JP2006163135A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly convey recording paper after fixing without staining it. <P>SOLUTION: The image forming apparatus ejects the recording paper S with ejection rollers 91 and 92 after fixing toner images on the recording paper by passing the recording paper S transferring the toner images in an image forming part through a fixing part 60 having heating rollers 61 and 62. The image forming apparatus is provided with exhaust ducts 110 and 120 exhausting airs A1 and A2 of both front and rear sides of the recording paper on both the front and rear sides of the recording paper S between the fixing part 60 and the ejection rollers 91 and 92 respectively. The heating roller 62 of a lateral directional side conveying the recording paper toward a lateral direction out of the heating rollers 61 and 62 is at a higher temperature than the other heating roller 61. The exhaust ducts 110 and 120 extend in an axial line direction of the heating roller and communicate with a single exhaust fan 130 at the final termination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image in which a recording sheet onto which a toner image has been transferred in an image forming unit is passed through a fixing unit having a heating roller to fix the toner image on the recording sheet and then discharged to a discharging unit by a discharging roller. The present invention relates to a forming apparatus. In particular, it relates to the exhaust technology.

Conventionally, in order to prevent temperature unevenness in the longitudinal direction of the heating member due to the air flow, a rib extending along the direction intersecting the air flow direction is provided on the covering member that covers the upper part of the heating member, and the opening of the region divided by this rib is provided. An image forming apparatus in which the area is changed in the air flow direction is known (for example, see Patent Document 1).
In addition, the recording medium on which an image is formed is fixed by a heat fixing device in order to reduce the temperature rise of a member that may be touched by a user near the fixing device without sacrificing the fixing property. In addition, in the image forming apparatus for discharging the heat-fixed recording medium to a recording medium discharge portion provided at the top of the image forming apparatus main body, a bottom portion located near the end of the recording medium discharge portion on the heat fixing device side In addition, an image forming apparatus configured to provide a vent is also known (see, for example, Patent Document 2).
Japanese Patent Application Laid-Open No. 07-234626 JP 2003-186326 A

When the recording paper passes through the fixing unit and is heated, water vapor is generated from the recording paper, and condensation occurs on the surface of the paper guide or the like when the paper guide or the like forming the recording paper conveyance path is at a low temperature. This dew condensation causes the recording paper to become dirty and also hinders the smooth conveyance of the recording paper.
In the conventional image forming apparatus described above, only one side of the recording paper that has passed through the fixing unit is exhausted.
For this reason, water vapor is not exhausted on the other side of the recording paper, and condensation occurs on the surface of a paper guide or the like, which causes the recording paper to become dirty or hinder smooth conveyance of the recording paper.
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of smoothly conveying a recording sheet after fixing without fouling.

In order to achieve the above object, the image forming apparatus of the present invention fixes the toner image on the recording paper by passing the recording paper on which the toner image is transferred in the image forming unit through a fixing unit having a heating roller. And an image forming apparatus that discharges to a discharge portion by a discharge roller.
Between the fixing unit and the discharge roller, exhaust ducts for exhausting air on both sides of the recording paper are provided on both sides of the recording paper, and the ends of the exhaust ducts communicate with a single exhaust fan. In addition, at least a part of the exhaust duct is provided with a plurality of suction ports, and a plurality of air passages communicating with one or a plurality of the suction ports are provided. The end of the air passage having a long distance to the fan is opposed to a portion of the exhaust fan where exhaust power is strong by the exhaust fan, and the distance from the suction port to the exhaust fan in the air passage is An end of the short air passage is opposed to a portion of the exhaust fan where the exhaust force of the exhaust fan is weak.
According to such a configuration, water vapor generated from the recording paper that has passed through the fixing unit is most likely to be accumulated, and air on both sides of the recording paper (and hence water vapor) is exhausted between the fixing unit and the discharge roller. Condensation on a paper guide or the like forming a recording paper conveyance path is prevented, and as a result, the recording paper after fixing can be smoothly conveyed without being contaminated.
In addition, the end of the exhaust duct that exhausts the air on both sides of the recording paper is connected to a single exhaust fan, so the air on both sides of the recording paper can be exhausted with a single exhaust fan. Therefore, cost reduction and size reduction of the image forming apparatus can be achieved.
Moreover, at least a part of the exhaust duct is provided with a plurality of suction ports and a plurality of air passages communicating with one or a plurality of the suction ports, and among these air passages, from the suction port to the exhaust fan. The end of the air passage having a long distance between the exhaust fan and the exhaust fan is opposed to a portion where the exhaust fan has a strong exhaust force. The air passage has a short distance from the suction port to the exhaust fan. Since the end portion of the road is opposed to a portion of the exhaust fan where the exhaust power of the exhaust fan is weak, a suction port far from the exhaust fan among the plurality of suction ports in the exhaust duct is exhausted by the exhaust fan. A suction port located at a close distance from the exhaust fan is sucked through a short air path by a weak part of the exhaust fan. . The longer the air path, the greater the attenuation of the suction force by the exhaust fan. Consequently, according to the present invention, the suction action at the plurality of suction ports in the exhaust duct is not necessarily changed without changing the size of the suction port. It can be substantially equalized.
That is, according to the present invention, it is possible to satisfactorily exhaust both the front and back sides of the recording paper by the intake action that effectively uses the strong and weak parts of the exhaust force of the fan.
In order to achieve the above object, the image forming apparatus according to the present invention passes the recording paper onto which the toner image has been transferred in the image forming section through a fixing section having a heating roller, thereby placing the toner image on the recording paper. An image forming apparatus that, after fixing, discharges to a discharge portion with a discharge roller,
Between the fixing unit and the discharge roller, exhaust ducts for exhausting air on both sides of the recording paper are provided on both sides of the recording paper, and the ends of the exhaust ducts communicate with a single exhaust fan. In addition, the exhaust duct is provided with a plurality of suction ports and is provided with a plurality of air passages communicating with one or a plurality of the suction ports. Among these air passages, more air is supplied from the suction ports. An end portion of the air passage to be sucked is made to face a portion of the exhaust fan where the exhaust force by the exhaust fan is strong.
According to such a configuration, water vapor generated from the recording paper that has passed through the fixing unit is most likely to be accumulated, and air on both sides of the recording paper (and hence water vapor) is exhausted between the fixing unit and the discharge roller. Condensation on a paper guide or the like forming a recording paper conveyance path is prevented, and as a result, the recording paper after fixing can be smoothly conveyed without being contaminated.
In addition, the end of the exhaust duct that exhausts the air on both sides of the recording paper is connected to a single exhaust fan, so the air on both sides of the recording paper can be exhausted with a single exhaust fan. Therefore, cost reduction and size reduction of the image forming apparatus can be achieved.
In addition, the exhaust duct is provided with a plurality of suction ports and is provided with a plurality of air passages that communicate with one or more of the suction ports, and more air is sucked from the suction ports among the air passages. Since the end of the air path to be made is opposed to a portion of the exhaust fan where exhaust power is strong by the exhaust fan, out of the plurality of suction ports in the exhaust duct, The displacement can be increased.
Therefore, according to the present invention, even if the size of the suction port is not necessarily changed, the exhaust on both the front and back sides of the recording sheet is effectively performed by the intake action that effectively uses the strong and weak exhausting portions of the fan. Can be performed satisfactorily.
In particular, if the recording paper onto which the toner image is transferred in the image forming unit is configured to pass from the lower side to the upper side with respect to the fixing unit having the heating roller, condensation is likely to occur on the paper guide and the like above the fixing unit. However, according to the present invention, it is possible to prevent such dew condensation and smoothly convey the recording paper after fixing.
Further, when the recording paper on which the toner image is transferred in the image forming unit is passed from the lower side to the upper side through the fixing unit having the heating roller, the recording paper is discharged in the lateral direction. Water vapor tends to be trapped inside the movement path that moves upward and moves laterally. However, according to the present invention, since such water vapor can be properly discharged, the recording paper after fixing is not soiled and smooth. Can be conveyed.
In addition, there is a return path for switching back the recording paper having a toner image fixed on one side by the fixing unit between the fixing unit and the discharge roller and returning it to the image forming unit. If the paper guide forming the path is provided above the fixing unit, condensation tends to occur on the paper guide forming the return path. According to the present invention, such condensation is prevented. As a result, the recording paper after fixing can be smoothly conveyed without being stained, and a beautiful image can be smoothly formed on both sides of the recording paper.
Further, if the fixing unit has a pair of heating rollers, water vapor is more likely to be generated on both sides of the recording paper. However, according to the present invention, such water vapor can be discharged properly. , The recording paper after fixing can be smoothly conveyed without being stained.
In addition, the fixing unit has a pair of heating rollers, and among the heating rollers, the heating roller on the lateral side where the recording paper is conveyed in the lateral direction is hotter than the other heating roller. In some cases, water vapor is more easily generated on the high-temperature heating roller side of the recording paper, but according to the present invention, such water vapor can be properly discharged. It becomes possible to convey smoothly without getting dirty.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic front view showing the internal structure of an embodiment of an image forming apparatus according to the present invention.
This image forming apparatus is a color image forming apparatus capable of vertically feeding A4 size recording paper (including letter size) and forming a monochrome (single color) image or a full color image on both sides thereof. An image carrier unit 20 that forms an image forming unit and is accommodated in a case 11, an exposure unit 30 as an exposure unit, and a developing device (developing device) 40 as a developing unit. Further, an intermediate transfer body unit 50 and a fixing unit (fixing unit) 60 as fixing means are provided.
The case 11 is provided with a frame (not shown) of the apparatus main body 10, and each unit is attached to the frame.

  The image carrier unit 20 includes a photoconductor 21 having a photosensitive layer on the outer peripheral surface, and a corona charger (scorotron charger) 22 as a charging unit that uniformly charges the outer peripheral surface of the photoconductor 21. The outer peripheral surface of the photoconductor 21 uniformly charged by the corona charger 22 is selectively exposed with the laser light L from the exposure unit 30 to form an electrostatic latent image. The developer 40 is applied with toner as a developer to form a visible image (toner image), and this toner image is primary-transferred to an intermediate transfer belt 51 which is an intermediate transfer body of the intermediate transfer body unit 50 by a primary transfer portion T1. In addition, the secondary transfer portion (transfer portion) T2 performs secondary transfer onto the recording paper to be transferred.

In the case 11, a conveyance path 16 that conveys a recording sheet on which an image is formed on one side by the secondary transfer section T <b> 2 toward a recording sheet discharge section (sheet discharge tray) 15 on the top surface of the case 11, and this conveyance path 16 is provided with a return path 17 for switching back the recording paper conveyed toward the recording paper discharge section 15 and returning it to the secondary transfer section T2 to form an image on the other side.
Reference numeral 70 denotes a duplex unit configured to be detachable from the apparatus main body, and the return path 17 is completed by mounting the duplex unit 70.
Reference numeral 71 denotes a drive motor for returning the recording paper, and 72 denotes a recording paper return roller driven from the motor 71 via a drive mechanism (not shown) such as a timing belt.

A paper feed cassette 18 for stacking and holding a plurality of recording papers is provided at the lower part of the case 11, and a paper feed roller 19 for feeding the recording papers one by one toward the secondary transfer portion T2. Is provided.
Below the duplex unit 70, there is provided a multi-purpose tray 81 that forms a manual paper feed unit 80, and a paper feed roller 82 that feeds the recording paper set on the multi-purpose tray 81 one by one. It is provided on the main body.

  The developing device 40 is a rotary developing device (rotary developing device), and a developing device cartridge (not shown) for each color in which yellow toner, cyan toner, magenta toner, and black toner are accommodated with respect to the rotating body main body 41. It is detachably attached. As the rotating body 41 rotates at 90 ° pitch in the direction of arrow R, the developing roller (not shown) provided in each developing device cartridge is selectively brought into contact with the photosensitive member 21, and the surface of the photosensitive member 21. Can be selectively developed.

The exposure unit 30 irradiates the laser 21 with the laser light L.
The intermediate transfer body unit 50 includes a unit frame (not shown), the intermediate transfer belt 51 as an intermediate transfer body stretched around a drive roller 54 and a plurality of driven rollers rotatably supported by the frame. The intermediate transfer belt 51 is circulated and driven in the direction of the arrow in the figure. The primary transfer portion T1 is formed at the contact portion between the photosensitive member 21 and the intermediate transfer belt 51, and the secondary transfer portion T2 at the pressure contact portion between the driving roller and the secondary transfer roller 10b provided on the main body side. Is formed.
The secondary transfer roller 10b can be brought into contact with and separated from the drive roller 54 (and therefore with respect to the intermediate transfer belt 51), and when it comes into contact, a secondary transfer portion T2 is formed.
Accordingly, when a color image is formed, a one-color image is formed on the intermediate transfer belt 51 for each rotation of the intermediate transfer belt 51 with the secondary transfer roller 10b being separated from the intermediate transfer belt 51. As a result of multiple rotations of the intermediate transfer belt 51, images of a plurality of colors are superimposed on the intermediate transfer belt 51 to form a color image on the intermediate transfer belt 51, and then the secondary transfer roller 10b contacts the intermediate transfer belt 51. When the recording paper is supplied to the contact portion (secondary transfer portion T2), a color image (toner image) is transferred (secondary transfer) from the intermediate transfer belt 51 onto the recording paper.
The recording paper onto which the toner image has been transferred passes through the fixing unit 60 to melt and fix the toner image, and is discharged toward the paper discharge tray 15.

The fixing unit 60 includes a pair of heating rollers 61 and 62 (see FIG. 2), and the recording paper S passes through the fixing unit 60 from below to above. Further, the recording sheet S passes from the lower side to the upper side with respect to the fixing unit 60 and is then discharged in the lateral direction by the switchback roller pair 93 and the discharge roller pairs 91 and 92.
During the fixing operation (image formation), the heating roller 61 is heated to about 165 degrees C and the heating roller 62 is heated to about 190 degrees C. Accordingly, the heating roller 62 on the lateral side where the recording paper S is conveyed in the lateral direction is hotter than the other heating roller 61.

This image forming apparatus is provided between a discharge roller pair 91 and 92 for discharging the recording paper that has passed through the fixing unit 60 onto the discharge tray 15, and between the fixing unit 60 and the discharge roller pair 91 and 92. And a switchback roller pair 93 that switches back the recording paper that has passed through the fixing unit 60 and returns the recording paper to the image forming unit including the photosensitive member 21 and the like.
The switchback roller pair 93 is provided in the paper discharge path 16a from the fixing unit 60 to the paper discharge roller pair 91, 92. The switchback of the recording paper is such that the rear end of the recording paper is the switchback roller pair 93. Immediately before passing through the nip portion, the paper discharge roller pairs 91 and 92 and the switchback roller pair 93 are reversed to supply the recording paper to the return path 17.
The recording paper supplied to the return path 17 is conveyed by the return roller 72, and supplied to the secondary transfer portion T2 through a gate roller pair 10g that determines the supply timing of the recording paper to the secondary transfer portion T2.

FIG. 2 is an enlarged schematic view of the main part of the image forming apparatus, and FIG. 3 is a plan view of the exhaust duct.
As shown in these drawings, in this image forming apparatus, air on the front side S1 of the recording paper S is provided on both sides of the front side S1 and the back side S2 of the recording paper S between the fixing unit 60 and the discharge rollers 91 and 92. A first exhaust duct 110 (see FIG. 6) that exhausts as shown by arrow A1 and a second exhaust duct 120 (see FIG. 4) that exhausts the air on the back side S2 of the recording paper S as shown by arrow A2 are provided. It is.
As shown in FIG. 3, these exhaust ducts 110 and 120 extend in the axial direction (vertical direction in FIG. 3) of the heating roller pair 61 and 62 of the fixing unit 60, respectively. It communicates with the fan 130.

FIG. 5 is a perspective view showing an exhaust fan (fan unit) 130.
2, 3, and 5, reference numeral 131 denotes a number of communication ports that allow the exhaust ducts 110 and 120 and the exhaust fan 130 to communicate with each other.
In FIG. 5, reference numeral 132 denotes an attachment portion for attachment to the apparatus main body frame.
As shown in FIG. 3, the suction force or blowing force by the fan 130 is weak in the central region F1 and strong in the outer peripheral region F2.

6A and 6B are views showing the first exhaust duct 110 in which a sheet member 113 to be described later is omitted. FIG. 6A is a plan view, and FIG. 6B is a cross-sectional view taken along line bb in FIG.
The first exhaust duct 110 includes a bottom plate 111 inclined as shown in FIGS. 2 and 3, a side plate 112 integral with the bottom plate 111, and a sheet member 113 (FIG. 2) that closes the top of the duct. At the end, as shown in FIG. 6B, a connection port 117 to the exhaust fan 130 is provided. A paper guide 17a that forms the upper part of the return path 17 is integrally formed at the bottom.
A plurality of suction ports 114a to 114m are provided in the bottom plate 111 along the axial direction (vertical direction in FIG. 3) of the heating roller pairs 61 and 62 of the fixing unit 60, and correspond to these suction ports 114a to 114m. Partition plates 116 a to 116 e forming the air paths 115 a to 115 g are provided integrally with the bottom plate 111.
The suction ports 114a to 114m are all open to the front side S1 (FIG. 2) of the recording paper S.
Therefore, the air A1 sucked from the suction port 114a is exhausted to the outside by the exhaust fan 130 through the air passage 115a, and the air A1 sucked from the suction ports 114b and 114c is exhausted by the exhaust fan 130 through the air passages 115b and 115a. Air A1 exhausted to the outside of the machine and sucked from the suction ports 114d and 114e is exhausted to the outside by the exhaust fan 130 through the air passages 115c, 115d and 115f, and is sucked from the suction ports 114f, 114g and 114h. Is exhausted to the outside by the exhaust fan 130 through the air passages 115d and 115f, and the air A1 sucked from the suction ports 114i and 114j is exhausted to the outside by the exhaust fan 130 through the air passages 115e and 115f. , 114l, 114m, the air A1 is exhausted through the air passage 115g It is exhausted to the outside of the apparatus by § down 130.

In this embodiment, of the air passages 115a, 115f, and 115g, the end of the air passage 115a having a long distance from the suction ports 114a to 114c to the suction fan 130 is used as the suction fan in the suction fan 130. The end portion of the air passage 115g having a short distance from the suction ports 114k to 114m to the suction fan 130 in the air passage is opposed to the portion F2 where the suction force is strong by the suction fan 130. It is made to oppose the weak site | part F1. Of the air passages, the air passage 115f having a medium distance from the suction ports 114d to 114j to the suction fan 130 has a weak suction force by the suction fan at the end of the suction fan 130. It is made to oppose between the site | part F1 and the strong site | part F2.
Therefore, even if the size of each suction port is not changed so much, it is possible to exhaust air from each suction port substantially evenly.

As shown in FIGS. 2 to 4, the second exhaust duct 120 is formed in an elongated rod shape as a whole, and includes a bottom plate 121, a side plate 122 integral with the bottom plate 121, and a lid member 123 that closes the upper portion of the duct (FIG. 2). ). A connection port 127 with the exhaust fan 130 is provided at the end.
A plurality (two in the drawing) of suction ports 124a and 124b are provided from the side plate 122 to the bottom plate 121 along the axial direction (vertical direction in FIG. 3) of the heating roller pairs 61 and 62 of the fixing unit 60. A partition plate 126 that forms air passages 125 a and 125 b corresponding to the suction ports 124 a and 124 b is provided integrally with the bottom plate 121.
The suction ports 124a and 124b are both open on the back side S2 (FIG. 2) of the recording paper S.
Therefore, the air A2 sucked from the suction port 124a is exhausted to the outside by the exhaust fan 130 through the air passage 125a, and the air A2 sucked from the suction port 124b is exhausted to the outside by the exhaust fan 130 through the air passage 125b. Is done.

In this embodiment, the recording sheet S on which the toner image is transferred by the image forming unit is passed from the lower side to the upper side through the fixing unit 60 having a heating roller, and then discharged in the horizontal direction. Since water vapor tends to be trapped on the inner side (second exhaust duct 120 side) of the moving path in which the recording paper S moves upward and moves in the lateral direction, as shown in FIG. 2 End portions 127 of the air passages 125a and 125b of the exhaust duct 120 are opposed to a portion F2 of the exhaust fan 130 where the exhaust fan has a strong exhaust force.
Therefore, it is possible to satisfactorily discharge water vapor that tends to stay inside the movement path of the recording paper S.

According to the image forming apparatus as described above, the following effects can be obtained.
(A) The recording paper S on which the toner image has been transferred in the image forming unit is passed through a fixing unit 60 having a heating roller to fix the toner image on the recording paper S. An image forming apparatus that discharges to the discharge unit 15, air A 1 and A 2 on both sides of the recording sheet S is exhausted to both sides of the recording sheet S between the fixing unit 60 and the discharge rollers 91 and 92. Since the exhaust ducts 110 and 120 are provided, the water vapor generated from the recording paper S that has passed through the fixing unit 60 is most likely to be trapped between the fixing unit 60 and the discharge rollers 91 and 92 on both sides of the recording paper S. Air (and hence water vapor) A1, A2 is exhausted.
Therefore, condensation on the paper guide 10h (see FIG. 2) that forms the conveyance path of the recording paper S is prevented, and as a result, the fixed recording paper S can be smoothly conveyed without being contaminated.

(B) Since the ends of the exhaust ducts 110 and 120 for exhausting the air A1 and A2 on both sides of the recording sheet S are connected to the single exhaust fan 130, the recording sheet S is formed by one exhaust fan 130. Thus, the air A1 and A2 on both sides can be exhausted, and the cost can be reduced and the image forming apparatus can be downsized.

(C) Moreover, at least a part of the exhaust ducts 110 and 120 is provided with a plurality of suction ports and a plurality of air passages 115a, 115f and 115g communicating with one or more of these suction ports. Of the paths 115a, 115f, and 115g, the end of the air path 115a having a long distance from the suction ports 114a to 114c to the exhaust fan 130 is made to face the portion F2 of the exhaust fan 130 where the suction force by the exhaust fan is strong. Among the air passages, the end of the air passage 115g having a short distance from the suction ports 114k to 114m to the exhaust fan 130 is opposed to the portion F1 of the exhaust fan 130 where the suction force by the suction fan is weak. Therefore, among the plurality of suction ports in the exhaust duct 110, the suction port 114 located at a distance from the exhaust fan 130. To 114c are sucked through the long air passage 115a by the portion F2 having a strong suction force by the exhaust fan 130, and the suction ports 114k to 114m at a short distance from the exhaust fan 130 are short by the portion F1 having a weak suction force by the exhaust fan 130. The air is sucked through the air passage 115g. The longer the air path, the greater the attenuation of the suction force by the exhaust fan 130. As a result, according to this embodiment, a plurality of exhaust ducts 110 in the exhaust duct 110 are not necessarily changed without changing the size of the suction ports 114a to 114m. The suction action at the suction ports 114a to 114m can be substantially equalized.
In other words, according to this embodiment, the exhaust on both the front and back sides of the recording paper S can be satisfactorily performed by the intake action that effectively uses the strong portion F2 and the weak portion F1 of the fan 130. It becomes possible.

(D) The exhaust ducts 110 and 120 are provided with a plurality of suction ports and are provided with a plurality of air passages that communicate with one or a plurality of these suction ports. Since the ends 127 of the air passages 125a and 125b in which the air is to be sucked are opposed to the portion F2 of the exhaust fan 130 where exhaust power is strong by the exhaust fan, of the plurality of suction ports in the exhaust ducts 110 and 120, The amount of exhaust from the suction ports 124a and 124b where a large amount of air is desired to be sucked can be increased.
Therefore, according to this embodiment, it is possible to satisfactorily exhaust both the front and back sides of the recording sheet S by the intake action of the fan 130 that effectively uses the strong part F2 and the weak part of the exhaust force by the fan. It becomes.

(E) In particular, when the recording paper S on which the toner image has been transferred in the image forming unit is configured to pass from below to above the fixing unit 60 having a heating roller, a paper guide above the fixing unit 60 is provided. Condensation is likely to occur at 10 h or the like, but according to this image forming apparatus, such condensation can be prevented and the fixed recording paper S can be smoothly conveyed without being stained.
(F) The recording sheet S on which the toner image is transferred in the image forming unit is passed from the lower side to the upper side through the fixing unit 60 having a heating roller, and then discharged in the lateral direction. Water vapor tends to accumulate inside the movement path (second exhaust duct 120 side) in which the recording sheet S moves upward and moves in the horizontal direction. Since the air can be properly discharged by the exhaust duct 120, the recording paper S after fixing can be smoothly conveyed without being contaminated.

(G) A return path 17 is provided for switching back the recording paper S on which the toner image is fixed on one side by the fixing unit between the fixing unit 60 and the discharge rollers 91 and 92 to the image forming unit. If the paper guide 17a (see FIG. 2) that forms the return path 17 is provided above the fixing unit 60, condensation tends to occur on the paper guide 17a that forms the return path 17. According to this image forming apparatus, it is possible to prevent such dew condensation, smoothly convey the recording sheet S after fixing, and smoothly form clean images on both sides of the recording sheet. Become.

(H) When the fixing unit 60 has a pair of heating rollers, water vapor is more likely to be generated on both sides of the recording paper S. According to this image forming apparatus, such water vapor is Since the first exhaust duct 110 and the second exhaust duct 120 can appropriately discharge, the recording sheet S after fixing can be smoothly conveyed without being contaminated.
(J) The fixing unit 60 has a pair of heating rollers. Among the heating rollers, the heating roller 62 on the lateral direction side where the recording paper S is conveyed in the lateral direction is the other heating roller. When the temperature is higher than 61, water vapor is more easily generated on the high-temperature heating roller 62 side of the recording paper S. According to this image forming apparatus, such water vapor is second exhausted. Since the paper can be properly discharged by the duct 120, the recording paper S after fixing can be smoothly conveyed without being stained.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the gist of the present invention.

1 is a schematic front view showing an internal structure of an embodiment of an image forming apparatus according to the present invention. The partial expansion schematic of FIG. The top view of an exhaust duct. The perspective view of a 2nd exhaust duct. The perspective view of a fan (fan unit). (A) is a top view of a 1st exhaust duct, (b) is bb sectional drawing in Fig. (A).

Explanation of symbols

  S: recording paper, 17: return path, 17a: paper guide, 60: fixing unit, 61, 62: heating roller, 91, 92: discharge roller, 110, 120: exhaust duct, 130: exhaust fan.

Claims (7)

An image forming apparatus in which a recording paper on which a toner image has been transferred in an image forming section is passed through a fixing section having a heating roller to fix the toner image on the recording paper and then discharged to a discharge section by a discharge roller. There,
Between the fixing unit and the discharge roller, exhaust ducts for exhausting air on both sides of the recording paper are provided on both sides of the recording paper, and the ends of the exhaust ducts communicate with a single exhaust fan. In addition, at least a part of the exhaust duct is provided with a plurality of suction ports, and a plurality of air passages communicating with one or a plurality of the suction ports are provided. The end of the air passage having a long distance to the fan is opposed to a portion of the exhaust fan where exhaust power is strong by the exhaust fan, and the distance from the suction port to the exhaust fan in the air passage is An image forming apparatus characterized in that an end portion of a short air passage is opposed to a portion of the exhaust fan where the exhaust force of the exhaust fan is weak. An image forming apparatus in which a recording paper on which a toner image has been transferred in an image forming section is passed through a fixing section having a heating roller to fix the toner image on the recording paper and then discharged to a discharge section by a discharge roller. There,
Between the fixing unit and the discharge roller, exhaust ducts for exhausting air on both sides of the recording paper are provided on both sides of the recording paper, and the ends of the exhaust ducts communicate with a single exhaust fan. In addition, the exhaust duct is provided with a plurality of suction ports and is provided with a plurality of air passages communicating with one or a plurality of the suction ports. Among these air passages, more air is supplied from the suction ports. An image forming apparatus, wherein an end portion of an air passage to be sucked is opposed to a portion of the exhaust fan where exhaust power is strong by the exhaust fan.   3. The image forming apparatus according to claim 1, wherein the recording paper onto which the toner image has been transferred in the image forming unit is passed from below to above the fixing unit having the heating roller.   2. The recording paper on which the toner image is transferred in the image forming unit is passed from the lower side to the upper side with respect to the fixing unit having the heating roller, and then discharged in the lateral direction. Or the image forming apparatus according to 2;   A recording paper having a toner image fixed on one side by the fixing unit; and a return path for returning the recording paper to the image forming unit by switching back between the fixing unit and the discharge roller. 5. The image forming apparatus according to claim 1, wherein a paper guide for forming the image is provided above the fixing unit.   The image forming apparatus according to claim 1, wherein the fixing unit includes a pair of heating rollers.   The fixing unit has a pair of heating rollers, and among the heating rollers, the heating roller on the lateral side where the recording paper is conveyed in the lateral direction is hotter than the other heating roller. The image forming apparatus according to claim 4.

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