JP2013008510A - Heater and image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater having high reliability and an image heating device equipped with the heater having high reliability in an image heating device capable of switching resistance values according to commercial power supply.SOLUTION: A heat element is placed at both ends side of a substrate in a short direction along a longitudinal direction in a first conductive path and a heat element is placed in a center of the substrate in the short direction sandwiched between the first conductive paths in a second conductive path, in which a resistance temperature coefficient of the heat element in the second conductive path is set to be larger than that of the heat element in the first conductive path.

Description

  The present invention relates to an image heating apparatus mounted on an image forming apparatus capable of forming a toner image on a recording material such as a copying machine, a printer, or a facsimile employing an electrophotographic system, and a heater used in the apparatus. More specifically, the present invention relates to a universal heater and an image heating apparatus that can be used for both power supply voltages 100V / 200V. Examples of the image heating device include a fixing device that fixes an unfixed image formed on a recording material, and a gloss processing heating device that improves the glossiness of an image by heating the image fixed on the recording material. It is done.

  A film heating method has been proposed and put into practical use as a heating method in a fixing device mounted on a photocopier or an electrophotographic printer. In this film heating system, a heat-resistant thin film (fixing film), which is a heating rotator, is brought into close contact with a heating rotator (elastic roller) as a pressure member and is slid and conveyed. Then, a heated material as a recording material carrying an unfixed image is introduced into a pressure nip formed by a heating body and a pressure rotating body with the fixing film interposed therebetween, and is conveyed together with the fixing film. As a result, the unfixed image is heat-fixed on the transfer material by the heat from the heating body applied through the fixing film and the pressing force of the pressure nip portion.

  In this film heating type fixing device, since the entire fixing device can be constituted by a low heat capacity member, it is possible to save power and shorten the wait time (quick start property). As the heating body, for example, a heat generation pattern using a plate-like ceramic base material with a low heat capacity such as alumina (Al2O3) or aluminum nitride (AlN) and using silver palladium (Ag / Pd) / Ta2N or the like on one surface is used. . Then, a power supply electrode pattern made of a low resistance material such as Ag for energizing the heat generation pattern is formed by screen printing or the like, and the heat generation pattern formation surface is covered with a thin glass protective layer.

  This heating body generates heat by energizing the heating pattern through the power supply electrode pattern, and the entire heating body rapidly rises in temperature. The temperature rise of the heating body is detected by a thermistor as a temperature detection means disposed in contact with or near the heating body and fed back to the energization drive control unit. The energization control unit controls energization of the heat generation pattern so that the heating body temperature detected by the thermistor is maintained at a predetermined substantially constant temperature (fixing temperature). Thereby, the heating body is controlled to be heated to a predetermined fixing temperature.

  In the image heating apparatus using such a resistance heating element, the voltage of the commercial power supply is 100V system (ex. 100V (Japan) to 127V (Mexico)) and 200V system (ex. 200V (North Korea) to 240V (India)). ) Needs to be addressed. Here, when heaters having the same resistance value are used, the electric power supplied to the heater is proportional to the square of the voltage. Therefore, when the commercial power supply voltage is 200 V, the maximum electric power value that can be supplied to the heater is 4 compared to 100 V. Double. When the maximum power that can be supplied to the heater is increased, harmonic current, flicker, and the like generated by heater power control such as phase control and wave number control are increased.

  In addition, since the electric power generated when the image heating apparatus runs out of heat increases four times, an electrical cutoff circuit with faster response is required. For this reason, image heating apparatuses having heaters with different resistance values are often used in regions where the commercial power supply voltage is 100V and 200V. As a means for realizing a universal image heating apparatus that can be shared between a region where a commercial power supply voltage of 100 V is supplied and a region where a commercial power supply voltage of 200 V is supplied, the resistance value of the heater is set using a switch means such as a relay. A method of switching has been devised.

  In the image heating apparatus described in Patent Document 1, the first conductive path has a first conductive path and a second conductive path that extend in the heater longitudinal direction, and only the first conductive path is energized. In the case where the second conductive path is connected in parallel and energized, the resistance value of the heater is switched.

JP 2000-147931 A

  However, in the above method, when the heater resistance value is switched between the commercial power supply 100V and the 200V, the heat generation distribution in the short direction (paper feeding direction) of the heater is different. In particular, when the heat generation distribution in the short direction of the heater becomes non-uniform, the stress applied to the heater of the image heating apparatus becomes large and breakage tends to occur, and the reliability of the image heating apparatus decreases. It was.

  In view of such problems, an object of the present invention is to provide a heater capable of improving reliability and an image heating apparatus including the heater.

  In order to achieve the above object, a representative configuration of a heater according to the present invention includes a substrate having a longitudinal direction and a short direction intersecting the longitudinal direction, and a positive resistance temperature characteristic provided on the substrate. And a heating resistor that generates heat when energized via an electrode provided at an end in the longitudinal direction, wherein the heating resistor includes the first conductive path and the first resistor in the substrate. The first conductive path is provided in a second conductive path electrically connected in parallel with the conductive path, and the first conductive path is applied when a first power supply voltage is applied and a second lower than the first power supply voltage. Commonly used when a power supply voltage is applied, and in the first conductive path, the heating resistor is located at both ends of the substrate in the short direction along the longitudinal direction, The second conductive path is the second power source Used in the case where pressure is applied, and in the second conductive path, the heating resistor is located in the middle of the short direction sandwiched by the first conductive path along the longitudinal direction, The resistance temperature coefficient of the heating resistor of the second conductive path is made larger than the resistance temperature coefficient of the heating resistor of the first conductive path.

  In addition, a typical configuration of the image heating apparatus according to the present invention is provided on a heating rotation member that is rotatable and can be heated in a direction crossing the rotation direction, and an inner peripheral side of the heating rotation member. And a pressure member that forms a nip portion via the heating rotation member that slides and rotates on the heater, and sandwiches and conveys the recording material carrying an image in the nip portion. An image heating apparatus for heating the image, wherein the heater is the above-described heater, and a direction intersecting the rotation direction is the longitudinal direction.

  According to the present invention, by suppressing the heat generation at the central portion in the short direction of the heater substrate, the temperature distribution of the heater substrate can be made uniform, the thermal stress applied to the heater can be reduced, and a highly reliable heater and An image heating apparatus can be provided.

(A), (b) is the schematic of the heater which concerns on the 1st Embodiment of this invention. 1 is a schematic view of an image forming apparatus equipped with a heater and an image heating apparatus according to an embodiment of the present invention. It is the schematic of the image heating apparatus which concerns on embodiment of this invention. 1 is a circuit diagram according to a first embodiment of the present invention. (A) thru | or (g) is a figure explaining the effect of 1st Embodiment. (A) thru | or (c) is a figure showing the comparison with the comparative example 1 and the comparative example 2. FIG. (A), (b) is the schematic of the heater which concerns on 2nd Embodiment. (A), (b) is a figure explaining the effect of 2nd Embodiment (and 3rd Embodiment). (A), (b) is the schematic of the heater which concerns on 3rd Embodiment.

<< First Embodiment >>
(Image forming device)
FIG. 2 shows an outline of the configuration of an image forming apparatus equipped with a heater and an image heating apparatus according to an embodiment of the present invention. Only one sheet of recording paper loaded on the paper feed cassette 101 is sent out from the paper feed cassette 101 by the pickup roller 102, and conveyed toward the registration roller 104 by the paper feed roller 103. Further, the recording paper is conveyed to the process cartridge 105 by the registration roller 104 at a predetermined timing.

  The process cartridge 105 is integrally composed of a charging unit 106, a developing roller 107 as a developing unit, a cleaner 108 as a cleaning unit, and a photosensitive drum 109 as an electrophotographic photosensitive member. Then, an unfixed toner image is formed on the recording paper by a series of processes of a known electrophotographic process. The surface of the photosensitive drum 109 is uniformly charged by the charging unit 106, and then image exposure based on the image signal is performed by the scanner unit 111 which is an image exposure unit.

  Laser light emitted from the laser diode 112 in the scanner unit 111 is scanned in the main scanning direction (perpendicular to the paper surface) via the rotating polygon mirror 113 and the reflecting mirror 114. Then, the photosensitive drum 109 is rotated to scan in the sub-scanning direction (in-plane direction), and a two-dimensional latent image is formed on the surface of the photosensitive drum 109. The latent image on the photosensitive drum 109 is visualized as a toner image by the developing roller 107, and the toner image is transferred onto the recording paper conveyed from the registration roller 104 by the transfer roller 110.

  Subsequently, the recording paper to which the toner image has been transferred is conveyed to the image heating device 115 and subjected to heat and pressure processing, and the unfixed toner image on the recording paper is fixed to the recording paper. The recording paper is further discharged out of the image forming apparatus main body by the intermediate paper discharge roller 116 and paper discharge roller 117, and a series of printing operations is completed. The motor 118 applies driving force to each unit including the image heating device 119.

(Image heating device)
FIG. 3 shows an outline of the configuration of the image heating apparatus according to the embodiment of the present invention. The image heating device 115 is a pressure member driving type / tensionless type film heating type heating device. An endless heat-resistant film (fixing film) 202 that is a heating rotation member is rotatable, and can be heated in a direction intersecting the rotation direction by the heater 400. A film guide 201 made of a heat resistant resin having a longitudinal direction in the direction perpendicular to the paper surface of FIG. 3 serves as an inner surface guide member of an endless heat resistant film (fixing film) 202. The film 202 has a thin heat-resistant film surface coated with a fluorine resin or the like, but an element tube made of metal or the like may be used.

  The ceramic heater 400 provided on the inner peripheral side of the film 202 is fitted into a groove formed along the longitudinal direction on the lower surface of the film guide 202, and the endless heat-resistant film 202 is a film guide including the heater 400. 201 is externally fitted. The stay 204 is a rigid member whose longitudinal direction is the direction perpendicular to the paper surface of FIG. 3, and is disposed inside the film guide 201. The inner peripheral length of the endless heat-resistant film 202 is, for example, about 3 mm larger than the outer peripheral length of the film guide 201 including the heater 400, and thus the film 202 is longer than the film guide 201 including the heater 400. Is fitted loosely outside.

  A heater 400 as a heating body is formed by screening an electric resistance material (heat generation patterns 401 to 404) such as Ag / Pd (silver palladium) on the surface of a heater substrate 205 made of alumina, aluminum nitride or the like, which is a high thermal conductivity material. Apply by printing. Similarly, an electrically conductive material (conductive pattern) such as Ag is applied by screen printing or the like, and glass, fluorine resin, or the like is coated thereon as a protective layer 207 as an electrical insulator. The heater substrate 205 has a longitudinal direction and a short direction that intersects the longitudinal direction. The longitudinal direction is a direction that intersects the rotational direction of the endless heat-resistant film 202 (rotational axis direction), and the short direction is passed through. The direction.

  The pressure roller 208 forms a fixing portion N that is a pressure nip with the film 202 interposed between the pressure roller 208 and the heater 400. The pressure roller 208 is a rotating body that drives the film 202, and has a core shaft 209 made of aluminum, iron, stainless steel, or the like, and a roller portion 210 of a heat-resistant rubber elastic body that has good releasability, such as silicon rubber, that is sheathed on the shaft. It consists of. A coating layer in which a fluororesin is dispersed is provided on the surface of the pressure roller in order to convey the recording material P and the fixing film 202 and to prevent toner contamination.

  One end of the cored bar 209 is driven to rotate counterclockwise by being driven by a motor. The endless heat-resistant film 202 is rotationally driven in the clockwise direction while the inner surface thereof is in close contact with the surface of the heater 400 by the rotation of the pressure roller 208. When the endless heat-resistant film 202 is not driven, it is tension-free with respect to the substantially entire circumferential length portion of the remaining portion excluding the portion that is nipped and conveyed in the press-contact nip portion N between the heater 400 and the pressure roller 208. . When the pressure roller 208 is driven to rotate, a moving force is applied to the film 202 by a frictional force with the rotary pressure roller 208 at the nip portion N.

  Then, the film 202 is rotated in the clockwise direction while the inner surface of the film is slid on the surface of the heater 400 (= the surface of the protective layer 207) at substantially the same rotational speed as the pressure roller 208. At the time of driving the film, tension is applied to the film only at the nip portion N and at the upstream side of the nip portion N in the film moving direction and between the film inner surface guide portion and the nip portion in the vicinity of the nip portion. .

  Thus, in a state where the film drive and the heating element layer of the heater 400 are energized, the recording material P carrying the unfixed toner image is rotated and pressed with the rotating film 202 of the nip portion N as a fixing portion. It is introduced between the roller 208 and the image bearing surface upward. Then, the recording material P passes through the nip portion N together with the film 202, and the thermal energy of the heater 400 in contact with the inner surface of the film at the nip portion N is applied to the recording material P through the film 202. . Further, the toner image is thermally fixed by the applied pressure at the nip portion N. In order to detect the temperature of the heater 400, a thermistor 211 is provided.

  The thermistor 211 is pressed against the ceramic heater 400 with a predetermined pressure by a spring or the like, and detects the temperature of the ceramic heater 400. Further, when the means for controlling the power supplied to the ceramic heater 400 fails and the ceramic heater 202 reaches a thermal runaway, an excessive temperature rise prevention means 212 such as a fuse is provided on the ceramic heater 202 as a device for preventing an excessive temperature rise. It is arranged in. The excessive temperature rise prevention means 212 is, for example, a temperature fuse or a thermo switch. When the heater 400 reaches a thermal runaway due to a failure of the power supply control means and the excessive temperature rise prevention means 212 reaches a predetermined temperature or more, the excessive temperature rise prevention means 212 is opened and the energization to the heater 400 is cut off.

  FIG. 4 shows a heater circuit (drive circuit and control circuit) according to this embodiment. In the figure, reference numeral 301 denotes a commercial AC power supply connected to the image forming apparatus. The image forming apparatus supplies the input voltage from the AC power supply 301 to the heater 400 to cause the heater 400 to generate heat. Power supply to the heater 400 is performed by energization / interruption of the triac 302. Resistors 303 and 304 are bias resistors for the triac 302, and the phototriac coupler 305 is a device for ensuring a creepage distance between the primary and secondary.

  Then, the triac 302 is turned on by energizing the light emitting diode 305b of the phototriac coupler 305. The resistor 306 is a resistor for limiting the current of the phototriac coupler 305, and turns on / off the phototriac coupler 305 by the transistor 307. The transistor 307 operates according to a heater drive signal from the CPU 309 via the resistor 308.

  The temperature detected by the thermistor 211 is detected as a partial pressure between the resistor 310 and the thermistor 211 and is A / D input to the CPU 309 as a TH signal. As an internal process of the CPU 309, based on the detected temperature of the thermistor 211 and the set temperature of the heater 400, the power ratio to be supplied is calculated by PI control, for example. Further, it is converted into a control level of a phase angle (phase control) and a wave number (wave number control) corresponding to the supplied power ratio, and the CPU 309 outputs an ON signal to the transistor 307 according to the control conditions.

  The voltage detection unit 311 detects the voltage of the AC power supply 301, determines whether the range of the power supply voltage is a 100V system (for example, 100V to 127V) or a 200V system (for example, 200V to 240V), and outputs it to the CPU 309. Yes. The transistor 315 operates according to the ON signal from the CPU 309 via the resistor 316.

  When the voltage detection unit 311 detects 100 V, the transistor 315 is turned on, and a current is passed through the secondary coil of the relay 314, whereby the primary circuit of the relay 314 is turned on. The resistor 317 is a current limiting resistor, and the diode 318 is a back electromotive voltage prevention element. When the primary circuit of the relay 314 is in the ON state, the conductive path in which the heat generation patterns 401 and 402 are connected in series and the conductive path in which the heat generation pattern 403 is connected in parallel are connected in parallel. Since the two conductive paths are connected in parallel, the heater 400 has a low resistance value.

  When the voltage detection unit 311 detects 200 V, the transistor 315 is turned off and the primary circuit of the relay 314 is turned off. When the primary circuit of the relay 314 is in the OFF state, the current flows only through the conductive path in which the resistors 401 and 402 are connected in series, so that the resistance value of the heater 400 is high. In this manner, the resistance value of the heater 400 can be switched according to the voltage range of the power supply voltage by turning on and off the primary side circuit of the relay 314. In this embodiment, an example in which the relay is controlled via the CPU has been described. However, the transistor 315 may be directly controlled by the output of the voltage detection unit 311.

  The current detection unit 313 is used to detect the current flowing through the heater 400 via the current transformer 312. The current detection unit outputs a current detection result Iin to the CPU 309. For example, the current detection unit 313 can detect an overcurrent flowing through the heater 400 that is generated when the primary circuit of the relay 314 is turned on regardless of the power supply voltage of 200V. The three AC conductive paths connecting the circuit board having the heater driving circuit and the control circuit and the image heating apparatus 115 are connected to the image heating apparatus via connectors 320, 321, and 322 on the circuit board. .

  When the excessive temperature rise prevention means 212 detects the overheated state of the heater, the excessive temperature rise prevention means 212 interrupts the current between the common contact of the first conductive path and the second conductive path and the connector 322 on the circuit board, and from the ACH side All current paths supplied to the image heating device can be interrupted.

(heater)
FIG. 1A and FIG. 1B are schematic diagrams for explaining a heater 400 used in this embodiment. FIG. 1A shows a heat generation pattern, a conductive pattern, and electrodes formed on the substrate 205. FIG. 1A also shows a schematic diagram for explaining the connection between the heater drive circuit and the control circuit shown in FIG. The heater 400 has heat generation patterns 401, 402, and 403. Reference numeral 405 denotes a conductive pattern that connects the heat generation pattern and the electrode. In the first conductive path, the heat generation patterns 401 and 402 located at both ends in the short direction are connected in series, and AC power is supplied through the connector 320, the electrode 407, the electrode 408, and the connector 322. .

  The second conductive path is a single pattern of the heat generation pattern 403, and AC power is supplied through the connector 321, the electrode 409, the electrode 408, and the connector 322. In the heater 400, the first conductive path is energized only when the commercial power supply voltage is high (200V), and the relay 314 is turned on when the commercial power supply voltage is low (100V). By doing so, the first conductive path and the second conductive path are connected in parallel and energized.

  FIG. 1B shows a detailed view of the heat generation patterns 401, 402, and 403 of the heater 400. Each heat generation pattern is arranged symmetrically from the substrate center in the short direction of the heater 400. In the figure, the dimensions of a, b and c are 1.0 mm, b is 2.0 mm, and c is 1.5 mm. In addition, although all the heat generation patterns have the same width, the present invention is not particularly limited thereto.

(The resistance value and resistance temperature coefficient of the heating resistor)
1) Resistance value of the heating resistor Regarding the resistance value of the heating resistor, when the commercial power supply voltage is 200V and only the first conductive path is energized, and when the commercial power supply voltage is 100V, the first conductive path and the second conductive path In the case where the paths are connected in parallel and energized, it is preferable to have the same heat generation amount. When the integrated electric energy input within the fixing device startup time t is the same, the startup time t of the fixing device can be made uniform from room temperature to the fixing temperature (about 200 ° C.).

  Specifically, assuming that each heat generation pattern has the same resistance temperature coefficient (TCR), heat generation occurs when the resistance values of the heat generation patterns 401 and 402 are 30 Ω (the resistance at room temperature between the longitudinal ends when the electrodes are removed). The resistance value of the pattern 403 is set to 20Ω, which is about 2/3. If the resistance at room temperature between the longitudinal ends when the electrodes are removed is 20Ω, the same power is applied both when 100V and 200V are applied.

  More specifically, when the applied voltage is V and the resistance value is R, the power is given by V × V / R, so the power at the beginning of applying 200 V is 200 × 200 / (30 + 30) W. On the other hand, the power when 100V is initially applied is [100 × 100 / (30 + 30) + 100 × 100/20] W, which is the same value as the power when 200V is initially applied.

  Incidentally, if the heating value of the heating resistor on each end in the short side when 100V is applied is Q, the heating value of the heating resistor at the center in the short direction is 6Q, while the heating value of 200V is applied. The amount of heat generated by the heating resistor at each end in the short direction is 4Q. As a result, the total calorific value becomes the same value as 8Q when both 100V and 200V are applied.

2) Resistance temperature coefficient of the heating resistor When the heating resistor has a positive resistance temperature characteristic, the resistance value becomes larger than the time when heating is started after a predetermined time has elapsed after heating is started, and is proportional to the reciprocal of the resistance value. The calorific value becomes smaller. In the present embodiment, the temperature coefficient of resistance (TCR) of each heat generation pattern is different from 400 ppm / ° C. for the heat generation patterns 401 and 402 and 750 ppm / ° C. for the heat generation pattern 403.

  For this reason, the temperature rising at the start-up time t when 100 V is applied is lower than when 200 V is applied. When 200V is applied, only 400ppm / ° C heat generating resistor generates heat, whereas when 100V is applied, 400ppm / ° C and 750ppm / ° C heat generating resistors generate heat. The increase in the total resistance value is caused by the fact that the increase in 100V is greater. Therefore, in this embodiment, the resistance value of the heat generation pattern 403 is set to be smaller than the original 20Ω so that the temperature rising at the rising time t does not decrease when 100 V is applied.

  Specifically, the resistance of the heat generation patterns 401 and 402 remains 30Ω (when the electrodes are omitted, the room temperature resistance between the longitudinal ends), but the resistance of the heat generation pattern 403 is 19.4Ω (when the electrodes are excluded). , Resistance at room temperature between the longitudinal ends). As a result, the integrated electric power supplied to the fixing device by the start-up time t is equalized when applying 100V and 200V, respectively, and the start-up speed of the fixing device from room temperature to the fixing temperature (about 200 ° C.) is equal. I made it.

(Thermal stress of the heater substrate)
FIG. 5A shows the configuration of the heater 400, and FIGS. 5B to 5F show a heat temperature distribution simulation for explaining the heat generation distribution in the heater short direction and the stress generated in the heater base material, The stress simulation result is shown. This simulation is a measurement of the back surface temperature distribution of the substrate 205 of the heater 400 when the pressure roller 208 is not rotated. As the heater substrate, an alumina substrate having a linear expansion coefficient of 7.2 × 10 ⁻⁶ / ° C., a Young's modulus of 340 GPa, and a bending strength of 420 MPa is used. The conditions such as the sheet resistance value, input power, and thermal conductivity used in performing this simulation do not limit the present invention.

  FIG. 5B is a distribution of the substrate backside temperature of the heater 400 in the short-side direction of the substrate measured after a predetermined time has elapsed since supplying power to the heater 400 when the power supply voltage is 100 V and the relay 314 is ON. FIG. 5C shows a distribution in the short-side direction of the stress applied in the longitudinal direction of the heater 400, which is simulated from the temperature distribution. At this time, the positive stress is tensile stress, and the negative stress is compressive stress. Of these, the tensile stress contributes to the breakage of the substrate, and the breakage of the substrate occurs when it becomes larger than a predetermined value.

  FIG. 5D is a distribution of the substrate 400 substrate backside temperature in the short-side direction of the heater 400 measured after a predetermined time has elapsed since supplying power to the heater 400 when the power supply voltage is 200 V and the relay 314 is OFF. FIG. 5E shows a distribution in the short-side direction of the stress applied in the longitudinal direction of the heater 400, which is simulated from the temperature distribution. FIG. 5F and FIG. 5G are graphs for comparing the results of 100V and 200V. When 100 V is applied, heat generation of the heat generation pattern 403 at the center is suppressed, so that the temperature peak near the center is lower than when 200 V is applied.

  As a result, the tensile stress for the 200V system is as high as 0.3 MPa (MAX near the substrate center), whereas the tensile stress for the 100V system is as high as 0.75 MPa (MAX near the substrate edge). Therefore, it is important to reduce the tensile stress at the time of applying 100 V at which the central heating element generates heat in order to improve the breakage of the heater substrate.

(Heater comparison example)
1) Comparative Example 1
FIGS. 6A to 6C show comparative examples for explaining the effects of the present embodiment. The structure of the heater 500 as a comparative example, the heat generation distribution in the short side direction of the heater, and the heater base material, respectively. The simulation result for demonstrating the stress which generate | occur | produces is shown. In Comparative Example 1, the temperature coefficient of resistance (TCR) of the heat generation patterns 501, 502, and 503 are all 400 ppm / ° C. The resistance values of the heat generation patterns 501 and 502 are 30Ω (when the electrodes are removed, the resistance at room temperature between the longitudinal ends), whereas the resistance value of the heat generation pattern 503 is 2/3 of that of 19.4Ω. (When the electrode is removed, the resistance at room temperature between the longitudinal ends). In addition, each pattern width, pattern space | interval, and longitudinal dimension shape are the same as this embodiment.

2) Comparative Example 2
In Comparative Example 2, the TCRs of the heat generation patterns 501, 502, and 503 are all 750 ppm / ° C., and the resistance value of the heat generation pattern 503 is 2/3 of the resistance value of the heat generation patterns 501 and 502. The heater of Comparative Example 2 has the same resistance as that of Comparative Example 1 because the TCR is high and the resistance at high temperature increases and the accumulated power amount until the start-up time t decreases compared to the heater of this embodiment and Comparative Example 1. In relation, the start-up temperature of the fixing device is lowered. Therefore, by lowering the resistance values of the heat generation patterns 501, 502, and 503 with respect to Comparative Example 1, the fixing device is started up from the room temperature to the fixing temperature (about 200 ° C.) with respect to Embodiment 1 and Comparative Example 1. Same speed.

Therefore, the resistance values of the heat generation patterns 501, 502, and 503 are respectively 29.1Ω, 29.1Ω, and 19.4Ω (room temperature resistance between the longitudinal ends when the electrodes are removed). Each pattern width, pattern interval, and longitudinal dimension are the same as in this embodiment.
In both Comparative Example 1 and Comparative Example 2, similarly to the first embodiment, the heat generation distribution after a predetermined time was measured and the thermal stress was calculated.

  FIGS. 6B and 6C show the temperature distribution data and thermal stress distribution data of this embodiment, Comparative Example 1 and Comparative Example 2 when 100 V is applied. In FIG. 6B, compared to Example 1 of the present embodiment, Comparative Example 1 has a lower temperature at the center portion in the short direction of the heater. This is probably because it does not move to the center. Moreover, the reason why the comparative example 1 is colder at the end side in the short direction of the heater is that the heat generation at the end side does not move to the central part as in the first embodiment but is released to the outside of the substrate. This is probably because of this.

  As shown in FIG. 6C, in this embodiment, Comparative Example 1 and Comparative Example 2, the tensile stress at the edge of the substrate is the highest, which is 380 MPa, 640 MPa, and 541 MPa, respectively. From the results of the present embodiment and Comparative Example 1, in the present embodiment, the heat generation in the central portion in the short direction is suppressed, so that the heat generation distribution of the entire substrate becomes uniform. As a result, the tensile stress generated in the substrate is reduced. In addition, as in Comparative Example 2, even when the resistance temperature coefficient (TCR) of all the heating element patterns is high and the heaters start up slowly, the heat generation distribution is more uniform in this embodiment. It can be seen that the tensile stress generated in the substrate is reduced.

  Next, the result of actually creating a heater under the above conditions, applying the maximum power, and measuring the time until the substrate breaks is shown. The heater substrate used at this time is an alumina substrate having a longitudinal dimension of 270 mm, a lateral dimension of 10 mm, and a thickness of 1 mm. In addition, the excessive temperature rise prevention unit 212 used in the present embodiment is activated in about 5 seconds when thermal runaway occurs with power of 1300 W (voltage 140 V applied to a resistance value of 15Ω). We know that power will be cut off. When the circuit runs out of power at 1300 W, the time until the substrate breaks is 6 seconds in the present embodiment, 3.7 seconds in the comparative example 1, and 4.6 seconds in the comparative example 2. Only in the configuration, it has been confirmed that the overheating means 212 operates before the substrate breaks.

  According to the embodiment described above, it is possible to reduce the tensile stress generated on the substrate by having a uniform heat generation distribution on the substrate. As a result, a highly reliable heater and an image heating apparatus including the heater are provided. Can be provided.

<< Second Embodiment >>
In the first embodiment, one heat generation pattern is provided in the second conductive path. However, in the present embodiment, two heat generation patterns are electrically provided in parallel in the second conductive path. The description of the same configuration as that of the first embodiment is omitted. FIG. 7A shows a heat generation pattern, a conductive pattern, and an electrode formed on the substrate 205. The heater 700 has heat generation patterns 701, 702, 703, and 704. Reference numeral 705 denotes a conductive pattern.

  In the first conductive path, the heat generation patterns 701 and 702 are connected in series, and AC power is supplied through the connector 720, the electrode 707, the electrode 708, and the connector 722. In the second conductive path, heat generation patterns 703 and 704 provided symmetrically with respect to the central position in the short direction are connected in parallel, and AC power is supplied via the connector 721, electrode 709, electrode 708, and connector 722. Has been. In the heater 700, when the commercial power supply voltage is in the high range (200V), only the first conductive path is energized, and when the commercial power supply voltage is in the low range (100V), the relay 314 is turned on, The conductive path and the second conductive path are connected in parallel to conduct electricity.

  FIG. 7B is a detailed view of the heat generation patterns 701, 702, 703, and 704 of the heater 700. Each heat generation pattern is arranged symmetrically from the substrate center in the short direction of the heater 400. In the figure, the dimensions of a, b, c, and d are 1.0 mm, b is 2.0 mm, c is 0.5 mm, and d is 1.5 mm. In addition, although all the heat generation patterns have the same width, the present invention is not particularly limited thereto.

  When the commercial power supply voltage is 200 V and only the first conductive path is energized, and when the commercial power supply voltage is 100 V and the first conductive path and the second conductive path are connected in parallel and energized, the fixing device is started up. It is only necessary that the integrated power amount input within the time t is the same. Thereby, the start-up time t of the fixing device can be made uniform from the room temperature to the fixing temperature (about 200 ° C.). If each heat generation pattern has the same resistance temperature coefficient (TCR), the resistance value of the heat generation patterns 703 and 704 is about 40% of the resistance value of the heat generation patterns 701 and 702 (when the electrodes are excluded, the room temperature between both ends of the longitudinal direction) Resistance). In addition, each resistance value of the heat generation patterns 701 and 702 is 30Ω (when the electrodes are removed, the resistance at room temperature between the longitudinal ends).

  However, in the present embodiment, the resistance temperature coefficient (TCR) of each heat generation pattern is 400 ppm / ° C. for 701 and 702 and 750 ppm / ° C. for 703 and 704. For this reason, in the above “resistance relationship of the heat generation pattern when the TCR is the same”, the temperature rising at the start-up time t when 100 V is applied is lower than when 200 V is applied.

  The reason for this is as follows. First, when the fixing device is started up from room temperature, the maximum power is input in order to start it up as quickly as possible. Therefore, since 100 V supplied from the commercial power supply voltage is supplied at a constant voltage, it is greatly affected by the temperature characteristics of the resistance of the heat generation pattern. At 200V, only 400ppm / ° C exothermic resistors generate heat, whereas at 100V, 400ppm / ° C and 750ppm / ° C exothermic resistors generate heat, so the total resistance value with increasing temperature The rise of 100V is larger.

  Therefore, in order to speed up the rise of the heat generation patterns 703 and 704 to the fixing temperature, the resistance value is determined as follows. That is, the resistance of the heat generation patterns 701 and 702 is 30Ω (resistance at room temperature between the longitudinal ends when the electrodes are removed), and the resistance of the heat generation patterns 703 and 704 is 38.8Ω (between the longitudinal ends when the electrodes are removed). Room temperature resistance). As a result, the integrated electric energy supplied to the fixing device by the start-up time t is aligned at the time of applying 100 V and 200 V, respectively, and the starting speed of the fixing device from room temperature to the fixing temperature (about 200 ° C.) is equal. I made it.

  FIGS. 8A and 8B are simulation results for explaining the heat generation distribution in the heater short direction of the heater 700 and the stress generated in the heater base material. In this simulation, the temperature distribution on the back surface of the substrate 705 of the heater 700 is measured when the pressure roller 208 is not rotated. Further, the conditions such as the sheet resistance value, input power, and thermal conductivity used in performing this simulation do not limit the present invention.

  FIG. 8A shows the temperature distribution of the heater 400 after a certain period of time after supplying power to the heater 700 when the power supply voltage is 200 V and the relay 314 is OFF. FIG. 8B shows the result of simulating the stress distribution of the heater 700 in the temperature distribution. As can be seen from this result, the temperature distribution on the back surface of the substrate is more uniform in this embodiment than in the first embodiment. As a result, the maximum tensile stress at the substrate edge is It turns out that this embodiment has become small with 300 MPa with respect to 384 MPa of 1 embodiment.

  This is because the heating pattern is not only set to have a high temperature coefficient of resistance (TCR) of the heating element in the center, but also divided into two heating elements in the center in the short direction (paper passing direction). This is because the exothermic peak at the center portion is relatively reduced by shifting toward the upstream and downstream sides.

  Next, the result of actually creating a heater under the above conditions, applying the maximum power, and measuring the time until the substrate breaks is shown. The heater substrate used at this time is an alumina substrate having a longitudinal dimension of 270 mm, a lateral dimension of 10 mm, and a thickness of 1 mm. In addition, the excessive temperature rise prevention unit 212 used in the present embodiment is activated in about 5 seconds when thermal runaway occurs with power of 1300 W (voltage 140 V applied to a resistance value of 15Ω). We know that power will be cut off. When the circuit runs out of power at 1300 W, the time until the substrate breaks is 8.0 seconds in this embodiment, which is longer than the configuration of the first embodiment, and the temperature rises before the substrate breaks. It was confirmed that the means 212 was activated.

  With the configuration of the present embodiment described above, a highly reliable heater and an image heating apparatus provided with the heater can be provided that has a uniform heat generation distribution on the substrate and can reduce the tensile stress generated on the substrate. can do.

<< Third Embodiment >>
In the second embodiment, the two heat generation patterns provided in the first conductive path are electrically connected in series. However, in the present embodiment, they are electrically connected in parallel. The description of the same configuration as that of the first embodiment is omitted. FIGS. 9A and 9B are schematic drawings for explaining the heater 1000 used in the present embodiment. FIG. 9A shows a heat generation pattern and a conductive pattern formed on the substrate. The heater 1000 has heat generation patterns 1001, 1002, 1003, and 1004. Reference numeral 1005 denotes a conductive pattern. In the first conductive path, the heat generation patterns 1001 and 1002 are electrically connected in parallel, and AC power is supplied via the connector 320, the electrode 1007, the electrode 1008, and the connector 322.

  In the second conductive path, the heat generation patterns 1003 and 1004 are connected in parallel, and AC power is supplied through the connector 321, the electrode 1009, the electrode 1008, and the connector 322. In the heater 1000, when the commercial power supply voltage is in the high range (200V), only the first conductive path is energized, and when the commercial power supply voltage is in the low range (100V), the first conductive path and the second It is characterized by conducting electricity by connecting conductive paths in parallel.

  FIG. 9B shows a detailed view of the heat generation patterns 1001, 1002, 1003, and 1004 of the heater 1000. Each heat generation pattern is arranged symmetrically from the substrate center in the short direction of the heater 400. In the figure, the dimensions of a, b, c, and d are 1.0 mm, b is 2.0 mm, c is 0.5 mm, and d is 1.5 mm. In addition, although all the heat generation patterns have the same width, the present invention is not particularly limited thereto.

  When the commercial power supply voltage is 200V and only the first conductive path is energized, and when the commercial power supply voltage is 100V and the first conductive path and the second conductive path are connected in parallel and energized, the fixing temperature ( It is preferable to align the start-up time t of the fixing device up to about 200 ° C.). For this purpose, it is only necessary that the integrated electric power input within the start-up time t of the fixing device is the same. If each heat generation pattern has the same resistance temperature coefficient (TCR), the resistance value of the heat generation patterns 1003 and 1004 needs to be about 1/3 of 40Ω with respect to the resistance value 120Ω of each of the heat generation patterns 1001 and 1002. There is.

  However, in the present embodiment, the resistance temperature coefficient (TCR) of each heat generation pattern is 400 ppm / ° C. for 1001 and 1002, and 750 ppm / ° C. for 1003 and 1004. For this reason, in the above “resistance relationship of the heat generation pattern when the TCR is the same”, the temperature rising at the start-up time t when 100 V is applied is lower than when 200 V is applied.

  The reason for this is as follows. First, when the fixing device is started up from room temperature, the maximum power is input in order to start it up as quickly as possible. Therefore, since 100 V supplied from the commercial power supply voltage is supplied at a constant voltage, it is greatly affected by the temperature characteristics of the resistance of the heat generation pattern. At 200V, only 400ppm / ° C exothermic resistors generate heat, whereas at 100V, 400ppm / ° C and 750ppm / ° C exothermic resistors generate heat, so the total resistance value with increasing temperature The rise of 100V is larger.

  Therefore, in order to speed up the rise of the heat generation patterns 1003 and 1004 to the fixing temperature, the resistance value is set as follows. That is, the resistance of the heat generation patterns 1001 and 1002 is 120Ω (resistance at room temperature between the longitudinal ends when the electrodes are removed), and the resistance of the heat generation patterns 1003 and 1004 is 38.8Ω (excluding the electrodes, both longitudinal ends). Room temperature resistance). As a result, the integrated electric power supplied to the fixing device by the start-up time t is equalized when applying 100V and 200V, respectively, and the start-up speed of the fixing device from room temperature to the fixing temperature (about 200 ° C.) is equal. I made it.

  With respect to the heat generation distribution in the heater short direction of the heater 1000 and the stress generated in the heater base material, the same results as in the second embodiment shown in FIG. 8 are obtained. Also, the result of measuring the time until the substrate breaks was 8.0 seconds as in the second embodiment. Therefore, it has been confirmed that the configuration of the present embodiment takes a longer time to break the substrate than the configuration of the first embodiment.

  As described above, according to the present embodiment described above, a highly reliable heater and an image heating apparatus including the heater can be provided that has a uniform heat generation distribution on the substrate and can reduce the tensile stress generated in the substrate. be able to.

(Modification)
As described above, the technical matters described in the embodiments can be appropriately combined within the scope of the present invention.
For example, in the third embodiment, two heating resistors are used for the second conductive path. However, it is possible to use one heating resistor as described in the first embodiment. is there.

115..Image heating device, 314..Relay, 400..Heater, 401..First heating pattern, 402..Second heating pattern, 403..Third heating pattern, 407 to 409..Electrode

Claims (8)

A substrate comprising a longitudinal direction and a transverse direction intersecting the longitudinal direction;
A heating resistor provided on the substrate, having a positive resistance temperature characteristic, and generating heat by energization through an electrode provided at an end in the longitudinal direction;
A heater having
The heating resistor is provided in a first conductive path in the substrate and a second conductive path electrically connected in parallel with the first conductive path,
The first conductive path is commonly used when a first power supply voltage is applied and when a second power supply voltage lower than the first power supply voltage is applied, and the first conductive path is used. In the path, the heating resistor is positioned at both ends of the substrate in the short direction along the longitudinal direction,
The second conductive path is used when the second power supply voltage is applied, and in the second conductive path, the heating resistor is disposed along the longitudinal direction in the first conductive path. Located in the middle of the short direction sandwiched between
A heater characterized in that a resistance temperature coefficient of the heating resistor of the second conductive path is larger than a resistance temperature coefficient of the heating resistor of the first conductive path.   2. The heater according to claim 1, wherein, with respect to the first conductive path, the heating resistors positioned on both ends of the substrate in the short direction are electrically provided in series.   2. The heater according to claim 1, wherein, with respect to the first conductive path, the heating resistors located on both ends in the short direction of the substrate are electrically provided in parallel.   The heater according to any one of claims 1 to 3, wherein the heating resistor is provided symmetrically with respect to a center position of the substrate in the short direction with respect to the first conductive path.   The heater according to any one of claims 1 to 4, wherein the heating resistor is provided at a central position in the lateral direction of the substrate with respect to the second conductive path.   5. The heater according to claim 1, wherein the heating resistor is provided symmetrically with respect to a center position of the substrate in the short direction with respect to the second conductive path. A heating rotation member that is rotatable and capable of heating in a direction intersecting the rotation direction;
A heater provided on the inner peripheral side of the heating rotation member;
A pressure member that forms a nip portion through the heating rotation member that slides and rotates on the heater;
An image heating apparatus that heats the image by sandwiching and conveying a recording material carrying an image in the nip portion,
The image heating apparatus according to claim 1, wherein the heater is the heater according to claim 1, and a direction intersecting the rotation direction is the longitudinal direction.   The image heating apparatus according to claim 7, further comprising an excessive temperature rise prevention unit that is activated by an excessive temperature rise of the heater.