JP2017054103A - Image heating device and heater used for image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce unevenness in temperature of a heater.SOLUTION: A heater of the present invention comprises: a substrate; a first conductor and a second conductor that are provided on the substrate along the longitudinal direction of the substrate; a heating element that is provided between the first conductor and second conductor and generates heat when supplied with a power through the first conductor and second conductor; and electrodes to which conductive members for supplying power are connected. The calorific value of areas corresponding to the positions at which the electrodes of the heating element are provided is set larger than the calorific value of the other areas.SELECTED DRAWING: Figure 3

Description

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

  As an image heating apparatus, there is an apparatus having a cylindrical film, a heater that contacts an inner surface of the film, and a roller that forms a nip portion together with the heater via the film. When small-size paper is continuously printed by an image forming apparatus equipped with this image heating device, a phenomenon (temperature increase of the non-sheet passing portion) occurs in which the temperature of the region where the paper does not pass in the longitudinal direction of the nip portion gradually increases. If the temperature of the non-sheet passing part becomes too high, the parts in the device will be damaged, or if printing on large size paper with the non-sheet passing part temperature rise, the non-sheet passing part of small size paper The toner may be offset to the film at a high temperature in a region corresponding to.

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

JP 2014-59508 A

  By the way, although the conductive member for supplying electric power is connected to a heater, it is possible that the temperature distribution of a heater becomes non-uniform | heterogenous by heat dissipation from a conductive member or the electrode to which this conductive member is connected.

  An object of the present invention is to provide a heater and an image heating apparatus that can prevent the temperature distribution from becoming non-uniform.

  In order to solve the above-mentioned problems, the present invention is directed to a substrate, a first conductor provided on the substrate along a longitudinal direction of the substrate, and the first conductor of the substrate being short of the substrate. A second conductor provided at a different position in the direction, and electric power provided between the first conductor and the second conductor and supplied via the first conductor and the second conductor In a heater used in an image heating apparatus having a heating element that generates heat and an electrode to which a conductive member for supplying electric power to the heating element is connected, corresponding to the position where the electrode of the heating element is provided The heat generation amount of the area to be set is set larger than the heat generation amount of the other areas.

  According to the present invention, it is possible to suppress the temperature distribution of the heater from becoming uneven.

Cross section of image forming apparatus Sectional drawing of the image heating apparatus of Example 1 Heater configuration diagram of Example 1 Heater control circuit diagram of Example 1 Control flowchart diagram of Embodiment 1 Heater configuration diagram of Example 2 Diagram showing thermistor layout in the image heating device

Example 1
FIG. 1 is a 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 scans the photoconductor 19 charged to a predetermined polarity by the charging roller 16. As a result, an electrostatic latent image is formed on the photoreceptor 19. Toner is supplied from the developing unit 17 to the electrostatic latent image, and a toner image corresponding to image information is formed on the photoreceptor 19. On the other hand, the recording paper (recording material) P loaded on the paper feeding cassette 11 is fed one by one by the pickup roller 12 and conveyed toward the registration roller 14 by the roller 13. Further, the recording paper P is conveyed from the registration roller 14 to the transfer position in accordance with 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 paper P in the process in which the recording paper P passes the transfer position. Thereafter, the recording paper P is heated by an image heating device (fixing device) 200, and the toner image is heated and fixed on the recording paper P. The recording sheet P carrying the fixed toner image is discharged to a tray above the laser printer 100 by rollers 26 and 27. Reference numeral 18 denotes a cleaner for cleaning the photoconductor 19, and 28 denotes a paper feed tray (manual feed tray) having a pair of recording paper regulating plates whose width can be adjusted according to the size of the recording paper P. The paper feed tray 28 is provided to accommodate recording paper P having a size other than the standard size. A pickup roller 29 feeds the recording paper P from the paper feed tray 28, and a motor 30 drives the image heating device 200 and the like. Power is supplied to the image heating apparatus 200 from a control circuit 400 connected to a commercial AC power supply 401. The photosensitive member 19, the charging roller 16, the scanner unit 21, the developing device 17, and the transfer roller 20 described above constitute an image forming unit that forms an unfixed image on the recording paper P.

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

  Further, from the paper feed tray 28, it is possible to feed and print indefinite form paper including a DL envelope (110 mm × 220 mm) and a COM10 envelope (about 105 mm × 241 mm). The laser printer 100 of this example is a laser printer that basically feeds paper vertically (conveys so that the long side is parallel to the conveyance direction). The recording paper P having the largest (largest) width among the standard recording paper P widths (widths of the recording paper on the catalog) supported by the apparatus is Letter paper and Legal paper. The width of is about 216 mm. In this embodiment, the recording paper P having a paper width smaller than the maximum size supported by the laser printer 100 is defined as a small size paper.

  FIG. 2 is a cross-sectional view of the image heating apparatus 200. The image heating apparatus 200 includes a cylindrical film 202, a heater 300 that contacts the inner surface of the film 202, and a pressure roller (nip part forming member) 208 that forms a fixing nip N together with the heater 300 via the film 202. Have. 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, an elastic layer such as heat resistant rubber may be provided on the surface layer of the film 202. The pressure roller 208 includes a cored bar 209 made of iron or aluminum and an elastic layer 210 made of silicone rubber or the like. The heater 300 is held by a holding member 201 made of heat resistant resin. The holding member 201 also has a guide function for guiding the rotation of the film 202. Reference numeral 204 denotes a metal stay for applying a spring pressure (not shown) to the holding member 201. The pressure roller 208 receives power from the motor 30 and rotates in the direction of the arrow. As the pressure roller 208 rotates, the film 202 is driven and rotated. The recording paper P carrying an unfixed toner image is heated and fixed while being nipped and conveyed by the fixing nip portion N.

  The heater 300 is heated by heating resistors 302a and 302b provided on a ceramic substrate 305 described later. Thermistors TH1, TH2, and TH3, which are examples of temperature detection elements, are in contact with the heating resistor surface side of the substrate 305 and the sheet passing area (sheet passing) of the laser printer 100. Similarly, a protection element 212 such as a thermo switch or a temperature fuse that is operated by abnormal heat generation of the heater 300 and cuts off the power supplied to the heater 300 is also in contact.

  FIG. 3A is a cross-sectional view of the heater 300 in the short direction. The heater 300 includes a conductor (second conductor) 303 provided on the substrate 305 along the longitudinal direction of the heater 300. Further, conductors 301 a and 301 b are provided on the substrate 305 along the longitudinal direction of the heater 300 at different positions in the lateral direction of the conductor 303 and the heater 300. The conductor (first conductor) 301a is disposed on the upstream side in the conveyance direction of the recording paper P, and the conductor 301b is disposed on the downstream side. Hereinafter, the term “conductor 301” is used when referring to both the conductor 301a and the conductor 301b.

  Furthermore, the heater 300 includes heating resistors (heating elements) 302 a and 302 b that are provided between the conductor 301 and the conductor 303 and generate heat by electric power supplied via the conductor 301 and the conductor 303. Have. The heating resistors 302a and 302b are heating materials having the same sheet resistance per unit length (sheet resistance). The heating resistor 302a is disposed on the upstream side in the conveyance direction of the recording paper P, and the heating resistor 302b is disposed on the downstream side. Hereinafter, when referring to both the heating resistor 302a and the heating resistor 302b, they are described as the heating resistor 302.

  When the heat generation distribution in the short direction of the heater 300 (the conveyance direction of the recording paper P) is asymmetric, the stress generated on the substrate 305 when the heater 300 generates heat increases. When the stress generated in the substrate 305 increases, the substrate 305 may be cracked. Therefore, the heating resistor 302 is separated into a heating resistor 302a disposed on the upstream side in the conveyance direction and a heating resistor 302b disposed on the downstream side so that the heat generation distribution in the short direction of the heater 300 is symmetric. I have to. The heater 300 may have a configuration in which the heating resistor 302 is not divided into upstream and downstream.

  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 heating resistor 302, the conductor 301, and the conductor 303. Further, the layer 1 on the sliding surface (the surface in contact with the film) of the heater 300 has a surface protective layer 308 made of a slidable glass or polyimide coating.

Next, a plan view of each layer of the heater 300 will be described with reference to FIG. The heater 300 includes a plurality of heat generating blocks in the longitudinal direction of the heater 300, each of which includes a set of a first conductor 301, a second conductor 303, a heating resistor 302, and an electrode described later. The heater 300 of this embodiment has a total of five heat generating blocks at the center and both ends in the longitudinal direction of the heater 300.
Each of the five heat generating blocks includes heat generating resistors 302 a-1 to 302 a-5 and heat generating resistors 302 b-1 to 302 b-5 that are symmetrically formed with respect to the center in the short direction of the heater 300. Hereinafter, when referring to both the heating resistors 302a-1 and 302b-1, they are referred to as a heating resistor 302-1 (or a heating block 302-1). The same applies to the heat generation blocks 302-2 to 302-5. The conductor 303 is also divided into five conductors 303-1 to 303-5. In this embodiment, the recording paper P is transported in the short direction of the heater 300 around the transport reference position X.

  Therefore, the division position is divided symmetrically at a position corresponding to the paper size with the conveyance reference position X as the central axis. That is, the heat generating blocks 302-1 and 302-5 are arranged symmetrically with respect to the reference position X, and the heat generating blocks 302-2 and 302-4 are arranged symmetrically with respect to the reference position X. In the apparatus of this example, the reference position X is also the center of the heat generation area (all areas from the heat generation block 302-1 to the heat generation block 302-5) in the heater longitudinal direction. In this embodiment, when fixing the image formed on the DL envelope or the COM10 envelope, the heat generating block 302-3 is caused to generate heat. When fixing an image formed for A5 paper, the heat generating blocks 302-2 to 302-4 are heated. When fixing an image formed for Letter paper, Legal paper, or A4 paper, the heat generating blocks 302-1 to 302-5 are heated. Note that the number of divisions and division positions are not limited to five as in this embodiment.

  The electrodes E1 to E5 are electrodes for supplying power to the heat generating blocks 302-1 to 302-5 via the conductors 303-1 to 303-5, respectively. The electrodes E8-1 and E8-2 are electrodes having different polarities from the electrodes E1 to E5. These electrodes are connected to electric contacts for power supply (not shown) (for example, conductive members such as cables). When a voltage is applied between the conductor 301 and the conductor 303, a current flows through the heating resistor along the paper transport direction.

  The surface protective layer 307 which is the back surface layer 2 of the heater 300 is formed except for the portions of the electrodes E1 to E5, E8-1, and E8-2, and an electrical contact is connected to each electrode from the back surface side of the heater 300. It has a possible configuration. Each electrical contact is electrically connected to each electrode by a technique such as biasing with a spring or welding. Each electrical contact is connected to a control circuit 400 of the heater 300 described later via a conductive material such as a cable or a thin metal plate provided between the stay 204 and the holding member 201.

  Here, the characteristics of the heat generation block 302 will be described. The electrodes E2 to E4 are arranged in the region of the heat generation block 302 in the heater longitudinal direction and overlap the heat generation region in the heater longitudinal direction. Therefore, the heat of the heat generating block 302 is easily radiated through the electrodes E2 to E4. Therefore, the periphery of the electrodes E2 to E4 is easily affected by heat dissipation. Therefore, in this embodiment, the amount of heat generated in the heat generating region overlapping with the electrodes E2 to E4 is increased. Specifically, as shown in FIG. 3B, the width W2 of the region where the electrodes overlap is made narrower than the width W1 of the heating resistor in the region where the electrodes do not overlap, in the short direction of the heater. ing. As a result, the amount of heat generated in the region of width W2 is made larger than that of the region of width W1. In the present embodiment, the width W2 is configured to be 10% narrower than the width W1 so that heat dissipation and heat generation are balanced.

  In addition, you may adjust the emitted-heat amount according to factors, such as the thickness of an electrode, the material of an electrode, and the heat radiation from the electrical contact connected to an electrode. For example, a heat generating block having a large amount of current may be configured to have a contact configuration that can withstand a large current. In this case, the heat dissipation amount is larger than that of a contact configuration having a small current. The method of adjusting the heat generation amount is not limited to the width adjustment in the short direction of the heat generation resistor, and the heat generation amount may be adjusted by the thickness or material of the heat generation resistor.

  Thus, by intentionally increasing the heat generation of the heating resistor in the portion corresponding to the electrode, the temperature difference between the portion overlapping with each electrode and the portion not overlapping in the same heat generation block can be reduced.

  As shown in FIG. 3C, the holding member 201 of the heater 300 includes thermistors (temperature detection elements) TH1, TH2, TH3 and a protection element 212, and electrical contacts of electrodes E1 to E5, E8-1 and E8-2. A hole is provided for this purpose. Between the stay 204 and the holding member 201, the thermistors (temperature detection elements) TH1, TH2, and TH3, the protection element 212, and the electrical contacts that contact the electrodes E1 to E5, E8-1, and E8-2 are provided. is set up. In this embodiment, the thermistor TH1 is at a position for detecting the temperature of the heat generating block 302-3, and the thermistor TH2 is disposed at a position for detecting the temperature of the heat generating block 302-2. The thermistor TH3 is at a position for detecting the temperature of the heat generating block 302-5.

  FIG. 4 is a circuit diagram of the control circuit 400 according to the first embodiment. Reference numeral 401 denotes a commercial AC power source connected to the laser printer 100. The AC power supply 401 is connected to the electrodes E8-1 and E8-2 of the heater 300 via the relay 450 and the protection element 212. The electrodes E1 to E5 are connected to triacs 416, 426, and 436 which are driving means (driving elements). By controlling the triacs 416, 426, and 436, the heat generation of the heating resistor 302 is controlled. The electrode E3 is connected to the triac 416. By controlling the triac 416, the heat generation of the heat generation block 302-3 is controlled. The electrodes E2 and E4 arranged symmetrically with respect to the conveyance reference X, which is the reference of the position of the recording paper P when conveying the recording paper P, are connected to a triac 426 (first drive element). By controlling the triac 426, the heat generation of the heat generation blocks 302-2 (second heat generation block) and 302-4 (third heat generation block) is controlled. The heat generation blocks 302-2 and 302-4 are a heat generation block group driven by one triac 426. Similarly, the electrodes E1 and E5 arranged symmetrically with respect to the transport reference X are connected to a triac 436 (second drive element). By controlling the triac 436, the heat generation of the heat generation blocks 302-1 (first heat generation block) and 302-5 (fourth heat generation block) is controlled. The heat generation blocks 302-1 and 302-5 are a heat generation block group driven by one triac 436.

  Here, the arrangement of the thermistor (temperature detection element) will be described. In the heater having a plurality of heat generating blocks in the longitudinal direction, it is preferable to directly monitor the temperature of each heat generating block in order to monitor abnormal heat generation of the heater. For this purpose, it is necessary to arrange a thermistor as a temperature detecting element in each heat generating block.

  However, in order to dispose the thermistor (thermistor unit), not only the thermistor but also a space for disposing a member for supporting the thermistor, a spring for biasing the thermistor toward the heater, a cable connected to the thermistor, etc. . If the thermistors are arranged for all five heat generating blocks, the space required for arranging these members increases. Since the space surrounded by the stay 204 and the holding member 201 is limited, it is difficult to arrange five thermistor units. As described above, when the heat generating block is subdivided, there is a merit that it is possible to deal with more paper sizes, but there is a problem that it is difficult to secure a space for arranging the thermistor.

  FIG. 7 is a side view showing the holding member 201, the stay 204, and the space between them, and is a diagram for explaining the thermistor arrangement and the cable wiring direction. The holding member 201 that holds the heater is provided with shafts 201-1, 201-2, and 201-3 that hold the thermistors TH1 to TH3. The thermistors TH1 to TH3 are provided with holes TH1-a, TH2-a, and TH3-a into which the shafts 201-1, 201-2, and 201-3 are inserted, respectively. The positions of the thermistors TH1 to TH3 are determined by the shafts 201-1, 201-2 and 201-3 and the holes TH1-a, TH2-a and TH3-a. The thermistors TH1 to TH3 are urged toward the heater 300 by a spring (not shown). TH1-b, TH2-b, and TH3-b are cables connected to the thermistors TH1 to TH3. 201h1 to 201h3 are holes provided in the holding member 201 for arranging the thermistors TH1 to TH3. In addition to the hole for inserting the thermistor, the holding member 201 has a hole for electrical contact of the protective element 212 and the electrodes E1 to E5, E8-1, and E8-2 as shown in FIG. In FIG. 7, these holes and elements are omitted.

  As described above, the heat generation blocks 302-2 and 302-4 forming the heat generation block group are driven by the triac 426. When a failure occurs such that the triac 426 does not operate normally and power is continuously supplied to the heater, both the heat generating blocks 302-2 and 302-4 continue to generate heat. That is, the heat generating blocks 302-2 and 302-4 always operate in synchronization. Therefore, if the thermistor is arranged only in any one of these, the temperature of both the heat generating blocks 302-2 and 302-4 can be substantially monitored by this thermistor. Similarly, the thermistors may be arranged in any one of the heat generating blocks 302-1 and 302-5 forming the heat generating block group.

  Therefore, as shown in FIG. 3C, the fixing device of this example has a heat generation block group (here, the first heat generation block) including heat generation blocks 302-2 (second heat generation block) and 302-4 (third heat generation block). The thermistor TH2 (first temperature detection element) corresponding to the first heat generation block group) is disposed in the heat generation block 302-2 (second heat generation block). Further, the thermistor TH3 (second heat generation block) corresponding to the heat generation block group (herein referred to as the second heat generation block group) having the heat generation blocks 302-1 (first heat generation block) and 302-5 (fourth heat generation block). Are arranged in the heat generation block 302-5 (fourth heat generation block). The thermistor is not provided in the heat generating block 302-1 (first heat generating block) and the heat generating block 302-4 (third heat generating block).

  The first heat generation block group and the second heat generation block group are in a relationship of heat generation block groups adjacent to each other. In the apparatus of this example, the thermistors are arranged so that the thermistors arranged in the heat generating block groups adjacent to each other are not arranged in the two heat generating blocks in the adjacent positional relationship. Specifically, the heat generation block adjacent to the heat generation block 302-2 (second heat generation block) in which the thermistor TH2, which is the thermistor of the first heat generation block group, is disposed excluding the heat generation block 302-3. Block 302-1 (first heat generation block). The heat generation block 302-1 (first heat generation block) is a heat generation block of the second heat generation block group, but the thermistor TH3 of the second heat generation block group is the heat generation block 302-1 (first heat generation block). The heat generation block 302-2 (second heat generation block) is not adjacent to the heat generation block 302-5 (fourth heat generation block). With this configuration, it is possible to prevent a plurality of thermistors from being concentrated at one place, and to secure a space for arranging the thermistors. Moreover, since the several hole (201h1-201h3) provided in the holding member 201 for arrange | positioning a several thermistor does not concentrate on one place, the rigidity fall of the holding member 201 can be suppressed.

  Further, as shown in FIG. 7, the cables connected to the thermistors TH2 and TH3 are respectively directed outward from one end e1 and the other end e2 of the internal space surrounded by the stay 204 and the holding member 201. Wiring. Specifically, the cable TH2-b of the thermistor TH2 is drawn out of the internal space from the end e1, and the cable TH3-b of the thermistor TH3 is pulled out of the internal space from the end e2 opposite to the end e1. Has been drawn to. As described above, since the cable is divided into the end portions e1 and e2, the internal space needs to be unnecessarily wide as compared with the configuration in which all the cables of all the thermistors are pulled out from only one end portion. Absent. For this reason, the enlargement of the apparatus can be suppressed. Note that the end of the thermistor TH1 from which the cable TH1-b is pulled out may be either e1 or e2.

  As described above, the device of the present embodiment in which the device for reducing the number of thermistors, the device for arranging the thermistors, and the device for pulling out the cable is more effective when the number of divided heat generating blocks is increased. .

  Next, the operation of the triac 416 will be described. Resistors 413 and 417 are bias resistors for driving the triac 416, and the phototriac coupler 415 is a device for securing a creepage distance between the primary and secondary. Then, the triac 416 is turned on by energizing the light emitting diode of the phototriac coupler 415. The resistor 418 is a resistor for limiting the current flowing from the power supply voltage Vcc to the light emitting diode of the phototriac coupler 415. Then, the phototriac coupler 415 is turned on / off by the transistor 419. The transistor 419 operates in accordance with the FUSER1 signal from the CPU 420. Since the circuit operation of the triacs 426 and 436 is the same as that of the triac 416, the description is omitted.

  The relay 450 is used as a power cut-off means for cutting off the power supply to the heater 300 by the outputs from the thermistors TH1, TH2, and TH3 when the heater 300 abnormally generates heat due to a failure or the like. When the RLON 440 signal output from the CPU 420 is in a high state, the transistor 453 is turned on, and the secondary coil of the relay 450 is energized from the power supply voltage Vcc2, and the primary contact of the relay 450 is turned on. When the RLON 440 signal is in the low state, the transistor 453 is turned off, the current flowing from the power supply voltage Vcc2 to the secondary coil of the relay 450 is cut off, and the primary contact of the relay 450 is cut off.

  Next, the operation of the protection circuit 455 using the relay 450 will be described. When any one of the detected temperatures by the thermistors TH1, TH2, and TH3 exceeds a preset predetermined value, the comparison unit 451 operates the latch unit 452 to latch the RLOFF signal in the low state. When the RLOFF signal is set to the low state, even if the CPU 420 sets the RLON440 signal to the high state, the transistor 453 is maintained in the OFF state, so that the relay 450 is maintained in the cutoff state. When the detected temperatures by the thermistors TH1, TH2, and TH3 do not exceed the set predetermined values, the RLOFF signal of the latch unit 452 is in an open state. For this reason, when the CPU 420 sets the RLON 440 signal to the high state, the relay 450 is in the energized state, and power can be supplied to the heater 300.

  The zero cross detection unit 430 is a circuit that detects a zero cross of the AC power supply 401 and outputs a ZEROX signal to the CPU 420. The ZEROX signal is used for controlling the heater 300.

  Next, a temperature control method for the heater 300 will be described. The temperature of the heater 300 is detected by the thermistor TH1 and input to the CPU 420 as a TH1 signal. The thermistors TH2 and TH3 are also detected by the CPU 420 in the same manner. In the internal processing of the CPU (control unit) 420, the power to be supplied is calculated by PI control, for example, based on the detected temperature of the thermistor TH1 and the set temperature of the heater 300. Furthermore, it is converted into a control level of a phase angle (phase control) and a wave number (wave number control) corresponding to the supplied power, and the triacs 416 and 436 are controlled according to the control conditions. In this embodiment, the temperature of the heater 300 is controlled based on the heater temperature detected by the thermistor TH1. The temperature of the film 202 may be detected by a thermistor or a thermopile, and the temperature control of the heater 300 may be performed based on this detected temperature.

  FIG. 5 is a flowchart for explaining a control sequence of the image heating apparatus 200 by the CPU 420. When a print request is generated in S501, the relay 450 is turned on in S502. Subsequently, in S503-1, it is determined whether the width of the recording material is 157 mm or more. In the laser printer 100 according to the present embodiment, the process proceeds to S504 in the case of Letter paper, Legal paper, A4 paper, and indeterminate paper having a width of 220 mm or more fed from the paper feed tray 28. Then, the energization ratio of the triacs 416, 426, and 436 is set to 1: 1: 1.

  If the width of the recording material is smaller than 157 mm, the process proceeds to S503-2, and it is determined whether the width of the recording material is 115 mm or more. In the present embodiment, the process proceeds to S505 when it corresponds to A5 paper. Then, the energization ratio of the triacs 416, 426, and 436 is set to 1: 1: 0.

  Further, when the width of the recording material is smaller than 115 mm, it corresponds to a DL envelope, a COM10 envelope, etc., and the process proceeds to S506. Then, the energization ratio of the triacs 416, 426, and 436 is set to 1: 0: 0.

  The recording material width determination method in S503-1, S503-2 includes a method using a paper width sensor provided in the paper feed cassette 11 or the paper feed tray 28, a flag provided on the recording material P conveyance path, and the like. Any method such as a method using a sensor may be used. Other methods include a method based on the width information of the recording material P set by the user, a method based on image information for forming an image on the recording material P, and the like.

  In step S507, using the set energization ratio, the image forming process speed is set to full speed, and the fixing process is performed while controlling the temperature so that the temperature detected by the thermistor TH1 is maintained at the target set temperature of 200 ° C.

  In S508, it is determined whether or not the maximum temperature TH2Max of the thermistor TH2 and the maximum temperature TH3Max of the thermistor TH3 set in the CPU 420 are exceeded. If it is detected based on the thermistor signals TH2 to TH3 that the temperature rise at the non-sheet passing portion has deteriorated and the temperature at the end of the heat generating area has exceeded a predetermined upper limit value, the process proceeds to S510. Then, the image forming process speed is set to a half speed, and the fixing process is performed while controlling the temperature so that the temperature detected by the thermistor TH1 is maintained at the target set temperature 170 ° C. The fixing process is continued in the state of S510 until the end of the print job is detected in S511. When the image forming process speed is set to a half speed, the fixing property can be obtained even at a lower temperature than the full speed, so that the fixing target temperature can be reduced and the temperature of the non-sheet passing portion can be suppressed. If the temperature of each thermistor does not exceed the maximum temperature in S508, the process proceeds to S509. In S509, the process proceeds to S507 until the print job is completed, and the fixing process is continued.

  The above processing is repeated, and when the end of the print job is detected in S509 and S511, the relay 440 is turned off in S512, and the image formation control sequence is ended in S513.

  As described above, the heat generation amount of the heating resistor corresponding to the region where the electrode portions in the heating block overlap is set higher than that of the other heating resistor portions in the same heating block. Thereby, the influence of the heat radiation at the electrode part can be reduced, and a more uniform temperature distribution can be formed in the heater longitudinal direction.

(Example 2)
In the present embodiment, a heater 600 that considers the arrangement of electrodes in the heat generation region will be described. About the same structure as Example 1, description is abbreviate | omitted using the same symbol.

  FIG. 6 shows a heater 600 in this embodiment. As shown in FIG. 6A, the electrode E3 is positioned in relation to the lengths L1 and L2 with respect to the electrode E8-1 and the electrode E8-2, respectively. The lengths L1 and L2 are not necessarily set to the same length, and different lengths may be set depending on the arrangement of the thermistor and the protection element 212 or the like. In the heater 600, length L1> length L2.

  A current path from the electrode E3 to the electrode E8-1 and the electrode E8-2 will be described with reference to FIG. Here, the heat generation block 602-3 in FIG. 6A is described by being divided into four areas centering on the electrode E3. That is, the conductor 601 illustrated in FIG. 6A is divided into four areas A5a, A5b, A6a, and A6b for convenience as illustrated in FIG. 6B. The heating resistor of the heating block 602-3 is divided into areas A1a, A1b, A2a, and A2b, and the conductor 603-3 is divided into areas A3a, A3b, A4a, and A4b. Current paths are formed in four directions from the electrode E3 toward the electrodes E8-1 and E8-2. The current path connecting the electrodes E3 and E8-1 includes resistance components of the conductor areas A3a and A3b, the heating resistor areas A1a and A1b, and the conductor areas A5a and A5b. On the other hand, the current path connecting the electrode E3 and the electrode E8-2 includes resistance components of the conductor areas A4a and A4b, the heating resistor areas A2a and A2b, and the conductor areas A6a and A6b.

  FIG. 6C shows an equivalent circuit of the heater 600. In this embodiment, since the relationship of length L1> length L2 is established, the resistance value of the conductor is higher in the current path connecting E3 and E8-1 than in the current path connecting E3 and E8-2. . This difference in resistance value causes a difference in voltage drop, resulting in a difference in heat generation between the areas A1a and A1b and the areas A2a and A2b, and the temperatures of the areas A1a and A1b are lower than those in the areas A2a and A2b.

  Therefore, the areas A1a and A1b on the current path from E3 to E8-1 are set so that the amount of heat generated is larger than the areas A2a and A2b. More specifically, the width W3 of the heating resistors in the heater short direction in the areas A1a and A1b is made shorter than the width W1 of the heating resistors in the areas A2a and A2b. The shorter the width of the heating resistor in the heater short direction, the greater the amount of heat generated.

  On the other hand, the magnitude relationship between the heat generation amount of the heat generation block 602-2 and the heat generation amount of the heat generation block 602-4 is that the electrodes E2 and E4 are located at the target position with respect to the conveyance reference (center in the longitudinal direction of the heater) X. And W3 without the difference. The magnitude relationship between the heat generation amount of the heat generation block 602-1 and the heat generation amount of the heat generation block 602-5 is the same without providing a difference such as the widths W1 and W3. Note that the width W4 of the high heat generation region corresponding to the electrode E3 is narrower than the width W3.

  As described above, in the configuration in which the resistance value of the conductor on the current path is biased due to the position of the electrode E3, the heating value imbalance is adjusted by providing a difference in the resistance value of the heating resistor. do it. As a result, a heater that generates heat more uniformly without being affected by the difference in voltage drop can be provided.

300, 600 Heater 302, 602 Heating resistor TH1, TH2, TH3 Temperature detection element

Claims (10)

A substrate,
A first conductor provided on the substrate along a longitudinal direction of the substrate;
A second conductor provided at a position different from the first conductor of the substrate in a short direction of the substrate;
A heating element that is provided between the first conductor and the second conductor and generates heat by the power supplied via the first conductor and the second conductor;
An electrode to which a conductive member for supplying power to the heating element is connected;
In a heater used in an image heating apparatus having
The heater characterized in that the amount of heat generated in a region corresponding to the position where the electrode of the heating element is provided is set to be larger than the amount of heat generated in other regions.   The heater according to claim 1, wherein the electrode is provided in a region where the heating element is provided in the longitudinal direction.   3. The heater according to claim 1, wherein the heater includes a plurality of heat generating blocks in the longitudinal direction, each of which includes a set of the first conductor, the second conductor, the heating element, and the electrode. The heater described in 1. A tubular film,
A heater in contact with the inner surface of the film;
In an image heating apparatus that heats an image formed on a recording material with the heat of the heater via the film,
An image heating apparatus, wherein the heater is the heater according to any one of claims 1 to 3. A tubular film,
A heater in contact with the inner surface of the film;
In an image heating apparatus that heats an image formed on a recording material with the heat of the heater via the film,
The heater has a substrate and first to fourth heat generating blocks formed on the substrate at different positions in the longitudinal direction of the substrate,
The first to fourth heat generating blocks are arranged in this order along the longitudinal direction,
The apparatus further includes a first drive element that drives the second heat generation block and the third heat generation block, a second drive element that drives the first heat generation block and the fourth heat generation block, and A first temperature detecting element for detecting the temperature of the second heat generating block, and a second temperature detecting element for detecting the temperature of the fourth heat generating block,
An image heating apparatus, wherein the first heat generating block and the third heat generating block are not provided with a temperature detecting element.   The apparatus further includes a holding member that is disposed in the internal space of the film and holds the heater, and the holding member is provided with holes for inserting the first and second temperature detection elements, respectively. The image heating apparatus according to claim 5, wherein:   The apparatus further includes a stay that reinforces the holding member, and the first and second temperature detecting elements are arranged in a space surrounded by the holding member and the stay. The image heating apparatus according to 5 or 6.   The cable connected to the first temperature detection element and the cable connected to the second temperature detection element are led out from the space and from different directions in the longitudinal direction. The image heating apparatus according to any one of claims 5 to 7.   The first heat generation block and the fourth heat generation block are arranged symmetrically with respect to a recording material conveyance reference position, and the second heat generation block and the third heat generation block are boundaryd with respect to the conveyance reference position. The image heating apparatus according to claim 5, wherein the image heating apparatus is arranged symmetrically. The heat generating block is provided between the first conductor and the second conductor provided on the substrate along the longitudinal direction, and between the first conductor and the second conductor. The image heating apparatus according to claim 5, further comprising: a body and a heating element that generates heat by electric power supplied via the second conductor.

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