JP2013235181A - Image heating device and image forming device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device configured to prevent temperature increase in a non-paper-passing part and to achieve power saving when a width of a recording material is unknown.SOLUTION: When a width of a recording material is unknown, heating member control is performed to sequentially select a heating member with a larger longitudinal width or to select adjacent two heating members in descending order of longitudinal width, on the basis of temperatures detected by temperature detection members 311-314 for ends temperature increase detection objects arranged at longitudinal ends of at least two or more heating members 301-304 having different longitudinal widths.

Description

  The present invention relates to an image heating apparatus suitable for use as a fixing device (fixing device) mounted in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, and an image forming apparatus including the image heating apparatus as a fixing device. .

  A film heating type fixing device is known as a fixing device (fixing device) mounted on an electrophotographic copying machine or printer. This type of fixing device has a heater having an energizing heating element on a ceramic substrate, a fixing film that moves while contacting the heater, a pressure roller that forms a nip portion with the heater via the fixing film, and the like. Yes. The recording material carrying the unfixed toner image is heated while being nipped and conveyed by the nip portion of the fixing device, whereby the image on the recording material is heated and fixed on the recording material.

  This type of fixing device has the merit that the time required to start energization of the heater and raise the temperature to a fixable temperature is short. Therefore, a printer equipped with this fixing device can shorten the time (FPOT: first printout time) until the first image is output after the print command is input. This type of fixing device also has an advantage that power consumption during standby waiting for a print command is small.

  By the way, when a small-size recording material is continuously printed at the same print interval as a large-size recording material in a printer equipped with a fixing device using a fixing film, the area where the recording material of the heater does not pass (non-sheet passing area) is excessive. It is known that the temperature rises to a non-sheet passing portion temperature. If the non-sheet passing area of the heater is excessively heated, the holder and the pressure roller that support the heater may be damaged by heat.

  Therefore, a printer equipped with the above-described fixing device has a control for widening the print interval when continuously printing on a small size recording material than when continuously printing on a large size recording material. Keeping the temperature down.

  However, the control for extending the print interval is to reduce the number of output sheets per unit time, and it is desirable to suppress the number of output sheets per unit time to the same level or slightly less than in the case of a large size recording material.

  Therefore, in order to prevent any decrease in throughput by reducing the number of output sheets per unit time, a plurality of heaters with different longitudinal widths of energization heating elements or a plurality of heaters with different heat generation orientation distributions of energization heating elements are used. The heater is switched according to the recording material width of the recording material. Further, Patent Document 1 also proposes a fixing device that switches the heater based on the information of the temperature detection element even when the paper width (recording material width) is not known, not the standard paper size.

JP 2008-197307 A

  Copiers and printers have been required to increase printing speed and save power. Further, not only a standard size recording material but also a recording material whose recording material width is unknown has been required to increase the printing speed and to save power.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image heating apparatus capable of achieving both prevention of non-sheet passing portion temperature rise and power saving when the recording material width of the recording material is unknown, and an image including the image heating apparatus. It is to provide a forming apparatus.

In order to achieve the above object, the configuration of the image heating apparatus according to the present invention is as follows.
An image that includes a rotating body and at least two or more heating members that heat the rotating body, conveys a recording material carrying an image together with the rotation of the rotating body, and heats the image with the heat of the rotating body In the heating device,
The heating members have different longitudinal widths in the longitudinal direction perpendicular to the recording material conveyance direction,
A temperature detecting member that is arranged at an end in the longitudinal direction for each of the heating members and detects an end temperature;
When the recording material width in the width direction orthogonal to the recording material conveyance direction of the recording material is unknown, the temperature detection member arranged at the end in the longitudinal direction of the heating member having the widest longitudinal width is the end temperature increase detection target, A first heating member control for starting the heating temperature control using the heating member having the widest longitudinal width;
When the end temperature detected by the temperature detection member of the end temperature increase detection target exceeds the predetermined temperature during the first heating member control, the first heating member control is used. A second heating member control to switch to a heating temperature control using a combination of the heating member and the heating member having the next longer longitudinal width;
When the end temperature detected by the temperature detection member that is the end temperature increase detection target when the second heating member control is being performed exceeds the predetermined temperature, the length of the heating member having the next longest width Heating using a heating member having a narrower longitudinal width among the two heating members used in the second heating member control, with the temperature detection member arranged at the end in the direction as an end temperature rise detection target A third heating member control to switch to temperature control;
Heating member switching control for sequentially switching the second heating member control and the third heating member control from a heating member with a long longitudinal width to a narrow heating member according to the number of the heating members. Features.

  According to the present invention, when the recording material width of the recording material is unknown, an image heating apparatus capable of achieving both prevention of non-sheet passing portion temperature rise and power saving, and an image forming apparatus including the image heating apparatus Can be provided.

Schematic configuration schematic diagram of an image forming apparatus Control block diagram of an example of an image forming apparatus 2A and 2B are diagrams illustrating a fixing device according to a first embodiment, where FIG. 1A is a schematic diagram of a cross-sectional side configuration of the fixing device, FIG. 2B is a schematic diagram of a cross-sectional configuration of a fixing heater, and FIG. Diagram showing the relationship between the body width and the paper width Driving control circuit diagram of the heater of the fixing device according to the first embodiment. 7 is a flowchart showing heater control of the fixing device according to the first embodiment. FIG. 6 is a diagram illustrating a relationship between an energization heating element and an electrode in a heater of a fixing device according to Embodiment 2. Drive control circuit diagram of heater of fixing device of embodiment 2 7 is a flowchart showing heater control of the fixing device according to the second embodiment.

[Example 1]
(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration schematic diagram of an example image forming apparatus in which the image heating apparatus according to the present invention is mounted as a fixing device (fixing device). This image forming apparatus (hereinafter also referred to as a printer) is an electrophotographic printer.

  The image forming apparatus shown in the present embodiment includes an image forming unit 100A that forms an image on a recording material, and a fixing unit that heats and fixes an unfixed toner image (unfixed image) formed on the recording material (hereinafter referred to as “fixed unit”). 110) and the like.

  In the image forming unit 100A, reference numeral 101 denotes a process cartridge that is detachably attached to the image forming apparatus main body 100 that constitutes the casing of the image forming apparatus. Reference numeral 102 denotes a photosensitive drum as an image carrier. Reference numeral 103 denotes a semiconductor laser as a light source. Reference numeral 105 denotes a rotating polygon mirror that is rotated by the scanner motor 104. A laser beam 106 is emitted from the semiconductor laser 103 and scans the outer peripheral surface (surface) of the photosensitive drum 101.

  Reference numeral 107 denotes a charging roller for uniformly charging the surface of the photosensitive drum 102. Reference numeral 108 denotes a developing device (developing device) for developing the electrostatic latent image formed on the surface of the photosensitive drum 102 by the laser beam 106 with toner. Reference numeral 109 denotes a transfer roller for transferring an unfixed toner image developed by the developing unit 108 to a predetermined recording sheet (hereinafter referred to as a sheet) S as a recording material.

  The process cartridge 101 is a cartridge in which the photosensitive drum 101, the charging roller 107, the developing device 108, and the like are integrated.

  In the fixing device 110, 111 is a fixing heater, 123 is a fixing film, and 124 is a pressure roller.

  Reference numeral 112 denotes a paper feed cassette for storing paper S, which is attached to the image forming apparatus main body 100 from the direction of arrow A in FIG. Reference numeral 113 denotes a paper feed roller that feeds the paper S from the paper feed cassette 112 and sends it to the transport path by one rotation. The feed roller 114 and the retard roller 115 are a pair of rollers for separating the sheets S from the sheet bundle one by one and feeding them to the conveyance path when the sheet S picked up by the pickup roller 113 is a sheet bundle. Reference numeral 116 denotes an intermediate roller for conveying the sheet S fed from the cassette to the image forming unit 100A. Reference numeral 117 denotes a pre-transfer roller that feeds the conveyed paper S to a transfer nip Nt between the photosensitive drum 102 and the transfer roller 109.

  118 is for synchronizing the writing (recording / printing) of the image on the surface of the photosensitive drum 102 and the sheet conveyance with respect to the fed sheet S, and measuring the length of the fed sheet S in the conveyance direction. The top sensor. Reference numeral 119 denotes a fixing sensor for detecting the presence or absence of the sheet S after fixing. A transport roller 120 discharges the paper S after the toner image is fixed to a paper discharge transport path. Reference numeral 121 denotes a paper discharge roller that discharges the paper S to a paper discharge tray 122 on which the paper is stacked. Reference numeral 125 denotes a multipurpose tray for storing the manually fed paper S. By rotating the multi-pickup roller 126 once, the paper S is fed from the multipurpose tray 125 and sent to the downstream pre-transfer roller 117.

  FIG. 2 is a control block diagram of an example of the image forming apparatus shown in FIG. In FIG. 2, reference numeral 201 denotes image code data sent from an external device (external device) such as a host computer (not shown), which is developed into bit data necessary for printing by the printer, and for reading and displaying the printer internal information. It is a printer controller.

  A printer engine controller 202 (hereinafter also referred to as an engine controller) 202 controls the printing operation of each unit of the image forming apparatus according to an instruction from the printer controller 201 and notifies the printer controller 201 of printer internal information. The printer engine controller 202 includes a CPU and a memory such as a RAM and a ROM, and firmware is mounted on the CPU. Reference numeral 203 denotes a high voltage control unit that performs high voltage output control in each process such as charging, development, and transfer in accordance with an instruction from the printer engine controller 202.

  An optical system control unit 204 controls driving / stopping of the scanner motor 104 and lighting of the laser beam in accordance with an instruction from the engine controller 202. Reference numeral 205 denotes a fixing device controller that drives / stops energization of the fixing heater in accordance with an instruction from the printer engine controller 202.

  Reference numeral 206 denotes a sensor input unit that notifies the engine controller 202 of paper presence / absence states of a top sensor 118, a fixing sensor 119, and a paper surface position sensor (not shown), and a temperature state detected by a temperature detection element described later.

  A sheet conveyance control unit 207 drives / stops a motor / roller or the like for conveying a recording sheet in accordance with an instruction from the printer engine controller 202. The paper conveyance control unit includes a paper feed roller 113, a feed retard roller pair 116, a pre-transfer roller 117, a photosensitive drum 102, a fixing film 123, a pressure roller 124, a conveyance roller 120, and a paper discharge roller 121 shown in FIG. It controls the driving / stopping operation.

  A printing operation (printing operation) of the image forming apparatus according to the present exemplary embodiment will be described. The photosensitive drum 102 is rotationally driven in the direction of the arrow in accordance with a print command input from an external device. First, the photosensitive drum 102 is uniformly charged to a predetermined potential and polarity by the charging roller 107. Next, the charged surface on the surface of the photosensitive drum 102 is subjected to scanning exposure by the laser beam 106 emitted from the semiconductor laser 103, and an electrostatic latent image (electrostatic image) is formed on the charged surface on the surface of the photosensitive drum 102. Is done. The electrostatic latent image is developed with toner by the developing unit 108 and visualized as a toner image.

  On the other hand, the paper S is fed from the paper feed cassette 112 by the paper feed roller 113 and sent to the pre-transfer roller 117. Alternatively, the paper S is fed from the multi-purpose tray 125 by the multi-pickup roller 126 and sent to the pre-transfer roller 117. The pre-transfer roller 117 feeds the sheet S to the transfer nip portion Nt at a predetermined timing set so that the toner image formation start position on the surface of the photosensitive drum 102 matches the image writing position of the sheet S. The sheet S enters the transfer nip Nt after the top sensor 118 detects the leading end on the same side as the sheet conveying direction (recording material conveying direction).

  In the transfer nip portion Nt, the sheet S is sandwiched between the surface of the photosensitive drum 102 and the surface of the transfer roller 109 and is transported to the state (nip transport). In this conveyance process, the transfer roller 109 transfers the toner image from the surface of the photosensitive drum 102 onto the paper S, and the paper S carries an unfixed toner image.

  The sheet S carrying the unfixed toner image is separated from the surface of the photosensitive drum 102 and is introduced into a fixing nip portion (nip portion) N between the fixing film 123 and the pressure roller 124 of the fixing device 110. Then, when the sheet S passes through the fixing nip portion N, the toner image is heated and fixed on the sheet S. The sheet S on which the toner image is heat-fixed is discharged onto the sheet discharge tray 122 as a printed matter (print) by the conveyance roller 120 and the sheet discharge roller 121 after the rear end opposite to the sheet conveyance direction is detected by the fixing sensor 119. Is done.

(2) Fixing device 110
In the following description, regarding the fixing device and the members constituting the fixing device, the longitudinal direction refers to a direction orthogonal to the paper transport direction on the surface of the paper. The short side direction is a direction parallel to the paper transport direction on the paper surface. The longitudinal width refers to the dimension in the longitudinal direction. Regarding the paper, the width direction means a direction orthogonal to the paper transport direction on the surface of the paper. The paper width (recording material width) is a dimension in the width direction.

  3, (a) is a schematic diagram of the cross-sectional side configuration of the fixing device, (b) is a schematic diagram of the cross-sectional side configuration of the fixing heater, and (c) is the longitudinal width of the four energization heating elements of the fixing heater and the paper sheet. It is a figure showing the relationship with a width | variety. A fixing device 110 shown in FIG. 3A is a pressure roller driving type film heating type fixing device using an endless film (cylindrical film) described in, for example, Japanese Patent Application Laid-Open No. 04-44075. .

  The fixing device 110 shown in this embodiment includes a fixing heater (ceramic surface heater) 111 as a heating source, a heater holder 303 as a support member, a cylindrical heat-resistant film 123 as a rotating body, and a heating member as a backup member. A pressure roller 124 is included. The fixing heater 111, the heater holder 303, the heat resistant film (hereinafter referred to as a fixing film) 123, and the pressure roller 124 are all members that are long in the longitudinal direction.

  In the fixing device 110 of this embodiment, the fixing heater 111 is supported on the center of the bottom surface in the short direction of the heat-resistant and rigid heater holder 303 having a semicircular arc-shaped cross section, and the fixing film 123 is loosely removed from the heater holder 303. It is configured to be fitted. Both ends of the heater holder 303 in the longitudinal direction are supported by side plates on both sides in the longitudinal direction of a fixing frame (not shown).

  The pressure roller 124 disposed so as to face the fixing heater 111 through the fixing film 123 has an elastic layer 124b on the outer peripheral surface of the core metal 124a. Both ends in the longitudinal direction of the cored bar 124a are rotatably supported by side plates on both sides in the longitudinal direction of the fixing frame via bearings. The bearings at both ends in the longitudinal direction of the metal core 124a are pressed by a pressure member such as a pressure spring (not shown) to press the pressure roller 124 against the fixing heater 111 with the fixing film 123 interposed therebetween. As a result, the elastic layer 124 b of the pressure roller 124 is elastically deformed, and the outer peripheral surface (surface) of the pressure roller 124 and the outer peripheral surface (surface) of the fixing film 123 form a fixing nip portion N having a predetermined width.

  As shown in FIGS. 3B and 3C, the fixing heater 111 has an elongated ceramic insulating substrate (hereinafter referred to as a substrate) 305 having electrical insulation, good thermal conductivity, and low heat capacity. . On the back surface of the substrate 305 (the surface on the fixing nip portion N side), four energization heating elements (hereinafter referred to as heaters) 301, 302, 303, as at least two (two or more) heating members. 304 is formed along the longitudinal direction of the substrate 305. The four heaters 301, 302, 303, and 304 have different longitudinal widths. The heaters 301, 302, 303, and 304 are arranged in the order of increasing longitudinal width.

  The heater 301 having the widest longitudinal width is electrically connected to a common electrode 351 provided at one end portion in the longitudinal direction of the substrate 305 and an electrode 361 provided at the other end portion in the longitudinal direction of the substrate 305 via a conductive member 301a. It is connected. Next, the heater 302 having the wider longitudinal width is electrically connected to the common electrode 351 and the electrode 362 provided at the other longitudinal end of the substrate 305 through the conductive member 302a.

  Next, the heater 303 having the longest longitudinal width is electrically connected to the common electrode 351 and the electrode 363 provided at the other longitudinal end of the substrate 305 through the conductive member 303a. The heater 304 having the shortest longitudinal width is electrically connected to the common electrode 351 and the electrode 364 provided at the other longitudinal end of the substrate 305 via a conductive member 304a.

  In FIG. 3B, reference numeral 300 denotes a protective layer such as a glass layer. The protective layer 300 is formed on the back surface of the substrate 305 so as to cover the heaters 301, 302, 303, 304 and the conductive members 301a, 302a, 303a, 304a.

  In FIG. 3C, the dotted line CL at the center in the longitudinal direction of the substrate 305 is the central conveyance reference line of the paper S, and the heaters 301, 302, 303, and 304 are symmetrical with respect to the central conveyance reference line CL. The sheet S is conveyed in a state where the center of the sheet width coincides with the center conveyance reference line CL. In the fixing device 110 of this embodiment, as shown in the example of L1 to L7 in the drawing, the sheet S having various sheet widths is passed (introduced) to the fixing nip portion N and is not fixed. The toner image T is heat-fixed.

  Reference numerals 307 and 308 denote two power feeding connectors (hereinafter referred to as connectors). The connector 307 is attached to the common electrode 351 side of the substrate 305 and electrically connects the common electrode 351 and the heater drive circuit side. The connector 308 is attached to each electrode 361 to 364 side of the substrate 305 to electrically connect each electrode 361 to 364 and the heater driving circuit side.

  A second temperature detection member that detects the temperature of the central portion in the longitudinal direction of the fixing heater 111, that is, the temperature in the central portion in the longitudinal direction between the heater 303 and the heater 304, is provided at the central portion in the longitudinal direction on the surface of the protective layer 300. The temperature detection element 310 is arranged. An excessive temperature rise prevention means 306 is disposed in the vicinity of the temperature detection element 310.

  Further, a temperature detection element 311 as a temperature detection member or a first temperature detection member for detecting the temperature of the end of the heater 301 in the longitudinal direction is disposed inside the longitudinal end on the surface of the protective layer 300. . In addition, a temperature detection element 312 as a temperature detection member or a first temperature detection member for detecting the end temperature of the heater 302 in the longitudinal direction is disposed inside the temperature detection element 311 in the longitudinal direction on the surface of the protective layer 300. Has been.

  Also, a temperature detection element 313 as a temperature detection member or a first temperature detection member for detecting the end temperature of the heater 303 in the longitudinal direction is arranged inside the temperature detection element 312 in the longitudinal direction on the surface of the protective layer 300. Has been. A temperature detection element 314 serving as a temperature detection member for detecting the end temperature of the heater 304 in the longitudinal direction or a first temperature detection member is disposed inside the temperature detection element 313 in the longitudinal direction on the surface of the protective layer 300. Has been.

  As shown in FIG. 3A, the fixing heater 111 has a surface opposite to the side on which the heaters 301 to 304 of the substrate 305 are provided as a surface side (fixing film sliding surface side), and this surface side faces downward. Thus, it is exposed to the outside and fixedly supported at the center of the lower surface of the heater holder 303. Further, an excessive temperature rise prevention unit 306 (for example, a fuse or a thermostat) is in contact with the surface of the protective layer 300 of the fixing heater 111. The position of the heater holder 303 is corrected, and the heat sensitive surface of the excessive temperature rise prevention means 306 is brought into contact with the surface of the protective layer 300 of the heater 111 with a spring (not shown). Although not shown in FIG. 3A, the temperature detecting elements 310 to 314 are also in contact with the surface of the protective layer 300 of the fixing heater 111 in the same manner.

  FIG. 4 is a drive control circuit diagram of the fixing heater 111. In FIG. 4, 401 is an AC power source of the image forming apparatus. By supplying power from the AC power source 401 to the heaters 301 to 304 of the fixing heater 111 of the fixing device 110 via the AC filter 402 and the relay 450, the heaters 301 to 304 generate heat.

  Supply of electric power to the heater 301 is controlled by energization and interruption of the triac 410 as a heater drive circuit (heating member drive means). Resistors 411 and 412 are bias resistors for the triac 410. The phototriac coupler 413 is a device for ensuring a creepage distance between the primary and secondary. The triac 410 is turned on by energizing the light emitting diode of the phototriac coupler 413. The resistor 414 is a resistor for limiting the current of the phototriac coupler 413, and turns on / off the phototriac coupler 413 by the transistor 415. The transistor 415 controls according to the ON1 signal from the engine controller 202 via the resistor 416.

  Similarly, power supply to the heater 302 is controlled by energization and shut-off of the triac 420 as a heater drive circuit (heating member drive means). Resistors 421 and 422 are bias resistors for the triac 420. The phototriac coupler 423 is a device for ensuring a creepage distance between the primary and secondary. The triac 420 is turned on by energizing the light emitting diode of the phototriac coupler 423. The resistor 424 is a resistor for limiting the current of the phototriac coupler 423, and turns on / off the phototriac coupler 423 by the transistor 425. The transistor 425 is controlled according to the ON2 signal from the engine controller 202 via the resistor 426.

  Similarly, power supply to the heater 303 is controlled by energization and shut-off of the triac 430 as a heater drive circuit (heating member drive means). Resistors 431 and 432 are bias resistors for the triac 430. The phototriac coupler 433 is a device for ensuring a creepage distance between the primary and secondary. The triac 430 is turned on by energizing the light emitting diode of the phototriac coupler 433. The resistor 434 is a resistor for limiting the current of the phototriac coupler 433, and turns on / off the phototriac coupler 433 by the transistor 435. The transistor 435 is controlled according to the ON3 signal from the engine controller 202 via the resistor 436.

  Similarly, power supply to the heater 304 is controlled by energization and shut-off of the triac 440 as a heater drive circuit (heating member drive means). Resistors 441 and 442 are bias resistors for the triac 440. The phototriac coupler 443 is a device for ensuring a creepage distance between the primary and secondary. The triac 440 is turned on by energizing the light emitting diode of the phototriac coupler 443. The resistor 444 is a resistor for limiting the current of the phototriac coupler 443, and turns on / off the phototriac coupler 443 by the transistor 445. The transistor 445 performs control according to the ON4 signal from the engine controller 202 via the resistor 446.

  Further, the AC power supply 401 is input to the zero cross detection circuit 403 through the AC filter 402. The zero-cross detection circuit 403 sends a pulse signal (hereinafter referred to as a ZEROX signal) to the engine controller 202 that the commercial power supply voltage is below a certain threshold value. The engine controller 202 detects the edge of the pulse of the ZEROX signal, and turns ON / OFF the triacs 410, 420, 430, and 430 using the ON1 to ON4 signals by phase control or wave number control.

  A temperature detection element (for example, a thermistor temperature sensing element) 310 for detecting the temperature of the central portion in the longitudinal direction of the fixing heater 111 is insulated so as to ensure an insulation distance from the heaters 301 to 304 on the fixing heater 111. It arrange | positions through the protective layer 300 which has a proof pressure. The temperature detected by the temperature detection element 310 is detected as a partial pressure between the resistor 490 and the temperature detection element 310, and A / D is input to the engine controller 202 as a TH0 signal. The temperature of the fixing heater 111 is monitored by the engine controller 202 as a TH0 signal.

  The engine controller 202 calculates the electric power to be supplied to the heaters 301 to 304 by comparing the TH0 signal with the set temperature of the fixing heater 111 set inside the engine controller 202. And it converts into the phase angle (phase control) or wave number (wave number control) corresponding to the electric power which should be supplied. The engine controller 202 sends ON1-ON4 signals to the transistors 416, 426, 436, 446 according to the control conditions. Here, the set temperature (hereinafter also referred to as a fixing target temperature) is a temperature necessary for heating and fixing the unfixed toner image T.

  Similarly, the temperature detection element 311 for detecting the end temperature of the heater 301 is divided by a resistor 491 and input as a TH1 signal. A temperature detection element 312 for detecting the end temperature of the heater 302 is divided by a resistor 492 and input as a TH2 signal. A temperature detecting element 313 for detecting the end temperature of the heater 303 is divided by a resistor 493 and input as a TH2 signal. A temperature detection element 314 that detects the end temperature of the heater 304 is divided by a resistor 494 and input as a TH4 signal.

  The temperature detection elements 310 to 314, the triacs 410, 420, 430, 440, etc. fail, and the engine controller 202 determines that the temperature is detected or the heater drive circuit has failed. In this case, the engine controller 202 turns off the RLD signal, turns off the relay 450, and cuts off the power supply to the heaters 301 to 304. Relay 450 is turned on / off by transistor 452.

  Transistor 452 operates according to the RLD signal from engine controller 202 via resistor 453. The resistor 454 is a resistor for protecting the transistor 452. The diode 451 is an element that absorbs a back electromotive voltage generated when the relay 450 is turned off. Normally, the relay 450 is controlled to be turned on by the RLD signal before starting the power control to the heaters 301 to 304 by the ON1 to ON4 signals from the engine controller 202. Then, after the control of power supply to the heaters 301 to 304 is terminated, the heater is controlled to be turned off by the RLD signal.

  Although not shown in FIG. 4, the excessive temperature rise prevention means 306 is, for example, a thermal fuse or a thermo switch, and when the heater drive circuit fails and the heaters 301 to 304 become thermal runaway, the excessive temperature rise prevention means 306 It serves as a last resort to prevent. When the heaters 301 to 304 are brought into thermal runaway due to a failure of the power supply control means, and the excessive temperature rise prevention means 306 reaches a predetermined temperature or more, the excessive temperature rise prevention means 306 becomes OPEN, and the power supply to the heater is cut off. Thus, it inserts between the common electrode 351 and the electrodes 361-364.

  The common electrode 351 is connected from the hot side terminal of the AC power supply 401 via the relay 450. The electrodes 361 to 364 are connected to the neutral terminal of the AC power supply 401 via triacs 410, 420, 430, and 430 that control the heaters 301 to 304.

(3) Heat Fixing Operation of Unfixed Toner Image of Fixing Device 110 In the fixing device 110 of this embodiment, the pressure roller 124 is rotated in a predetermined counterclockwise direction indicated by an arrow by a drive motor (not shown) in response to a print command. Rotated at speed. The rotation of the pressure roller 124 is transmitted to the surface of the fixing film 123 by the pressure friction force between the surface of the pressure roller 124 and the surface of the fixing film 123 in the fixing nip portion N. As a result, the fixing film 123 follows the rotation of the pressure roller 124 while the inner peripheral surface (inner surface) of the fixing film 123 is in contact with the surface of the substrate 205 of the fixing heater 111 and rotates around the heater holder 303 in the clockwise direction of the arrow. . In order to reduce the frictional force between the surface of the substrate 205 and the inner surface of the fixing film 123, slidable grease may be applied to the interface between the inner surface of the fixing film 123 and the surface of the substrate 205.

  Further, the heaters 301 to 304 of the fixing heater 111 are energized according to the print command. As a result, the fixing heater 111 rapidly heats up the heaters 301 to 304 to heat the fixing film 123. Then, the TH0 signal of the temperature detection element 310 and the set temperature of the fixing heater 111 are compared, the phase angle or wave number corresponding to the power supplied to the heaters 301 to 304 is determined and appropriately controlled, and the temperature of the fixing heater 111 is set. Keep at temperature.

  In a state where the drive motor is rotated and the heaters 301 to 304 are energized and the temperature of the fixing heater 111 is maintained at the set temperature, the sheet S carrying the unfixed toner image T is fixed with the toner image carrying surface facing upward. It is introduced into the nip N. The sheet S is nipped between the surface of the fixing film 123 and the surface of the pressure roller 124 at the fixing nip portion N and is conveyed (nipped and conveyed) in that state. In this conveyance process, the toner image T on the sheet S is heated and fixed to the sheet S by the heat of the fixing film 123 and the nip pressure of the fixing nip N. The sheet S is separated from the surface of the fixing film 123 and is fixed by the fixing nip N. Discharged.

  Next, heater control during printing will be described. When the standard paper size is automatically detected by the paper feed cassette, or when the user specifies the paper size from the multi-purpose tray, the fixing device 110 uses the detected or specified paper size information. Heating fixing is performed by selecting the heaters 301 to 304. On the other hand, if it is determined that the standard paper size cannot be detected by the paper feed cassette and is determined to be a non-standard size, or if the user does not specify the paper size on the multi-purpose tray, the paper width is unknown, so the fixing device 110 The heater 301 having the widest longitudinal width is selected to perform heat fixing. In this embodiment, when the paper width is unknown, the heater control as shown in Table 1 is performed. When edge temperature rise occurred, one heater and two heaters adjacent in the longitudinal width were selected.

FIG. 5 is a flowchart showing heater control performed by the engine controller 202 based on the end temperature detected by the thermistors 310 to 314 when the paper width is unknown.

  First, assuming the paper size with the largest paper width (L1 in FIG. 4C), only the heater 301 having the longest longitudinal width is driven and lit at a 100% lighting ratio (S501). The fixing target temperature is controlled by the thermistor 310 at the center so that the fixing target temperature becomes 190 ° C. The thermistor subject to temperature rise detection is the thermistor 311 located at the end of the heater 301 (S502).

  That is, temperature control (heating temperature control) is started using the heater 301 with the thermistor 311 as the end temperature increase detection target. This temperature control is the first heater control (first heating member control).

  If the temperature rises at the edge and the temperature detected by the thermistor 311 exceeds 250 ° C. during printing (S503), it is determined that the actual paper width is narrower than L1, and the process proceeds to S505. In S505, assuming the paper size L2, the heater 301 and the heater 302 having the second largest longitudinal width are driven at a 50% lighting ratio to control the temperature.

  That is, when the detected temperature of the thermistor 311 exceeds 250 ° C. (predetermined temperature) during the first heater control, the heater 301 and the heater 302 used in the first heater control are combined. Switch to the used temperature control (heating temperature control). This temperature control is the second heater control (second heating member control).

  If the temperature of the end of the thermistor 311 exceeds 250 ° C. during printing (S506), it is determined that the actual sheet width is narrower than L2, and the process proceeds to S508. In S508, assuming the paper size L3, only the heater 302 is driven to light up at a 100% lighting ratio. In step S509, the end temperature increase detection target is switched to the thermistor 312.

  That is, when the detected temperature of the thermistor 312 exceeds 250 ° C. (predetermined temperature) during the second heater control, the thermistor 312 is set as the end temperature increase detection target. And it switches to the temperature control (heating temperature control) which uses the heater 302 with a narrower longitudinal width among the two heaters 301 and 302 used in the second heater control. This temperature control is the third heater control (third heating member control).

  If the temperature rises at the end and the temperature detected by the thermistor 312 exceeds 250 ° C. during printing (S510), it is determined that the actual paper width is narrower than L3, and the process proceeds to S512. In S512, assuming the paper size L4, the heater 302 and the heater 303 having the third longest width are driven at a lighting ratio of 50% to control the temperature.

  If the temperature of the end of the thermistor 312 exceeds 250.degree. C. while printing, the temperature of the thermistor 312 exceeds 250.degree. C. (S513), the actual paper width is determined to be narrower than L4, and the process proceeds to S515. In S515, assuming that the paper size is L5, only the heater 303 is driven to light at a 100% lighting ratio. In S516, the end temperature increase detection target is switched to the thermistor 313.

  If the temperature of the end of the thermistor 313 exceeds 250 ° C. while printing, the temperature of the thermistor 313 exceeds 250 ° C. (S517), the actual paper width is determined to be narrower than L5, and the process proceeds to S519. In S519, assuming the paper size L6, the heater 303 and the heater 304 having the fourth longest width are driven at a 50% lighting ratio to control the temperature.

  If the temperature rises at the edge and the temperature detected by the thermistor 313 exceeds 250 ° C. during printing (S520), it is determined that the actual paper width is narrower than L6, and the process proceeds to S522. In S522, assuming the paper size L7, only the heater 304 is driven at a 100% lighting ratio to light it. In S523, the end temperature increase detection target is switched to the thermistor 314.

  That is, in S510 and subsequent steps, the second heater control and the third heater control are sequentially switched from a heater having a long longitudinal width to a narrow heater according to the number of heaters. This control is heater switching control (heating member switching control).

  If the temperature of the end of the thermistor 314 exceeds 250 ° C. while printing, the actual paper is determined to be an illegal paper narrower than the minimum paper size L7, and the process proceeds to S525. . In S525, control is performed to gradually widen the interval between the front and rear sheets (paper interval) so that the edge temperature rise does not exceed 250 ° C.

  Between the front and rear sheets, the fixing target temperature is set to 160 ° C. which is lower than 190 ° C., and the heater 304 is cooled. The above-described control is performed until printing is finished (S504, S507, S511, S514, S518, S521, S526).

  By performing such control, even when the sheet width is unknown, optimal heater control can be performed by combining one heater or two heaters having adjacent longitudinal lengths. Furthermore, even on a sheet having a sheet width corresponding to the length between two adjacent heaters, the printing can be performed without reducing the throughput.

  As described above, in a configuration having a plurality of heaters having different longitudinal widths, when the sheet width is unknown, the heaters having a longer longitudinal width are sequentially set to 1 based on the temperature detected by the thermistor to be detected for detecting the end temperature rise. A book is selected, or two heaters that are adjacent to each other in the order of increasing longitudinal width are selected. Therefore, it is possible to select an appropriate heater according to the paper width of the paper, and it is possible to prevent the temperature rise of the non-sheet passing portion and to suppress wasteful power (power saving). Further, since the sheet interval is not widened so as not to raise the temperature at the edge, the printing speed can be increased.

[Example 2]
In the fixing device 110 according to the first exemplary embodiment, the fixing heater 111 includes four heater driving circuits for four heaters. That is, there are drive circuits 410 to 416 for the heater 301 and drive circuits 420 to 426 for the heater 302. There are driving circuits 430 to 436 for the heater 303, and driving circuits 440 to 446 for the heater 304.

  In this embodiment, a fixing device 110 having two heater drive circuits by combining the heaters 301 to 304 of the fixing heater 111 as described below will be described. Members common to the fixing device 110 according to the first exemplary embodiment are denoted by the same reference numerals, and description of the members is omitted.

  FIG. 6 is a diagram illustrating the relationship between the heaters 301 to 304 and the electrodes 351 to 354, 361 and 362 in the fixing heater 111 of the fixing device 110 according to the present embodiment.

  The heater 301 is electrically connected to the first common electrode 361 provided at the other end in the longitudinal direction of the substrate 305 and the electrode 351 provided at one end in the longitudinal direction of the substrate 305 through the conductive member 301a. ing. The heater 302 is electrically connected to the second common electrode 362 provided at the other longitudinal end of the substrate 305 and the electrode 352 provided at one longitudinal end of the substrate 305 through the conductive member 302a. ing.

  The heater 303 is electrically connected to the first common electrode 361 and the electrode 353 provided at one end in the longitudinal direction of the substrate 305 through a conductive member 303a. The heater 304 is electrically connected to the second common electrode 362 and an electrode 354 provided at one end in the longitudinal direction of the substrate 305 via a conductive member 304a.

  The connector 307 is attached to the first and second common electrodes 361 and 362 side of the substrate 305, and electrically connects the common electrodes 361 and 362 and the heater drive circuit side. The connector 308 is attached to each electrode 361 to 364 side of the substrate 305 to electrically connect each electrode 351 to 354 and the heater driving circuit side.

  FIG. 7 is a drive control circuit diagram of the fixing heater 111 of the fixing device 110 of this embodiment. Description of the same part as Example 1 is abbreviate | omitted, and a different part is demonstrated.

  In the present embodiment, when the heaters 301 to 304 are numbered as N (N = 1, 2, 3,...) From the longest width, the odd-numbered heaters 301 and 303, the even-numbered heaters 301 and 304. The heater 302 and the heater 304 form two heater driving circuits one by one.

  The SEL1 signal functions as a heater selection switch (odd heating member selection means) for selecting an odd-numbered heater. Either the heater 301 or the heater 303 is selectively driven by turning on / off the switching relay (odd heating member switching means) 460 by this SEL1 signal. Transistor 462 operates according to the SEL1 signal from engine controller 202 via resistor 463. The resistor 464 is a resistor for protecting the transistor 462. The diode 461 is an element that absorbs a back electromotive voltage generated when the relay 460 is switched.

  Normally, when switching the heater 301 and the heater 303, the switching relay 460 waits until the driving current is reduced by turning off the heater driving in advance in order to prevent contact fusion of the switching relay, and then opens the switching relay. Wait until it is released. After that, after waiting until the switching relay is connected to another heater and connected, the other heater can be finally driven. Therefore, it takes about several hundreds of milliseconds to switch the heater.

  Similarly, the SEL2 signal functions as a heater selection switch (even-numbered heating member selection means) for selecting an even-numbered heater. Either the heater 302 or the heater 304 is selectively driven by turning on / off the switching relay circuit (even heating member switching means) 470 by the SEL2 signal. Transistor 472 operates in accordance with the SEL2 signal from engine controller 202 via resistor 473. The resistor 474 is a resistor for protecting the transistor 472. The diode 471 is an element that absorbs a back electromotive voltage generated when the relay 470 is switched.

  Normally, when switching between the heater 302 and the heater 304, the switching relay 470 waits until the driving current is reduced by turning off the heater driving in advance in order to prevent contact fusion of the switching relay, and then opens the switching relay. Wait until it is released. After that, after waiting until the switching relay is connected to another heater and connected, the other heater can be finally driven. Therefore, it takes about several hundreds of milliseconds to switch the heater.

  On the other hand, the triacs 410 and 420 as heater driving circuits (heating member driving means) include odd-numbered heater driving circuits (odd-number driving means) 410 to 416 and even-numbered heater driving circuits 420 to 426 ( Even number drive means). For this reason, the number of heater drive circuits can be reduced as compared with the first embodiment.

  The reason why the heater driving circuit is divided into the odd-numbered system and the even-numbered system is that, as in the first embodiment, when the sheet width is unknown, one heater or two heaters whose longitudinal widths are adjacent to each other. This is because it becomes advantageous when the heaters are controlled in sequence in combination. Specifically, when one heater and two heaters adjacent to each other in the longitudinal width are sequentially switched, during the period in which only one heater is driven, the other non-driven system ( (Drive OFF) can be switched by a switching relay. As a result, the next time the two heaters whose longitudinal widths are adjacent to each other are driven, the heaters have already been switched and no waiting time is required.

  Next, heater control during printing will be described. Heater control as described in Table 2 is performed. During the period in which only one of the odd-numbered heater driving circuit and the even-numbered heater driving circuit is being driven, the heater switching by the switching relay is performed in the heater driving circuit on the non-driven side.

FIG. 8 is a flowchart showing heater control performed by the engine controller 202 when the paper width is unknown. The flowchart shown in FIG. 8 is obtained by adding S801, S802, and S803 to the flowchart shown in FIG. In FIG. 8, S501 to S526 are the same as S501 to S526 in the flowchart shown in FIG. 5, and thus the description thereof is omitted, and only the added S801, S802, and S803 are described.

  In S801, the odd-numbered heater is switched to the first widest heater 301 and the even-numbered heater is switched to the second widest heater 302 by switching the switching relays 460 and 470. When switching is made here, the connection time of the switching relays 460 and 470 is awaited. If it is devised to switch to these combinations at the end of printing, this switching time becomes unnecessary.

  S802 is after driving only the heater 302 in S508, and since the odd-numbered drive is turned off, the odd-numbered switching relay 470 switches the heater 301 to the heater 303 when the odd-numbered drive current disappears. . S803 is after driving only the heater 303 in S515, and the even-numbered drive is turned off. Therefore, when the even-numbered drive current disappears, the even-numbered switching relay 460 is transferred from the heater 302 to the heater 304. Switch. During the period when only one of the odd-numbered heater drive circuit and the even-numbered heater drive circuit is driven, the heater is switched to a heater having a narrow longitudinal width by the switching relay in the heater drive circuit on the non-driven side. .

  In this embodiment, four heaters are grouped into two odd-numbered and two even-numbered triac drive circuits, and one heater in the group is selected by a switching relay. However, the number of heaters is not limited as long as it is two or more. For example, five heaters may be grouped into two odd number three and even number two triac drive circuits, and one heater may be selected in the group.

  As described above, in a configuration having a plurality of heaters having different longitudinal widths, when the sheet width is unknown, the heaters having a longer longitudinal width are sequentially set to 1 based on the temperature detected by the thermistor to be detected for detecting the end temperature rise. A book is selected, or two heaters that are adjacent to each other in the order of increasing longitudinal width are selected. Therefore, the same function and effect as those of the fixing device according to the first embodiment are obtained. Further, since the sheet interval is not widened so as not to raise the temperature at the edge, the printing speed can be increased. Furthermore, the number of heater drive circuits by the triac can be reduced to two in two systems, thereby reducing the number of heater drive circuits.

[Example 3]
In the fixing device 110 according to the first exemplary embodiment, the example in which the heater control is performed using the end temperature of the energization heating elements 301 to 304 detected by the thermistors 311 to 314 has been described. Of the thermistors 311 to 314, the thermistor 311 can be used as a temperature detection element that detects the temperature between the heater 301 and the heater 302 (temperature between heating members). Similarly, the thermistor 312 can be used as a temperature detection element that detects the temperature between the heater 302 and the heater 303 (temperature between heating members). Similarly, the thermistor 313 can be used as a temperature detection element that detects the temperature between the heater 303 and the heater 304 (temperature between heating members).

  In the fixing device 110 according to the present exemplary embodiment, when the paper width is unknown, the engine controller 202 uses the heater temperature (temperature between the heating members) detected by the thermistors 311 to 314 at the longitudinal ends of the heaters 301 to 304 based on the heater temperature. It is configured to perform control. This heater control performs the following processing only in S502, S505, and S509 shown in FIGS.

  In step S <b> 502, the thermistor to be detected for detecting the end temperature rise is the thermistor 311 positioned between the heater 301 and the heater 302. That is, temperature control (heating temperature control) is started using the thermistor 311 as an end temperature increase detection target and using the heater 301 having the first longest width. This temperature control is the first heater control (heating member control).

  In S505, assuming the paper size L2, the heater 301 and the heater 302 having the second largest longitudinal width are driven at a 50% lighting ratio to control the temperature. That is, when the detected temperature of the thermistor 311 exceeds 250 ° C. (predetermined temperature) during the first heater control (see S503), the heater 301 and the heater 302 used in the first heater control. Switch to temperature control (heating temperature control) used in combination. This temperature control is the second heater control (heating member control).

  In step S <b> 509, the end temperature increase detection target is switched to the thermistor 312 located between the heater 302 and the heater 303. That is, when the detected temperature of the thermistor 312 exceeds 250 ° C. (predetermined temperature) during the second heater control (see S506), the thermistor 312 is set as the end temperature increase detection target. And it switches to the temperature control (heating temperature control) which uses the heater 302 with a narrower longitudinal width among the two heaters 301 and 302 used in the second heater control. This temperature control is the third heater control (heating member control).

  In S510 and subsequent steps, the second heater control and the third heater control are sequentially switched from a heater having a long longitudinal width to a narrow heater in accordance with the number of heaters. This control is heater switching control (heating member switching control).

  As described above, in a configuration having a plurality of heaters having different longitudinal widths, when the sheet width is unknown, the heaters having a longer longitudinal width are sequentially set to 1 based on the temperature detected by the thermistor to be detected for detecting the end temperature rise. A book is selected, or two heaters that are adjacent to each other in the order of increasing longitudinal width are selected. Therefore, the same function and effect as those of the fixing device according to the first embodiment are obtained. Further, since the sheet interval is not widened so as not to raise the temperature at the edge, the printing speed can be increased.

[Other embodiments]
The switching of the heater lighting ratio in the fixing devices according to the first and second embodiments may be performed immediately after the temperature exceeds 250 ° C. during the conveyance of the paper at the fixing nip, or the paper is conveyed at the fixing nip. It may be carried out after waiting between the front and back sheets (between recording materials).

  The number of heaters is not limited to four with different longitudinal widths, and may be two, three, five, etc. as long as there are a plurality of heaters. For example, when there are two pairs of heaters having the same longitudinal width, the heater control may be applied by counting the two pairs as one when arranging in order of increasing longitudinal width. Even in the case of multiple heaters that have a temperature gradient such as heating the central part in the longitudinal direction and heating the end part in a large amount, rather than multiple heaters with different longitudinal widths, the heating distribution is arranged in order from the longitudinal width direction. Heater control may be applied.

  The plurality of heaters having different longitudinal widths is not limited to the energization heating element of the fixing heater in the film heating type fixing device. For example, in a roller heating type fixing device mounted in an image forming apparatus, heater control may be applied using a plurality of halogen heaters having different longitudinal widths as a plurality of heaters having different longitudinal widths. In an electromagnetic induction heating type fixing device mounted on an image forming apparatus, heater control may be applied using coils wound around a plurality of magnetic bodies having different longitudinal widths as a plurality of heaters having different longitudinal widths. .

  The heater lighting ratio is 100% for the heater 301, 75% for the heater 301 and 25% for the heater 302, 50% for the heater 301 and 50% for the heater 302, 25% for the heater 301, 75% for the heater 302, and 75% for the heater 302. Finer control may be performed such as 100%.

  In each embodiment, the end temperature rise is determined as a condition that the end temperature exceeds 250 ° C. However, for example, the temperature difference between the end temperature and the central portion exceeds 60 ° C. (predetermined value). good. Alternatively, the temperature increase rate of the edge temperature may be set as a condition (whether the temperature increase exceeds 50 ° C. (predetermined value) from the front end of the paper to the rear end of the paper in the heat fixing of the toner image of one paper).

  The image heating apparatus according to the present invention is not limited to use as a fixing apparatus that heat-fixes an unfixed toner image on a sheet, but is an apparatus that presupposes an unfixed toner image on a sheet, or a toner image that is heat-fixed on a sheet. It can also be used as a device for increasing the gloss of the surface.

  In the fixing devices according to the first to third embodiments, instead of the pressure roller, a sliding member having a small sliding resistance with respect to the paper is used, and a paper that carries an image at a nip portion between the sliding member and the fixing film. The image may be heated with the rotation of the fixing film and heated with the heat of the fixing film.

100A: image forming unit, 110: fixing device, 123: fixing film, 301, 302, 303, 304: energization heating element, 310, 311, 312, 313, 314: temperature detection element (thermistor), S: paper, T : Unfixed toner image

Claims (8)

An image that includes a rotating body and at least two or more heating members that heat the rotating body, conveys a recording material carrying an image together with the rotation of the rotating body, and heats the image with the heat of the rotating body In the heating device,
The heating members have different longitudinal widths in the longitudinal direction perpendicular to the recording material conveyance direction,
A temperature detecting member that is arranged at an end in the longitudinal direction for each of the heating members and detects an end temperature;
When the recording material width in the width direction orthogonal to the recording material conveyance direction of the recording material is unknown, the temperature detection member arranged at the end in the longitudinal direction of the heating member having the widest longitudinal width is the end temperature increase detection target, A first heating member control for starting the heating temperature control using the heating member having the widest longitudinal width;
When the end temperature detected by the temperature detection member of the end temperature increase detection target exceeds the predetermined temperature during the first heating member control, the first heating member control is used. A second heating member control to switch to a heating temperature control using a combination of the heating member and the heating member having the next longer longitudinal width;
When the end temperature detected by the temperature detection member that is the end temperature increase detection target when the second heating member control is being performed exceeds the predetermined temperature, the length of the heating member having the next longest width Heating using a heating member having a narrower longitudinal width among the two heating members used in the second heating member control, with the temperature detection member arranged at the end in the direction as an end temperature rise detection target A third heating member control to switch to temperature control;
Heating member switching control for sequentially switching the second heating member control and the third heating member control from a heating member with a long longitudinal width to a narrow heating member according to the number of the heating members. An image heating apparatus. An image that includes a rotating body and at least two or more heating members that heat the rotating body, conveys a recording material carrying an image together with the rotation of the rotating body, and heats the image with the heat of the rotating body In the heating device,
The heating members have different longitudinal widths in the longitudinal direction perpendicular to the recording material conveyance direction,
A temperature detection member arranged between the heating members in the recording material conveyance direction to detect the temperature between the heating members;
When the recording material width in the width direction perpendicular to the recording material conveyance direction of the recording material is unknown, the end of the temperature detection member arranged between the heating member with the largest longitudinal width and the heating member with the next largest longitudinal width As a temperature rise detection target, a first heating member control that starts heating temperature control using the heating member with the widest longitudinal width, and
When the first heating member control is performed, when the temperature between the heating members detected by the temperature detection member of the end temperature increase detection target exceeds a predetermined temperature, the first heating member control is used. A second heating member control for switching to a heating temperature control using a combination of the heating member and the heating member having the next longer longitudinal width;
When the temperature between the heating members detected by the temperature detection member of the end portion temperature increase detection target when performing the second heating member control exceeds a predetermined temperature, Next, the temperature detection member disposed between the heating member with the wide longitudinal width is set as the end temperature rise detection target, and the longitudinal width is narrow among the two heating members used in the second heating member control. A third heating member control to switch to heating temperature control using the heating member,
Heating member switching control for sequentially switching the second heating member control and the third heating member control from a heating member with a long longitudinal width to a narrow heating member according to the number of the heating members. An image heating apparatus. An image that includes a rotating body and at least two or more heating members that heat the rotating body, conveys a recording material carrying an image together with the rotation of the rotating body, and heats the image with the heat of the rotating body In the heating device,
The heating members have different longitudinal widths in the longitudinal direction perpendicular to the recording material conveyance direction,
A temperature detecting member that is arranged at an end in the longitudinal direction for each of the heating members and detects an end temperature;
When the recording material width in the width direction orthogonal to the recording material conveyance direction of the recording material is unknown, the temperature detection member arranged at the end in the longitudinal direction of the heating member having the widest longitudinal width is the end temperature increase detection target, A first heating member control for starting the heating temperature control using the heating member having the widest longitudinal width;
When the temperature increase rate of the end temperature detected by the temperature detection member that is the end temperature increase detection target during execution of the first heating member control exceeds the predetermined value, the first heating member control A second heating member control that switches to a heating temperature control that is used in combination with the heating member that is used next and the heating member that has the next longer longitudinal width;
When the temperature increase rate of the edge temperature detected by the temperature detection member to be detected at the edge temperature exceeds the predetermined value during the second heating member control, the heating with the next longest width is performed. With the temperature detection member arranged at the end in the longitudinal direction of the member as the end temperature increase detection target, the heating member with the narrower longitudinal width of the two heating members used in the second heating member control is selected. A third heating member control to switch to the used heating temperature control;
Heating member switching control for sequentially switching the second heating member control and the third heating member control from a heating member with a long longitudinal width to a narrow heating member according to the number of the heating members. An image heating apparatus. An image that includes a rotating body and at least two or more heating members that heat the rotating body, conveys a recording material carrying an image together with the rotation of the rotating body, and heats the image with the heat of the rotating body In the heating device,
The heating members have different longitudinal widths in the longitudinal direction perpendicular to the recording material conveyance direction,
A first temperature detecting member that is disposed at an end in the longitudinal direction of each of the heating members and detects an end temperature;
A second temperature detecting member that is disposed in the central portion in the longitudinal direction between the heating members and detects the central temperature;
When the recording material width in the width direction orthogonal to the recording material conveyance direction of the recording material is unknown, the temperature detection member disposed at the longitudinal end of the heating member having the widest longitudinal width is set as the end temperature increase detection target, A first heating member control for starting the heating temperature control using a heating member having a wide longitudinal width;
The temperature of the end temperature detected by the first temperature detection member that is the end temperature increase detection target and the temperature of the center temperature detected by the second temperature detection member when performing the first heating member control When the difference exceeds a predetermined value, a second heating member control that switches to heating temperature control using a combination of the heating member with the widest longitudinal width and the heating member with the next longitudinal width;
When the temperature difference between the end temperature and the center temperature exceeds a predetermined value during the second heating member control, the second heating member is disposed at the longitudinal end of the heating member having the next longest width. Heating temperature control of an image using a heating member having a narrower longitudinal width among the two heating members used in the second heating member control with the first temperature detection member as an end temperature increase detection target A third heating member control to switch to,
Heating member switching control for sequentially switching the second heating member control and the third heating member control from a heating member with a long longitudinal width to a narrow heating member according to the number of the heating members. An image heating apparatus.   When the heating members are numbered N (N = 1, 2, 3,...) In order of increasing longitudinal width, the odd number driving means and the even number heating members for driving the odd number heating members. Two heating member driving means for driving the even number driving means, odd heating member selecting means for selecting one of the odd numbered heating members, and even number for selecting one of the even numbered heating members 5. The image heating apparatus according to claim 1, further comprising: a heating member selection unit.   When driving only the odd-numbered heating members, the even-numbered heating member switching means for selecting the even-numbered heating member to be driven next by the even-numbered heating member selection means, and the even-numbered heating members The odd-numbered heating member switching means for selecting the odd-numbered heating member to be driven next by the odd-numbered heating member selection means when driving only the heating member. The image heating apparatus according to 5.   The image heating apparatus according to claim 1, wherein the heating temperature control is switched between the front and rear recording materials.   An image forming apparatus comprising: an image forming unit that forms an unfixed image on a recording material; and a fixing unit that heat-fixes an unfixed image formed on the recording material on the recording material by the image forming unit. An image forming apparatus according to claim 1, wherein the image forming apparatus is an image heating apparatus according to claim 1.