Image heating device and heater used in the image heating device

Abstract

In an image heating device having multiple heating blocks that can be independently controlled in the longitudinal direction of the heater, it is possible to detect the temperature of multiple heating blocks while suppressing the increase in the size of the heater. [Solution] The heater is provided with a first temperature sensing element corresponding to a first heat-generating block, a second temperature sensing element corresponding to a second heat-generating block, a first conductor electrically connected to the first temperature sensing element, a second conductor electrically connected to the second temperature sensing element, and a common conductor electrically connected to the first and second temperature sensing elements.

Description

Technical Field

[0001] The present invention relates to an image heating apparatus such as a fixing device mounted on an electrophotographic recording-type image forming apparatus such as a copying machine or a printer, or a gloss imparting apparatus that improves the glossiness of a toner image by reheating a fixed toner image on a recording material. The present invention also relates to a heater used in the image heating apparatus.

Background Art

[0002] As an image heating apparatus, there is known an apparatus including a cylindrical film, a heater in contact with the inner surface of the film, and a roller that forms a nip portion together with the heater via the film. When small-sized paper is continuously printed by an image forming apparatus equipped with this image heating apparatus, a phenomenon occurs in which the temperature of a region where paper does not pass in the longitudinal direction of the nip portion gradually rises (temperature rise in non-sheet-passing portions). If the temperature of the non-sheet-passing portion becomes excessively high, it will damage various parts in the apparatus, and when printing on large-sized paper in a state where temperature rise in the non-sheet-passing portion has occurred, high-temperature offset of toner to the film may occur in the region corresponding to the non-sheet-passing portion for the small-sized paper.

[0003] As one method for suppressing this temperature rise in non-sheet-passing portions, an apparatus has been proposed in which a heating resistor on the heater is divided into a plurality of groups (heating blocks) in the longitudinal direction of the heater, and the heat generation distribution of the heater is switched according to the size of the recording material (Patent Document 1).

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] Incidentally, considering the possibility of equipment failure, it is preferable to have a configuration that monitors the temperature of each heat-generating block. This is because if one of the multiple heat-generating blocks becomes uncontrollable and overheats, the power supply can be quickly stopped if the temperature of each heat-generating block is monitored.

[0006] However, increasing the number of heat-generating blocks also increases the number of temperature-sensing elements needed to monitor the temperature. Placing numerous temperature-sensing elements within the heater's substrate area would result in a larger heater. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the present invention provides a heater for use in an image heating device, the heater comprising a substrate, a first heating block formed on the substrate and generating heat when power is supplied, and a second heating block formed in the longitudinal direction of the substrate at a position different from the position where the first heating block is formed and controlled independently of the first heating block, wherein the heater further comprises a first temperature sensing element provided at a position corresponding to the first heating block, a second temperature sensing element provided at a position corresponding to the second heating block, a first conductor electrically connected to the first temperature sensing element, a second conductor electrically connected to the second temperature sensing element, and a common conductor electrically connected to the first and second temperature sensing elements. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress the need to increase the size of the heater. [Brief explanation of the drawing]

[0009] [Figure 1] Cross-sectional view of an image forming apparatus. [Figure 2] Cross-sectional view of the image heating device. [Figure 3] Heater configuration diagram of Example 1. [Figure 4] Heater control circuit diagram of Example 1. [Figure 5]Heater control flowchart for Example 1. [Figure 6] Heater configuration diagram for Example 2. [Figure 7] Heater control circuit diagram for Example 2. [Figure 8] Heater control flowchart for Example 2. [Figure 9] A diagram showing a modified version of the heater. [Figure 10] A diagram showing a modified version of the heater. [Figure 11] A diagram showing the power supply control pattern for the heater. [Modes for carrying out the invention]

[0010] (Example 1) Figure 1 is a cross-sectional view of a laser printer (image forming apparatus) 100 using electrophotographic recording technology. When a print signal is generated, the scanner unit 21 emits a laser beam modulated according to the image information and scans the photoreceptor 19, which has been charged to a predetermined polarity by the charging roller 16. This forms an electrostatic latent image on the photoreceptor 19. Toner is supplied from the developer unit 17 to this electrostatic latent image, and a toner image corresponding to the image information is formed on the photoreceptor 19. Meanwhile, the recording material (recording paper) P loaded in the paper feed cassette 11 is fed one sheet at a time by the pickup roller 12 and transported toward the registration roller 14 by the roller 13. Furthermore, the recording material P is transported from the registration roller 14 to the transfer position in time with the timing when the toner image on the photoreceptor 19 reaches the transfer position formed by the photoreceptor 19 and the transfer roller 20. As the recording material P passes through the transfer position, the toner image on the photoreceptor 19 is transferred to the recording material P. After that, the recording material P is heated by the image heating device (fixing device) 200 and the toner image is heat-fixed to the recording material P. The recording material P, which carries the fixed toner image, is discharged into a tray at the top of the laser printer 100 by rollers 26 and 27. 18 is a cleaner for cleaning the photoreceptor 19. 30 is a motor that drives the image heating device 200, etc. Power is supplied to the image heating device 200 from a control circuit 400 connected to a commercial AC power supply 401. The photoreceptor 19, charging roller 16, scanner unit 21, developer unit 17, and transfer roller 20 described above constitute the image forming unit that forms the unfixed image on the recording material P. 15 indicates a cartridge as a replacement unit. 22 is a light source, 23 is a polygon mirror, and 24 is a reflective mirror.

[0011] The laser printer 100 in this embodiment supports multiple recording material sizes. The paper feed cassette 11 can accommodate Letter paper (approximately 216mm x 279mm) and Legal paper (approximately 216mm x 356mm). Furthermore, it can accommodate A4 paper (210mm x 297mm), Executive paper (approximately 184mm x 267mm), JIS B5 paper (182mm x 257mm), and A5 paper (148mm x 210mm).

[0012] The printer in this example is basically a laser printer that feeds paper vertically (feeds the paper so that its long side is parallel to the feeding direction). The configuration proposed in this example can also be applied to printers that feed paper horizontally. The widest (largest width) standard recording materials supported by the device (according to the catalog) are Letter paper and Legal paper, both with a width of approximately 216 mm. Recording materials P with a paper width smaller than the maximum size supported by the device are defined as small-size paper in this embodiment.

[0013] Figure 2 is a cross-sectional view of the image heating device 200. The image heating device 200 includes a cylindrical film 202, a heater 300 that contacts the inner surface of the film 202, and a pressure roller (nip forming member) 208 that forms a fixing nip portion N together with the heater 300 via the film 202. The base layer of the film 202 is made of a heat-resistant resin such as polyimide, or a metal such as stainless steel. The film 202 may also be provided with an elastic layer such as heat-resistant rubber. The pressure roller 208 has a core metal 209 made of a material such as iron or aluminum, and an elastic layer 210 made of a material such as silicone rubber. The heater 300 is held by a holding member 201 made of a heat-resistant resin such as liquid crystal polymer. The holding member 201 also has a guide function that guides the rotation of the film 202. The pressure roller 208 receives power from the motor 30 and rotates in the direction of the arrow. As the pressure roller 208 rotates, the film 202 follows and rotates. The recording material P, which carries the unfixed toner image, is heated and fixed while being held and transported in the fixing nip section N. Thus, the apparatus 200 has a cylindrical film 202 and a heater 300 that contacts the inner surface of the film 202, and heats the image formed on the recording material with the heat from the heater 300 via the film 202.

[0014] The heater 300 includes a ceramic substrate 305, and a heating resistor (heating element) provided on the substrate 305 that generates heat when supplied with electric power (see FIG. 3). A glass surface protective layer 308 is provided on the surface of the substrate 305 on the fixing nip N side (first surface) to ensure slidability of the film 202. A glass surface protective layer 307 is provided on the surface of the substrate 305 opposite to the fixing nip N side (second surface) to insulate the heating resistor. An electrode (E4 is shown as a representative example herein) is exposed on the second surface, and the heating resistor is electrically connected to the AC power supply 401 when a power feeding electrical contact (C4 is shown as a representative example herein) contacts the electrode. A detailed description of the heater 300 will be given later.

[0015] Reference numeral 202 denotes a protective element 212 such as a thermostat or a thermal fuse that is activated by abnormal heat generation of the heater 300 to cut off power supplied to the heater 300. The protective element 212 is disposed in contact with the heater 300, or disposed with a slight gap relative to the heater 300. Reference numeral 204 denotes a metal stay for applying a spring pressure (not shown) to the holding member 201, and also serves to reinforce the holding member 201 and the heater 300.

[0016] FIG. 3(A) and FIG. 3(B) are configuration diagrams of the heater 300 according to Embodiment 1. FIG. 3(A) is a cross-sectional view of the heater 300 near the conveyance reference position X of the recording material P shown in FIG. 3(B). FIG. 3(B) is a plan view of each layer of the heater 300. FIG. 3(C) is a plan view of a holding member that holds the heater 300.

[0017] The printer of this example is a center-reference printer that conveys recording material with the center in the width direction of the recording material (direction perpendicular to the conveyance direction) aligned with the conveyance reference position X.

[0018] Next, the configuration of the heater 300 will be described in detail. On the back layer 1 of the heater 300, which is the heater surface opposite to the heater surface that contacts the film 202, a plurality of heating blocks, each consisting of a first conductor 301, a second conductor 303, and a heating resistor (heating element) 302, are provided in the longitudinal direction of the heater 300. The heater 300 in this embodiment has a total of seven heating blocks HB1 to HB7. If one of the seven heating blocks is designated as the first heating block and the other heating block as the second heating block, the heater 300 has the following configuration. That is, the heater 300 has a substrate and a first heating block formed on the substrate that generates heat when power is supplied. Furthermore, it has a second heating block formed at a different position in the longitudinal direction of the substrate than where the first heating block is formed, and which is controlled independently of the first heating block. The independent control of the heating blocks will be described later.

[0019] Each heating block includes a first conductor 301 provided along the longitudinal direction of the substrate, and a second conductor 303 provided along the longitudinal direction of the substrate at a different position from the first conductor 301 in the short direction of the substrate. Furthermore, it includes a heating resistor 302 provided between the first conductor 301 and the second conductor 303, which generates heat due to the power supplied through the first conductor 301 and the second conductor 303.

[0020] Each heating block's heating resistor 302 is divided into heating resistors 302a and 302b, which are formed symmetrically with respect to the center of the substrate with respect to the short-side direction of the heater 300. The first conductor 301 is divided into conductor 301a, which is connected to heating resistor 302a, and conductor 301b, which is connected to heating resistor 302b. Since heating resistors 302a and 302b are formed symmetrically with respect to the center of the substrate, the substrate is less likely to crack even when the heater generates heat and thermal stress is generated in the substrate.

[0021] Since the heater 300 has seven heat-generating blocks HB1 to HB7, the heat-generating resistor 302a is divided into seven parts, 302a-1 to 302a-7. Similarly, the heat-generating resistor 302b is divided into seven parts, 302b-1 to 302b-7. Furthermore, the second conductor 303 is also divided into seven parts, 303-1 to 303-7. Note that the heat-generating resistors 302a-1 to 302a-7 are located on the upstream side of the transport direction of the recording material P within the substrate 305, and the heat-generating resistors 302b-1 to 302b-7 are located on the downstream side of the transport direction of the recording material P within the substrate 305.

[0022] The back surface layer 2 of the heater 300 is provided with an insulating (glass in this embodiment) surface protection layer 307 that covers the heating resistor 302, the first conductor 301, and the second conductor 303. However, the surface protection layer 307 does not cover the electrode portions E1 to E7, E8-1, and E8-2 that the power supply electrical contacts C1 to C7, C8-1, and C8-2 contact. Electrodes E1 to E7 are electrodes for supplying power to the heating blocks HB1 to HB7 via the second conductors 303-1 to 303-7, respectively. Electrodes E8-1 and E8-2 are electrodes for supplying power to the heating blocks HB1 to HB7 via the first conductors 301a and 301b.

[0023] Incidentally, since the resistance of the conductor is not zero, it affects the heat distribution in the longitudinal direction of the heater 300. Therefore, electrodes E8-1 and E8-2 are provided separately at both ends in the longitudinal direction of the heater 300 so that the heat distribution does not become uneven even when affected by the electrical resistance of the first conductors 301a, 301b and the second conductors 303-1 to 303-7.

[0024] As shown in Figure 2, the space between the stay 204 and the retaining member 201 is provided with a safety element 212, electrical contacts C1-C7, C8-1, and C8-2. As shown in Figure 3(C), the retaining member 201 is provided with holes HC1-HC7, HC8-1, and HC8-2 through which electrical contacts C1-C7, C8-1, and C8-2, which are connected to electrodes E1-E7, E8-1, and E8-2, pass. The retaining member 201 is also provided with a hole H212 through which the heat-sensitive part of the protective element 212 passes. The electrical contacts C1-C7, C8-1, and C8-2 are electrically connected to the corresponding electrodes by methods such as spring biasing or welding. The protective element 212 is also biased by a spring, and its heat-sensitive part is in contact with the surface protective layer 307. Each electrical contact is connected to the control circuit 400 of the heater 300, which will be described later, via a conductive material such as a cable or a thin metal plate provided in the space between the stay 204 and the retaining member 201.

[0025] By providing electrodes on the back surface of the heater 300, it is not necessary to provide areas on the substrate 305 for wiring that electrically connects to each of the second conductors 303-1 to 303-7, thus reducing the width of the substrate 305 in the shorter direction. Therefore, the size increase of the heater can be suppressed. As shown in Figure 3(B), electrodes E2 to E6 are provided within the area where the heating resistor is provided in the longitudinal direction of the substrate.

[0026] As will be described later, the heater 300 in this example can form various heat distributions by independently controlling multiple heat-generating blocks. For example, a heat distribution can be set according to the size of the recording material. Furthermore, the heat-generating resistor 302 is made of a material having PTC (Positive Temperature Coefficient). By using a material with PTC, it is possible to suppress the temperature rise of the non-paper-feeding area even when the edge of the recording material and the boundary of the heat-generating block do not coincide.

[0027] Multiple thermistors (temperature sensing elements) T1-1 to T1-4 and T2-4 to T2-7 are formed on the sliding surface layer 1 of the heater 300 on the sliding surface side (the side that contacts the film) for detecting the temperature of each heat-generating block HB1 to HB7. The material of the thermistor can be any material with a large positive or negative TCR (Temperature Coefficient of Resistance). In this example, the thermistors were constructed by thinly printing a material with an NTC (Negative Temperature Coefficient) onto a substrate. Since one or more thermistors are provided corresponding to each of the heat-generating blocks HB1 to HB7, the temperature of all heat-generating blocks can be detected.

[0028] If one of the thermistors T1-1 to T1-4 is designated as the first temperature sensing element, and the other temperature sensing element among the thermistors T1-1 to T1-4 is designated as the second temperature sensing element, then the heater 300 has the following configuration. That is, the heater 300 has a first temperature sensing element provided at a position corresponding to the first heat-generating block, and a second temperature sensing element provided at a position corresponding to the second heat-generating block.

[0029] Thermistors T1-1 to T1-4 are each electrically connected to conductive patterns ET1-1 to ET1-4 provided on the substrate 305. If we define the conductive pattern connected to the first temperature sensing element as the first conductive pattern and the conductive pattern connected to the second temperature sensing element as the second conductive pattern, then the heater 300 has the following configuration: The heater 300 has a first conductive pattern electrically connected to the first temperature sensing element and a second conductive pattern electrically connected to the second temperature sensing element. Furthermore, the heater 300 has a common conductive pattern EG1 electrically connected to both the first and second temperature sensing elements. Hereinafter, the set of thermistors T1-1 to T1-4, conductive patterns ET1-1 to ET1-4, and common conductive pattern EG1 will be referred to as thermistor group TG1.

[0030] The heater 300 is also provided with a thermistor group TG2, which consists of thermistors T2-4 to T2-7, conductive patterns ET2-4 to ET2-7, and a common conductive pattern EG2. Thermistor groups TG1 and TG2 are formed on the substrate surface opposite to the substrate surface on which the first and second heat-generating blocks are formed on the substrate 305.

[0031] In this example, at least one corresponding thermistor is placed for each of the heat-generating blocks HB1 to HB7. However, the reliability of the device can be improved by placing only one corresponding thermistor for at least two heat-generating blocks. Nevertheless, it is preferable to place at least one corresponding thermistor for all heat-generating blocks, as in this example.

[0032] As in this example, by using common conductive patterns EG1 and EG2 to combine the first and second temperature sensing elements into a single pair, the following effects can be obtained. Specifically, compared to the case where two conductive patterns are connected to each thermistor T1-1 to T1-4 without using a common conductive pattern, the cost of the conductive patterns can be reduced, and the increase in heater size can be suppressed.

[0033] On the side of the fixing nip portion N of the substrate 305 (sliding surface layer 2), an insulating (in this example, made of glass) surface protection layer 308 is formed by coating to ensure the sliding properties of the film 202. The surface protection layer 308 covers the thermistors T1-1 to T1-4, T2-4 to T2-7, conductive patterns ET1-1 to ET1-4, ET2-4 to ET2-7, and common conductive patterns EG1 and EG2. However, in order to ensure connection with electrical contacts, as shown in Figure 3(B), parts of the conductive patterns ET1-1 to ET1-4, ET2-4 to ET2-7, and parts of the common conductive patterns EG1 and EG2 are exposed at both ends of the heater 300.

[0034] Figure 4 is a circuit diagram of the control circuit 400 for the heater 300. 401 is a commercial AC power supply connected to the laser printer 100. Power control of the heater 300 is performed by energizing / cutting off triacs 411-414. Triacs 411-414 operate according to FUSER1-FUSER4 signals from the CPU 420, respectively. Note that the drive circuits for triacs 411-414 are omitted in Figure 4.

[0035] As can be seen from Figures 3 and 4, the seven heating blocks HB1 to HB7 are divided into four groups (Group 1: HB4, Group 2: HB3 and HB5, Group 3: HB2 and HB6, Group 4: HB1 and HB7). The control circuit 400 of the heater 300 has a circuit configuration that allows independent control of the four groups. Triac 411 can control Group 1, triac 412 can control Group 2, triac 413 can control Group 3, and triac 414 can control Group 4.

[0036] The zero-cross detection unit 421 is a circuit that detects the zero-crossing of the AC power supply 401 and outputs a ZEROX signal to the CPU 420. The ZEROX signal is used as a reference signal for phase control of the triacs 411 to 414, etc.

[0037] Next, we will explain the method for detecting the temperature of heater 300. First, we will explain thermistor group TG1. The CPU 420 receives signals (Th1-1 to Th1-4) which are obtained by dividing the voltage Vcc using the resistance values ​​of thermistors (T1-1 to T1-4) and resistors (451 to 454). For example, signal Th1-1 is a signal obtained by dividing the voltage Vcc using the resistance value of thermistor T1-1 and resistor 451. Since thermistor T1-1 has a resistance value that corresponds to the temperature, when the temperature of the heat-generating block HB1 changes, the level of signal Th1-1 input to the CPU also changes. The CPU 420 converts the input signal Th1-1 into a temperature corresponding to its level. The processing of signals Th1-2 to Th1-4, which correspond to the other thermistors T1-2 to T1-4 in thermistor group TG1, is similar, so we will omit the explanation.

[0038] Next, we will explain thermistor group TG2. Similar to TG1, the CPU420 receives a signal (Th2-4~Th2-7) obtained by dividing the voltage Vcc using the resistance values ​​of the thermistors (T2-4~T2-7) and resistors (464~467). The method of conversion to temperature by the CPU420 is the same as for thermistor group TG1, so we will omit the explanation.

[0039] Next, the power control (heater temperature control) to the heater 300 will be explained. During the fixing process, each of the heating blocks HB1 to HB7 is controlled so that the detected temperature of the thermistors (T1-1 to T1-4) in the thermistor group TG1 is maintained at the set temperature (control target temperature). Specifically, the power supplied to group 1 (heating block HB4) is controlled by controlling the drive of triac 411 so that the detected temperature of thermistor T1-4 is maintained at the set temperature. The power supplied to group 2 (heating blocks HB3 and HB5) is controlled by controlling the drive of triac 412 so that the detected temperature of thermistor T1-3 is maintained at the set temperature. The power supplied to group 3 (heating blocks HB2 and HB6) is controlled by controlling the drive of triac 413 so that the detected temperature of thermistor T1-2 is maintained at the set temperature. The power supplied to group 4 (heat-generating blocks HB1 and HB7) is controlled by controlling the drive of the triac 414 so that the temperature detected by thermistor T1-1 maintains the set temperature. In this way, each thermistor in thermistor group TG1 is used to perform control to keep each heat-generating block at a constant temperature.

[0040] The CPU 420 calculates the power supply based on the set temperature (target control temperature) of each heat-generating block and the detected temperature of each thermistor (T1-1 to T1-4) within the thermistor group TG1, for example, by PI control. Furthermore, the calculated power supply is converted into control timings such as the corresponding phase angle (phase control) and wavenumber (wavenumber control), and triacs 411 to 414 are controlled at these control timings. Note that the set temperature of each group in this example is 250°C when fixing the largest size of plain paper. When fixing smaller size plain paper, the set temperature of group 1 is set to 250°C, and the set temperatures of the other groups are set lower than 250°C. The set temperature of each group should be set appropriately according to information such as the size, type, and surface properties of the recording material.

[0041] Relays 430 and 440 are installed as means to cut off power to the heater 300 if the heater 300 overheats due to factors such as equipment failure. Next, the circuit operation of relays 430 and 440 will be explained.

[0042] When the RLON signal output from CPU420 goes high, transistor 433 turns ON, energizing the secondary coil of relay 430 from the DC power supply (voltage Vcc), and the primary contact of relay 430 turns ON. When the RLON signal goes low, transistor 433 turns OFF, interrupting the current flowing from the power supply (voltage Vcc) to the secondary coil of relay 430, and the primary contact of relay 430 turns OFF. Similarly, when the RLON signal goes high, transistor 443 turns ON, energizing the secondary coil of relay 440 from the power supply (voltage Vcc), and the primary contact of relay 440 turns ON. When the RLON signal goes low, transistor 443 turns OFF, interrupting the current flowing from the power supply (voltage Vcc) to the secondary coil of relay 440, and the primary contact of relay 440 turns OFF.

[0043] Next, the operation of the protection circuit (hardware circuit that does not go through the CPU 420) using relays 430 and 440 will be explained. If the level of any one of signals Th1-1 to Th1-4 exceeds a predetermined value set inside the comparison unit 431, the comparison unit 431 operates the latch unit 432, and the latch unit 432 latches the RLOFF1 signal in a Low state. When the RLOFF1 signal is in a Low state, even if the CPU 420 sets the RLON signal to a High state, the transistor 433 remains in the OFF state, so the relay 430 can remain in the OFF state (safe state). Note that in the non-latched state, the latch unit 432 outputs the RLOFF1 signal in an open state.

[0044] Similarly, if the level of any one of the signals Th2-4 to Th2-7 exceeds a predetermined value set inside the comparison unit 441, the comparison unit 441 activates the latch unit 442, and the latch unit 442 latches the RLOFF2 signal in a Low state. When the RLOFF2 signal is in a Low state, even if the CPU 420 sets the RLON signal to a High state, the transistor 443 remains in the OFF state, so the relay 440 can remain in the OFF state (safe state). In the non-latched state, the latch unit 442 outputs the RLOFF signal in an open state. In this example, the predetermined value set inside the comparison unit 431 and the predetermined value set inside the comparison unit 441 are both values ​​corresponding to 300°C.

[0045] Next, the protection operation of the circuit using the two thermistor groups TG1 and TG2 will be described. As shown in Figures 3 and 4, each of the four groups (groups 1 to 4) described above is assigned one thermistor from thermistor group TG1 and one thermistor from thermistor group TG2. Furthermore, each of the heat-generating blocks HB1 to HB7 is assigned at least one thermistor. Specifically, in group 1 (HB4), thermistors T1-4 from thermistor group TG1 and T2-4 from thermistor group TG2 are assigned. In group 2 (HB3 and HB5), thermistors T1-3 from thermistor group TG1 and T2-5 from thermistor group TG2 are assigned. In group 3 (HB2 and HB6), thermistors T1-2 from thermistor group TG1 and T2-6 from thermistor group TG2 are assigned. In group 4 (HB1 and HB7), thermistor T1-1 from thermistor group TG1 and thermistor T2-7 from thermistor group TG2 are arranged in correspondence. Furthermore, at least one of the eight thermistors is arranged corresponding to each of the heat-generating blocks HB1 to HB7. This thermistor layout improves the reliability of the circuit's protective operation in the event of equipment failure. This is explained below.

[0046] For example, consider a scenario where any of thermistors T1-1 to T1-4 in thermistor group TG1 fail. Even if the group containing the heat-generating block corresponding to the failed thermistor becomes uncontrollable due to the thermistor failure, the heat-generating block group containing the failed thermistor also contains a thermistor from thermistor group TG2 (any of T2-4 to T2-7). Therefore, the protection circuit will activate (stop power supply) via the thermistor in thermistor group TG2.

[0047] Next, we will explain the advantages of a configuration in which at least one of the eight thermistors is positioned in relation to each of the heat-generating blocks HB1 to HB7.

[0048] For example, suppose thermistor T2-5, which corresponds to group 2, is placed not in the position corresponding to heat block HB5, but in the position corresponding to heat block HB3, which is in the same group 2 as heat block HB5. In this case, thermistor T1-3 of thermistor group TG1 and thermistor T2-5 of thermistor group TG2 are placed in the position corresponding to heat block HB3, and there is no thermistor in the position corresponding to heat block HB5. Even in this configuration, the temperature of group 2 can be monitored. However, in this configuration, if there is a contact failure between electrode E3 and electrical contact C3, heat block HB3 may not generate heat, but heat block HB5, which is in the same group 2 as heat block HB3, may generate heat. Furthermore, even if heat block HB5 of group 2 generates abnormal heat, the two thermistors T1-3 and T2-5, which correspond to group 2, cannot monitor this, and the protection circuit will not activate.

[0049] In contrast, in this example, thermistors T1-3 of thermistor group TG1 are positioned at the location corresponding to heat-generating block HB3, and thermistor T2-5 of thermistor group TG2 is positioned at the location corresponding to heat-generating block HB5. Therefore, even if electrode E3 and electrical contact C3 experience poor contact and only heat-generating block HB5 of group 2 generates heat, the temperature can be monitored by thermistor T2-5 and the protection circuit can be activated. In this way, since at least one of the eight thermistors is positioned corresponding to each of the heat-generating blocks HB1 to HB7, the reliability of the device is improved.

[0050] Figure 5 is a flowchart illustrating the control sequence of the control circuit 400 by the CPU 420. When a print request occurs in S100, relays 430 and 440 are turned ON in S101.

[0051] In S102, the triac 414 is PI-controlled so that the temperature detected by thermistor T1-1 (signal Th1-1) reaches the target control temperature, thereby controlling the power supplied to the heat-generating blocks HB1 and HB7.

[0052] In S103, the triac 413 is PI-controlled so that the temperature detected by thermistor T1-2 (signal Th1-2) reaches the target control temperature, thereby controlling the power supplied to the heat-generating blocks HB2 and HB6.

[0053] In S104, the triac 412 is PI-controlled so that the temperature detected by thermistors T1-3 (signal Th1-3) reaches the target control temperature, thereby controlling the power supplied to the heat-generating blocks HB3 and HB5.

[0054] In S105, the triac 411 is PI-controlled to control the power supplied to the heat-generating block HB4 so that the temperature detected by thermistor T1-4 (signal Th1-4) reaches the target control temperature.

[0055] As described above, the target temperature for each heat-generating block is set according to the recording material size information. In this example, the device sets the target temperature for heat-generating block HB4, which includes the transport standard X, to the same temperature regardless of the recording material size, while the target temperatures for the other heat-generating blocks are changed according to the recording material size. The smaller the recording material size, the lower the target temperature for the heat-generating blocks other than heat-generating block HB4.

[0056] In S106, it is determined whether the heating of the non-paper-feeding section of the heater 300 is below a predetermined threshold temperature (allowable temperature) Tmax. In this example, Tmax is set to 280°C, which is higher than the control target temperature of 250°C for the heat-generating block HB4 and lower than the predetermined value of 300°C set in the comparison unit 431 and the comparison unit 441. Furthermore, the positional relationship between the thermistor in thermistor group TG1 and the reference X is different from that of thermistor group TG2. The thermistors in thermistor group TG2 are positioned further outward from the transport reference position X in the longitudinal direction of the heater 300 within each heat-generating block compared to the thermistors in thermistor group TG1. As shown in Figure 3(B), this relationship can be easily understood by comparing the distance from the reference X of thermistors T1-4 corresponding to heat-generating block HB4 and the distance from the reference X of thermistor T2-4 corresponding to heat-generating block HB4. This layout allows the thermistor in the thermistor group TG2 to detect any temperature increase in the non-paper-passing area within a single heating block.

[0057] If the temperatures of thermistors T2-4 to T2-7 are below the threshold temperature Tmax in S106, the process proceeds to S108, and the control steps S102 to S106 are repeated until the end of the print job is detected in S108.

[0058] If the temperatures of thermistors T2-4 to T2-7 exceed the threshold temperature Tmax in S106, the image formation process speed of the image forming apparatus 100 is reduced, and the fixing process is performed with the control target temperatures of thermistors T1-1 to T1-4 lowered in S107. Reducing the image formation process speed ensures fixing performance even at lower temperatures compared to the full speed, thus suppressing the temperature rise of the non-paper-feeding section.

[0059] The above process is repeated, and when the end of the print job is detected in S108, relays 430 and 440 are turned OFF in S109, and the image formation control sequence is terminated in S110.

[0060] (Example 2) Next, we will describe Example 2, in which the heater 300 and the heater control circuit 400 described in Example 1 are replaced with a heater 600 and a control circuit 700. The same symbols are used for components similar to those in Example 1, and their explanations will be omitted. The heater 600 in Example 2 differs from the heater 300 in the configuration of the sliding surface layer 1. The control circuit 700 is configured to allow independent control of all heating blocks HB1 to HB7.

[0061] Figure 6 shows the configuration diagram of heater 600 in Example 2. The configuration other than the sliding surface layer 1 is the same as that of heater 300, so its explanation is omitted.

[0062] The sliding surface layer 1 of the heater 600 is equipped with thermistors T3-1a to T3-4a, T3-1b to T3-3b, T4-4a to T4-7a, T4-5b to T4-7b, and T5, for detecting the temperature of each of the heat-generating blocks HB1 to HB7. Since each of the heat-generating blocks HB1 to HB7 is associated with two or more thermistors, the configuration ensures that the temperature of all heat-generating blocks can be detected even if one thermistor fails.

[0063] Thermistor group TG3 comprises seven thermistors T3-1a to T3-4a and T3-1b to T3-3b, conductive patterns ET3-1a to ET3-4a, ET3-3b, and ET3-12b, and a common conductive pattern EG3.

[0064] Similarly, thermistor group TG4 has seven thermistors T4-4a to T4-7a and thermistors T4-5b to T4-7b, conductive patterns ET4-4a to ET4-7a, ET4-5b, ET4-67b, and a common conductive pattern EG4.

[0065] First, let's explain thermistor group TG3. Thermistors T3-1b and T3-2b are thermistors for detecting the temperatures of heat-generating blocks HB1 and HB2, and are configured with the two thermistors connected in parallel between conductive pattern ET3-12b and common conductive pattern EG3. Even if the temperature of either heat-generating block HB1 or HB2 rises, the resistance value of either thermistor T3-1b or thermistor T3-2b will drop significantly. Therefore, temperature detection for both heat-generating blocks HB1 and HB2 can be performed with a single conductive pattern ET3-12b for detecting thermistor resistance. Consequently, the cost of forming the conductive pattern wiring can be reduced compared to connecting and wiring conductive patterns to each of thermistors T3-1b and T3-2b. In addition, the width of the substrate 305 in the short direction can be shortened. Similarly, thermistors T4-6b and T4-7b are also connected in parallel.

[0066] Common conductive patterns EG3 and EG4 are connected on the substrate 305 by conductive pattern EG34, and are used for disconnection detection as explained in Figure 7. Disconnection detection enhances safety in the event of a disconnection failure.

[0067] Each heat-generating block HB3 is equipped with two thermistors, T3-3a and T3-3b. The temperature can be detected by conductive patterns ET3-3a and ET3-3b for resistance detection, and a common conductive pattern EG3.

[0068] Within the range of the heat-generating block HB3, the thermistor T3-3b, located far from the transport reference position X, is a thermistor for detecting the end temperature, while the thermistor T3-3a, located close to the transport reference position X, is a thermistor for temperature control. If necessary, multiple thermistors may be provided in a single heat-generating block.

[0069] The explanation for thermistor group TG4 is the same as for thermistor group TG3, so the explanation is omitted.

[0070] Thermistor T5 is a standalone thermistor formed between the conductive patterns ET5 and EG5 used for resistance detection. If necessary, a standalone thermistor may be used in combination with a thermistor group.

[0071] Figure 7 shows the circuit diagram of the control circuit 700 of the heater 600 in Embodiment 2. Power control of the heater 600 is performed by energizing / cutting off triacs 711 to 717. Triacs 711 to 717 operate according to FUSER1 to FUSER7 signals from the CPU 420, respectively. The control circuit 700 of the heater 600 has a circuit configuration that allows for independent control of seven heat-generating blocks HB1 to HB7 by seven triacs 711 to 717.

[0072] Next, the method for detecting the temperature of heater 600 will be explained. The CPU 420 receives a signal obtained by dividing the voltage Vcc using the resistance values ​​of thermistors T3-1a~T3-4a, T3-1b, T3-2b of thermistor group TG3 and the resistance value of resistor 751~756 (Th3-1a~Th3-4a, Th3-3b, Th3-12b). Similarly, the CPU 420 receives a signal obtained by dividing the voltage Vcc using the resistance values ​​of thermistors T4-4a~T4-7a, T4-5b~T4-7b of thermistor group TG4 and the resistance value of resistor 771~776. This signal is indicated as Th4-4a~Th4-7a, Th4-5b, Th4-67b. Similarly, the CPU receives a signal obtained by dividing the voltage using the resistance value of thermistor T5 and the resistance value of resistor 761 (Th5). The CPU420 converts each input signal into a temperature corresponding to its level.

[0073] The CPU420 calculates the power supply based on the set temperature (target control temperature) of each heat-generating block and the temperature detected by each thermistor, for example, using PI control. Furthermore, it converts the calculated power supply into control timings such as the corresponding phase angle (phase control) and wavenumber (wavenumber control), and controls triacs 711-717 at these control timings.

[0074] Next, the operation of the protection circuit using relays 430 and 440 will be described. Based on the Th3-1a to Th3-4a signals of thermistor group TG3 and the Th4-5b and Th4-67b signals of thermistor group TG4, if any one of the detected temperatures exceeds a predetermined value set for each, the comparison unit 431 activates the latch unit 432.

[0075] Similarly, based on the Th4-4a to Th4-7a signals of thermistor group TG4 and the Th3-3b and Th3-12b signals of thermistor group TG3, if any one of the detected temperatures exceeds a predetermined value set for each, the comparison unit 441 activates the latch unit 442.

[0076] Next, we will explain the disconnection detection circuit 780. The disconnection detection circuit 780 is a circuit used to enhance safety in the event of a disconnection in the common conductive patterns EG3 and EG4.

[0077] The circuit operation of the disconnection detection circuit 780 is described below. When the connection between the common conductive patterns EG3 and EG4 is broken, resistors 781 and 782 pull up to the power supply voltage Vcc, causing the disconnection detection signal ThSafe to go high. Note that resistors 781 and 782 are placed as two resistors to account for short-circuit failures. When the disconnection detection signal ThSafe goes high, latch units 432 and 442 are activated.

[0078] Next, the effects of the wire break detection circuit 780 and the conductive pattern EG34 will be explained. First, we will describe the case where neither the conductive pattern EG34 nor the wire break detection circuit 780 is present, and the common conductive pattern EG3 and common conductive pattern EG4 are connected to GND, as in the configuration of Example 1. In this case, if the common conductive pattern EG3 is broken, all the thermistors in the thermistor group TG3 will stop working, and the protection circuit that stops the power supply to the heat-generating blocks HB1 to HB3 will not work. Similarly, if the common conductive pattern EG4 is broken, all the thermistors in the thermistor group TG4 will stop working, and the protection circuit that stops the power supply to the heat-generating blocks HB5 to HB7 will not work.

[0079] Next, we will describe the case where there is a conductive pattern EG34 connecting common conductive patterns EG3 and EG4, but there is no disconnection detection circuit 780, and the common conductive patterns EG3 and EG4 are connected to GND, just like in the configuration of Example 1. In this case, due to the effect of conductive pattern EG34, even if either common conductive pattern EG3 or EG4 is disconnected, it will be connected to GND via conductive pattern EG34. Therefore, temperature detection by thermistor groups TG3 and TG4 will be possible. However, if the connector (not shown) connecting the conductive patterns of thermistor group TG3 (ET3-1a to ET3-4a, and ET3-12b, ET3-3b, EG3) to the control circuit 700 is disconnected, all the thermistors of thermistor group TG3 will stop working. Therefore, the protection circuit that stops power supply to the heat-generating blocks HB1 to HB3 will not work. Similarly, if the connector connecting the conductive patterns of thermistor group TG4 (ET4-4a to ET4-7a, and ET4-67b, ET4-5b, EG4) to the control circuit 700 is disconnected, all the thermistors in thermistor group TG4 will cease to function. As a result, the protection circuit that stops power supply to the heat-generating blocks HB5 to HB7 will not work.

[0080] In contrast, the device in this example has a conductive pattern body EG34 and a disconnection detection circuit 780. This allows for the detection of both fault conditions: a disconnection of the common conductive patterns EG3 and EG4, and a disconnection of the connector connecting the thermistor groups TG3 and TG4 to the control circuit 700.

[0081] Figure 8 is a flowchart illustrating the control sequence of the control circuit 700 by the CPU 420. Configurations similar to those in Figure 5 are explained using the same symbols.

[0082] In S201, the triac 711 is PI-controlled to control the power supplied to the heat-generating block HB1 so that the temperature detected by the thermistor T3-1a (signal Th3-1a) reaches a predetermined target temperature.

[0083] In S202, the triac 712 is PI-controlled to control the power supplied to the heat-generating block HB2 so that the temperature detected by the thermistor T3-2a (signal Th3-2a) reaches a predetermined target temperature.

[0084] In S203, the triac 713 is PI-controlled to control the power supplied to the heat-generating block HB3 so that the temperature detected by the thermistor T3-3a (signal Th3-3a) reaches a predetermined target temperature.

[0085] In S204, the triac 714 is PI-controlled to control the power supplied to the heat-generating block HB4 so that the temperature detected by the thermistor T5 (signal Th5) reaches a predetermined target temperature.

[0086] In S205, the triac 715 is PI-controlled to control the power supplied to the heat-generating block HB5 so that the temperature detected by the thermistor T4-5a (signal Th4-5a) reaches a predetermined target temperature.

[0087] In S206, the triac 716 is PI-controlled to control the power supplied to the heat-generating block HB6 so that the temperature detected by the thermistor T4-6a (signal Th4-6a) reaches a predetermined target temperature.

[0088] In S207, the triac 717 is PI-controlled to control the power supplied to the heat-generating block HB7 so that the temperature detected by the thermistor T4-7a (signal Th4-7a) reaches a predetermined target temperature.

[0089] In S208, it is determined whether the temperature rise of the non-paper-feeding section of the heater 300 is below a predetermined threshold temperature (allowable temperature) Tmax.

[0090] In S208, if the temperatures of thermistors T3-4a, T4-4a, T3-3b, and T4-5b are below the threshold temperature Tmax, the process proceeds to S108, and the control steps S201 to S208 are repeated until the end of the print job is detected in S108.

[0091] (Example 3) The heater 800 in Figure 9 is an example in which the heating resistor 802 is placed on the side of the fixing nip portion N, and the thermistor group TG6 is placed on the opposite side of the fixing nip portion N. The same symbols are used for configurations similar to those in Example 1, and their explanation is omitted.

[0092] Figure 9(A) shows a cross-sectional view of the central part of the heater 800 (near the transport reference position X). Only a conductive pattern is formed on the back layer 1, and the chip thermistor T6-2 is bonded on top of it. 810 and 811 are electrodes of the chip thermistor T6-2. Conductive patterns EG6 and ET6-2 are connected to the chip thermistor T6-2 via electrodes 810 and 811. By positioning the thermistor group TG6 on the opposite side of the fixing nip portion N, as in the heater 800, the flatness required for the sliding surface layer is eliminated, and a thicker chip thermistor T6-2 can be installed.

[0093] The thermistor group TG6 provided on the back layer 1 of the heater 800 has three chip thermistors T6-1 to T6-3, conductive patterns ET6-1 to ET6-3 for detecting the thermistor resistance values, and a common conductive pattern EG6.

[0094] The sliding surface layer 1 of the heater 800 is provided with three heat-generating blocks HB1 to HB3. The heat-generating resistor 802 is divided into three parts, 802-1 to 802-3, and is powered via the first conductor 801 and the three divided second conductors 803-1 to 803-3. The second conductors 803-1 to 803-3 are connected to electrodes E1 to E3, and the first conductor 801 is connected to electrode E8. By using electrode E8 as a common electrode and providing switch elements such as triacs to electrodes E1 to E3, the three heat-generating blocks HB1 to HB3 can be controlled independently. The sliding surface layer 2 of the heater 800 is provided with glass having sliding and insulating properties as a protective layer 808.

[0095] By the way, in heater 800, in order to supply power to the heat-generating blocks HB1 to HB3, the first conductor 801 and the second conductor 803 need to be wired to both ends in the short direction of the heater. Therefore, especially when the number of heat-generating blocks increases, the area required for wiring the first conductor 801 and the second conductor 803 increases, resulting in a larger heater.

[0096] As with the heater 300 described in Example 1 and the heater 600 described in Example 2, providing electrodes E2 to E6 within the heating region eliminates the need for wiring between the first conductor 301 and the second conductor 303, thus allowing for an increase in the number of heating blocks without increasing the size of the heater. In a configuration where electrodes E2 to E6 are provided within the heating region, electrodes E2 to E6 must be provided on the opposite side of the fixing nip portion N in order to connect the electrical contacts C2 to C6. Therefore, a configuration in which heating blocks (HB1 to HB7) are formed on the opposite side of the fixing nip portion N and the thermistor groups (TG1, TG2, TG3, TG4) are formed on the side of the fixing nip portion N is effective.

[0097] When the number of heat-generating blocks is small, a method can be applied in which a thermistor group TG6 using multiple chip thermistors is placed on the opposite side of the fixing nip portion N, as in the heater 800 described in this embodiment.

[0098] (Example 4) The example 4 shown in Figure 10 has a different shape for the heating resistor compared to the heaters of Examples 1 and 2. The heating resistors 902a and 902b of the heater 900 shown in Figure 10(A) are continuous (not divided) in the longitudinal direction.

[0099] Figure 10(A) is a plan view of the back layer 1 of the heater 900. Since the conductor 303 is divided into seven sections in the longitudinal direction, the heating elements 902a and 902b are configured to allow independent temperature control in the regions of heating blocks HB1 to HB7. Because the heater 900 does not divide the heating elements 902a and 902b, it generates heat continuously in the longitudinal direction even in the divided gap regions of the conductor 303, and there are no regions where the amount of heat generated is 0 (zero), so the heater can generate heat more uniformly in the longitudinal direction.

[0100] The heater 1000 shown in Figure 10(B) is divided into multiple heating resistors, each consisting of heating resistors 1002a and 1002b connected in parallel.

[0101] Figure 10(B) is a plan view of the back layer 1 of the heater 1000. The heating resistor 1002a is divided into multiple parts and connected in parallel between the conductor 303 and the conductor 301a. Similarly, the heating resistor 1002b is divided into multiple parts and connected in parallel between the conductor 303 and the conductor 301a.

[0102] The divided heating resistors 1002a and 1002b are positioned at an angle to the longitudinal and transverse directions of the heater 1000, and overlap in the longitudinal direction of the heater 1000. This reduces the influence of the gaps between the divided heating resistors and improves the uniformity of the heat distribution in the longitudinal direction of the heater 1000. Furthermore, in the heater 1000, the divided heating resistors at the outermost ends of adjacent heating blocks overlap in the longitudinal direction, even in the gaps between heating blocks, thus making the heat distribution in the longitudinal direction of the heater 1000 more uniform. The outermost heating resistors of adjacent heating blocks are, for example, the heating resistor at the right end of heating block HB1 and the heating resistor at the left end of heating block HB2.

[0103] Furthermore, the heat distribution of the heat-generating resistors 1002a and 1002b can be adjusted by changing the width, length, spacing, and inclination of the divided heat-generating resistors. By adopting the configuration of heater 900 and heater 1000, temperature unevenness in the gaps between multiple heat-generating blocks can be suppressed.

[0104] (Example 5) Figure 11 shows the current waveforms flowing to each heat-generating block in the control circuit 400 shown in Example 1. Figure 11(A) is the drive pattern of the triac 411 (table of current waveforms flowing to heat-generating block HB4) set for each duty cycle of the power supplied to the heater 300. Similarly, Figure 11(B) is the drive pattern of the triacs 412 to 414 (table of current waveforms flowing to heat-generating blocks HB1 to HB3 and HB5 to HB7).

[0105] The CPU420 calculates the power level (duty cycle) to be supplied to the heater for each control cycle, and then selects a waveform corresponding to the duty cycle for each heat-generating block to be supplied. In this embodiment, the control method uses four half-waves as one control cycle to set the energization control pattern for each triac and controls the power supplied to the heater 300.

[0106] The following describes an example of a power supply control pattern for triac 411 with a duty cycle of 25%. In power supply control pattern A of triac 411 shown in Figure 11(A), half-waves 1 and 2 are controlled with a phase angle of 90° to supply 50% of the power, and half-waves 3 and 4 are turned OFF. As a result, an average of 25% of the power is supplied to the heating block HB4 of heater 300. Power supply control pattern A is a power supply pattern that performs phase control on half-waves 1 and 2.

[0107] Furthermore, in the energization control pattern for triacs 412-414 shown in Figure 11(B), the 3rd to 4th half-waves are controlled with a phase angle of 90° to supply 50% of the power, while the 1st to 2nd half-waves are turned OFF. As a result, an average of 25% of the power is supplied to the heating blocks HB1-HB3 and HB5-HB7 of heater 300. Energy control pattern B is an energization pattern that performs phase control on the 3rd to 4th half-waves.

[0108] Because the heating block HB4 of heater 300 has a lower resistance than the other heating blocks, the current fluctuation during phase control is larger compared to the other heating blocks. Therefore, in this example, the timing of the phase control current flowing through heating block HB4 (1st half-wave to 2nd half-wave) is staggered from the timing of the phase control current flowing through the other heating blocks HB1 to HB3 and HB5 to HB7 (3rd half-wave to 4th half-wave). This suppresses the fluctuation in the phase control current flowing throughout heater 300. The same applies to duty cycles other than 25%.

[0109] As shown in Figure 11, by synchronizing the control timing of multiple triacs (synchronous control of multiple triacs), the harmonic current of the image heating device 200 can be reduced in this example. Figure 11 is an example of synchronous control; for example, synchronous control of multiple triacs may be performed to reduce flicker.

[0110] Furthermore, the same method can be used to synchronize multiple triacs 711-717 of the control circuit 700.

[0111] The advantages of synchronous control of multiple triacs include reduced harmonic currents and flicker, and the ability to satisfy harmonic current and flicker specifications even when the total resistance of the heater 300 is set low. If the resistance of the heater 300 can be set low, the maximum power that can be supplied to the heater 300 from the AC power supply 401 can be increased.

[0112] The above-described embodiments used a central-reference printer in which the recording material is transported with its center in the width direction aligned with the transport reference position X. However, the present invention can also be applied to a one-sided-reference printer in which one end in the width direction of the recording material is transported with one end of the heater in the longitudinal direction aligned with the transport reference position. [Explanation of symbols]

[0113] 200 Image heating device 300 Heater 301 First Conductor 302 Heat-generating resistor 303 Second conductor 305 substrate E1~E7, E8-1, E8-2 electrode HB1~HB7 Heating Blocks

Claims

1. A substrate, a first heat-generating block formed on the substrate which generates heat when power is supplied, A second heat-generating block is formed in the longitudinal direction of the substrate at a position different from the position where the first heat-generating block is formed, and is controlled independently of the first heat-generating block. In a heater used in an image heating device having, The heater further includes a first temperature sensing element provided at a position corresponding to the first heat-generating block, and a second temperature sensing element provided at a position corresponding to the second heat-generating block. A heater characterized by having a first conductive pattern electrically connected to the first temperature sensing element, a second conductive pattern electrically connected to the second temperature sensing element, and a common conductive pattern electrically connected to the first and second temperature sensing elements.

2. The heater according to claim 1, wherein the first and second heating blocks each include a first conductor provided along the longitudinal direction, a second conductor provided along the longitudinal direction at a different position from the first conductor in the short direction of the substrate, and a heating element provided between the first conductor and the second conductor, which generates heat by power supplied through the first conductor and the second conductor.

3. The first temperature sensing element, the second temperature sensing element, the first conductive pattern, The heater according to claim 1, characterized in that the second conductive pattern and the common conductive pattern are formed on the substrate surface opposite to the substrate surface on which the first and second heat-generating blocks are formed.

4. An image heating device comprising a cylindrical film and a heater in contact with the inner surface of the film, wherein the device heats an image formed on a recording material by the heat of the heater through the film, An image heating device characterized in that the heater is the heater described in any one of claims 1 to 3.

Images