JP2007331931A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device achieving noise reduction, energy saving, compactness and weight reduction without a strong cooling mechanism, which does not cause frictional trace due to strong friction of a guide member and paper when guiding the paper so as to be bent in order to largely change the conveyance direction of the toner-fixed paper, which prevents fusing of toner chipped from the paper to the guide member even when a toner fixing surface contacts the guide member in perfecting printing, and which prevents such troubles even when the fixing device peripheral temperature increases accompanying continuous printing operations, such as large quantity of printing, in particular. <P>SOLUTION: This image forming device has the guide member which guides the conveyance direction of the paper delivered from a fixing device. The guide member consists of a guide member body and a roller guide. The roller guide is rotatably fixed on the guide member body so that part of its circumferential side may project from the side contacting the paper of the guide member body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly, to a copying machine, a printer, a facsimile machine, and the like in which a roller guide is disposed on a sheet contact surface of a guide member that guides a conveyance direction of a sheet on which toner is fixed by a fixing apparatus. The present invention relates to an image forming apparatus.

In an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile, the toner image formed on the surface of the photosensitive drum 102 is supplied from a paper feed cassette 103 or a manual feed tray 104 as shown in FIG. It is transferred to the paper. The sheet on which the toner image has been transferred is heated and pressed by the fixing device 105, and the toner is fixed on the sheet. The sheet on which the toner has been fixed in the fixing device 105 is discharged from the discharge roller 106, the transfer destination is sorted by the guide member 107, and sent to the upper transfer roller 108 or the lower transfer roller 109.
When toner fixing on both sides of the paper is completed in the case of single-sided printing or double-sided printing, the paper 120 is discharged from the discharge roller 106 and transferred to the upper conveying roller 108 by the guide member 107 as shown in FIG. Be guided. At this time, the sheet 120 comes into contact with the guide member 107 on the opposite side of the toner fixing surface 121. Then, the sheet 120 passes through the upper conveyance roller 108 and is discharged from a discharge tray (not shown) at the top of the image forming apparatus 101.

On the other hand, when double-sided printing is performed, when printing on the opposite side of the paper surface on which toner has already been fixed, the paper 120 is discharged from the discharge roller 106 as shown in FIGS. It is guided to the lower conveyance roller 109 by the guide member 107. At this time, the toner fixing surface 121 of the paper 120 comes into contact with the guide member 107.
Then, the sheet that has passed through the lower conveying roller 109 is turned over by the duplex unit 110 and conveyed to the lower side of the photosensitive drum 102, and the surface opposite to the sheet surface on which the toner has been fixed is the surface of the photosensitive drum 102. Confront. The toner image is transferred to the opposite paper surface, and the toner is fixed by the fixing device 105. As in the case of single-sided printing, the sheet on which the toner is fixed and discharged from the discharge roller 106 is distributed to the transport destination by the guide member 107, guided to the upper transport roller 108, and discharged from the discharge tray.

  As described above, the guide member 107 must be guided to the upper conveyance roller 108 or the lower conveyance roller 109 so that the sheet is largely bent in order to greatly change the conveyance direction of the sheet 120 on which the toner is fixed. And the sheet 120 is rubbed strongly. At this time, since the toner immediately after being fixed at a high temperature in the fixing device 105 is fixed on the hot paper 120 in a soft state, the paper 120 is softly fixed on the paper 120 by being rubbed strongly with the guide member 107. Toner is scraped from the paper 120 and a rubbing trace is generated on the paper 120.

Further, in double-sided printing, when the paper 120 is guided to the lower transport roller 109, the toner fixing surface 121 contacts the guide member 107 as described above, so that the paper 120 is rubbed strongly with the guide member 107. The soft toner shaved from the paper 120 is fused to the guide member 107, and the fused toner also causes a paper jam.
In particular, in a situation where a large amount of copying is performed continuously and toner is put on the entire surface of the paper, the ambient temperature of the fixing device 105 and the temperature of the paper 120 being conveyed itself increase with the continuous printing operation. And toner fusing easily occurs.

In order to solve the problem of toner fixing in such a high temperature state, an image forming apparatus in which only the fixing pressure is switched while fixing temperature is fixed has been proposed (for example, see Patent Document 1 below).
The image forming apparatus can perform double-sided printing and can switch the process speed, and the control unit can only fix the fixing pressure depending on the process speed of the selected resolution mode and the single-sided printing mode or the double-sided printing mode. And the fixing temperature is kept constant. Further, the control unit switches the fixing pressure depending on whether printing is performed on the front surface or the back surface in the double-sided printing mode.

According to the image forming apparatus, when an image is formed by switching the process speed, only the fixing pressure is switched according to the process speed, so that the fixing temperature is kept constant without causing problems such as waiting for a time due to the temperature switching, The front and back image quality in the duplex printing mode can be made constant.
However, by fixing the fixing temperature in such an image forming apparatus, the toner is fixed at a constant high temperature in the fixing apparatus even though the increase in the temperature around the fixing apparatus and the temperature of the conveyed paper can be suppressed. There is no change in the immediately following paper rubbing against the guide member, especially when the toner fixing surface of the paper comes into contact with the guide member during double-sided printing, and the problem that soft toner is fused to the guide member is eliminated. Can not.
JP 2002-23546 A

  The present invention has been made to solve the above-described problems of the prior art, and in order to greatly change the transport direction of the toner-fixed paper, the guide member is used when guiding the paper so as to be largely bent. Even if the toner fixing surface is in contact with the guide member in double-sided printing, the toner scraped off from the paper is fused to the guide member and causes a paper jam. In particular, it is an object of the present invention to provide an image forming apparatus capable of preventing these problems even when the temperature around the fixing device rises with continuous printing operations such as mass copying. Further, it is an object of the present invention to provide an image forming apparatus that can achieve low noise, energy saving, small size and light weight without providing a powerful cooling mechanism.

  The invention according to claim 1 includes a guide member that guides a conveyance direction of the sheet discharged from the fixing device, and the guide member includes a guide member main body and a cylindrical roller guide, An image characterized in that a part of the circumferential surface protrudes from a surface of the guide member main body that contacts the paper and is rotatably attached to the guide member main body so as to contact the paper. The present invention relates to a forming apparatus.

  According to a second aspect of the present invention, the guide member main body includes a substantially triangular prism-shaped flat main body including right and left side surfaces of a substantially triangular shape, and upper and lower front surfaces, a lower front surface, and a rear surface of the guide member main body, and the guide main body. The plurality of guide bodies are fixed so that the left and right side surfaces thereof are perpendicular to the switching shaft, and the shape is overlapped when viewed from the axial direction, The switching shaft is rotated by a predetermined angle so that the upper front surface or the lower front surface of the guide body is in contact with the paper, and the roller guide is formed as a boundary between the upper front surface and the lower front surface in the circumference thereof. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is attached so as not to include a tip portion.

  The invention according to claim 3 relates to the image forming apparatus according to claim 2, wherein the roller guides are respectively attached to the left and right side surfaces of the substantially triangular shape.

  The invention according to claim 4 relates to the image forming apparatus according to claim 2, wherein the roller guide is attached to only one of the substantially triangular left and right side surfaces.

  A fifth aspect of the present invention relates to the image forming apparatus according to any one of the second to fourth aspects, wherein the roller guide is attached so that a part of the circumference thereof overlaps.

  The invention according to claim 6 relates to the image forming apparatus according to any one of claims 2 to 5, wherein the plurality of roller guides are configured to have the same diameter.

  According to the first aspect of the present invention, the sheet immediately after toner fixing does not directly contact the surface of the guide member body on the side in contact with the sheet, but contacts the roller guide that is rotatably attached to the guide member body. Since the roller guide rotates and is transported without causing friction, the roller guide is strongly rubbed and no rubbing trace is generated. In particular, even when the toner fixing surface is opposed to the surface of the guide member main body in double-sided printing, the toner is not scraped from the paper, and the scraped toner is fused to the guide member main body to cause a paper jam. There is nothing. Therefore, even when the temperature around the fixing device rises due to continuous printing operations such as large-volume copying, these problems can be prevented and low noise, energy saving, small size without a powerful cooling mechanism. It is possible to reduce the weight.

  According to the second aspect of the present invention, the sheet immediately after toner fixing does not directly contact the upper front surface or the lower front surface of the guide main body, but contacts the roller guide rotatably attached to the guide main body. Since it is conveyed without causing friction due to rotation, there is no rubbing trace due to strong rubbing, and even in double-sided printing, the toner is scraped from the paper and fused to the guide body, causing a paper jam. It is possible to prevent this. In addition, the roller guide is attached within the circumference so as not to include the tip portion formed as the boundary between the upper front surface and the lower front surface, so that the paper contacts the upper front surface or the lower front surface. This can be prevented and the sheet can be stably conveyed.

  According to the third aspect of the present invention, the roller guides are attached to the left and right sides of the substantially triangular shape, respectively, so that it is possible to convey the paper more stably.

  According to the fourth aspect of the present invention, the roller guide is attached only to one of the right and left side surfaces of the substantially triangular shape. Therefore, positioning and attachment can be performed more easily during the attachment.

  According to the fifth aspect of the present invention, by attaching the roller guides so as to partially overlap, it is possible to attach a large number of sheets so that there is no portion where the sheet directly contacts the guide main body.

  According to the invention which concerns on Claim 6, the surface of the roller guide which contacts a sheet | seat is formed gently by the roller guide being comprised by the diameter of the same size, and it can be made to produce more friction.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of an image forming apparatus according to the invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an example of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a partially enlarged view showing the periphery of the guide member in FIG. FIG. 3 is an enlarged left side view of the guide member in FIG. FIG. 4 is a front view of the guide member of FIG. 3 viewed from the right side of the drawing.
An image forming apparatus 1 according to the present invention includes a photosensitive drum 102 that forms a toner image on a surface and transfers the toner image onto a sheet, a paper feed cassette 3 that is provided in the image forming apparatus and supplies the sheet, and an outer side of the image forming apparatus. The paper feed tray 4, the fixing device 5 for fixing the toner transferred onto the paper, the discharge roller 6 for discharging the paper on which the toner has been fixed by the fixing device 5, and the paper transport direction. A guide member 7, an upper conveying roller 8, a lower conveying roller 9, and a duplex unit 10 used for duplex printing are provided.

  3 and 4, the guide member 7 includes a plurality of guide bodies 20, a switching shaft 23, a cylindrical left side roller guide 26 and a right side roller guide 27 (hereinafter simply referred to as roller guides 26 and 27). It is comprised. The plurality of guide bodies 20 are flat, substantially triangular prisms having the same shape, and are fixed to the switching shaft 23 so as to be perpendicular to the switching shaft 23 at equal intervals and overlap with each other when viewed from the axial direction. The number and interval of the guide bodies 20 fixed to the switching shaft 23 are set according to the maximum paper width and the minimum paper width of the paper to be conveyed. For example, when the maximum paper width is A4 vertical size and the minimum paper width is postcard horizontal size, the distance between adjacent guide main bodies 20 is narrower than the postcard horizontal size (107 mm), and the distance between the guide main bodies 20 at both ends is A4 vertical size. If it is slightly narrower than the size (297 mm), the required number of guide main bodies 20 is four or more. In order to carry it stably, it is better that the number of guide main bodies 20 is large. However, considering the cost and the like, about six as shown in FIG. 4 are appropriate.

  Further, each guide body 20 has a left side roller guide 26 and a right side roller guide 27 rotated on the left side surface and the right side surface, which are substantially triangular surfaces, with the upper front surface 24 and the lower front surface 25 interposed therebetween. The shafts 28 and 29 are rotatably provided. The left side roller guide 26 and the right side roller guide 27 are attached so as to slightly protrude from the upper front surface 24 and the lower front surface 25 when viewed from the axial direction of the switching shaft 23. Moreover, the roller guides 26 and 27 are attached so that a part of the circumference thereof overlaps when viewed from the axial direction of the switching shaft 23. As a result, a large number of sheets can be attached, and there can be no portion where the sheet directly contacts the guide body 20. The tip 21 of the guide body 20 has a pointed shape, and the roller guides 26 and 27 are not attached in the vicinity of the tip 21 so as not to include the tip 21 part in the circumference thereof.

  Here, the guide member 7 provided in the image forming apparatus according to the present invention is obtained by attaching roller guides 26 and 27 to a conventionally known guide member (corresponding to the guide main body 20 and the switching shaft 23). Not only the guide main body 20 and the switching shaft 23 but also the roller guides 26 and 27 can be attached to a conventionally known guide member to constitute the guide member 7 in the present invention. That is, at least a part of the circumferential surface of the roller guides 26 and 27 protrudes from the surface (upper front surface 24 or lower front surface 25) of the guide member main body (guide main body 20) in contact with the paper, and the paper is guided by the guide member main body. What is necessary is just to come in contact with the roller guides 26 and 27, without contacting directly with the surface.

  The upper conveying roller 8 is in a direction in which the paper is guided by the guide member 7 when the toner fixing is finished in the case of single-sided printing or when the toner fixing on both sides of the paper is finished in the case of double-sided printing. The sheet is conveyed in the upper direction of the image forming apparatus 1 and discharged from a discharge port (not shown). On the other hand, the lower conveying roller 9 conveys the sheet to the duplex unit 10 in the direction in which the sheet is guided by the guide member 7 when the toner fixing to one side of the sheet is completed in the case of duplex printing.

Accordingly, the guide member 7 grasps the printing condition input to the image forming apparatus 1 as to single-sided printing or double-sided printing, and the printing status indicating which side of the double-sided printing has been finished, and the discharge roller 6. The sheet discharged from the sheet is guided to the upper transport roller 8 or the lower transport roller 9. In order to guide in this way, the guide member 7 is provided with a switching shaft 23. The switching shaft 23 rotates by a predetermined angle in the A direction or the B direction as shown in FIG. 3 in order to switch the conveyance direction by the guide body 20 in accordance with the printing conditions and the printing situation.
The rotation angle of the switching shaft 23 in the A direction and the B direction is such that the sheet discharged from the discharge roller 6 is not conveyed to the lower conveyance roller 9 side and the upper conveyance roller 8 side opposite to the side to be guided, respectively. In addition, it is set as appropriate in relation to the arrangement of the discharge roller 6, the guide member 7, the upper transport roller 8 and the lower transport roller 9.

When the switching shaft 23 is rotated by a predetermined angle in the direction A shown in FIG. 3, the leading edge of the sheet discharged from the discharge roller 6 hits the upper front 24 side, and the sheet flows to the upper conveying roller 8 side. At this time, as described above, in the case of single-sided printing, the paper printing surface, that is, the toner fixing surface 15 is opposite to the upper front 24 side of the guide member 7, but in the case of double-sided printing, Since the toner fixing is finished, the toner fixing surface comes into contact with the upper front surface 24 side of the guide member.
On the other hand, when the switching shaft 23 is rotated by a predetermined angle in the direction B shown in FIG. 3, the leading edge of the sheet discharged from the discharge roller 6 hits the lower front 25 side, and the sheet flows to the lower conveying roller 9 side. In this case, as described above, the toner fixing surface 15 of the sheet that has finished toner fixing on one side of the sheet by double-sided printing contacts the lower front surface 25 side of the guide member.

  Here, in the guide member 7 in the image forming apparatus according to the present invention, the paper discharged from the discharge roller 6 does not directly contact the upper front surface 24 or the lower front surface 25 of the guide main body 20, and can rotate to the guide main body 20. The sheet comes into contact with the attached roller guides 26 and 27. Accordingly, when the paper is conveyed so as to be rubbed strongly with the upper front 24 side or the lower front 25 side, the roller guides 26 and 27 rotate, so that even if the paper comes into contact with the rotation surface of the roller guides 26 and 27, the friction occurs. It is conveyed without.

Therefore, the sheet is not strongly rubbed against the upper front 24 or the lower front 25, and no rubbing trace is generated. Even when the toner fixing surface 15 faces the upper front 24 side or the lower front 25 side particularly in double-sided printing, It is not scraped from the top of the paper, and the shaved toner is not fused to the guide member 7 to cause a paper jam.
Further, when the toner fixing surface 15 comes into contact with the roller guides 26 and 27, the roller guides 26 and 27 rotate even if the toner slightly adheres to the rotating surfaces of the roller guides 26 and 27. In other words, the toner does not fuse with the guide member and cause a paper jam.
Further, the roller guides 26 and 27 rotate to receive the paper on the entire rotation surface of the roller guides 26 and 27, so that the roller guides 26 and 27 do not exist and directly contact the upper front 24 or the lower front 25. In addition, there is no possibility that specific portions of the upper front 24 and the lower front 25 are scraped due to the leading edge of the sheet being concentrated on a certain portion, and the life of the members can be extended.

FIG. 5 is a left side view showing a guide member in another example of the embodiment of the image forming apparatus according to the present invention. FIG. 6 is a front view of the guide member of FIG. 5 viewed from the right side of the drawing. The configuration of another example of the embodiment of the image forming apparatus according to the present invention is exactly the same as the schematic configuration shown in FIG. 1 except for the shape of the guide member. Since the basic configuration of the guide member 37 is the same as that of the guide member 7, the same reference numeral is used for the same configuration.
The guide member 37 includes a plurality of guide bodies 20, a switching shaft 23, a lower roller guide 31, and an upper roller guide 32 (hereinafter also simply referred to as roller guides 31, 32). Therefore, it is the same as the guide member 7 except that the roller guides 31 and 32 are different.

In the guide member 37, a lower roller guide 31 is provided in the vicinity of the left side surface of each guide body 20 so as to be rotatable by a rotating shaft 35, and the upper roller guide 32 is separated from the left side surface by the thickness of the lower roller guide 31. Is rotatably provided by a rotating shaft 36. The lower roller guide 31 and the upper roller guide 32 are arranged so as to slightly overlap when viewed from the axial direction, and are attached so as to slightly protrude from the upper front surface 24 and the lower front surface 25.
The lower roller guide 31 of the guide member 37 has the same shape and size as the left side roller guide 26 of the guide member 7 and is attached to the left side surface of the guide body 20 at exactly the same position. The upper roller guide 32 has basically the same shape and size as the right side roller guide 27, but has a longer rotation shaft 36 on the left side corresponding to the right side where the right side roller guide 27 is disposed. It is attached.

Therefore, the guide member 7 and the guide member 37 are only different in whether the roller guides are arranged on both side surfaces of the guide main body 20 or only on one side. Therefore, in the image forming apparatus provided with the guide member 37, as in the image forming apparatus provided with the guide member 7, the paper discharged from the discharge roller 6 directly contacts the upper front surface 24 or the lower front surface 25 of the guide body 20. Without contact, the roller guides 31 and 32 rotatably attached to the guide main body 20 are brought into contact with and conveyed without friction, and the same effect can be obtained.
When the roller guides 26 and 27 are arranged on both sides of the guide body 20 as in the guide member 7 and when the roller guides 31 and 32 are arranged on one side of the guide body 20 as in the guide member 37, the former both sides The surface arrangement is considered to be slightly higher in sheet conveyance stability, but the latter one-side arrangement is considered to be easier to position and attach than the both-side arrangement when the roller guides 31 and 32 are attached. In the case of the single-sided arrangement, even if it is arranged on the right side, it is possible to achieve the same effect as the arrangement on the left side as shown in FIG.

In the guide members 7 and 37, four roller guides are attached to the upper front surface 24 and the lower front surface 25 as illustrated, but at least one roller guide is provided on each of the upper front surface 24 and the lower front surface 25. A guide must be attached. In order to prevent the upper front surface 24 or the lower front surface 25 from contacting and rubbing the paper, it is better that the number of roller guides is larger. It is appropriate to attach a roller guide.
In addition, if the number of roller guides is increased, and in particular, if the diameter of the roller guides is decreased and arranged more, not only the upper front surface 24 or the lower front surface 25 is not contacted, but also the surface of the roller guide that contacts the paper is formed gently. Therefore, it is possible to prevent more friction. However, since the tip 21 does not cause friction with the paper, it is not necessary to attach a roller guide.
Further, by arranging the roller guides so as to overlap in the guide members 7 and 37 when viewed from the axial direction, it is possible to prevent the sheet from coming into contact with the upper front surface 24 or the lower front surface 25 through the gap between the roller guides.

  Moreover, although the guide members 7 and 37 illustrated the roller guides having the same size (the same size diameter), they may be attached in combination with different sizes. If the size of the diameter is the same, the surface of the roller guide that comes into contact with the paper is gently formed, and it is possible to prevent friction. When combining different sizes, the roller guide should protrude by the same width from the upper front surface 24 and the lower front surface 25 when viewed from the axial direction, so that the surface of the roller guide in contact with the paper is formed gently. Then, it is possible to prevent friction from occurring.

Next, a sheet conveying operation during single-sided printing in the image forming apparatus according to the present invention will be described with reference to FIGS. 1 shows a schematic configuration of an example of an embodiment of the image forming apparatus according to the present invention as described above, and also shows a sheet conveyance path during single-sided printing.
First, in the input unit (not shown) of the image forming apparatus 1, single-sided printing conditions and the size and number of sheets of paper are set.
When the start button is pressed, the paper in the paper feed cassette 3 is transported under the photosensitive drum 2 having a toner image formed on the surface, and the toner image is transferred to the paper in accordance with the contents set in the input unit.
The sheet on which the toner image has been transferred is conveyed to the fixing device 5 and heated and pressurized to fix the toner on the sheet. The sheet on which the toner is fixed is discharged from the discharge roller 6.
At this time, the guide member 7 grasps that single-sided printing paper is discharged from the setting contents in the input unit, and rotates the switching shaft 23 by a predetermined angle in the A direction to switch the conveyance direction to the upper conveyance roller 8 direction.

The front end of the sheet 13 discharged from the discharge roller 6 hits the upper front 24 side of the guide member 7 and is guided toward the upper conveying roller 8 while contacting the roller guides 26 and 27 on the upper front 24 as shown in FIG. The
The sheet 13 guided to the upper conveying roller 8 is discharged from a discharge tray (not shown) at the top of the image forming apparatus 1 and single-sided printing ends.

As described above, even when the sheet 13 discharged immediately after toner fixing at a high temperature in the fixing device 5 is largely switched in the transport direction by the guide member 7, the discharged sheet 13 remains on the upper front 24 side of the guide member 7. Since the roller guides 26 and 27 are in contact with each other, friction does not occur due to the rotation of the roller guides 26 and 27. Therefore, it is possible to avoid the occurrence of rubbing traces due to friction caused by direct contact with the upper front surface 24. In single-sided printing, the surface opposite to the toner fixing surface 15 is in contact with the upper front surface 24 side of the guide member 7. Even in this case, if there are no roller guides 26 and 27, the opposite side of the toner fixing surface 15 is present. When the surface is rubbed strongly, the toner on the toner fixing surface 15 side is crushed and a rubbing trace is generated.
Therefore, even in an image forming apparatus that does not perform double-sided printing and only performs single-sided printing, the use of the guide member to which the roller guide is attached can eliminate problems after toner fixing.

FIG. 7 is a schematic configuration diagram illustrating a sheet conveyance path via a duplex unit in an example of the image forming apparatus according to the same embodiment as that of FIG. FIG. 8 is a partially enlarged view showing the periphery of the guide member in FIG.
Based on FIGS. 3, 4, 7, and 8, a sheet conveying operation from single-sided printing to double-sided printing in double-sided printing in the image forming apparatus according to the present invention will be described.
The toner image formed on the surface of the photosensitive drum 2 in accordance with the double-sided printing under a printing condition set in advance in an input unit (not shown) of the image forming apparatus 1 and the setting contents such as the size and number of sheets is supplied to the paper feed cassette 3 or the hand. It is transferred to the paper 13 supplied from the difference tray 4.
The sheet on which the toner image has been transferred is heated and pressed by the fixing device 5, and the sheet 13 on which the toner has been fixed is discharged from the discharge roller 6. The process up to this point is exactly the same as in the case of single-sided printing described above.

When the sheet 13 on which toner is fixed is discharged from the discharge roller 6, the guide member 7 grasps that the sheet 13 is printed on one side in double-sided printing based on the setting contents and the conveyance state to the input unit, and switches. The shaft 23 is rotated in the B direction by a predetermined angle to switch the transport direction to the lower transport roller 9 direction.
The leading edge of the sheet 13 discharged from the discharge roller 6 hits the lower front surface 25 side of the guide member 7 and is guided toward the lower conveying roller 9 while contacting the roller guides 26 and 27 on the lower front surface 25 as shown in FIG. The At this time, the toner fixing surface 15 contacts the lower front surface 25 side.
The sheet 13 guided to the lower transport roller 9 is transported to the duplex unit 10 and turned upside down, and transported to the lower side of the photosensitive drum 2 with the printing surface facing downward.

As described above, even when the sheet 13 discharged immediately after the toner fixing at the high temperature in the fixing device 5 is largely switched by the guide member 7, the discharged sheet 13 remains on the lower front 25 side of the guide member 7. Since the roller guides 26 and 27 are in contact with each other, friction does not occur due to the rotation of the roller guides 26 and 27. Therefore, it is possible to avoid the generation of rubbing traces caused by direct contact with the lower front surface 25 to generate friction and rubbing strongly. Further, since there is no strong rubbing, even if the toner fixing surface comes into contact with the lower front 25 side, the toner is scraped off from the paper and fused to the guide member 7 to prevent paper jamming.
In particular, even when the temperature around the fixing device rises due to continuous printing operations such as mass copying, it is possible to prevent these problems, and it is not necessary to provide a powerful cooling mechanism. It becomes possible to reduce the size and weight.

As described above, the sheet 13 conveyed to the lower side of the photosensitive drum 2 with the printing surface on the lower side is then fixed with the toner 13 on the sheet 13 onto which the toner image has been transferred, as in the case of single-sided printing. The paper is discharged from the discharge roller 6, guided by the guide member 7 in the direction of the upper conveyance roller 8, and discharged from the discharge tray, thereby completing double-sided printing. However, unlike the case of single-sided printing, the surface that has been printed first and the toner is fixed contacts the upper front 24 side of the guide member 7.
In this case, since the discharged paper 13 comes into contact with the roller guides 26 and 27 on the upper front surface 24 side of the guide member 7, friction does not occur due to the rotation of the roller guides 26 and 27, thereby avoiding the generation of rubbing traces. In addition, the toner is not scraped off from the paper and fused to the guide member 7 to cause a paper jam.

  The present invention is suitably used for an image forming apparatus such as a copying machine, a printer, and a facsimile machine having a guide member that guides a conveyance direction of a sheet on which toner is fixed by a fixing device.

1 is a schematic configuration diagram illustrating an example of an embodiment of an image forming apparatus according to the present invention. It is the elements on larger scale which expand and show the guide member periphery in FIG. It is a left side enlarged view which expands and shows the guide member in FIG. It is the front view which looked at the guide member of FIG. 3 from the paper surface right direction. It is a left view which shows the guide member in the other example of embodiment of the image forming apparatus which concerns on this invention. It is the front view which looked at the guide member of FIG. 5 from the paper surface right direction. FIG. 2 is a schematic configuration diagram illustrating a sheet conveyance path via a duplex unit in an example of the image forming apparatus according to the same embodiment as in FIG. 1. It is the elements on larger scale which expand and show the guide member periphery in FIG. FIG. 10 is a schematic configuration diagram illustrating a sheet conveyance path during single-side printing together with a schematic configuration of a conventional image forming apparatus. It is the elements on larger scale which expand and show the guide member periphery in FIG. FIG. 10 is a schematic configuration diagram illustrating a sheet conveyance path via a duplex unit together with a schematic configuration of a conventional image forming apparatus. It is the elements on larger scale which expand and show the guide member periphery in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Paper feed cassette 4 Manual feed tray 5 Fixing apparatus 6 Discharge roller 7 Guide member 8 Upper conveyance roller 9 Lower conveyance roller 10 Both-side unit 26 Left side roller guide 27 Right side roller guide

Claims (6)

A guide member for guiding the conveyance direction of the paper discharged from the fixing device;
The guide member includes a guide member main body and a cylindrical roller guide, and the roller guide partially protrudes from the surface of the guide member main body on the side in contact with the paper, and the paper An image forming apparatus, wherein the image forming apparatus is rotatably attached to the guide member main body so as to come into contact with the image forming apparatus. The guide member main body has a substantially triangular left and right side surface, a plurality of flat triangular guide bodies each having an upper front surface, a lower front surface, and a rear surface, and a switching shaft for switching the direction of the guide main body. Configured,
The plurality of guide bodies are fixed so that the left and right side surfaces thereof are perpendicular to the switching shaft, and the shapes are overlapped when viewed from the axial direction,
The switching shaft rotates by a predetermined angle so that the upper front surface or the lower front surface of the guide body is in contact with the paper,
The image forming apparatus according to claim 1, wherein the roller guide is attached so as not to include a tip portion formed as a boundary between the upper front surface and the lower front surface in a circumference thereof.   The image forming apparatus according to claim 2, wherein the roller guides are respectively attached to the left and right side surfaces of the substantially triangular shape.   The image forming apparatus according to claim 2, wherein the roller guide is attached only to one of the substantially triangular left and right side surfaces.   The image forming apparatus according to claim 2, wherein the roller guide is attached so that a part of a circumference thereof overlaps.   The image forming apparatus according to claim 2, wherein the plurality of roller guides are configured to have the same diameter.

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