JP2010072399A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device can prevent overheating of a non-paper-sheet-passing area of a heating roller and tacking after ejecting a paper sheet, while saving energy. <P>SOLUTION: A wind blows over the whole width of a blowing port 201 (whole width in a direction orthogonal to a conveying direction of a recording sheet), because a sidewall guide 301 is brought into an opened state, when outside air sucked into an air duct 200 by a fan unit 100 blows from the blowing port 201. The wind blowing from the blowing port 201 blows into an intake port 211, because a lid 212 is opened. The wind blowing into the intake port 211 is guided to a blowing port 213 by partitioning walls 602a-602d. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for eliminating partial overheating of a fixing device while saving energy.

Image forming apparatuses such as printers, copiers, and facsimiles have always been required to increase the printing speed. For this reason, for example, if the fixing device heats and melts the toner and raises the fixing temperature when the toner is pressure-bonded to the recording sheet, the toner can be melted earlier and pressure-bonded to the recording sheet to shorten the fixing time. it can.
Now, the fixing device presses the toner onto the recording sheet with the heating roller and the pressure roller, and heat is taken away from the circumferential surface of the heating roller by the recording sheet. The roller itself must continue to be heated.

However, in a device that forms an image on recording sheets of different sizes, when a recording sheet having a small size (hereinafter referred to as “small size paper”) is continuously passed, the small size paper on the circumferential surface of the heating roller does not pass. The area (hereinafter referred to as “non-sheet passing area”) is not deprived of heat by the small size paper.
For this reason, if a large-size sheet is fed in a state where the non-sheet-passing area is overheated, high temperature offset or uneven gloss may occur due to toner overmelting. Further, when the overheating further progresses, a PFA (Tetrafluoroethylene-perfluoroalkylvinylether copolymer) tube covering the fixing roller and the pressure roller may be melted and broken.

In order to solve such a problem, for example, in an electromagnetic induction heating type image forming apparatus, a technique for controlling a magnetic flux distribution generated by an exciting coil by rotating a magnetic core that guides a magnetic flux to a heating roller has been proposed. (See Patent Document 1). In this way, by controlling the magnetic flux distribution in accordance with the size of the recording sheet, it is possible to reduce the magnetic flux density in the non-sheet passing area and thereby reduce the amount of heat generation.
JP 2005-309146 A

However, when the speed of the image forming apparatus is further increased, further heating is required to prevent a temperature drop during continuous sheet passing in the sheet passing region. Then, since there is a limit in reducing the magnetic flux density, it is not possible to sufficiently suppress overheating of the non-sheet passing region.
On the other hand, using a toner that melts at a lower temperature, such as a polymerized toner containing a wax component, there is a possibility that a high speed can be realized without increasing the fixing temperature too much, while the melting point temperature is high. Since the toner is harder to solidify than the toner, the recording sheets may stick to each other after being discharged (tacking).

In the prior art, the recording sheet is cooled by driving the fan at the maximum output regardless of the size of the recording sheet. However, considering the recent increase in environmental awareness, it goes without saying that energy saving should be considered when solving the above-mentioned problems.
The present invention has been made in view of the above-described problems, and provides an image forming apparatus that prevents overheating of a non-sheet passing area of a heating roller and tacking after paper discharge while saving energy. For the purpose.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a fixing device that melts toner with a heating rotator and press-fits a recording sheet, a fan, and the recording sheet from the fixing device to the outside of the apparatus. The first air duct that guides the wind of the fan to the conveying path of the fan and the determination of whether the temperature of the non-sheet passing area where the recording sheet on the circumferential surface of the heating rotator does not pass during fixing is higher or lower than a predetermined temperature In the case where the recording sheet width in the direction orthogonal to the means and the recording sheet conveyance direction is smaller than the predetermined width, if the temperature of the non-sheet passing region is lower than the predetermined temperature, the width direction dimension of the blowout port of the first blower pipe The width of the blowout port of the first blower pipe, the power supply control means for reducing the amount of power supplied to the fan, and the temperature of the non-sheet passing area. Is higher than the specified temperature , Characterized in that it comprises a second air duct for guiding capture wind blown from the first blower duct to the non-paper passing area, the.

In this way, when the small-size paper is passed, if the temperature of the non-paper passing area of the heating roller is lower than the predetermined temperature, the blowing width of the first blower pipe is narrowed to reduce the amount of power supplied to the fan. Therefore, tacking can be prevented while saving energy as compared with the conventional technique in which the fan is always driven at the maximum output.
Further, if the temperature of the non-sheet passing area is higher than the predetermined temperature, the fan wind is sent to the non-sheet passing area, so that overheating of the non-sheet passing area can be prevented.

In this case, if the temperature of the non-sheet passing region is higher than a predetermined temperature, the blowing width regulating means may make the width direction dimension of the blowing port larger than the recording sheet width. In this way, it is possible to send wind more effectively to the second blower tube, and thus to the non-sheet passing region.
Further, the image forming apparatus according to the present invention is characterized in that the blow-out width regulating means sets the width direction dimension of the blow-out port to be equal to or larger than the sheet width when the recording sheet width is larger than a predetermined width. In this way, large-size paper can be reliably cooled, so that tacking of large-size paper can be prevented.

In this case, the recording sheet may be passed through the gap between the first blower pipe and the second blower pipe on the recording sheet conveyance path from the fixing device to the outside of the apparatus. Further, if the fixing device includes a ventilation guide that guides the air blown from the second blower pipe to the non-sheet passing area, the non-sheet passing area of the heating roller can be cooled more effectively.
The image forming apparatus according to the present invention is characterized in that when the temperature of the non-sheet passing region is higher than a predetermined temperature, the fixing device reduces the conveyance speed of the recording sheet passing through the fixing device. Even in this case, the non-sheet passing area of the heating roller and the recording sheet can be effectively cooled.

  The image forming apparatus according to the present invention also includes a fixing device that melts toner with a heating rotator and press-bonds the recording sheet to a recording sheet, a fan, and a recording sheet on the circumferential surface of the heating rotator that does not pass during fixing. The determination means for determining whether the temperature of the sheet passing area is higher or lower than the predetermined temperature, and when the recording sheet width in the direction orthogonal to the conveyance direction of the recording sheet is smaller than the predetermined width, the temperature of the non-sheet passing area is Only when the temperature is higher than the predetermined temperature, a blower pipe that guides the wind from the fan to the non-sheet passing region is provided.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a fan unit 100, a temperature sensor 101, a fixing unit 102, a control unit 103, imaging units 110Y to 110K, an exposure unit 111, an intermediate transfer belt 112, and a secondary transfer roller 113. , A cleaner 114, a paper feed cassette 115, a pickup roller 116, a paper discharge roller 118, and a paper discharge tray 119, and toner bottles 120Y to 120K are mounted.

The imaging units 110Y to 110K develop the electrostatic latent image formed by the exposure device 111 to form yellow (Y), magenta (M), cyan (C), and black (K) toner images. Primary transfer is performed on the transfer belt 112. Residual toner on the intermediate transfer belt 112 is removed by a cleaner 114.
The paper feed cassette 115 stores the recording sheet P therein. The recording sheets P are taken out one by one by the pickup roller 116 and sent out to the conveyance path. The secondary transfer roller 113 electrostatically transfers the toner image on the intermediate transfer belt 112 onto the recording sheet.

The fixing device 102 melts the toner and presses the toner onto the recording sheet. Thereafter, the recording sheet is discharged onto a discharge tray 119 by a discharge roller 118.
The control unit 103 monitors the temperature of the non-sheet passing area on the outer periphery of the heating roller of the fixing device 102 with the temperature sensor 101 and supervises the overall operation of the image forming apparatus 1. In addition, the toner bottles 120Y to 120K are detachably mounted, and supply toner of each color to the imaging units 110Y to 110K, respectively.

The fan unit 100 constitutes a cooling system together with a blower pipe to be described later, and blows air to a recording sheet passing through the paper discharge path 117 and a non-sheet passing area on the outer periphery of the heating roller provided in the fixing unit 102 under the control of the control unit 103. And cool them.
Note that the image forming apparatus 1 employs a center sheet passing method in which the recording sheet is transported approximately at the center in the direction orthogonal to the recording sheet transport direction in the recording sheet transport path.

[2] Configuration of Cooling System Next, a cooling system included in the image forming apparatus 1 will be described.
(1) Configuration of Cooling System FIG. 2 is a diagram illustrating a configuration of a cooling system included in the image forming apparatus 1. As shown in FIG. 2, the cooling system 2 includes blast pipes 200 and 210.

The blower tube 200 has a built-in fan unit 100, and blows out the outside air taken in by the fan unit 100 from the blowout port 201.
The blower pipe 210 is disposed such that the intake port 211 faces the blowout port 201 of the blower tube 200. The blower pipe 210 takes in the blown air from the blower tube 200 and heats the fixing unit 102 from the blowout port 213. The air is blown to the non-sheet passing area on the outer periphery of the roller 220.

Further, the air duct 210 is provided with a lid 212, and the lid 212 opens and closes the intake port 211. When the intake port 211 is closed by the lid 212, the air blown from the blower port 201 of the blower pipe 200 passes through the gap between the discharge rollers 118 and moves onto the discharge tray 119.
In addition to the heating roller 220 and the pressure roller 221, the fixing device 102 includes a ventilation guide 222 that guides the air blown from the outlet 213 of the blower pipe 210 to the non-sheet passing region of the heating roller 220.

Further, a paper passing rib 223 is provided on the ventilation guide 222. The recording sheet on which the toner image is fixed by the heating roller 220 and the pressure roller 221 is guided to the paper discharge roller 118 by the paper passing rib 223, the paper passing guide 230, and the blower pipes 200 and 210.
(2) Configuration of the blower tube 200 Next, the configuration of the blower tube 200 will be described.

FIGS. 3A and 3B are diagrams showing the main configuration of the blower pipe 200, wherein FIG. 3A is a plan view seen from the fan unit 100 side, and FIG. 3B is a perspective view.
As shown in FIG. 3, the air duct 200 is configured such that a side wall guide 301 is rotatably supported in a housing 303 by a support shaft 302. The side wall guide 301 is reciprocally rotated as indicated by an arrow to a position 301a indicated by a broken line by a driving mechanism described later.

When the side wall guide is at the position 301, the wind is sent over the entire outlet 201, so that the large size paper can be cooled over the whole. Further, when the side wall guide is at the position 301a, the wind blowing width is narrowed, so that the wind is sent only to the small size paper passing position.
When small size paper is passed, if the side wall guide is placed at the position 301, air is sent to the intake port 211 of the air duct 210 in addition to the entire small size paper. Further, the outlet 201 is covered with a mesh filter, which prevents foreign matter from entering the paper discharge path 117 and the recording sheet from getting into the delivery tube 200.

4A and 4B are diagrams showing a drive mechanism of the side wall guide 301, where FIG. 4A is a plan view seen from the fan unit 100 side, and FIG. 4B is a side view. As shown in FIG. 4, the side wall guide 301 is rotationally driven when the rotational driving force of the motor 404 is transmitted to the support shaft 302 via the pulley 403, the belt 402 and the pulley 401.
FIGS. 5A and 5B are views showing an overview of the blower pipe 200 in use, where FIG. 5A is a plan view seen from the fan unit 100 side, and FIG. 5B is a perspective view. As shown in FIG. 5, the blower pipe 200 is provided with an upper lid 501 in the use state, and sucks outside air only from the upper side of the fan unit 100.

(2) Configuration of the blower tube 210 Next, the configuration of the blower tube 210 will be described.
6A and 6B are diagrams showing the configuration of the air duct 210, wherein FIG. 6A is an external perspective view, and FIG. 6B is a perspective view showing the internal structure with a broken line. As shown in FIG. 6, the air duct 210 includes a housing 602, a back cover 603, and the like, and the housing 602 is formed with an intake port 211. Further, the back cover 603 has a notch and forms a blowout port 213 together with the housing 602.

A lid 212 is held on the housing 602 via a support shaft 601, and is rotated by a drive mechanism (not shown). Further, the housing 602 is provided with partition walls 602 a to 602 d, and guides wind from the intake port 211 to the blowout port 213.
FIGS. 7A and 7B are also diagrams showing the configuration of the blower pipe 210, where FIG. 7A is a top view of the housing 602, and FIG. 7B is a bottom view with the back cover 603 attached. As shown in FIG. 7, the wind taken in at the intake port 211 passes through the space partitioned by the partition walls 602 a to 602 d and blows out from the blowout port 213.

(3) Blowing route during overheating of non-sheet passing area Next, a blowing route through the blow pipes 200 and 210 will be described.
FIG. 8 is a cross-sectional view showing an air blowing path indicated by an arrow when small-size paper is continuously passed and the non-paper passing area of the heating roller 220 is overheated. As shown in FIG. 8, the blower pipe 200 sucks outside air from the upper part of the image forming apparatus 1 by the fan unit 100 and blows air from the blowout port 201.

When the small size paper passes between the outlet 201 and the intake port 211, the wind hits the small size paper and the small size paper is cooled.
Regardless of whether or not the small size paper is passing, the wind from the blowout port 201 blows into the intake port 211 and then blows out from the blowout port 213. The wind blown from the blowout port 213 is guided to the non-sheet passing region of the heating roller 220 by the ventilation guide 222 and the sheet passing rib 223.

In this case, as shown in FIG. 9, when the outside air sucked into the blower pipe 200 by the fan unit 100 is blown out from the blowout port 201, the side wall guide 301 is in an open state. Wind blows over the entire width of the outlet 201 (full width in the direction perpendicular to the recording sheet conveyance direction).
Further, since the lid 212 is opened, the wind blown from the blowout port 201 blows into the intake port 211. The wind blown into the intake port 211 is guided to the outlet port 213 by the partition walls 602a to 602d.

By doing so, even if the non-sheet passing area of the heating roller 220 is overheated by continuously passing small-size paper, overheating can be eliminated by applying wind to the non-sheet passing area. .
(4) Open / Closed State of Sidewall Guide 301 and Lid 212 Next, the open / closed state of the side wall guide 301 and the lid 212 will be described.

(A) When Large Size Paper is Passed FIG. 10 is a diagram illustrating an open / closed state of the side wall guide 301 and the lid 212 when passing large size paper. When passing large size paper, it is necessary to cool the large size paper over its entire width. Further, since the large size paper contacts almost the entire width of the heating roller 220, the non-sheet passing area is small and there is no possibility of overheating.

For this reason, when passing large size paper, as shown in FIG. 10, the side wall guide 301 is opened and air is blown from the entire outlet 201 to cool the large size paper. Further, since it is not necessary to send wind to the heating roller 220 to cool the non-sheet passing area, the lid 212 is closed so that the wind does not blow into the take-in port 211.
(B) When passing small size paper (when not overheating)
FIG. 11 is a diagram illustrating an open / close state of the side wall guide 301 and the lid 212 when the small-size paper is passed and the non-paper passing area of the heating roller 220 is not overheated. In order to cool the small size paper, it is sufficient to send wind only to the range through which the small size paper passes.

  For this reason, as shown in FIG. 11, the side wall guide 301 is closed to limit the blowing width of the wind from the blowing port 201 of the blower pipe 200, and the wind is sent only to the range through which the small size paper passes. When the side wall guide 301 is closed, the amount of air blown by the fan unit 100 can be reduced, so that the output of the fan constituting the fan unit 100 can be reduced and the power consumption can be reduced.

(C) When passing small size paper (overheating)
FIG. 12 is a diagram illustrating an open / closed state of the side wall guide 301 and the lid 212 when a small-size sheet is passed and the non-sheet passing area of the heating roller 220 is overheated. As shown in FIG. 12, when the non-sheet passing region of the heating roller 220 is overheated during the passage of small size paper, the side wall guide 301 is opened so that the wind blows out from the entire outlet 201 of the blower tube 200.

Further, the air duct 210 opens the cover 212 of the intake port 211, takes in the air blown from the air outlet 201 of the air duct 200, and sends it from the air outlet 213 to the non-sheet passing area of the heating roller 220.
As a result, it is possible to cool the small size paper and suppress overheating of the non-sheet passing region of the heating roller 220.

(5) Configuration of Fixing Device 102 Next, the configuration of the fixing device 102 will be described.
FIG. 13 is an external perspective view showing the configuration of the fixing device 102. As shown in FIG. 13, the fixing device 102 stores a heating roller 220 and a pressure roller 221 in a housing 1301.

The housing 1301 includes a ventilation guide 222 and a paper passage rib 223 provided on the ventilation guide 222, and heats the wind from the outlet 213 of the blower pipe 210 by the ventilation guide 222 and the paper passage rib 223. The sheet is sent to the non-sheet passing area of the roller 220.
The sheet passing rib 223 prevents the wind from the outlet 213 from hitting the sheet passing area of the heating roller 220. This prevents a temperature drop in the paper passing area of the heating roller 220, so that the energy efficiency of the fixing device 102 is maintained. The sheet passing rib 223 also serves as a part of the sheet discharge path 117 that guides the recording sheet on which the toner image is fixed to the sheet discharge tray 119.

The wind that hits the non-sheet passing area of the heating roller 220 is exhausted from an exhaust port 1302 provided in the housing 1301.
[3] Operation of Cooling System 2 Next, the operation of the cooling system 2 will be described with particular attention paid to the control flow by the control unit 103.

(1) Configuration of Control Unit 103 Prior to describing the flow of control by the control unit 103, the configuration of the control unit 103 will be described first.
FIG. 14 is a diagram illustrating a main configuration of the control unit 103. As shown in FIG. 14, the control unit 103 includes a central processing unit (CPU) 1401, a read only memory (ROM) 1402, a random access memory (RAM) 1403, and an input / output interface (input / output interface) 1404 as internal buses. 1405 is connected.

  The input / output interface 1404 is connected to the fan unit 100, the temperature sensor 101, the paper feed cassette 115, the imaging units 110 </ b> Y to 110 </ b> K, the side wall guide 301, and the lid 212 of the intake port 211 of the blower pipe 210. Information such as the temperature of the paper region is acquired, and control output for opening and closing the side wall guide 301 and the lid 212 is performed.

(2) Control Flow by Control Unit 103 Next, a control flow by the control unit 103 will be described.
FIG. 15 is a flowchart showing a flow of control of the cooling unit 2 by the control unit 103. As shown in FIG. 15, when the control unit 103 first receives an image forming job from the user (S1501: YES), the control unit 103 refers to the content of the received image forming job.

  As a result, when an image is formed using small size paper (S1502: YES), a small size paper image forming process is executed (S1503). When image formation is not performed using small-size paper (S1502: NO), large-size paper image formation processing is executed (S1504). After completion of the image forming process, the process again proceeds to step S1501 to wait for the next image forming job.

Note that the image forming apparatus 1 conveys the recording sheet at the same speed and timing regardless of the temperature of the non-sheet passing area of the heating roller 220.
(3) Large-size paper image forming process Next, the large-size paper image forming process (S1504) will be described.
FIG. 16 is a flowchart showing the large-size paper image forming process. As shown in FIG. 16, in the large-size paper image forming process, the control unit 103 first opens the side wall guide 301 (S1601), and blows the entire large-size paper passing through the paper discharge path 117. be able to.

Further, the lid 212 of the intake port 211 of the blower tube 210 is closed (S1602), so that the wind does not hit the heating roller 220. Then, the output of the fan unit 100 is maximized and a sufficient air volume is supplied to the entire outlet 201 of the blower pipe 200 (S1603). After executing the image formation (S1604), the control unit 103 returns to the upper routine.
(4) Small Size Paper Image Forming Process Next, the small size paper image forming process (S1503) will be described.

FIG. 17 is a flowchart showing a small-size paper image forming process. As shown in FIG. 17, in the small-size paper image forming process, the control unit 103 first closes the side wall guide 301 (S1701), and the range in which the wind blows out from the outlet 201 of the blower tube 200 is reduced to the small-size paper. Narrow it together.
Further, the lid 212 of the intake port 211 of the blower pipe 210 is closed (S1702) so that the wind does not hit the heating roller 220. Further, the output of the fan unit 100 is halved at the maximum (S1703), and image formation is started (S1704). Even when the output of the fan unit 100 is halved at the maximum, since the side wall guide 301 is closed, a sufficient air volume can be sent to the entire small size paper.

  Thereafter, if the image formation is not completed (S1705: NO), the temperature sensor 101 measures the temperature t of the non-sheet passing area of the heating roller 220 (S1706). If the temperature t obtained by the measurement is higher than the predetermined temperature T (S1707: YES), the side wall guide 301 is opened (S1708), the lid 212 is opened (S1709), and the output of the fan unit 100 is maximized (S1710). .

In this way, when the non-sheet passing area of the heating roller 220 becomes hot to some extent, the air is sent and cooled, so that overheating of the non-sheet passing area can be prevented.
If the measured temperature t is lower than the predetermined temperature T (S1707: NO), the side wall guide 301 is closed (S1711), the lid 212 is closed (S1712), and the output of the fan unit 100 is halved at the maximum (S1713). ). In this way, the power consumption of the fan unit can be reduced while properly cooling the small size paper.

[4] Modifications As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) Although not particularly mentioned in the above embodiment, the small-size paper is, for example, the maximum width of a recording sheet that can be conveyed by the image forming apparatus 1 (hereinafter, “maximum sheet width that can be conveyed”). The recording sheet width is about two-thirds or less of the above, and a larger size paper than the small size paper may be used.

Further, the size of the fan unit 100 is, for example, about one third of the maximum sheet width that can be conveyed, and the fan unit 100 may be arranged approximately at the center of the recording sheet conveying position in the direction orthogonal to the recording sheet conveying direction. In this way, the wind can be sent almost uniformly over the entire width of the recording sheet.
In addition, it is desirable that the size of the outlet 201 of the blower tube 200 in the direction orthogonal to the recording sheet conveyance direction is substantially the same as the maximum sheet width that can be conveyed. Further, the size of the blow-out port 201 in the recording sheet conveyance direction may be approximately one-fourth that of the fan unit 100.

Further, the width of the intake port 211 and the blowout port 213 of the blower tube 210 in the direction orthogonal to the recording sheet conveyance direction may be, for example, approximately one sixth of the maximum sheet width that can be conveyed. The interval between the partition walls 602a and 602b and the interval between the partition walls 602c and 602d may be, for example, approximately one sixth of the maximum sheet width that can be conveyed.
Further, the intake port 211 and the blowout port 213 of the blower tube 210 have substantially the same width in the recording sheet conveyance direction. The lid 212 is sized so as to completely close the intake port 211.

(2) Although the case where the recording sheet is conveyed at the same speed regardless of the temperature of the non-sheet passing region of the heating roller 220 has been described in the above embodiment, it goes without saying that the present invention is not limited to this. Instead, it may be as follows.
That is, when the temperature of the non-sheet passing region of the heating roller 220 exceeds a predetermined temperature, the recording sheet conveyance speed may be decreased. In particular, if the conveyance speed when passing through the fixing device 102 is reduced, the temperature drop in the paper passing area of the heating roller 220 can be suppressed, and therefore it is not necessary to overheat the heating roller 220 excessively. Therefore, the temperature rise in the non-sheet passing area of the heating roller 220 can be suppressed.

(3) In the above embodiment, the case where the lid 212 is provided in the intake port 211 of the blower pipe 210 has been described. However, it goes without saying that the present invention is not limited to this, and the following may be used instead. good.
That is, the same effect can be obtained by providing a lid at the outlet 213 without providing the lid 212 at the intake port 211.

Further, a sliding lid may be provided at the outlet 213. If a slide type lid is provided, the blowout width of the wind can be changed more finely according to the width of the recording sheet, so that only the necessary area of the heating roller 220 is cooled and the temperature of other areas is lowered. Can be prevented.
(4) In the above-described embodiment, the case where the toner on the recording sheet is melted and pressure-bonded using the heating roller has been described, but it is needless to say that the present invention is not limited to this. The same effect can be obtained even if the present invention is applied to a belt-fixing type image forming apparatus for melting and pressure bonding. That is, the effect of the present invention can be obtained as long as the image forming apparatus melts and presses the toner using a heating rotator, whether it is a heating roller or a heating belt.

(5) Although not particularly mentioned in the above embodiment, it is needless to say that the arrangement of the heating roller and the pressure roller is not limited to that shown in FIG. Even if they are replaced, the effect of the present invention is the same.
(6) In the above embodiment, the case where the outlet 201 of the blower pipe 200 is covered with the mesh filter has been described. Needless to say, the present invention is not limited to this, and the outlet 201 is provided with a mesh filter. Even if it is not, the effect of the present invention can be obtained.

  The image forming apparatus according to the present invention is useful as a technique for eliminating partial overheating of the fixing unit while saving energy.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of a cooling system provided in an image forming apparatus 1. FIG. It is a figure which shows the main structures of the ventilation pipe | tube 200, Comprising: (a) is the top view seen from the fan unit 100 side, (b) is a perspective view. It is a figure which shows the drive mechanism of the side wall guide 301, Comprising: (a) is the top view seen from the fan unit 100 side, (b) is a side view. It is a figure which shows the external appearance of the ventilation pipe | tube 200 in use condition, Comprising: (a) is the top view seen from the fan unit 100 side, (b) is a perspective view. It is a figure which shows the structure of the ventilation pipe | tube 210, Comprising: (a) is an external appearance perspective view, (b) is the perspective view which showed the internal structure with the broken line. It is a figure which shows the structure of the ventilation pipe | tube 210, Comprising: (a) is a top view of the housing | casing 602, (b) is a bottom view in the state which attached the back cover 603. FIG. FIG. 5 is a cross-sectional view showing an air blowing path indicated by an arrow when a small size paper is continuously passed and a non-sheet passing region of the heating roller 220 is overheated. FIG. 5 is an exploded perspective view showing an air blowing path indicated by an arrow when a small size paper is continuously passed and a non-sheet passing region of the heating roller 220 is overheated. It is a figure which shows the open / closed state of the side wall guide 301 and the lid | cover 212 at the time of passing large sized paper. FIG. 10 is a diagram illustrating an open / closed state of the side wall guide 301 and the lid 212 when a small-size sheet is passed and the non-sheet passing area of the heating roller 220 is not overheated. FIG. 6 is a diagram illustrating an open / closed state of a side wall guide 301 and a lid 212 when a small-size sheet is passed and a non-sheet passing area of a heating roller 220 is overheated. 2 is an external perspective view showing a configuration of a fixing device 102. FIG. 3 is a diagram illustrating a main configuration of a control unit 103. FIG. 4 is a flowchart showing a flow of control of the cooling unit 2 by the control unit 103. It is a flowchart which shows a large sized paper image formation process. It is a flowchart which shows a small size paper image formation process.

Explanation of symbols

1 ……………… Image forming apparatus 100 ……………… Fan unit 101 ……………… Temperature sensor 102 ……………… Fixer 103 ……………… Control unit 117… ……………… Discharge path 200, 210 …… Blower pipe 201, 213 …… Blowout port 211 ……………… Take-in port 212 ……………… Cover 220 ……………… Heating roller 222… …………… Ventilation guide 223 ……………… Paper passing ribs 301, 301a… Sidewall guide

Claims (7)

A fixing device that melts the toner with a heating rotator and press-bonds it to the recording sheet;
With fans,
A first air duct that guides the wind of the fan to the conveyance path from the fixing device to the outside of the apparatus,
Determining means for determining whether the temperature of the non-sheet passing region where the recording sheet on the circumferential surface of the heating rotator does not pass at the time of fixing is higher or lower than a predetermined temperature;
When the recording sheet width in the direction orthogonal to the recording sheet conveyance direction is smaller than the predetermined width,
If the temperature of the non-sheet passing area is lower than the predetermined temperature, the blow width regulating means for narrowing the width direction dimension of the blow outlet of the first blower pipe to the recording sheet width;
In addition to narrowing the widthwise dimension of the outlet of the first air duct, the power supply control means for reducing the power supply to the fan;
An image forming apparatus comprising: a second air duct that takes in the air blown from the first air duct and guides it to the non-paper area only when the temperature of the non-paper area is higher than a predetermined temperature. 2. The image forming apparatus according to claim 1, wherein when the temperature of the non-sheet-passing area is higher than a predetermined temperature, the blowing width regulating unit makes the width direction dimension of the blowing port larger than the recording sheet width. . 2. The image forming apparatus according to claim 1, wherein when the recording sheet width is larger than a predetermined width, the blow-out width regulating unit sets a width direction dimension of the blow-out port to be equal to or greater than the sheet width. 2. The image forming apparatus according to claim 1, wherein the recording sheet is passed through a gap between the first blower pipe and the second blower pipe on the recording sheet conveyance path from the fixing device to the outside of the apparatus. The image forming apparatus according to claim 1, wherein the fixing device includes a ventilation guide that guides the air blown from the second air blowing pipe to a non-sheet passing region. The image forming apparatus according to claim 1, wherein the fixing device reduces a conveyance speed of the recording sheet passing through the fixing device when the temperature of the non-sheet passing region is higher than a predetermined temperature. A fixing device that melts the toner with a heating rotator and press-bonds it to the recording sheet;
With fans,
Determining means for determining whether the temperature of the non-sheet passing region where the recording sheet on the circumferential surface of the heating rotator does not pass at the time of fixing is higher or lower than a predetermined temperature;
When the recording sheet width in the direction orthogonal to the recording sheet conveyance direction is smaller than the predetermined width,
An image forming apparatus comprising: a blower pipe that guides wind from the fan to the non-sheet passing area only when the temperature of the non-sheet passing area is higher than a predetermined temperature.

Images