JP2020027124A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can stably rotate a fan that exhausts air to the outside of the apparatus.SOLUTION: An image forming apparatus comprises: a duct unit 200 that is attached to the exterior of an apparatus body 1 and forms a channel for exhausting air exhausted from exhaust ports 227, 228 to the outside of the apparatus body 1; a duct exhaust port 244 that is provided at a downstream end of the duct unit 200 in a direction in which air flows and for exhausting the air exhausted from the exhaust ports 227, 228 to the outside; a fan 102 that is provided inside the duct unit 200 and on the upstream side of the duct exhaust port 244 in the direction in which air flows, and for exhausting air from the duct exhaust port 244; a sensor 32 that detects the number of rotations of the fan 102; and a CPU 21 that controls the fan 102 such that the number of rotations detected by the sensor 32 falls within a predetermined range for a target number of rotations.SELECTED DRAWING: Figure 20

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, it has been known that heat is applied to components contained in a fixing member and a wax of a toner to release fine particles. These fine particles are called ultra fine particles (UFP) different from ozone and toner dust, and reduction of the discharge amount of the ultra fine particles is an issue.

  Before an image is formed on a recording material, it is necessary to prevent the temperature inside the apparatus main body from exceeding a certain value because toner does not adhere inside the apparatus main body. Further, a recording material such as paper on which a toner image is formed may be heated by the fixing device, and dew condensation may occur inside the apparatus main body. Further, even in an environment with high humidity, dew condensation may occur inside the apparatus main body. If such dew adheres to the conveyance guide and the like and adheres to the recording material, there is a possibility that the image quality is impaired. Therefore, it is necessary to prevent the occurrence of dew condensation inside the apparatus main body.

  In Patent Literature 1, a box body disposed along an exterior surface of an apparatus main body and a duct section covering an exhaust port of the apparatus main body are provided. The box body portion includes a filter chamber for housing the filter in opposition to the apparatus main body, a first ventilation section for allowing exhaust gas to flow from the duct section to the filter chamber, and a second ventilation section for discharging exhaust gas from the filter chamber to the outside. Section is provided. The first ventilation section and the second ventilation section are located on opposite sides of the area center of gravity of the filter when viewed from the rear side of the apparatus main body.

JP-A-2017-32833

  However, a ventilation fan is provided in the duct part of Patent Document 1. Noise due to the operation sound of the blower fan affects the operation sound of the entire image forming apparatus. For this reason, it is necessary to minimize the noise caused by the operating noise of the fan. For example, consider a case in which the number of revolutions of the fan is controlled with a predetermined pulse width (Duty) by a PWM (Pulse Width Modulation) signal.

  At this time, even if a drive signal is issued to the fan with the same pulse width (Duty), the actual number of revolutions of the fan varies due to the variation of the voltage of the power supply board and the individual difference of the fan. Thus, the rotation speed of the fan varies, and the rotation speed of the fan becomes larger than the rotation speed to be controlled. In that case, for example, when the fan arranged outside the apparatus main body and arranged so as to be covered only under the cover member or the duct is rotated, the operating noise of the entire image forming apparatus becomes loud.

  Further, it is necessary to rotate the fan to blow air from the inside of the apparatus body to the outside in order to reduce the emission amount of ultra-fine particles (UFP), increase the temperature inside the apparatus body, and dew inside the apparatus body. Therefore, when the rotation of the fan varies and the number of rotations of the fan decreases, the efficiency of exhausting air from the inside of the apparatus body to the outside decreases.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus capable of stably rotating a fan for exhausting air to the outside of the apparatus.

  A typical configuration of an image forming apparatus according to the present invention for achieving the above object is an image forming apparatus that forms an image by heating a toner image transferred to a recording material in a fixing unit and fixing the toner image on the recording material. A first exhaust port for exhausting the air heated by the fixing unit to the outside of the apparatus main body, and an air exhausted from the first exhaust port attached to an exterior of the apparatus main body, for discharging air exhausted from the first exhaust port to the outside of the apparatus main body. A duct that forms a flow path for exhausting air into the duct, and a second exhaust port that is provided at a downstream end of the duct in a direction in which air flows, and that exhausts air exhausted from the first exhaust port to the outside. A fan provided inside the duct and upstream of the second exhaust port in the direction in which air flows, and for generating an airflow for exhausting the air from the second exhaust port; Detect A rotation speed detector for the rotational speed rotational speed detected by the detection unit, and having a control unit which controls the fan to be within a predetermined range with respect to the target rotational speed, the.

  ADVANTAGE OF THE INVENTION According to this invention, the fan which exhausts out of a machine can be rotated stably.

FIG. 2 is a schematic sectional view of the image forming apparatus. FIG. 3 is a schematic sectional view of a fixing device. FIG. 3 is a schematic diagram of a fixing device, a fan, and a cooling duct. FIG. 2 is an internal explanatory diagram of the image forming apparatus. 5 is a graph for explaining fan drive timing. FIG. 2 is a perspective view of the image forming apparatus as viewed from the rear side. It is a schematic diagram of a duct unit. It is a perspective view of a duct unit. It is a perspective view of a duct unit. It is sectional drawing of a duct unit. It is sectional drawing of a duct unit. It is sectional drawing of a duct unit. It is a perspective view of a lower unit. It is a perspective view of a lower unit. It is sectional drawing of a lower unit. It is a graph which shows the temperature distribution in the duct of a duct unit. 6 is a graph showing a relationship between a flow rate of air supplied from a supply port of a duct in the duct unit, a flow rate of air exhausted from a duct exhaust port, and a temperature inside the image forming apparatus. FIG. 3 is a layout diagram of a duct unit and an electric unit when the image forming apparatus is viewed from the back side. It is a flowchart which shows constant rotation speed control of a fan. It is a figure which shows the relationship between the rotation speed of a fan, an inside temperature, dust, an operation sound, and dew condensation.

  An embodiment of the image forming apparatus according to the present invention will be specifically described with reference to the drawings.

(1st Embodiment)
<Image forming apparatus>
Hereinafter, first, the overall configuration of the image forming apparatus according to the first embodiment of the present invention will be described with reference to the drawings together with the operation during image formation. It should be noted that the dimensions, materials, shapes, relative arrangements, and the like of the components described are not intended to limit the scope of the present invention thereto unless otherwise specified.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus H according to the present embodiment. As shown in FIG. 1, the image forming apparatus H is an electrophotographic image forming apparatus that forms an image on a sheet using four color toners of yellow, magenta, cyan, and black. The image forming apparatus H includes an image forming unit that transfers a toner image to a sheet to form an image, a sheet feeding unit that supplies the sheet to the image forming unit, and a fixing unit that fixes the toner image on the sheet. .

  The image forming unit includes a process unit 103 (103Y, 103M, 103C, 103K) that forms a toner image of each color using the toner of each color. The exposure apparatus 104 (104Y, 104M, 104C, 104K), the intermediate transfer belt 6, the secondary transfer roller 8, the secondary transfer opposing roller 9, and the like are provided.

  Each process unit 103 includes a photosensitive drum 3, a charging roller 4, a developing device having a developing sleeve 5, and a primary transfer roller 7. The process units 103Y, 103M, 103C, and 103K use yellow, magenta, cyan, and black toners, respectively, and the configuration other than the color of the toner used is the same in each process unit.

  Next, the image forming operation will be described. First, when the controller board 120 shown in FIG. 18 receives the image forming job signal, the sheet S (recording material) loaded and stored in the sheet cassette 101 is sent to the registration roller 12 by the pickup roller 2, the feed roller 10, and the transport roller 11. It is. Next, the sheet S is sent to the secondary transfer section formed by the secondary transfer roller 8 and the secondary transfer opposing roller 9 after the skew correction and the timing correction are performed by the registration roller 12.

  On the other hand, in the image forming section, first, the surface of the photosensitive drum 3 is charged by the charging roller 4. Thereafter, image data transmitted from an external device or the like (not shown) is processed by the controller substrate 120, and the exposure device 104 irradiates the surface of the photosensitive drum 3 of each color with laser light according to the processing result. Thus, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 3.

  Thereafter, toner of each color is attached to the electrostatic latent image formed on the surface of the photoconductor drum 3 by the developing sleeve 5 to form a toner image on the surface of the photoconductor drum 3. The toner image formed on the surface of the photoconductor drum 3 is primarily transferred to the intermediate transfer belt 6 by applying a primary transfer bias to the primary transfer roller 7. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 6.

  Thereafter, as the secondary transfer opposing roller 9 receiving a driving force from a driving source (not shown) rotates, the intermediate transfer belt 6 is driven to rotate, and the toner image is sent to the secondary transfer unit. Then, a secondary transfer bias is applied to the secondary transfer roller 8 in the secondary transfer section, so that the toner image on the intermediate transfer belt 6 is transferred to the sheet S.

  Next, the sheet S to which the toner image has been transferred is conveyed to the fixing device 50. The fixing device 50 serves as a fixing unit. The fixing belt 20 includes the heater 16 (FIG. 2). The fixing device 50 presses the fixing belt 20 and rotates by a driving force of a driving source (not shown). A pressure roller 22 is provided.

  The sheet S conveyed to the fixing device 50 is heated and pressed while being nipped and conveyed in a fixing nip portion N formed by the fixing belt 20 and the pressure roller 22, whereby the toner image on the sheet S is formed. Is fixed on the sheet S. Thereafter, the sheet S on which the toner image is fixed is discharged to the discharge tray 106 by the discharge roller 70.

  In the present embodiment, the toner contains paraffin wax, and the wax melted by the heat of the fixing process is interposed at the interface between the fixing belt 20 and the toner image so that the toner does not adhere to the fixing belt 20. I have. The melting point of this wax is about 75 ° C., and the target temperature of the fixing nip is 170 ° C.

  The wax is not limited to those described above, and a compound containing the molecular structure of wax, such as a resin obtained by reacting a resin molecule of a toner with a wax molecular structure such as a hydrocarbon chain, may be used. Instead of wax, other substances having a releasing effect, such as silicone oil, can also be used.

  When images are formed on both sides of the sheet S, the sheet S is guided to the reversing path 13 after the fixing device 50 fixes the toner image on the surface. Thereafter, the reversing roller 14 rotates in the reverse direction while holding the sheet S, and the sheet S is sent again to the secondary transfer unit after the front and back sides are inverted via the re-feeding path 15. Next, an image is formed on the back surface in the same manner as the front surface of the sheet S, and thereafter, the sheet S is discharged to the discharge tray 106.

  Here, the image forming apparatus H can be equipped with a sheet processing apparatus (not shown) that performs binding processing, folding processing, and the like on the sheet S on which an image is formed by the image forming unit. In the image forming apparatus H of the present embodiment, the sheet processing apparatus is connected to the left side in FIG. 1 via a not-shown relay unit or the like. That is, the sheet processing apparatus is mounted on the image forming apparatus H on the side opposite to the fixing device 50 in the left-right direction (width direction) of the image forming apparatus H.

<Fixing device>
Next, the configuration of the fixing device 50 will be described.

  FIG. 2 is a schematic sectional view of the fixing device 50. As shown in FIG. 2, the fixing device 50 includes a fixing belt 20, a pressure roller 22, a heater 16 that generates heat when energized, and a heater holder 17 that holds the heater 16. Further, the image forming apparatus includes a guide member 23, a fixing discharge roller 26, a main thermistor 19, and a sub thermistor 18.

  The pressure roller 22 is formed by forming a silicone rubber layer having a thickness of about 3 mm on a stainless steel core by injection molding, and coating a PFA resin tube having a thickness of about 40 μm thereon. The pressure roller 22 has both ends of the core metal rotatably held by bearings (not shown) attached to the frame 24, and rotates by the driving force of a driving source (not shown).

  The fixing belt 20 is an endless cylindrical member, and is loosely fitted to the heater holder 17. The heater holder 17 is urged toward both ends of the pressure roller 22 toward the pressure roller 22 by a biasing mechanism (not shown) with a force of 98 N on one side, that is, a total of 196 N. As a result, the heater 16 comes into pressure contact with the pressure roller 22 via the fixing belt 20, and a fixing nip portion N is formed. The urging mechanism can release the urging to remove the sheet S at the time of jam clearance.

  When the pressure roller 22 rotates, the fixing belt 20 in contact with the pressure roller 22 is driven to rotate around the outer periphery of the heater holder 17 while causing the inner peripheral surface of the fixing belt 20 to contact and slide with the heater 16 by frictional force. In order to ensure the slidability between the heater holder 17 and the inner peripheral surface of the fixing belt 20, grease is applied to the inner peripheral surface of the fixing belt 20.

  The main thermistor 19 is provided so as to be in contact with the back surface of the heater 16 and detects the temperature of the heater 16. The sub thermistor 18 is provided in elastic contact with the inner peripheral surface of the fixing belt 20 and detects the temperature of the fixing belt 20. The main thermistor 19 and the sub thermistor 18 are connected to the CPU 21 via an A / D converter (not shown). The CPU 21 controls the energization of the heater 16 by the heater drive circuit 28 based on the outputs of the main thermistor 19 and the sub thermistor 18 and controls the temperature of the heater 16. The main thermistor 19 is arranged near the center of the heater 16 in the longitudinal direction. The sub thermistor 18 is provided near the end of the fixing belt 20 in the longitudinal direction.

  The guide member 23 guides the sheet S to the fixing nip N by contacting the sheet S. In the present embodiment, the guide member 23 is formed of polyphenylene sulfide (PPS) resin.

  When the fixing process is performed, first, the sheet S carrying the unfixed toner image is introduced into the fixing nip N. Next, in the fixing nip portion N, the sheet S is nipped and conveyed while the toner image carrying surface side is in contact with the outer peripheral surface of the fixing belt 20. In this transport process, the heat of the heater 16 is applied to the toner image on the sheet S via the fixing belt 20, and the unfixed toner image is melted and fixed on the sheet S. Thereafter, the sheet S that has passed through the fixing nip N is separated from the fixing belt 20 by a curvature, and is conveyed to the discharge roller 70 by the fixing discharge roller 26.

<Cooling section>
Next, a cooling unit that cools the fixing nip N will be described.

  When the sheet S conveyed to the fixing device 50 is large, in the fixing nip portion N, the sheet S passes through substantially the entire area in the sheet width direction orthogonal to the sheet S conveying direction. As a result, heat in almost the entire area of the fixing nip N is taken by the sheet S, and the temperature of the fixing nip N becomes substantially constant in the sheet width direction.

  On the other hand, when the sheet S conveyed to the fixing device 50 is small, in the fixing nip portion N, the sheet S passes only near the center in the sheet width direction. For this reason, in the fixing nip portion N, heat near the center in the sheet width direction is taken by the sheet S, but heat at both ends is not taken away, and the temperature at both ends becomes higher than the temperature near the center.

  In this case, if the temperature of the heater 16 is increased in order to maintain the fixing property at the central portion, the temperature at the central portion becomes a desired temperature, but the temperature at both ends continues to increase, thereby adversely affecting the fixing device 50 such as deformation of members. May be exerted. Therefore, the image forming apparatus H includes fans 95 and 96 and a cooling duct 30 as a cooling unit for cooling the fixing nip N in order to suppress a temperature rise at both ends of the fixing nip N in the sheet width direction.

  FIG. 3 is a schematic diagram of the fixing device 50, the fans 95 and 96, and the cooling duct 30. FIG. 4 is an internal explanatory view of the image forming apparatus H, and is a perspective view in a state where a part of an exterior of the apparatus main body is made transparent. FIG. 5 is a graph for explaining the drive timing of the fans 95 and 96.

  As shown in FIGS. 3 to 5, two fans 95 and 96 for cooling the fixing belt 20 and a cooling duct 30 are provided at both ends in the rotation axis direction of the fixing belt 20. The cooling ducts 30 are located at both ends of the fixing belt 20, and when the fixing device 50 performs the fixing process on the small-sized sheet S, the cooling duct 30 sends air to a non-passing area where the small-sized sheet S does not pass. invite. The driving of the fans 95 and 96 is turned on when the detected temperature of the sub thermistor 18 is equal to or higher than a predetermined value, and turned off when the detected temperature is equal to or lower than the predetermined value.

  With such a configuration, it is possible to suppress the temperature of the non-passage area from rising when the fixing process is continuously performed on the small-sized sheet S. In the present embodiment, although centrifugal fans such as sirocco fans are used as the fans 95 and 96, other types of fans can be used.

<Overview of duct unit>
Next, an outline of the duct unit 200 that removes dust exhausted from the image forming apparatus H will be described. In the image forming apparatus H, a duct unit 200 is attached to the apparatus main body 1. An upper cover 111 and a lower cover 112 as exterior covers are provided on the back side of the apparatus main body 1, and the duct unit 200 is attached to the apparatus main body 1 via the upper cover 111 and the lower cover 112. The duct unit 200 forms a flow path for exhausting the air warmed by the fixing device 50 to the outside of the apparatus main body 1.

  As described above, when heat is applied to the toner image on the sheet S for the fixing process in the fixing device 50, a part of the wax included in the toner is vaporized, and the vaporized wax is cooled in the air. It condenses to air containing dust. The present inventor has found that much of this dust adheres to the vicinity of the sheet inlet 400 of the fixing device 50, and particularly in a high-temperature environment, the dust has a large particle size and tends to adhere to the vicinity of the sheet inlet 400. ing.

  Here, in the BLUE ANGEL standard in Europe, the emission standard of ultra fine particles (ULTRA FINE PARTILES) is specified, and it is desired that the image forming apparatus H also reduce the emission amount of ultra fine particles. Therefore, the image forming apparatus H is equipped with a duct unit 200 for removing dust heated by the fixing device 50.

  FIG. 6 is a perspective view of the image forming apparatus H as viewed from the rear side. As shown in FIG. 6, a duct unit 200 is provided on the exterior of the image forming apparatus H so as to protrude rearward. The duct unit 200 includes an upper unit 220 having an upper duct 224 and a lower unit 240 having a lower duct 241 connected to the upper duct 224.

  FIG. 7 is a schematic diagram of the duct unit 200. As shown in FIG. 7A, a fan 91 and a fan 92 for exhausting heat are provided near the fixing device 50. The fans 91 and 92 are held by a fan holder 280, respectively, and the fan holder 280 is fastened to the rear side plate 80 (FIG. 4).

  Further, the fan 91 exhausts air around the fixing device 50. Further, the fan 92 is disposed in the vicinity of the conveyance path of the sheet S above the fan 91 (downstream in the sheet conveyance direction), and exhausts the air around the discharge unit 75 to the outside of the machine. The discharge unit 75 is a space above the fixing device 50 and a space around the discharge roller 70. The fans 91 and 92 are provided on the back side of the image forming apparatus H with respect to the rear side plate 80 (FIG. 4).

  The air containing dust generated in the fixing device 50 is exhausted from the exhaust port 227 of the apparatus main body 1 by the airflow generated by the fan 91, and is carried into the upper duct 224 from the air supply port 230 of the upper duct 224. The air containing dust carried upward by natural convection is exhausted from the exhaust port 228 of the apparatus main body 1 by the airflow generated by the fan 92, and is carried into the upper duct 224 from the air supply port 231 of the upper duct 224.

  The upper duct 224 has two air supply ports 230 and 231. It has an inner duct 233 provided on the inner surface of the cover member 225 to guide air exhausted from the inside of the apparatus main body 1 through the respective air supply ports 230 and 231. Further, an inner duct 233 is connected to the lower duct 241 of the lower unit 240, and the outer duct 226 guides air exhausted from the inside of the apparatus main body 1 to the lower unit 240 through the inner duct 233.

  The air exhausted from the exhaust ports 227 and 228 is separated from each other by a partition wall portion 229a that is a part of the inner duct 233, then merges at a junction 229b, and is conveyed to the lower duct 241 via the outer duct 226. . That is, the partition wall 229a that separates the air supplied from the air supply port 230 and the air supplied from the air supply port 231 is provided upstream of the junction 229b in the direction in which the air flows.

  The air carried to the lower duct 241 is carried to the duct exhaust port 244 (second exhaust port) side by the airflow generated by the fan 102. After the dust is collected by the filter 260 provided on the exhaust path between the exhaust ports 227 and 228 and the duct exhaust port 244, the dust is exhausted from the duct exhaust port 244 to the outside of the image forming apparatus H.

  As described above, the filter 260 is disposed downstream of the junction 229b where the air supplied from the air supply port 230 and the air supplied from the air supply port 231 merge. Thus, as compared with a configuration in which air merges in the filter 260, the area of a surface entering the filter 260 can be reduced, and the size of the filter 260 can be reduced.

  Also, as shown in FIG. 7B, by arranging the center line L1 of the fan 102 and the center line L2 of the upper duct 224 so as not to overlap with each other, the air in the lower duct 241 flows in the radial direction, and The dust can be efficiently collected by passing through a wide range of 260.

<Detailed configuration of duct unit>
Next, a detailed configuration of the duct unit 200 will be described.

  8 and 9 are perspective views of the duct unit 200. FIG. FIGS. 10 and 11 are cross-sectional views of the duct unit 200 when cut along the LL section shown in FIG. 8 and the HH section shown in FIG. 9, respectively. FIG. 12 is a sectional view of the duct unit 200 when cut along the JJ section shown in FIG. Here, FIGS. 8 and 10 are diagrams illustrating a case where the upper unit 220 is in a closed state, and FIGS. 9, 11 and 12 are diagrams illustrating a case where the upper unit 220 is in an open state.

  As shown in FIGS. 8 to 12, the upper unit 220 has shaft portions 221a and 221b. The shaft portions 221a and 221b are coaxially arranged and inserted into holes (not shown) formed in the upper cover 111, which is an exterior of the apparatus main body 1 of the image forming apparatus H. Accordingly, the upper unit 220 is supported by the upper cover 111 so as to be rotatable about the shaft portions 221a and 221b, and opens and closes with respect to the apparatus main body 1 of the image forming apparatus H by rotating. In addition, the open / close sensor 25 as a detecting unit detects that the upper unit 220 is in an open state with respect to the apparatus main body 1.

  The upper unit 220 includes a cover member 225 serving as an exterior cover, and an upper duct 224 provided inside the cover member 225. The cover member 225 is an opening / closing cover for exposing a user interface 130 such as the LAN cable connection portion 122 and the HDD insertion portion 121a provided on the apparatus main body 1 facing the cover member 225.

  Here, in the image forming apparatus H of the present embodiment, the user interface 130 is disposed on the back side of the apparatus main body 1 and on the side opposite to the side surface on which the sheet processing apparatus is mounted in the left-right direction, that is, on the fixing apparatus 50 side. ing.

  A hard disk drive 121 (hereinafter, HDD 121: Hard Disk Drive) can be inserted into and removed from the HDD insertion portion 121a. That is, with the upper unit 220 closed, the user interface 130 provided on the apparatus main body 1 is provided at a position covered by the inner duct 233 of the duct unit 200. Therefore, when the upper unit 220 is opened, the user interface 130 can be accessed, and the insertion and removal of the HDD 121 and the connection of a LAN cable (not shown) can be performed.

  The cover member 225 is provided with a sheet metal 223 for magnet catch, and a part of the upper cover 111 facing the sheet metal 223 is provided with a magnet catch 222. The cover member 225 is configured to be attractable to the apparatus main body 1 side (apparatus main body side) by the magnet catch 222.

  The magnet catch 222 urges the cover member 225 in the closing direction by magnetic force via the sheet metal 223 to attract the sheet metal 223 and hold the cover member 225 in a closed state. That is, the upper unit 220 is held in the closed state by the magnetic force of the magnet catch 222. In the present embodiment, although the magnet catch 222 is used to maintain the closed state of the upper unit 220, the upper unit 220 may be biased in a closing direction by another biasing unit.

  When the upper unit 220 is closed, the air supply port 230 is connected to an exhaust port 227 from which air in the apparatus main body 1 is exhausted by the fan 91, and the air supply port 231 is connected to the air in the apparatus main body 1 by the fan 92. It is connected to the exhaust port 228 to be discharged. The outer duct 226 of the upper duct 224 is connected to the lower duct 241 of the lower unit 240.

  That is, the inner duct 233 as the first duct is provided to be able to open and close with respect to the apparatus main body 1. When the upper unit 220 is closed with respect to the apparatus main body 1, an exhaust path from the exhaust ports 227 and 228 to the duct exhaust port 244 via the inner duct 233 is formed. When the upper unit 220 is opened with respect to the apparatus main body 1, the user interface 130 is exposed and becomes accessible. The lower duct 241 is configured as a second duct fixed to the apparatus main body 1.

  The air heated by the fixing device 50 is exhausted from the exhaust ports 227 and 228 by the fans 91 and 92, and supplied to the inner duct 233 of the upper duct 224 from the air supply ports 230 and 231. Thereafter, air is carried from the inner duct 233 to the outer duct 226 and from the outer duct 226 to the lower duct 241. In a state where the upper unit 220 of the duct unit 200 is closed with respect to the apparatus main body 1, the inner duct 233 prevents the HDD 121 from being exposed to the airflow. This prevents high-temperature air discharged from the exhaust port 228 from directly touching the HDD 121.

  Here, a sealing member 231 a is fixed to the air supply port 231 with a double-sided tape in order to seal a gap at a connection portion with the exhaust port 228. Since the size of the gap varies depending on the molding variation of the component itself, mounting play, or the like, it is preferable that the sealing member 231a compresses an elastic member thicker than the gap. In the present embodiment, Opseala JKX-1105 (manufactured by Sanwa Kako Co., Ltd.) is used as the sealing member 231a.

  Further, a sealing member 226a is fixed to the outer duct 226 with a double-sided tape in order to seal a gap between the fixing portion and the cover member 225. The sealing member 226a is preferably configured to compress the elastic member similarly to the sealing member 231a. In this embodiment, Calmflex F-2 (manufactured by Inoac Corporation) is used as the sealing member 226a.

  Further, a sealing member 241a is fixed to the lower duct 241 with a double-sided tape in order to seal a gap at a connection portion with the outer duct 226. In the present embodiment, Opseala JKX-1105 (manufactured by Sanwa Kako Co., Ltd.) is used as the sealing member 241a. Further, PF-050H (manufactured by DIC Corporation) is used on the surface to suppress wear of the sealing member 241a due to opening and closing of the upper unit 220.

  When the upper unit 220 is opened and closed, in order to suppress the wear of the sealing member 241a, the sealing member 241a is compressed in a direction (horizontal direction in the present embodiment) orthogonal to the rotation axis direction of the upper unit 220. Is desirable. However, if the connecting portion 250 with the lower duct 241 is formed according to the outer shape of the outer duct 226, the outer duct 226 and the lower duct 241 interfere when opening and closing the upper unit 220.

  Therefore, as shown in FIG. 12, the connecting portion 250 of the lower duct 241 with the outer duct 226 has a region F along the outer shape of the outer duct 226 and an end 225 a of the cover member 225 when the upper unit 220 rotates. And a region G along the passing trajectory. Thus, when opening and closing the upper unit 220, the outer duct 226 and the lower duct 241 do not interfere. Further, when the upper unit 220 is closed, the sealing member 241a can be compressed in a direction orthogonal to the axial direction of the shaft portions 221a and 221b.

  As described above, in the present embodiment, the upper unit 220 is configured to be openable and closable with respect to the apparatus main body 1, and the sealing member 241 a is provided between the apparatus main body 1 and the upper unit 220. Accordingly, a configuration in which the user interface 130 is provided near the position where the fixing device 50 is provided, which is the side opposite to the side surface on which the sheet processing apparatus is mounted, in the left-right direction of the apparatus main body 1 is considered. Even with such a configuration, it is possible to suppress a decrease in the exhaust efficiency of the duct unit 200 without reducing the operability of the user.

  FIG. 13 is a perspective view of the lower unit 240 with the fan holder 280 of the lower unit 240 removed. FIG. 14 is a perspective view of the lower unit 240 with the lower duct 241 and the filter 260 of the lower unit 240 removed. FIG. 14 shows a state in which the upper duct 224 is also removed.

  As shown in FIGS. 13 and 14, the lower duct 241 is open on the upper duct 224 side, and the opened portion is connected to the outer duct 226. The lower duct 241 is screw-fixed to fixing portions 280a, 111a, 112a provided on the upper cover 111, the lower cover 112, and the fan holder 280. The upper cover 111 (first plate-like member) and the lower cover 112 (second plate-like member), which are plate-like members, are exteriors of the apparatus main body 1, and the lower unit 240 is composed of the lower duct 241 and the upper cover 111. , The lower cover 112 forms an air flow path.

  Note that the upper cover 111 is provided with a sealing member 111b for sealing a gap at a connection portion with the lower duct 241. In the present embodiment, Opseala JKX-1105 (manufactured by Sanwa Kako Co., Ltd.) is used as the sealing member 111b, and the sealing member 111b is attached to a rib 111d provided on the upper cover 111.

  In the lower unit 240, the fan 102 and the filter 260 are provided inside the lower duct 241. A duct exhaust port 244 is provided below the lower duct 241. The duct exhaust port 244 is an exhaust port provided at the downstream end of the lower duct 241 in the direction in which air flows.

  The filter 260 has a configuration in which a filter medium 262 is fixed to a resin frame 261. The filter medium 262 is provided in a pleated shape in the frame body 261, thereby increasing the surface area and increasing the dust collection efficiency. Further, the strength is ensured by dividing the filter medium 262 into two and holding it by the frame body 261. In this embodiment, FM-9406WP (manufactured by Japan Vilene Co., Ltd.) is used as the filter medium 262.

  The vertical position of the filter 260 is regulated by the four positioning portions 243, and the filter 260 is held by being sandwiched between the inside of the lower duct 241 and the upper cover 111. Further, a sealing member 260a for sealing a gap with respect to the lower duct 241, the upper cover 111, and the lower cover 112 is provided all around the frame 261 of the filter 260. In this embodiment, Calmflex F-2 (manufactured by Inoac Corporation) is used as the sealing member 260a.

  The fan 102 is held by a fan holder 280 (holding member), and the fan holder 280 is screw-fixed to the lower cover 112. The fan 102 is provided downstream of the filter 260 in the airflow exhausted from the duct exhaust port 244. The fan 102 generates an airflow for exhausting from the duct exhaust port 244 of the lower duct 241.

  If the distance between the filter 260 and the fan 102 is too small, the airflow generated by the fan 102 may pass through only a part of the filter 260, and the dust collection efficiency may be reduced. Therefore, in the present embodiment, the gap between the filter 260 and the fan 102 is secured to about 40 mm to maintain the dust collection efficiency. That is, the distance on the exhaust path between the filter 260 and the fan 102 is preferably 40 mm or more.

  Further, the fan holder 280 is provided with a sealing member 280c for sealing a gap with the lower cover 112. Further, a sealing member 280d is provided to seal a gap with the lower duct 241. In the present embodiment, Opseala JKX-1105 (manufactured by Sanwa Kako Co., Ltd.) is used as the sealing members 280c and 280d.

  A bundle 283 (electric wire) for electrically connecting the fan 102 and a substrate (not shown) provided inside the image forming apparatus H is held by the fan holder 280. The bundled wire 283 electrically connects the fan 102 to a substrate (not shown) provided inside the apparatus main body 1 (inside the upper cover 111 and the lower cover 112) via the relay connector 284.

  FIG. 15 is a cross-sectional view of the lower unit 240 taken along the line KK shown in FIG. FIG. 15 is a sectional view showing a state where the lower duct 241 and the filter 260 are attached. As shown in FIG. 15, at the position between the upper cover 111 and the lower cover 112 as an exterior of the apparatus main body 1 facing the lower duct 241, an opening for passing the bundled wire 283 from inside the apparatus main body 1 of H is provided. 285 are formed.

  Further, the fan holder 280 is disposed to face the opening 285 with an interval, and is orthogonal to the rotation axis direction of the fan 102 (the direction of the line D shown in FIG. 15) (the front-back direction of the image forming apparatus H). A cover 280b that covers the opening 285 when viewed from above is provided. The cover portion 280b extends obliquely in a direction opposite to the flow of air flowing through the lower duct 241. That is, in the direction orthogonal to the rotation axis direction of the fan 102, the distal end of the cover 280b is located farther from the opening 285 than the base end. Further, the cover portion 280b is inclined such that the distal end portion is farther from the upper cover 111 than the base end portion.

  By providing the cover 280b in this manner, when air flows in the duct unit 200, an air flow E swirling near the opening 285 can be generated. The airflow E can suppress the air inside the apparatus main body 1 (inside the apparatus main body 1 from the upper cover 111 and the lower cover 112) from flowing into the lower duct 241 through the opening 285. For this reason, it is possible to suppress an undesired flow of air from occurring in the apparatus main body and to prevent adverse effects such as scattering of toner, and to improve the exhaust efficiency of the lower duct 241.

  In the present embodiment, the angle θ between the direction of the rotation axis of the fan 102 and the direction in which the cover 280b extends along the air flow path (the inclination angle of the cover 280b) is 10 °. By setting the angle θ to be equal to or greater than 10 ° and equal to or less than 45 °, a swirling airflow E is easily generated, and the above-described effect can be improved.

  Further, in the upper cover 111 constituting a part of the lower duct 241, the lower end 111 c on the side close to the lower cover 112 (the opening 285) is bent inside the lower duct. That is, the lower end 111c of the upper cover 111 is inclined in a direction away from the lower cover 112 (outside the apparatus body 1). With such a configuration, the opening width of the opening 285 can be maintained, so that it is easy to secure a space for passing the bundle of the fan 102 and other wiring. Further, even in the configuration in which the opening 285 for arranging the bundled wire 283 is provided, it is possible to suppress the air in the apparatus main body 1 from flowing into the duct unit 200 from the opening 285.

<About the temperature distribution and air flow rate of the duct unit>
Next, the temperature distribution of the duct unit 200 and the air flow rate will be described.

  First, the temperature distribution of the duct unit 200 will be described. FIG. 16 is a graph showing a temperature distribution in the duct of the duct unit 200. As shown in FIG. 16, the duct unit 200 is provided outside the image forming apparatus H, and is configured to be exposed to the outside air. Therefore, while the internal temperature near the inlet of the upper duct 224 is as high as 76 ° C., the internal temperature near the inlet 241x of the lower duct 241 and upstream of the filter 260 in the direction of air flow drops to 47 ° C. . That is, the filter 260 has a small difference in temperature between the first temperature of the air at the inlet of the duct and the second temperature of the air passing through the filter 260 by exposing the duct unit 200 to the outside air. It is provided at a position where the temperature becomes 20 ° C. or more (a predetermined temperature difference).

  Here, the inlets of the upper duct 224 are the air supply port 230 and the air supply port 231, and are on the upstream end side of the upper duct 224 in the direction in which the air in the duct unit 200 flows. The inlet 241x of the lower duct 241 is the upstream end side of the lower duct 241 in the direction of air flow in the duct unit 200, and is the end side opposite to the duct exhaust port 244 across the filter 260. That is.

  As described above, the duct unit 200 is configured to be exposed to the outside air, and by lowering the temperature of the air in the duct before the air reaches the filter 260, the aggregation of dust sufficiently proceeds near the filter 260. Therefore, since the aggregation facilitates collection by the filter 260, the efficiency of collecting dust by the filter 260 can be improved.

  In the vicinity of the duct exhaust port 244, the temperature of the air drops to 41 ° C. Therefore, it is possible to suppress the temperature of the air exhausted from the duct exhaust port 244 from becoming high, and to prevent the user from feeling uncomfortable.

  Next, the flow rate of air supplied and exhausted to the upper duct 224 and the lower duct 241 will be described. FIG. 17 shows a flow rate A of air supplied from the air supply port 230 of the upper duct 224, a flow rate B of air taken in from the air supply port 231 and a flow rate C of air exhausted from the duct exhaust port 244. 6 is a graph showing a relationship between the temperature of the image forming apparatus H and the temperature inside the apparatus.

  Here, the flow rate A of the air taken in from the air supply port 230 of the upper duct 224 is substantially equal to the flow rate of the air discharged from the exhaust port 227 of the apparatus main body 1 by the fan 91. The flow rate B of the air supplied from the air supply port 231 is substantially equal to the flow rate of the air discharged from the exhaust port 228 of the apparatus main body 1 by the fan 92. Further, the flow rate C of the air exhausted from the duct exhaust port 244 is substantially equal to the flow rate of the air exhausted outside the duct unit 200 by the fan 102.

  As shown in FIG. 17, when the relationship of the flow rates is C <A + B, the air heated by the fixing device 50 cannot be sufficiently exhausted, and heat is accumulated in the upper duct 224 and the lower duct 241, so that the image forming apparatus H is Raise the temperature. In this case, a problem such as toner sticking may occur.

  Therefore, the flow rate of the air supplied from the air supply ports 230 and 231 per unit time is set to be equal to or less than the flow rate of the air exhausted from the duct exhaust port 244 per unit time. That is, the relationship between the flow rates A, B, and C is C ≧ A + B. Thus, the air heated by the fixing device 50 can be sufficiently exhausted, and the temperature rise of the image forming apparatus H can be suppressed. In the present embodiment, the above-described flow rate relationship is satisfied by increasing the rotation speed of the fan 102 or increasing the size of the fan 102 with respect to the fans 91 and 92.

<Arrangement of duct unit>
Next, the arrangement of the duct unit 200 will be described.

  FIG. 18 is an arrangement diagram of the duct unit 200 and the electric system unit when the image forming apparatus H is viewed from the back side. As shown in FIG. 18, a controller board 120 having an electronic circuit for performing arithmetic processing for outputting received image data as an image is disposed on the back side of the apparatus main body 1 of the image forming apparatus H. A power supply board 123 for supplying power to the apparatus main body, an engine control board 124, an HDD 121, and the like are arranged.

  Although not shown in FIG. 18, the upper cover 111 and the lower cover 112 are provided outside as an exterior cover of the image forming apparatus H so as to cover the controller board 120, the power supply board 123, the engine control board 124, and the like. ing. That is, the controller board 120, the power supply board 123, and the engine control board 124 are provided inside the upper cover 111 and the lower cover 112.

  These electric units, especially electronic components such as the CPU mounted on the power supply board 123 and the controller board 120 are weak to heat and need to be cooled. Therefore, fans 97 and 98 for cooling electronic components mounted on these boards are provided near the controller board 120 and the power supply board 123. Further, the fans 97 and 98 and the louvers 113 and 114 which are the exterior covering the fans 97 and 98 are located at positions respectively overlapping the controller board 120 and the power supply board 123 when viewed from the back side of the apparatus main body 1 of the image forming apparatus H. It is provided in. Further, a louver 115 is provided as an exterior of the image forming apparatus H at a position overlapping the engine control board 124 when viewed from the rear side of the apparatus main body 1 of the image forming apparatus H.

  As described above, the air passing through the duct unit 200 is relatively high-temperature air heated by the fixing device 50. Therefore, when the duct unit 200 is located at a position overlapping with the electric system unit when the image forming apparatus H is viewed from the rear side, the electric system unit is easily heated by the high-temperature air passing through the duct unit 200. Become.

  Therefore, when viewed from the rear side of the apparatus main body 1 of the image forming apparatus H, the duct unit 200, the controller board 120, the HDD 121, the power supply board 123, and the engine control board 124 are arranged so as not to overlap. That is, when the image forming apparatus H is viewed from the back, the upper duct 224 is disposed beside the controller board 120, and the lower duct 241 is positioned so that a part of the lower duct 241 is located below the controller board 120 in the vertical direction. Has been arranged. Thereby, the air in the image forming apparatus H can be exhausted to the outside through the duct unit 200 without impairing the cooling efficiency of the electric system unit.

  With such a configuration, it is possible to suppress the temperature of the electric system unit requiring cooling from rising. Further, since the duct unit 200 does not block the louvers 113, 114, and 115, it is possible to prevent the cooling of the electric system unit from being hindered.

  In the present embodiment, the duct unit 200 is arranged so as to avoid the controller board 120, the HDD 121, the power supply board 123, and the engine control board 124. However, the configuration is not limited to this. Other configurations may be used as long as the duct unit 200 is arranged at least at a position avoiding the heat-sensitive electrical system unit. In addition, a configuration may be adopted in which the duct unit 200 is provided at a position where the duct unit 200 overlaps in the front-rear direction of the apparatus main body 1 with respect to a substrate of a driving system such as a motor driver on which heat-sensitive electronic components are not mounted.

<Constant speed control of fan 102>
Next, constant speed control of the fan 102 will be described with reference to FIG. FIG. 19 is a flowchart showing constant rotation speed control of the fan 102. Here, as a general method of controlling the rotation speed of the fan, a method of controlling the rotation speed of the fan with a predetermined pulse width (Duty) using a PWM (Pulse Width Modulation) signal is used.

  However, even if the drive signal is issued with the same pulse width (Duty), the actual rotation speed of the fan varies due to the variation of the voltage of the power supply board and the individual difference of the fan. The other fans (fan 91 and fan 92) installed in the apparatus main body 1 are set to have a higher pulse width (Duty) so that a required air volume can be secured even when the variation is the largest. I have. That is, the fan 91 and the fan 92 are rotated at a constant pulse width without performing the constant rotation speed control.

  The operating noise of the fan increases in proportion to the pulse width (Duty). However, the operating noise of the other fans is shielded by the peripheral unit, the exterior, the duct unit 200, and the like because they are arranged in the apparatus main body 1. Is done. Therefore, the effect on the operation sound of the entire image forming apparatus H is small.

  However, the fan 102 is only covered by the lower duct 241 outside the apparatus main body 1, and the lower surface of the lower duct 241 is provided with the duct exhaust port 244, so that the fan 102 communicates with the outside air. Therefore, the setting of the pulse width (Duty) for driving the fan 102 directly affects the operation sound of the image forming apparatus H. In addition, as described above, in order to satisfy the relationship of the flow rate in the duct C ≧ A + B, it is necessary to increase the rotation speed of the fan 102 or to increase the size of the fan 102 itself than the fans 91 and 92. For this reason, the movable sound of the fan 102 provided outside the apparatus main body 1 tends to be louder than other fans. Therefore, in the present embodiment, a fan capable of controlling the constant rotation speed is used as the fan 102.

  In the fan 102 of the present embodiment, a sensor 32 serving as a rotation speed detecting unit for detecting the rotation speed r of the fan 102 is incorporated. The CPU 21 serving as a control unit controls the fan 102 such that the rotation speed r of the fan 102 detected by the sensor 32 (the rotation speed detection unit) falls within a predetermined range e (within the range) with respect to the target rotation speed N. I do. The CPU 21 controls the fan 102 while performing feedback control on the pulse width (Duty) d of the PWM (pulse width modulation) signal.

  In step S1 of FIG. 19, the CPU 21 serving as a control unit starts a print job of the image forming apparatus H. Further, the CPU 21 turns on the fan 102 and controls the rotation speed r of the fan 102 with a predetermined pulse width (Duty) d based on a PWM (pulse width modulation) signal.

  Next, in step S2, the CPU 21 measures the rotation speed r of the fan 102 using the sensor 32 shown in FIG. Thereafter, in step S3, the CPU 21 determines whether or not the difference between the rotation speed r of the fan 102 measured by the sensor 32 and a preset target rotation speed N is smaller than a predetermined range e.

  If the difference between the rotation speed r of the fan 102 and the target rotation speed N is smaller than the predetermined range e in step S3, the process proceeds to step S4 and ends. If the difference between the rotation speed r of the fan 102 and the target rotation speed N is equal to or more than the predetermined range e, the process proceeds to step S5, and the CPU 21 determines that the target rotation speed N is the rotation speed of the fan 102 measured by the sensor 32. It is determined whether it is larger than r.

  If the target rotation speed N is larger than the rotation speed r of the fan 102 measured by the sensor 32 in step S5, the process proceeds to step S6, where the CPU 21 determines the pulse width (Duty) d of the PWM (pulse width modulation) signal. Is increased by an addition value U of the pulse width (Duty).

  In step S5, when the rotation speed r of the fan 102 measured by the sensor 32 is larger than the target rotation speed N, the process proceeds to step S7, where the CPU 21 determines the pulse width (Duty) d of the PWM (pulse width modulation) signal. Is reduced by the added value U of the pulse width (Duty).

  At this time, the CPU 21 measures the elapsed time from the time when the pulse width (Duty) d of the PWM (pulse width modulation) signal is changed in steps S6 and S7 by using the timer 31. Then, when it is detected in step S8 that the time measured by the timer 31 has passed the predetermined time t, the process returns to step S2.

  FIG. 20 is a diagram showing the relationship among the rotation speed r of the fan 102, the temperature inside the machine, the dust, the operation noise, and the condensation. The horizontal axis in FIG. 20 indicates the rotation speed r of the fan 102. As shown in FIG. 20, when the rotation speed r of the fan 102 decreases, exhaust in the apparatus main body 1 is obstructed. For this reason, the dew condensation at the upper discharge portion 75 of the fixing device 50 shown by the graph a in FIG. 20 increases, the temperature inside the device main body 1 shown by the graph b increases, and the amount of dust in the device main body 1 shown by the graph f decreases To increase.

  On the other hand, when the rotation speed r of the fan 102 increases, the operating sound of the entire image forming apparatus H shown by the graph g increases. Therefore, the threshold value of the rotation speed r of the fan 102 is set to the threshold value Nc with respect to the dew condensation of the discharge unit 75 in the upper part of the fixing device 50 shown by the graph a in FIG. The lower limit value of the rotation speed r of the fan 102 is set to be equal to or more than the threshold value Nc (not less than the threshold value) of the rotation speed r of the fan 102 with respect to the dew condensation in the apparatus main body 1 (inside the main body).

  Further, a threshold value Nt is set for the temperature in the apparatus main body 1 shown by the graph b. The lower limit value of the rotation speed r of the fan 102 is set to be equal to or more than the threshold value Nt of the rotation speed r of the fan 102 with respect to the temperature inside the apparatus main body 1 (inside the main body). The threshold value Nd is set for the dust amount in the apparatus main body 1 shown by the graph f. The lower limit value of the rotation speed r of the fan 102 is set to be equal to or more than the threshold value Nd (not less than the threshold value) of the rotation speed r of the fan 102 with respect to the amount of dust in the apparatus main body 1 (inside the main body).

  The minimum value of the variation in the rotation speed r of the fan 102 is set to N1. Further, the maximum value of the variation of the rotation speed r when performing the constant rotation speed control of the fan 102 is set to N2. When the maximum value of each of the thresholds Nc, Nt, Nd is MAX (Nc, Nt, Nd), it is necessary to set the rotation speed r of the fan 102 so as to satisfy the following equation (1).

[Equation 1]
MAX (Nc, Nt, Nd) <N1

  The maximum value of the operating sound increases by the variation of the rotation speed r of the fan 102. Therefore, assuming that the maximum value of the variation in the rotational speed r of the fan when the conventional constant duty control is performed is N3, the following equation (2) is obtained.

[Equation 2]
N2 <N3

  Thus, by performing the constant rotation speed control of the fan 102, the operating noise of the entire image forming apparatus H can be reduced. Here, the difference between the maximum value N2 of the variation of the rotation speed r when performing the constant rotation speed control of the fan 102 and the minimum value N1 of the variation of the rotation speed r of the fan 102 is defined as Δ (N2−N1). Further, the difference between the maximum value N3 of the variation in the rotation speed r of the fan when the conventional constant duty control is performed and the minimum value N1 of the variation in the rotation speed r of the fan 102 performing the constant rotation speed control is Δ (N3 −N1).

  In the present embodiment, there is a difference of Δ (N3-N1) ≒ 1000 rotations from Δ (N2-N1) ≒ 100 rotations. In the present embodiment, the difference between the target rotation speed N and the predetermined range e of the rotation speed r of the fan 102 with respect to the target rotation speed N is within 100 rotations. In this way, the fan 102 provided outside the apparatus main body 1 and having little shielding is controlled at a constant rotation speed.

  This makes it possible to select the minimum number of rotations r of the fan 102, so that the operating noise of the entire image forming apparatus H can be reduced. In addition, since the variation in the rotation speed of the fan 102 is reduced by using the constant rotation speed control, it is possible to suppress the wind noise of the fan 102 from being noticeable due to the variation in the rotation speed of the fan 102.

  Thereby, it is possible to achieve both the control of the rotation speed of the fan 102 and the reduction of the operation sound. Accordingly, it is possible to achieve both reduction in the amount of ultrafine particles (UFP) discharged, suppression of temperature rise inside the apparatus main body 1, suppression of dew condensation inside the apparatus main body 1, and reduction of the operation noise of the entire image forming apparatus H. Further, it can conform to the emission standard of ultrafine particles (UFP) specified in the BLUE ANGEL standard in Europe.

  Further, according to the present invention, the fan 102 that exhausts air to the outside of the apparatus can be stably rotated.

e: a predetermined range of the rotation speed r of the fan 102 with respect to the target rotation speed N N: a target rotation speed of the fan 102 r: a rotation speed of the fan 102 H: image forming apparatus 1: apparatus main body 21: CPU (control unit)
32 ... Sensor (rotation speed detector)
102: Fan 200: Duct unit (duct)
227 ... exhaust port (first exhaust port)
228 ... exhaust port (first exhaust port)
244 duct exhaust port (second exhaust port)

Claims (7)

In an image forming apparatus that forms an image by heating a toner image transferred to a recording material in a fixing unit and fixing the toner image on the recording material,
A first exhaust port for exhausting the air warmed by the fixing unit to the outside of the apparatus main body; and an air outlet attached to an exterior of the apparatus main body and exhausting the air exhausted from the first exhaust port to the outside of the apparatus main body. A duct forming a flow path for exhausting,
A second exhaust port provided at a downstream end of the duct in the direction in which air flows, and for exhausting air exhausted from the first exhaust port to the outside;
A fan that is provided inside the duct and upstream of the second exhaust port in a direction in which air flows, and that generates an airflow for exhausting the air from the second exhaust port;
A rotation speed detection unit that detects the rotation speed of the fan,
A control unit that controls the fan such that the rotation speed detected by the rotation speed detection unit falls within a predetermined range with respect to a target rotation speed;
An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein a difference between the predetermined range and the target rotation speed is within 100 rotations. 3.   The image forming apparatus according to claim 1, wherein a lower limit value of the number of rotations of the fan is set to be equal to or larger than a threshold value of the number of rotations of the fan with respect to a dust amount in the apparatus main body.   The image forming apparatus according to claim 1, wherein a lower limit of the number of rotations of the fan is set to be equal to or more than a threshold of the number of rotations of the fan with respect to a temperature in the apparatus main body.   The image forming apparatus according to claim 1, wherein a lower limit of the number of rotations of the fan is set to be equal to or greater than a threshold of the number of rotations of the fan with respect to dew condensation in the apparatus main body.   The image forming apparatus according to claim 1, wherein a filter that collects dust is provided inside the duct.   The image forming apparatus according to any one of claims 1 to 6, wherein the duct is attached to the exterior on the back side of the apparatus main body.