JP5451268B2 - Image heating device - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used in an image forming apparatus that employs an electrophotographic process, an electrostatic recording process, or the like typified by a copying machine, a printer, a facsimile, or a complex machine thereof, and induces heating an image on a recording material. The present invention relates to a heating type image heating apparatus. Examples of the image heating device include a fixing device that heats and fixes an unfixed image formed on a recording material as a fixed image, and a glossiness increasing device that increases the glossiness of an image by heating the image fixed on the recording material. Can be mentioned.

  The present applicant, as an image heating apparatus capable of reducing power consumption during standby, is an electromagnetic induction type image heating apparatus (hereinafter referred to as an induction heating apparatus) that heats the entire circumference of a rotatable image heating member. ) Is proposed (Patent Document 1). In this apparatus, a plurality of exciting coils are arranged along the rotation direction of the image heating member in order to heat approximately the entire circumferential direction of the image heating member.

JP 2008-15082 A

  In order to prevent the high-frequency magnetic fields generated by the plurality of exciting coils from canceling each other, currents having the same frequency must be applied to the coils. However, when a plurality of high frequency power supplies are prepared for a plurality of coils, it is difficult to obtain the same frequency due to variations in elements of the high frequency power supply. Therefore, it is desirable to apply a high-frequency current to a plurality of coils with one high-frequency power source. Here, in an induction heating apparatus in which a plurality of coils are connected in parallel to a high-frequency power source and a high-frequency current is applied at a constant voltage, when a coil among the plurality of coils is disconnected, the coil is not disconnected. A larger current than usual is applied to the remaining coils. More specifically, as an example of a device in which two first and second coils are connected in parallel to a high-frequency power source as a plurality of coils, when one coil is disconnected, the number of coils is 2 with respect to the other coil. Double current will be applied. In the induction heating device, the amount of heat generation depends on the strength of the alternating magnetic field (= proportional to the square of the amount of current applied to the coil), so if one is broken, the other coil generates heat from the image heating member. The amount will be four times the normal amount. Therefore, when a coil of a plurality of coils is disconnected, the image heating member is locally overheated by the remaining coils that are not disconnected, and the other coils and other parts of the apparatus are also disconnected. May cause thermal damage. The present invention relates to a further improvement of the induction heating apparatus as disclosed in Patent Document 1, and an object thereof is to reliably avoid thermal damage of the apparatus when a coil of a plurality of coils is disconnected.

  In order to achieve the above object, a typical configuration of an image heating apparatus according to the present invention includes a rotatable image heating member that generates heat by a magnetic flux generated from a coil and heats an image on a recording material, and the image heating member. Are arranged along the circumferential direction of the image heating member, and a plurality of coils connected in parallel to the same high-frequency power source and applied with a high-frequency current, A plurality of temperature detection means for detecting the temperature of each coil-corresponding heating region of the plurality of coils of the image heating member, and any one of the plurality of temperature detection means has a temperature equal to or higher than a predetermined temperature. When detected, the energization of each coil from the high frequency power supply is stopped.

  According to the present invention, even when a coil of a plurality of coils is disconnected, local heat generation by a coil that is not disconnected can be prevented. As a result, the coil itself and other parts of the apparatus are not damaged, and thermal damage to the apparatus can be avoided reliably.

FIG. 5A is a schematic configuration diagram of an example of an image forming apparatus in the first embodiment, and FIG. 5B is an enlarged cross-sectional model of a main part of a fixing apparatus (an induction heating type image heating apparatus using a plurality of coils) in the first embodiment. Figure (A) is an exploded perspective view of coil assembly, and (b) is a block diagram of a control system. (A) is a flowchart for explaining an abnormal temperature detection configuration in the first embodiment, (b) is a flowchart for explaining an abnormal temperature detection configuration in the second embodiment. (A) is a flowchart for explaining the abnormal temperature detection configuration in the third embodiment, (b) is a block diagram of a control system for explaining the abnormal temperature detection configuration in the fifth embodiment. (A) is a block diagram of a control system for explaining a modified configuration of the abnormal temperature detection configuration in the fifth embodiment, and (b) to (e) are schematic diagrams of various apparatus configurations in the sixth embodiment.

  Example 1 << Example of Image Forming Apparatus >> FIG. 1A is a schematic view of an example of an image forming apparatus provided with an induction heating type image heating apparatus according to the present invention as a fixing device F. FIG. This image forming apparatus is a digital image forming apparatus of a laser scanning exposure system using an electrophotographic process (a copying machine, a printer, a facsimile, a composite function machine thereof). Reference numeral 41 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a drum) as an image carrier, which is rotationally driven at a predetermined peripheral speed in a clockwise direction R41 of an arrow. A primary charger (contact charging roller) 42 uniformly charges the surface of the rotating drum 41 to a predetermined negative dark potential Vd in this embodiment. A laser beam scanner 43 is an image exposure unit. The scanner 43 outputs a laser beam L modulated in response to a digital image signal input from a host device (not shown) such as an image reading device, a computer, or a counterpart facsimile, and scans the uniformly charged surface of the drum 41. Exposure. As a result, the absolute value of the potential of the exposed portion of the drum surface is reduced to a bright potential Vl, and an electrostatic latent image corresponding to the image signal is formed on the drum surface. The electrostatic latent image is visualized (reversed development) as a toner image T by the negatively charged toner adhering to the exposure light potential Vl portion of the drum surface by the developing unit 44. On the other hand, a recording material (heated material) P fed from a feeding portion (not shown) is a transfer nip portion TN that is a pressure contact portion between a transfer roller 45 and a drum 41 as a transfer member to which a transfer bias is applied. It is transported at an appropriate timing. Then, the toner images T on the drum are sequentially transferred onto the surface of the recording material P at the nip portion TN. The recording material P passes through the nip portion TN, is separated from the drum 41, and is introduced into the fixing device F. In the fixing device F, the toner image T on the recording material is fixed as a fixed image by heat and pressure. The recording material P is discharged out of the apparatus as an image formed product (print, copy). The surface of the drum 41 from which the recording material P has been separated is cleaned by removing the transfer residual toner by the cleaning device 46 and repeatedly used for image formation.

  << Fixing Device F >> FIG. 1B is an enlarged cross-sectional view of the main part of the fixing device F, FIG. 2A is an exploded perspective view of a coil assembly, and FIG. 1B is a block diagram of a control system. This apparatus F is a heating roller type induction heating type image heating apparatus using a plurality of coils (excitation coils). That is, a fixing roller (heating roller) 101 is provided as a rotatable image heating member (rotating heating body) that heats an image on a recording material by generating heat by a magnetic flux generated from a coil. Moreover, it is arrange | positioned along the circumferential direction of the roller 101, has a plurality of coils connected in parallel to the same high frequency power supply 108 and to which a high frequency current is applied. The apparatus of the present embodiment has first and second coils 103 and 104. Moreover, it arrange | positions along the circumferential direction of the roller 101, and is the 1st as a some temperature detection means as which the temperature of each coil corresponding | compatible heating area | region H1 and H2 of the said some coil 103 and 104 of the roller 101 is each detected. And second thermistors 106 and 107. Further, an elastic pressure roller 102 is provided as a pressure member (a pressure unit that presses against the roller 101 and clamps the recording material P) to form a nip portion (fixing nip portion) N by being in pressure contact with the roller 101. . The roller 101 mainly includes a core metal 101 a made of a hollow metal conductor that generates heat by induction using magnetic flux generated from the coils 103 and 104. Examples of the metal conductor are conductive magnetic materials such as iron, nickel, and SUS430, and alloys thereof. A heat-resistant release layer 101b made of a fluororesin or the like is formed on the outer peripheral surface of the core metal 101a. In order to improve the quality of the color image, a heat-resistant elastic layer such as silicone rubber or fluororubber may be provided between the cored bar 101a and the release layer 101b. The roller 101 is rotatably disposed between the left and right side plates of an apparatus frame (not shown), and is driven to rotate at a predetermined speed in the clockwise direction indicated by the arrow a by the drive source M. In the hollow portion of the roller 101, the first and second coils 103 and 104 that are connected in parallel to the same high-frequency power source 108 and generate a high-frequency magnetic field when a high-frequency current is applied are provided on the roller 101. Arranged along the circumferential direction. The coils 103 and 104 are formed by winding a bundle of heat-resistant insulating coated litz wires into a cylindrical coil holder 105 made of heat-resistant and electrically insulating engineering plastic or the like in the longitudinal direction of the roller 101. It is fixed by winding along. The assembly of the coils 103 and 104 and the coil holder 105 is a coil assembly 110. FIG. 2A is an exploded perspective view of the coil assembly 110. The coils 103 and 104 are horizontally long coils that extend in parallel to the longitudinal direction of the roller 101, that is, the rotation axis direction of the roller 101, and are curved and wound a plurality of times along the inner peripheral surface of the roller 101. . The coils 103 and 104 are located on the opposite sides of the outer peripheral surface of the cylindrical coil holder 105 approximately 180 ° from each other. The coil assembly 110 is inserted into the hollow portion of the roller 101. In the assemble 110, the left and right ends of the coil holder 105 are held on the left and right sides of the device frame (not shown) in a state where a predetermined constant gap (gap) is held between the roller inner surface and the coils 103 and 104. A non-rotating fixed support is provided for the member. The coils 103 and 104 are positioned inside the roller so as not to be exposed to the outside from the openings at both ends of the roller 101. In the configuration of this embodiment, the first and second coils 103 and 104 have substantially the same coil length, resistance, number of turns, and gap with the roller 101. H <b> 1 and H <b> 2 are heating regions corresponding to the coils of the first coil 103 and the second coil 104 of the roller 101. Let H1 be the first heating region and H2 be the second heating region. That is, the first heating region H1 represents a region where the roller 101 is heated by the first excitation coil 103, and the second heating region H2 represents a region where the roller 101 is heated by the second excitation coil 104. In the apparatus of the present embodiment, the first coil 103 corresponds to a substantially half-circumferential portion of the roller 101 in the circumferential direction, and therefore the first heating region H1 also corresponds to a substantially half-circumferential portion of the roller 101 in the circumferential direction. Yes. The second coil 104 corresponds to the other substantially half-circumferential portion of the roller 101 in the circumferential direction. Therefore, the second heating region H2 also corresponds to the other substantially half-circumferential portion of the roller 101 in the circumferential direction. Reference numerals 106 and 107 are arranged along the circumferential direction of the roller 101, and the first and second temperature detection units detect the temperatures of the first heating area H1 and the second heating area H2, respectively. It is a thermistor. The thermistors 106 and 107 detect the temperature in pressure contact with or close to the surface of the roller 101. Or you may make it press-contact or adjoin to the inner surface side of the roller 101. FIG. The pressure roller 102 is made of a core metal 102a that is a hollow metal body, a heat-resistant elastic layer 102b made of silicone rubber or the like formed concentrically around the core metal, and a fluororesin that covers the outer peripheral surface of the elastic layer. A release layer 102c is provided. The rollers 102 are arranged in parallel to the rollers 101 and are rotatably disposed between the left and right side plates of the apparatus frame (not shown). The roller 102 is pressed against the roller 101 against the elasticity of the elastic layer 102b with a predetermined pressing force by a pressing mechanism (not shown). As a result, a fixing nip portion (heat and pressure nip portion) having a predetermined width in the recording material conveyance direction C for sandwiching and conveying the recording material P between the roller 101 and the roller 102 to heat and fix the toner image T. ) N is formed.

<< Image Fixing Operation >> The image fixing operation is as follows. The roller 101 is rotationally driven at a predetermined speed in the clockwise direction a of the arrow by a driving source M controlled by a control means (control circuit: CPU) 109. Following the rotation of the roller 101, the roller 102 also rotates in the counterclockwise direction b indicated by the arrow. The control means 109 activates the high frequency power source 108 and applies a high frequency current of a predetermined voltage to the first and second coils 103 and 104 connected in parallel to the power source 108. As a result, a high-frequency magnetic field is generated in the first and second coils 103 and 104, and an eddy current is induced in the core metal 101 a of the roller 101 by the action of the high-frequency magnetic field. The temperature is raised. In the apparatus according to the present embodiment, the roller 101 is heated by the first and second coils 103 and 1041 in the circumferential direction of the roller 101. Then, the temperature of the first heating region H 1 of the roller 101 heated by the first exciting coil 103 is detected by the first thermistor 106, and the detected temperature information is input to the control means 109. Further, the temperature of the second heating region H <b> 2 of the roller 101 heated by the second exciting coil 104 is detected by the second thermistor 107, and the detected temperature information is input to the control means 109. The control unit 109 sets the temperature of the roller 101 to a predetermined image heating temperature T ₀ (target temperature, fixing temperature: main) based on one or both of the detected temperature information input from the first and second thermistors 106 and 107. In the embodiment, the temperature is controlled at 190 ° C. That is, the control means 109 increases the temperature of the roller 101 to a predetermined image heating temperature T ₀ and maintains it at the predetermined temperature based on the detected temperature information of the thermistors 106 and 107. The high-frequency current to the second coils 103 and 104 is controlled. Then, the recording material P carrying the unfixed toner image T is introduced into the fixing nip portion N while the roller 101 rises to the predetermined image heating temperature T ₀ and is maintained at that temperature. The recording material P is nipped and conveyed through the fixing nip portion N, whereby the toner image is fixed by heating and pressing as a fixed image on the recording material surface.

<< Induction Heat Generation Principle >> Next, the principle of induction heat generation of the roller 101 will be described with reference to FIG. A high-frequency current I ₀ is applied from the power source 108 to the first coil 103 and the second coil 104. The coil 103 and the coil 104 are connected in parallel to the power source 108, a current of _{I 1} and _{I 2} are applied respectively, the high-frequency currents _{I 1} and _{I 2} generates a high frequency magnetic field, respectively. The coil 103 and the coil 104 are connected to the power source 108 in parallel with each other. Therefore, I ₁ and I ₂ are high-frequency currents having the same frequency f as the current I ₀ generated by the power supply 108, and the current values satisfy Equation 1. Under the influence of the high frequency magnetic field generated by the coils 103 and 104, an eddy current that generates a magnetic field in a direction to cancel the high frequency magnetic field generated by the coils 103 and 104 is induced in the cored bar 101a of the roller 101. This eddy current flows in a concentrated manner on the surface of the core metal 101a on the side of the coils 103 and 104 due to the skin effect, and generates Joule heat with power proportional to the skin resistance _RS of the core metal 101a. Here, the frequency of the high frequency current applied to the coil is f (Hz), the magnetic permeability of the cored bar 101a is μ (H / m), and the specific resistance of the cored bar 101a is ρ (Ω · m). The skin depth δ (m) and the skin resistance R _S (Ω) through which most of the eddy current flows are expressed by Equations 2 and 3. Further, the electric power W generated in the cored bar 101a is expressed by Equation 4 with the eddy current induced in the cored bar 101a being I _f (A). In general, it is known that the eddy current _If depends on the amount of change in the magnetic field generated by the coil. The strength of the magnetic field is H (A / m), the number of turns of the coil is n (times), and the coil Assuming that the current applied to is I (A), it is expressed by Equation 5. The electric power W generated in the cored bar 101a is expressed by Equation 6. Here, the current flowing through the first coil 103 is I ₁ (A), the number of turns of the first coil 103 is n ₁ (times), the power generated by the first coil 103 is W ₁ (W), The current flowing through the second exciting coil 104 is defined as I ₂ (A). The number of turns of the second coil 104 is n ₂ (times), and the power generated by the second coil 104 is W ₂ (W). In the configuration of the present embodiment, each of the first coil 103 and the second coil 104 is designed such that the resistance, the number of turns, and the gap with the roller 101 are substantially the same. Therefore, since the relationship shown in Expression 7 holds, the heat generation amount W of the roller 101 in the configuration of this embodiment is expressed by Expression 8 and Expression 9.

<< Abnormality Detection Configuration >> Next, in the configuration of this embodiment, for example, a case is considered in which no current flows through the first coil 103 but only current flows through the second coil 104 due to disconnection or the like. Since the current I ₁ flowing through the first coil 103 is zero, the current I ₂ flowing through the second coil 104 flows at a current value equivalent to twice that in the normal state from Equation 7. That is, the heat generation amount W _2err when a current flows only through the second coil 104 is equivalent to four times the heat generation amount W ₂ of the second coil 104 in a normal state. In this state, the second coil 104 generates excessive heat than usual. Therefore, there is a possibility that other members of the device arranged around the second heating region H2 by the second coil 104 and the second coil 104 itself may be damaged. Therefore, in this embodiment, the control means 109 stops energization from the high-frequency power source 109 to the coils 103 and 104 when any of the plurality of temperature detection means 106 and 107 detects a temperature equal to or higher than a predetermined temperature. It is characterized by. This abnormality detection configuration will be described with reference to FIG. When heating of the fixing device F is started, the control unit 109 determines that one of the detected temperatures T ₁ and T ₂ of the first and second thermistors 106 and 107 is _{equal to} or higher than a predetermined error temperature T _err (above a predetermined temperature). Is determined) (S101, S102). The error temperature T _err is stored in advance in the memory unit of the control unit 109. In this embodiment, the error temperature _Terr is set to 230 ° C. Control means 109, if any of the detected temperatures _{T 1} and _{T 2} is the error temperature _{T err} or stops the energization of the coils 103, 104 from the power source 109. That is, heating of the roller 101 is stopped (I ₀ OFF), and an error is displayed on the display unit 111 (S104, S107). The first coil 103 and the second coil 104 are connected to the power supply 108 in parallel with each other. For this reason, when the high-frequency current I ₀ is stopped, the application of current to both the coils 103 and 104 is stopped. When both the detected temperatures T ₁ and T ₂ are lower than the error temperature T _err , the control unit 109 raises the temperature of the roller 101 to a predetermined image heating temperature T ₀ and adjusts the temperature so as to be maintained at that temperature. Control. That is, the high-frequency current I ₀ from the power source 108 to the first and second coils 103 and 104 is controlled based on the detected temperature information of the thermistors 106 and 107 (S103, S105, S106). As described above, in the configuration of this embodiment, an abnormality occurs only in one of the first coil 103 and the second coil 104, and a high-frequency current is applied only to the other coil. However, it is possible to reliably avoid thermal damage to the apparatus. That is, when either the first thermistor or the second thermistor detects a temperature exceeding a predetermined error temperature due to the abnormality of the coil, the application of the high-frequency current to both the first coil and the second coil is stopped (cut off). . Therefore, it is possible to prevent local heat generation of the coil without any abnormality, and it is possible to reliably avoid thermal damage to the device without damaging the coil itself or other parts of the device. it can.

[Example 2]: An abnormality detection configuration in Example 2 will be described with reference to FIG. In the present embodiment, there is provided a temperature difference determining means for measuring a difference between the detected temperatures of the plurality of temperature detecting means 106 and 107 and determining whether or not the detected temperature difference is equal to or greater than a predetermined value. Then, according to the determination by the temperature difference determination means, the power supply from the power source 108 to the coils 103 and 104 is stopped. When heating of the fixing device F is started, the temperature difference determination function unit (temperature difference determination unit) of the control unit 109 measures the difference between the detected temperatures of the temperature detection units 106 and 107, and the difference between the detected temperatures is detected. It is determined whether or not the predetermined value is exceeded. That is, the absolute value [Delta] T of the difference between the detected temperature T ₂ of the detected temperatures T ₁ and a second thermistor 107 of the first thermistor 106, preset by the predetermined being the memory temperature difference error temperature [Delta] T _{err (present} It is determined whether the temperature is 20 ° C. or higher in the example (S201). When ΔT is equal to or _larger than ΔT _err , the control unit 109 stops energization of the coils 103 and 104 from the power source 109, that is, stops heating the roller 101 (I ₀ : OFF), and displays the display unit. An error is displayed in 111 (S203, S206). The first coil 103 and second coil 104, because it is connected in parallel to each other with respect to the power source 108 and stops the high-frequency current I _0, the application of the current stops to both the coil 103, 104 Is done. When ΔT is lower than ΔT _err , the control unit 109 controls the temperature so that the temperature of the roller 101 is raised to a predetermined image heating temperature T ₀ and maintained at that temperature. That is, the high-frequency current I ₀ from the power source 108 to the first and second coils 103 and 104 is controlled based on the detected temperature information of the thermistors 106 and 107 (S202, S204, S205). In this embodiment, when an abnormality occurs in one of the first coil 103 and the second coil 104 and ΔT is equal to or greater than ΔT _err , the control means 109 receives power from the power source 109 to each coil 103. The energization to 104 is stopped. Therefore, it is possible to prevent local heat generation of the coil without any abnormality, and it is possible to reliably avoid thermal damage to the device without damaging the coil itself or other parts of the device. it can.

[Embodiment 3]: An abnormality detection configuration in Embodiment 3 will be described with reference to FIG. In the present embodiment, there is provided a change amount determining means for measuring a change amount of the detected temperature of each of the plurality of temperature detecting means 106 and 107 and determining whether any of the detected temperature change amounts is equal to or greater than a predetermined value. Have. Then, according to the determination by the change amount determination means, the power supply from the power source 108 to the coils 103 and 104 is stopped. When heating of the fixing device F is started, the timer t and the memory count n in the control means 109 are reset (S301), and the timer t starts counting (S302). The control means 109 is in a state in which the detected temperatures T ₁ and T _{2 of} the first and second thermistors 106 and 107 are equal to or lower than a predetermined image heating temperature T ₀ and the timer t is set at every elapse of a predetermined time (in this embodiment, 5 seconds). T1 (n) and T2 (n) are stored in every) (S303, S304, S306, S307). The change amount determination function unit (change amount determination means) of the control means 109 measures the amount of change in the detected temperature of each of the thermistors 106 and 107, and determines whether the amount of change in any of the detected temperatures is greater than or equal to a predetermined value. To do. That is, T1 (n) and T2 (n) are compared with the previously stored temperatures T1 (n-1) and T2 (n-1). If the difference is equal to or higher than a predetermined temperature difference error temperature Terr (15 ° C. in this embodiment) (S308, S309), the control unit 109 stops energization of the coils 103 and 104 from the power source 109. That is, the heating of the roller 101 is stopped (I ₀ OFF), and an error is displayed on the display unit 111 (S310, S312). That is, if the difference is equal to or higher than the predetermined temperature difference error temperature Terr, it is determined that the temperature rise is larger than usual, that is, excessive heating is performed by any of the coils 103 and 104, and the current I ₀ is determined. Is stopped and an error is displayed. Thereafter, when T1 and T2 reach the image heating temperature target temperature T, the warm-up operation ends (S303, S305). In the present embodiment, when an abnormality occurs in one of the coils 103 and 104 and the amount of change in the detection temperatures T ₁ and T ₂ of the thermistors 106 and 107 is detected to be greater than or equal to a predetermined value, the control means 109 The energization from the power source 109 to the coils 103 and 104 is stopped. Therefore, it is possible to prevent local heat generation of the coil without any abnormality, and it is possible to reliably avoid thermal damage to the device without damaging the coil itself or other parts of the device. it can.

  [Example 4]: In Example 3, the first detection temperature T1 (n) and the previous detection temperature T1 (n-1) are set to ΔT1 (n). Further, the second detection temperature T2 (n) and the previous detection temperature T2 (n-1) are set to ΔT2 (n). Then, if | ΔT1 (n) −ΔT2 (n) |, which is the absolute value of the difference between ΔT1 (n) and ΔT2 (n), is larger than a predetermined value, it may be determined that the abnormality is present. That is, a change amount difference judging unit is provided for measuring a change amount of the detected temperature of each of the plurality of temperature detecting means 106 and 107 and judging whether or not a difference between the detected temperature change amounts is not less than a predetermined value. . Then, a configuration may be adopted in which energization from the power source 108 to each of the coils 103 and 104 is stopped in accordance with the determination by the change amount difference determination means.

  [Embodiment 5]: An abnormality detection configuration of the present embodiment will be described with reference to FIG. In this embodiment, the first and second temperature detecting means 106 and 107 are changed from the thermistor to the thermo switch. The thermo switches 106 and 107 are both connected in series with the +24 VDC power supply and the relay switches 411 and 412. The high frequency power supply 108 is supplied with power from the commercial power supply 410. Here, considering a case where no current flows through the first coil 103 but only through the second coil 104, the heating region of the roller 101 corresponding to the second coil 104 (second heating region H2). Is heated with a higher power than usual, and the temperature rises. At this time, when the second thermo switch 107 detects a predetermined cutoff temperature (200 ° C. in this embodiment), the second thermo switch 107 is turned off. When the second thermo switch 107 is turned off, the power supply to the relay switch 412 connected in series with the second thermo switch 107 is cut off, so that the power supply from the commercial power supply 410 to the high frequency power supply 408 is also cut off. That is, energization from the power source 109 to the coils 103 and 104 is stopped. Conversely, when no current flows through the second coil 104 and current flows only through the first coil 103, the first thermo switch 106 is similarly cut off and the power supply to the relay switch 411 is cut off. The power supply from the commercial power supply 410 to the high frequency power supply 408 is also cut off. That is, energization from the power source 109 to the coils 103 and 104 is stopped. As described above, when any one of the plurality of temperature detecting means 106 and 107 detects a temperature equal to or higher than a predetermined temperature, energization from the power source 108 to the coils 103 and 104 is stopped. Therefore, it is possible to prevent local heat generation of the coil without any abnormality, and it is possible to reliably avoid thermal damage to the device without damaging the coil itself or other parts of the device. it can. In the present embodiment, as the temperature detection means 106 and 107, a temperature fuse or the like that is disconnected at a predetermined temperature can be substituted. Further, as shown in FIG. 5A, it is also possible to connect a first thermo switch 106 and a second thermo switch 107 in series and use a common relay switch 412. In the apparatus of the present embodiment, the rise of the roller 101 to the image heating temperature T0 and the temperature control are based on the temperature detected by a temperature detecting means (thermistor) that detects the temperature of the roller 101, which is provided separately. Made.

[Embodiment 6] The configurations of Embodiments 1 to 5 described above are not described to limit the present invention, and various modifications can be made according to the image heating apparatus to be applied. . It is also possible to adopt a configuration in which the configurations of the first to fifth embodiments are appropriately combined. For example, the present invention can be applied even when the number of turns, the winding length, the resistance, and the gap between the roller 101 and the first coil 103 and the second coil 104 are appropriately changed. An exciting coil, a schematic diagram so in (b) of FIG. 5, three sets 103 (1) to 103 (3) apparatus configuration used, in the schematic view so in (c) of FIG. 5, four sets 103 (1) -103 (4) used device configuration, or a device configuration using five or more sets. As the image heating member 101, not only a roller type but also an endless belt made of magnetic metal or nonmagnetic metal, or an endless belt that can be rotated via a fixed image heating member made of magnetic metal or nonmagnetic metal is heated. Even so, the present invention is applicable. Furthermore, as shown in (d) and (e) of FIG. 5 , an apparatus configuration in which all or some of the plurality of coils are arranged outside the image heating member may be used.

  F .. Induction heating type image heating device (fixing device), 101... Image heating member, 103 · 104 · · Multiple coils, H1 · H2 · · Heating area corresponding to coils, 106 · 107 · · Multiple temperature detection 108, high frequency power supply

Claims (6)

A rotatable image heating member that generates heat by the magnetic flux generated from the coil and heats the image on the recording material, and is disposed along the circumferential direction of the image heating member, and is connected in parallel to the same high-frequency power source. And a plurality of coils to which a high-frequency current is applied, and a circumferential direction of the image heating member, and detecting temperatures of the heating regions corresponding to the coils of the plurality of coils of the image heating member, respectively. A plurality of temperature detection means, and when the current does not flow through any of the plurality of coils, the plurality of temperatures due to an overheating phenomenon caused by an increase in high-frequency current applied to another coil An image heating apparatus characterized in that energization of each coil from the high-frequency power supply is stopped when any of the detecting means detects a temperature equal to or higher than a predetermined temperature.   The image heating apparatus according to claim 1, wherein the plurality of temperature detection units are thermo switches or temperature fuses.   The image heating apparatus according to claim 2, wherein the plurality of temperature detection units are connected to each other in series. A rotatable image heating member that generates heat by the magnetic flux generated from the coil and heats the image on the recording material, and is disposed along the circumferential direction of the image heating member, and is connected in parallel to the same high-frequency power source. And a plurality of coils to which a high-frequency current is applied, and a circumferential direction of the image heating member, and detecting temperatures of the heating regions corresponding to the coils of the plurality of coils of the image heating member, respectively. includes a plurality of temperature detecting means, the difference between the respective detected temperature measurement of said plurality of temperature sensing means, and the temperature difference determination means the difference between the detected temperature is judged whether a predetermined amount or more, a plurality of any of the temperature difference determination means that the difference of the detection temperature by heating phenomenon caused by the increase in the high-frequency current applied to the other coil when the current does not flow in the coil is a predetermined or more of the coil Judgment Image heating apparatus wherein the energization of the high-frequency power supply to the coils is stopped when. A rotatable image heating member that generates heat by the magnetic flux generated from the coil and heats the image on the recording material, and is disposed along the circumferential direction of the image heating member, and is connected in parallel to the same high-frequency power source. And a plurality of coils to which a high-frequency current is applied, and a circumferential direction of the image heating member, and detecting temperatures of the heating regions corresponding to the coils of the plurality of coils of the image heating member, respectively. A plurality of temperature detection means; and a change amount determination means for measuring a change amount of the detected temperature of each of the plurality of temperature detection means and determining whether any change amount of the detected temperature is equal to or greater than a predetermined value. And when the current does not flow through any of the plurality of coils, the amount of change in the detected temperature is greater than or equal to a predetermined amount due to an overheating phenomenon caused by an increase in high-frequency current applied to another coil. Above An image heating apparatus according to claim wherein the energization from the high-frequency power source to each coil is stopped when the reduction amount determining means determines. A rotatable image heating member that generates heat by the magnetic flux generated from the coil and heats the image on the recording material, and is disposed along the circumferential direction of the image heating member, and is connected in parallel to the same high-frequency power source. detecting respective plurality of coils of high-frequency current is applied, are arranged along a circumferential direction of said image heating member, said image heating member, the temperature of each coil corresponding heating region of said plurality of coils Te A plurality of temperature detection means; and a change amount difference determination means for measuring a change amount of each detected temperature of the plurality of temperature detection means and determining whether or not a difference between the change amounts of the detected temperatures is greater than or equal to a predetermined value. And when the current does not flow through any one of the plurality of coils, a difference in the amount of change in the detected temperature is predetermined due to an overheating phenomenon caused by an increase in the high-frequency current applied to the other coil. That's it An image heating apparatus according to claim wherein the energization from the high-frequency power source to each coil is stopped when the change amount difference determining means determines.