JP2009237221A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of efficiently cooling a paper conveying belt by surely sending air for cooling blown toward the paper conveying belt in a direction opposite to the moving direction of the paper conveying belt. <P>SOLUTION: The image forming apparatus is configured to include: a first blower means for blowing the air for cooling to the upstream side of a cleaning means in a belt running direction, in the non-transfer running area of a recording medium conveying belt; and a second blower means for blowing air toward the non-transfer running area side of the recording medium conveying belt from the transfer area side of the recording medium conveying belt, with respect to a negative pressure forming gap formed between the recording medium conveying belt and a fixing means, to generate negative pressure in the negative pressure forming gap and guiding the air for cooling blown to the recording medium conveying belt by the first blower means upward by the negative pressure generated in the negative pressure forming gap. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

JP 2003-29540 A JP 2003-208043 A JP 2004-325858 A JP-A-2005-241934

  Conventionally, in the image forming apparatus, a toner image formed on a photosensitive drum is transferred onto a recording sheet, and then an unfixed toner image transferred onto the recording sheet is heated and pressurized by a fixing unit. The unfixed toner image transferred onto the recording paper is fixed by heating and pressing with a fixing device, thereby forming a full-color or monochrome image.

  At that time, in the fixing device, since the unfixed toner image transferred onto the recording paper is fixed by heating and pressing, heat is released from the fixing device to the inside of the image forming device, It causes the temperature inside the device to rise. Therefore, the image forming apparatus is configured to prevent the temperature inside the image forming apparatus from excessively rising by discharging the heat released from the fixing device to the outside.

  As a technique for preventing the temperature rise in the image forming apparatus, for example, Japanese Patent Application Laid-Open No. 2003-29540, Japanese Patent Application Laid-Open No. 2003-208043, Japanese Patent Application Laid-Open No. 2004-325858, Japanese Patent Application Laid-Open No. 2005-241934, and the like. Various proposals have already been proposed.

  An image forming apparatus according to Japanese Patent Application Laid-Open No. 2003-29540 includes an intermediate transfer belt that carries a toner image that has been intermediately transferred from a photosensitive member, and a transfer paper that has received the paper transfer of the toner image from the intermediate transfer belt. In a color image forming apparatus provided with a heat fixing unit, air is blown to the surface of the intermediate transfer belt in the vicinity of the intermediate transfer belt and downstream of the paper transfer position to cool it. For this purpose, a fan is provided.

  In addition, an image forming apparatus according to Japanese Patent Application Laid-Open No. 2003-208043 includes an image forming unit that forms a toner image on a sheet, and the image forming unit that is disposed above the image forming unit and formed on the image forming unit. Fixing means for fixing the toner image by applying heat to the sheet; cooling means for sucking air from outside the apparatus main body to cool the object to be cooled; and discharging air discharged from the cooling means from the fixing means And a duct for guiding the toner image of the sheet to the surface on which the toner image is formed.

  Further, the transfer device according to the above-mentioned Japanese Patent Application Laid-Open No. 2004-325858 applies a charge having a polarity opposite to that of the toner to the back surface of the transfer belt, thereby attracting and conveying the sheet, and forming a toner image formed on the photoreceptor on the sheet. In the transfer device for transferring, a plurality of fans are provided at positions facing the transfer belt of the transfer device that houses the transfer belt, and an air flow is formed inside the transfer belt by the air blown by these, and the air current is generated inside the transfer belt by the air flow. The generated ozone is discharged.

In addition, an image forming apparatus according to Japanese Patent Application Laid-Open No. 2005-241934 includes an image carrier that carries a toner image, a transfer unit that transfers the toner image to a transfer material, and a heating unit that heats the transfer material. An image forming apparatus having a cooling unit that cools the heated transfer material at a facing portion, wherein the transfer unit contacts the transfer material heated by the heating unit.
The cooling means is configured to cool the transfer means when no transfer material is present at the facing portion.

  By the way, the problem to be solved by the present invention is that the transfer means can be cooled by the cooling means when the transfer material is not present in the facing portion, as disclosed in JP-A-2005-241934. Compared to the case of the configuration, the cooling air blown toward the paper transport belt can be reliably sent in the direction opposite to the moving direction of the paper transport belt, and the paper transport belt can be cooled efficiently. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

That is, the invention described in claim 1 includes an image forming unit that forms a plurality of toner images of different colors,
A recording medium conveying belt for conveying the recording medium from the lower side to the upper side while holding the recording medium;
Transfer means for transferring a plurality of toner images formed by the image forming unit to a recording medium conveyed by the recording medium conveying belt;
A fixing unit disposed on an upper portion of the recording medium conveying belt via a gap for forming a negative pressure, and performing a fixing process on the recording medium conveyed by the recording medium conveying belt;
A cleaning unit that is disposed in a non-transfer travel region located on the opposite side of the transfer region of the plurality of toner images of the recording medium transport belt and removes foreign matters such as toner attached to the recording medium transport belt;
A first air blowing unit that blows cooling air to a non-transfer running region of the recording medium conveying belt and upstream of the cleaning unit in a belt running direction;
By blowing air from the transfer area side of the recording medium conveyance belt to the non-transfer running area side with respect to the negative pressure forming gap formed between the recording medium conveyance belt and the fixing unit. The negative pressure generated in the gap for forming the negative pressure is generated in the gap for forming the negative pressure by generating a negative pressure in the gap for forming the negative pressure and blowing the cooling air blown to the belt for transporting the recording medium by the first blowing unit. An image forming apparatus comprising: a second air blowing unit for guiding the air upward.

According to a second aspect of the present invention, the recording medium disposed outside the non-transfer running area of the recording medium conveying belt and fixed by the fixing means is reversed. Including a recording medium conveying path for both sides for conveying again to the recording medium conveying belt at
2. The image formation according to claim 1, wherein the first air blowing unit is configured to be able to blow cooling air to a recording medium that moves in the recording medium conveying path for both sides. Device.

  According to the first aspect of the present invention, the cooling air blown toward the recording medium conveying belt can be reliably sent in the direction opposite to the traveling direction of the recording medium conveying belt. The conveying belt can be efficiently cooled.

  According to the second aspect of the present invention, in the image forming apparatus configured to be able to form images on both sides of the recording medium, the recording medium that has been subjected to fixing processing by the fixing unit and heated is again When the recording medium is conveyed to the recording medium conveying belt, the heated recording medium can be efficiently cooled.

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

Embodiment 1
FIG. 2 shows a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention.

  In FIG. 2, reference numeral 1 denotes a main body of a tandem-type full-color printer as an image forming apparatus main body. Inside the printer main body 1, an image forming unit 2 is arranged at the upper and lower sides of the printer main body 1. It is arrange | positioned up and down along the perpendicular direction which is a direction. Further, inside the full color printer main body 1, a recording medium onto which toner images of a plurality of colors formed by the image forming unit 2 are transferred is adsorbed to one side (right side in the illustrated example) of the image forming unit 2. The control unit 4 having a control circuit and the like is provided on the other side (left side in the illustrated example) of the image forming unit 2. Power supply circuit units 5 each including a high-voltage power supply circuit and the like are disposed obliquely below 2. A paper feeding device 6 for feeding recording paper 37 or the like as a recording medium is disposed at the bottom of the full color printer main body 1.

  The image forming unit 2 includes four process cartridges 7Y, 7M, 7C, and 7K that form toner images of yellow (Y), magenta (M), cyan (C), and black (K) in order from the bottom. These four process cartridges 7Y, 7M, 7C, and 7K are arranged in parallel at regular intervals along the vertical direction.

  These four process cartridges 7Y, 7M, 7C, and 7K are configured in the same manner except for the color of the image to be formed. As shown in FIG. 2, at a predetermined rotational speed along the direction of the arrow. The surface of the photosensitive drum 8 is rotated by a photosensitive drum 8 as an image bearing member that is driven to rotate, a charging roll 9 for primary charging that uniformly charges the surface of the photosensitive drum 8, and an image exposure device 21 described later. An image exposure passage 10 for performing image exposure corresponding to each color to form an electrostatic latent image, and developing means for developing the electrostatic latent image formed on the photosensitive drum 8 with a corresponding color toner. Developing device 11 and a cleaning device 12 for cleaning residual toner remaining on the photosensitive drum 8.

  As shown in FIG. 2, the image exposure apparatus 21 is configured in common to four process cartridges 7Y, 7M, 7C, and 7K of yellow (Y), magenta (M), cyan (C), and black (K). Four semiconductor lasers 14 that emit laser beams LB based on image data of each color of yellow (Y), magenta (M), cyan (C), and black (K), and the four semiconductor lasers 14 A collimator lens 15 that collimates the four laser beams LB emitted from each other, a reflection mirror 16 that reflects the laser beam LB emitted from the semiconductor laser 14, and a laser beam LB reflected by the reflection mirror 16. The rotary polygon mirror 17 that deflects and scans the laser beam LB reflected by the rotary polygon mirror 17 and the image forming units 7Y, 7M, 7C, and 7K. A plurality of reflecting mirrors 18, 19 for scanning exposure on the photosensitive drum 8, and is configured with a transparent glass 20 that transmits the laser beam LB. The reflection mirrors 18 and 19 have a function of changing the focal length (f) according to the deflection angle (θ) of the laser beam LB.

  On the other hand, as shown in FIG. 2, a control unit 4 is disposed inside the full-color printer main body 1, and the control unit 4 includes, for example, an image for performing predetermined image processing on image data. A processing device 30 is provided. The image processing apparatus 30 sequentially outputs image data of each color of yellow (Y), magenta (M), cyan (C), and black (K) to the image exposure apparatus 10, and the image exposure apparatus 10 outputs the image data. The four laser beams LB emitted according to the above are scanned and exposed on the respective photosensitive drums 8Y, 8M, 8C, and 8K to form electrostatic latent images. The electrostatic latent images formed on the photosensitive drums 8Y, 8M, 8C, and 8K are respectively yellow (Y), magenta (M), cyan (C), and cyan by developing devices 11Y, 11M, 11C, and 11K. The toner image is developed as a black (K) color toner image.

  Further, as shown in FIG. 2, the paper transport belt unit 3 is provided with a paper transport belt 31 that circulates and moves without a break as an endless belt, and the paper transport belt 31 includes each process cartridge 7Y, Recording paper 37 as a recording medium to which toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K) formed by 7M, 7C, and 7K are electrostatically adsorbed It is comprised so that it may convey in the state which carried out. The paper transport belt unit 3 is integrally formed with a transport roll 49 provided in a reversing paper transport path 50 (to be described later). When a jam or the like of the recording paper 37 occurs, the printer body By opening the front cover 32, it is possible to move to a retracted position rotated clockwise with respect to the printer body 1.

  As shown in FIG. 2, the paper transport belt 31 includes a drive roll 33, a follower roll 34, a first idler roll 35, and a second idler, which are arranged as a stretch roll arranged vertically along the vertical direction. It is stretched between the roll 36 with a predetermined tension. For example, the drive roll 33 is rotationally driven through a gear or the like by a drive motor (not shown) and circulates in a clockwise direction at a predetermined speed. Is configured to do. For example, the distance between the driving roll 33 and the driven roll 34 is set to be substantially equal to the length of the A3 size recording sheet 37, but is not limited thereto, and the distance between the driving roll 33 and the driven roll 34 is not limited thereto. Of course, it may be set arbitrarily. As the paper transport belt 31, for example, a flexible synthetic resin film such as polyimide or polyimide amide formed in an endless belt shape is used.

  Further, an image quality adjustment pattern is transferred onto the paper transport belt 31 at a predetermined timing, and yellow (Y), magenta (M), cyan (C) of the paper transport belt 31 is configured. ), The non-transfer running area 31b on the opposite side of the running area 31a where the black (K) process cartridges 7Y, 7M, 7C, and 7K are disposed is used for adjusting the image quality transferred onto the paper conveying belt 31. A pattern detection device 38 for optically detecting the pattern is disposed, and the toner constituting the image quality adjustment pattern on the paper transport belt 31 is disposed downstream of the pattern detection device 38 in the belt movement direction. A cleaning device 40 having a cleaning blade 39 for removing foreign substances such as the like is disposed.

  Further, on the surface of the driven roll 34, as shown in FIG. 2, a suction roll 41 for electrostatically attracting the recording paper 37 to the surface of the paper transport belt 31 is applied via the paper transport belt 31. It arrange | positions so that it may contact | connect. For example, the suction roll 41 is configured by covering the surface of a metal core bar with a conductive rubber similarly to the charging roll 9 of the process cartridges 7Y, 7M, 7C, and 7K. A bias voltage for adsorption is applied. The suction roll 41 is configured to electrostatically charge the transfer paper 37 sent from the paper supply device 6 and suck it onto the surface of the paper transport belt 31.

  Yellow (Y), magenta (M), cyan (C), and black (K) toners formed on the photosensitive drums 8Y, 8M, 8C, and 8K of the process cartridges 7Y, 7M, 7C, and 7K. As shown in FIG. 2, the images are transferred onto the recording paper 37 conveyed while being attracted to the surface of the paper conveying belt 31 in a superimposed manner by the transfer rolls 42Y, 42M, 42C, and 42K. Is done. The transfer rolls 42Y, 42M, 42C, and 42K are integrally attached to the paper transport belt unit 3 side.

  As shown in FIG. 2, the recording sheet 37 is fed from a sheet feeding device 6 disposed at the bottom of the printer body 1. The paper feeding device 6 includes a paper tray 43 that stores recording paper 37 having a desired size and material, and the recording paper 37 having a desired size and material is fed from the paper tray 43 by a feeding roll 44. In addition to being fed, the sheets are fed one by one by the supply roll 45 and the separating roll 46 and conveyed to the suction position on the sheet conveying belt 31 through the registration roll 43 at a predetermined timing. It has become.

  The recording paper 37 is a sheet-like member, for example, various sizes such as A4 size, A3 size, B5 size and B4 size, and thick paper such as plain paper and coated paper, an OHP sheet, etc. Various materials are used.

  Then, as shown in FIG. 2, the recording paper 37 on which the toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are transferred in a multiple manner are recorded on the recording paper 37 itself. After being separated from the paper conveyance belt 31 by the rigidity (so-called stiffness), it is conveyed to the fixing device 47, and the toner image of each color is fixed on the recording paper 37 by heat and pressure by the fixing device 47. The fixing device 47 includes a heating roll 48 and a pressure belt 49 or a pressure roll that is in pressure contact with the heating roll 48, and is transferred onto the recording paper 37 by the heating roll 48 and the pressure belt 49. An unfixed toner image is configured to be fixed on the recording paper 37.

  The sheet conveying belt 31 and the fixing device 47 are arranged close to each other with a small negative pressure forming gap 51 therebetween, and the recording sheet 37 separated from the fixing device 47 is conveyed by a sheet. The belt 31 is conveyed to the fixing device 47 by the conveying force of the belt 31. Thereafter, the recording paper 37 on which the toner images of the respective colors are fixed is discharged from the discharge port 53 by the discharge roll 52 onto the discharge tray 54 provided at the upper part of the full-color printer main body 1 with the print surface facing down. The printing operation is finished.

  The full-color printer is capable of printing not only full-color images but also desired color images such as monochrome, and yellow (Y) and magenta (M) depending on the color of the image to be printed. , Cyan (C), black (K), or some of the process cartridges 7Y, 7M, 7C, and 7K form a toner image.

  Further, when images are formed on both sides of the recording paper 37 by the full-color printer, the recording paper 37 on which the image is fixed on one side by the fixing device 44 is not directly discharged onto the discharge tray 46 by the discharge roll 45. In the state where the trailing edge of the recording sheet 37 is held by the discharge roll 52, the discharge roll 52 is reversed, and the transfer path of the recording sheet 37 is switched to the upper transfer path 55 by a switching gate (not shown). 1 is conveyed to a reversing paper conveyance path 50 provided with conveyance rolls 56 and 57 provided along one side surface. Then, the recording paper 37 conveyed to the reversing paper conveyance path 50 is conveyed again to the suction position of the paper conveyance belt 31 by the registration roll 43 with the front and back sides reversed, and a toner image is formed on the back surface. After the transfer, the fixing device 47 performs a fixing process with heat and pressure, and the paper is discharged onto a discharge tray 54 provided on the upper portion of the printer main body 1 by a discharge roll 52.

  In FIG. 2, reference numeral 58 denotes a paper feed roll for feeding a transfer material of a desired size and material from a manual feed tray 59 provided on the side surface of the printer body 1, and reference numeral 60 denotes a paper feed roll 58. Each of the conveyance rolls that convey the paper-recorded recording medium to the registration roll 43 is shown.

  Furthermore, in this embodiment, as shown in FIG. 3, the yellow (Y), magenta (M), cyan (C), and black (K) process cartridges 7Y, 7M, 7C, and 7K are rotationally driven. The upper first unit 121 having the photosensitive drum 8 and the charging roll 9 and the cleaning device 12, and the lower second unit having the developing device 11 for developing the electrostatic latent image formed on the photosensitive drum 8. Unit 122.

  As shown in FIG. 3, the first unit 121 and the second unit 122 are connected to the photosensitive drum 8 and the developing roll 116 via a fulcrum 123 provided at the end opposite to the photosensitive drum 8. Are connected to each other so as to be swingable in the direction in which they are separated from each other, and are provided at both end portions along the axial direction of the photosensitive drum 8 of the first unit 121 and the developing roll 116 of the second unit 122. The urging means 124 such as a coil spring is urged so as to come into contact with the non-tracking roll.

  The process cartridges 7Y, 7M, 7C, and 7K configured as described above are individually provided by opening a front cover 32 that is openable and closable on the front surface of the printer body 1, as shown in FIG. It is configured to be detachable with respect to the printer main body 1, and when the photosensitive drum 8 is deteriorated or when the developer stored in the developing device 11 becomes empty, the process cartridge 7Y, The user can easily perform maintenance by removing it from the printer body 1 every 7M, 7C, and 7K and replacing it with new process cartridges 7Y, 7M, 7C, and 7K.

  Further, in the developer accommodating chamber 13 of the developing device 11 of the process cartridges 7Y, 7M, 7C, and 7K, as shown in FIG. 4, a one-component developer 110 consisting only of toner, or two consisting of toner and carrier. The developer 110 of the component is accommodated, and the developer 110 is agitated in the developer accommodating chamber 13, and is an end portion on the developing device 11 side in the longitudinal direction of the developer accommodating chamber 13. Two film-shaped agitators 112 as a developer agitating member for discharging the developer 110 from the developer discharge port 111 formed at one end of the developer are arranged in parallel.

  As shown in FIGS. 4 and 5, these two film-like agitators 112 discharge the developer 110 from the developer discharge port 111 while stirring the developer 110 stored in the developer storage chamber 13. For this purpose, a synthetic resin film 112b made of a Mylar film or the like is provided so as to protrude toward the outer periphery in the radial direction of the rotating shaft 112a made of synthetic resin. The synthetic resin film 112b is set to have such a length that the tip thereof is in contact with one side surface from the bottom surface of the developer storage chamber 13, and the developer 110 adheres to the bottom surface and one side surface of the developer storage chamber 13. In this way, the developer 110 is scraped into the developer discharge port 111.

  In addition, the developer 110 transports the developer 110 from the developer accommodating chamber 13 to the developing chamber 113 of the developing device 11 between the developer accommodating chamber 13 and the developing chamber 113 communicating with the developer discharging port 111. An agent transport device 130 is provided.

  In this embodiment, a one-component developer 110 made only of toner is accommodated in the developer accommodating chamber 13, and the developer accommodating chamber 13 is a toner accommodating chamber.

  As shown in FIG. 4, an agitation auger 114 that conveys the developer 110 supplied into the developing chamber 113 along the direction of the arrow while being agitated is rotatably disposed in the developing chamber 113. In addition, a supply auger 115 for supplying development to a developing roll 116 as a developer carrying member while agitating and conveying the developer 110 is disposed in parallel with the agitating auger 114. Further, the partition wall 117 provided between the stirring auger 114 and the supply auger 115 has a developer at both end portions along the axial direction of the stirring auger 114 and the supply auger 115 as shown in FIG. Passages 118 and 119 for delivering 110 are provided.

  In the developing device 11, as shown in FIGS. 4 and 5, the layer thickness of the developer 110 supplied to the developing roll 116 by the supply auger 115 is regulated to a predetermined value by the layer thickness regulating roll 120. On the other hand, the photosensitive drum 8 is conveyed to a developing area facing the photosensitive drum 8, and the electrostatic latent image formed on the surface of the photosensitive drum 8 is developed with toner of a predetermined color.

  As the developer 110 accommodated in the developing device 11, a two-component developer 110 composed of toner and carrier is used, but a one-component developer composed only of toner may be used. Of course it is good.

  Further, as shown in FIG. 3, the cleaning device 12 removes the transfer residual toner remaining on the surface of the photosensitive drum 8 by the cleaning blade 26, and the removed transfer residual toner is put inside the cleaning device 12. It is comprised so that it may collect | recover and accommodate.

By the way, in this embodiment, an image forming unit that forms a plurality of toner images of different colors,
A recording medium conveying belt for conveying the recording medium from the lower side to the upper side while holding the recording medium;
Transfer means for transferring a plurality of toner images formed by the image forming unit to a recording medium conveyed by the recording medium conveying belt;
A fixing unit disposed on an upper portion of the recording medium conveying belt via a gap for forming a negative pressure, and performing a fixing process on the recording medium conveyed by the recording medium conveying belt;
A cleaning unit that is disposed in a non-transfer travel region located on the opposite side of the transfer region of the plurality of toner images of the recording medium transport belt and removes foreign matters such as toner attached to the recording medium transport belt;
A first air blowing unit that blows cooling air to a non-transfer running region of the recording medium conveying belt and upstream of the cleaning unit in a belt running direction;
By blowing air from the transfer area side of the recording medium conveyance belt to the non-transfer running area side with respect to the negative pressure forming gap formed between the recording medium conveyance belt and the fixing unit. The negative pressure generated in the gap for forming the negative pressure is generated in the gap for forming the negative pressure by generating a negative pressure in the gap for forming the negative pressure and blowing the cooling air blown to the belt for transporting the recording medium by the first blowing unit. And second air blowing means for guiding upward.

In this embodiment, the recording medium disposed outside the non-transfer running area of the recording medium conveying belt and subjected to the fixing process by the fixing unit is recorded again with the front and back reversed. A double-sided recording medium conveyance path for conveying to a medium conveyance belt,
The first air blowing means is configured to be able to blow cooling air to the recording medium moving in the double-side recording medium conveyance path.

  That is, in this embodiment, as shown in FIG. 1, the upper part of the front side (right side in FIG. 1) in the printer main body 1 and slightly above the upper end of the paper transport belt 31, A first cooling fan 71 serving as a first blowing unit that blows cooling air to the upstream side in the belt traveling direction of the cleaning device is disposed at the same position as the lower end surface and outside the reversing paper conveyance path 50. Is provided. As this 1st cooling fan 71, what provided the several rotary blade in the outer periphery of the rotating shaft of a drive motor is used, for example.

  As shown in FIGS. 1, 7, and 8, the first cooling fan 71 is a front side of the printer main body 1, and is an intake port that is opened in the ceiling surface of the recess 72 that accommodates the manual feed tray 59. As shown in FIGS. 73 to 75 and FIG. 6, air is sucked from the outside of the printer main body 1 through the intake opening 76 located at the lower end of the manual feed tray 59.

  As shown in FIG. 1, the first cooling fan 71 is disposed so as to blow cooling air A <b> 1 directly toward the upper end portion 50 a of the sheet conveyance path 50 for reversal, and the reversing fan 71. The cooling air A2 is directly blown to the upstream side in the belt running direction of the cleaning device through the slit provided in the upper end portion 50a of the paper transport path 50. . As shown in FIG. 1, the first cooling fan 71 blows air upward from the front side of the paper conveyance path 50 for reversal, cools the back side of the operation panel P, and upper end surface of the printer main body 1. The cooling air A <b> 3 is formed so as to exhaust the air from the exhaust port 77 provided to the outside.

  Further, the region 31b of the sheet conveying belt 31 to which the cooling air A2 is blown by the first cooling fan 71 is located on the downstream side of the belt traveling of the pattern detection device 38 disposed at the upper end of the sheet conveying belt 31. As described later, it is configured to move above the paper transport belt 31 through a gap between the paper transport belt 31 and the pattern detection device 38. In the width direction orthogonal to the traveling direction of the paper transport belt 31, cooling air A2 is directly blown by the first cooling fan 71 to the area where the pattern detection device 38 is not provided.

  A part of the cooling air A3 is exhausted to the outside from the discharge port 53 and the exhaust port 77 via the transport path 55.

  Further, as shown in FIGS. 1 and 6, the printer main body 1 has a second position below the inclined discharge surface of the discharge tray 54 and at a position corresponding to the rear end of the paper discharge direction. A second blower fan 78 is provided as a blower. As the second cooling fan 78, for example, as in the first cooling fan 71, a fan provided with a plurality of rotating blades on the outer periphery of the rotation shaft of the drive motor is used. In addition, as this 2nd ventilation fan 78, you may use the thing with larger ventilation volume than the 1st cooling fan 71. FIG.

  The outside fresh air A4 sucked from the air inlet 79 opened on the side surface of the printer main body 1 by the second cooling fan 78 is used for cooling the fixing device formed in the lower portion of the discharge tray 54 in the printer main body 1. The air is sent to the outer periphery of the fixing device 47 through the air passage 80. In the air passage 80 for cooling the fixing device, the corner portion where the housing 47 of the fixing device 47 is located is supplied with cooling air A4 blown through the air passage 80 for cooling the fixing device on the bottom surface of the fixing device 47. A first branch air passage 81 that blows air substantially horizontally along the second branch air passage 82 that blows upward along a standing wall on the front side of the fixing device 47 is a branch portion.

  The first branch air passage 81 branched by the branch portion is formed along a substantially horizontal direction, and a part thereof is discharged from the paper discharge portion of the fixing device 47 through the inside of the fixing device 47. The other portion communicates with a negative pressure forming gap 51 formed between the sheet conveying belt 31 and the fixing device 47.

  In addition, the cooling air introduced by the second cooling fan 78 and passing through the negative pressure forming gap 51, together with the cooling air A1 to A3 introduced by the first cooling fan 71, is used for reversal. Part of the paper is transported to the outside through an exhaust port 77 opened at the upper end of the printer body 1 and the other part is ejected to join the paper transport path 50 for reversal. The air is exhausted from the port 53 to the outside of the printer main body 1.

  In the above configuration, in the full-color printer according to this embodiment, the cooling air blown toward the recording medium conveyance belt is directed in the direction opposite to the traveling direction of the recording medium conveyance belt as follows. Therefore, the recording medium conveying belt can be efficiently cooled.

  That is, in the full-color printer according to this embodiment, as shown in FIG. 2, the process cartridges 2Y, 2M, 2C, and 2K for yellow (Y), magenta (M), cyan (C), and black (K) are provided. Image exposure is performed on the photosensitive drums 3Y, 3M, 3C, and 3K according to the image data of each color by the image exposure device 5, and the surface of the photosensitive drums 3Y, 3M, 3C, and 3K is yellow (Y). , Magenta (M), cyan (C), black (K) electrostatic latent images corresponding to the image data of each color are formed and static images formed on the surfaces of the photosensitive drums 3Y, 3M, 3C, 3K. The electrostatic latent image is developed by the developing devices 6Y, 6M, 6C, and 6K to form toner images of corresponding colors.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images formed on the photosensitive drums 3Y, 3M, 3C, and 3K are multiplexed on the intermediate transfer belt 10. Then, it is secondarily transferred onto the recording paper 18, fixed by the fixing device 19, and discharged onto a discharge tray provided on the upper portion of the printer main body 1.

  By the way, the full-color printer is configured to fix the unfixed toner image secondarily transferred onto the recording paper 18 on the recording paper 18 by heating and pressurizing the recording paper 18 by the fixing device 19. Yes. For this reason, the inside of the printer main body 1 rises as it is due to heat released from the fixing device 19, and each process cartridge of yellow (Y), magenta (M), cyan (C), and black (K). The toner in the 2Y, 2M, 2C, and 2K developing devices 11 aggregates to generate blocking toner, which may cause defective development.

  Therefore, in the full-color printer, as shown in FIG. 6, the second cooling fan 78 is driven at a predetermined timing (including at least during printing) such as when in standby or when the internal temperature rises to a predetermined value or more. At the same time, by driving the first cooling fan 71 in conjunction with the printing operation, external air A1 to A4 is introduced into the inside of the printer main body 1, and the first and second cooling fans 71 and 78 introduce the air. The inside of the printer main body 1 is cooled by the introduced cooling air A1 to A4.

  At this time, the second cooling fan 78 introduces air outside the printer main body 1 from an air inlet 79 opened at the upper end on the back side of the printer main body 1, and the cooling fan introduced from the air inlet 79. The air A4 is blown to the outer periphery of the fixing device 47 through the fixing device cooling air passage 80 formed in the lower portion of the discharge tray 54. A part of the cooling air A 4 blown through the fixing device cooling air passage 80 is sent substantially horizontally along the bottom surface of the fixing device 47, and a part of the cooling air A 4 is sent to the fixing device 47. The air is discharged from the paper discharge unit of the fixing device 47 to the outside via the paper discharge port 53 via the inside. The other portion is sent to the non-transfer running area 31b of the paper transport belt 31 through the negative pressure forming gap 51 formed between the paper transport belt 31 and the fixing device 47, and the first portion. Along with the air A1 to A3 for cooling introduced by the cooling fan 71, a part of the air is exhausted to the outside from an exhaust port 77 opened at the upper end portion of the printer body 1 through the paper transport path 50 for reversal. The other portions are exhausted to the outside of the printer main body 1 from a paper discharge port 53 that joins the paper conveyance path 50 for reversal.

  At this time, since the gap 51 for forming negative pressure is set to be narrower than the other passage between the sheet conveying belt 31 and the fixing device 47, the gap 51 for forming negative pressure is set to be smaller. The flowing cooling air A5 becomes a negative pressure with respect to other regions as the flow velocity increases and the pressure decreases as understood from Bernoulli's theorem, as compared with the flow through other passages. As a result, the cooling air A1 to A3 introduced by the first cooling fan 71 is sucked by the cooling air A5 that has passed through the negative pressure forming gap 51 and has become negative pressure, and the sheet conveying belt. 31 flows upward in the direction opposite to the traveling direction of 31 and merges with the air A5 that has passed through the gap 51 for forming a negative pressure. The other part is exhausted to the outside of the printer main body 1 from the paper discharge port 54 that joins the reversing paper transport path 50.

  Accordingly, the cooling air A2 blown onto the upper portion of the sheet conveying belt 31 by the first cooling fan 71 flows upward in the direction opposite to the traveling direction of the sheet conveying belt 31, and the negative pressure forming gap is formed. The upper part of the sheet conveying belt 41 and the upper part of the sheet conveying path 50 for reversal can be efficiently cooled by merging with the air A5 that has passed 51.

  By the way, the inventors have 25 pm between the present invention related to the prototype shown in FIG. 2 and an image forming apparatus in which Japanese Patent Application Laid-Open No. 2005-241934 is applied to the prototype shown in FIG. During the double-sided image formation, an experiment was conducted to compare the cooling effect using a cooling fan having a diameter of 80 × 80 and a thickness of 25 mm.

  FIG. 9 is a graph showing the results of the experiment.

  As is apparent from FIG. 9, in the present invention, the temperature can be lowered by −13.2 ° C. in the auger on the supply side of the developing device and by −7.2 ° C. in the trimmer portion, as compared with the prior art. I understood.

  Further, in the present invention relating to the prototype shown in FIG. 2, the present inventors set the temperature of the end of the auger on the supply side of the black developing device and the end of the auger on the supply side of the yellow development device as a function of time. Experiments that measure over time were performed.

  FIG. 10 is a graph showing the results of the experiment.

  As is apparent from FIG. 10, in the present invention, the auger on the supply side of the black developing device can be suppressed to a target value of 62 ° C. or less, and the trimmer portion of the black developing device can be controlled at the target value. It turned out that it can suppress to a certain 46 degrees C or less.

FIG. 1 is a configuration diagram showing a main part of a tandem full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram showing a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a sectional view showing the process cartridge. FIG. 4 is a sectional view showing the developing device. FIG. 5 is a perspective configuration diagram showing the developing device. FIG. 6 is a block diagram showing an air flow of the tandem type full color printer as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 7 is a perspective configuration diagram showing the printer body. FIG. 8 is a perspective configuration diagram showing an air intake port of the printer main body. FIG. 9 is a graph showing experimental results. FIG. 10 is a graph showing experimental results.

Explanation of symbols

  1: printer main body, 50: sheet conveyance path for reversal, 59: manual feed tray, 71: first cooling fan, 76: opening for intake, 77: exhaust port, 78: second blower fan.

Claims (2)

An image forming unit for forming a plurality of toner images of different colors;
A recording medium conveying belt for conveying the recording medium from the lower side to the upper side while holding the recording medium;
Transfer means for transferring a plurality of toner images formed by the image forming unit to a recording medium conveyed by the recording medium conveying belt;
A fixing unit disposed on an upper portion of the recording medium conveying belt via a gap for forming a negative pressure, and performing a fixing process on the recording medium conveyed by the recording medium conveying belt;
A cleaning unit that is disposed in a non-transfer travel region located on the opposite side of the transfer region of the plurality of toner images of the recording medium transport belt and removes foreign matters such as toner adhering to the recording medium transport belt;
A first air blowing unit that blows cooling air to a non-transfer running region of the recording medium conveying belt and upstream of the cleaning unit in a belt running direction;
By blowing air from the transfer area side of the recording medium conveyance belt to the non-transfer running area side with respect to the negative pressure forming gap formed between the recording medium conveyance belt and the fixing unit. The negative pressure generated in the gap for forming the negative pressure is generated in the gap for forming the negative pressure by generating a negative pressure in the gap for forming the negative pressure and blowing the cooling air blown to the belt for transporting the recording medium by the first blowing unit. An image forming apparatus comprising: a second air blowing means for guiding the air upwardly. The recording medium disposed outside the non-transfer running area of the recording medium conveying belt and fixed by the fixing means is conveyed again to the recording medium conveying belt with its front and back reversed. It has a recording medium conveyance path for both sides,
2. The image formation according to claim 1, wherein the first air blowing unit is configured to be able to blow cooling air to a recording medium that moves in the recording medium conveying path for both sides. apparatus.

Images