JP4095305B2 - Image forming apparatus with sheet cooling function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a laser printer that employs an electrophotographic method, and more particularly to an image forming apparatus having a function of cooling a sheet.
[0002]
[Prior art]
As shown in FIG. 6, there is a conventional in-line type multicolor image forming apparatus in which a plurality of photosensitive drums are arranged in a line. Such a multi-color image forming apparatus is roughly divided into a multi-color image forming apparatus 110 of a horizontal arrangement type in which a plurality of photosensitive drums 111 are arranged in a horizontal direction, as shown in FIG. 6, and as shown in FIG. In addition, there is a vertically arranged multicolor image forming apparatus 120 in which a plurality of photosensitive drums 121 are arranged in the vertical direction.
[0003]
The general horizontal arrangement type multicolor image forming apparatus 110 can reduce the height, but requires a large installation area. On the other hand, the vertical arrangement type multi-color image forming apparatus 120 can be reduced in height although the height is increased.
[0004]
In addition, the multicolor image forming apparatus generates a larger amount of heat in the power supply unit than the monochrome image forming apparatus, and the fixing device for fixing the toner image on the sheet has to be mixed and fixed with toner. For this reason, a large amount of heat was generated. For this reason, the multicolor image forming apparatus needs to be designed in consideration of the temperature rise in the apparatus main body and the cooling of the sheet more than the monochrome image forming apparatus.
[0005]
Specifically, the multi-color image forming apparatus arranges parts that are vulnerable to heat (photosensitive drum, toner, scanner unit, etc.) away from the heat source, or lengthens the sheet conveyance path after fixing and removes the sheet. Some devices have been devised such as cooling and discharging.
[0006]
The vertical multi-color image forming apparatus 120 having the merit of reducing the installation area as described above has a fixing device as a heat source provided at the uppermost part of the apparatus main body, and is suitable for exhaust heat of the fixing device. However, since the distance from the fixing device to the sheet discharge portion cannot be increased, the sheet cannot be reliably cooled.
[0007]
Therefore, as one of the countermeasures against heat, the multicolor image forming apparatus is provided with more cooling fans for exhaust heat, cooling fans for sheet cooling, and the like near the heat generation source than the monochrome image forming apparatus.
[0008]
[Problems to be solved by the invention]
However, in recent years, multicolor image forming apparatuses have been reduced in price and size, and the number of cooling fans has to be reduced.
[0009]
Further, in the vertical arrangement type multi-color image forming apparatus, since the distance from the fixing device to the sheet discharge portion is short, it is difficult to dispose cooling means such as a cooling fan and a duct.
[0010]
In particular, an overhead projector sheet on which a color image is printed (hereinafter referred to as an “OHP sheet”) has a large amount of toner, and thus cooling immediately after fixing is particularly important.
[0011]
Further, if the cooling capacity for the OHP sheet is insufficient, the subsequent sheet rubs against the sheet discharged first (the sheet on the discharge sheet tray) in a state where the toner on the OHP sheet is melted. During the discharge of the subsequent sheet, the sheets may stick to each other, and the subsequent sheet may push out the preceding sheet on the sheet discharge unit. As a result, the stackability of the sheet on the sheet discharge unit is deteriorated, and the sheet may fall from the sheet discharge unit.
[0012]
Further, when a conventional multicolor image forming apparatus automatically forms a toner image on both sides of a sheet, if the sheet after fixing the toner image formed on one side is insufficiently cooled, When an image is formed on the surface (second surface), the high temperature of the sheet may be transmitted to the photosensitive drum to increase the temperature of the photosensitive drum. For this reason, if toner images are continuously formed on both surfaces of a large number of sheets, it may cause a temperature rise in the entire sheet path, and the transfer device that transfers the toner image on the photosensitive drum to the sheet surely transfers the toner image to the sheet. In some cases, it could not be transferred.
[0013]
In addition to the above problems, the heat of discharged sheets cannot be ignored. In many cases, the sheet discharge unit is configured as an exterior part, and the heat of the sheet on the sheet discharge unit is transmitted through the exterior of the multicolor image forming apparatus, and the temperature inside the apparatus main body of the multicolor image forming apparatus is increased. was there.
[0014]
The present invention, for example, reliably cools the OHP sheet after fixing without increasing the number of cooling fans or the like as cooling means, and transfers heat from the sheet discharged to the sheet discharge portion into the apparatus main body. It is an object of the present invention to provide an image forming apparatus that has refused.
[0015]
An object of the present invention is to provide an image forming apparatus capable of reliably cooling a sheet before forming an image on the second surface.
[0016]
[Means for Solving the Problems]
  In order to achieve the above object, an image forming apparatus having a sheet cooling function according to the present invention includes an image forming unit that forms a toner image on a sheet, and an image forming unit disposed above the image forming unit. A fixing unit that fixes the toner image formed on the sheet by applying heat to the sheet, a cooling unit that cools an object to be cooled by sucking air from outside the apparatus main body, and discharged from the cooling unit. A duct for guiding air to the surface on which the toner image of the sheet discharged from the fixing unit is formed;In order to form a toner image on the other side of the sheet on which the toner image is formed on one side by the image forming unit, the sheet re-feeding and conveying unit that reverses the sheet and conveys the sheet to the image forming unit again. The sheet on which the toner image is fixed can be rotated forward and discharged to the sheet stacking means, and the sheet on which the toner image is fixed is rotated forward and conveyed to the sheet stacking means, and then reversely rotated. A pair of sheet discharge rollers capable of switchback conveyance to the sheet refeed conveyance means,WithThe duct guides air to the surface on which the toner image of the sheet discharged by the pair of sheet discharge rollers is formed, and the surface on which the toner image of the sheet being conveyed by the sheet discharge roller pair is switched back. AndThe sheet discharged from the fixing unit is stacked on the upper surface of the duct.The sheet stacking meansIt has become.
[0017]
  In order to achieve the above object, an image forming apparatus having a sheet cooling function according to the present invention includes a plurality of image carriers arranged in a vertical direction, and the image carriers are horizontally disposed facing each other. An image forming unit that forms a toner image on a sheet, and the toner image formed on the sheet by the image forming unit. Fixing means for fixing by applying heat to the sheet;In order to form a toner image on the other side of the sheet on which the toner image is formed on one side by the image forming unit, the sheet re-feeding and conveying unit that reverses the sheet and conveys the sheet to the image forming unit again. The sheet having the toner image fixed thereon can be rotated forward and discharged to a sheet stacking unit, and the sheet having the toner image fixed thereon can be rotated forward and conveyed to the sheet stacking unit, and then reversely rotated. A pair of sheet discharge rollers capable of switchback conveyance to the sheet re-feed conveyance means;A cooled object disposed on the opposite side of the image bearing member with the exposure means interposed therebetween, a cooling means for cooling the cooled object by sucking air from outside the apparatus main body, and discharged from the cooling means. A duct that guides air to the surface on which the toner image of the sheet discharged from the fixing unit is formed,The duct guides air to the surface on which the toner image of the sheet discharged by the pair of sheet discharge rollers is formed, and the surface on which the toner image of the sheet being conveyed by the sheet discharge roller pair is switched back. AndThe sheet discharged from the fixing unit is stacked on the upper surface of the duct.The sheet stacking meansIt has become.
  An image forming apparatus having a sheet cooling function according to the present invention includes a stay that eliminates air from passing between the object to be cooled and the plurality of exposure units.
[0019]
The cooling unit of the image forming apparatus having the sheet cooling function according to the present invention is disposed above the body to be cooled and on the opposite side of the fixing unit.
[0020]
The duct of the image forming apparatus having the sheet cooling function of the present invention extends from the cooling unit to the sheet discharge portion of the fixing unit.
[0021]
The duct of the image forming apparatus having a sheet cooling function of the present invention has an air guide that guides a part of the air discharged by the cooling unit into the duct so as to face a part of the cooling unit. Yes.
[0023]
  The duct of the image forming apparatus having a sheet cooling function according to the present invention intersects with a discharge direction of the sheet discharged from the fixing unit as it is separated from the cooling unit, andThe sheet stacking meansIs formed in a divergent shape so that the width in the direction along the line is widened.
[0024]
The cooling means of the image forming apparatus having the sheet cooling function of the present invention is a cooling fan that discharges air.
[0025]
  The object to be cooled of the image forming apparatus having the sheet cooling function of the present invention is an electrical unit.
  An image forming apparatus having a sheet cooling function of the present inventionThe electrical unit is disposed on the opposite side of the fixing unit with the exposure unit in between.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
A full-color laser beam printer that is an image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. As an embodiment of the present invention, a full-color laser beam printer having a plurality of photosensitive drums has been taken up, but the present invention can also be applied to a monochrome copying machine and printer having a single photosensitive drum. . Therefore, the image forming apparatus of the present invention is not limited to a full color laser beam printer. Moreover, the numerical value taken up by this embodiment is a reference numerical value, Comprising: It is not a numerical value which limits this invention.
[0027]
(Overall configuration of full-color laser beam printer)
FIG. 1 is a longitudinal sectional view showing an overall configuration of a full-color laser beam printer (hereinafter simply referred to as “printer”) 100 which is an embodiment of a multicolor image forming apparatus.
[0028]
The printer 100 includes, in the apparatus main body 101, four photosensitive drums (image carriers) 1a, 1b, 1c, and 1d arranged in parallel in the vertical direction (up and down direction). Each of the photosensitive drums 1a, 1b, 1c, and 1d is individually rotated counterclockwise in the drawing by a driving unit (not shown). Around each photosensitive drum 1a, 1b, 1c, 1d, charging devices 2a, 2b, 2c, 2d for uniformly charging the surface of the photosensitive drum in order according to the rotation direction of each photosensitive drum, based on image information. Scanner units (exposure means) 3a, 3b, 3c, 3d that irradiate a laser beam to form an electrostatic latent image on the photosensitive drum, and a developing device that attaches toner to the electrostatic latent image and develops it as a toner image 4a, 4b, 4c, 4d, an electrostatic transfer device 5 for transferring a toner image on the photosensitive drum to a sheet (transfer material) S, and a cleaning device for removing transfer residual toner remaining on the surface of the photosensitive drum after transfer 6a, 6b, 6c, 6d, etc. are arranged.
[0029]
The photosensitive drums 1a, 1b, 1c, and 1d, the charging devices 2a, 2b, 2c, and 2d, the developing devices 4a, 4b, 4c, and 4d, and the cleaning devices 6a, 6b, 6c, and 6d are each integrally formed into a cartridge. Process cartridges 7a, 7b, 7c and 7d are formed. An example of the sheet is an OHP sheet.
[0030]
Note that the symbol “1” is used when only a photoconductor drum is designated without designating a specific photoconductor drum. Similarly, for the charging device, scanner unit, developing device, electrostatic transfer device, cleaning device, and process cartridge, reference numerals “2”, “3”, “4”, “5”, “6”, and “7” are used. use. Further, “9”, “10”, and “12” are used for a polygon mirror, an imaging lens, and a transfer roller, which will be described later.
[0031]
Next, the photosensitive drum 1 will be described in order.
[0032]
The photosensitive drum 1 is formed, for example, by applying an organic photoconductive layer (OPC photosensitive member) to the outer peripheral surface of an aluminum cylinder having a diameter of about 30 mm. Both ends of the photosensitive drum 1 are rotatably supported by a support member. A rotational force from a drive motor (not shown) is transmitted to one end of the photosensitive drum 1. Therefore, the photosensitive drum 1 is rotated counterclockwise by the drive motor.
[0033]
The charging device 2 of this embodiment employs a contact charging method. As the charging member, a conductive roller formed in a roller shape is used. The charging device 2 causes the conductive roller to contact the surface of the photosensitive drum 1 and applies a charging bias voltage to the conductive roller so that the surface of the photosensitive drum 1 is uniformly charged. It has become.
[0034]
The scanner units 3a, 3b, 3c, 3d are arranged in a substantially horizontal direction with respect to the photosensitive drums 1a, 1b, 1c, 1d, and image light corresponding to an image signal is not shown by a laser diode (not shown). The polygon mirrors 9a, 9b, 9c, 9d rotated at high speed by the scanner motor are irradiated. The image light reflected from the polygon mirror 9 selectively exposes the surfaces of the charged photosensitive drums 1a, 1b, 1c, and 1d through the imaging lenses 10a, 10b, 10c, and 10d. As a result, an electrostatic latent image is formed on the photosensitive drum 1.
[0035]
Each of the developing devices 4a, 4b, 4c, and 4d includes a developing device that stores toner of each color of yellow, magenta, cyan, and black.
[0036]
  The electrostatic transfer belt 11 is a belt having a circumferential length of about 700 mm and a thickness of about 150 μm. The electrostatic transfer belt 11 is wound around four rollers of a driving roller 13, driven rollers 14a and 14b, and a tension roller 15, and all the photosensitive drums 1a. , 1b, 1c, 1d, and circulates in the direction of the arrow in the figure. The electrostatic transfer belt 11 electrostatically attracts a sheet (sheet) S to the outer peripheral surface on the left side in the drawing, and brings the sheet S into contact with the photosensitive drum 1.RuTherefore, it is supposed to circulate. Thus, the sheet S is conveyed to the transfer position by the electrostatic transfer belt 11 and the toner image on the photosensitive drum 1 is transferred. The electrostatic transfer belt 11 includes 10¹¹10¹⁴A film-like member having a volume resistivity of Ω · cm and a thickness of about 150 μm is used.
[0037]
The transfer rollers 12a, 12b, 12c, and 12d are arranged in parallel at positions facing the four photosensitive drums 1a, 1b, 1c, and 1d, and are in contact with the electrostatic transfer belt 11 from the inside. A positive charge is applied from the transfer roller 12 to the sheet S via the electrostatic transfer belt 11, and a negative polarity on the photosensitive drum 1 is applied to the sheet in contact with the photosensitive drum 1 by an electric field generated by the charge. The toner image is transferred.
[0038]
Thus, when the electrostatic transfer belt 11 circulates, the toner image is transferred to the sheet S while the sheet S is conveyed upward from the driven roller 14a side to the driving roller 13 side.
[0039]
The sheet supply unit 16 conveys the sheet S to an image forming unit (image forming unit) 45 such as a process cartridge 7 or the like. A plurality of sheets S are stored in the sheet supply cassette 17. At the time of image formation, the half-moon-shaped sheet supply roller 18 rotates according to the image forming operation, separates the sheets S in the sheet supply cassette 17 one by one, and feeds them to the registration roller pair 19. ing.
[0040]
The fixing device (fixing unit) 20 fixes the toner images of a plurality of colors transferred to the sheet S to the sheet S. The fixing device 20 includes a heating roller 21a that rotates and applies heat to the sheet, and a pressure roller 21b that presses the sheet and applies pressure to the sheet S.
[0041]
The printer 100 can form images on both sides of a sheet. Therefore, in order to form a toner image on the other side of the sheet on which the toner image is formed on one side by the process cartridge 7, the sheet refeed conveyance mechanism that reverses the front and back and feeds the sheet to the process cartridge 7 again. (Sheet refeeding and conveying means) 50 is provided. If the sheet is formed only on one side of the sheet, the sheet refeeding and conveying mechanism 50 is not necessarily required.
[0042]
The sheet refeed / conveying mechanism 50 sequentially forwards and reverses a sheet trailing edge detection sensor 51 that detects that the trailing edge of the sheet has passed through the last photosensitive drum 1d, and a sheet on which a toner image is formed on one surface. The sheet discharge roller pair 23 that feeds, the sheet reverse conveyance path 52 that guides the sheet from the fixing device 20 to the registration roller pair 19, and the sheet discharge roller pair 23 passes through the fixing roller pair 21 after the trailing edge of the sheet has passed. Are provided with a flapper 53 for guiding the sheet to the sheet reverse conveyance path 52 and a plurality of pairs of sheet reverse conveyance rollers 54 for conveying the sheet along the sheet reverse conveyance path 52. The sheet trailing edge detection sensor 51 may be provided near the upstream side of the sheet discharge roller pair 23.
[0043]
(Image forming operation of full-color laser beam printer)
At the time of image formation, the half-moon shaped sheet supply roller 18 rotates according to the image forming operation, separates the sheets S in the sheet supply cassette 17 one by one, and feeds them to the registration roller pair 19. The leading edge of the sheet S abuts against the registration roller pair 19 that has stopped rotating, and temporarily stops, so that a loop is formed on the sheet S. As a result, the skew of the sheet S is straightened. Thereafter, the rotation of the electrostatic transfer belt 11 and the image writing position are synchronized, and the sheet S is conveyed to the electrostatic transfer belt 11 by the rotation of the registration roller pair 19.
[0044]
On the other hand, the process cartridges 7a, 7b, 7c, and 7d are sequentially driven in accordance with the printing timing, and the photosensitive drums 1a, 1b, 1c, and 1d are rotated in the counterclockwise direction in accordance with the drive. Then, the scanner units 3a, 3b, 3c, and 3d corresponding to the process cartridges 7a, 7b, 7c, and 7d are sequentially driven. By this driving, the charging device 2 applies a uniform charge to the peripheral surface of the photosensitive drum 1. The scanner unit 3 exposes the peripheral surface of the photosensitive drum 1 in accordance with an image signal to form an electrostatic latent image on the peripheral surface of the photosensitive drum 1. A developing roller in the developing device 4 forms (develops) a toner image on the peripheral surface of the photosensitive drum 1 by transferring toner to a low potential portion of the electrostatic latent image.
[0045]
At the timing when the leading edge of the toner image on the peripheral surface of the photosensitive drum 1a at the most upstream position is rotated to the point facing the electrostatic transfer belt 11, the print start position of the sheet S coincides with that point. Then, the registration roller pair 19 starts to rotate and feeds the sheet S to the electrostatic transfer belt 11.
[0046]
The sheet S is pressed against the outer periphery of the electrostatic transfer belt 11 so as to be sandwiched between the electrostatic adsorption roller 22 and the electrostatic transfer belt 11. When a voltage is applied between the electrostatic transfer belt 11 and the electrostatic attraction roller 22, charges are induced in the dielectric sheet S and the dielectric layer of the electrostatic transfer belt 11. It is electrostatically attracted to the outer periphery of the electrotransfer belt 11. As a result, the sheet S is stably adsorbed to the electrostatic transfer belt 11 and conveyed to the most downstream transfer roller 12d.
[0047]
In this way, the toner image on each photoconductive drum 1 is sequentially transferred to the sheet S by the electric field formed between each photoconductive drum 1 and the transfer roller 12 while being conveyed. The sheet S to which the four color toner images have been transferred is separated from the electrostatic transfer belt 11 by the curvature of the driving roller 13 through which the electrostatic transfer belt 11 circulates, and is carried into the fixing device 20.
[0048]
When the sheet S on which the toner image on the photosensitive drum 1 is transferred passes through the fixing device 20, heat and pressure are applied while being conveyed by the fixing roller pair 21. As a result, toner images of a plurality of colors are fixed on the surface of the sheet S.
[0049]
The sheet S on which the toner image is fixed by the fixing device 20 is discharged out of the apparatus main body 101 by the sheet discharge roller pair 23 with the surface on which the toner image is formed facing down from the sheet discharge unit 24. It is loaded on the tray 39.
[0050]
The above description of the image forming operation is a description of a case where a toner image is formed on one side of a sheet. Next, an image forming operation when a toner image is formed on both sides of a sheet will be described.
[0051]
When the user is instructed to form an image on both sides of the sheet and the toner image is formed on one side of the sheet, the sheet is fixed with the toner image when passing through the fixing roller pair 21, and the discharge sheet tray 39. The surface on which the toner image is formed is cooled by air.
[0052]
Then, after the sheet trailing edge detection sensor 51 detects that the trailing edge of the sheet has passed, the flapper 53 is activated after a predetermined time when the trailing edge of the sheet is supposed to pass the flapper 53. Then, the sheet discharge roller pair 23 reversely rotates and conveys the sheet in a switchback manner. As a result, the sheet is guided to the flapper 53 and fed into the sheet reversal conveyance path 52 with the portion that has been the rear end as a leading end.
[0053]
Thereafter, the sheet is conveyed through the sheet reversal conveyance path 52 by the sheet reversal conveyance roller pair 54 and sent to the registration roller pair 19 whose rotation is stopped. When the sheet is skewed, the sheet is straightened. Then, the sheet is sent to the electrostatic transfer belt 11 by the registration roller pair 19 in accordance with the position of the first toner image on the photosensitive drum 1a. The sheet is fed to the first photosensitive drum 1a by the electrostatic transfer belt 11, and a toner image is formed on the other surface.
[0054]
  Finally, the sheet is fed into the fixing device 20, and the toner image formed on the other surface is fixed, and the discharged sheet tray (Sheet stacking means) It is discharged to 39 and loaded.
[0055]
Next, the arrangement of the heat generating parts and the arrangement of the cooling means, which are characteristic parts of the present invention, will be described with reference to FIG.
[0056]
As shown in FIG. 1, a power source 31 is disposed at the lower left side of the apparatus main body 101. The power supply 31 is attached to the bottom plate 32 of the apparatus main body 101. The periphery of the power supply 31 is covered with sheet metal parts that constitute the frame of the apparatus main body 101. A stay 33 is provided above the power supply 31.
[0057]
A scanner unit 3 and an electrical unit (cooled body) 34 are arranged above the stay 33. The electrical unit 34 is close to the scanner unit 3. The back stay 35 divides the electrical unit 34 and the scanner unit 3 so that air does not travel between the electrical unit 34 and the scanner unit 3.
[0058]
The power source 31 and the electrical unit 34, which are heating elements, are arranged at a position far from the photosensitive drum 1 and the toner to minimize the amount of heat transmitted from the power source 31 and the electrical unit 34 to the photosensitive drum 1 and the toner. .
[0059]
Further, an upper stay 36 that is a component part of the main body frame is provided above the electrical unit 34. A cooling fan (cooling means) 37 is disposed on the upper stay 36 so as to be substantially upward. The blowing direction of the cooling fan 37 is set in the direction of arrow A in FIG. The cooling fan 37 is securely fixed to the apparatus main body 101 with a holder (not shown) so that the vibration of the cooling fan 37 does not affect other parts.
[0060]
Above the cooling fan 37, an upper cover 38, which is an exterior component of the apparatus main body 101, is provided. The upper cover 38 also serves as the discharge sheet tray 39. All sheets discharged from the inside of the apparatus main body are stacked on the discharge sheet tray 39. Further, an air guide rib (air guide) 40 that covers about １ ／ of the cooling fan 37 is integrally provided on the discharge sheet tray 39 and the upper cover 38 at a position located directly above the cooling fan 37. With this air guide rib 40, about 1/3 of the exhaust of the cooling fan 37 is guided to the discharge sheet tray 39.
[0061]
Further, a duct 41 is disposed below the discharge sheet tray 39. The duct 41 is connected so that there is no gap from the exhaust part of the cooling fan 37 to the sheet discharge part 24 of the fixing device 21.
[0062]
Next, the flow of air for cooling the sheet S will be described with reference to FIG.
[0063]
Outside air into the apparatus main body 101 flows from an opening 44 formed on the left side of the sheet supply cassette 17 in FIG. Thereafter, the air passes through the opening 32 a of the bottom plate 32 in the direction of arrow C and flows toward the power source 31. The opening 32a of the bottom plate 32 is a round hole having a diameter of about 6 mm, and many holes are formed. The opening ratio of the bottom plate 32 is set to about 50%. Of course, the larger the aperture ratio of the bottom plate 32, the better the air flow. However, the bottom plate 32 is set in consideration of safety so that there is no object touching the power supply unit or any object falling on the sheet supply cassette 17.
[0064]
The power supply 31 is covered with frame parts, an exterior, and the like. For this reason, the air that has flowed along the path indicated by the arrow C is guided to the exterior of the power source 31 and flows along the path indicated by the arrow D toward the electrical unit 34. Similarly to the bottom plate 32, the stay 33 also has an opening 33a.
[0065]
Thereafter, the air is sucked into the cooling fan 37 and flows upward in the apparatus main body 101. Similarly to the bottom plate 32, an opening 36 a is formed in the upper stay 36.
[0066]
The air is sucked into the cooling fan 37, passes through the opening 36a, and is discharged out of the apparatus main body 101. About one third of the air carried out to the outside is guided by the air guide rib 40 in the direction of arrow F, that is, to the discharge sheet tray 39 side. The remaining approximately 2/3 of the air is discharged in the direction of arrow E, that is, outside the apparatus main body 101. This ratio is determined based on the data obtained by obtaining the wind speed necessary for cooling the sheet S from experimental values, and is not limited to this.
[0067]
3 is a cross-sectional view taken along line GG in FIG. FIG. 3 is a diagram for facilitating understanding of the air flow indicated by the arrow E shown in FIG. As shown in FIG. 3, in the air flow indicated by the arrow E, the air is exhausted to the outside of the apparatus main body 101 through the exhaust hole 42 formed on the side of the upper cover 38. The cooling fan 37 is attached to the apparatus main body 101 by being inclined in the exhaust direction, and exhausts air by reducing resistance.
[0068]
In the air flow indicated by the arrow F, the air is guided to the duct 41 and exhausted from the lower side of the sheet discharge portion 24 to the upper side in the arrow H direction. As a result, air can be blown to the print image surface side of the sheet S discharged from the fixing device 20, and the sheet S is cooled. When the sheet covers the discharge sheet tray 39 while being discharged from the fixing device 20, the air blown to the print image surface side temporarily accumulates between the sheet S and the discharge sheet tray 39, and the discharge sheet tray 39 or The preceding sheet that has already been discharged to the discharge sheet tray 39 can be cooled to prevent heat from being transmitted to the inside of the apparatus main body 101.
[0069]
In this embodiment, an extension 41 a of the duct 41 is provided in the fixing device 20, and the exhaust port of the duct 41 is extended to the vicinity of the sheet discharge unit 24. As a result, the duct 41 can effectively cool the sheet.
[0070]
Next, the shape of the duct 41 and the mounting structure will be described with reference to FIGS. FIG. 4 is a view of the apparatus main body 101 as viewed from above. As described above, the duct 41 is disposed so as to connect the cooling fan 37 and the sheet discharge portion 24 of the fixing device 20. The shape of the duct 41 is formed so as to increase in width as it approaches the sheet discharge portion 24. That is, the duct 41 is formed so as to widen toward the end.
[0071]
By forming the duct 41 so as to widen toward the end, the air of the cooling fan 37 can be guided and blown uniformly over a wide area of the image surface of the sheet S. Furthermore, the wind speed of the air is a gentle wind speed that does not affect the conveyance of the discharged sheet. If the air speed is higher than necessary, the sheet is blown upward or the leading edge of the sheet flutters, deteriorating the sheet discharge stackability.
[0072]
Further, the duct 41 and the discharge sheet tray 39 have a large air flow area on the back surface 39 a of the discharge sheet tray 39. For this reason, the heat of the discharged sheet is difficult to be transmitted into the apparatus main body 101. In addition, the back surface 39a of the discharge sheet tray 39 is cooled by the air flow, and an air curtain is formed inside the discharge sheet tray 39 and the apparatus main body 101, thereby minimizing the transfer of heat from the discharged sheets. Can be suppressed.
[0073]
FIG. 5 is a perspective view of the upper cover 38 as viewed from the back side. As shown in FIG. 5, the duct 41 has four corners attached to the back surface 39 a of the discharge sheet tray 39 with screws 43. By using both the upper portion of the duct 41 and the back surface 39a of the discharge sheet tray 39, the back surface 39a of the discharge sheet tray 39 can be cooled as described above. Further, the shape of the duct part can be simplified, and the cost of the part can be reduced.
[0074]
In the above printer 100, a part of the air discharged from the cooling fan is blown to the sheet, but all the discharged air may be blown.
[0075]
【The invention's effect】
The image forming apparatus of the present invention includes a duct for guiding the air discharged from the cooling unit to the surface on which the toner image of the sheet discharged from the fixing unit is formed, and the air is formed on the surface of the sheet on which the toner image is formed. Therefore, it is possible to cool the sheet and the toner on the sheet without increasing the cost and size of the image forming apparatus without newly installing a cooling means. For example, it is possible to attach an OHP sheet. Sticking can be prevented.
[0076]
When a plurality of image carriers are arranged in the vertical direction and the image carriers are exposed from the side by exposure means, the layout of each element in the apparatus main body should not waste space. Therefore, the object to be cooled and the sheet can be cooled at a low cost, and the entire image forming apparatus can be downsized.
[0077]
Even when the image forming apparatus can form images on both sides of the sheet, each side of the sheet can be cooled to prevent the temperature of the image forming means from rising and form a good quality image on the sheet. can do.
[0078]
When the cooling means is disposed above the cooled object, the heat of the cooled object can be efficiently exhausted and the influence of the heat on the image carrier and toner can be minimized.
[0079]
Furthermore, if the upper part of the duct is a discharge sheet stacking unit on which the sheet discharged from the fixing unit is stacked, the heat insulation effect between the discharged sheet and the inside of the apparatus main body is increased, and the discharged sheet It is possible to minimize the amount of heat transferred to the device body.
[0080]
Further, when the duct is formed in a divergent shape so that the width in the direction intersecting the discharge direction of the sheet discharged from the fixing unit increases as the distance from the cooling unit increases, It is possible to cool with a good balance in a wide area in the width direction.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an overall configuration of a full-color laser beam printer which is an aspect of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing the flow of air in FIG.
3 is a cross-sectional view taken along line GG in FIG. 2;
4 is a plan view of the full-color laser beam printer of FIG. 1. FIG.
FIG. 5 is a perspective view of the upper cover as viewed from the back side.
FIG. 6 is a cross-sectional view of a conventional multicolor image forming apparatus.
FIG. 7 is a cross-sectional view of another conventional multicolor image forming apparatus.
[Explanation of symbols]
    S Transfer material (sheet)
    1 (1a, 1b, 1c, 1d) Photosensitive drum (image carrier)
    2 (2a, 2b, 2c, 2d) Charging device
    3 (3a, 3b, 3c, 3d) Scanner unit (exposure means)
    4 (4a, 4b, 4c, 4d) Developing device
    5 Electrostatic transfer device
    6 (6a, 6b, 6c, 6d) Cleaning device
    7 (7a, 7b, 7c, 7d) Process cartridge
    9 (9a, 9b, 9c, 9d) Polygon mirror
  10 (10a, 10b, 10c, 10d)
  11 Electrostatic transfer belt
  12 (12a, 12b, 12c, 12d) Transfer roller
  20 Fixing device (fixing means)
  21 Fixing roller pair
  21a Heating roller
  21b Pressure roller
  23 Sheet discharge roller pair
  24 Sheet discharge unit
  31 Power supply
  33a opening
  34 Electrical unit (cooled object)
  36 Upper Stay
  36a opening
  37 Cooling fan (cooling means)
  39 Ejection sheet tray (Sheet stacking means)
  39a Back side of discharge sheet tray
  40 Air guide rib (air guide)
  41 Duct
  41a Duct extension
  42 Exhaust hole
  44 opening
  45 Image forming unit (image forming means)
  50 Sheet refeed conveyance mechanism (sheet refeed conveyance means)
100 Full color laser beam printer (image forming device)
101 Main unit

Claims (10)

Image forming means for forming a toner image on a sheet;
A fixing unit disposed above the image forming unit and fixing the toner image formed on the sheet by the image forming unit by applying heat to the sheet;
A cooling means for sucking air from outside the apparatus main body to cool the object to be cooled;
A duct for guiding the air discharged from the cooling unit to the surface on which the toner image of the sheet discharged from the fixing unit is formed ;
In order to form a toner image on the other side of the sheet on which the toner image is formed on one side by the image forming unit, the sheet re-feeding and conveying unit that reverses the sheet and conveys the sheet to the image forming unit again. When,
The sheet on which the toner image is fixed can be rotated forward and discharged to the sheet stacking unit, and the sheet on which the toner image is fixed is rotated forward and conveyed to the sheet stacking unit, and then the sheet is rotated in reverse. A pair of sheet discharge rollers capable of switchback conveyance to the refeed conveyance means ,
The duct guides air to the surface on which the toner image of the sheet discharged by the pair of sheet discharge rollers is formed, and the surface on which the toner image of the sheet being conveyed by the sheet discharge roller pair is switched back. and, and the upper surface of the duct, the sheet discharged from the fixing means is in said sheet stacking means to be mounted,
An image forming apparatus having a sheet cooling function. Image formation for forming a toner image on a sheet having a plurality of image carriers arranged in the vertical direction and a plurality of exposure means for exposing the image carrier from the side facing each of the plurality of image carriers Means,
A fixing unit disposed above the image forming unit and fixing the toner image formed on the sheet by the image forming unit by applying heat to the sheet;
In order to form a toner image on the other side of the sheet on which the toner image is formed on one side by the image forming unit, the sheet re-feeding and conveying unit that reverses the sheet and conveys the sheet to the image forming unit again. When,
The sheet on which the toner image is fixed can be rotated forward and discharged to the sheet stacking unit, and the sheet on which the toner image is fixed is rotated forward and conveyed to the sheet stacking unit, and then the sheet is rotated in reverse. A pair of sheet discharge rollers capable of switchback conveyance to the refeed conveyance means;
A cooled object disposed on the opposite side of the image carrier with the exposure means interposed therebetween;
A cooling means for sucking air from outside the apparatus main body to cool the object to be cooled;
A duct for guiding the air discharged from the cooling unit to the surface on which the toner image of the sheet discharged from the fixing unit is formed,
The duct guides air to the surface on which the toner image of the sheet discharged by the pair of sheet discharge rollers is formed, and the surface on which the toner image of the sheet being conveyed by the sheet discharge roller pair is switched back. and, and the upper surface of the duct, the sheet discharged from the fixing means is in said sheet stacking means to be mounted,
An image forming apparatus having a sheet cooling function.   3. The image forming apparatus having a sheet cooling function according to claim 2, further comprising a stay that eliminates air flow between the object to be cooled and the plurality of exposure units.   The image forming apparatus having a sheet cooling function according to claim 1, wherein the cooling unit is disposed above the cooled body and on the opposite side of the fixing unit. The duct from said cooling means, an image forming apparatus including a sheet cooling function according possible to claim 1 or 2, characterized in that extends to the sheet discharging portion of the fixing means. The duct according to claim 1, characterized in that it has an air guide for guiding a part of the air discharged by the opposite to a portion with the cooling means of the cooling means into the duct, 5 An image forming apparatus having the sheet cooling function according to any one of the above. As the duct is separated from the cooling unit, the duct is widened in a direction that intersects with the discharge direction of the sheet discharged from the fixing unit and in a direction along the sheet stacking unit. claim 1, 2, 5, characterized in that is formed on an image forming apparatus including a sheet cooling function according to any one of 6. The cooling means according to claim 1, characterized in that a cooling fan for discharging the air, an image forming apparatus including a sheet cooling function according to any one of 2, 5 to 7. The cooled body, the image forming apparatus including a sheet cooling function according to any one of claims 1 to 4, characterized in that it is the electrical unit. The image forming apparatus according to claim 9 , wherein the electrical unit is disposed on an opposite side of the fixing unit with the exposure unit interposed therebetween.

Images