JP5585384B2 - Fixing device, image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device including a peeling unit that peels a sheet from a heating unit such as a fixing belt, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Image forming apparatuses such as electrophotographic copying machines, printers, facsimiles, and multi-functional machines having these functions include a fixing device that fixes a toner image transferred to a recording medium.

  In such a fixing device, a nip portion formed by a heating portion such as a fixing roller and a fixing belt heated to a predetermined temperature by a heating source and a pressure portion disposed opposite to the heating portion. A sheet or the like, which is a recording medium carrying a toner image, is sandwiched, pressed and heated, and the toner (image) carried on the sheet is melted, fixed to the sheet, and fixed.

  Conventionally, heat generating members such as halogen lamps and heaters have been used as heating sources for heating and heating the heating unit, but in response to demands for speeding up and power saving of image forming apparatuses such as copying machines, A technique for raising the temperature of the heating part by electromagnetic induction has been proposed.

  For example, an alternating magnetic flux is applied to a heat roller made of a hollow cylindrical magnetic metal member such as iron, cobalt, nickel, or an alloy thereof to generate an eddy current by electromagnetic induction, and the heat roller is heated and heated by the eddy current. A fixing device that raises the temperature of a fixing belt stretched around a heat generating roller has been proposed (see Patent Document 1).

  Also, a fixing device has been proposed in which an alternating magnetic flux is applied to the fixing belt that presses the paper to generate an eddy current due to electromagnetic induction in the fixing belt, and the fixing belt itself generates heat and rises in temperature due to the generated eddy current (patent) Reference 2).

  The fixing device that raises the temperature of the fixing belt by electromagnetic induction is higher in efficiency than a method of heating and raising the temperature of the fixing roller and the fixing belt using a conventional halogen lamp or the like, with less power, The fixing belt can be quickly heated up to a predetermined fixing temperature.

  By the way, in the fixing method in which the paper is pressurized and heated, the toner (image) carried on the paper is pressed against and heated by a heating part such as a fixing belt, so that the molten toner adheres to the heating part and the nip part is removed. The paper after passing does not separate from the heating unit.

  As a countermeasure, for example, a surface of the heating unit that comes into contact with the paper is coated with, for example, a fluorine resin to impart releasability. However, even when a heating part having such a releasability is used, the melted toner is soft and highly viscous, so that it easily adheres to the surface of the heating part, and the paper after passing through the nip part becomes the heating part. May adhere and wrap around. In view of this, it has been proposed to provide a peeling claw on the downstream side of the nip portion in the paper conveyance direction, and to peel the paper discharged from the nip portion from the heating portion with the peeling claw to prevent wrapping (see Patent Document 3). .

  However, in the fixing device provided with such a peeling claw, the peeling claw may damage the surface of the heating unit, which affects the life of the heating unit. Further, when the thickness of the toner (image) carried on the paper is relatively thin and the viscosity thereof is high, the toner can be peeled off without any problem. However, like an image on which a large amount of toner is mounted, a full color image, When the thickness of the toner (image) is relatively thick, the toner (image) immediately after passing through the nip portion may be damaged by the peeling claw, resulting in an image defect. In particular, when fixing a color image, it is necessary to sufficiently develop the toner, so the toner must be heated and melted sufficiently, and the toner just after passing through the nip has a low viscosity, so more and more images It becomes easy to produce a defect.

  A technique has been proposed in which air is blown between a sheet and a heating unit without using a peeling claw to separate the sheet from the heating unit (see Patent Document 4).

  Such a system in which air is blown between the paper and the heating unit and the paper is peeled off from the heating unit (hereinafter also referred to as an air peeling method) damages the heating unit such as the image, the paper, and the fixing roller. Even if the paper is difficult to peel, stable peeling can be performed.

  In such an air separation method, the air blown between the paper and the heating unit may hit the heating unit, and the temperature of the surface of the heating unit heated to a predetermined temperature may be lowered. A decrease in the temperature of the heating part causes a fixing failure. Therefore, Patent Document 4 proposes a technique for increasing the temperature of air to be blown by providing a heating mechanism for heating the air to be blown. As a result, a decrease in the temperature of the surface of the heating portion is prevented, and the occurrence of poor fixing is prevented.

JP-A-2005-77607 JP-A-2005-77609 JP 59-188681 A JP 2005-157179 A

  The technique of the air separation method proposed in Patent Document 4 prevents a decrease in the temperature of the surface of the heating unit and prevents the occurrence of fixing failure, but has a dedicated heating mechanism for heating the air to be blown. Necessary and complicated structure.

  It is an object of the present invention to provide a fixing device having a simple structure that does not require a dedicated air heating means for heating air for an air peeling system.

  The above problem is solved by the following means.

1. A fixing device for fixing a toner image on a recording medium,
An electromagnetic induction coil, a heating source having an electromagnetic induction heating part that is heated by magnetic flux generated by the electromagnetic induction coil, a heating part that is heated by the heating source, and a heating part that is in contact with the heating part to form a nip part A fixing unit having a pressure unit;
A blowing unit having a blowing duct for blowing air to the recording medium discharged from the nip portion, and a connecting duct for connecting the blowing duct and the fixing unit in communication with each other;
A blower that blows air inside the fixing unit to the blowing duct via the connection duct;
Equipped with a,
The air blowing unit sucks air from the outside of the fixing unit to the inside thereof, and blows air sucked into the fixing unit to the connection duct,
The electromagnetic induction coil is disposed in a path through which air sucked into the fixing unit by the blower is blown to the connection duct;
A fixing device characterized by the above.

2 . 2. The fixing device according to claim 1 , further comprising an intake portion that takes air into the inside of the blowing unit from the outside.

3 . 3. The fixing device according to 2 , wherein the intake portion includes an opening / closing door that opens and closes a part of the spray unit.

4 . An image forming apparatus having a fixing device for fixing a toner image on a recording medium,
The fixing device includes an electromagnetic induction coil, a heating source having an electromagnetic induction heating unit that generates heat by a magnetic flux generated by the electromagnetic induction coil , a heating unit heated by the heating source, and a nip by contacting the heating unit. A fixing unit having a pressurizing part forming a part, a blowing duct for blowing air to the recording medium discharged from the nip part, and a connection duct for connecting the blowing duct and the fixing unit in communication with each other And a blowing unit that blows the air inside the fixing unit to the blowing duct through the connection duct ,
The air blowing unit sucks air from the outside of the fixing unit to the inside thereof, and blows air sucked into the fixing unit to the connection duct,
The electromagnetic induction coil is disposed in a path through which air sucked into the fixing unit by the blower is blown to the connection duct;
An image forming apparatus.
5. An image forming apparatus having a fixing device for fixing a toner image on a recording medium,
The fixing device includes a fixing unit having a heating source, a heating unit heated by the heating source, and a pressure unit that forms a nip portion in contact with the heating unit, and a recording medium discharged from the nip unit. A blowing unit that blows air against the blowing unit, and a blowing unit having a connection duct that connects the blowing duct and the fixing unit in communication with each other;
An intake for taking air into the interior of the spraying unit from the outside;
A control unit for controlling the amount of air taken in from the intake unit;
A detection unit that detects the temperature of air downstream of the intake unit with respect to the flow direction of the air flowing through the inside of the blowing unit;
The control unit performs control to increase the air amount when the temperature detected by the detection unit is higher than a target temperature, and to reduce the air amount when the temperature is lower than the target temperature;
An image forming apparatus.

6 . 6. The image forming apparatus according to 5 above, further comprising a blower that blows air inside the fixing unit to the blowing duct through the connection duct.

7 . 7. The image forming apparatus according to 6 , wherein the heating source includes an electromagnetic induction coil and an electromagnetic induction heating unit that generates heat by a magnetic flux generated by the electromagnetic induction coil.

8 . The air blowing unit sucks air from the outside of the fixing unit to the inside thereof, and blows air sucked into the fixing unit to the connection duct,
The electromagnetic induction coil is disposed in a path through which air sucked into the fixing unit by the blower is blown to the connection duct;
8. The image forming apparatus as described in 7 above.

9 . An intake for taking air into the interior of the spraying unit from the outside;
A control unit for controlling the amount of air taken in from the intake unit;
A detection unit that detects the temperature of air downstream of the intake unit with respect to the flow direction of the air flowing through the inside of the blowing unit;
The control unit performs control to increase the air amount when the temperature detected by the detection unit is higher than a target temperature, and to reduce the air amount when the temperature is lower than the target temperature,
5. The image forming apparatus as described in 4 above.

10 . The intake part has an open / close door that opens and closes a part of the spray unit;
The controller increases the air volume by opening the door when the temperature detected by the detector is higher than the target temperature, and closes the door when the temperature is lower than the target temperature. Reducing the amount of air,
10. The image forming apparatus as described in any one of 5 to 9 above.

  According to the present invention, it is possible to provide a fixing device having a simple structure that does not require a dedicated air heating means for heating air for the air peeling method.

1 is a diagram illustrating an image forming apparatus A equipped with a fixing device 30 according to the present invention. 1 is a diagram illustrating a fixing device 30 as an example of an embodiment of the present invention. FIG. 6 is a diagram for explaining the operation of the intake section 35 and the air flow accompanying the operation of the intake section 35. 3 is a block diagram of a control system that controls the operation of the image forming apparatus A. FIG. 6 is a diagram illustrating an example of a basic screen displayed on an operation display unit 80. FIG. It is a figure which shows the screen of the paper setting column A1 displayed when the A01 button in a basic screen is touched. It is a figure which shows the paper setting column A2 when the A12 button in the paper setting column A1 is touched. It is a flowchart explaining the operation | movement which controls the temperature of airflow A1. It is a figure explaining an example of the fixing device which heats up a fixing belt with a halogen lamp.

  Embodiments of the present invention will be described below. In addition, the description of this column does not limit the technical scope and terms used in the claims.

  FIG. 1 is a diagram illustrating an image forming apparatus A equipped with a fixing device 30 according to the present invention.

  The image forming apparatus A is called a tandem color image forming apparatus, and performs color image formation by four sets of image forming units.

  The document placed on the document table is scanned and exposed by the optical system of the document image scanning exposure device of the image reading device SC, read into the line image sensor, and the photoelectrically converted image information signal is sent to the image processing unit ( (Not shown), after analog processing, A / D conversion, shading correction, image compression processing, and the like, it is input to the optical writing unit of the image forming unit.

  The four image forming units include an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and an image forming unit that forms a cyan (C) image. 10C is an image forming unit 10K that forms a black (K) color image, and is denoted by symbols Y, M, C, and K representing colors formed after the common symbol 10, respectively.

  The image forming unit 10Y includes a photosensitive drum 1Y that is an image carrier, and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y arranged around the photosensitive drum 1Y.

  Similarly, the image forming unit 10M includes a charging unit 2M, an optical writing unit 3M, a developing device 4M, and a drum cleaner 5M that are disposed around a photosensitive drum 1M that is an image carrier. The charging unit 2C, the optical writing unit 3C, the developing device 4C, and the drum cleaner 5C arranged around the photosensitive drum 1C that is the carrier, and the image forming unit 10K is the periphery of the photosensitive drum 1K that is the image carrier. And a charging unit 2K, an optical writing unit 3K, a developing device 4K, and a drum cleaner 5K.

  Photosensitive drums 1Y, 1M, 1C, and 1K in the image forming units 10Y, 10M, 10C, and 10K, charging units 2Y, 2M, 2C, and 2K, optical writing units 3Y, 3M, 3C, and 3K, a developing device 4Y, 4M, 4C, and 4K and drum cleaners 5Y, 5M, 5C, and 5K have the same content. In the following description, symbols Y, M, C, and K are not used unless particularly distinguished.

  The image forming unit 10 writes an image information signal on the photosensitive drum 1 in the optical writing unit 3, and forms a latent image based on the image information signal on the photosensitive drum 1. Then, the latent image is developed by attaching toner to the latent image by the developing device 4, and a toner image which is a visible image is formed on the photosensitive drum 1.

  In each of the image forming units 10Y, 10M, 10C, and 10K, the photosensitive drums 1Y, 1M, 1C, and 1K are respectively yellow (Y), magenta (M), cyan (C), and black (K). Images are formed.

  The intermediate transfer belt 6 is wound around a plurality of rollers and supported so as to be able to run.

  The images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the traveling intermediate transfer belt 6 by the primary transfer units 7Y, 7M, 7C, and 7K to be Y (yellow) and M (magenta). ), C (cyan), and K (black) color layers are superimposed.

  The paper transport unit 20 transports the paper S that is a recording medium. The paper S is stored in the paper feed trays 291, 292, 293, fed by the first paper feed unit 21, passed through the registration roller 22, and conveyed to the secondary transfer unit 7 A, and the intermediate transfer belt on the paper S. 6 color image is transferred. The sheet S on which the color image has been transferred is fixed with the toner image on the sheet S by applying heat and pressure in the fixing device 30, and is discharged to the outside through the fixing conveyance roller 23 and the discharge roller 25. .

  Further, the image forming apparatus A includes a paper reversing unit 24, and the fixed paper is guided from the fixing conveyance roller 23 to the paper reversing unit 24 so as to be reversed and discharged, or image formation is performed on both sides of the paper. Is possible.

  The size and number of sheets S can be set when performing image formation from the operation display unit 80 installed at the upper part of the main body of the image forming apparatus A.

  In the description of the image forming apparatus A, the color image formation has been described. However, the present invention includes a case of forming a monochrome image.

  A condition (job condition) for image formation can be input from the operation display unit 80 installed on the upper part of the main body of the image forming apparatus A. The job conditions input from the operation display unit 80 include the selection result of the size and basis weight of the paper S.

  The image forming apparatus A has a control unit 90. The control unit 90 controls the operation of each mechanism unit of the image forming apparatus A by executing a program stored based on the job condition input from the operation display unit 80, and the image based on the input job condition. Perform formation. The control unit 90 also functions as a control unit that controls the operation of the fixing device 30, specifically, the amount of air taken in from the intake unit 35 in the fixing device 30 described later.

  The operation display unit 80 has a touch panel type LCD screen, and the type of paper stored in the paper feed trays 291, 292, and 293 in FIG. 1, for example, the thickness of the paper can be set via the screen. it can. The setting of the sheet thickness performed via the operation display unit 80 will be described later.

  FIG. 2 is a diagram illustrating a fixing device 30 as an example of the embodiment of the present invention.

  The fixing device 30 includes a fixing unit 31 and a spraying unit 32. The fixing unit 31 includes a heat generating roller 311, a fixing roller 312 arranged so that the axis of the heat generating roller 311 is parallel to the heat generating roller 311, and a heat generating roller 311, inside a fixing housing 31 H including an upper fixing housing 31 H 1 and a lower fixing housing 31 H 2. It has an endless fixing belt 315 that is stretched around the fixing roller 312 and a pressure roller 313 that presses the fixing belt 315 that is stretched around the fixing roller 312. Then, the fixing belt 315 is driven in the direction indicated by the arrow b by rotating the fixing roller 312 in the direction indicated by r2 by a fixing roller driving motor (not shown). The fixing belt 315 is circulated and driven between the heated heat roller 311 and the fixing roller 312, and rotates the heat roller 311 in the r1 direction and rotates the pressure roller 313 in the r3 direction in the drawing.

  The heat roller 311 is made of a hollow cylindrical magnetic metal member such as iron, cobalt, nickel, or an alloy thereof. It is preferable to adopt a structure with a low heat capacity and a fast temperature rise.

  The fixing roller 312 is configured by covering a metal core such as stainless steel with a heat-resistant silicone rubber in a solid or foamed form. The pressure roller 313 is configured by providing a heat-resistant and highly toner-releasing elastic member on the surface of a metal core such as stainless steel.

  The fixing roller 312 and the pressure roller 313 are in pressure contact with each other via the fixing belt 315, and a nip portion N for sandwiching the sheet S and heating and pressurizing the sheet S at a portion where the fixing belt 315 and the pressure roller 313 are in contact with each other. It is formed.

  The tension roller 314 presses the fixing belt 315 stretched between the heat generating roller 311 and the fixing roller 312 from the side surface of the drawing by the urging force of the tension roller spring 314S. The tension roller 314 presses the fixing belt 315 to generate a constant tension on the fixing belt 315, and acts to ensure that the circulation drive between the heat generating roller 311 and the fixing roller 312 of the fixing belt 315 is performed.

  A magnetic flux generator 318 is disposed above the heat roller 311 so as to face the heat roller 311.

  The magnetic flux generation unit 318 includes an electromagnetic induction coil 318L which is a magnetic flux generation means, a coil guide plate 318G, and an electromagnetic induction coil core 318C made of a ferromagnetic material such as ferrite disposed outside the electromagnetic induction coil 318L. Composed.

  The electromagnetic induction coil 318L winds a single wire (a litz wire bundled with thin wires) along the axial direction of the heat roller 311 and the wound portion faces the outer peripheral surface of the heat roller 311 so as to be a semi-cylinder. The coil guide plate 318G having a shape is configured to follow.

  The electromagnetic induction coil 318L is connected to a drive power supply (not shown) that supplies an alternating current whose polarity changes at a high frequency. When the alternating current is supplied from the drive power supply, the magnetic induction coil 318L has a magnetic pole at a portion facing the heating roller 311. Forms an alternating magnetic flux that alternately switches in both directions.

  The heat generating roller 311 that generates heat by generating an overcurrent by the alternating magnetic flux is formed using a metal having magnetism such as nickel or an alloy thereof as a base material.

  The alternating magnetic flux formed by the electromagnetic induction coil 318L generates an eddy current in the heat generating roller 311 facing the electromagnetic induction coil 318L. The heat generating roller 311 generates heat due to Joule heat generated by the generated eddy current and the electric resistance of the base material, and the temperature rises.

  The fixing belt 315 circulated between the heat generating roller 311 and the fixing roller 312 in the direction indicated by the arrow B melts the toner carried on the paper S and adheres to the paper S in the process of contacting the heat generating roller 311. The temperature is raised to a temperature at which

  By the rotation driving of the fixing roller 312 in the r2 direction, the fixing belt 315 is driven to circulate in the direction of arrow b in FIG. 2, and the heat generating roller 311 also rotates in the clockwise direction of r31. Further, the pressure roller 313 also rotates in the r3 direction.

  By supplying a high-frequency alternating current to the electromagnetic induction coil 318L, an alternating magnetic flux is formed at a portion where the electromagnetic induction coil 318L and the heat generating roller 311 face each other. This alternating magnetic flux generates an eddy current in the heat generating roller 311.

  The heat generating roller 311 generates heat due to Joule heat generated by the eddy current and the electric resistance of the heat generating roller 311, and the temperature of the fixing belt 315 that is passed over and contacted with the heat generating roller 311 is increased to a temperature at which the toner can be melted. To do. The heat generating roller 311 that functions as the electromagnetic induction heating unit that generates heat by the magnetic induction coil 318L and the magnetic flux generated by the electromagnetic induction coil 318L functions as a heating source that heats the fixing belt 315 that is a heating unit.

  The fixing belt 315 is an endless belt having a composite layer structure in which, for example, a polyimide resin is used as a base material and the surface thereof is covered with a release layer made of an elastic member such as silicon rubber or fluorine rubber. The fixing belt 315 is heated by receiving heat conduction from the heat generating roller 311 at a contact portion with the heat generating roller 311 where the temperature is increased due to an overcurrent generated by the magnetic flux generator 318. As the fixing belt 315, any belt can be used as long as it has good thermal conductivity and hardly undergoes deformation such as bending. For example, those having heat resistance such as fluorine resin such as PFA, polyamide resin, PEEK resin, PES resin, and PPS resin can be used.

  The fixing belt 315 that has been heated is circulated and driven, and the toner that has been conveyed from the secondary transfer portion 7A at the nip portion N where the fixing belt 315 and the pressure roller 313 across the fixing roller 312 face each other. While sandwiching the sheet S to which the image has been transferred, the toner carried on the sheet S is melted by pressurization and heating, and is fixed to the sheet S, that is, the toner image is fixed to the sheet S. As described above, the pressure roller 313 functions as a pressure unit that forms the nip portion N in contact with the fixing belt 315 that functions as a heating unit.

  In the figure, reference numeral 31F denotes a blowing fan. The blowing fan 31F takes outside air around the fixing device 30 into the upper fixing housing 31H1 through the first housing opening 31H1h1 disposed in the upper fixing housing 31H1, and blows it to the magnetic flux generation unit 318.

  In the electromagnetic induction coil 318L that generates the alternating magnetic flux, the temperature of the electromagnetic induction coil 318L and its surroundings increases due to Joule heat generated by energizing the electromagnetic induction coil 318L itself and heat radiation from the heating roller or the fixing belt. . The rise in temperature of the electromagnetic induction coil 318L causes an increase in the electrical resistance of the electromagnetic induction coil 318L, which may increase the required power and may impair the insulation properties of the electromagnetic induction coil 318L and its surroundings. Since heat is removed from the magnetic flux generation unit 318 including the electromagnetic induction coil 318L by the air blown by the blowing fan 31F, the temperature of the magnetic flux generation unit 318 is suppressed to an appropriate range, and the occurrence of such a problem is prevented.

  The air that has been deprived of heat from the electromagnetic induction coil 318L and raised in temperature is sent to the blowing unit 32 through the housing second opening 31H1h2 disposed in the upper fixing housing 31H1 by the action of a blower fan 33F described later.

  The spray unit 32 includes a spray duct 33 and a connection duct 34. The connection duct 34 is a housing having a connection first opening 34h1 and a connection second opening 34h2 at both ends. The connection first opening 34h1 is connected to the upper fixing housing 31H1 so as to face the housing second opening 31H1h2 disposed in the upper fixing housing 31H1, and the connection second opening 34h2 indicated by a chain line in the figure is connected to a blowing duct described later. It is connected to the blowing duct housing 33H so as to face the duct third opening 33Hh3 arranged in the housing 33H. The connection second opening 34h2 and the duct third opening 33Hh3 are configured to have the same dimensions and the same shape.

  By arranging the connection first opening 34h1 to face the housing second opening 31H1h2 and the connection second opening 34h2 to face the duct third opening 33Hh3, the fixing unit 31 and the blowing duct 32 communicate with each other, that is, fixing. The air flow between the unit 31 and the blowing duct 32 is enabled and connected.

  The blowing duct 33 includes a blowing duct housing 33H, a blower fan 33F, a temperature sensor 33T, and an intake portion 35.

  The blowing duct housing 33H is a housing having a duct first opening 33Hh1, a duct second opening 33Hh2, and a duct third opening 33Hh3. Air can freely flow through the duct first opening 33Hh1, the duct second opening 33Hh2, and the duct third opening 33Hh3. The blowing duct housing 33H is arranged such that the duct first opening 33Hh1 is positioned in the vicinity of the downstream side of the nip portion N in the sheet conveyance direction, and the duct second opening 33Hh2 is opened on the left side surface of the image forming apparatus A. A duct third opening 33Hh3 indicated by a chain line in the drawing is connected to a connection duct 34 described later. The intake 35 is disposed between the duct second opening 33Hh2 and the duct third opening 33Hh3 in the blowing duct housing 33H.

  The blower fan 33F functions as a blower that blows the air inside the fixing unit 31 to the blowing duct 33 via the connection duct 34, and the air in the blowing duct housing 33H is the first opening 33Hh1. Blow out from. The arrow A1 shown in the figure represents the air flow blown out from the first opening 33Hh1.

  The air flow A1 blown from the duct first opening 33Hh1 is blown onto the paper S sent out from the nip portion N, whereby the paper S on which the toner image has been fixed is peeled off from the fixing belt 315, and the paper S adheres to the fixing belt 315. And wrapping is prevented.

  The temperature sensor 33T functioning as a detection unit is arranged on the downstream side of the intake unit 35 with respect to the flow direction of the air flowing inside the blowing unit, and detects the temperature of the air downstream of the intake unit 35.

  The intake portion 35 includes an opening / closing door 351, a partition wall 352, an urging spring 353, a connection plate 355, and a solenoid 35S. The partition wall 352 is provided with a partition opening 352 h that penetrates the front and back surfaces.

  One end of the opening / closing door 351 is hinged to the partition wall 352 so as to be rotatable. The biasing spring 353 is a tension spring having one end fixed to the open / close door 351 and the other end fixed to the duct housing 33H, and biases the open / close door 351 to rotate in the direction of the partition 352. One end of the opening / closing door 351 is hinged to the partition wall 352 and is urged by the urging spring 353. The opening / closing door 351 is in contact with the partition wall 352, and the partition opening 352h disposed in the partition wall 352 is closed by the opening / closing door 351. In the state where the partition opening 352h is closed by the opening / closing door 351, the air on the front and back of the partition 352 is not circulated through the partition opening 352h.

  The solenoid 35S is a type of solenoid in which the movable iron core 35SP is drawn into the main body when energized, and is fixed to the blowing duct housing 33H. One end of the connecting plate 355 is fixed to the movable iron core 35SP of the solenoid 35S and the other end is fixed to the open / close door 351 so as to be freely rotatable. When the solenoid 35S is energized, the solenoid 35S rotates in a direction to separate the opening / closing door 351 from the partition wall 352 against the urging force of the urging spring 353. When the opening / closing door 351 is separated from the partition wall 352, the partition opening 352h is opened, and the air on the front and back of the partition wall 352 can be circulated through the partition opening 352h. Energization / non-energization of the solenoid 35 </ b> S is performed under the control of the control unit 90.

  FIG. 3 is a diagram for explaining the operation of the intake portion 35 and the air flow associated with the operation of the intake portion 35. FIG. 3A is a diagram showing a state where the solenoid 35S of the intake portion 35 is not energized. In a state where the solenoid 35S is not energized, the opening / closing door 351 contacts the partition wall 352 by the biasing force of the biasing spring 353, and the partition opening 352h disposed in the partition wall 352 is blocked by the opening / closing door 351. In a state where the partition opening 352h is closed by the opening / closing door 351, the air on the front and back of the partition 352 is not circulated through the partition opening 352h.

  In the drawing, A3 indicates the flow of air blown to the connection duct 34 (air flow). The air flow A3 flows along the magnetic flux generator 318 in the process of being blown to the connection duct 34, takes heat from the magnetic flux generator 318 including the electromagnetic induction coil 318L, and cools the magnetic flux generator 318. Therefore, the airflow A3 blown to the connection duct 34 is heated by the heat taken from the magnetic flux generator 318.

  The heated air sent into the connection duct 34 is sent into the blowing duct 33, and is converted into the air flow A2 by the blower fan 33F, and further the air flow A1 blown out from the duct first opening 33Hh1 is sent out from the nip portion N. S is sprayed. By blowing the airflow A1 onto the paper S, the paper S on which the toner image has been fixed is prevented from adhering to and wrapped around the fixing belt 315 and is peeled off from the fixing belt 315. In this manner, blowing air between the sheet S and the fixing belt 315 to separate the sheet S from the fixing belt 315 does not require a member that contacts the fixing belt 315 or the sheet S. The toner image immediately after passing through the nip portion N is not damaged, and image defects are not caused.

  Further, since the air flow A1 blown out from the duct first opening 33Hh1 is heated by the heat taken from the magnetic flux generation unit 318, the surface of the fixing belt 315 (heated) by the blowing of the air flow A1 is increased. The decrease in temperature can be suppressed and the occurrence of fixing failure can be prevented. Furthermore, energy consumed for raising the temperature of the fixing belt 315 whose temperature has been lowered to a temperature at which fixing can be performed can be saved. Further, since the air flow A1 cools the magnetic flux generation unit 318 and uses air heated by the heat taken from the magnetic flux generation unit 318, a dedicated heating source for raising the air flow A1 is not required. The configuration of the fixing device can be simplified.

  The air flow A1 blown from the duct first opening 33Hh1 is also blown to the fixed paper discharged from the nip portion N together with the fixing belt 315 on the downstream side of the nip portion N in the paper conveyance direction.

  As described above, the temperature of the air flow A1 is preferably higher so as not to lower the temperature of the fixing belt 315.

  By the way, it is known that curling (curling of paper) occurs when the fixed paper is rapidly cooled. Therefore, from the viewpoint of curling prevention, it is preferable that the temperature of the air flow blown to the fixed paper is high. The inventor pays attention to this point, and the degree of curling that occurs depends on the thickness of the paper (paper thickness), the degree of curling that occurs with thin paper is remarkable, and the degree of curling that is thicker is more noticeable with thinner paper. It was found by experiments that there was no. Thus, as one of the reasons that the curl depends on the paper thickness, the shrinkage of the surface of the paper to be cooled and the paper strain are considered.

  On the other hand, an air flow having a temperature higher than a predetermined temperature causes the toner fixed on the paper S discharged from the nip portion N to be softened. If the paper S holding the softened toner passes through the fixing conveyance roller 23 and the paper discharge roller 25, the toner may be roughened and cause image defects. Therefore, from the viewpoint of preventing image defects due to toner softening, it is preferable that the temperature of the air flow blown to the fixed paper is not too high.

  In view of the above, the inventor has found that it is preferable to change the temperature of the air flow blown to the fixed paper according to the paper thickness in consideration of the curling prevention and the image defect.

  When a large amount of image formation and fixing is performed, the continuous operation time of the magnetic flux generation unit 318 becomes longer, and thus the temperature rise of the magnetic flux generation unit 318 increases. Therefore, the temperature of the air flow A3 that takes heat from the magnetic flux generation unit 318 and is blown to the connection duct 34 is increased, and the temperature of the air flow A1 that is blown out from the duct first opening 33Hh1 is also increased.

  The image forming apparatus A equipped with the above-described fixing device 30 controls the temperature of the air flow A1 within a preset range to prevent occurrence of fixing failure and paper curl due to a decrease in the temperature of the fixing belt 315. It prevents the occurrence of image defects caused by blowing an air stream at a temperature that is too high.

  As described above, the fixing device 30 introduces the air heated by the heat taken from the magnetic flux generator 318 to the blowing duct 33 and blows it out from the duct first opening 33Hh1 as the air flow A1. When the temperature of the air in the blowing duct 33 exceeds a predetermined value, the image forming apparatus A takes in the air outside the fixing device into the blowing duct 33 through the intake portion 35 and mixes the taken-in air to generate the air flow A1. Control the temperature to a preset range.

  FIG. 3B is a diagram showing a state where the solenoid 35S is energized. When the solenoid 35S is energized, the solenoid 35S rotates in a direction to separate the opening / closing door 351 from the partition wall 352 against the biasing force of the biasing spring 353. When the opening / closing door 351 is separated from the partition wall 352, the partition opening 352h is opened, and the air on the front and back of the partition wall 352 can be circulated through the partition opening 352h, that is, fixed to the blowing duct 33 through the intake portion 35. It is possible to take in air outside the device 30.

  The blower fan 33F forms an air flow A2 toward the first opening 33Hh1 by the air in the blowing duct 33, but opens to the left side surface of the image forming apparatus A when the partition opening 352h of the intake portion 35 is opened. Air is blown into the duct 33 from outside through the duct second opening 33Hh2 and the intake portion 35. The arrow A4 represents the flow of air taken in via the intake 35 (air flow A4).

  The air (air flow A4) taken in via the intake portion 35 is mixed with the air (air flow A3) sent via the connection duct 34 by the action of the blower fan 33F, and goes to the duct first opening 33Hh1. Air flow A2 is obtained. At this time, the temperature of the air flow A2 is lower than the temperature of the heated air (air flow A3) sent through the connection duct 34.

  When the temperature of the air flow A2 exceeds a preset temperature, the image forming apparatus A operates the open / close door 351 of the intake portion 35 to take in external air into the duct 33 through the partition wall opening 352h. The outside air taken into the blowing duct 33 is mixed with the air (air flow A3) sent through the connection duct 34, and the temperature of the air flow A2 is controlled to a preset range.

  Specifically, the control unit 90 controls the energization / non-energization of the solenoid 35S based on the detection result of the temperature sensor 33T that detects the temperature of the air flow A2, thereby controlling the amount of air taken in from the intake unit 35. In addition, the temperature of the fixing belt 315 is not lowered by the air flow A1 blown from the first opening 33Hh, and the occurrence of image defects due to softening of the toner fixed on the paper S is prevented. Furthermore, by changing the temperature at which the solenoid 35S is energized and de-energized according to the thickness of the paper (paper thickness), the air flow A1 is increased to a temperature range that is preferable for curling prevention when the paper is thin. In the case of paper, the temperature is controlled within a preferable temperature range for image quality. When it is not necessary to control the temperature of the air flow A1 due to the characteristics of the paper and toner, the intake portion 35 is not provided and the duct second opening 33Hh2 is closed, so that external air is taken into the blowing duct 33. There may be no configuration.

  The image forming apparatus A performs image formation based on job information input via the operation display unit 80. The job information input via the operation display unit 80 includes information on the size and thickness of the paper that is the recording medium.

  FIG. 4 is a block diagram of a control system that controls the operation of the image forming apparatus A. In the drawing, the periphery of the portion necessary for the operation of the embodiment of the present invention is mainly described, and other well-known portions of the image forming apparatus are omitted.

  The control unit 90 is a computer system having a CPU 91, a ROM 92, and a RAM 93. The control unit 90 controls the operations of the image reading device SC, the image forming units 10Y, 10M, 10C, and 10K, the paper transport unit 20, the fixing device 30, and the operation display unit 80 of the image forming apparatus A. It functions as a control unit that controls the amount of air taken in from the intake unit 35.

  The CPU 91 controls the operation of each unit of the image forming apparatus A based on the job conditions input via the operation display unit 80 by executing a program stored in the ROM 92, and forms an image on the sheet S1.

  The ROM 92 stores a program and constant data for operating the image forming apparatus A based on job conditions input via the operation display unit 80. In the present embodiment, two constants t1 and t2 for controlling the temperature of the air flow A1 in the fixing device 30 are stored.

  Here, t1 is the upper limit value of the air temperature in the blowing duct 33 that makes the air flow A1 a temperature that does not cause curling of the thin paper and does not soften the toner fixed on the paper. is there. Further, t2 is an upper limit value of the air temperature in the blowing duct 33 that brings the temperature of the toner fixed on the paper without softening without curling the thick paper. The thick paper is not curled as compared with the thin paper even when the low-temperature air flow A1 is blown, so t2 is lower than t1, that is, the toner fixed on the paper. The temperature is set at a low risk of softening. The two constants t1 and t2 are numerical values determined in advance through an experiment based on the configuration of the image forming apparatus A and the characteristics of the paper and toner used.

  The ROM 92 stores screen information to be displayed on the operation display unit 80. The screen displayed on the operation display unit 80 will be described later.

  The RAM 93 can store and read a plurality of information, and stores data generated or acquired when the CPU 91 executes control of the image forming apparatus A. The data stored in the RAM 93 includes job condition information including paper thickness information input via the operation display unit 80, and temperature information t of the air flow A2 detected by the temperature sensor 33T.

  Reference numeral 99 denotes a bus. Each part of the image forming apparatus A is connected to the bus 99 together with the control unit 90 to enable mutual information exchange.

  The control unit 90 controls the operation of each device and mechanism unit connected to the bus 99 based on the job information input from the operation display unit 80, and applies the job to the sheet selected based on the job information. Image formation is performed based on the information.

  Further, the temperature of the air flow A1 is controlled within a preset range according to the paper thickness of the paper to prevent the occurrence of fixing failure and curling of the paper due to a decrease in the temperature of the fixing belt 315. Prevents image defects caused by spraying.

  FIG. 5 is a diagram illustrating an example of a basic screen displayed on the operation display unit 80.

  A paper setting field A0 is displayed on the basic screen, and an A01 button, an A02 button, and an A03 button are displayed in the paper setting field A0. The A01 button displays the type information of the paper classified by the size of the paper stored in the paper feed tray 291 and the thickness of the paper. Similarly, the A02 button displays information on the size and type of paper stored in the paper feed tray 292, and the A03 button displays information on the size and type of paper stored in the paper feed tray 293. In the example shown in the figure, the paper feed tray 1 contains paper that is classified as A4 size plain paper, the paper feed tray 2 contains paper that is classified as A3 size plain paper, and the paper feed tray 3 contains paper. It is displayed that a sheet classified as an A4 size letter is stored. The classification of plain paper or thick letters depends on the thickness (basis weight) of the stored paper, which will be described in detail later.

  When the user touches the A01, A02, and A03 buttons displayed on the basic screen, the size and thickness of the paper stored in the paper feed trays 291, 292, and 293 can be set.

FIG. 6 is a diagram showing a screen of the paper setting field A1 displayed when the A01 button on the basic screen is touched. The A11 button, A12 button, and A1Y button are displayed in the paper setting field A1, and the size (A4) of the paper stored in the paper feed tray 291 is displayed in the display field A111 next to the A11 button. In the display column A121, a basis weight range, which is a scale representing the thickness of the paper stored in the paper feed tray 291, 64 to 99 g / m ² is displayed.

  In FIG. 6, when the basis weight of the paper stored in the paper feed tray 291 is not within the range displayed in the display field A121, the value can be changed by touching the A12 button.

FIG. 7 is a diagram showing the paper setting field A2 when the A12 button in the paper setting field A1 is touched. An A21 button, A22 button, A23 button, and A2Y button are displayed in the paper setting field A2. The A21 button has a basis weight range of 64-99 g / m ² , the A22 button has a basis weight range of 100-199 g / m ² , and the A23 button has a basis weight range of 200-299 g / m 2. ² is displayed.

  The user touches any one of the A21 button, A22 button, and A23 button including the basis weight of the paper stored in the paper feed tray 291. When the user touches the A2Y button, the paper setting field A2 switches to the paper setting field A1. The basis weight range of the paper touched in the paper setting field A2 is displayed in the display field A121.

  When the basis weight range is confirmed, when the A1Y button shown in the paper setting field A1 is touched, the basis weight range information of the confirmed sheet is stored in the RAM 93 of the control unit 90, and then the setting returns to the basic screen. To do.

In the basic screen, the types of paper stored in the paper feed trays 291, 292, and 293 are classified by the paper thickness (basis weight) and displayed as plain paper or thick letters. In the present embodiment, the basis weight is 99 g / m ² , the following paper is displayed as plain paper, the basis weight is 100 g / m ² , and the above paper is displayed as a thick letter on the A01 button, A02 button, and A03 button.

Note that it corresponds the highest value 299 g / ^{m 2,} range up to the image forming apparatus A in the range of the basis weight to be displayed basis weight of minimum 34g / ^{m 2} range is displayed on the A23 button, the A23 button Although it is the range of the thickness of the paper, the present invention is not limited to this numerical range and may be adapted to a wider range.

  Next, an operation in which the image forming apparatus A controls the temperature of the air flow A1 will be described.

  FIG. 8 is a flowchart for explaining the operation of controlling the temperature of the air flow A1. Note that a program for executing this flowchart is stored in the ROM 92 and executed by the CPU 91.

In step S1, the CPU 91 confirms whether or not the paper being executed (during image formation) is plain paper. The type of paper being executed is based on the paper thickness of the paper selected from one of the paper feed trays 291, 292, and 293 based on the job information input from the operation display unit 80. The CPU 91 determines that the selected paper having a basis weight of 99 g / m ² or less is plain paper, and determines that a thick letter having a basis weight of 100 g / m ² or more is not plain paper.

  When the paper being executed is plain paper (Yes in step S1), the process proceeds to step S2.

  In step S <b> 2, it is confirmed whether or not the detection result t of the temperature sensor 33 </ b> T that detects the temperature of the air flow A <b> 2 is equal to or greater than a constant t <b> 1 stored in the ROM 92. t1 is the upper limit value of the air temperature in the blowing duct 33 that brings the air flow A1 to a temperature that does not cause curling of the thin paper and does not soften the toner fixed on the paper.

  When t is t1 or more (step S2 Yes), the CPU 91 proceeds to step S4, turns on (energizes) the solenoid 35S, and proceeds to step S6. When the solenoid 35S is energized in step S4, the opening / closing door 351 is separated from the partition wall 352, and external air is taken into the attracting duct 33 through the opened partition opening 352h. By taking in external air, the air temperature in the blowing duct 33 decreases.

  When t is not equal to or greater than t1 in step S2 (No in step S2), the process proceeds to step S5, the solenoid 35S is turned off (non-energized), and the process proceeds to step S6. When the solenoid 35S is not energized in step S5, the open / close door 351 comes into contact with the partition wall 352, and external air is not taken into the duct 33 through the closed partition opening 352h. Since the external air is not taken in, the air temperature in the blowing duct 33 does not decrease, but rises with the operation of the magnetic flux generator 318.

  If the paper being executed in the job is not plain paper in step S1 described above (No in step S1), the process proceeds to step S3.

  In step S <b> 3, it is confirmed whether or not the detection result t of the temperature sensor 33 </ b> T that detects the temperature of the air flow A <b> 2 is equal to or greater than a constant t <b> 2 stored in the ROM 92. t2 is an upper limit value of the air temperature in the blowing duct 33 that causes the air flow A1 to be a temperature at which the toner fixed on the paper is not softened without curling the thick paper.

  When t is t2 or more (step S3 Yes), the CPU 91 proceeds to step S4, turns on (energizes) the solenoid 35S, and proceeds to step S6. By energizing the solenoid 35S in step S4, external air is taken into the attracting duct 33 through the opened partition opening 352h, and the air temperature in the blowing duct 33 is lowered.

  When t is not equal to or greater than t2 in step S3 (No in step S3), the process proceeds to step S5, the solenoid 35S is turned off (non-energized), and the process proceeds to step S6. In step S5, outside air is not taken into the duct 33 through the partition opening 352h closed by deenergization of the solenoid 35S in step S5, the air temperature in the blowing duct 33 is not lowered, and the magnetic flux generating unit 318 It rises with movement.

  In step S6, it is confirmed whether or not job execution is continuing. When the job execution is continuing (Yes in step S6), the process returns to step S, and the processes in steps S1 to S6 are repeated until the job execution is completed.

  In step S6, when the job execution is not continuing, that is, when the job execution is completed (No in step S6), the process proceeds to step S7.

  In step S7, the solenoid 35S is turned off (non-energized) to close the partition opening 352h, and the operation for controlling the temperature of the air flow A1 is completed.

  As described above, when the temperature in the blowing duct 33 detected by the temperature sensor 33T is higher than the target temperature, the CPU 91 opens the door 351 to increase the amount of air taken in from the outside, and when the temperature is lower than the target temperature. Controls the temperature of the air flow A1 to an appropriate range by closing the open / close door 351 and reducing the amount of air taken in from the outside.

  In addition, by setting a target temperature corresponding to the type of paper, and in this embodiment, the range of paper thickness (basis weight), the air flow A1 having an appropriate temperature according to the type of paper is blown. Can do. In this embodiment, the type of paper is classified according to the range of the thickness (basis weight) of the paper. However, for example, the paper type is classified depending on whether or not the paper is surface-treated, such as whether or not the paper is coated. You may do it.

  In the fixing device 30, an eddy current is generated in the heat generating roller 311 by the alternating magnetic flux generated by the electromagnetic induction coil 318 </ b> L to generate heat, and the temperature of the fixing belt 315 contacting the heat generating roller 311 is raised. For example, an endless belt made of a nickel electroformed body may be used, and an eddy current may be generated in the fixing belt itself to directly generate heat. Furthermore, the fixing belt may be configured to be heated by a heat generating member such as a halogen lamp without depending on electromagnetic induction.

  FIG. 9 is a diagram for explaining an example of a fixing device that raises the temperature of the fixing belt by a halogen lamp. In the figure, reference numeral 311X denotes an upper roller, which contains a halogen heater HH1 in the center. A fixing roller 312X includes a halogen heater HH2 in the center. In addition, members denoted by the same reference numerals as those of the fixing device shown in FIG. 2 have the same functions as the members described in FIG.

  An endless fixing belt 315 spanned between the upper roller 311X and the fixing roller 312X is in contact with the upper roller 311X heated and heated by the halogen heater HH1 and the fixing roller 312X heated and heated by the halogen heater HH2. The sheet S is nipped in the nip portion N where the fixing belt 315 and the pressure roller 313 come into contact with each other, and the toner image carried on the sheet S is fixed by heating and pressing.

  The air heated by the fixing belt 315, the upper roller 311X and the fixing roller 312X in the upper fixing housing 31H1 flows through the duct first opening 33Hh1 of the blowing unit 32 by the action of the blowing fan 31F and the blower fan 33F. It becomes A1 and is attracted to the paper S discharged from the nip portion N, and peels off from the fixing belt 315.

  A decrease in the temperature of the surface of the fixing belt 315 (heated) due to the blowing of the heated air flow A1 is suppressed, and the occurrence of fixing failure can be prevented. Furthermore, energy consumed for raising the temperature of the fixing belt 315 whose temperature has been lowered to a temperature at which fixing can be performed can be saved.

  The CPU 91 executes the flowchart shown in FIG. 8 to control the temperature of the air flow A1. That is, when the temperature in the blowing duct 33 detected by the temperature sensor 33T is higher than the target temperature, the opening / closing door 351 is opened to increase the amount of air taken in from the outside, and when the temperature is lower than the target temperature, the opening / closing door 351 is opened. The temperature of the air flow A1 is controlled to an appropriate range by reducing the amount of air that is closed and taken in from the outside.

A Image forming apparatus 10Y, 10M, 10C, 10K Image forming unit 6 Intermediate transfer belt 7Y, 7M, 7C, 7K Primary transfer unit 7A Secondary transfer unit 20 Paper transport unit 21 Paper feed unit 24 Paper reversing unit 25 Paper discharge roller 291 , 292, 293 Feed tray 30 Fixing device 31 Fixing unit 31F Blowing fan 31H Fixing housing 31H1 Upper fixing housing 31H2 Lower fixing housing 311 Heating roller 312 Fixing roller 313 Pressing roller 314 Tension roller 315 Fixing belt 318 Magnetic flux generating unit 32 Spraying unit 33 blowing duct 33F blowing fan 33H blowing duct housing 33T temperature sensor 34 connection duct 35 intake 35S solenoid 35SP movable iron core 351 open / close door 352 partition 353 biasing spring 355 contact Plate 80 the operation display unit 90 control unit N nip S Paper

Claims (10)

A fixing device for fixing a toner image on a recording medium,
An electromagnetic induction coil, a heating source having an electromagnetic induction heating part that is heated by magnetic flux generated by the electromagnetic induction coil, a heating part that is heated by the heating source, and a heating part that is in contact with the heating part to form a nip part A fixing unit having a pressure unit;
A blowing unit having a blowing duct for blowing air to the recording medium discharged from the nip portion, and a connecting duct for connecting the blowing duct and the fixing unit in communication with each other;
A blower that blows air inside the fixing unit to the blowing duct through the connection duct ;
The air blowing unit sucks air from the outside of the fixing unit to the inside thereof, and blows air sucked into the fixing unit to the connection duct,
The electromagnetic induction coil is disposed in a path through which air sucked into the fixing unit by the blower is blown to the connection duct;
A fixing device characterized by the above. The fixing device according to claim 1 , further comprising an intake portion that takes air into the inside from the outside of the blowing unit. The fixing device according to claim 2 , wherein the intake portion includes an opening / closing door that opens and closes a part of the spraying unit. An image forming apparatus having a fixing device for fixing a toner image on a recording medium,
The fixing device includes an electromagnetic induction coil, a heating source having an electromagnetic induction heating unit that generates heat by a magnetic flux generated by the electromagnetic induction coil , a heating unit heated by the heating source, and a nip by contacting the heating unit. A fixing unit having a pressurizing part forming a part, a blowing duct for blowing air to the recording medium discharged from the nip part, and a connection duct for connecting the blowing duct and the fixing unit in communication with each other And a blowing unit that blows the air inside the fixing unit to the blowing duct through the connection duct ,
The air blowing unit sucks air from the outside of the fixing unit to the inside thereof, and blows air sucked into the fixing unit to the connection duct,
The electromagnetic induction coil is disposed in a path through which air sucked into the fixing unit by the blower is blown to the connection duct;
An image forming apparatus. An image forming apparatus having a fixing device for fixing a toner image on a recording medium,
The fixing device includes a fixing unit having a heating source, a heating unit heated by the heating source, and a pressure unit that forms a nip portion in contact with the heating unit, and a recording medium discharged from the nip unit. A blowing unit that blows air against the blowing unit, and a blowing unit having a connection duct that connects the blowing duct and the fixing unit in communication with each other;
An intake for taking air into the interior of the spraying unit from the outside;
A control unit for controlling the amount of air taken in from the intake unit;
A detection unit that detects the temperature of air downstream of the intake unit with respect to the flow direction of the air flowing through the inside of the blowing unit;
The control unit performs control to increase the air amount when the temperature detected by the detection unit is higher than a target temperature, and to reduce the air amount when the temperature is lower than the target temperature,
An image forming apparatus. The image forming apparatus according to claim 5 , further comprising a blower that blows air inside the fixing unit to the blowing duct through the connection duct. The image forming apparatus according to claim 6 , wherein the heating source includes an electromagnetic induction coil and an electromagnetic induction heating unit that generates heat by a magnetic flux generated by the electromagnetic induction coil. The air blowing unit sucks air from the outside of the fixing unit to the inside thereof, and blows air sucked into the fixing unit to the connection duct,
The electromagnetic induction coil is disposed in a path through which air sucked into the fixing unit by the blower is blown to the connection duct;
The image forming apparatus according to claim 7 . An intake for taking air into the interior of the spraying unit from the outside;
A control unit for controlling the amount of air taken in from the intake unit;
A detection unit that detects the temperature of air downstream of the intake unit with respect to the flow direction of the air flowing through the inside of the blowing unit;
The control unit performs control to increase the air amount when the temperature detected by the detection unit is higher than a target temperature, and to reduce the air amount when the temperature is lower than the target temperature,
The image forming apparatus according to claim 4 . The intake part has an open / close door that opens and closes a part of the spray unit;
The controller increases the air volume by opening the door when the temperature detected by the detector is higher than the target temperature, and closes the door when the temperature is lower than the target temperature. Reducing the amount of air,
The image forming apparatus according to any one of claims 5 to 9 .

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