JP2009162808A - Image heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image heating apparatus which can shorten warming up time for having the temperature of a heating rotor raised to the temperature for heating an image carried on recording material and shut down a heating action of the heating body when the heating body is out of control. <P>SOLUTION: The image heating apparatus includes a heating body 11 emitting radiant heat and the heating rotor 30 which is heated to the temperature corresponding to the radiant heat emitted by the heating body and heats an image T carried on the recording material P. In this case, a heat transmitting rotor 21 forming a heat transmitting nip section N1 by being brought into contact with the heating rotor and a safety element 22 for sensing the temperature of the heat transmitting rotor are provided in the image heating apparatus. The heat transmission rotor is heated by radiation of the radiated heat emitted by the heating body and transmits the heat for heating the image carried on the recording material to the heating rotor through the heat transmitting nip section. The safety element senses when the temperature of the heat transmitting rotor which is heated by radiation of the radiated heat emitted by the heating body exceeds the temperature corresponding to the heat for heating the image held on the recording material and shuts down the heating action of the heating body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image heating apparatus suitable for use as a heat fixing apparatus mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  A heat roller type heat fixing device is known as a heat fixing device mounted on an electrophotographic copying machine or printer.

  FIG. 8 shows a schematic model diagram of an example of a heat roller type heat fixing device.

  Reference numeral 500 denotes a fixing roller as a heating rotator. In the fixing roller 500, a halogen lamp 510 as a heating unit is disposed inside a hollow cored bar 501 made of aluminum or stainless steel. The halogen lamp 510 is energized from a power source (not shown) to generate heat, and the fixing roller 500 is moved from the inside of the hollow cored bar 501 to the toner of the toner image T on the transfer material P as a material to be heated. Heat to a temperature sufficient to melt.

  Further, in order to fix the toner on the transfer material P onto the transfer material P without offsetting, an elastic layer 502 formed of a thin silicone rubber or the like is formed on the outer peripheral surface of the hollow core metal 501 of the fixing roller 500. Has been. Further, a release layer 503 made of polytetrafluoroethylene (PTFE) and perfluoroalkoxytetrafluoroethylene copolymer (PFA) having excellent release properties is formed on the outer peripheral surface of the elastic layer 502. Yes.

  Reference numeral 520 denotes a pressure roller as a pressure member for the fixing roller 500. The pressure rollers 520 are arranged substantially in parallel with the fixing roller 500, and are held in a state of being pressed against the fixing roller 500 by being urged by pressure springs (not shown) at both ends of the roller. The pressure roller 520 is formed with an elastic layer 522 formed of a thick silicone rubber or foamed silicone rubber on the outer peripheral surface of the core metal 521. Further, a release layer 523 made of PTFE or PFA is formed on the outer peripheral surface of the elastic layer 522 as the outermost layer. Due to the elasticity of the pressure roller 520, a sufficient nip width can be formed at the nip portion (fixing nip portion) N between the fixing roller 500 and the pressure roller 520.

  A thermistor 530 is in contact with the surface of the fixing roller 500. The thermistor 530 detects the temperature of the outer peripheral surface (surface) of the fixing roller 500 and outputs the detection signal to the temperature control unit. The temperature control unit performs on / off control of power supply to the halogen lamp 510 so as to heat the toner image T on the transfer material P at a predetermined temperature based on a detection signal from the thermistor 530.

  A thermo switch 540 as a safety element is disposed at a position where the surface temperature of the fixing roller 500 can be sensed.

  Then, the fixing roller 500 and the pressure roller 520 are rotated, and the transfer material P carrying the unfixed toner image T in the nip portion N is introduced with the image surface facing the fixing roller 500 and is nipped and conveyed. As a result, the toner image T on the transfer material P is heated and fixed on the surface of the transfer material P under the heat of the fixing roller 500 and the pressure of the nip portion N.

  For the hollow cored bar 501 of the fixing roller 500, a material, an outer diameter, and a wall thickness are selected so that the heat capacity is kept as small as possible and the mechanical strength and the allowable deflection of pressure are satisfied while having higher thermal conductivity. Is done. For example, in the case of aluminum, an outer diameter of 20 to 50 mm and a wall thickness of 1.5 to 3 mm are required.

  Further, the elastic layer 502 which is an intermediate layer and the release layer 503 which is an outermost layer have a low thermal conductivity, and thus cannot be formed thick from the viewpoint of fixability. The elastic layer 502 is usually formed with a thickness of 0.1 to 2.5 mm (or no elastic layer), and the release layer 503 is usually formed with a thickness of 10 to 50 μm.

  The pressure roller 520 has a thickness of about 2 to 4 mm and 40 to 65 ° (ASKER-C, 9.8 N) in order to obtain a nip width sufficient for the toner to melt during conveyance of the transfer material P. A roller surface hardness of about (when loaded) is required.

  However, the heat roller type heat fixing device basically needs to sufficiently store the respective members from the hollow cored bar 501 to the release layer 503 of the fixing roller 500 before the heat fixing operation for the transfer material P. Therefore, in the heat roller type heat fixing device, before the heat fixing operation for the transfer material P, the warm-up time for sufficiently storing each member from the hollow cored bar 501 to the release layer 503 of the fixing roller 500 is set. It took tens of seconds to minutes.

  A heat fixing device mounted on an image forming apparatus is required to greatly reduce the warm-up time. As a heat fixing apparatus that can satisfy this requirement, an external radiation heating type heat fixing apparatus as disclosed in Patent Documents 1 and 2 has been proposed.

  FIG. 9 shows a schematic model diagram of an example of a heat fixing device of an external radiation heating method.

  Reference numeral 610 denotes a radiant heater such as a halogen lamp. Reference numeral 611 denotes a curved reflector made of thin stainless steel or the like. The reflector 611 covers the periphery of the heating body 610. The reflection plate 611 has an optical reflection performance by mirror-reflecting the inner surface of the reflection plate 611 on the heating body 610 side.

  The fixing roller 600 has an elastic layer 602 made of silicone rubber, foamed silicone rubber, or the like on the outer peripheral surface of the core metal 601, and a release layer 603 made of PFA or the like as an outermost layer on the outer peripheral surface of the elastic layer 602. Have. The fixing roller 600 is disposed opposite the notch opening 611 a of the reflection plate 611, and the outer peripheral surface (surface) of the fixing roller 600 is heated by the radiant heat of the heating body 610.

  Unlike the heat roller type heat fixing device, the external radiation heating type heat fixing device does not require high thermal conductivity over the entire fixing roller 600, and therefore the thickness of the elastic layer 602 can be set as appropriate. In general, the softer surface of the fixing roller 600 facing the toner image carrying surface of the transfer material P has a higher effect of wrapping the transfer material P surface and the toner image T, so that the toner image T is heated and fixed at a lower temperature. It is preferable to set an appropriate thickness and low hardness.

Reference numeral 620 denotes a pressure member for the fixing roller 600. The pressure members 620 are arranged substantially in parallel with the fixing roller 600 and are held in a state of being pressed against the fixing roller 600 by being urged by pressure springs (not shown) at both longitudinal ends.
The pressure member 620 is formed with an elastic layer 622 made of silicone rubber, foamed silicone rubber or the like on the outer peripheral surface of the cored bar 621, and a mold release made of PTFE or PFA as the outermost layer on the outer peripheral surface of the elastic layer 622. It is a solid elastic pressure roller on which a layer 623 is formed. The pressure member 620 is not limited to a solid elastic pressure roller, and is a hollow member in which an elastic layer is formed on the outer peripheral surface of a hollow pipe made of metal or the like, and a release layer is formed on the outer peripheral surface of the elastic layer. An elastic pressure roller may be used.

  Either one of the fixing roller 600 and the pressure roller 620, or both the fixing roller 600 and the pressure roller 620 is provided with an appropriate elasticity, so that the nip portion N between both the fixing roller 600 and the pressure roller 620 is provided. A sufficient nip width can be formed.

  A thermistor 630 is in contact with the surface of the fixing roller 600. The thermistor 630 detects the temperature of the outer peripheral surface (surface) of the fixing roller 600 and outputs the detection signal to the temperature control unit. The temperature control unit performs on / off control of power supply to the halogen lamp 610 so as to heat the toner image T on the transfer material P at a predetermined temperature based on a detection signal from the thermistor 630.

  Then, the fixing roller 600 and the pressure roller 620 are rotated, and the transfer material P carrying the unfixed toner image T in the nip portion N is introduced with the image surface facing the fixing roller 600 and is nipped and conveyed. As a result, the toner image T on the transfer material P is heated and fixed on the surface of the transfer material P under the heat of the fixing roller 600 and the pressure of the nip portion N.

This heating and fixing device can locally heat the surface of the fixing roller 600 with radiant heat energy from the heating body 610, and the fixing roller is heated during the heating operation of the toner image T on the transfer material P. Heat transfer from the surface to the toner image T is an important factor. In other words, even if the heat accumulation inside the fixing roller 600 is not sufficient, the heat is not an important factor for the heat fixing property of the toner image T itself. Accordingly, the speed at which the surface temperature of the fixing roller 600 is raised to the fixable temperature with respect to the toner image T on the transfer material P is fast, so that the so-called warm-up time is greatly increased. It becomes possible to shorten to.
Japanese Patent Laid-Open No. 7-152271 JP 2002-43026 A

  The external radiant heating type heat fixing device has the advantage that the warm-up time can be greatly shortened as described above, but when the heated body runs out of control and heats up abnormally, the heating body is immediately heated. Is required to stop. As a method of monitoring the runaway of the heating element, there is a method of monitoring the temperature of the heating element and the current supplied to the heating element, but if the heating element runs away, a thermal fuse is used to immediately stop the heating operation of the heating element. It is preferable to use a safety element represented by a thermo switch or the like.

  In general, the following points should be noted when a safety element is arranged in a heat fixing device.

  (1) The temperature of the location where the safety element is located is a temperature range in which both the normal heating state (normal state) and the heated body runaway state (abnormal state) can be reliably distinguished. It is a specification that does not work and works when the heated object runs away.

  (2) During normal heating, the safety element should be placed in a location where the safety element does not hinder normal heating performance and does not malfunction.

  (3) The safety element should operate reliably during the heating element runaway, regardless of whether the heat fixing device is driven or not, and whether there is paper jam or paper wrapping.

  Considering the above points to consider, the position where the thermo switch 640 as a safety element is arranged in the heat fixing apparatus shown in FIG. 9 will be examined. For example, on the back side of the reflecting plate 611 corresponding to the position A, a halogen lamp 610 as a heating source is interposed between the fixing roller 600 and the thermo switch 640, so that the thermo switch 640 determines whether or not the temperature of the fixing roller 600 is in a normal range. Can hardly be distinguished. That is, the arrangement for satisfying (1) is difficult. Between the halogen lamp 610 corresponding to the position B and the fixing roller 600, since the radiant heat from the halogen lamp 610 is shielded by the thermo switch 640, the heating performance of the fixing roller 600 may be lowered. Further, since the thermo switch 640 itself is radiantly heated, it may malfunction. That is, it is difficult to arrange to satisfy (2). At the position facing the surface of the fixing roller 600 corresponding to the position C, when the fixing roller 600 is rotationally driven by the heat fixing device, the thermo switch 640 can be operated when the fixing roller 600 reaches an abnormal temperature. However, when the heat fixing device does not rotate the fixing roller 600, it is difficult to quickly operate the thermo switch 640 against a local temperature rise of the fixing roller 600. That is, it is difficult to arrange to satisfy (3).

  Accordingly, the object of the present invention is to shorten the warm-up time for raising the temperature of the heating rotator to the temperature for heating the image carried on the recording material, and to interrupt the heating operation of the heating element when the heating element runs away. An object of the present invention is to provide an image heating apparatus which can be used.

  In order to achieve the above object, an image heating apparatus includes: a heating body that emits radiant heat; and a heating rotator that heats an image carried by a recording material that is heated to a temperature corresponding to the radiant heat generated by the heating body. A heat transfer rotator that forms a heat transfer nip portion in contact with the heating rotator, and a safety element that senses the temperature of the heat transfer rotator. Heat for radiantly heating by the radiant heat generated by the recording material is transmitted to the heating rotating body via the heat transfer nip portion, and the safety element is radiantly heated by the radiant heat generated by the heated body. And detecting that the temperature of the heat transfer rotating body exceeds the temperature corresponding to the heat for heating the image carried by the recording material, and interrupting the heating operation of the heating body.

  According to the present invention, the warm-up time for raising the temperature of the heating rotator to the temperature for heating the image carried on the recording material can be shortened, and the heating operation of the heating element can be interrupted when the heating element runs away. An image heating apparatus can be provided.

  The present invention will be described with reference to the drawings.

[Example 1]
(1) Example of Image Forming Apparatus FIG. 7 is a structural model diagram of an example of an image forming apparatus in which the image heating apparatus according to the present invention can be mounted as a heat fixing apparatus. This image forming apparatus is a color image forming apparatus (full color laser printer) that forms an image on a transfer material such as recording paper or an OHP sheet using an electrophotographic image forming system. In this image forming apparatus, the maximum sheet passing width of the transfer material (recording material) P is 216 mm, and the image forming process speed of the transfer material P is 240 mm / second.

  The image forming apparatus according to the present exemplary embodiment forms first to fourth toner images of each color of yellow Y, magenta M, cyan C, and black Bk on an image forming apparatus main body 101 that constitutes a housing of the image forming apparatus. Have four image forming stations SY, SM, SC, and SBk. Each station S (Y to Bk) has a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 102 as an image carrier. Around each photosensitive drum 102, a charging roller (charging means) 103, a laser scanner unit (exposure means) 104, a developing device (developing means) 105, a transfer roller (transfer means) 106, and a cleaning device ( Cleaning means) 107 is provided. An electrostatic conveyance belt (transfer material conveyance unit) 108 is disposed so as to face the photosensitive drum 101 of each station S (Y to Bk). The electrostatic conveyance belt 108 is stretched around two axes of a driving roller 109a and a driven roller 109b. A transfer roller T is formed between the photosensitive drum 101 and the electrostatic conveyance belt 108 by disposing the transfer roller 106 so as to face the respective photosensitive drums 102 with the electrostatic conveyance belt 108 interposed therebetween.

  When a print signal is input, the image forming apparatus according to the present exemplary embodiment sequentially drives predetermined members of the stations S (Y to Bk) according to a predetermined image formation control sequence. The photosensitive drums 102 of the stations S (Y to Bk) are rotated at a predetermined peripheral speed (process speed) in the direction of the arrow by a rotation drive system (not shown). In synchronization with the photosensitive drum 102, the electrostatic conveyance belt 108 is also rotated by the driving roller 109a in the direction of the arrow by the rotational driving system at a peripheral speed corresponding to the rotational peripheral speed of the photosensitive drum 102.

  First, in the first color yellow Y station SY, the outer peripheral surface (front surface) of the photosensitive drum 102 is uniformly charged to a predetermined polarity and potential by the charging roller 103. Next, the laser beam L corresponding to the image data (image information) is scanned and exposed on the surface of the photosensitive drum 101 by the laser scanner unit 104. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the uniformly charged photosensitive drum 102. The latent image is developed by the developing device 105 with yellow toner (developer), and a heat-meltable yellow toner image (development image) is formed on the surface of the photosensitive drum 102. A similar image forming process is performed at each of the magenta M, cyan C, and black K stations S (M to Bk). Then, a toner image (development image) of each color is formed on the surface of the photosensitive drum 102 of each station S (Y to Bk).

  On the other hand, the transfer material P stacked and stored in the feeding cassette 110 is sent to the registration roller pair 112 by the pickup roller 111. Next, the transfer material P is transported onto the outer peripheral surface (front surface) of the electrostatic transport belt 108 by the registration roller pair 112. The transfer material P is conveyed from the transfer portion Tn on the upstream side in the rotation direction to the transfer portion Tn on the downstream side in the rotation direction by the rotation of the electrostatic conveyance belt 108. In the conveying process, the toner image on each photosensitive drum 102 is transferred onto the transfer material P by the transfer roller 106 in the order of being transferred onto the surface of the transfer material P by the transfer roller Tn. The image is carried as an unfixed toner image.

  In each station S (Y to Bk), the transfer residual toner remaining on the surface of the photosensitive drum 102 after the transfer of the toner image to the transfer material P is removed by a cleaning blade provided in the cleaning device 107. Thus, the photosensitive drum 102 is repeatedly used for the next image formation.

  The transfer material P separated from the surface of the electrostatic conveyance belt 108 and exiting the transfer portion Tn is introduced into the nip portion N2 of the heat fixing device 100. The fixing device 100 sandwiches and conveys the unfixed toner image carried by the transfer material P at the nip portion N2. The toner image is heated and fixed on the surface of the transfer material P by applying heat and pressure to the toner image in the conveying process.

  The transfer material P exiting the fixing device 100 is discharged onto a discharge tray 114 provided on the upper part of the image forming apparatus main body 101 by a discharge roller 113.

(2) Heat Fixing Device FIG. 1 is a cross-sectional side view of an example of the heat fixing device 100. The heat fixing apparatus 100 is an external radiation heating type heat fixing apparatus.

  In the following description, regarding the heat fixing device and the members constituting the heat fixing device, the longitudinal direction is a direction orthogonal to the transfer material conveyance direction on the surface of the transfer material. The short side direction is a direction parallel to the transfer material conveyance direction on the surface of the transfer material. The width is a dimension in the short direction.

2a) Overall Configuration of Heat Fixing Device The heat fixing device 100 shown in this embodiment includes a heating body 11, a reflector 12, a heat transfer rotating body 21, a safety element 22, a heating rotating body 30, and a pressure rotation. It has a body 40, temperature detection means 51 and the like. The heating body 11, the reflector 12, the heat transfer rotating body 21, the heating rotating body 30, and the pressure rotating body 40 are members that are elongated in the longitudinal direction.

  A fixing roller is used as the heating rotator 30. In the fixing roller 30, an elastic layer 32 made of silicone rubber, foamed silicone rubber, or the like is formed on the outer peripheral surface of a solid core 31 with a thickness of about 2 to 4 mm, and the outermost surface of the elastic layer 32 is formed on the outermost surface. A release layer 33 made of PTFE, PFA or the like is formed as an outer layer. The roller hardness of the fixing roller 30 is 45 to 65 ° (ASKER-C, at 9.8 N load). The core metal 31 is not limited to a solid core metal but may be a hollow core metal. In this embodiment, the fixing roller 30 uses solid aluminum having an outer diameter of 14 mm as the core 31, uses foamed silicone rubber having a thickness of 3 mm as the elastic layer 32, and PFA having a thickness of 30 μm as the release layer 33. The elastic tube 32 was covered with a resin tube. The fixing roller 30 is rotatably held at both ends of a cored bar 31 by an apparatus frame (not shown).

  A pressure roller is used as the pressure rotator 40. The pressure roller 40 is formed by forming an elastic layer 42 made of silicone rubber, foamed silicone rubber or the like on the outer peripheral surface of a hollow core metal 41 with a thickness of about 0.1 to 4 mm, and on the outer peripheral surface of the elastic layer 42. A release layer 43 made of PTFE, PFA or the like is formed as the outermost layer. The cored bar 41 is not limited to a hollow cored bar and may be a solid cored bar. Further, the release layer 43 may be formed on the cored bar 41 without forming the elastic layer 42. The pressure roller 40 shown in this embodiment uses hollow stainless steel having an outer diameter of 18 mm and a thickness of 1 mm as the core metal 41, silicone rubber having a thickness of 2 mm as the elastic layer 42, and a thickness as the release layer 43. The elastic layer 42 was covered with a 30 μm PFA resin tube. Under the fixing roller 30, the pressure roller 40 arranged in parallel with the fixing roller 30 has both ends of a cored bar 41 rotatably held by the apparatus frame. The pressure roller 40 is pressed toward the fixing roller 30 with a predetermined pressure by a pressing means such as a pressure spring (not shown). With the applied pressure, the outer peripheral surface (surface) of the pressure roller 40 is brought into contact with the outer peripheral surface (surface) of the fixing roller 30 to elastically deform the elastic layers 42 and 32 of both rollers 40 and 30. Thus, a nip portion (fixing nip portion) N2 is formed between the surface of the fixing roller 30 and the surface of the pressure roller 40.

  A cylindrical pipe (hereinafter referred to as a heat transfer pipe) having heat resistance and heat conductivity is used as the heat transfer rotating body 21. The heat transfer pipe 21 arranged in parallel with the fixing roller 30 above the fixing roller 30 has both ends of the heat transfer pipe 21 held rotatably by the apparatus frame. The heat transfer pipe 21 is pressed toward the fixing roller 30 with a predetermined pressing force by a pressing means such as a pressing spring (not shown). By applying the applied pressure, the outer peripheral surface (surface) of the heat transfer pipe 21 is brought into contact with the surface of the fixing roller 30 and the elastic layer 32 of the fixing roller 30 is elastically deformed, whereby the surface of the fixing roller 30 and the surface of the heat transfer pipe 21 are interposed. A heat transfer nip portion N1 is formed.

  The heat transfer pipe 21 is a low heat capacity member depending on the material and configuration in order to efficiently raise the temperature of the heat transfer pipe 21 itself by radiant heat energy (hereinafter referred to as radiant heat) generated by the heating element 11 as described later. Further, in order to efficiently release heat by making the width of the heat transfer nip N1 wide, a high pressure-resistant member (margin for plastic deformation and breakage with respect to high pressure) depending on the material and configuration of the heat transfer pipe 21. There is a member). In this embodiment, a member formed of aluminum, stainless steel, or ceramic material in the shape of a thin hollow pipe was used as the base material 21a (FIG. 3) of the heat transfer pipe 21. That is, the base material 21a is formed using a material that does not undergo plastic deformation with respect to the applied pressure capable of forming the heat transfer nip portion N1. The detailed configuration of the heat transfer pipe 21 will be described later.

  The nip portion N2 is preferably formed with a width of 5 mm or more over the entire lengthwise direction of the fixing roller 30 and the pressure roller 40. Further, the heat transfer nip portion N1 is preferably formed to have a width of 5 mm or more over the entire longitudinal direction of the heat transfer pipe 21 and the fixing roller 30. In this embodiment, the pressing force from the heat transfer pipe 21 to the fixing roller 30 and the pressing force from the pressure roller 40 to the fixing roller 30 are set to 98 to 392 N (10 to 40 kgf), respectively. The nip portions N1 and N2 having a width are formed. The heat-fixing device of this embodiment can secure the width of each nip portion N1, N2 to 5 mm or more and can withstand the applied pressure for forming each nip portion N1, N2, so that the heat transfer pipe 21, It is not limited to the rotating body configuration / pressure configuration of the fixing roller 30 and the pressure roller 40.

  The heating body 11 is a rod-shaped heat source that emits radiant heat. In the present embodiment, a halogen lamp having a rated power of 800 W (when 100 V is input) is used as the heating element 11. The halogen lamp 11 is disposed at a location where the surface of the heat transfer pipe (heat transfer rotating body) 20 is radiantly heated by the radiant heat generated by the halogen lamp 11. The halogen lamp 11 is fixed and held at both ends of the halogen lamp 11 by the apparatus frame. The heating element 11 is not limited to a halogen lamp, and a carbon-based heating element may be used as long as a desired amount of radiant heat can be obtained.

  As the reflector 12, a curved curved plate made of stainless steel having optical reflection performance and heat resistance was used. The curved reflector 12 is formed in a substantially semi-elliptical shape in cross section and has a notch opening 12a on the heat transfer pipe 21 side. The inner surface of the curved reflector 12 is mirror-finished. A halogen lamp 11 is disposed inside the reflector 12. The curved reflector 12 is configured such that both ends of the curved reflector 12 are fixedly held on the apparatus frame, and the radiant heat generated by the halogen lamp 11 is reflected by the inner surface of the curved reflector 12 so as to be radiated in the direction of the notch opening 12a. It is configured. As a method for increasing the thermal radiation efficiency of the curved reflector 12, for example, a heat insulating member or the like may be disposed on the outer surface of the curved reflector 12.

  The safety element 22 is an element for detecting an abnormal temperature rise in the heat transfer pipe 21 and interrupting the heating operation of the halogen lamp 11 (energization operation of the heating body), that is, the energization to the halogen lamp 11. The safety element 22 is connected in series with the halogen lamp 11 in the energization circuit of the halogen lamp 11 (FIG. 2). In this embodiment, a thermal fuse having a rated operating temperature of 230 ° C. is used as the safety element 22. The safety element 22 is not limited to a thermal fuse, and a thermo switch or a thermostat may be used. The safety element 22 is supported by a support member (not shown) attached to the apparatus frame and is disposed inside the heat transfer pipe 21 so as to be in contact with the inner peripheral surface (inner surface) of the heat transfer pipe 21. In the present embodiment, the safety element 22 is disposed so as to contact the inner surface of the heat transfer pipe 21. However, if the runaway of the halogen lamp 11 can be detected in a short time, the safety element 22 may be disposed outside the heat transfer pipe 21. . When the safety element 22 is disposed outside the heat transfer pipe 21, the safety element 22 is disposed at a location that is not directly radiantly heated by the radiant heat generated by the halogen lamp 11. Similarly, when a non-contact type thermo switch or the like is used as the safety element 22, it may be arranged inside the heat transfer pipe 21 or outside the heat transfer pipe 21.

  A temperature detecting element such as a thermistor is used as the temperature detecting means 51. The temperature detection element 51 is held by a holding member provided in the apparatus frame and is in contact with the surface of the fixing roller 30. The temperature detecting element 51 is arranged in a region (paper passing region) through which a large size transfer material and a small size transfer material always pass in the longitudinal direction of the fixing roller 30. Alternatively, the temperature detection element 51 is arranged in a region (paper passing region) through which the large transfer material P passes in the longitudinal direction of the fixing roller 30 and a region (paper passing region) through which the small transfer material P passes. The

2b) Heat Fixing Operation of Heat Fixing Device The heat fixing operation of the heat fixing device 100 will be described with reference to FIGS.

  FIG. 2 is an explanatory diagram of a power supply control system of the heat fixing apparatus 100.

  When a driving gear (not shown) provided at one end of the cored bar 41 of the pressure roller 40 is rotationally driven by the fixing motor M (FIG. 1), the pressure roller 41 rotates in the arrow direction. By the rotation of the pressure roller 41, a rotational force acts on the fixing roller 30 by the frictional force between the surface of the pressure roller 40 and the surface of the fixing roller 30 at the nip portion N2. Due to the rotational force, the fixing roller 30 is driven to rotate in the direction of the arrow at substantially the same peripheral speed as that of the pressure roller 40. The rotational force acts on the heat transfer pipe 21 by the frictional force between the surface of the fixing roller 30 and the heat transfer pipe 21 in the heat transfer nip portion N1 due to the rotational force of the fixing roller 30. Due to the rotational force, the heat transfer pipe 21 is driven to rotate in the direction of the arrow at a circumferential speed substantially the same as the rotational speed of the fixing roller 30.

  The MPU 61 (FIG. 2) as the control means turns on the triac 62 as the energization control means. As a result, the halogen lamp 11 is energized from the power source 63 through the safety element 22. The halogen lamp 11 emits radiant heat when energized, and the radiant heat is radiated intensively to the surface of the heat transfer pipe 21 through the notch opening 12a of the curved reflector 12. The surface of the heat transfer pipe 21 is heated by the radiant heat generated by the halogen lamp 11 and the temperature is raised. The heat on the surface of the heat transfer pipe 21 heated by the radiant heat generated by the halogen lamp 11 is transmitted to the surface of the fixing roller 30 through the heat transfer nip portion N1. The surface of the fixing roller 30 is heated to a temperature corresponding to the heating temperature of the surface of the heat transfer pipe 21 and the temperature is raised. The temperature detection element 51 detects the surface temperature of the fixing roller 30. The MPU 61 takes in the output signal (temperature detection signal) of the temperature detection element 51 and controls the power supplied to the halogen lamp 11 by the triac 62 based on the output signal, thereby changing the surface temperature of the fixing roller 30 to a predetermined fixing temperature ( Maintain target temperature).

  In a state where the surface temperature of the fixing roller 30 is maintained at the fixing temperature and the rotation peripheral speed of the fixing roller 30 is stabilized by the rotation of the pressure roller 40, the transfer material P carrying the unfixed toner image T in the nip portion N2 is obtained. Is introduced. Then, the transfer material P is nipped and conveyed by the fixing roller 30 and the pressure roller 40 at the nip portion N2, and the heat of the surface of the fixing roller 30 and the pressure of the nip portion N2 are applied to the toner image T of the transfer material P. The image T is heated and fixed on the surface of the transfer material P.

2c) Details of Heat Transfer Pipe (Heat Transfer Rotator) FIG. 3 is an explanatory diagram of the layer structure of the heat transfer pipe 21.

  The heat transfer pipe 21 shown in the present embodiment is obtained by providing a release layer 21b on the outer peripheral surface of a base material 21a in which aluminum, stainless steel, or a ceramic material is formed into a thin hollow pipe shape. As the release layer 21b, a thin film having a thickness of about 1 to 10 μm was used by applying and baking PFA or PTFE. The longitudinal length of the heat transfer pipe 21 was set to 240 mm.

  As described in the section 2a), the heat transfer pipe 21 needs to be a low heat capacity member and a high pressure resistant member. The specific required performance of the heat transfer pipe 21 of the present embodiment is as follows.

i) High-speed temperature rising performance when the heat transfer pipe 21 is radiantly heated When the heat transfer pipe 21 is radiantly heated while rotating the heat transfer pipe 21 by applying 800 W of electric power to the halogen lamp 11, the temperature rises from room temperature (25 ° C) to 200 ° C. The time is within 15 seconds, preferably within 8 seconds.

ii) Low deflection amount and load safety when the heat transfer pipe 21 is supported at both ends and equally distributed load In order to form the longitudinal shape of the heat transfer nip portion N1 along the longitudinal direction of the heat transfer pipe 21 with a substantially uniform width. The maximum deflection y of the heat transfer pipe 21 is within 1 mm, preferably within 0.5 mm, with respect to the load 98 to 392N (10 to 40 kgf) applied to the heat transfer pipe 21. Here, the maximum deflection amount y is calculated by the following equation.

y = 5 × p × L ⁴ / (384 × E × I)
p: Load per unit length (in case of equally distributed load, p = total load / L)
L: Support interval E: Young's modulus I: Second moment of section = π × (R ⁴ −r ⁴ ) / 64
R: pipe outer diameter r: pipe inner diameter Further, the ratio of the maximum stress σa caused by load deflection to the tensile strength (extreme stress against fracture / deformation) σs of each material, that is, the safety factor (= σs / σa) is 200%. Above, preferably 300% or more. Here, the maximum stress σa is calculated by the following equation.

^{σa = p × L 2 / (} 8 × Z)
Z: Section modulus = π × (R ⁴ −r ⁴ ) / (32 × R)
The inventor made a preliminary study on the material and configuration (outer diameter, thickness) of the base material 21a to select a member for the heat transfer pipe 21, and estimated a member configuration that satisfies the required performance. Table 1 shows the physical properties related to the bending and heat of the materials examined in this example, and Table 2 to Table 4 summarize the determination results for the above i) and ii) in the form of .DELTA..DELTA.x.

  In each of Tables 2 to 4, when the base material 21a has a configuration of “good” in the overall determination, the heat transfer pipe 21 has a high self-temperature raising performance and has a pressure resistance against pressurization, whereby the heat transfer nip N1 Can be formed with a width of 5 mm or more. Therefore, heat can be efficiently transferred to the surface of the fixing roller 30.

  The temperature transition of the surface of the heat transfer pipe 21 and the surface of the fixing roller 30 when the printing operation is started from the room temperature state where the warm-up operation is not performed in advance using the image forming apparatus equipped with the heat fixing apparatus having the following configuration. The results measured with a radiation thermometer are shown in FIG.

  In the heat fixing device, as an example of the base material 21a of the heat transfer pipe 21, an aluminum nitride pipe having an outer diameter of 20 mm and a thickness of 0.5 mm and having a comprehensive judgment in Table 4 was used. The pressure for forming the heat transfer nip N1 was 245N (25 kgf), and the pressure for forming the nip N2 was 245N. Further, the control value (fixing temperature) of the surface temperature of the fixing roller 30 by the temperature detecting element 51 was set to 170 ° C.

  As shown in FIG. 4, the surface temperature of the fixing roller 30 reached 170 ° C. within 8 seconds from the start of printing. At this time, the heat transfer pipe 21 was maintained at about 200 ° C. The transfer material P introduced into the nip portion N2 at a timing of 8 seconds from the start of printing was discharged out of the apparatus within 10 seconds from the start of printing with the toner image T having good fixability. As described above, when the base material 21a is ◯ in the comprehensive determination, the transfer material P can be discharged in a short time without performing a warm-up operation in advance, and so-called on-demand characteristics can be maintained.

  Further, in each of Tables 2 to 4, even when the base material 21a has a configuration of Δ in the comprehensive judgment, the temperature rise performance of the heat transfer pipe 21 is slightly inferior to ○, or the pressure cannot be set so large. There are limitations. However, it is possible to sufficiently heat the transfer material P by a preliminary warm-up operation for several seconds. That is, it has a performance that can greatly shorten the warm-up time as compared with the conventional heat roller system. Here, the fact that the pressure cannot be set too large means that the heat transfer nip portion N1 cannot be set too large.

  Regarding the temperature rise performance of the base material 21a, the heat capacity per heat transfer pipe 21 (longitudinal length 240 mm) of this example is 72 [J / K] or less, that is, the heat capacity per unit cross-sectional volume is 300 [J / K]. (K · m)] or less, the required temperature raising performance can be achieved.

  Next, Table 5 shows the results describing the operating state of the thermal fuse 22 with the rated operating temperature of 230 ° C. and the state of the heating and fixing device 100 when the halogen lamp 11 of the heating and fixing device 100 runs away.

  The member of the heat transfer pipe 21 was an aluminum nitride pipe having an outer diameter of 20 mm and a thickness of 0.5 mm as the base material 21a, as in the above example.

  As shown in Table 5, regardless of whether or not the heat fixing device 100 is driven (whether or not the rotation of the fixing roller 30 is being performed), when the halogen lamp 11 goes out of control, the heating current to the halogen lamp 11 is cut off. I was able to. The same result was obtained when the halogen lamp 11 was runaway while the transfer material (paper) was forcibly wound around the fixing roller 30.

  In the heat fixing device 100 of this embodiment, the heat transfer pipe 21 is radiantly heated by the radiant heat generated by the halogen lamp 11 during the normal heating operation by the halogen lamp 11. The heat transfer pipe 21 transfers heat for fixing the toner image T carried by the transfer material P to the fixing roller 30 via the heat transfer nip portion N1. That is, the heat transfer pipe 21 can be heated by the radiant heat generated by the halogen lamp 11, and the heat of the heat transfer pipe 21 can be transmitted to the surface of the fixing roller 30 through the heat transfer nip portion N1, so that the heating efficiency is not greatly reduced and on demand. Sex can be maintained. That is, it is possible to shorten the warm-up time during the normal heating operation by the halogen lamp 11. Further, in the heat fixing apparatus 100 of the present embodiment, the safety element 22 is disposed at a location where the temperature of the heat transfer pipe 21 can be sensed. As described above, the heat transfer pipe 21 is radiantly heated by the radiant heat generated by the halogen lamp 11 and transfers heat for fixing the toner image T carried by the transfer material P to the fixing roller 30 via the heat transfer nip portion N1. Is. Therefore, when the halogen lamp 11 runs away in a stationary state in which the fixing roller 30 is not rotationally driven (the temperature at which the heat transfer pipe 21 is heated and fixed to the toner image T carried by the transfer material P (fixing temperature)). The safety element 22 can be activated.

  Therefore, according to the heat fixing apparatus 100 of this embodiment, the warm-up time for raising the temperature of the fixing roller 30 to the temperature for heating the toner image T carried on the transfer material P can be shortened. Further, when the halogen lamp 11 runs away, the safety element 22 can block the heating operation of the halogen lamp 11. The warm-up time for raising the temperature of the fixing roller 30 can be shortened, and when the halogen lamp 11 runs away, the heating operation of the halogen lamp 11 can be cut off.

[Example 2]
Another example of the image heating apparatus according to the present invention will be described.

  The heat fixing apparatus shown in the present embodiment has the same configuration as that of the heat fixing apparatus 100 of the first embodiment, except that the temperature detection element is disposed at a location where the temperature of the heat transfer pipe can be monitored.

  In this embodiment, the same members / portions as those in the heat fixing apparatus of Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted. The same applies to Example 3.

  FIG. 5 is a cross-sectional side view of the heat fixing apparatus 100 according to this embodiment.

  In the heat fixing apparatus 100 of the present embodiment, for example, a temperature detection element 51 is disposed inside the heat transfer pipe 21 as a place where the temperature of the heat transfer pipe 21 can be monitored. The temperature detection element 51 is held by a holding member provided in the apparatus frame and is in contact with the inner peripheral surface (inner surface) of the heat transfer pipe 21. This temperature detecting element 51 detects the temperature of the inner surface of the heat transfer pipe 21.

  By disposing the temperature detection element 51 at a location where the temperature of the heat transfer pipe 21 can be monitored, the thermal resistance between the halogen lamp 11 and the temperature detection element 51 can be reduced. Thus, it is possible to perform energization control.

  Specifically, it is possible to prevent overshooting of the temperature of the heat transfer pipe 21 with respect to a predetermined fixing temperature, so that a margin can be secured for malfunction of the safety element 22. Further, the temperature ripple of the heat transfer pipe 21 and thus the fixing roller 30 can be reduced. Therefore, it is possible to prevent uneven fixing of the toner image T onto the transfer material P due to the temperature ripple of the fixing roller 30 (periodic unevenness of excessive fixing and insufficient fixing), and the margin for setting the control temperature can be increased.

  Furthermore, when the halogen lamp 11 runs out of control, in addition to the safety means of turning off the power by operating the safety element 22, it is possible to function the safety means of turning off the power by operating the safety circuit by detecting the abnormal temperature of the temperature detecting element 51. It becomes. Therefore, it is possible to increase a margin for safety when the halogen lamp 11 runs away.

  As a secondary effect, since the temperature detection element 51 is not in direct contact with the surface of the fixing roller 30, the temperature detection element 51 is not contaminated with offset toner or the like. Therefore, the detection responsiveness does not deteriorate due to durability or the like as compared with the case where the fixing roller 30 contact type temperature detection element 51 is used. Further, the surface of the fixing roller 30 is not damaged. Therefore, the configuration in which the temperature detecting element 51 is brought into contact with the inner surface of the heat transfer pipe 21 can be an advantageous configuration for extending the durability life of the heat fixing device.

  In the present embodiment, the temperature detection element 51 is arranged in the vicinity of the outlet of the heat transfer nip portion N1 on the inner surface of the heat transfer pipe 21 in the rotation direction of the heat transfer pipe 21. The arrangement location of the temperature detection element 51 is not limited to the vicinity of the outlet of the heat transfer nip portion N1, and the temperature detection element 51 may be brought into contact with the inner surface of the heat transfer pipe 21 within the range of the heat transfer nip portion N1. Alternatively, the temperature detection element 51 may be brought into contact with the inner surface of the heat transfer pipe 21 in the vicinity of the inlet portion of the heat transfer nip N1 inside the heat transfer pipe 21. Alternatively, the temperature detection element 51 may be brought into contact with the inner surface of the heat transfer pipe 21 at a position facing the halogen lamp 11 inside the heat transfer pipe 21. Alternatively, the temperature detection element 51 may be brought into contact with the outer peripheral surface of the heat transfer pipe 21.

  Further, the temperature detection element 51 is located in a region corresponding to a region (paper passing region) in which a large size transfer material and a small size transfer material always pass in the longitudinal direction of the fixing roller 30 in the longitudinal direction of the heat transfer pipe 21. Be placed. Alternatively, the temperature detection element 51 is configured such that in the longitudinal direction of the heat transfer pipe 21, an area corresponding to an area (paper passing area) through which the large transfer material P passes in the longitudinal direction of the fixing roller 30, and a small transfer material P. Are arranged in areas corresponding to areas through which the paper passes (paper passing area).

  The heat fixing apparatus 100 of the present embodiment has the same configuration as the heat fixing apparatus 100 of the first embodiment except that the temperature detection element 51 is disposed at a location where the temperature of the heat transfer pipe 21 can be monitored. The same effects as those of the heat fixing apparatus 100 can be obtained. Further, in the heat fixing apparatus 100 of the present embodiment, the temperature detecting element 51 is disposed at a location where the temperature of the heat transfer pipe 21 can be monitored, so that the margin for the energization control design for the halogen lamp 11 and the halogen lamp 11 A margin for safety in case of runaway can be secured.

[Example 3]
Another example of the image heating apparatus according to the present invention will be described.

  The heat fixing apparatus 100 shown in the present embodiment is provided with a heat absorption layer 21c that can promote absorption of radiant heat generated by the halogen lamp 11 on the outer peripheral surface of the base material 21b of the heat transfer pipe 21, and the outer periphery of the heat absorption layer 21c. A release layer 21b is provided on the surface. Except for this point, the heat fixing apparatus 100 shown in this embodiment has the same configuration as the heat fixing apparatus 100 of the first embodiment.

  FIG. 6 is an explanatory diagram of the layer configuration of the heat transfer pipe 21 in the heat fixing apparatus 100 according to the present embodiment.

  The material of the base material 21a of the heat transfer pipe 21 is the same as the material of the base material 21a of Example 1, and the configuration of the heat transfer pipe 21 is a low heat capacity member having pressure resistance.

  The heat absorption layer 21c is a layer designed to efficiently absorb the radiant heat generated by the halogen lamp 11. The heat absorption layer 21c is formed on the outer peripheral surface of the base material 21a (on the surface on the heat transfer nip portion side).

  As the heat absorption layer 21c, there is a method in which a black layer such as a resin layer in which a matte black heat resistant paint (for example, # 8000C manufactured by Okitsumo Co., Ltd.) or carbon black is dispersed is formed to about 10 to 100 μm. Thus, when the heat absorption layer 21c is formed in a black body, it is preferable to use a release layer 21b in which a transparent PFA resin or the like is formed in a thin film of about 5 to 20 μm.

  Further, there is a method of forming a layer of a material having higher thermal conductivity than the base material 21a as the heat absorption layer 21c. For example, when aluminum nitride having a thermal conductivity of 200 W / m · K is used as the base material 21a, a silver paste having a thermal conductivity of 400 W / m · K is applied and baked as the heat absorbing layer 21c, and is about 10 to 100 μm. This is achieved by forming

  As an alternative to the heat absorption layer 21c, there is a method of forming the release layer 21b and the base material 21a as a good heat absorber. Specifically, a fluororesin in which a black member such as carbon black is dispersed can be formed as the release layer 21b to improve the radiation heat absorption performance. Moreover, the absorption performance of a radiant heat can be improved by using black aluminum nitride etc. as the base material 21a. Further, heat transfer efficiency to the surface of the fixing roller 30 in the heat transfer nip portion N1 is improved by dispersing good heat conductive particles such as silicon carbide in the release layer 21b and forming the outermost layer with a high heat conductive member. There is also a method.

  The heat fixing device 100 of the present embodiment has the same configuration as the heat fixing device 100 of the first embodiment except that the heat absorption layer 21c is provided on the outer peripheral surface of the base material 21b of the heat transfer pipe 21. The same effect as the heat fixing device 100 of Example 1 can be obtained. In addition, since the heat fixing device 100 of the present embodiment is provided with the heat absorption layer 21c on the outer peripheral surface of the base material 21b of the heat transfer pipe 21, the temperature rise performance of the heat transfer pipe 21 can be improved. In particular, it is possible to improve the performance of efficiently storing radiant heat near the outer peripheral surface of the heat transfer pipe 21 and transmitting it to the surface of the fixing roller 30 at the heat transfer nip portion N1. As a result, the warm-up time for raising the temperature of the fixing roller 30 to a temperature for heating the toner image T carried on the transfer material P can be further shortened.

[Other examples]
1) In the heat fixing apparatus shown in each embodiment, the pressure rotator 40 is not limited to a pressure roller, and a thin elastic layer is formed on a thin polyimide resin or SUS substrate of about several tens of μm. It may be a film-like member having a release layer formed on the layer, or a heat-resistant pad member. When a film-like member is used as the pressure rotator 40, the film-like member is pressed substantially uniformly against the fixing roller 30 by a rigid pressure member disposed inside the film-like member, and the gap between the film-like member and the fixing roller 30 The nip portion N is formed in When a heat resistant pad member is used as the pressure rotating body 40, a sliding layer is provided on the surface of the heat resistant pad member on the fixing roller 30 side. Then, the heat-resistant pad member is pressed substantially uniformly against the fixing roller 30 by a rigid pressure member disposed on the side opposite to the fixing roller 30 to form a nip portion N between the heat-resistant pad member and the fixing roller 30.

  2) The heat fixing device shown in each embodiment is not limited to use as a device for heating and fixing an unfixed toner image carried on a transfer material to the transfer material, but the image fixed on the transfer material is heated to gloss the image. It may also be used as a device for increasing the image quality, or as a device for assuming an image on a transfer material.

  The image heating device according to the embodiment of the present invention has been described above. However, the image heating device according to the present invention is not limited to the heat fixing device according to the embodiment, and can be modified within the technical idea of the image heating device. .

Cross-sectional side view of an example of a heat fixing apparatus according to Embodiment 1 Explanatory drawing of the electric power feeding control system of the heat fixing apparatus which concerns on Example 1. FIG. Explanatory drawing of the layer structure of the heat transfer pipe in the heat fixing apparatus which concerns on Example 1. FIG. Explanatory drawing of temperature rising transition of the heat transfer pipe surface and the fixing roller surface in the heat fixing apparatus according to the first embodiment. Cross-sectional side view of an example of a heat fixing apparatus according to Embodiment 2 Explanatory drawing of the layer structure of the heat transfer pipe in the heat fixing apparatus which concerns on Example 2. FIG. Configuration model diagram of an example of an image forming apparatus Schematic model of an example of a conventional heat roller type fixing device Schematic model diagram of an example of a conventional external radiation heating type fixing device

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Heat fixing apparatus, 11 ... Heating body, 21 ... Heat transfer rotary body, 30 ... Heating rotary body, 22 ... Safety element, 51 ... Temperature detection element, N1 ... Heat transfer nip part, N2 Nip, P Transfer material, T Unfixed toner image

Claims (5)

In an image heating apparatus comprising: a heating body that emits radiant heat; and a heating rotator that heats an image carried by a recording material that is heated to a temperature corresponding to the radiant heat generated by the heating body.
A heat transfer rotor that forms a heat transfer nip in contact with the heating rotor;
A safety element for sensing the temperature of the heat transfer rotor;
Have
The heat transfer rotator transmits heat to the heating rotator via the heat transfer nip portion to heat the image that is radiantly heated by the radiant heat generated by the heater and that is carried by the recording material.
The safety element senses that the temperature of the heat transfer rotating body radiantly heated by the radiant heat generated by the heating body exceeds the temperature corresponding to the heat for heating the image carried by the recording material, and the heating body An image heating apparatus characterized in that the heating operation is interrupted.   The heat transfer rotator includes a base material that is formed using a material that does not plastically deform with respect to the applied pressure that can form the heat transfer nip portion, and per unit sectional volume of the heat transfer rotator. The image heating apparatus according to claim 1, wherein the heat capacity is 300 [J / (K · m)] or less.   The image heating apparatus according to claim 1, further comprising a temperature detection element that detects a temperature of the heating rotator.   The image heating apparatus according to claim 1, further comprising a temperature detection element that detects a temperature of the heat transfer rotating body.   The heat transfer rotator has a base material formed using a material that is not plastically deformed against the applied pressure that can form the heat transfer nip portion, and the surface of the base material on the heat transfer nip portion side. The image heating apparatus according to claim 1, further comprising a heat absorption layer capable of promoting absorption of radiant heat generated by the heating body.