JP2011039328A - Transfer fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer fixing device which reduces troubles causing shock jitters on an output image by the speed variation of a transfer fixing belt without degrading the ability to be separated from a thermal transfer belt with respect to a recording medium sent out from a nip part, and to provide an image forming apparatus. <P>SOLUTION: The transfer fixing device is configured so that the transfer fixing belt 27 slacks upstream of a primary transfer part 100 in the running direction of the transfer fixing belt 27, yet downstream of the nip part in the running direction of this belt 27. At the position where the transfer fixing belt 27 slacks and at the position near the nip part, a pressing member 85 is provided to partially deform the transfer fixing belt 27 by pressing a widthwise part of the transfer fixing belt 27 from the external circumferential surface side of the transfer fixing belt 17. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transfer fixing device for transferring and fixing a toner image on a recording medium, and an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a composite machine including the same. , About.

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a technique using a transfer fixing device that simultaneously performs a transfer process and a fixing process is known (see, for example, Patent Documents 1 to 3).
An image forming apparatus provided with such a transfer fixing device is less likely to cause a decrease in image quality even when a recording medium having a rough surface is used, compared to an image forming apparatus that performs a transfer process and a fixing process separately. There are advantages.

Specifically, in an image forming apparatus that performs a transfer process and a fixing process separately, when a recording medium with a rough surface is used, an intermediate transfer body such as an intermediate transfer belt cannot follow the surface characteristics of the recording medium. A small gap is formed between the recording medium and the recording medium. For this reason, abnormal discharge occurs in the portion where the minute gap is formed, and the image carried on the intermediate transfer member is not normally transferred onto the recording medium, and the image becomes rough as a whole.
On the other hand, in an image forming apparatus provided with a transfer and fixing device, heat is applied to a toner image simultaneously with transfer, so that the toner is softened and melted to form a block-like lump having viscoelasticity. Therefore, even if a minute gap is formed between the fixing member and the recording medium using a recording medium having a rough surface, the image is transferred as a lump to that portion. Therefore, the image is good and has a high image quality without being distorted.

  Further, the image forming apparatus provided with the transfer fixing device is not fixed on the recording medium conveyed to the nip portion (the contact position between the transfer fixing member and the pressure member) where the transfer / fixing process is performed. Since the toner image is not carried, restrictions on the transport path of the recording medium are reduced as compared with an image forming apparatus that performs the transfer process and the fixing process separately. That is, an image forming apparatus that performs a transfer process and a fixing process separately is not fixed on a recording medium conveyed to a nip portion (a contact position between a fixing member and a pressure member) in which the fixing process is performed. Since the toner image is carried, restrictions are imposed on the conveyance path from the transfer unit to the fixing unit so as not to contact the unfixed toner image. Therefore, the image forming apparatus provided with the transfer fixing device has a high degree of design freedom with respect to the recording medium conveyance path, and can improve the conveyance of the recording medium.

  On the other hand, Patent Documents 2 and 3 disclose that upstream of the nip portion (transfer fixing portion) of the transfer fixing belt so that the speed fluctuation of the transfer fixing belt affects the primary transfer portion and no shock jitter occurs on the output image. In addition, a technique is disclosed in which a weak tension portion (a portion in which the transfer fixing belt is slack) is provided on the downstream side, and the speed change of the transfer fixing belt is absorbed by the weak tension portion.

  The above-described conventional transfer fixing device (the transfer fixing device disclosed in Patent Documents 2 and 3) is provided with a weak tension portion of the transfer fixing belt upstream or downstream of the nip portion so that a shock jitter does not occur on the output image. Therefore, the separation of the recording medium sent from the nip portion with respect to the transfer fixing belt is disadvantageous.

  Specifically, since the looseness of the transfer fixing belt is formed on the downstream side of the nip portion, the transfer fixing belt is loosely wound around the opposing roller pressed against the pressure member via the transfer fixing belt at the position of the nip portion. Thus, the curvature of the transfer fixing belt at the position where the recording medium is separated from the transfer fixing belt after the transfer fixing process is increased. For this reason, the recording medium sent out from the nip portion is not easily separated from the transfer fixing belt. When such a separation failure occurs, a jam (paper jam) of the recording medium occurs.

In particular, it is a transfer and fixing device that employs a system in which the surface of the recording medium is heated before being fed into the nip portion, and is a thin and weak recording medium (for example, a sheet of about 45 to 55K). .)), The above-mentioned separation failure cannot be ignored because the recording medium is easily curled in the direction in which the recording medium is in close contact with the transfer fixing belt.
In addition, since the transfer and fixing belt is designed to achieve both the transfer process and the fixing process, an intermediate transfer belt (a primary transfer process and a secondary transfer process are performed in an image forming apparatus that performs the transfer process and the fixing process separately). The range of material selection will be narrower than For this reason, there is a limit to measures for improving the releasability (surface property) on the outer peripheral surface of the transfer and fixing belt from the material side of the transfer and fixing belt.

  The present invention has been made to solve the above-described problems, and does not deteriorate the separation of the recording medium sent from the nip portion with respect to the transfer fixing belt. An object of the present invention is to provide a transfer fixing device and an image forming apparatus in which a problem that shock jitter is generated is reduced.

  According to a first aspect of the present invention, there is provided a transfer fixing device for transferring and fixing a toner image onto a recording medium, wherein the toner image is transferred onto the image carrier at a primary transfer portion facing the image carrier. A transfer fixing belt that is stretched around a plurality of roller members, and a pressure member that forms a nip portion that is pressed against the transfer fixing belt to convey a recording medium; The transfer fixing belt is loosened in the running direction upstream of the transfer fixing belt with respect to the primary transfer portion and downstream in the running direction of the transfer fixing belt with respect to the nip portion. A part or all of the transfer fixing belt in the width direction at the position where the slackness of the transfer fixing belt is generated and in the vicinity of the nip portion. Face side In which further comprising a pressing member for locally deforming the transfer fixing belt and Luo pressed.

  According to a second aspect of the present invention, in the transfer fixing device according to the first aspect of the present invention, the pressing member is configured to be able to contact and separate from the transfer fixing belt, and recording to the nip portion. When the medium is not transported, it is controlled so as to be separated from the transfer fixing belt.

  According to a third aspect of the present invention, there is provided the transfer fixing device according to the second aspect of the present invention, wherein the pressing member is arranged such that the transfer fixing belt is moved at a timing when the leading end portion of the recording medium is sent out from the nip portion. By pressing, the recording medium is controlled so as to be separated from the transfer-fixing belt until the rear end portion of the recording medium is sent out from the nip portion.

  A transfer fixing device according to a fourth aspect of the present invention is the transfer fixing device according to any one of the first to third aspects, wherein the pressing member is configured to be able to contact and separate from the transfer fixing belt. When the thickness of the recording medium conveyed to the nip portion is a predetermined value or more, the recording medium is controlled so as to be separated from the transfer fixing belt.

  A transfer fixing device according to a fifth aspect of the present invention is the transfer fixing device according to any of the first to fourth aspects of the present invention, wherein the pressing member is configured to be able to contact and separate from the transfer fixing belt. When the range in which an image is not formed from the leading end of the recording medium conveyed to the nip portion is a predetermined value or more, it is controlled so as to be separated from the transfer fixing belt.

  A transfer fixing device according to a sixth aspect of the present invention is the transfer fixing device according to any one of the first to fifth aspects, wherein the transfer fixing belt is deformed toward the position at which the transfer fixing belt is deformed by the pressing member. The image forming apparatus further includes air blowing means for sending air from the outer peripheral surface side of the fixing belt.

  A transfer fixing device according to a seventh aspect of the present invention is the transfer fixing device according to any one of the first to sixth aspects, wherein the pressing member is brought into contact with the pressing member via the transfer fixing belt. The image forming apparatus further includes a regulating member that regulates a deformation amount and / or shape of the transfer fixing belt to be deformed.

  The transfer fixing device according to an eighth aspect of the present invention is the transfer fixing device according to any one of the first to seventh aspects of the present invention, wherein the tip of the pressing member contacts the outer peripheral surface of the transfer fixing belt. At the same time, the central portion is a separation claw that guides the conveyance of the recording medium.

  A transfer fixing apparatus according to a ninth aspect of the present invention is the transfer fixing apparatus according to any one of the first to eighth aspects, wherein the transfer fixing belt is one of the plurality of roller members. A driving roller disposed downstream of the primary transfer portion in the running direction of the transfer and fixing belt and upstream of the nip portion in the running direction of the transfer and fixing belt; An opposing roller that is in pressure contact with the pressure member via the transfer fixing belt at the position of the nip portion, and whose rotational speed is variably controlled. By variably controlling the rotation speed of the roller, the roller is generated on the upstream side in the running direction of the transfer fixing belt with respect to the primary transfer portion and on the downstream side in the running direction of the transfer fixing belt with respect to the nip portion. The slack of the transfer fixing belt and the slack of the transfer fixing belt that occurs downstream in the running direction of the transfer fixing belt with respect to the driving roller and upstream in the running direction of the transfer fixing belt with respect to the nip portion. And to adjust.

  A transfer fixing apparatus according to a tenth aspect of the invention is the recording apparatus according to any one of the first to ninth aspects, wherein the recording is heated by the heating body and conveyed toward the nip portion. A heat transfer member that heats the transfer fixing surface of the recording medium while guiding the medium, and an urging member that urges the recording medium guided by the heat transfer member toward the heat transfer member It is.

  An image forming apparatus according to an eleventh aspect of the present invention includes the transfer fixing apparatus according to any one of the first to tenth aspects.

  In the present invention, since a pressing member that presses and locally deforms the transfer fixing belt that has slackened at a position in the vicinity of the downstream side of the nip portion is provided, transfer fixing of the recording medium sent from the nip portion is provided. It is possible to provide a transfer fixing device and an image forming apparatus that can reduce a problem that shock jitter is generated on an output image due to a change in speed of the transfer fixing belt without reducing the separation property with respect to the belt.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. It is an enlarged view showing a part of the transfer fixing device. It is the figure which looked at the heating apparatus installed in a transfer fixing apparatus in the width direction. FIG. 6 is a diagram illustrating a state in which the transfer fixing belt is slack. It is the figure which looked at the vicinity of a counter roller in the width direction. It is a figure which shows the state which has pressed the slack part of the transfer fixing belt with the press member. It is a figure which shows a part of transfer fixing apparatus in Embodiment 2 of this invention. It is a figure which shows a part of transfer fixing apparatus in Embodiment 3 of this invention. It is a figure which shows a part of another transfer fixing apparatus. It is a figure which shows a part of transfer fixing apparatus in Embodiment 4 of this invention. It is a figure which shows the fixing device in Embodiment 5 of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is an apparatus main body of a color copying machine as an image forming apparatus, 2 is a writing section (exposure section) that emits laser light based on input image information, and 20Y, 20M, 20C, and 20BK are colors (yellow, magenta). , Cyan, and black), 21 is a photosensitive drum as an image carrier accommodated in each of the process cartridges 20Y, 20M, 20C, and 20BK, 22 is a charging unit that charges the photosensitive drum 21, 23Y, 23M, 23C, and 23BK are developing devices that develop the electrostatic latent image formed on the photosensitive drum 21, and 24 is a transfer bias that transfers the toner image formed on the photosensitive drum 21 to the transfer fixing belt 27. A roller 25 indicates a cleaning device that collects untransferred toner on the photosensitive drum 21.

  Reference numeral 27 denotes a transfer and fixing belt as a transfer and fixing member onto which toner images of a plurality of colors are transferred, 29 denotes a belt cleaning device for cleaning the transfer and fixing belt 27 after the transfer / fixing process, and 32Y, 32M, 32C, and 32BK. Is a toner replenishing unit that replenishes each developing device 23Y, 23M, 23C, and 23BK with toner of each color, 51 is a document conveying unit that conveys the document D to the document reading unit 55, and 55 is a document reading unit that reads image information of the document D. , 61 is a paper feeding unit for storing a recording medium P such as transfer paper, 66 is a transfer fixing device for transferring and fixing a toner image on the recording medium P, and 67 is for heating the recording medium P just before the transfer / fixing process. A heating device 68 is a pressure roller as a pressure member that presses against the transfer fixing belt 27 to form a nip portion (transfer fixing portion), and 85 is a central portion in the width direction of the transfer fixing belt 27 on the outer peripheral surface. A pressing member that presses from 88 heater for heating the transfer-fixing belt 27, 91 denotes a brush-like member as an urging member for urging the heating apparatus 67 P the recording medium.

Here, the transfer fixing device 66 includes a transfer fixing belt 27, a pressure roller 68 as a pressure member, a belt cleaning device 29, a pressing member 85, a heating device 67, a brush roller 91 as an urging member, a heater 88, Etc.
The process cartridges 20Y, 20M, 20C, and 20BK are obtained by integrating the photosensitive drum 21, the charging unit 22, and the cleaning device 25, respectively. Then, image formation of each color (yellow, magenta, cyan, black) is performed on the photosensitive drum 21 in each of the process cartridges 20Y, 20M, 20C, and 20BK.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport roller of the document transport unit 51 and placed on the contact glass 53 of the document reading unit 55. Then, the document reading unit 55 optically reads the image information of the document D placed on the contact glass 53.

  Specifically, the document reading unit 55 scans the image of the document D on the contact glass 53 while irradiating light emitted from the illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, an image processing unit (not shown) performs color conversion processing, color correction processing, spatial frequency correction processing, and the like on the basis of RGB color separation image signals, so that yellow, magenta, cyan, and black are processed. Get color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. Then, laser light (exposure light) based on the image information of each color is emitted from the writing unit 2 toward the photosensitive drums 21 of the corresponding process cartridges 20Y, 20M, 20C, and 20BK.

On the other hand, the four photosensitive drums 21 (image carriers) are rotated clockwise in FIG. First, the surface of the photosensitive drum 21 is uniformly charged at a position facing the charging unit 22 (a charging process). Thus, a charged potential is formed on the photosensitive drum 21. Thereafter, the surface of the charged photosensitive drum 21 reaches the irradiation position of each laser beam.
In the writing unit 2, laser light corresponding to the image signal is emitted from the light source corresponding to each color. The laser light is incident on the polygon mirror 3 and reflected, and then passes through the lenses 4 and 5. The laser light after passing through the lenses 4 and 5 passes through different optical paths for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  The laser beam corresponding to the yellow component is reflected by the mirrors 6 to 8 and then irradiated onto the surface of the photosensitive drum 21 of the first process cartridge 20Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 21 by the polygon mirror 3 that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 21 charged by the charging unit 22.

  Similarly, the laser beam corresponding to the magenta component is reflected by the mirrors 9 to 11 and then irradiated to the surface of the photosensitive drum 21 of the second process cartridge 20M from the left side of the paper, thereby causing an electrostatic latent image corresponding to the magenta component. An image is formed. The cyan component laser light is reflected by the mirrors 12 to 14 and then irradiated on the surface of the photosensitive drum 21 of the third process cartridge 20C from the left side of the paper, thereby forming an electrostatic latent image of the cyan component. The black component laser light is reflected by the mirror 15 and then irradiated to the surface of the photosensitive drum 21 of the fourth process cartridge 20BK from the left side of the paper, thereby forming an electrostatic latent image of black component.

Thereafter, the surface of the photosensitive drum 21 on which the electrostatic latent images of the respective colors are formed reaches positions facing the developing devices 23Y, 23M, 23C, and 23BK, respectively. Then, the respective color toners are supplied from the developing devices 23Y, 23M, 23C, and 23BK onto the photosensitive drum 21, and the latent image on the photosensitive drum 21 is developed (this is a developing step).
Thereafter, the surface of the photosensitive drum 21 after the development process reaches a position (a primary transfer portion) facing the transfer fixing belt 27 stretched and supported by the plurality of roller members 28A to 28C. Here, a transfer bias roller 24 is installed at each facing position so as to contact the inner peripheral surface of the transfer fixing belt 27. Then, at the position of the transfer bias roller 24, the images (toner images) of the respective colors formed on the photosensitive drum 21 are sequentially superimposed and transferred onto the transfer fixing belt 27 (this is a primary transfer step). .

Then, the surface of the photosensitive drum 21 after the primary transfer process reaches a position facing the cleaning device 25. Then, the untransferred toner remaining on the photosensitive drum 21 is collected by the cleaning device 25 (this is a cleaning process).
Thereafter, the surface of the photosensitive drum 21 passes through a static elimination unit (not shown), and a series of image forming processes on the photosensitive drum 21 is completed.

On the other hand, the surface of the transfer and fixing belt 27 on which the toner images of the respective colors on the photosensitive drum 21 are transferred and carried are run in the direction of the arrow in the figure and contacted with the pressure roller 68 (pressure member). The contact position (the nip part) is reached. That is, the toner image primarily transferred to the transfer fixing belt 27 at the position of the primary transfer portion passes through the position of the heater 88, and is a nip portion (transfer fixing portion) between the transfer fixing belt 27 and the pressure roller 68. To reach. Here, in the transfer fixing device 66 according to the first embodiment, unlike the conventional one, the heating amount of the heater 88 that directly heats the transfer fixing belt 27 itself is set small.
Then, the toner image T on the transfer fixing belt 27 is transferred and fixed to the transfer fixing surface (front surface) of the recording medium P at the nip portion (transfer fixing portion) (in the transfer / fixing step). is there.). Specifically, the transfer fixing surface of the recording medium P is heated by the heating device 67 immediately before the nip portion, and the toner image preheated by the heater 88 is further heated and melted by the heat of the transfer fixing surface at the nip portion. At the same time, the toner image is fixed on the transfer fixing surface by the pressure of the nip portion. The configuration and operation of the transfer fixing device 66 will be described in more detail later with reference to FIGS.
Thereafter, the surface of the transfer fixing belt 27 reaches the position of the belt cleaning unit 29. Then, deposits such as residual toner on the transfer fixing belt 27 are collected by the belt cleaning device 29, and a series of transfer fixing processes on the transfer fixing belt 27 is completed.

Here, the recording medium P transported to the nip portion of the transfer fixing device 66 is transported from the paper feed unit 61 via the transport guide 63, the registration roller 64, the heating device 67, and the like.
Specifically, the transfer paper P fed by the paper feed roller 62 from the paper feed unit 61 that stores the recording medium P passes through the conveyance guide 63 and is guided to the registration roller 64. The recording medium P that has reached the registration roller 64 is conveyed toward the nip portion (transfer fixing portion) between the transfer fixing belt 27 and the pressure roller 68 in synchronization with the toner image on the transfer fixing belt 27. At this time, the recording medium P conveyed toward the nip portion is guided to the heat transfer plate 67b (see FIG. 2) of the heating device 67 and attached to the heat transfer plate 67b by the brush-like roller 91. While being energized, only the transfer and fixing surface of the recording medium P is heated by the heating device 67 (heat transfer plate 67b).
Thereafter, the recording medium P on which the full-color image has been transferred and fixed passes through the paper discharge conveyance path, and is discharged as an output image outside the apparatus main body 1 by the paper discharge roller 80, and a series of image forming processes is completed. In the image forming apparatus according to the first embodiment, the conveyance speed (or process linear speed) of the recording medium P is set to about 300 mm / second.

The toner used in Embodiment 1 is preferably suitable for low-temperature fixing. Specifically, the softening point (1/2 outflow temperature) of the toner is preferably about 100 ° C.
As the toner binder resin, one having the following composition can be used.
For example, homopolymers of styrene such as polyester, polystyrene, poly p-chlorostyrene, polyvinyltoluene and the like; and styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers. Styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate Copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Examples thereof include styrenic copolymers such as polymers.
Moreover, the following resin can also be mixed and used. Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or fat Examples thereof include cyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffin, and paraffin wax. Among these, those containing a polyester resin are preferred in order to obtain sufficient fixing properties. In particular, the crystalline polyester resin is sufficiently softened and melted at the time of paper contact, and an image can be formed with high color reproducibility as well as fixing strength. The polyester resin is obtained by condensation polymerization of alcohol and carboxylic acid, and the alcohol used is polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butane. Diols such as diol, neopentyl glycol, 1,4-butenediol, 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyexethylenated bisphenol A, polyoxypropylenated bisphenol A, etc. And a divalent alcohol simple substance obtained by substituting these with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, and other divalent alcohol simple substance.
Examples of the carboxylic acid used to obtain the polyester resin include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, Adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, acid anhydrides thereof, lower alkyl esters and linolenic acid Dimers and other divalent organic acid monomers can be mentioned.
In order to obtain a polyester resin to be used as a binder resin, it is also preferable to use not only a polymer with only the above bifunctional monomer but also a polymer containing a component with a trifunctional or higher polyfunctional monomer. It is. Examples of the polyhydric alcohol monomer having three or more valences that are such polyfunctional monomers include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sarbitane, pentaesitol, dipenta. Esitol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol , Trimethylolethane, trimethylolpropane, 1.3.5-trihydroxymethylbenzene, and others.
Examples of the trivalent or higher polyvalent carboxylic acid monomer include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2 -Methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, embol trimer acid, acid anhydrides thereof, and the like.

Further, the toner used in the first exemplary embodiment can contain a release agent for the purpose of improving the release property of the toner on the surface of the transfer fixing belt 27 in the transfer fixing step. As the release agent, all known ones can be used, and in particular, defree fatty acid type carnauba wax, montan wax, oxidized rice wax, and ester wax can be used alone or in combination. As the carnauba wax, those having fine crystallinity, an acid value of 5 or less, and a particle diameter of 1 μm or less when dispersed in a toner binder are preferable. The montan wax generally refers to a montan wax refined from minerals, and like a carnauba wax, it is microcrystalline and preferably has an acid value of 5 to 14. The oxidized rice wax is obtained by air-oxidizing rice bran wax, and the acid value is preferably 10-30. When the acid value of each wax is less than the respective range, the low temperature fixing temperature rises and the low temperature fixing becomes insufficient. On the contrary, when the acid value exceeds each range, the cold offset temperature rises and the low-temperature fixing becomes insufficient. The added amount of the wax is 1 to 15 parts by weight, preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder resin. If it is less than 1 part by weight, the releasing effect is thin and the desired effect is difficult to obtain. On the other hand, if the amount exceeds 15 parts by weight, problems such as significant spent on the carrier occur.
Further, as an external additive, for the purpose of improving the fluidity of the toner, silica, titanium oxide, alumina, and the like, and if necessary, fatty acid metal salts, polyvinylidene fluoride, and the like may be added.
In particular, since the transfer fixing device 66 can sufficiently heat the toner, even if a relatively large amount of an additive such as submicron large particle size silica is used, the fixing property and the fixing temperature are not affected. Therefore, an external additive prescription considering fluidity and transferability is possible.

Next, with reference to FIGS. 2 to 6, the characteristic transfer fixing device 66 in the first embodiment will be described in detail.
FIG. 2 is an enlarged view showing a part of the transfer fixing device 66. FIG. 3 is a view of the heating device 67 as viewed from the X direction in FIG. 2 in the width direction. FIG. 4 is a diagram illustrating a state in which the transfer fixing belt 27 is slack. FIG. 5 is a top view of the vicinity of the opposing roller 28B as viewed in the width direction. FIG. 6 is a diagram illustrating a state where the slack portion on the downstream side of the nip portion of the transfer fixing belt 27 is pressed by the pressing member 85.
As shown in FIG. 2, the transfer fixing device 66 includes a transfer fixing belt 27, a pressure roller 68 as a pressure member, a belt cleaning device 29, a pressing member 85, a heating device 67, and a brush roller 91 as an urging member. , Heater 88, and the like.

  Here, the transfer fixing belt 27 as a transfer fixing member is an endless belt having a multilayer structure in which an elastic layer and a release layer are sequentially formed on a base material (base layer). The base material (base layer) is formed of a polyimide resin having a layer thickness of 80 μm. The elastic layer is for following the irregularities on the surface of the recording medium P, and is formed of silicone rubber having a layer thickness of 200 μm. The release layer is for securing release properties with respect to the toner and paper powder on the belt surface, and is formed of a fluororesin having a layer thickness of 10 μm.

1 and 2, the transfer and fixing belt 27 is stretched and supported by a plurality of roller members 28A to 28C.
One of the plurality of roller members is a driving roller 28A for driving the transfer fixing belt 27. Specifically, the drive roller 28A is disposed downstream of the primary transfer unit 100 in the traveling direction of the transfer fixing belt 27 and upstream of the nip portion (transfer fixing unit) in the traveling direction of the transfer fixing belt 27. Has been. The shaft portion on one end side of the drive roller 28A is connected to a drive motor (not shown), and rotates in the counterclockwise direction of FIG. 2, so that the transfer fixing belt wound around the outer peripheral surface thereof. The transfer fixing belt 27 is caused to run counterclockwise in FIG.

Referring to FIG. 1, one of a plurality of roller members that stretch and support the transfer fixing belt 27 is a driven roller 28 </ b> C, and is counterclockwise in FIG. 1 due to frictional resistance with the transfer fixing belt 27. Follow.
Here, a belt cleaning device 29 is installed at the position of the driven roller 28 </ b> C so as to face the outer peripheral surface of the transfer and fixing belt 27. The belt cleaning device 29 is provided with a cleaning blade 29a. Then, the transfer fixing belt 27 after the transfer / fixing process is cleaned by the cleaning blade 29a. That is, after the toner image T formed on the transfer fixing belt 27 is transferred and fixed on the recording medium P at the nip portion, the toner remaining on the transfer fixing belt 27 is mechanically scraped off by the cleaning blade 29a. The toner scraped off by the cleaning blade 29a falls by its own weight and is collected in the belt cleaning device 29.

  Referring to FIG. 2, one of a plurality of roller members that stretch and support the transfer and fixing belt 27 is a counter roller 28B, and rotates counterclockwise in FIG. A pressure roller 68 (pressure member) is installed at the position of the facing roller 28 </ b> B so as to face the outer peripheral surface of the transfer fixing belt 27. The counter roller 28B is connected to a variable speed drive motor (not shown), and its rotational speed is variably controlled. Then, the slack of the upstream and downstream sides of the nip portion of the transfer fixing belt 27 is adjusted while variably controlling the rotation speed (rotation speed) of the facing roller 28B. This will be described in detail later.

Here, the pressure roller 68 has a surface layer (release layer) formed on a cylindrical cored bar made of aluminum or the like, and rotates in the clockwise direction in FIG. The pressure roller 68 is pressed against the opposing roller 28B via the transfer fixing belt 27 by a pressure mechanism (not shown). Thus, a desired nip portion (transfer fixing portion) is formed between the pressure roller 68 and the transfer fixing belt 27.
As the surface layer of the pressure roller 68, PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), or the like is used. be able to.

The heating device 67 is disposed in the vicinity of the entrance side of the nip portion in the transfer fixing device 66. The heating device 67 includes a heating body 67a, a heat transfer plate 67b as a heat transfer member, an electrode 67c, and the like.
The heating element 67a is sandwiched between the heat transfer plate 67b and the electrode 67c. In the first embodiment, as the heating element 67a, a resistance heating element whose resistance rapidly increases when a predetermined Curie point is reached is used. Specifically, a positive temperature coefficient thermistor made of a barium titanate semiconductor ceramic body is used as the heating body 67a. In the first embodiment, as shown in FIG. 3, ten heating elements 67a (positive characteristic thermistors) are arranged in parallel in the width direction.
The heat transfer plate 67b as a heat transfer member is a stainless steel plate having a plate thickness of 0.2 mm. The heat transfer plate 67b extends from the vicinity of the registration roller 64 to the vicinity of the nip portion, and functions as a guide plate (guide plate) that guides the recording medium P conveyed toward the nip portion. Further, the heat transfer plate 67b contacts the transfer fixing surface (front surface) of the recording medium P conveyed toward the nip portion, and heat generated by the heating body 67a is recorded on the recording medium P (transfer fixing surface). It has the function of transferring heat to Furthermore, the AC power supply 71 is connected to the heat transfer plate 67b, and functions as one of the electrodes.

An AC power supply 71 is connected to the electrode 67c and the heat transfer plate 67b that sandwich the heating body 67a, and a voltage of AC 100 volts is applied to both ends of the heating body 67a when the switch 72 is connected. Thereby, an electric current flows in the heating body 67a, and the heating body 67a generates heat. Further, the heat of the heating body 67a is transmitted from the heat transfer plate 67b to the transfer fixing surface of the recording medium P.
In the first embodiment, as the material of the heat transfer plate 67b, heat conductivity is high, heat capacity in the same volume is low, and relatively inexpensive copper is used. Therefore, heating efficiency is high and relatively inexpensive. A heating device 67 can be provided.

Here, it is preferable to use a heating body 67a having a Curie point lower than the ignition point of the recording medium P. As a result, the heating body 67a is prevented from malfunctioning due to its self-temperature control function, causing the temperature to rise above the ignition point of the recording medium P.
Specifically, in the first embodiment, the Curie point of the heating body 67a is set to 200 ° C. Thereby, when the temperature of the heating body 67a exceeds 200 ° C., the resistance between the electrode 67c and the heat transfer plate 67b rapidly increases, and the current flowing in the heating body 67a decreases. Specifically, when the temperature of the heating body 67a is 210 ° C., the current flowing in the heating body 67a decreases to ½, and when the temperature of the heating body 67a is 220 ° C., the current flowing in the heating body 67a is ¼. To drop.
The heating element 67a configured in this manner is heated to 190 to 200 ° C. after 6 seconds with 1200 watts of power, and thereafter does not increase to 210 ° C. or more by the self-temperature control function. When the heating body 67a is controlled at 210 ° C. or lower, it is controlled to a desired temperature by PID control or the like using a temperature sensor (not shown). Even if the control circuit fails, safety cannot be ensured because it cannot exceed 210 ° C. as described above. Moreover, in this Embodiment 1, since the several heating body 67a is arranged in parallel in the width direction, each self-temperature control is performed by the several heating body 67a, and the temperature nonuniformity of the width direction is 10 degreeC. It can be:

  As described above, the heating device 67 configured in this way heats only the transfer fixing surface (front surface) of the recording medium P immediately before the transfer / fixing process. In other words, the heating device 67 causes the recording medium P to nip before the temperature of the back surface of the recording medium P (the back surface with respect to the transfer fixing surface) rises (before heat is transferred from the front surface to the back surface). The transfer fixing surface is heated so as to be conveyed to the section.

The inventor of the present application made a recording when the recording medium P (thick paper 300 g paper) was brought into contact with a copper plate (thickness 1 mm) heated to 160 ° C. for 60 msec and then conveyed (running) in the air at an ambient temperature of 40 ° C. The temperature fluctuation of the transfer fixing surface of the medium P was simulated. As a result, the recording medium P heated to about 140 ° C. by the copper plate is only 110 m. It was found that the temperature decreased until. Therefore, in order to increase the heating efficiency of the recording medium P before the transfer and fixing step, it is necessary to place a heat transfer member (heat transfer plate) for heating the recording medium as close to the nip as possible.
In the first embodiment, the heat transfer plate 67b is formed in a plate shape, the tip thereof is as close as possible to the nip portion, and the length in the transport direction is set as long as possible. The heating efficiency of the previous recording medium P can be improved.

  The inventor of the present application sets the heating temperature of the heat transfer plate 67b to 140 to 200 ° C. without installing the brush-like member 91, and the recording medium P (made by Ricoh Company, “ The temperature fluctuation of the transfer fixing surface of the copy paper 6200 ") was confirmed. As a result, it was found that the temperature drop on the transfer and fixing surface of the recording medium P was 15 ° C. or less at 0 to 60 msec after being sent from the heat transfer plate 67b.

Here, the heat transfer plate 67b in Embodiment 1 has a guide surface (a surface in contact with the recording medium P) for guiding the recording medium P covered with nickel plating containing fluororesin particles. Yes. Specifically, 30 vol% PTFE (polytetrafluoroethylene) is dispersed in a nickel plating film. Such a coating has a hardness in a precipitated state of about Hv300, is harder than a normal resin coating, and is excellent in slipping property, wear resistance, and releasability. Therefore, it is possible to reduce the problem of toner and paper powder adhering to the heat transfer plate 67b and to improve the durability of the heat transfer plate 67b.
The guide surface of the heat transfer plate 67b (the surface that contacts the recording medium P) can be covered with diamond-like carbon (DLC) or graphite-like carbon (GLC) having high wear resistance.

The heating device 67 in the first embodiment heats the transfer and fixing surface so that the temperature of the transfer and fixing surface of the recording medium P is higher than the surface temperature of the transfer and fixing belt 27 that is supplementarily heated by the heater 88. is doing. That is, the toner image T carried on the transfer fixing belt 27 is heated and melted mainly by heat received from the recording medium P at the nip portion.
In the first embodiment, the transfer fixing surface of the recording medium P is heated, and the temperature for obtaining sufficient gloss on the output image can be set independently, so the temperature of the transfer fixing belt 27 (fixing setting) Temperature) can be lowered. Further, since the recording medium P is heated immediately before the transfer / fixing process, the adhesion between the toner T and the recording medium P is not increased more than necessary without being heated excessively.
That is, according to the configuration of the first embodiment, it is possible to perform low-temperature fixing, reduce the warm-up time of the apparatus, and improve energy saving. In addition, since heat transfer to the transfer fixing belt 27 can be suppressed, durability of the transfer fixing belt 27 can be improved. Furthermore, since the heating temperature of the transfer fixing belt 27 is reduced, thermal deterioration of the transfer fixing belt 27 can be suppressed.

  Further, the transfer fixing device 66 according to the first embodiment presses (biases) the recording medium P guided to the nip portion by the heat transfer plate 67b against the heat transfer plate 67b by the brush-like roller 91 (biasing member). ) Is configured as follows. With this configuration, in order to improve the adhesion force and the adhesion time of the recording medium P to the heat transfer plate 67b, the surface of the recording medium P is reliably raised to the target temperature by the heat transfer plate 67b and fixed. Defects can be suppressed.

Here, the brush-like roller 91 is a roller-like member having heat resistance in which a brush cloth in which polyimide fibers, aramid fibers, etc. are planted is spirally wound on a core metal, and is clockwise in FIG. Rotate to. Then, the recording medium P that has passed the position of the registration roller 64 is guided to the heat transfer plate 67b, and is urged by the brush roller 91 and pressed against the heat transfer plate 67b immediately before the nip portion. After being heated by the hot plate 67b, it is fed into the nip portion.
The brush-like roller 91 according to the first embodiment has an outer diameter of 30 mm, a bristle bristle length of 10 mm, a brush bristle yarn thickness of 1330 T / 120 F, and a bristle bristle density of 100,000- 150,000 / inch ² is set. Further, the brush bristles of the brush-like roller 91 are not limited to those described above, and fluorine resin, heat-resistant resin or metal, or those whose surfaces are coated with a low wear material, or the like is used. You can also. By imparting heat resistance to the brush-like roller 91, it is possible to reduce a problem that the brush bristles of the brush-like roller 91 are thermally deteriorated by the heat of the heat transfer plate 67b.

The brush-like roller 91 is preferably rotationally driven so that the linear velocity at the contact position with the recording medium P is equal to or higher than the conveyance speed of the recording medium P. That is, the brush-like roller 91 is preferably rotated in the clockwise direction in FIG. 2 at a speed equal to or higher than the conveyance speed of the recording medium P.
With such a configuration, when the recording medium P enters the contact position between the brush-like roller 91 and the heat transfer plate 67b, it is possible to prevent a problem that the transportability is lowered due to being caught by the brush-like roller 91. In the first embodiment, the linear velocity at the contact position of the brush roller 91 with the recording medium P is set to be 1 to 3% faster than the conveyance speed of the recording medium P.

Further, the brush-like roller 91 as an urging member makes point contact or line contact at a plurality of locations with the recording medium P guided by the heat transfer plate 67b. By suppressing the contact area with the recording medium P as much as possible and pressing the recording medium P against the heat transfer plate 67b, the heat is transferred to the brush-like roller 91 side, thereby preventing the heating efficiency of the recording medium P from being reduced. In addition, it is possible to suppress a problem that the transportability of the recording medium P is lowered.
In the first embodiment, the pressure width (nip width) of the brush roller 91 pressed against the heat transfer plate 67b is set to be 3 to 12 mm (corresponding to a pressure of about 3 to 5 kgf). To do.)

As described above, the transfer fixing device 66 according to the first exemplary embodiment minimizes the heating of the transfer fixing belt 27 by the heater 88 and immediately before the amount of heat necessary for heating and melting the toner is conveyed to the nip portion. This is supplemented by efficiently heating the recording medium P. However, in this case, the transfer and fixing belt 27 receives a large amount of heat from the heated recording medium P and has a non-uniform distribution, and is the width direction of the transfer and fixing belt 27 (the direction perpendicular to the conveyance direction of the recording medium). ) Causes temperature unevenness, and it becomes easy to generate defective fixing images such as uneven fixing and offset.
On the other hand, a heat pipe that equalizes the temperature distribution in the width direction of the surface of the transfer fixing belt 27 after passing through the nip portion is installed downstream of the nip portion in the running direction of the transfer fixing belt 27. You can also. The heat pipe makes the temperature distribution in the width direction of the surface of the transfer and fixing belt 27 uniform by efficiently convection of heat inside the heat pipe. Accordingly, even when the recording medium P immediately before being conveyed to the nip portion is heated by the heating device 67 with the heating of the transfer fixing belt 27 being minimized, fixing defects such as uneven fixing and offset occur. Can be suppressed.

In the first embodiment, a resistance heating element (positive characteristic thermistor) is used as the heating element 67a of the heating device 67 so that the heat transfer plate 67b is heated by the heating element 67a. On the other hand, the heat transfer plate 67b may be formed of a metal material whose magnetic permeability decreases when reaching a predetermined Curie point, and the heat transfer plate 67b can be heated by electromagnetic induction. In such a case, the same effect as described above can be obtained.
Specifically, the heating device includes a heat transfer plate made of a magnetic shunt alloy such as nickel or iron and having a thickness of about 0.3 mm, an induction coil (heating body) facing the heat transfer plate, and the like. With such a configuration, when a high frequency voltage of 20 kHz is applied to the induction coil, the heat transfer plate is heated by electromagnetic induction and heat is transferred to the transfer fixing surface of the recording medium P. In the heat transfer plate, the ratio of the nickel component in the magnetic shunt alloy is set to about 40%, and when the temperature reaches 200 ° C. (Curie point), the magnetic permeability rapidly decreases and is heated by electromagnetic induction. Disappear. Specifically, the heat transfer plate configured in this manner is heated to 190 to 200 ° C. after 3 seconds with 1200 watts of power, and then heated to 210 ° C. or more by the self-temperature control function. Absent.

  In the first embodiment, a plate-shaped heat transfer plate 67b is used as the heat transfer member. On the other hand, a roller-shaped heat transfer roller can also be used as the heat transfer member. Specifically, the heat transfer roller has a heater as a heating member fixed therein, and is in pressure contact with the brush roller 91 to form a nip. The heat transfer roller rotates in the counterclockwise direction of FIG. 2 to convey the recording medium toward the nip portion while heating the recording medium.

Hereinafter, the configuration and operation of the pressing member 85 that are characteristic of the transfer fixing device 66 according to the first embodiment will be described in detail with reference to FIGS.
Referring to FIG. 4, the transfer fixing device 66 according to the first embodiment is the upstream side of the transfer fixing belt 27 in the running direction with respect to the primary transfer unit 100 and the running of the transfer fixing belt 27 with respect to the nip portion. The transfer and fixing belt 27 is configured to be loose on the downstream side in the direction. Further, the transfer and fixing belt 27 is configured to be slack on the upstream side in the running direction of the transfer and fixing belt 27 with respect to the nip portion. That is, the transfer fixing belt 27 is stretched with a gentle curvature with respect to the virtual locus of the belt shown by the one-dot chain line in FIG. 4 (the locus of the belt when there is no belt slack) in the range before and after the nip portion. Has been.

  Specifically, referring to FIG. 4, the peripheral length of transfer fixing belt 27 is set to be longer than the peripheral length stretched without slack by three roller members 28 </ b> A to 28 </ b> C. Further, on the upstream side of the primary transfer unit 100, a load is applied to the transfer fixing belt 27 in the conveying direction so as to sandwich the transfer fixing belt 27 between the driven roller 28C and the cleaning blade 29a (belt cleaning device 29). Yes. Further, on the downstream side of the primary transfer unit 100, the transfer fixing belt 27 is driven with a sufficient driving force by the driving roller 28A. Accordingly, the tension of the transfer fixing belt 27 in the primary transfer unit 100 is always increased, and the other range is a weak tension unit. As a result, it is possible to prevent the occurrence of a shock jitter on the output image. Specifically, the moment when the leading edge of the recording medium P enters the nip portion (the contact position between the transfer fixing belt 27 and the pressure roller 68) and the moment when the trailing edge of the recording medium P is sent out from the nip portion. In this case, the speed fluctuation of the transfer fixing belt 27 is likely to occur. The speed fluctuation causes a shock jitter (a phenomenon in which the output image expands and contracts in a direction corresponding to the traveling direction of the transfer fixing belt 27) in the primary transfer process performed in the primary transfer unit 100. . Thus, in order to prevent the speed fluctuation of the transfer fixing belt 27 from affecting the primary transfer portion 100, the tension of the transfer fixing belt 27 in the range from the driving roller 28A through the nip portion to the driven roller 28C is 1 It is necessary to set so as to be smaller than the tension of the transfer fixing belt 27 in the next transfer unit 100. In the first embodiment, since the tension of the transfer fixing belt 27 in the primary transfer unit 100 is always increased and the other range is set to be a weak tension unit, the transfer generated in the transfer fixing unit is set. The speed fluctuation of the fixing belt 27 is absorbed by the weak tension portion, and a problem that a shock jitter is generated on the output image is prevented.

  Further, in the first embodiment, the counter roller 28B is configured to be able to vary the rotational speed of the driving roller 28A that drives the transfer fixing belt 27 at a constant speed. Then, by variably controlling the rotation speed of the opposing roller 28B, the transfer fixing belt 27 is located upstream of the primary transfer portion 100 in the running direction of the transfer fixing belt 27 and the nip portion (transfer fixing portion). The slack of the transfer fixing belt 27 generated on the downstream side in the running direction (the slack on the downstream side of the nip portion) and the transfer to the nip portion on the downstream side of the transfer fixing belt 27 in the running direction with respect to the drive roller 28A. The slack of the transfer and fixing belt 27 that occurs on the upstream side in the running direction of the fixing belt 27 (the slack on the upstream side of the nip portion) is adjusted. As a result, even when slippage occurs between the drive roller 28A and the transfer fixing belt 27, by adjusting the rotation speed of the opposing roller 28B, slack that is biased toward the upstream side or downstream side of the nip portion is eliminated. Without causing it, slack can be generated in a balanced manner on the upstream side and downstream side of the nip portion. Therefore, the effect of suppressing shock jitter on the output image by providing the weak tension portion is stably exhibited.

In the first embodiment, displacement sensors 110A and 110B that detect the amount of slack at both ends in the width direction of the transfer fixing belt 27 on the upstream side of the nip portion, and both ends in the width direction of the transfer fixing belt 27 on the downstream side of the nip portion. Displacement sensors 110C and 110D for detecting the amount of slack are provided. In addition, the transfer fixing device 66 according to the first embodiment can vary the pressure balance in the width direction of the pressure roller 68 with respect to the opposing roller 28B by varying the pressure applied to both ends of the pressure roller 68 in the width direction. It is configured as follows. And based on the detection result of these displacement sensors 110A-110D, the rotational speed of the opposing roller 28B and the pressure balance by the pressure roller 68 are varied.
Specifically, the detection results of the displacement sensors 110A and 110B upstream of the nip portion are compared with the detection results of the displacement sensors 110C and 110D downstream of the nip portion. When it is determined that the belt slack on the downstream side is small, the rotational speed of the opposing roller 28B is accelerated, and it is determined that the belt slack on the upstream side of the nip is small and the belt slack on the downstream side of the nip is large. First, the rotational speed of the opposing roller 28B is reduced to balance the belt slack on the upstream side and downstream side of the nip portion. Further, the detection results of the displacement sensors 110A and 110C at one end in the width direction and the detection results of the displacement sensors 110B and 110D at the other end in the width direction are compared, and it is determined that the balance of the belt slack at both ends in the width direction is poor. If it is, the pressure balance by the pressure roller 68 is varied to correct the belt slack balance at both ends in the width direction.

Here, in the first embodiment, with reference to FIG. 4, the position where the transfer fixing belt 27 is loosened (slack part) and a position near the nip part (a position downstream of the nip part). )) Is provided with a pressing member 85. The pressing member 85 is configured to be able to contact and separate from the outer peripheral surface of the transfer fixing belt 27 by rotating around a shaft portion 85a connected to a drive motor (not shown). Then, referring to FIG. 6, the central portion in the width direction of the transfer fixing belt 27 is pressed from the outer peripheral surface side of the transfer fixing belt 27, and the central portion in the width direction of the slack portion on the downstream side of the nip portion of the transfer fixing belt 27. Deform locally.
With such a configuration, the leading end portion of the recording medium P delivered from the nip portion is deformed into a concave shape by the pressing member 85 without being in close contact with the transfer fixing belt 27 whose curvature is increased due to belt slack, and the curvature is increased. The curvature is separated from the transfer fixing belt 27 at the position where it becomes smaller. Therefore, a problem that the separation failure of the recording medium P occurs with respect to the transfer fixing belt 27 after the transfer fixing process is suppressed. In particular, since the transfer fixing device 66 according to the first embodiment heats the surface of the recording medium P with the heating device 67 before being fed into the nip portion, the recording medium is thin and weak. (For example, a sheet of about 45 to 55K) is easily curled in the direction in which the recording medium P is in close contact with the transfer and fixing belt 27. Even in such a case, transfer and fixing is performed by the pressing member 85. By forming the concave portion on the downstream side of the nip portion of the belt 27, it is possible to suppress the separation failure of the recording medium P.
In the first embodiment, only a part (width direction central portion) on the downstream side of the nip portion of the transfer and fixing belt 27 is pressed by the pressing member 85, so that the entire weak tension portion of the transfer and fixing belt 27 is pressed. There is no major loss of balance. Accordingly, it is possible to suppress the separation failure of the recording medium P with respect to the transfer fixing belt 27 while maintaining the effect of suppressing the shock jitter on the output image by providing the weak tension portion.

  In the first exemplary embodiment, only a part in the width direction (the center in the width direction) on the downstream side of the nip portion of the transfer fixing belt 27 is pressed by the pressing member 85, but the entire weak tension portion in the transfer fixing belt 27 is pressed. If the general balance can be maintained to some extent, the entire width direction downstream of the nip portion of the transfer fixing belt 27 can be pressed by the pressing member 85 over the entire width direction.

  Here, the pressing member 85 according to the first embodiment functions as a separation claw whose leading end abuts on the outer peripheral surface of the transfer fixing belt 27 and whose central portion guides the conveyance of the recording medium P. Specifically, the surface of the pressing member 85 is coated with a low friction material such as PFA having a low friction coefficient. As shown in FIG. 6, the shape of the lower surface from the front end portion of the pressing member 85 to the shaft portion 85 a is gently changed in the state where the pressing member 85 is in contact with the outer peripheral surface of the transfer fixing belt 27. It is formed along the transport path. As a result, even if the leading end of the recording medium P sent out from the nip portion is in close contact with the transfer fixing belt 27, the recording medium P is transferred to the transfer fixing belt by the pressing member 85 that also functions as a separation claw. 27 is mechanically separated from 27 and guided to the conveyance path.

In the first embodiment, the pressing member 85 is preferably controlled to be separated from the transfer fixing belt 27 when the recording medium P is not conveyed to the nip portion. That is, when the recording medium P is not conveyed to the nip portion, the pressing member 85 is separated from the transfer fixing belt 27 as shown in FIG. 4, and when the recording medium P is conveyed to the nip portion, as shown in FIG. As shown, the pressing member 85 presses the slack portion of the transfer fixing belt 27.
Thereby, damage to the surface of the transfer fixing belt 27 by the pressing member 85 can be reduced.

At that time, the pressing member 85 presses the transfer fixing belt 27 at a timing when the leading end portion of the recording medium P is sent out from the nip portion, and the transfer is performed until the trailing end portion of the recording medium P is sent out from the nip portion. It is further preferable that the distance between the fixing belt 27 and the fixing belt 27 is controlled. That is, at the timing immediately before the leading end portion of the recording medium P is sent out from the nip portion and comes into close contact with the transfer fixing belt 27, the transfer fixing belt 27 is pressed by the pressing member 85 to form a recess. Then, after the leading end portion of the recording medium P is reliably separated from the transfer fixing belt 27, the pressing member 85 is separated from the transfer fixing belt 27.
Thereby, the time for the pressing member 85 to press the transfer fixing belt 27 can be reduced to the minimum necessary, and the effect of suppressing the shock jitter on the output image can be reliably maintained by providing the weak tension portion. The separation failure of the recording medium P with respect to the transfer fixing belt 27 can be efficiently suppressed.

  In the first embodiment, the pressing member 85 can be controlled to be separated from the transfer fixing belt 27 when the thickness of the recording medium P conveyed to the nip portion is equal to or larger than a predetermined value. Specifically, when the recording medium P (thick paper) having a large thickness and a strong stiffness is passed, it is easy to be separated from the transfer fixing belt 27 even if the transfer fixing belt 27 is loose on the downstream side of the nip portion. The shock when being sent to the nip portion is increased. Therefore, when passing such thick paper, priority is given to suppressing shock jitter on the output image by providing a weak tension portion, and the pressing member 85 is pressed against the transfer fixing belt 27 for transfer fixing. Control to improve the margin for the separation failure of the recording medium P with respect to the belt 27 is not performed. Note that the thickness of the recording medium P can be detected by a paper thickness sensor (not shown) provided in the paper feeding unit 61 and the conveyance path.

  Further, in the first embodiment, the pressing member 85 is controlled so as to be separated from the transfer fixing belt 27 when the range in which an image is not formed from the front end portion of the recording medium P conveyed to the nip portion is a predetermined value or more. It can also be made. Specifically, when the margin of the leading edge of the image formed on the recording medium P is wide (when the leading margin is long in the transport direction), the leading edge of the recording medium P is the transfer fixing belt. 27, the transfer fixing belt 27 is easily separated from the transfer fixing belt 27 even if the transfer fixing belt 27 is loose. Therefore, in such a case, in order to reduce damage to the transfer fixing belt 27 due to the pressing member 85 pressing the transfer fixing belt 27, the pressing member 85 is pressed against the transfer fixing belt 27 to transfer the fixing belt. Thus, the control for improving the margin for the separation failure of the recording medium P with respect to the recording medium P is not performed. It should be noted that a range where no image is formed from the leading end of the recording medium P can be detected from image data input to and output from the writing unit 2.

  As described above, according to the first embodiment, the pressing member 85 that presses and locally deforms the transfer fixing belt 27 that is slackened at a position near the downstream side of the nip portion is provided. In addition, the separation property of the recording medium P sent from the nip portion with respect to the transfer fixing belt 27 is not deteriorated, and the problem that shock jitter occurs on the output image due to the speed fluctuation of the transfer fixing belt 27 can be reduced.

In the first embodiment, the present invention is applied to the transfer fixing device 66 in which the heating device 67 and the heater 88 are installed. However, only one of the heating device 67 and the heater 88 is installed. Of course, the present invention can also be applied to the transfer fixing device 66 (a device that performs only paper heating or a device that does not perform paper heating).
In the first exemplary embodiment, the heater 88 (heating unit) is installed at a position facing the outer peripheral surface of the transfer fixing belt 27, but the heater 88 (heating unit) is positioned at a position facing the inner peripheral surface of the transfer fixing belt 27. ) Can also be installed.
Even in these cases, the same effects as those of the first embodiment can be obtained.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is an enlarged view showing a part of the transfer fixing device according to the second embodiment, and corresponds to FIG. 6 in the first embodiment. The transfer fixing device according to the second embodiment is different from that of the first embodiment in that a blower fan 115 as a blower is installed in the vicinity of the pressing member 85.

Referring to FIG. 7, the transfer fixing device 66 according to the second embodiment is also similar to that of the first embodiment, the transfer fixing belt 27, the pressure roller 68 (pressure member), the pressing member 85, and the heating. The apparatus 67, the brush roller 91, the heater 88, etc. are comprised. The pressing member 85 abuts on the downstream side of the nip portion of the transfer and fixing belt 27 to locally deform the slack portion of the transfer and fixing belt 27, thereby suppressing a shock jitter on the output image by providing a weak tension portion. The separation failure of the recording medium P with respect to the transfer fixing belt 27 can be suppressed while maintaining the effect.
In the second embodiment, a weak contact force is added to the three roller members 28A to 28C that stretch and support the transfer fixing belt 27 so that wrinkles and undulations do not occur in the slack portion of the transfer fixing belt 27. Thus, a tensioner 116 is provided so as to contact the inner peripheral surface of the transfer fixing belt 27.

Here, referring to FIG. 7, transfer fixing device 66 according to the second embodiment feeds air from the outer peripheral surface side of transfer fixing belt 27 toward the position where transfer fixing belt 27 is deformed by pressing member 85. A blower fan 115 as a blower is installed.
Specifically, a duct is installed at the blower opening of the blower fan 115, and the air sent from the blower fan 115 is blown toward the concave portion of the transfer fixing belt 27 deformed by the pressing member 85. As a result, the leading end portion of the recording medium P conveyed to the concave portion of the transfer fixing belt 27 deformed by the pressing member 85 is separated by the curvature of the concave portion, and the transfer fixing belt 27 is driven by the force of the air blown into the concave portion. Air separation will occur.

  As described above, according to the second embodiment, similarly to the first embodiment, the transfer fixing belt 27 that is slackened at a position near the downstream side of the nip portion is pressed to be locally deformed. Since the pressing member 85 is provided, the separability of the recording medium P sent from the nip portion with respect to the transfer fixing belt 27 is not deteriorated, and the shock jitter is generated on the output image due to the speed fluctuation of the transfer fixing belt 27. The trouble which arises can be reduced.

Embodiment 3 FIG.
8 and 9, the third embodiment of the present invention will be described in detail.
FIG. 8 is an enlarged view showing a part of the transfer fixing device according to the third embodiment, and corresponds to FIG. 6 according to the first embodiment. FIG. 9 is an enlarged view showing a modified example of another transfer fixing device, and corresponds to FIG. 6 in the first embodiment.
The transfer fixing device according to the third embodiment is that the restriction members 121 and 122 for restricting the deformation amount and shape of the transfer fixing belt 27 deformed by the pressing member 85 are provided. Is different.

  Referring to FIG. 8, similarly to the first embodiment, the transfer fixing device 66 according to the third embodiment also has a transfer fixing belt 27, a pressure roller 68 (pressure member), a pressing member 85, and a heating member. The apparatus 67, the brush roller 91, the heater 88, etc. are comprised. The pressing member 85 abuts on the downstream side of the nip portion of the transfer and fixing belt 27 to locally deform the slack portion of the transfer and fixing belt 27, thereby suppressing a shock jitter on the output image by providing a weak tension portion. The separation failure of the recording medium P with respect to the transfer fixing belt 27 can be suppressed while maintaining the effect.

Here, referring to FIG. 8, the transfer fixing device 66 according to the third embodiment is in contact with the pressing member 85 via the transfer fixing belt 27 and is deformed by the pressing member 85. A stepped roller 121 is provided as a regulating member that regulates the shape.
Specifically, in the stepped roller 121, the outer diameter of the width direction central portion 121a (the length in the width direction is set to about 10 to 20 mm) is about 2 to 6 mm than the outer diameter of both ends in the width direction. It is formed to be smaller. Then, the pressing member 85 abuts the widthwise central portion 121a of the stepped roller 121 via the transfer fixing belt 27, so that the deformation amount and shape of the concave portion of the transfer fixing belt 27 deformed by the pressing member 85 are desired. Regulated by things. Therefore, the problem that the transfer fixing belt 27 is greatly deformed by the pressing member 85 and the weak tension portion disappears is suppressed. Note that both end portions in the width direction of the stepped roller 121 are in contact with each other with a small force so as to follow the transfer and fixing belt 27 in which slack is generated.

Further, the regulating member that regulates the deformation amount and shape of the transfer fixing belt 27 deformed by the pressing member 85 is not limited to the stepped roller 121 described above, and an elastic roller 122 as shown in FIG. Can also be used.
Specifically, the elastic roller 122 is provided with an elastic layer made of foamed urethane or the like, and the elastic member 122 is elastically deformed by a predetermined amount when the pressing member 85 contacts the elastic roller 122 via the transfer fixing belt 27. Thus, the deformation amount and shape of the concave portion of the transfer fixing belt 27 deformed by the pressing member 85 are restricted to a desired one. Therefore, the problem that the transfer fixing belt 27 is greatly deformed by the pressing member 85 and the weak tension portion disappears is suppressed. The elastic roller 122 is configured to contact the inner peripheral surface of the transfer fixing belt 27 with a relatively weak contact force when the pressing member 85 is separated from the transfer fixing belt 27. It functions as a tensioner that prevents wrinkles and undulations at the slack portion 27.

  As described above, according to the third embodiment, as in the above-described embodiments, the transfer fixing belt 27 that is slackened at a position near the downstream side of the nip portion is pressed to be locally deformed. Since the pressing member 85 is provided, the separability of the recording medium P sent from the nip portion with respect to the transfer fixing belt 27 is not deteriorated, and the shock jitter is generated on the output image due to the speed fluctuation of the transfer fixing belt 27. The trouble which arises can be reduced.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 10 is an enlarged view showing a part of the transfer fixing device according to the fourth embodiment, and corresponds to FIG. 6 in the first embodiment. In the transfer fixing apparatus according to the fourth embodiment, the pressing member 86 presses the transfer fixing belt 27 from the inner peripheral surface side, and the pressing member 85 presses the transfer fixing belt 27 from the outer peripheral surface side. It is different from the one.

  Referring to FIG. 10, similarly to the first embodiment, the transfer fixing device 66 in the fourth embodiment is also the transfer fixing belt 27, the pressure roller 68 (pressure member), the pressing member 86, and the heating. The apparatus 67, the brush roller 91, the heater 88, etc. are comprised.

Here, referring to FIG. 10, in the transfer fixing device 66 according to the fourth embodiment, the pressing member 86 is on the downstream side of the nip portion of the transfer fixing belt 27 and the width of the inner peripheral surface of the transfer fixing belt 27. The slack portion of the transfer fixing belt 27 is locally deformed by contacting the central portion in the direction.
Even in such a case, a convex portion is formed in the slack portion on the downstream side of the nip portion of the transfer fixing belt 27 by the pressing member 86, and the leading end portion of the recording medium P that has reached the position is transferred by the curvature of the convex portion. It is separated from the fixing belt 27. Accordingly, it is possible to suppress the separation failure of the recording medium P with respect to the transfer fixing belt 27 while maintaining the effect of suppressing the shock jitter on the output image by providing the weak tension portion.

  As described above, according to the fourth embodiment, the pressing member 86 that presses and locally deforms the transfer and fixing belt 27 that is slackened at a position near the downstream side of the nip portion is provided. In addition, the separation property of the recording medium P sent from the nip portion with respect to the transfer fixing belt 27 is not deteriorated, and the problem that shock jitter occurs on the output image due to the speed fluctuation of the transfer fixing belt 27 can be reduced.

Embodiment 5 FIG.
A fifth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 11 is a diagram illustrating a fixing device according to the fifth embodiment. The fifth embodiment is different from the first embodiment in which the pressing member 85 is installed in the transfer fixing device 66 in that the pressing member 185 is installed in the fixing device 166.

The image forming apparatus according to the fifth embodiment is not provided with the transfer fixing device 66 that performs the transfer process and the fixing process at the same time as the image forming apparatus according to each of the above embodiments, and the transfer apparatus that performs the transfer process. In addition, a fixing device 166 that performs only the fixing process is installed.
Here, the fixing device 166 includes a heating roller 128A, a fixing roller 128B, a fixing belt 127, a pressure roller 168, a pressing member 185, and the like.
The fixing belt 127 is stretched between a heating roller 128A and a fixing roller 128B. The fixing belt 127 is configured such that belt slack occurs on the downstream side of the nip portion (the position where the fixing roller 128B and the pressure roller 168 are in pressure contact). Specifically, the circumferential length of the fixing belt 127 is formed large in advance, and the range from the fixing roller 128B functioning as a driving roller to the heating roller 128A is configured to be a weak tension portion.
A heater 188 is installed inside the heating roller 128A, and the fixing belt 127 is heated via the heating roller 128A. Then, the toner image on the recording medium P fed into the nip portion is fixed on the recording medium P by the heat of the fixing belt 127 and the pressure contact force between the fixing roller 128 </ b> B and the pressure roller 168.

Here, the pressing member 185 is configured to be rotatable about the shaft portion 185a, and comes into contact with the slack portion of the fixing belt 127 at the timing when the leading end portion of the recording medium P is sent from the nip portion. The fixing belt 127 is deformed.
As a result, even when a slack portion is provided on the downstream side of the nip portion of the fixing belt 127, it is possible to reduce the problem of reducing the separation of the recording medium P sent from the nip portion with respect to the fixing belt 127.
Note that when the transfer process and the fixing process are performed separately as in the fifth embodiment, unlike the above-described embodiments, the shock that occurs when the recording medium P is sent into and out of the fixing nip portion. Therefore, there is no problem that shock jitter occurs on the output image. Therefore, there is no merit of intentionally forming the slack portion on the downstream side of the nip portion of the fixing belt 127 for the purpose of suppressing shock jitter on the output image. However, when it is desired to extend the mechanical life of the fixing belt 127 without giving a strong tension to the fixing belt 127, the configuration as in the fifth embodiment is effective. In the fifth embodiment, the image formed on the recording medium P is formed on the downstream side of the nip portion of the fixing belt 127 even when the leading edge margin of the image is narrow or the thin paper with weak stiffness is passed. Since the slack portion thus formed is deformed by the pressing member 185, the recording medium P sent from the nip portion can be satisfactorily separated from the fixing belt 127.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 image forming apparatus body (apparatus body),
27 transfer fixing belt (transfer fixing member),
28A Drive roller (roller member),
28B opposing roller (roller member),
28C roller member,
66 transfer fixing device,
67 heating device, 67a heating body, 67b heat transfer plate (heat transfer member),
68 Pressure roller (pressure member),
85 pressing member (separation claw),
88 heaters,
91 brush-like roller (biasing member),
100 primary transfer part,
115 blower fan (fan means),
121 stepped rollers (regulating members), 122 elastic rollers (regulating members),
P Recording medium.

JP 2006-91101 A JP 2008-170908 A JP 2008-145680 A

Claims (11)

A transfer fixing device for transferring and fixing a toner image to a recording medium,
A toner image formed on the image carrier at a primary transfer portion facing the image carrier, and a transfer fixing belt stretched around a plurality of roller members;
A pressure member that forms a nip portion to which the recording medium is conveyed in pressure contact with the transfer fixing belt;
With
The transfer fixing belt is configured to be slack on the upstream side in the running direction of the transfer fixing belt with respect to the primary transfer portion and on the downstream side in the running direction of the transfer fixing belt with respect to the nip portion,
At a position where the slack of the transfer fixing belt is generated and in the vicinity of the nip portion, a part or all of the transfer fixing belt in the width direction is arranged on the outer peripheral surface side or inner peripheral surface side of the transfer fixing belt. And a pressing member for locally deforming the transfer and fixing belt by pressing from the above.   The pressing member is configured to be able to come into contact with and separate from the transfer fixing belt, and is controlled to be separated from the transfer fixing belt when the recording medium is not conveyed to the nip portion. The transfer fixing device according to claim 1.   The pressing member presses the transfer and fixing belt at a timing when the leading end portion of the recording medium is sent out from the nip portion, and the transfer fixing belt until the trailing end portion of the recording medium is sent out from the nip portion. The transfer fixing device according to claim 2, wherein the transfer fixing device is controlled so as to be separated from the transfer fixing device.   The pressing member is configured to be able to come into contact with and separate from the transfer fixing belt, and is controlled to be separated from the transfer fixing belt when the thickness of the recording medium conveyed to the nip portion is a predetermined value or more. The transfer fixing apparatus according to claim 1, wherein the transfer fixing apparatus is characterized in that:   The pressing member is configured to be able to come into contact with and separate from the transfer fixing belt, and when the range in which an image is not formed from the leading end portion of the recording medium conveyed to the nip portion is a predetermined value or more, The transfer fixing device according to claim 1, wherein the transfer fixing device is controlled to be separated.   The air blower for feeding air from the outer peripheral surface side of the transfer-fixing belt toward a position where the transfer-fixing belt is deformed by the pressing member is further provided. The transfer fixing apparatus described.   2. A regulating member for regulating a deformation amount and / or shape of the transfer fixing belt deformed by the pressing member by contacting the pressing member via the transfer fixing belt. The transfer fixing device according to claim 6.   8. The pressing member according to claim 1, wherein a tip portion of the pressing member is in contact with an outer peripheral surface of the transfer fixing belt, and a central portion thereof is a separation claw for guiding conveyance of the recording medium. A transfer fixing apparatus according to claim 1. One of the plurality of roller members that drives the transfer and fixing belt, and is downstream of the primary transfer portion in the running direction of the transfer and fixing belt and the transfer portion to the nip portion. A driving roller disposed upstream of the fixing belt in the traveling direction;
An opposing roller that is one of the plurality of roller members and presses the pressure member via the transfer fixing belt at the position of the nip portion, and the rotation speed of which is variably controlled;
With
By variably controlling the rotation speed of the facing roller, it is generated on the upstream side in the running direction of the transfer and fixing belt with respect to the primary transfer portion and on the downstream side in the running direction of the transfer and fixing belt with respect to the nip portion. The transfer and fixing belt is loosened, and the transfer and fixing belt is generated on the downstream side in the running direction of the transfer and fixing belt with respect to the driving roller and on the upstream side in the running direction of the transfer and fixing belt with respect to the nip portion. The transfer fixing apparatus according to claim 1, wherein slackness is adjusted. A heat transfer member that is heated by a heating body and that heats the transfer fixing surface of the recording medium while guiding the recording medium conveyed toward the nip portion;
A biasing member that biases the recording medium guided by the heat transfer member toward the heat transfer member;
The transfer fixing apparatus according to claim 1, comprising:   An image forming apparatus comprising the transfer fixing device according to claim 1.

Images