JP2006058514A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of regulating the biasing of a belt with simple constitution. <P>SOLUTION: The fixing device has a nip surface formed by bringing two endless belts into contact with each other and performs processing to fix toner on recording paper by making the recording paper to which the toner is transferred pass through the nip surface. The fixing device has a nip end roller on which either of the two endless belts is stretched and laid and which is positioned at the end of the nip surface, and a nip outside roller on which the other of the two endless belts is stretched and laid and which is positioned at a part other than the nip surface. The nip end roller and the nip outside roller have belt biasing regulating members for regulating the biasing of the belt on both sides in a shaft direction on the rollers, and a space between the biasing regulating members of the nip end roller is made wider than that of the nip outside roller. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device using a belt used for image formation, such as an electrophotographic copying machine, a printer, and a FAX.

  In recent years, colorization has become widespread in electrophotographic copying machines, printers, fax machines, and the like.

  In the case of color printing, in the fixing device, if the toner is not sufficiently melted, the color of the toner in the lower layer cannot be seen through, so that the color gamut becomes narrow and the color developability deteriorates.

  In order to widen the color gamut, it is necessary to increase the nip time during fixing, that is, to increase the nip length and to transfer heat to the toner. In roller fixing using a heating roller and a pressure roller, In order to increase the nip width, the roller diameter becomes large, the separation effect due to the curvature of the paper is reduced, and there is a problem that the paper cannot be separated from the roller.

  For this reason, the separation claw is brought into contact with the roller to forcibly separate the paper.

  In order to prevent the roller from being scratched by the separation claw, oil is also applied, but the oil application device increases the cost, and by applying oil, the image is written with a ballpoint pen or the like. There is a problem that becomes difficult.

  In this way, instead of the roller fixing method having various problems, the following fixing device using two belts has been proposed as means for increasing the nip length.

That is, in a double-sided image fixing apparatus capable of fixing double-sided images on a recording material in a batch, a front-side fixing belt unit in which an endless front-side fixing belt is wound around a plurality of roll groups including a front-side heating roll with a built-in heat source; A back-side fixing belt unit in which an endless back-side fixing belt is wound around a plurality of roll groups including a back-side heating roll with a built-in heating source, and the back-side fixing belt is disposed in contact with the front-side fixing belt. In the contact area between the front side fixing belt and the back side fixing belt, the front side heating roll and the back side heating roll are displaced with respect to the moving direction of the two fixing belts (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-174878

  As in Patent Document 1, in the fixing device using two belts, the nip length can be made longer than that of the roller fixing described above, so that the toner in a plurality of layers such as a color is sufficiently melted. Thus, the color of the toner in the lower layer can be seen through, and the color gamut can be widened.

  On the other hand, in a fixing device using a belt, there is a problem that the belt is shifted. In order to cope with this problem, in Patent Document 1, any one of the rollers that stretch the belt can be tilted by a steering. As the roll, the tilt amount of the steering roll is controlled according to the amount of deviation.

  However, when trying to regulate the deviation with the above-described configuration, there is a problem that the apparatus becomes large or the control becomes complicated.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a fixing device that can regulate the deviation of the belt with a simple configuration.

  The object of the present invention can be achieved by the following configurations.

  (1) In a fixing device having a nip surface formed by bringing two endless belts into contact with each other, passing the recording paper onto which the toner is transferred to the nip surface, and fixing the toner onto the recording paper. One of the two endless belts is stretched and a nip end roller positioned at the end of the nip surface, and the other of the two endless belts is stretched and the nip is positioned other than the nip surface. The nip end roller and the nip outer roller have a belt side deviation regulating member that regulates the deviation of the belt on both sides in the axial direction on the roller, and the piece of the nip end roller The fixing device is characterized in that an interval between the deviation regulating members is wider than an interval between the deviation regulating members of the outer nip roller.

  (2) The fixing device according to (1), further including a pressing member that presses the nip end roller through the two endless belts.

According to the first aspect of the present invention, there is provided a nip surface formed by bringing two endless belts into contact with each other, passing the recording paper onto which the toner is transferred to the nip surface, and fixing the toner to the recording paper. In the fixing device, one of the two endless belts is stretched, and a nip end roller positioned at an end of the nip surface and the other of the two endless belts are stretched, and the nip A nip outer roller located on a surface other than the surface, and the nip end roller and the nip outer roller have belt deviation regulating members for regulating the deviation of the belt on both axial sides of the roller,
Since the gap between the deviation regulating members of the nip end roller is wider than the gap between the deviation regulating members of the nip outer roller, the gap between the two deviation regulating members is different. Narrow belts do not rub at the end when passing over a roller with a large spacing between offset regulating members, so that they are not damaged or torn. The deviation of the belt can be regulated.

Therefore, compared to a configuration in which the roller that stretches the belt is freely tiltable and the tilt of the roller is controlled in accordance with the amount of deviation, the belt is reliably displaced with a simple configuration without damaging the belt. Can be regulated.
In addition, since the nip length can be increased by using two belts, the toner on the recording paper is crushed by applying a load, and the toner is sufficiently melted in a long nip time, so that the fixing property and the color developing property are excellent. A fixing device can be provided.

  According to the invention of claim 2, by having a pressing member that presses the nip end roller via the two endless belts, the toner is further crushed by applying a load to the toner. Fixability and color development can be ensured more reliably.

  Hereinafter, an example of an embodiment of the present invention will be described. The description in this column does not limit the technical scope of the claims and the meaning of the terms, and the assertive explanation in the following embodiments of the present invention shows the best mode, It does not limit the meaning or technical scope of the terms of the present invention.

  First, an image forming apparatus using a fixing device according to the present invention will be described with reference to FIG.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus.

  In addition, in the following description including FIG. 1, the same number is attached | subjected to the member which has the same function and structure.

  According to FIG. 1, the image forming apparatus GS includes an image forming apparatus main body GH and an image reading apparatus SC provided on the upper part of the image forming apparatus main body GH.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus, and arranges image forming units that form yellow, magenta, cyan, and black color toner images along the moving direction of the intermediate transfer member. The color toner image formed on the image carrier of each image forming unit is transferred onto the intermediate transfer member and superimposed, and then transferred onto the recording paper at once.

  In the figure, an analog signal scanned and exposed by an optical system on a document image placed on the image reading device SC, read into a line image sensor CCD, and photoelectrically converted by the line image sensor CCD is converted into an analog signal by an image processing unit. After processing, A / D conversion, shading correction, image compression processing, and the like are performed, the image is sent to an exposure optical system 3 serving as an image writing unit.

  In the figure, four sets of processes for forming images for each color of yellow (Y), magenta (M), cyan (C) and black (K) are provided on the peripheral edge of the intermediate transfer belt 6 as an intermediate transfer body. The unit 100 serves as a color toner image forming means in the order of Y, M, C, K in the vertical direction along the intermediate transfer belt 6 with respect to the rotation direction of the intermediate transfer belt 6 in the vertical direction indicated by the arrows in the drawing. Has been placed.

  Each of the four process units 100 has a common structure, and each includes a photosensitive drum 1 as an image carrier, a charger 2 as a charging unit, an exposure optical system 3 as an image writing unit, and development. It comprises a developing device 4 as a means and a photoreceptor cleaning device 190 as an image carrier cleaning means.

  The photosensitive drum 1 is an organic material having a layer thickness (film thickness) of about 20 to 40 μm as a photosensitive layer on the outer periphery of a cylindrical substrate formed of a metallic member such as aluminum having an outer diameter of about 40 to 100 mm. A photoconductive layer (OPC) is formed. The photosensitive drum 1 is rotated in the direction indicated by the arrow.

  Around the photosensitive drum 1, an image forming unit including a charger 2, an exposure optical system 3, and a developing device 4 as a set is arranged with respect to the rotation direction of the photosensitive drum 1 indicated by an arrow in the drawing. .

  The charger 2 is attached in close proximity to the photosensitive drum 1 in a direction orthogonal to the moving direction of the photosensitive drum 1 (in the direction perpendicular to the paper surface in the drawing). The charger 2 includes a discharge wire as a corona discharge electrode that applies a predetermined potential to the organic photosensitive layer of the photosensitive drum 1, and performs charging action by corona discharge having the same polarity as the toner. A uniform potential is applied.

  The exposure optical system 3 rotationally scans laser light emitted from a semiconductor laser (LD) light source (not shown) in the main scanning direction by a rotating polygon mirror (no symbol), an fθ lens (no symbol), and a reflection mirror (reference symbol). None), the photosensitive drum 1 is exposed to an electrical signal corresponding to the image signal (image writing), and an electrostatic latent image corresponding to the original image is formed on the photosensitive layer on the surface of the photosensitive drum 1. To do.

  The developing device 4 accommodates a two-component developer of each color of yellow (Y), magenta (M), cyan (C) or black (K) charged to the same polarity as the charging polarity of the photosensitive drum 1, A developing roller 4a which is a developer carrying member is provided. The developing roller 4a is kept in a predetermined gap from the photosensitive drum 1 by an abutment roller (not shown), and rotates in the forward direction and the rotational direction of the photosensitive drum 1. During development, the developing roller 4a On the other hand, by applying a DC voltage having the same polarity as that of the toner or a developing bias voltage in which an AC voltage is superimposed on the DC voltage, reversal development is performed on the exposed portion on the photosensitive drum 1.

  The intermediate transfer belt 6 is a semiconductive endless (seamless) resin belt member having a volume resistivity of about 1E + 7 to 1E + 9 Ω · cm and a surface resistivity of about 1E + 10 to 1E + 12 Ω / □. The intermediate transfer belt 6 is wound around a plurality of roller members including a tension roller 6a, and is supported rotatably in a vertical method. It is also possible to use a drum-shaped intermediate transfer member.

  The primary transfer roller 7 as a first transfer unit for each color is made of a roller-like conductive member using foamed rubber such as silicon or urethane, and a photosensitive drum for each color with the intermediate transfer belt 6 interposed therebetween. 1, and the back surface of the intermediate transfer belt 6 is pressed to form a transfer area with the photosensitive drum 1. A DC constant current having a polarity opposite to that of the toner is applied to the primary transfer roller 7 by constant current control, and the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 6 by a transfer electric field formed in the transfer area. The

  The image forming process (image forming process) will be described below.

  When the image recording is started, the photosensitive drum drive motor (not shown) is rotated to rotate the Y photosensitive drum 1 in the direction indicated by the arrow in the figure, and a potential is applied to the Y photosensitive drum 1 by the Y charger 2. . After the Y photosensitive drum 1 is applied with a potential, the Y exposure optical system 3 performs exposure (image writing) with an electrical signal corresponding to the first color signal, that is, the Y image data. An electrostatic latent image corresponding to a yellow (Y) image is formed on the body drum 1. The latent image is reversely developed by the Y developing device 4 to form a toner image made of yellow (Y) toner on the Y photosensitive drum 1. The Y toner image formed on the Y photosensitive drum 1 is transferred onto the intermediate transfer belt 6 by a primary transfer roller 7 as a primary transfer means.

  By a similar process, magenta (M), cyan (C), and black (K) toner images are sequentially formed on the intermediate transfer belt 6 in a superimposed manner.

  The toner remaining on the peripheral surface of each photoreceptor drum 1 after the transfer is cleaned by the photoreceptor cleaning device 190.

  On the other hand, the recording paper k as a transfer material accommodated in the paper feed cassettes 20A, 20B, and 20C is fed by the feed roller 21 and the paper feed roller 22A provided in the paper feed cassettes 20A, 20B, and 20C, respectively, and conveyed. The roller 22B, 22C, 22D and the registration roller 23 are conveyed to a secondary transfer roller 7A as a secondary transfer means to which a voltage having a polarity opposite to that of the toner is applied. In the transfer area of the secondary transfer roller 7A, intermediate transfer is performed. The superimposed color toner images formed on the belt 6 are collectively transferred onto the recording paper k.

  The recording sheet k on which the color image has been transferred is fixed by a fixing device 17 according to the present invention, which will be described later, and is sandwiched between paper discharge rollers 24 and placed on a paper discharge tray 25 outside the apparatus.

  Further, after the color image is transferred onto the recording paper k by the secondary transfer roller 7A, the residual toner is removed from the intermediate transfer belt 6 that has separated the curvature of the recording paper k by the intermediate transfer body cleaning device 190A.

  In the description of the image forming apparatus, the color image formation is described. However, the present invention includes a case where a monochrome image is formed.

  Next, details of the fixing device 17 according to the present invention will be described with reference to FIG.

  FIG. 2 is a central sectional view of the fixing device 17.

  A heating belt 171 is one of two endless belts, and is stretched between a fixing roller 172 having an elastic layer and a heating roller 173 having a heating source.

  Reference numeral 174 denotes a pressure belt, which is the other endless belt, and is stretched between a pressure roller 175 and a support roller 176.

  Reference numeral 177 denotes a pressure member made of a compression spring, which presses the pressure roller 175 against the fixing roller 172 via the heating belt 171 and the pressure belt 174.

  As shown in the figure, the heating roller 173 is disposed on the upstream side of the fixing roller 172 in the conveyance direction of the recording paper k conveyed in the direction indicated by the arrow X.

  The support roller 176 is arranged so that the heating belt 171 and the pressure belt 174 are in contact with each other to form a nip surface 178 on the upstream side of the heating roller 173 when viewed in the recording paper conveyance direction.

  The nip surface 178 is formed from the nip point between the fixing roller 172 and the pressure roller 175 to the point where the contact between the heating belt 171 and the pressure belt 174 is completed on the upstream side in the recording paper conveyance direction.

  Of the rollers that stretch the heating belt 171, the heating roller 173 is a nip end roller positioned at the end of the nip surface 178, and among the rollers that stretch the pressure belt 174, the support roller 176 is a nip surface. Nip outer roller disposed at a position other than 178.

  As shown in FIG. 3, which is an axial sectional view of these rollers, the heating roller 173 and the support roller 176 arranged in this way are offset control members 180A, 180B and 181A, 181B that control the offset of the belt. On both sides of the roller in the axial direction.

  In FIG. 3, the gap AW between the deviation regulating members 180A and 180B of the heating roller 173 is substantially equal to the width of the heating belt 171 and the gap BW between the deviation regulating members 181A and 181B of the support roller 176 is the pressure belt. It is approximately equal to the width of 174 and narrower than the interval AW.

  The interval BW is wider than the width CW in the direction perpendicular to the conveyance direction of the recording paper k.

  In FIG. 2, reference numeral 182 denotes a pressing member that presses the heating belt 171 and the pressure belt 174 to the pressure roller 173 side.

  As shown in FIG. 4, the pressing member 182 slides the low friction sliding sheet 182 </ b> A made of PTFE, PFA or the like sliding on the pressure belt 174 along the outer periphery of the heating roller 173. For this purpose, an elastic member 182B such as silicon rubber, a holding member 182C that holds the elastic member 182B, a pressing spring 182D that includes a compression spring that presses the holding member 182C toward the heating roller 173, and the like are included.

  Whether or not to use the pressing member 182 can be selected in consideration of required fixing performance, color development performance, other fixing conditions, and the like.

  In FIG. 2, rotation in a predetermined direction is transmitted to a fixing roller 172, a heating roller 173, and a pressure roller 175 from a driving motor (not shown), and the heating belt 171, the pressure belt 174, and the support roller 176 are transmitted to the predetermined roller. Rotate in the direction.

  The heating roller 173 can be driven and rotated via the heating belt 171 by the rotation of the fixing roller 172, but the pressing force is applied to the heating roller 173 from the pressing member 182, and the driving force from the heating belt 171 is applied. Since there is a risk of slipping only with this, it is preferable to drive directly as in this embodiment.

  Reference numeral 183 denotes a temperature sensor comprising a thermistor, which is disposed in contact or non-contact with the surface of the heating roller 173, measures the surface temperature of the heating roller 173, and based on the measurement result, temperature control means (not shown). The heating belt 171 is controlled so as to maintain a constant temperature.

  Here, materials and configurations of the heating belt 171, the fixing roller 172, the heating roller 173, the pressure belt 174, the pressure roller 175, and the support roller 176 will be described.

  The heating belt 171 and the pressure belt 174 have an endless metal belt using, for example, a nickel electroformed belt having a thickness of about 60 to 200 μm as a base, an endless shape using polyimide or polyamide, and heat resistance. A coating layer of PFA or PTFE with a thickness of about 20 to 40 μm on the surface as a release layer is applied to the outside (outer peripheral surface) of the resin belt coated with an insulating silicon rubber with a thickness of about 100 to 300 μm. Use what you gave.

  As the fixing roller 172, for example, a cylindrical metal pipe 172A having a thickness of about 0.8 to 3 mm using STKM (carbon steel pipe for mechanical structure), and a thickness (wall) on the outer peripheral surface of the metal pipe 172A, for example. Thickness) Elastic layer 172B made of a silicon rubber member having a thickness of 2 to 4 mm and a rubber hardness of about 5 to 30 Hs (JIS, A rubber hardness), or a sponge member having a thickness of about 2 to 5 mm, and an elastic layer 172B And a release layer 172C coated with a PTFE or PFA tube having a thickness of about 40 to 100 μm, and is formed as a soft soft roller having an outer diameter of about 30 to 50 mm.

  As in the present embodiment, the fixing roller 172 preferably has an elastic layer 172B. By doing so, a small radius is formed at the nip exit of the fixing roller 172 when pressed by the pressure roller 175. Therefore, the effect of separating the curvature of the recording paper k is enhanced, and the recording paper k is reliably separated from the fixing roller 172.

  As the heating roller 173, for example, aluminum (A5052), a cylindrical metal pipe 173A having a thickness of about 0.8 to 3 mm, and PTFE having a thickness of about 20 to 50 μm, for example, on the outer peripheral surface of the metal pipe 173A It is composed of a release layer 173B covering a PFA tube, formed as a roller having an outer diameter of about 30 to 60 mm, and has a halogen lamp HLa as a heating member therein.

  As the pressure roller 175, a cylindrical metal pipe 175A having a thickness of about 0.8 to 3 mm using, for example, STKM (carbon steel pipe for mechanical structure), and a thickness of 40 to about the outer peripheral surface of the metal pipe 175A, for example. The release layer 175B covers a PTFE or PFA tube of about 100 μm, and is formed as a roller having an outer diameter of about 30 to 50 mm.

  As the support roller 176, for example, a cylindrical metal pipe 176A having a thickness of about 0.3 to 1.0 mm using STKM (carbon steel pipe for mechanical structure), and a thickness of 20 on the outer peripheral surface of the metal pipe 176A, for example. It consists of a release layer 176B that covers a PTFE or PFA tube of about 40 μm, and is formed as a roller having an outer diameter of about 15-30 mm.

  Next, the operation of the fixing device 17 configured as described above will be described.

  The recording sheet k transferred with toner transferred from the transfer unit of the image forming apparatus is first heated with the heating roller 173 and the pressing member 182 via the heating belt 171 and the pressure belt 174 by the rotation of the drive motor. Then, while being nipped and conveyed by the heating belt 171 and the pressure belt 174, the pressure is applied and heated, and the fixing roller 172 is further connected via the heating belt 171 and the pressure belt 174. And the pressure roller 175 are pressurized and heated, and after the toner is melted and fixed on the recording paper k, it is discharged outside the apparatus.

  As described above, the recording paper k is pressed and heated by the long nip surface 178 as compared with the conventionally used roller fixing method in which the pressure roller is pressed against the heating roller for fixing. Therefore, the toner is sufficiently melted, and a fixed image having excellent fixability and color developability can be obtained.

  Further, the heating belt 171 is regulated by the deviation regulating members 180A and 180B of the heating roller 173, and the pressure belt 174 is regulated by the deviation regulating members 181A and 181B of the support roller 176. .

  By configuring in this way, the end in the width direction of the pressure belt 174 contacts the deviation regulating members 173A and 173B on the heating roller 173, and the deviation is regulated without being torn or damaged. be able to.

  Therefore, even if two belts are used in an overlapping manner, the deviation of these belts can be regulated with a simple configuration.

  In order to enhance the effect of regulating the deviation of the belt, it is preferable to regulate the deviation by providing a deviation regulating member on a roller having a large belt holding angle as in the present embodiment.

  In addition to the present embodiment, the fixing device can be configured as shown in FIGS. 5A to 5C, for example.

  5A has the same basic configuration as that of FIG. 2, but the heating roller 173 is arranged on the upstream side of the support roller 176 in the recording paper conveyance direction.

  Therefore, the gap between the deviation regulating members 180A and 180B on the heating roller 173 is narrower than the gap between the deviation regulating members 181A and 181B on the support roller 176.

  In FIG. 5B, the heating roller 173 is disposed on the upstream side in the recording paper conveyance direction, and the support roller 176 is brought into contact with the heating roller 173. A fixing roller 172 is disposed downstream, and a pressure roller 175 is disposed further downstream.

  Therefore, the deviation regulating members 180A, 180B, and 181A, 181B are attached to the fixing roller 172 and the pressure roller 175, and the gap between the deviation regulating members 180A and 180B is greater than the deviation regulating members 181A and 181B. It is wider than the interval.

  The fixing roller 172 does not need to have an elastic layer, but preferably has a diameter as small as possible in order to prevent the recording paper k from being wound.

  FIG. 5C has the same basic configuration as FIG. 5B, but the fixing roller 172 is disposed downstream of the pressure roller 175 in the recording paper transport direction.

  Therefore, the deviation regulating members 180A, 180B, and 181A, 181B are attached to the fixing roller 172 and the pressure roller 175, and the gap between the deviation regulating members 180A and 180B is greater than the deviation regulating members 181A and 181B. It is narrower than the interval.

  Also in this case, in order to prevent the recording paper k from being wound around the fixing roller 172, it is preferable that the diameter is as small as possible.

1 is a schematic configuration diagram of an image forming apparatus. FIG. 3 is a central sectional view of the fixing device 17. The axial direction sectional drawing of a heating roller and a support roller. Detailed sectional drawing of a pressing member. The center sectional view of other embodiments of a fixing device.

Explanation of symbols

17 Fixing device 171 Heating belt 172 Fixing roller 173 Heating roller 174 Pressure belt 175 Pressure roller 176 Support roller 177 Pressure member 178 Nip surface 180A, 180B, 181A, 181B Deviation regulating member 182 Pressure member 183 Temperature sensor k Recording paper

Claims (2)

In a fixing device having a nip surface formed by contacting two endless belts, passing a recording paper onto which toner is transferred to the nip surface, and fixing the toner to the recording paper.
A nip end roller that stretches one of the two endless belts and is positioned at an end of the nip surface;
The other of the two endless belts is stretched, and has a nip outer roller located at a position other than the nip surface,
The nip end roller and the nip outer roller have belt side deviation regulating members on both sides in the axial direction on the roller for regulating belt deviation.
The fixing device according to claim 1, wherein an interval between the deviation regulating members of the nip end roller is wider than an interval between the deviation regulating members of the outer nip roller. The fixing device according to claim 1, further comprising a pressing member that presses the nip end roller through the two endless belts.

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