JP2015222288A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to accurately detect a temperature of a fixing nip part and to prevent deterioration of a heating rotating body due to excessive temperature rise of an end, without arranging a dedicated temperature detecting element in the fixing nip part.SOLUTION: A fixing apparatus includes: a fixing belt 52; a halogen heater 53 for heating the fixing belt; a nip forming member 54 arranged on the inside of the fixing belt 52; and a pressure roller 51 which forms a nip part N together with a circumferential part of the fixing belt 52 in cooperation with the nip forming member 54, and frictionally drives the fixing belt 52. Signal detection means 80 supplies a current to a metal member 81 in a surface part of the nip forming member 54, and detects a temperature-dependent signal which changes in accordance with the current and a temperature of the fixing belt 52 in the nip part N.

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a fixing device that fixes an image on a recording medium and an image forming apparatus including the fixing device.

  In an image forming apparatus such as a printer, a copying machine, or a facsimile, an unfixed toner image is formed on a recording medium sheet, printing paper, photosensitive paper, electrostatic recording paper by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording. Or the like, and fixed and recorded. As a fixing device for fixing an unfixed toner image, a contact heating method fixing device such as a heat roller method, a film heating method, and an electromagnetic induction heating method is widely used.

  In the image forming apparatus provided with such a fixing device, in recent years, demands for energy saving and high speed are increasing. In particular, warm-up time (time required from normal temperature to printable temperature (reload temperature) such as when the power is turned on) and first print time (after receiving a print request, printing operation is performed after printing preparations. It is desired to shorten the time until paper discharge is completed. In addition, as the productivity of image forming devices increases, the number of sheets passed per unit time increases, and the amount of heat required by the fixing device increases, so the amount of heat during fixing is insufficient at the beginning of continuous printing. It is necessary to prevent so-called temperature drop.

  Therefore, a fixing device that directly heats an endless belt having a low heat capacity without using a metal heat conductor is configured so that a good fixing property can be obtained even when mounted on a highly productive image forming apparatus. Have been proposed (see, for example, Patent Document 1).

  Also, in order to achieve both suppression of heating element cracking of the heater and shortening the startup time of the heating element, a plurality of heating patterns with different resistance temperature characteristics are attached to the heater substrate, and these heating patterns are selected. In addition, there has been proposed one that is electrically energized (see, for example, Patent Document 2).

  However, in a conventional fixing device using an endless belt having a low heat capacity, it has been difficult to maintain a uniform temperature distribution throughout the entire length of the fixing nip portion. That is, when a small-sized recording medium passes, heat is consumed for heating the recording medium (recording paper and unfixed toner on the recording medium) in the sheet passing width area, but in the non-sheet passing width area, the recording medium is consumed. The heat is not deprived. Therefore, heat accumulates on the heating roller and the belt, and the temperature of the nip portion in the non-sheet passing width region becomes higher than the temperature of the nip portion in the sheet passing width region maintained at a predetermined temperature. An increase can occur. When such an end temperature rise occurs, there is a concern that deterioration or destruction of the heating roller or the belt may occur due to reaching the heat resistant temperature of the material.

  In contrast, for example, by installing a temperature sensor in the non-sheet-passing width region, detecting the temperature rise of the heating roller in the non-sheet-passing width region, and reducing the productivity before reaching the heat resistant temperature, the end of the heating roller Temperature rise can be suppressed.

  However, the maximum temperature arrival position in the axial direction of the fixing belt due to the rise in the edge temperature (the position at which the highest temperature among the temperatures in the respective positions in the axial direction) varies depending on the size of the transfer paper to be passed. Also, temperature sensors cannot be installed for all paper sizes due to cost and installation space limitations. For this reason, if the temperature sensor is installed according to the paper size that is most frequently passed among the paper sizes where the edge temperature rise is a problem, the temperature sensor may be the maximum of the fixing belt when the edge temperature rises depending on the paper size. The temperature cannot be detected accurately.

  It is also conceivable that the maximum temperature is indirectly estimated by acquiring the temperature distribution in the axial direction at the time of continuous paper size passing in advance and grasping the temperature difference between the temperature at the temperature sensor installation position and the maximum temperature. However, the temperature difference greatly depends on the paper conveyance error and the tolerance of the heater heat distribution, and must be different for each model. Therefore, in practice, even if the indirectly predicted temperature is different from the target, the fixing belt may not be noticed and the fixing belt may exceed the heat resistant temperature.

  Further, in a fixing device using an endless belt having a low heat capacity, a temperature sensor (temperature detection element) for controlling the heater temperature is provided in the sheet passing width region, and a temperature sensor for monitoring an end temperature rise in the non-sheet passing width region. Must be installed respectively. In this case, in order to control the fixing temperature within the sheet passing width region, it is preferable to monitor the temperature of the nip portion where the toner is melted and fixed to the paper, and the edge temperature rise is monitored within the non-sheet passing width region. For this purpose, it is preferable to monitor the temperature at the nip inlet or the nip where the temperature is highest in the circumferential direction. However, due to space problems, temperature sensors are often installed at positions in the circumferential direction other than the nip portion, and there are cases where temperature sensors are displaced in the circumferential direction. Therefore, the accuracy is reduced as compared with the control using the temperature of the nip portion directly. Also in the detection of the end temperature rise, the risk of false detection increases compared to the case where the temperature of the nip portion is directly used.

  The present invention has been made to solve the above-described conventional problems, and can accurately detect the temperature of the fixing nip without arranging a dedicated temperature detecting element in the fixing nip, Providing a highly durable fixing device that can prevent deterioration of the heated rotating body due to a rise in the end temperature, and at the same time, accurately detecting the temperature of the fixing nip and improving the control accuracy in the fixing operation area. An object of the present invention is to provide an image forming apparatus having high image quality and excellent durability.

  In order to achieve the above object, the fixing device according to the present invention has an endless belt-shaped heating rotator, a heat source for heating the heating rotator, and a nip forming member disposed inside the heating rotator. The heating rotator is disposed to face the nip forming member with the heating rotator interposed therebetween, and forms a nip portion together with a part of the circumferential direction of the heating rotator in contact with the nip forming member. A pressure rotating body that rotates so as to frictionally drive the body, a conductor portion provided in the nip forming member, a current supplied to the conductor portion, and the current and the nip portion Signal detecting means for detecting a temperature-dependent signal that changes in accordance with the temperature of the heating rotator.

  With this configuration, it is possible to accurately detect the temperature during the fixing operation of the nip portion from the temperature-dependent signal without disposing a dedicated temperature detection element in the nip portion. Here, a temperature-dependent signal can be generated by using a part of the nip forming member as a conductor portion and changing its electric resistance value according to temperature. The conductor portion that generates the temperature-dependent signal may be disposed within the paper passing width region in the axial direction of the heating rotator and the pressure rotating member, or may be disposed outside the paper passing width region. It is good to arrange in the surface layer part or close to it.

  The fixing device of the present invention may include a control unit that controls the heating output of the heat source based on the temperature-dependent signal. With this configuration, the optimum fixing operation control can be executed by executing the heating output control of the heat source that affects the heating at the fixing nip portion based on the temperature-dependent signal.

  In the fixing device of the present invention, the conductor portion may include an in-region conductor portion disposed in a fixing operation region in the axial direction of the pressure rotator of the nip forming member. With this configuration, a temperature-dependent signal corresponding to the temperature of the fixing nip that contributes to the fixing operation is detected, and control accuracy such as fixing temperature control can be improved.

  In the fixing device of the present invention, the conductor portion may include an out-of-region conductor portion arranged outside the fixing operation region in the axial direction of the pressure rotator of the nip forming member.

  With this configuration, a temperature-dependent signal corresponding to the end temperature outside the fixing operation area is detected, and control for preventing an increase in the end temperature of the fixing belt and the pressure roller is possible. For example, even if the productivity of the image forming apparatus is temporarily reduced by performing fixing operation control that suppresses the end temperature rise when detecting a temperature-dependent signal indicating the end temperature rise of a predetermined level, it is excessive. Edge temperature rise can be suppressed, and safety and durability are improved.

  The fixing device of the present invention further includes a temperature detection element that detects the temperature of the thermal rotator outside the formation region of the nip portion in the circumferential direction of the heating rotator, and the detected temperature of the temperature detection element and the temperature The heating output of the heat source may be controlled based on the dependence signal.

  With this configuration, an error in the detection temperature of the temperature detection element installed outside the formation region of the fixing nip portion in the circumferential direction is corrected based on the temperature-dependent signal, or an abnormality in the detection temperature of the temperature detection element is converted into the temperature-dependent signal. Based on the detection.

  In the fixing device according to the aspect of the invention, the temperature detection element may include an in-region detection element arranged in a fixing operation region in the axial direction of the pressure rotator of the nip forming member. Good.

  With this configuration, it is possible to correct the detection temperature of the temperature detection element that generates a detection error because it is arranged outside the formation region of the fixing nip portion in the circumferential direction based on the temperature-dependent signal, and the axis of the pressure rotator Control accuracy such as fixing temperature control within the fixing operation region in the direction can be improved.

  In the fixing device according to the aspect of the invention, the temperature detection element may include an out-of-region detection element disposed outside the fixing operation region in the axial direction of the pressure rotator of the nip forming member. Good.

  With this configuration, the end temperature of the nip forming member outside the fixing operation area is detected by the temperature detection element, and control is performed to prevent an increase in the end temperature of the fixing belt or the pressure roller based on the detected temperature. It becomes possible. Further, if the detected temperature of the temperature detecting element is used together with the temperature-dependent signal outside the fixing operation area, the maximum temperature when the end temperature rises can be detected with high accuracy.

  An image forming apparatus according to the present invention includes a fixing device having any one of the above-described configurations, and an image forming unit that supports an image formed of an unfixed developer on a recording sheet, and supports the image. The recording sheet is passed through the fixing device to fix the image on the recording sheet.

  With this configuration, it is possible to accurately detect the temperature of the fixing nip without arranging a dedicated temperature detection element in the nip of the fixing device, and to prevent deterioration of the heating rotator due to an excessive end temperature rise. it can. As a result, the image forming apparatus has high image quality and excellent durability.

  The in-region conductor portion and the out-of-region conductor portion of the nip forming member can be effectively formed by inserting a metal member having a high resistance temperature coefficient whose resistance value is temperature-dependent into the nip forming member. In addition, a temperature-dependent signal can be detected by extending a metal member to an arbitrary section including a position where the temperature is desired to be measured in the axial direction of the heating rotator and passing a current through the metal member.

  According to the present invention, it is possible to accurately detect the temperature of the fixing nip portion without disposing a dedicated temperature detecting element in the fixing nip portion, and to prevent the heating rotating body from being deteriorated due to an excessive rise in the end portion temperature. Providing a highly durable fixing device that can be used, and also providing an image forming device with high image quality and durability that can accurately detect the temperature of the fixing nip and increase the control accuracy in the fixing operation area. can do.

1 is a schematic configuration diagram of an image forming apparatus including a fixing device according to a first embodiment of the present invention. 1 is a schematic configuration diagram of a main part of a fixing device according to a first embodiment of the present invention. 1 is an enlarged cross-sectional view of a main part of a fixing device according to a first embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view of a main part of a fixing device according to a second embodiment of the present invention. It is explanatory drawing of the edge part temperature detection system in the fixing device which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
1 to 3 show a fixing device and an image forming apparatus including the fixing device according to the first embodiment of the present invention.

  First, the configuration will be described.

  An image forming apparatus 1 according to the present embodiment is a so-called tandem color image forming apparatus that performs primary transfer and secondary transfer, for example, a color laser printer. Part 30, transfer part 40, and fixing part 50. The image forming apparatus 1 also includes a control unit 100 that controls the operations of the paper feeding unit 20, the image forming unit 30, the transfer unit 40, and the fixing unit 50, and the control unit 100 is also included in the image forming apparatus main body 10. It is stored.

  The paper feed unit 20 has at least one stage of paper feed cassette 21 that stores a plurality of transfer sheets Sp that are cut sheet-like printing paper in a stacked state. Sheet-size transfer paper Sp is set in the vertical or horizontal paper feeding direction. Here, the recording medium such as the transfer paper Sp includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper. Although not shown in detail, the image forming apparatus 1 is provided with a manual paper feed mechanism.

  The paper feeding unit 20 further includes a plurality of paper feeding rollers 22 positioned on the uppermost layer side of the transfer paper Sp stored in the paper feeding cassette 21 and a plurality of pairs of registration rollers 23 arranged at predetermined positions in the paper feeding direction. And have. The paper feed roller 22 picks up the uppermost transfer paper Sp in the paper feed cassette 21 and conveys it to the registration roller 23 side. The registration roller 23 conveys the transfer sheet Sp to the transfer unit 40 in accordance with the operating states of the image forming unit 30 and the transfer unit 40, and can control the conveyance timing and conveyance speed of the transfer sheet Sp ( Details will be described later).

  The image forming unit 30 includes an exposure unit 31 and four image forming units 32Y, 32M, 32C, and 32K arranged in parallel from the right side to the left side in FIG. The exposure unit 31 is disposed on the lower side with respect to the image forming units 32Y, 32M, 32C, and 32K.

  The exposure unit 31 forms an image of each color using light for exposure (optical writing) of each color, for example, laser beams La, Lb, Lc, and Ld, based on an image read by an image reading device (not shown) and input image data. It is generated as the process progresses. The exposure unit 31 is composed of a laser beam scanning device using a laser diode, for example. Of course, a light emitting element such as an LED (Light Emitting Diode) may be used.

  Specifically, the exposure unit 31 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like (no symbol), and the photoreceptors of the image forming units 32Y, 32M, 32C, and 32K based on image data. The drum 33 can be irradiated with laser light for optical writing.

  The image forming units 32Y, 32M, 32C, and 32K contain developers of different colors among yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. Except for the above, the configuration is the same.

  Each of the image forming units 32Y, 32M, 32C, and 32K includes a photosensitive drum 33, a developing unit 34, a charger 35, a cleaning device 36, and the like. The photosensitive drum 33 is a drum-like one. After the surface is uniformly charged by the charger 35, the surface is irradiated with laser light for optical writing from the exposure unit 31 to thereby form an electrostatic latent image. Can be formed.

  In each of the image forming units 32Y, 32M, 32C, and 32K, when the photosensitive drum 33 of each color is exposed by light writing of each color from the exposure unit 31, an electrostatic latent image of each color is formed. The electrostatic latent image formed on the photosensitive drum 33 is developed when it reaches the developing nip portion between the photosensitive drum 33 and the developing unit 34. That is, the thin layered toner on the developing roller 34a is transferred onto the electrostatic latent image (unexposed portion or exposed portion) formed on the photosensitive drum 33, and is visualized as a toner image. .

  The image forming unit 30 performs the optical writing process of each color by the exposure unit 31 and the electrophotographic process of each color in the four image forming units 32Y, 32M, 32C, and 32K by superimposing toner images for color mixing and the transfer unit 40. This is executed according to the order of image transfer.

  The cleaning device 36 is a known device that can scrape and remove the transfer residual toner on the photosensitive drum 33 when the photosensitive drum 33 rotates.

  The transfer unit 40 is disposed above the image forming units 32Y, 32M, 32C, and 32K.

  The transfer unit 40 includes four primary transfer rollers 41a, 41b, 41c, 41d and an endless belt-shaped intermediate transfer belt 42 (transfer body) as primary transfer means. The transfer unit 40 also includes a cleaning backup roller 43 that supports the intermediate transfer belt 42, a secondary transfer backup roller 44, and a tension roller 45. The transfer unit 40 further includes a secondary transfer roller 47 and a belt cleaning device 48 as secondary transfer means.

  The intermediate transfer belt 42 is stretched by a secondary transfer backup roller 44, a cleaning backup roller 43, and a tension roller 45 so as to be able to run around (rotate) and with a predetermined tension. Further, the secondary transfer backup roller 44 or the cleaning backup roller 43 is rotationally driven, so that the intermediate transfer belt 42 runs in the direction of arrow H in FIG.

  The four primary transfer rollers 41 a, 41 b, 41 c, and 41 d form a primary transfer nip by sandwiching the intermediate transfer belt 42 between each of the photosensitive drums 33. A power source (not shown) is connected to each primary transfer roller 41a, 41b, 41c, 41d, and a predetermined DC voltage (DC) and / or AC voltage (AC) is supplied to each primary transfer roller 41a, 41b, 41c and 41d are applied.

  The secondary transfer roller 47 sandwiches the intermediate transfer belt 42 between the secondary transfer backup roller 44 and forms a secondary transfer nip. Similarly to the primary transfer rollers 41a, 41b, 41c, and 41d, a power source (not shown) is also connected to the secondary transfer roller 47, and a predetermined DC voltage (DC) and / or AC voltage (AC) is supplied to the secondary transfer roller 47. It is applied to the transfer roller 47.

  The belt cleaning device 48 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 42. A waste toner transfer hose (not shown) extending from the belt cleaning device 48 is connected to an entrance of a waste toner container (not shown).

  A bottle container 60 is provided in the upper part of the printer main body, and four toner bottles 62Y, 62M, 62C, and 62K containing replenishing toner are detachably mounted on the bottle container 60, respectively. . A replenishment path (not shown) is provided between the toner bottles 62Y, 62M, 62C and 62K and the developing units 34 of the image forming units 32Y, 32M, 32C and 32K. The toner is replenished from the toner bottles 62Y, 62M, 62C, and 62K to the developing units 34 through the replenishment path.

  A fixing unit 50 for fixing the unfixed image transferred to the transfer paper Sp is disposed downstream of the position of the secondary transfer roller 47 in the paper transport direction.

  As shown in FIG. 2, the fixing unit 50 includes a pressure roller 51, a fixing belt 52, a halogen heater 53, a heat insulating nip forming member 54, a stay 55, a reflecting member 56, a temperature sensor 57, and a separating member 58. Furthermore, it is configured to include a pressing means (not shown).

  The pressure roller 51 is a counter rotating body that is provided so as to be rotatable facing the fixing belt 52. The fixing belt 52 is a fixing rotating body that rotates while being heated to a temperature at which a fixing operation is possible, and the halogen heater 53 is a heating source (heat source) that heats the fixing belt 52. The nip forming member 54 is disposed inside the fixing belt 52 and supported by a stay 55 as a support member. The reflection member 56 reflects light emitted from the halogen heater 53 to the fixing belt 52.

  Specifically, the pressure roller 51 includes a cored bar 51a, an elastic layer 51b made of foamable silicone rubber or fluororubber provided on the surface of the cored bar 51a, and a PFA provided on the surface of the elastic layer 51b. Alternatively, a release layer 51c made of PTFE or the like is used.

  The pressure roller 51 is pressed toward the fixing belt 52 by the pressing means, and is pressed against the nip forming member 54 side with a predetermined pressure via the fixing belt 52. Then, at the location where the pressure roller 51 and the fixing belt 52 are in pressure contact, the elastic layer 51b of the pressure roller 51 is crushed within the elastic range so that a predetermined width in the vertical direction (circumferential direction) in FIG. A nip portion N (fixing nip portion) is formed.

  The pressure roller 51 is also rotationally driven by a drive source such as a motor (not shown) provided in the printer main body. When the pressure roller 51 is rotationally driven, the fixing belt 52 is driven to rotate by being frictionally driven by the pressure roller 51 in the nip portion N.

  In the present embodiment, the pressure roller 51 is a solid roller, but may be a hollow roller. In this case, a heating source such as a halogen heater may be provided inside the pressure roller 51. . Further, when the elastic layer 51b is not provided, the heat capacity is reduced, but when the unfixed toner is crushed and fixed, minute unevenness on the belt surface is transferred to the image, and uneven glossiness may occur in the solid image portion. Therefore, it is preferable to provide the elastic layer 51b having a thickness of 100 μm or more. The elastic layer 51b may be solid rubber, but when there is no heating source inside the pressure roller 51, sponge rubber may be used. Sponge rubber has higher heat insulating properties, and the fixing belt 52 is less likely to lose heat. Further, the fixing rotator such as the fixing belt 52 and the opposing rotator such as the pressure roller 51 may be configured not to press each other but to simply contact without pressing.

  The fixing belt 52 is composed of a thin and flexible endless belt member (including a film), and is composed of an inner peripheral base layer and an outer peripheral release layer. The inner peripheral base layer is made of a metal material such as nickel or SUS or a resin material such as polyimide (PI). The release layer on the outer peripheral side is formed of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or the like. Further, 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.

  At least one, for example, a plurality of halogen heaters 53 are provided in parallel with each other with both ends fixed to a side plate (not shown) of the fixing unit 50.

  Each halogen heater 53 is configured so that its output is controlled by a power supply unit provided in the printer body so as to emit infrared light and generate radiant heat. The output control is based on the temperature detected by the temperature sensor 57. Done. By controlling the output of the halogen heater 53, the temperature of the fixing belt 52 (fixing temperature) can be set to a desired temperature. As a heating source for heating the fixing belt 52, in addition to the halogen heater, an IH (induction heating) type heater, a resistance heating element, a carbon heater, or the like may be used.

  In the present embodiment, the left portion of the fixing belt 52 in FIG. 2 can be directly heated by the halogen heater 53 (direct heating method). That is, nothing is interposed between the halogen heater 53 and the left portion of the fixing belt 52 in FIG. 2, and heat from the halogen heater 53 is directly applied to the fixing belt 52 at that portion.

  Further, in order to reduce the heat capacity of the fixing belt 52, the fixing belt 52 is made thinner and smaller in diameter. Specifically, the thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 52 are set in a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the total thickness is set. It is set to 1 mm or less. The diameter of the fixing belt 52 is set to 20 to 40 mm, for example. In order to further reduce the heat capacity, the thickness of the entire fixing belt 52 is desirably set to 0.2 mm or less, for example, and more desirably 0.16 mm or less. Further, the diameter of the fixing belt 52 is desirably set to, for example, 30 mm or less.

  The nip forming member 54 is a heat-insulating strip plate member disposed such that its longitudinal direction extends in parallel to the axial direction of the fixing belt 52 and the axial direction of the pressure roller 51, and the posture thereof is maintained by the stay 55. Has been fixed. As a result, the bending of the nip forming member 54 due to the pressure from the pressure roller 51 is suppressed, and a uniform nip width is obtained in the entire axial direction of the pressure roller 51 and the fixing belt 52. The stay 55 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the bending prevention function of the nip forming member 54. However, the stay 55 may be made of resin. .

  The nip forming member 54 is a heat resistant member having a heat resistant temperature of, for example, 200 ° C. or higher. Accordingly, it is possible to prevent the nip forming member 54 from being deformed due to heat in the toner fixing temperature range, to ensure a stable state of the nip portion N, and to stabilize the output image quality. For the nip forming member 54, a general heat resistant resin such as polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN) or the like can be used. Further, as a general heat resistant resin, polyamide imide (PAI), polyether ether ketone (PEEK), or the like can be used.

  Further, the nip forming member 54 has a low friction sheet (not shown) on the surface portion that contacts the fixing belt 52. When the fixing belt 52 rotates, the fixing belt 52 slides with respect to the low friction sheet, so that the driving torque generated in the fixing belt 52 is reduced and the load due to the frictional force on the fixing belt 52 is reduced. It is like that.

  The reflecting member 56 is disposed between the stay 55 and the halogen heater 53 and is fixed to the stay 55. The reflecting member 56 is made of a metal material having a high melting point that can withstand radiation heating from the halogen heater 53, and reflects infrared light emitted from the halogen heater 53 toward the stay 55 toward the fixing belt 52. It has a reflecting surface 56a. As a result, the amount of infrared light (radiant heat) irradiated to the fixing belt 52 can be increased, and the fixing belt 52 can be efficiently heated. Further, since it is possible to suppress the radiant heat from the halogen heater 53 from being transmitted to the stay 55 and the like, energy saving can be achieved.

  Instead of providing the reflecting member 56 as in the present embodiment, the surface 55a (see FIG. 3) of the stay 55 on the halogen heater 53 side may be subjected to a mirror surface treatment such as polishing or painting as a reflecting surface. In that case, the reflectance of the reflecting surface of the reflecting member 56 or the stay 55 is desirably 90% or more.

  However, the shape and material of the stay 55 cannot be freely selected in order to ensure its strength. Accordingly, when the reflecting member 56 is provided separately from the stay 55 as in the present embodiment, the weight of the selection of the shape and material is increased, and the functions of the stay 55 and the reflecting member 56 can be enhanced. Further, by providing the reflecting member 56 between the halogen heater 53 and the stay 55, the position of the reflecting member 56 with respect to the halogen heater 53 is reduced, so that the fixing belt 52 can be efficiently heated.

  In FIG. 2, for the convenience of drawing, the reflecting surface 56 a of the reflecting member 56 is formed in a concentric shape centering on the axis of the halogen heater 53 at each cross-sectional position with respect to the halogen heater 53. However, in this case, the light emitted from the halogen heater 53 is reflected toward the halogen heater 53, and the heating efficiency is reduced accordingly. Therefore, it is preferable to improve the heating efficiency by the reflected light by setting a part or all of the reflective surface 56a to reflect the light emitted from the halogen heater 53 toward the fixing belt 52 side.

  In this embodiment, the diameter of the pressure roller 51 is set to 20 to 40 mm, for example, so that the diameter of the fixing belt 52 and the diameter of the pressure roller 51 are substantially equal. However, the configuration is limited to this configuration. is not. For example, the fixing belt 52 may be formed so that the diameter thereof is smaller than the diameter of the pressure roller 51. In that case, since the curvature of the fixing belt 52 at the exit side of the nip portion N is smaller than the curvature of the pressure roller 51, the recording medium discharged from the nip portion N is easily separated from the fixing belt 52.

  The temperature sensor 57 is a temperature detection element that detects the temperature of the fixing belt 52 in a rotation section other than the nip portion N in the circumferential direction of the fixing belt 52. The temperature sensor 57 is within the maximum sheet passing width region in the axial direction of the pressure roller 51 of the nip forming member 54 (fixing operation region; hereinafter, also referred to as a sheet passing width region in the axial direction of the nip forming member 54). The in-area sensing element is provided. The temperature detected by the temperature sensor 57 is taken into the control unit 100.

  The separation member 58 contacts the outer peripheral surface of the fixing belt 52 in the vicinity of the nip portion N and downstream of the nip portion N, and bends the fixing belt 52 away from the transfer paper Sp, thereby fixing the fixing belt 52. And the transfer paper Sp that has passed through the nip portion N are separated.

  A pair of paper discharge rollers 71 for discharging the paper to the outside of the apparatus is provided downstream of the fixing unit 50 in the paper conveyance direction. Further, a paper discharge tray 72 for stocking paper discharged outside the apparatus is provided on the upper surface of the image forming apparatus main body 10.

  On the other hand, in the image forming apparatus main body 10, the transfer paper Sp is passed from the paper feed cassette 21 through the secondary transfer nip between the secondary transfer roller 47 and the secondary transfer backup roller 44 to transfer the transfer paper after the secondary transfer. A transport path 11 for discharging Sp out of the apparatus through the fixing unit 50 is provided. Along the conveyance path 11, the paper feed roller 22, the registration roller 23, the secondary transfer roller 47, the fixing unit 50, and the paper discharge roller 71 are sequentially arranged.

  The control unit 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. In the ROM, various control programs and system data for image formation of the image forming apparatus 1 are stored. The control unit 100 controls the paper feeding unit 20, the image forming unit 30, the transfer unit 40, and the fixing unit 50 to operate in a predetermined operation sequence in response to a print request from a device (not shown), for example. Under the control of the control unit 100, the toner image formed by the exposure, development and transfer in the image forming unit 30 is transferred to the transfer paper Sp fed from the paper feeding unit 20 by the transfer unit 40 and fixed. By being heated and pressurized by the unit 50, a print output is made.

  By the way, in the present embodiment, the effect of the fixing temperature control within the sheet passing width region (sheet passing portion) of the fixing unit 50 and the fixing belt 52 and the pressurization outside the sheet passing width region (non-sheet passing portion) of the fixing unit 50 are described. A configuration that increases the detection accuracy of the end temperature of the roller 51 is employed.

  That is, the fixing unit 50 can detect the temperature of the fixing belt 52 at the nip N, which is a contact area between the nip forming member 54 and the fixing belt 52. Further, by directly detecting the temperature of the nip portion N, optimal control for the fixing operation at the sheet passing portion of the fixing portion 50 is executed, and the safety at the non-sheet passing portion of the fixing portion 50 can be improved. To be able to.

  Specifically, the surface layer portion on the front surface side of the nip forming member 54 that contacts a part of the circumferential direction (nip forming region) of the fixing belt 52 has a thin plate shape extending in the longitudinal direction of the nip forming member 54 or A film-like metal member 81 (conductor portion) is provided. That is, the nip forming member 54 is configured by integrally laminating two or more layers including a metal member 81 that is a surface layer portion and a heat-resistant member 82 that backs and supports the metal member 81.

  Further, as shown in FIG. 3, a temperature detection circuit 80 (signal detection means) including a power source 83 and a current detection unit 84 is wired to the metal member 81. The power source 83 is a DC power source having a positive terminal connected to a predetermined position in the longitudinal direction of the metal member 81, for example, one end in the longitudinal direction. The current detector 84 is provided so as to be interposed between a specific position in the longitudinal direction of the metal member 81, for example, the other end in the longitudinal direction, and the negative terminal of the power supply 83. That is, the power source 83, the metal member 81, and the current detection unit 84 are connected in series.

  The temperature detection circuit 80 can apply a voltage from the power source 83 to the metal member 81 that is the surface layer portion of the nip forming member 54, and supply a current corresponding to the electrical resistance to the metal member 81. The temperature detection circuit 80 detects the current as a temperature-dependent signal that changes according to the voltage of the power supply 83 and the temperature of the fixing belt 52 (fixing heating temperature) in the nip portion N by the current detection unit 84. ing.

  Further, the metal member 81 is located outside the fixing operation area in the axial direction of the pressure roller 51 in the nip forming member 54 (outside of the maximum sheet passing width area), and a temperature-dependent signal when supplying current from the power supply 83. Are formed by one and the other outer region conductor portions 91 and 92. Here, the one and other out-of-region conductor portions 91 and 92 are provided on both end sides in the longitudinal direction of the nip forming member 54, but the out-of-region conductor portion referred to in the present invention is at least of the nip forming member 54. It may be provided on one end side. Further, the one and the other outer region conductor portions 91 and 92 may be connected in series to the temperature detection circuit 80 or may be connected to the corresponding temperature detection circuit 80.

  As the one and other out-of-region conductor portions 91 and 92 of the metal member 81, a metal material having a high temperature dependency of the metal resistivity (high temperature coefficient), for example, copper or the like may be used. Table 1 below shows the relationship (reference value) between the metal low efficiency and the temperature coefficient of each metal.

ここで、金属低効率については、摂氏０度、２０度、１００度の値（単位：１０ｎΩｍ）をそれぞれ示し、温度係数については、これらの温度での値の平均値を示している。

Here, for metal low efficiency, values of 0 ° C., 20 ° C., and 100 ° C. (unit: 10 nΩm) are shown, and for the temperature coefficient, an average value of values at these temperatures is shown.

  Next, a temperature control method of the fixing belt 52 in the sheet passing width region (sheet passing portion) in the fixing unit 50 of the image forming apparatus 1 of the present embodiment will be described.

  Based on the temperature of the fixing belt 52 detected by the temperature sensor 57 and the temperature-dependent signal detected by the temperature detection circuit 80, the control unit 100 determines the number of operations (number of processed sheets) of the fixing unit 50 per predetermined unit time. At least one of the heating output of the halogen heater 53 is controlled. Here, the number of operations of the fixing unit 50 and the heating output of the halogen heater 53 can vary depending on the number of printed outputs per unit time (productivity).

  The control unit 100, for example, based on the temperature deviation between the temperature of the fixing belt 52 at the nip N in the sheet passing width region detected by the temperature sensor 57 and the target control temperature of the fixing belt 52. The temperature of 52 is controlled by the heating output control of the halogen heater 53. In this case, the control unit 100 controls the energization time (duty ratio) per unit time of the halogen heater 53 via a fixing temperature controller (not shown) so that the detected temperature of the temperature sensor 57 matches the target control temperature. The heating output of the halogen heater 53 is controlled.

  The control unit 100 executes such fixing temperature control, and on the other hand, based on the temperature-dependent signal detected by the temperature detection circuit 80, the end temperature of the fixing belt 52 rises at both ends in the longitudinal direction of the nip forming member 54. It has a function to check for the presence or absence. That is, the control unit 100 has a control program and a working memory area for checking the end temperature rise.

  The control unit 100 further determines the number of operations of the fixing unit 50 per predetermined unit time (the number of processed sheets) and the halogen heater 53 based on the temperature of the fixing belt 52 outside the sheet passing width region detected by the temperature detection circuit 80. The control which restrict | limits at least one among the heating outputs of is performed.

  For example, when the temperature of the fixing belt 52 outside the sheet passing width region detected by the temperature detection circuit 80 reaches a predetermined temperature that significantly exceeds the target control temperature, the control unit 100 fixes the fixing unit per predetermined unit time. Reduce productivity corresponding to 50 operations. That is, the number of processed sheets such as the number of prints per unit time is reduced, and the number of operations of the fixing unit 50 per unit time corresponding to the number of processed sheets is reduced, so that the heating output of the halogen heater 53 that increases or decreases in accordance with the number of processed sheets. Reduce.

  In this case, by reducing the productivity of the image forming apparatus 1, the duty for energizing the halogen heater 53 per unit time is lowered, and the end temperature rise in the fixing unit 50 is mitigated.

  In the present embodiment, the temperature detection circuit 80 allows the maximum temperature on the entire circumference of the fixing belt 52 on the outer side of the maximum sheet passing width region via the one and other region outer conductor portions 91 and 92 of the metal member 81. The temperature of the nip portion N can be acquired. As a result, the control unit 100 can detect the end portion temperature with higher accuracy than the case of acquiring the temperature at a portion other than the nip portion N, and can reduce the productivity at an appropriate timing.

  Next, the basic operation of the image forming apparatus 1 will be described.

  When the image forming operation is started, the respective photoconductive drums 33 in the respective image forming units 32Y, 32M, 32C, and 32K are rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductive drum 33 is charged. The device 35 is uniformly charged to a predetermined polarity. The surface of each charged photoconductive drum 33 is irradiated with laser light from the exposure unit 31 to form an electrostatic latent image on the surface of each photoconductive drum 33. At this time, the image information to be exposed on each photosensitive drum 33 is single-color image information obtained by separating a desired full-color image into yellow, magenta, cyan, and black color information. In this way, the electrostatic latent images formed on the respective photosensitive drums 33 are supplied with toner by the developing units 34, whereby the electrostatic latent images are visualized (visualized) as toner images. The

  When the image forming operation is started, the secondary transfer backup roller 44 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 42 is caused to run in the direction indicated by the arrow in the figure. The primary transfer rollers 41a, 41b, 41c, and 41d are applied with a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 41a, 41b, 41c, 41d and each photosensitive drum 33.

  Thereafter, when each color toner image on the photoconductive drum 33 reaches the primary transfer nip as the photoconductive drums 33 rotate, the transfer electric field formed in the primary transfer nip causes a transfer on each photoconductive drum 33. The toner images are sequentially superimposed and transferred onto the intermediate transfer belt 42. Thus, a full-color toner image is carried on the surface of the intermediate transfer belt 42. Further, the toner on each photosensitive drum 33 that could not be transferred to the intermediate transfer belt 42 is removed by the cleaning device 36. Thereafter, the surface of each photosensitive drum 33 is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

  In the lower part of the image forming apparatus, the paper feed roller 22 starts to rotate, and the transfer paper Sp is sent out from the paper feed cassette 21 to the transport path 11. The transfer paper Sp sent to the transport path 11 is timed by the registration roller 23 and sent to the secondary transfer nip between the secondary transfer roller 47 and the secondary transfer backup roller 44. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 42 is applied to the secondary transfer roller 47, thereby forming a transfer electric field in the secondary transfer nip.

  Thereafter, when the toner image on the intermediate transfer belt 42 reaches the secondary transfer nip as the intermediate transfer belt 42 rotates, the transfer electric field formed in the secondary transfer nip causes a transfer on the intermediate transfer belt 42. The toner images are collectively transferred onto the transfer paper Sp. At this time, the residual toner on the intermediate transfer belt 42 that could not be transferred onto the transfer paper Sp is removed by the belt cleaning device 48, and the removed toner is conveyed to a waste toner container (not shown) and collected.

  Thereafter, the transfer paper Sp is conveyed to the fixing unit 50, and the toner image on the transfer paper Sp is fixed to the transfer paper Sp by the fixing unit 50. Then, the transfer paper Sp is discharged out of the apparatus by the paper discharge roller 71 and stocked on the paper discharge tray 72.

  The above is the image forming operation when a full color image is formed. A single color image can be formed by using any one of the four image forming units 32Y, 32M, 32C, and 32K. A two-color or three-color image can also be formed using the image forming unit.

  Next, the operation will be described.

  In the image forming apparatus 1 of the present embodiment configured as described above, a current flows through the metal member 81 of the nip forming member 54 in the fixing unit 50 and changes according to the current and the temperature of the fixing belt 52 in the nip N. The temperature dependent signal is detected by the temperature detection circuit 80. Therefore, it is possible to accurately detect the temperature during the fixing operation of the nip portion N from the temperature-dependent signal without disposing a dedicated temperature detection element in the nip portion N.

  In addition, since the control unit 100 that controls the heating output of the halogen heater 53 based on the temperature-dependent signal is included, the heating output control of the halogen heater 53 that affects the heating at the nip portion N is executed based on the temperature-dependent signal. Thus, optimal fixing operation control can be executed.

  In the present embodiment, out-of-region conductor portions 91 and 92 that generate a temperature-dependent signal when current is supplied are disposed outside the fixing operation region in the axial direction of the fixing belt 52 of the nip forming member 54. . Accordingly, a temperature-dependent signal corresponding to the end temperature outside the fixing operation area of the fixing belt 52 is detected, and control for preventing an increase in the end temperature of the fixing belt 52 and the pressure roller 51 is possible. Become.

  For example, when a temperature-dependent signal indicating an end temperature rise of a predetermined level is detected, fixing operation control for suppressing the end temperature rise is executed. Thereby, even if the productivity of the image forming apparatus 1 temporarily decreases, an excessive increase in the end temperature can be suppressed, and the safety and durability of the fixing unit 50 are improved.

  Further, in the present embodiment, based on the detection temperature of the temperature sensor 57 that detects the temperature of the fixing belt 52 outside the formation region of the nip portion N in the circumferential direction of the fixing belt 52 and the temperature-dependent signal from the temperature detection circuit 80. Thus, the heating output of the halogen heater 53 is controlled. In addition, in the present embodiment, the temperature sensor 57 is an in-region detection element disposed in the fixing operation region in the axial direction of the pressure roller 51 in the nip forming member 54.

  Therefore, for example, the relationship between the two detection values in a state in which the end portion temperature does not increase is mapped in advance, and the temperature sensor installed outside the formation region of the nip portion N in the circumferential direction of the fixing belt 52. The detected temperature error 57 can be corrected based on the temperature-dependent signal. As a result, it is possible to improve control accuracy such as fixing temperature control within the fixing operation region in the axial direction of the pressure roller 51. Furthermore, it is possible to detect an abnormality in the detected temperature of the temperature sensor 57 based on the temperature-dependent signal from the temperature detection circuit 80.

  As described above, in this embodiment, the temperature of the nip portion N can be accurately detected without installing a temperature sensor in the nip portion N, and the temperature at the end portion in the axial direction of the fixing belt 52 can be accurately detected. it can. Therefore, it is possible to provide the image forming apparatus 1 including the highly durable fixing unit 50 that can prevent the deterioration of the fixing belt 52 due to an excessive increase in the end temperature. In addition, it is possible to provide the image forming apparatus 1 with high image quality and excellent durability that can detect the temperature of the nip portion N with high accuracy and increase the control accuracy in the fixing operation region.

(Second Embodiment)
FIG. 4 shows a second embodiment of the fixing device and the image device according to the present invention.

  Each embodiment described below has an overall configuration similar to that of the first embodiment described above. Therefore, components that are the same as or similar to those in the first embodiment are denoted by reference numerals of corresponding components in FIGS. 1 to 3, and differences from the first embodiment will be described below.

  In the second embodiment shown in FIG. 4, in addition to the one and other outer conductor portions 91 and 92 of the metal member 81, in the fixing operation region in the axial direction of the nip forming member 54, that is, within the maximum sheet passing width region. An in-region conductor portion 93 (metal member, conductor portion) is disposed on the side.

  The in-region conductor portion 93 is a metal member having a high resistance temperature coefficient, and an additional temperature detection circuit 80A (signal detection means) including a power source 85 and a current detection portion 86 is wired to the in-region conductor portion 93. ing. The power source 85 is a DC power source having a positive terminal connected to a predetermined position in the longitudinal direction of the in-region conductor portion 93, for example, one end portion in the longitudinal direction. The current detection unit 84 is provided so as to be interposed between a specific position in the longitudinal direction of the in-region conductor portion 93, for example, the other end in the longitudinal direction, and the negative terminal of the power supply 85.

  The additional temperature detection circuit 80A applies a voltage from the power supply 85 to the in-region conductor portion 93 which is the surface layer portion of the nip forming member 54 in the sheet passing width region, and supplies a current corresponding to the electric resistance to the in-region conductor portion 93. Can be supplied. The temperature detection circuit 80A detects the current as a temperature-dependent signal that changes according to the voltage of the power supply 85 and the temperature of the fixing belt 52 at the nip N in the sheet passing width region by the current detection unit 86. It has become.

  Other configurations are the same as those of the image forming apparatus 1 of the first embodiment.

  In this embodiment, the same effect as that of the first embodiment can be expected.

  In addition, in the present embodiment, since an additional temperature detection circuit 80A is provided in the sheet passing width region in addition to the temperature sensor 57 that is the in-region detection element, an error in the detection temperature of the temperature sensor 57 is used as a temperature-dependent signal. Based on this, it can be corrected accurately. That is, a temperature-dependent signal corresponding to the temperature of the nip N that contributes to the fixing operation in the fixing unit 50 is detected, and the control accuracy such as fixing temperature control by the control unit 100 can be improved.

  For example, a map or the like that associates the detected values of the temperature-dependent signals of the temperature sensor 57 and the additional temperature detection circuit 80A can be created, and the temperature of the fixing belt 52 at the nip portion N can be detected with higher accuracy. As a result, optimal fixing temperature control in the fixing unit 50 is possible, and the image forming apparatus 1 having high image quality and excellent durability can be provided.

(Third embodiment)
FIG. 5 shows a third embodiment of the fixing device and the image device according to the present invention.

  Here, FIG. 5A is a cross-sectional view of the axial end portion of the fixing device according to the third embodiment of the present invention, FIG. 5B is an explanatory view of the end temperature detection method, and FIG. (C) is explanatory drawing of arrangement | positioning of a metal member.

  In the third embodiment, on the outer side of the maximum sheet passing width region of the fixing unit 50, outside the sheet passing width region (non-sheet passing portion) in the axial direction of the nip forming member 54, a temperature sensor as an out-of-region detecting element 97 is provided. In the fixing unit 50 of the image forming apparatus 1 of the present embodiment, the temperature sensor 97 detects the temperature (edge temperature) of the fixing belt 52 in the non-sheet passing portion.

  Depending on the size of the transfer paper Sp to be passed, the installation position of the temperature sensor 97 is not necessarily the maximum temperature. Therefore, the temperature distribution in the axial direction during continuous passing of the transfer paper Sp of each size is obtained by a prior experiment or the like, and the temperature difference between the detected temperature and the maximum temperature at the installation position of the temperature sensor 97 is grasped. Thus, a method of indirectly detecting the maximum temperature is conceivable.

  However, although the maximum temperature is predicted based on the detected temperature value of the temperature sensor 97, the actual maximum temperature (the temperature of the fixing belt at the position where the maximum temperature is reached) as shown in FIG. The maximum temperature assumed may be low. In that case, there is a concern that the actual maximum temperature may exceed the heat resistance temperature of the fixing belt 52.

  In the present embodiment, apart from the temperature sensor 97, one and the other outside conductor portions 91 and 92 (which may be either one) disposed outside the sheet passing width region are provided, and the temperature detection circuit 80 causes the outside of the sheet passing width region. A temperature-dependent signal (current) corresponding to the temperature of the nip portion N is detected. Then, in addition to the temperature detected by the temperature sensor 97, the maximum temperature value of the non-sheet passing portion that the temperature sensor 97 indirectly predicts from the outside of the nip portion N using the temperature-dependent signal from the temperature detection circuit 80 is supplementarily used. It can be determined based on the temperature-dependent signal that it has deviated from the target value. As a result, when the predicted value of the maximum temperature of the non-sheet passing portion deviates from the target, the risk of exceeding the heat resistance temperature of the fixing belt 52 can be effectively avoided by reducing the productivity early.

  That is, the end temperature can be detected with higher accuracy than when only the temperature other than the nip portion N is detected by the temperature sensor 97, and productivity can be lowered at an appropriate timing. Even if the property decreases, an excessive increase in the end temperature can be suppressed.

  In each of the embodiments described above, the outer region conductor portions 91 and 92 and the inner region conductor portion 93 made of a metal having a high resistance temperature coefficient whose resistance value depends on temperature are provided on the surface layer portion of the nip forming member 54. did. Of these, at least the in-region conductor portion 93 needs to be easily heated to the fixing temperature in the vicinity of the inner peripheral surface of the fixing belt 52, but does not necessarily have to slide directly on the fixing belt 52. For example, a sufficiently thin low friction resin film that covers the in-region conductor portion 93 is provided between the in-region conductor portion 93 and the fixing belt 52, or a low-friction and highly durable metal thin film is coated. Also good.

  Further, in each of the above-described embodiments, the surface layer portion of the nip forming member 54 is illustrated substantially flat. However, the surface layer portion of the nip forming member 54 in the nip portion N and the outer peripheral surface of the pressure roller 51 may have a curved cross section, and the curved unevenness and the cross sectional shape are not particularly limited. Needless to say.

  Further, in each of the above-described embodiments, the metal member is divided into the outer conductor portions 91 and 92 and the inner conductor portion 93, but it is also possible to integrate them. Moreover, although metal members, such as these conductor parts 91, 92, 93, etc. were illustrated as strip | belt-plate shape, the linear shape etc. which have plate shape, film | membrane shape, a specific pattern shape, etc. of arbitrary shapes may be sufficient.

  The heat-resistant member 82 and the like for backing and supporting the metal member 81 is an example in which a resin is used as a heat-resistant member having electrical insulation, but the material is not particularly limited.

  As described above, the present invention can accurately detect the temperature during the fixing operation of the fixing nip portion from the temperature-dependent signal without disposing a dedicated temperature detecting element in the fixing nip portion, and has an excessive end portion. It is possible to prevent deterioration of the heating rotator due to temperature rise. Therefore, the present invention provides a highly durable fixing device, and at the same time, can detect the temperature of the fixing nip portion with high accuracy and improve the control accuracy in the fixing operation region, and has excellent durability with high image quality. There is an effect that an image forming apparatus can be provided. The present invention is useful for a fixing device that fixes an image on a recording medium and an image forming apparatus that includes the fixing device.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image forming apparatus main body 11 Conveyance path 20 Paper feed part 23 Registration roller 30 Image forming part 31 Exposure unit 32Y, 32M, 32C, 32K Image forming unit 33 Photosensitive drum (photosensitive body)
34 Development Unit 35 Charger 40 Transfer Units 41a, 41b, 41c, 41d Primary Transfer Roller 42 Intermediate Transfer Belt 47 Secondary Transfer Roller 50 Fixing Unit 51 Pressure Roller (Pressure Rotator, Opposing Member)
52 Fixing belt (heating rotator, fixing member)
53 Halogen heater (heat source, heating means)
54 Nip forming member 55 Stay 55a Surface (reflection surface)
56 reflective member 56a reflective surface 57 temperature sensor (temperature detection element, in-region detection element)
80 Temperature detection circuit (signal detection means)
80A Additional temperature detection circuit (signal detection means)
81 Metal member (conductor part)
82 Heat-resistant member 83, 85 Power source 84, 86 Current detection portion 91, 92 Out-of-region conductor portion 93 In-region conductor portion (metal member, conductor portion)
97 Temperature sensor (temperature sensing element, out-of-range sensing element)
100 Control unit (control means)
N Nip (fixing nip)
Sp transfer paper (recording medium)

JP2013-137470A JP 2013-073206 A

Claims (8)

An endless belt-shaped heating rotator, a heat source for heating the heating rotator, a nip forming member disposed inside the heating rotator, and the heating rotator sandwiched between the nip forming members A pressure rotator that is disposed so as to face each other and rotates to frictionally drive the heating rotator while forming a nip portion together with a portion of the heating rotator in contact with the nip forming member in the circumferential direction; A fixing device comprising:
A conductor portion provided in the nip forming member; and a signal detection unit that supplies a current to the conductor portion and detects a temperature-dependent signal that varies depending on the current and the temperature of the heating rotating body in the nip portion; A fixing device.   The fixing device according to claim 1, further comprising a control unit that controls a heating output of the heat source based on the temperature-dependent signal.   3. The in-region conductor portion disposed in a fixing operation region in the axial direction of the pressure rotator of the nip forming member, wherein the conductor portion includes an in-region conductor portion. Fixing device.   4. The region according to claim 1, wherein the conductor portion includes an out-of-region conductor portion arranged outside the fixing operation region in the axial direction of the pressure rotator of the nip forming member. The fixing device according to claim 1. A temperature detection element that detects the temperature of the thermal rotator outside the formation region of the nip portion in the circumferential direction of the heating rotator,
The fixing device according to claim 2, wherein a heating output of the heat source is controlled based on a temperature detected by the temperature detecting element and the temperature-dependent signal.   The fixing device according to claim 5, wherein the temperature detection element includes an in-region detection element arranged in a fixing operation region in the axial direction of the pressure rotator of the nip forming member. .   The temperature detection element includes an out-of-area detection element arranged outside the fixing operation area in the axial direction of the pressure rotator of the nip forming member. The fixing device described. A fixing device according to any one of claims 1 to 7,
An image forming unit that carries an image formed of an unfixed developer on a recording sheet,
An image forming apparatus, wherein the recording sheet carrying the image is passed through the fixing device to fix the image on the recording sheet.

Images