Image heating device and heater used in image heating device

Abstract

The present disclosure relates to an image heating apparatus and a heater used in the image heating apparatus. In the image heating apparatus having a plurality of heating blocks independently controllable in a long side direction of the heater, the size of the heater can be suppressed from increasing, and the temperatures of the plurality of heating blocks can be detected. The heater has a first temperature sensor corresponding to a first heating block, a second temperature sensor corresponding to a second heating block, a first electric conductor electrically coupled to the first temperature sensor, a second electric conductor electrically coupled to the second temperature sensor, and a common electric conductor electrically coupled to the first temperature sensor and the second temperature sensor.

Description

[0001] This application is a divisional application of the Chinese invention patent application with the application date of August 12, 2016, application number 201680052256.4, and invention name “Image heating device and heater used in image heating device”. Technical Field

[0002] The present invention relates to an image heating device, such as a fuser installed in an image forming apparatus for electrophotographic recording (such as a copier and printer), or a gloss-imparting device that reheats a toner image fixed to a recording material to improve the gloss of the toner image. The present invention further relates to a heater used in the image heating device. Background Art

[0003] The image heating device includes a tubular film, a heater in contact with the inner surface of the film, and a roller that forms a nip portion with the heater through the film. When continuously printing on small sheets using an image forming apparatus having an image heating device, a phenomenon may occur in which the temperature of the area of ​​the nip portion where the paper does not pass through in the long direction gradually rises (temperature rise in the non-passing portion). Excessive temperature rise in the non-passing portion may damage components within the device. When printing on large paper when the temperature in the non-passing portion rises, thermal offset of the toner may occur in the area on the film corresponding to the non-passing portion of the small paper.

[0004] As one of the solutions for suppressing such a temperature rise in the non-paper-passing portion, a device including a plurality of long-side heating resistor groups (heating blocks) in a heater has been proposed, wherein the heating distribution of the heater is changed according to the size of the recording material (PLT1).

[0005] Citation List

[0006] Patent Literature

[0007] PTL1: Japanese Patent Publication No. 2014-59508 Summary of the Invention

[0008] In consideration of the occurrence of a malfunction in such a device, the device may be configured to monitor the temperature of each heating block. Even when one of the plurality of heating blocks is uncontrollable and abnormal heating occurs, power supply can be quickly stopped based on the result of the temperature monitoring of each heating block.

[0009] However, as the number of heating blocks increases, the number of temperature sensors each used to monitor the temperature also increases. Providing many temperature sensors in the area of ​​the substrate of the heater may increase the size of the heater.

[0010] Solution to the problem

[0011] One aspect of the present invention provides a heater for use in an image heating device, the heater including a substrate, a first heating block, a second heating block, a first temperature sensor, a second temperature sensor, a first conductive pattern, a second conductive pattern, and a common conductive pattern, wherein the first heating block is arranged on the substrate and is configured to generate heat from power supplied thereto, the second heating block is arranged at a position different from that of the first heating block in the long side direction of the substrate and is configured to individually control the first heating block, the first temperature sensor is arranged at a position corresponding to the first heating block, the second temperature sensor is arranged at a position corresponding to the second heating block, the first conductive pattern is electrically coupled to the first temperature sensor, the second conductive pattern is electrically coupled to the second temperature sensor, and the common conductive pattern is electrically coupled to the first temperature sensor and the second temperature sensor.

[0012] Another aspect of the present invention provides a heater that can be used in an image heating device, the heater including a substrate, a heating component, a temperature sensor, and an electrode in contact with an electrical contact for supplying power to the heating component, the heating component being arranged on one surface of the substrate and being configured to generate heat from the power supplied thereto, the temperature sensor being arranged on another surface on the opposite side of the one surface of the substrate and being configured to detect the temperature of the heater, wherein the electrode is placed in an area having the heating component on the one surface of the substrate in the long side direction of the heater.

[0013] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

[0014] Beneficial effects of the present invention

[0015] According to the present invention, it is possible to suppress an increase in the size of the heater. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a cross-sectional view of the image forming apparatus.

[0017] Figure 2 is a cross-sectional view of an image heating device.

[0018] Figure 3A The configuration of the heater according to the first exemplary embodiment is illustrated.

[0019] Figure 3B The configuration of the heater according to the first exemplary embodiment is illustrated.

[0020] Figure 3C The configuration of the heater according to the first exemplary embodiment is illustrated.

[0021] Figure 4A heater control circuit according to a first exemplary embodiment is illustrated.

[0022] Figure 5 is a heater control flow chart according to the first exemplary embodiment.

[0023] Figure 6A The configuration of a heater according to a second exemplary embodiment is illustrated.

[0024] Figure 6B The configuration of a heater according to a second exemplary embodiment is illustrated.

[0025] Figure 7 A heater control circuit according to a second exemplary embodiment is illustrated.

[0026] Figure 8 is a heater control flow chart according to the second exemplary embodiment.

[0027] Figure 9A Variations of the heater are described below.

[0028] Figure 9B Variations of the heater are described below.

[0029] Figure 10A Variations of the heater are described below.

[0030] Figure 10B Another modified example of the heater will be described below.

[0031] Figure 11A The energization control mode of the heater will be described with examples.

[0032] Figure 11B Another heater energization control mode will be described as an example. DETAILED DESCRIPTION

[0033] First embodiment

[0034] Figure 1is a sectional view of a laser printer (image forming apparatus) 100 that applies an electrophotographic recording technique. In response to the occurrence of a print signal, a scanner unit 21 emits laser light modulated based on image information so that a photosensitive member 19 that is electrostatically charged to a predetermined polarity by a charging roller 16 can be scanned. Thereby, an electrostatic latent image is formed on the photosensitive drum 19. A toner is supplied to the electrostatic latent image from a developing unit 17 so that a toner image according to the image information is formed on the photosensitive member 19. On the other hand, recording materials (recording paper) P stacked in a paper cassette 11 are fed one by one by a pick-up roller 12, and are conveyed toward a resistance roller 14 by a roller 13. In synchronization with the arrival of the toner image on the photosensitive member 19 at a transfer position formed by the photosensitive member 19 and a transfer roller 20, each recording material P is conveyed from the resistance roller 14 to the transfer position. During the passage of the recording material P through the transfer position, the toner image on the photosensitive member 19 is transferred to the recording material P. Thereafter, the recording material P is heated by an image heating apparatus (fixing apparatus) 200 so that the toner image is heated and fixed to the recording material P. The recording material P bearing the fixed toner image is output to a tray in an upper portion of the laser printer 100 by rollers 26 and 27. A cleaner 18 cleans the photosensitive member 19. A motor 30 drives the image heating apparatus 200 and the like. Electric power is supplied to the image heating apparatus 200 from a control circuit 400 connected to a commercial alternating current (AC) power source 401. The photosensitive member 19, the charging roller 16, the scanner unit 21, the developing unit 17, and the transfer roller 20 are components of an image forming unit configured to form an unfixed image on the recording material P. A cartridge 15 is a replaceable unit. The laser printer 100 further includes a light source 22, a polygon mirror 23, and a mirror 24.

[0035] The laser printer 100 according to this example embodiment supports a plurality of sizes of recording materials. Letter paper (about 216 mm x 279 mm) and Legal paper (about 216 mm x 356 mm) can be set in the paper cassette 11. In addition, A4 paper (210 mm x 297 mm), Executive paper (about 184 mm x 267 mm), JIS B5 paper (182 mm x 257 mm), and A5 paper (148 mm x 210 mm) can be set therein.

[0036] The printer in this embodiment is a laser printer that is basically configured to feed paper vertically (or can feed paper in a manner such that the long side of the paper can be parallel to the feeding direction). This configuration is also applicable to printers that feed paper horizontally. Letter paper and legal paper are the largest (widest) among the conventional recording materials supported by the device (based on the width of the recording material on the catalog) and have a width of approximately 216 mm. In the following description of this exemplary embodiment, recording material P having a paper width less than the maximum size supported by the device will be referred to as small paper.

[0037] Figure 2 : is a cross-sectional view of the image heating device 200. The image heating device 200 has a tubular film 202, a heater 300 and a pressure roller (pressing portion forming member) 208, the heater 300 is in contact with the inner surface of the film 202, and the pressure roller 208 forms a fixing pressing portion N together with the heater 300 through the film 202. The film 202 has a base layer made of a heat-resistant resin (such as polyimide) or a metal (such as stainless steel). The film 202 may have an elastic layer of heat-resistant rubber. The pressure roller 208 has a cored rod 209 made of iron, aluminum, etc. and an elastic layer 210 made of silicone rubber. The heater 300 is held by a holding member 201 of a heat-resistant resin (such as a liquid crystal polymer). The holding member 201 has a guiding function for guiding the rotation of the film 202. The pressure roller 208 receives power from the motor 30 to rotate in the following manner. Figure 2 The pressure roller 208 rotates in the direction indicated by the arrow shown. The rotation of the pressure roller 208 is followed by the rotation of the film 202. The recording material P carrying the unfixed toner image is compressed and conveyed by the fixing nip portion N to be heated and fixed. The apparatus 200 described above includes the tubular film 202 and the heater 300 in contact with the inner surface of the film 202. The image formed on the recording material is heated by the heater 300 through the film 202.

[0038] The heater 300 has a ceramic substrate 305 and a heating resistor (heat generating member) (see Figures 3A to 3C ), a heating resistor is provided on the substrate 305 for generating heat for supplying power. A surface protective layer 308 of glass for providing slidability to the film 202 is provided on the surface (first surface) of the substrate 305 close to the fixing nip portion N. A surface protective layer 307 of glass for insulating the heating resistor is provided on the opposite surface (second surface) of the plane close to the fixing nip portion N of the substrate 305. The second surface has an exposed electrode (representatively indicated by E4), and when an electrical contact (representatively indicated by C4) for feeding power touches the electrode, the heating resistor is electrically coupled to the AC power source 401. The details of the heater 300 will be described below.

[0039] The protection element 212 (such as a temperature switch and a temperature fuse) is configured to block the power supply to the heater 300 in response to abnormal heating of the heater 300. The protection element 212 may be close to the heater 300 or may be placed in a gap in the heater 300. The metal support 204 for applying a sprint pressure (not illustrated) to the holding member 201 plays a role in reinforcing the holding member 201 and the heater 300.

[0040] Figure 3A and 3B The configuration of the heater 300 according to the first exemplary embodiment is illustrated. Figure 3A The example shows Figure 3B 1 and 2. A cross-sectional view of the heater 300 in the vicinity of a transport reference position X on the recording material P is shown. Figure 3B 3 is a plan view of each layer of the heater 300. Figure 3C is a plan view of a holding member configured to hold the heater 300 .

[0041] The printer according to this embodiment is a center reference printer configured to convey a recording material by placing the center of the recording material in the width direction (orthogonal to the conveyance direction) at a conveyance reference position X.

[0042] Next, the details of the configuration of the heater 300 will be described. There are multiple heating blocks on the back surface layer 1 of the heater 300 (which is the heater surface on the opposite side of the heater surface in contact with the film 202), each of which has a group of first conductors 301, second conductors 303 and heating resistors (heating components) 302 in the long side direction of the heater 300. The heater 300 of this exemplary embodiment has a total of seven heating blocks HB1 to HB7. Assuming that one of the seven heating blocks is the first heating block and the other heating block is the second heating block, the heater 300 has the following configuration. That is, the heater 300 has a substrate and a first heating block arranged on the substrate, and the first heating block is used to generate heat by receiving power supply. The heater 300 further has a second heating block, which is arranged at a position different from the position of the first heating block in the long side direction of the substrate and is controlled independently of the first heating block. The independent control of the heating blocks will be described below.

[0043] Each heating block includes a first conductor 301 and a second conductor 303. The first conductor 301 is disposed along the longitudinal direction of the substrate, and the second conductor 303 is disposed along the longitudinal direction of the substrate at a position different from that of the first conductor 301 in the transverse direction of the substrate. Each heating block further includes a heating resistor 302 disposed between the first conductor 301 and the second conductor 303. The heating resistor 302 generates heat from the power supplied through the first conductor 301 and the second conductor 302.

[0044] The heating resistor 302 in the heating block can be divided into a heating resistor 302a and a heating resistor 302b at positions symmetrical to each other about the center of the substrate in the short-side direction of the heater 300. The first conductive body 301 can be divided into a conductive body 301a connected to the heating resistor 302a and a conductive body 301b connected to the heating resistor 302b. Because the heating resistors 302a and 302b are placed at positions symmetrical to each other about the center of the substrate, the substrate is less likely to be damaged even when the heater generates heat and thermal stress occurs in the substrate.

[0045] Because the heater 300 has seven heating blocks HB1 to HB7, the heating resistor 302a includes seven heating resistors 301a-1 to 302a-7. Similarly, the heating resistor 302b includes seven heating resistors 302b-1 to 302b-7. The second electrical conductor 303 includes seven electrical conductors 303-1 to 303-7. The heating resistors 302a-1 to 302a-7 are placed upstream in the direction of transport of the recording material P within the substrate 305, while the heating resistors 302b-1 to 302b-7 are placed downstream in the direction of transport of the recording material P within the substrate 305.

[0046] The back surface layer 2 of the heater 300 has an insulating surface protection layer 307 (glass in this exemplary embodiment) on it. The insulating surface protection layer 307 covers the heating resistor 302, the first electrical conductor 301, and the second electrical conductor 303. In this case, the surface protection layer 307 does not cover the electrodes E1 to E7 and E8-1 and E8-2. The electrodes E1 to E7, E8-1 and E8-2 are in contact with the electrical contacts C1 to C7 and C8-1 and C8-2 for feeding power. The electrodes E1 to E7 supply power to the heating blocks HB1 to HB7 through the second electrical conductors 303-1 to 303-7, respectively. The electrodes E8-1 and E8-2 feed power to the heating blocks HB1 to HB7 through the first electrical conductors 301a and 301b.

[0047] Since the resistance value of the electrical conductor is not equal to zero, the resistance has an influence on the heating distribution in the longitudinal direction of the heater 300. Therefore, the electrodes E8-1 and E8-2 are separated at both ends in the longitudinal direction of the heater 300 to prevent uneven heating distribution even when affected by the resistance of the first electrical conductors 301a and 301b and the second electrical conductors 303-1 to 303-7.

[0048] like Figure 2 As shown, the safety element 212 and the electrical contacts C1 to C7, C8-1 and C8-2 are placed between the support 204 and the retaining member 201. Figure 3C As shown, the retaining member 201 has holes HC1 to HC7, HC8-1, and HC8-2, 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 extend. The retaining member 201 further has a hole H212, through which the heat-sensitive portion of the protective element 212 extends. The electrical contacts C1 to C7, C8-1, and C8-2 are electrically coupled to the corresponding electrodes by spring push, welding, or other solutions. The protective element 212 is also pushed by the spring, and the heat-sensitive portion contacts the surface protective layer 307. The electrical contacts are connected to the control circuit 400 in the heater 300 via cables or conductive members (such as a thin metal plate provided between the support 204 and the retaining member 201), which will be described below.

[0049] Providing an electrode on the back surface of the heater 300 can eliminate the need for providing an area on the substrate 305 for wiring for electrically connecting the second conductors 303-1 to 303-7, thereby reducing the width in the short side direction of the substrate 305. Therefore, it is possible to prevent the size of the heater from increasing. Figure 3B As shown, the electrodes E2 to E6 are provided in the region having the heating resistor in the longitudinal direction of the substrate.

[0050] The heater 300 of this embodiment controls a plurality of heating blocks individually so that various heating profiles can be formed, which will be described below. For example, a heating profile according to the size of the recording material can be defined. In addition, the heating resistor 302 can be formed by a material having a PTC (positive temperature coefficient). Even when the end of the recording material does not match the boundary of the heating block, the use of a material having a PTC can also suppress the temperature rise of the non-paper portion.

[0051] The heater 300 has a plurality of thermistors (temperature sensors) T1-1 to T1-4 and T2-4 to T2-7 on the sliding surface layer 1 closer to the sliding surface (in contact with the membrane). These thermistors are configured to sense the temperature of the heating blocks HB1 to HB7. The thermistors can be made of a material with a large positive or negative TCR (temperature coefficient of resistance). According to this embodiment, the thermistors are formed by thinly printing a material with an NTC (negative temperature coefficient) on a substrate. One or more thermistors provided for each of the heating blocks HB1 to HB7 can sense the temperature of all the heating blocks.

[0052] Assuming that one of the thermistors T1-1 to T1-4 is a first temperature sensor and another of the thermistors T1-1 to T1-4 is a second temperature sensor, the heater 300 has the following configuration: that is, the heater 300 has a first temperature sensor at a position corresponding to the first heating block and a second temperature sensor at a position corresponding to the second heating block.

[0053] Thermistors T1-1 to T1-4 are electrically coupled to conductive patterns ET1-1 to ET1-4, respectively, on substrate 305. Assuming that the conductive pattern to be connected to the first temperature sensor among the conductive patterns ET1-1 to ET1-4 is the first conductive pattern, and the conductive pattern to be connected to the second temperature sensor is the second conductive pattern, heater 300 has the following configuration. That is, heater 300 has a first conductive pattern electrically coupled to the first temperature sensor and a second conductive pattern electrically coupled to the second temperature sensor. Heater 300 further has a common conductive pattern EG1 electrically coupled to the first and second temperature sensors. Hereinafter, a group of thermistors T1-1 to T1-4, conductive patterns ET1-1 to ET1-4, and common conductive pattern EG1 will be referred to as a thermistor group TG1.

[0054] The heater 300 further includes a thermistor group TG2 including thermistors T2-4 to T2-7, conductive patterns ET2-4 to ET2-7, and a common conductive pattern EG2. The thermistor groups TG1 and TG2 are disposed on a substrate surface of the substrate 305 opposite to the substrate surface having the first and second heating blocks.

[0055] According to this example, at least one corresponding thermistor is provided for each of the heating blocks HB1 to HB7. However, providing one corresponding thermistor for at least two heating blocks can also improve the reliability of the device. However, as in this embodiment, at least one corresponding thermistor may be provided for all heating blocks.

[0056] By treating the first temperature sensor and the second temperature sensor as a group using the common conductive patterns EG1 and EG2 as in this embodiment, the following effects can be provided. That is, compared to the case where two conductive patterns are connected to each of the thermistors T1-1 to T1-4 without using a common conductive pattern, the cost for the conductive patterns can be reduced, and the size of the heater can be prevented from increasing.

[0057] In order to obtain the sliding property of the film 202, the surface (sliding surface layer 2) of the substrate 305 near the fixing nip portion N is coated with an insulating surface protection layer 308 (glass in this embodiment). The surface protection layer 308 covers the thermistors T1-1 to T1-4 and T2-4 to T2-7, the conductive patterns ET1-1 to ET1-4 and ET2-4 to ET2-7, and the common conductive patterns EG1 and EG2. However, in order to obtain the connection with the electrical contacts, such as Figure 3B As shown, portions of the conductive patterns ET1 - 1 to ET1 - 4 and ET2 - 4 to ET2 - 7 and portions of the common conductive patterns EG1 and EG2 are exposed at both ends of the heater 300 .

[0058] Figure 4 4 is a circuit diagram of a control circuit 400 in the heater 300. A commercial AC power source 401 is connected to the laser printer 100. Power control of the heater 300 is performed by energizing / de-energizing triacs 411 to 414. The triacs 411 to 414 operate according to FUSER1 to FUSER4 signals from the CPU 420. Figure 4 The driving circuit for the bidirectional thyristors 411 to 414 is not illustrated.

[0059] from Figures 3A to 3C and Figure 4 It can be understood that 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, and Group 4: HB1 and HB7). The control circuit 400 in the heater 300 has a circuit configuration capable of controlling these four groups independently of each other. Triacs 411, 412, 413, and 414 can control Group 1, Group 2, Group 3, and Group 4, respectively.

[0060] The zero-crossing detection unit 421 is a circuit configured to detect zero-crossing of the AC power source 401, and outputs a ZEROX signal to the CPU 420. The ZEROX signal may be used as a reference signal for controlling the phases of the triacs 411 to 414, for example.

[0061] Next, a method for detecting the temperature of the heater 300 will be described. First, the thermistor group TG1 will be described. The CPU 420 receives signals (Th1-1 to Th1-4) obtained by dividing the voltage Vcc by the resistance values ​​of thermistors (T1-1 to T1-4) and the resistance values ​​of resistors (451 to 454). For example, the signal Th1-1 is a signal obtained by dividing the voltage Vcc by the resistance value of thermistor T1-1 and the resistance value of resistor 451. Because thermistor T1-1 has a resistance value according to temperature, when the temperature of the heating 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. Because the same processing is performed on the signals Th1-2 to Th1-4 corresponding to the other thermistors T1-2 to T1-4 in thermistor group TG1, any repeated description will be omitted.

[0062] Next, thermistor group TG2 will be described. In thermistor group TG2, like thermistor group TG1, the CPU 420 receives signals (Th2-4 to Th2-7) obtained by dividing the voltage Vcc by the resistance values ​​of thermistors (T2-4 to T2-7) and the resistance values ​​of resistors (464 to 467). Because the method for converting to temperature applied by the CPU 420 is the same as the method for converting to temperature applied to thermistor group TG1, any repeated description will be omitted.

[0063] Next, the power control for the heater 300 (temperature control for the heater) will be described. During the fixing process, the heating blocks HB1 to HB7 are controlled so that the temperature sensed by the thermistors (T1-1 to T1-4) in the thermistor group TG1 can be maintained at the set temperature (control target temperature). More specifically, the power supplied to group 1 (heating block HB4) is controlled by controlling the drive of the triac 411 so that the temperature sensed by thermistor T1-4 can be maintained at the set temperature. The power supplied to group 2 (heating blocks HB3 and HB5) is controlled by controlling the drive of the triac 412 so that the temperature sensed by thermistor T1-3 can be maintained at the set temperature. The power supplied to group 3 (heating blocks HB2 and HB6) is controlled by controlling the drive of the triac 413 so that the temperature sensed by thermistor T1-2 can be maintained at the set temperature. The power supplied to group 4 (heating blocks HB1 and HB7) is controlled by controlling the driving of the triac 414 so that the temperature sensed by thermistor T1-1 can be maintained at the set temperature. The thermistors in thermistor group TG1 are used to perform control for maintaining the heating blocks at a predetermined temperature.

[0064] The CPU 420 calculates the amount of power to be supplied by, for example, performing PI control based on the set temperature (control target temperature) of the heating block and the temperature sensed by the thermistors (T1-1 to T1-4) within the thermistor group TG1. In addition, the amount of power to be supplied is converted into a control time for a corresponding phase angle (phase control) or a wave number (wave number control), and the bidirectional thyristors 411 to 414 are controlled based on the control time. To fix plain paper of the largest size, the set temperature of each group in the apparatus of this embodiment is 250°C. To fix plain paper of a smaller size, the set temperature of group 1 is 250°C, and the set temperatures of the other groups are lower than 250°C. The set temperature of each group can be defined based on information such as the size, type, and surface properties of the recording material.

[0065] The relay 430 and the relay 440 are installed as a unit for shutting off power to the heater 300 when the temperature of the heater 300 excessively rises due to, for example, a malfunction in the device. Next, circuit operations of the relay 430 and the relay 440 will be described.

[0066] When the RLON signal output from CPU 420 becomes a high state, transistor 433 becomes a conducting state and energizes the secondary coil from the DC power supply (voltage Vcc) to relay 430. The primary contact of relay 430 becomes an open (ON) state. When the RLON signal becomes a low state, transistor 433 becomes an off state. The current fed from the power supply (voltage Vcc) to the secondary coil of relay 430 is blocked, and the primary contact of relay 430 becomes a closed (OFF) state. In addition, when the RLON signal becomes a high state, transistor 443 becomes a conducting state. The secondary coil from the power supply (voltage Vcc) to relay 440 is energized, and the primary contact of relay 440 becomes an open state. When the RLON signal becomes a low state, transistor 443 becomes an off state. The current fed from the power supply (voltage Vcc) to the secondary coil of relay 440 is blocked, and the primary contact of relay 440 becomes a closed state.

[0067] Next, the operation of the protection circuit utilizing relays 430 and 440 (or a hardware circuit not implemented by CPU 420) will be described. When the level of one of signals Th1-1 to Th1-4 exceeds a predetermined value set in comparison unit 431, comparison unit 431 activates latch unit 432, which latches the RLOFF1 signal to a low state. When the RLOFF1 signal is low, transistor 433 remains off even if CPU 420 turns the RLON signal high. Therefore, relay 430 can remain closed (or in a safe state). Latch unit 432 outputs the RLOFF1 signal in a non-latched mode, indicating an open state.

[0068] Furthermore, when the level of one of signals Th2-4 to Th2-7 exceeds a predetermined value set in comparison unit 441, comparison unit 441 operates latch unit 442, which latches the RLOFF2 signal to a low state. When the RLOFF2 signal is low, transistor 443 remains off even if CPU 420 turns the RLON signal high, allowing relay 440 to remain in a closed state (or safe state). Latch unit 442 outputs the RLOFF signal for an open state in a non-latched state. Both the predetermined value set in comparison unit 431 and the predetermined value set in comparison unit 441 are equivalent to 300°C.

[0069] Next, the protection operation of the circuit using the two thermistor groups TG1 and TG2 will be described. Figures 3A to 3C and Figure 4 As shown, each of the four groups (groups 1 to 4) is provided with one thermistor in thermistor group TG1 and one thermistor in thermistor group TG2. At least one thermistor is provided for each of the heating blocks HB1 to HB7. More specifically, for group 1 (HB4), thermistors T1-4 in thermistor group TG1 and thermistors T2-4 in thermistor group TG2 are placed accordingly. For groups 2 (HB3 and HB5), thermistors T1-3 in thermistor group TG1 and thermistors T2-5 in thermistor group TG2 are placed accordingly. For groups 3 (HB2 and HB6), thermistors T1-2 in thermistor group TG1 and thermistors T2-6 in thermistor group TG2 are placed accordingly. For group 4 (HB1 and HB7), thermistor T1-1 from thermistor group TG1 and thermistor T2-7 from thermistor group TG2 are placed accordingly. At least one of the eight thermistors is placed correspondingly for each of the heating blocks HB1 to HB7. This thermistor placement improves the reliability of the protection operation performed by the circuit in the event of a device failure. This will be described below.

[0070] For example, assume that one of thermistors T1-1 to T1-4 in thermistor group TG1 fails. Even when the group including the heating block corresponding to the failed thermistor is uncontrollable due to the failed thermistor, the group of heating blocks including the failed thermistor also includes the thermistor (one of T2-4 to T2-7) in thermistor group TG2. Therefore, the protection circuit operates by the thermistor in thermistor group TG2 (which stops the power supply).

[0071] Next, an advantage of the configuration in which at least one of the eight thermistors is placed corresponding to one of the heating blocks HB1 to HB7.

[0072] For example, assume a case where the thermistor T2-5 corresponding to group 2 is placed at a position corresponding to the heating block HB3 in the same group 2 as the heating block HB5, instead of a position corresponding to the heating block HB5. In this case, the thermistors T1-3 in the thermistor group TG1 and the thermistor T2-5 in the thermistor group TG2 are placed at positions corresponding to the heating block HB3, and no thermistor is placed at a position corresponding to the heating block HB5. In this configuration as well, the temperature of group 2 can be monitored. However, when the electrode E3 and the electrical contact C3 in this configuration have a contact failure, there is a possibility that the heating block HB3 can not be heated, while the heating block HB5 in the same group 2 as the heating block HB3 can be heated. Even when the heating block HB5 of group 2 abnormally generates heat, the two thermistors T1-3 and T2-5 corresponding to group 2 cannot monitor it, and the protection circuit does not work.

[0073] On the other hand, according to this embodiment, the thermistor T1-3 in the thermistor group TG1 is placed at a position corresponding to the heating block HB3, and the thermistor T2-5 in the thermistor group TG2 is placed at a position corresponding to the heating block HB5. Therefore, even when the electrode E3 and the electrical contact C3 have a contact failure and only the heating block HB5 in group 2 generates heat, the temperature can be monitored with the thermistor T2-5, and the protection circuit can be made to operate. As described above, because at least one of the eight thermistors is placed corresponding to one of the heating blocks HB1 to HB7, the reliability of the apparatus can be improved.

[0074] Figure 5 is a flowchart illustrating a control sequence of the control circuit 400 in the CPU 420. If a print request occurs in S100, the relays 430 and 440 are made to be in an on state in S101.

[0075] In S102, the triac 414 is subjected to PI control so that the temperature sensed by the thermistor T1-1 (signal Th1-1) can reach a control target temperature to control the power to be supplied to the heating blocks HB1 and HB7.

[0076] In S103, the triac 413 is subjected to PI control so that the temperature sensed by the thermistor T1-2 (signal Th1-2) can reach a control target temperature to control the power to be supplied to the heating blocks HB2 and HB6.

[0077] In S104, the triac 412 is subjected to PI control so that the temperature sensed by the thermistor T1-3 (signal Th1-3) can reach the control target temperature to control the power to be supplied to the heating blocks HB3 and HB5.

[0078] In S105, the triac 411 is subjected to PI control so that the temperature sensed by the thermistor T1-4 (signal Th1-4) can reach the control target temperature to control the power to be supplied to the heating block HB4.

[0079] As described above, the control target temperature of each heating block is set based on information about the size of a given recording material. In the apparatus according to this embodiment, the control target temperature of the heating block HB4 including the conveyance reference X is set to one temperature regardless of the size of the recording material, while the control target temperatures of the other heating blocks are changed based on the size of the recording material. As the size of the recording material decreases, the control target temperatures set for the heating blocks other than the heating block HB4 are lowered.

[0080] In S106, it is determined whether the temperature rise in the non-passing paper portion is equal to or lower than a predetermined threshold temperature (margin temperature) Tmax. According to this embodiment, Tmax is set to be higher than the control target temperature of 250°C of the heating block HB4, and is set to 280°C which is a temperature lower than the predetermined value of 300°C set for the comparison units 431 and 441. The positional relationship between the thermistors in the thermistor group TG1 and the reference X is different from the positional relationship between the thermistors in the thermistor group TG2 and the reference X. The thermistors in the thermistor group TG2 are placed on the outer side in the long side direction of the heater 300 with respect to the conveyance reference position X, compared to the thermistors in the thermistor group TG1. As shown in FIG. 6, the relationship can be easily understood by comparing the distance from the reference X to the thermistor T1-4 corresponding to the heating block HB4 and the distance from the reference X to the thermistor T2-4 corresponding to the heating block HB4. Because of this arrangement, the thermistors in the thermistor group TG2 can detect the temperature rise in the non-passing paper portion, if any, occurring within one heating block. Figure 3B

[0081] When it is determined in S106 that the temperatures sensed by the thermistors T2-4 to T2-7 are equal to or lower than the threshold temperature Tmax, the process moves to S108. The control in S102 to S106 is repeated until it is detected in S108 that the print job ends.

[0082] ​If it is determined in S106 that the temperatures of thermistors T2-4 to T2-7 are higher than threshold temperature Tmax, then in S107 the image forming process speed of image forming apparatus 100 is reduced, and the control target temperatures of thermistors T1-1 to T1-4 are lowered so that the fixing process can then be performed. The reduced process speed of image formation can improve the fixing performance even at a lower temperature than full-speed processing. Therefore, a temperature rise in the non-paper-passing portion can be suppressed.

[0083] The above processing is repeated, and if the end of the print job is detected in S108, the relay 430 and the relay 440 are turned off in S109. Then, the control sequence for image formation is ended in S110.

[0084] Second Exemplary Embodiment

[0085] Next, a second exemplary embodiment will be described. In the second exemplary embodiment, the heater 300 and the control circuit 400 for the heater according to the first exemplary embodiment are replaced with a heater 600 and a control circuit 700. Similar numbers refer to similar parts in the descriptions of the first and second exemplary embodiments, and any repeated descriptions will be omitted. The heater 600 according to the second exemplary embodiment differs from the heater 300 in the configuration of the sliding surface layer 1. The control circuit 700 has heating blocks HB1 to HB7, all of which are independently controlled.

[0086] Figure 6A and 6B The configuration of the heater 600 according to the second exemplary embodiment is illustrated. Since the configuration other than the sliding surface layer 1 is the same as that of the heater 300, any repeated description will be omitted.

[0087] The heater 600 has thermistors T3-1a to T3-4a, T3-1b to T3-3b, T4-4a to T4-7a, T4-5b to T4-7b, and T5 on the sliding surface layer 1. These thermistors are configured to detect the temperatures of the heating blocks HB1 to HB7. Since two or more thermistors are associated with all the heating blocks HB1 to HB7, even when one of the thermistors fails, the temperatures of all the heating blocks can be detected.

[0088] The thermistor group TG3 has seven thermistors T3 - 1 a to T3 - 4 a and T3 - 1 b to T3 - 3 b , conductive patterns ET3 - 1 a to ET3 - 4 a and ET3 - 3 b , ET3 - 12 b , and a common conductive pattern EG3 .

[0089] Furthermore, the thermistor group TG4 has seven thermistors T4 - 4 a to T4 - 7 a and thermistors T4 - 5 b to T4 - 7 b , conductive patterns ET4 - 4 a to ET4 - 7 a , ET4 - 5 b and ET4 - 67 b , and a common conductive pattern EG4 .

[0090] First, thermistor group TG3 will be described. Thermistors T3-1b and T3-2b are configured to detect the temperature of heating blocks HB1 and HB2, and these two thermistors are connected in parallel between conductive pattern ET3-12b and common conductive pattern EG3. Similarly, when the temperature of one of heating blocks HB1 and HB2 rises, the resistance value of one of thermistors T3-1b and T3-2b decreases significantly. Therefore, the temperature of both heating blocks HB1 and HB2 can be detected using a single conductive pattern ET3-12b configured to detect the resistance value of the thermistors. Therefore, compared to a case where the conductive patterns are connected and wired to thermistors T3-1b and T3-2b, the cost of wiring for forming the conductive patterns can be reduced. The width of the substrate 305 in the short side direction can be reduced. In addition, thermistors T4-6b and T4-7b can be connected in parallel.

[0091] The common conductive patterns EG3 and EG4 are connected on the substrate 305 through the conductive pattern EG34, for example Figure 7 Disconnection detection is shown. Performing such a disconnection detection can increase the safety level when a disconnection fault occurs.

[0092] Two thermistors T3 - 3 a and T3 - 3 b are provided for one heating block HB3 , and the conductive patterns ET3 - 3 a and ET3 - 3 b configured to detect resistance values ​​and the common conductive pattern EG3 provide a configuration that can detect temperature.

[0093] Within the range of the heating block HB3, the thermistor T3-3b placed at a position spaced apart from the conveyance reference position X is configured to detect the temperature of the edge, and the thermistor T3-3a placed at a position close to the conveyance reference position X is configured for temperature adjustment. A plurality of thermistors may be provided for one heating block as needed.

[0094] Since the configuration and operation of the thermistor group TG4 are the same as those of the thermistor group TG3 , any repeated description will be omitted.

[0095] Thermistor T5 is a single thermistor provided between the conductive patterns ET5 and EG5 for detecting a resistance value. A single thermistor may be combined with a thermistor group as needed.

[0096] Figure 7 is a circuit diagram of a control circuit 700 for heater 600 according to a second exemplary embodiment. Power control for heater 600 is performed by energizing / de-energizing triacs 711 to 717. Triacs 711 to 717 operate based on FUSER1 to FUSER7 signals from CPU 420. Control circuit 700 for heater 600 has a circuit configuration in which seven triacs 711 to 717 are used to independently control seven heating blocks HB1 to HB7.

[0097] Next, how to detect the temperature of the heater 600 will be described. The CPU 420 receives signals (Th3-1a to Th3-4a, Th3-3b, Th3-12b) obtained by dividing the voltage Vcc by the resistance values ​​of thermistors T3-1a to T3-4a, T3-1b, and T3-2b in thermistor group TG3 and the resistance values ​​of resistors 751 to 756. The CPU 420 further receives signals obtained by dividing the voltage Vcc by the resistance values ​​of thermistors T4-4a to T4-7a, T4-5b to T4-7b in thermistor group TG4 and the resistance values ​​of resistors 771 to 776. These signals are Figure 7 The CPU further receives a signal (Th5) obtained by dividing the voltage Vcc by the resistance value of thermistor T5 and the resistance value of resistor 761. The CPU 420 converts the received signals into temperatures based on their levels.

[0098] The CPU 420 calculates the power supply amount by executing PI control based on the set temperature (control target temperature) of the heating block and the temperature sensed by the thermistor, for example. The calculated power supply amount is converted into a control time for a corresponding phase angle (phase control) or wave number (wave number control), and triacs 711 to 717 are controlled based on the control time.

[0099] Next, a description will be given of the operation of the protection circuit using the relays 430 and 440. Based on the Th3-1a to Th3-4a signals of the thermistor group TG3 and the Th4-5b and Th4-67b signals of the thermistor group TG4, if one of the sensed temperatures exceeds a respectively set predetermined value, the comparison unit 431 causes the latch unit 432 to operate.

[0100] Furthermore, 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, the comparison unit 441 causes the latch unit 442 to operate if one of the sensed temperatures exceeds respectively set predetermined values.

[0101] Next, a description will be given of the disconnection detection circuit 780. The disconnection detection circuit 780 is a circuit that can be used to improve safety in the event that the common conductive patterns EG3 and EG4 are disconnected.

[0102] The circuit operation of disconnection detection circuit 780 will now be described. When common conductive patterns EG3 and EG4 are disconnected, resistors 781 and 782 pull up power supply voltage Vcc, causing disconnection detection signal ThSafe to go high. Resistors 781 and 782 are provided to account for malfunctions caused by resistor short circuits. When disconnection detection signal ThSafe goes high, latch units 432 and 442 are activated.

[0103] Next, the effects of disconnecting the detection circuit 780 and the conductive pattern EG34 will be described. First, a case will be described in which the common conductive pattern EG3 and the common conductive pattern EG4 are connected to GND, as in the configuration of the first exemplary embodiment, without both the conductive pattern EG34 and the disconnection detection circuit 780. In this case, when the common conductive pattern EG3 is disconnected, all thermistors in thermistor group TG3 are disabled. Consequently, the protection circuit configured to terminate power supply to the heating blocks HB1 to HB3 does not operate. Furthermore, when the common conductive pattern EG4 is disconnected, all thermistors in thermistor group TG4 are disabled. Consequently, the protection circuit configured to terminate power supply to the heating blocks HB5 to HB7 does not operate.

[0104] Next, a description will be given of a case where, although a conductive pattern EG34 connecting the common conductive patterns EG3 and EG4 is provided, the common conductive patterns EG3 and EG4 are connected to GND as in the configuration of the first exemplary embodiment, without disconnecting the detection circuit 780. In this case, due to the effect of the conductive pattern EG34, one of the common conductive patterns EG3 and EG4 is connected to GND via the conductive pattern EG34 even when the other is disconnected. Therefore, temperature detection can be performed by thermistor groups TG3 and TG4. However, the connector (not shown) configured to connect the conductive patterns (ET3-1a to ET3-4a and ET3-12b, ET3-3b and EG3) of the thermistor group TG3 and the control circuit 700 is disconnected, and all thermistors of the thermistor group TG3 are disabled. Therefore, the protection circuit that terminates the power supply to the heating blocks HB1 to HB3 does not work. Furthermore, the connector connecting the conductive patterns (ET4-4a to ET4-7a, ET4-67b, ET4-5b, and EG4) of thermistor group TG4 and the control circuit 700 is disconnected, disabling all thermistors of thermistor group TG4. Consequently, the protection circuit that terminates power to the heating blocks HB5 to HB7 does not operate.

[0105] On the other hand, the device of this embodiment has the conductive pattern EG34 and the disconnection detection circuit 780. Therefore, it is possible to detect both fault states where the common conductive patterns EG3 and EG4 are disconnected and where the connector connecting the thermistor groups TG3 and TG4 and the control circuit 700 is disconnected.

[0106] Figure 8 is a flowchart illustrating a control sequence on the control circuit 700 to be executed by the CPU 420. Similar numbers are in Figure 5 and Figure 8 1 and 2 refer to similar components, and any duplicate description will be omitted.

[0107] In S201 , the bidirectional thyristor 711 is PI-controlled so that the temperature sensed by the thermistor T3 - 1 a (signal Th3 - 1 a ) may reach a predetermined target temperature to control power to be supplied to the heating block HB1 .

[0108] In S202 , the bidirectional thyristor 712 is PI-controlled so that the temperature sensed by the thermistor T3 - 2 a (signal Th3 - 2 a ) may reach a predetermined target temperature to control power to be supplied to the heating block HB2 .

[0109] In S203 , the bidirectional thyristor 713 is PI-controlled so that the temperature sensed by the thermistor T3 - 3 a (signal Th3 - 3 a ) may reach a predetermined target temperature to control power to be supplied to the heating block HB3 .

[0110] In S204 , the bidirectional thyristor 714 is PI-controlled so that the temperature sensed by the thermistor T5 (signal Th5 ) may reach a predetermined target temperature to control the power to be supplied to the heating block HB4 .

[0111] In S205 , the bidirectional thyristor 715 is PI-controlled so that the temperature sensed by the thermistor T4 - 5 a (signal Th4 - 5 a ) may reach a predetermined target temperature to control power to be supplied to the heating block HB5 .

[0112] In S206 , the bidirectional thyristor 716 is PI-controlled so that the temperature sensed by the thermistor T4 - 6 a (signal Th4 - 6 a ) may reach a predetermined target temperature to control power to be supplied to the heating block HB6 .

[0113] In S207 , the bidirectional thyristor 717 is PI-controlled so that the temperature sensed by the thermistor T4 - 7 a (signal Th4 - 7 a ) may reach a predetermined target temperature to control the power to be supplied to the heating block HB7 .

[0114] In S208 , it is determined whether the temperature rise in the non-paper-passing portion is equal to or lower than a predetermined threshold temperature (tolerance temperature) Tmax.

[0115] When it is determined in S208 that the temperatures sensed by thermistors T3-4a, T4-4a, T3-3b, and T4-5b are equal to or lower than the threshold temperature Tmax, the process moves to S108. Then, the control in S201 to S208 is repeated until the end of the print job is detected in S108.

[0116] Third Exemplary Embodiment

[0117] Figure 9A and 9B The heater 800 has a heating resistor 802 near the fixing nip portion N and a thermistor group TG6 on the opposite side of the fixing nip portion N. Like numerals refer to like parts in the description of the first and third exemplary embodiments, and any description will be omitted.

[0118] Figure 9A 800 is a cross-sectional view of the central area (near the transmission reference position X) of the heater 800. The back surface layer 1 has only a conductive pattern, and a chip thermistor T6-2 is bonded thereto. The heater 800 further has electrodes 810 and 811 for the chip thermistor T6-2. The chip thermistor T6-2 is connected to the conductive pattern EG6 and the conductive pattern ET6-2 via the electrode 810 and the electrode 811. Placing the thermistor group TG6 on the opposite side of the fixing nip portion N as in the heater 800 eliminates the necessity of the flatness of its sliding surface layer, making it possible to install a thick chip thermistor T6-2.

[0119] The thermistor group TG6 provided in the back surface layer 1 of the heater 800 has three chip thermistors T6 - 1 to T6 - 3 , conductive patterns ET6 - 1 to ET6 - 3 configured to detect resistance values ​​of the thermistors, and a common conductive pattern EG6 .

[0120] The sliding surface layer 1 of the heater 800 has three heating blocks HB1 to HB3. The heating resistor 802 is divided into three parts 802-1 to 802-3 and receives power via a first conductor 801 and three 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. A switching element (such as a triac) is provided for each of the electrodes E1 to E3, wherein electrode E8 is provided as a common electrode so that the three heating blocks HB1 to HB3 can be controlled independently of each other. The sliding surface layer 2 of the heater 800 has a protective layer 808 of glass, which has both sliding and insulating properties.

[0121] In heater 800, first and second conductors 801 and 803 can be connected by wiring at both ends of the heater in the short-side direction to supply power to heating blocks HB1 to HB3. Due to this necessity, as the number of heating blocks increases, the area for wiring first and second conductors 801 and 803 may increase, thereby increasing the size of the heater.

[0122] The electrodes E2 to E6 can be arranged in the heating area as in the heater 300 according to the first exemplary embodiment and the heater 600 according to the second exemplary embodiment, so that the area required for wiring the first conductor 301 and the second conductor 303 is not required. Therefore, the size of the heater does not increase while the number of heating blocks can be increased. In a configuration with electrodes E2 to E6 in the heating area, it may be necessary to provide electrodes E2 to E6 on the opposite side of the fixing nip portion N for connecting the electrical contacts C2 to C6. To this end, heating blocks (HB1 to HB7) can be provided on the opposite side of the fixing nip portion N, and the thermistor group (TG1, TG2, TG3, and TG4) can be formed near the fixing nip portion N.

[0123] When a smaller number of heating blocks are provided, as in the heater 800 according to this embodiment, the thermistor group TG6 having a plurality of chip thermistors may be placed on the opposite side of the fixing nip portion N.

[0124] Fourth exemplary embodiment

[0125] Figure 10A and 10B The heater according to the fourth exemplary embodiment illustrated in FIG. 8 is different from the heaters according to the first and second exemplary embodiments in the shape of a heating resistor. Figure 10A The heating resistors 902 a and 902 b in the heater 900 are shown to be continuous (or not divided) in the long side direction.

[0126] Figure 10A : This is a plan view of the back surface layer 1 of heater 900. Because the conductor 303 is divided into seven sections in the longitudinal direction, the heating resistors 902a and 902b are independently temperature-controlled in the regions of heating blocks HB1 to HB7. Because the heating resistors 902a and 902b are not divided, heater 900 continuously generates heat in the longitudinal direction even in the gap regions where the conductor 303 is divided. Therefore, there are no regions where the heating value is equal to 0 (zero), and the heater can thus generate heat uniformly in the longitudinal direction.

[0127] Figure 10B The heater 1000 shown has heating resistors 1002a and 1002b that are further divided into a plurality of heating resistors connected in parallel.

[0128] Figure 10B 1 is a plan view of the back surface layer 1 of the heater 1000. The heating resistor 1002a is divided into a plurality of heating resistors connected in parallel between the connected conductor 303 and the conductor 301a. In addition, the heating resistor 1002b is divided into a plurality of heating resistors connected in parallel between the conductor 303 and the conductor 301a.

[0129] The heating resistors obtained by dividing the heating resistors 1002a and 1002b are inclined in the long and short directions of the heater 1000 and overlap with each other in the long direction of the heater 1000. This can reduce the influence of the gaps between the multiple divided heating resistors, thereby improving the uniformity of the heating distribution in the long direction of the heater 1000. In the heater 1000, because the divided heating resistors at the edges of adjacent heating blocks overlap with each other in the long direction, a more uniform heating distribution can be provided in the long direction of the heater 1000 even in the gaps between the heating blocks. The heating resistors at the edges of adjacent heating blocks can, for example, be the heating resistor at the right end of the heating block HB1 and the heating resistor at the left end of the heating block HB2.

[0130] Uniformity in heating distribution of the heating resistors 1002a and 1002b can be achieved by adjusting the width, length, interval, tilt, etc. of the divided heating resistors. The use of the configuration of the heater 900 or the heater 1000 can suppress temperature unevenness in the gaps between the plurality of heating blocks.

[0131] Fifth exemplary embodiment

[0132] Figure 11A and 11B The waveform of the current fed to the heating block in the control circuit 400 according to the first exemplary embodiment is illustrated. Figure 11AThe table illustrates the driving modes for the triac 411 (or the waveforms of the current to be fed to the heating block HB4), which are defined for each duty cycle of the power to be supplied to the heater 300. In addition, Figure 11B A table illustrating driving patterns for the triacs 412 to 414 (or waveforms of currents to be fed to the heating blocks HB1 to HB3 and HB5 to HB7 ).

[0133] The CPU 420 calculates the level of power (duty cycle) to be supplied to the heater in each control cycle, and then selects a waveform according to the duty cycle for each heating block to which the power is supplied. In the control method according to this exemplary embodiment, four half-waves are defined as one control cycle to set the power-on control mode for each triac, thereby controlling the power to be supplied to the heater 300.

[0134] An example of a energizing control pattern for the bidirectional thyristor 411 will be described, in which the duty ratio is equal to 25%. Figure 11A In the illustrated energization control mode A for triac 411, a 90° phase angle is used to control the supply of 50% power from the first half-wave to the second half-wave, and power is turned off from the third half-wave to the fourth half-wave. Therefore, an average of 25% power is supplied to heating block HB4 of heater 300. In energization control mode A, phase control is performed from the first half-wave to the second half-wave.

[0135] exist Figure 11B In the illustrated energization control pattern for triacs 412 to 414, the third and fourth half-waves are controlled with a 90° phase angle to supply 50% power, and the power is turned off during the first and second half-waves. Therefore, an average of 25% power is supplied to heating blocks HB1 to HB3 and HB5 to HB7 of heater 300. Energization control pattern B performs phase control during the third and fourth half-waves.

[0136] Because the resistance value of heating block HB4 of heater 300 is lower than that of the other heating blocks, the amount of current variation during phase control is greater than that of the other heating blocks. According to this embodiment, the period for feeding phase-controlled current to heating block HB4 (from the first half-wave to the second half-wave) is different from the period for feeding phase-controlled current to the other heating blocks HB1 to HB3 and HB5 to HB7 (from the third half-wave to the fourth half-wave). Therefore, fluctuations in the phase-controlled current fed to the entire heater 300 can be suppressed. This also applies to duty cycles other than 25%.

[0137] like Figure 11A and 11BAs shown, control cycles for a plurality of triacs may be synchronized for control (this is referred to as synchronous control on a plurality of triacs), so that harmonic currents in the image heating device 200 may be reduced. Figure 11A and 11B Exemplary synchronous control is illustrated and may be performed on multiple triacs to reduce flicker, for example.

[0138] The same method can be applied to the triacs 711 to 717 in the control circuit 700 to perform synchronous control on the plurality of triacs.

[0139] Synchronous control of multiple triacs can advantageously reduce harmonic currents and flicker, and can further satisfy standards for preventing harmonic currents and flicker even when the total resistance value of the heater 300 is set low. When a lower resistance value can be set for the heater 300, the maximum power that can be supplied to the heater 300 from the AC power source 401 can be increased.

[0140] In the exemplary embodiments described above, a center-reference printer is used in which a recording material is conveyed by placing the center of the recording material in the width direction at the conveyance reference position X. However, the present invention is also applicable to a one-side-reference printer in which one end in the long side direction of a heater is defined as the conveyance reference position and a recording material is conveyed by placing one end in the width direction of the recording material at the conveyance reference position.

[0141] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0142] This application claims the benefit of Japanese Patent Application No. 2015-179567, filed September 11, 2015, which is hereby incorporated by reference herein in its entirety.

[0143] Reference Symbol List

[0144] 200 Image Heating Equipment

[0145] 300 Heater

[0146] 301 First Conductor

[0147] 302 heating resistor

[0148] 303 Second Conductor

[0149] 305 substrate

[0150] E1 to E7, E8-1, E8-2 electrodes

[0151] HB1 to HB7 heating blocks

Claims

1. A heater for use in an image heating device, the heater comprising: substrate; a first heating block, the first heating block being disposed on the substrate and configured to generate heat by power supplied to the first heating block, the first heating block being controlled by a first switching element; a second heating block disposed at a position different from that of the first heating block in the longitudinal direction of the substrate and configured to generate heat by power supplied to the second heating block, the second heating block being controlled by a second switching element; a third heating block, the third heating block being provided at a position different from those of the first heating block and the second heating block in the long side direction of the substrate and at a position symmetrical to the first heating block with respect to the transfer reference position in the long side direction, and being configured to generate heat by power supplied to the third heating block, the third heating block being controlled by the first switching element; a fourth heating block, the fourth heating block being provided at a position different from those of the first, second, and third heating blocks in the longitudinal direction of the substrate and symmetrical to the second heating block with respect to the transfer reference position in the longitudinal direction, and being configured to generate heat by power supplied to the fourth heating block, the fourth heating block being controlled by the second switching element; a first temperature sensor, the first temperature sensor being disposed at a position corresponding to the first heating block; a second temperature sensor, the second temperature sensor being disposed at a position corresponding to the second heating block; a third temperature sensor, the third temperature sensor being arranged at a position corresponding to the third heating block; a fourth temperature sensor, the fourth temperature sensor being arranged at a position corresponding to the fourth heating block; a first conductive pattern electrically coupled to a first temperature sensor; a second conductive pattern electrically coupled to a second temperature sensor; a first common conductive pattern electrically coupled to the first temperature sensor and the second temperature sensor; a third conductive pattern, the third conductive pattern being electrically coupled to a third temperature sensor; a fourth conductive pattern electrically coupled to a fourth temperature sensor; as well as A second common conductive pattern is electrically coupled to the third temperature sensor and the fourth temperature sensor.

2. The heater according to claim 1, wherein Each of the first to fourth heating blocks has a first conductor, a second conductor, and a heat-generating component, wherein the first conductor is arranged along the long side direction, the second conductor is arranged along the long side direction at a position different from the position of the first conductor in the short side direction of the substrate, and the heat-generating component is arranged between the first conductor and the second conductor and is configured to generate heat by power supplied through the first conductor and the second conductor.

3. The heater according to claim 1, wherein First to fourth temperature sensors, first to fourth conductive patterns, first and second common conductive patterns are provided on a substrate surface opposite to the substrate surface having the first to fourth heating blocks.

4. The heater according to claim 1, wherein The heater has a first group including a first temperature sensor, a third temperature sensor, a first conductive pattern, a third conductive pattern and a first common conductive pattern, and a second group including a second temperature sensor, a fourth temperature sensor, a second conductive pattern, a fourth conductive pattern and a second common conductive pattern.

5. An image heating device for heating an image formed on a recording material, the image heating device comprising: tubular membrane; a heater disposed in the interior space of the membrane; a first switching element configured to control electric power; as well as a second switching element configured to control electric power; Wherein, the heater comprises: substrate; a first heating block, the first heating block being disposed on the substrate and configured to generate heat by power supplied to the first heating block, the first heating block being controlled by a first switching element; a second heating block provided at a position different from that of the first heating block in the longitudinal direction of the substrate and configured to generate heat by power supplied to the second heating block, the second heating block being controlled by a second switching element; a third heating block, the third heating block being provided at a position different from those of the first heating block and the second heating block in the long side direction of the substrate and at a position symmetrical to the first heating block with respect to the transfer reference position in the long side direction, and being configured to generate heat by power supplied to the third heating block, the third heating block being controlled by the first switching element; a fourth heating block, the fourth heating block being provided at a position different from those of the first, second, and third heating blocks in the longitudinal direction of the substrate and symmetrical to the second heating block with respect to the transfer reference position in the longitudinal direction, and being configured to generate heat by power supplied to the fourth heating block, the fourth heating block being controlled by the second switching element; a first temperature sensor, the first temperature sensor being disposed at a position corresponding to the first heating block; a second temperature sensor, the second temperature sensor being disposed at a position corresponding to the second heating block; a third temperature sensor, the third temperature sensor being arranged at a position corresponding to the third heating block; a fourth temperature sensor, the fourth temperature sensor being arranged at a position corresponding to the fourth heating block; a first conductive pattern electrically coupled to a first temperature sensor; a second conductive pattern electrically coupled to a second temperature sensor; a first common conductive pattern electrically coupled to the first temperature sensor and the second temperature sensor; a third conductive pattern, the third conductive pattern being electrically coupled to a third temperature sensor; a fourth conductive pattern electrically coupled to a fourth temperature sensor; and A second common conductive pattern is electrically coupled to the third temperature sensor and the fourth temperature sensor.

6. The image heating device according to claim 5, further comprising: A roller is configured to form a nip portion with the heater through the film to nip the recording material.

Images