JP2010249994A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for reliably sucking hot air regardless of the size of recording paper in an image forming apparatus adapted to suck hot air around a heat roller by a suction fan and to eject the hot air to the outside of the apparatus through a ventilation duct. <P>SOLUTION: The image forming apparatus 1 includes: the heat roller 20; the ventilation duct 23 provided with one end opened to the periphery of the heat roller 20 and with the other end opened to the outside 16 of the apparatus; the suction fan 24 causing air flow inside the ventilation duct 23; movable fins 26, 27 provided at the ventilation duct 23; and a control device 50 controlling the operation of the movable fins 26, 27 according to the position of a contactless area 67 when detecting the formation of the contactless area 67 not in contact with the recording paper, on the surface of the heat roller 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus that heats and fixes an image formed on a recording sheet with a heat roller, and in particular, an image forming apparatus that sucks hot air around the heat roller with an intake fan and discharges it to the outside through a ventilation duct. About.

  Image forming apparatuses for recording images such as characters and graphics on recording paper include printers, copiers, and facsimiles. One of image forming methods by this image forming apparatus is an electrophotographic method. In an image forming apparatus employing this electrophotographic method, a fixing process is required in which the toner image formed on the photosensitive drum is transferred to the recording paper and then the transferred toner image is fixed on the recording paper. A fixing unit for execution is provided. The fixing unit includes a heat roller containing a heater, and fixes the toner image on the recording sheet by heating the recording sheet while feeding the recording sheet to the downstream side.

  In the conventional image forming apparatus configured as described above, when the hot air discharged from the heat roller stays in the apparatus and the temperature rises, the cleaning unit is provided at various locations inside the apparatus, for example, in the vicinity of the fixing unit. Problems are likely to occur. More specifically, the cleaning unit cleans the photosensitive drum after transferring the toner image, and removes the cleaning blade that removes waste toner remaining on the surface of the photosensitive drum without being transferred to the recording paper. It comprises a screw mechanism or the like that conveys waste toner to a predetermined collection container. Here, when the temperature inside the apparatus rises, the waste toner melts inside the cleaning unit, and when the printing operation ends and the temperature inside the apparatus falls, the melted waste toner coagulates. If it does so, drive load, such as a motor which drives a screw mechanism, will become large, and the problem which a motor locks will arise.

  Therefore, in the conventional image forming apparatus, an exhaust unit for discharging the hot air to the outside of the apparatus is provided so that the hot air discharged from the heat roller does not stay inside the apparatus (see, for example, FIG. 2 of Patent Document 1). The exhaust unit includes a ventilation duct having one end opened around the heat roller and the other end opened outside the apparatus, and an intake fan provided inside the ventilation duct. According to this exhaust unit, the hot air discharged from the heat roller is sucked by the intake fan and discharged to the outside of the apparatus through the ventilation duct, so that the temperature inside the apparatus does not rise.

JP 2008-164905 A

  However, in the conventional image forming apparatus, depending on the paper size of the recording paper, the hot air emitted from the heat roller may not be sufficiently discharged to the outside of the apparatus. There is a problem that occurs. More specifically, when a recording paper having a small paper size is used and the width of the recording paper is narrower than the width in the axial direction of the heat roller, the heat roller has an area that does not contact the recording paper when the recording paper passes. Arise. Since the area not in contact with the recording paper is not deprived of heat by the recording paper, the surface temperature of the heat roller is higher than that in the area in contact with the recording paper. Therefore, even if the temperature of the air around the heat roller is compared, the temperature of the air is higher around the area not in contact with the recording paper than around the area in contact with the recording paper. On the other hand, in the conventional image forming apparatus, the air suction speed by the intake fan constituting the exhaust unit is constant regardless of the position of the heat roller in the axial direction. Therefore, when recording paper with a small paper size is used, the area of the heat roller that comes into contact with the recording paper can sufficiently suck the hot air released to the surroundings, but the area that does not come into contact with the recording paper The hot air released to the surroundings cannot be sufficiently sucked. As a result, the temperature inside the apparatus rises, leading to the above-described problems.

  The present invention has been made in view of such a problem. In an image forming apparatus that draws hot air around a heat roller with an intake fan and discharges it through the ventilation duct to the outside of the apparatus, the present invention is based on the paper size of the recording paper. Therefore, it is possible to provide a means for reliably sucking hot air.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a heat roller that heats and fixes an image formed on a recording paper, one end opening around the heat roller, and the other end outside the apparatus. A ventilation duct provided in an open state; an intake fan for generating an air flow in the ventilation duct; a movable fin provided on the heat roller side of the intake fan in the ventilation duct; And a control device that controls the operation of the movable fin according to the position of the non-contact area when the occurrence of the non-contact area that does not contact the recording paper on the surface is detected.

  In the image forming apparatus according to the present invention, the control device may be configured such that the air flow speed in the non-contact area is the surface of the heat roller and the air flow in the contact area in contact with the recording paper. The operation of the movable fin is controlled so as to be faster than the speed.

  In the image forming apparatus according to the present invention, the control device controls the operation of the movable fin by controlling the operation of a motor or solenoid that drives the movable fin.

  In the image forming apparatus according to the present invention, the control device detects a position of the non-contact area in the heat roller based on a paper width and a conveyance position of the recording paper.

  In the image forming apparatus according to the present invention, the control device detects the paper width of the recording paper based on the paper size of the recording paper designated by the user.

  In the image forming apparatus according to the present invention, the control device detects the paper width of the recording paper based on the paper width of the original detected by the scanner mechanism that reads the image of the original and the enlargement / reduction ratio specified by the user. It is.

  According to the image forming apparatus of the present invention, since the control device controls the operation of the rotating fin according to the position of the non-contact area generated in the heat roller, it is discharged from the non-contact area regardless of the recording paper size. It is possible to prevent the generated hot air from staying and the temperature inside the apparatus from rising.

  Further, according to the image forming apparatus of the present invention, the control device is configured such that the air flow speed in the non-contact area is the surface of the heat roller and the air flow speed in the contact area in contact with the recording paper. Since the operation of the movable fin is controlled so as to be faster, the periphery of the non-contact region where high-temperature hot air is released can be reliably cooled.

  In addition, according to the image forming apparatus of the present invention, the control device can easily and reliably control the operation of the movable fins only by controlling the operation of the motor or the solenoid.

  Further, according to the image forming apparatus according to the present invention, the control device can easily and reliably detect the position of the non-contact area in the heat roller.

  According to the image forming apparatus of the present invention, the control device can easily and reliably reduce the width of the recording paper when the control device is configured as a facsimile machine or a printer having no image reading unit for reading an image of a document. Can be detected. Further, since it is not necessary to provide a separate mechanism for detecting the paper width of the recording paper, the apparatus can be reduced in size and cost can be reduced.

  Further, according to the image forming apparatus of the present invention, the control device can easily and reliably detect the width of the recording paper when configured as a copier having an image reading unit. Further, since it is not necessary to provide a separate mechanism for detecting the paper width of the recording paper, the apparatus can be reduced in size and cost can be reduced.

1 is a schematic longitudinal sectional view showing an image forming apparatus 1 according to an embodiment of the present invention. The schematic perspective view which shows the state in which the rotation part 39 is located in the home position 65 about the exhaust unit 17 provided with the drive mechanisms 28 and 29. FIG. The schematic perspective view which shows the state which the rotation part 39 rotated from the home position 65 about the exhaust unit 17 provided with the drive mechanisms 28 and 29. FIG. The schematic perspective view which shows the state which the rotation part 39 is located in the home position 65 about the exhaust unit 17 provided with the drive mechanisms 44 and 45. FIG. The schematic perspective view which shows the state which the rotation part 39 rotated from the home position 65 about the exhaust unit 17 provided with the drive mechanisms 44 and 45. FIG. FIG. 3 is a block diagram for explaining control of the image forming apparatus 1. FIG. 6 is an explanatory diagram for explaining the operation and effect of the exhaust unit 17 when printing on A3 size recording paper, and is a plan view schematically illustrating the exhaust unit 17 and the heat roller 20. FIG. 6 is an explanatory diagram for explaining the operation and effect of the exhaust unit 17 when printing on A4 size recording paper, and is a plan view schematically illustrating the exhaust unit 17 and the heat roller 20. FIG. 6 is an explanatory diagram for explaining the operation and effect of the exhaust unit 17 when printing on A4 size recording paper, and is a plan view schematically illustrating the exhaust unit 17 and the heat roller 20.

  First, the configuration of an image forming apparatus according to an embodiment of the present invention will be described. The image forming apparatus according to the present embodiment adopts an electrophotographic system as its image forming system, and as a copy facsimile multifunction peripheral having a facsimile communication function, an Internet facsimile communication function, a printer function, etc. in addition to a document copying function. It is configured. Here, FIG. 1 is a schematic longitudinal sectional view showing the image forming apparatus 1. FIG. 1 shows a printer mechanism 2 for printing an image on recording paper in the copy facsimile multifunction machine. Above the printer mechanism 2, an operation unit for a user to perform various operations, and A scanner unit or the like for reading an image of a document is provided.

  As shown in FIG. 1, the printer mechanism 2 constituting the image forming apparatus 1 includes a paper feed cassette 3 that stores recording paper, a separation paper feeding unit 4 that sequentially feeds recording paper from the paper feed cassette 3, and a surface. The photosensitive drum 5 on which the photosensitive layer is formed, the transfer roller 6 provided in close contact with the photosensitive drum 5, the charging unit 7 for charging the surface of the photosensitive drum 5, and the surface of the photosensitive drum 5 are irradiated with light. An exposure unit 8, a developing unit 9 that supplies toner to the surface of the photosensitive drum 5, a cleaning unit 10 that cleans the surface of the photosensitive drum 5, and a fixing unit 12 that heats and pressurizes the recording paper conveyed through the conveyance path 11. A pair of paper discharge rollers 13 for discharging the recording paper from the downstream end of the transport path 11, a paper discharge tray 14 for storing the discharged recording paper, and an exhaust for discharging the air inside the apparatus 15 to the outside 16 of the apparatus. Is provided with a knit 17, a.

  According to the printer mechanism 2 configured as described above, when the image forming operation is started, the surface of the photosensitive drum 5 is uniformly charged by the charging unit 7 and light is irradiated from the exposure unit 8 so that the photosensitive drum 5 is exposed to light. An electrostatic latent image is formed on the surface of the drum 5, and a toner image is formed by supplying toner from the developing unit 9 to the electrostatic latent image. On the other hand, with the start of the image forming operation, the recording paper stored in the paper feeding cassette 3 is taken out by the separation paper feeding unit 4 and is fed into the transport path 11. The recording paper is conveyed downstream along the conveyance path 11 and is brought into close contact with the photosensitive drum 5 by the transfer roller 6, whereby the toner image on the photosensitive drum 5 is transferred. Further, the recording paper is conveyed downstream through the conveyance path 11 and is heated and pressurized by the fixing unit 12, whereby the toner image is fixed on the recording paper. Thereafter, the recording paper is discharged to the paper discharge tray 14 by the paper discharge roller pair 13. On the other hand, after the toner image is transferred, the surface of the photosensitive drum 5 that has not been transferred to the recording paper and remains on the surface is removed by the cleaning unit 10, and then the surface is charged again by the charging unit 7. Further, the hot air released from the fixing unit 12 and the ozone gas released from the charging unit 7 are discharged to the outside of the apparatus 16 by the exhaust unit 17.

  The charging unit 7 is a so-called contact-type charging device, and applies a predetermined bias voltage from a charging bias application circuit (not shown) to a charging brush 18 provided in contact with the surface of the photosensitive drum 5 as shown in FIG. Is configured to apply. As the charging unit 7, a so-called non-contact charging device using corona discharge can be used instead of the contact type in this embodiment. In such a charging unit 7, ozone gas is generated during charging, although the degree varies depending on the method.

  As shown in FIG. 1, the fixing unit 12 includes a heat roller 20 that houses and rotates a heater 19, and a press roller 21 that is provided in close contact with the heat roller 20 and rotates according to the heat roller 20. is there. The fixing unit 12 configured as described above is disposed at a position downstream of the photosensitive drum 5 in the transport path 11 with a predetermined gap 22 from the cleaning unit 10. The fixing unit 12 pressurizes and heats the toner image on the recording paper by heating it with the heat of the heater 19 while the recording paper is nipped between the heat roller 20 and the press roller 21 and fed downstream. Fix on recording paper.

  FIG. 2 is a schematic perspective view showing the exhaust unit 17. As shown in FIGS. 1 and 2, the exhaust unit 17 includes a ventilation duct 23 that is a box-shaped member with an open top, an intake fan 24 provided at a downstream portion of the ventilation duct 23 in the intake direction, An ozone filter 25 provided immediately downstream of the intake fan 24, a pair of left and right movable fins 26, 27 provided along the intake direction from the upstream end of the ventilation duct 23 in the intake direction, and each movable fin 26, 27, a pair of left and right drive mechanisms 28, 29 provided in the vicinity of 27.

  The ventilation duct 23 is for forming an air passage 30 that is a passage for air. The ventilation duct 23 is formed such that the width of the upstream end portion in the intake direction is slightly wider than the width of the heat roller 20 in the axial direction in plan view. The width of the ventilation duct 23 is gradually narrowed in the intake direction, so that the width of the downstream end portion in the intake direction is approximately the same as that of the intake fan 24 in plan view. In addition, as shown in FIG. 2, a vent 31 is formed in the upstream portion of the ventilation duct 23 in the intake direction by partially opening the bottom. As shown in FIG. 1, the ventilation duct 23 configured as described above is disposed on the stay 32 that extends horizontally in the apparatus interior 15 at the upstream end portion in the intake direction, and covers the upper part thereof. Thus, the upper exterior housing 33 that constitutes the paper discharge tray 14 is provided. As a result, the air passage 30 surrounded by the stay 32, the ventilation duct 23 and the upper exterior housing 33 is formed.

  The intake fan 24 is for generating an air flow in the air passage 30 from the upstream side in the intake direction to the downstream side in the intake direction. As shown in FIG. 2, the intake fan 24 is provided with a plurality of blade members 34 protruding, and is driven to rotate by a motor (not shown), thereby sucking air upstream in the intake direction and downstream in the intake direction. Discharge. As shown in FIG. 1, due to the air flow generated by the intake fan 24, the hot air discharged from the fixing unit 12 and the ozone gas generated in the charging unit 7 pass through the suction holes 35 formed in the stay 32 and the air passage. 30 flows into the interior. Further, the hot air and ozone gas flow into the ventilation duct 23 through the vent 31, flow further down the air passage 30, pass through the intake fan 24, and pass from the exhaust port 36 to the outside of the apparatus 16. Discharged. At this time, ozone gas is removed from the air by the ozone filter 25 provided in the ventilation duct 23. Accordingly, the hot air discharged from the fixing unit 12 does not stay and the temperature inside the apparatus 15 does not rise, and the ozone gas generated in the charging unit 7 does not adversely affect the surrounding environment. The intake fan 24 can change the air suction speed by adjusting its rotational speed.

  The pair of left and right movable fins 26 and 27 are for changing the shape of the air passage 30. As shown in FIG. 2, each movable fin 26, 27 is a plate-like member made of resin or the like, and is fixed to a bottom portion of the ventilation duct 23, and a ventilation duct at one end of the fixing portion 37. 23, and a rotation shaft 39 provided so as to be rotatable around the support shaft 38. In addition, the shape, the number, the installation position, the rotation direction, and the like of the movable fins 26 and 27 are not limited to this embodiment, and can be appropriately changed in design.

  The pair of left and right drive mechanisms 28 and 29 are for driving the movable fins 26 and 27. As shown in FIGS. 1 and 2, each drive mechanism 28, 29 is disposed at a position below the ventilation duct 23 in the apparatus interior 15, and its drive shaft passes through the ventilation duct 23 and protrudes into the air passage 30. The motor 40, the pinion 42 fixed to the portion of the drive shaft 41 of the motor 40 that protrudes into the air passage 30, and the protrusions provided on the rotating portions 39 of the movable fins 26 and 27 to mesh with the pinion 42. And a rack 43. According to the drive mechanisms 28 and 29 configured as described above, when the motor 40 is turned on and the drive shaft 41 rotates forward or backward, the rack 43 meshed with the pinion 42 reciprocates, and as shown in FIG. Thus, the rotating part 39 integrated with the rack 43 rotates clockwise or counterclockwise around the support shaft 38. As a result, the distance between the left and right movable fins 26 and 27 and the distance between the side wall of the ventilation duct 23 and each movable fin 26 and 27 change. In this manner, by changing the shape of the air passage 30 by changing the shape of the movable fins 26 and 27, the suction speed of the air by the intake fan 24 is changed in a direction substantially perpendicular to the intake direction, that is, the axis of the heat roller 20. It can be changed depending on the position in the direction.

  FIG. 4 is a schematic perspective view showing drive mechanisms 44 and 45 according to another embodiment. In this embodiment, the drive mechanisms 44 and 45 are provided inside the air passage 30 so as to protrude from the solenoid 47 into which the plunger 46 protrudes or sinks, and the rotating portions 39 of the movable fins 26 and 27. And a pressed piece 48 fixed to the tip of the plunger 46. According to the drive mechanisms 44 and 45 configured in this manner, when the solenoid 47 is energized to cause the plunger 46 to protrude or immerse, the pressed piece 48 is pressed or pulled accordingly, as shown in FIG. As described above, the rotating portion 39 integrated with the pressed piece 48 rotates clockwise or counterclockwise around the support shaft 38. Thereby, there exists an effect similar to the case of the said drive mechanisms 28 and 29. FIG.

  Next, control of each part constituting the image forming apparatus 1 will be described with reference to the drawings. FIG. 6 is a block diagram for explaining the control of the image forming apparatus 1. The image forming apparatus 1 is connected to the control device 50 with an NCU (Network Control Unit) 51, a modem 52, a scanner mechanism 53, a codec 54, an operation unit 55, a printer interface 56, and a ROM (Read Only Memory). ) 57, a RAM (Random Access Memory) 58, an image memory 59, and the printer mechanism 2 are connected via a system bus 60.

  The NCU 51 is a network control device that controls connection and disconnection between the modem 52 and the public switched telephone network 61, and transmits dial pulses according to the telephone number of the communication partner and detects incoming calls. The modem 52 modulates / demodulates transmission / reception data, that is, modulates transmission data, which is a digital signal, into an analog voice signal and sends it to the public switched telephone network 61 via the NCU 51, and conversely from the public switched telephone network 61 to the NCU 51. The analog audio signal received via the digital signal is demodulated into a digital signal.

  The scanner mechanism 53 reads image data of a document, and details are not shown in the figure, but a scanning carriage that irradiates light to the document to be read, and a CCD color line that converts reflected light from the document into an electrical signal. It includes a sensor, an A / D converter that converts an electrical signal into a digital signal, an image processing circuit, and the like. The image data read by the scanner mechanism 53 is compression encoded by the codec 54 and stored in the image memory 59.

  The operation unit 55 includes various operation keys such as a start key for instructing the start of a document reading operation, a numeric keypad for inputting a facsimile number and the number of copies, a cursor key for performing various settings, and the like. This operation is performed in the operation unit 55. The printer interface 56 is used to electrically connect the image forming apparatus 1 to the personal computer 62 and send and receive print commands and print data when using the printer function of the image forming apparatus 1.

  The printer mechanism 2 is composed of various components as described with reference to FIG. 1, and the exhaust unit 17 which is one of the components includes the movable fins 26, 27 and an intake fan 24.

  The control device 50 controls each part of the image forming apparatus 1 while storing in the RAM 58 data that needs to be temporarily stored in accordance with a control program (not shown) stored in the ROM 57. In particular, the control device 50 controls the operation of the movable fins 26 and 27 constituting the printer mechanism 2 according to the paper size of the recording paper to be printed. The operation control of the movable fins 26 and 27 is performed by controlling the rotation of the motor 40 that constitutes the drive mechanisms 28 and 29 or the energization of the solenoid 47 that constitutes the drive mechanisms 44 and 45. Note that the recording paper size is specified by the user with the paper size specified by the user in the operation unit 55 or the paper size of the original detected by the scanner mechanism 53 when the copying function of the image forming apparatus 1 is used. The control device 50 calculates from the enlarged / reduced magnification. When the facsimile communication function of the image forming apparatus 1 is used, the control paper 50 determines the paper size of the recording paper according to the size of the image data received by facsimile. When the printer function of the image forming apparatus 1 is used, the paper size of the recording paper is designated by the user on the personal computer 62 as a client. The control device 50 also controls the rotational speed of the intake fan 24 that constitutes the printer mechanism 2.

  Next, the function and effect of the exhaust unit 17 of the image forming apparatus 1 will be described. FIGS. 7 to 9 are explanatory views for explaining the function and effect of the exhaust unit 17, and are plan views schematically showing the exhaust unit 17 and the heat roller 20. 7 to 9, for convenience of explanation, illustration of members other than the heat roller 20 constituting the stay 32 and the fixing unit 12 shown in FIG. 1 is omitted. Although the exhaust unit 17 of the type that drives the movable fins 26 and 27 by the motor 40 will be described here, the effect of the exhaust unit 17 of the type that drives the movable fins 26 and 27 by the solenoid 47 is the same.

  First, when the paper size of the recording paper to be printed is large and the paper width is approximately the same as the width of the heat roller 20 in the axial direction, for example, the A3 size in the image forming apparatus 1 capable of handling up to A3 size. When printing on a recording sheet, the heat roller 20 nips the recording sheet substantially along its axial direction. Therefore, as shown in FIG. 7, almost the entire length in the axial direction of the heat roller 20 is a contact area 63 that contacts the recording paper, and the non-contact area 64 that does not contact the recording paper is at both axial ends of the heat roller 20. Only slightly occurs. As a result, the heat roller 20 has its entire length in the axial direction coming into contact with the recording paper and is equally deprived of heat, so that the surface temperature of the heat roller 20 is substantially constant regardless of the position in the axial direction. Accordingly, the hot air released from the fixing unit 12 has a substantially constant temperature regardless of the position of the heat roller 20 in the axial direction. In this case, the control unit positions the rotating unit 39 of the movable fins 26 and 27 at the home position 65 shown in FIG. The home position 65 is a position where the air suction speed by the intake fan 24 is constant regardless of the position of the heat roller 20 in the axial direction. As described above, when hot air having a constant temperature is released over the entire fixing unit 12, the air around the heat roller 20 is sucked at the same suction speed over the entire fixing unit 12, thereby fixing the fixing unit 12. The hot air released from the unit 12 can be reliably sucked and discharged to the outside of the apparatus 16. Thereby, it can prevent that a malfunction arises in each part when hot air stays and the temperature of the apparatus inside 15 rises. In the present invention, the width of the recording paper means the length of the recording paper in a direction substantially orthogonal to the transport direction.

  On the other hand, when the paper size of the recording paper to be printed is small and the paper width is narrower than the axial width of the heat roller 20, for example, the image forming apparatus 1 capable of handling up to A3 size prints on A4 size recording paper. In this case, in the image forming apparatus 1 in which the recording paper is conveyed with the center in the width direction aligned with the center in the axial direction of the heat roller 20, the heat roller 20 nips the recording paper only in the central portion in the axial direction. Therefore, as shown in FIG. 8, a contact region 66 is generated at the axial center portion of the heat roller 20, and a wide non-contact region 67 is generated at each axial end portion of the heat roller 20. Here, the surface temperature of the heat roller 20 is higher in the non-contact area 67 where heat is not taken away by the recording paper than in the contact area 66 where heat is taken away by the recording paper. Accordingly, the hot air discharged from the fixing unit 12 is hotter at both axial ends of the heat roller 20 than at the axial center.

  When high-temperature hot air is released from both axial ends of the heat roller 20 as described above, the control device 50 positions the rotating portions 39 of the left and right movable fins 26 and 27 from the home position 65 indicated by a dotted line in FIG. Rotate to 68 respectively. That is, the control device 50 turns on the motor 40 shown in FIG. 2 to rotate its drive shaft 41, or energizes the solenoid 47 shown in FIG. The rotating portion 39 of the left movable fin 26 positioned on the left side is rotated by a predetermined angle clockwise from the home position 65 toward the paper surface of FIG. 8, while the right movable is positioned on the right side in the intake direction. The rotating portion 39 of the fin 27 is rotated counterclockwise from the home position 65 toward the paper surface of FIG. 8 by an angle substantially equal to that of the left movable fin 26. Then, in the left air passage 69 and the right air passage 70 sandwiched between the side wall of the ventilation duct 23 and the left and right movable fins 26 and 27, the passage width is larger than that when the rotating portion 39 is located at the home position 65. By narrowing and reducing the cross-sectional area of the passage, the suction speed of air by the intake fan 24 is increased. In this way, by increasing the suction speed of air by the intake fan 24 at both axial ends of the heat roller 20 from which high-temperature hot air is released, high-temperature hot air is reliably sucked and discharged to the outside of the apparatus 16. Can do. Therefore, hot air does not stay and the temperature inside the apparatus 15 does not rise.

  Note that the angle at which the rotating portion 39 of the left and right movable fins 26 and 27 is rotated is appropriately set by the control device 50 according to the size of the recording paper to be printed. For example, when printing on B5 size recording paper, which is narrower than A4 size, the details are not shown in the figure, but both non-contact areas wider than those in A4 size are formed at both ends in the axial direction of the heat roller 20, respectively. To occur. In this case, the control device 50 rotates the left and right movable fins 26 and 27 by setting the rotation angle larger than that of the A4 size. Thereby, in the left air passage 69 and the right air passage 70 sandwiched between the side wall of the ventilation duct 23 and the left and right movable fins 26 and 27, the passage width is further narrowed and the passage cross-sectional area is increased as compared with the case of the A4 size. By making it smaller, the air suction speed by the intake fan 24 is further increased. In this way, in the case of the B5 size in which a wider non-contact region is generated than in the case of the A4 size, the hot air is sucked at a both ends in the axial direction of the heat roller 20 more rapidly than in the case of the A4 size. It can be reliably sucked and discharged to the outside of the apparatus 16.

  In this embodiment, the left and right movable fins 26 and 27 are moved symmetrically. However, depending on the position of the non-contact area generated in the heat roller 20, the control device 50 causes the left and right movable fins 26 and 27 to be asymmetrical. May be operated. For example, as shown in FIG. 9, when an A4 size recording sheet is conveyed with one end in the width direction aligned with one end in the axial direction of the heat roller 20, only the other end in the axial direction of the heat roller 20 is not in contact. Region 71 occurs. In this case, the control device 50 keeps the rotating portion 39 of the left movable fin 26 at the home position 65 and moves the rotating portion 39 of the right movable fin 27 from the home position 65 toward the paper surface of FIG. Rotate to position 72 around. As described above, the high temperature generated in the non-contact region 71 can be achieved only by reducing the width of the right air passage 70 and increasing the air suction speed by the intake fan 24 only on the side where the hot air is discharged from the heat roller 20. The hot air can be reliably sucked and discharged to the outside 16 of the apparatus.

  8 and 9, when the rotating portion 39 of the left and right movable fins 26, 27 is rotated, the rotating portion 39 is provided in the central air passage 73 sandwiched between the left and right movable fins 26, 27. Since the passage width is increased and the passage cross-sectional area is increased as compared with the case where is positioned at the home position 65, the suction speed of air by the intake fan 24 is reduced. Accordingly, when the hot air discharged from the central portion in the axial direction of the heat roller 20 cannot be sufficiently sucked due to the decrease in the suction speed, the control device 50 controls the intake fan 24 to increase its rotation speed. Also good. Of course, depending on the shape of the air passage 30, the control device 50 can also reduce the rotational speed of the intake fan 24.

  Further, the drive mechanisms 28, 29, 44, and 45_ according to the present embodiment all change the shape of the air passage 30 by rotating only the rotating portions 39 of the movable fins 26 and 27. 37 may also be configured to be able to rotate around the support shaft 38, and the shape of the air passage 30 may be changed by deforming the entire movable fins 26, 27 with the drive mechanisms 28, 29, 44, 45. Further, as a means for changing the shape of the air passage 30, the drive mechanisms 28, 29, 44, other than the method of deforming the movable fins 26, 27 by the drive mechanisms 28, 29, 44, 45 as in the present embodiment. The movable fins 26 and 27 may be moved in a predetermined direction at 45.

  Further, as a means for preventing the temperature inside the apparatus 15 from rising, a method of cooling the heat roller 20 by sucking the air outside the apparatus 16 with the intake fan 24 and discharging it around the heat roller 20 may be adopted. it can. Also in this case, as in the present embodiment, in the air passage 30 corresponding to the non-contact region of the heat roller 20, if the passage width is narrowed and the air blowing speed by the intake fan 24 is increased, the temperature becomes higher than that in the contact region. The non-contact area can be reliably cooled.

  The image forming apparatus can be configured not only as a copy facsimile multifunction machine but also as a copy-only machine having only a copy function, a facsimile-only machine having only a facsimile communication function, or a printer.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 16 Outside apparatus 20 Heat roller 23 Ventilation duct 24 Intake fan 26, 27 Movable fin 50 Control apparatus 63, 66 Contact area 64, 67, 71 Non-contact area 40 Motor 47 Solenoid 53 Scanner mechanism

Claims (6)

A heat roller that heats and fixes the image formed on the recording paper;
A ventilation duct having one end opened around the heat roller and the other end opened outside the apparatus;
An intake fan that creates an air flow inside the ventilation duct;
A movable fin provided on the heat roller side of the intake fan in the ventilation duct;
A control device that controls the operation of the movable fin according to the position of the non-contact area when detecting the occurrence of a non-contact area that does not contact the recording paper on the surface of the heat roller;
An image forming apparatus comprising:   The control device is configured so that the velocity of the air flow in the non-contact region is higher than the velocity of the air flow in the contact region on the surface of the heat roller and in contact with the recording paper. The image forming apparatus according to claim 1, wherein the operation is controlled.   The image forming apparatus according to claim 1, wherein the control device controls an operation of the movable fin by controlling an operation of a motor or a solenoid that drives the movable fin.   The image forming apparatus according to claim 1, wherein the control device detects a position of the non-contact area in the heat roller based on a paper width and a conveyance position of the recording paper.   5. The image forming apparatus according to claim 1, wherein the control device detects a paper width of the recording paper based on a paper size of the recording paper designated by a user.   5. The control apparatus according to claim 1, wherein the control device detects a paper width of the recording paper based on a paper width of the original detected by a scanner mechanism that reads an image of the original and an enlargement / reduction ratio designated by a user. An image forming apparatus according to claim 1.

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