JP2008152957A - Heating device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive heating device of high fixing efficiency capable of both ensuring the ability to fix the entire recording material evenly and preferably and preventing malfunction of a safety element and an image forming device equipped with the heating device. <P>SOLUTION: In a film heating type heating device having a plurality of resistance heating elements of different widths and an image forming device equipped with the heating device, only the widest resistance heating element is provided with a restriction portion formed by reducing the width of only one part in the longitudinal direction of the heating element. The restriction portion is positioned where the heating element is in contact with a safety element having a mechanism for shutting off current to the resistance heating element when a failure occurs. The substrate of the heating element is accommodated in the fixing nip region and a plurality of resistance heating elements is disposed in place on the entire width of the substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating device such as a copying machine or a laser beam printer, and an image forming apparatus including the heating device.

  2. Description of the Related Art Conventionally, in a recording material heating apparatus for image heating and fixing, for example, a material to be heated includes a heating roller maintained at a predetermined temperature and a pressure roller pressed against the heating roller through an elastic layer. In many cases, a heat roller method is used in which the recording material is heated while being nipped and conveyed. In addition, various systems and configurations such as a flash heating system, an open heating system, and a hot plate heating system are known and put into practical use.

  Recently, instead of such a method, a heating body (heater), a heating body support (stay), a heat-resistant film (fixing film) conveyed while being opposed to the heating body, and a fixing film are provided. It has a pressure body (pressure roller) that attaches the recording material as the material to be heated to the heating body, and forms and supports the recording material surface by applying the heat of the heating body to the recording material through the fixing film. An image heating and fixing method (heating device of a film heating method) has been devised (for example, see Patent Documents 1 and 2). As a heating body of this heating apparatus, a structure in which a resistance heating element is formed on a ceramic substrate, the resistance heating element is heated by power feeding, and the recording material is heated is generally used. The temperature of the heating body is detected by a temperature measuring element such as a thermistor that is in contact with or bonded to the heating body, and the temperature of the heating body is controlled by the CPU based on the detected temperature.

  In addition, as a safety measure when the temperature sensor that detects the temperature of the heating element, the CPU that controls the temperature, the electrical circuit for temperature control, etc. fails and the temperature of the heating element becomes abnormally high, it is connected in series with the resistance heating element. A safety element such as a connected thermo switch or thermal fuse is brought into contact with the back surface (non-film sliding surface) of the heating element substrate. If the temperature of the heating element exceeds the operating temperature of the safety element, go to the resistance heating element. It has a configuration that can cut off power.

  In such a film heating type heating apparatus or image heating and fixing apparatus, a low heat capacity heating body can be used as the heating body. For this reason, it is possible to save power and shorten the wait time (quick start) as compared with conventional devices such as a heat roller method and a belt heating method.

  In the above-described film heating type heating apparatus, in order to effectively use the width of the heating body substrate in the recording material conveyance direction, the substrate is placed in the press nip formed by the heating body and the pressure roller, and the entire substrate width is resisted. A configuration in which a heating element is provided has been devised. In this configuration, since the resistance heating element is provided over the entire width of the substrate, it is necessary to place the entire substrate in the nip so that the resistance heating element does not exist outside the nip portion (the resistance heating element is placed in the nip portion). If it is outside, the part becomes very hot and the heating element may be damaged).

The wider the width of the resistance heating element in the recording material conveyance direction, the better the fixing efficiency. However, since the resistance heating element is generally made of an expensive material such as silver palladium, the effect of the width of the resistance heating element on the cost is affected. Is very big. Therefore, in order to reduce the cost without impairing the fixing efficiency as much as possible, a configuration in which a plurality (about 4 to 5) of resistance heating elements are arranged on the entire substrate with a predetermined interval has been devised and put into practical use. . In this configuration, the total width of the resistance heating element can be reduced, so that the cost can be reduced and the resistance heating element can be disposed on the entire substrate, so that the temperature of the entire substrate can be uniformly increased in the width direction in the nip. Fixing efficiency is also good.
JP-A-4-44075 JP-A-4-44076 JP-A-4-44077 JP-A-4-44078 JP-A-4-44079 JP-A-4-44080 JP-A-4-44081 JP-A-4-44082 JP-A-4-44083 JP-A-4-204980 JP-A-4-204981 JP-A-4-204982 JP-A-4-204983 JP-A-4-204984

  In the above-described film heating type heating apparatus, the temperature of the heating body tends to be lower in the portion where the safety element is in contact with the back surface of the heating body substrate than in other portions. This is because the other part of the heating element back surface is in contact with a stay (heating body support) formed of a resin such as liquid crystal polymer, but the heat escape from the heating element back surface to the stay is not very large. On the other hand, the part where the safety element is in contact is because heat escape from the heating element back surface to the safety element is large. Originally, in a film heating type heating apparatus, if the heat leak from the back surface of the heating body to the stay is large, the fixing efficiency deteriorates. Therefore, heat insulation is attempted by reducing the thermal conductivity of the material of the stay. On the other hand, the safety element has a configuration in which heat is easily removed as much as possible in order to speed up the operation at an abnormally high temperature. Due to the difference in the configuration described above, the temperature of the heating body is lowered at the safety element contact portion, and the fixability tends to deteriorate only at that portion.

  As one of the means for compensating for the fixing failure of the safety element abutting portion, the width of the resistance heating element corresponding to the safety element abutting portion is made narrower than the other portions to increase the partial resistance. A configuration in which the amount of heat generated at the contact portion is increased has been put to practical use. Hereinafter, the portion where the width of the resistance heating element is narrowed in the safety element abutting portion is described as a throttle portion, and the ratio of the width reduction is referred to as a throttle amount. The amount of squeezing is the amount that indicates the percentage of the squeezed part when the resistance value per unit volume of the resistive heating element other than the squeezed part is 100%, and the thickness of the resistive heating element is constant. Assuming that there is no partial variation in the volume resistance value possessed by the resistance material, it is expressed by the following equation.

Aperture amount (%) = (Width of heating element other than throttle part) / (Heating element width of throttle part)
Since the resistance value and the calorific value are proportional, the amount of restriction may be considered as the ratio of the calorific value per unit volume. It is desirable to set the aperture so that the fixing properties of the aperture and other parts are equal.If the aperture is too small, the fixing failure of the aperture cannot be compensated, and if it is too large, the temperature of the aperture increases too much. The possibility of malfunction of the safety element during normal use increases. Therefore, in order to prevent the fixing defect of the diaphragm portion and the malfunction of the safety element, it is required to suppress the manufacturing variation of the diaphragm amount.

  On the other hand, in the configuration in which the plurality of resistance heating elements (about 4 to 5) described above are arranged over the entire width of the substrate, the resistance heating element is 1 in comparison with one or two resistance heating elements that are common in conventional heating devices. The heating element width per book becomes narrow. The manufacturing variation (deviation from the design value) of the assumed heating element width is constant regardless of the heating element width. Therefore, the thinner the heating element width, the greater the influence of the deviation amount. There is a tendency for the deviation to increase. Therefore, if the width of the resistance heating element provided with the narrowed portion is narrow, it may be difficult to achieve both the fixing property of the narrowed portion and the prevention of malfunction of the safety element. In particular, when a thermo switch with quick response is used as a safety element, it is necessary to take a large margin to prevent malfunction, and thus it is difficult to achieve both compatibility. Increasing the width of the heating element is less affected by the amount of displacement and the displacement of the aperture amount is reduced, but the cost increases as described above.

  An object of the present invention is to provide a heating device that is inexpensive and has good fixing efficiency, and that can achieve both of ensuring a uniform fixing property throughout the recording material and preventing malfunction of a safety element, and an image forming apparatus including the heating device. Is to provide.

  In order to achieve the above object, a first invention according to the present application is a heating apparatus that heats a material to be heated by a heating body including at least a substrate, a plurality of resistance heating elements, and an electrode that supplies power to the resistance heating element. The plurality of resistance heating elements include those having different widths in the direction in which the material to be heated is conveyed. Only the resistance heating element having the widest width has a width in the conveyance direction in the longitudinal direction of the resistance heating element. Is characterized in that there is a region different from the width of other portions.

  According to a second aspect of the present invention, in the above-described heating device, only the resistance heating element having the widest width in the conveyance direction of the heated material has a width in the conveyance direction of the heated material in a part of the longitudinal direction of the resistance heating element. A region that is narrower than the width of other portions exists.

  According to a third invention of the present application, in the heating device described above, the resistance heating is generated in a portion corresponding to a region of the longitudinal direction of the resistance heating element, the width of the heated material transport direction being different from the width of the other portion. A safety element connected in series with the body is in contact with the safety element, and the safety element is configured to cut off power supply to the resistance heating element when the temperature exceeds a predetermined temperature.

  According to a fourth aspect of the present application, in the above-described heating device, the safety element is a thermo switch or a thermal fuse.

  According to a fifth aspect of the present application, at least a heating body, a heat resistant film that contacts and slides one surface with the heating body, and another surface contacts a material to be heated, drives the heat resistant film, and heat resistant film And a pressure member for bringing the heated material into close contact with the heating body, and the heat-resistant film and the heated material are sandwiched and conveyed together in a nip formed by the heating body and the pressure member. The heating apparatus which heats a heating material WHEREIN: This heating apparatus is the structure of any one of Claims 1-4, It is characterized by the above-mentioned.

  A sixth invention according to the present application is characterized in that, in the above-described heating device, the substrate of the heating body exists in a nip portion formed by the heating body and the pressure member in the heated material conveyance direction. .

  According to a seventh aspect of the present application, there is provided an image forming apparatus comprising: an image forming unit that forms an image on a recording material; and an image heating unit that heats the image on the recording material. A device is provided.

  In the heating device of the film heating system, conventional heating is performed by arranging a plurality of resistance heating elements including those having different widths over the entire substrate width of the heating element, and providing a throttle portion only on the widest resistance heating element. This makes it possible to satisfy all the items of improvement in fixing efficiency, low cost, and improvement in aperture accuracy, which were difficult with the apparatus. By improving the accuracy of the aperture amount, uniform and good fixability can be obtained over the entire recording material, and the malfunction of the safety element during normal use can be prevented, improving the quality and reliability of the heating device and the image forming apparatus.

(Example 1)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 5 shows the main part of a laser beam printer as an image forming apparatus in this embodiment. 101 is an organic photosensitive drum as an image carrier, 102 is a charging roller as a charging member, 103 is a laser exposure device, 104 is a developing device including a developing sleeve and a developing blade, and one-component magnetic toner, 105 is a cleaning blade, and 106 is A transfer roller 107 is a heat fixing device. In the image forming apparatus of this embodiment, the maximum sheet passing width is A4 size (paper width: 210 mm).

  The organic photosensitive drum 101 is rotationally driven at a predetermined peripheral speed and is uniformly charged to a negative predetermined potential in this example by the charging roller 102. Then, scanning exposure of the image information by the laser beam from the laser exposure device 103 is performed on the uniformly charged surface of the organic photosensitive drum 101, and an electrostatic latent image corresponding to the scanning exposure pattern is formed on the organic photosensitive drum 101. .

  Next, the negative toner charged in the developing device 104 adheres to the exposed bright portion of the electrostatic latent image on the organic photosensitive drum 101, and the electrostatic latent image becomes a visible image as a toner image (reversal development).

  On the other hand, the sheet feeding roller 108 is rotationally driven at a predetermined sheet feeding control timing, and one sheet of recording material P such as paper is separated and fed from the sheet feeding cassette 109, and includes a conveying roller 110, a registration roller 111, and the like. The toner image on the organic photosensitive drum 101 is sequentially applied to the surface of the recording material P through a path 112 and introduced into a transfer nip portion that is a contact portion between the organic photosensitive drum 101 and the transfer roller 106. Transcribed.

  The recording material P that has exited the transfer nip is separated from the surface of the organic photosensitive drum 101, introduced into a fixing device 107 as an image heating and fixing device through a sheet path 113, and subjected to a heat fixing process of a toner image. The paper is discharged onto the paper discharge tray 115 through the path 114.

  Further, the surface of the organic photosensitive drum 101 after separation of the recording material is cleaned by removing the transfer residual toner by the cleaning blade 105, and is repeatedly used for image formation.

  Next, the heating device 107 in the present embodiment will be described. FIG. 4 is a schematic configuration diagram of a film heating type heating apparatus according to the present embodiment. This apparatus is a tensionless type apparatus disclosed in Japanese Patent Laid-Open Nos. 4-44075 to 44083 and 4-204980 to 204984.

  This tensionless type film heating type heating device uses an endless belt-shaped or cylindrical heat-resistant film, and at least part of the circumference of the film is always tension-free (in a state where no tension is applied), The film is a device that is rotationally driven by the rotational driving force of the pressure member.

  Reference numeral 1 denotes a stay, which is a heat resistant and rigid member as a heating body holding member and a film guide member. Reference numeral 3 denotes a ceramic heater as a heating body, which is disposed and held on the lower surface of the stay 1 along the length of the stay. Reference numeral 2 denotes an endless (cylindrical) heat-resistant film that is externally fitted to a stay 1 that is a film guide member including a heating element 3. The inner peripheral length of the endless heat-resistant film 2 and the outer peripheral length of the stay 1 including the heating element 3 are about 3 mm larger than that of the film 2, so that the film 2 is fitted with a margin in the peripheral length. ing.

  The stay 1 can be composed of a high heat resistant resin such as polyimide, polyamideimide, PEEK, PPS, liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass, or the like. In this example, a liquid crystal polymer was used.

  Film 2 has a film thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more, heat resistant single layer film such as PTFE, PFA, FEP, polyimide, polyamide, etc. in order to reduce heat capacity and improve quick start performance A composite layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of a film such as imide, PEEK, PES, or PPS can be used. In this embodiment, a polyimide film having a film thickness of about 50 μm coated with PTFE on the outer peripheral surface was used. The outer diameter of the film 2 was 18 mm.

  Reference numeral 4 denotes a pressure roller as a film outer surface contact driving means for forming a pressure nip portion (fixing nip portion) N with the film 2 sandwiched between the heating member 3 and rotating the film 2. The pressure roller 4 is composed of a cored bar 4a, an elastic layer 4b, and an outermost release layer 4c. The film 2 is sandwiched by a bearing means / biasing means (not shown) with a predetermined pressing force. It is disposed in pressure contact with the surface. In this embodiment, the core metal 4a is an aluminum core, the elastic layer 4b is silicone rubber, and the release layer 4c is a PFA tube having a thickness of about 30 μm. The outer diameter of the pressure roller 4 was 20 mm, and the thickness of the elastic layer 4b was 3 mm.

  The pressure roller 4 is rotationally driven by the drive system M in a clockwise direction indicated by an arrow at a predetermined peripheral speed. By the rotational driving of the pressure roller 4, a rotational force acts on the film 2 by the frictional force between the pressure roller and the film outer surface at the pressure nip portion N, and the film 2 has a heating body at the fixing nip portion N on the inner surface side. 3, while being in close contact with the surface of 3, the outer periphery of the stay 1 is driven counterclockwise in the counterclockwise direction indicated by the arrow at a rotational speed substantially equal to the rotational speed of the pressure roller 4.

  FIG. 2 is a diagram illustrating a front view of the heating body 3 and a circuit for performing energization control in this embodiment. Moreover, FIG. 3 is sectional drawing of the heating body 3 in a present Example.

  The heating element 3 is an elongated heat-resistant / insulating / good heat-conductive substrate 7 whose longitudinal direction is a direction perpendicular to the conveying direction a of the recording material P as a material to be heated, the surface of the substrate (film sliding surface) ) Side of the resistance heating element 6 formed along the length of the substrate, the heat-resistant overcoat layer 8 protecting the surface of the heating element on which the resistance heating element is formed, and the feeding electrode at the longitudinal end of the resistance heating element 6 It is a heating element with a low heat capacity as a whole consisting of 9 · 10 and the like.

The resistance heating element 6 of this example is composed of three pastes in the form of a line band on the heating element substrate 7 by screen printing a paste prepared by kneading silver, palladium, glass powder (inorganic binder), and organic binder. It was obtained by forming. Details of the shape of the resistance heating element will be described later. As a material for the resistance heating element, an electrical resistance material such as RuO ₂ or Ta ₂ N may be used in addition to silver palladium (Ag / Pd).

  Reference numeral 7 denotes a heating body substrate having heat resistance and insulation, and for example, a ceramic material such as alumina or aluminum nitride is used. In this embodiment, an alumina substrate having a width of 7 mm, a length of 270 mm, and a thickness of 1 mm is used. The power feeding electrodes 9 and 10 used a screen printing pattern of silver palladium. 8 is an overcoat layer of the resistance heating element 6, and its main purpose is to ensure electrical insulation between the resistance heating element 6 and the surface of the heating element 3 and the slidability of the film 2. In this example, a heat-resistant glass layer having a thickness of about 50 μm was used as the overcoat layer 8.

  FIG. 2 also shows the back surface (non-film sliding surface) of the heating element 3. Reference numeral 5 denotes a temperature measuring element provided for detecting the temperature of the heating body. In this embodiment, an external contact type thermistor separated from the heating body 3 is used as the temperature measuring element. The external contact type thermistor 5 is provided with a heat insulating layer on a support, for example, and an element of the chip thermistor is fixed on the support, and the element is directed downward (on the back side of the heating body) with a predetermined pressurizing force. It is configured so as to abut. In this example, a highly heat-resistant liquid crystal polymer was used as the support, and ceramic paper was laminated as the heat insulating layer. The external contact type thermistor 5 is provided in the minimum sheet passing area and communicates with the CPU 11.

  Reference numeral 14 denotes a safety element provided to cut off the energization of the resistance heating element 6 when the temperature of the heating element 3 is abnormally increased, and is in contact with the back surface of the substrate 7 with a predetermined pressure. . As the safety element, a thermo switch, a thermal fuse, or the like can be used. In this embodiment, a thermo switch having a mechanism capable of interrupting current by reversing the bimetal at a predetermined temperature is used. As described above, the thermal switch contact portion has a large escape of heat and the temperature of the heating element 3 is partially lowered. Therefore, in order to compensate for this, the throttle portion 15 is provided at a portion corresponding to the thermo switch contact portion. . Details of the aperture 15 will be described later. Similar to the external contact type thermistor 5, the thermo switch 14 is also provided in the minimum sheet passing area.

  The heating body 3 is fixedly disposed by exposing the surface side on which the overcoat layer 8 is formed and holding it on the lower surface side of the stay 1. By adopting the above configuration, the entire heating element can be reduced in heat capacity as compared with the heat roller system, and a quick start becomes possible.

  The heating element 3 rises in temperature when the resistance heating element 8 generates heat over the entire length by feeding power to the feeding electrodes 9 and 10 at the longitudinal end of the resistance heating element. The temperature rise is detected by the external contact type thermistor 5, the output of the external contact type thermistor 5 is A / D converted and taken into the CPU 11, and the electric power supplied to the resistance heating element by the triac 12 based on the information is phase controlled. Alternatively, the temperature of the heating element 3 is controlled by controlling the wave number or the like. That is, the heating body 3 is fixed by controlling the energization so that the heating body 3 is heated when the temperature detected by the external contact type thermistor 5 is lower than a predetermined set temperature, and the temperature is lowered when the temperature is higher than the set temperature. At a constant temperature. In this embodiment, the output is changed in 21 steps from 5 to 100% from 0 to 100% by phase control. The output 100% indicates the output when the heater 3 is fully energized.

  Pressure contact formed by the heating body 3 and the pressure roller 4 with the film 2 sandwiched in a state where the temperature of the heating body 3 rises to a predetermined level and the rotational peripheral speed of the film 2 is stabilized by the rotation of the pressure roller 4 A recording material P to be image-fixed as a heated material is introduced into the nip portion N from an image forming portion (transfer portion). Then, when the recording material P is nipped and conveyed together with the film 2 through the pressure nip N, the heat of the heating body 3 is applied to the recording material P through the film 2 and an unfixed visible image (toner on the recording material P). Image) T is heat-fixed on the surface P of the recording material. The recording material P that has passed through the pressure nip N is separated from the surface of the film 2 and conveyed.

  In this embodiment, in order to effectively use the substrate width and improve the fixing efficiency, a resistance heating element is disposed over the entire substrate width, and the substrate is placed in the nip. That is, in FIG. 4, the nip width N is larger than the substrate width of 7 mm. In this embodiment, the design center value of the nip width is set to 8 mm, and the heating body 3 is always set within the nip even if the pressing force, the pressure roller hardness, and the like are affected in manufacturing.

  FIG. 1 is a front view of a heating body 3 in the present embodiment. In FIG. 1, the overcoat layer 8 is omitted for simplicity. Hereinafter, the shape of the resistance heating element 6 of the present embodiment will be described in detail. As shown in FIG. 1, in this embodiment, three resistance heating elements 6 are provided, and in the conveyance direction a of the recording material P, one upstream side and two downstream sides are connected in parallel. The upstream heating element width A is 2 mm, and the two downstream heating element widths A / 2 are both 1 mm. Therefore, the total heating element width is 4 mm. As described above, in this embodiment, the resistance heating element 6 is arranged over the entire substrate width as much as possible, and the distance d from the substrate end to the resistance heating element end in the transport direction a is 0.5 mm. Since the overcoat layer 8 needs to reliably cover the resistance heating element 6 in order to ensure insulation, the minimum value of d is about 0.5 mm. The distance C between the heating elements was 1 mm. Note that the thickness of the three resistance heating elements 6 was about 10 μm.

  In this embodiment, only the thick resistance heating element on the upstream side is provided with the throttle portion 15, and the heating element width is narrowed only in the throttle portion in the shape shown in FIG. The design value of the heating element width of the aperture 15 is 1.6 mm, and the aperture is 125% according to the above formula. In the configuration of the heating apparatus of this example, the fixing property of the throttle part can be made equal to that of other parts by setting the throttle amount to 125%. The longitudinal position of the aperture 15 corresponds to the thermoswitch contact portion, and the distance from the center of the resistance heating element 6 in the longitudinal direction to the center of the aperture 15 is 25 mm. The length of the throttle part 15 in the longitudinal direction was 7 mm.

  In this example, the total resistance value of the resistance heating element 6 at room temperature (resistance between the power feeding electrodes 9 and 10) was 20Ω. Therefore, the resistance value of the upstream resistance heating element is about 10Ω, and the resistance value of the downstream resistance heating element is about 20Ω.

  As in the present embodiment, by providing the diaphragm portion only in the structure having a plurality of resistance heating elements and having the widest width, the accuracy of the diaphragm amount is improved. Assuming that the thickness of the resistance heating element 6 is constant and there is no partial variation in the volume resistance value possessed by the resistance material, the amount of drawing is determined only by the width of the resistance heating element 6. Here, the influence of factors other than variations in thickness and volume resistance, that is, the influence of the heat generation width on the drawing amount will be discussed. The variation in heating element width due to screen printing deviation (deviation from the design value) is constant regardless of the heating element width. Therefore, the thinner the heating element width, the greater the influence of the deviation amount, and the design of the aperture amount. The deviation from the value tends to increase. Table 1 compares how much the aperture amount deviates from the design value when the heating element width deviates from the design value (in the case of the heating element width of 1 mm and 2 mm). Comparison). Here, the deviation (tolerance) from the design value of the heating element width was set to 0.1 mm. This degree of tolerance is necessary in manufacturing.

  In Table 1, the column of the design value is a throttle portion necessary for obtaining a throttle amount of 125% and a heating element width other than the throttle portion. The column for deviation 1 shows the case where the heating element width has shifted to the plus side by 0.1 mm, and the column for deviation 2 shows the case where the heating element width has shifted to the minus side by 0.1 mm. The calculated value of the aperture amount is obtained by calculating the aperture amount according to the above formula from the aperture portion and the width of the heating element other than the aperture portion. The difference in the aperture amount indicates how much the aperture amount deviates from the design value when the displacement is 1 or 2. As shown in Table 1, it can be seen that the wider the heating element width, the smaller the displacement of the aperture (2 mm is about 1/2 of 1 mm), and the accuracy of the aperture is improved.

  In this embodiment, if a restriction portion is provided also in the resistance heating element having a width of 1 mm on the downstream side, as described above, the accuracy of the restriction amount of the downstream resistance heating element is deteriorated. In addition, the accuracy of the amount of restriction of the entire resistance heating element is also deteriorated. Therefore, as in the present embodiment, a configuration in which the throttle portion is provided only in the widest upstream heating element is desirable.

  In the following, the present embodiment is compared with three types of conventional examples in terms of fixing efficiency, cost, and aperture accuracy. FIGS. 6-8 is a front view of the heating body of the prior art examples 1-3. 6 to 8, the overcoat layer is omitted for simplicity. Further, the difference between the heating elements of the conventional examples 1 to 3 and the heating element of this example is only the shape of the resistance heating element 6, and all other configurations and materials, the total resistance of the resistance heating element 6, etc. Suppose they are the same.

  FIG. 6 is a front view of the heating body of Conventional Example 1. In Conventional Example 1, the number of resistance heating elements is two, and the shape is symmetrical in the upstream and downstream directions in the transport direction a. The heating element width A is 2 mm, and the total heating element width is 4 mm as in this embodiment. The heating element pattern of Conventional Example 1 is generally used in a configuration in which the resistance heating element 6 is not arranged over the entire width of the substrate and the substrate is not stored in the nip. The resistance heating element 6 is brought to the center in the width direction of the substrate 7. It is a pattern. The distance C between the heating elements is 0.5 mm, and the distance d from the substrate end to the resistance heating element end is 1.25 mm. In Conventional Example 1, since the resistance heating element 6 is not disposed over the entire width of the substrate, the fixing efficiency is inferior to that of this example. Since the total heating element width is the same as in this embodiment, the amount of silver palladium used is the same and the cost is the same. The accuracy of the aperture amount is also the same because the width of the heating element provided with the aperture is 2 mm as in this embodiment.

  FIG. 7 is a front view of a heating body of Conventional Example 2. Conventional Example 2 has a configuration in which the heating element width is made as wide as possible based on the configuration of Conventional Example 1. The heating element width B is 2.75 mm, and the total heating element width is 5.5 mm. The distance C between the heating elements is 0.5 mm, and the distance d from the substrate edge to the resistance heating element edge is also 0.5 mm. In Conventional Example 2, since the resistance heating element 6 is disposed over the entire substrate width and the total heating element width is large, the fixing efficiency is superior to that of the present embodiment, but the cost is very high. The accuracy of the aperture amount is superior to that of this embodiment because the width of the heating element provided with the aperture is wider than that of this embodiment.

  FIG. 8 is a front view of a heating body of Conventional Example 3. In Conventional Example 3, four resistance heating elements 6 are connected in parallel, two on the upstream side and two on the downstream side. Conventional example 3 also has a pattern in which resistance heating elements 6 are arranged over the entire width of the substrate. The four heating element widths A / 2 are all 1 mm, and the total heating element width is 4 mm as in this embodiment. The distances C and D between the heating elements are 0.6 mm and 0.8 mm, respectively, and the distance d from the substrate end to the resistance heating element end is a minimum of 0.5 mm. In Conventional Example 3, the resistance heating element 6 is disposed over the entire substrate width, and the total heating element width is the same as in this embodiment, so that the fixing efficiency is considered to be substantially equivalent to that in this embodiment. As a result of actually mounting and comparing the heating element of Conventional Example 3 on the heating device of this example, the electric power necessary to obtain the same fixing ability was almost the same. The cost is the same as in this embodiment. However, the accuracy of the aperture amount deteriorates as described above because the width of the heating element provided with the aperture portion is 1 mm, which is narrower than the present embodiment.

  Table 2 summarizes the comparison between the present embodiment and the conventional examples 1 to 3 in terms of the fixing efficiency, cost, and aperture accuracy described above.

  “◯” is equivalent to this example, “優” is superior to this example, and “x” means inferior to this example. As shown in Table 2, it can be seen that this embodiment is the most balanced configuration in terms of fixing efficiency, cost, and aperture accuracy. Conventional Example 2 is superior to the present embodiment in terms of fixing efficiency and aperture accuracy, but the cost increase relative to the present embodiment is very large and the balance is poor. Although the total heating element widths of the conventional examples 1 and 3 do not need to match those of this embodiment, the overall balance is better when the cost is the same and the accuracy of the fixing efficiency and the aperture amount is compared with this embodiment. Therefore, the total heating element width is the same as that of this example.

(Example 2)
In this embodiment, a heating element having a resistance heating element having a shape different from that of the first embodiment is used. The configurations of the heating element, the heating device, and the image forming apparatus other than the shape of the resistance heating element are the same as those in the first embodiment.

  FIG. 9 is a front view of the heating body 3 in the present embodiment. Also in FIG. 9, the overcoat layer is omitted for simplicity. As shown in FIG. 9, in the present embodiment, five resistance heating elements 6 are provided, and one upstream side and four downstream sides are connected in parallel. The upstream heating element width A is 2 mm, and the four downstream heating element widths A / 4 are both 0.5 mm. Therefore, the total heating element width is 4 mm as in the first embodiment. Also in this embodiment, the resistance heating element 6 is arranged as much as possible over the entire substrate width, and the distance C between the heating elements and the distance d from the substrate edge to the resistance heating element edge are both 0.5 mm.

  The thickness of the resistance heating element 6 was set to about 10 μm for all the five heating elements as in the first embodiment. Further, the material of the resistance heating element 6 was the same as that used in Example 1 with screen-printed silver palladium.

  Also in the present embodiment, the narrowed portion 15 is provided only on the upstream thick resistance heating element. The design value of the heating element width of the aperture 15 is 1.6 mm, and the aperture is 125%. Also in the configuration of the heating apparatus of the present example, the fixing property of the throttle part can be made equal to that of other parts by setting the throttle amount to 125%. The position and length in the longitudinal direction of the aperture 15 are the same as those in the first embodiment.

  Also in this example, the total resistance value (resistance between the power feeding electrodes 9 and 10) of the resistance heating element 6 at room temperature was 20Ω. Therefore, the resistance value of the upstream resistance heating element is about 10Ω, and the resistance value of the downstream resistance heating element is about 40Ω.

  In this embodiment as well, as described in the first embodiment, it is possible to achieve a balanced configuration of three points of fixing efficiency, cost, and aperture accuracy. Moreover, since the resistance heating elements on the downstream side are increased to four, the temperature distribution in the substrate width direction becomes more uniform than in Example 1, and the temperature of the entire substrate can be efficiently increased in the nip. Fixing efficiency is further improved.

The front view of the heating body which concerns on 1st Example of this invention The figure showing the front view of the heating body which concerns on 1st Example of this invention, and the circuit which performs electricity supply control Sectional drawing of the heating body which concerns on 1st Example of this invention Schematic configuration diagram of a heating device according to the present invention 1 is a schematic configuration diagram showing a main part of a laser beam printer according to the present invention. Front view of heating body of Conventional Example 1 Front view of heating body of Conventional Example 2 Front view of heating body of Conventional Example 3 The front view of the heating body which concerns on 2nd Example of this invention

Explanation of symbols

1 stay 2 fixing film 3 heating element (heater)
4 Pressure roller 5 Temperature sensor (external contact type thermistor)
6 Resistance heating element 7 Heating substrate 8 Overcoat layer 9 · 10 Power supply electrode 11 CPU
12 Triac 13 AC power supply 14 Safety element (thermo switch)
15 Aperture
N Nip part
P Recording material
T toner
A Recording material transport direction

Claims (7)

  In a heating device that heats a material to be heated by a heating element including at least a substrate, a plurality of resistance heating elements, and an electrode that supplies power to the resistance heating element, the plurality of resistance heating elements have a width in a direction in which the material to be heated is conveyed Only the resistance heating element having the widest width includes a region in which the width in the conveyance direction of the heated material is different from the width of the other part in the longitudinal direction of the resistance heating element only. Heating device.   The heating device according to claim 1, wherein only the resistance heating element having the widest width in the conveyance direction of the heated material has a width in the conveyance direction of the heated material in a part of the longitudinal direction of the resistance heating element as compared with the width of the other portion. A heating device characterized in that a thinning region exists.   3. The heating device according to claim 1 or 2, wherein the resistance heating element is connected in series to a part of the longitudinal direction of the resistance heating element corresponding to a region where the width of the heated material conveyance direction is different from the width of the other part. A heating device, wherein the safety element is in contact with the safety element, and the power supply to the resistance heating element is cut off when the safety element reaches or exceeds a predetermined temperature.   4. The heating apparatus according to claim 3, wherein the safety element is a thermo switch or a thermal fuse.   At least a heating body, a heat-resistant film that contacts and slides one surface with the heating body, and the other surface contacts the material to be heated, drives the heat-resistant film, and the material to be heated is heated through the heat-resistant film. A heating device that heats the heated material by sandwiching and transporting the heat-resistant film and the heated material together through a nip formed by the heating body and the pressurized member. A heating apparatus having the configuration according to any one of claims 1 to 4.   6. The heating apparatus according to claim 5, wherein the substrate of the heating body is present in a nip portion formed by the heating body and the pressure member in the direction of transporting the heated material.   7. The image forming apparatus according to claim 1, wherein the image forming apparatus includes an image forming unit that forms an image on a recording material, and an image heating unit that heats the image on the recording material. An image forming apparatus comprising a heating device.

Images