JP2016206256A - Fixing device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image formation device that suppress reduction in energy efficiency for maintaining fixability, and can suppress dew condensation slip.SOLUTION: A fixing device includes a first rotary body driven by a drive source, a second rotary body forming a nip between the first rotary body and the second rotary body and is a hollow rotary body to be driven by the first rotary body in a heated state, and regulation members regulating pulling of the second rotary body at either end part of a long-side direction orthogonal to a recording member conveyance direction, and holds/conveys a recording member having a non-fixing toner image carried at a nip part. The fixing device comprises air-blow means that includes an air-blow fan and an air-blow channel, and forms heated air in at least a part of the air-blow channel to blow the heated air toward the first rotary body. The regulation member includes opening, respectively, and forms the heated air by causing air to pass through an interior of the hollow rotary body via openings of the either end part as the air-blow channel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fixing device and an image forming apparatus suitable for an image forming apparatus employing an electrophotographic recording method or an electrostatic recording method, such as a copying machine or a printer.

  A fixing device mounted on an image forming apparatus such as a copying machine or a printer using an electrophotographic system has a pair of rotating bodies that form a nip portion, and the other rotating body is driven by the rotation of one rotating body. A configuration in which the motor is driven and rotated is mainly used. The fixing device heats the recording material carrying the unfixed toner image at the nip portion while heating the recording material to fix the unfixed toner image on the recording material. When the fixing device is warmed up, the rotating body in contact with the unfixed toner image is heated by a heater or self-heated to a temperature at which the unfixed toner image can be fixed on the recording material. Heat.

  On the other hand, the rotating body on the side that does not come into contact with the unfixed toner image is not heated by the heater, and may not be sufficiently warmed during the warm-up period. As described above, when the recording material that has absorbed moisture is heated at the nip portion while the rotating body that does not come into contact with the unfixed toner image is not heated, water vapor is generated from the recording material, and the surface of the rotating body is condensed by the water vapor. There are things to do.

  When the rotating body on the side not in contact with the unfixed toner image is condensed, the frictional force at the nip portion is reduced. Then, the driving force from the driving-side rotator is not easily transmitted to the driven-side rotator, and the driven-side rotator does not rotate and the recording material may not be conveyed (condensation slip).

  Therefore, in order to suppress dew condensation on the rotating body on the side not in contact with the unfixed toner image, a configuration is disclosed in which air is blown to the rotating body on the side not in contact with the unfixed toner image using a blower fan (Patent Document 1). ). The fixing device of Patent Document 1 has a duct that is long in the axial direction of the pressure roller, and air is sent from an opening at an end portion in the longitudinal direction of the duct by a blower fan, and the wind faces the pressure roller of the duct It is the structure which blows off toward the pressure roller from the several hole provided in the part to carry out.

  In Patent Document 1, water vapor can be diffused by blowing air uniformly onto the surface of the pressure roller in the axial direction of the pressure roller, and condensation of the pressure roller can be suppressed. Thereby, dew condensation slip can be suppressed.

JP 2007-206275 A

  However, in the fixing device of Patent Document 1, since the air outside the device is directly blown onto the pressure roller by the blower fan, the temperature of the surface of the pressure roller decreases in the entire area in the axial direction of the pressure roller. Therefore, in order to maintain the fixing property, there is a problem that a large amount of electric power is supplied to the heater and energy efficiency is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus that can suppress a decrease in energy efficiency in order to maintain fixability and can suppress condensation slip.

  In order to achieve the above object, the fixing device according to the present invention forms a nip portion between a first rotating body driven by a driving source and the first rotating body, and is heated while being heated. A second rotator that is a hollow rotator driven by the first rotator, and a regulating member that regulates the deviation of the second rotator at both ends in the longitudinal direction perpendicular to the recording material conveyance direction. A fixing device that sandwiches and conveys a recording material carrying an unfixed toner image at the nip portion, and includes a blower fan and a blower path, and forms heated air in at least a part of the blower path, Blower means for blowing air toward the first rotator, the restricting members each having an opening, and passing the inside of the hollow rotator through the openings at both ends as the air passage. Forming the heated wind And

  The image forming apparatus according to the present invention includes an image forming unit that forms an unfixed toner image on a recording material, and a fixing device that sandwiches and conveys the recording material carrying the unfixed toner image at a nip portion. The second rotator is a hollow rotator that is driven by the first rotator in a heated state by forming the nip portion between the first rotator driven by the first rotator and the first rotator. A fixing member that is provided on the image forming apparatus main body and that restricts the second rotating body at both ends in the longitudinal direction perpendicular to the recording material conveyance direction, and a blower fan And an air blowing unit that forms a heated air in at least a part of the air flow path and blows air toward the first rotating body, wherein the restriction member Each having an opening, The heated wind is formed by passing the inside of the hollow rotating body through the openings at both ends as an air path.

  According to the present invention, it is possible to suppress a decrease in energy efficiency in order to maintain fixability, and to suppress condensation slip.

1 is a cross-sectional view of an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. FIG. 3 is a schematic diagram of a longitudinal section of a blowing unit in the fixing device according to the first embodiment. FIG. 3 is a schematic cross-sectional view of a blowing unit in the fixing device according to the first embodiment. FIG. 3 is a schematic cross-sectional view of a fixing film in the fixing device according to the first embodiment. FIG. 3 is a schematic diagram of a heater in the fixing device according to the first embodiment. FIG. 3 is a schematic diagram of a pressure roller and a duct in the fixing device according to the first embodiment. 3 is a flowchart of image formation in the image forming apparatus equipped with the fixing device according to the first embodiment. It is a schematic diagram of the longitudinal section of the ventilation means in the fixing device which concerns on 2nd Embodiment. It is a schematic diagram of the longitudinal cross-section of the ventilation means of the fixing device in a conventional example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<< First Embodiment >>
(Image forming device)
FIG. 1 is a configuration diagram of an image forming apparatus equipped with a fixing device according to the present embodiment. This image forming apparatus is an electrophotographic laser printer, and forms an image on a recording material according to image information input from an external device (not shown) such as a host computer.

  In the image forming apparatus shown in the present embodiment, when a print command is input from an external device, a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 61 as an image carrier is moved in a direction indicated by an arrow (process speed). ). In the photosensitive drum 61, the outer peripheral surface (surface) of the photosensitive drum 61 is uniformly charged to a predetermined polarity and potential by a charger 62.

  Image information is written on the charged surface of the photosensitive drum 61 by a laser scanner 63 as an exposure means. The laser scanner 63 outputs a laser beam L modulated in accordance with a time-series electric digital pixel signal of image information input from an external device to the printer. The laser scanner 63 scans and exposes the charged surface of the photosensitive drum 61 with the laser beam L. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 61.

  The electrostatic latent image is developed as a toner image (developed image) by the developing device 64 using toner (developer). A toner image on the surface of the photosensitive drum 61 (hereinafter referred to as a toner image) is obtained by rotating the photosensitive drum 61 and the outer peripheral surface (front surface) of the transfer roller 67 disposed so as to face the surface of the photosensitive drum 61. To the transfer nip between the two. The above is the configuration of the image forming unit.

  On the other hand, the recording materials P stacked on the sheet stacking table 68a of the feeding cassette 68 are picked up one by one by a feeding roller 69 driven at a predetermined control timing, and are conveyed by a conveying roller 70 and a conveying roller 70a. Sent to the registration department. In the registration unit, the leading edge of the recording material P is temporarily received by the nip portion between the registration roller 71 and the roller 71a to correct the skew of the recording material P. Thereafter, the recording material P is fed to the transfer nip portion at a predetermined timing in the registration portion.

  The predetermined timing here is a timing at which the front end portion of the recording material P reaches the transfer nip portion when the front end portion of the toner image on the surface of the photosensitive drum 61 reaches the transfer nip portion.

  The recording material P fed to the transfer nip portion is nipped and conveyed by the photosensitive drum 61 and the transfer roller 67. In the process of conveying the recording material P, the toner image on the surface of the photosensitive drum 61 is transferred to the recording material P by the transfer bias applied to the transfer roller 67, and the recording material P is separated from the surface of the photosensitive drum 61 and fixed. 72.

  The fixing device 72 heats and fixes the unfixed toner image to the recording material P by applying heat and pressure to the recording material P carrying the unfixed toner image at a nip portion N described later, and the recording material P is fixed to the nip portion. Eject from N. The recording material P discharged from the nip portion N of the fixing device 72 is conveyed to the discharge roller 74 by the intermediate discharge roller 73. Then, the discharge roller 74 discharges the recording material P onto the discharge tray 75. After the recording material P is separated, the transfer residual toner is removed by the cleaner 65 on the surface of the photosensitive drum 61, and the image is repeatedly used for image formation.

  In this image forming apparatus, the photosensitive drum 61, the charger 62, the developing device 64, and the cleaner 65 are integrated into a process cartridge 66. The cartridge 66 is detachably attached to the image forming apparatus main body 76 constituting the housing of the printer.

  The image forming apparatus main body 76 is provided with a cooling fan 77 for cooling the temperature raising member. The cooling fan 77 is rotated appropriately to take outside air into the image forming apparatus main body 76 to cool the temperature rising portions such as the image forming unit and the electrical board. An environment detection member 78 is provided in the vicinity of the cooling fan 77. When the outside air is taken in by the cooling fan 77, the temperature and humidity of the environment in which the image forming apparatus is installed are detected. The detection result is fed back to the temperature control sequence of the fixing device 72.

  Further, a movable regulation guide (not shown) for loading various types of recording materials having different sizes is provided on the sheet stacking table 68a of the feeding cassette 68. The regulation guide is displaced according to the size of the recording material P, and the recording material P is stacked on the sheet stacking board 68a, whereby various recording materials of different sizes are fed from the feeding cassette 68 by the feeding roller 69. You can pick up one by one.

  Note that the image forming apparatus of the present embodiment is an image forming apparatus compatible with A4 size paper, and has a printing speed of 52 sheets / minute (A4 landscape).

(Fixing device)
Hereinafter, a fixing device according to an embodiment of the present invention will be described with reference to FIGS. In the following description, regarding the fixing device 72 and members constituting the fixing device 72 according to the present embodiment, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material, and a heating rotator described later. It is a direction orthogonal to the rotation direction. The short direction is a direction parallel to the recording material conveyance direction on the surface of the recording material. The width is a dimension in the short direction. Regarding the recording material, the width direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material.

  As shown in FIG. 3, the fixing device 72 is in a heated state in which a nip portion N is formed between the pressure roller 20 as the first rotating body driven by the drive source and the pressure roller 20. The fixing film 10 as a second rotating body driven by the pressure roller 20 is provided. Then, the recording material carrying the unfixed toner image is nipped and conveyed at the nip portion N.

  And it has the heater 30 as a heating source or a heat generating body, the heater holder 41 holding the heater 30, and the pressurization stay 42 as a rigid body so that the inner peripheral surface of the fixing film 10 may be contacted. Further, as shown in FIG. 2, there are pressurizing means 43 that pressurizes the nip portion N, and a fixing flange 45 as a regulating member that regulates the shift of the fixing film 10 in the longitudinal direction. The fixing flange 45 may be configured as a member (a member in the image forming apparatus) provided in the main body of the image forming apparatus, or may be configured as a member in the fixing apparatus.

  The heater 30, the fixing film 10, the heater holder 41, the pressure stay 42, and the pressure roller 20 are all elongated members in the longitudinal direction. With such a fixing device 72, the pressure roller 20 is rotationally driven, and the fixing film 10 is driven and rotated by a frictional force acting between the pressure roller 20 and the fixing film 10.

1) Fixing Film As shown in FIG. 4, a fixing film 10 as an endless belt (endless belt) includes a base layer 11 formed into an endless film shape from a material having heat resistance and flexibility, and the base layer 11. And a releasable layer 12 provided on the outer peripheral surface. Further, an elastic layer 13 such as silicone rubber may be provided between the outer peripheral surface of the base layer 11 and the inner peripheral surface side of the release layer 12 in order to improve fixability and image quality.

  As the base layer 11, a heat-resistant resin such as polyimide, polyamideimide, polyetheretherketone or the like is used to form a thin-walled flexible endless belt. The material of the base layer 11 is not limited to a heat resistant resin, and a thin metal such as stainless steel (SUS) or nickel (Ni) having higher thermal conductivity may be used.

  On the outer peripheral surface of the base layer 11, a fluororesin such as PFA, PTFE, FEP or the like is coated as a release layer 12 alone or blended, or a tube is covered. PFA is a perfluoroalkoxy resin, PTFE is a polytetrafluoroethylene resin, and FEP is a tetrafluoroethylene-hexafluoropropylene resin.

  The thickness of the release layer 12 needs to be 5 μm or more from the viewpoint of durability. On the other hand, if the release layer 12 is too thick, the thermal conductivity is lowered and the fixability is affected. Thus, in order to achieve both durability and fixability, the thickness of the release layer 12 is set to 5 μm or more and 50 μm or less.

  When the elastic layer 13 is provided between the outer peripheral surface of the base layer 11 and the inner peripheral surface of the release layer 12, heat can be uniformly applied by wrapping the unfixed toner image T carried by the recording material P. For this reason, it is possible to follow the unevenness formed by the recording material P and the toner image T, suppress the roughness in the halftone image, and obtain uniform and sufficient fixing properties.

  Further, the elastic layer 13 can wrap the toner image T carried by the recording material P as the thickness of the elastic layer 13 is increased, and can be uniformly heated and fixed on the surface of the recording material P. That is, as the thickness of the elastic layer 13 is increased, the effect of wrapping the unfixed toner image T can be improved. However, if the thickness of the elastic layer 13 is too thick, the heat capacity becomes too large, and the rise of the fixing film 10 is delayed, and the on-demand characteristic peculiar to the film heating method is lowered.

Therefore, when providing the elastic layer 13, the thickness of the elastic layer 13 shall be 50 micrometers or more and 500 micrometers or less. Further, the thermal conductivity of the elastic layer 13 is preferably as high as possible, and is preferably 0.5 W / m · K or more. ZnO, Al ₂ O ₃ , SiC, metallic silicon, etc. so as to achieve such thermal conductivity The heat conductive filler is mixed in silicone rubber and adjusted.

  In the fixing film 10, the outer diameter of the fixing film 10 is preferably smaller because the heat capacity can be suppressed. However, if the outer diameter is made too small, the width of the nip portion N becomes narrow, so it cannot be made extremely small.

  Therefore, in the fixing film 10 of the present embodiment, SUS is used as the material of the base layer 11 in consideration of conditions such as the speed (process speed) of the image forming apparatus, and the thickness (thickness) of the base layer 11 is 30 μm. The inner diameter of this is 24 mm. The elastic layer 13 is made of silicone rubber having a thermal conductivity of 1.3 W / m · K and has a thickness of 250 μm. As the release layer 12, a PFA coating is used, and the thickness of the release layer 12 is 14 μm.

2) Heater holder The heater holder 41 shown in FIG. 3 has a semicircular cross-sectional shape with a heat resistant resin such as liquid crystal polymer, phenol resin, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), etc. It is formed as follows. The lower the thermal conductivity of the heater holder 41, the higher the thermal efficiency when the inner surface of the fixing film 10 is heated by the heater 30. Therefore, a hollow filler such as a glass balloon or a silica balloon may be included in the heat resistant resin forming the heater holder 41.

  On the lower surface of the heater holder 41 (the surface on the pressure roller 20 side), a groove for holding the heater is provided along the longitudinal direction of the heater holder 41. And the board | substrate 31 (FIG. 5) of the heater 30 is hold | maintained by the ditch | groove so that the protective sliding layer 34 (FIG. 5) mentioned later of the heater 30 may be exposed from this ditch | groove. The fixing film 10 is loosely fitted on the outer periphery of the heater holder 41. The heater holder 41 to which the fixing film 10 is externally fitted has both end portions in the longitudinal direction of the heater holder 41 held by the apparatus lateral frame 48 (FIG. 2).

3) Pressure roller The pressure roller 20 shown in FIG. 3 is provided on a core metal 21, an elastic layer 22 provided on the outer peripheral surface of the core metal 21, and an outer peripheral surface of the elastic layer 22. And a release layer 23. The cored bar 21 is formed in a round shaft shape from a material such as aluminum or iron. The material of the cored bar 21 is not limited to aluminum or iron, and a ceramic porous body having high strength, low heat capacity, and high heat insulation effect may be used.

  The elastic layer 22 is made of silicone rubber (solid rubber layer) or a sponge layer formed by foaming silicone rubber to have a heat insulating effect. The elastic layer 22 is not limited to the silicone rubber or the sponge layer, and has a porous material formed by adding a hollow filler, or a water-absorbing polymer and water in the silicone rubber layer in order to have a more heat insulating effect. A foam rubber layer may be used.

  On the elastic layer 22 described above, a release layer 23 of fluororesin such as purple alloalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene resin (FEP) or the like is formed. The release layer 23 may be a tube coated or a surface coated with a paint.

  Such a pressure roller 20 is disposed below the fixing film 10 so as to face the heater 30. In the pressure roller 20, both end portions in the longitudinal direction of the core metal 21 are rotatably held by the apparatus lateral frame 48.

  When the fixing device 72 is mounted on a relatively high-speed image forming apparatus, it is necessary to form an appropriate nip width at the nip portion N and to secure a certain heat capacity. Therefore, the pressure roller 20 in which the elastic layer 22 is formed using solid rubber having a thickness (thickness) of 3.5 mm was used. The release layer 23 is covered with a PFA tube having a thickness of 50 μm in consideration of durability. Further, the outer diameter of the pressure roller 20 is set to 30 mm.

4) Heater FIG. 5 is a configuration diagram of the heater 30. The heater 30 is a plate-like heating element that heats the fixing film 10 while being in contact with the inner peripheral surface of the fixing film 10. The heater 30 has a substrate 31 that is elongated in the longitudinal direction. The substrate 31 is an insulating ceramic substrate such as alumina or aluminum nitride, or a heat-resistant resin substrate such as polyimide, PPS, or liquid crystal polymer. A heating resistor 32 such as Ag / Pd (silver palladium), RuO2, or Ta2N is linearly formed on the surface of the substrate 31 (surface on the pressure roller 20 side) along the longitudinal direction of the substrate 31 by screen printing or the like. Alternatively, it is formed by applying a thin strip.

  The heating resistor 32 has a thickness of about 10 μm and a width of about 1 to 5 mm. In addition, on the surface of the substrate 31, power supply electrodes 33 for supplying power to the heating resistor 32 are provided inside both longitudinal ends of the substrate 31. Further, a protective sliding layer 34 may be provided on the surface of the substrate 31 so as to protect the heating resistor 32 as long as the thermal efficiency of the heating resistor 32 is not impaired. However, it is preferable that the thickness of the protective sliding layer 34 is sufficiently thin and the surface property of the heating resistor 32 is improved. As the protective sliding layer 34, a heat resistant resin such as polyimide or polyamideimide, a glass coat, or the like is often used.

  In the heater 30, when aluminum nitride or the like having good thermal conductivity is used as the substrate 31, the heating resistor 32 is formed on the back surface (the surface opposite to the pressure roller 20) of the substrate 31. Also good.

5) Fixing Flange The fixing flange 45 shown in FIG. 2 is held by the apparatus lateral frame 48. The position of the fixing film 10 in the longitudinal direction is regulated by receiving the offset of the fixing film 10 by the planar end regulating surface 46 facing the end surface of the end of the base layer 11 of the fixing film 10.

6) Pressurization stay The pressurization stay 42 shown in FIG. 3 is formed in a U-shaped cross-section downward with a material such as a metal having rigidity. The pressure stay 42 is disposed inside the fixing film 10 at the center in the short direction of the upper surface of the heater holder 41 (the surface opposite to the pressure roller 20). Then, both ends in the longitudinal direction of the pressure stay 42 are directed toward the axis of the pressure roller 20 by the pressure means 43 such as a spring through the fixing flange 45 held by the apparatus lateral frame 48 (FIG. 2). Is energized.

  As a result, the surface of the substrate 31 of the heater 30 is pressed against the surface of the pressure roller 20 via the fixing film 10, and the elastic layer 22 of the pressure roller 20 is elastically deformed along the substrate 31. As a result, a nip portion N having a predetermined width necessary for heating and fixing the toner image T is formed between the surface of the pressure roller 20 and the surface of the fixing film 10.

(Fixing operation)
Hereinafter, a fixing processing operation using the fixing device 72 of the present embodiment will be described. First, the control unit 44 (FIG. 2) drives a motor M as a drive source in response to a print command to drive the drive gear G provided at the longitudinal end of the core bar 21 of the pressure roller 20. Rotate. Thereby, the pressure roller 20 rotates in the arrow direction at a predetermined peripheral speed (process speed). At that time, a rotational force opposite to the rotational direction of the pressure roller 20 acts on the fixing film 10 by the frictional force between the surface of the pressure roller 20 and the surface of the fixing film 10 in the nip portion N.

  As a result, the fixing film 10 is driven to rotate in the direction of the arrow at the substantially same peripheral speed as the pressure roller 20 while the inner surface of the fixing film 10 is in contact with the protective sliding layer 34 of the heater 30.

  Further, as shown in FIG. 5, the control unit 44 energizes the heating resistor 32 from the power source 37 through the power supply electrode 33 of the heater 30 in accordance with the print command. Due to the energization, the heating resistor 32 generates heat, and the heater 30 rapidly rises in temperature to heat the fixing film 10. The temperature of the heater 30 is detected by a thermistor 35 as a first temperature detection member provided on the back surface of the substrate 31, and the thermistor 35 outputs a temperature detection signal of the heater 30 to the control unit 44. The thermistor 35 is disposed in a region where recording materials P of various sizes that can be used in the printer always pass in the recording material conveyance region of the nip portion N in the longitudinal direction of the heater 30.

  Furthermore, the control unit 44 takes in the temperature detection signal from the thermistor 35 and controls the amount of power supplied to the heating resistor 32 so that the heater 30 maintains the target temperature based on the temperature detection signal. That is, the control unit 44 appropriately sets the duty ratio, wave number, and the like of the voltage applied to the heating resistor 32 so that the heater 30 maintains a predetermined temperature control temperature based on the temperature detection signal from the main thermistor 35. I have control.

  A thermo protector 36 such as a thermo switch or a thermal fuse is arranged on the back surface of the substrate 31 of the heater 30. An input terminal (not shown) of the thermo protector 36 is connected in series with the power source 37, and an output terminal (not shown) is connected in series with the heating resistor 32 of the heater 30. Thus, when the heater 30 is in a runaway state due to a failure of the thermistor 35 or the like, the thermoprotector 36 detects an abnormal temperature rise of the heater 30 and shuts off the energization to the heating resistor 32.

  The recording material P carrying the unfixed toner image T is introduced into the nip portion N and conveyed while the rotation of the pressure roller 20 and the fixing film 10 is stable and the detection temperature of the heater 30 is maintained at the target temperature. Is done. The recording material P is nipped and conveyed at the nip portion N by the surface of the fixing film 10 and the surface of the pressure roller 20. In the conveyance process in the nip portion N, the toner image T of the recording material P is heated and fixed on the surface of the recording material P by supplying heat from the fixing film 10 and applying pressure.

(Condensation slip)
Here, the condensation slip will be described. When the recording material P is left for a long time in a high humidity environment, the recording material P 1 contains a large amount of moisture. Moisture contained in the recording material is instantly evaporated by the heat of the nip portion N 2 and becomes water vapor. The water vapor is more likely to be generated from the non-image forming surface side than the image forming surface side of the recording material P, that is, the pressure roller 20 side of the both surfaces of the recording material P from the surface of the fixing film 10 side. It is easy to generate from the surface. This is because the toner T on the recording material prevents the release of water vapor on the image forming surface side of the recording material P.

  The water vapor released to the pressure roller 20 side spreads from the downstream side in the rotation direction of the pressure roller 20 in the nip portion N to the upstream side by convection generated by the rotation of the pressure roller 20. When the pressure roller 20 is not warmed, water vapor in the vicinity of the pressure roller 20 is condensed on the surface of the pressure roller 20, and slippage occurs between the pressure roller 20 and the fixing film 10. It becomes easy.

  If slip occurs between the pressure roller 20 and the fixing film 10, the fixing film 10 may not be driven to rotate at the same rotational speed as the pressure roller 20. As a result, the conveyance speed of the recording material P at the nip portion N is significantly lower than the conveyance speed at the transfer portion, and the recording material is pushed into the transfer portion due to slack, or the recording material P is within the conveyance path. An image defect occurs because the toner image scatters and rubs. As described above, a phenomenon in which the rotation speed of the fixing film 10 is reduced due to the condensation of the pressure roller 20 and the image is defective is referred to as a condensation slip.

  Condensation slip is likely to occur when there is a large difference in the easiness of warming between the rotating body that contacts the unfixed toner image and the rotation that does not contact the unfixed toner image. That is, as in the present embodiment, the fixing film 10 is thin and has a small heat capacity and is directly heated by the heater 30 and is easily warmed. On the other hand, the pressure roller 20 has a rubber layer and the like and has a large heat capacity and is difficult to warm. Is the case.

  Such a situation is often regarded as completion when the temperature of the rotating body that comes into contact with the unfixed toner image reaches a fixable temperature when the fixing device is warmed up, and the unfixed toner at that time does not come into contact. This is because the temperature of the rotating body on the side is not controlled.

(Air blowing means to suppress condensation)
Hereinafter, the dew condensation-suppressing air blowing means, which is a characteristic configuration of the fixing device 72 of the present embodiment, will be described with reference to FIGS. 1 to 3 and FIG. 6. The dew condensation-suppressing blower in the present embodiment includes a blower fan and a blower passage, and heated blower is formed in at least a part of the blower passage and blows dew condensation toward the pressure roller 10.

  In the present embodiment, the flange 45 fixedly disposed at both ends in the longitudinal direction of the fixing film 10 has an opening 47 on each end regulating surface 46 as a ventilation member. And at least a part of the air passage forms an air passage 100 (FIG. 2) passing through the inside of the fixing film 10 that is a hollow rotating body in the longitudinal direction through the openings 47 at both ends, and is heated here. A blast is formed.

  Further, the air duct 50 (FIGS. 2 and 3), which is a first duct that forms a part of the air passage, has a long shape along the axial direction (longitudinal direction) of the pressure roller 20, and the pressure roller 20 is provided on the side opposite to the fixing film 10. One end 53 in the longitudinal direction of the air duct 50 (the direction perpendicular to the recording material conveyance direction) is provided with an opening, and the opposite end 54 is closed. The air duct 50 has holes 52 as a plurality of holes for discharging the wind taken from the opening 53 toward the pressure roller 20.

  Further, a connecting duct 80 (FIG. 2) that is a second duct that forms a part of the air passage is provided on the side surface of the fixing device 72, and the connecting duct 80 is formed on the end regulating surface 46 of one flange 45. It arrange | positions so that the opening part 47 and the opening part 53 of the end surface of the ventilation duct 50 may be connected.

  In addition, the blower fan 79 in the present embodiment is provided on the flange 45 side where the connecting duct 80 is not connected, and the opening of the end regulating surface 46 of the flange 45 via the fan duct 81 which is the third duct. The unit 47 is connected. The blower fan 79 is provided such that air is blown (wind is blown) in the direction of the connecting duct 80 through the opening 47 of the end regulating surface 46 of the flange 45 and the inside of the fixing film 10 by rotation. ing.

  Accordingly, when the blower fan 79 rotates, the air in the fixing film 10 is pushed by the wind of the blower fan 79 and moves to the connecting duct 80 through the opening 47 of the flange 45. Then, after the air in the fixing film is taken into the blower duct interior 55 from the opening 53 of the blower duct 50, it flows along the axial direction of the pressure roller 20. The wind blows out toward the surface of the pressure roller 20 from a plurality of holes 52 provided in a region 51 of the air duct 50 facing the pressure roller 20.

  In the dew condensation-suppressing blower means according to the present embodiment having such a blower passage, the wind from the blower fan 79 is heated while passing through the inside of the heated fixing film 10 in the longitudinal direction. For this reason, it is suppressed that energy efficiency falls (increasing the power supply to a heater) in order to maintain fixability, and a condensation slip is suppressed by performing the warmed ventilation to the pressure roller 20. The

  Here, the place where the hole 52 of the air duct is provided in the recording material conveyance direction will be described. The water vapor generated at the nip portion N wraps around in the rotation direction of the pressure roller 20 from the downstream side of the nip portion N in the rotation direction of the fixing film 10. Therefore, if the hole 52 is provided in the vicinity of the vertical line vl (FIG. 3) that extends from the axial center of the pressure roller 20 to the region 51 of the duct 50 or on the downstream side of the vertical line vl in the recording material conveyance direction, water vapor is effectively generated. Can diffuse.

  Next, control of the blower fan 79 (FIG. 2) will be described. As a condition in which condensation slip is likely to occur, the temperature of the pressure roller 20 is relatively low in a high humidity environment. Therefore, whether or not to drive the blower fan 79 is determined from the installation environment of the image forming apparatus and the warming condition of the pressure roller 20. In this embodiment, the environment sensor 78 (FIG. 1) is disposed as an environment detection member for detecting the environment in which the image forming apparatus 1 is installed, and the heater 30 is disposed on the back side of the heater 30 as a member for detecting the warming condition of the pressure roller 20. The temperature detected by the thermistor 35 and the number of prints described later are used.

  The reason why the temperature detected by the thermistor 35 is used is that the heater 30 forms the nip portion N with the pressure roller 20 via the fixing film 10, so before the heater 30 is controlled (at the time of blowing air to suppress condensation). This is because the temperature of the pressure roller 20 can be estimated.

  Here, the control of the blower fan 79 during image formation will be described with reference to the flowchart of FIG. First, at the time of receiving a print signal (Step 1), the environmental sensor 78 as a humidity detecting member that detects the environmental humidity detects a high humidity environment (humidity higher than a predetermined value) (Step 2). Then, it is determined whether or not the detected temperature of the thermistor 35 is less than 120 ° C. (Step 3) at the start of printing (at the start of warm-up of the heat fixing device 72). When the above-described two conditions are satisfied, after the start of image formation (Step 4), driving of the blower fan 79 for suppressing condensation is started at the timing when the first sheet of the print reaches the nip portion N (Step 5).

  Thereafter, when the image formation is completed within 30 sheets from the start of printing, the blower fan 79 is stopped simultaneously with the completion of the image formation (Step 12), and the process ends (Step 13). If printing continues for 30 sheets or more, the blower fan 79 is operated up to the 30th sheet, and the driving is stopped when the 30th sheet passes through the nip portion N (Step 8). For the 31st and subsequent sheets, the fan 79 remains stopped until image formation is completed.

  Here, when the temperature detected by the thermistor 35 at the start of printing is 120 ° C. or higher, it has been confirmed that the pressure roller 20 does not reach a temperature under any conditions during the period until the printing is completed. This is because the temperature of the pressure roller 20 during continuous printing tends to increase as the number of continuous prints increases, although it is low in the initial stage of printing.

  Further, in the fixing device 72 of the present embodiment, the number of sheets reaching the temperature at which the pressure roller 20 does not condense during continuous printing is 30 regardless of the temperature of the pressure roller 20 at the initial stage of printing. . Therefore, even if the blower fan 79 for suppressing condensation is driven at the initial stage of printing, the drive of the blower fan 79 is stopped after the 31st sheet of continuous printing.

  In the present embodiment, when the temperature behind the heater 30 detected by the thermistor 35 is lower than 120 ° C., it is estimated that the pressure roller 20 is a temperature at which dew condensation occurs lower than the threshold temperature. On the contrary, when the temperature of the back side of the heater 30 detected by the thermistor 35 is 120 ° C. or higher, the pressure roller 20 is estimated to be a temperature at which the dew condensation does not occur because it is higher than the threshold temperature.

  As described above, in the present embodiment, by using the detected temperature of the thermistor 35 at the start of printing and the number of prints in combination, it is estimated whether or not the temperature of the pressure roller 20 is in a temperature range in which condensation occurs, and a blower fan 79 for suppressing condensation. The drive is controlled.

  Further, as another means for determining the degree of warming of the pressure roller 20, the pressure roller surface temperature may be directly detected by a temperature detection member such as a thermopile. In this case, only when the pressure roller surface temperature is lower than a predetermined threshold temperature during the sheet passing, it is possible to drive the blower fan 79 for suppressing condensation. Further, a fixing prediction count that predicts the temperature of the pressure roller 20 by adding or subtracting a unique count value at the time of passing paper, at the time of paper gap, at the time of stopping, or the like may be used. As long as the temperature of the pressure roller 20 can be estimated as described above, the method is not limited to the above method.

<Performance evaluation>
As performance evaluation of this embodiment, in a high temperature and high humidity environment (32.5 ° C./80%), the presence / absence of image failure due to condensation slip and fixability were confirmed, and compared with the conventional configuration as two comparative examples. The evaluation paper was A4 size paper (60 g / mm 2) left for a long time in the environment described above, the print pattern was a solid black image, and 50 sheets were printed continuously from the state where the heat fixing device was at the same temperature as the room temperature. . The image forming apparatus used is an A4 size paper compatible machine with a printing speed of 52 sheets / minute and FPOT 7.0 seconds.

  In the present embodiment and the two comparative examples, the same heater control was considered. In addition, all the fixing devices started printing from a state where they were left until the temperature of the pressure roller was approximately the same as the room temperature.

In the present embodiment, the total air volume from the blower fan is 0.007 [m ³ / min]. FIG. 9 shows a longitudinal section of a blower fan 79 and a fixing device 72 in a conventional image forming apparatus as Comparative Example 1. In Comparative Example 1, the blower fan 79 and the fan duct 81 are arranged so that the air outside the fixing device blows directly onto the pressure roller. Further, no opening is provided in the end regulating surface 46 of the flange 45. Other configurations and fan control are the same as those in the embodiment. Further, the total air volume from the fan of Comparative Example 1 is 0.007 [m ³ / min], which is the same as that of the present embodiment.

  In Comparative Example 2, the fan 79, the fan duct 81, and the air duct 50 are removed from Comparative Example 1, and the other configurations are the same as those in the present embodiment.

  Table 1 shows the evaluation results of the present embodiment, Comparative Example 1, and Comparative Example 2 described above. As evaluation items, image defects due to condensation slip and image defects due to fixing property deterioration were evaluated. ○ indicates that no image defect occurred, and x indicates that an image defect occurred.

  In Comparative Example 1, no image defect occurred due to condensation slip. This is because it was possible to suppress the dew condensation on the entire surface of the pressure roller by blowing air to the pressure roller. However, because air at room temperature was blown onto the pressure roller, the solidity of the solid black image or the back of the subsequent paper was soiled with the initial 10 sheets with relatively low pressure roller temperatures. An image defect due to deterioration occurred. Since then, the pressure roller has warmed up, so the fixing property has been improved. In order to improve this fixing failure, it is necessary to raise the target temperature of the heater, and the energy efficiency deteriorates.

  In Comparative Example 2, since no wind was blown to the pressure roller, no defective image occurred due to deterioration of fixing property in all 50 sheets. However, image defects due to condensation slip occurred on 9 out of 50 printed sheets. Further, when the paper was continued to some extent, the pressure roller was warmed, so that no condensation slip occurred.

  On the other hand, in this embodiment, no image defect occurred. The start of driving the blower fan is set at the moment when the first printed sheet reaches the nip portion N. The heater at this time is sufficiently warmed, and the air in the fixing film is warmed by the heat of the heater. This is because by blowing this warmed air on the pressure roller, water vapor can be blown off almost without lowering the pressure roller temperature.

  Also, since the heat capacity of air is sufficiently small compared to the heat capacity of the fixing film, even if warm air is discharged and air at room temperature is introduced instead, the power consumption of the fixing device and the surface temperature of the fixing film are also large. There was no change. This is because the heater directly heats the fixing film, and air hardly affects the heating mechanism.

  As described above, in this embodiment, it is possible to maintain both the fixing property and suppress the condensation slip without substantially reducing the energy efficiency.

  In this embodiment, the fan stop timing is set to the moment when the 30th recording material passes through the nip. However, since the pressure roller temperature varies depending on the configuration of the pressure roller, the process speed, the length between sheets, the heater start-up time, and the like, the fan stop timing may be changed according to the status of the product.

  In this embodiment, the blower fan is provided in the image forming apparatus, but may be provided in the fixing device. Furthermore, in this embodiment, although the opening part of the ventilation duct was provided in the edge part of the pressure roller axial direction of a ventilation duct, you may provide in the lower surface etc. of a ventilation duct.

<< Second Embodiment >>
In the present embodiment, a fixing device capable of suppressing condensation slip while further suppressing the temperature drop of the pressure roller 20 as compared with the first embodiment will be described. The image forming apparatus is required to further improve the throughput and shorten the FPOT, and it is considered that the image forming apparatus is increasingly disadvantageous for the condensation slip. For example, if the interval between the preceding paper and the succeeding paper during continuous printing is shortened to improve the throughput, heat is hardly supplied from the rotating body that contacts the unfixed toner image to the rotating body that does not contact the unfixed toner image. Therefore, it is difficult for the pressure roller to warm up, which is disadvantageous for condensation slip.

  Also, if the heat capacity of the rotating body that comes into contact with the unfixed toner image is further reduced to shorten the FPOT so that it quickly warms up, the warming up occurs before the rotating body that does not contact the unfixed toner image warms up. Will be disadvantageous to condensation slip.

  FIG. 8 shows a longitudinal section of a blower unit including the blower fan and the blower passage according to the present embodiment that meets such a request. In the present embodiment, the dew condensation-suppressing blower fan 79 is disposed in the connecting duct 80 as the second duct, and the driving gear side of the pressure roller of the fixing device 72 is covered with the side cover 82, thereby connecting the connecting duct. An opening 47 of the flange 45 on the side not connected to 80 is also in the fixing device. In this state, when the blower fan 79 is driven and the heated air in the fixing film (air blow path 100) is sucked into the connecting duct 80, the warm air is blown to the pressure roller 20 to compensate for it. Air in the fixing device flows from the opening 47 of the flange 45.

  At this time, the warm air blown to the pressure roller 20 is again sucked into the fixing film from the opening 47 of the flange 45, whereby the warmed air in the fixing device starts to circulate. By circulating the warm air in the fixing device in this way, warmer air can be blown onto the pressure roller 20, and a decrease in the pressure roller surface temperature can be suppressed. Therefore, in this embodiment, it is possible to suppress condensation slip while minimizing a decrease in energy efficiency.

  Here, at least one of the connection duct 80 and the fan 79 in the connection duct may be provided on the image forming apparatus side.

(Modification)
Although the preferred embodiments of the present invention have been described in the above-described embodiments, the present invention is not limited to these embodiments, and various modifications are possible within the scope of the gist.

(Modification 1)
In the above-described embodiments, the fixing device includes a cylindrical fixing film, a heater that contacts the inner surface of the fixing film, and a pressure roller that forms a nip portion together with the heater via the fixing film. . However, the fixing device includes a first rotating body that is driven by a driving source and a second rotating body that is driven by the first rotating body by forming a nip portion between the first rotating body and the first rotating body. The second rotating body is not limited to this as long as heat is transmitted from the inside to the outer surface.

  For example, a cylindrical fixing film, a heater that is contained in the fixing film and that heats the inner surface of the fixing film with radiant heat, a nip portion forming member that contacts the inner surface of the fixing film, and the nip portion through the fixing film together with the nip portion forming member And a pressure roller that forms the surface. Also, a cylindrical belt (film) that self-heats by electromagnetic induction or energization, a nip forming member that contacts the inner surface of the cylindrical belt, and pressurization that forms a nip through the belt together with the nip forming member And a device having a roller.

(Modification 2)
In the above-described embodiment, the recording material is conveyed so that the center in the width direction coincides with the center in the longitudinal direction perpendicular to the recording material conveyance direction of the nip portion of the fixing device, but the present invention is not limited to this. Any one end in the width direction of the recording material may be conveyed in accordance with the end in the longitudinal direction perpendicular to the recording material conveyance direction of the nip portion of the fixing device.

(Modification 3)
In the above-described embodiment, the endless belt is provided on the first rotating body. However, the endless belt may be provided on the second rotating body facing the first rotating body. An endless belt may be provided on both the first rotating body and the second rotating body.

  In the above-described embodiment, the case where the rotating body (pressure roller) as the rotating body and the pressing body presses the fixing rotating body (fixing belt) is shown. However, the present invention is not limited to this, and the present invention can be similarly applied to a case where a rotating body as an opposing body is pressed from a fixing belt (film) as a fixing rotating body, not as a pressing body. Here, the opposing body is a member that faces the fixing rotator, presses against the fixing rotator, forms a fixing nip portion, and clamps the moving recording material at the fixing nip portion.

  In the above-described embodiment, the recording paper is described as the recording material. However, the recording material in the present invention is not limited to paper. Generally, a recording material is a sheet-like member on which a toner image is formed by an image forming apparatus. For example, regular or irregular plain paper, cardboard, thin paper, envelope, postcard, seal, resin sheet, OHP sheet, Includes glossy paper. In the above-described embodiment, for the sake of convenience, the recording material (sheet) P has been described using terms such as passing paper, paper passing portion, and non-paper passing portion. It is not limited.

  In the above-described embodiment, the fixing device that fixes an unfixed toner image on the sheet has been described as an example. However, the present invention is not limited to this, and the toner that is assumed on the sheet in order to improve the gloss of the image. The present invention can be similarly applied to a device that heats and presses an image (also a fixing device in this case).

10..Fixing film, 20..Pressure roller, 50..Blower duct (fan path), 79..Blower fan, 80..Connection duct (fan path), 100..Blower path

Claims (12)

A first rotating body driven by a driving source;
Forming a nip portion between the first rotating body and a second rotating body that is a hollow rotating body driven by the first rotating body in a heated state;
A regulating member that regulates the second rotating body at both ends in the longitudinal direction perpendicular to the recording material conveyance direction;
A fixing device for holding and conveying a recording material carrying an unfixed toner image at the nip portion,
A blower fan and a blower passage, forming a heated air in at least a part of the blower passage, and having a blower for blowing air toward the first rotating body;
Each of the regulating members includes an opening,
The fixing device, wherein the heated wind is formed by passing the inside of the hollow rotating body through the openings at both ends as the air passage. The blowing means is
A first duct having a hole facing the first rotating body;
A second duct that is provided on the upstream side of the first duct as a part of the air passage, and that connects the first duct with a side close to the first duct among the openings at the both ends. ,
The fixing device according to claim 1, further comprising:   The said blower fan is provided in the inside of the 3rd duct connected to the upstream of the opening of the side far from the said 2nd duct among the opening of the said both ends. Fixing device.   The fixing device according to claim 2, wherein the blower fan is provided inside the second duct.   5. The fixing device according to claim 2, wherein the hole portion is provided at least downstream of the nip portion in the recording material conveyance direction. A temperature detecting member for detecting the temperature of the first rotating body;
6. The fixing device according to claim 1, wherein the blower fan is driven when the temperature of the first rotating body is a temperature at which condensation occurs lower than a threshold temperature. . Has a humidity detection member that detects environmental humidity,
The fixing device according to claim 1, wherein the blower fan is driven when the humidity detected by the humidity detection member is higher than a predetermined value.   8. The fixing device according to claim 6, wherein the blower fan is driven when the number of recording materials passing through the nip portion is lower than a predetermined value.   The fixing device according to claim 1, wherein the first rotating body is a pressure roller, and the second rotating body is a cylindrical film.   The fixing device according to claim 9, further comprising a heating source that is in contact with an inner peripheral surface of the film or provided inside the film.   The fixing device according to claim 9, wherein the film self-heats by electromagnetic induction or energization. An image forming unit for forming an unfixed toner image on a recording material;
As a fixing device for nipping and conveying the recording material carrying the unfixed toner image at a nip portion,
A first rotating body driven by a driving source;
Forming the nip portion between the first rotating body and a second rotating body that is a hollow rotating body driven by the first rotating body in a heated state;
The fixing device comprising:
A regulating member that is provided in the image forming apparatus main body and regulates the shift of the second rotating body at both ends in the longitudinal direction perpendicular to the recording material conveyance direction;
A blower unit comprising a blower fan and a blower passage, forming a heated air in at least a part of the blower passage, and blowing air toward the first rotating body,
An image forming apparatus having
Each of the regulating members includes an opening,
The image forming apparatus, wherein the heated wind is formed by passing the inside of the hollow rotating body through the openings at both ends as the air passage.