JP2011053413A - Heating device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film heating type heating device, including a heating body which has structure keeping temperature distribution of the heating body within the width of a fixing nip at an appropriate condition, attaining power saving, shortening of waiting time and reduction of cost, and hardly causing cracks due to thermal stresses, and to provide a high-performance low-cost image forming apparatus that includes the heating device. <P>SOLUTION: The heating device includes the heating body 1, provided with the heating body that is energized to generate heat and a temperature detection element on a substrate, and arranged to be fixedly supported; a fixing film 3 movingly sliding over the heating body; and a pressure member forming the fixing nip by coming in press-contact with the heating body via the fixing film, wherein recording material that carries an unfixed image is held and conveyed between the fixing film and the pressure member in the fixing nip, and the unfixed image is fixed on the recording material with heat from the heating body via the fixing film. When the width of a contact part of the fixing film with a pressure roller 4 is equal to or under the width of a contact part of the heating body 1 with the fixing film 3, the heating body is arranged inside the width of a heating nip, and the width of the heating body is set equal to or below 6 mm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a recording material heating apparatus for heat fixing an image.

  More specifically, the present invention relates to a film heating type heating device that applies heat energy to a recording material via a heat-resistant fixing film to heat and fix an image, and an image forming apparatus including the heating device.

  Conventionally, in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, it is formed and supported on a recording material such as a transfer material, a photosensitive paper or an electrostatic recording paper by an appropriate image forming process of a transfer method or a direct method. As a heating device for heating and fixing an unfixed toner image of the image information, a recording material is formed by a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and being in pressure contact with the heating roller. A heat roller type apparatus that heats while nipping and conveying is widely used.

  In addition, various systems and configurations such as a flash heating system, an open heating system, a hot plate heating system, a belt heating system, and a high frequency heating system are known.

  FIG. 7 shows a cross-sectional configuration model view of the main part of a film heating type heating apparatus.

  Reference numeral 1 denotes a heating element (heater) having a low heat capacity, which is fixedly supported on a heating element support member (stay) 2 having rigidity, high heat resistance and heat insulation. Reference numeral 3 denotes a thin heat-resistant film (fixing film) such as polyimide or stainless steel. Reference numeral 4 denotes an elastic pressure roller as a pressure member. The heating body 1 and the pressure roller 4 are pressed against each other with a predetermined pressing force across the fixing film 3, and a fixing nip portion Na having a predetermined width is formed between the fixing film 3 and the pressure roller 4. 3, heating nip portions Nb each having a predetermined width are formed. The fixing film 3 moves and passes through the heating nip portion Nb while being in close contact with and sliding on the surface of the heating body 1 in the direction of the arrow by the rotational driving force of the pressure roller 4 or another driving member.

  In a state where the fixing film 3 is driven to move and the heating body 1 rises to a predetermined temperature and is adjusted in temperature, an unfixed toner image Ta is carried between the fixing film 3 and the pressure roller 4 in the fixing nip Na. By introducing the recording material P thus made with the toner image carrying surface side toward the fixing film 3, the recording material P moves and passes along with the fixing film 3 in the fixing nip portion Na.

  In the process of passing through the fixing nip portion, the heat of the heating body 1 is applied to the recording material P through the fixing film 3 and the toner image is heated and fixed on the surface of the recording material P. The recording material P that has passed through the fixing nip Na is separated from the surface of the fixing film 3 and conveyed. Tb is a heat-fixed toner image.

  The heating element 1 is a linear heating element having a low heat capacity as a whole, with a direction perpendicular to the moving direction of the fixing film 3 (perpendicular to the drawing) at the fixing nip Na, and a ceramic heater is generally used. The heater 1 includes a heat-resistant, insulating, low heat capacity, and high heat conductive ceramic substrate (heater substrate) 11 such as aluminum nitride, and is formed on the surface of the substrate in a linear or narrow strip shape along the length of the substrate. The heating element 12 that generates and heats electricity is used as a basic configuration. Reference numeral 13 denotes a heater back surface protective layer such as heat-resistant glass covering the heating element forming surface of the heater substrate 11. Reference numeral 14 denotes a temperature detection element such as a thermistor provided in contact with the back side of the heater substrate 11. Reference numeral 15 denotes a heater surface protective layer made of heat-resistant glass or the like covering the fixing film contact sliding surface of the heater substrate 11, and also has a function of reducing the frictional force with the fixing film 3. The width Wc of the heating body 1 in the moving direction of the fixing film 3 is generally set wider than the fixing nip width Wa.

  Power is supplied from a power supply circuit (not shown) between power supply electrodes (not shown) at both longitudinal ends of the heat generator 12 to generate heat from the heat generator 12, and the heating element 1 having a low heat capacity as a whole quickly rises due to the generated heat. To do. The temperature rise of the heating element 1 is detected by the temperature detecting element 14 brought into contact with the back side of the substrate 11, and the temperature detection information is input to a control system (not shown). The control system controls the power supplied to the heating element 12 based on the input temperature detection information so that the heating body temperature or the fixing nip temperature is maintained at a predetermined constant temperature.

  Compared to other heating devices such as a heat roller method, such a film heating type device can use a low heat capacity one as the heating element 1 and a thin film low heat capacity one as the fixing film 3. There are advantages such as saving power and shortening the wait time (the time from when the apparatus is turned on until it is ready for print output), quick start, and suppression of temperature rise in the machine.

JP-A-4-44075

  In the conventional film heating type heating apparatus, when the fixing film moving direction of the fixing nip Na is the fixing nip width Wa, the heating element 12 of the heating body 1 has two or three places in the fixing nip width direction. The temperature detecting element 14 is disposed in the vicinity of the center of the fixing nip width Wa on the back surface side of the heating body substrate 11.

  The temperature distribution of the heating element 1 in the fixing nip width Wa is the highest temperature portion where the heating element 12 is located. In this conventional apparatus, the heating element 12 is from the center of the fixing nip width Wa. Since the heating element 1 is located at two places several mm apart, the temperature distribution of the heating element 1 within the fixing nip width Wa is two high temperature parts at the center of the heating element 12 as shown in the graph of FIG. From there, the temperature decreases toward the recording material inlet side (nip inlet) and the recording material outlet side (nip outlet) of the fixing nip portion Na.

  The temperature detection element 14 detects the temperature near the center position of the fixing nip width Wa and inputs the temperature information to the control system. Based on the input temperature information, the control system maintains the temperature of the central portion in the fixing nip width Wa at a predetermined constant control temperature T0 (for example, 190 ° C.) for appropriately heating and fixing the unfixed toner image. Thus, the power supplied to the heating element 12 is controlled.

  The fixing film 3 is a single layer film such as PTFE, PFA, FEP, etc. having heat resistance and thermoplasticity, or PTFE, PFA, FEP, etc. on the outer peripheral surface of the film based on polyimide, polyamideimide, PEEK, PES, PPS, etc. Some are composed of a coated composite layer film, but some are based on a metal material such as stainless steel, aluminum, or nickel having higher thermal conductivity. However, if a material such as metal having high rigidity is used for the fixing film 3, both ends of the heating nip portion Nb are separated from the heater surface protective layer 15, and the heating nip portion width Wb becomes narrower than the fixing nip portion width Wa. appear.

  The fixing film 3 is heated only at the heating nip portion Nb in contact with the heater surface protective layer 15. Therefore, the heating nip portion width Wb is reduced, so that the amount of heat transferred to the fixing film 3 is reduced, and the advantage of using a metal material having high thermal conductivity for the fixing film 3 is reduced. Further, heating the recording material inlet side and the outlet side from the heating nip portion Nb of the heating body 1 does not increase the temperature of the fixing film 3 but leads to an increase in power consumption and an increase in wait time. .

  If the rotation speed of the fixing film 3 is increased to improve the printing speed, the time during which the unfixed toner Ta stays in the fixing nip Na is shortened, the toner temperature cannot be raised to an appropriate temperature, and the fixing property cannot be secured. Therefore, it is necessary to dispose the heating element 12 at an appropriate position and to transfer more heat to the fixing film 3 more efficiently.

  Further, when the temperature of the heating element 1 is increased, temperature unevenness occurs between the high temperature portion and the low temperature portion in the substrate 11 and a temperature difference is generated, so that thermal stress is generated. In addition, when the recording material P is passed through one surface of the substrate 11, the temperature of the paper passing portion of the substrate 11 is temporarily greatly reduced, so that the difference between the low temperature portion and another high temperature portion is further increased. Since the thermal stress further increases, the substrate 11 itself may be warped or cracked due to the repetition thereof, and these tend to be prominent when the width of the substrate 11 is increased.

  In order to avoid this problem, a heater using a substrate made of aluminum nitride, silicon carbide, or the like, which has better thermal conductivity than alumina and has a low thermal expansion coefficient, has been developed. However, the substrate 11 made of these materials is expensive and leads to an increase in cost.

  Therefore, an object of the present invention is to maintain a heating body temperature distribution in the fixing nip width in an appropriate state for a heating apparatus of a film heating method, to save power, shorten a wait time, and to crack a heater substrate due to thermal stress at a low cost. An object of the present invention is to provide a heating device having a heating body having a difficult structure and a high-performance and low-cost image forming apparatus having the heating device.

  The present invention is a heating apparatus and an image forming apparatus having the following configurations.

(1) A heating element that is provided with a heating element and a temperature detection element that generate heat when energized on the substrate and is fixedly supported, a fixing film that slides on the heating element, and a heating element via the fixing film And a pressure member that forms a fixing nip portion by pressure contact with the recording material carrying an unfixed image between the fixing film and the pressure member of the fixing nip portion, and through the fixing film In a heating device that fixes an unfixed image on a recording material by heat from a heating member, the fixing film moving direction width of the contact portion between the fixing film and the pressure roller is the fixing nip width Wa, and the contact portion between the heating member and the fixing film is The fixing film moving direction width is the heating nip width Wb, and when Wa ≧ Wb,
A heating device characterized in that the center of the heating element is disposed within the width of the heating nip.

(2) A heating element that is provided with a heating element and a temperature detection element that generate heat when energized on the substrate and is fixedly supported, a fixing film that slides on the heating element, and a heating element that passes through the fixing film And a pressure member that forms a fixing nip portion by pressure contact with the recording material carrying an unfixed image between the fixing film and the pressure member of the fixing nip portion, and through the fixing film In a heating device that fixes an unfixed image on a recording material by heat from a heating member, the fixing film moving direction width of the contact portion between the fixing film and the pressure roller is the fixing nip width Wa, and the contact portion between the heating member and the fixing film is The fixing film moving direction width is the heating nip width Wb, and when Wa ≧ Wb,
A heating apparatus characterized in that a fixing film moving direction width of the heating body is within 6 mm.

(3) A heating element which is provided with a heating element and a temperature detection element that generate heat when energized on the substrate and is fixedly supported, a fixing film that slides on the heating element, and a heating element via the fixing film And a pressure member that forms a fixing nip portion by pressure contact with the recording material carrying an unfixed image between the fixing film and the pressure member of the fixing nip portion, and through the fixing film In a heating device that fixes an unfixed image on a recording material by heat from a heating member, the fixing film moving direction width of the contact portion between the fixing film and the pressure roller is the fixing nip width Wa, and the contact portion between the heating member and the fixing film is The fixing film moving direction width is the heating nip width Wb, and when Wa ≧ Wb,
The heating device according to claim 1, wherein the fixing film is made of stainless steel, aluminum, or nickel.

(4) A heating element that is provided with a heating element and a temperature detection element that generate heat when energized on the substrate and is fixedly supported, a fixing film that slides on the heating element, and a heating element that passes through the fixing film And a pressure member that forms a fixing nip portion by pressure contact with the recording material carrying an unfixed image between the fixing film and the pressure member of the fixing nip portion, and through the fixing film In a heating device that fixes an unfixed image on a recording material by heat from a heating member, the fixing film moving direction width of the contact portion between the fixing film and the pressure roller is the fixing nip width Wa, and the contact portion between the heating member and the fixing film is The fixing film moving direction width is the heating nip width Wb, and when Wa ≧ Wb,
The heating apparatus according to claim 2, wherein the fixing film is made of stainless steel, aluminum, or nickel.

  (5) An image forming apparatus comprising the heating device according to any one of (1) to (4) as an image heating fixing device.

(Function)
By placing the center of the heating element within the heating nip width and keeping the heating element width within 6 mm, the temperature distribution of the heating element in the fixing nip is kept in an appropriate state, saving power, reducing the wait time, and reducing costs. Thus, it is possible to provide a heating device having a heating body having a structure in which cracking due to thermal stress hardly occurs, and a high-performance and low-cost image forming apparatus having the heating device.

  According to the present invention, for a heating device of a film heating method and an image forming apparatus equipped with the heating device, the heating body temperature distribution in the fixing nip width Wb is maintained in an appropriate state, power saving and weight time reduction, and It is possible to provide a heating device having a heating body with a structure that is less likely to crack due to thermal stress at low cost, and a high-performance and low-cost image forming apparatus having the heating device.

1 is a schematic configuration diagram of an example of an image forming apparatus. FIG. 3 is a structural model diagram of an image heating and fixing apparatus portion. Omitted middle part of the heating element, partially cut away back model view. The enlarged model figure of a fixing nip part, and the temperature distribution figure of the heating body in a fixing nip part width. FIG. 6 is an enlarged model view of a fixing nip portion of a fixing device having a configuration A according to Embodiment 2. FIG. 6 is an enlarged model view of a fixing nip portion of a fixing device having a configuration B according to Embodiment 2; (A) * (b) * (c) is a schematic diagram of another example of composition form of a heating device of a film heating system, respectively.

(Example)
Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

<Embodiment Example 1> (FIGS. 1 to 3)
(1) Example of Image Forming Apparatus FIG. 1 is a schematic diagram of an example of an image forming apparatus. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process.

  Reference numeral 31 denotes an electrophotographic photosensitive drum (hereinafter abbreviated as a drum) as an image carrier, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined process speed (peripheral speed, image forming speed).

  The drum 31 is subjected to a primary charging process uniformly at a predetermined polarity and potential by a charging roller 32 as a charging means during the rotation process. This example is negatively charged. S <b> 1 is a charging bias application power source for the charging roller 32.

  Next, the drum of the exposure light portion is subjected to scanning exposure L by laser light intensity-modulated in accordance with the time-series electric digital pixel signal of the target image information output from the laser scanner LS on the primary charging surface. The potential is attenuated, and an electrostatic latent image corresponding to target image information is formed on the drum peripheral surface.

  Next, the electrostatic latent image is reversely developed as a toner image with a negative developer (negatively charged toner) by a reversal developing device 33 as a developing means (toner adheres to the exposed bright portion of the drum surface). Reference numeral 33a denotes a developing roller (or developing sleeve). S2 is a developing bias application power source for the developing roller 33a.

  Next, in the transfer portion 34a, which is a pressure nip portion between the drum 31 and the transfer roller 34 as a transfer means, the toner image is fed to the transfer portion 34a from a paper supply portion (not shown) at a predetermined timing. It is sequentially transferred onto the surface of the material (transfer material) P. S 3 is a power supply for applying a transfer bias to the transfer roller 34. In this example, the back surface of the recording material P is charged positively by a transfer roller 34 to which a transfer bias is applied. The toner image has a negative polarity on the drum 31 surface side. Is transferred to the recording material P surface side by electrostatic force.

  The recording material that has passed through the transfer portion 34a is neutralized by a static elimination needle 35 (or a separation charger), separated from the surface of the drum 31 in cooperation with an unillustrated separation means, conveyed to a heat fixing device 37, and introduced to a toner image. After being subjected to the heat fixing process, it is output as a print. Alternatively, in the case of the double-sided print mode or the multiple print mode, it is introduced into the refeeding unit to the transfer unit 34a.

  The surface of the drum 31 after separation of the recording material is subjected to the removal of residual deposits such as transfer residual toner by the cleaning device 36 and is repeatedly used for image formation.

(2) Heat fixing device 37
FIG. 2 is an enlarged model view of the heat fixing device 37, and FIG. 3 is an enlarged model view of the fixing nip portion.

a) Overall Configuration and Operation of Apparatus 37 The heat fixing apparatus 37 of this example is a so-called tensionless type film heating type apparatus disclosed in Patent Document 1 and the like.

  Reference numeral 1 denotes a heating body, which is a horizontally long linear heating body having a low heat capacity and having a longitudinal direction in a direction perpendicular to the conveying direction of the recording material P. In the heating element 1, reference numeral 11 denotes a heat-resistant / insulating / low heat capacity / high heat conductive heater substrate whose longitudinal direction is perpendicular to the conveying direction of the recording material P. In this example, the thickness is 1 mm and the width is 5. This is an aluminum nitride substrate having a length of 5 mm and a length of 240 mm.

  When the fixing film moving direction of the fixing nip Na is the fixing nip width Wa, the fixing nip width Wa is set to 8.0 mm in this example. In addition, when the fixing film moving direction of the heating nip portion Nb is the fixing nip portion width Wb, the heating nip portion width Wb is set to 4.0 mm in this example.

  In this example, as shown in FIG. 4, in the fixing nip width Wa, the fixing nip width center, the heating element center, and the temperature detection element 14 are configured to coincide with each other, and the heating element 12 and the temperature detection element 14 are connected to the heater substrate. 11, the heating element 1 is configured.

  The cylindrical fixing film 3 is loosely fitted on the assembly including the stay 2 and the heating body 1 described above. The fixing film 3 can be made of a heat-resistant film having a film thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more, in order to reduce the heat capacity and improve the quick start property. A composite layer film having a thickness of 50 μm and a film outer peripheral surface coated with PFA was used.

  The elastic pressure roller 4 has a core metal 4a and a rubber elastic layer 4b having good releasability, such as silicon rubber, formed concentrically and integrally with the core metal, and both end shafts of the core metal 4a are rotatably supported by bearings. I'm allowed.

b) Evaluation The graph in FIG. 3 shows the temperature distribution in the fixing nip width. The temperature control is set to 190 ° C. at the detection temperature of the thermistor which is the temperature detection element 14. The temperature distribution of the heater substrate 11 of the heating body 2 at this time was set so that both the thermistor 14 partial temperature T1 and the heating element 12 partial temperature T2 were about 190 ° C. (T1 = T2 = 190 ° C.).

  The fixing device having the configuration of this example and the fixing device having the conventional configuration shown in FIG. 7, that is, the width Wc of the heating element 1 is 10 mm, and the heating element 12 is separated by 2 mm from the center of the fixing nip width Wa. 1 is used in the printer shown in FIG. 1 for the wait time in the morning (time from the start of heating up of the heating element 1 until T1 and T2 reach the set temperature), during the wait time and continuously after that. The power consumption in the paper and the amount of heat transferred to the toner were evaluated.

  As a result, the conventional fixing device (FIG. 7) has a shorter wait time, lower power consumption during the wait time and during continuous paper passage, and an increased amount of heat transferred to the toner compared to the fixing device of this example. The effect was confirmed.

  This is because the heating element 12 is close to the heating nip portion Nb in the configuration as in this example, so that the heat generated in the heating element 12 quickly raises the temperature of the heating nip portion Nb and shortens the wait time. It is because it is connected to. Since the heat generated in the heating element 12 is efficiently transferred to the heating nip portion Nb, the amount of heat transferred to the unfixed toner is increased.

  Further, in the case of the fixing device having the conventional configuration, the volume of the heater substrate 11 is large, so that time is required for both T1 and T2 to reach a predetermined temperature due to the heat generated by the heating element 12, both during the wait time and during continuous paper feeding. This has led to an increase in power consumption.

  Further, since the heater substrate 11 has a reduced width Wc and the heating element 12 is close to the heating nip Nb, the heat generated from the heating element 12 in response to the temperature drop of the fixing nip Na due to the passage of the recording material P. Increases the temperature of the heating nip portion Nb early, and the temperature adjustment response for keeping the temperature of the fixing nip portion Na constant is improved. For this reason, the temperature at the center of the fixing nip width Wa becomes constant, and a fixed level of fixing performance without variation can be secured.

  Further, as the heating efficiency for the recording material P, it is preferable that the heating element 12 is provided at the center portion of the fixing nip width Wa, and the power consumption can be reduced.

  The above-described effect becomes more prominent as the width Wc of the heating body 1 becomes narrower. However, if the width is smaller than the heating nip width Wb, the corners at both ends of the heating body 1 come into contact with the inner surface of the film when the fixing film 3 slides. For this reason, the inner surface of the film is scraped and the deterioration of the fixing film is accelerated. Therefore, in this example, the width Wc of the heating element 1 is set to 5.5 mm with a margin with respect to the heating nip width Wb of 4 mm. The amount of the margin need not be constant, and may be appropriately adjusted according to the shape and material of the heating element support member 2, the pressure roller 4, and the fixing film 3.

<Embodiment example 2> (FIGS. 4 to 5)
In this example, the fixing substrate (FIG. 4) in which the heater substrate material of the fixing device having the conventional configuration shown in FIG. 7 is changed from aluminum nitride to alumina having a low material cost, and the fixing device (FIG. 3) in the configuration of the first embodiment. The endurance test in which the recording material P is continuously fed after the wait time is finished in both of the configurations B (FIG. 5) in which the heater substrate material is changed from aluminum nitride to alumina. Other apparatus configurations are the same as those in the first embodiment.

  In the case of the configuration of this example, it was confirmed that only a portion of the alumina heater substrate attached to the configuration A had cracks.

  This is because, when the recording material P is passed, the temperature of the paper passing portion of the heater substrate 11 is temporarily greatly reduced, so that the difference between the low temperature portion and the other high temperature portion further increases and the thermal stress further increases. Then, it is considered that cracks occurred in the heater substrate 11 itself due to the repetition. This is because when the length in the width direction of the heater substrate 11 is increased, or when the thermal expansion coefficient of the heater substrate material is increased, the thermal conductivity of the same material is further decreased, and this tends to be noticeable. In the case of the configuration B, the thermal stress increases by changing the material to alumina having a large thermal expansion coefficient and a low thermal conductivity, but the thermal stress is relieved because the heater substrate width Wc is short, and no cracks appear. It is done.

  In the case of the configuration of this example, since the thermal stress applied to the heater substrate 11 at the time of continuous paper feeding can be reduced, a material with lower cost can be used. Alternatively, a safety margin against heater substrate cracking can be obtained even when the same material is used.

<Embodiment 3> (FIG. 6)
(A), (b), and (c) of FIG. 6 each show another configuration example of the heating device of the film heating system.

  In (a), an endless belt-like fixing film 3 is suspended between three substantially parallel members of a heating body 1 fixedly supported on a stay 2, a driving roller 5, and a driven roller 6 (tension roller). The fixing film 3 is stretched and the fixing film 3 is sandwiched between the heating body 1 and the pressure roller 4 is pressed to form the fixing nip portion Na. By rotating the driving roller 5 in the clockwise direction indicated by the arrow by the driving system M, the fixing film 3 is driven to rotate while being in close contact with the heating body 1. The pressure roller 4 is driven to rotate. The recording material P is introduced between the fixing film 3 and the pressure roller 4 in the fixing nip portion Na, and is nipped and conveyed to heat and fix the unfixed toner image.

  For (b), an endless belt-like fixing film 3 is suspended between two members of a heating member 1 fixedly supported on a stay 2 and a driving roller 5, and fixing is performed by driving the driving roller 5 to rotate. The film 3 is configured to rotate.

  The film (c) is not an endless belt-like film as the fixing film 3 but a long end film wound in a roll, and this is wound from the feed shaft 7 side through the heating body 1 to the winding shaft. It is configured to travel to the 8 side at a predetermined speed.

  It goes without saying that the present invention can be applied to the film heating type heating apparatus having such a configuration to obtain the same effects as those of the apparatuses of the first and second embodiments.

  The heating device of the present invention is not only an image heating and fixing device of the embodiment, but also, for example, a device for heating a recording material carrying an image to improve surface properties (gloss etc.), a device for hypothetical dressing, It can be used as a heating device for feeding a sheet-like material to dry or laminate.

DESCRIPTION OF SYMBOLS 1 Heating body 2 Heating body support member 3 Fixing film 4 Pressure roller 4a Core metal 4b Rubber elastic layer 5 Drive roller 6 Driven roller 7 Feeding shaft 8 Winding shaft 11 Heater board 12 Heating element 13 Surface protection layer 14 Temperature detection element 15 Heater surface protective layer 31 Electrophotographic photosensitive drum 32 Charging roller 33 Reverse developing device 33a Developing roller 34 Transfer roller 34a Transfer portion 35 Static elimination needle 36 Cleaning device 37 Heating fixing device Na Fixing nip portion Nb Heating nip portion P Recording material S1 Charging bias Applied power source S2 Development bias applied power source S3 Transfer bias applied power source Ta Unfixed toner image Tb Fixed toner image Wa Fixing nip width Wb Heating nip width Wc Heater substrate width

Claims (5)

A heating element that generates heat when energized and a temperature detection element are provided on the substrate, a heating element that is fixedly supported, a fixing film that slides on the heating element, and the heating element that is in pressure contact with the heating element. A pressure member that forms a fixing nip portion, and sandwiches and conveys a recording material carrying an unfixed image between the fixing film and the pressure member in the fixing nip portion, and from a heating body via the fixing film. In a heating device for fixing an unfixed image to a recording material by the heat of the fixing film, the fixing film moving direction width of the contact portion between the fixing film and the pressure roller is the fixing nip width Wa, and the fixing film movement at the contact portion between the heating body and the fixing film When the direction width is the heating nip width Wb and Wa ≧ Wb,
A heating device characterized in that the center of the heating element is disposed within the width of the heating nip.   2. The heating apparatus according to claim 1, wherein a width of the heating body in the moving direction of the fixing film is 6 mm or less.   The heating apparatus according to claim 1, wherein the base layer of the fixing film is made of stainless steel, aluminum, or nickel.   The heating apparatus according to claim 2, wherein a material of the base layer of the fixing film is stainless steel, aluminum, or nickel.   An image forming apparatus comprising the heating device according to claim 1 as an image heating and fixing device.

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