JP2008170771A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturized fixing device in which the cooling effect of a pressure belt member pressure-welded to a fixing member is superior. <P>SOLUTION: In a fixing device 30 having a pressure belt 32 pressure-welded to a fixing roller 31 and rolling, at least one roller among a plurality of rollers freely rollably suspended with the pressure belt 32 is a cooling roller 35, having a plurality of air-jet apertures perforated to a hollow cylindrical face. The cooling roller 35 is connected with a blast means 37 feeding pressurized air into the cooling roller 35 and jetting the pressurized air from the air jet apertures 35a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an unfixed toner image formed on a transfer material, mounted on an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, by a fixing member and a pressure member. The present invention relates to a fixing device that fixes an image by applying pressure and heat, and an image forming apparatus including the fixing device.

  Conventionally, a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions has a fixing roller maintained at a predetermined temperature and an elastic layer. A heat roller fixing system that presses and heats a transfer material on which an unfixed toner image is formed is sandwiched and conveyed by a fixing nip formed by a pressure roller that is in pressure contact with the fixing roller. Widely used from monochrome machines to color machines.

  The conventional heat roller fixing type fixing device is disadvantageous in terms of power saving because it is necessary to heat the fixing roller having a large heat capacity when heating the toner on the transfer material. There is a problem that it takes time to warm up, and the time until warming up (warm up time) becomes long.

  In order to solve the above problems, a belt-shaped fixing belt or a belt-shaped pressure member is used, the heat capacity is lowered by the fixing member, and a temperature-controlled heater is brought into direct pressure contact with the fixing belt to achieve heat transfer efficiency. In recent years, a belt fixing type fixing device and an image forming apparatus have been proposed and used in recent years, which greatly improve the image quality and achieve a quick start that requires little power saving and warm-up time.

  The fixing device proposed in Patent Document 1 includes an endless belt that is rotatably stretched around a plurality of support rollers with respect to a fixing rotating body having a heating unit, and an endless belt that is disposed inside the endless belt. A pressure member fixedly arranged so as to be pressed against the fixing rotator from the inner peripheral side thereof, and formed between an endless belt pressed by the fixing rotator and the pressure member. This is a belt nip method in which an unfixed toner image formed on a recording material is fixed by passing the recording material through a fixing nip portion.

  The fixing device proposed in Patent Document 2 forms a closed space that surrounds the pressure belt, and an air supply duct, an air discharge duct, and a cooling fan that blows air toward the pressure belt in the closed space. It is provided.

The fixing device proposed in Patent Document 3 is provided with a heat radiating body for releasing heat in contact with ambient air on the back surface of the fixing belt.
JP 2001-201979 A JP 2006-119243 A JP 2004-78045 A

  When image formation is continuously performed on the recording material in the image forming apparatus, the recording material continuously passes through the fixing nip portion formed between the fixing rotating body and the endless belt while holding the gap between the sheets. For this reason, the endless belt receives excessive heat from the fixing rotator when the recording material passes between sheets not existing in the fixing nip, and the temperature of the entire area of the endless belt excessively increases. This may disturb the unfixed toner image formed on the recording material.

  In addition, when a small-sized recording material is continuously fed with respect to the maximum width of the recording material in the fixing nip (maximum length in the direction orthogonal to the conveyance direction), the non-sheet passing portion of the endless belt The temperature increases excessively with respect to the temperature of the sheet passing portion, and temperature unevenness occurs in the longitudinal direction of the endless belt (width direction orthogonal to the conveying direction). As a result, unevenness occurs in the temperature at which the unfixed toner image formed on the recording material is melted, resulting in image quality degradation. Alternatively, the friction coefficient in the fixing nip portion may be uneven and image displacement may occur. Such a problem of image defects occurs particularly remarkably in the case of recording materials such as coated paper and cardboard.

  For the above-described image degradation due to excessive temperature rise of the endless belt, conventionally, a cooling means such as a fan is disposed in the vicinity of the endless belt to cool the endless belt acutely.

  However, in the fixing device disclosed in Patent Document 1, hot air from the fixing device reaches the image forming means around the fixing device due to the flow of air by the cooling means that cools the outer peripheral surface of the endless belt, and the image formation is performed. Problems such as blocking that the toner on the image carrier in the means melts and adheres occur.

  In the fixing device disclosed in Patent Document 2, a cooling unit is provided in a closed space surrounding the pressure belt, which increases the size of the device. Further, when cooling air is applied from the outside of the fixing belt, the cooling air hits only a part of the fixing belt, so that the cooling effect is small.

  In the fixing device disclosed in Patent Document 3, the heat dissipating body installed in a narrow space on the inner surface side of the fixing belt has little cooling effect on the heat dissipating body itself.

  An object of the present invention is to provide a fixing device that has an excellent cooling effect and is miniaturized, and an image forming apparatus including the fixing device.

  The above object can be achieved by the following solutions.

  1. In a fixing device having a pressure belt member that rotates while being pressed against a fixing member, at least one of a plurality of rollers that rotatably stretch the pressure belt member is perforated on a hollow cylindrical surface. A cooling roller having a plurality of air ejection holes, and the cooling roller is connected to blowing means for sending pressurized air into the cooling roller and ejecting the pressurized air from the air ejection holes. A fixing device characterized.

  2. Image forming means for forming a toner image on an image carrier, paper feeding means for supplying a recording material to the image carrier, transfer means for transferring the toner image to the recording material, and the transferred toner image An image forming apparatus comprising: the fixing device according to 1 above, wherein the fixing device is fixed to the recording material.

  The fixing device and the image forming apparatus of the present invention can obtain the following effects by the configuration described above.

  1. A cooling effect through cold air that cools the inner surface side of the heated pressure belt member by blowing air from a cooling device, and a cooling effect that cools the pressure belt member by heat conduction from a cooling roller that contacts the pressure belt member; Thus, a fixing device having an excellent cooling effect of the pressure belt member is provided.

  2. According to the image forming apparatus provided with the fixing device of the present invention, a stable and uniform fixing process can be performed and a good image can be obtained. Further, it is possible to prevent the heat of the pressure belt member from being transmitted to members around the fixing device and adversely affecting the peripheral members.

  Embodiments of the present invention will be described below. The description in this column does not limit the technical scope of the claims or the meaning of terms.

  FIG. 1 is a configuration diagram showing an example of an image forming apparatus according to the present invention.

  The image forming apparatus includes an image forming apparatus main body A and an image reading apparatus B.

  The image forming apparatus main body A is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 6, a sheet feeding and conveying unit, a fixing device 30, and the like. Become.

  An image reading device B including an automatic document feeder DF and a document image scanning exposure device SC is installed on the upper part of the image forming apparatus main body A. The document d placed on the document table of the automatic document feeder DF is transported by a transport means, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device SC, and is applied to the line image sensor CCD. Is read.

  A signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 8Y are disposed around the photoreceptor 1Y. In the image forming unit 10M that forms a magenta (M) color image, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 8M are arranged around the photoreceptor 1M. In the image forming unit 10C for forming a cyan (C) color image, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 8C are arranged around the photoreceptor 1C. An image forming unit 10K that forms a black (K) image has a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 8K arranged around the photoreceptor 1K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure device 3C, and the charging unit 2K and the exposure device 3K constitute a latent image forming unit.

  The developing units 4Y, 4M, 4C, and 4K include a two-component developer composed of a toner having a small particle size of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier.

  The intermediate transfer member 6 is wound around a plurality of rollers and is rotatably supported by a driving unit (not shown).

  The fixing device 30 heats and presses the toner image on the recording material P at a fixing nip portion formed between a heated fixing member (fixing roller) 31 and a pressure belt member (pressure belt) 32. To settle.

  The respective color images formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred (primary transfer) by the primary transfer units 7Y, 7M, 7C, and 7K onto the rotating intermediate transfer body 6 to form a color. A toner image obtained by combining the images is formed. The recording material P accommodated in the paper feeding cassette 20 is fed by the paper feeding means 21 and is conveyed to the secondary transfer means 7A through the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, and the like. A color image is transferred onto the recording material P (secondary transfer). The recording material P to which the color image has been transferred is heated and pressurized in the fixing device 30 to fix the color toner image on the recording material P. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording material P by the secondary transfer means 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 from which the recording material P is separated by curvature.

  The image forming apparatus for forming a color image has been described above. However, an image forming apparatus for forming a monochrome image may be used, or an intermediate transfer member may or may not be used.

  Next, the main configuration of the belt nip type fixing device 30 according to the present invention will be described.

  FIG. 2 is a cross-sectional view of the belt nip type fixing device 30 according to the present invention. FIG. 3 is an enlarged cross-sectional view of the fixing roller 31 and the pressure belt 32.

  The fixing device 30 according to the present invention includes a fixing roller 31 above the sheet passing path and a pressure belt 32 below the sheet passing path.

  Through a fixing nip formed between the fixing roller 31 and the pressure belt 32, the single color toner image or the multicolor toner image on the recording material P is fixed by heating and pressing.

  The fixing roller 31 has a halogen lamp (heating means) H incorporated therein, and a cylindrical core 31A made of aluminum, iron, or the like, and an elastic made of silicone rubber having high heat resistance and covering the cylindrical core 31A. The layer 31B and the release layer 31C made of a fluororesin such as PFA (perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) which further covers the elastic layer 31B.

  On the outer peripheral surface of the fixing roller 31, an oil supply unit 41, an external heating unit 42, a cleaning unit 43, a separation claw 44, a temperature sensor (not shown), and the like are arranged.

  The pressure belt 32 is composed of a base formed of polyimide having a thickness of about 100 μm and a release layer formed of PFA or PTFE having a thickness of about 25 μm covering the outer surface of the base. Is formed.

  The pressure belt 32 includes an entrance roller 33 near the introduction portion of the recording material P, an exit roller 34 that is disposed near the exit portion of the recording material P and presses against the fixing roller 31 via the pressure belt 32, and a cooling roller 35. The outer periphery is wound and stretched, and comes into contact with the outer peripheral surface of the fixing roller 31.

  The separation claw 45 abuts on the outer peripheral surface of the pressure belt 32 around which the exit roller 34 is wound, and separates the leading end portion of the recording material P from the pressure belt 32.

  The elevating means 46 holds a pressure unit having a pressure belt 32, an entrance roller 33, an exit roller 34, a cooling roller 35 and the like so as to be movable up and down, and presses the pressure belt 32 and the pressing means 36 against the fixing roller 31. .

  The pressing pad 36A that presses the pressure belt 32 from the inside is formed of a silicone rubber having a hardness of about 10 ° JISA, and is formed of a heat-resistant resin. The holding member 36B that holds the pressing pad 36A, and the compression spring that biases the holding member 36B Along with 36C, it is held in a holder 36D made of heat-resistant resin. Here, the pressing pad 36A, the holding member 36B, the compression spring 36C, and the holder 36D are collectively referred to as pressing means 36.

  In the fixing device 30 configured as described above, the fixing roller 31 heated by the halogen lamp H and driven by driving means (not shown) rotates in the clockwise direction shown in the figure. The pressing pad 36A is pressed by the compression spring 36C via the holding member 36B, and the pressing pad 36A presses the pressure belt 32 against the fixing roller 31.

  Accordingly, the pressure belt 32 rotates counterclockwise as shown in the figure by the fixing roller 31 rotated by driving of the motor M1, and is pressed against the fixing roller 31 by the pressing pad 36A and elastically deforms. A wide fixing nip portion is formed between the roller 31 and the roller 31. Unfixed toner on the conveyed recording material P is heated and pressed at the fixing nip portion to be fixed.

  The exit roller 34 rotates by driving the motor M2 to rotate the pressure belt 32. The inlet roller 33 and the cooling roller 35 are driven to rotate by the rotation of the pressure belt 32.

  FIG. 4 is a side view of the cooling roller 35.

  The cooling roller 35 is a roller having a plurality of air ejection holes 35 </ b> A perforated on a hollow cylindrical surface, and a blowing means (fan) 37 connected to the cooling roller via a blower pipe 38 is provided via the blower pipe 38. The pressurized air is fed into the interior, and the pressurized air is ejected from the air ejection holes 35A to cool the inner surface of the pressure belt 32.

  The inside of the pressure belt 32 stretched around a plurality of rollers (33, 34, 35) is formed in a closed space 300 shown in FIG. 3 that is shielded by the side walls 39A, 39B of the fixing device 30. An air flow path having a fan 37, a blower pipe 38, a cooling roller 35, and an exhaust pipe 40 for discharging the air in the closed space 300 to the outside of the apparatus is formed.

  The pressurized air blown into the cooling roller 35 by the fan 37 is ejected from the plurality of air ejection holes 35 </ b> A and enters the closed space 300 to enter the inner surface of the pressure belt 32, the inlet roller 33, and the outlet roller 34. Cooling. The cooling roller 35 may be a steering roller, a tension roller, an entrance roller 33, an exit roller 34, or the like.

  The material of the cooling roller 35 is preferably a metal having a high thermal conductivity, and an aluminum alloy or the like is suitable. The cooling roller 35 was set to an outer diameter of 37 mm, a thickness of 1.5 mm, an air hole diameter of 2 mm, and an air hole interval of 4 mm.

  The plurality of air ejection holes 35A drilled in the hollow cylindrical surface of the cooling roller 35 are arranged with an inclination angle θ of about 20 °, for example, in a direction orthogonal to the rotation axis of the cooling roller 35. Alternatively, the air ejection holes 35A are arranged in a spiral shape with an inclination angle θ.

  If the air ejection holes 35A are arranged in a straight line in the direction of the rotation axis (θ = 90 °) and the rows are arranged in parallel, the air ejection holes 35A intermittently contact the inner peripheral surface of the pressure belt 32. This affects the rotation of the pressure belt 32.

  Further, when the air ejection holes 35A are arranged in a straight line in the direction orthogonal to the rotation axis direction (θ = 0 °) and the respective rows are arranged in parallel, the portion that contacts the inner peripheral surface of the pressure belt 32 is not The contact portion is formed and cooled unevenly, which affects the rotation of the pressure belt 32.

  A cooling roller 35 formed of a metal material having a good thermal conductivity, such as an aluminum alloy, is cooled by a fan 37 and is in contact with the inner surface of a heated pressure belt 32 so as to be rotatable, and is pressurized by heat conduction. The inner surface of the belt 32 is cooled. Therefore, the cooling effect through the air that cools the inner surface side of the pressure belt 32 by the air blown from the fan 37 and the cooling effect that is cooled by the heat conduction from the cooling roller 35 that contacts the pressure belt 32 are added. A fixing device excellent in the cooling effect of the pressure belt 32 is provided.

  FIG. 5 is a timing chart for explaining an example of air blowing control during continuous printing in the paper conveyance state. FIG. 6 is a block diagram of the control unit 9 of the image forming apparatus.

  When the main power source of the image forming apparatus main body A is turned on, the image forming units 10Y, 10M, 10C, and 10K, the transfer unit, and the fixing device 30 are in a standby state. During this standby state, the fan 37 sends pressurized air into the cooling roller 35 via the blower pipe 38, and jets pressurized air from the air ejection holes 35A to forcibly cool the inner surface of the pressure belt 32. The air pressure in this standby state is a high pressure of 0.2 MPa (megapascal).

  When the print start button of the image forming apparatus main body A is turned on, the control unit 9 starts image forming processing and paper feeding. The control means 9 switches the drive of the fan 37 to low-pressure air blowing almost simultaneously or after a predetermined time has elapsed. The air pressure during the sheet passing state of the fixing nip portion is a low pressure of 0.1 MPa. Therefore, during the time when the recording material P passes through the fixing nip portion of the fixing device 30, the cooling roller 35 is ejected with low-pressure air pressure to cool the inner surface of the pressure belt 32.

  When the sensor PS arranged downstream of the fixing nip portion in the recording material conveyance direction detects that the rear end portion of the first recording material P has passed through the fixing nip portion, the control unit 9 drives the fan 37 with high-pressure air. Switch to. The air pressure during conveyance between the sheets is a high pressure of 0.2 MPa.

  When the image forming process for the second recording material P is started, the control unit 9 switches the driving of the fan 37 to low-pressure air blowing again. The air pressure within the time during which the second recording material P passes through the fixing nip portion is a low pressure of 0.1 MPa.

  After the second recording material P passes through the fixing nip portion, the control unit 9 switches the driving of the fan 37 to high-pressure air blowing. The air pressure during conveyance of the recording material P between the sheets is a high pressure of 0.2 MPa. Thereafter, the same blow pressure switching control is performed for the subsequent recording material P.

  When the series of image forming processes is completed, the recording material P of the last page is fixed by the fixing device 30, and when the sensor PS detects the passage of the trailing end of the recording material P, the control unit 9 drives the fan 37. By stopping, the closed space 300 on the inner surface side of the pressure belt 32 returns to atmospheric pressure.

  When image formation is continuously performed on the recording material P in the image forming apparatus main body A, the recording material P continuously holds the fixing nip portion formed between the fixing roller 31 and the pressure belt 32 while holding the gap between the sheets. Then pass. When the sheet of recording material P passes through the fixing nip portion, the pressure belt 32 receives excessive heat from the fixing roller 31 and the temperature of the entire area of the pressure belt 32 rises excessively. By cooling the air by blowing the air onto the inner surface of the pressure belt 32 by the cooling means, the unfixed toner image formed on the recording material P is prevented from being disturbed.

  Further, when the recording material P having a small size is continuously passed with respect to the maximum width of the recording material P in the fixing nip portion (the maximum length in the direction orthogonal to the conveyance direction), the pressure belt 32 is not in contact. The temperature of the sheet passing portion is excessively increased with respect to the temperature of the sheet passing portion, and temperature unevenness occurring in the longitudinal direction of the pressure belt 32 (width direction orthogonal to the conveying direction) is caused by the cooling means having the cooling roller 35. It will be resolved.

  In addition, unevenness occurs in the temperature at which the unfixed toner image formed on the recording material P is melted, resulting in image quality deterioration, unevenness in the friction coefficient in the fixing nip portion, image misalignment, The cooling roller 35 also eliminates image degradation that occurs particularly noticeably in the case of the recording material P such as thick paper.

  In the above embodiment of the fixing device, the fixing roller 31 is disposed as the heating rotator. However, the present invention is not limited to this, and the fixing roller 31 is rotated by being heated by a heating source instead of the fixing roller 31. The present invention can also be applied to a fixing device having a configuration in which a belt is arranged.

  In the description of the image forming apparatus main body A, color image formation has been described. However, a case where a monochrome image is formed is also included in the present invention.

Configuration of an image forming apparatus according to the present invention 1 is a cross-sectional view of a belt nip type fixing device according to the present invention. The expanded sectional view of a fixing roller and a pressure belt. The side view of a cooling roller. 6 is a timing chart for explaining an example of air blowing control during continuous printing in a paper conveyance state. FIG. 3 is a block diagram of control means of the image forming apparatus.

Explanation of symbols

9 Control means 30 Fixing device 31 Fixing member (fixing roller)
32 Pressure belt member (Pressure belt)
33 Inlet roller 34 Outlet roller 35 Cooling roller 35A Air ejection hole 36 Pressing means 36A Pressing pad 37 Blower means (fan)
38 Air duct 40 Air exhaust pipe 300 Closed space A Image forming apparatus body P Recording material

Claims (10)

In a fixing device having a pressure belt member that rotates in pressure contact with a fixing member,
At least one roller among the plurality of rollers that rotatably stretch the pressure belt member is a cooling roller having a plurality of air ejection holes perforated in a hollow cylindrical surface,
The fixing device, wherein the cooling roller is connected to a blowing unit that sends pressurized air into the cooling roller and jets the pressurized air from the air ejection hole. The plurality of rollers that stretch the pressure belt member include the cooling roller, an inlet-side inlet roller that feeds a recording material to a fixing nip portion where the fixing member and the pressure belt member are in pressure contact, and the fixing roller The fixing device according to claim 1, further comprising a separation roller that separates the recording material discharged from the nip portion. The jetting pressure of the pressurized air of the blower is switched to the first pressure at the start of image formation, and to the second pressure lower than the first pressure within the time for the recording material to pass through the fixing nip portion. The fixing device according to claim 1, wherein the fixing device is provided. The cooling roller that is formed in a closed space shielded by both side walls inside the pressure belt member stretched between the plurality of rollers, and blows air from the air blowing means toward the pressure belt member. The fixing device according to claim 1, wherein an air circulation path is formed by an air exhaust unit that exhausts air in the closed space to the outside of the apparatus. The fixing device according to claim 1, wherein the plurality of air ejection holes of the cooling roller are arranged with an inclination angle in a rotation direction of the cooling roller. The fixing device according to claim 1, wherein the cooling roller is made of a heat conductive metal material. The fixing device according to claim 1, wherein the cooling roller is a roller that applies tension to the pressure belt member. The fixing device according to claim 1, wherein the cooling roller is connected to the air blowing unit via the air blowing pipe. 9. The cooling roller according to claim 1, wherein the cooling roller is disposed on the downstream side of the separation roller and on the upstream side of the inlet roller with respect to the traveling direction of the pressure belt member. The fixing device according to Item 1. Image forming means for forming a toner image on an image carrier, paper feeding means for supplying a recording material to the image carrier, transfer means for transferring the toner image to the recording material, and the transferred toner image An image forming apparatus comprising the fixing device according to claim 1, wherein the fixing device is fixed to the recording material.

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