JP4749046B2 - Fixing device, image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus employing an image forming method using electrophotography, such as a copying machine, a facsimile machine, a printer, and the like, and a fixing apparatus using belt fixing used in the image forming apparatus. The present invention relates to the prevention of temperature unevenness.

  The demand for resource saving and energy saving is increasing for the preservation of the global environment. Also in the field of electrophotography, there is an active movement to reduce power consumption to save energy, and research is being conducted on fixing at low temperature especially in the fixing field where power consumption is severe.

  In an electrophotographic image forming apparatus, a fixing temperature of about 200 ° C. to 150 ° C. is generally used at present, and the startup time of the fixing device from room temperature is also about 1 minute to 5 minutes. In order to save energy and reduce the fixing start-up time, it is desired that the fixing can be performed at 150 ° C. or lower, preferably around 100 ° C.

  In order to realize fixing at such a temperature, naturally, the softening point or melting point of the toner must be lowered to 100 ° C. or lower, but generally the same kind of organic polymer substance has a decrease in melt viscosity when the melting point is lowered. Is inevitable. This is due to the fact that the melting point of the resin depends on the molecular weight. Naturally, if the molecular weight is low, the entanglement of the molecular chains is loosened, and the melt viscosity is lowered by weakening the interaction. Accordingly, when fixing is performed using an ultra-low melting point toner, a sudden drop in viscosity occurs after the melting point, so that the effective rubber area width is narrow so that the toner on the paper is not offset to the fixing heating body side. It becomes difficult.

  In order to solve such a problem, it is considered to prevent the offset of the toner image by using a fixing belt and releasing the solidified heat by keeping the melted toner in close contact and then separating it from the belt.

  As a countermeasure against this, as disclosed in Japanese Patent Application Laid-Open No. H10-228707, a cooling fan is provided in which a duct for supplying fresh air is connected to the surface of an endless belt hung on the fixing roller, so that the toner in a molten state is placed on the transfer paper. Condensation prevents offset. Patent Document 1

In Japanese Patent Laid-Open No. 10-221982, a fixing belt hung on a plurality of rollers, a heating unit, and leading and trailing ends of a recording paper conveyance path are provided with guide rollers between them. They are transported in close contact. In this case, there is a problem of paper floating or image blurring at a portion where the guide roller does not contact.
Patent Document 1
Japanese Patent Application Laid-Open No. 2000-89593 includes an endless fixing belt that is bridged between a heating roller and a fixing roller, and a pressure roller that is in pressure contact from below, and the fixing roller and the heating roller are in contact with the pressure roller. A nip is formed between them. In this case, there is a problem of image blur due to conveyance of the recording paper with a high curvature in the fixing nip.
Japanese Patent Laid-Open No. 5-019466 Japanese Patent Laid-Open No. 10-221982 JP 2000-89593 A

  However, when fixing by applying heat from the fixing belt to the paper and toner, if a small size paper is passed, the heat is taken away from the center of the belt and the temperature at the center is returned to the specified value. And the heater lights up. Then, there is a problem in that the temperature rises excessively at the end of the fixing belt, and the toner is offset at the end of the image when a large size paper is subsequently passed.

  The present invention relates to a fixing device capable of preventing an increase in the temperature of an end portion while maintaining energy at the time of paper conveyance in a fixing device using contact conveyance and achieving energy saving, and image formation including the same. A device is provided.

According to a first aspect of the present invention, there is provided a fixing device that sandwiches a recording medium between a pair of endless belts and conveys the recording medium in a state in which an image surface is in close contact with a fixing belt that is one of the pair of endless belts. in the fixing belt, and has a portion formed in the resin in contact with the surface on the image surface of the recording medium, having a heat conductive member extending in a direction perpendicular to Shudo direction of the fixing belt the even pressure belt which is the other of the pair of endless belts, have a heat conductive member extending in a direction perpendicular to Shudo direction of pressurizing belt, provided on the pressure belt wherein heat conductive member, the fixing belt and said pressure belt is characterized that you have been arranged so as to face a region not provided the thermally conductive member of the fixing belt at the time of contact.

Those according to the second aspect, forming the fixing device according to claim 1, wherein the thermally conductive member formed on the fixing belt is a copper foil, the copper foil with the resin of the fixing belt It arrange | positions at the back surface side of the part which carried out.

Rukoto those according to the claim 3 is the fixing device according to claim 2, wherein said pressure belt also having a heat conduction member that is formed by copper foil on the back side of the contact surface with the fixing belt It is characterized by.

Those according to the claim 4 is the fixing device according to claim 1, before Kijo wear the thermally conductive member formed on the belt, in a direction intersecting perpendicularly Shudo direction as the endless belt wherein the copper der Rukoto arranged to extend.

Those according to the claim 5 is the fixing device according to claim 4, arranged to extend in a vertical direction intersecting the relative Shudo direction as the endless belt as pressure belt also the thermal conductive member of copper and wherein the Rukoto to have a line.

Those according to the claim 6 is the fixing device according to any one of claims 1 to 5, characterized by Rukoto such a surface layer was coated with a highly releasable resin of the pair of endless belts.

Those according to the claim 7 is the fixing device according to claim 6, before the polyfluoroethylene mixed with high releasability resins Kibe Le preparative Table layer surface and said tare Rukoto.

Those according to the claim 8 is an image forming apparatus according to claim Rukoto such a fixing device according to any one of claims 1 to 7.

  The present invention can constitute an energy-saving fixing system by heating-contact conveyance using toner having a low melting point, and can prevent temperature unevenness in the width direction of an endless belt used for fixing, thereby enabling good color image formation.

The best mode for carrying out the present invention will be described below.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus including a fixing device. When operating as a copier, after the original G is read by the reading unit 1, the image forming unit 2 converts it into a write signal as digital data, and when operating as a printer, converts the image signal from the computer into a write signal. . The writing signal is obtained by adding black to the three primary colors of yellow, magenta, and cyan, and optical writing is performed from the polygon mirror 3 to the photosensitive unit 4 to 7 of each color. In each color photoconductor unit 4 to 7, a toner image is formed on the photoconductor by a process of charging, writing, and developing in accordance with each color, and this toner image is superimposed on the intermediate transfer belt 8 and a secondary transfer roller. 11 is collectively transferred onto the recording paper. The recording paper on which the toner image is placed is conveyed to the fixing device 13 by the conveying belt 12, and the toner is heated and fixed, and then discharged to the paper discharge unit 17. In the figure, 9 is a registration roller pair, 10 is a call roller pair, 14 is a paper feed tray, 15 is a recording paper in the paper feeding tray, and 16 is a recording paper being conveyed.

  FIG. 2 is a cross-sectional view schematically showing the fixing device shown in FIG. An endless fixing belt 23 is stretched between the heating roller 21 and the overstretching roller 22, and a heater 24 is inserted in the heating roller 21 so that the fixing belt 23 is heated to a predetermined temperature. It has become. The pressure belt 25 is wound around the pressure roller 26 and the under-stretching roller 27 and is driven while being in contact with the fixing belt 23. The heating roller 21 and the pressure roller 26 are pressurized by a spring of about 50N on one side so that the conveyed recording paper 28 receives heat while being pressed at the paper entrance. Then, the toner T forming the toner image is melted, and the recording paper 28 is conveyed while being in close contact with the fixing belt. In the close-contact conveyance unit, the upper and lower belts 23 and 25 are applied with a tension of about 1 N / mm to convey the sheet, and the toner on the recording sheet 28 is radiated and solidified. If the control temperature of the heating roller 21 of the fixing device 13 is 130 ° C., the paper feed speed is 300 mm / second, and the nip width of the upper and lower belts 23 and 25 is 90 mm, for example, the recording paper 28 as a recording medium is nipped. The time spent is 300 milliseconds.

  In the present invention, a recording medium is conveyed while being sandwiched between an endless fixing belt and a pressure belt, and after the toner image on the surface of the recording medium is brought into close contact with the fixing belt and heated and radiated, the toner surface is removed from the fixing belt. That is, a recording medium such as a paper carrying toner is separated. When such a configuration is used, the toner image is solidified at the time of separation from the fixing belt, so that even when toner that melts at about 100 ° C. is used, the low-viscosity toner is prevented from being offset to the fixing belt side. Temperature fixing becomes easy. Therefore, a good energy saving fixing system can be obtained. In such a system, it is necessary to apply a certain tension to a pair of endless belts suspended in order to hold the recording medium between the pair of belts as described above, and if the tension is too weak, the recording medium will float on the contact surface. However, if the tension is too strong, the belt tends to stretch or break, which is not preferable. A preferable tension is 0.01 to 5 N / mm, more preferably 0.05 to 4 N / mm, and still more preferably 0.1 to 2 N / mm.

  In the present invention, after the nip between the heating roller and the pressure roller, the recording medium held between the pair of endless belts is kept in close contact for 50 to 1000 milliseconds, so that the toner is kept warm and sufficient heat is transmitted to the toner. Thus, if the time held between the two is short, the toner does not receive the necessary heat and the fixing performance is lowered. On the other hand, if the holding time is too long, the entire belt surface area increases, and heat dissipation increases, which is also not preferable. A preferable holding time is 60 to 800 milliseconds, more preferably 80 to 700 milliseconds, still more preferably 100 to 500 milliseconds, and still more preferably 200 to 400 milliseconds.

  Of the pair of endless belts, a fixing belt that contacts and heats the recording medium has a portion formed of resin, and a heat conductive member is integrally formed in a direction perpendicular to the circumferential direction of the belt. I am doing so. In this way, even if a small size paper is passed and the temperature is lowered at the center of the resin belt, the temperature is quickly uniformized in the width direction by the heat conductive member, and the temperature is controlled at the center of the belt. Further, an excessive temperature rise at the belt end portion is prevented, and good heat fixing conveyance is possible. That is, an energy-saving fixing system by heating-contact conveyance using a toner having a low melting point can be realized, and a good color print can be obtained.

  Further, the above-described heat conductive member may be formed as a tape-like copper foil and attached from the back surface of the fixing belt to be integrated. A schematic configuration of the fixing belt is shown in FIG. As shown in the figure, a copper foil tape 31 is embedded in the back surface of the heat-resistant resin layer 32 of the fixing belt 23 so as to be embedded in the width direction (up and down direction of the drawing sheet, that is, the direction perpendicular to the circumferential direction). In this way, the thermal conductivity in the width direction can be increased without affecting the circumferential movement of the fixing belt 23 (in the horizontal direction of the drawing in the drawing), and good heat-fixing conveyance is possible. . In the figure, 33 is a release resin for the surface layer of the heat-resistant resin layer 32. Note that the direction in which the copper foil tape 31 is applied is not limited to a direction completely perpendicular to the circumferential movement direction, but may be a slight angle.

  Further, the copper wire may be mixed in the width direction perpendicular to the circumferential direction of the fixing belt. A schematic configuration of this fixing belt is shown in FIG. As shown in the figure, a copper strand 41 is mixed in the width direction in the heat resistant resin layer 42 of the fixing belt 23. In this way, the thermal conductivity in the width direction can be increased without affecting the circumferential movement of the fixing belt 23, and satisfactory heat fixing conveyance can be achieved.

  Although illustration is omitted, the pressure belt 25 is also integrally formed with a copper foil tape attached from the back surface in the same manner as the fixing belt 23, but the copper foil tape attached portions of the upper and lower belts 23 and 25 do not contact each other. Combine like so. FIG. 6 shows a schematic diagram of the close-contact conveyance unit for the paper 28 at this time. By doing so, the temperature unevenness on the pressure belt side when passing small-size paper can be made uniform, and the contact force from the upper and lower belts of the close-contact conveyance unit can be made uniform. In addition, it is possible to prevent poor adhesion due to the floating of the paper, and it is possible to carry out good heat fixing conveyance. In particular, the contact force with respect to the recording paper during the close-contact conveyance is made uniform, and a better color print can be obtained.

  Although not shown, the pressure belt 25 can also be integrally formed by mixing copper wires inside the heat-resistant resin layer in the same manner as the fixing belt 23. In this case as well, the copper wires of the upper and lower belts can be formed. Combine so that the mixed parts do not hit each other. FIG. 7 shows a schematic diagram of the close-contact conveyance unit for the paper 28 at this time. In this way, the temperature unevenness on the pressure belt 25 side when small-size paper is passed can be made uniform, and the contact force from the upper and lower belts of the close-contact conveyance unit can be made uniform. Thus, adhesion failure due to the floating of the paper 28 is prevented.

  The heat-resistant resin layer 32 of the fixing belt 23 can use a resin mixed with polyimide. By doing so, heat resistance and mechanical strength can be ensured even if a heat conductive member is integrally formed on the back side of the belt, and it is possible to achieve good heat-fixing and conveyance, and the fixing belt has high strength and high durability. A device is obtained.

  Moreover, it can comprise so that a pair of belt may contain the elastic layer. As shown in FIGS. 6 and 7, by including an elastic layer when the recording paper 28 is conveyed while being sandwiched between a pair of belts 23, 25, the contact force from the upper and lower belts 23, 25 becomes uniform, and the paper Adhesion failure due to the lifting of the toner is prevented, and favorable heat-fixing conveyance is possible, and a better color print can be obtained.

  The elastic layer can be formed by providing a silicon rubber layer on the base resin layer. The contact between the upper and lower belts 23 and 25 is made uniform through the silicon rubber layer that is easy to mold and easily deformed, and the poor adhesion due to the floating of the paper is prevented. become.

  Further, as shown in the cross-sectional views of FIGS. 3 and 5, when the surface layers of the belts 23 and 25 are covered with a high release resin layer, for example, in FIG. 5, the elastic body 51 is covered with a tubular resin surface layer 52. As a result, even when the belt containing the heat conductive member 31 is pressed from the back by a roller, surface tension is stably generated, thereby preventing poor adhesion due to paper floating. Also, the toner is well separated from the belt surface. In this way, it is possible to carry out good heat fixing conveyance.

  Further, as described above, the high release resin layer on the surface of the belt can be formed by coating with a tube or the like mixed with polyfluorinated ethylene. In this way, the durability and releasability of the surface layer are improved, the surface tension is made uniform, the adhesion failure due to the floating of the paper can be prevented, and very good heat fixing conveyance is possible.

  As shown in FIG. 3, the fixing belt has a structure in which a copper foil tape 31 is embedded on the back surface of an insulating polyimide film 32, and the surface layer is coated with a polyfluorinated ethylene resin as a release resin 33. Yes. The polyimide film thickness at this time is 100 μm, the copper foil tape portion is 30 μm, and the coating layer is 30 μm. With such a configuration, even if 20 postcard-size papers are passed through while controlling the belt center at 130 ° C., the A3 size paper of the entire image is passed, so that the edge offset is prevented. A high-quality color print was obtained over the entire width.

The toner used was as follows.
Used toner: cyclized isoprene 30 wt%
Polyester: 60wt%
Carnauba wax: 10wt%
Carbon black: 10 parts by weight Negatively chargeable charge control agent: 1 part by weight This toner has a softening point of 80 ° C. and a minimum fixing temperature of 85 ° C.

  An apparatus similar to that in Example 1 was used, but a fixing belt formed by mixing a strand 41 of copper fine wire in a polyimide film 42 as shown in FIG. 4 was used. The polyimide film thickness at this time is 100 μm, the copper wire is 5 μm × 10 wire, and the coating layer 43 is 30 μm. With such a configuration, even if 20 postcard-size papers are passed through while controlling the belt center at 130 ° C., the A3 size paper of the entire image is passed, so that the edge offset is prevented. A high-quality color print was obtained over the entire width.

  The same apparatus as in Example 1 was used, but as shown in FIG. 5, as a fixing belt and a pressure belt, a 100 μm thick silicon rubber layer 51 and a polyfluorinated ethylene tube layer 52 were laminated on the polyimide film 32, The thing of the structure which affixed the 30-micrometer-thick copper foil tape 31 from the back surface was used. Then, as shown in FIG. 6, a close-contact conveyance unit sandwiched between the fixing belt and the pressure belt so that the copper foil pasting portions were alternately combined was formed. With such a configuration, even if 100 postcard-size papers are passed through while controlling the central part of the belt at 130 ° C., the A3 size paper of the entire image is passed, so that the edge offset is prevented. In addition, a high-quality color print was obtained over the entire width.

  The same apparatus as in Example 1 was used, but as a fixing belt and a pressure belt, a silicon rubber layer of 100 μm and a polyfluorinated ethylene tube layer were laminated on a polyimide film, and a 5 μm × 10 wire copper stranded wire inside the polyimide substrate. The thing of the structure which formed integrally was used. Then, as shown in FIG. 7, a close-contact conveyance unit sandwiched between the belts was formed so that the copper foil pasting portions of the fixing belt and the pressure belt were alternately combined. With such a configuration, even if 100 postcard-size papers are passed through while controlling the central part of the belt at 130 ° C., the A3 size paper of the entire image is passed, so that the edge offset is prevented. In addition, a high-quality color print was obtained over the entire width.

Sectional drawing which shows schematic structure of image forming apparatus provided with fixing device Sectional drawing which shows the outline of the fixing device shown in FIG. Sectional drawing which shows schematic structural example of an example of the belt used for the fixing apparatus which concerns on this invention. Sectional drawing which shows the schematic structural example of the other example of the belt used for the fixing apparatus which concerns on this invention. Sectional drawing which shows the schematic structural example of the further another example of the belt used for the fixing apparatus which concerns on this invention. Sectional drawing of one Example of the fixing device which concerns on this invention Sectional drawing of the other Example of the fixing device based on this invention

Explanation of symbols

1: Reading unit 1
2: Image forming unit 3: Polygon mirror 4-7: Photosensitive unit 8: Intermediate transfer belt 9: Registration roller pair 10: Calling roller pair 11: Secondary transfer roller 12: Conveying belt 13: Fixing device 14: Paper feed tray 15: Recording paper, recording paper 17: Paper discharge unit 21: Heating roller 22: Upper tension roller 23: Fixing belt 24: Heater 25: Pressure belt 26: Pressure roller 27: Lower tension roller 28: Recording paper 31 : Copper foil tape 32: Heat resistant resin layer 33: Release resin 41: Copper strand 42: Heat resistant resin layer 51: Elastic body 52: Tubular resin surface layer T: Toner

Claims (8)

In a fixing device that sandwiches a recording medium between a pair of endless belts and conveys the recording medium in a state in which an image surface is in close contact with a fixing belt that is one of the pair of endless belts.
The fixing belt, and having a portion formed of a resin on contact with the surface on the image surface of the recording medium, having a heat conductive member extending in a direction perpendicular to Shudo direction of the fixing belt,
Also other pressure belt is of the pair of endless belts, have a heat conductive member extending in a direction perpendicular to Shudo direction of pressurizing belt,
The heat conductive member provided on the pressure belt is disposed so as to face a region of the fixing belt where the heat conductive member is not provided when the fixing belt and the pressure belt contact each other. which it does fixing device according to claim Rukoto. The fixing device according to claim 1,
Fixing the heat conducting member formed on the belt is a copper foil, the fixing device characterized by copper foil is disposed on the back side of the portion formed in the resin of the fixing belt. The fixing device according to claim 2 ,
The pressure belt also fixing device according to claim Rukoto that having a heat conducting member formed of copper foil on the back side of the contact surface with the fixing belt. The fixing device according to claim 1 ,
The thermally conductive member formed before Kijo wear belt, the fixing device, characterized in copper der Rukoto arranged to extend in a direction intersecting perpendicularly Shudo direction as the endless belt. The fixing device according to claim 4 .
The pressure belt also fixing device according to claim Rukoto which have a copper wire arranged to extend in a vertical direction intersecting with respect to Shudo direction as the endless belt as the heat conducting member. The fixing device according to any one of claims 1 to 5,
The fixing device according to claim Rukoto such a surface layer was coated with a highly releasable resin of the pair of endless belts. The fixing device according to claim 6 .
Before mixing the polyfluoroethylene the highly releasable resin Kibe Le preparative Table layer surface fixing device according to claim tare Rukoto. Image and an image forming unit for forming an image on a recording medium, to fix the image which is the formed on the recording medium, wherein Rukoto such a fixing device according to any one of claims 1 to 7 Forming equipment.