JP2014059380A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a sensor for sensing a position of belt end of a fixing part from malfunctioning or failing due to high heat, without increasing size and cost of an image forming device.SOLUTION: An image forming device includes: an image forming part which forms a toner image on a photoreceptor; a transfer part 70 which transfers the toner image to a transfer material S; a fixing part 80 which fixes the toner image by pressing and heating the transfer material S with the toner image transferred thereon held between a belt 81 and a roller 85, and has an angle changing mechanism for changing an angle of a shaft of a roller 82, on which the belt 81 is stretched, with respect to a belt rotation direction; a sensor 86 for detecting a position of an end of the belt 81 in the fixing part 80; a control part for controlling the angle changing mechanism on the basis of a detection result of the sensor 86 to perform belt steering; and an air duct 90 installed near the fixing part 80. The sensor 86 is arranged in the air duct 90.

Description

  The present invention relates to an image forming apparatus that transfers a toner image formed on a photosensitive member to a transfer material such as paper, and in particular, presses and heats a transfer material onto which a toner image has been transferred between a roller and a belt. The present invention relates to an image forming apparatus that fixes a toner image by using the above method.

  The charged photoconductor is exposed based on the image data to form an electrostatic latent image, and a toner image is formed by attaching toner to the photoconductor, and this toner image is transferred to a transfer material (hereinafter simply referred to as paper). Image forming apparatuses such as copiers, printers, facsimiles, and multi-function machines have been widely used in which a toner image is fixed by heating and pressing the paper onto which the toner image is transferred in a fixing unit. Yes.

  In such an image forming apparatus, when a fixing unit configured to sandwich a sheet between rollers and a roller is used, the belt is prevented from being offset in the sheet width direction (direction perpendicular to the sheet passing direction). Therefore, a technique called belt steering has been conventionally employed. In this belt steering, the position of the belt end is detected by a sensor, and the angle of the shaft of the roller that stretches the belt with respect to the belt rotation direction is changed to suppress the deviation of the belt.

  When the position of the belt end of the fixing unit is detected by the sensor, the temperature of the belt reaches about 200 ° C., so it is necessary to prevent malfunction or failure of the sensor due to high heat. For this reason, conventionally, an expensive sensor with a specially improved heat resistance has been used, such as disposing the sensor as far from the belt as possible, installing a dedicated fan or duct for cooling the sensor.

  Further, although not related to a sensor for detecting the position of the belt end of the fixing unit, it is a technique for preventing a temperature rise of a sensor that is arranged in the vicinity of the fixing unit and detects a correction patch mark image on a paper conveying belt. Is known (for example, see Patent Document 1).

JP 2008-52215 A

  However, disposing the sensor far away from the belt leads to an increase in the size of the fixing unit and the entire image forming apparatus. In addition, installing a dedicated fan or duct for cooling the sensor leads to an increase in power consumption and an increase in the number of parts. In addition, the use of an expensive sensor with specially improved heat resistance also leads to an increase in cost.

  In addition, the technique disclosed in Patent Document 1 also changes the arrangement and configuration of ducts and air inlets in the image forming apparatus, and there is a concern about the increase in size and cost of the image forming apparatus.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to prevent malfunction and failure due to high heat of a sensor that detects the position of a belt end of a fixing unit without increasing the size and cost of an image forming apparatus. To do.

  In order to solve the above problems and achieve the object of the present invention, an image forming apparatus of the present invention includes an image forming unit that forms a toner image on an image carrier, a transfer unit that transfers the toner image to a transfer material, and a toner. An angle that changes the angle of the shaft of the roller that stretches the belt with respect to the belt rotation direction by fixing the toner image by sandwiching the transfer material onto which the image has been transferred between the belt and the roller and applying pressure and heating. A change mechanism, an air duct installed around the fixing unit, a sensor arranged in an air duct for detecting the position of the belt end of the fixing unit, and a belt by controlling the angle change mechanism based on the detection result of the sensor. A control unit that performs steering.

  According to the image forming apparatus of the present invention, the sensor for detecting the position of the end portion of the belt of the fixing unit is arranged in the air duct installed around the fixing unit and cooled. Thereby, the malfunctioning and failure of the sensor due to the influence of high heat can be prevented.

FIG. 2 is a diagram illustrating the configuration of an image forming unit, an intermediate transfer belt, a secondary transfer unit, a fixing unit, and the like of an image forming apparatus according to an embodiment of the present invention. 2 is a diagram illustrating a configuration of a fixing unit of the image forming apparatus according to the exemplary embodiment of the present invention. FIG. FIG. 3 is a diagram illustrating a configuration of a belt position detection unit of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an installation position of a belt position detection unit of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an installation position of a belt position detection unit of the image forming apparatus according to the embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus according to the embodiment of the present invention. It is a figure which shows the table data of the steering detection pattern in the image forming apparatus which concerns on embodiment of this invention. 6 is a flowchart showing duct fan control processing in the image forming apparatus according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows configurations of an image forming unit, an intermediate transfer belt, a secondary transfer unit, a fixing unit, and the like of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 forms an image on a sheet by an electrophotographic method, and tandem format in which toners of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk) are superimposed. The color image forming apparatus. The image forming apparatus 1 includes a document transport unit 10, a paper storage unit 20, an image reading unit 30, an image forming unit 40, an intermediate transfer belt 50, a secondary transfer unit 70, and a fixing unit 80.

  The document transport unit 10 includes a document feeder 11 on which a document is set and a plurality of rollers 12. The documents G set on the document feeder 11 of the document transport unit 10 are transported one by one to the reading position of the image reading unit 30 by a plurality of rollers 12. The image reading unit 30 reads an image of the document G transported by the document transport unit 10 or the document placed on the document table 13 and generates an image signal.

  The paper storage unit 20 is disposed in the lower part of the apparatus main body, and a plurality of paper storage units 20 are provided according to the size of the paper S. The sheet S is fed by the sheet feeding unit 21 and sent to the transport unit 23, and is transported by the transport unit 23 to the secondary transfer unit 70 that is a transfer position. Further, a manual feed portion 22 is provided in the vicinity of the paper storage portion 20. From the manual feed section 22, paper of a size not stored in the paper storage section 20, tag paper having a tag, special paper such as an OHP sheet is sent to the transfer position.

  An image forming unit 40 and an intermediate transfer belt 50 are disposed between the image reading unit 30 and the paper storage unit 20. The image forming unit 40 includes four image forming units 40Y, 40M, 40C, and 40K in order to form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk). .

  The first image forming unit 40Y forms a yellow toner image, and the second image forming unit 40M forms a magenta toner image. The third image forming unit 40C forms a cyan toner image, and the fourth image forming unit 40K forms a black toner image. Since these four image forming units 40Y, 40M, 40C, and 40K have the same configuration, only the first image forming unit 40Y will be described here.

  The first image forming unit 40Y includes a drum-shaped photoconductor 41, a charging unit 42 arranged around the photoconductor 41, an exposure unit 43, a developing unit 44, and a cleaning unit 45. The photoreceptor 41 is rotated counterclockwise by a drive motor (not shown). The charging unit 42 applies a charge to the photoconductor 41 and uniformly charges the surface of the photoconductor 41. The exposure unit 43 performs exposure scanning on the surface of the photoconductor 41 based on the image data read from the document G, and forms an electrostatic latent image on the photoconductor 41.

  The developing unit 44 attaches yellow toner to the electrostatic latent image formed on the photoconductor 41 that is an image carrier. As a result, a yellow toner image is formed on the surface of the photoreceptor 41. The developing unit 44 of the second image forming unit 40M attaches magenta toner to the photoconductor 41, and the developing unit 44 of the third image forming unit 40C attaches cyan toner to the photoconductor 41. Then, the developing unit 44 of the fourth image forming unit 40K adheres black toner to the photoconductor 41.

  The toner adhering to the photoreceptor 41 is transferred to an intermediate transfer belt 50 showing an example of an image carrier. The cleaning unit 45 removes toner remaining on the surface of the photoreceptor 41 after being transferred to the intermediate transfer belt 50.

  The intermediate transfer belt 50 is formed in an endless shape, and is rotated clockwise by a drive motor (not shown) in a direction opposite to the rotation direction of the photoconductor 41. A primary transfer portion 51 is provided at a position on the intermediate transfer belt 50 that faces the photoreceptor 41 of each of the image forming units 40Y, 40M, 40C, and 40K. The primary transfer unit 51 transfers the toner image formed on the photoreceptor 41 to the intermediate transfer belt 50 by applying a polarity opposite to that of the toner to the intermediate transfer belt 50.

  As the intermediate transfer belt 50 rotates, the toner images formed by the four image forming units 40Y, 40M, 40C, and 40K are sequentially transferred onto the surface of the intermediate transfer belt 50. As a result, yellow, magenta, cyan, and black toner images are superimposed on the intermediate transfer belt 50 to form a color image.

  A secondary transfer unit 70 is disposed near the intermediate transfer belt 50 and downstream of the conveyance unit 23. The secondary transfer unit 70 is formed in a roller shape and presses the sheet S sent by the transport unit 23 toward the intermediate transfer belt 50. The secondary transfer unit 70 transfers the color image formed on the intermediate transfer belt 50 onto the paper S sent by the transport unit 23. The cleaning unit 52 removes toner remaining on the surface of the intermediate transfer belt 50 after being transferred to the paper S. A fixing unit 80 is provided on the paper transfer side of the secondary transfer unit 70. The fixing unit 80 pressurizes and heat-fixes the toner image transferred to the paper S. A heat insulating air duct 90 is installed at the boundary between the fixing unit 80 and the intermediate transfer belt 50 so that the heat of the fixing unit 80 does not affect the intermediate transfer belt 50. An upper end portion of the air duct 90 communicates with an air inlet of a main duct (not shown) provided in the image forming apparatus 1. A duct fan 91 is provided near the upper end of the air duct 90, and air outside the image forming apparatus 1 is sucked into the air duct 90 by the duct fan 91. The lower end of the air duct 90 communicates with the exhaust port of the main duct described above, and the air in the air duct 90 is discharged to the outside of the image forming apparatus 1.

  A switching gate 24 is disposed downstream of the fixing unit 80. The switching gate 24 switches the transport path of the paper S that has passed through the fixing unit 80. That is, the switching gate 24 moves the paper S straight when performing face-up paper discharge in single-sided image formation. As a result, the paper S is discharged by the pair of paper discharge rollers 25. The switching gate 24 guides the paper S downward when face-down paper discharge and double-sided image formation in single-sided image formation.

When face-down paper discharge is performed, the paper S is guided downward by the switching gate 24, and then the front and back sides are reversed by the paper reverse conveyance unit 26 and conveyed upward. As a result, the paper S is discharged by the pair of paper discharge rollers 25.
When double-sided image formation is performed, the sheet S is guided downward by the switching gate 24, the front and back sides are reversed by the sheet reversing conveyance unit 26, and sent again to the transfer position by the refeed path 27.

  Further, a post-processing device that folds the paper S or performs stapling processing or the like on the paper S may be disposed downstream of the pair of paper discharge rollers 25.

  FIG. 2 shows a detailed configuration of the fixing unit 80 shown in FIG. 1 together with a belt position detecting unit 86 used for belt steering. FIG. 2A is a side view as seen from the same direction as FIG. 2B is a perspective view. The actual installation position of the belt position detection unit 86 in the image forming apparatus 1 will be described later with reference to FIGS. The fixing unit 80 presses and heat-fixes the toner image transferred onto the paper S by sandwiching the paper S between the endless belt 81 and the pressure roller 85.

  The belt 81 is stretched around a heating / steering roller 82, a pressure roller 83, and an auxiliary roller 84. The heating / steering roller 82 includes a heat generation lamp (not shown) that is a heat source, and raises the temperature of the belt 81 to about 200 ° C. The heating / steering roller 82 is rotated clockwise by a drive motor (not shown) to rotate the belt 81. The fixing unit 80 is provided with an angle changing mechanism such as a stepping motor (not shown) for changing the angle of the shaft of the heating / steering roller 82 with respect to the rotation direction of the belt 81.

  The belt position detector 86 is for detecting the position of the end of the belt 81. FIG. 3 shows the configuration of the belt position detector 86, FIG. 3A is a top view, and FIG. 3B is a perspective view. The belt position detection unit 86 is obtained by attaching an elongated shaft rod-shaped actuator 87, two belt position detection sensors 88, and a fail-safe sensor 89 to a base made of a transparent material.

  The actuator 87 is urged by a spring and its tip is pressed against the end of the belt 81 to follow the change in the position of the belt 81 in the paper width direction (vertical direction in FIG. 3A) indicated by the arrow in the figure. The slope changes.

  The belt position detection sensor 88 and the fail safe sensor 89 are reflection type optical sensors having a light emitting portion and a light receiving portion, and detect the position of the end portion of the belt 81 by detecting the tilt position of the actuator 87. Among these, the belt position detection sensor 88 is for detecting in which of the P0 to P3 in FIG. 3A the end of the belt 81 is located by the combination of the output signals of the two sensors. On the other hand, the fail-safe sensor 89 determines the position of the belt 81 due to some abnormality (for example, damage to the heating / steering roller 82, the pressure roller 83, or the auxiliary roller 84 in FIG. This is for detecting that the end of the belt 81 has reached a predetermined limit position at which there is a possibility of wheel-removal because the control becomes impossible.

  The heat resistance temperature of the belt position detection sensor 88 and the fail safe sensor 89 is about 90 ° C. On the other hand, since the temperature of the belt 81 reaches about 200 ° C. as described above, it is necessary to prevent malfunction and failure of these sensors 88 and 89 due to high heat. However, the sensors 88 and 89 are arranged far away from the belt 81, a dedicated duct fan or duct for cooling the sensors 88 and 89 is installed, or the sensors 88 and 89 are expensive with specially improved heat resistance performance. Use of such a device leads to an increase in size and cost of the image forming apparatus.

  Therefore, as shown in FIG. 4, the heat insulation air duct of FIG. 1 is installed at the boundary between the fixing unit 80 and the intermediate transfer belt 50 so that the heat of the fixing unit 80 does not affect the intermediate transfer belt 50. A belt position detection unit 86 is disposed in 90. A transparent material is used for a portion of the partition wall of the air duct 90 where the belt position detection unit 86 is disposed. Further, a hole for allowing the actuator 87 to pass is provided in the partition wall of the air duct 90.

  FIG. 5 shows the arrangement of the belt position detector 86 in the air duct 90 in more detail. The fail-safe sensor 89 plays an important role in detecting that the position of the belt 81 has become uncontrollable as described above. In particular, since malfunction or failure is not allowed, the flow of air in the air duct 90 In the direction F (the direction from the upper side to the lower side in FIG. 1), it is installed upstream of the belt position detection sensor 88. A rib 92 for guiding the air flow F in the air duct 90 to the fail safe sensor 89 is formed in the partition wall of the air duct 90. Thereby, the fail safe sensor 89 is cooled in preference to the belt position detection sensor 88.

  FIG. 6 shows the configuration of the control system of the image forming apparatus 1. The image forming apparatus 1 includes, for example, a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102 for storing programs executed by the CPU 101, and a RAM (Random Access Memory) used as a work area of the CPU 101. 103. Further, it has a hard disk drive (HDD) 104 as a mass storage device and an operation display unit 105. As the ROM 102, an electrically erasable programmable ROM is usually used.

  The CPU 101 is an example of a control unit, and is connected to the ROM 102, the RAM 103, the HDD 104, and the operation display unit 105 via the system bus 107, and controls the entire apparatus. In addition, the CPU 101 is connected to the image reading unit 30, the image processing unit 110, the image forming unit 40, the paper feeding unit 21, the fixing unit 80, the belt position detection unit 86, and the duct fan 91 in the air duct 90 via the system bus 107. Has been.

  The HDD 104 stores image data of an original image obtained by reading by the image reading unit 30, or stores output image data and the like. The operation display unit 105 is a touch panel including a display such as a liquid crystal display (LCD) or an organic ELD (Electro Luminescence Display). The operation display unit 105 displays an instruction menu for the user, information about the acquired image data, and the like. Further, the operation display unit 105 includes a plurality of keys, and receives input of various instructions, data such as characters and numbers by a user's key operation, and outputs an input signal.

  The image reading unit 30 optically reads a document image and converts it into an electrical signal. For example, when reading a color original, image data having luminance information of 10 bits for each of RGB per pixel is generated. Image data generated by the image reading unit 30 and image data transmitted from a PC (personal computer) 120 showing an example of an external device connected to the image forming apparatus 1 are sent to the image processing unit 110 for image processing. Is done. The image processing unit 110 performs processes such as analog processing, A / D conversion, shading correction, and image compression on the received image data.

  In this example, a personal computer is used as an external device. However, the present invention is not limited to this, and various other devices such as a facsimile device can be used as the external device.

  For example, when a color image is formed by the image forming apparatus 1, R, G, B image data generated by the image reading unit 30 or the like is input to a color conversion LUT (look up table) in the image processing unit 110. Then, the image processing unit 110 performs color conversion on the R, G, and B data to Y, M, C, and Bk image data. Then, correction of gradation reproduction characteristics, screen processing such as halftone dots with reference to the density correction LUT, or edge processing for emphasizing thin lines is performed on the color-converted image data.

  The image forming unit 40 receives the image data processed by the image processing unit 110 and forms an image on the paper S.

  From the belt position detection unit 86, a signal indicating the detection result of the position of the end of the belt 81 by the belt position detection sensor 88 and the fail safe sensor 89 is transmitted to the CPU 101.

  The CPU 101 controls the belt 81 by controlling the angle changing mechanism of the fixing unit 80 using the table data of the steering detection pattern as shown in FIG. 7 stored in the ROM 102 based on the detection result of the belt position detection sensor 88. Perform belt steering. Among the table data, P0, P1, P2, and P3 in “before transition” and “after transition” of “state transition” represent positions P0 to P3 of the end portion of the belt 81 shown in FIG. 3A. As shown in FIG. 7, for example, when the position of the end portion of the belt 81 changes from P1 to P2, the CPU 101 changes the angle of the heating / steering roller 82 by 18 ° to move the belt 81 to the P1 side. Induce. For example, when the position of the end portion of the belt 81 changes from P2 to P1, the CPU 101 changes the angle of the heating / steering roller 82 by -18 ° (18 ° opposite to the change from P1 to P2). As a result, the belt 81 is guided to the P2 side.

  When the fail-safe sensor 89 detects that the belt 81 has reached the above limit position, the CPU 101 immediately stops the drive motor that rotates the heating / steering roller 82.

  FIG. 8 shows processing executed by the CPU 101 for controlling the duct fan 91 in the air duct 90. This process starts when the power of the image forming apparatus 1 is turned on, and the CPU 101 performs a start-up operation of the image forming apparatus 1 (step S1), and determines whether or not the fixing unit 80 is activated. It repeats until it starts (step S2). When the fixing unit 80 is activated, the CPU 101 starts the operation of the duct fan 91 in synchronization therewith (step S3) and ends the process.

  According to the image forming apparatus according to this embodiment, the belt position detection unit 88 that detects the position of the end of the belt 81 of the fixing unit 80 and the belt position detection unit 86 to which the fail-safe sensor 89 is attached include the fixing unit 80. In order to prevent the heat of the toner from affecting the intermediate transfer belt 50, the heat is placed in the air duct 90 originally installed at the boundary between the fixing unit 80 and the intermediate transfer belt 50 and cooled. Thereby, these sensors 88 and 89 are arranged far away from the belt 81, a dedicated fan or duct for cooling the sensors 88 and 89 is installed, and the heat resistance performance is specially enhanced as the sensors 88 and 89. There is no need to use expensive items. For this reason, it is possible to prevent malfunction and failure of the sensors 88 and 89 due to the influence of high heat without causing an increase in size and cost of the image forming apparatus.

  Further, as shown in FIG. 5, the belt position detection sensor 88 and the fail safe sensor 89 include the fail safe sensor 89 that plays an important role in detecting that the position of the belt 81 becomes uncontrollable. Cooling can be performed with priority over the detection sensor 88.

[Modification]
The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention described in the claims.

  For example, in the above-described embodiment, the example in which the image forming unit 40 is provided with the four image forming units 40Y, 40M, 40C, and 40K to form a color image has been described. However, a single color in which only one image forming unit is provided. You may apply to the image forming apparatus which forms an image.

  Further, an example in which the intermediate transfer belt 50 is provided as a transfer material for transferring the toner image formed on the photoconductor 41 and the image is secondarily transferred from the intermediate transfer belt 50 to the paper S has been described. The present invention may be applied to an image forming apparatus that directly transfers a toner image.

  In the above-described embodiment, the belt position detection unit 86 is installed at the boundary between the fixing unit 80 and the intermediate transfer belt 50 so that the heat of the fixing unit 80 does not affect the intermediate transfer belt 50. It arrange | positions in the air duct 90 for heat insulation. However, the present invention is not limited to this, and the belt position detection unit 86 may be disposed in an air duct installed around the fixing unit 80 at a location other than the boundary between the fixing unit 80 and the intermediate transfer belt 50. For example, when an air duct for heat insulation is installed at the boundary between the fixing unit 80 and the paper discharge unit (the paper discharge roller 25 in FIG. 1), the belt position detection unit 86 may be arranged in the air duct. . Alternatively, when an air separation mechanism for separating the paper heated by the belt 81 and the pressure roller 85 from the belt 81 and the pressure roller 85 is provided, the air separation mechanism has an air duct. A belt position detector 86 may be arranged.

  In the above-described embodiment, as shown in FIG. 8, the duct fan 91 in the air duct 90 is operated in synchronization with the activation of the fixing unit 80 after the start-up operation of the image forming apparatus 1. Yes. However, the present invention is not limited to this, and the duct fan 91 is operated in synchronization with the start-up operation of the image forming apparatus 1, or the duct fan 91 is operated in synchronization with the rotation start of the belt 81 after the fixing unit 80 is started. May be. Further, after the rotation of the belt 81 is started, the duct fan 91 may be operated in synchronization with the start of lighting of the heating lamp inside the heating / steering roller 82.

  In the above-described embodiment, the belt position detection unit 86 including the actuator 87, the belt position detection sensor 88, and the fail safe sensor 89 is disposed in the air duct 90. However, when the position of the end portion of the belt 81 is directly detected by a sensor without using an actuator, the sensor may be disposed in the air duct 90.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Document conveyance part, 20 ... Paper storage part, 21 ... Paper feed part, 22 ... Manual feed part, 23 ... Conveyance part, 30 ... Image reading part, 40 ... Image formation part, 40Y, 40M , 40C, 40K ... Image forming unit, 41 ... Photoconductor, 50 ... Intermediate transfer belt, 70 ... Secondary transfer unit, 80 ... Fixing unit, 81 ... Belt, 82 ... Heating / steering roller, 83 ... Pressure roller, 85 DESCRIPTION OF SYMBOLS ... Pressure roller, 86 ... Belt position detection part, 87 ... Actuator, 88 ... Belt position detection sensor, 89 ... Fail safe sensor, 90 ... Air duct, 91 ... Duct fan, 92 ... Rib, 101 ... CPU, 102 ... ROM

Claims (7)

An image forming unit for forming a toner image on the image carrier;
A transfer portion for transferring the toner image to a transfer material;
A fixing unit that fixes the toner image by sandwiching a transfer material onto which the toner image has been transferred between a belt and a roller and applying pressure and heating;
An angle changing mechanism that changes an angle of a shaft of a roller that stretches the belt with respect to a belt rotation direction;
An air duct installed around the fixing unit;
A sensor disposed in the air duct for detecting a position of an end of the belt of the fixing unit;
A control unit that controls the angle change mechanism based on a detection result of the sensor to perform belt steering;
An image forming apparatus. An intermediate transfer belt for transferring the toner image formed on the photoreceptor;
The image forming apparatus according to claim 1, wherein the air duct is installed at a boundary between the fixing unit and the intermediate transfer belt. A paper discharge unit for discharging the paper on which the toner image is fixed by the fixing unit;
The image forming apparatus according to claim 1, wherein the air duct is installed at a boundary between the fixing unit and the paper discharge unit. An air separation mechanism for separating the pressurized and heated paper from the belt;
The image forming apparatus according to claim 1, wherein the air duct is an air duct included in the air separation mechanism. The image forming apparatus according to claim 1, further comprising: a control unit configured to operate a duct fan provided in the air duct in synchronization with activation of the fixing unit after the start-up operation of the image forming apparatus. The sensor includes a fail-safe sensor for detecting that the end of the belt has reached a predetermined limit position and stopping the rotation of the belt,
The image forming apparatus according to claim 1, wherein the fail-safe sensor is installed upstream of the other sensors in the direction of air flow in the air duct. The sensor includes a fail-safe sensor for detecting that the end of the belt has reached a predetermined limit position and stopping the rotation of the belt,
The image forming apparatus according to claim 1, wherein a rib for guiding an air flow to the fail-safe sensor is formed in the air duct.