JP2007102010A - Heat fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve safety in a fixing device using a ceramic heater. <P>SOLUTION: A heat fixing device comprises the ceramic heater, a heater holder, a pressure stay, a pressure roller, a high heat-conductive member which is disposed on the heater holder with a gap so as not to come into direct contact with the ceramic heater, a gap layer on the surface other than a heater contact surface between the ceramic heater and the heater holder, and a temperature protection means like a thermo switch or a thermal fuse which stops power supply to the heater in accordance with the temperature of the heater. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heating and fixing apparatus that heats a recording material that carries an image in a nip formed by first and second fixing members.

  More specifically, image information formed on a recording material (paper, printing paper, transfer material sheet, OHT sheet, glossy paper, glossy film, etc.) by timely image forming process means such as electrophotography, electrostatic recording, and magnetic recording. The present invention relates to a heat fixing apparatus that heat-fixes an unfixed toner image corresponding to the above on a recording material surface.

  In particular, the present invention relates to an on-demand fixing device using a thin sleeve, which is suitable for use in a color image forming apparatus, is low-cost and has a short fixing device rise time (so-called warm-up time).

  In recent years, colorization has progressed in image forming apparatuses such as printers and copiers. As a fixing device used in such a color image forming apparatus, heat roller fixing having an elastic layer on a fixing member is well known. An example of a fixing device using such a fixing roller having an elastic layer is shown in FIG.

  In this fixing device, unfixed toner is rotated at a contact nip portion (fixing nip) N of two heating rollers, which is composed of a fixing roller 1601 and a pressure roller 1602 that are rotationally driven in the direction of an arrow and adjusted to a predetermined fixing temperature. The recording material P on which the image t is placed is configured to pass therethrough.

  When the unfixed toner image t passes through the nip portion N, it is heated and pressed by the fixing roller 1601 and the pressure roller 1602 to be fixed on the recording material P as a completed image (permanently fixed image).

  Each of the rollers 1601 and 1602 includes a halogen heater H at the center, and the radiant energy generated from the heater H is absorbed by the aluminum cores 1601a and 1602a inside each roller and heated. The thermistors 1603 and 1604 are arranged in elastic contact with the surfaces of the rollers 1601 and 1602, and the rollers 1601 and 1602 with respect to the halogen heater H based on the temperatures detected by the thermistors 1603 and 1604. Power supply is controlled and temperature adjustment is performed.

  Elastic layers 1601b and 1602b made of silicone rubber having a thickness of 2 mm are provided around the aluminum cores 1601a and 1602a of the rollers 1601 and 1602, respectively. PFA (tetrafluoroethylene / perfluoroalkyl ether copolymer / tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin), FEP (tetrafluoroethylene / hexafluoropropylene copolymer) to prevent paper dust and the like from sticking Coating layers 1601c and 1602c are formed of a resin having good releasability and heat resistance, such as a coalescence / tetrafluoroethylene / hexafluoropropylene copolymer resin).

  The reason why the elastic layer 1601b is provided on the fixing roller 1601 side, which is a fixing member in contact with the unfixed toner t, in the fixing nip portion N is to fix the toner image surface as uniformly as possible.

  By providing the elastic layer 1601b on the fixing roller 1601 side, when the toner image t passes through the fixing nip N, the elastic layer 1601b is deformed along the toner layer, so that the toner that is unevenly placed on the image. However, it is encased in the elastic layer 1601b and uniformly heated so that uniform fixing is achieved.

  An image fixed uniformly in this way has no gloss unevenness, and has a feature that the light transmittance of the image is excellent particularly when an OHT (transparent sheet for overhead projector) is fixed.

  However, in a heat roller type fixing device having such an elastic layer, the heat capacity of the heat roller itself increases, and the time required to raise the temperature of the fixing roller 1601 to a temperature suitable for toner image fixing. There was a problem that (warm-up time) was long. Further, the cost of the fixing member is also expensive.

  On the other hand, as a low-cost fixing device with a short warm-up time, a film fixing type fixing device used in a black and white printer or the like is well known. An example of such a film fixing device is shown in FIG.

  In this fixing device, a thin fixing film 1711 is sandwiched between a heater 1712 fixedly supported by a support member 1715 and an elastic pressure roller 1714 to form a fixing nip portion N. The fixing film 1711 is attached to the heater 1712. The recording material P carrying the toner image t is nipped and conveyed between the fixing film 1711 and the pressure roller 1714 in the fixing nip portion, and is moved from the heater 1712 via the fixing film 1711. In this configuration, the toner image on the recording material is heated by heat. The unfixed toner image t on the recording material P receives heat and pressure when passing through the fixing nip portion N, and is fixed on the recording material P as a completed fixed image (permanently fixed image).

  The fixing film 1711 is, for example, an endless film made of a heat-resistant resin having a thickness of about 50 μm, and a release layer (such as a fluororesin coating layer) having a thickness of about 10 μm is formed on the surface. The heater 1712 is a ceramic. A resistance heating element is formed on a substrate. Temperature detection means 1713 is brought into contact with the heater 1712, the temperature of the heater 1712 is detected, and temperature control is performed by a control means (not shown) so that the temperature of the heater 1712 becomes a desired temperature.

  Further, in order to reduce the heat capacity of the fixing film 1711, the fixing film 1711 is not provided with an elastic layer.

  In the fixing device having such a configuration, since the heat capacity of the fixing film 1711 is very small, the power of the heater 1712 is turned on, and then the temperature of the fixing nip portion N is raised to a temperature capable of fixing the toner image in a short time. It is possible.

  Particularly in recent years, from the viewpoint of energy saving, a film heating type fixing device that heats through a film having a small heat capacity has attracted attention as a method of high heat transfer efficiency and quick start-up of the device. These are technologies that reduce the heat capacity as much as possible to improve quick start and energy savings and improve controllability to meet high-speed, high-quality print requirements.

  However, when a film fixing device using the fixing film 1711 not provided with such an elastic layer is used as a fixing device of a color image forming apparatus, unevenness due to the presence or absence of the surface of the recording material P or the toner layer or unevenness of the toner itself. As a result, the surface of the fixing film 1711 cannot follow, and there is a difference in heat applied from the fixing film between the convex portion and the concave portion. The convex part that is in good contact with the fixing film conducts heat well from the fixing film, and the concave part is less likely to conduct heat from the fixing film than the convex part.

  In a color image, since a plurality of color toner layers are mixed and used, the unevenness of the toner layer is larger than that of a black and white image, and if the fixing film as a fixing member does not have an elastic layer, uneven glossiness of the fixed image may occur. When the recording material is OHT, the image quality deteriorates due to an increase in image quality, and the transparency is poor when a fixed image is projected, resulting in a decrease in image quality.

  Accordingly, a fixing device that constitutes a low-cost color on-demand fixing device by using a fixing belt (fixing film) having an elastic layer as disclosed in Patent Document 1 for a film fixing device has been proposed. Yes.

  In the heater 5 as a heating means, a heating element 8 is patterned on a heater substrate 6 made of a heat-resistant insulating material such as ceramic, the surface is protected by heat-resistant glass, and the temperature detection is performed on the back surface of the heater substrate 6. The element 7 is arranged, and the temperature control of the fixing device is performed by detecting the temperature of the back surface of the substrate. In addition, a substrate such as ALN with high thermal conductivity is used as the heater substrate, the heater surface is opposite to the film, the heater substrate side is in contact with the film, and a high heat resistant resin such as PI or PTFE is applied to the contact surface. Some are coated to make a lubricating member.

  FIG. 18 is a front view of the heating element forming surface of the heater 5, and the heating element is formed in a single band shape. The heating element 8 is an energization heating element made of silver palladium (Ag / Pd), RuO 2, Ta 2 N, or the like, and generates heat when energized from the energizing electrode 11 formed on the surface of the heater substrate 6.

  In addition, the fixing film has a heat capacity of 100 μm or less, more preferably 40 μm or less and more than 20 μm, in order to reduce the heat capacity and improve the quick start property. PTFE, PFA, PPS having both heat resistance, releasability and durability Single layer film or composite layer film with polyamide, polyamideimide, polyimide, PEEK, PES, etc. film coated with PTFE, PFA, EEP as a release layer, or a metal layer such as Ni or stainless steel It is.

As described above, various image forming apparatuses such as printers using the fixing device as described above eliminate the need for preheating during standby, lower the preheating temperature, and wait due to high heating efficiency and rising speed. It has many advantages such as elimination of time, cost, etc., starting with the introduction of black and white machines as well as color machines to small and low speed machines, and in the future, it is expected to be introduced to large and medium speed machines. Yes.
Japanese Patent Laid-Open No. 11-15303 (Japanese Patent No. 3051085)

  However, in the conventional fixing device, it is necessary to match the heat generation positions of the fixing nip and the heater in order to ensure safety in the event of an abnormality. Therefore, it is difficult to change the structure around the nip, and it is necessary to increase the temperature and pressure in order to pursue high image quality. However, increasing the temperature and increasing the pressure increase the fixing power and the torque of the motor, that is, increase the power consumption, making it difficult to provide an image forming apparatus that has high image quality, high-speed throughput, and is energy-saving and inexpensive.

  The present invention has been made in view of the above problems, and has an object to ensure safety by controlling a temperature rising point at the time of an apparatus abnormality to make a safety element respond at a high speed and preventing an excessive temperature rising. And

  The present invention for solving the above-described problems is a heater having a heater substrate on which a heating element is formed, a heater holder that holds the heater, and heat resistance that rotates around the heater holder while an inner surface is in contact with the heater. An unfixed material on the material to be heated by passing the heating region together with the heat resistant rotating body while closely contacting the material to be heated to the surface of the heat resistant rotating body facing the heater arrangement side. In the heat fixing device for permanently fixing an image, a seat surface that directly contacts the heater between the surface opposite to the heat-resistant rotating body rubbing surface of the heater and the heater holder and receives a load applied to the heater, and a heater seat surface It has a space layer or heat insulation layer configured to prevent the heat of the heater from being transmitted to the heater holder in the longitudinal direction in a more concave shape, and is provided with a portion with more space layer or heat insulation layer and a portion with less space. To.

  According to the present invention, when an abnormality occurs without affecting the heater temperature during normal printing, it is possible to lengthen the time until failure of the heater and to increase the operating speed of the temperature protection element. It is possible to provide a fixing device with high image quality and high throughput, such as a pressure distribution in a heater and a fixing nip, at a lower cost than before.

Example 1
FIG. 1 shows the best representation of the first embodiment. In this example, as an example, the fixing device F will be described as a heating device of a fixing belt heating method and a pressurizing rotating body driving method (tensionless type).

1) Overall configuration of device F
Reference numeral 101 denotes a fixing belt as a first fixing member, which is a cylindrical (endless belt-shaped) member in which an elastic layer is provided on the belt-shaped member. The fixing belt 101 will be described in detail in section 3) below.

  Reference numeral 102 denotes a pressure roller as a second fixing member, which includes a cored bar portion 102a and a rubber portion 102b. Reference numeral 103 denotes a heat-resistant / rigid heater holder having a substantially semicircular arc shape in cross section, and 104 a fixing heater as a heat source, which is disposed on the lower surface of the heater holder 103 along the length of the holder. The fixing belt 101 is loosely fitted on the heater holder 103. In the present embodiment, the fixing heater 101 is a ceramic heater as described in detail in section 2) below.

  The heater holder 103 is a member that holds the heater 104 and rotates and holds the fixing heating sleeve. Since the heater holder is required to have heat resistance and insulating properties, strength as a structural body is required, and moldability is also important, engineering plastics reinforced with glass fibers, for example, LCP materials made of wholly aromatic polyester resins, etc. Is often used. In the present embodiment, Zenite 7755M (trade name) manufactured by DuPont is used as the liquid crystal polymer. The maximum usable temperature of Zenite 7755M is about 270 ° C.

  The pressure roller 102 is formed by forming a silicone rubber layer 102b having a thickness of about 3 mm on a stainless steel core metal 102a by injection molding and covering a PFA resin tube having a thickness of about 40 μm thereon. The pressure roller 102 is disposed such that both ends of the core bar are rotatably supported by bearings between a side plate (not shown) on the back side and a front side of the apparatus frame 105. On the upper side of the pressure roller 102, the heating assembly including the heater 104, the heater holder 103, the fixing belt 101, and the like is disposed in parallel with the pressure roller 102 with the heater 104 facing downward, and is provided inside the heater holder 103. A pressure mechanism comprising a pressure stay 106 and pressure springs 107 provided at both ends of the pressure stay is biased in the axial direction of the pressure roller 102 with a force of 98 N (10 kgf) on one side and a total pressure of 196 N (20 kgf). Thus, the fixing heater 104 is pressed against the elastic layer of the pressure roller 102 via the fixing belt 101 with a predetermined pressing force against the elasticity of the elastic layer, and a fixing nip having a predetermined width necessary for heat fixing is obtained. Part N is formed. The pressurizing mechanism has a pressure releasing mechanism including a pressure releasing stay 108, a pressure releasing cam 109, and a motor M2, and rotates the motor M2 and rotates the pressure releasing cam 109 at the time of jam processing. Is removed, and the transfer material P can be easily removed.

  A switch 110 detects whether the fixing belt 101 and the pressure roller 102 are released from pressure or are pressed.

  A temperature protection element 111 is disposed inside the pressure stay 106 and the sleeve guide 103 so as to come into contact with the fixing heater 104, and stops power supply to the fixing heater 104 when the temperature becomes abnormally high.

  The pressure roller 102 is rotationally driven by the driving means M in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed. A rotational force acts on the cylindrical fixing belt 101 by the pressure frictional force at the fixing nip portion N between the outer surface of the pressure roller 102 and the fixing belt 101 by the rotation driving of the pressure roller 102, and the fixing belt 101 is The inner surface of the fixing heater 104 slides in close contact with the downward surface of the fixing heater 104, and the outer periphery of the heater holder 103 is rotated in the clockwise direction indicated by the arrow. Grease is applied to the inner surface of the fixing belt 101 to ensure slidability between the heater holder 103 and the inner surface of the fixing belt 101.

  The pressure roller 102 is driven to rotate, and the cylindrical fixing belt 101 is driven and rotated, and the fixing heater 104 is energized. The fixing heater 104 is heated up to a predetermined temperature, and the temperature is adjusted. In this state, a transfer material P carrying an unfixed toner image is introduced between the fixing belt 101 and the pressure roller 102 in the fixing nip N, and the toner image carrying surface side of the transfer material P is fixed to the fixing nip N. The fixing belt 101 is in close contact with the outer surface of the fixing belt 101, and is nipped and conveyed through the fixing nip N together with the fixing belt 101. In this nipping and conveying process, heat of the fixing heater 104 is applied to the transfer material P via the fixing belt 101, and an unfixed toner image on the transfer material P is heated and pressurized on the transfer material P to be melted and fixed. . The recording material P that has passed through the fixing nip N is discharged from the fixing belt 101.

2) Fixing heater 104
In this embodiment, the fixing heater 104 as a heat source is formed by applying a conductive paste containing a silver / palladium alloy in a film having a uniform thickness on a substrate made of aluminum oxide (alumina) or aluminum nitride by screen printing. In this way, a ceramic heater is used in which a resistance heating element is formed and a glass coat made of pressure-resistant glass is applied.

This fixing heater 104 is
1． A horizontally long alumina substrate or aluminum nitride substrate a having a direction perpendicular to the paper passing direction as a longitudinal direction;
2． A conductive paste containing a silver-palladium (Ag / Pd) alloy, which is coated in a linear or strip shape by screen printing along the length on the surface side of the substrate a, and which generates heat when current flows, has a thickness of about 10 μm, A resistance heating element layer having a width of about 1 to 5 mm,
3． As the power supply pattern for the resistance heating element layer, the first and second electrode portions and the extended electric circuit portion, which are similarly patterned by screen printing of silver paste on the surface side of the alumina substrate a,
Four. A thin glass coat or polyimide having a thickness of about 10 μm, which can withstand the rubbing with the fixing belt 101 and is formed on the resistance heating element layer and the extension circuit portion to ensure protection and insulation. coat,
Etc.

  In the heater of the present embodiment, an air layer is sandwiched between the heater and the heater holder in a portion other than the outer peripheral portion of the heater substrate, and the heat efficiency can be further improved by configuring so as not to transmit the heat generated by the heater to the heater holder side as much as possible. I am doing so.

  Further, there is provided an end stop portion that narrows the heater pattern width corresponding to the end sheet passing position in the heater longitudinal direction by about 3% to 10% compared to the center portion. The reason for this is to prevent a temperature drop at the end when the fixing unit is started up by making the resistance at the end larger than that at the center.

3) Fixing belt 101
The fixing belt 101 has a thickness of 30 μm to 50 μm after a silicone rubber layer is formed as an elastic layer on an endless film formed of a polyimide resin or a metal such as Ni or stainless steel in a cylindrical shape with a thickness of 50 μm by a ring coating method. It is formed by covering a PFA resin tube to a certain extent.

  For the silicone rubber layer, it is desirable from the viewpoint of temperature rise to use a material having as high a thermal conductivity as possible and to reduce the heat capacity of the fixing belt 101. In this example, a material having a thermal conductivity of about 4.19 × 10 −3 J / sec · cm · K and a silicone rubber having a high thermal conductivity were used.

  On the other hand, it is desirable to make the rubber layer of the fixing belt 101 as thick as possible from the viewpoint of image quality such as OHT permeability and minute gloss unevenness on the image. According to the study by the present inventors, it has been found that a rubber thickness of 200 μm or more is necessary to obtain a satisfactory level of image quality. The silicone rubber layer in this example was 250 μm thick.

  Further, by providing a fluororesin layer on the surface of the fixing belt 101, the releasability of the surface is improved, and the offset phenomenon that occurs when the toner once adheres to the surface of the fixing belt 101 and moves to the transfer material P again. Can be prevented.

  Further, when the fluororesin layer on the surface of the fixing belt 101 is a PFA tube, a uniform fluororesin layer can be formed more easily.

  FIG. 2 shows a cross-sectional view of a conventional heater and heater holder.

  FIG. 2 shows the structure of the heater holder and the heater around the heater. FIG. 2A is a view of the heater and the heater holder from the heater surface and the fixing sleeve side. The heater pattern is a perspective view.

  In FIG. 2, 1 is a heater substrate, 2 is a heater, 3 is a heat insulation layer or space layer, and 4 is a heater holder. In the longitudinal direction, B is the center of the heater throttle position (electrode side), C is the heater heat generation center position, and D is the center of the heater throttle position (counter electrode side).

  2A to 2C are cross-sectional views of the heater and the heater holder in the cross section A-A '. 3A to 3C are cross-sectional views taken along line B-B '. A temperature rise curve is shown in FIG.

  Consider a case in which power is supplied to the device and temperature control becomes impossible due to a failure in the temperature control circuit. In the failed state, there is a risk that electric power is continuously supplied to the heater 2, so the seating surface portion of the heater holder 4 that is in direct contact with the heater 2 is softened. The temperature rise curve in this case is shown in FIG. In FIG. 4, point a is the temperature in this state. 2A and 3A show the positional relationship between the heater 2 and the heater holder 4 at the temperature of point a. The heater 2 is not touching the heater holder 4 except for the heater seating surface.

  Since the heater 2 is pressurized from the upper side of FIG. 4 by a pressure roller (not shown), the heater 2 is buried in the heater holder 4 when the heater seating surface of the heater holder 4 is softened. Further, since the resistance value increases as the temperature of the heater 2 rises, the input power to the heater 2 decreases. Further, when the heater 2 becomes high temperature, the heat dissipation increases due to the temperature difference from the surroundings, so the temperature rise curve of the heater 2 rises quickly and the slope becomes gentle with time.

  The temperature in this state is point b in FIG. FIGS. 2-b and 3-b show the positional relationship between the heater 2 and the heater holder 4 at the temperature of point b. The heater 2 is in a state where it does not touch the heater holder 4 except for the heater seating surface as before.

  A process of increasing the temperature of the heater 2 will be described. If power is continuously supplied to the heater 2, the temperature rise continues while the temperature gradient becomes smaller. The end of the heater 2 has a higher heater resistance value to correct the normal temperature distribution, and has a higher heating value (provided with a constricted portion in the heater pattern). Reach temperature. Since the heater has a positive resistance-temperature characteristic, when the temperature rises, the resistance value further rises, and the heat generation ratio of the end throttle portion further increases with respect to the central portion. Therefore, the temperature of the heater end tends to rise even faster than the temperature rise of the heater in the temperature protection element at the center of the heater.

  At this time, a temperature protection element typified by a thermo switch or the like works to cut off the power supply to the heater 2.

  However, when a temperature protection element such as a thermo SW is activated, the heater end throttle is at a higher temperature than the vicinity of the temperature protection element. If the resistance value of the heater is lowered to achieve a high-throughput fixing device that requires more power, the temperature difference between the temperature protection element vicinity and the end will further increase, and the temperature at the time of abnormality will be increased. The difference becomes large, and the possibility of causing the warpage of the heater and the deformation of the holder due to the thermal stress increases.

  That is, by reducing the temperature difference between the heater end portion and the temperature protection element portion at the time of abnormality, it is possible to supply more power to the heater, and a high-throughput fixing device can be realized.

  The operation according to the first embodiment will be described with reference to FIGS. Since power is continuously supplied to the heater, the portion of the heater holder 4 that is in contact with the heater 2 is softened. In FIG. 7, point a is the temperature in this state. FIGS. 5A and 6A show the positional relationship between the heater and the heater holder at the temperature of point a. The heater is not touching the heater holder except for the heater seat surface. In FIG. 5, 1 is a heater substrate, 2 is a heater, 3 is a heat insulation layer or space layer, 4 is a heater holder, and 5 is a heat conductive member.

  Since the heater 2 is pressurized by a pressure roller (not shown), the heater 2 is buried in the heater holder 4 when the heater seating surface of the heater holder 4 is softened. When the heater end is buried up to the good heat conducting member 5 of the heater holder 4, the good heat conducting member 5 and the heater holder 4 take away the heat of the heater 2, so that the temperature rise of the heater 2 becomes moderate.

  The temperature in this state is point b in FIG. FIGS. 5B and 6B show the positional relationship between the heater 2 and the heater holder 4 at the temperature of point b. It is in the state which touched the good heat conductive member 5 provided in the heater edge part heater holder 4. FIG.

  Further, it has been confirmed that the temperature rise in the portion without the good heat conducting member 5 is faster than the conventional example.

  The reason for this can be explained as follows.

  Since the temperature rise at the end of the heater is moderated by the good heat conducting member (= the resistance rises gently), the increase in the overall resistance of the heater is moderate as compared with the case where there is no good heat conducting member. As a result, the amount of power input to the entire heater is larger than in the past. At the same time, the temperature distribution in the longitudinal direction, that is, the temperature distribution at the heater end and the center (near the temperature protection element) is also reduced, so that the temperature at the center (near the temperature protection element) rises quickly. The protection element operates faster.

  FIG. 8 shows a diagram representing the configuration of this embodiment as an elevational view. Each point A, A ′, B, C, and D in FIG. 5 corresponds to each point A, A ′, B, C, and D in FIG. 8. FIG. 9 shows a block diagram of an electric circuit. In FIG. 9, 900 is a commercial AC power supply, 901 is a triac that supplies power to the heater, 902 is a main body controller including a CPU, 903 is a triac drive circuit, 904 is a line filter, 905 is a relay, 906 is a DC power supply voltage It is a line that supplies the same 24V voltage as the motor of the apparatus main body and the power source of the high-voltage power source. 910 is a fixing device, 911 is a heater, 912 is a thermistor, 913 is a temperature protection element, and a temperature fuse or a thermo switch is used.

  In this way, when an abnormality occurs, the temperature protection element provided in the heater unit operates and has a safe configuration in which energization to the heater is stopped.

  As described above, it is possible to apply larger electric power to the heater by reducing the temperature difference between the heater end portion and the temperature protection element portion at the time of abnormality. Accordingly, a high-throughput fixing device can be realized, and a more secure fixing device can be realized.

(Example 2)
The operation according to the second embodiment will be described with reference to FIGS.

  In FIG. 10, 1 is a heater substrate, 2 is a heater, 3 is a space layer or heat insulation layer, and 4 is a heater holder.

  In Example 1, the good heat conductive member was present in a portion where the space layer or the heat insulating layer 3 was small. In the present embodiment, the material of the heater holder 4 is raised instead of the good heat conducting member and is integrally formed.

  Since power is continuously supplied to the heater 2 at the time of abnormality, the portion of the heater holder 4 that is in contact with the heater 2 is softened. In FIG. 12, point a is the temperature in this state. Further, FIGS. 10A and 11A show the positional relationship in the sectional view of the heater 2 and the heater holder 4 at the temperature of point a. The heater 2 is not in contact with the heater holder 4 except for contact with the heater seat surface. Since the heater 2 is pressed in such a manner that the fixing sleeve is sandwiched between the pressure rollers, the heater 2 is buried in the heater holder 4. When the heater 2 is buried up to the seat surface portion of the heater holder 4, the heat absorption surface at the end of the heater comes into contact with the heater holder 4, so that the heater holder 4 takes away the heat of the heater 2. At the same time, at the softening point (glass transition point) of the heater holder resin, it is difficult to increase the temperature even when heated, as with the melting point. Therefore, the temperature rise of the heater becomes moderate near the softening point as point b. Furthermore, as the heater 2 is buried, the heater 2 comes into close contact with the heater holder 4, and the temperature rise of the heater 2 becomes more gradual.

  As a result, it is possible to reduce the temperature difference between the heater temperature of the temperature protection element portion and the heater end portion without attaching a special member. As a result, it is possible to input a larger amount of power to the heater, and it is possible to realize a high-throughput fixing device and to have an advantage that accuracy is easily obtained because of the integral molding. In this embodiment, the distance from the heater surface to the end heat absorption surface is about 100 μm. Moreover, since it is an integral molding, the shape is stable, and variation can be suppressed.

(Example 3)
A diagram that best represents Example 3 is shown in FIG. A duplicate description of the first and second embodiments will be omitted. The configuration of the fixing device is the same as in FIG.

  FIG. 14 shows a comparison of the heater seating surface portion of the heater holder that holds the heater in direct contact with the heater in FIG.

  As shown in FIG. 13, the contact surface (seat surface) between the heater and the heater holder corresponding to the heater end portion is widened so that the heater seat surface area in the vicinity of the temperature protection element is minimized.

  Further, as shown in FIG. 14, the heater seat surface from the paper center position of the heater holder is also symmetrical with respect to the paper center so that the normal heater temperature is symmetric with respect to the paper position. It is trying to become. FIG. 14 shows a temperature distribution in the longitudinal direction of the fixing device corresponding to the time point d in FIG.

  The operation in such a configuration will be described.

  An example of the temperature distribution at the time of abnormality is shown in FIG. The temperature distribution at the time of abnormality is that the heater seat surface that is in direct contact with the heater is narrower at the center, so the temperature at the center of the heater (near the temperature protection element of the heater) is higher than that at the heater end. Is getting bigger. Also, because of the temperature dependence (TCR) of the resistance, the resistance value rises when the temperature starts to rise, so although the power supply power decreases, the portion where the resistance value rises compared to the surrounding area further increases the temperature. The temperature of the heater around the protection element further rises, and the temperature protection element operates quickly. FIG. 15 shows a comparison of the temperature rise process between the center and the end.

  As described above, since the temperature protection element of the fixing device can be operated quickly, even if the heater temperature is likely to rise due to the increase in fixing power and the configuration in the fixing nip, safety is sufficiently satisfied. It is possible to construct a fixing device with high image quality and high throughput.

(A) is a diagram showing the first embodiment, (b) is a lateral view of the fixing device in a pressurized state. Longitudinal cross section of heater and heater holder Cross section of the heater and heater holder in the short direction Diagram showing temperature rise Longitudinal transverse cross-sectional view of the heater and heater holder of Example 1 Cross-sectional view in the short-side direction of the heater and heater holder of Example 1 The figure showing the temperature rise of Example 1 Elevation of Example 1 Connection diagram of heater drive circuit and safety element Longitudinal transverse cross-sectional view of the heater and heater holder of Example 2 Example 2 Transverse cross-sectional view of heater and heater holder Example 2 Diagram showing temperature rise Elevation of Example 2 The figure showing the temperature distribution of the fixing device cross section direction of Example 3. The figure showing the temperature rise of Example 3 A figure showing a conventional example A figure showing a conventional example

Explanation of symbols

101 Fusing belt
102 Pressure roller
103 Fusing belt
104 Fixing heater
105 Fusing unit frame

Claims (6)

A heater having a heater substrate on which a heating element is formed; a heater holder that holds the heater; and a heat-resistant rotating body that rotates around the heater holder while an inner surface is in contact with the heater. In a heating and fixing apparatus that passes through a heating region together with the heat resistant rotator while closely contacting a surface of the heat resistant rotator facing the heater arrangement side, and permanently fixes an unfixed image on the heated material,
The heater is in direct contact with the heater between the surface opposite to the heat-resistant rotating body rubbing surface of the heater and the heater holder, and the heater receives heat applied to the heater from the heater seat surface to the concave shape in the longitudinal direction. A heat fixing device having a space layer or a heat insulating layer configured not to be transmitted to a heater holder, and having a portion having a large space layer or a heat insulating layer and a portion having a small amount.   2. The heat fixing apparatus according to claim 1, wherein a part having a small space layer or a heat insulating layer is arranged in a part where the temperature rise of the heater is the fastest, and a part having a large space layer or heat insulating layer in the other part is arranged. .   A temperature protection element that is placed in direct contact or non-contact with a part of the heater, detects that the heater temperature has exceeded a certain level, and stops energizing the heater. The heat fixing device according to claim 1, wherein a space layer or a heat insulating layer between the heater and the heater holder is larger than a space layer or a heat insulating layer provided in another portion.   4. The member according to claim 1, wherein a member having a higher thermal conductivity than the other part or a member having a larger heat capacity than the other part is arranged in the space layer or the part having less heat insulation layer. Heat fixing device.   The portion where the temperature of the heater temperature rises the fastest is a heater end throttle portion in which the resistance pattern of the heater is narrowed to make the resistance value higher than other portions. The heat fixing apparatus as described.   The portion having a large amount of the space layer or the heat insulating layer indicates that the space layer or the heat insulating layer has a large area in the depth direction from the area facing the heater surface or the heater surface. The heat fixing apparatus according to claim 1, wherein an area facing the heater surface or a thickness in a depth direction from the heater surface is small.

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