JP2019028188A - Image heating device - Google Patents

Abstract

An image heating apparatus capable of shortening the start-up time and suppressing the occurrence of fixing failure by supplying a predetermined power corresponding to the resistance value of a heater until the product lifetime, and an image formation provided with the same Providing the device. Voltage detecting means for detecting an input voltage in an image heating apparatus that heats a toner image on a recording material through a fixing member by a heating resistor that generates heat when energized or a heating body including the heating resistor. Calculating means for calculating the electric power supplied to the heating resistor, resistance value storing means for storing the resistance value of the heating resistor measured in advance, and an energization counter value representing energization deterioration of the heating resistor, It has a table for predicting resistance fluctuation due to energization deterioration of the heating resistor, corrects the resistance value of the heating resistor from the energization counter value and the table, and corrects the resistance value and the voltage value detected by the voltage detection means. Based on the target maximum supply power value, the calculation means calculates the supply power. [Selection] Figure 8

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copiers and printers, a film heating type fixing device capable of shortening the wait time, miniaturizing the apparatus, and increasing the speed has been widely used. For example, a heat-resistant resin film (hereinafter referred to as a fixing film) as a heating member is sandwiched between a ceramic heater as a heating body and a pressure roller as a pressure member, and a pressure nip portion (hereinafter referred to as a fixing nip portion). And a recording material on which an unfixed toner image is formed and supported between the fixing film and the pressure roller in the fixing nip portion is introduced and conveyed together with the fixing film. The unfixed toner image is fixed on the surface of the recording material by the pressure of the fixing nip portion while applying the heat of the ceramic heater through.

  As a method for controlling the heater to a set temperature, a method for controlling the energization time to the heater is generally employed. There are two types of methods for controlling the energization time: wave number control for controlling energization / non-energization of the power supply waveform every integer multiple of the frequency and phase control for controlling the phase angle of energization every half cycle of the power supply waveform. Is generally used.

  On the other hand, the heater resistance value has a tolerance for each heater. There is also a variation in the voltage value applied to the heater. For this reason, even if the heater is energized at the same energization rate, the electric power varies and the heater temperature cannot be accurately controlled.

  In order to prevent this, it is known to provide a correction means for correcting the energization rate so that the same power is output even if the resistance value of the heater and the voltage applied to the heater vary.

  Patent Document 1 discloses a technique for providing a resistance value recording unit that records a resistance value of a heater in advance and performing control so as to supply electric power according to the recorded resistance value.

Japanese Patent No. 3320172

  However, the heater deteriorates due to repeated energization, and the resistance value of the heater varies with continuous use. Therefore, if the heater resistance value measured in the manufacturing stage is continuously used until the product lifetime, the resistance value changes due to the deterioration of energization, so that the predetermined power cannot be supplied and the start-up time is extended and fixing failure occurs. Problems arise.

  Accordingly, an object of the present invention is to provide an image heating apparatus capable of shortening the start-up time and suppressing occurrence of fixing failure by supplying predetermined power corresponding to the resistance value of the heater until the product lifetime. The present invention provides an image forming apparatus including the above.

In order to achieve the above object, an image heating apparatus according to the present invention includes:
In the image heating apparatus that heats the toner image on the recording material via the fixing member 41 by the heating resistor 432 that generates heat by energization or the heating body 43 including the heating resistor 432,
A voltage detection means 102 for detecting an input voltage; a calculation means 100 for calculating power supplied to the heating resistor 432; a resistance value storage means 105 for storing a resistance value of the heating resistor 432 measured in advance; An energization counter value representing energization deterioration of the heating resistor 432 and a table for predicting resistance fluctuation due to energization deterioration of the heating resistor 432, and the resistance value of the heating resistor 432 from the energization counter value and the table. , And the supply power is obtained by the calculation means 100 based on the corrected resistance value, the voltage value detected by the voltage detection means 102 and the target maximum supply power value.

  According to the image heating apparatus of the present invention, even when the product is continuously used, a predetermined power corresponding to the resistance value of the heater is supplied, so that the start-up time is shortened and the occurrence of fixing failure is suppressed. It becomes possible.

1 is a schematic diagram of an image forming apparatus in a first embodiment. FIG. 2 is a schematic diagram of a fixing device in the first embodiment. It is a schematic diagram of the fixing film in the first embodiment. It is a figure explaining the example of arrangement | positioning of the temperature detection means of the rotating shaft direction in a 1st Example. It is a figure explaining the structure of the heating body in a 1st Example. FIG. 3 is a block diagram illustrating a control system of the fixing device in the first embodiment. It is a figure for demonstrating the resistance value change of a heating resistor. 3 is a flowchart showing a fixing device life detection sequence in the first embodiment. It is a schematic diagram of the fixing device in the second embodiment. It is a schematic diagram of the fixing film in a 2nd Example. It is a figure explaining the structure of the heating member in a 2nd Example. It is a schematic diagram of the fixing film in a 3rd Example. It is a figure explaining the structure of the heating member in a 3rd Example.

  Next, specific examples (examples) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.

  FIG. 1 is a cross-sectional view of a color electrophotographic printer that is an example of an image forming apparatus according to the present embodiment, and is a cross-sectional view along the sheet conveyance direction. In this embodiment, the color electrophotographic printer is simply referred to as “printer”.

  The printer shown in FIG. 1 includes an image forming unit 10 for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drum 11 is charged in advance by a charger 12. Thereafter, a latent image is formed on the photosensitive drum 11 by the laser scanner 13. The latent image becomes a toner image by the developing device 14. The toner image on the photosensitive drum 11 is sequentially transferred by the primary transfer blade 17 to, for example, an intermediate transfer belt 31 that is an image carrier. After the transfer, the toner remaining on the photosensitive drum 11 is removed by the cleaner 15. As a result, the surface of the photosensitive drum 11 becomes clean and prepares for the next image formation.

  On the other hand, the sheets P are sent one by one from the paper feed cassette 20 or the multi paper feed tray 25 and sent to the registration roller pair 23. The registration roller pair 23 receives the sheet P once, and straightens it when the sheet is skewed. The registration roller pair 23 feeds the sheet between the intermediate transfer belt 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31. The color toner image on the intermediate transfer belt is transferred onto the sheet P by, for example, a secondary transfer roller 35 which is a transfer body. Thereafter, the toner image on the sheet is fixed to the sheet by the sheet being heated and pressed by the fixing device 40.

  Next, the fixing device used in this embodiment will be described.

  In FIG. 2, a film heating type heating device (tensionless type) as shown in the schematic configuration diagram of the fixing device 40 is used.

  Reference numeral 43 denotes a ceramic heater (hereinafter referred to as a heater) as a heating body. The heater 43 is basically composed of a thin and thin plate-like ceramic substrate whose longitudinal direction is perpendicular to the drawing, and an energization heating resistor layer provided on the surface of the substrate. It is a low heat capacity heater that raises the temperature with a good rise characteristic. In addition, the energization region is switched according to the longitudinal width size of the recording material.

  Reference numeral 41 denotes a cylindrical (endless) heat-resistant fixing film as a heating member that transmits heat, and is loosely fitted to a support member including the heater 43 described above. The fixing film 41 in this embodiment is as shown in FIG. 3 and is a fixing film having a four-layer composite structure of a surface layer, an elastic layer, a base layer, and an inner surface layer.

  As the surface layer 41a, a fluororesin material having a thickness of 100 μm or less, preferably 10 to 70 μm can be used. For example, examples of the fluororesin layer include PTFE, FEP, PFA, and the like. In this example, a PFA tube having a thickness of 10 μm was used.

  For the base metal layer 41b, a heat-resistant material having a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more can be used in order to improve the quick start property. For example, a metal film such as SUS or nickel can be used. In this example, a cylindrical nickel metal film having a thickness of 30 μm and a diameter of 25 mm was used.

  The elastic layer 41c is sandwiched between the surface layer 41a and the base layer 41b. In addition, in order to reduce the heat capacity and improve the quick start, a filler for increasing the thermal conductivity was added. In this example, a silicone rubber having a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 1.3 W / m · K, and a thickness of 200 μm was used.

  For the inner surface layer 41d, a resin having high durability and high heat resistance such as polyimide resin is suitable. In this example, a polyimide precursor solution obtained by reacting approximately equimolar amounts of an aromatic tetracarboxylic dianhydride or a derivative thereof and an aromatic diamine in an organic polar solvent was used. This solution is applied to the inner surface of the base metal layer 41b, dried and heated, and a polyimide resin layer formed by a dehydration ring-closing reaction is used as an inner surface layer 41d. Specifically, in this example, an N-methyl-2-pyrrolidone solution of a polyimide precursor composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and paraphenylenediamine is used as the polyimide precursor solution. Was used. Then, a polyimide resin having a thickness of 15 μm is formed and used as an inner surface layer 41d.

  Reference numeral 44 denotes a heat-resistant elastic pressure roller as a pressure member, which is composed of a cored bar and an elastic layer made of a heat-resistant rubber such as silicone rubber or fluorine rubber, or a foam of silicone rubber, and rotates both ends of the cored bar. The bearing is supported freely. The fixing film 41 and the heater 43 are arranged on the upper side of the pressure roller 44 in parallel with the pressure roller 44 with respect to the heater 43 side, and are pressed by a pressing member (not shown). Then, a fixing nip portion N having a predetermined width as a heating portion is formed by pressing the lower surface of the heater 43 and the upper surface of the pressure roller 44 against the elasticity of the roller elastic layer.

  As shown in FIG. 4, the pressure roller 44 issues a drive means M rotation command from the control unit, and is rotated by the drive means via the transmission means G in the counterclockwise direction indicated by the arrow at a predetermined rotational peripheral speed. The A rotational force acts on the cylindrical fixing film 41 by the pressure frictional force at the fixing nip N between the pressure roller 44 and the fixing film 41 by the rotation driving of the pressure roller 44, and the fixing film 41 is attached to the heater 43. It is driven to rotate in the clockwise direction of the arrow while sliding in close contact with the downward surface. The support member is also a rotation guide member for the cylindrical fixing film 41.

  The pressure roller 44 is driven to rotate, so that the cylindrical fixing film 41 is driven and rotated, and the heater 43 is energized so that the heater quickly rises in temperature and rises to a predetermined temperature. In this state, the recording material P carrying the unfixed toner image T is introduced between the fixing film 41 and the pressure roller 44 in the fixing nip N, and the toner image carrying side surface of the recording material P is fixed in the fixing nip N. The fixing film 41 is in close contact with the outer surface of the fixing film 41, and is nipped and conveyed together with the fixing film 41 through the fixing nip N.

  In this nipping and conveying process, the recording material P is heated by the heat of the fixing film 41 heated by the heater 43, and the unfixed toner image T on the recording material P is heated and pressurized on the recording material P to be melted and fixed. . The recording material P that has passed through the fixing nip N is separated from the surface of the fixing film 41 and is discharged and conveyed.

  Reference numeral 45a denotes a contact-type thermometer (thermistor) on the back of the heater, which measures the temperature of the heater 43. As shown in FIG. 4, the heater back thermistor is arranged at three locations in the rotation axis direction. The central part is arranged at a position of ± 150 [mm] from the center in the longitudinal central part and the end part.

  Reference numeral 45 b denotes a contact thermometer (thermistor) on the back of the film, which measures the temperature of the inner surface of the fixing film 41 heated by the heater 43. The temperature detection result is transferred to the control unit.

  The process speed of this image forming apparatus is 250 [mm / s], and the productivity of A4 size plain paper is 60 ppm for both monochrome colors.

  In this fixing device, the electric power supplied to the heater is adjusted so that the central film back thermistor 45b1 becomes 170 [° C.].

  The temperature control of the central film back side thermistor 45b1 is changed according to the environment in which the image forming apparatus is installed and the paper type to be passed.

  When the environment in which the image forming apparatus is set is 23 [° C.] and plain paper 1 (81 g paper or less) is passed, the center film back thermistor 45b1 is set to 170 [° C.]. .

  When the environment in which the image forming apparatus is set is 23 [° C.] and plain paper 2 (105 g paper or less) is passed, the center film back thermistor 45b1 is set to 180 [° C.]. .

  Hereinafter, the heater will be described in detail.

  Next, the heater 43 of the present embodiment will be described in detail with reference to FIG.

  The heater 43 includes a substrate 431, a heating resistor 432 formed on the substrate 431, and an insulating coating layer 433 that covers the heating resistor 432.

  The substrate 431 is a member that determines the size and shape of the heater 43, and a ceramic material such as alumina or aluminum nitride having excellent heat resistance, thermal conductivity, and electrical insulation is used as the material. In this embodiment, alumina having a length in the longitudinal direction of 400 mm, a length in the short direction of 8.0 mm, and a thickness of about 1 mm is used. The thermal conductivity of the heater is 20 [W / m * K].

  A heating resistor 432 and a conductor pattern are formed on the substrate 431 by screen printing. The conductor pattern is a pattern for allowing a current to flow from the power source to the heating element. In the present embodiment, a silver paste that is a low resistivity material or an alloy paste in which a small amount of palladium is mixed with silver is used as the conductor pattern. The heating resistor 432 is made of a silver-palladium alloy paste so as to have a desired resistance value.

  The heating resistor material is a paste, and is composed of palladium such as 432B and glass fiber such as 432C in silver 432A so as to have a desired resistance value.

  The heating resistor 432 and the conductor pattern are covered with an insulating coating layer 433 made of heat-resistant glass, and are electrically protected so as not to cause a leak or a short circuit.

  The resistance value of the heater 43 has a tolerance of about ± 7% due to variations in the thickness and width of the heating resistor 432 and the volume low efficiency of the resistance material itself. Therefore, the actual resistance value of the heater 43 is measured in advance, and the value is stored in a memory provided in the fixing device.

  The low heat capacity fixing device of this embodiment does not wait for the fixing device in a standby temperature state. The standby temperature state is a mode in which the temperature of the fixing device is always controlled at a constant temperature so that fixing failure does not occur when paper comes. The demerit of standby is that the temperature is always controlled at a constant temperature, so there is an adverse effect of increasing power consumption.

  The control of the fixing unit has an advantage of reducing power consumption because the heater is energized when a job is received and the heater power is turned off after the paper is passed. However, there is a demerit that it takes time to start printing since the fixing device is heated from a cold state to a temperature at which paper can be passed. Therefore, at the time of start-up, control is performed so that the maximum power is supplied to the heater and the start-up time is shortened.

  FIG. 6 is a block diagram of the heater control unit. A voltage detection circuit 102 detects an input voltage. Reference numeral 100 denotes a controller that controls the temperature control and power control of the heater. The control unit 100 corrects the supply power required by the calculation means by correcting the resistance value of the calculation means, the temperature control means for controlling the power supply based on the result of the temperature detection means, the calculation means for calculating the supply power to the heater 43. It has a function as a means for obtaining from the resistance value and the input voltage.

  Reference numeral 103 denotes a switching circuit that switches a voltage applied to the heater, and the controller 100 switches the power supplied to the heater 43 in accordance with the temperature of the heater 43.

  The control unit 100 inputs an AC input voltage value from the voltage detection circuit 102 to the control unit. The output of the temperature detection means 104 is also input to the control unit. The control unit 100 secures a memory area (ROM) in which the number of startups of the fixing device can be stored, and stores an integrated value of the number of startups in that area.

  The heater is obtained by printing a heating resistor on a ceramic substrate, and has excellent thermal response. For this reason, if the normal energization control for the heater is performed on / off, the ripple becomes large with respect to the temperature control temperature, and it becomes impossible to control to a stable temperature. For this reason, power control is performed such that constant power is applied to this control.

  Here, the power control for the heater 43 will be described. Power control for the heater is performed by phase control. A waveform pattern with respect to the power ratio in the phase control is tabulated.

Since the heater is a resistive load, the power W is W = V ² / R
V: voltage applied to the heater R: resistance value of the heater.

  Since the resistance value of the heater varies greatly, a value measured in advance is stored in the memory.

  The voltage detected by the voltage detection circuit is input.

The corrected supply maximum power ratio Wmax (%) is Wmax = target maximum power / V ² × R × 100 (%)
Ask for.

  For example, if the target maximum power is 100 W at 1000 W and 8 Ω, if 100% maximum output is attempted, 1250 W is output, but the corrected maximum supply power ratio is output at 80%, so that the target maximum power is 1000 W. Can be output.

  The heater 43 deteriorates due to repeated energization, and the resistance value of the heating resistor 432 increases due to the deterioration. As the cause, the material of the paste-like heating resistor is made of materials having different linear expansion coefficients such as silver and palladium. Therefore, micro cracks occur between materials due to repeated energization, the cross-sectional area through which current flows decreases, and the resistance value increases. When the resistance value increases, the power applied to the heater 43 decreases because the applied voltage is constant. For this reason, it takes a long time to reach the target temperature, and the delay in the start-up time and the fixing property cannot be satisfied.

  Therefore, in this example, the heater resistance value is corrected based on the energization counter and the energization counter-resistance value table indicating the progress of deterioration of the heater due to repeated energization, thereby suppressing the delay of the start-up time and the occurrence of fixing failure.

  When the power supplied to the heater 43 is obtained, the resistance value increased due to energization deterioration is obtained, and the detected voltage value is used. FIG. 7 is a graph showing the amount of change in resistance value when the heat cycle test in which the temperature is changed from room temperature to high temperature is repeated. In this example, the input power was 1000 W and the heater temperature was 200 ° C. It can be seen from FIG. 7 that the resistance value of the heater increases as the number of repeated heat cycles increases. Therefore, in this example, the number of start-ups of the fixing device is used as the energization counter. The number of start-ups is counted when the heater temperature starts from 50 ° C. or lower, and the number of times of start-up is stored in a memory area (ROM).

  Table 1 is a table showing the relationship between the number of start-ups as the energization counter and the resistance increase rate.

  The resistance value is corrected by obtaining the resistance value increase rate using the number of start-ups stored in the memory area (ROM) and the table in Table 1, and correcting the increase rate from the initial resistance value measured in advance. . In addition, as a correction of the resistance value, it is also possible to correct the temperature effect fluctuation using the heater temperature detection result and the temperature coefficient of the heating resistor.

  The control operation will be described with reference to the flowchart of FIG.

In the heater power calculation routine, first, in S101, the control unit 100 reads the input voltage value detected by the voltage detection circuit. In step S102, the initial resistance value stored in the resistance value memory 105 is read. In S103, the number of start-ups that is an energization counter is read from the memory area (ROM). In this example, the detection voltage is 100 V, the initial resistance is 8Ω, and the energization counter is 1.1 million times. In S104, the resistance increase rate is obtained from the energization counter-resistance change rate table, and the increase is corrected from the initial resistance value. Here, since the rate of increase is 10%, the corrected resistance value is 8.8Ω. Finally, the corrected supply power rate can be obtained by calculating using the detected voltage value, the correction resistance value, and the target maximum supply power value in S105. When the target supply power is 1000 W, the corrected supply power rate is 88%. Supplying a maximum supply power of 1000 W to the heater 43 at a corrected supply power rate of 88% actually obtained, using a paper with an A3 size basis weight of 105 g / m ^2, and displaying a solid image from the state in which the fixing device is cooled to room temperature. The start-up time and the presence or absence of toner peeling when 20 sheets were printed continuously were confirmed. The results are shown in Table 2. As a result, the startup time until reaching the temperature at which printing can be started was 10 seconds, and no toner peeling occurred.

  As a comparative example, when the resistance value correction is not performed, the corrected supply power rate is 80%, so the actual maximum supply power is reduced to 909 W, the startup time is as long as 11 seconds, and the toner is peeled off. Also occurred.

  As described above, in this example, even when the product continues to be used, the predetermined power corresponding to the resistance value of the heater is supplied to reduce the startup time and the occurrence of fixing failure. It becomes possible.

  A fixing device and an image forming apparatus including the same according to a second embodiment of the present invention will be described. Since the configuration of the image forming apparatus is the same as that of the first embodiment, description thereof is omitted. Since the fixing device configuration is different, it will be described below.

● Fixing device The fixing device will be described. FIG. 9 is a schematic configuration diagram illustrating the configuration of the fixing device 40.

  Reference numeral 1000 denotes a cylindrical fixing film provided with a heating element. A pressure roller 44 forms a fixing nip with the fixing film.

  A support stay (not shown) disposed inside the fixing film 1000 connected to the fixing flange supports a nip forming member (not shown) that pressurizes and urges the fixing film 1000 toward the pressure roller 44.

  The nip forming member is in contact with the pressure roller through the fixing film to form a fixing nip.

  In this embodiment, the applied pressure is 156.8 N on one end side, and the total applied pressure is 313.6 N (32 kgf). The nip width N of the fixing device is in the range of 8 mm to 9 mm. The longitudinal heat generation area of the fixing film and the longitudinal rubber surface length of the pressure roller are 320 mm, and the diameter of the fixing film and the pressure roller is φ24 mm.

  The support stay is preferably made of a material that is difficult to bend even when a high pressure is applied. In this embodiment, SUS304 is used.

  The nip forming member is a heat insulating member such as a heat resistant resin. From the viewpoint of energy saving, it is desirable to use a material with low heat conduction to the support stay. For example, heat-resistant glass, polycarbonate, liquid crystal polymer, or other heat-resistant resin is used. In this example, Sumika Super E5204L manufactured by Sumitomo Chemical Co., Ltd. was used.

  The pressure roller 44 is disposed such that both end portions of the core bar are rotatably supported by bearings between the rear side plate and the front side plate of the apparatus frame.

  Reference numeral 45 denotes a thermistor as temperature detecting means. It has a function of detecting the temperature of the outer surface of the fixing film 1000.

As shown in FIG. 9, the thermistor 45 is connected to the control unit 100 (CPU) as control means via the A / D converter 120. The control unit 100 samples the output from the thermistor at a predetermined cycle, and reflects the obtained temperature information in the energization control to the fixing film as a heating element. That is, the control unit 100 determines the energization control content to the heating element based on the output of the thermistor 45 and controls the energization supplied from the power supply unit 79 to the heating element of the fixing film 1000 via the power feeding unit 1050. . Note that the above-described control in the fixing device of this embodiment is performed so that the temperature detected by the thermistor 45 is constant in consideration of the temperature for fixing the toner image on the recording material P.
The control unit 100 performs rotation control of the motor M under predetermined conditions. When the motor M is rotated, the pressure roller rotates through the pressure roller gear.

  The fixing film 1000 is driven by the pressure roller 44 and rotates at a predetermined speed.

  Grease is applied to the inner surface of the fixing film 1000 to reduce wear on the inner surface of the fixing film 1000 caused by friction between the nip forming member and the inner surface of the fixing film 1000.

  The power supply electrode portion 1050 is in contact with a power supply member 81 that is electrically connected to the power supply portion 79. The power supply member 81 is an alloy member made of silver and palladium disposed on a stainless steel plate spring-shaped arm, and the electrical connection is maintained well by pressing the power supply member 81 against the power supply electrode portion 1050. Is done. In accordance with the temperature detected by the thermistor 45 installed on the inner surface of the fixing film 1000, the control unit 100 performs energization control by the power supply unit 79.

● Rotating Heating Element Next, the configuration of the fixing film 1000 that is a rotating heating element will be described in detail with reference to FIG. FIG. 10 is a schematic diagram of the layer structure of the fixing film longitudinally, and the arrow A direction (Z direction) is the inner peripheral side. The fixing film 1000 in this embodiment has a three-layer composite structure of a base layer 1010, a heat generating layer 1020, and a release layer 1040 in order from the inner peripheral side to the outer peripheral side. Further, a feeding electrode portion 1050 is provided at the end portion in the rotation axis direction.

  For the base layer 1010, a heat-resistant material having a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more can be used in order to reduce the heat capacity and improve the quick start property. For example, a resin belt such as polyimide, polyimide amide, PEEK, PTFE, PFA, or FEP can be used. In this example, a cylindrical polyimide belt having a thickness of 30 μm and a diameter of 25 mm was used.

  The release layer 1040 was a PFA tube having a thickness of 20 μm. The release layer 1040 is bonded to the heat generating layer 1020 with an adhesive made of silicone resin. In addition, a PFA coat may be used as the release layer, and the PFA tube and the PFA coat can be used properly according to the required thickness, mechanical and electrical strength.

  Furthermore, power supply electrode portions 1050 are formed at both ends of the fixing film 1000, and the power supply electrode portions 1050 are electrically connected to both ends of the heat generating layer 1020. The feeding electrode portion 1050 is formed on both ends of the fixing film 1000 over the entire circumference. The power supply electrode portion 1050 is made of a material having conductive characteristics including silver and palladium.

  The heat generating layer 1020 will be described with reference to FIG. FIG. 11 illustrates the heat generating layer 1020 with the fixing film 1000 from the top and the release layer 1040 omitted. In FIG. 11, the X direction indicates the longitudinal direction of the fixing film 1000, and the Y direction indicates the circumferential direction of the fixing film 1000. Since the feeding electrode portion 1050 is formed over the entire periphery of the end portion of the fixing film, the current flows in the X direction.

  The thickness of the heat generating layer is 200 μm or less, preferably 100 μm or less and 10 μm or more.

  The heat generating layer 1020 is set to a predetermined electrical resistivity by uniformly dispersing the conductive filler 2000 in an insulating resin such as a polyimide resin. As an example of the conductive filler, carbon nanotubes, carbon nanofibers, carbon microcoils, graphite fibers, graphite flakes, graphite chips, silver particles, aluminum particles, and nickel particles are used.

  Glass fiber fibers are incorporated for resistance adjustment and heating element strength improvement.

  The total resistance value of the heat generating layer is 8Ω. The resistance value may be determined as appropriate according to the amount of heat generated as a fixing device, and can be adjusted as appropriate according to the mixing ratio of the conductive filler.

  As shown in this embodiment, the heating element layer is made of a composite material such as a PI-based resin, a conductive filler, and glass fiber. Therefore, as described in the first embodiment, the linear expansion coefficient differs between the materials, microcracks are generated, and the resistance value is fluctuated compared to the initial value.

  Also in the present embodiment, the resistance value is corrected from the energization counter-resistance value change rate table as shown in the first embodiment. Since the power calculation logic is the same as that of the first embodiment, it will be omitted.

  A fixing device and an image forming apparatus including the fixing device according to a third embodiment of the present invention will be described. Since the configuration of the image forming apparatus is the same as that of the first embodiment, description thereof is omitted. Since the fixing device configuration is different, it will be described below.

  Next, the fixing unit 40 of the present embodiment will be described.

  FIG. 12 is a cross-sectional view showing the configuration of the fixing unit 40 of the present embodiment.

  As shown in FIG. 12, the fixing unit 40 faces the fixing film 41, a heater 43 as a heating source, a fixing film 41 as an example of a fixing member that fixes the toner image by being heated by the heater 43, and the fixing film 41. A pressure roll 44 as an example of a pressure member arranged in this manner and a pressing pad 46 pressed from the pressure roll 44 via the fixing film 41 are provided.

  The fixing unit 40 further includes a frame (not shown) that supports components such as the pressure pad 46 and a temperature sensor 45 that contacts the inner peripheral surface of the fixing film 41 and measures the temperature of the fixing film 41. Yes.

<Description of heater unit configuration>
The heater unit is a heater 43 as an example of a heating member that is a heat generation source, and a heat diffusion member that defines the shape of the heater 43 in an arch shape, supports the heater 43, and diffuses the heat generated by the heater 43. The heat diffusion plate 50 and a pressing member 52 for pressing the heater unit against the fixing film 41 are configured.

  The heat diffusing plate needs to be made of a material having excellent heat conductivity and heat resistance. In the present embodiment, a stainless steel plate having a thickness of 0.3 mm, for example, is used as the heat diffusion plate 50. In addition, as a stainless steel material used as the thermal diffusion plate 50, SUS430 etc. are mentioned, for example.

  In the present embodiment, the heater 43 functions as an example of a heating member that heats the fixing film 41 by contacting the inner peripheral surface of the fixing film 41.

  FIG. 13 is a diagram showing the structure of the heater 43 of the present embodiment. FIG. 13A is a perspective view showing the heater 43, and FIG. 13B is a cross-sectional view of the heater 43 shown in FIG.

The heater 43 is a so-called film heater and has flexibility. And in the state of being pinched | interposed into the thermal-diffusion board 50 in the actual usage form, it is bent by circular arc shape as shown in FIG.
However, in order to make the explanation easy to understand, FIGS. 13A to 13B show the planar heater 43 before being bent into an arc shape.

  As shown in the figure, the heater 43 of the present embodiment employs a structure in which a heat generating layer 432 is sandwiched between insulating layers 433.

  In the present embodiment, the heat generating layer 432 functions as an example of a heat generating portion in which the wiring draws a predetermined pattern. The heat generating layer 432 is made of a conductive material and generates heat when energized. In this embodiment mode, the heat generating layer 432 has a structure in which a conductive filler 432B, glass fiber 432C, and the like are added to a stainless steel foil having a thickness of 30 μm. Examples of the stainless steel foil used for the heat generating layer 432 include SUS430 and SUS304. In addition to the stainless steel foil, the heating layer 432 may be a resistance heating body that generates heat when energized, such as copper, aluminum, or nickel.

  The total resistance value is adjusted to 8 [Ω] by adding additives to the stainless steel foil.

  The heat generating layer 432 generates heat more uniformly by drawing a predetermined pattern.

  The insulating layer 433 is a layer for insulating the heat generating layer 432 and protecting the heat generating layer 432 from being bent or the like. In this embodiment, the insulating layer 433 has a two-layer structure of an insulating layer 433a and an insulating layer 433b. Then, the heat generation layer 432 is sandwiched between the insulating layer 433a and the insulating layer 433b, and the heat generation layer 432 is included in the insulating layer 433 by performing thermocompression bonding. Therefore, in this case, the insulating layer 433a and the insulating layer 433b are bonded and integrated.

  The insulating layer 433 needs to be made of a material having insulating properties and excellent heat resistance. In the present embodiment, for example, a thermosetting polyimide having a thickness of 25 μm to 50 μm is used as the insulating layer 433a. As the insulating layer 433b, for example, thermoplastic polyimide having a thickness of 25 μm to 50 μm is used.

  Also in this embodiment, an additive is added to the heating element material in order to set the resistance value of the heating element to a predetermined value. Therefore, due to the difference in the linear expansion coefficient of each material as described in the first embodiment, a sudden temperature change may cause distortion between materials, and the resistance value of the heating element may vary depending on durability. Therefore, also in the present embodiment, the resistance value is corrected from the energization counter-resistance value change rate table as shown in the first embodiment. Since the power calculation logic is the same as that of the first embodiment, it will be omitted.

10 image forming unit, 11 photosensitive drum, 12 charger, 13 laser scanner,
14 developing unit, 15 cleaner, 17 primary transfer blade, 20 paper feed cassette,
25 Multi-feed tray, 23 Registration roller pair, 31 Intermediate transfer belt,
35 secondary transfer roller, 40 fixing device, 41 fixing film,
41a fixing film surface layer, 41b fixing film base layer,
41c fixing film elastic layer, 41d fixing film inner surface layer, 43 heating element,
431 base material, 432 heat generating layer, 433 insulating layer, 44 pressure roller,
45a Heater back contact thermistor, 45b Film back contact thermistor,
46 heater holder, 100 control unit, P recording material (paper),
T toner image, N fixing nip

Claims (3)

In the image heating apparatus that heats the toner image on the recording material via the fixing member 41 by the heating resistor 432 that generates heat by energization or the heating body 43 including the heating resistor 432,
Voltage detection means 102 for detecting an input voltage, or current detection means for detecting a current flowing through the heating resistor 432;
Computing means 100 for computing the power supplied to the heating resistor 432;
Resistance value storage means 105 for storing the resistance value of the heating resistor 432 measured in advance;
An energization counter value representing the energization deterioration of the heating resistor 432;
A table for predicting resistance variation due to deterioration of energization of the heating resistor 432;
From the energization counter value and the table, the resistance value of the heating resistor 432 is corrected,
Based on the corrected resistance value and the voltage value detected by the voltage detection means 102, or the current value detected by the current detection means and the target maximum supply power value,
An image heating apparatus characterized in that a power supply is obtained by the arithmetic means (100). The image heating apparatus according to claim 1, wherein the energization counter is an integrated value of the number of start-ups of the image heating apparatus. The image heating apparatus according to claim 1, wherein the heating member is a heat-generating fixing member that generates heat from the fixing member 41 or an elastically deformable planar heat-generating member.