JP2009251180A - Fixing device, image forming apparatus and method for molding heat roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat roller capable of easily obtaining uniform temperature distribution in an axial direction independently of paper feeding width, ensuring rigidity, shortening rise time caused by thinning, and improving processability and versatility. <P>SOLUTION: In a fixing device, a fixing belt 14 is trained about a heat roller composed of a first and a second heat rollers 22, 23 and a small-diameter roller arranged on the downstream side of the second heat roller 23 in a conveying direction of a recording material and having a heat insulating layer. The first heat roller 22 has a center portion thinner than end portions in an axial direction in a paper feed area set along the axial direction on an inner peripheral surface of the heat roller 22 and includes a heat source 8a having a light emitting area on a position corresponding to the thin area. The second heat roller 23 has end portions thinner than a center portion in an axial direction in a paper feed area set along the axial direction on an inner peripheral surface of the second heat roller 23 and includes a heat source 8b having a light emitting area on a position corresponding to the thin area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic recording apparatus such as a copying machine, a facsimile machine, and an electrophotographic printer, which heats an image made of heat-meltable toner formed on a recording material surface such as paper or film to form a permanently fixed image on the recording material surface. The present invention relates to a fixing device of a heat fixing method for fixing to a toner, an image forming apparatus including the fixing device, and a method for forming a heating roller used in the fixing device.

2. Description of the Related Art Conventionally, in an image forming apparatus, as a method for fixing a toner image formed on one surface of a recording medium such as paper or film, a heat fixing method is generally used in which toner is melted and fixed on one surface by heat. Further, even in such a heat fixing method, the belt fixing method is most widely used because it is excellent in thermal efficiency and safe.
The fixing device used in this belt fixing method has an endless layer having a release layer made of a fluororesin or the like on the one side of the recording medium (the surface to which the toner adheres) at the nip portion sandwiched between two rollers. The toner is fixed on the recording medium by heating and pressurizing through the fixing belt.
In order to form a nip portion that is a portion to be heated and pressed, a side through the fixing belt is used as a fixing roller, and a side positioned on the other surface side of the recording medium is fixed by an urging unit. A pressure roller urged toward the roller is used, and the recording medium is nipped and conveyed at the pressure contact portion between the two rollers, and at the same time, the final fixing toner image formed on one surface side of the recording medium is heated at the nip portion. Then, the toner is fixed on one surface of the recording medium.

The fixing belt is stretched around a heating roller including a fixing roller and a heat source, and the heat is transferred to the temperature necessary for the fixing through the heating roller heated by the heat source. As the heat source provided inside the heating roller, a halogen lamp, a ceramic heater, or the like is provided along the axial direction.

Further, a temperature sensor is in contact with the surface of the fixing belt that contacts at the position corresponding to the heating roller, and the temperature of the nip portion is maintained at the optimum toner fixing temperature based on the detection temperature result of the temperature sensor. The power supply amount of the heat source is controlled. In such a fixing device, an aluminum alloy base is used for the heating roller so as to ensure thermal conductivity and rigidity in view of the heating efficiency from the heat source.
A general configuration of a heating roller using such an aluminum alloy as a base is that a cylindrical metal cylindrical tube is formed as the base and the outer peripheral surface of the base is used to suppress empty sliding with the fixing belt. Is coated with a resin layer made of fluorine resin or the like.
In some cases, a surface treatment such as alumite treatment or sand blasting is applied to the surface of the substrate instead of the resin layer. The heating roller may be provided with a detent member in order to suppress twisting and meandering due to conveyance of the fixing belt.
When forming a heating roller having such a configuration, a cylindrical long cylindrical tube is extruded from an aluminum alloy material, drawn, and this long cylindrical tube is cut into a predetermined length to form a metal cylindrical tube. Furthermore, the outer peripheral surface of the metal cylindrical tube is made uniform by cutting or grinding, and then the surface is roughened by sandblasting or the like, and further, a paint made of fluororesin or the like is applied and baked to form a resin layer. A film was formed and a predetermined finishing treatment was performed.
At this time, in many forming methods, when the outer peripheral surface of the metal cylindrical tube is processed, an outer diameter cutting process using a diamond tool is performed. Further, the metal cylindrical tube is thinned to a predetermined thickness at the same time by this cutting process.

On the other hand, due to the recent demand for energy saving and cost reduction, the heating roller is required to be further thinned in order to improve thermal conductivity. That is, it is possible to reduce the time required to reach a fixing temperature by reducing the thickness of the metal cylindrical tube (also referred to as a rise time of the fixing roller or a warm-up time), and to promote power saving in a copying machine or the like. For this reason, various proposals have been conventionally made (for example, see Patent Documents 1 to 7).
Patent Document 1 discloses a technique in which a halogen heater is independently controlled according to a sheet passing size by a heating roller incorporating two pairs of halogen heaters corresponding to a small size, center light distribution and end light distribution. Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique that can provide a narrow preheating chamber at the entrance of the fixing device and preheat the recording medium before fixing to suppress a temperature drop due to paper passing.
Patent Document 3 discloses a technique for obtaining a fixing device having a simple configuration. Patent Document 4 discloses a means that achieves both suppression of end temperature rise and reduction of rise time. Patent Document 5 discloses a superheated roller incorporating a plurality of halogen heaters.
Patent Document 6 discloses a technique in which an unevenness is provided on the inner peripheral portion of the heating roller, and a heat source is provided in which a light emitting region is disposed in an area corresponding to the unevenness. Patent Document 7 discloses a technique having a fixing belt having a large peripheral length and a fixing roller having a low hardness elastic layer.
Japanese Patent No. 3184489 JP-A-9-34283 Japanese Patent Laid-Open No. 9-12781 JP-A-10-115993 Japanese Patent Laid-Open No. 11-22469 JP 2006-337521 A JP 2006-11061 A

However, in the technique of Patent Document 1, since the inner diameter is increased in order to incorporate two pairs of heaters, and the heat capacity is increased, it takes time to raise the temperature, so that the rise time is delayed. Further, with the technique of Patent Document 2, the entire fixing device becomes large. Furthermore, since the temperature of the preheating chamber itself cannot be controlled, it depends on the atmosphere, and this technique has nothing to do with shortening the rise time.
In the technique of Patent Document 3, since the heat transfer member is brought into contact with the axial direction, the heat capacity is increased, and there is nothing related to shortening the rise time. The technology of Patent Document 4 has a planar heating element, but is provided with ring-shaped electrode members on the inner peripheral surfaces of both end portions to suppress heat dissipation from the inside, and the manufacturing cost is high and during runaway Reliability is regarded as a problem.
In the technique of Patent Document 5, the heating roller has a large diameter / a large heat capacity and requires a rise time. In addition, since the heating roller has a two-layer structure, the manufacturing method is complicated, and a difference in thermal expansion when heated is likely to occur, which may cause image defects. With the technique of Patent Document 6, it is difficult to form the unevenness provided on the inner peripheral surface, and it is difficult to ensure accuracy, resulting in an increase in cost.

In the technique of Patent Document 7, the fixing roller needs to have a low-hardness elastic layer in order to form a nip portion for increasing the circumference of the fixing belt and fusing and pressing the recording medium in view of layout (general) In particular, the material forming the elastic layer is silicon rubber or the like, which has high heat insulating properties and is difficult to warm up). Therefore, there exists a subject that heat capacity will become large. Therefore, those skilled in the art have tackled the development of means to meet the demand for further energy saving.
However, when the metal cylindrical tube is thinned, the core metal rigidity is lowered, and there arises a problem of conveyance troubles such as fixing belt, empty sliding, twisting, and meandering. In addition, when the thickness is reduced, the heat capacity of the heating roller itself is reduced, and a small size paper (for example, A4 paper is passed through the A3 paper compatible machine) is continuously passed. Therefore, the temperature outside the sheet passing area does not decrease due to the sheet passing, and the temperature rises with respect to the sheet passing part.
Therefore, a method is adopted in which halogen heaters having different light distributions in the axial direction are inserted and independently controlled in the axial direction. However, since two or more halogen heaters are inserted into the inner periphery, the inner diameter of the heating roller becomes larger, and the diameter cannot be reduced (due to improved thermal efficiency and lower heat capacity), and the heat capacity of the heating roller itself increases. , It takes time to raise the temperature. Thus, there is a contradictory relationship between handling small-size paper (suppressing the edge temperature rise) and shortening the rise time (power saving / energy saving), and a technology that satisfies both is desired.
In view of the above, the object of the present invention is to easily obtain a uniform temperature distribution in the axial direction regardless of the sheet passing width, and to ensure rigidity and at the same time shorten the rise time due to thinning. It is an object of the present invention to provide a fixing device having a heating roller that can be realized, and that can improve processability and versatility, and an image forming apparatus including the fixing device.

In order to solve the above-described problem, the invention according to claim 1 includes an endless fixing belt including a heating roller having a heat source, a pressure roller pressed against the heating roller via the fixing belt, A fixing device for fixing an unfixed toner image through a recording material carrying an unfixed toner image at a nip portion between the fixing belt and the pressure roller.
The fixing belt is stretched around a first heating roller and a second heating roller, and a small-diameter roller having a heat insulating layer disposed downstream of the second heating roller in the conveyance direction of the recording material. A roller is disposed downstream of the first heating roller in the recording material conveyance direction, and a nip portion of the recording material is formed by the first and second heating rollers and the pressure roller, and the first heating is performed. The roller is provided with a heat source having a light emitting area at a position corresponding to the thin area in the axial direction with respect to the sheet passing area set along the axial direction on the inner peripheral surface. The second heating roller has an axial end that is thinner than the center in the axial direction with respect to a paper passing area set along the axial direction on the inner peripheral surface thereof, and has a light emitting area at a position corresponding to the thin area. Have a heat source And wherein the fixing device according to symptoms.
According to a second aspect of the present invention, there is provided the fixing device according to the first aspect, wherein a material of the metal cylindrical tube serving as a base of the first and second heating rollers of the heating roller is a manganese-based aluminum alloy. .
According to a third aspect of the present invention, there is provided a fixing device for fixing a transfer image on a recording material through a recording material into a nip between a photosensitive drum having a toner image and a transfer belt for transferring the toner image. An image forming apparatus having a configuration in which the transferred image is fixed onto the recording material by sending to the image forming apparatus, wherein the fixing apparatus is the fixing apparatus according to claim 1.

  According to a fourth aspect of the present invention, there is provided a heating roller forming method for forming a heating roller used as a heating roller of a fixing device, wherein a surface side of a metal cylindrical tube having a metal material as a base is recessed along a circumferential direction. After forming the step, a step of forming a circular protrusion on the inner surface of the metal cylindrical tube, and forming the circular protrusion in a region below the paper passing region set along the axial direction of the metal cylindrical tube, And a step of forming a thin-walled metal cylindrical tube having a uniform surface by cutting the surface side of the metal cylindrical tube to remove a recessed portion.

According to the present invention, the first and second heating rollers raise the temperature of the fixing belt to a desired temperature, and the first heating roller has a halogen heater having a light distribution in the center, and the second heating roller has Built-in halogen heater with light distribution at the end. The fixing belt is stretched by a fixing roller, a first heating roller having a built-in heat source, and a small-diameter roller having a heat insulating layer disposed downstream of the nip portion in the conveyance direction of the recording material.
The temperature is raised to the temperature necessary for the above-described fixing through the first and second heating rollers respectively heated by the heat source. Here, with respect to the nip portion sandwiched between the first and second heating rollers and the pressure roller, the first heating roller is disposed on the upstream side in the conveyance direction of the recording medium, and the second heating roller is disposed on the downstream side in the conveyance direction. A heating roller is arranged. Here, the amount of heat and pressure necessary to melt the toner are applied at the nip portion sandwiched between the first and second heating rollers and the pressure roller, thereby fixing the toner on the recording paper.
Furthermore, the inner peripheral surfaces of the first and second heating rollers are made of a thin wall portion (the above-mentioned circumferential irregularity portion) that is paired with the light distribution of the halogen heater, so that the heat absorption efficiency from the halogen heater can be improved. It becomes. Further, the portion other than the light distribution that is not required for temperature rise is conversely thickened, so that a reduction in the rigidity of the metal cylindrical tube can be suppressed.
In the first and second heating rollers, the center of the sheet passing area is within an area below the sheet passing area with respect to the sheet passing area set along the axial direction on the inner peripheral surface of the thin metal cylindrical tube of aluminum alloy. Two or more by arranging the first and second heating rollers according to the sheet passing size separately in the sheet passing area by integrally forming the circular recesses that are equally distributed from left to right. There is no need to incorporate a halogen heater.
Since the inner diameter that can contain one halogen heater is sufficient, the diameter can be reduced (= lower heat capacity). Further, a thin wall portion that is paired with the light distribution of the halogen heater is formed on the inner peripheral surfaces of the first and second heating rollers, so that the heat absorption efficiency from the halogen heater can be increased.
Further, the portions other than the light distribution that are not required for temperature increase are conversely thickened, so that a reduction in the rigidity of the roller core can be suppressed. According to the heating roller of the present invention, it is possible to easily process a highly rigid roller metal core having a small heat capacity and a short rise time.
Therefore, it is possible to suppress the deviation of the temperature distribution in the axial direction when heating in order to replenish the heat taken away by the passing of the recording medium, and heat is appropriately applied to a necessary portion (in this case, in the axial direction). It is kept uniform. Moreover, the heating rate of the heating unit (in this case also in the axial direction) is increased, and the power consumption can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an image forming apparatus to which the present invention can be applied. FIG. 2 is an enlarged schematic view showing a belt fixing type fixing device used in the image forming apparatus.
Referring to FIGS. 1 and 2, the image forming apparatus 1 includes a sheet feeding unit 2 at the lower right of the main body, and a transfer belt 3 and a photosensitive drum 4a formed above the sheet feeding unit 2. 4b, 4c, 4d, a transfer sheet P is passed through the transfer paper P to the transfer paper P by the transfer roller 10, and the transfer paper P is used to fix the transfer image thereon. The transfer image is sent to the fixing device 5 and the transferred image is fixed on the transfer paper P.
The image forming apparatus 1 shown in FIG. 1 further includes a support roller 6, a charging roller 7, a developing unit 8, a cleaning unit 9, and an optical writing unit 11 that stretch and drive the transfer belt 3.
The photosensitive drum 4a constitutes an image forming unit together with the charging roller 7, the developing means 8, and the cleaning means 9, and this image forming unit is a photosensitive if the image forming unit including the photosensitive drum 4a is a black image forming unit. Since the image forming units including the body drums 4b, 4c, and 4d have the same configuration for yellow, cyan, and magenta, respectively, only parts of the image forming unit including the photosensitive drum 4a are denoted by reference numerals. .

Also in the heat fixing method, the belt fixing method as shown in FIG. 2 is most widely used because it is superior in thermal efficiency and is safe. The fixing device 5 used in this belt fixing method is fluorine on the side located on one side (the surface to which the toner s adheres) of the transfer paper P that is a recording body at the nip portion formed by the two rollers 12 and 13. The toner s is fixed on the transfer paper P by heating and pressing through an endless fixing belt 14 having a release layer made of resin or the like.
In order to form a nip portion that is a portion to be heated and pressed, the side of the two rollers 12 and 13 that passes through the fixing belt 14 is the fixing roller 12, and the side that is positioned on the other surface side of the transfer paper P is used. The pressure roller 13 is biased toward the fixing roller 12 by a biasing means (not shown).
The transfer paper P is sandwiched and conveyed by the nip portion where the two rollers 12 and 13 are pressed, and at the same time, the final fixed toner image formed on one surface side of the transfer paper P is heated by this nip portion. The toner s is fixed on one side.
The fixing belt 14 is stretched around a heating roller 12a including a fixing roller 12 and a heat source 8 (two heat sources 8a and 8b in FIG. 2), and is heated by the heat source 8 (or 8a and 8b). Heat is transferred to the temperature required for the fixing described above. The heat source 8 provided inside the heating roller 12a is provided with a halogen lamp, a ceramic heater or the like along the axial direction of the heating roller 12a.
Further, a temperature sensor 16 is in contact with the surface of the fixing belt 14 that contacts at a position corresponding to the heating roller 12a. Based on the temperature detection result of the temperature sensor 16, the temperature of the nip portion becomes an optimum toner fixing temperature. The power supply amount of the heat sources 8a and 8b is controlled so as to be maintained. The optimum toner fixing temperature is detected by the temperature sensor 17.
Further, in such a fixing device 5, a heating roller 12a based on an aluminum alloy is used so as to ensure thermal conductivity and rigidity in view of the heating efficiency from the heat sources 8a and 8b.

FIG. 2 also shows an auxiliary heat source 18 for heating the pressure roller 13, a temperature sensor 19 for detecting the temperature of the pressure roller 13, a small-diameter roller 20 for preventing the fixing belt 14 from sagging, and a fixing belt 14. An urging means 21 for urging the small-diameter roller 20 for tension and a transfer paper P separating mechanism 24 are shown.
FIG. 3 is a schematic sectional view showing the heating roller of the fixing device together with an enlarged portion in a circle. As will be described later with reference to FIG. 4, the heating rollers 22 and 23 of the fixing device 5 are made of an aluminum alloy as a base. As a general configuration, a cylindrical metal cylindrical tube (element tube) as shown in FIG. 15 is formed as a base body, and the outer peripheral surface of the base body is covered with a resin layer 15b made of a fluororesin or the like in order to suppress slippage with the fixing belt.
In some cases, a surface treatment such as alumite treatment or sandblasting may be applied to the surface of the substrate instead of the resin layer 15b. The heating rollers 22 and 23 may be provided with a detent member (not shown) in order to suppress twisting and meandering due to the conveyance of the fixing belt.
In the case of forming the heating rollers 22 and 23 having such a configuration, a cylindrical long cylindrical tube is extruded from an aluminum alloy material, pultruded, and the long cylindrical tube is cut into a predetermined length to obtain a metal. The cylindrical tube 15 is made uniform, and the outer peripheral surface of the metal cylindrical tube 15 is made uniform by cutting or grinding, then roughened by sandblasting or the like, and further coated with a paint made of fluororesin or the like and then fired. Thus, the resin layer 15b is formed and a predetermined finishing process is performed.
At this time, in many forming methods, when the outer peripheral surface of the metal cylindrical tube 15 is processed, an outer diameter cutting process using a diamond tool is performed. Further, the metal cylindrical tube 15 is simultaneously thinned to a predetermined thickness by this cutting process.
On the other hand, due to the recent demand for energy saving and cost reduction, the heating roller is required to be further thinned in order to improve thermal conductivity. That is, the time required to reach a fixing temperature by thinning the metal cylindrical tube 15 (also referred to as a rise time of the fixing roller or a warm-up time) is shortened to save power in a copying machine or the like as an image forming apparatus. It is hoped that the chemistry will be promoted.

FIG. 4 is a schematic diagram showing the configuration of the fixing device according to the embodiment of the present invention. In FIG. 4, the fixing device 5 of the heat fixing system is arranged in parallel in the axial direction with a first heating roller 22, a second heating roller 23, a pressure roller 13, a fixing belt 14, and independently controlled corresponding to each heat source. Temperature sensors 16 and 17 serving as temperature detecting means. These temperature sensors 16 and 17 detect the outer surface temperatures of the first and second heating rollers 22 and 23.
Further, the fixing device 5 includes an urging means (not shown) that urges the pressure roller 13 toward the nip portion, and heat sources 8a and 8b provided on the axes of the first and second heating rollers 22 and 23, respectively. (Halogen heater). Further, although not shown, a bearing that rotatably supports the first and second heating rollers 22 and 23 on a support frame or the like, and a cleaning roller (not shown) that removes the toner s attached to the surface of the fixing belt 14 by offset. Can also be provided.
In the general fixing device shown in FIG. 2, the nip portion is formed by the fixing roller 12 and the pressure roller 13. In addition, when a heat source (halogen heater) 18 provided to heat the pressure roller 13 and the recording paper P on which the toner s is fixed wraps around the fixing belt 14 at the time of paper discharge, it is forcibly separated. Therefore, the separation mechanism 24 may be provided that contacts the surface of the fixing belt 14 on the downstream side of the sheet passing.
However, in the fixing device of the present invention, as shown in FIG. 4, by arranging a small diameter roller 32 having a heat insulating layer on the downstream side of the conveyance of the nip portion, the recording medium P conveyed by the curvature of the small diameter roller 20. Since it is naturally separated from the surface of the fixing belt 14 from “koshi”, the separation mechanism 24 required in a general fixing device is not required.

FIGS. 5A and 5B are sectional views showing the first and second heating rollers according to the present invention along the axial direction along the lines AA ′ and BB ′ of the fixing device of FIG. 4, respectively. . Next, the first and second heating rollers 22 and 23 according to the present invention will be described in detail.
A metal cylindrical tube 15 having a resin layer 15b formed on the outer surface thereof as shown in FIG. 3 is used as the first and second heating rollers 22 and 23, and the recording medium P is passed through the inner peripheral surface thereof. Corresponding to the paper area, the circumferential recesses 22c and 23c are formed integrally in the axial direction of the first and second heating rollers 22 and 23 and are equally distributed from the center to the left and right in the range below the paper passing area. Yes. The outer circumferences of both ends of the first and second heating rollers 22 and 23 are supported by the bearing 10.
On the inner peripheral surface of the first heating roller 23, a circular recess 22 c is formed in the inner peripheral surface of the second heating roller 23. Is integrally formed with a circumferential recess 23c that is thinner than the other region in the region that forms a pair with respect to the light distribution of the halogen heater 8b at the end different from the first heating roller 22 described above.
Specifically, the schematic shape of the metal cylindrical tube 15 (FIG. 3) constituting the first heating roller 22 is formed using a manganese-based aluminum alloy as a base, and has an outer diameter of 18 mm, a length of 350 mm, and a journal portion outer diameter of φ10. The thickness of the thick portion is 0.6 mm, and the thickness of the thin portion (circular recess 22c) is 0.3 mm.
Specifically, the schematic shape of the metal cylindrical tube 15 constituting the second heating roller 23 is formed using a manganese-based aluminum alloy as a base, and has an outer diameter φ18 mm, a length 350 mm, a journal portion outer diameter φ10, a thickness. The thickness of the meat part is 0.6 mm, and the thickness of the thin part (circular recess 23c) is 0.3 mm.
When the sheet passing area L with respect to the first and second heating rollers 22 and 23 is about 320 mm (general area), the circumferential recess 22c or 23c is the center of the metal cylindrical tube 15 (sheet passing area) in the illustrated example. L = 200 mm in the center) and areas other than the center area are equally distributed to the left and right in the figure. The length of the thin cross-sectional shape of the circumferential recess 22c or 23c corresponds to the length of the light emitting region (light distribution) of the built-in halogen heaters 8a and 8b as shown in FIG.

Next, the small-diameter roller 32 having the heat insulating layer 32b disposed on the downstream side of the nip portion in the conveyance direction of the recording body will be described. The small-diameter roller 32 forms a heat insulating layer 32b on a cored bar 32a (a trunk part outer diameter φ8, a trunk part length 350 mm) made of stainless steel. The heat insulating layer 32b is bonded to a 1 mm thick nonwoven fabric.
In the present embodiment, the small-diameter roller 20 is provided as a tension roller that goes around the first and second heating rollers 22 and 23 and applies a tension force F to the fixing belt 14. The operation is stretched by the urging member 21 so that the belt tension becomes a desired tension force F (10N in the present embodiment), although the operation is not described in detail.
Next, the pressure roller 13 forms an elastic layer 13b on a cored bar 13a (body diameter Φ30, wall thickness 2 mm, body length 354 mm) made of an iron-based material. This elastic layer 13b is generally made of a resin material made of foamable silicon rubber and has a rubber thickness of 10 mm.
By arranging the first and second heating rollers 22 and 23 according to the paper passing area separately, it is not necessary to incorporate two or more halogen heaters in one heating roller. Since the inner diameter that can contain the heater is sufficient, it is possible to reduce the diameter (= lower heat capacity).
Furthermore, by disposing the second heating roller 23 on the downstream side of the nip portion in the recording paper conveyance direction, the entire fixing device can be saved in space and the heat capacity is reduced, so that the rise time is shortened. In addition, an increase in end temperature at the time of passing a small size recording medium can be reduced due to the improvement in thermal efficiency.
The first and second heating rollers 22, 23 pass through the inner passage of the thin-walled aluminum cylindrical tube 15 made of aluminum alloy along the axial direction in a region below the paper passage region. The center of the paper region and the circumferential recesses 22c and 23c arranged so as to be equally distributed to the left and right from the center are integrally formed.

As a result, the first and second heating rollers 22 and 23 corresponding to the sheet passing size are arranged separately from each other in the sheet passing area, so that it is not necessary to incorporate two or more halogen heaters, and one halogen Since the inner diameter that can contain the heater is sufficient, it is possible to reduce the diameter (= lower heat capacity).
Further, thin portions are formed on the inner peripheral surfaces of the first and second heating rollers 22 and 23 in a range corresponding to the length of the light emission region (light distribution distribution) of the halogen heater, and the heat absorption efficiency from the halogen heaters 8a and 8b. Can be increased.
Furthermore, the portion other than the light emitting region (light distribution distribution) that is not required for temperature increase is conversely thickened, so that a decrease in rigidity of the roller cored bar 15a (FIG. 3) can be suppressed. As described above, according to the heating rollers 22 and 23 of the present invention, it is possible to easily process a highly rigid roller metal core having a small heat capacity and a short rise time.
Therefore, it is possible to suppress the deviation of the temperature distribution in the axial direction when heating in order to replenish the heat taken away by the passing of the recording medium, and heat is appropriately applied to a necessary portion (in this case, in the axial direction). It is kept uniform. Moreover, the heating rate of the heating unit (in this case also in the axial direction) is increased, and the power consumption can be reduced.
Further, by using a manganese-based aluminum alloy for the thin metal cylindrical tube 15 constituting the heating roller, the thermal conductivity is higher than that of other aluminum alloys and the creep resistance is high. And a material suitable for a heating roller to which pressure (tension pressure by a fixing belt) is applied.
Further, the manganese-based aluminum alloy is suitable for plastic working (spinning work) when applying the circumferential convex portions 22d and 23d formed on the inner peripheral surface of the present invention. Therefore, it is possible to easily and inexpensively process a highly rigid heating roller that has a small heat capacity and can shorten the rise time.

FIG. 6 is a cross-sectional view showing a method for manufacturing a heating roller used in the present invention. FIG. 6 is an explanatory view showing a method of forming the metal cylindrical tube used as the second heating roller in FIG. 5 described above in time series (a) to (e).
In this heating roller processing method, first, the metal cylindrical tube 15 is formed. Specifically, the processing shown in FIGS. 6A to 6D is performed to form a desired thickness t (in the embodiment of the present invention, a thickness of 0.6 mm), and then a predetermined resin layer is formed on the surface. Form. The method for forming this resin layer is within the scope of the prior art and will not be described.
Next, a method for forming the metal cylindrical tube 15 will be described with reference to FIG. First, as shown in FIG. 6A, a cylindrical body 15 is formed, in which an aluminum alloy is used as a base, and support portions (journal portions) 15c supported by bearings 10 (FIG. 5) are formed at both ends.
At this time, the thickness T of the cylindrical body 15 depends on the thickness t of the formed metal cylindrical tube 15 (thickness of the thick portion in the present embodiment is 0.6 mm) and the pushing amount H of the circumferential recess 23c. In consideration of the above, the thickness is set to at least the thickness obtained by adding the thickness t and the pushing amount H. In this embodiment, a cylindrical wall thickness T of 1.2 mm is used.

Next, as shown in FIG. 6 (b) where the reference numerals used in FIG. 5 are also shown, a drawing tool 30 (roller tool) for fixing the tool post of the NC lathe in a state where the cylinder 15 is fixed to the NC lathe. The drawing tool 30 is pressed against the outer peripheral surface of the cylindrical body 15 while rotating. FIG. 6 (FIG. 6) shows an example in which the second heating roller 23 described with reference to FIG. 5B is formed. When the first heating roller 22 is formed, the pressing position of the squeezing tool 30 is changed.
At this time, the pressing position of the squeezing tool 30 against the cylindrical body 15 is the outer peripheral surface at a position corresponding to a region other than the circumferential recess 23c (FIG. 5B), whereby the outer peripheral surface of the cylindrical body 15 has an inner diameter. At the same time as being recessed, a region other than the circumferential protrusion 23 d is formed to protrude on the inner peripheral surface of the cylindrical body 15.
In the drawing process according to the present embodiment, the difference between the circumferential concave portion 23c and the circumferential convex portion 23d is set to a predetermined 0.3 mm by setting the pressing amount by pressing to 0.4 to 0.45 mm, and the desired thickness described above. A difference (difference between 0.6 and 0.3 mm) was obtained.
The rotation speed of the main shaft of the drawing tool 30 at this time is 1000 rpm, the pushing speed at the time of pressing is φ0.1 mm / rev, and the drawing tool 30 has a structure having a rotation mechanism by a bearing provided with a roller-like tool on the shank. Using. By satisfying this relationship, it is possible to obtain an appropriate cross-sectional shape.

FIG. 6C is a cross-sectional view showing the shape after drawing in the present embodiment. From this state, as shown in FIG. 6D, the cutting tool (diamond tool) 31 is moved along the axial direction of the cylinder 15 to cut the outer peripheral surface of the cylinder 15 several times to remove the recess. Then, as shown in FIG. 6E, it is processed into a metal cylindrical tube 15 having a predetermined equivalent wall thickness t.
Thus, in forming the metal cylindrical tube 40 from the cylindrical body 15, it can be processed by using the NC lathe which is a general-purpose processing machine by using the roller tool 30, so it is necessary to introduce a dedicated machine. In addition, stable production is possible with respect to repeatability.
The metal material of the metal cylindrical tube 15 shown in FIG. 6A is made of a manganese-based aluminum alloy as a substrate. Manganese-based aluminum alloy has a higher thermal conductivity than other aluminum alloys and has a high creep resistance. Therefore, manganese-based aluminum alloy is a material suitable for a heating roller to which heat and pressure (tension pressure by a fixing belt) are applied. In this embodiment, the product name “CM10” manufactured by Sumitomo Light Metal Co., Ltd. is used for the manganese-based aluminum alloy.
As shown in FIG. 6, the forming method of the heating roller, particularly the second heating roller, is such that the surface side of the thin metal cylindrical tube 15 having a metal material as a base is recessed along the circumferential direction. The circumferential projections 15d and 15d are formed on the left and right sides of the center of the sheet passing region within the region below the sheet passing region set along the axial direction of the cylindrical tube 15. After uniformly forming by sorting, the surface side of the cylindrical tube 15 is cut to remove the recessed portion, and the thin metal cylindrical tube 40 having a uniform surface can be easily formed.

網がけ部は、評価上ＮＧ。 FIG. 7 is a cross-sectional view showing a heating roller evaluation method according to the present invention. The temperature measurement points were measured by the temperature sensor 25 at the position of the temperature sensor 17 shown in FIG. 2 before the nip, and at five positions with respect to the sheet passing width shown in FIG.
Table 1 shows the evaluation results when the heating roller according to the present invention is used.
In the evaluation of the present invention, the rise time under the medium speed machine fixing conditions with a linear speed of 203 mm / s and a fixing temperature of 15 ° C., and the edge temperature rise when 100 sheets of A4 and A5 portraits were passed through. evaluated. The edge temperature rise needs to be 200 ° C. or less in the hot offset region of the fixing temperature, and the smaller the difference from the fixing temperature 150 ° C. that is the control value, the better.
In the fixing device 5 (FIG. 2) used in this embodiment, the total power of the halogen heater on the heating roller side is 1200 W, and the center and the end are equally distributed. Other parts are common.
The temperature measurement point is the part of the temperature sensor 17 shown in FIG. 2 before the nip, and the five parts (centers 1, 2, 3, end 4) in the axial direction with respect to the sheet passing width shown in FIG. 5) was measured.
For temperature measurement, a contact-type temperature sensor (E-type thermocouple) is brought into contact with the center 1, and the maximum temperature from the temperatures of the centers 2, 3 and ends 4, 5 is determined as the end temperature, maximum-minimum. Was the temperature difference.
[Table 1]

The shaded area is NG for evaluation.

1 is a schematic diagram illustrating an image forming apparatus to which the present invention can be applied. 1 is an enlarged schematic diagram illustrating a belt-fixing type fixing device used in an image forming apparatus. 2 is a schematic cross-sectional view showing a heating roller of a fixing device together with an enlarged portion in a circle. FIG. 1 is a schematic diagram illustrating a configuration of a fixing device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the first and second heating rollers according to the present invention along the axial direction along the lines AA and BB of the fixing device of FIG. It is sectional drawing which shows the manufacturing method of the heating roller used for this invention. It is sectional drawing which shows the evaluation method of the heating roller by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 3 Transfer belt, 5 Fixing apparatus, 8a Heat source, 8b Heat source, 13 Pressure roller, 14 Fixing belt, 15 Metal cylindrical tube (element tube), 22 1st heating roller, 22c Thin part (circular recessed part) , 23 Second heating roller, 23c Thin portion (circumferential concavity), 32 small diameter roller, L paper passing area, P recording material (transfer paper)

Claims (4)

An endless fixing belt including a heating roller having a heat source, and a pressure roller that is pressed against the heating roller via the fixing belt, and is undetermined at a nip portion between the fixing belt and the pressure roller In a fixing device for fixing an unfixed toner image through a recording material carrying a contact toner image,
The fixing belt is stretched around a first heating roller and a second heating roller, and a small-diameter roller having a heat insulating layer disposed downstream of the second heating roller in the conveyance direction of the recording material. A roller is disposed downstream of the first heating roller in the recording material conveyance direction, and a nip portion of the recording material is formed by the first and second heating rollers and the pressure roller, and the first heating is performed. The roller is provided with a heat source having a light emitting area at a position corresponding to the thin area in the axial direction with respect to the sheet passing area set along the axial direction on the inner peripheral surface. The second heating roller has an axial end that is thinner than the center in the axial direction with respect to a paper passing area set along the axial direction on the inner peripheral surface thereof, and has a light emitting area at a position corresponding to the thin area. Have a heat source A fixing device for the butterflies.   2. The fixing device according to claim 1, wherein a material of the metal cylindrical tube serving as a base of the first and second heating rollers of the heating roller is a manganese-based aluminum alloy.   In order to fix the transfer image on the recording material through the recording material to the nip between the photosensitive drum having the toner image and the transfer belt for transferring the toner image, the transfer image is sent onto the recording material. An image forming apparatus having a configuration for fixing to an image forming apparatus, wherein the fixing apparatus is the fixing apparatus according to claim 1.   In a heating roller molding method for molding a heating roller used as a heating roller of a fixing device, a step of recessing a surface side of a metal cylindrical tube having a metal material as a base along the circumferential direction, and an inner surface of the metal cylindrical tube Forming the circumferential convex portion, and forming the circumferential convex portion in a region below the paper passing region set along the axial direction of the metal cylindrical tube, and then cutting the surface side of the metal cylindrical tube And a step of forming a thin metal cylindrical tube having a uniform surface by removing the recessed portion.

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