JP2011033778A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that satisfactorily separates transfer paper from a fixing belt or fixing roller without damaging a fixing member such as the fixing belt or fixing roller and moreover, suppresses the occurrence of a defective image caused by dew condensation. <P>SOLUTION: The fixing device includes: a pair of a heating roller and the fixing roller disposed in parallel with each other with a space between them; the fixing belt provided so as to be rotatable by the heating roller and fixing roller; and a pressure roller provided so as to be in contact with the fixing roller via the fixing belt. In the fixing device, a nip part is formed between the fixing belt and pressure roller and fixes an image on transfer paper on which an unfixed image is formed. In the fixing device, a separation plate formed of metal for separating transfer paper ejected from the nip part, from the fixing belt is disposed downstream of the nip part in the direction of movement of the transfer paper with a space left from the fixing belt. In addition, a blower means is provided for blowing air toward the space from downstream of the fixing belt in the direction of rotation of the belt. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device used for fixing an image in an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile, and an image forming apparatus having such a fixing device.

  An apparatus using an electrophotographic method, for example, a laser printer, has a rotating photosensitive drum, and after the photosensitive layer of the photosensitive drum is uniformly charged, it is exposed to a laser beam from a laser scanning unit and statically exposed. An electrostatic latent image is formed. Further, the laser printer develops the electrostatic latent image with toner to form a toner image, transfers the toner image onto a transfer paper, and further passes the transfer paper through a heat fixing device to thermally fix the toner image. It is configured.

  In such a conventional heat fixing device, for example, an adhesion preventing layer (also referred to as a release layer) made of a fluororesin layer or the like for preventing toner adhesion on the outer peripheral surface of a cored bar made of a hollow cylindrical body such as aluminum. ) Is used. In such a fixing roller, a heater such as a halogen lamp is disposed along the rotation center line in the hollow portion of the core metal, and the fixing roller is heated from the inside by its radiant heat.

  In addition, a pressure roller that is parallel to the fixing roller and is in pressure contact with the fixing roller is provided, and the toner adhering to the transfer paper is fixed by passing the transfer paper between the pressure roller and the fixing roller. There is also a technique in which fixing is performed on a transfer paper by pressing while being melted by heat of a roller.

  At this time, since the toner melts and is discharged in close contact with the fixing roller, the transfer paper is separated from a heat-resistant resin made of polyimide, polyamideimide, or PPS (polyphenylene sulfide) to peel off the transfer paper from the fixing roller. Has been brought into contact with the fixing roller.

  In recent years, with colorization, as a method of fixing transfer paper on which several color toners are laminated, an elastic layer made of silicone rubber is formed on a polyimide or metal belt, and fluorine is used to prevent toner adhesion. A fixing belt provided with an anti-adhesion layer made of a resin layer or the like is used.

  When a separation claw used for a hard type fixing roller is brought into contact with a fixing belt or a fixing roller having an elastic layer used in a fixing device using color toner, the separation claw bites into the elastic layer. The problem of being damaged arises. For this reason, various studies have been made on the technology relating to the transfer paper / fixing roller (fixing belt) separation mechanism.

  That is, in Japanese Patent Laid-Open No. 2001-83832 (Patent Document 1), a recording sheet discharged from a nip portion between a fixing roller and a pressure roller has a continuous curvature by bending an edge. It is disclosed that peeling is performed by a release sheet.

  Japanese Patent Laying-Open No. 2003-122175 (Patent Document 2) discloses that the separation member that contacts the fixing member is displaced when the leading edge of the transfer paper passes through the separation member.

  In Japanese Patent Application Laid-Open No. 2003-029564 (Patent Document 3), an action member that is arranged in a transfer path of a transfer paper, contacts a recording medium being conveyed and exerts a predetermined action on the recording medium, and one side is an action member. And a plate-like peeling member that is disposed in contact with or in proximity to peel the recording medium being conveyed from the action member, and the peeling member has a rough surface on the side where the recording medium being conveyed contacts. .

  However, in these techniques, since the separation member contacts the fixing member, the durability is low, and as a result, there is a possibility that stable separation can not be ensured. Although a method of always applying a lubricant such as silicone oil to prevent wear is also conceivable, the apparatus cost and running cost are increased, and the fixing device is increased in size.

  On the other hand, when the peeling member is separated from the fixing member, an image is formed on the entire area where the transfer paper image can be formed like a photographic image, that is, an image having only a minimum margin is formed, that is, a state In the case of fixing the image with the above, in consideration of the existence of a wide variety of transfer papers, it is impossible to separate them without reducing the gap with the fixing member to a distance close to the thickness of the transfer paper and without providing a peeling member. This method is also expected to be difficult to solve, resulting in poor separation and it is difficult to obtain a complete jamming prevention effect.

  Japanese Patent Application Laid-Open No. 2002-91222 (Patent Document 4) relates to a technique using a release sheet for releasing a sheet from a fixing member, performing a surface treatment such as etching on the release sheet, then applying an adhesive, and further heating. Although a technique is disclosed in which a fluororesin sheet is bonded to a dried metal plate and this release sheet is joined to a support member by laser spot welding, this technique requires a very large number of steps. There is a problem that it becomes expensive.

  In addition, according to the technique described in Japanese Patent Application Laid-Open No. 2003-122175 (Patent Document 5), there is a problem that the means for displacing the separation plate to be used is required, the structure becomes complicated, and the cost increases.

  Here, in the heat fixing device as described above, when the transfer paper left in a high humidity environment is passed, the water contained in the transfer paper evaporates at the high temperature nip portion.

  When a large amount of the moisture-absorbed paper is continuously passed through the nip portion, a large amount of water evaporates, the amount of water vapor in the vicinity of the nip portion increases, and the water vapor concentration becomes the saturated water vapor concentration. As a result, a phenomenon that water droplets adhere to the separating member or the like (condensation) occurs, which causes a problem of adhering on the fixed image and causing an image defect.

  Here, in recent years, due to demands for energy saving, the power consumption of the fixing apparatus during standby is suppressed, that is, the apparatus is left at room temperature during standby and the temperature is increased only during use. In such a fixing device, the nip is heated up to a fixing temperature required at the start of fixing. However, since the temperature of the separation member in the fixing device is low at the start of fixing, the above-described problem due to water vapor is particularly problematic. It has become apparent.

  Here, in the technique described in Japanese Patent Application Laid-Open No. 2004-13022 (Patent Document 6), a blower fan is provided near the fixing inlet guide on the upstream side of the nip portion of the transfer paper conveyance, and the blower fan is used during image formation. To drive air near the surface opposite to the nip of the pressure roller. With this configuration, when the transfer paper left at high humidity is continuously passed, By preventing stagnation in the fixing device, it is possible to suppress the occurrence of a failure due to condensation of a sheet metal or a resin member in the fixing device without affecting the fixed image.

  However, in this technique, the air is blown to the surface opposite to the nip portion of the rotating body (the pressure member described above) that does not generate heat in the fixing device, but when applied to a recent high-speed image forming apparatus. Therefore, it is difficult to maintain the nip portion at a temperature sufficient for image fixing, and as a result, adverse effects such as deterioration of fixing property occur.

  In Japanese Patent Laid-Open No. 5-134513 (Patent Document 7), after fixing an image on transfer paper, air is blown from a blower arranged on the lower surface of the fixing device to a vicinity of a guide member for discharging the transfer paper. In addition, a technique for preventing condensation of water vapor generated at the time of fixing the transfer paper by switching the air path between before and after using a partition plate is described. Similarly, since the air is blown to the surface opposite to the nip portion of the member that does not generate heat (the pressure member described above), there is a problem that the temperature of the nip portion is lowered when applied to a high-speed image forming apparatus. End up.

  In Japanese Patent Application No. 61-246210 (Patent Document 8), a belt-type conveying means for conveying an image-fixed recording paper is provided on the recording paper discharge side in the fixing device. A technique for preventing condensation of water vapor generated at the time of fixing the transfer paper by providing a device for rotating a liquid absorbing member such as a sponge as water removal means on the transport surface is described. In addition, there arises a problem that it becomes large.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the problems associated with a separating plate used in a fixing device of an electrophotographic image forming apparatus.

  That is, the present invention reduces a fixing device capable of satisfactorily separating transfer paper from these members without causing damage to fixing members such as a fixing belt and a fixing roller, and suppressing generation of defective images due to condensation. The purpose is to provide at a cost.

  In order to solve the above-mentioned problem, the fixing device of the present invention is rotated by a pair of heating roller and fixing roller, which are provided in parallel with a gap therebetween, and the heating roller and the fixing roller. An unfixed image between the fixing belt and the pressure roller, the fixing belt being provided, and a pressure roller provided so as to contact the fixing roller via the fixing belt. In a fixing device in which a nip portion for fixing an image is formed on a transfer paper on which a sheet is formed, a plate-shaped member made of metal for separating the transfer paper discharged from the nip portion from the fixing belt. A separation plate is provided on the downstream side of the nip portion in the transfer paper moving direction with a gap from the fixing belt, and blows air from the downstream in the rotation direction of the fixing belt toward the gap. Blowing means is a fixing device, characterized in that it is provided.

  The fixing device according to the present invention is the fixing device according to claim 1, wherein a heating source for heating the air is provided on the upstream side of the gap in the blowing direction by the blowing unit. It is characterized by being.

  According to a fixing device of the present invention, as described in claim 3, in the fixing device according to claim 1 or 2, the air blowing range in which the air blowing range by the air blowing means is changed in accordance with the width of the transfer paper. An adjusting means is provided.

  According to a fixing device of the present invention, as described in claim 4, the fixing device according to any one of claims 1 to 3, wherein the surface of the separation plate on the fixing belt side is provided with the fixing device. A plurality of parallel air guide grooves for guiding air into the gap are provided.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus having the fixing device according to any one of the first to fourth aspects.

  According to the fixing device of the present invention, the plate-shaped separation plate made of metal for separating the transfer paper discharged from the nip portion from the fixing belt is disposed downstream of the nip portion in the transfer paper moving direction. In addition, since there is provided air blowing means that is provided with a gap from the fixing belt and that blows air toward the gap from the downstream side in the rotation direction of the fixing belt, a complicated processing process or a high set is required. Without requiring the attaching accuracy, the transfer paper can be well separated from the fixing members such as the fixing belt and the fixing roller, and the generation of defective images due to condensation can be suppressed.

  According to the fixing device of the second aspect, since the heating source for heating the air is provided on the upstream side of the gap in the blowing direction by the blowing unit, an image caused by condensation more effectively. Disturbance can be prevented.

  Further, according to the fixing device of the third aspect, since the air blowing range adjusting means for changing the air blowing range by the air blowing means in accordance with the width of the transfer paper is provided, in the region where the water vapor is generated. Only air can be blown, and at this time, condensation can be prevented more efficiently.

  According to the fixing device of claim 4, the surface of the separation plate on the side of the fixing belt is provided with a plurality of parallel air guide grooves that guide the air into the gap. Since rectified and uniform ventilation is possible, it is possible to prevent condensation more effectively. Furthermore, since a plurality of air guide grooves are provided in this way, heat exchange between the blown air and the separation plate is efficiently performed, so that a higher dew condensation prevention effect can be obtained.

  In addition, according to the image forming apparatus of the present invention, since the fixing device is provided, jamming is prevented and disturbance caused by condensation is prevented in advance even when moisture-absorbing paper is used. A good fixed image can be obtained.

1 is a diagram schematically illustrating a full-color laser printer as a color image forming apparatus having a fixing device 10 according to the present invention. FIG. 1A is a model diagram of a full-color laser printer. FIG. 1B is a model diagram showing the inside of the image forming unit. FIG. 2 is an enlarged model view of the vicinity of a fixing unit of a color image forming apparatus having the fixing device 10 according to the present invention (however, the air blowing means is omitted). It is a model figure which shows an example of the separator plate used by this invention. FIG. 3A is a front view of the conveyance path side. FIG. 3B is a side view. FIG. 3C is a rear view of the fixing belt 4 side. FIG. 3D is a partially enlarged view showing that a plurality of parallel air guide grooves 1 a provided on the back surface of the separation plate 1 for guiding the air flow to the gap α are provided. 3 (e) and FIG. 3 (d) are cross-sectional views of the illustrated portion. It is a model figure which shows an example of the crossflow fan used with the fixing device of this invention. FIG. 4A is a cross-sectional view. FIG. 4B is a side view. 1 is a model diagram of a fixing device 10 of the present invention. FIG. 3 is a model diagram of the fixing device 10 of the present invention (a model diagram showing a shielding plate 9d).

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

  FIG. 1A schematically shows a full color laser printer as a color image forming apparatus having a fixing device 10 according to the present invention.

  This color laser printer has a configuration in which a two-stage sheet feeding unit 42 is disposed below the apparatus main body 41 and an image forming unit 43 is disposed thereon.

In such printers, plain paper (hereinafter simply referred to as plain paper) generally used for copying and the like, OHP sheets, 90K paper (basis weight: equivalent to about 100 g / m ² or more) such as cards and postcards, envelopes, etc. Any of so-called special sheets (hereinafter simply referred to as special sheets) having a larger heat capacity than the plain paper can be used as the sheet-like medium.

  Further, the image forming unit 43 is provided with a transfer belt device 44 arranged so that the paper feed side is on the bottom and the paper discharge side is on the top. The transfer belt device 44 has an endless transfer belt 46 that is wound around a plurality of roller groups 45 (not shown). One of the rollers 47 is driven by a drive source (not shown), so that the transfer belt 46 is rotationally driven. Is done.

  Four image forming units 51M, 51C, 51Y, and 51Bk for magenta (M), cyan (C), yellow (Y), and black (Bk) are sequentially provided on the upper running side of the transfer belt 46 from the upstream side of the transfer belt rotation. Are arranged in parallel.

  Each image forming unit 51M, 51C, 51Y, 51Bk is provided with a photoconductor 52 as an image carrier as schematically shown in FIG. 1B, and the photoconductor 52 is driven by a driving means (not shown). In the figure, it is rotated in the clockwise direction.

  Around the photosensitive member 52, there are provided a charging roller 53 as a charging unit, an optical writing unit 54 in which laser beam writing is performed by an optical writing device 54a, a developing device 55, and a cleaning device 56.

  The developing device 55 is a two-component developing device, and toner is supplied by a toner supply / conveyance device 57 (not shown) according to the amount of consumed toner.

  These image forming units 51M, 51C, 51Y, and 51Bk form magenta, cyan, yellow, and black images, respectively, and these single color images are transferred onto the transfer belt 46 so as to be superimposed one after another to form a color image. Then, these color images are transferred from the transfer belt 46 to the transfer paper by the transfer roller 48 and the second transfer roller 49, and the transfer paper on which the image has been transferred is sent to the fixing device 10. The fixing device 10 is pressed and heated by a nip portion formed between the fixing belt and the pressure roller, and the image is fixed on the transfer paper and sent to an upper tray (not shown).

Next, the fixing device 10 according to the present invention will be described with reference to FIG.
The fixing device 10 includes a fixing roller 2, a heating roller 3, a fixing belt 4, a nip portion 8, a pressure roller 5, and a separation plate 1 made of metal (in this example, a fluororesin layer is provided on the surface). Is provided).

  The fixing roller 2 includes a cored bar 2a and an elastic layer 2b made of an elastic body arranged around the cored bar 2a. The heating roller 3 has a heat source 3a of a halogen heater inside.

  The pressure roller 5 is configured by laminating an elastic layer 5b and a fluororesin layer 5c as a release layer on a metal core 5a. The pressure roller 5 includes a heat source 5d such as the halogen heater described above.

  The fixing belt 4 is configured by laminating a belt base 4a made of a heat-resistant resin (not shown), an elastic layer 4b made of silicone, and a release layer 4c made of fluororesin in this order, and further, a shifting operation at the time of rotation inside the both ends of the belt. 4d (not shown) is provided.

  When the transfer paper P fixed from the nip 8 between the fixing belt 4 and the pressure roller 5 is discharged, the fixing device 10 is in close contact with the fixing belt 4 by the toner s fixed on the transfer paper P. The transferred transfer paper P is peeled off by the separation plate 1. Further, the fixing device 10 has an inlet guide member 11 on the upstream side of the nip portion 8 on the transfer paper P conveyance path and an outlet guide member 12 on the conveyance path on the downstream side of the nip portion 8 so as to face the separation plate 1. The transfer paper P is conveyed and guided.

  The separation plate 1 is made of a sheet metal made of a metal such as iron, stainless steel, and aluminum because of its high rigidity and heat resistance (in this example, iron coated with a fluororesin). As shown in FIG. The front end portion 1e is formed so as to be thinner as it approaches the belt 4, and is integrally formed.

  FIG. 3A is a front view of the separating plate 1 in this example, FIG. 3B is a side view thereof, and FIG. 3C is a rear view of the fixing belt 4 side thereof. FIG. 3D is a partially enlarged view showing that a plurality of parallel air guide grooves 1a provided on the back surface of the plate 1 for guiding the air flow to the gap α are provided, and FIG. A cross-sectional view of the illustrated portion is shown in FIG.

  The separation plate 1 is pivotable by the shaft holes 1i provided on the side surfaces at both ends thereof being fitted to the mounting shafts 7 (not shown) provided in the frame portion of the fixing device 10 so as to be rotatable. Further, abutting portions 1f are provided at both ends where the transfer paper P at both ends of the separation plate 1 does not pass, and these abutting portions 1f abut near both ends of the fixing belt 4. Further, as described above, the clearance α is ensured between the front end portion 1e of the separation plate 1 and the fixing belt 4 by the biasing force from the frame portion of the fixing device 10 by the abutting spring 6 (not shown). At this time, the gap α can be adjusted to a desired width by the amount of protrusion of the abutting portion 1f from the main body of the separation plate 1 and the amount of urging by the abutting spring 6, but in the present invention, as described later, As a result, the initial end of the transfer paper that slightly floats from the fixing belt when it comes out of the nip portion is guided to the separation plate 1. However, it is usually sufficient if it is maintained at about 0.2 mm or more and 1 mm or less, and manufacturing is easy, and the manufacturing cost is low.

  As described above, the fixing device shown in FIG. 2 includes a pair of the heating roller 3 and the fixing roller 2 provided in parallel at an interval, and the fixing belt 4 provided rotatably by the heating roller 3 and the fixing roller 2. And a pressure roller 3 provided so as to be in contact with the fixing roller 2 via the fixing belt 4, and a transfer sheet on which an unfixed image is formed between the fixing belt 4 and the pressure roller 5. A fixing device in which a nip portion 8 for fixing an image is formed, and a plate-like separation plate made of metal for separating the transfer paper P discharged from the nip portion 8 from the fixing belt 4 1 is provided on the downstream side of the nip 8 in the moving direction of the transfer paper P with a gap from the fixing belt 4.

Next, the air blowing means will be described.
In this example, a cross flow fan 9 having a model sectional view in FIG. 4A and a model side view in FIG. According to such a cross flow fan, although it is a small diameter, it can blow widely and uniformly.

  The illustrated cross flow fan 9 is composed of 12 rotor blades 9b subdivided at intervals of 40 mm. As described above, the rotating blades 9b subdivided at intervals of 40 mm have the bending angle in the longitudinal direction improved by changing the mounting angle in the rotating direction (15 degrees in this example).

  Such a cross flow fan 9 is installed in the vicinity of the separation plate 1 and is blown from the nip portion 8 toward the gap α from the downstream side in the rotation direction of the fixing belt 4 as schematically shown in FIG. An air passage 9 a surrounding the cross flow fan 9 is formed.

  The airflow generated by the air flow by the cross flow fan 9 is supplied to the gap α between the separation plate 1 and the fixing belt 4. Since the gap α is a bottleneck here, the speed of the airflow increases and the nip portion Since the leading edge of the transfer paper P discharged from 8 hits the image forming surface of the transfer paper P and is guided to the transfer paper P conveyance path of the separation plate 1, the transfer paper P is reliably peeled off from the fixing belt 4. Further, according to this air blowing, the stagnation of air near the nip portion 8 can be prevented, so that condensation near the nip portion can be extremely effectively prevented.

  Moreover, since the air blowing means is provided in the fixing device 10 and is directly supplied to the gap α that has become a bottleneck as described above, even a small air blowing means is highly effective.

  Further, the air passage 9a is formed so as to take in air near the heating roller 3 (above the heating roller 3). That is, a guide for forming the air passage 9a of the blower inflow portion is provided above the heating roller 3 as a heat generation source, and the air warmed by the radiant heat generated from the heat generation source is taken toward the nip portion 8. Since the air is blown, dew condensation in the vicinity of the separation plate 1 and the nip portion 8 can be effectively prevented.

  Furthermore, since the transfer paper P is cooled by blowing and the image just fixed is firmly fixed to the transfer paper P, it is possible to prevent the toner from reattaching to the separation plate 1.

  In this example, the heating roller 3 is used as a heating source. However, if necessary, a heating source such as an electric heater may be provided, and such a heating source is used in combination with the heating roller 3. May be.

  In general, an image forming apparatus is compatible with transfer papers of various sizes. In the case of a transfer sheet having a narrow width, the transfer sheet is generally fed so that the center thereof coincides with the center of the sheet passing portion in the width direction. Here, it has air blowing range adjusting means for changing the air blowing range by the air blowing means according to the width of the transfer paper so as to blow only the paper feeding portion based on the paper type information from the image forming apparatus control unit. By blowing air only to the area where water vapor is generated, it becomes possible to reduce the amount of air blown by the air blowing means, and as a result, it is sufficient to reduce the power supplied to the air blowing means when forming images on transfer paper with a short width. Condensation can be prevented.

  Here, as shown in FIG. 5, the air blowing range adjusting means has an openable / closable shielding plate 9d that sets the air blowing range to blow the air blowing range in accordance with the sheet passing width of the transfer paper P, The shielding plates 9d are arranged in parallel, such as at least one at each end in the width direction of the transfer paper P, or one at each end and one near the center of the shielding plate at both ends. Has been.

  These shielding plates 9d are opened and closed by a linear cylinder (not shown) so as to be within a predetermined blowing range by a signal from the control unit of the apparatus main body 41 (paper width of the transfer paper to be passed through: size information such as A3 and B5). At this time, the rotational speed of the cross flow fan 9 is also controlled so that the air blowing speed in the gap formed is always constant. Since the electrode supply is small, it is efficient.

Examples are shown below.
The separation plate 1 used was manufactured as follows. That is, using a hot-dip galvanized steel sheet (SGCD1), rolling was performed around the portion corresponding to the tip portion 1e using a high flex press NS-2 300 ton made by Aida Engineering Co. to a tip thickness t = 0.2 mm. .

  Next, PTFE (polytetrafluoroethylene) resin in solid content ratio: 60 wt%, polyimide resin: 35 wt%, and fluororesin paint obtained by dispersing 5 wt% carbon black as an additive in these materials are used for transfer paper P. The contact surface 1g and the entire back surface 1h were sprayed on the entire surface by spray coating, dried at 150 ° C., and left in a 360 ° C. atmosphere for 20 minutes for baking to form a surface coating 1d.

  The separation plate thus formed was attached to the fixing device 10 so that the distance α between the separation plate and the fixing belt was 0.3 to 0.5 mm.

Further, the cross flow fan as the air blowing means described above is the above-described cross flow fan shown in FIG. 4 and is rotationally driven by the DC motor 9c (24V) (about 2600 rpm), and the air volume in the gap α is 1 to 2 m ^3. / Min.

  The air path is formed in the same manner as in the example shown in FIG. 4, and a cross flow fan 9 is provided as a blowing unit that blows air toward the gap α from the downstream in the rotation direction of the fixing belt 4, and the blowing direction by the cross flow fan 9 in the gap α A heating roller 3 is provided on the upstream side as a heating source for heating the air.

  The fixing device 10 manufactured as described above and, for comparison, a fixing device 10 ′ (comparative example) that is provided with the separating plate 1 in the same manner as the fixing device 10 but is not provided with a blowing means and an air passage are manufactured by Ricoh. A color MFP (multifunctional image forming apparatus) “Imagio MPC 2500” was mounted and a paper passing test was conducted.

  The test conditions were as follows. Using a transfer paper that was left in an environment of 30 ° C. and 90% RH (relative humidity) for 12 hours, a red solid image that was a two-color image of magenta M and yellow Y was set to 3 mm at the leading edge margin. (Paper width) was changed for a while and whether or not an abnormal image was generated when 200 sheets were continuously fed in double-sided image formation (printing copy) was examined.

  In the comparative example, image formation was performed by passing A3 paper. At this time, the width (the entire width of the sheet passing area) is 297 mm, condensation occurs on the surface of the separation plate 1 from the 12th sheet, and an abnormal image (waterdrop image, ie, water droplet image, that is, from the 16th sheet) Condensed water droplets adhered to the transfer paper P, resulting in an image in which the second side (back side) image was not charged during toner image formation and the toner was missing in the form of tears.

  In the present embodiment (Embodiment 1), similarly, however, the cross flow fan 9 was operated simultaneously with the start of sheet feeding and the air was blown to the gap α. It did not occur and good paper feeding and image formation were possible.

  In addition, image formation was similarly performed on B5 paper with vertical conveyance (paper width: 182 mm), and air blown to the gap α corresponding to the paper width was closed by shielding plates 9d at both ends of the paper passage area. In the state (Example 2 ventilation width: 185 mm), the power supply to the fan is set to 60% of the power supply amount in Example 1, and the wind speed in the gap α is at the same level as in Example 1. went. At this time, no condensation was observed as in Example 1, and no condensation was observed even when 300 sheets were added (a total of 500 sheets), and good results were obtained.

  Further, in the same manner as described above, however, a large number of minute air guide grooves 1a formed on the back surface 1h of the contact surface 1g using a press die formed into a convex shape by etching before forming the surface film 1d for producing the separator. A separator plate having the above structure was prepared. The shape of the air guide groove 1a formed here is formed as shown in FIG. 6 as a model. The cross-sectional shape is 300 μm wide and 15 μm deep, and the interval (pitch) between adjacent air guide grooves is 0.5 mm.

DESCRIPTION OF SYMBOLS 1 Separation plate 2 Fixing roller 3 Heating roller 4 Fixing belt 8 Nip part 10 Fixing device 2a Core metal 2b Elastic layer 3a Heat source 5a Core metal 5b Elastic layer 5d Heat source P Transfer paper s Toner

JP 2001-83832 A JP 2003-122175 A JP 2003-029564 A JP 2002-91222 A JP 2003-122175 A JP 2004-13022 A Japanese Patent Laid-Open No. 5-134513 Japanese Patent Application No. 61-246210

Claims (5)

A pair of heating roller and fixing roller provided in parallel at a distance, a fixing belt rotatably provided by the heating roller and the fixing roller, and abutting the fixing roller via the fixing belt A fixing roller having a nip portion for fixing an image on a transfer sheet on which an unfixed image is formed between the fixing belt and the pressure roller. ,
A plate-shaped separation plate made of metal for separating the transfer paper discharged from the nip portion from the fixing belt has a gap with the fixing belt on the downstream side of the nip portion in the transfer paper moving direction. Provided, and
The fixing device according to claim 1, further comprising a blowing unit that blows air from a downstream side of the fixing belt in a rotation direction toward the gap.   The fixing device according to claim 1, wherein a heating source for heating the air is provided upstream of the gap in the blowing direction by the blowing unit.   The fixing device according to claim 1, further comprising a blowing range adjusting unit that changes a blowing range of the blowing unit in accordance with a width of the transfer paper.   The surface of the separation belt on the side of the fixing belt is provided with a plurality of parallel air guide grooves that guide the air into the gap. The fixing device according to Item.   An image forming apparatus comprising the fixing device according to claim 1.

Images