JP2016148833A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that includes heat sources at both ends that can simplify electric control.SOLUTION: A fixing device 150 comprises: an endless belt member 80 that has flexibility; a pressure member 84 that is arranged opposite to the belt member 80; a heat source 82 that heats at least the center part of a paper feed area in the longitudinal direction of the belt member 80; a nip forming member 88 for forming a nip for holding and conveying a recording medium between the belt member 80 and the pressure member 84; and a plurality of heat sources at both ends 112 that are provided in the nip forming member 88 and heat the inside of the belt member 80 in the vicinity of the ends in the width direction. The heat sources at both ends 112 are electrically connected in series with each other.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Image forming apparatuses such as copying machines and printers include a fixing device having a heater, and various sizes of paper are used for image formation. For this reason, if the heater length of the fixing device is set to a length corresponding to the maximum size paper, the temperature rise at the end, which is a non-sheet passing portion, will increase when a small size paper is passed. Need to slow down and reduce productivity. In order to cope with this problem, a first halogen heater having a dense light distribution at the center and a second halogen heater having a dense light distribution near the end are disposed inside the fixing roller. There is known a fixing device that turns on only a first halogen heater when a sheet of a size is used.

  In addition, although the frequency of use of the entire paper is very low, special large size paper such as A3 Nobi or 13 inches that is slightly larger than the A3 size may be used. Even if a halogen heater having a light distribution corresponding to such a large size paper is separately provided, there is a problem that the diameter size of the fixing roller based on downsizing is restricted, which is difficult.

  Therefore, a nip forming unit is provided inside a thin and flexible endless belt member that quickly rises to the fixing temperature, and a contact pressure between the belt member, a pressure roller that pressurizes the belt member, and the nip forming unit. A fixing device that forms a nip is known (see, for example, “Patent Document 1”). In this fixing device, a plurality of halogen heaters having different light distributions are arranged inside the belt member, and a large size is provided at both ends of the belt member in the width direction and upstream of the nip in the rotation direction of the belt member. The end heat source that can handle the paper is arranged in contact with the inner surface or the outer surface of the belt member. By arranging this end heat source, it is possible to cope with a large size paper with a simple configuration without adding a halogen heater dedicated to the large size.

In the configuration described in “Patent Document 1”, since the end heat sources are arranged at positions corresponding to both ends in the width direction of the belt member, it is necessary to simultaneously turn on and off the end heat sources, and a control circuit thereof. There is a problem that becomes complicated. In addition, when one of the end heat sources fails, the other is energized, and there is a problem in that an electrical failure is likely to occur.
SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device having each end heat source that can solve the above-described problems and simplify electrical control.

  The present invention includes an endless belt member having flexibility, a pressure member disposed to face the belt member, and a heat source that heats at least a central portion of a sheet passing region in the longitudinal direction of the belt member. A nip forming member for forming a nip for nipping and conveying a recording medium between the belt member and the pressure member, and provided in the nip forming member and in the vicinity of an end in the width direction of the belt member And a plurality of end heat sources for heating the inner surface of each of the plurality of end heat sources, wherein each of the end heat sources is electrically connected in series.

  According to the present invention, electrical control can be simplified compared to a configuration in which each end heat source is individually turned on and off, and when one of the end portions breaks down, the electrical connection between both ends can be disconnected simultaneously. Therefore, safety can be ensured.

1 is a schematic view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic view of a fixing device used in an embodiment of the present invention. FIG. 3 is a schematic view in the vicinity of a nip portion of a fixing device used in an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a support structure for a fixing belt used in an embodiment of the present invention. It is the schematic which shows the light distribution distribution of the halogen heater used for one Embodiment of this invention, and the positional relationship of an edge part heater. It is the schematic which shows the nip formation unit used for one Embodiment of this invention. It is the schematic explaining the contact state of the edge part heater and nip formation member used for one Embodiment of this invention, and a fixing belt. It is the schematic explaining the other example of the contact state of the edge part heater and nip formation member used for one Embodiment of this invention, and a fixing belt. FIG. 10 is a schematic diagram illustrating still another example of the contact state between the end heater and the nip forming member and the fixing belt used in the embodiment of the present invention. It is a circuit block diagram of the halogen heater and the edge part heater to which the 1st Embodiment of this invention is applied. It is a circuit block diagram of the halogen heater and the edge part heater to which the 2nd Embodiment of this invention is applied. It is a diagram which shows the temperature rising characteristic of the halogen heater and edge part heater which are used for one Embodiment of this invention. It is a circuit block diagram of the halogen heater and edge part heater to which the 3rd Embodiment of this invention is applied. It is a figure explaining the sliding sheet used for each embodiment. It is a figure explaining the edge part heater used for each embodiment. It is a figure explaining the positional relationship of the resistance heating element and fixing belt used for each embodiment. It is a figure which shows the nip formation unit used for the modification of each embodiment. It is a figure explaining the metal fixing belt used for each embodiment. It is a figure which shows the positional relationship of the light distribution of a halogen heater and the edge part heater in the modification of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, prior to describing this embodiment, a conventional configuration and problems will be described. If the recording medium is small, turn on a halogen heater with a dense light distribution in the center. If the recording medium is large, turn on a halogen heater with a dense light distribution near the edge together with appropriate on / off distribution. By doing so, it supports paper of various sizes.

  Here, referring to the paper size and frequency of use, most of the normally used paper is up to A3 size, and A3 size paper is passed in the vertical direction. In particular, A4 or LT size paper, which is frequently used, is often passed in the horizontal direction in order to increase productivity. Therefore, if a heating width of about 300 mm is secured as the fixing device, in most cases, 99% or more of the recording medium can be covered depending on the model. On the other hand, although the frequency of use for the whole is very low, it is required to support paper having a size larger than the A3 width, such as A3 Nobi or 13 inches.

  In the case of a heating method using a halogen heater, a plurality of heaters corresponding to small size paper are provided inside a fixing roller having a diameter of about 30 mm, so the number of heaters cannot be easily increased. For this reason, it is necessary to lengthen the halogen heater having a dense end portion light distribution according to the paper width larger than the A3 width. As described above, when the frequency of use is considered, the heating of about 300 mm width is overwhelmingly large. However, when the above-described long halogen heater is used, it is heated to the vicinity of 330 mm width, and the difference energy consumption is wasted. . Furthermore, when the paper is passed in A3 or A4 horizontal (A4Y) size, the temperature near the end of the 330 mm width rises, and in order to cool this, it is necessary to reduce productivity or install a fan. It was. In the case where the reflector is provided, there is a problem that the temperature at the heater end abnormally increases. In order to deal with such a problem, the device described in Patent Document 1 has been proposed.

  Below, the 1st Embodiment of this invention which can eliminate the problem of the patent document 1 mentioned above is described. First, an outline of the configuration of an image forming apparatus to which this embodiment can be applied will be described with reference to FIG. The image forming apparatus 100 is a tandem color printer in which image forming units that form a plurality of color images are arranged in parallel along the moving direction of the intermediate transfer belt.

  The image forming apparatus 100 includes a photosensitive drum 20Y as an image carrier that can form images corresponding to colors separated into yellow (Y), cyan (C), magenta (M), and black (Bk). , 20C, 20M, 20Bk. A visible toner image formed on each photoconductive drum 20 is superimposed on an intermediate transfer belt 11 as an intermediate transfer member that is movable in the direction of arrow A1 while facing each photoconductive drum 20, and is primary. Transcribed. Thereafter, the sheet S as a recording medium is collectively transferred by the secondary transfer process. Around each photosensitive drum 20, an apparatus for performing an image forming process according to the rotation of each photosensitive drum 20 is disposed.

  A device for performing image forming processing will be described on behalf of the photosensitive drum 20Bk that forms a black image. Around the photosensitive drum 20Bk, a charging device 30Bk, a developing device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk that perform image forming processing are sequentially arranged along the rotation direction of the photosensitive drum 20Bk. After charging by the charging device 30Bk, the optical writing device 8 performs optical writing on the surface of the photosensitive drum 20Bk based on the image information to form an electrostatic latent image. The electrostatic latent image is visualized as a toner image by the developing device 40Bk.

  The toner images formed on the respective photoconductive drums 20 are primarily transferred to the same position on the intermediate transfer belt 11 while the intermediate transfer belt 11 moves in the A1 direction. In this primary transfer, the timing is shifted from the upstream side toward the downstream side in the A1 direction by applying a voltage from each primary transfer roller 12 disposed opposite to each photoconductor drum 20 with the intermediate transfer belt 11 interposed therebetween. Done. The photosensitive drums 20Y, 20C, 20M, and 20Bk are arranged in this color order from the upstream side in the moving direction of the intermediate transfer belt 11. Each of the photosensitive drums 20Y, 20C, 20M, and 20Bk is provided in an image station for forming yellow, cyan, magenta, and black images, respectively.

  The image forming apparatus 100 is disposed so as to face four image stations that perform image forming processing for each color and above each photosensitive drum 20, and includes an intermediate transfer belt 11 and primary transfer rollers 12Y, 12C, and 12M. , 12Bk, and an intermediate transfer belt unit 10. In addition, the image forming apparatus 100 includes a secondary transfer roller 5 that is disposed to face the intermediate transfer belt 11 and serves as a secondary transfer unit that is driven by the intermediate transfer belt 11. The image forming apparatus 100 includes an intermediate transfer belt cleaning device 13 that is disposed to face the intermediate transfer belt 11 and cleans the upper surface of the intermediate transfer belt 11. The optical writing device 8 is disposed below the four image stations so as to face them.

  The optical writing device 8 is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, a rotating polygon mirror as a deflecting means, and the like. The optical writing device 8 emits writing light Lb corresponding to each color to each photoconductor drum 20 to form an electrostatic latent image on each photoconductor drum 20. In FIG. 1, for the sake of convenience, the writing light is labeled Lb for only the black image station, but the same applies to other image stations.

  Below the image forming apparatus 100, a sheet feeding device 61 is provided as a sheet feeding cassette on which sheets S transported between the photosensitive drums 20 and the intermediate transfer belt 11 are stacked. The sheet S conveyed from the sheet feeding device 61 is transferred between the intermediate transfer belt 11 and the secondary transfer roller 5 by the registration roller pair 4 at a predetermined timing in accordance with the toner image formation timing by the image station. It is fed out toward the secondary transfer part. The fact that the leading edge of the paper S has reached the registration roller pair 4 is detected by a sensor (not shown).

  The sheet S on which the toner image is transferred is sent to the fixing device 150 where heat and pressure are applied to fix the toner image on the sheet S. The fixed sheet S is discharged onto the upper surface of the main body of the image forming apparatus as a discharge tray by the discharge roller pair 7. Below the upper surface of the image forming apparatus main body, toner bottles 9Y, 9C, 9M, and 9Bk filled with toners of yellow, cyan, magenta, and black are provided.

In addition to the intermediate transfer belt 11 and each primary transfer roller 12, the intermediate transfer belt unit 10 includes a driving roller 72 and a driven roller 73 around which the intermediate transfer belt 11 is wound. The driven roller 73 also has a function as a tension applying unit for the intermediate transfer belt 11. For this reason, the driven roller 73 is provided with a biasing unit using a spring or the like. The intermediate transfer belt unit 10, each primary transfer roller 12, the secondary transfer roller 5, and the intermediate transfer belt cleaning device 13 constitute a transfer device 71.
The sheet feeding device 61 includes a feeding roller 3 that abuts on the upper surface of the uppermost sheet S, and the uppermost sheet S is moved by rotating the feeding roller 3 counterclockwise. The sheet is fed toward the registration roller pair 4.

  The intermediate transfer belt cleaning device 13 provided in the transfer device 71 has a cleaning brush and a cleaning blade arranged to face and contact the intermediate transfer belt 11. The intermediate transfer belt cleaning device 13 scrapes and removes foreign matters such as residual toner on the intermediate transfer belt 11 with a cleaning brush and a cleaning blade. The intermediate transfer belt cleaning device 13 also has a discharge means (not shown) for carrying out and discarding the residual toner removed from the intermediate transfer belt 11.

  As shown in FIG. 2, the fixing device 150 includes a fixing belt 80 as an endless belt member that is thin and flexible, and a pressure roller 84 as a pressure member disposed to face the fixing belt 80. have. Inside the fixing belt 80, a nip forming unit 86 is provided for forming a nip portion N that sandwiches and conveys the sheet S as a recording medium between the fixing belt 80 and the pressure roller 84. The nip forming unit 86 includes a nip forming member 88 disposed inside the fixing belt 80 so as to face the pressure roller 84, and a stay member that holds the nip forming member 88 against the pressure applied from the pressure roller 84. 90. The nip forming member 88 slides on the inner surface of the fixing belt 80 through the low friction sheet 6 as a sliding sheet as shown in FIG. Further, by applying a lubricant such as fluorine grease or silicone oil to the low friction sheet 6, the sliding torque can be reduced. Further, the nip forming member 88 may be in direct contact with the inner surface of the fixing belt 80 without providing the low friction sheet 6.

  The stay member 90 has a box shape having an opening on the side opposite to the nip portion N side, and halogen heaters 82a and 82b as heat sources are disposed therein. The fixing belt 80 is directly heated by radiant heat from the inner surface side by the halogen heaters 82 a and 82 b on the opening side of the stay member 90. In order to increase the heating efficiency of the halogen heaters 82 a and 82 b, a plate-like reflection member 94 that reflects light emitted from the halogen heaters 82 a and 82 b to the fixing belt 80 is provided on the inner surface of the stay member 90. The reflecting member 94 is provided to suppress wasteful energy consumption due to the stay member 90 being heated by radiant heat or the like from the halogen heaters 82a and 82b. The same effect can be obtained by performing heat insulation or mirror treatment on the inner surface of the stay member 90 instead of the reflecting member 94.

  As shown in FIG. 3, the pressure roller 84 has a structure in which a silicone rubber layer 84b is provided on a hollow metal roller 84a. In order to obtain releasability, a release layer having a layer thickness of 5 to 50 μm made of PFA (perfluoroalkoxy fluororesin) or PTFE (polytetrafluoroethylene) is provided on the surface of the rubber layer 84b. The pressure roller 84 is rotated by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus via a gear. The pressure roller 84 is pressed toward the fixing belt 80 by a spring or the like, and the rubber layer 84b is crushed and deformed to form a predetermined nip width Nw in the sheet conveyance direction. The pressure roller 84 may be a solid roller, but a hollow roller is more preferable because it has a smaller heat capacity. The pressure roller 84 may have a heating source such as a halogen heater inside. The rubber layer 16b may be solid rubber, but if there is no heater inside the pressure roller, sponge rubber may be used. Sponge rubber is more preferred because it increases heat insulation and makes it difficult for heat of the fixing belt 80 to be taken away.

  The fixing belt 80 is a metal belt such as nickel or SUS having a layer thickness of 30 to 50 μm, or an endless belt using a resin material such as polyimide, or a film. The surface layer of the belt has a release layer such as a PFA or PTFE layer, and has a release property so that toner does not adhere. In addition, an elastic layer formed of a silicone rubber layer or the like may be provided between the belt substrate and the PFA or PTFE layer. When there is no silicone rubber layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, subtle irregularities on the belt surface are transferred to the image and uneven fixing (glossy) This causes a problem that unevenness remains.

  In order to improve the above problems, it is necessary to provide a silicone rubber layer of 100 μm or more. As a result, deformation of the silicone rubber layer absorbs subtle irregularities and improves fixing unevenness. The fixing belt 80 is rotated by contact friction by the rotation of the pressure roller 84. The fixing belt 80 is sandwiched and rotated at the nip portion N, but both ends are held in a cylindrical shape except for the nip portion N, and the cross-sectional shape of the fixing belt 80 is stably maintained in a circular shape. As shown in FIG. 2, a separation member 32 that separates the sheet S from the fixing belt 80 is provided on the downstream side of the nip portion N in the sheet conveyance direction.

  In the present embodiment, the shape of the nip portion N is flat as shown in FIGS. 1 and 3. However, the shape of the nip portion N may be a concave shape or other shape that protrudes toward the fixing belt 80 when viewed from the pressure roller 84 side. There may be. As for the shape of the nip portion N, the discharge direction at the front end of the sheet is closer to the pressure roller 84 in the concave shape, and the separation is improved, so that the occurrence of jam is suppressed. In this case, the nip forming surface of the nip forming member 88 is formed in a concave shape. In this case, the contact surfaces of the end heaters 112a and 112b, which are end heat sources to be described later, provided integrally with the nip forming member 88. Also, a shape along the nip forming surface may be used.

  Due to the action of the stay member 90, it is possible to prevent the nip forming member 88 that receives pressure from the pressure roller 84 from being bent and to obtain a uniform nip width in the axial direction. In the present embodiment, the pressure roller 84 is pressed toward the fixing belt 80 to form the nip portion N. However, the nip forming unit 86 is pressed toward the pressure roller 84 to form the nip portion N. It is good. The stay member 90 has a sufficient bending strength to support the nip forming member 88. Examples of the material include metal materials such as stainless steel and iron, and metal oxides such as ceramics.

  As shown in FIG. 4, the fixing belt 80 is rotatably supported at both ends in the axial direction by flanges 36 as support members protruding in the axial direction from the side plate 34. Although FIG. 4 shows a support structure on one side in the axial direction of the fixing belt 80, the other side has the same structure. The flange 36 that guides both ends of the fixing belt 80 has an outer diameter substantially equal to the inner diameter of the fixing belt 80, and has a length of 5 to 10 mm inward from both ends of the fixing belt 80. Since the fixing belt 80 is guided by the flange 36, the cross-sectional shape thereof is maintained in a circular shape even during traveling (during rotation). A portion corresponding to the nip portion N of the flange 36 is opened to place the nip forming unit 86 at a predetermined position. The stay member 90 has a length that extends over the entire axial direction of the fixing belt 80, and is supported in a state in which both sides thereof are fixed and positioned on the side plate 34.

  As shown in FIG. 5, the halogen heater 82 a is a halogen heater corresponding to a small-sized sheet S having a dense light distribution at the center in the longitudinal direction of the fixing belt 80. The halogen heater 82b is a halogen heater corresponding to a sheet S of A3 size or the like having a light distribution distribution at both ends in the same longitudinal direction. When the paper S is a small size, only the halogen heater 28a is turned on, and the non-sheet passing portion is prevented from being heated unnecessarily.

  The difference between the A3 size width, the A4Y width with the A4 size turned sideways, and A3 nobi (329 mm) and 13 inches (330 mm) is 32 to 33 mm. Therefore, if only the both ends in the axial direction of the fixing belt 80 are heated, both ends can be heated by a width of 16 to 16.5 mm, which is half of the above, as shown in FIG. The width of paper can be expanded to nobi. In other words, if the portions where the light distribution distribution at both ends of the halogen heater 82b is not dense can be heated, it is possible to cope with a large size paper S such as A3 Nobi. Therefore, as the end heaters 112a and 112b used as the end heat source, a small heater having an axial length of about 20 mm is sufficient.

  When passing a large size paper S such as A3 Nobi or 13 inches, the halogen heaters 82a and 82b and the end heaters 112a and 112b are energized. When passing paper of A3 size or smaller, only the halogen heaters 82a and 82b or the halogen heater 82a are energized, and the end heaters 112a and 112b are not energized. If the halogen heater 82b is configured to be able to handle large-size paper S such as A3 Novi, even when the large-size paper S is not passed, that portion is heated and wasteful energy is consumed. become. According to the configuration of the present embodiment, the above problem can be solved by adding a simple configuration in which end heaters 112a and 112b are added to both ends of the fixing belt 80 or in the vicinity of both ends.

  In the present embodiment, both the end heaters 112a and 112b may have PTC characteristics. If it has a PTC characteristic, the resistance value increases above the set temperature, so that the temperature does not rise above the set temperature, and a safe fixing device without the risk of combustion or belt breakage can be realized. Further, in this embodiment, the end heaters 112a and 112b are provided inside the fixing belt 80, so that the belt end can be heated from the inside without obstructing the traveling movement of the fixing belt 80. Then, by constituting the belt contact surfaces of the end heaters 112a and 112b with another member made of a smooth material, the sliding resistance can be reduced and the belt running can be stabilized.

  As shown in FIG. 6, two protrusions 90 b and 90 c extending in the longitudinal direction of the fixing belt 80 are formed on the side surface 90 a on the pressure roller 84 side of the stay member 90. The rectangular parallelepiped nip forming member 88 is accommodated and positioned between the ridges 90b and 90c, and is fixed to the side surface 90a by means such as adhesion. At both ends in the longitudinal direction of the nip forming member 88, concave portions 88a and 88b as stepped portions are formed, and end heaters 112a and 112b are respectively accommodated and fixed by means such as adhesion. A surface of the nip forming member 88 facing the pressure roller 84 forms a nip forming surface 88c.

Here, the end heaters 112a and 112b will be described. The end heaters 112a and 112b used in the present embodiment are the same, and FIG. 15 shows the end heater 112a as a representative.
The end heater 112a is configured by patterning a resistance heating element 52 as a heating member on a ceramic base 51 having an outer shape of about 10 mm × 20 mm, and laminating an insulating layer 53 of a thin glass layer thereon. A terminal 54 connected to the power source and the switching element is provided at the end of the end heater 112a.

As described above, the end heaters 112a and 112b have the resistance heating element 52 on one surface side, and one surface side having the resistance heating element 52 mainly generates heat, and the other surface side has too much. It is configured not to receive heat. The end heaters 112a and 112b used in this embodiment have a resistance heating element 52 on the side in contact with the recesses 88a and 88b, and a terminal 54 is provided on each of the surface heaters.
As shown in FIG. 16, the end heaters 112 a and 112 b have the resistance heating element 52 disposed on the side not in contact with the fixing belt 80, so that the supplied power can be supplied even if the insulating layer 53 is damaged. Configured to not reach. In particular, when the fixing belt 80 is made of metal as will be described later, other components in the image forming apparatus, for example, a known contact thermistor for the fixing belt may be adversely affected through the metal in the fixing belt. Rise. Therefore, the above-described configuration is more suitable for securing a creepage distance between the fixing belt 80 and the resistance heating element 52.

  As shown in FIG. 7A, the surface of the end heaters 112a and 112b contacting the inner surface of the fixing belt 80 and the nip forming surface 88c are in the direction of the arrow F (the drag direction) which is the direction of pushing the inner surface of the fixing belt 80. ) Have the same height. In other words, the surfaces of the end heaters 112a and 112b that are in contact with the inner surface of the fixing belt 80 are configured to be extended surfaces in the longitudinal direction of the nip forming surface 88c. In the present embodiment, since the end heaters 112a and 112b are integrally provided to the nip forming member 88 necessary for forming the nip, the end heaters 112a and 112b are disposed inside the fixing belt 80. And space saving can be achieved.

  Further, since the surfaces of the end heaters 112a and 112b that are in contact with the inner surface of the fixing belt 80 and the nip forming surface 88c are located at the same height (on the same plane), sufficient pressing force by the pressure roller 84 is applied to the fixing belt. 80 and the end heaters 112a and 112b. Thereby, belt running can be realized in a state where the fixing belt 80 and the end heaters 112a and 112b are in close contact with each other, and good heating efficiency by the end heaters 112a and 112b can be maintained by improving heat transfer. In addition, since the heating part for the fixing belt 80 by the end heaters 112a and 112b exists in the nip region, there is a problem of re-melting of the untransferred toner due to heating at a part different from the nip part N as in Patent Document 1. Does not occur. Furthermore, since the pressure roller 84 also serves as an urging means for bringing the end heaters 112a and 112b and the fixing belt 80 into close contact with each other in order to improve heat transfer, it is not necessary to press only the end heaters 112a and 112b. Thus, the configuration can be simplified as compared with the conventional case. In other words, since the end heaters 112a and 112b and the fixing belt 80 are brought into close contact with each other by using a pressing force for forming the nip portion N, the running performance and heat transfer in the configuration disclosed in Patent Document 1 are described. There is no trade-off problem with defects.

  In the present embodiment, the shape of the concave portion formed in the nip forming member 88 is a shape in which the end portion in the axial direction is opened. However, as shown in FIG. 7B, as concave portions 88a and 88b surrounded by four sides. Also good. Moreover, it is good also as a structure by which the front and back of the axial direction were block | closed and the both sides orthogonal to an axial direction were open | released.

  Moreover, as shown in FIG. 8, it is good also as a structure which supports the edge part heaters 112a and 112b with the elastic member 38 in recessed part 88a, 88b. As shown in FIG. 8A, the surface of the end heaters 112a and 112b contacting the inner surface of the fixing belt 80 and the nip forming surface 88c are the same height when no pressure is applied by the pressure roller 84. Not. However, as shown in FIG. 8B, when the nip portion N is formed by the pressure applied by the pressure roller 84, the elastic member 38 is deformed and contacts the inner surface of the fixing belt 14. , 112b have the same height as the nip forming surface 88c. As the elastic member 38, a rubber member or a spring can be employed.

  As described above, since the end heaters 112a and 112b are fixed and positioned on the nip forming member 88 which is a separate member, the contact surfaces of the end heaters 112a and 112b with the inner surface of the fixing belt 80 and the nip forming surface 88c. There is a possibility that the height will deviate at the assembly stage. Even in such a case, if the end heaters 112a and 112b are supported by the elastic member 38, it is possible to absorb the manufacturing error and make the surface height the same when forming the nip.

  In the present embodiment, the end heaters 112a and 112b are integrally provided in the nip forming unit 86, but the present invention is not limited to this. As shown in FIG. 9, the end heaters 112 a and 112 b may be provided in the nip region independently of the nip forming unit 86. For example, the structure fixed to the supporting members 42a and 42b fixed to the side plate 34 is employable. Also in this case, the surfaces of the end heaters 112a and 112b contacting the inner surface of the fixing belt 80 and the nip forming surface 88c are set to the same height. Also in this example, the end heaters 112 a and 112 b may be displaced by the elastic member 38.

  In the present embodiment, the stay member 90 and the halogen heaters 82a and 82b are integrally provided as the nip forming unit 86. However, a single product having an integrated structure of the nip forming member 88 and the end heaters 112a and 112b is also provided. It is a nip forming unit according to the invention.

Further, as shown in FIG. 19, the lengths of the end heaters 112a and 112b complement the reduced heat distribution output at the extreme end of the halogen heater 82b, and can also be used for A3 size paper. It may be a size. Further, the end heaters 112a and 112b are not limited to the arrangement configuration at both ends, and for example, a plurality of pairs may be provided according to various paper sizes.
The end heaters 112a and 112b may be disposed further outward in the longitudinal direction than the halogen heater 82b. In such a case, more paper sizes can be accommodated, and heating can be performed with high accuracy, which is more desirable.

  When heaters having PTC characteristics are used as the end heaters 112a and 112b, it usually takes longer to raise the temperature than when halogen heaters are used. For this reason, if the end heaters 112a and 112b and the halogen heaters 82a and 82b are heated at the same timing, only the inner side of the central portion is heated first, and wasteful energy is consumed. Further, when heat is taken away by passing paper, the heating time for the end heaters 112a and 112b to return to the target temperature is longer than that of the halogen heater due to the characteristics of PTC.

For this reason, it becomes possible to perform heating control with no temperature variation between the central portion and the end portion by reducing the productivity in accordance with the heating cycle of the end heaters 112a and 112b. That is, when the end heaters 112a and 112b for heating both ends of the fixing belt 80 or in the vicinity of both ends are used, the halogen heaters 82a and 82b corresponding to other normal size papers are controlled to be heated in accordance with the temperature rise at the ends. To do. Thereby, when the calorific value of the end heaters 112a and 112b is low, it is possible to prevent only the heater heating unit corresponding to the normal size paper from being heated first, and to consume more energy than necessary. Further, the transport speed when transporting the paper S of the size using the end heaters 112a and 112b is made slower than the transport speed of the paper S of other sizes. Thus, by reducing the productivity of the large-sized paper S that is not frequently used, the heaters (end heaters 112a and 112b) at both ends can be simplified and reduced in cost and efficiency can be improved.
In the present embodiment, a configuration having two halogen heaters as fixing heat sources is shown, but the present invention is not limited to this, and a configuration having three or more halogen heaters for small-size paper may be used.

FIG. 17 shows a modification of the nip forming unit.
The nip forming unit 63 includes a nip forming member 88, end heaters 112 a and 112 b, and a stay member 64 that holds the nip forming member 88 against the pressure applied from the pressure roller 16.
The stay member 64 integrally includes a receiving portion 64 a configured similarly to the stay member 90 to receive the nip forming member 88 and a leg portion 64 b having a substantially triangular cross-sectional shape. Between the leg portion 64b and the fixing belt 14, halogen heaters 82a and 82b are disposed as fixing heat sources for directly heating the fixing belt 14 from the inner surface side by radiant heat.
In order to increase the heating efficiency of the halogen heaters 82a and 82b, a reflecting member 65 made of an arc-shaped plate member that reflects the light emitted from the halogen heaters 82a and 82b to the fixing belt 80 includes a leg portion 64b and halogen heaters 82a and 82b. It is provided between.

Even if the above-described nip forming unit 63 is used in place of the nip forming unit 86, the same effect as that of the above-described embodiment can be obtained.
Instead of providing the reflecting member 65, the outer surface of the leg portion 64b may be heat-insulated or mirror-finished. In this case, the heating efficiency is slightly reduced as compared with the case where the reflecting member 65 is provided.

Here, the metal fixing belt will be described. The fixing belt 80 shown in FIGS. 2, 14, 16, and 17 is rotated by the rotation of the pressure roller 84 that is in contact with the outer peripheral surface thereof, and conveys heat from the heat source toward the nip N. In the fixing device having such a configuration, a load applied to the fixing belt 80 is large, and a resin material such as polyimide may have insufficient strength.
For this reason, metal materials such as stainless steel, nickel, aluminum, and copper having excellent strength are often used as the base material of the fixing belt 80.

As shown in a model in FIG. 18, a base material 46 containing a metal material is used, an elastic layer 47 is formed on the outer peripheral surface, and a release layer 48 is formed on the outer peripheral surface by a known method. The illustrated fixing belt 14 can be configured.
Here, the performance required for the base material 46 includes durability when forming the fixing belt 80, flexibility, and heat resistance that can withstand use at a fixing temperature. The elastic layer 47 and the release layer 48 are also included. It forms so that these performances may be satisfied.
Further, nickel is more suitable as the base material 46 of the fixing belt 80 than stainless steel. This is because the strength is high, the durability is excellent, and an endless belt can be easily manufactured by an electroforming process.

  The electrical connection configuration of the halogen heaters 82a and 82b and the end heaters 112a and 112b in the above embodiments is shown in FIG. 10 as the first embodiment and FIG. 11 as the second embodiment. When the sheet S is transported on the basis of the center, the end heaters 112a and 112b are always driven at the same time. Therefore, in the first embodiment, the end heaters 112a and 112b are electrically connected in series to the power source 120, respectively. By adopting such a connection configuration, electric control can be simplified as compared with a configuration in which the end heaters 112a and 112b are individually turned on and off. Further, when one end heater 112a or 112b breaks down, the electrical connection between them can be cut off at the same time, so that safety can be ensured. The halogen heater 82a is turned on and off by the switch 120a, the halogen heater 82b is turned on by the switch 120b, and the end heaters 112a and 112b are turned on and off by the switch 120c.

  The heating by the end heaters 112a and 112b is a case where the paper S having a size larger than the A3 size is passed. At that time, the halogen heater 82b for heating both ends is turned on simultaneously. Therefore, in the second embodiment, a wiring connecting the halogen heater 82b in series with the end heaters 112a and 112b is provided, and the power supply is controlled while the path is switched by the switches 121a, 121b, and 121c. With this configuration, it is possible to achieve the same effect as that of the first embodiment while further simplifying the control device. Here, since the halogen heater 82b and the end heaters 112a and 112b have different temperature characteristics, the temperature of both is adjusted by switching the path.

  When passing the small-sized paper S, the switches 120a and 121a are turned on and only the halogen heater 82a is driven. When passing a large size paper S up to A3 size, the switches 120a, 121a, 120b, 121b are turned on and both the halogen heaters 82a, 82b are driven. When passing a sheet having a size larger than A3 size, the switches 120a, 121a, 120b, and 121b are turned on, and the switches 120c and 121c are controlled to be turned on and off, respectively. As a result, the halogen heaters 82a and 82b are driven, and the end heaters 112a and 112b are appropriately turned on and off. In the case of the electrical connection shown in FIG. 10, since the halogen heaters 82a and 82b and the end heaters 112a and 112b are connected in parallel with each other, the on / off control is independently performed by the switches 120a, 120b, and 120c. can do.

  The heating operation based on the circuit configuration shown in each embodiment is temperature-controlled by a temperature sensor 125 (see FIG. 2) disposed near the outside of the fixing belt 80. Therefore, a safety device such as a thermostat 126 (see FIG. 2) needs to be provided in the vicinity of the outside of the fixing belt 80 in order to prevent the temperature sensor 125 from running away when it fails. In the second embodiment, the end heaters 112a and 112b are always driven simultaneously with the halogen heater 82b. For this reason, if the thermostat 126 is provided in the vicinity of the outer side of the fixing belt 80 in the vicinity of the halogen heater 82b, the abnormalities of the end heaters 112a and 112b can be detected simultaneously, and the safety device can be simplified. .

  On the other hand, in the second embodiment, the end heaters 112a and 112b cannot be driven independently. For this reason, when the heating performance of the end heaters 112a and 112b is inferior to that of the halogen heater 82b, the region heated by the end heaters 112a and 112b is lower in temperature than the region heated by the halogen heater 82b. turn into. In addition, there is a problem that it is impossible to perform control for eliminating the generated temperature difference.

  Therefore, in the second embodiment, it is necessary to select each heater so that the heating performance of the end heaters 112a and 112b is higher than that of the halogen heater 82b. Specifically, in the temperature rise characteristic curve of each heater shown in FIG. 12, the characteristic curve of the end heater indicated by the solid line is set so that the temperature rise rate per hour is faster than the characteristic curve of the halogen heater indicated by the broken line. Select a heater. When the switch 121c is turned on under this condition, the region heated by the end heaters 112a and 112b reaches the target temperature earlier than the region heated by the halogen heater 82b, and a high belt temperature can be maintained. . In order to equalize the temperature difference, if the switch 121c is turned off and the switch 121b is turned on, only the heating region of the halogen heater 82b can be raised in temperature. Therefore, the temperature control can be performed to the same temperature as the previously heated region. it can.

  In the first embodiment, since the end heaters 112a and 112b can be controlled on and off independently, this is not restrictive, and the heating performance of the end heaters 112a and 112b and the halogen heater 82b may be superior. Therefore, in the first embodiment, the degree of freedom of selection of the end heaters 112a and 112b is improved as compared with the second embodiment.

  As described above, according to the present invention, according to the first embodiment, only the end heater 112 is independently heated even when the heating power of the end heater 112 is inferior to the heating power of the halogen heater 82. Can be driven. Thereby, the heating temperature by the end heater 112 can be controlled to the same temperature as the heating temperature by the halogen heater 82, and the degree of freedom of heater selection can be improved. Further, according to the second embodiment, if a safety device such as the thermostat 126 is provided in the halogen heater 82 in order to prevent the runaway when the temperature sensor 125 fails, the abnormality of the end heater 112 can be prevented at the same time. And the safety device can be simplified.

  In an image forming apparatus such as a copying machine or a multi-function machine having a fixing device, a series machine is usually handled by changing a linear speed, a fixing temperature, a fixing pressure, etc. according to productivity (CPM or PPM). At this time, it may be necessary to use the circuit configuration shown in the first embodiment and the circuit configuration shown in the second embodiment separately. FIG. 13 shows a circuit configuration in the third embodiment of the present invention in which a common wiring portion between the circuit configuration shown in the first embodiment and the circuit configuration shown in the second embodiment is extracted. In FIG. 13, the circuit configuration and the second embodiment shown in the first embodiment are selected depending on whether the connecting portion 1 coming out from the end heater 112b connected in series is connected to the contact A or the contact B. The circuit configuration shown in the embodiment can be easily switched. The circuit configuration shown in the first embodiment is configured by connecting the connecting portion 1 to the contact A, and the circuit configuration shown in the second embodiment is configured by connecting the connecting portion 1 to the contact B.

  With this configuration, the fixing device is configured in the state shown in FIG. 13, and the connection portion 1 is selectively connected to the contact A or the contact B, whereby the circuit configuration can be easily used properly. Thereby, when dividing a series machine according to the response performance, the linear velocity, and productivity of the end heater 112, a common fixing device can be used and productivity can be improved.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such specific embodiments, and unless specifically limited by the above description, the present invention described in the claims is not limited. Various modifications and changes are possible within the scope of the gist. The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

80 Belt member (fixing belt)
84 Pressure member (Pressure roller)
82a, 82b Heat source (halogen heater)
88 Nip forming member 100 Image forming apparatus 112a, 112b End heat source (end heater)
150 Fixing device

JP 2014-178370 A

Claims (10)

An endless belt member having flexibility;
A pressure member disposed opposite to the belt member;
A nip for forming a nip that has a heat source that heats at least a central portion of the sheet passing region in the longitudinal direction of the belt member, and that conveys the recording medium between the belt member and the pressure member. Members,
A plurality of end heat sources that are provided on the nip forming member and heat an inner surface near the end in the width direction of the belt member;
A fixing device in which the end heat sources are electrically connected in series. The fixing device according to claim 1.
A fixing device having a nip forming surface in contact with the inner surface, the nip forming surface being provided at the same height as a surface for heating the inner surface of the end heat source. The fixing device according to claim 1.
The nip forming surface is in contact with the inner surface, and the surface facing the belt member is arranged in order from the longitudinal end to the first end heat source, the nip forming surface, and the second end heat source. A fixing device. The fixing device according to claim 2.
The fixing device, wherein the nip forming surface is in contact with the inner surface through a sliding sheet. The fixing device according to claim 2.
Each of the end heat sources can be in contact with an inner surface of the belt member, and a surface of each of the end heat sources that is in contact with the inner surface is disposed in an extended surface of the nip forming surface. Fixing device to do. In the fixing device according to any one of claims 1 to 5,
The fixing device, wherein the heat sources are further connected in series to the end heat sources, and a single lighting circuit of the heat sources is connected in parallel to a power supply. In the fixing device according to any one of claims 1 to 6,
When each of the end heat sources is operated, the heat source is controlled to be heated in accordance with the temperature rise. In the fixing device according to any one of claims 1 to 6,
The fixing device, wherein the end heat sources and the heat sources are connected in parallel. In the fixing device according to any one of claims 1 to 6,
The fixing device, wherein each of the end heat sources and the heat sources can be selected to be connected in series to each other or in parallel to each other.   An image forming apparatus comprising the fixing device according to claim 1.

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