JP2000267495A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely and easily prevent the occurrence of the local temperature elevation of a rotating body for heat fixing which occurs in the difference in the size of recording materials of a fixing device of an image forming device without the induction of unnecessary temperature elevation. SOLUTION: A heat absorbing device 4, which is disposed with an air suction duct 5 for sucking the gas including the heat released from the surface of a rotating body 21 for heat fixing of the fixing device near this rotating body 21 of the heat fixing device and discharges the gas sucked by this air suction duct 5 to the outside of the image forming device, is included in the fixing device. Particularly when a device of a divided suction type is used as the air suction duct, the selection of the air suction regions of such air suction ducts, the regulation of an air suction rate, etc., are properly executed in accordance with the width size information of the recording material P and the surface temperature information of the rotating body 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a multifunction machine, etc., and more particularly, to a method for thermally fixing an unfixed toner image carried on a recording material. The present invention relates to an image forming apparatus provided with a fixing device having a heat fixing rotary member.

[0002]

2. Description of the Related Art In an image forming apparatus provided with a fixing device of this type, various sizes of recording materials such as recording paper are selected and used, and the conveying direction thereof is either vertical feeding or horizontal feeding. Is selected and used, the width of the recording material in the conveying direction when the image is actually conveyed in the apparatus during image formation is also different. A pass area where the recording material comes into contact with and passes through the rotator and a non-pass area where the recording material does not pass are generated, and the surface temperature of the rotator portion in the non-pass area is higher than the pass area.

[0003] For example, such a phenomenon occurs when the maximum usable recording paper size in the image forming apparatus is the A3 size (vertical feed), and the recording paper of a size smaller than that size (A4 size vertical feed, B5 size). This occurs remarkably when a large number of plates (for example, vertical feed or horizontal feed) are continuously used and passed through the fixing device. This is because the area through which the recording paper P passes
The heat of the heat fixing rotary body is absorbed and absorbed by the paper or toner during the heat fixing, whereas the non-passage area is generated because such consumption is not performed. Then, the heat-fixing rotator, which is the non-passage area, is at a considerably high temperature.

Therefore, conventionally, in order to eliminate the occurrence of a local temperature rise of the heat fixing rotary member due to the difference in the width size during the conveyance of the recording material, for example, the surface of a heating roll in a fixing device is removed. A device has been proposed in which the temperature is detected by a plurality of temperature sensors, and cooling air is blown by a cooling fan to a location where the temperature is high to control the temperature of the roll (JP-A-9-274408).

[0005]

However, in such a device that blows cooling air, the blown cooling air is heated by the heat of the heating rolls, and becomes hot air to fill the fixing device. Leaks into the main body of the image forming apparatus and becomes full. As a result, the temperature of the inside of the fixing apparatus and the inside of the image forming apparatus rises due to the heat generated by the hot air, and the components and the inside of the image forming apparatus near the fixing apparatus increase. The other components themselves are exposed to high heat and rise in temperature, which adversely affects the reliability of the components.

Accordingly, it is an object of the present invention to prevent the occurrence of a local temperature rise of a heat-fixing rotating body due to a difference in the size of a recording material without the possibility of inducing an unnecessary temperature rise. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an image having a fixing device having a heat fixing rotating member for heat fixing an unfixed toner image carried on a recording material. In the forming apparatus, an intake duct for sucking a gas containing heat released from the surface of the rotating body is disposed near the rotating body for thermal fixing in the fixing device, and the gas sucked by the intake duct is formed in the image forming apparatus. An image forming apparatus including a heat absorbing device that exhausts air out of the image forming apparatus.

Here, the intake duct in the heat absorbing device is
If it is possible to surely suck in the fixing device the gas (hot air) containing heat released from the surface of the part where the temperature of the heat-fixing rotating body such as a heating roll and a heating belt rises locally, Although there is no particular limitation on the structure and installation state, from the viewpoint of more reliably preventing a local temperature rise in the rotating body, it is preferable that the rotating body for heat fixing (for example, recording) It is preferable that the intake duct be of a divided intake type that can be individually suctioned for each divided area (to correspond to the size of the material). In this case, the hot air from the locally heated portion of the heat fixing rotating body can be concentrated and accurately sucked by the divided ducts arranged corresponding to the portion. Becomes

In the above-mentioned image forming apparatus, a size recognizing means for recognizing a width size of the recording material when the recording material is conveyed is provided. It is preferable to provide a control device that adjusts the intake air amount, selects an intake region of the intake duct of the divided intake type, or performs both adjustment of the intake amount and selection of the intake region.

As the size recognizing means, a means dedicated to detecting and recognizing the size of the recording material conveyed to the fixing device at the time of fixing may be provided, but usually, a central control unit provided on the main body side of the image forming apparatus is used. A means for obtaining the size information grasped by the department is provided. If the control device is not a split-suction type intake duct, the control unit changes the rotation speed of the intake fan connected to the intake duct and the cross-sectional area of the flow path of the intake duct according to the size information of the recording material. It is configured so that the intake volume of the duct can be adjusted.

Further, in the above-mentioned image forming apparatus, a temperature measuring means for measuring the surface temperature of the heat fixing rotary member is provided in place of the size recognizing means, and the heat absorbing device is provided with:
Adjusting the intake air amount of the heat absorbing device according to the temperature information measured by the temperature measuring means, or selecting the intake region of the intake duct of the divided intake type, or adjusting both the intake air amount and selecting the intake region A control device for performing the control may be provided.

A temperature sensor or the like is used as the temperature measuring means. Further, only one temperature measuring means may be provided so as to be able to measure the surface temperature of a portion where a local temperature rise of the heat fixing rotating body can occur, but the temperature measuring means may be provided in the direction of the rotating shaft of the rotating body. It is preferable that a plurality be provided along. In this case, the actual state of the actual surface temperature of the heat fixing rotary member can be accurately measured and grasped, and the intake air cooling by the accurate heat absorbing device according to the measured information can be realized.

In the case of an image forming apparatus in which control is performed by a control device using the above-described divided intake type intake duct, if the intake region can be arbitrarily selected and individual intake can be performed, the duct or the duct can be used. Although there is no particular limitation on the structure, configuration, and the like of the control device, preferably, the divided intake type intake duct has a structure having an intake port and an intake path for each intake area, and opens and closes the plurality of intake paths. The controller is connected to one intake fan via a suction path switching mechanism for switching, and the control device operates at least one of the suction path switching mechanism and the intake fan (such as a suction path switching state and a rotation state of the intake fan). ) Is controlled to perform at least one of adjustment of the intake air amount or selection of the intake region.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a schematic diagram showing one embodiment of an image forming apparatus to which the present invention is applied. This image forming apparatus is basically provided inside the main body 10 of the apparatus.
An image forming system unit 1 having a configuration in which a toner image is formed by a known electrophotographic process, and the toner image is transferred directly or via an intermediate transfer body to a recording sheet P as a recording material; Roll-nip type fixing device 2 for introducing recording paper P carrying unfixed toner image T transferred in step 2 and fixing the unfixed toner image T
And a plurality of paper feed trays 3 in which recording papers P (P _{1 to} P ₃ ) of various sizes are individually stored. In FIG. 1, reference numeral 11 denotes a paper transport belt that transports the recording paper P from the image forming system unit 1 to the fixing device 2, reference numeral 12 denotes a discharge roll pair that discharges the fixed recording paper P outside the apparatus main body, , Chain line indicates recording paper P
1 shows a transfer route of the first embodiment.

The fixing device 2 includes a rotating heating roll 21 serving as a heat fixing rotating body and a pressing roll 22 rotating by being pressed against the heating roll 21 in a main body (frame or heat insulating cover) 20 of the fixing device 2. And are arranged. As for the heating roll 21, a heating source 23 is provided inside the roll.
And the surface of the roll is heated to a predetermined fixing temperature. Further, the pressing roll 22 may be configured as a heating and pressing roll provided with a heating function by providing a heating source inside the roll as necessary. The fixing device 2 is configured such that the nip portion between the heating roll 21 and the pressure roll 22 is
The recording paper P carrying the unfixed toner image T is fed in from the paper introduction port 20a side, and the recording paper P after fixing after passing through the nip portion from the paper discharge port 20b side of the apparatus body 20. It is being discharged.

As the recording paper P _{1 to} P ₃ of each size stored in the paper feed tray 3, those having a required size according to the image forming conditions are selected. Are fed from the corresponding paper feed tray 3 to the image forming system unit 1 one by one by a paper feeding mechanism (not shown). In this image forming apparatus, as shown in FIG. 1B, all the recording papers P are commonly conveyed while being brought to the same one end side (the front side F of the apparatus main body 10) in the conveying direction. The paper is conveyed by a registration method.

This image forming apparatus is provided with a heat absorbing device 4 as shown in FIGS.

That is, the heat-absorbing device 4 in this embodiment is a split-intake-type intake duct 5 that is disposed inside the upper body 20 of the fixing device 2 so that the intake side is provided inside.
The operation state of the suction fan 6 to which the exhaust side of the suction duct 5 is connected, the suction path switching mechanism 7 for switching each suction path of the suction duct 5, and the suction path switching mechanism 7 (and / or the suction fan 6). And a control device 8 for controlling. In addition, in the schematic perspective view of FIG.
For convenience (to make it easy to understand the structure of each part, etc.), the outlines of parts that are not originally represented by solid lines are specially illustrated in the drawing method of the intake fan and the like (in other schematic perspective views) Is the same).

First, the intake duct 5 is disposed inside the upper main body 20 of the fixing device 2 with a width extending over the entire area of the heating roll 21 in the axial direction, and the intake duct 50 is provided with an intake port 52. A hollow structure having an exhaust side 51 disposed inside the main body 10 of the image forming apparatus so as to connect the intake side 50 and the intake fan 6. The first suction passage 54 and the second suction passage 55 are formed by dividing an inner space of the exhaust side portion 51 into two by a partition plate 53. In the intake duct 5, the partition plate 53 connects the intake port 52 to a first intake port 52 a connected to the first suction path 54 and a second intake port 52 b connected to the second suction path 55. Has been divided. A filter or the like (not shown) is provided inside the suction passage of the intake duct 5 or behind the intake fan 6 as necessary.

Here, as shown in FIG. 4, the position of the partition plate 53 which divides the intake port 52 into two parts is, for example, as shown in FIG. When classified into two groups, a size group (for example, A3 size paper vertical feed) and a "small size group (for example, A4 size paper vertical feed, B5 size paper vertical or horizontal feed)", the surface of the heating roll 21 has "Small size group" recording paper P
(Small) paper passing area 21a that contacts and passes at the time of fixing;
Since the non-sheet passing area 21b through which the recording sheet P (small) does not pass at all occurs, the position is set to a position that matches the boundary line L between the sheet passing area 21a and the non-sheet passing area 21b. As a result, the suction area by the first suction port 52a becomes the paper passing area 21 and the suction area by the second suction port 52b becomes the non-paper passing area 21b.

The suction path switching mechanism 7 is an opening / closing mechanism which is arranged to be swingable about a support shaft 71 at a position within the exhaust side 51 of the intake duct 5 and on the front side of the intake fan 6. It comprises a gate plate 70 and a gate opening / closing device 72 made of a solenoid or the like that swings the opening / closing gate plate 70 to open and close. Further, the suction path switching mechanism 7 uses an opening / closing gate plate 70 by the gate opening / closing device 72.
A gate fully open position: G in which the first suction path 54 and the second suction path 55 are simultaneously opened to communicate with the intake fan 6
1 and a gate half-open position G2 in which the first suction path 54 is closed and only the second suction path 55 is opened.

As shown in FIG. 2, the control device 8 comprises a control circuit board in which, for example, a microcomputer which operates according to a preset control program is incorporated. Each operation of the suction path switching mechanism 7 (gate opening / closing device) is controlled. In this embodiment, the control circuit board is connected to, for example, a central control unit on the side of the image forming apparatus, and receives size information (data signal S) of the recording paper P to be used at the time of image formation. A size recognizing unit 80 for recognizing the width size of the recording paper P at the time of conveyance is provided, and controls the gate opening / closing device 72 of the suction path switching mechanism 7 based on information on the width size from the size recognizing unit 80. The open / close gate 70 is moved to the fully open position G1 or the half open position G2.
(See FIG. 5). And
The control device 8 is set to operate the heat absorbing device 4 during image formation (including continuous ones) and when the heating roll 21 of the fixing device 2 is at or above a predetermined fixing temperature. .

Next, the operation of the image forming apparatus equipped with such a heat absorbing device 4 will be described with reference to FIGS.

First, recording sheets P1 to P3 of a predetermined size
Is started, the recording paper P of the corresponding size is supplied from the paper feed tray 3 to the image forming system 1, and the toner image T formed by the image forming system 1 is transferred. The heating roll 21 which is fed to the fixing device 2 through the paper transport belt 11 and heated to the fixing temperature by the recording paper P carrying the unfixed toner image T
Then, the unfixed toner image T is thermally fixed by passing through the nip portion of the pressure roll 22. After the fixing, the recording paper P is discharged out of the apparatus main body 10 by the discharge roll pair 12. Basic image formation is performed in this manner. However, when continuous image formation is performed,
The sequence of operations is repeated.

When the image formation is performed, the control device 8 of the heat absorbing device 4 stores the size information S of the recording paper P used for image formation from the image forming apparatus main body 10 as shown in FIG. Based on the size, the size recognition unit 80 recognizes the width size of the recording paper P when the recording paper P is conveyed (Step 10: S10). Thereafter, it is determined whether the width size is the “small size group” described above (Step S10). S11).

At this time, in the case of the "large size group" instead of the "small size group", the open / close gate plate 70 of the suction path switching mechanism 7 is moved to the fully open position G1 by a control command from the control device 8. Then, the gate opening / closing device 72 operates (S12). As a result, both the first suction path 54 and the second suction path 55 are opened as shown in FIG.
5, suction is performed from both the first intake port 52a and the second intake port 52b. Therefore, in this case, the gas containing heat released from the heating roll 21 (thick arrow indicated by a dotted line in FIG. 5) is supplied to the first intake port 52a and the second intake port 52a.
b, and is guided to the intake fan 6 side through the respective suction passages 54 and 55 and finally exhausted to the outside of the apparatus main body 10.

That is, in this case, the gas containing heat released from the surface of the heating roll 21 which is entirely in the paper passing area is sucked by the heat absorbing device 8, and as a result, the surface of the heating roll 21 Is uniformly intake-cooled throughout.

On the other hand, if it is determined in step S11 that the group is the "small size group", the gate opening / closing device 72 operates so that the opening / closing gate plate 70 in the suction path switching mechanism 7 is located at the fully open position G2. (S13). As a result, as shown in FIG. 5B, the first suction path 54 is closed and only the second suction path 55 is opened.
And the suction force by the
Suction is performed only from the second intake port 52b. Therefore,
In this case, the gas containing heat mainly discharged from the non-sheet passing area 21b (FIG. 4) generated on the surface of the heating roll 21 when the recording sheet P (small) of the "small size group" passes passes through the second sheet. The rear device body 1 is concentratedly sucked only from the second suction port 52b and guided to the suction fan 6 through the second suction path 55.
Exhausted outside 0.

That is, in this case, the "small size group"
Roll P 2 (Small) passes through the heating roll 2
1, a non-sheet-passing area 21b tends to heat up due to the occurrence of a sheet-passing area 21a and a non-sheet-passing area 21b, but a second air inlet provided corresponding to the non-sheet-passing area 21b. Is switched to operate only the second suction path 55 connected to the heat absorbing device 8.
As a result, the surface of the heating roll 21 serving as the non-sheet passing area 21b is appropriately and efficiently suction-cooled. For this reason, a local temperature rise in the non-sheet passing area 21b of the heating roll 21 is reliably prevented. Further, since cooling is performed by taking in air and exhausting the air to the outside of the apparatus, hot air heated when the heating roll is cooled in the fixing device and the image forming apparatus does not stay inside as in the related art.

[Second Embodiment] FIG. 7 is a schematic diagram of a main part showing another embodiment of an image forming apparatus to which the present invention is applied.
In the image forming apparatus according to this embodiment, a temperature sensor 9 for measuring the surface temperature of the heating roll 21 is applied instead of the size recognizing means (recognizing unit 80), and a part of the heat absorbing device 4 is changed accordingly. Other than that, the configuration is the same as that of the image forming apparatus according to the first embodiment.

That is, in this embodiment, the two temperature sensors 9a and 9b for individually measuring the surface temperatures of the paper passing area 21a and the non-paper passing area 21b of the heating roll 21 are provided in the respective areas 21a, 21a. The temperature sensors 9a and 9b measure the surface temperatures T ₁ and T ₂ of the regions 21a and 21b, respectively, and send the results to the control device 8 to obtain the temperature information ( The temperature difference: whether T ₂ −T ₁ exceeds the threshold value) controls the gate opening / closing device 72 of the suction path switching mechanism 7 to move the opening / closing gate 70 to any of the fully open position G1 or the half open position G2. To select the intake area of the intake duct 5.

The image forming apparatus having such a heat absorbing device 4 operates as follows. First, when the image forming operation is started, as shown in FIG.
The surface temperatures T ₁ and T ₂ of the paper passing area 21a and the non-paper passing area 21b of the heating roll 21 are measured by the control (Step 20: S20), and based on the measurement results, the controller 8 based on the measurement results. Surface temperature T ₁ and non-sheet passing area 21
The temperature difference between b and the surface temperature T ₂ is a preset threshold value: Tx
Then, it is determined whether or not it has become larger (S21). This determination is

At this time, if the temperature difference is less than the threshold value, it is considered that the non-sheet passing area 21b is not particularly heated up compared to the sheet passing area 21a, and the suction path switching mechanism 7
The gate opening / closing device 72 is operated so that the opening / closing gate plate 70 is located at the fully open position G1 (S22). Thus, as in the first embodiment, suction is performed from both the first suction port 52a and the second suction port 52b, and gas containing heat released from the heating roll 21 is supplied to both the suction ports 52a. , 52b and exhausted out of the apparatus body 10 (see FIG. 5a).

On the other hand, if the temperature difference is equal to or greater than the threshold value, it is considered that the non-sheet passing area 21b is locally heated up as compared with the sheet passing area 21a, and the opening / closing gate in the suction path switching mechanism 7 is opened. The gate opening / closing device 72 operates so that the plate 70 is located at the fully open position G2 (S
23). Thus, as in the case of Embodiment 1, only the second suction path 55 is opened, suction is performed only from the second suction port 52b, and heat mainly discharged from the non-sheet passing area 21b is included. The gas is concentrated and sucked only from the second intake port 52b and is exhausted out of the apparatus main body 10.

Therefore, also in this embodiment, since the surface of the heating roll 21 serving as the non-sheet passing area 21b is accurately and efficiently suction-cooled, the fixing of the "small size group" of the recording paper P is continued. Even when the heating is performed, the local temperature rise of the non-sheet passing area 21b of the heating roll 21 is reliably prevented. In addition, since the heat absorbing device 4 is selectively operated in accordance with the actual surface temperature state of the heating roll 21, it is possible to prevent a local temperature rise of the heating roll 21 that is more accurate and more realistic.

[Other Embodiments] In both Embodiments 1 and 2, the control device 8 of the heat absorbing device 4 controls the open / close state of the open / close gate plate 70 of the suction path switching mechanism 6 to control the intake duct 5 However, the controller 8 controls only the rotation state of the intake fan 6 to adjust the intake amount of the intake duct 5 or to open or close the intake duct. Gate plate 70
May be configured to control and control both the open / closed state and the rotation state of the intake fan 6. In this case, the control of the rotation state of the intake fan 6 is performed, for example, as shown in parentheses in FIG. 6 and FIG. If P is a small size group, it may be set to operate so as to be "high-speed rotation". Also in this case, it is possible to prevent a local temperature rise in the non-sheet passing area 21b of the heating roll 21. The control device 8
May be incorporated in the central control unit of the image forming apparatus main body 10.

Further, in the first and second embodiments, the case where a divided intake type in which the intake passage and the intake port are divided into two is used as the intake duct 5 is exemplified. However, for example, as illustrated in FIG. An intake duct 5 that only partially opens and closes as necessary may be used. That is, the opening / closing slide plate 7 capable of opening and closing a portion corresponding to the above-described paper passing area 21a of the heating roll 21 among the one intake port 52 extending over the entire area in the rotation axis direction of the heating roll 21.
5 is provided, and the opening / closing slide plate 75 is used in Embodiment 1,
2, the width size information of the recording paper P and the heating roll 21
Is configured to be slid in the front-rear direction by a slide drive device 76 such as a solenoid based on the surface temperature information of the solenoid. Thereby, when the recording paper of the small size group is used, or when the temperature of the non-sheet passing area 21b becomes higher than the sheet passing area 21a by a predetermined temperature difference or more, the opening / closing slide plate 75 closes the intake port 52. By making a part closed and opening only the portion of the suction port 52 corresponding to the non-sheet passing area 21b, it is possible to perform intensive suction, and a local portion of the non-sheet passing area 21b of the heating roll 21 is provided. It is possible to reliably prevent a temperature rise.

Further, as the intake duct 5, a single intake duct having only an intake port opposed to only the non-sheet passing area 21b of the heating roll 21 is used, and the intake fan 6 according to the width size information and the surface temperature information. May be turned on / off to cool the non-sheet passing area 21b. When the split intake type intake duct 5 is used, each intake path 5 is replaced with the intake path switching mechanism 7.
A dedicated intake fan is provided for each of the intake fans 4 and 55, and the respective intake fans are appropriately combined in accordance with width size information and surface temperature information to perform ON / OFF operations, thereby selecting an intake area. You may do so.

[0040]

As described above, according to the image forming apparatus of the present invention, since the intake air is cooled by the heat absorbing device, there is a possibility that an unnecessary temperature rise due to the generation of hot air as in the prior art may be induced. In addition, it is possible to reliably and simply prevent a local temperature rise of the heat fixing rotating body due to a difference in the width size of the recording material.

[Brief description of the drawings]

FIGS. 1A and 1B show the entire image forming apparatus according to a first embodiment, wherein FIG. 1A is a schematic front view thereof, and FIG.

FIG. 2 is a schematic perspective view showing a heat absorbing device according to the first embodiment.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is an explanatory diagram showing a paper passing area and a non-paper passing area of a heating roll.

5A and 5B are diagrams illustrating an operation state of the heat absorbing device, in which FIG. 5A is an explanatory diagram in the case of performing intake from both intake ports, and FIG. 5B is an explanatory diagram in the case of performing intake from one of the intake ports. .

FIG. 6 is a flowchart showing an example of the operation of the heat absorbing device.

FIG. 7 is a schematic perspective view showing a heat absorbing device in the image forming apparatus according to the second embodiment.

FIG. 8 is a flowchart showing another example of the operation of the heat absorbing device.

FIG. 9 is a schematic perspective view showing another configuration example of the heat absorbing device.

[Explanation of symbols]

2: fixing device, 4: heat absorbing device, 5: intake duct, 6: intake fan, 7: intake path switching mechanism, 8: control device, 9 ...
Temperature sensor (temperature measuring means), 21: heating roll (rotating body for heat fixing), 52: intake port, 54, 55: intake path, 8
0: size recognition unit, T: unfixed toner image, P: recording paper (recording material).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA12 DA32 DC10 EA12 ED25 EF09 JB14 JB15 JB24 JB28 JC08 ZA07 2H033 AA03 AA23 BA29 CA07 CA17 CA26 5H323 AA36 CA08 CB25 CB33 CB43 DA04 DB11 DB17 EE10 FF01 MM02

Claims (5)

[Claims] 1. An image forming apparatus comprising: a fixing device having a heat fixing rotary member for thermally fixing an unfixed toner image carried on a recording material; An image, comprising: a suction duct for sucking gas containing heat released from the surface of the rotating body; and a heat absorbing device for exhausting the gas sucked by the suction duct out of the image forming apparatus. Forming equipment. 2. The image according to claim 1, wherein the intake duct of the heat absorbing device is a divided intake type intake duct that can individually suck in each area divided in the rotation axis direction of the heat fixing rotating body. Forming equipment. 3. A size recognizing means for recognizing a width size of the recording material when the recording material is conveyed is provided, and the heat absorbing device adjusts an intake air amount of the heat absorbing device according to the size information recognized by the size recognizing device. 3. The image forming apparatus according to claim 1, further comprising a control device for selecting an intake region of the divided intake duct or adjusting both the intake amount and the intake region. And a temperature measuring means for measuring a surface temperature of the heat fixing rotating body, and the heat absorbing device adjusts an intake air amount of the heat absorbing device according to temperature information measured by the temperature measuring device. 3. The image forming apparatus according to claim 1, further comprising a control device for selecting an intake region of the divided intake duct or adjusting both the intake amount and the intake region. 5. An intake duct of a divided intake type having a structure having an intake port and an intake path for each intake area, and one intake fan via an intake path switching mechanism for opening and closing the plurality of intake paths. The control device is configured to control at least one operation state of the suction path switching mechanism or the intake fan to perform at least one of adjustment of an intake amount or selection of an intake region. The image forming apparatus according to claim 4.