JP2004045950A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device equipped with a belt fixing device which prolongs the life of a belt member base body and to prolong the life of the belt member base body by cooling only end parts of the belt member. <P>SOLUTION: The image forming device has the belt fixing device which is equipped with the endless belt member and a cooling means and in which the cooling means cools the end parts of the belt member in a direction orthogonal to a moving direction of the belt member. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus including a belt fixing device used for image forming such as a copier, a printer, and a facsimile.
[0002]
[Prior art]
Conventionally, as a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, a heating rubber roller having an elastic layer and maintained at a predetermined temperature, and pressed against the heating rubber roller, 2. Description of the Related Art A heat roller fixing system in which a transfer material having an unfixed toner image formed thereon is heated while being nipped and conveyed by a pressure rubber roller having an elastic layer is often used.
[0003]
However, in this type of apparatus, the heat resistance and heat capacity of the heat-generating rubber roller are large, so that the warm-up time is long, the temperature inside the elastic layer is high, and the life of the heat-generating rubber roller is shortened.
[0004]
In addition, many color images have a large solid area, and many of the solid images are other than black. When a hard roller is used as the heating rubber roller and the pressure rubber roller, there is a problem that image quality is deteriorated because unevenness of gloss occurs according to unevenness of a transfer material (recording paper) and a toner layer.
[0005]
In order to solve these problems, an endless belt member (fixing belt) is used, and the fixing belt is supported and stretched by a plurality of roller members. A pressure roller (external pressure roller) opposed to the support pressure roller with the fixing belt interposed therebetween, and a heating roller (supporting heat roller) having a heating member for heating the fixing belt therein, and rotating the fixing belt. Fixing device for fixing a toner image on a recording sheet at a belt nip portion provided on the upstream side of the supporting pressure roller in a direction and a fixing nip portion provided between the supporting pressure roller and the external pressing roller. Is disclosed in Japanese Patent Application Laid-Open No. 10-307496.
[0006]
[Problems to be solved by the invention]
However, in the belt fixing device disclosed in the above-mentioned Japanese Patent Application Laid-Open No. H10-307496, if the deviation of the belt member (fixing belt) is regulated by abutting against a flange or the like, the mechanical load and the thermal load are reduced. Due to the excessive load, a problem arises in that the base member is cracked at the end of the fixing belt (the end of the belt member in a direction perpendicular to the moving direction of the fixing belt) and cannot be used.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus including a belt fixing device that solves the above problem and extends the life of a base member of a belt member. It is intended to prolong the service life.
[0008]
[Means for Solving the Problems]
The object is to transfer an unfixed toner image onto a transfer material, and then pressurize and heat the unfixed toner image with a belt fixing device, and fix the image on the transfer material by fixing. The belt fixing device includes an endless belt member and a cooling unit, and the cooling unit cools an end of the belt member in a direction orthogonal to a moving direction of the belt member. This is achieved by a forming device.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope. In the following description of the embodiments, an end of the belt member means an end of the belt member in a direction orthogonal to a moving direction of the belt member.
[0010]
An image forming process and each mechanism of an embodiment of an image forming apparatus using a belt fixing device according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a color image forming apparatus showing an embodiment of an image forming apparatus using a belt fixing device according to the present invention. FIG. 2 is a schematic cross-sectional view of an example of a belt fixing device. FIG. 3 is a rear view of the belt fixing device provided with the cooling means of the first example of the end portion of the belt member according to the present invention, and FIG. 4 is a view showing the second example of the end portion of the belt member according to the present invention. FIG. 5 is a schematic cross-sectional configuration diagram of a belt fixing device provided with a cooling unit. FIG. 5 is a perspective view of the cooling unit of FIG. 4 and a rear view of the belt fixing device.
[0011]
In FIG. 1, the image forming apparatus GS includes an image forming apparatus main body GH and an image reading apparatus YS.
[0012]
An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is provided above the image forming apparatus main body GH. A document D placed on a document table of the automatic document feeder 201 is conveyed by a conveying means, and one side or both sides of the document is scanned and exposed by an optical system of a document image scanning and exposing device 202, and is sent to a line image sensor CCD. Is read. At this time, the original D conveyed from the original platen is determined by the gloss level detection sensor PKa used as a gloss level selecting means to determine the gloss of the original image, the monochrome / color of the original image, and the double-sided image. Done.
[0013]
The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing section, and then to an image writing section (exposure means) 3Y, 3M, 3C. Send a signal to 3K.
[0014]
The automatic document feeder 201 has an automatic double-sided document conveying means. Since the automatic document feeder 201 can continuously read the contents of a large number of documents D conveyed from the document mounting table at once and accumulate it in the storage means (electronic RDH function), the copying function This is conveniently used when copying the contents of many originals, or when transmitting many originals D by facsimile function.
[0015]
The image forming apparatus main body GH is called a tandem-type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 6 as a belt-shaped intermediate transfer body, It comprises a paper feeder including a paper mechanism (ADU mechanism) and a belt fixing device 17 as a fixing means.
[0016]
The image forming unit 10Y that forms a yellow (Y) color image includes a photosensitive drum 1Y as an image forming body, a charging unit 2Y as a Y toner image forming unit disposed around the photosensitive drum 1Y, and an exposure. There is a unit 3Y, a developing device 4Y and an image forming body cleaning unit 8Y. The image forming unit 10M that forms an image of magenta (M) color includes a photosensitive drum 1M as an image forming body, a charging unit 2M as a M toner image forming unit, an exposing unit 3M, a developing device 4M, and an image forming unit. It has a cleaning unit 8M. The image forming section 10C for forming a cyan (C) color image includes a photosensitive drum 1C as an image forming body, a charging section 2C as a C toner image forming section, an exposing section 3C, a developing device 4C, and an image forming section. It has a cleaning unit 8C. An image forming unit 10K for forming a black (K) color image includes a photosensitive drum 1K as an image forming body, a charging unit 2K as a K toner image forming unit, an exposing unit 3K, a developing device 4K, and an image forming unit. It has a cleaning unit 8K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit. The development by the developing devices 4Y, 4M, 4C, and 4K is performed by reversal development in which a development bias in which an AC voltage is superimposed on a DC voltage having the same polarity (negative polarity in the present embodiment) as the polarity of the toner to be used is applied. .
[0017]
The intermediate transfer belt 6 is wound around a plurality of rollers and is rotatably supported.
[0018]
The outline of the image forming process will be described below.
The image of each color formed by the image forming units 10Y, 10M, 10C, and 10K has a primary transfer transfer bias (not shown) of the opposite polarity (positive in this embodiment) to the toner used. By the primary transfer rollers 7Y, 7M, 7C and 7K as transfer means, the images are sequentially transferred (primary transfer) onto the rotating intermediate transfer belt 6 to form a combined color image (color toner image). . The recording paper P stored in the paper feed cassettes 20A, 20B, and 20C is fed by a feed roller 21 and a paper feed roller 22A provided in the paper feed cassettes 20A, 20B, and 20C, respectively, and is fed by transport rollers 22B, 22C, and 22D. Then, the sheet is conveyed to a secondary transfer roller 7A as a secondary transfer means via a registration roller 23 and the like, and a color image is collectively transferred onto one surface (front surface) of the recording paper P (secondary transfer).
[0019]
The recording paper P to which the color image has been transferred is subjected to a fixing process by the belt fixing device 17, is sandwiched by the discharge rollers 24, and is placed on a discharge tray 25 outside the apparatus.
[0020]
The untransferred toner remaining on the peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is cleaned by the image forming body cleaning means 8Y, 8M, 8C, and 8K and enters the next image forming cycle.
[0021]
On the other hand, after the color image is transferred onto the recording paper P by the secondary transfer roller 7A, the residual toner is removed from the intermediate transfer belt 6 from which the recording paper P is separated by the curvature by the intermediate transfer body cleaning means 8A.
[0022]
Although the above image forming process has been described with reference to color image formation, it goes without saying that not only color image formation but also monochrome image formation and double-sided image formation are performed.
[0023]
According to FIG. 2, a belt fixing device 17 according to the present invention includes a fixing belt 27 as an endless belt member, and a supporting pressure roller that supports and stretches the fixing belt 27 on one of the inner peripheral surfaces of the fixing belt 27. 17a, an external pressure roller 17b which is in contact with the external pressure roller 17b with the fixing belt 27 interposed therebetween, and presses (presses) the support pressure roller 17a, and has a halogen heater HLa as a heating member therein for fixing. The fixing belt 27 is stretched by providing a roller member of a support heating roller 17c that supports and stretches the fixing belt 27 at the other inner peripheral surface of the belt 27. The fixing belt 27 that is heated by the support heating roller 17c is sandwiched therebetween. A fixing nip portion Nb is formed between the supporting pressure roller 17a and the external pressure roller 17b, and a gap between the fixing belt 27 and the external pressure roller 17b is formed. To form a belt nip Na, is to fix the toner image on the recording sheet P (or color toner image) by applying heat and pressure through the fixing nip portion Nb with the belt nip Na.
[0024]
As the fixing belt 27, a nickel electroformed belt having an inner diameter of about 60 to 150 mm and a thickness of about 20 to 80 μm, or a heat-resistant resin belt having a thickness of about 50 to 200 μm is used as a base. (Peripheral surface) coated with silicon rubber having a thickness of about 100 to 500 μm, and subjected to a PFA (perfluoroalkoxy) or PTFE coating processing having a thickness of about 30 to 50 μm as a release layer, or a PFA tube Is used.
[0025]
The supporting pressure roller 17a is, for example, a cylindrical metal pipe 171a having a thickness of about 2 to 5 mm using a steel material such as STKM (carbon steel pipe for machine structure), and a thickness of 0 mm on the outer peripheral surface of the metal pipe 171a. As a soft roller having an outer diameter of about 25 to 70 mm, a silicon rubber layer 172a of about 0.5 to 5 mm is provided, and a PFA (perfluoroalkoxy) tube 173a having a thickness of about 30 to 70 μm is provided outside the silicon rubber layer 172a. Be composed.
[0026]
The external pressure roller 17b is, for example, a cylindrical metal pipe 171b having a thickness of about 2 to 5 mm using steel or aluminum such as STKM (carbon steel pipe for machine structure) and an outer peripheral surface of the metal pipe 171b. A silicone rubber layer 172b having a thickness of 1 to 3 mm, and a release layer 173b using a PFA (perfluoroalkoxy) tube having a thickness of about 20 to 50 μm outside the silicone rubber layer 172b; It is configured as a soft roller of about 80 mm. Further, a halogen heater HLa as a heating member may be provided inside the external pressure roller 17b as shown by a dotted line in the figure.
[0027]
A supporting and heating roller 17c in which a halogen heater HLa as a heating member for heating the fixing belt 27 is provided is a cylindrical metal pipe 171c having a thickness of about 1 to 2 mm using, for example, an aluminum material as a base, and A PFA (perfluoroalkoxy) coating 172c having a thickness of about 10 to 30 μm is formed on the outer peripheral surface of the pipe 171c, and is configured as a roller member having an outer diameter of about 30 to 70 mm. A ring-shaped flange Tb is provided at both ends of the supporting and heating roller 17c as a regulating member for preventing the fixing belt 27 from shifting.
[0028]
The support pressure roller 17a is rotationally driven by a drive motor (not shown), and the fixing belt 27 is supported and conveyed by the rotation of the support pressure roller 17a to be driven to rotate. The external pressure roller 17b may be driven to rotate, the fixing belt 27 may be supported and transported by the external pressure roller 17b, and the fixing belt 27 may be driven to rotate.
[0029]
A belt nip Na formed between the fixing belt 27 and the external pressure roller 17b and a fixing nip Nb formed between the support pressure roller 17a and the external pressure roller 17b pass through the entrance guide 17s. The toner image (or color toner image) on the recording paper P entering the fixing area is heated under pressure to be fixed and fixed on the recording paper P.
[0030]
In addition, a temperature sensor TS1 that contacts the support heating roller 17c is provided to control the temperature of the support heating roller 17c. The temperature of the outer peripheral surface of the fixing belt 27 may be detected by a non-contact sensor.
[0031]
As described at the beginning, in the belt fixing device, when the bias of the belt member (fixing belt) is abutted against a flange or the like to control the bias, the fixing is reduced due to a mechanical load and a thermal load. At the end of the belt (the end of the belt member in a direction perpendicular to the direction of movement of the fixing belt), the base is cracked and cannot be used.
[0032]
In other words, as a method for regulating the deviation of the belt member, a method of regulating the movement of the belt member that attempts to shift the end of the belt member to the end with the above-described regulating member such as the flange is often used because it is inexpensive and stable. The belt member is heated to a temperature required for fixing, for example, 180 ° C., and the strength of the base using the metal member or the resin member is reduced due to heat, such as embrittlement or cross-linking of a polymer. For this reason, the base member is cracked or cracked from the end where the stress is concentrated due to the deviation control by the restricting member, so that it cannot be used. In the present invention, as described below, by cooling only the non-image area of the end portion which does not affect the fixing of the toner image (toner image) on the transfer material, the temperature of the end portion is reduced, and the strength due to heat is reduced. This prevents the belt member from lowering and extends the life of the belt member.
[0033]
As a first example of the cooling means, as shown in FIG. 3, a cooling fan RFa composed of, for example, a propeller fan is used as a blower, is wound around the supporting heating roller 17c, and is controlled by the flange Tb to control the bias. The fixing belt 27 to which the mechanical load of the fixing belt 27 and the thermal load of the support heating roller 17c are applied is cooled by the cooling fan RFa, for example, outside air is fixed to the end outside the image area of the fixing belt 27 (in the non-image area, The end portion of the fixing belt 27 made of a base member using a metal member or a resin member is cooled by blowing (blowing) the air onto the fixing belt 27 in the direction perpendicular to the moving direction of the belt 27 (outside the image area). . At this time, the air blower is provided with a partition wall KFa using a plate material made of, for example, a heat-resistant resin member so that only the end of the fixing belt 27 is cooled, and air is blown from the cooling fan RFa to the end of the fixing belt 27. Preferably, a path SRa is formed, and air is blown from the cooling fan RFa to the end of the fixing belt 27 through the blowing path SRa. It is also possible to provide a temperature sensor (not shown) at the end of the fixing belt 27 to control the blowing of the cooling fan RFa.
[0034]
4 and 5 show a second example, in which a cooling member as a cooling means is brought into contact with the end of the belt member. The belt fixing device 17 of the present invention has the configuration described with reference to FIG. 2, and the cooling means is formed of, for example, an aluminum bar as a cooling member, and the edge cooling unit is driven to rotate by the fixing belt 27 by the rotation shaft Ja. The roller 17r is provided opposite to the supporting pressure roller 17a with the fixing belt 27 interposed therebetween, is wound around the supporting heating roller 17c, is controlled by the flange Tb, and the mechanical load by the flange Tb and the supporting heating roller 17c To the end outside the image area of the fixing belt 27 (the end outside the image area of the fixing belt 27 in a direction orthogonal to the moving direction of the fixing belt 27 in the non-image area) to which the thermal load is applied. Then, the end cooling roller 17r is brought into contact with the end cooling roller 17r to cool only the end of the fixing belt 27 made of a base member using a metal member or a resin member. At this time, as shown in FIG. 5A, a fin FN made of, for example, an aluminum material is provided at the end of the end cooling roller 17r as a heat radiating means on the end cooling roller 17r, and the end cooling roller 17r rotates. Accordingly, the fan Fa of the end cooling roller 17r is rotated like a blade, or a metal plate KP made of, for example, a copper material is provided as a heat transport path of the fin FN as shown in FIG. One end of the metal plate KP is attached to the fin FN, and the other end is brought into contact with the end cooling roller 17r to radiate heat from the end cooling roller 17r so that only the end of the fixing belt 27 is cooled. I do.
[0035]
As described above, the fixing belt 27 is driven by the support pressure roller 17a or the external pressure roller 17b, and the recording holding the toner image (toner image) conveyed to the fixing area by the entry guide plate 17s or the like. The external pressure roller 17b presses the paper P and the fixing belt 27 with the supporting pressure roller 17a interposed therebetween, and a toner image (toner image) is recorded by heat of the fixing belt 27 and pressure by the external pressure roller 17b. Although the toner is fixed on the paper P, the rubber of the fixing belt 27 is brought into contact with the toner layer (toner image) on the recording paper P via a rubber or a thin release layer, so that the rubber is deformed and the recording is performed. Following the unevenness of the paper P and the toner layer, uniform contact and uniform fixing without gloss unevenness are performed, so that the toner image (toner image) maintains an appropriate gloss. Paper P is separated from the fixing belt 27 in a stable manner.
[0036]
In the above description of the present embodiment, a configuration in which one of the members in contact with the transfer material in the nip portion is a belt member and one is a roller member (a configuration having a nip portion including a belt nip portion and a fixing nip portion). As described above, it goes without saying that a configuration in which a nip portion is formed with a belt member as a pair and a transfer material is sandwiched therebetween is similarly effective.
[0037]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the crack of the base material of a belt member at the belt member edge part (the belt member edge part of the direction orthogonal to the moving direction of a belt member) by a mechanical load and a thermal load is suppressed. Accordingly, it is possible to provide an image forming apparatus including a belt fixing device having a long life belt member.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus using a belt fixing device according to the present invention.
FIG. 2 is a schematic sectional configuration diagram of an example of a belt fixing device.
FIG. 3 is a rear view of the belt fixing device provided with the cooling unit of the first example of the end portion of the belt member according to the present invention.
FIG. 4 is a schematic cross-sectional configuration diagram of a belt fixing device provided with a cooling unit of a second example of an end portion of the belt member according to the present invention.
5 is a perspective view of the cooling unit of FIG. 4 and a rear view of the belt fixing device.
[Explanation of symbols]
1Y, 1M, 1C, 1K Photoconductor drums 2Y, 2M, 2C, 2K Charging means 3Y, 3M, 3C, 3K Exposure means 4Y, 4M, 4C, 4K Developing device 7A Secondary transfer rollers 7Y, 7M, 7C, 7K 1 Next transfer roller 8A Intermediate transfer body cleaning means 8Y, 8M, 8C, 8K Image forming body cleaning means 10Y, 10M, 10C, 10K Image forming unit 17 Belt fixing device 17a Support pressure roller 17b External pressure roller 17c Support heat roller 17s Entry guide plate 17r End cooling roller 27 Fixing belt HLa Halogen heater KFa Partition Na Belt nip Nb Fixing nip RFa Cooling fan SRa Ventilation path P Recording paper

Claims (5)

After transferring the unfixed toner image onto the transfer material, in the image forming apparatus that presses and heats the unfixed toner image with a belt fixing device and fixes the unfixed toner image on the transfer material to perform fixing.
The belt fixing device,
An endless belt member,
Cooling means,
An image forming apparatus, wherein the cooling means cools an end of the belt member in a direction orthogonal to a moving direction of the belt member. The image forming apparatus according to claim 1, wherein the cooling unit is a blower. The image forming apparatus according to claim 2, wherein the blower has a blower passage. The image forming apparatus according to claim 1, wherein the cooling unit is configured to contact a cooling member with an end of the belt member. The image forming apparatus according to claim 4, wherein the cooling member has a heat radiating unit or a heat transport path to the heat radiating unit.

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