwoven paper or the like. Therefore, it is possible to smoothly carry the paper that comes into contact with the synthetic resin film. As a result, effective dew condensation measures can be taken without hindering the conveyance of the paper.

  By the way, in particular, the conveyance of the sheet is often hindered at a portion where the vertical conveyance path extending upward from the fixing unit abuts on the horizontal conveyance path directed in the perpendicular direction at the upper end thereof. The reason is considered to be that the contact resistance is very large compared to the straight portion because the leading edge of the paper is pressed against the inner upper portion of the lateral conveyance path by the elastic restoring force against the bending of the paper at the portion.

  Therefore, according to the second aspect of the present invention, the conveyance path includes a vertical conveyance path that extends upward from the fixing unit and a horizontal conveyance path that extends in a direction perpendicular to the upper end of the vertical conveyance path. Since the synthetic resin film is disposed on the inner upper side of the path, the paper entering the horizontal conveyance path from the vertical conveyance path is smoothly conveyed in contact with the synthetic resin film.

  For example, according to the invention described in claim 3, the horizontal conveyance path is a discharge path toward the discharge section, and the synthetic resin film is disposed on the inner upper portion of the discharge path. The sheet is conveyed smoothly in contact with the synthetic resin film.

  Alternatively, according to the invention described in claim 4, the lateral conveyance path is a return path that reverses the direction of the back surface of the paper and returns it to the transfer portion, and the synthetic resin film is formed on the inner upper portion of the return conveyance path Since the sheet is disposed, the sheet returning to the transfer section is smoothly conveyed in contact with the synthetic resin film.

  According to the invention of claim 5, since the synthetic resin film is affixed to the inner wall of the conveyance path via a heat insulating member, a non-contact state between the inner wall of the conveyance path and the synthetic resin film is ensured. The Therefore, since the synthetic resin film is heated in a short time by the conveyed paper, a more reliable dew condensation measure can be taken.

  For example, according to the invention described in claim 6, since the synthetic resin film is cantilevered by the heat insulating member, a non-contact state between the inner wall of the conveyance path and the synthetic resin film is secured. Therefore, since the synthetic resin film is heated in a short time by the conveyed paper, a more reliable dew condensation measure can be taken.

  FIG. 1 is a schematic diagram mainly showing an internal configuration of a copying machine according to an embodiment of the present invention.

  As shown in FIG. 1, a copying machine (an example of an image forming apparatus) 1 according to this embodiment includes an image forming unit 100, a document feeding unit 200, and a document reading unit disposed in or on a main body housing 2, respectively. 300 includes a sheet feeding unit 400 and an operation display unit 500.

  The original reading unit 300 reads an original and generates image data corresponding to the original, and a CCD (Charge Coupled Device) sensor that generates image data from an optically acquired original image and an exposure. A scanner 301 having a lamp or the like is provided, and a first contact glass 302 for reading an apparatus original and a second contact glass 303 for reading an ADF original are provided on the upper surface thereof.

  The document feeding unit 200 (ADF) feeds a document to the document reading unit 300, and includes a document tray 201 on which the document is placed, a loading roller, and the like, and a loading drive unit that loads the document from the document tray 201. 202, a conveyance roller 204 that conveys a document in the conveyance path 203, a discharge roller 205 that discharges the document conveyed by the conveyance roller 204, and a document discharge tray on which the document discharged by the discharge roller 205 is placed (stacked) 208 and the like.

  The paper feed unit 400 feeds paper to the image forming unit 100, and includes paper feed cassettes 401 and 402 that store paper of various sizes (recording paper), and these paper feed cassettes 401 and 402. A conveyance path 403 for conveying the sheet from the image forming unit 100 to the image forming unit 100. Each of the paper feed cassettes 401 and 402 includes pick-up rollers 404 and 405 for taking out the stored paper, and paper feed rollers 406 and 407 for feeding the paper one by one to each conveyance path. The conveyance path 403 is provided with a conveyance roller 408 for conveying the paper and a registration roller 409 for waiting the conveyed paper in front of the image forming unit 100.

  The paper feed unit 400 may include a manual paper feed unit (not shown) including a manual feed tray that is configured to be freely opened and closed on one side (right side) of the main body housing 2. In this case, the sheet conveyance path from the manual sheet feeding unit is configured to merge on the upstream side of the registration roller 409.

  The image forming unit 100 forms (prints) a predetermined image on the sheet conveyed by the sheet feeding unit 400, and is a photosensitive member that is rotatably supported in the direction of the arrow shown in FIG. The drum 101, the charging unit 102, the developing unit 103, the cleaning unit 104, the laser scanning unit 105, the transfer roller (transfer unit) 106, and the transfer roller 106 disposed around the photosensitive drum 101 are disposed on the downstream side. The fixing roller (fixing unit) 107 is provided.

  The charging unit 102 uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. The laser scanning unit 105 irradiates the surface of the photosensitive drum 101 with a laser beam based on the image data, and forms an electrostatic latent image on the surface of the photosensitive drum 101. The developing unit 103 makes the image (original image) appear by attaching toner to the electrostatic latent image. The transfer roller 106 is configured to transfer the toner image that has been made visible on the photosensitive drum 101 to the paper in a state where the conveyed paper is pressed against the photosensitive drum 101.

  The fixing roller 107 fixes the toner image transferred to the paper. The fixing roller 107 includes a heat roller and a pressure roller, and the toner on the paper is melted by the heat of the heat roller, and pressure is applied by the pressure roller to fix the toner on the paper. The cleaning unit 104 cleans the toner remaining on the surface of the photosensitive drum 101 after the transfer of the image onto the paper is completed.

  A paper discharge tray (discharge unit) 108 on which the discharged paper is stacked is provided on the upper portion of the main body housing 2, and the paper conveyed from the fixing roller 107 via the vertical conveyance path 109 is conveyed horizontally. The paper is discharged onto the paper discharge tray 108 by the discharge roller 110 in the path 115. A heat insulating sheet 116 and a PET film 117, which are features of the present invention, are attached to the inner side of the upper side of the horizontal conveyance path 115 (described later).

  The discharge roller 110 is configured to be reversely rotated so as to reverse the direction of the back surface of the paper conveyed from the fixing roller 107 side when performing duplex printing on the paper (the discharge roller 110 is a reverse roller). ) The discharge roller 110 conveys the sheet conveyed from the fixing roller 107 side until the rear end side of the sheet comes near the position of the discharge roller 110, that is, temporarily discharges the leading end side of the sheet to the outside of the discharge roller 110. Thereafter, the discharge roller 110 is rotated in the reverse direction, and the discharge portion of the sheet is drawn into the discharge roller 110 (carried in).

  The sheet drawn into the discharge roller 110 is transported along the transport path 113 by the transport roller 111 and the transport roller 112 and is sent again toward the image forming unit 100 (registration roller 409). In this way, image formation is performed on the back surface of the paper whose front surface is reversed (the first image-formed surface is used as the front surface). The paper is discharged onto the paper discharge tray 108 via the discharge roller 110.

  The branch guide 114 switches the transport direction from the fixing roller 107 to the discharge roller 110 and the transport direction from the discharge roller 110 to the transport path 113 (conveyance rollers 111 and 112) in paper reversal. It has a configuration. As described above, the copying machine 1 includes the discharge roller 110, the transport rollers 111 and 112, the transport path 113, and the like to configure a switchback mechanism for performing sheet reversal.

  The operation display unit 500 inputs predetermined instructions in response to user operations, and includes a start key 501 for the user to input a print execution instruction, a numeric keypad 502 for inputting the number of copies to be printed, and the like. A display 503 (display) including a liquid crystal display (LCD) or the like on which various operation buttons and the like are displayed, as well as operation guide information for inputting various copying operation settings and the like is displayed.

  FIG. 2 is a schematic diagram showing a connecting portion between the vertical conveyance path and the horizontal conveyance path.

  As shown in FIG. 2, a horizontal conveyance path 115 is provided between the discharge roller 110 and the conveyance roller 111, and a vertical conveyance path 109 from the fixing roller 107 is provided so as to abut against the horizontal conveyance path 115. ing. Here, a case is shown where switching in the transport direction from the fixing roller 107 toward the discharge roller 110 is performed by the branch guide 114 in FIG. A PET film (synthetic resin film) 117 is attached to the inner upper portion of the horizontal conveyance path 115 via a heat insulating sheet (heat insulating member) 116.

  FIG. 3 is a perspective view showing an upper structure of the horizontal conveyance path, and FIG. 4 is an exploded perspective view showing a method of attaching a heat insulating sheet and a PET film to the upper structure. 3 and 4, the paper carry-in direction (A direction in FIG. 3) is the vertical direction, the paper carry-out direction (B or C direction in FIG. 3) is the left-right direction, and the direction perpendicular to them is the front-back direction. That's it.

  As shown in FIGS. 3 and 4, the upper structure 115a of the horizontal conveyance path 115 is formed in a casing (cuboid shape) that is entirely long, and the upper structure 115a of the horizontal conveyance path 115 is illustrated. 2 is coupled to the vertical conveyance path 109 in FIG. The sheet P conveyed from the vertical conveyance path 109 is always guided to the sheet discharge tray 108 or the switchback mechanism via the horizontal conveyance path 115. In addition, the discharge roller 110 and the transport roller 111 are disposed opposite to the upper structure 115a and the lower structure (only the upper rollers 110a and 111a are shown in FIGS. 3 and 4). Thus, the paper P is discharged to the paper discharge tray 108, and the paper is transported to the switchback mechanism by the transport roller 111.

  In other words, on both the left and right sides of the upper structure 115a, roller shafts 110b and 111b extending in the front-rear direction are pivotally supported at both front and rear ends, respectively. Four upper rollers 110a and four upper rollers 111a of the conveying roller 111 are attached. Pulleys 110c and 110d are attached to the front and rear ends of the roller shaft 110b, and a pulley 111c is attached to the rear end of the roller shaft 111b. An annular belt 118 is wound around the pulleys 110d and 111c so as to be able to go around.

  When the pulley 110c is rotationally driven by a motor (not shown) during single-sided printing, the rotational force is transmitted to the upper roller 110a of the discharge roller 110 via the roller shaft 110b and is carried in from the direction A in FIG. The sheet P is discharged in the direction B in FIG. 3 while being sandwiched between the lower roller (not shown) disposed opposite to the upper roller 110a (discharge path).

  The rotational force is transmitted from the pulley 110d to the pulley 111c via the annular belt 118, and further transmitted to the upper roller 111a of the conveying roller 111 via the roller shaft 111b. At this time, the branch guide 114 in FIG. With this function, the sheet P does not come into contact with the upper roller 111a of the transport roller 111.

  On the other hand, at the time of double-sided printing, the leading edge of the paper P once protrudes toward the paper discharge tray 108 by the discharge roller 110. Immediately after that, the motor is reversed, so that the rotational force is discharged via the roller shaft 110b. The paper P that has been transmitted to the upper roller 110a and is about to be discharged in the B direction in the figure is now conveyed in the C direction.

  That is, the rotational force at the time of reverse rotation is transmitted from the pulley 110d to the pulley 111c via the annular belt 118, and further transmitted to the upper roller 111a of the conveying roller 111 via the roller shaft 111b. P is conveyed in the direction C in the drawing (return path) while being sandwiched between lower rollers (not shown) arranged to face the upper roller 111a of the conveying roller 111.

  Here, as shown in FIG. 4, the heat insulating sheet (heat insulating member) 116 has a long shape made of a water absorbent sheet such as a nonwoven fabric, and has an upper structure 115 a sandwiched between both roller shafts 110 b and 111 b. Affixed to the front and rear sides of the casing portion 115b.

  The PET film 117 has a substantially rectangular shape that is substantially the same length as that of the heat insulating sheet 116, and the thickness thereof is preferably about 0.125 mm.

  The PET film 117 is attached to the upper portion so as to be cantilevered from the heat insulating sheet 116. That is, the PET film 117 is attached in a state of being slightly lifted (non-contact state) from the casing portion 115b. Therefore, when the paper P is carried into the lateral transport path 115, the leading edge of the paper P Contacts the surface of the PET film 117 on both the front and rear sides, but the frictional resistance of the surface of the PET film 117 is very small, so that the paper P is smoothly guided in the B or C direction.

  Subsequently, a paper discharging or conveying operation in the copying machine will be described.

  First, at the time of single-sided printing, as shown in FIG. 2, the leading edge of the paper P conveyed from the fixing roller 107 through the vertical conveyance path 116 is abutted against the PET film 117 in an inclined state when entering the horizontal conveyance path 115. . By this abutment, the leading edge of the paper P slides smoothly on the surface of the PET film 117 and is smoothly guided to the discharge roller 110 side.

  At this time, the PET film 117 is heated by the paper P heated by the fixing roller 107, but the heat insulating sheet 117 prevents the heat transfer to the upper structure 115a of the lateral conveyance path 115. Only 117 heats up quickly. Accordingly, the temperature difference between the paper P and the horizontal conveyance path 115 is eliminated in a very short time when the operation is started in a cold region or in winter, so that dew condensation in the horizontal conveyance path 115 is prevented. For this reason, the paper P is discharged onto the paper discharge tray 108 by the discharge roller 110 of the lateral conveyance path 115 without getting wet by condensation.

  On the other hand, during double-sided printing, the paper once protrudes greatly toward the paper discharge tray 108 by the discharge roller 110 of the horizontal conveyance path 115, but when the trailing edge of the paper P has completely entered the horizontal conveyance path 115 from the vertical conveyance path 109. In addition, the discharge roller 110 reverses.

  By the reverse rotation of the discharge roller 110, the paper P is now transported from the paper discharge tray 108 side to the transport roller 111 side. Also at this time, since the inside of the horizontal conveyance path 115 is not condensed, the paper P is smoothly guided to the conveyance roller 111 side. The sheet P is further guided by the conveying rollers 111 and 112 through the return path 113 and downstream of the transfer roller 106 in a state where the direction of the back surface is reversed with respect to the original sheet P. Then, the transfer process is performed again on the back surface of the paper P. Thereafter, as in the case of single-sided printing, the double-sided printed paper P is discharged onto the paper discharge tray 108 by the discharge roller 110 of the horizontal conveyance path 115 without getting wet by condensation.

  As described above, according to the present embodiment, the PET film 117 is attached to the casing portion 115 b of the upper structure 115 a of the lateral conveyance path 115 via the heat insulating sheet 116. Since this PET film 117 is extremely thin and has a small heat capacity, it is heated in a very short time by the paper P heat-fixed by the fixing roller 107. Therefore, due to the contact between the conveyed paper P and the PET film 117, the temperature difference between the two immediately disappears, and no condensation occurs on the surface of the PET film 117.

  Moreover, since the surface of the PET film 117 is smooth, its friction coefficient is very small compared to the friction coefficient of nonwoven paper or the like. Therefore, it is possible to smoothly carry the paper P that is in contact with the PET film 117. As a result, it is possible to take effective dew condensation measures without disturbing the conveyance of the paper P.

  In the above embodiment, the prevention of condensation of the copying machine 1 has been described. However, the present invention can of course be applied to other image forming apparatuses (such as a printer).

1 is a schematic diagram mainly showing an internal configuration of a copying machine according to an embodiment of the present invention. It is a schematic diagram which shows the connection part of a vertical conveyance path and a horizontal conveyance path. It is a perspective view which shows the upper structure of a horizontal conveyance path. It is a disassembled perspective view which shows the affixing method of the heat insulation sheet and PET film to the upper structure in FIG. FIG. 10 is a schematic diagram illustrating a conveyance path in a conventional image forming apparatus. It is a schematic diagram which shows the dew condensation prevention means.

Explanation of symbols

1 Copying machine (image forming device)
2 Main body housing 100 Image forming unit 101 Photosensitive drum 105 Laser scanning unit 107 Fixing roller (fixing unit)
108 Paper discharge tray 109 Vertical transport path (transport path)
110 Discharge roller 111 Conveyance roller 114 Branch guide 115 Horizontal conveyance path (conveyance path)
116 Heat insulation sheet (heat insulation member)
117 PET film (synthetic resin film)
200 Document Feeding Unit 300 Document Reading Unit 400 Paper Feeding Unit 500 Operation Display Unit

Claims (6)

In an image forming apparatus comprising: a fixing unit that thermally fixes a sheet onto which a toner image has been transferred by a transfer unit; and a conveyance path that conveys the thermally fixed sheet from the fixing unit to a predetermined position.
An image forming apparatus, wherein the sheet is conveyed along a surface of the synthetic resin film by disposing a synthetic resin film in a non-contact state on an inner wall of the conveyance path.   The conveyance path includes a vertical conveyance path that extends upward from the fixing unit, and a horizontal conveyance path that extends in a direction perpendicular to the upper end of the vertical conveyance path. The synthetic resin film is disposed on the inner upper portion of the horizontal conveyance path. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided.   The image forming apparatus according to claim 2, wherein the horizontal conveyance path is a discharge path toward a discharge portion, and the synthetic resin film is disposed on an inner upper portion of the discharge path.   3. The horizontal conveying path is a return path that reverses the direction of the back surface of the paper and returns it to the transfer portion, and the synthetic resin film is disposed on the inner upper side of the return path. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the synthetic resin film is attached to an inner wall of the conveyance path via a heat insulating member.   The image forming apparatus according to claim 5, wherein the synthetic resin film is cantilevered by the heat insulating member.

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