JP6896900B2 - Heater used for image heating device and image heating device - Google Patents

Description

The present invention is a fuser mounted on an electrophotographic recording type image forming apparatus such as a copying machine or a printer, or a gloss imparting device for improving the glossiness of a toner image by reheating a fixed toner image on a recording material. , Etc. relating to an image heating device. It also relates to a heater used in this image heating device.

As the image heating device, there is a device having a tubular film, a heater that contacts 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 device, a phenomenon occurs in which the temperature of a region through which the paper does not pass gradually rises in the longitudinal direction of the nip portion (temperature rise in the non-passing portion). If the temperature of the non-passing part becomes too high, each part in the device will be damaged, or if you print on a large size paper with the non-passing part warming up, the non-passing part of the small size paper The toner may be offset to the film at high temperature in the area corresponding to.

As one of the methods for suppressing the temperature rise of the non-paper-passing portion, the heat generation resistor on the heater is divided into a plurality of groups (heat generation blocks) in the longitudinal direction of the heater, and the heat generation distribution of the heater is distributed according to the size of the recording material. A switching device has been proposed (Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-559508

By the way, considering the failure of the device, it is preferable to have a configuration in which the temperature is monitored for each heat generating block. This is because even if one of the plurality of heat generation blocks becomes uncontrollable and abnormal heat generation occurs, the power supply can be stopped quickly if the temperature is monitored for each heat generation block.

However, as the number of heat generating blocks increases, so does the number of temperature detecting elements for monitoring the temperature. If a large number of temperature detection elements are provided in the area of the heater substrate, the heater becomes large.

In the present invention for solving the above-mentioned problems, a substrate, a first heat generating block formed on the substrate and generating heat by supplying electric power, and the first heat generating block formed in the longitudinal direction of the substrate are formed. The second heat generation block, which is formed at a position different from the vertical position and generates heat by supplying electric power, is formed at a position different from both the first heat generation block and the second heat generation block in the longitudinal direction. In a heater used in an image heating device having a third heat generation block that generates heat by supplying electric power, the first heat generation block is a heat generation block controlled by a first switch element for controlling electric power. The second and third heat generation blocks are heat generation blocks controlled by a second switch element for controlling electric power, and the heater is further provided at a position corresponding to the first heat generation block. The first temperature detection element, the second temperature detection element provided at a position corresponding to the second heat generation block, the first conductive pattern electrically connected to the first temperature detection element, and the above. A first detection element group having a second conductive pattern electrically connected to the second temperature detecting element and a first common conductive pattern electrically connected to the first and second temperature detecting elements. A third temperature detection element provided at a position corresponding to the third heat generation block and a temperature detection element provided at a position corresponding to the first heat generation block, the first in the longitudinal direction. A fourth temperature detection element provided at a position different from the position where the temperature detection element is provided, a third conductive pattern electrically connected to the third temperature detection element, and the fourth temperature detection. Having a second detection element group having a fourth conductive pattern electrically connected to the element and a second common conductive pattern electrically connected to the third and fourth temperature detecting elements. It is a feature.

According to the present invention, it is possible to suppress an increase in the size of the heater.

Sectional view of image forming apparatus. Cross-sectional view of the image heating device. The heater block diagram of Example 1. The heater control circuit diagram of Example 1. The heater control flowchart of Example 1. The heater block diagram of Example 2. FIG. The heater control circuit diagram of Example 2. The heater control flowchart of Example 2. The figure which showed the deformation example of a heater. The figure which showed the deformation example of a heater. The figure which showed the energization control pattern of a heater.

(Example 1)
FIG. 1 is a cross-sectional view of a laser printer (image forming apparatus) 100 using an electrophotographic recording technique. When the print signal is generated, the scanner unit 21 emits a laser beam modulated according to the image information, and the charging roller 16 scans the photoconductor 19 charged with a predetermined polarity. As a result, an electrostatic latent image is formed on the photoconductor 19. Toner is supplied from the developer 17 to the electrostatic latent image, and a toner image corresponding to the image information is formed on the photoconductor 19. On the other hand, the recording material (recording paper) P loaded on the paper feed cassette 11 is fed one by one by the pickup roller 12 and conveyed toward the resist roller 14 by the roller 13. Further, the recording material P is conveyed from the resist roller 14 to the transfer position at the timing when the toner image on the photoconductor 19 reaches the transfer position formed by the photoconductor 19 and the transfer roller 20. The toner image on the photoconductor 19 is transferred to the recording material P in the process of passing the recording material P through the transfer position. After that, the recording material P is heated by the image heating device (fixing device) 200, and the toner image is heated and fixed to the recording material P. The recording material P carrying the fixed toner image is discharged to the tray above the laser printer 100 by the rollers 26 and 27. Reference numeral 18 denotes a cleaner for cleaning the photoconductor 19. Reference numeral 30 denotes a motor for driving the image heating device 200 and the like. Power is supplied to the image heating device 200 from the control circuit 400 connected to the commercial AC power supply 401. The photoconductor 19, the charging roller 16, the scanner unit 21, the developing device 17, and the transfer roller 20 as described above form an image forming portion for forming an unfixed image on the recording material P. Reference numeral 15 indicates a cartridge as a replacement unit. Further, 22 is a light source, 23 is a polygon mirror, and 24 is a reflection mirror.

The laser printer 100 of this embodiment corresponds to a plurality of recording material sizes. Letter paper (about 216 mm × 279 mm) and Legal paper (about 216 mm × 356 mm) can be set in the paper feed cassette 11. Further, A4 paper (210 mm × 297 mm), Executive paper (about 184 mm × 267 mm), JIS B5 paper (182 mm × 257 mm), and A5 paper (148 mm × 210 mm) can be set.

The printer of this example is basically a laser printer that feeds the paper vertically (the long side of the paper is conveyed so as to be parallel to the conveying direction). The configuration of the present proposal can be similarly applied to a printer that feeds paper horizontally. The largest (larger) recording material among the widths of the standard recording materials (widths of the recording materials on the catalog) supported by the apparatus is Letter paper and Legal paper, and these widths are about 216 mm. Is. A recording material P having a paper width smaller than the maximum size supported by the apparatus is defined as a small size paper in this embodiment.

FIG. 2 is a cross-sectional view of the image heating device 200. The image heating device 200 includes a tubular film 202, a heater 300 that contacts the inner surface of the film 202, and a pressure roller (nip portion forming member) 208 that forms a fixing nip portion N together with the heater 300 via the film 202. Has. The material of the base layer of the film 202 is a heat-resistant resin such as polyimide or a metal such as stainless steel. Further, the film 202 may 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 a liquid crystal polymer. The holding member 201 also has a guide function for guiding the rotation of the film 202. The pressurizing 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 is driven to rotate. The recording material P carrying the unfixed toner image is heated and fixed by being sandwiched and conveyed by the fixing nip portion N. As described above, the apparatus 200 has the tubular film 202 and the heater 300 in contact with the inner surface of the film 202, and heats the image formed on the recording material by the heat of the heater 300 through the film 202. ..

The heater 300 has a ceramic substrate 305 and a heating element (heating element) (see FIG. 3) that is provided on the substrate 305 and generates heat by supplying electric power. A glass surface protective layer 308 is provided on the surface (first surface) of the substrate 305 on the side of the fixing nip portion N in order to ensure the slidability of the film 202. A glass surface protective layer 307 is provided on the surface (second surface) of the substrate 305 opposite to the surface on the N side of the fixing nip portion in order to insulate the heat generating resistor. An electrode (here, E4 is shown as a representative) is exposed on the second surface, and an electric contact for power supply (here, C4 is shown as a representative) comes into contact with the electrode to generate a heat-generating resistor. Is electrically connected to the AC power supply 401. A detailed description of the heater 300 will be described later.

No. 202 is a protective element 212 such as a thermo switch or a thermal fuse that operates due to abnormal heat generation of the heater 300 to cut off the electric power supplied to the heater 300. The protective element 212 is arranged in contact with the heater 300 or with a slight gap with respect to the heater 300. Reference numeral 204 is 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.

3 (A) and 3 (B) show a configuration diagram of the heater 300 of the first embodiment. FIG. 3A shows a cross-sectional view of the heater 300 near the transport reference position X of the recording material P shown in FIG. 3B. FIG. 3B shows a plan view of each layer of the heater 300. FIG. 3C is a plan view of a holding member that holds the heater 300.

The printer of this example is a center-referenced printer that transports the center of the recording material in the width direction (direction orthogonal to the transport direction) in accordance with the transport reference position X.

Next, the configuration of the heater 300 will be described in detail. A pair of a first conductor 301, a second conductor 303, and a heating element (heating element) 302 is formed on the back surface layer 1 of the heater 300, which is the heater surface opposite to the heater surface in contact with the film 202. A plurality of heat generating blocks made of the heater 300 are provided in the longitudinal direction of the heater 300. The heater 300 of this embodiment has a total of seven heat generating blocks HB1 to HB7. Assuming that one of the seven heat generation blocks is the first heat generation block and the other one heat generation block is the second heat generation block, the heater 300 has the following configuration. That is, the heater 300 has a substrate and a first heat generation block formed on the substrate and generating heat by supplying electric power. Further, it has a second heat generation block that is formed at a position different from the position where the first heat generation block is formed in the longitudinal direction of the substrate and is controlled independently of the first heat generation block. The independent control of the heat generation block will be described later.

Each heat generating block has a first conductor 301 provided along the longitudinal direction of the substrate and a position different from the first conductor 301 in the lateral direction of the substrate along the longitudinal direction of the substrate. It has a second conductor 303 provided. Further, it has a heat generating resistor 302 that is provided between the first conductor 301 and the second conductor 303 and generates heat by the electric power supplied via the first conductor 301 and the second conductor 303. ..

The heat generation resistor 302 of each heat generation block is divided into a heat generation resistor 302a and a heat generation resistor 302b formed at positions symmetrical with respect to the center of the substrate with respect to the lateral direction of the heater 300. Further, the first conductor 301 is divided into a conductor 301a connected to the heat generating resistor 302a and a conductor 301b connected to the heat generating resistor 302b. Since the heat-generating resistor 302a and the heat-generating resistor 302b are formed at positions symmetrical with respect to the center of the substrate, the substrate is less likely to crack even if the heater generates heat and thermal stress is generated on the substrate.

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. Further, the second conductor 303 is also divided into seven, 303-1 to 303-7. The heat generating resistors 302a-1 to 302a-7 are arranged in the substrate 305 on the upstream side in the transport direction of the recording material P, and the heat generating resistors 302b-1 to 302b-7 are recorded materials in the substrate 305. It is arranged on the downstream side in the transport direction of P.

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

By the way, since the resistance value of the conductor is not zero, it affects the heat generation distribution in the longitudinal direction of the heater 300. Therefore, the electrodes E8-1 and E8-2 so that the heat generation distribution does not become non-uniform even under the influence of the electric resistance of the first conductors 301a and 301b and the second conductors 303-1 to 303-7. Is provided separately at both ends of the heater 300 in the longitudinal direction.

As shown in FIG. 2, a safety element 212, electrical contacts C1 to C7, C8-1 and C8-2 are provided in the space between the stay 204 and the holding member 201. As shown in FIG. 3C, the holding member 201 has holes through which the electrical contacts C1 to C7, C8-1 and C8-2 connected to the electrodes E1 to E7, E8-1 and E8-2 are passed. HC1 to HC7, HC8-1 and HC8-2 are provided. Further, the holding member 201 is also provided with a hole H212 through which the heat-sensitive portion of the protective element 212 is passed. The electrical contacts C1-C7, C8-1 and C8-2 are electrically connected to the corresponding electrodes by a method such as spring urging or welding. The protective element 212 is also urged by a spring, and its heat-sensitive portion is in contact with the surface protective layer 307. Each electric contact is connected to the control circuit 400 of the heater 300, which will be described later, via a conductive member such as a cable or a thin metal plate provided in the space between the stay 204 and the holding member 201.

By providing the electrodes on the back surface of the heater 300, it is not necessary to provide a region for wiring electrically connected to each of the second conductors 303-1 to 303-7 on the substrate 305, so that the substrate 305 is short. The width in the hand direction can be shortened. Therefore, it is possible to suppress an increase in the size of the heater. As shown in FIG. 3B, the electrodes E2 to E6 are provided in the region where the heat generating resistor is provided in the longitudinal direction of the substrate.

As will be described later, the heater 300 of this example can form various heat generation distributions by independently controlling a plurality of heat generation blocks. For example, the heat generation distribution can be set according to the size of the recording material. Further, the heat generation resistor 302 is made of a material having PTC (Positive Temperature Coefficient). By using a material having PTC, it is possible to suppress the temperature rise of the non-passing paper portion even in the case where the edge portion of the recording material and the boundary of the heat generating block do not match.

A plurality of thermistors (temperature detection elements) T1-1 to detect the temperature of each heat generating block HB1 to HB7 are provided on the sliding surface layer 1 on the sliding surface (the surface in contact with the film) of the heater 300. T1-4 and T2-4 to T2-7 are formed. The material of the thermistor may be any material having a large positive or negative TCR (Temperature Coefficient of Response). In this example, a material having NTC (Negative Temperature Coefficient) was thinly printed on a substrate to form a thermistor. Since one or more thermistors are provided corresponding to all of the heat generation blocks HB1 to HB7, the temperatures of all the heat generation blocks can be detected.

Assuming that one of the thermistors T1-1 to T1-4 is the first temperature detecting element and the other one of the thermistors T1-1 to T1-4 is the second temperature detecting element, the heater The 300 has the following configuration. That is, the heater 300 has a first temperature detection element provided at a position corresponding to the first heat generation block and a second temperature detection element provided at a position corresponding to the second heat generation block. ..

The thermistors T1-1 to T1-4 are electrically connected to the conductive patterns ET1-1 to ET1-4 provided on the substrate 305, respectively. Assuming that the conductive pattern connected to the first temperature detecting element among the conductive patterns ET1-1 to ET1-4 is the first conductive pattern and the conductive pattern connected to the second temperature detecting element is the second conductive pattern, the heater 300 Has the following configuration. That is, the heater 300 has a first conductive pattern that is electrically connected to the first temperature detecting element and a second conductive pattern that is electrically connected to the second temperature detecting element. Further, the heater 300 has a common conductive pattern EG1 that is electrically connected to the first and second temperature detecting elements. Hereinafter, the set of thermistors T1-1 to T1-4, the conductive patterns ET1-1 to ET1-4, and the common conductive pattern EG1 will be referred to as a thermistor group TG1.

The heater 300 is also provided with a thermistor group TG2 composed of a set 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 of the substrate 305 opposite to the substrate surface on which the first and second heat generating blocks are formed.

In this example, at least one corresponding thermistor is arranged for each of all the heat generating blocks HB1 to HB7, but even if one corresponding thermistor is arranged for at least two heat generating blocks, the apparatus is used. Reliability is improved. However, as in this example, it is preferable to place at least one corresponding thermistor for all heating blocks.

By using the common conductive patterns EG1 and EG2 as in this example, if the first and second temperature detecting elements are combined into one set, the following effects can be obtained. That is, the cost of the conductive pattern can be reduced and the size increase of the heater can be suppressed as compared with the case where two conductive patterns are connected to the thermistors T1-1 to T1-4 without using the common conductive pattern. it can.

Insulating (in this example, made of glass) surface protective layer 308 is formed by coating on the surface (sliding surface layer 2) of the substrate 305 on the fixing nip portion N side to ensure the slidability of the film 202. Has been done. The surface protective layer 308 covers the thermistors T1-1 to T1-4, T2-4 to T2-7, the conductive patterns ET1-1 to ET1-4, ET2-4 to ET2-7, and the common conductive patterns EG1 and EG2. ing. However, in order to secure the connection with the electrical contacts, as shown in FIG. 3B, at both ends of the heater 300, a part of the conductive patterns ET1-1 to ET1-4 and ET2-4 to ET2-7, And a part of the common conductive patterns EG1 and EG2 is exposed.

FIG. 4 is a circuit diagram of the control circuit 400 of the heater 300. Reference numeral 401 denotes a commercial AC power supply connected to the laser printer 100. The power control of the heater 300 is performed by energizing / shutting off the triacs 411 to 414. The triacs 411 to 414 operate according to the FUSER1 to FUSER4 signals from the CPU 420, respectively. In FIG. 4, the drive circuits of the triacs 411 to 414 are omitted.

As can be understood from FIGS. 3 and 4, the seven heat generation 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). It is divided into. The control circuit 400 of the heater 300 has a circuit configuration capable of independently controlling four groups. The triac 411 can control group 1, the triac 412 can control group 2, the triac 413 can control group 3, and the triac 414 can control group 4.

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

Next, a method of detecting the temperature of the heater 300 will be described. First, the thermistor group TG1 will be described. A signal (Th1-1 to Th1-4) obtained by dividing the voltage Vcc by the resistance value of the thermistor (T1-1 to T1-4) and the resistance value of the resistance (451 to 454) is input to the CPU 420. .. For example, the signal Th1-1 is a signal obtained by dividing the voltage Vcc by the resistance value of the thermistor T1-1 and the resistance value of the resistor 451. Since the thermistor T1-1 has a resistance value according to the temperature, when the temperature of the heat generating block HB1 changes, the level of the signal Th1-1 input to the CPU also changes. The CPU 420 converts the input signal Th1-1 into a temperature according to the level. Since the processing of the signals Th1-2 to Th1-4 corresponding to the other thermistors T1-2 to T1-4 of the thermistor group TG1 is the same, the description thereof is omitted.

Next, the thermistor group TG2 will be described. Similar to TG1, the thermistor group TG2 also has a signal (Th2-4) in which the voltage Vcc is divided by the resistance value of the thermistor (T2-4 to T2-7) and the resistance value of the resistance (464 to 467) in the CPU 420. ~ Th2-7) is input. The method of converting to temperature by the CPU 420 is the same as that of the thermistor group TG1, so the explanation is omitted.

Next, power control to the heater 300 (heater temperature control) will be described. During the fixing process, each of the heat generating blocks HB1 to HB7 is controlled so that the detection temperature of the thermistors (T1-1 to T1-4) in the thermistor group TG1 maintains the set temperature (control target temperature). Specifically, the electric power supplied to the group 1 (heat generation block HB4) is controlled by controlling the drive of the triac 411 so that the detection temperature of the thermistor T1-4 maintains the set temperature. The electric power supplied to the group 2 (heat generation blocks HB3 and HB5) is controlled by controlling the drive of the triac 412 so that the detection temperature of the thermistor T1-3 maintains the set temperature. The electric power supplied to the group 3 (heat generation blocks HB2 and HB6) is controlled by controlling the drive of the triac 413 so that the detection temperature of the thermistor T1-2 maintains the set temperature. The electric power supplied to the group 4 (heat generation blocks HB1 and HB7) is controlled by controlling the drive of the triac 414 so that the detection temperature of the thermistor T1-1 maintains the set temperature. As described above, each thermistor in the thermistor group TG1 is used when performing control for keeping each heat generating block at a constant temperature.

The CPU 420 calculates the power supply by, for example, PI control, based on the set temperature (control target temperature) of each heat generating block and the detection temperature of each thermistor (T1-1 to T1-4) in the thermistor group TG1. Further, the calculated power supply is converted into control timings such as the corresponding phase angle (phase control) and wave number (wave number control), and the triacs 411 to 414 are controlled at this control timing. The set temperature of each group of the apparatus of this example when fixing the maximum size plain paper is 250 ° C. When the small size plain paper is fixed, the set temperature of the group 1 is set to 250 ° C, and the set temperature of the other groups is lower than 250 ° C. The set temperature of each group may be appropriately set according to information such as the size, type, and surface property of the recording material.

The relay 430 and the relay 440 are mounted as means for cutting off the electric power to the heater 300 when the heater 300 is overheated due to a factor such as a failure of the device. Next, the circuit operation of the relay 430 and the relay 440 will be described.

When the RLON signal output from the CPU 420 is in the High state, the transistor 433 is turned on, the DC power supply (voltage Vcc) is energized to the secondary coil of the relay 430, and the primary contact of the relay 430 is turned ON. Become. When the RLON signal is in the Low state, the transistor 433 is turned off, the current flowing from the power supply (voltage Vcc) to the secondary coil of the relay 430 is cut off, and the primary contact of the relay 430 is turned off. Similarly, when the RLON signal is in the High state, the transistor 443 is turned on, the power supply (voltage Vcc) is energized to the secondary coil of the relay 440, and the primary contact of the relay 440 is turned ON. When the RLON signal is in the Low state, the transistor 443 is turned off, the current flowing from the power supply (voltage Vcc) to the secondary coil of the relay 440 is cut off, and the primary contact of the relay 440 is turned off.

Next, the operation of the protection circuit (hard circuit not via the CPU 420) using the relay 430 and the relay 440 will be described. When the level of any one of the 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 lowers the RLOFF1 signal. Latch in the state. When the RLOFF1 signal is in the Low state, even if the CPU 420 sets the RLON signal in the High state, the transistor 433 is kept in the OFF state, so that the relay 430 can be kept in the OFF state (safe state). The latch portion 432 outputs the RLOFF1 signal in the open state in the non-latch state.

Similarly, when 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 operates the latch unit 442, and the latch unit 442 operates the latch unit 442. Latch the signal in the Low state. When the RLOFF2 signal is in the Low state, even if the CPU 420 sets the RLON signal in the High state, the transistor 443 is kept in the OFF state, so that the relay 440 can be kept in the OFF state (safe state). The latch portion 442 outputs the RLOFF signal in the open state in the non-latch state. The predetermined value set inside the comparison unit 431 and the predetermined value set inside the comparison unit 441 in this example are both values corresponding to 300 ° C.

Next, the circuit protection operation using the two thermistor groups TG1 and TG2 will be described. As shown in FIGS. 3 and 4, each of the above-mentioned four groups (groups 1 to 4) corresponds to one thermistor in the thermistor group TG1 and one thermistor in the thermistor group TG2. Have been placed. Further, at least one thermistor is correspondingly arranged for each of all the heat generating blocks HB1 to HB7. Specifically, in group 1 (HB4), thermistors T1-4 in the thermistor group TG1 and thermistors T2-4 in the thermistor group TG2 are arranged correspondingly. In group 2 (HB3 and HB5), thermistor T1-3 in the thermistor group TG1 and thermistor T2-5 in the thermistor group TG2 are arranged correspondingly. In group 3 (HB2 and HB6), thermistor T1-2 in the thermistor group TG1 and thermistor T2-6 in the thermistor group TG2 are arranged correspondingly. In group 4 (HB1 and HB7), thermistor T1-1 in the thermistor group TG1 and thermistor T2-7 in the thermistor group TG2 are arranged correspondingly. Further, at least one thermistor out of eight thermistors is arranged correspondingly to each of all the heat generating blocks HB1 to HB7. Such a thermistor layout improves the reliability of the circuit protection operation in the event of equipment failure. This will be described below.

For example, it is assumed that any of the thermistors T1-1 to T1-4 in the thermistor group TG1 fails. Even if the group with the heat generation block corresponding to the failed thermistor becomes uncontrollable due to the failure of the thermistor, the thermistors (T2-4 to T2-7) in the thermistor group TG2 are included in the group of heat generation blocks with the failed thermistor. Either) is also placed. Therefore, the protection circuit operates (stops the power supply) via the thermistor in the thermistor group TG2.

Next, the merit of the configuration in which at least one thermistor out of eight thermistors is correspondingly arranged for each of all the heat generating blocks HB1 to HB7 will be described.

For example, it is assumed that the thermistor T2-5 corresponding to the group 2 is arranged not at a position corresponding to the heat generation block HB5 but at a position corresponding to the heat generation block HB3 which is the same group 2 as the heat generation block HB5. In this case, the thermistor T1-3 of the thermistor group TG1 and the thermistor T2-5 of the thermistor group TG2 are arranged at positions corresponding to the heat generation block HB3, and there is no thermistor at a position corresponding to the heat generation block HB5. Even with such a configuration, the temperature of Group 2 can be monitored. However, in this configuration, when the electrode E3 and the electric contact C3 have poor contact, the heat generation block HB3 does not generate heat, but the heat generation block HB5, which is the same group 2 as the heat generation block HB3, may generate heat. Then, even if the heat generation block HB5 of the group 2 generates abnormal heat, the two thermistors T1-3 and T2-5 corresponding to the group 2 cannot monitor this, and the protection circuit does not work.

On the other hand, in this example, the thermistor T1-3 of the thermistor group TG1 is arranged at a position corresponding to the heat generation block HB3, and the thermistor T2-5 of the thermistor group TG2 is arranged at a position corresponding to the heat generation block HB5. There is. Therefore, even if the electrode E3 and the electrical contact C3 have a poor contact and only the heat generating block HB5 in the group 2 generates heat, this temperature can be monitored by the thermistor T2-5 to operate the protection circuit. As described above, at least one of the eight thermistors is arranged correspondingly to each of the heat generating blocks HB1 to HB7, so that the reliability of the apparatus is improved.

FIG. 5 is a flowchart illustrating a control sequence of the control circuit 400 by the CPU 420. When a print request is generated in S100, the relay 430 and the relay 440 are turned on in S101.

In S102, the triac 414 is PI-controlled so that the detection temperature (signal Th1-1) of the thermistor T1-1 reaches the control target temperature, and the electric power supplied to the heat generation blocks HB1 and HB7 is controlled.

In S103, the triac 413 is PI-controlled so that the detection temperature (signal Th1-2) of the thermistor T1-2 reaches the control target temperature, and the electric power supplied to the heat generation blocks HB2 and HB6 is controlled.

In S104, the triac 412 is PI-controlled so that the detected temperature (signal Th1-3) of the thermistor T1-3 reaches the control target temperature, and the electric power supplied to the heat generating blocks HB3 and HB5 is controlled.

In S105, the triac 411 is PI-controlled so that the detection temperature (signal Th1-4) of the thermistor T1-4 reaches the control target temperature, and the electric power supplied to the heat generation block HB4 is controlled.

As described above, the control target temperature of each heat generating block is set according to the recording material size information. In the apparatus of this example, the control target temperature of the heat generation block HB4 including the transport reference X is set to the same temperature regardless of the recording material size, and the control target temperature of the other heat generation blocks is changed according to the recording material size. The smaller the size of the recording material, the lower the control target temperature of the heat generation blocks other than the heat generation block HB4.

In S106, it is determined whether or not the temperature rise of the non-passing portion of the heater 300 is equal to or less than 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. of the heat generation block HB4 and lower than the predetermined value of 300 ° C. set in the comparison unit 431 and the comparison unit 441. Further, the positional relationship between the thermistor and the reference X in the thermistor group TG1 and the positional relationship between the thermistor and the reference X in the thermistor group TG2 are different. The thermistors of the thermistor group TG2 are arranged outside the transfer reference position X in the longitudinal direction of the heater 300 in each heat generating block as compared with the thermistors of the thermistor group TG1. As shown in FIG. 3B, if the distance from the reference X of the thermistor T1-4 corresponding to the heat generation block HB4 and the distance from the reference X of the thermistor T2-4 corresponding to the heat generation block HB4 are compared. This relationship is easy to understand. With such a layout, even if the temperature of the non-passing paper portion rises in one heat generating block, it can be detected by the thermistor of the thermistor group TG2.

When the temperature of the thermistors T2-4 to T2-7 is equal to or lower than the threshold temperature Tmax in S106, the process proceeds to S108, and the control of S102 to S106 is repeated until the end of the print JOB is detected in S108.

When the temperature of thermistors T2-4 to T2-7 exceeds the threshold temperature Tmax in S106, the process speed of image formation of the image forming apparatus 100 is reduced in S107, and the thermistors T1-1 to T1-4 are controlled. The fixing process is performed with the target temperature lowered. By lowering the process speed of image formation, the fixability can be ensured even at a temperature lower than the full speed, so that the temperature rise of the non-passing portion can also be suppressed.

When the above processing is repeated and the end of the print JOB is detected in S108, the relay 430 and the relay 440 are turned off in S109, and the image formation control sequence is terminated in S110.

(Example 2)
Next, a second embodiment in which the heater 300 and the heater control circuit 400 described in the first embodiment are changed to the heater 600 and the control circuit 700 will be described. The same symbols will be used for the same configuration as in the first embodiment, and the description thereof will be omitted. The heater 600 of the second embodiment has a different structure of the sliding surface layer 1 than the heater 300. The control circuit 700 has a configuration in which all the heat generating blocks HB1 to HB7 can be independently controlled.

FIG. 6 shows a configuration diagram of the heater 600 of the second embodiment. Since the configuration other than the sliding surface layer 1 is the same as that of the heater 300, the description thereof will be omitted.

Thermistors T3-1a to T3-4a, T3-1b to T3-3b, T4-4a to T4-7a, for detecting the temperature of each of the heat generating blocks HB1 to HB7, are formed on the sliding surface layer 1 of the heater 600. T4-5b to T4-7b and T5 are arranged. Since two or more thermistors are associated with all of the heat generating blocks HB1 to HB7, the temperature of all the heat generating blocks can be detected even if one thermistor fails.

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

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

First, the thermistor group TG3 will be described. Thermistors T3-1b and thermistors T3-2b are thermistors for detecting the temperatures of the heat generating blocks HB1 and HB2, and have a configuration in which two thermistors are connected in parallel between the conductive pattern ET3-12b and the common conductive pattern EG3. It has become. Even when the temperature of either the heat generating blocks HB1 or HB2 rises, the resistance value of either the thermistor T3-1b or the thermistor T3-2b greatly decreases. Therefore, the temperature detection of both the heat generating blocks HB1 and HB2 can be performed by one conductive pattern ET3-12b for detecting the resistance value of the thermistor. Therefore, the cost of forming the wiring of the conductive pattern can be reduced as compared with the case of connecting and wiring the conductive pattern to each of the thermistor T3-1b and the thermistor T3-2b. Further, the width of the substrate 305 in the lateral direction can be shortened. Similarly, the thermistor T4-6b and the thermistor T4-7b are also connected in parallel.

The common conductive patterns EG3 and EG4 are connected on the substrate 305 by the conductive pattern EG34, and are used for the disconnection detection described with reference to FIG. 7. By detecting the disconnection, it is possible to improve the safety in the event of a disconnection failure.

Two thermistors T3-3a and T3-3b are installed for one heat generation block HB3, and the conductive patterns ET3-3a and ET3-3b for detecting the resistance value and the common conductive pattern EG3 respectively. The configuration is such that temperature can be detected.

In the range of the heat generation block HB3, the thermistor T3-3b arranged at a position far from the transfer reference position X is a thermistor for detecting the end temperature, and the thermistor T3-3a arranged at a position close to the transfer reference position X. Is a temperature control thermistor. If necessary, a plurality of thermistors may be provided in one heat generation block.

Since the description of the thermistor group TG4 is the same as that of the thermistor group TG3, the description thereof will be omitted.

The thermistor T5 is a single thermistor formed between the conductive patterns ET5 and EG5 for detecting the resistance value. If necessary, a single thermistor may be used in combination with a thermistor group.

FIG. 7 shows a circuit diagram of the control circuit 700 of the heater 600 of the second embodiment. The power control of the heater 600 is performed by energizing / shutting off the triacs 711 to 717. The triacs 711 to 717 operate according to the FUSER1 to FUSER7 signals from the CPU 420, respectively. The control circuit 700 of the heater 600 has a circuit configuration in which the seven heat generating blocks HB1 to HB7 can be independently controlled by the seven triacs 711 to 717.

Next, a method of detecting the temperature of the heater 600 will be described. A signal (Th3-1a to Th3) in which the voltage Vcc is divided by the resistance values of the thermistors T3-1a to T3-4a, T3-1b, and T3-2b of the thermistor group TG3 and the resistance values of the resistors 751-756 in the CPU 420. -4a, Th3-3b, Th3-12b) are input. Similarly, a signal obtained by dividing the voltage Vcc by the resistance values of the thermistors T4-4a to T4-7a and T4-5b to T4-7b of the thermistor group TG4 and the resistance values of the resistors 771 to 776 is input to the CPU 420. To do. This signal is indicated by Th4-4a to Th4-7a, Th4-5b, and Th4-67b. Similarly, a signal (Th5) divided by the resistance value of the thermistor T5 and the resistance value of the resistor 761 is input to the CPU. The CPU 420 converts each input signal into a temperature according to the level.

The CPU 420 calculates the power supply based on the set temperature (control target temperature) of each heat generation block and the detection temperature of each thermistor, for example, by PI control. Further, the calculated power supply is converted into control timings such as the corresponding phase angle (phase control) and wave number (wave number control), and the triacs 711 to 717 are controlled at this control timing.

Next, the operation of the protection circuit using the relay 430 and the relay 440 will be described. Based on the Thermistor Group TG3 Th3-1a to Th3-4a signals and the thermistor Group TG4 Th4-5b and Th4-67b signals, if any one of the detection temperatures exceeds the set predetermined value, the comparison unit 431 Operates the latch portion 432.

Similarly, when any one of the detection temperatures exceeds a predetermined value set based on the Th4-4a to Th4-7a signals of the thermistor group TG4 and the Th3-3b and Th3-12b signals of the thermistor group TG3, respectively. The comparison unit 441 operates the latch unit 442.

Next, the disconnection detection circuit 780 will be described. The disconnection detection circuit 780 is a circuit used to enhance safety when the common conductive patterns EG3 and EG4 are disconnected.

The circuit operation of the disconnection detection circuit 780 will be described. When the connection between the common conductive patterns EG3 and EG4 is broken, the disconnection detection signal ThSafe is in the High state because the resistor 781 and the resistor 782 pull up to the power supply voltage Vcc. Two resistors are arranged for the resistor 781 and the resistor 782 in consideration of a short-circuit failure of the resistor. When the disconnection detection signal ThSafe is in the High state, the latch portion 432 and the latch portion 442 are operated.

Next, the effects of the disconnection detection circuit 780 and the conductive pattern EG34 will be described. First, a case where both the conductive pattern EG34 and the disconnection detection circuit 780 are not provided and the common conductive pattern EG3 and the common conductive pattern EG4 are connected to GND will be described as in the configuration of the first embodiment. In this case, if the common conductive pattern EG3 is disconnected, all thermistors of the thermistor group TG3 will not operate, so that the protection circuit for stopping the power supply to the heat generating blocks HB1 to HB3 will not work. Similarly, if the common conductive pattern EG4 is disconnected, all thermistors of the thermistor group TG4 will not operate, so that the protection circuit for stopping the power supply to the heat generating blocks HB5 to HB7 will not work.

Next, although it has the conductive pattern EG34 that connects the common conductive patterns EG3 and EG4, it does not have the disconnection detection circuit 780, and the common conductive patterns EG3 and EG4 have the same configuration as in the first embodiment, respectively. The case where it is connected to GND will be described. In this case, due to the effect of the conductive pattern EG34, even if either one of the common conductive patterns EG3 and EG4 is disconnected, the conductor is connected to GND via the conductive pattern EG34. Therefore, the temperature can be detected by the thermistor groups TG3 and TG4. However, if the connector (not shown) connecting the conductive pattern (ET3-1a to ET3-4a, ET3-12b, ET3-3b, EG3) of the thermistor group TG3 and the control circuit 700 is disconnected, the thermistor of the thermistor group TG3 will be released. Everything stops working. Therefore, the protection circuit for stopping the power supply to the heat generating blocks HB1 to HB3 does not work. Similarly, when the connector connecting the conductive pattern (ET4-4a to ET4-7a, ET4-67b, ET4-5b, EG4) of the thermistor group TG4 and the control circuit 700 is disconnected, all the thermistors of the thermistor group TG4 operate. Will not be. Therefore, the protection circuit for stopping the power supply to the heat generating blocks HB5 to HB7 does not work.

On the other hand, the device of this example has a conductive pattern body EG34 and a disconnection detection circuit 780. As a result, it is possible to detect both failure states when the common conductive patterns EG3 and EG4 are disconnected or when the connector connecting the thermistor group TG3 or TG4 and the control circuit 700 is disconnected.

FIG. 8 is a flowchart illustrating a control sequence of the control circuit 700 by the CPU 420. The same symbols will be used for the same configuration as in FIG. 5, and the description thereof will be omitted.

In S201, the triac 711 is PI-controlled so that the detection temperature (signal Th3-1a) of the thermistor T3-1a reaches a predetermined target temperature, and the electric power supplied to the heat generation block HB1 is controlled.

In S202, the triac 712 is PI-controlled so that the detection temperature (signal Th3-2a) of the thermistor T3-2a reaches a predetermined target temperature, and the electric power supplied to the heat generation block HB2 is controlled.

In S203, the triac 713 is PI-controlled so that the detection temperature (signal Th3-3a) of the thermistor T3-3a reaches a predetermined target temperature, and the electric power supplied to the heat generation block HB3 is controlled.

In S204, the triac 714 is PI-controlled so that the detection temperature (signal Th5) of the thermistor T5 reaches a predetermined target temperature, and the electric power supplied to the heat generation block HB4 is controlled.

In S205, the triac 715 is PI-controlled so that the detection temperature (signal Th4-5a) of the thermistor T4-5a reaches a predetermined target temperature, and the electric power supplied to the heat generation block HB5 is controlled.

In S206, the triac 716 is PI-controlled so that the detection temperature (signal Th4-6a) of the thermistor T4-6a reaches a predetermined target temperature, and the electric power supplied to the heat generation block HB6 is controlled.

In S207, the triac 717 is PI-controlled so that the detection temperature (signal Th4-7a) of the thermistor T4-7a reaches a predetermined target temperature, and the electric power supplied to the heat generation block HB7 is controlled.

In S208, it is determined whether or not the temperature rise of the non-passing portion of the heater 300 is equal to or less than a predetermined threshold temperature (allowable temperature) Tmax.

In S208, when the temperatures of the thermistors T3-4a, T4-4a, T3-3b, and T4-5b are equal to or lower than the threshold temperature Tmax, the process proceeds to S108, and control of S201 to S208 is performed until the end of print JOB is detected in S108. repeat.

(Example 3)
The heater 800 of FIG. 9 is an example in which the heat generating resistor 802 is arranged on the side of the fixing nip portion N and the thermistor group TG6 is arranged on the opposite side of the fixing nip portion N. The same symbols will be used for the same configuration as in the first embodiment, and the description thereof will be omitted.

FIG. 9A shows a cross-sectional view of the central portion (near the transport reference position X) of the heater 800. Only the conductive pattern is formed on the back surface layer 1, and the chip thermistor T6-2 is adhered from above. Reference numerals 810 and 811 are electrodes of the chip thermistor T6-2. The conductive pattern EG6 and the conductive pattern ET6-2 are connected to the chip thermistor T6-2 via the electrodes 810 and 811. By arranging the thermistor group TG6 on the opposite side of the fixing nip portion N like the heater 800, the flatness required for the sliding surface layer becomes unnecessary, and the thick tip thermistor T6-2 can be installed.

The thermistor group TG6 provided on the back surface layer 1 of the heater 800 includes three chip thermistors T6-1 to T6-3, a conductive pattern ET6-1 to ET6-3 for detecting the resistance value of the thermistor, and a common conductive pattern EG6. have.

Three heat generating blocks HB1 to HB3 are provided on the sliding surface layer 1 of the heater 800. The heat generation resistor 802 is divided into three parts 802 to 802-3, and power is supplied via the first conductor 801 and the second conductor 803 to 803-3 divided into three parts. It is being supplied. The second conductors 803-1 to 803-3 are connected to the electrodes E1 to E3, and the first conductor 801 is connected to the electrodes E8. By using the electrode E8 as a common electrode and providing switch elements such as triacs on the 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 slidability and insulating properties as a protective layer 808.

By the way, in the heater 800, in order to supply power to the heat generating blocks HB1 to HB3, it is necessary to wire the first conductor 801 and the second conductor 803 to both ends in the short side direction of the heater. Therefore, in particular, when the number of heat generating blocks increases, the area for wiring the first conductor 801 and the second conductor 803 increases, and the heater becomes large.

When the electrodes E2 to E6 are provided in the heat generating region as in the heater 300 described in the first embodiment and the heater 600 described in the second embodiment, it is necessary for wiring the first conductor 301 and the second conductor 303. Since a large area is not required, the number of heat generating blocks can be increased without increasing the size of the heater. In the configuration in which the electrodes E2 to E6 are provided in the heat generating region, it is necessary to provide the electrodes E2 to E6 on the opposite side of the fixing nip portion N in order to connect the electrical contacts C2 to C6. Therefore, it is effective to form the heat generating blocks (HB1 to HB7) on the opposite side of the fixing nip portion N and the thermistor groups (TG1, TG2, TG3, TG4) on the side of the fixing nip portion N.

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

(Example 4)
In Example 4 shown in FIG. 10, the shape of the heat generating resistor is different from that of the heaters of Example 1 and Example 2. The heat generating resistors 902a and 902b of the heater 900 shown in FIG. 10A are continuous (not divided) in the longitudinal direction.

FIG. 10A is a plan view of the back surface layer 1 of the heater 900. Since the conductor 303 is divided into seven in the longitudinal direction, the heating elements 902a and 902b have a configuration in which the temperature can be independently controlled in the regions of the heating blocks HB1 to HB7. Since the heater 900 does not divide the heating elements 902a and 902b, even in the divided gap region of the conductor 303, heat is continuously generated in the longitudinal direction, and there is no region where the amount of heat generated becomes 0 (zero). The heater can be heated more uniformly in the longitudinal direction.

In the heater 1000 shown in FIG. 10B, the heat generating resistors 1002a and 1002b are further divided into a plurality of heat generating resistors connected in parallel.

FIG. 10B is a plan view of the back surface layer 1 of the heater 1000. The heat generating resistor 1002a is divided into a plurality of parts, and is connected in parallel between the conductor 303 and the conductor 301a. Similarly, the heat generating resistor 1002b is divided into a plurality of parts, and is connected in parallel between the conductor 303 and the conductor 301a.

The divided heat generating resistors 1002a and 1002b are arranged so as to be inclined with respect to the longitudinal direction and the lateral direction of the heater 1000, and overlap in the longitudinal direction of the heater 1000. As a result, the influence of the gap between the plurality of divided heat generating resistors can be reduced, and the uniformity of the heat generation distribution in the longitudinal direction of the heater 1000 can be improved. Further, in the heater 1000, even in the gaps between the heat generating blocks, the divided heat generating resistors at the most end portions of the adjacent heat generating blocks overlap each other in the longitudinal direction, so that the heat generation distribution in the longitudinal direction of the heater 1000 Can be made more uniform. The heat-generating resistors at the ends of the adjacent heat-generating blocks are, for example, the heat-generating resistors at the right end of the heat-generating block HB1 and the heat-generating resistors at the left end of the heat-generating block HB2.

Further, the heat generation distribution of the heat generation resistors 1002a and 1002b can be performed by adjusting the width, length, interval, inclination, etc. of the divided heat generation resistors. By adopting the configuration of the heater 900 and the heater 1000, it is possible to suppress temperature unevenness in the gap between the plurality of heat generating blocks.

(Example 5)
FIG. 11 shows the current waveforms flowing through each heat generating block in the control circuit 400 shown in the first embodiment. FIG. 11A is a drive pattern of the triac 411 (a table of current waveforms flowing through the heat generation block HB4) set for each duty ratio of the electric power supplied to the heater 300. Similarly, FIG. 11B is a drive pattern of the triacs 421 to 414 (a table of current waveforms flowing through the heat generating blocks HB1 to HB3 and HB5 to HB7).

When the CPU 420 calculates the level (duty ratio) of the electric power supplied to the heater for each control cycle, the CPU 420 selects a waveform corresponding to the duty ratio for each heat generation block to be supplied. In the control method of this embodiment, the energization control pattern of each triac is set with the quarter wave as one control cycle, and the electric power supplied to the heater 300 is controlled.

Hereinafter, an example of the energization control pattern of the triac 411 when the duty ratio is 25% will be described. In the energization control pattern A of the triac 411 shown in FIG. 11 (A), the first half wave to the second half wave are controlled at a phase angle of 90 ° to supply 50% of the power, and the third half wave to the fourth half wave are turned off. doing. Therefore, 25% of the electric power is supplied to the heat generating block HB4 of the heater 300 on average. The energization control pattern A is an energization pattern in which phase control is performed for one half wave to two half waves.

Further, in the energization control pattern of the triacs 421 to 414 shown in FIG. 11B, the third half wave to the fourth half wave are controlled at a phase angle of 90 ° to supply 50% of the power, and one half wave to two and a half waves. The waves are off. Therefore, 25% of the electric power is supplied to the heat generating blocks HB1 to HB3 and HB5 to HB7 of the heater 300 on average. The energization control pattern B is an energization pattern that controls the phase in the third half wave to the fourth half wave.

Since the heat generation block HB4 of the heater 300 has a lower resistance value than the other heat generation blocks, the amount of fluctuation of the current during phase control is larger than that of the other heat generation blocks. Therefore, in this example, the timing at which the phase control current flows through the heat generation block HB4 (1 half wave to 2 half wave) and the timing at which the phase control current flows through the other heat generation blocks HB1 to HB3 and HB5 to HB7 (3 and a half waves). Waves to 4 half waves) are shifted. As a result, the fluctuation value of the phase control current flowing through the entire heater 300 can be suppressed. The same applies to duty ratios other than 25%.

As shown in FIG. 11, by synchronizing and controlling the control timings of the plurality of triacs (synchronous control of the plurality of triacs), the harmonic current of the image heating device 200 can be reduced in this example. FIG. 11 shows an example of synchronous control. For example, synchronous control of a plurality of triacs may be performed so as to reduce flicker.

The triacs 711 to 717 of the control circuit 700 can also be synchronously controlled by a plurality of triacs by the same method.

The merits of the synchronous control of the plurality of triacs are that the harmonic current and flicker can be reduced, and that even if the total resistance value of the heater 300 is set low, the harmonic current and flicker specifications can be satisfied. If the resistance value of the heater 300 can be set low, the maximum power that can be supplied from the AC power supply 401 to the heater 300 can be further increased.

The plurality of examples described above have been described using a center-referenced printer that transports the center of the recording material in the width direction in accordance 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 longitudinal direction of the heater is used as a transport reference position and one end in the width direction of the recording material is aligned with the transport reference position.

200 Image heating device 300 Heater 301 First conductor 302 Heat generation resistor 303 Second conductor 305 Substrate E1 to E7, E8-1, E8-2 Electrodes HB1 to HB7 Heat generation block

Claims (7)

The substrate, the first heat generating block formed on the substrate and generating heat by supplying electric power, and the position different from the position where the first heat generating block is formed in the longitudinal direction of the substrate are formed and the electric power is generated. A second heat generation block that generates heat by supplying electric power, and a third heat generation block that is formed at a position different from both the first heat generation block and the second heat generation block in the longitudinal direction and generates heat by supplying electric power. In the heater used for the image heating device having,
The first heat generation block is a heat generation block controlled by a first switch element for controlling electric power.
The second and third heat generation blocks are heat generation blocks controlled by a second switch element for controlling electric power.
The heater further includes a first temperature detection element provided at a position corresponding to the first heat generation block, a second temperature detection element provided at a position corresponding to the second heat generation block, and the above. A first conductive pattern electrically connected to the first temperature detecting element, a second conductive pattern electrically connected to the second temperature detecting element, and electrically connected to the first and second temperature detecting elements. A first detection element group having a first common conductive pattern connected to the
A third temperature detection element provided at a position corresponding to the third heat generation block and a temperature detection element provided at a position corresponding to the first heat generation block, wherein the first temperature detection element is provided in the longitudinal direction. A fourth temperature detection element provided at a position different from the position where the temperature detection element is provided, a third conductive pattern electrically connected to the third temperature detection element, and the fourth temperature detection element. A second detection element group having a fourth conductive pattern electrically connected to the third and fourth temperature detecting elements and a second common conductive pattern electrically connected to the third and fourth temperature detecting elements.
A heater characterized by having. The heater according to claim 1, wherein the first common conductive pattern and the second common conductive pattern are electrically connected to each other. The first to third heating blocks are respectively provided with the first conductor along the longitudinal direction and the first conductor at different positions in the lateral direction of the substrate. A second conductor provided along the direction, and a second conductor provided between the first conductor and the second conductor, via the first conductor and the second conductor. The heater according to claim 1 or 2, further comprising a heating element that generates heat by the electric power supplied to the heater. Claim 1 is characterized in that the first and second detection element groups are formed on a substrate surface opposite to the substrate surface on which the first and second heat generation blocks of the substrate are formed. The heater according to any one of 3 to 3. In an image heating device having a tubular film and a nip forming unit having a heater and contacting the inner surface of the film, and heating an image formed on a recording material by the heat of the heater through the film. ,
An image heating device according to any one of claims 1 to 4, wherein the heater is the heater according to any one of claims 1 to 4. The device further includes first and second relays provided in the power supply path from the power supply to the heater, a first protection circuit for latching the first relay to the OFF state, and the second relay. It has a second protection circuit that latches in the OFF state,
When the signal from any of the temperature detection elements in the first detection element group exceeds a predetermined value, the first protection circuit latches the first relay in the OFF state.
When the signal from any of the temperature detection elements in the second detection element group exceeds a predetermined value, the second protection circuit latches the second relay in the OFF state.
The image heating device according to claim 5. The image heating device according to claim 5 or 6 , further comprising a roller that forms a nip portion that sandwiches and conveys a recording material together with the heater via the film.

Images