JP6673033B2 - Fixing device and image forming device - Google Patents

Description

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

  In recent years, the market demand for energy saving and high speed has been increasing for image forming apparatuses such as copiers, printers, facsimile machines, and multifunction peripherals having at least two of these functions. Above all, various proposals have been made because the fixing device consumes a large amount of power and has a large room for energy saving.

  Further, in the image formation in the image forming apparatus, various sizes of recording materials are targeted. In the case of image formation using toner, the image formation may be performed at a small size but full of the standard paper size. . At this time, a recording material one size larger than the paper standard size is used (for example, an A3 nobby size slightly larger than the A3 size), or a 13-inch size is used. Therefore, further improvement has been desired in order to cope with these special-size recording materials.

  In order to solve such a problem, Patent Document 1 discloses that a plurality of halogen heaters having different light distributions in the width direction of the belt (paper width direction) are provided inside the endless belt, and both ends in the longitudinal direction of the belt member It has been proposed to provide an end heater in contact with the inner or outer surface of the belt at a position upstream of the nip in the direction of rotation of the belt.

  However, in the fixing device disclosed in Patent Document 1, if the contact pressure of the end heater with respect to the fixing belt is increased in order to increase the efficiency of heat transfer from the end heater to the fixing belt, the distance between the end heater and the fixing belt is increased. The frictional force increases. This may lead to poor running of the fixing belt, which lowers the reliability. On the other hand, if the contact pressure of the end heater with respect to the fixing belt is reduced in order to avoid the poor running of the fixing belt, heat transfer to the fixing belt becomes insufficient. This may lead to an excessive temperature rise of the end heater, which lowers the reliability.

  Accordingly, the present applicant has devised a fixing device that can improve the heating efficiency of a plurality of radiant heat sources used for fixing and can cope with a special-size recording material such as A3 Novi without losing reliability and quality. Not published but suggested. That is, a plurality of radiant heat sources provided inside a flexible endless belt, having different light distributions in the longitudinal direction, partitioned by stay members, and a nip provided inside the belt. A plurality of contact heat transfer heat sources provided at respective ends of the forming member and respectively heating longitudinal ends of the belt; and a nip forming member and the plurality of contact heat transfer heat sources opposed to the belt. And a heat transfer assisting member that covers the respective surfaces and moves heat in the longitudinal direction of the belt.

  The present invention improves the heating efficiency of a plurality of radiant heat sources used for fixing, and a fixing device that can cope with a recording material of a special size such as A3 nob without losing reliability and quality. When the sum is larger than the maximum power that can be supplied to the fixing device, the priority is to use power to the necessary heat source within the allowable power consumption range to prevent fixing failure due to temperature drop etc. And

  The object is to provide an endless belt having flexibility, a pressure member facing the belt outside the belt, and provided inside the belt and separated from each other by a stay member. First and second radiant heat sources for heating the central area and both sides in the longitudinal direction, respectively, and a nip forming member provided inside the belt and forming a fixing nip between the belt and the pressure member. Provided at each end of the nip forming member, a plurality of contact heat transfer heat sources for heating the longitudinal ends of the belt, and the nip forming member and the plurality of contact heat transfer heat sources, A heat transfer assisting member that covers each surface facing the belt and moves heat in the longitudinal direction of the belt, wherein the fixing device includes a heat transfer auxiliary member, and the belt heated by the radiant heat source. At least one temperature detecting means for detecting the temperature of the area, and another temperature detecting means for detecting the temperature of the area of the belt heated by the contact heat transfer type heat source, the radiation type heat source and the The sum of the rated power of the contact heat transfer type heat source is larger than the maximum power that can be supplied to the fixing device, and the maximum lighting rate of each of the radiant heat source and the contact heat transfer type heat source is determined by the contact between the radiant heat source and the contact type heat source. The problem is solved by changing according to the operation state so that the sum of the respective input powers to the heat transfer type heat source does not become larger than the maximum power.

  The fixing device of the present invention can prevent heat interference by separating a plurality of radiant heat sources from each other by a stay member, thereby improving heating efficiency, and attach a longitudinal end of the belt to each end of the nip forming member. Equipped with multiple contact heat transfer heat sources to heat, it can not only handle special size recording materials without losing reliability and quality, but also the sum of the rated power of the radiation heat source and the contact heat transfer heat source is the fixing device When set to be larger than the maximum power that can be supplied to the radiant heat source and the contact heat transfer heat source, the maximum lighting rate of each of the radiant heat source and the contact heat transfer heat source Is changed according to the operation state so that the sum of the power does not become larger than the maximum power.Therefore, the power is preferentially used for a necessary heat source within an allowable power consumption range, and a fixing failure due to a temperature drop or the like is prevented. Can be prevented .

FIG. 1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional configuration diagram illustrating an embodiment of a fixing device. FIG. 2 is a perspective view illustrating a basic configuration of a nip forming unit. It is a schematic diagram which shows arrangement | positioning of the heating part of a halogen heater and an end heater. It is a schematic diagram which shows the positional relationship of each heating part of a halogen heater and an end heater. It is a figure explaining the position of the temperature detection part provided for the end heater. 5 is a graph illustrating a temperature rise over time in the heater configuration according to the embodiment. 8A and 8B are diagrams illustrating a lighting rate and a temperature change of each heater before and after reloading in the heater configuration according to the present embodiment, where 8a is a case where the printing target is an A3 super size, and 8b is a case where the printing target is an A3 or smaller size. FIG. 9A is a diagram showing a lighting rate and a temperature change of each heater to be changed at the time of A3 super-size printing in accordance with a previous job in the heater configuration according to the present embodiment. Is a large-size print target.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 is a color laser printer. Four image forming units 4Y, 4C, 4M, and 4K are provided side by side in the center of the printer body along the direction in which the intermediate transfer belt 30 extends. I have. Each of the image forming units 4Y, 4C, 4M, and 4K stores a developer of each color of yellow (Y), cyan (C), magenta (M), and black (K) corresponding to a color separation component of a color image. Have the same configuration.

  Specifically, each of the image forming units 4Y, 4C, 4M, and 4K constituting the image station includes a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, A developing device 7 for supplying toner to the surface of the photoconductor 5 and a cleaning device 8 for cleaning the surface of the photoconductor 5 are provided. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4K are indicated by reference numerals, and the other image forming units 4Y, 4C, and 4M are denoted by reference numerals. Omitted.

  An exposure device 9 for exposing the surface of the photoconductor 5 is provided below the image forming units 4Y, 4C, 4M, and 4K. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with a laser beam based on image data.

  A transfer device 3 is provided above the image forming units 4Y, 4C, 4M, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, and a secondary transfer roller 36 as secondary transfer means. Further, the transfer device 3 includes a secondary transfer backup roller 32 that stretches the intermediate transfer belt 30, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35. The intermediate transfer belt 30 travels (rotates) in a direction indicated by an arrow in the drawing as the secondary transfer backup roller 32 is driven to rotate. The belt cleaning device 35 has a cleaning brush and a cleaning blade arranged so as to contact the intermediate transfer belt 30.

  Each of the four primary transfer rollers 31 forms a primary transfer nip by sandwiching the intermediate transfer belt 30 with each of the photoconductors 5. Further, a power supply of the printer main body is connected to each primary transfer roller 31 so that a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to each primary transfer roller 31. .

  The secondary transfer roller 36 forms a secondary transfer nip by sandwiching the intermediate transfer belt 30 between the secondary transfer roller 36 and the secondary transfer backup roller 32. Similarly to the primary transfer roller 31, the power source of the printer body is connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. It is supposed to be.

  A bottle accommodating section 2 is provided at an upper portion of the printer main body, and four toner bottles 2Y, 2C, 2M, and 2K accommodating toner for replenishment are detachably mounted on the bottle accommodating section 2. As is well known, a supply path is provided between each of the toner bottles 2Y, 2C, 2M, and 2K and each of the developing devices 7. The toner is supplied to the device 7.

  On the other hand, a paper feed tray 10 containing paper P as a recording material, a paper feed roller 11 for carrying out the paper P from the paper feed tray 10, and the like are provided below the printer body. Here, the recording material includes, in addition to plain paper, cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, and OHP sheets. Further, as is well known, a manual paper feed mechanism may be provided.

  A transport path R for discharging the paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus is provided in the printer body. In the transport path R, a pair of registration rollers 12 as transporting means for transporting the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 36 in the paper transport direction. Further, a fixing device 20 for fixing an unfixed image transferred to the sheet P is provided downstream of the position of the secondary transfer roller 36 in the sheet conveyance direction. Further, a pair of paper discharge rollers 13 for discharging paper out of the apparatus is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R. A paper discharge tray 14 for stocking paper discharged outside the apparatus is provided on the upper surface of the printer body.

  The basic operation of the printer according to the present embodiment is well known in the related art, and can be easily understood by those skilled in the art from the description of the basic configuration described above.

  FIG. 2 is a schematic cross-sectional configuration diagram illustrating an embodiment of the fixing device 20. The fixing device 20 includes a fixing belt 21 that is an endless belt that forms a thin and flexible cylindrical body, and a pressing roller 22 that is a pressing member that comes into contact with the fixing belt 21 from the outer peripheral side. Have. The fixing belt 21 is heated by radiant heat of halogen heaters 23A and 23B (hereinafter, also referred to as a first halogen heater 23A and a second halogen heater 23B) as a plurality of fixing heat sources disposed inside (in the loop). The halogen heater represents a radiant heat source as a fixing heat source which is a main heat source.

  Further, a nip forming member 24 that forms a fixing nip N with the pressure roller 22 via the fixing belt 21 and a stay member 25 (support member) that supports the nip forming member 24 are disposed inside the fixing belt 21. Have been. The nip forming member 24 arranged in the width direction of the fixing belt 21 is fixed and supported by the stay member 25, thereby preventing the nip forming member 24 from being bent by the pressure from the pressure roller 22, A uniform nip width can be obtained in the axial direction (longitudinal direction) of the pressure roller 22. The nip forming member 24 is made of a heat-resistant member having a high mechanical strength and a heat-resistant temperature of 200 ° C. or more, particularly a heat-resistant resin such as a polyimide (PI) resin, a polyetheretherketone (PEEK) resin, and reinforced with glass fibers. It is composed of This prevents deformation of the nip forming member 24 due to heat in the toner fixing temperature range, secures a stable fixing nip state, and stabilizes output image quality. The stay member 25 and the halogen heaters 23A and 23B are fixed at both ends in the longitudinal direction to a side plate of the fixing device 20 or a holder provided separately. At both ends in the longitudinal direction of the nip forming member 24, end heaters 26a and 26b as end heat sources different from a main heat source (fixing heat source) are integrally attached. As the end heater, a contact heat transfer type heat source which is a resistance heating element such as a ceramic sweater is generally used.

  A heat transfer assisting member 27, also referred to as a heat equalizing member, for facilitating heat transfer in the longitudinal direction of the fixing belt is provided on each surface of the nip forming member 24 and the end heater 26 facing the inner peripheral surface of the fixing belt 21. The fixing belt 21 is disposed so as to cover and prevent heat from remaining in the end region of the fixing belt 21 when small-sized paper is passed or when the end heater 26 is turned on. The heat is moved in the longitudinal direction of the heat transfer assisting member 27 to eliminate the temperature unevenness in the longitudinal direction. Therefore, the heat transfer assisting member 27 is formed of a material having high thermal conductivity that enables heat transfer in a short time, for example, copper (398 W / mk) or aluminum (236 W / mk). In the description of FIG. 2, the surface of the heat transfer assisting member 27 facing the inner peripheral surface of the fixing belt 21 is a surface that directly contacts the fixing belt 21 and is a nip forming surface, and is formed flat. May have a concave shape or other shapes. If the nip forming surface has a concave shape, the discharge direction of the leading end of the sheet is closer to the pressure roller, so that the separation property is improved and the occurrence of jam is suppressed.

  As is well known, at an appropriate position on the outer peripheral side of the fixing belt 21, for example, at the upstream side in the belt rotation direction of the fixing nip, a temperature detecting unit for detecting the temperature of each area of the belt heated by the halogen heaters 23 </ b> A and 23 </ b> B. A temperature sensor 29 (in this case, two in accordance with the halogen heaters 23A and 23B light distribution) is provided, and the sheet P is transferred from the fixing belt 21 downstream of the fixing device 20 in the sheet conveying direction. A separating member 41 for separating is provided. Further, a releasable pressing means for pressing the pressing roller 22 against the fixing belt 21 is also provided.

  In order to reduce the heat capacity, the endless fixing belt 21 having a small thickness and a small diameter such as a film is made of a metal material such as nickel or SUS or a resin material such as polyimide on the inner peripheral side and a PFA. (Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), or the like, and is constituted by a release layer on the outer peripheral side. An elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer. When the thickness of the elastic layer is set to about 100 μm, minute irregularities on the belt surface can be absorbed by the elastic deformation of the elastic layer when the unfixed toner is crushed and fixed, and generation of gloss unevenness can be avoided. From the viewpoint of reducing the heat capacity, the fixing belt 21 is set to have a thickness of 1 mm or less as a whole and a diameter of 20 to 40 mm. The thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in the ranges of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm. In order to further reduce the heat capacity, the thickness of the entire fixing belt 21 is preferably set to 0.2 mm or less, more preferably 0.16 mm or less, and the diameter is set to 30 mm. It is desirable to do the following.

  The stay member 25 having a T-shaped cross section has an upright portion 25a on the side opposite to the fixing nip N side, and the halogen heaters 23A and 23B as main heat sources are arranged so as to be separated by the upright portion 25a. One of the halogen heaters 23A and 23B has a heat-generating portion in the center in the longitudinal direction corresponding to small-size paper, and the other has heat-generating portions on both longitudinal sides corresponding to large-size paper. The halogen heaters 23 </ b> A and 23 </ b> B are configured to generate heat by being output controlled by a power supply unit provided in the printer main body. The output control is performed by a temperature sensor 29 provided on the outer periphery of the fixing belt 21. This is performed based on the temperature detection result (detection state) in each area. By controlling the output of such a heater, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature.

  Reflecting members 28A and 28B are arranged between the stay member 25 and the halogen heaters 23A and 23B. Accordingly, the heating efficiency of the halogen heaters 23A and 23B with respect to the fixing belt 21 can be increased, and wasteful energy consumption due to the heating of the stay member 25 by the radiant heat from the halogen heaters 23A and 23B can be suppressed. Similar effects can be obtained by performing heat insulation or mirror finishing on the surface of the stay member 25 instead of providing the reflection members 28A and 28B.

  The pressure roller 22 includes a cored bar, an elastic layer provided on the surface of the cored bar made of foamable silicone rubber or fluororubber, and a release layer provided on the surface of the elastic layer made of PFA or PTFE. It is configured. At a place where the pressure roller 22 is pressed against the fixing belt 21 by a pressing means such as a spring and pressed against the fixing belt 21, the elastic layer of the pressure roller 22 is crushed to form a fixing nip N having a predetermined width. You. The pressure roller 22 is rotationally driven by a drive source such as a motor provided in the printer body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the fixing nip N, and the fixing belt 21 is driven to rotate. The fixing belt 21 rotates while being sandwiched by the fixing nip N, and runs by being guided by side plate flanges disposed at both ends except the fixing nip N.

  In the present embodiment, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heat source such as a halogen heater may be provided inside the pressure roller 22. The elastic layer may be solid rubber, but if there is no heat source inside the pressure roller, sponge rubber may be used. Sponge rubber is more preferable because the heat insulating property is enhanced and the heat of the fixing belt 21 is hardly deprived.

  FIG. 3 is a perspective view showing a basic configuration of the nip forming unit. As shown in FIG. 3, the nip forming unit includes a nip forming member 24, a stay member 25, a heat transfer assisting member 27, and end heaters 26a and 26b. In the nip forming unit, the surface of the nip forming member 24 opposite to the fixing nip N side is integrated with the flat surface of the stay member 25 on the fixing nip N side. At this time, a concave and convex shape such as a boss and a pin may be formed on each surface, and these may be fitted in a shape-restricted manner. The heat transfer assisting member 27 is fitted and integrated so as to cover the surface of the substantially rectangular parallelepiped nip forming member 24 facing the inner peripheral surface of the fixing belt 21. The heat transfer assisting member 27 and the nip forming member 24 may be integrated with each other by providing claws or the like, but may be bonded or the like. At both ends in the longitudinal direction of the nip forming member 24, concave portions 24a and 24b as step portions are formed, and end heaters 26a and 26b are accommodated and fixed at these portions. The positional relationship between these end heaters 26a and 26b and the halogen heaters 23A and 23B will be described later.

  The surface of the heat transfer assisting member 27 facing the inner peripheral surface of the fixing belt 21 is configured as a belt sliding contact surface 27a, but the nip forming surface is substantially the nip forming surface due to mechanical strength. The surface 24c faces the pressure roller 22.

  As described above, in the present embodiment, the end heaters 26 a and 26 b are provided integrally with the nip forming member 24 necessary for forming the fixing nip. It can be arranged in a small space inside.

  Further, since the surfaces of the end heaters 26a and 26b facing the inner surface of the fixing belt 21 and the surface of the nip forming member 24 facing the fixing belt 21 are located at the same height (on the same plane), the pressure roller Is applied through the heat transfer assisting member 27. As a result, the fixing belt 21 is in indirect contact with the end heaters 26a and 26b, so that stable belt running can be achieved. Further, the fixing belt 21 and the end heaters 26a and 26b are in contact with a sufficient contact pressure, and good heating is maintained. With these configurations, the reliability of the fixing device 20 is improved. Further, the heating portion of the fixing belt 21 by the end heaters 26a and 26b is within the nip region. Therefore, the problem of re-melting of untransferred toner due to heating at a portion different from the fixing nip N (quality reduction) does not occur.

  Next, a description will be given of an arrangement configuration of a heat source that can cope with a recording material of a special size such as A3 paper. FIG. 4 is a schematic diagram showing the arrangement of the heat generating portions of the halogen heater and the end heater. As shown in FIG. 4, a first halogen heater 23A having a dense light distribution at a central portion in the longitudinal direction and a second halogen heater 23B having a dense light distribution at both sides in the longitudinal direction are arranged. I have. That is, the first halogen heater 23 </ b> A heats a central area of the fixing belt 21, and the second halogen heater 23 </ b> B heats a side area of the fixing belt 21.

  The heat generating portion 40A of the first halogen heater 23A corresponds to a small-sized recording material such as A4 vertical size, and the heat generating portion 40B of the second halogen heater 23B has an A3 vertical size which cannot be covered by the first halogen heater 23A. Covers the side area of the largest standard size recording material that can be used. That is, the heat generating portion 40 including the heat generating portions 40A and 40B of both halogen heaters corresponds to the maximum standard size paper width and does not cover the nobi size paper width larger than the maximum standard size.

  On the other hand, the end heaters 26a and 26b are located at positions corresponding to both ends in the longitudinal direction of the second halogen heater 23B, and have heat generating parts 42a and 42b for heating both ends of a paper size larger than the maximum standard size. Further, a part of the heat generating portions 42a and 42b of the end heaters 26a and 26b overlaps with the heat generating portion 40B of the halogen heater 23B. Thereby, the fixing device 20 can cope with both ends of the nobi size paper width larger than the maximum standard size. The power density of the end heaters 26a and 26b can be higher than the power density of the first halogen heater 23A and the second halogen heater 23B.

  Here, the amount of heat (heating output) actually output by the halogen heater and the end heater will be described. FIG. 5 is a schematic diagram showing the positional relationship between the heat generating units of the second halogen heater 23B and the end heater 26b and the state of the heating output of each heater. The upper part of FIG. 5 shows the state of the right end of the heat generating part of the second halogen heater 23B, and the lower part of FIG. 5 shows the state of the left part of the heat generating part of the end heater 26b.

  In general, the halogen heater has a reduced heating output at a longitudinal end of a heat generating portion (a portion where a filament is spirally wound). This depends on the winding density of the filament, and the lower the winding density, the more likely it is to decrease. As shown in the upper part of FIG. 5, the heating portion 40B of the second halogen heater 23B has a portion from a portion where a predetermined heating output is output at 100 (%) to a portion where a sagging of the heat amount occurs and the heating output becomes 50%. It is common to define.

  As for the end heater 26b, as shown in the lower part of FIG. 5, the heating output decreases at the longitudinal end of the heat generating portion 42b (the portion where the heat generating pattern 37 is provided). That is, at the end, 100% of the output is not output with respect to the predetermined heating output, and the heating output sags.

  For this reason, if the heating output drops at the ends of the second halogen heater 23B and the end heater 26b, good fixing is performed particularly at the end of the recording material having a larger size than the maximum standard size. May not be.

  Therefore, in the present embodiment, as shown in FIG. 5, a boundary Bh at which the heating output of the heating portion 40B of the second halogen heater 23B starts to decrease and a boundary Bc at which the heating output of the heating portion 42b of the end heater 26b starts to decrease. And is matched. In an actual apparatus, since the second halogen heater 23B and the end heater 26b are arranged apart from each other in space, the boundary Bh and Bc in the longitudinal direction coincide with each other in the projected state. The same applies to the other end heater 26a.

  Thus, in the area where the halogen heater 23B and the both end heaters 26a and 26b overlap, the heating output does not decrease and 100% of the predetermined heating output can be maintained. Therefore, good fixation can be ensured even at both ends of a recording material having a larger size than the maximum standard size.

  As described above, in the present embodiment, the boundary Bh of the second halogen heater 23B and the boundary Bc of the end heater 26b match. However, as described above, since the nip forming unit includes the heat transfer assisting member 27 having a good thermal conductivity, it is possible to level out a certain amount of heating output. For this reason, a predetermined allowable range may be provided in the arrangement of the boundary where the heating output of both end heaters 26a and 26b starts to decrease.

  Next, another temperature detecting means for detecting the temperature of the end heater 26, which is different from the temperature sensor 29 shown in FIG. 2, will be described. Using a contact-type sensor (for example, a thermistor) for detecting the temperature of the fixing belt 21 has the advantage of being inexpensive and of high accuracy. There is a possibility that minute gloss unevenness or the like may occur. For this reason, especially in a color image output device, it has become mainstream not to use a contact type sensor within a fixed size paper width. However, in the case of a recording material of the noble size, the nobby part is the ear part when forming an image up to immediately before the end of the paper of the maximum standard size, a line image called a register mark used for printing position alignment, or a small area for color confirmation. Is used as a part where solid patches are formed, and are often cut off in the end, so even if contact traces are generated by the contact-type temperature detection means, minute gloss unevenness etc. will appear as an abnormal image It can not be said. Therefore, in the present embodiment, as shown in FIG. 6, temperature detecting means 45a and 45b for detecting the temperatures of the end heaters 26a and 26b (the drawing is omitted because 45a is provided at the opposite end). The contact type thermistor is provided outside the fixing belt 21 and outside the paper width of the maximum standard size and inside the paper width of the noble size larger than the maximum standard size in the longitudinal direction of the fixing belt 21. As a result, the temperature can be detected at low cost and with high accuracy without revealing an abnormal image such as minute gloss unevenness. These temperature detecting means 45a and 45b detect the temperatures of the end heaters 26a and 26b, respectively, and the end heaters 26a and 26b are controlled independently in accordance with the respective detection states. No temperature detecting means is provided for each of the end heaters 26a and 26b, and a temperature detecting means is provided for only one end of the fixing belt 21, and both end heaters 26a and 26b are controlled in accordance with the detection state. You may do so.

  In the configuration of the above embodiment, since the end heater 26 heats the fixing belt 21 via the heat transfer assisting member 27, as shown in FIG. 7, a halogen heater 23A that heats the fixing belt 21 by direct radiant heat is used. , 23B, it takes time to raise the belt temperature. For this reason, the belt region of the A3 ridge portion is heated to a temperature at which fixing can be performed at a temperature lower than that of the second halogen heater 23B through the fixing belt 21 and the heat transfer assisting member 27, although the heating by the end heater 26 is slow. It takes time to reach. It is possible to increase the rated power of the end heater 26 in order to increase the rate of temperature rise in the belt region of the A3 nod portion. However, the power (maximum power that can be supplied) that can be used in the fixing device 20 or the image forming apparatus 1 is limited, and only by increasing the rated power of the end heater 26, the first halogen heater 23A and the second halogen It becomes necessary to lower the rated power of the heater 23B, and the warm-up time is reduced due to the oversized paper of the oversize that is used by far.

  Therefore, while increasing the rated power of the end heater 26 and controlling the power of the end heater 26 and the halogen heaters 23A and 23B, which are the main fixing heat sources, a reduction in the warm-up time is prevented.

  Table 1 shows the rated power of each heater, the maximum lighting rate in each operation state, and the maximum power at that time. The operating states "before reload" and "after reload" mean that a predetermined temperature at which printing can be performed from a normal temperature state (reload temperature: a temperature recognized in a belt area generally heated by a main heat source) such as when the power is turned on. Before and after. After the reloading and preparation for printing, a printing operation / printing operation as an operation state is performed, and the image is fixed on the paper by the fixing device.

  As shown in Table 1, the total of the rated power of each heater is 1500 W, which exceeds 200 W which is the maximum power that can be used in the fixing device 20, and the maximum lighting rate of each heater from the normal temperature state to the reload temperature is 100 W. % Cannot be heated. Therefore, until the reload temperature is reached, the maximum lighting rate of the end heater 26 is limited, and the supplied electric power, that is, the electric power consumption is suppressed. During this time, the first halogen heater 23A for heating the central region in the longitudinal direction of the fixing belt 21 and the second halogen heater 23B for heating both sides in the longitudinal direction can be fully lit (maximum lighting rate 100%), and the belt temperature can be quickly increased to the reload temperature. Can be raised. If the end heater 26 is not turned on at this time, heat moves from the belt area where the second halogen heater 23B is heating to the non-heating area corresponding to the end heater 26, and the heat is applied to the second halogen heater 23B. The temperature rise in the belt region is slower. Therefore, the end heater 26 is also turned on with reduced power (maximum lighting rate 30%) so that the sum of the input powers of the heaters falls within the range of the maximum usable power. It is desirable to suppress.

  Next, lighting control after reloading will be described. As shown in FIG. 8A, if the paper size to be printed is larger than A3, the lighting rates of the first halogen heater 23A and the second halogen heater 23B, which were 100% of the maximum lighting rate before reloading, are changed to the time after reloading. While the lighting rate of the end heater 26 is increased to 100% (90% after the job is determined). The halogen heaters 23A and 23B are at a certain temperature or higher (higher than the reload temperature), and do not require heating at a lighting rate of 100%. The lighting rate of the end heater 26 is accordingly increased in order to increase the temperature of the end nob where the temperature has not reached.

  On the other hand, if the paper size to be printed is smaller than A3, as shown in FIG. 8B, the end heater 26 is not reloaded until the predetermined temperature is reached during the period from the reload to the start of the printing operation until the predetermined temperature is reached. Heating is performed with the later setting (maximum lighting rate 100%), and heating is performed with the lighting rate lowered from the start of the printing operation (maximum lighting rate 40%). At this time, heat moves from the area corresponding to the second halogen heater 23B to the edge ridge, and follows the target temperature in the range of the specified maximum lighting rate so that the temperature at the edge of the paper passing area does not decrease. Temperature is controlled as follows.

  Next, control under operating conditions other than the warm-up operation will be described. Consider a case where the temperature of each belt region at the start of heating is on the vertical axis (time zero) of each graph on the upper side of FIG. As shown in FIG. 9A, for example, when the previous job is a small-size sheet passing operation, heating by the end heater is unnecessary, and the belt temperature is lower in the edge area than in the center area or the side area. For this reason, if a sheet exceeding A3 is passed in this state (the previous job is a small-size sheet passing), the fixing belt temperature of the nobby portion is low, and there is a possibility that a fixing failure may occur. Therefore, as shown in Table 2, the difference between the temperature of the side heated by the second halogen heater and the target temperature at the time of printing preparation, and the difference between the temperature of the side and the temperature of the edge heated by the end heater. The value is determined at the start of printing preparation, and if necessary, the lighting rate of the end heater (NOBI heater) is increased to prevent a fixing failure.

  On the other hand, for example, when the previous job is a large-size sheet feed, the second halogen heater that covers the side of the belt is also heated at a high lighting rate, and the heat transfer via the heat transfer auxiliary member is appropriate, so that FIG. As described above, the temperature of the edge portion is closer to the temperature of the central area and the side area than when the small-size sheet is passed, and the temperature can be increased with a smaller amount of heat as compared with the case of the small size. In this case (when the previous job is a large-size sheet passing and an A3-size sheet is passed), the lighting rate of the nob is reduced to give priority to the lighting of the second halogen heater, which is the side heater (at this time, the light from the side heater is turned off). Since the heat moves to the noble portion via the heat transfer assisting member, it is not necessary to increase the lighting rate of the noble portion.

  At the time of the printing operation, as shown in Table 1, the maximum lighting rate of each heater is defined and operated according to the paper size.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Bottle accommodating part 2C, 2K, 2M, 2Y Toner bottle 3 Transfer device 4C, 4K, 4M, 4Y Image forming part 5 Photoconductor 6 Charging device 7 Developing device 8 Cleaning device 9 Exposure device 10 Paper feed tray 11 Paper feed roller 12 Registration roller 13 Discharge roller 14 Discharge tray 20 Fixing device 21, 60 Fixing belt 22 Pressure roller 23A, 23B, 50A, 50B Halogen heater 24 Nip forming member 24a, 24b Recess 24c surface 25 Stay member 25A 1 member 25B 2nd member 25a Upright portion 26a, 26b End heater 27 Heat transfer assist member 27a Nip forming surface 28A, 28B, 70 Reflecting member 29 Temperature sensor 30 Intermediate transfer belt 31 Primary transfer roller 32 Secondary transfer backup roller 33 Cleaning Backup roller 34 Tension Roller 35 Belt Cleaning Device 36 Secondary Transfer Roller 37 Heating Pattern 41 Separating Member 40A, 40B, 42a, 42b Heating Part 45a, 45b Temperature Detector (Contact Thermistor)
Bc, Bh Boundary N Fixing nip P Paper α, β Irradiation angle

JP 2014-178370 A

Claims (6)

  An endless belt having flexibility, a pressing member facing the belt outside the belt, and provided inside the belt and separated from each other by a stay member; First and second radiant heat sources for heating both side portions in the direction, a nip forming member provided inside the belt and forming a fixing nip between the belt and the pressing member, and the nip forming A plurality of contact heat transfer type heat sources provided at respective ends of the member and respectively heating longitudinal ends of the belt, and the nip forming member and the plurality of contact heat transfer type heat sources facing the belt. A heat transfer assisting member that covers each surface and moves heat in the longitudinal direction of the belt, wherein the temperature of an area of the belt heated by the radiant heat source is controlled. At least one temperature detecting means for detecting the temperature of the belt and another temperature detecting means for detecting a temperature of a region of the belt heated by the heat source of the contact heat transfer type. The sum of the rated power of the heat source is larger than the maximum power that can be supplied to the fixing device, and the maximum lighting rates of the radiant heat source and the contact heat transfer heat source are determined by the radiation heat source and the contact heat transfer heat source. A fixing device, wherein the fixing device changes according to an operation state so that a sum of powers supplied to a mold heat source does not become larger than the maximum power.   The temperature detecting means for detecting the temperature of the belt area heated by the second radiant heat source and the another temperature detecting means for detecting the temperature of the belt area heated by the contact heat transfer heat source The fixing device according to claim 1, wherein a maximum lighting rate of the contact heat transfer type heat source is changed according to each of the detection states.   3. The fixing device according to claim 1, wherein the power density of the contact heat transfer type heat source is higher than the power densities of the first and second radiation type heat sources.   The contact heat transfer type heat source provided at each end of the nip forming member is controlled according to a detection state of the another temperature detection unit provided at one end of the belt. The fixing device according to claim 1, wherein:   The contact heat transfer type heat sources provided at respective ends of the nip forming member are independent of each other according to respective detection states of the different temperature detecting means provided at respective ends of the belt. The fixing device according to claim 1, wherein the fixing device is controlled by:   An image forming apparatus comprising the fixing device according to claim 1.

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